Shanxi announced Linfen pollution investigation results: 86 boilers have no desulfurization measures.

CCTV News:Recently, the problem of sulfur dioxide exceeding the standard in Linfen City, Shanxi Province has aroused widespread concern. As a typical resource-based city in the north, the ambient air quality in Linfen City has turned sharply since the winter of 2016, and heavy smog weather has continued to appear. Up to now, Linfen City has experienced six heavy pollution weather processes, which lasted for 48 days and issued 13 heavy pollution weather warnings. On January 4, 2017, the air quality index (AQI) of monitoring points in Linfen City continued to rise, and the concentration of SO2 (sulfur dioxide) was as high as 1,300 μ g/m3, exceeding the national third-class standard ("minimum requirements for people to be exposed to acute health damage in the short and medium term") by more than 1,000, ranking first in 388 cities in China, 719 higher than the second.

On the 15th, Shanxi Provincial Environmental Protection Department announced that after three days’ investigation and analysis, the joint expert group of the Ministry of Environmental Protection and Shanxi Province has preliminarily identified five reasons for the excessive concentration of sulfur dioxide in Linfen:

First, coal consumption is large.From 2013 to 2016, the city’s coal consumption in Linfen increased from 30 million tons to 36.6 million tons, of which coking coal accounted for a high proportion, accounting for 65.3%, followed by power generation coal of 9.7 million tons, accounting for 26.5%.

Second, residents’ loose coal combustion emissions have aggravated sulfur dioxide pollution in winter.According to preliminary estimates, the annual sulfur dioxide emissions from coal-fired heating (except cogeneration) in six counties and cities (districts) along the Fenhe River in Linfen City are about 38,000 tons, accounting for 45% of the annual sulfur dioxide emissions. When winter enters the heating season, the proportion is even more prominent, accounting for about 70%. Among them, the emissions from heating boilers other than cogeneration account for 13% of the living sources.

Third, the promotion and use of clean coke did not achieve the expected results.Although clean coke is widely used in urban areas, due to its high burning point and difficulty in bank up, some people abandon the distributed clean coke, some mix clean coke with inferior coal, and a small number of clean coke fail to meet the sulfur index, and the amount of sulfur dioxide emitted by residents in urban areas and surrounding areas is still large.

Fourth, the transformation of coal-fired heating boilers and clean energy lags behind.At present, there are still 86 130-ton coal-fired boilers in urban areas, and there are basically no desulfurization measures. Although clean coke is used, the sulfur dioxide emission is still very large, which has a direct impact on the sulfur dioxide index in urban areas.

Fifth, there is no on-line monitoring for central heating in Dongcheng, the desulfurization device is ineffective, the factory area is messy and the management measures are not in place.(CCTV reporter Hu Xiaodong)

Research: ferrets and cats are susceptible to Covid-19, which can cause "cat-to-cat transmission"

  Covid-19 is thought to originate from bats, and it is 96.2% similar to RaTG13 (collected by Shi Zhengli, Wuhan Institute of Virology, Chinese Academy of Sciences, in Yunnan, China in 2013) in nucleotide sequence level. However, it is a kind of novel coronavirus that has not been detected in humans and other animals before, and its appearance has brought many new problems to be solved urgently, including whether other pets, livestock and poultry may be infected by Covid-19 besides humans?

  On April 8th, local time, the top academic journal Science published the paper "Susceptibility of Ferrets, Cats, Dogs, and Different Domestic Animals to SARS-coronavirus-2" online. The purpose of this study is to find out some questions: Will Covid-19 be transmitted to other animal species, thus becoming a "reservoir" of infection? Covid-19 infection has many clinical manifestations in humans, ranging from mild infection to death, so how is it manifested in other animals? With the development of vaccines and antiviral drugs, which animals can be used to simulate the effects of these drugs or vaccines on humans most accurately?

  In order to solve these problems, research teams from the State Key Laboratory of Veterinary Biotechnology of Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences and the National High-level Biosafety Laboratory of Animal Disease Prevention and Control evaluated the susceptibility of different model experimental animals, pets and livestock to Covid-19, infected Covid-19 through experiments, observed the clinical manifestations and pathological changes of vaccinated animals and cohabiting animals, and detected the viral load of organs and tissues, the emission of respiratory and intestinal viruses, and the seroconversion of antibodies against Covid-19 in animals.

  Their research shows that Covid-19 has weak replication ability in dogs, pigs, chickens and ducks, but it can replicate efficiently in ferrets’ upper respiratory tract and cats’ respiratory system and digestive system. Experimental infected cats can spread Covid-19 through the air; Some cats can cause serious illness or even death after infection, and the illness of young cats is obviously more serious than that of older cats.

  Histopathological observation confirmed that virus infection in cats can cause lung inflammation and intestinal mucosal damage to varying degrees. Immunohistochemical study showed that there were a large number of virus infections in mucosal epithelium and olfactory bulb cells of upper respiratory tract (nasal cavity, maxilla, tonsil), mucous gland epithelial cells of trachea and bronchial mucosa, and intestinal mucosal epithelium.

  The correspondent of this paper is Chen Hualan, academician of China Academy of Sciences, chief scientist of the innovation team of animal influenza basic and prevention research in Harbin Veterinary Research Institute of China Academy of Agricultural Sciences, Bu Zhigao, director of Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences and director of the national high-level biosafety laboratory for animal disease prevention and control, and Wu Guizhen, secretary of the Party Committee of Institute of Viral Disease Prevention and Control of China CDC and director of BSL-3 laboratory. Previously, on March 31st, local time, the research team had taken the lead in publishing the research on the preprint platform bioRxiv.

  It is worth mentioning that the National High-level Biosafety Laboratory for Animal Disease Prevention and Control is one of the existing two P4 laboratories in China, and the other is in Wuhan National Biosafety Laboratory of Chinese Academy of Sciences. All the experiments of Covid-19 infection in this study were carried out in P4 laboratory, which was approved by the Ministry of Agriculture and Rural Affairs of China. Animal research and animal welfare programs were approved by the Animal Experimental Ethics Committee of China Academy of Agricultural Sciences.

  According to the press release issued by official website, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, different coronaviruses have been prevalent in mammals and poultry, but most of these coronaviruses are limited to specific species of animals and generally cannot infect humans. Similarly, several common coronaviruses in humans do not infect other animals. However, some coronaviruses from bats, such as SARS and MERS virus, can often infect many animals and humans.

  At present, Covid-19 is popular among a wide range of people in the world, and the risk of introducing animals in close contact with human beings is increasing. Therefore, it is urgent to study the susceptibility of domestic animals in close contact with human beings to Covid-19, evaluate whether domestic animals are exposed to Covid-19 hazards and become potential intermediate hosts, and provide scientific basis for prevention and control of Covid-19.

  In addition, in view of the current global epidemic situation of COVID-19, it is very likely that it will evolve into a common infectious disease, and it is urgent to establish a stable and reliable animal infection model to meet the needs of vaccine and drug research and development evaluation.

  The research team stressed that the monitoring of cat COVID-19 should be regarded as an auxiliary means to eliminate the current Covid-19 epidemic. They called for close monitoring and protection of cats in epidemic areas, avoiding their contact with infectious sources and preventing them from becoming possible transmission hosts or storage hosts.

  In addition, it was previously questioned that cats infected with COVID-19 were caused by large doses under laboratory conditions. However, in addition to this research, on April 3rd, Academician Jin Meilin, professor of the State Key Laboratory of Agricultural Microbiology of Huazhong Agricultural University, director of the Key Laboratory of Veterinary Diagnostic Preparations of the Ministry of Agriculture, director of the Research Center for Emerging Infectious Diseases of Wuhan Institute of Virology, Chinese Academy of Sciences, and researcher Shi Zhengli, director of the Key Laboratory of Highly Pathogenic Biology and Biosafety of Chinese Academy of Sciences, also published a study on the preprint platform bioRxiv. Through the investigation of cat serum, they found that the serum ELISA test of 102 cats collected after the outbreak of COVID-19 in Wuhan showed that the serum from 15 cats (14.7%) was positive for Covid-19 receptor binding domain (RBD).

  Nadia, a 4-year-old tiger from Bronx Zoo in new york, USA, was recently diagnosed with Covid-19. On April 5, local time, the US Department of Agriculture issued a statement confirming that a tiger in a zoo in new york was diagnosed with Covid-19, and several other lions and tigers also showed symptoms of respiratory diseases. Officials at the Bronx Zoo in new york said that nadia, three other tigers and three African lions had symptoms of dry cough and loss of appetite, but they are expected to recover. Public health officials believe that these animals were infected by an asymptomatic employee.

  Covid-19 can be replicated in the upper respiratory tract of ferrets for up to 8 days, but it will not cause serious illness or death.

  Ferrets are often used as animal models of human respiratory viruses. Therefore, the research team first tested ferrets’ sensitivity to Covid-19.

  Two Covid-19 strains were used in this study: F13-E from Wuhan South China Seafood Market and CTan-H from a patient infected with Covid-19.

  The research team inoculated 10 5 PFU (Plaque Forming Unit) F13-E or CTan-H into ferrets through nose respectively, and euthanized them on the 4th day after inoculation (P.I.). The turbinate, soft palate, tonsil, trachea, lung, heart, spleen, kidney, pancreas, small intestine, brain and liver of each ferret were collected, and the viral RNA was determined by qPCR and virus titration.

  Viral RNA:A in ferrets’ organs or tissues: A, F13-E, B, CTAN-H..

  The results showed that viral RNA and infectious virus were detected in the turbinate, soft palate and tonsil of all four ferrets, but not in other tissues.

  C, virus titer in organs or tissues of ferrets inoculated with F13-E, D and CTAN-H.

  The research team believes that these results show that Covid-19 can replicate in the upper respiratory tract of ferrets, but it has not been detected in other tissues.

  In order to study the replication dynamics of virus in ferrets, the research team intranasally inoculated 6 ferrets with 10^5pfu of F13-E(3) or CTan-H(3), and then placed them in three isolated cages. On the 2nd, 4th, 6th, 8th and 10th day, ferret nasal wash and rectal swab were collected for virus RNA detection and virus titration. At the same time, their body temperature and COVID-19 signs were monitored for two weeks.

  Viral RNA in the nasal wash of ferrets inoculated with F13-E(E) and CTan-H(F). Viral titers in the nasal wash of ferrets inoculated with F13-E(G) and CTan-H(H).

  The results showed that viral RNA was found in the nasal wash of all six ferrets on the 2nd, 4th, 6th and 8th day. Viral RNA was also found in some rectal swabs, but the copy number was significantly lower than that of nasal wash. Infectious virus was detected in nasal wash of all ferrets, but none of them was found in rectal swab.

  One ferret in each group developed fever and loss of appetite on the 10th and 12th days respectively. In order to investigate whether these symptoms are caused by virus replication in the lower respiratory tract, the research team euthanized the two ferrets on the 13th day and collected their organs for virus RNA detection.

  However, except for the ferret turbinate inoculated with CTan-H, the low copy number was detected, and no viral RNA was detected in any other tissues or organs.

  Pathological studies showed that two ferrets euthanized on the 13th day had severe lymphoplasmacytic vasculitis and vasculitis, the number of type II alveolar cells, macrophages and neutrophils in alveolar septa and alveolar cavities increased, and the lungs had mild bronchiolitis.

  The asterisk indicates that the animals were euthanized on the 13th day after inoculation, and the other four animals were euthanized on the 20th day.

  Covid-19 antibody was detected in all ferrets by ELISA and neutralization test, and the antibody titers of two ferrets euthanized on the 13th day were significantly lower than those euthanized on the 20th day.

  In order to further study whether Covid-19 was replicated in ferrets’ lungs, the research team inoculated 8 ferrets with 10^5 pfu of CTan-H through trachea, and euthanized 2 animals on the 2nd, 4th, 8th and 14th days, respectively, and detected virus RNA in tissues and organs.

  Among the two ferrets euthanized on the second day and the two ferrets euthanized on the fourth day, the researchers only detected viral RNA; in the turbinate and soft palate of one of them. Among the two ferrets euthanized on the eighth day, viral RNA; was detected in the soft palate of one ferret and in the turbinate, soft palate, tonsil and trachea of the other ferret. No viral RNA was detected in the two ferrets euthanized on the 14th day.

  These results indicate that Covid-19 can replicate in the upper respiratory tract of ferrets for up to 8 days without causing serious illness or death.

  At the end of the paper, the research team also mentioned that, comparatively speaking, Covid-19 is different from other influenza viruses that can replicate in the upper respiratory tract and lower respiratory tract of ferrets, and even human SARS-CoV. Covid-19 is only replicated in ferrets’ nasal bones, soft palate and tonsils. It can also replicate in the digestive tract, but even if the virus is inoculated in the trachea, the virus is still not detected in the lungs of ferrets.

  Cats are highly susceptible to "cat-to-cat transmission": the monitoring of cat Covid-19 should be regarded as an auxiliary means of epidemic prevention and control.

  It is worth noting that cats and dogs are in close contact with humans, so the research team thinks that besides laboratory animals like ferrets, it is very important to know the susceptibility of domestic animals that often live with humans to COVID-19 for the control of Covid-19.

  The research team first studied the replication of Covid-19 in cats. Five 8-month-old subadult domestic cats (inbred lines) were intranasally inoculated with 10^5pfu of CTan-H, and two of them were scheduled to be euthanized on the sixth day to evaluate the virus replication in their organs. Three cats were put in separate cages in the isolator. In order to monitor the spread of respiratory droplets, an uninfected cat was placed in a cage adjacent to each cat vaccinated with the virus.

  Because 8-month-old cats are aggressive, it is difficult to carry out routine nasal cleaning on them. In order to avoid possible harm, the research team collected the feces of these cats and checked the viral RNA in their organs after euthanasia.

  Virus RNA was detected in the nasal bone, soft palate and tonsils of two sub-adult domestic cats euthanized on the 6th day, and virus RNA was also detected in the trachea of one cat and the small intestine of the other cat. However, no viral RNA was detected in any lung samples of these two cats.

  Infectious viruses were detected in the nasal bones, soft palate, tonsils and trachea of these cats, but no infectious viruses were found in the small intestine with positive viral RNA.

  The spread of Covid-19 among cats.

  In the study of virus transmission, RNA virus was detected in the feces of two vaccinated cats on the third day, and RNA virus was detected in the feces of all three vaccinated cats on the fifth day. Among the three cats at risk of virus exposure, viral RNA was detected in the feces of one cat on the third day.

  Virus-infected cats with positive feces were euthanized on the 11th day. Virus RNA was detected in the soft palate and tonsils of the infected cats and in the nasal bones, soft palate, tonsils and trachea of the exposed cats, indicating that respiratory droplets spread between cats.

  On the 12th day, the research team euthanized the remaining cats. Viral RNA was detected in the tonsils of one virus-infected cat and the nasal bone, soft palate, tonsils and trachea of another virus-infected cat, but it was not detected in any organ or tissue of the two virus-exposed cats.

  Through ELISA and neutralization test, Covid-19 antibody was detected in all three cats inoculated with virus and one cat exposed to virus.

  Covid-19 replicates efficiently in respiratory system and digestive system of infected cats, causing pathological damage and inflammatory reaction. Histopathological and immunohistochemical study on cats that died or were euthanized three days after virus infection. (a) The arrangement of nasal mucosa epithelium is disordered, cilia fall off (arrow), and lymphocytes in lamina propria infiltrate (arrow). (b) The tonsil epithelial cells are degenerated and necrotic, and the surface of mucosal epithelium (asterisk) is covered with cell fragments and neutrophils (arrow). (c) Epithelial degeneration and necrosis of tracheal mucosa (arrow), with mucus (asterisk) mixed with a large number of cell fragments on the surface. (d) Epithelial necrosis of tracheal mucous glands and infiltration of lymphocytes (arrow). (e) Normal lung tissue structure of uninfected cats. (f) Aggregation of inflammatory cells in pulmonary blood vessels and coagulation of fibrin (arrow). (g) A large number of macrophages and lymphocytes infiltrated in alveoli, that is, alveolar septa. (h) Infiltration and proliferation of alveoli and alveolar septitis. (i) Some cells in the epithelium of small intestine are degenerated and necrotic, and lymphocytes in the lamina propria are moderately infiltrated (arrow). (j) A large number of epithelial cells of turbinate mucosa were positive for virus antigen (brown). (k) A large number of exfoliated cells in tonsil mucosa epithelium and mucosa surface were positive for virus antigen (brown). (l) A large number of virus antigens were positive (brown) in serous cells of tracheal mucous glands. (m) A large number of small intestinal mucosal epithelial cells were positive for virus antigen (brown). Ruler line A, I = 100 μ m, B-H, J-L = 200 μ m, M = 500 μ m

  The research team also repeated the above-mentioned replication and transmission research in sub-adult cats in young cats (70-100 days). Histopathological studies on the samples of young cats who died or were euthanized on the third day after being inoculated with the virus showed that the nasal cavity and tracheal mucosa epithelium and lungs of the two cats had a lot of damage.

  These results indicate that Covid-19 can be effectively replicated in cats, and young cats are more susceptible to infection. More importantly, the virus can spread from cat to cat through respiratory droplets.

  Next, the research team also studied the replication and spread of Covid-19 in dogs, and the results showed that dogs were less sensitive to Covid-19. Similar studies also show that pigs, chickens and ducks are not sensitive to Covid-19.

  Overall, the research team found that ferrets and cats are highly sensitive to Covid-19, dogs are less sensitive, and domestic animals including pigs, chickens and ducks are not sensitive to the virus.

  In addition, it is reported that Covid-19 uses angiotensin-converting enzyme 2 (ACE2) as its receptor to enter cells, and ACE2 is mainly expressed in type II lung cells and serous epithelial cells of ferrets’ tracheal-bronchial submucosal glands. Therefore, the research team believes that the potential mechanism to prevent Covid-19 from replicating in ferrets’ lower respiratory tract remains to be studied.

  The results of this study show that ferrets can be used as animal models for vaccine and drug evaluation in Covid-19. Dogs, pigs, chickens and ducks are not susceptible to Covid-19, which has important guiding significance for the traceability of virus hosts; More importantly, cats are highly susceptible to Covid-19.

  The research team called for close monitoring and protection of cats in epidemic areas to avoid contact with infectious sources and prevent them from becoming possible transmission hosts or storage hosts. The monitoring of cat COVID-19 should be regarded as an auxiliary means to eliminate the current Covid-19 epidemic.

  Paper link: https://science.sciencemag.org/content/sci/early/2020/04/07/science.abb7015.full.pdf.

Mao Zedong Thought is the first historic leap of Marxism in China.

  The Central Committee of the Communist Party of China’s Resolution on the Great Achievements and Historical Experience of the Party’s Hundred Years’ Struggle (hereinafter referred to as the Resolution) adopted by the Sixth Plenary Session of the 19th CPC Central Committee pointed out: "Mao Zedong Thought is Marxism–Leninism’s creative application and development in China, a correct theoretical principle and experience summary about China’s revolution and construction that has been proved by practice, and the first historic leap of China Marxism." This is a scientific summary and summary of Mao Zedong Thought. Seriously studying and implementing the spirit of the Resolution is of great theoretical and practical significance for continuing to hold high the great banner of Mao Zedong Thought and constantly pushing forward the China-oriented Marxism under the new historical conditions.

  First, the scientific theory formed and developed in China’s revolution and construction practice.

  The revolution in semi-colonial and semi-feudal China is confronted with the special national conditions that peasants account for the vast majority of the population, the backward and scattered small-scale peasant economy, small-scale production and its social influence are deeply rooted, and the economy and culture are very backward. What kind of road to choose to lead the China revolution to victory is the primary problem and an unprecedented problem in the history of Marxist development. Young the Communist Party of China (CPC) once simply applied Marxism–Leninism’s general principles about proletarian revolution and copied the experience of armed uprising in Russian October revolutionary cities, which made the China revolution suffer serious setbacks.

  In the arduous exploration of the whole party to find the revolutionary road in China, Comrade Mao Zedong led the autumn harvest uprising troops to change from attacking big cities to marching into the countryside, which was a decisive new starting point for the China revolution. In the practice of revolutionary struggle, Comrade Mao Zedong scientifically analyzed the international and domestic political situation, systematically answered the problems why the red regime in China existed, expounded the theory of the trinity of agrarian revolution, armed struggle and the construction of revolutionary base areas, and put forward that the China revolution should be centered on the countryside, which opened up the correct revolutionary road. The Resolution pointed out: "the Communist Party of China (CPC) people, with Comrade Mao Zedong as the main representative, combined Marxism–Leninism’s basic principles with China’s concrete reality, made a theoretical summary of a series of original experiences accumulated through hard exploration and great sacrifice, opened up the correct revolutionary road of encircling cities from rural areas and seizing political power by armed forces, founded Mao Zedong Thought, and pointed out the correct direction for winning the victory of the new-democratic revolution."

  The cause of Marxism in China is arduous and complicated, and it has never been smooth sailing. The process of Mao Zedong Thought’s formation and development runs through the process of fighting against "Left" and Right-leaning mistakes and profoundly summing up the historical experience in this respect. The Zunyi Conference held in 1935 actually established the leading position of Comrade Mao Zedong in the CPC Central Committee and the Red Army, and began to establish the leading position of the correct Marxist line with Comrade Mao Zedong as the main representative in the CPC Central Committee, which created important conditions for Mao Zedong Thought to mature. In October 1938, Comrade Mao Zedong clearly put forward the proposition of "China Marxism" at the Sixth Plenary Session of the Sixth Central Committee of the enlarged Party. At the turn of 1939 and 1940, in order to systematically clarify the Party’s theory and program, answer the question of where China is going, and better guide the revolutions in War of Resistance against Japanese Aggression and China, Comrade Mao Zedong published many important theoretical works, profoundly summarized and comprehensively expounded a series of major theoretical issues of the China Revolution, and formed a relatively systematic philosophy, military thinking, United front thinking and party building thinking. In particular, the systematic exposition of the theory of new democracy and the incisive demonstration of the Party’s policies and strategies are of great significance to guiding the China revolution. The creation of these theories marks the maturity of Mao Zedong Thought. The Seventh National Congress of the Communist Party of China established Mao Zedong Thought as the party’s guiding ideology and wrote it into party constitution. Under the guidance of Mao Zedong Thought, the Party United and led the people to create great achievements in the new-democratic revolution, and realized the national independence and people’s liberation that several generations of Chinese dreamed of.It has created fundamental social conditions for realizing the great rejuvenation of the Chinese nation.

  After the founding of New China, faced with the basic end of the new democratic revolution and the beginning of the socialist revolution, Comrade Mao Zedong further put forward and expounded the theory, principles and policies of the transition from new democracy to socialism, led the whole party and the people of the whole country to creatively open up a socialist transformation road suitable for China’s characteristics, successfully completed the task of the socialist revolution, and established the socialist system, laying an important foundation for all progress and development in China.

  After the establishment of the basic socialist system, how to build socialism in China is a brand-new task facing the Party. Comrade Mao Zedong has made arduous explorations on the road of socialist construction suitable for the situation in China. The Resolution pointed out: "Comrade Mao Zedong proposed to’ second combine’ Marxism–Leninism’s basic principles with China’s concrete reality, and the Communist Party of China (CPC) people, with Comrade Mao Zedong as the main representative, combined with the new reality to enrich and develop Mao Zedong Thought." In April, 1956, Comrade Mao Zedong made a speech on "On Ten Major Relations" at the enlarged meeting in the Political Bureau of the Central Committee, and initially put forward some new policies for China’s socialist economic and political construction, which indicated that our party had its own new and important understanding of how to build socialism. During this period, the party also put forward a series of important ideas on socialist construction, many of which are still of great guiding significance. It is also under the guidance of Mao Zedong Thought that the Party united and led the people to create great achievements in socialist revolution and construction, laying a fundamental political premise and institutional foundation for realizing the great rejuvenation of the Chinese nation.

  Second, enrich and develop Marxism–Leninism with original theoretical achievements.

  The Resolution pointed out: "Upholding and developing Marxism requires extremely arduous and challenging efforts by Marxists all over the world from theory to practice." Comrade Mao Zedong is a great pioneer of Marxism in China, and Mao Zedong Thought has added new contents to Marxism–Leninism’s theoretical treasure house with his original theoretical achievements.

  Starting from the historical and social conditions in China, Comrade Mao Zedong deeply studied the characteristics of the China Revolution and the laws of the China Revolution, developed Marxism–Leninism’s thought on the leadership of the proletariat in the democratic revolution, and established the theory of a new-democratic revolution led by the proletariat, based on the alliance of workers and peasants, for the masses, and against imperialism, feudalism and bureaucratic capitalism, which provided a basic basis for our party to become the core of the leadership of the whole nation and create a new road of the China Revolution.

  Comrade Mao Zedong and the Communist Party of China (CPC), based on the economic and political conditions for the transition to socialism created by the victory of the new-democratic revolution, adopted the policy of simultaneous socialist industrialization and socialist transformation, and implemented the specific policy of gradually transforming the private ownership of the means of production, thus theoretically and practically solving the difficult task of establishing a socialist system in China, a big country with nearly a quarter of the world’s population and backward economy and culture. During this period, the theory of people’s democratic dictatorship put forward by Comrade Mao Zedong greatly enriched Marxism–Leninism’s theory of proletarian dictatorship.

  After the establishment of the socialist system, Comrade Mao Zedong creatively put forward that the socialist society is a long historical stage, strictly distinguish and correctly handle the contradictions between the enemy and ourselves and among the people, correctly handle the ten major relations in China’s socialist construction, embark on an industrialization road suitable for China’s national conditions, respect the law of value, implement the policy of "long-term coexistence and mutual supervision" in the relationship between the party and the democratic parties, and implement the policy of "letting a hundred flowers blossom and a hundred schools of thought contend" in scientific and cultural work.

  In the practice of revolution and construction, Comrade Mao Zedong systematically solved the problem of how to build a revolutionary army with farmers as the main component into a new type of people’s army with proletarian nature, strict discipline and close ties with the people. The people’s war thought put forward systematically by Comrade Mao Zedong, and the thoughts on strengthening national defense, building modern revolutionary armed forces and developing modern national defense technology are all outstanding contributions to Marxist-Leninist military theory.

  Comrade Mao Zedong brilliantly demonstrated the extreme importance of policies and strategies, pointing out that policies and strategies are the life of the Party and the starting point and destination of all practical actions of revolutionary parties. We must formulate the Party’s policies according to the political situation, class relations, actual conditions and their changes, and combine principle with flexibility. Comrade Mao Zedong also put forward many important ideas with long-term significance in ideological and political work and cultural work.

  It is an extremely arduous task to build a Marxist proletarian party with broad masses in a country with a small number of proletarians and strong fighting capacity, and farmers and other petty bourgeoisie account for the majority of the population. Comrade Mao Zedong’s theory of party building successfully solved this problem. Comrade Mao Zedong clearly pointed out that there must be a great party to guide the great revolution, and party building is a "great project". He put forward the principle of building the party ideologically, adhering to democratic centralism, adhering to the three fine styles of integrating theory with practice, closely contacting the masses, criticizing and self-criticizing, and forming three magic weapons of United front, armed struggle and party building. Fully foresee the new challenges facing the country’s ruling, clearly put forward that we must continue to maintain the style of modesty, prudence, arrogance and rashness, and we must continue to maintain the style of hard struggle and actively explore major issues of party building under the ruling conditions. Many of these important expositions still have strong practical pertinence, which is an important ideological weapon for our party to strengthen the construction of the ruling party.

  The "Resolution" points out: "Mao Zedong Thought’s living soul is the position, viewpoint and method that runs through all components, which are embodied in three basic aspects: seeking truth from facts, mass line and independence." Comrade Mao Zedong applied dialectical materialism and historical materialism to all the work of proletarian political parties, and formed these positions, viewpoints and methods with the Communist Party of China (CPC) characteristics in the long and arduous struggle of China’s revolution and construction, which had a far-reaching impact on our party’s theoretical innovation and practical innovation.

  In the process of the formation and development of Mao Zedong Thought, many outstanding leaders of our party have made important contributions. Mao Zedong Thought is the crystallization of the Communist Party of China (CPC)’s collective wisdom. Mao Zedong’s scientific works are its concentrated summary.

  Third, inherit the excellent traditional culture

  "Resolution" pointed out that Marxist theory "must be China to take root and localization to be deeply rooted in people’s hearts". Mao Zedong Thought was created by "applying Marxism–Leninism’s scientific method to summarize China’s history, society and all revolutionary struggle experiences", "the highest expression and theoretical generalization of China’s national wisdom", "completely Marxist and completely China’s", with "fresh and lively China style and China style loved by China people".

  In the development of Marxism in China, the history of the nation and the present situation, the form and the content of the nation have always been inseparable, and Comrade Mao Zedong has always advocated the close combination of the two. Comrade Mao Zedong once pointed out against the error of "Left" dogmatism: "No matter the history of China in the past hundred years or in ancient times, it is still dark in the minds of many party member. Many scholars in Marxism–Leninism also said that they were Greek, but they were sorry for their ancestors and forgot. The air of seriously studying the status quo is not strong, and the air of seriously studying history is not strong. " Rectifying the style of study in Yan ‘an Rectification Movement is to emphasize the study of China’s realistic struggle, as well as the modern and ancient history of China, inherit the excellent traditional culture and create a Marxist national form.

  Comrade Mao Zedong pointed out that the culture of China for thousands of years is mainly feudal culture, so we must make a concrete analysis of it. There are many good things left by China’s history, but there are also many toxins and dross, which cannot be uncritically eclectic. "From Confucius to Sun Yat-sen, we should sum up", but "we must distinguish all the decadent things of the ancient feudal ruling class from the excellent people’s culture in ancient times, that is, something more or less democratic and revolutionary". It is a necessary condition for developing national new culture and improving national self-confidence to get rid of its feudal dross and absorb its democratic essence. The "national scientific mass culture" put forward and advocated by Comrade Mao Zedong is the "new culture of the Chinese nation" that "enhances national self-confidence".

  The "national" culture is to oppose imperialist oppression and uphold the dignity and independence of the Chinese nation. It belongs to our nation and has the characteristics of our nation. The Communist Party of China (CPC) people must combine Marxism with national characteristics, and only after a certain national form can it be useful, and it must never be applied subjectively. A "scientific" culture opposes all feudal and superstitious ideas, advocates seeking truth from facts, advocates objective truth, and advocates the consistency of theory and practice. "The current new culture in China is also developed from the ancient old culture. Therefore, we must respect our own history and never cut it off." The "popular" culture is democratic, should serve the broad masses of workers and peasants, and gradually become their culture. As for China’s fine historical tradition, "we want to inherit it, but the purpose is still for the people", and as for the historical and cultural forms of the past era, "we don’t refuse to use them, but these old forms have been transformed and added with new contents, which will become revolutionary things serving the people".

  Comrade Mao Zedong paid attention to combining the basic principles of Marxism with Chinese excellent traditional culture, so that Marxism could take root in China.

  Fourth, adhere to and develop Mao Zedong Thought.

  General Secretary of the Supreme Leader pointed out: Mao Zedong Thought has educated generations of the Communist Party of China (CPC) people, and it has trained a large number of backbones, which not only played an important role in the new democratic revolution, socialist revolution and socialist construction, but also played an important role in creating and building Socialism with Chinese characteristics in the new historical period. Many of Comrade Mao Zedong’s important works were written during the period of the new-democratic revolution and the period of socialist revolution and construction, but we still have to study them frequently. This is not only because history cannot be cut off, but if we don’t understand the past, it will hinder our understanding of current problems; And because many basic principles, principles and scientific methods contained in these works are of universal significance, they will play an important guiding role for us now and in the future. The Resolution pointed out that Mao Zedong Thought "provided scientific guidance for the development of the cause of the Party and the people". We must continue to adhere to Mao Zedong Thought, earnestly study and apply its stand, viewpoint and method to study new situations and solve new problems in practice. Comrade Deng Xiaoping pointed out: "We want to restore Mao Zedong Thought, adhere to Mao Zedong Thought and even develop Mao Zedong Thought. In these aspects, he has provided a foundation." It is in this sense that Mao Zedong Thought provided an important ideological foundation for the theoretical creation of our party.

  Comrade Mao Zedong said in "On Practice": "The movement of change in the objective real world will never end, and people’s understanding of truth in practice will never end. Marxism–Leninism did not end the truth, but constantly opened up the road to understanding the truth in practice. " Just as Marx must never be asked to provide ready-made answers to the problems that arose hundreds of years after his death, Comrade Mao Zedong must never be asked to undertake the task of solving a series of new problems that occurred in China and the world after his death. Real Marxism–Leninism people must know, inherit and develop Marxism–Leninism and Mao Zedong Thought according to the present situation. Comrade Mao Zedong pointed out that he is not a Marxist as Marx; Equal to Marx, not a Marxist; Only when you surpass Marx can you be a Marxist.

  Since the Third Plenary Session of the Eleventh Central Committee of the Party, our Party has persisted in proceeding from the reality of China, gained insight into the general trend of the times, grasped the historical initiative, made arduous explorations, constantly pushed forward the modernization of Marxism in China, guided the people of China to continuously push forward the great social revolution, successively founded Deng Xiaoping Theory, formed Theory of Three Represents and formed Scientific Outlook on Development, scientifically answered a series of basic questions about the construction of Socialism with Chinese characteristics, formed a theoretical system of Socialism with Chinese characteristics, and achieved a new leap in the sinicization of Marxism.

  Since the 18th National Congress of the Communist Party of China, the people of the Communist Party of China (CPC), with the Supreme Leader as the main representative, have persisted in combining the basic principles of Marxism with the concrete reality of China and the excellent traditional Chinese culture, persisted in Mao Zedong Thought, Deng Xiaoping Theory, Theory of Three Represents and Scientific Outlook on Development, profoundly summed up and made full use of the historical experience since the founding of the Party, and set out from the new reality, created Socialism with Chinese characteristics Thought of the Supreme Leader in a new era. This thought is contemporary China Marxism and 21st century Marxism, and it is the essence of Chinese culture and China spirit, and it has achieved a new leap of Marxism in China.

  The people of the Communist Party of China (CPC) and China cherish all the achievements in China’s revolution, construction, reform and Socialism with Chinese characteristics’s great practice in the new era, combining Marxism–Leninism’s basic principles with China’s concrete reality and with China’s excellent traditional culture, and apply and develop these achievements in new practice, enriching and developing our party’s theory with new principles and conclusions that are in line with reality, and ensuring that our cause is in Marxism–Leninism, Mao Zedong Thought, Deng Xiaoping Theory, the important thought of "Three Represents", the scientific development concept and the new supreme leader.

Guide: western medicine treatment of herpes zoster

Click on "Huanghuai nurse" above to follow.

guide language

The treatment scheme of herpes zoster can be roughly divided into traditional Chinese medicine therapy and western medicine therapy. Today, we will learn the western medicine therapy recommended by the guide.

Therapeutic goal of herpes zoster

Relieve acute pain; Shorten the duration of skin lesions; Prevent the spread of skin lesions; Prevent or reduce complications.

First, antiviral drugs

Commonly used drugs in clinical treatment of herpes zoster can effectively shorten the course of disease, accelerate the healing of rash, reduce the formation of new rash and reduce the spread of virus to internal organs. It should be used within 72 hours after the eruption, so as to quickly reach and maintain the effective concentration and obtain the best therapeutic effect. At present, the approved systemic antiviral drugs include acyclovir, valaciclovir, famciclovir, bromovudine and foscarnet sodium.

acyclovir

Function characteristics:

Acyclovir triphosphate is produced by phosphorylation of viral thymidine kinase in infected cells, which can inhibit viral DNA polymerase and stop the extension of viral DNA chain.

  Usage:

(1) Oral administration: 400-800 mg/time, 5 times/day, for 7 days;

(2) Intravenous drip: 5 ~ 10 mg/kg for patients with immune impairment or serious nervous system diseases, once every 8 hours, with a course of 7 days. 

Precautions:

Patients should drink plenty of water during the administration of acyclovir to prevent acyclovir from precipitating in renal tubules and damaging renal function.

Valaciclovir

Function characteristics:

The prodrug of acyclovir is quickly absorbed by oral administration and quickly converted into acyclovir in gastrointestinal tract and liver, and its bioavailability is 3~5 times that of acyclovir.

  Usage:

Oral administration: 300 ~ 1000 mg/time, 3 times/day, for 7 days.

Fanciclovir

Function characteristics:

The prodrug of penciclovir is rapidly converted into penciclovir after oral administration, and maintains a long half-life in cells. The mechanism of action is the same as that of acyclovir, the bioavailability is higher than that of acyclovir, and the frequency and dosage of administration are lower than that of acyclovir.

  Usage:

Oral administration: 250 ~ 500mg/time, 3 times/day, for 7 days.

brivudine tablets

Function characteristics:

The antiviral effect is highly selective, and the process of inhibiting virus replication is only carried out in virus-infected cells. 

Usage:

Oral administration: 125mg//day, l times/day, for 7 days.

Sodium foscarnet

Function characteristics:

Blocking the phosphate binding site of viral DNA polymerase in a non-competitive way, thus showing antiviral activity.

  Usage:

Intravenous drip: 40 mg/kg each time, once every 8 hours.

Note meaning 

Patients with renal insufficiency should reduce the dosage accordingly;

If renal function continues to decline, acyclovir should be stopped immediately and famciclovir or other antiviral drugs should be used to continue treatment;

For patients suspected of renal insufficiency, creatinine level should be detected before initial administration (creatinine level is not required for bromovudine).

Second, analgesics

Mild to moderate pain:Acetaminophen and tramadol can be selected; 

Moderate and severe pain:

1. Opioid drugs, such as morphine or oxycodone;

2. Drugs for the treatment of neuropathic pain, such as calcium channel regulator gabapentin and pregabalin, in addition to amitriptyline and 5% lidocaine patch. Severe acute pain during herpes zoster is a risk factor for post-herpetic neuralgia (PHN). Combined with calcium channel regulator can not only effectively relieve pain, but also reduce the occurrence of PHN. Studies have shown that early use of pregabalin can significantly reduce the pain score of herpes zoster, especially within 7 days of herpes occurrence, which can significantly reduce the incidence of PHN. The pain of elderly patients with herpes zoster is more common and severe, which seriously affects all aspects of life, such as anxiety, disorder and inability to work or live normally. Studies have shown that pregabalin combined with oxycodone can not only further reduce the incidence of PHN, but also improve the daily activities and sleep of patients and improve their quality of life.

Third, glucocorticoid

At present, there is still controversy about whether to use glucocorticoid to treat herpes zoster.

It is generally believed that systematic application of glucocorticoid in the early stage of acute onset of herpes zoster and gradual decrease can inhibit the inflammatory process, shorten the duration of acute pain and the healing time of skin lesions, but it is ineffective for the pain with PHN. 

Recommended dose:The initial dosage of prednisone is 30~40 mg//day, which is taken orally and gradually reduced, and the course of treatment is 1~2 weeks.

 Fourth, neurotrophic drugs

It is also helpful to relieve neuroinflammation and neuralgia. Commonly used drugs include mecobalamin, vitamin B1 and vitamin B12, etc., which are taken orally or injected intramuscularly.

Five, topical drugs

Mainly dry and anti-inflammatory. 

Blister fluid is not broken:Calamine lotion, acyclovir cream or penciclovir cream can be used externally. 

After herpes is broken:

3% boric acid solution wet compress;

1: 5000 furacilin solution wet compress;

0.5% neomycin ointment for external use;

2% mupirocin ointment. 

Ophthalmic herpes:3% Acyclovir Eye Ointment and Iodine Eye Drops for External Use.

References: [1] Herpes Zoster Expert Consensus Working Group. Herpes Zoster Expert Consensus in China [J]. Chinese Journal of Dermatology .2018,51 (6): 403-406.

Laiyuan/Yunque

Global news: US stocks fell for three consecutive days, the Dow fell below the 50-day moving average, and US bond yields soared, which continued to put pressure on the market.

  On Thursday, local time, with the soaring yield of 10-year US bonds and the "assistance" of the yield of 10-year British bonds, the risk appetite of market investors continued to be suppressed. The three major indexes of US stocks recorded a three-day losing streak. After the S&P 500 index, the Dow also fell below the 50-year moving average, which is usually regarded as a signal of a short-term downward trend.

  It should be noted that the American Association of Individual Investors released the latest market sentiment survey report on Thursday, and the bullish enthusiasm of American retail investors in the next six months has plummeted, directly from 44.7% to 35.9%, breaking the state of being better than the historical average in the past 10 weeks. It is enough to show that current investors are not optimistic about the future trend of the market.

  The relatively vague monetary policy direction of the Federal Reserve has played a great role. According to the latest calendar of the Federal Reserve in official website, Powell will deliver a speech at the annual meeting of Jackson Hole Central Bank on August 25th, local time. If you have memories, you should remember last year’s "nine minutes of darkness". Powell’s speech directly caused the S&P 500 index to plummet by 3%, and then it went from 4,200 to below 3,500 in the next two months.

  The market may be worried that Powell’s speech this year may still cause market turmoil before inflation is completely tamed, and monetary policy may continue to be tightened during the year. At present, according to the observation tool of CME Federal Reserve, the probability of raising interest rates again at the end of the year has risen to over 30%, while the hope of lowering interest rates is slim, which was originally the biggest catalyst in the market.

  In other important news, on Thursday (August 17th), local time, the latest report released by market research company Counterpoint Research showed that global smartphone shipments will drop by 6% to 1.15 billion units this year. If it is finally true, it will be the lowest level in ten years.

  North America is still the main drag on the global recovery, and the disappointing performance in the first half of the year may bring the year-on-year decline of shipments in this region to double digits. However, the high-end market still maintains some flexibility. The report pointed out that Apple will therefore be in a favorable position, and the company will usher in an important product upgrade in the second half of this year, which may make it perform strongly before the end of this year.

  In addition, on Thursday night, Beijing time, Musk, the world’s richest man, announced his arrival in Japan on the social media platform, but did not disclose the itinerary. A sudden visit to Japan has caused a lot of discussion in the market. The important daily activities of his social media platform X come from Japan, with a population of only one-third of that of the United States, but the daily activities are comparable to those of the United States.

  Musk’s team is still frantically seizing the satellite Internet business in low-earth orbit. Japanese Defense Minister Yasukazu Hamada has previously confirmed that the Japanese Self-Defense Force has started testing this equipment since March this year.

  It is worth mentioning that on the occasion of Musk’s visit to Japan, when Tesla’s redesigned Model 3 was exposed to mass production, did this trip take a fancy to the potential of the Japanese electric vehicle market? The share of electric vehicles in the Japanese market has just exceeded 2%, and the best-selling Mini-EV is Nissan SAKURA, which sold 33,000 vehicles in the whole fiscal year of 2022. Tesla and () are regarded as luxury brands.

  [overnight U.S. stocks]

  Among the large-scale Chinese stocks, Alibaba rose 1.78%, Baidu fell 0.54%, Netease fell 0.09%, Tencent Music rose 5.78%, and Pinduoduo rose 0.81%.

  Among the large US technology stocks, Apple fell 1.46%, Amazon fell 0.81%, Google A rose 0.95% and Netflix fell 3.00%.

  [global index]

  In the European stock market, the FTSE 100 index in Britain fell slightly by 0.63% to 7310 points. The French CAC40 index fell slightly by 0.94% to 7192 points. Germany DAX index fell slightly by 0.71% to 15,677 points.

  [global goods]

  The main contract of WTI crude oil closed at $80.16 per barrel, up 0.98%; The main contract of Brent crude oil closed at $83.90 per barrel, up 0.54%; The main contract of crude oil in the previous period closed at 639.00 yuan per barrel overnight, down 0.08%.

  Overnight, the Shanghai gold main contract closed down 0.30% to 455.42 yuan per gram; The main contract of Shanghai Bank closed down 0.02% to 5627.00 yuan per kilogram.

  [overnight news]

  Powell will deliver a speech at Jackson Hole’s annual meeting next week.

  The Federal Reserve also quietly updated official website’s calendar after the close, showing that Powell will deliver the annual meeting speech of Jackson Hole at 10: 05 local time on August 25th. Investors should still remember clearly that on August 26th last year, with Powell’s famous "9-minute speech", not only did the S&P 500 index drop by 3% that day, but in the next two months, it even fell from 4,200 to 3,500.

  US retail investors’ bullish enthusiasm plummeted

  The American Association of Individual Investors also released the latest market sentiment survey report on Thursday. The bullish enthusiasm of American retail investors in the next six months has "dived down", directly dropping from 44.7% to 35.9%, breaking the state of being better than the historical average in the past 10 weeks.

  Fed officials are increasingly wary of the stock market’s rise.

  According to the latest minutes of the Fed meeting, Fed staff pointed out at the FOMC policy meeting in July that stock prices generally rose, corporate bond spreads narrowed, asset valuation pressure was "significant", and the risk assessment in May was "moderate"; Also named residential and commercial real estate prices, calling them "relatively high in terms of fundamentals".

  Research report: global mobile phone shipments may fall to a 10-year low, and Apple is expected to go against the trend.

  The latest report released by Counterpoint Research, a market research company, shows that global smartphone shipments are expected to hit the worst year in a decade in 2023. Despite the overall decline in smartphone shipments, the high-end market still maintains a certain degree of flexibility. The report pointed out that Apple will therefore be in a favorable position, and the company will usher in an important product upgrade in the second half of this year, which may make it perform strongly before the end of this year.

  After energy and food, the signs of sticky inflation in the United States reappear, and the price of used cars rose for the first time in four months.

  According to statistics, the wholesale data of used cars in the first half of August in the United States rose for the first time in four months, and the market is worried. This is another sign that inflation may be stuck for a long time after the rebound of energy and food prices.

  The global bond market selling added fuel to the fire, and the demand for Japanese bond auctions was the worst since 1987.

  The auction results of 20-year Japanese bonds on Thursday may show that investors are increasingly betting that the Bank of Japan will soon relax the easing policy YCC to control the yield curve. As the global sovereign bond yield has reached a 15-year high, the rising Japanese bond yield threatens global bonds.

  [company news]

  Tesla’s modified Model 3 was exposed to lower bicycle costs or add a "price war" card.

  Tesla’s revised Model 3 may start mass production in Shanghai as early as next month. This electric car faucet is in the final stage of the production of the demonstration car, and the vehicle will be transported to the Tesla exhibition hall later this month. Large-scale production will follow closely, starting in September at the earliest. These people familiar with the matter added that Tesla will also increase production during the National Day holiday.

  One of the people familiar with the matter said that the revised Model 3 has been changed in terms of design and interior parts, making it more fashionable. He added that in the case of full production, its cost will be lower than the current version of Model 3, or as low as 200,000 yuan.

  Musk suddenly announced his arrival in Japan. What is he going to do?

  On Thursday night, Beijing time, Musk, the world’s richest man, announced on his social media platform X that he had arrived in Japan. In view of his extreme love of showing himself on the Internet, this totally unexpected trip triggered a hot discussion among netizens: What is he doing in Japan?

  The important daily activities of Musk’s social media platform X come from Japan, with a population of only one-third of that of the United States, but the daily activities are comparable to those of the United States. Musk’s team is still frantically seizing the satellite Internet business in low-earth orbit. Japanese Defense Minister Yasukazu Hamada has previously confirmed that the Japanese Self-Defense Force has started testing this equipment since March this year.

  Mardner: The latest version of COVID-19 vaccine can produce a strong response to EG.5 mutant.

  Mardner disclosed on Thursday that preliminary clinical trial data confirmed that the company’s COVID-19 vaccine updated in autumn and winter this year showed a strong immune response against the latest dominant mutant strain EG.5 Mardner’s vaccine was developed for XBB.1.5 mutant, which belongs to Omicron mutant family with EG.5. The latest version of the vaccine is expected to be supplied for autumn vaccination in the next few weeks, and is subject to the approval of relevant departments.

  [AI dynamic]

  Google’s Gemini, the "most powerful model of mankind", will be released in autumn.

  The media broke the news that Google’s "brand-new killer" Gemini combines the capabilities of GPT-4, Midjourney and Stable Diffusion, and can also provide analysis charts, create graphics with text descriptions, and use text or voice command control software.

  AI enters the consulting circle McKinsey launches the first AI chat application Lilli.

  McKinsey, the world’s largest consulting firm, launched Lilli, the first AI chat application, for consulting project assistance. Lilli has been tested in the company for two months, and it is reported that the effect is good, which can shorten the task that originally took several weeks to several hours.

  [financial calendar]

Dozens of dead birds fell from the sky! A rare scene on the streets of Russian cities leads netizens to speculate.

  Russian video screenshot today

  Overseas Network September 22ndAccording to the news of "Russia Today" on the 21st, some pictures and videos have been circulated on Russian social media platforms recently: a street in Barakovo is full of dead birds. This rare scene triggered a series of brain hole conjectures by netizens.

  According to reports, this incident occurred in Barakovo, Saratov State, southwestern Russia, which is famous for its large nuclear power plant. According to videos and pictures uploaded by Russian social media users, local residents witnessed the bodies of dozens of dead birds scattered on a road.

1600758482562342.png

  Source: Russia today

  Below the video, Russian netizens gave many conjectures about why dead birds fell from the sky. Some people blame it on natural phenomena, such as a strong wind or an accidental collision between two birds. Others think that fireworks and exhaust gas from factories may cause a large number of deaths, and some even say that it is related to 5G equipment, although this technology has not yet entered Russia.

  "At the beginning of the nuclear disaster TV series Chernobyl, all the birds died." A comment with the highest praise linked the incident to the American HBO hit drama. The animal medical department of Saratov State is currently investigating this incident, which some people think may be related to bird flu. (Overseas Network Zhang Qi)

Apocalypse of the Great Plague of the World: Polio: After dealing with human beings for more than 3,000 years, what is the "resurgence" of this mysterious virus?

◎ Science and Technology Daily reporter Zhang Jiaxing

"At the hospital, the doctor took him away from us soon. I never saw my son again. He died alone like that. We had no chance to say goodbye to him at all. Now there is only his wardrobe and tropical fish …"

The grief and separation described in the father’s intermittent gibberish in the novel Nemesis really and frequently occurred in North America, Europe and other places in the first half of last century.

The source of all tragedies is a virus called poliovirus. Thousands of infants and young children developed fever and inflammation for unknown reasons at first, and then suddenly they could not breathe spontaneously, were paralyzed and even died. In the classroom full of children’s voices in the past, several seats are vacant every day, some because of isolation, some because of illness, and no one knows which day "you at the same table" will disappear. Historical pictures show that in 1944, a sixth-grade classroom in Milwaukee, the largest city in Wisconsin, USA, was almost empty on the first day of school, and a teacher only taught one student. This scene is embarrassing.

On the other side of the city, the huge cylinder "iron lung" has "eaten" more and more children to help them breathe. Some people walk out of the "iron lung", some people fail to walk out alive, and some people spend the rest of their lives in the "iron lung", with their limbs and bodies in jars, only showing their heads to eat, drink and breathe …

Image source: vision china

According to records, on June 17th, 1916, new york officially announced the existence of epidemic polio infection. That year, the first polio epidemic broke out in new york, with more than 9,000 cases and 2,343 deaths. The polio epidemic in 1952 was by far the worst, with 57,628 cases reported in the United States alone.

Searching for "patient zero" thousands of years ago.

Who was the first "patient zero" infected with polio virus?

The most famous origin comes from the lithographs in ancient Egypt. A lithograph of the 18th dynasty in ancient Egypt (1403 -1365 BC) depicts a person with muscular atrophy in his right leg, which is regarded as the earliest verifiable document reflecting the pathological state of polio.

There are also manifestations of clinical manifestations of poliomyelitis in TCM books. The earliest record is found in Huangdi Neijing, such as Su Wen Wei Lun, which says, "The five internal organs are hot, which can make people sick and flaccid, and the cover is hot inside and flaccid outside."

Patients with polio sequelae in ancient Egyptian lithographs. Image source: shell

People know that the existence of poliovirus is only a short hundred years, but poliovirus has accompanied the evolution of human society like a ghost. The age is so long that the pursuit of polio virus zero infection is meaningless.

It can’t be traced back to the first "intruder" in the whole human society, but in some parts of human society, either because of the fear brought by the unknown, it is necessary to find an outlet to vent, or because of unspeakable political purposes, people will offend each other and even fight for who is the "patient zero" who brought it.

Gao Xi, a professor of history at Fudan University, pointed out in a speech that in the dark European Middle Ages, the scale, duration, coverage, number of deaths and variety of diseases that ravaged the European continent were unprecedented. Infectious diseases, including typhoid fever, smallpox, polio and scarlet fever, spread from one country to another and soon spread in Europe.

Countries go to war and blame each other for this. Among the people, rumors spread everywhere. Witches, Jews and children … Any group that is considered to be different may cause public anger at any time because of a rumor and be pushed into the painful abyss of publicly offending.

"At that time, a more common and excusable statement was that Columbus and his companions brought diseases from the New World to Europe and then spread them all over the world." Gao Wei said.

Ignorance leads to rumors and conviction. The haze of the virus enveloped the European continent at that time, and at the same time, human ignorance made the disaster spread like a virus.

Draw a circle and search for the cause of disease for a hundred years.

At first, people couldn’t relate the figurative and mechanized symptoms of sudden muscle paralysis and limb paralysis to a tiny microorganism, which is why polio has another name: polio.

At one time, polio was considered to be congenital and acquired. There was a secular view that children with polio had problems during embryo gestation, and even it was attributed to ghosts and gods. As a result, generations of polio patients had argued about their rights to get married and have children as adults for nearly half a century.

Back in the 20th century, before the Russian pathologist ivanovski discovered the virus, people knew nothing about this microorganism that could not be seen through the optical microscope. At that time, the disease was called: tooth paralysis, infantile spinal paralysis, primary paralysis of children, degenerative paralysis, anterior horn myelitis, early morning paralysis, etc., and it had no "half a cent" relationship with the virus.

In 1789, a British doctor named Michael Underwood made a clinical description of polio, which he called "weakness of lower limbs".

In 1840, Jacob von Heine, a German orthopedic surgeon, first separated the paralysis caused by polio from other forms of paralysis, calling it polio.

In 1887, Karl Oskar Medin, a Swedish scholar, went out to study individuals and regarded them as epidemics. He recorded an epidemic situation in Stockholm from an epidemiological point of view, and reported the epidemiological characteristics and nervous system complications of polio for the first time.

It was not until 1908, 10 years after the concept of Virus was accepted, that Austrian-born doctors Karl·Landsteiner and Erwin·Popper obtained samples from the central nervous system tissues of patients after death, and then isolated the virus by inoculating monkeys, finally associating paralysis and paralysis with the virus, and drew a closed-loop "circle" in finding the cause.

However, up to now, the closed-loop "circle" of polio caused by virus still can’t erase the prejudice brought by this terrible disease, especially the mutilation it brings is clearly visible, which will make people wonder whether it may be inherited in future generations or associated with "bad luck" regardless of scientific objectivity.

Together, NATO and Warsaw Pact are both healthy covenants.

In the summer of 1921, a cluster of small particles of poliovirus with a size of only 20 nanometers and a icosahedron swam in the water near Campobello Island on the Atlantic Ocean. Small particles drift with the tide, and their surrounding environment is as leisurely and quiet as the earth in ancient times.

A 38-year-old man dived into the water to enjoy the beauty of nature. A small wave came, and the small particles trapped by the sea water entered the man’s mouth and nose.

In just one day, the virus reached the man’s local lymphoid tissue, such as tonsils and other places to multiply and grow; Then the virus further invaded the blood stream, and on the third day, it reached various non-nerve tissues, such as heart, kidney, liver and pancreas, and propagated. The antibodies in the man’s body didn’t have time to stop this powerful offensive of the virus, and watched the virus break through the "blood-brain barrier" and go straight to the central nervous system.

After this trip, the man began to have incontinence, fever and facial paralysis. The paralyzed part began to spread from the hip, and gradually his legs were completely paralyzed, and then his waist … He was franklin roosevelt, who was later elected president of the United States. He was paralyzed for life from the waist down because of polio virus.

His infection and illness brought panic about this virus in the United States in the short term, but in the long run it sounded the "assembly number" for fighting polio virus.

With the emergence of vaccinia to contain smallpox, vaccines have become the "killer" for human beings to deal with viruses. Vaccine makers start with real viruses and try to eliminate their toxicity, so as to produce vaccines.

In 1953, the swimming pool in Elmira, New York, had a sign indicating that it was closed due to polio. Image source: shell

At the American Public Health Association conference in 1935, two groups of researchers reported their experiments on polio vaccine. In the first group of about 10 thousand children vaccinated, five died of polio and ten were paralyzed. There was no control group in this group of experiments, but John Ke Ermo, who led the experiment, said that the infection rate would be higher without vaccination. Such speculation without factual data made the scene in an uproar.

The second group is Maurice Brodie of new york University. One of the 7500 people vaccinated with the vaccine he developed was infected with polio; One of the 900 people vaccinated in the control group was infected with polio. Although the data is statistically significant, when the audience learned that the infection in the vaccinated population was caused by the vaccine, they all condemned Brody’s research for making healthy people suffer from polio.

Shortly after the report, Brody lost his position at new york University and was found to have committed suicide at home.

The research of vaccine is tortuous, but the scientific spirit and unremitting efforts will inevitably push forward the research and development of vaccine.

On April 12, 1955, the Journal of salk reported an exciting news with a full page: "’s vaccine works! 》(《SALK’S VACCINE WORKS! 》)

In 1947, jonas salk, an American scholar, set up a three-person research team to jointly overcome the problem of polio. Unlike most researchers who studied live attenuated polio vaccine at that time, salk’s research used inactivated virus as vaccine.

In the United States in 1952, under the threat of epidemic disease, the scale of human trials of vaccine research and development continued to expand. Salk’s vaccine was tested on 1.8 million children, making it the largest medical experiment in human history at that time. Almost the day after the test results were announced, millions of children across the United States were vaccinated against polio.

The debate between "dead" vaccine and "live" vaccine has not stopped because of large-scale vaccination.

Albert Bruce Sabin, who is developing research and development in parallel with salk, insists that only when the live virus enters the human body can the vaccinated people get immunity.

However, Sabin’s "live" vaccine was born a little late. When he developed an attenuated polio vaccine, salk’s vaccine had become the mainstream of the United States, and the government no longer supported his project, so he had to cooperate with other countries.

Disease is not political, and science has no borders. The research and development of attenuated polio vaccine spanned the two political and military camps "North Atlantic Treaty Organization" and "Warsaw Treaty Organization". In 1959, with the support of the Soviet Union, Sabin completed a large-scale clinical trial involving 10 million people, which verified the effectiveness, safety and accessibility of the vaccine.

Ark, leading billions of people away from polio.

In 1950s, poliovirus also occurred from time to time in all parts of China. Even if the weather is sultry, families will let their children stay at home, because there is an invisible and frightening polio virus outside, which will make children disabled after a fever. What is even more frightening is that this virus can be invisible like a "ghost", and healthy people who seem to have no symptoms may also carry it.

At that time, which of the three polio viruses was prevalent in China had not been determined, and the etiology and serology research was almost zero. In 1957, Gu Fangzhou, a scientist from China, led a team to isolate poliovirus from patients’ feces in 12 cities across the east and west, and found that the three types of virus had different characteristics. Through a large number of clinical practice studies, the popular virus types in China were determined, and the laboratory diagnostic criteria of poliovirus were established.

A large number of cases obtained from the investigation made Gu Fangzhou more and more worried. He reported to his superiors that if the incidence of polio was not high, the prevention work could be carried out slowly, but now the incidence is high, and a big outbreak will eventually occur somewhere in a certain year. The outbreak in Berlin in 1947 was a warning, and the pandemics in Nantong in 1955 and Wenzhou in 1956 in China have also sounded the alarm.

In 1959, Gu Fangzhou was ordered to go to the Soviet Union to study the development method and production technology of polio virus vaccine. He found that the existing technology was good, but neither the cost nor the inoculation period was suitable for China at that time. In Gu Fangzhou’s mind, public health should not be "bookish" at all, and any work should be useful and beneficial to the people.

At the international conference on polio vaccine in 1959, Gu Fangzhou, who is good at learning, made it clear that vaccines can be divided into "dead" and "live", and that dead vaccines are safe, but they will not form an immune barrier in human body. Attenuated live vaccines may theoretically restore their virulence, but they can become natural vaccines and form an immune barrier.

With the courage and rational judgment of scientists, Gu Fangzhou made a choice for all the people of China. He wrote to the Ministry of Health at that time, suggesting to choose an attenuated live vaccine that was not proved to be safe and had no mature production process, and personally brought the virus back to China from the Soviet Union.

Gu Fangzhou Image Source: Voice of China

In December, 1959, the polio live vaccine research collaboration group was established with the approval of the former Ministry of Health, with Gu Fangzhou as the team leader. Vaccine research and development started from scratch, and the team overcame the difficulties of material shortage and harsh environment, and finally got a vaccine sample. With the start of clinical trials of vaccines, it becomes a problem who will take them first.

At the risk of possible paralysis, Gu Fangzhou drank a small bottle of vaccine solution, and the rest of the lab joined the experiment.

The vaccine is harmless to adults, but how safe is it for children? "At that time, my son Xiaodong was just under one year old and qualified." Gu Fangzhou’s oral memory history records: "My own children don’t eat, let others eat, which is not very righteous."

With the development of clinical trials of vaccines, the epidemiological data of 2 million children after taking vaccines show that the epidemic peaks in Shanghai, Tianjin and Qingdao have basically disappeared, and domestic vaccines are safe and effective biological products to prevent polio epidemic.

China polio eradication confirmation report signing ceremony. Image source: Voice of China

In Gu Fangzhou’s polio immunization strategy, every child in China cannot be left behind. The oral vaccine rate should reach 95% to form an immune barrier. This means that children who are far away from the Tibetan Plateau, the desert in Xinjiang and the deep mountains in Guizhou must enter the protective barrier without exception. If there is a slight omission, the virus may recur. At that time, there was no cold chain, so it was very difficult for vaccines to circulate effectively in the country in a short period of time. The local method of mixing popsicles with wide-mouthed thermos flask is not very effective.

According to Biography of Gu Fangzhou, Gu Fangzhou, who came home after work, was still thinking about the immunization strategy. His son looked at him. He picked up the candy on the table and shook it in front of his son. His son held out his little hand urgently to make him laugh. Sugar! Gu Fangzhou started the research on vaccine sugar pills. He developed the polio vaccine "Sugar Pill", which made China enter a polio-free era.

In 2000, the World Health Organization announced that polio had been eradicated in the western Pacific, which was closely related to the effective immune barrier formed by polio vaccine in China with a population of more than one billion.

Play around and be alert to the resurgence of sophisticated viruses.

Extinction, doomsday, end …

Since April 8, 1994, when the World Health Organization announced that polio was basically extinct, a large number of reports used similar words to summarize the fate of polio virus.

However, contrary to expectations, polio has never become one of the few infectious diseases that can be eliminated.

In 2000, Cape Verde reported 33 cases of acute polio, including 7 deaths.

In recent years, there have also been cases of infection in Pakistan, and the number of cases has dropped from 306 in 2014 to 54 in 2015, 20 in 2016 and 8 in 2017.

By 2018, less than 30 cases of naturally occurring polio had been reported in Afghanistan and Pakistan.

On March 10th, in Mazar-e-Sharif, the capital of Balkh province in northern Afghanistan, a health department worker vaccinated children against polio. Image source: Xinhuanet

However, according to Science, workers found the virus in a vast area of Pakistan. This disturbing latest discovery shows that it still exists in the environment and is far from disappearing.

Will this virus, which has been dealing with human beings for more than 3000 years, resurface?

As far as the virus itself is concerned, one of the secrets that it has lasted for thousands of years is that more than 90% of the carriers are "secret". These secret infected people have no symptoms, but they provide a secret habitat for the virus to preserve its vitality and wait for the opportunity to revive.

For human beings, rumors can still fuel its "resurgence." For example, rumors that vaccines cause autism are exploited by some religious organizations. Some commentators believe that the resurgence of polio in Nigeria in 2016 after two years of extinction has a lot to do with Boko Haram, an extremist organization in the country. The organization spread rumors among local people, saying that the real purpose of polio vaccine is to sterilize Africans, which led to a large-scale protest in Nigeria, and even several immunization workers were shot dead by extremist organizations.

In the face of ancient viruses, human beings should always remember:

For human tragedies and disputes,

The virus looked on coldly in secret.

For the change and migration of the environment,

The virus "secretly" sees the needle.

Source: Science and Technology Daily

Original title: "Apocalypse of the Great Plague in the World: Polio: After dealing with human beings for more than 3,000 years, what is the" resurgence "of this mysterious virus"

Read the original text

7 categories of mainstream 3D printing technologies, all of which can be understood.

Many people think that 3D printing is to extrude materials from hot nozzles and stack them into shapes, but in fact 3D printing is far more than that! Today, Antarctic Bear will introduce seven kinds of 3D printing processes. Even 3D printing can clearly distinguish different 3D printing processes.

In fact, 3D printing, also known as additive manufacturing, is a general term, covering several completely different 3D printing processes. These technologies are worlds apart, but the key process is the same. For example, all 3D printing starts with a digital model, because the technology is digital in nature. Parts or products are originally electronic files designed by computer aided design (CAD) software or obtained from digital parts library. Then the design file is decomposed into slices or layers by special construction preparation software for 3D printing, and the path instructions to be followed by the 3D printer are generated. Next, you will understand the differences between these technologies and the typical uses of each technology.

Why are there seven types?

The types of additive manufacturing can be classified according to the products they produce or the types of materials they use, and the International Organization for Standards (ISO) divides them into seven general types (but these seven 3D printing categories can hardly cover more and more technical sub-types and mixed technologies). :

● Material extrusion

● Reduction polymerization

● Powder bed fusion

● Material spraying

● Adhesive spraying

● Directed energy deposition

● Sheet lamination

First, material extrusion

△ Material extrusion 3D printing

Material extrusion as the name implies: material is extruded through a nozzle. Usually, this material is a plastic filament, which is melted and extruded through a heated nozzle. The printer places materials on the building platform along the process path obtained by software. The filament then cools and solidifies to form a solid object. This is the most common form of 3D printing. At first glance, it sounds simple, but considering the extruded materials, including plastics, metals, concrete, bio-gel and various foods, it is actually a very broad category. The price of this type of 3D printer ranges from $100 to seven figures.

● Subtypes of material extrusion: fused deposition modeling (FDM), building 3D printing, micro 3D printing and biological 3D printing.

● Materials: plastic, metal, food, concrete, etc.

● Dimensional accuracy: 0.5% (lower limit: ±0.5mm)

● Common applications: prototype, electrical enclosure, shape and fit test, fixture and fixture, investment casting model, house, etc.

● Advantages: 3D printing method with the lowest cost and wide range of materials.

● Disadvantages: Generally, the material performance is low (strength, durability, etc.), and the dimensional accuracy is usually not high.

1. Fused Deposition Molding (FDM)

△FDM parts can be made of metal or plastic on various 3D printers.

FDM 3D printer is a multi-billion dollar market with thousands of machines, ranging from basic models to complex models of manufacturers. The FDM machine is called Fuse Manufacturing (FFF), which is exactly the same technology. Like all 3D printing technologies, FDM starts with a digital model and then converts it into a path that a 3D printer can follow. Using FDM, one filament (or several filaments at a time) on the bobbin is loaded into a 3D printer and then sent to the printer nozzle in the extrusion head. The nozzle or nozzles of the printer are heated to the required temperature to soften the filament, thus connecting successive layers to form a solid part.

When the printer moves the extrusion head along the specified coordinates on the XY plane, it will continue to lay the first layer. Then the extrusion head rises to the next height (Z plane), and the process of printing the cross section is repeated, building layer by layer until the object is fully formed. Depending on the geometry of the object, it is sometimes necessary to add a support structure to support the model when printing, for example, if the model has a steep overhang. These supports are removed after printing. Some supporting structure materials can be dissolved in water or another solution.

△FDM 3D printers provide a wide range of machines for amateurs, small businesses and manufacturers (sources: Creality, Raise3D, Stratasys).

2.3D biological printing

△3D bio-printing is similar to traditional 3D printing, but the raw materials are quite different.

3D biological printing or biological 3D printing is an additive manufacturing process in which organic or biological materials (such as living cells and nutrients) are combined to create a natural three-dimensional structure similar to tissues. In other words, bioprinting is a kind of 3D printing, which can produce anything from bone tissues and blood vessels to living tissues. It is used in various medical research and applications, including tissue engineering, drug testing and development, and innovative regenerative medicine therapy. The actual definition of 3D bioprinting is still developing. Essentially, the working principle of 3D bio-printing is similar to FDM 3D printing, and it belongs to the material extrusion series. (Although extrusion is not the only bio-printing method)

3D bio-printing uses the material (bio-ink) discharged from the needle to create a printed layer. These materials, called bio-inks, are mainly composed of living substances, such as cells in carrier materials, such as collagen, gelatin, hyaluronic acid, silk, alginate or nano-cellulose, which serve as molecular scaffolds for structural growth and nutrients.

3. Building 3D printing

△ Building 3D printing

Building 3D printing is a rapidly developing field of material extrusion. This technology involves the use of super-large 3D printers (usually up to tens of meters) to extrude building materials such as concrete from nozzles. These machines usually appear in the form of gantry or robotic arm systems. 3D architectural printing technology is now used in residential buildings, architectural features and construction projects from wells to walls. Some researchers say that it may significantly change the whole construction industry, because it reduces the demand for labor and construction waste.

There are dozens of 3D printed houses in the United States and Europe, and 3D building technology is being researched and developed, which will use materials found on the moon and Mars to build habitats for future expeditions. Printing with local soil instead of concrete as a more sustainable building method has also attracted attention.

Second, reduction polymerization

△ Reduction polymerization using laser

Barrel polymerization (also known as resin 3D printing) is a series of 3D printing processes, which uses a light source to selectively cure (or harden) photopolymer resin in a barrel. In other words, light is precisely directed at a specific point or area of liquid plastic to harden it. After the first layer is cured, the building platform will move up or down (depending on the printer) by a small amount (usually between 0.01 and 0.05 mm), and the next layer will be cured and connected with the previous layer. This process is repeated layer by layer until a 3D part is formed. After the 3D printing process is completed, the object is cleaned to remove the remaining liquid resin and post-cured (in the sun or ultraviolet room) to enhance the mechanical properties of the parts.

The three most common forms of barrel polymerization are stereolithography (SLA), digital light processing (DLP) and liquid crystal display (LCD), also known as mask stereolithography (MSLA). The fundamental difference between these types of 3D printing technologies lies in the light source and the way it is used to cure the resin.

△ vats polymerization uses light to harden photosensitive resin layer by layer.

Some 3D printer manufacturers, especially those that manufacture professional 3D printers, have developed unique and patented photopolymerization variants, so you may see different technical names in the market. Carbon, an industrial 3D printer manufacturer, uses a barrel polymerization technology called Digital Photosynthesis (DLS), Origin of Stratasys calls it Programmable Photopolymerization (P3), Formlabs provides a technology called Low-Force Stereolithography (LFS), and Azul 3D is the first to commercialize the barrel polymerization in the form of large-area rapid printing (HARP). There are also photolithography-based metal manufacturing (LMM), projection micro-stereolithography (PμSL) and digital composite manufacturing (DCM), which is a technology of filling photopolymer and can introduce functional additives (such as metal and ceramic fibers) into liquid resin.

● Types of 3D printing technology: Stereolithography (SLA), Liquid Crystal Display (LCD), Digital Light Processing (DLP), Micro Stereolithography (μSLA), etc.

● Material: photopolymer resin (castable, transparent, industrial, biocompatible, etc.)

● Dimensional accuracy: 0.5% (the lower limit is 0.15mm or 5nm, using μSLA).

● Common applications: injection molding polymer prototypes and end-use parts, jewelry casting, dental applications, consumer goods.

● Advantages: smooth surface finish and fine feature details.

1. Stereolithography (SLA)

△ Stereolithography (SLA) Examples of SLA 3D printing from 3D Systems, DWS and Formlabs.

SLA is the first 3D printing technology in the world. Stereolithography was invented by Chuck Hull in 1986. He applied for a patent for this technology and set up 3D Systems Company to commercialize it. Today, this technology can be used by enthusiasts and professionals from many 3D printer manufacturers. SLA uses laser beam to aim at a barrel of resin, selectively solidifies the cross section of the object in the printing area, and builds it layer by layer. When most SLA printers use solid-state lasers to cure components. One disadvantage of this barrel polymerization is that compared with our next method (DLP), the point laser may take longer to track the cross section of the object, and the latter will flash light to immediately harden the whole layer. However, laser can produce stronger light, which is required by some engineering-grade resins.

△SLA 3D printer uses one or more lasers to track and cure a single layer of resin at one time.

Micro-stereolithography (μSLA)

Micro-stereolithography technology can print micro-parts, and the resolution is between 2 microns (μm) and 50 microns. For reference, the average width of human hair is 75 microns. It is one of the "micro 3D printing" technologies. μSLA involves exposing photosensitive material (liquid resin) to ultraviolet laser. The difference lies in the special resin, the complexity of laser and the addition of lens, which will produce almost incredible small light spots.

△Nanoscribe and Microlight3D are two leading manufacturers of TPP 3D printers (source: Nanoscribe and Microlight3D).

Two-photon polymerization (TPP)

Another micro 3D printing technology, TPP (also called 2PP), can be classified as SLA, because it also uses laser and photosensitive resin, and it can print parts smaller than μSLA, as small as 0.1 micron. TPP uses pulsed femtosecond laser to focus on a narrow spot in a large barrel of special resin. This point is then used to cure a single 3D pixel, also called a voxel, in the resin. By curing these nano-scale to micron-scale voxels layer by layer in a predefined path. TPP is currently used in research, medical applications and the manufacture of micro parts, such as microelectrodes and optical sensors.

△ Micro 3D printing: TPP technology

2. Digital Light Processing (DLP)

△ DLP 3D printing parts of △Anycubic, Carbon and ETEC

DLP 3D printing uses a digital light projector (instead of a laser) to flash a single image of each layer on a layer or resin at the same time (or to expose a larger part for multiple times). DLP (more common than SLA) is used to produce larger parts or larger parts in a single batch, because no matter how many parts are in construction, each layer needs exactly the same exposure time, which is more efficient than the point laser method in SLA. The image of each layer consists of square pixels, resulting in a layer formed by small rectangular blocks called voxels. Light is projected onto the resin using a light emitting diode (LED) screen or a UV light source (lamp) and onto the construction surface through a digital micromirror device (DMD).

△ Digital Light Processing (DLP) resin 3D printer has a hobby version and a complete manufacturing machine.

Modern DLP projectors usually have thousands of micron-sized LEDs as light sources. Their on-off states are independently controlled, which can improve the XY resolution. Not all DLP 3D printers are the same. The power of light source, the lens it passes through, the quality of DMD and many other parts that make up a machine worth 300 dollars are quite different compared with a machine worth more than 200,000 dollars.

Top-down DLP

The light source of some DLP 3D printers is installed on the top of the printer, and shines down on the resin barrel instead of up. These "top-down" machines flash one layer of images from the top, curing one layer at a time, and then put the cured layer back in the vat. Every time the building board is lowered, the recoating machine installed at the top of the vat will move back and forth on the resin to level the new layer. According to the manufacturer, because the printing process will not resist gravity, this method can produce more stable parts output for larger prints. There is a limit to how much weight can be hung vertically from the building board when printing from bottom to top. The resin barrel also supports printed parts during printing, which reduces the need for supporting structures.

△BMF’s MicroArch S230 can print detailed parts of polymers or ceramics as small as 2 microns (source: BMF).

Projection microlithography (PμSL)

As a unique type of barrel aggregation itself, PμSL is classified as a subcategory of DLP. This is another micro 3D printing technology. PμSL uses ultraviolet rays from the projector to cure the specially formulated resin layer in micron scale (2 micron resolution and as low as 5 micron height). This additive manufacturing technology is developing continuously because of its low cost, accuracy, speed and the range of materials (including polymers, biomaterials and ceramics). It has shown the application potential from microfluidic and tissue engineering to micro-optics and biomedical micro-devices.

Metal Manufacturing Based on Lithography (LMM)

This is another "distant relative" of DLP. This method of 3D printing using light and resin can create tiny metal parts for applications such as surgical tools and micromechanical parts. In LMM, metal powder is uniformly dispersed in photosensitive resin, and then selectively polymerized by blue light exposure through a projector. After printing, the polymer components of the blank parts are removed, leaving all-metal degreased parts, which are completed in the sintering process in the furnace. Raw materials include stainless steel, titanium, tungsten, brass, copper, silver and gold.

△ Micro-metal 3d printing parts made on Incus 3D printing with LMM technology.

3. Liquid crystal display (LCD)

△ LCD 3D printing components from Elegoo, Photocentric and Nexa3D.

Liquid crystal display (LCD), also known as mask stereolithography (MSLA), is very similar to the above DLP, except that it uses LCD screen instead of digital micromirror device (DMD), which has a significant impact on the price of 3D printer. Like DLP, LCD photomask is digitally displayed and consists of square pixels. The pixel size of LCD photomask determines the granularity of printing. Therefore, the XY accuracy is fixed and does not depend on the zoom or zoom degree of the lens, just like DLP. Another difference between DLP printers and LCD technology is that the latter uses an array of hundreds of individual emitters instead of a single point emitting light source like a laser diode or DLP bulb.

△ Today, LCD resin 3D printing technology is shifting from consumer machines to industrial machines.

Similar to DLP, LCD can achieve faster printing time than SLA under some conditions. This is because the whole layer is exposed at one time instead of tracking the cross-sectional area with a laser spot. Due to the low cost of LCD unit, this technology has become the first choice in the field of low-cost desktop resin printers, but this does not mean that it has not been used professionally. Some industrial 3D printer manufacturers are breaking through the technical limits and achieving remarkable results.

Third, powder bed fusion

△ Powder bed fusion

Powder bed fusion (PBF) is a 3D printing process, in which a thermal energy source selectively melts powder particles (plastic, metal or ceramic) in a construction area to create solid objects layer by layer. Powder bed fusion 3D printer spreads a thin layer of powder material on the printing bed, usually using a blade, roller or wiper. The energy from the laser fuses a specific point on the powder layer, and then another powder layer is deposited and fused to the previous layer. This process is repeated until the whole object is manufactured, and the final product is wrapped and supported by unmelted powder.

△ Metal laser powder bed fusion process

PBF can manufacture parts with high mechanical properties (including strength, wear resistance and durability) for the end use of consumer goods, machinery and tools. 3D printers in this market segment are getting cheaper and cheaper (starting at around $25,000), but it is considered as an industrial technology.

● Types of 3D printing technology: selective laser sintering (SLS), laser powder bed melting (LPBF) and electron beam melting (EBM).

● Materials: plastic powder, metal powder and ceramic powder.

● Dimensional accuracy: 0.3% (lower limit: ±0.3mm)

● Common applications: production of functional parts, complex pipes (hollow design) and small batch parts.

● Advantages: functional components, excellent mechanical properties, complex geometry.

● Disadvantages: The cost of the machine is high, usually high-cost materials, and the construction speed is slow.

1. Selective laser sintering (SLS)

△ SLS 3D printing parts of △Sinterit

Selective laser sintering (SLS) uses lasers to make objects from plastic powder. First, a box of polymer powder is heated to a temperature just below the melting point of the polymer. A very thin layer of powder material (usually 0.1 mm thick) is then deposited on the building platform using a recoating blade or wiper. The laser begins to scan the surface according to the pattern arranged in the digital model. The laser selectively sintered the powder and solidified the cross section of the object. When scanning the whole cross section, the building platform moves down one layer in height. The recoating blade deposits a new layer of powder on the recently scanned layer, and the laser sinter the next cross section of the object onto the previously solidified cross section.

△ SLS 3D printing parts can be dusted and cleaned manually or automatically.

Repeat these steps until all objects are made. The unsintered powder remains in place to support the object, which reduces or eliminates the need for supporting structures. After the parts are taken out of the powder bed and cleaned, there is no need for other necessary post-treatment steps. Parts can be polished, coated or colored. There are many differentiation factors between SL3D printers, including not only their size, but also the power and quantity of laser, the spot size of laser, the time and mode of heating bed and the distribution mode of powder. The most common materials in SL3D printing are nylon (PA6, PA12), but flexible parts can also be printed with TPU and other materials.

△SLS 3D printer uses polymer powder and laser to form solid parts.

2. Micro-selective laser sintering (μSLS)

μSLS belongs to SLS or laser powder bed fusion (LPBF) described below. It uses laser to sinter powdery materials, such as SLS, but this material is usually metal rather than plastic, so it is more like LPBF. It is another micro 3D printing technology, which can create parts with micro (less than 5 μm) resolution.

△ Metal 3D MicroPrinting from 3D microprint

In μSLS, a layer of metal nanoparticle ink is coated on the substrate and then dried to produce a uniform nanoparticle layer. Next, the laser patterned with the digital micromirror array is used to heat the nanoparticles and sinter them into a desired pattern. This set of steps is then repeated to build each layer of the 3D component in the μSLS system.

3. Laser Powder Bed Fusion (LPBF)

△ Xact Metal test piece showing SLM accuracy (source: Xact Metal)

In all 3D printing technologies, this item has the most aliases. The formal name of this metal 3D printing method is laser powder bed melting (LPBF), which is also widely known as direct metal laser sintering (DMLS) and selective laser melting (SLM). In the early days of this technology development, machine manufacturers created their own names for the same process, and these names have been used to this day. In particular, these three terms refer to the same process, even though some mechanical details are different.

As a sub-type of powder bed fusion, LPBF uses a metal powder bed and one or more (up to 12) high-power lasers. LPBF 3D printer uses laser to selectively fuse metal powder layer by layer on a molecular basis until the model is completed. LPBF is a highly accurate 3D printing method, which is usually used to create complex metal parts for aerospace, medical and industrial applications.

△Sandvik’s LPBF metal 3D printing

Like SLS, LPBF 3D printers start with a digital model divided into slices. The printer loads the powder into the building chamber, and then spreads it into a thin layer on the building board with a scraper (such as a windshield wiper) or a roller. The laser tracks the layer onto the powder. Then the building platform moves down, and then a layer of powder is coated and blended with the first layer until the whole object is built. The building chamber is closed and sealed, and in many cases it is filled with inert gas, such as nitrogen or argon mixture, to ensure that the metal will not be oxidized during the melting process and help to remove the debris during the melting process. After printing, the parts are taken out of the powder bed, cleaned and often subjected to secondary heat treatment to eliminate stress. The remaining powder is recycled.

The differentiation factors of LPBF 3D printer include the type, intensity and quantity of lasers. A small compact LPBF printer may have one 30-watt laser, while the industrial version may have 12 1,000-watt lasers. LPBF machines use common engineering alloys, such as stainless steel, nickel superalloy and titanium alloy. Dozens of metals can be used in LPBF process.

△ LPBF 3D printers from One Click Metal, Farsoon and Kurtz Ersa.

3. Electron beam melting (EBM)

△ electron beam melting (EBM)

EBM, also known as Electron Beam Powder Bed Fusion (EB PBF), is a metal 3D printing method similar to LPBF, but using electron beam instead of fiber laser. This technology is used to manufacture parts, such as titanium orthopedic implants, turbine blades of jet engines and copper coils.

Electron beams generate more energy and heat, which are needed by some metals and applications. Moreover, EBM is not an inert gas environment, but is carried out in a vacuum chamber to prevent light beam scattering. The temperature of the building chamber can reach up to 1,000 °C, and even higher in some cases. Because the electron beam is controlled by electromagnetic beam, it moves faster than laser, and can even be separated to expose multiple areas at the same time.

△ Electron beam melting (EBM) metal 3D printers from JEOL, GE Additive and Wayland Additive.

One of the advantages of EBM over LPBF is that it can handle conductive materials and reflective metals such as copper. Another feature of EBM is that individual components can be nested or stacked in the building room, because they do not necessarily have to be connected to the building board, which greatly increases the volume output. Compared with laser, electron beam usually produces larger layer thickness and rougher surface features. Due to the high temperature in the building room, EBM printing parts may not need to be heat-treated after printing to relieve stress.

Fourth, material spraying

△ material injection

Material ejection is a 3D printing process in which tiny droplets of material are deposited and then solidified or solidified on the building board. Use photopolymer or wax droplets that will cure when exposed to light to build objects one layer at a time. The nature of the material spraying process allows different materials to be printed on the same object. One application of this technology is to manufacture parts with various colors and textures.

● Types of 3D printing technology: material ejection (MJ) and nanoparticle ejection (NPJ)

● Material: photosensitive resin (standard, pouring, transparent, high temperature resistant), wax.

● Dimensional accuracy: ±0.1 mm

● Common applications: full-color product prototypes, prototypes similar to injection molds, low-running injection molds, medical models, and fashion.

● Advantages: textured surface finish, full color and various materials available.

● Disadvantages: Limited materials are not suitable for mechanical parts requiring precision, and the cost is higher than other resin technologies used for visual purposes.

1. material injection (M-Jet)

△Stratasys’s material jet 3D printing parts

Material jet of polymer (M-Jet) is a 3D printing process, in which a layer of photosensitive resin is selectively deposited on the building board and cured by ultraviolet (UV). After one layer is deposited and solidified, the building platform reduces the thickness of one layer, and the process is repeated to build 3D objects. M-Jet combines the high precision of resin 3D printing with the speed of wire 3D printing (FDM) to create parts and prototypes with realistic colors and textures.

All material jet 3D printing technologies are not exactly the same. There are differences between printer manufacturers and proprietary materials. M-Jet machines deposit building materials from multiple rows of print heads in a line-by-line manner. This method enables the printer to manufacture multiple objects on a line without affecting the construction speed. As long as the models are arranged correctly on the construction platform and the space in each construction line is optimized, M-Jet can produce parts faster than many other types of resin 3D printers.

△ Material jet 3D printers from Stratasys, DP Polar/3D Systems and Mimaki.

The object made by M-Jet needs support, and it is printed by soluble materials at the same time during the construction process, which is removed in the post-processing stage. M-Jet is one of the few 3D printing technologies, which can provide objects made of multi-material printing and full color. There is no amateur version of the material jet machine. These machines are more suitable for professionals of automobile manufacturers, industrial design companies, art studios, hospitals and all kinds of product manufacturers. They want to create accurate prototypes to test concepts and bring products to market faster. Unlike barrel polymerization technology, M-Jet does not need post-curing, because the ultraviolet rays in the printer will completely cure each layer.

Aerosol jet

Aerosol Jet is a unique technology developed by a company named Optomec, which is mainly used for 3D printing electronic products. Components such as resistors, capacitors, antennas, sensors and thin film transistors are printed by aerosol spraying technology. It can be roughly compared to painting, but it is different from industrial coating process in that it can be used to print complete 3D objects.

Put the electronic ink into the atomizer, which will produce droplets with a diameter between 1 and 5 microns. Then the aerosol mist is transported to the deposition head and focused by the sheath gas, thus producing a high-speed particle spray. Because the whole process uses energy, this technology is sometimes called directional energy deposition, but because the material is in the form of droplets in this case, we include it in the material injection.

Plastic free forming

Arburg, a German company, has created a technology called plastic freeform molding (APF), which is a combination of extrusion technology and material injection technology. It uses commercially available plastic particles, which are melted in the injection molding process and moved to the unloading unit. The closing of the high-frequency nozzle produces a rapid opening and closing movement of up to 200 plastic droplets with a diameter of 0.2 to 0.4 mm per second. The droplets combine with the hardened material when cooling. Generally speaking, no post-treatment is needed. If supporting materials are used, they must be removed.

2. Nanoparticle Jet (NPJ)

△ Metal parts created by using nanoparticle injection technology and XJet 3D printer.

NanoParticle Jetting (NPJ) is one of the few proprietary technologies that are difficult to classify. It was developed by a company named XJet. It uses a printhead array with thousands of inkjet nozzles to spray millions of ultrafine material droplets onto the ultra-thin building tray at the same time, and simultaneously spray supporting materials. Metal or ceramic particles are suspended in a liquid. This process takes place at high temperature, and the liquid evaporates when spraying, leaving mostly metal or ceramic materials. Only a small amount of adhesive remains in the generated 3D parts, and these adhesives are removed in the post-sintering treatment.

V. Adhesive spraying

△ adhesive spraying

Adhesive spraying is a 3D printing process in which liquid adhesive selectively adheres to areas of a layer of powder. This technology type has the characteristics of powder bed fusion and material injection. Similar to PBF, adhesive spraying uses powder materials (metal, plastic, ceramics, wood, sugar, etc.), and like material spraying, liquid adhesive polymer is deposited from an inkjet. Whether it is metal, plastic, sand or other powder materials, the adhesive spraying process is the same.

First, the recoating blade coats a thin layer of powder on the building platform. Then, a print head with an inkjet nozzle passes over the bed and selectively deposits adhesive droplets to bond the powder particles together. After the layer is completed, the building platform moves down and the blade recoats the surface. Then repeat the process until the whole part is completed.

Adhesive spraying is unique in that there is no heat in the printing process. The binder acts as glue that binds the polymer powders together. After printing, the parts are wrapped in unused powder, which usually remains for curing. Then the parts are taken out of the powder bin, and the excess powder is collected and can be reused. From here on, according to different materials, post-treatment is needed, except for sand, which can usually be directly used as cores or molds from printers. When the powder is metal or ceramic, the post-treatment involving heating will melt the binder, leaving only the metal. Post-treatment of plastic parts usually includes coating to improve surface finish. You can also polish, paint and grind the polymer adhesive spraying parts.

The adhesive has high spraying speed and high productivity, so it can produce a large number of parts more economically and efficiently than other AM methods. Metal adhesive spraying can be used for a variety of metals and is very popular in end-use consumer goods, tools and bulk spare parts. However, the material selection of polymer adhesive injection is limited, and the structural performance of the produced parts is low. Its value lies in being able to make full-color prototypes and models.

● Subtypes of 3D printing technology: metal adhesive spraying, polymer adhesive spraying and sand adhesive spraying.

● Material: sand, polymer, metal, ceramics, etc.

● Dimensional accuracy: 0.2 mm (metal) or 0.3 mm (sand)

● Common applications: functional metal parts, full-color models, sand castings and molds.

● Advantages: low cost, large building volume, functional metal parts, excellent color reproduction, fast printing speed and unsupported design flexibility.

Disadvantages: It is a multi-step process for metals, and polymer parts are not durable.

1. Metal adhesive spraying

△ HP stainless steel 3D printing parts using metal spraying technology

Binder Jetting can also be used to manufacture solid metal objects with complex geometries, which is far beyond the capabilities of traditional manufacturing technologies. Metal adhesive spraying is a very attractive technology, which can be used to mass-produce metal parts and realize lightweight. Since adhesive spraying can print parts with complex patterns instead of solids, the weight of the parts obtained is greatly reduced, but the strength remains unchanged. The porosity characteristics of adhesive injection can also be used to realize lighter end parts for medical applications, such as implants.

Generally speaking, the material properties of metal binder sprayed parts are equivalent to those of metal parts produced by metal injection molding, and it is one of the most widely used manufacturing methods in mass production of metal parts. In addition, the adhesive spraying parts show higher surface smoothness, especially in the internal channels.

△ Metal adhesive jet 3D printer produces fine solid metal parts for end-use applications.

Metal adhesive spraying parts need secondary processing after printing to obtain good mechanical properties. Just coming out of the printer, the parts are basically composed of metal particles bonded together with polymer adhesives. These so-called "green parts" are too fragile to be used as they are. After the printed parts are taken out of the metal powder bed (called the process of powder removal), they will be heat-treated in the furnace (called the process of sintering). Both printing parameters and sintering parameters are adjusted according to the geometry, material and required density of specific parts. Bronze or other metals are sometimes used to penetrate the voids in the adhesive spraying parts, thus achieving zero porosity.

2. Plastic adhesive spraying

△ Plastic adhesive spraying

Plastic adhesive spraying is a process very similar to metal adhesive spraying, because it also uses powder and liquid adhesive, but its application is quite different. After printing, plastic parts will be taken out of their powder beds and cleaned, and usually can be used without further treatment, but these parts lack the strength and durability in the 3D printing process. The plastic adhesive spraying part can be filled with another material to improve the strength. Using polymers for adhesive spraying can produce multicolor parts for medical modeling and product prototyping.

3. Sand binder spraying

△ sand binder injection

Sand adhesive spraying and plastic adhesive spraying are different in printer and printing process, so they are distinguished here. Producing large sand casting molds, molds and cores is one of the most common uses of adhesive injection technology. The low cost and speed of this process make it an excellent solution for foundry, because it is difficult to produce fine pattern designs in a few hours with traditional technology.

The future of industrial development constantly puts high demands on foundries and suppliers. Sand 3D printing is at the beginning of its potential. After printing, the printer needs to remove the cores and molds from the construction area and clean them to remove any loose sand. The mold can usually be ready for casting immediately. After casting, the mold is disassembled and the final metal parts are removed.

4. Multi-jet fusion (MJF)

△ BASF and HP cooperated to develop a new industrial grade polypropylene for MJF.

Another unique and brand-specific 3D printing process, which is not easy to fall into any existing category, is actually not adhesive spraying, and this is HP’s Multi Jet Fusion. MJF is a polymer 3D printing technology, which uses powder materials, liquid fusion materials and refiners. The reason why it is not considered as adhesive spraying is that the heat is increased in this process, which will produce parts with higher strength and durability, and the liquid is not completely adhesive. The name of this process comes from multiple inkjet heads that perform the printing process.

In the process of Multi Jet Fusion printing, the printer lays a layer of material powder, usually nylon, on the printing bed. After that, the inkjet head passes through the powder and deposits a melting agent and a refining agent on it. Then the infrared heating device moves on the printed matter. No matter where the flux is added, the lower layers will melt together, while the areas with refiners will remain powdery. The powdery part falls off to produce the required geometry. This also eliminates the need for modeling support, because lower layers support layers printed on them. In order to complete the printing process, the whole powder bed and the printing parts in it are moved to a single processing station, and most of the loose unmelted powder is evacuated and can be reused.

Multi Jet Fusion is a multifunctional technology, which has been applied in many industries such as automobile, medical care and consumer goods.

△HP Jet Fusion 5200 series is one of the many sizes and styles of HP Multi Jet Fusion 3D printer (source: HP).

Six, powder directional energy deposition

Directional Energy Deposition (DED) is a 3D printing process. Metal materials are supplied and melted by powerful energy while being deposited. This is one of the most extensive 3D printing categories, including many subcategories, depending on the material form (wire or powder) and energy type (laser, electron beam, arc, supersonic, heat, etc.). Essentially, it has a lot in common with welding.

This technology is used for layer-by-layer printing, usually followed by CNC machining to achieve stricter tolerances. The combination of DED and CNC is very common. There is a sub-type of 3D printing called hybrid 3D printing, which contains a hybrid 3D printer with DED and CNC units in the same machine. This technology is considered to be a faster and cheaper substitute for small-batch metal castings and forgings, as well as a key maintenance for offshore oil and gas industries, aerospace, power generation and utilities.

△DED metal 3D printing technology can quickly create a solid metal part, and then it can be processed to strict tolerances.

● Subtypes of directional energy deposition: powder laser energy deposition, wire arc additive manufacturing (WAAM), wire electron beam energy deposition and cold spraying.

● Materials: various metals, wires and powder forms.

● Dimensional accuracy: ±0.1 mm

● Common applications: repairing high-end automotive/aerospace components, functional prototypes and final components.

● Advantages: high stacking rate, and the ability to add metal to existing components.

● Disadvantages: Because the supporting structure cannot be made, it is impossible to make complex shapes, and the surface smoothness and accuracy are usually poor.

1. Laser directed energy deposition

△ 3D printing metal using laser and powder metal

Laser-directed energy deposition (L-DED), also known as laser metal deposition (LMD) or laser engineering net shaping (LENS), uses metal powder or metal wire sent through one or more nozzles and melted by powerful laser to build platforms or metal parts. With the movement of nozzle and laser or the movement of parts on the multi-axis turntable, objects will be piled up layer by layer. The construction speed is faster than that of powder bed melting, but it will lead to the decrease of surface quality and precision, and usually requires a lot of post-processing. Laser DED printers usually have a sealed chamber filled with argon to avoid oxidation. When dealing with less reactive metals, they can also operate with only local argon or nitrogen.

Metals commonly used in this process include stainless steel, titanium and nickel alloy. This printing method is usually used to repair high-end aviation and automobile parts, such as jet engine blades, but it is also used to produce whole parts.

△Meltio M450 wire feeding laser DED 3D printer, Optomec LENS CS 600 metal powder feeding laser DED 3D printer and DMG Mori Lasertec 65 DED powder feeding laser DED 3D printer.

2. Electron beam directional energy deposition

△ electron beam DED 3D printing

Electron beam DED, also known as linear electron beam energy deposition, is a 3D printing process very similar to laser DED. It is carried out in a vacuum chamber and can produce very clean and high-quality metals. When a wire passes through one or more nozzles, it will be melted by the electron beam. The layer is constructed separately, the electron beam forms a tiny molten pool, and the welding wire is fed into the molten pool by a wire feeder. When dealing with high-performance metals and active metals (such as copper, titanium, cobalt and nickel alloy), electron beam is selected for DED.

DED machines are virtually unlimited in print size. For example, Sciaky, a 3D printer manufacturer, has an EB DED machine that can produce parts nearly 6 meters long at a speed of 3 to 9 kilograms of materials per hour. Electron beam DED is touted as one of the fastest methods to manufacture metal parts, although it is not the most accurate, which makes it an ideal machining technology to build large structures (such as fuselage) or replace parts (such as turbine blades).

△ 3D printing of wire by electron beam deposition

3. Line-controlled energy deposition

△Gefertec arc additive manufacturing (WAAM) printing

Wire Directed Energy Deposition, also known as wire arc additive manufacturing (WAAM), is a kind of 3D printing, which uses energy in the form of plasma or arc to melt the metal in the form of wire, and deposits the metal layer by layer on a surface, such as a multi-axis turntable, to form a shape by a robotic arm. This method is chosen instead of the similar technology of laser or electron beam because it does not need a sealed chamber and can use the same metal (sometimes the same material) as traditional welding.

Direct energy deposition is considered to be the most cost-effective choice in DED technology, which can use the existing arc welding robot and power supply, so the entry threshold is relatively low. But unlike welding, this technology uses complex software to control a series of variables in the process, including the thermal management of the robot arm and the tool path. This technology has no supporting structure to be removed, and the finished parts are usually CNC machined when necessary to achieve strict tolerance or surface polishing.

△Gefertec and WAAM3D’s line arc additive manufacturing 3D printer.

4. Cold spraying

△ cold spraying

Cold spraying is a DE3D printing technology, which sprays metal powder at supersonic speed to combine them without melting, and hardly produces thermal cracks or thermal stress. Since the early 2000s, it has been used as a coating process, but recently, several companies have used cold spraying for additive manufacturing, because it can print at a speed 50 to 100 times higher than that of a typical metal 3D process and does not require inert gas or vacuum chamber.

Like all DED processes, cold spraying will not produce prints with good surface quality or details, but the parts can be used directly from the printing bed.

5. Melting direct energy deposition

△ Melting Direct Energy Deposition: Aluminum parts printed by ElemX 3D liquid metal of Xerox.

Melting direct energy deposition is a 3D printing process, which uses heat to melt metal (usually aluminum) and then deposits it layer by layer on the building board to form 3D objects. The difference between this technology and metal extrusion 3D printing is that metal raw materials containing a small amount of polymer are used for extrusion, so that the metal can be extruded. Then the polymer is removed in the heat treatment stage, and pure metal is used to melt DED. One can also compare molten or liquid DED to material injection, but instead of a series of nozzles to deposit droplets, liquid metal usually flows out from the nozzles.

Variants of this technology are being developed, and molten metal 3D printers are rare. The advantage of using heat to melt and then deposit metal is that it can use less energy than other DED processes, and it is possible to directly use recycled metal as raw material instead of metal wire or highly processed metal powder.

VII. Lamination of sheets

△ Sheet lamination

Sheet lamination is technically a form of 3D printing, which is quite different from the above technologies. Its function is to stack and laminate very thin pieces of material together to create 3D objects or stacks, and then cut them by machinery or laser to form the final shape. The layers of materials can be fused together in a variety of ways, including heating and sound, depending on the material, ranging from paper to polymer to metal. When the parts are laminated and then laser cut or processed into the required shape, it will produce more waste than other 3D printing technologies.

Manufacturers use sheet lamination to produce cost-effective non-functional prototypes at a relatively high speed, which can be used in battery technology and composite materials, because the materials used can be interchanged in the printing process.

● Types of 3D printing technology: Laminated Object Manufacturing (LOM) and Ultrasonic Consolidation (UC)

● Materials: paper, polymer and sheet metal.

● Dimensional accuracy: ±0.1 mm

● Common applications: non-functional prototyping, multi-color printing and casting.

● Advantages: rapid production and compound printing.

● Disadvantages: low precision, much waste, and some parts need post-production.

Laminated additive manufacturing

△ Laminated additive manufacturing

Lamination is a 3D printing technology, in which sheets of materials are laminated and glued together, and then the layered objects are cut into the correct shape with a knife (or laser or CNC router). This technology is less common nowadays, because the cost of other 3D printing technologies has decreased, and the speed and ease of use have greatly increased.

△BCN3D viscous lithography manufacturing (VLM) 3D printing process using resin (source: BCN3D)

Viscosity lithography (VLM): VLM is a patented 3D printing process of BCN3D, which can laminate a thin layer of high-viscosity photosensitive resin onto a transparent transfer film. The mechanical system allows the resin to be laminated from both sides of the film, so that different resins can be combined to obtain a multi-material part and an easily detachable support structure. This technology has not been commercialized, but it can also belong to one of the laminated 3D printing technologies.

Composite-based additive manufacturing (CBAM):Startup Impossible Objects applied for a patent for this technology, which combines carbon, glass or Kevlar mats with thermoplastics to manufacture parts.

Selective Laminated Composite Manufacturing (SLCOM): Envision Tec, now called ETEC, owned by Desktop Metal, developed this technology in 2016, which uses thermoplastics as the base material and woven fiber composite.

Note: There are many kinds of 3D printing technologies. These are the seven most common additive manufacturing technologies in 3D printing, which do not cover all 3D printing technologies in the market.

Original title: "7 mainstream 3D printing technologies, all of which can be understood"

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The craftsman’s heart behind the network explosion should not let the inheritance get into too much money.

  CCTV News:Because of the broadcast of a food documentary, in recent days, "Zhangqiu Iron Pot" can be said to be a red overnight. This kind of iron pot forged by traditional manual skills has become a popular product snapped up by everyone.

  "Zhangqiu Iron Pot" is popular, but the business owner who produces iron pots has begun to worry? Why?

  China 3 on the tip of the tongue: "Twelve processes, 18 times of heat, more than a dozen hammer tools, large and small, 1000 degrees of high temperature smelting, 36,000 times of forging, each forging is the most powerful experience of iron, while injecting strength into the iron pot."

  Every season, "China on the tip of the tongue" will bring some food or utensils with it. The third season of "China on the tip of the tongue" broadcast in the Spring Festival this year will make Zhangqiu iron pot, which has always been unknown, popular overnight.

  In the documentary, not only Zhangqiu’s long history as the "hometown of blacksmiths" is presented, but also the tedious manual production process is displayed. In the dozens of minutes after the broadcast of the program, more than 2,000 iron pots in the inventory of Zhangqiu Iron Pot Online Store were robbed and emptied.

  At the same time, the experience store in Jinan, Shandong Province, which is being renovated, has also flooded into consumers from all over the country.

  The experience store, which was intended to be officially opened in March this year, had to open ahead of schedule because of the large number of visitors.

  In the hastily opened physical store, consumers not only bought all the goods in the store, but also the samples hanging on the wall.

  According to statistics, the sales of Zhangqiu iron pot on Tmall platform increased by nearly 6,000 times year-on-year. But the current reality is that Zhangqiu iron pot is hard to find.

  In desperation, four days after the China broadcast on the tip of the tongue, the merchants put up the slogan "Zhangqiu has no pot, Luoyang paper is expensive" on the homepage of the website, and removed all the pots and pans. At the same time, in the persuasion statement, consumers are advised to "consume rationally, I hope everyone will refund, and then buy slowly when the heat dissipates, so as not to let the inheritance get into too much money."

The cold wave is coming. You should know these questions about vaccines.

  CCTV News:Recently, COVID-19 vaccination for children aged 3-11 has been started, so which should be vaccinated first, influenza vaccine or COVID-19 vaccine? What problems should children pay attention to when they are vaccinated with COVID-19 vaccine? About vaccination, we know together.

  There is no difference in the protective effect between children vaccinated with COVID-19 vaccine and adults

  Is COVID-19 Vaccine Safe for Children?

  Jiang Rongmeng, Vice President of beijing ditan hospital, Chief Physician of Infectious Diseases:The inactivated vaccine of Covid-19 produced in China has been carried out in clinical experiments on people aged 3-17. After evaluation and demonstration, it is safe to use inactivated vaccine of COVID-19 in people aged 3-17.

  Is there any difference between the dose and dosage of Covid-19 vaccine for children and adults?

  Jiang Rongmeng, Vice President of beijing ditan hospital, Chief Physician of Infectious Diseases:There is no difference in dosage, dosage and process between children vaccinated with inactivated Covid-19 vaccine and adults.

  The interval between influenza vaccination and COVID-19 vaccination should be more than 14 days.

  Should children get the flu vaccine or COVID-19 vaccine first?

  Zhang Yuntao, Chairman of the Quality Committee of China Vaccine Association:You can get the flu at the same time when you hit COVID-19, but the interval must be greater than or equal to 14 days. At present, Covid-19 and the flu virus are different viruses, and there is no cross protection between them, so you must get the flu when you hit COVID-19.

  Vaccination against influenza or COVID-19 vaccine is not recommended if you are catching a cold and coughing.

  Can the child be vaccinated against COVID-19 or flu if he is allergic?

  Xu Baoping, Director of Respiratory Department of Beijing Children’s Hospital affiliated to Capital Medical University:The vast majority of children with allergies can be vaccinated, as long as they are not in the acute stage.

  Jiang Rongmeng, Vice President of beijing ditan hospital, Chief Physician of Infectious Diseases:If you have symptoms such as fever, diarrhea, or cough, you should still suspend the vaccination of COVID-19 vaccine, including influenza vaccine, and wait until these symptoms disappear and relieve, then evaluate and make an appointment for vaccination.

  Is it completely safe after vaccination?

  Even if you are vaccinated with influenza vaccine or Covid-19 vaccine, you should stick to personal protection, and at the same time actively exercise and enhance your immune function.

  Jiang Rongmeng, Vice President of beijing ditan hospital, Chief Physician of Infectious Diseases:It doesn’t mean that you won’t be infected after vaccination, so we should stick to these non-pharmaceutical and non-vaccine measures in our daily life, such as wearing masks, avoiding places where people gather, doing hand hygiene well, and not washing your hands and touching your eyes and nose, which is very important for us to prevent these respiratory virus infections.