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Tungsten (W) as a structural component has grown roots in many special applications owing to its radiation-shielding capabilities and its properties at elevated temperatures. The high ductile-brittle transition temperature (DBTT) and the very high melting point of tungsten however have limited its processability to certain technologies such as powder metallurgy. Laser powder bed fusion (LPBF) has been introduced in recent years as an alternative for manufacturing tungsten parts to overcome the design limitations posed by powder metallurgy technology. A review of the literature shows significant improvements in the quality of tungsten components produced by LPBF, implying a strong potential for manufacturing tungsten with this technology and a need for further research on this subject. This review paper presents the current state-of-the-art in LPBF of unalloyed tungsten, with a focus on the effect of process parameters on the developed structure/properties and identifies current knowledge gaps.

Background:As more than 37 million confirmed cases and 1 million deaths worldwide from COVID-19, we flied to think about supporting immunity, So, there are more than 150 coronavirus vaccines and clinical trials are being developed. The success of those vaccines depends mainly on immunologic memory. People who are at high risk of re-infection with COVID-19 don’t show any evidence of having B-cell memory. 10-20% of infected patients don’t develop antibody response. randomized controlled trials and cross-sectional studies proved variant results about the effect of chronic exercise on vaccination function.The aim of this review is to suggest that exercise is an important adjuvant strategy for prevention of re-infection and for development of better protective responses following vaccination.Methods:Embase, Medline and the Cochrane Central Register were used to search for specific keywords such as “COVID-19” OR “SARS-CoV-2” AND “Re-infection” for relevant publications up to 1st of Nov. 2020. The systematic review was performed using PRISMA protocol. Results:According to inclusion criteria, 6 case reports from search and one case from a press conference were identified. The average age of re-infected patients was 36 years. The average intervening period between initial infection and reinfection was 105 days. 75% of cases who have been tested for antibodies after 1st infection were negative, and turned seropositive after second infection. 57% of cases developing re-infection had worse clinical manifestation.Conclusion:Regular moderate intensity exercise not only can enhance the secondary antibody response of B cell memory but also decrease the severity of re-infection and the adverse reactogenicity of potential vaccines under development.

Background: As more than 37 million confirmed cases and 1 million deaths worldwide from COVID-19, we flied to think about supporting immunity, So, there are more than 150 coronavirus vaccines and clinical trials are being developed. The success of those vaccines depends mainly on immunologic memory. People who are at high risk of re-infection with COVID-19 don’t show any evidence of having B-cell memory. 10-20% of infected patients don’t develop antibody response. randomized controlled trials and cross-sectional studies proved variant results about the effect of chronic exercise on vaccination function.The aim of this review is to suggest that exercise is an important adjuvant strategy for prevention of re-infection and for development of better protective responses following vaccination.Methods: Embase, Medline and the Cochrane Central Register were used to search for specific keywords such as “COVID-19” OR “SARS-CoV-2” AND “Re-infection” for relevant publications up to 1st of Nov. 2020. The systematic review was performed using PRISMA protocol.Results: According to inclusion criteria, 6 case reports from search and one case from a press conference were identified. The average age of re-infected patients was 36 years. The average intervening period between initial infection and reinfection was 105 days. 75% of cases who have been tested for antibodies after 1st infection were negative, and turned seropositive after second infection. 57% of cases developing re-infection had worse clinical manifestation.Conclusion: Regular moderate intensity exercise not only can enhance the secondary antibody response of B cell memory but also decrease the severity of re-infection and the adverse reactogenicity of potential vaccines under development.