Selective laser melting (SLM) is characterized by highly localized heat input and short interaction times, which lead to large thermal gradients. In this research, nine different materials are processed via SLM and compared. The resulting microstructures are characterized by optical and scanning electron microscopy. Residual stresses are measured qualitatively using a novel deflection method and quantitatively using X-ray diffraction. Microcracking, surface oxidation and the anisotropy of the residual stress are discussed. The different phenomena interacting with the buildup of residual stress make it difficult to distinguish the possible correlations between material parameters and the magnitude of residual stresses.
Compared with vaccines, antivirals for curbing COVID-19 (SARS-CoV-2 infection) have been developed at a much lower pace. Favipiravir has proven efficacious (in hamsters) but only at a very high dose which may not be feasible in humans. Remdesivir is the sole antiviral approved by the US FDA, but it has not been extensively evaluated for its safety. EIDD-1931 and EIDD-2801 have not been evaluated clinically. Mpro (protease) inhibitors likewise need to be subjected to clinical efficacy and safety studies. Remdesivir is a C-nucleoside and this class of compounds should be further evaluated. Polyanionic substances interfering with virus adsorption to the host cells have not been explored. They may possibly be administered by inhalation. Corticosteroids (such as dexamethasone), while virus-stimulating rather than inhibitory, may counteract the ‘cytokine storm’. Combination of (two or more of) the compounds mentioned above may offer an increased benefit through a synergistic interaction.
Abstract Abrasive waterjet cutting is a manufacturing process that allows cutting a wide range of materials which are often difficult to process by means of conventional cutting methods. Similar to other beam type cutting processes, the waterjet is traditionally applied in a direction perpendicular to the surface to be cut. For cutting contours in pre-formed parts, 5- or 6-axis control is required to orient the waterjet beam perpendicular to the part surface along the cutting profile. In this paper, the results of experiments, performed to test the applicability of 3-axis nozzle control for cutting 3D profile parts, are presented. In these experiments, water pressure, feed rate, stand-off distance and inclination angle were varied as the most crucial process parameters. A case study of 3D cutting demonstrates that, with 3-axis control, tolerances of the order of magnitude of the positioning accuracy of the test set-up can be obtained.
Several guanosine analogues, i.e. acyclovir (and its oral prodrug valaciclovir), penciclovir (in its oral prodrug form, famciclovir) and ganciclovir, are widely used for the treatment of herpesvirus [i.e. herpes simplex virus type 1 (HSV-1), and type 2 (HSV-2), varicella-zoster virus (VZV) and/or human cytomegalovirus (HCMV)] infections. In recent years, several new guanosine analogues have been developed, including the 3-membered cyclopropylmethyl and -methenyl derivatives (A-5021 and synguanol) and the 6-membered D- and L-cyclohexenyl derivatives. The activity of the acyclic/carbocyclic guanosine analogues has been determined against a wide spectrum of viruses, including the HSV-1, HSV-2, VZV, HCMV, and also human herpesviruses type 6 (HHV-6), type 7 (HHV-7) and type 8 (HHV-8), and hepatitis B virus (HBV). The new guanosine analogues (i.e. A-5021 and D- and L-cyclohexenyl G) were found to be particularly active against those viruses (HSV-1, HSV-2, VZV) that encode for a specific thymidine kinase (TK), suggesting that their antiviral activity (at least partially) depends on phosphorylation by the virus-induced TK. Marked antiviral activity was also noted with A-5021 against HHV-6 and with D- and L-cyclohexenyl G against HCMV and HBV. The antiviral activity of the acyclic/carbocyclic nucleoside analogues could be markedly potentiated by mycophenolic acid, a potent inhibitor of inosine 5'-monophosphate (IMP) dehydrogenase. The new carbocyclic guanosine analogues (i.e. A-5021 and D- and L-cyclohexenyl G) hold great promise, not only as antiviral agents for the treatment of herpesvirus infections, but also an antitumor agents for the combined gene therapy/chemotherapy of cancer, provided that (part of) the tumor cells have been transduced by the viral (HSV-1, VZV) TK gene.
