4,552 publications from this institution
No abstract is provided for this article.
Trifluridine (TFT) and a structurally related analogue, 5-fluoro-2'-deoxyuridine (FDU), were investigated for their efficacy in the topical treatment of experimental keratitis caused by thymidine kinase-positive (TK+) and thymidine kinase-deficient (TK-) herpes simplex virus type 1 (HSV-1) strains. Bromovinyldeoxyuridine (BVDU) was used as a reference compound. Both 0.2% BVDU and 0.2% TFT eyedrops produced a highly significant healing of TK+HSV-1 keratitis as compared to the placebo and 0.2% FDU eyedrops (P much less than 0.005), whereas the latter compound did not differ from placebo eyedrops. In the treatment of TK HSV-1 keratitis, none of the drugs exhibited a beneficial healing effect, although the virus strain used was inhibited in vitro by TFT and FDU at a very low concentration (0.02-0.04 microgram/mL).
Absorptances and deposited energy profiles are calculated for thin layers of metallic powder placed on a reflective substrate at normal incidence of collimated radiation. Radiation transfer equation is analytically solved by the two-flux method. The effective optical parameters of the powder are estimated in geometrical optics approximation taking into account dependent scattering. The cases of specularly and diffusely reflecting particles are studied. Due to multiple reflections in an open pore system, laser radiation can penetrate in powder to considerable depths, much greater than the characteristic particle diameter. Total laser energy absorbed in a thin powder layer on a reflective substrate increases with its thickness but the deposited energy density decreases. Generally, the absorptance and the energy density for specular reflection are slightly greater than these values for diffuse reflection. The results obtained in the limit of deep powder bed essentially agree with known ray tracing simulations. The present model is in good agreement with experimentally observed correlation between effective absorptance of metallic powders and absorptance of corresponding dense metals.
Abstract The synthesis of a series of aryl bis(nucleosid-5′-yl)phosphates in which the nucleosides are either 2′,3′-dideoxy-(d2-) or 2′,3′-didehydro-2′,3′-dideoxy-(d4-) nucleosides is described. These were tested for anti-HIV activity and their efficacy and toxicity compared with the parent nucleosides. Only the 4-(methylsulphonyl)phenyl derivatives of d4T and d2A had any significant activity and had selectivity indices of the same order as the parent nucleosides. These findings can be explained by uptake of the triesters into cells followed by a slow release of nucleoside and nucleotide. In the case of some compounds (such as d2T and d2U) the 5′-monophosphate of which is known to inhibit thymidylate kinase, it is possible that the levels of nucleotide liberated are such that they are not processed into the 5′-triphosphate and hence no antiviral effect is seen.
No abstract is provided for this article.
No abstract is provided for this article.
Purpose Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation. Design/methodology/approach After each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing. Findings It is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure. Originality/value There has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.
Isatin/5-substituted Isatin was reacted with 2-aminothiazole, 2-aminopyridine, 4-methoxyaniline to form Schiff bases and the N-Mannich bases of the above Schiff bases were synthesized by reacting with formaldehyde and piperidine. The chemical structures of the synthesized compounds were confirmed by means of IR, 1H-NMR data and elemental analysis. Investigation of Anti-HIV activity was done against replication of HIV-1 (III B) and HIV-2 (ROD) in MT-4 cells. Azidothymidine (AZT) was used as the reference standard. The most active compound of the series was 3-(2-thiazolylimino)-5-bromo-1,3-dihydro-indol-2-one (VI) which demonstrated 28% and 10% protection against HIV-1 and HIV-2 respectively.
No abstract is provided for this article.
