Several approaches can be envisaged in the design of nucleoside and oligo- or polynucleotide analogues with selective antiviral activity: (i) deoxythymidine (dThd) or deoxycytidine (dCyd) analogues which are specifically recognized as substrate by the virus-induced dThd-dCyd kinase; (ii) adenosine analogues which impair transmethylation reactions (or polyamine biosynthesis), by virtue of an inhibition of S-adenosylhomocysteine hydrolase; (iii) (2'-5')-oligonucleotide analogues derived from pppA(2'p5'A)2, an important intermediate in the antiviral action of interferon; (iv) oligo(deoxy)nucleotides that are complementary to a well-defined nucleotide sequence of the viral genome; (v) single-stranded homopolynucleotides that act as antitemplates for virus-associated RNA or DNA polymerases; and (vi) double-stranded homopolynucleotides that may be pursued for their interferon-inducing potentials.
Characterization of different PA powders to determine their applicability for laser sintering
This study investigates the feasibility of manufacturing polyamide-12 microfiltration membranes through selective laser sintering (SLS). This process is different from traditional solvent casting methods, which have limited control over the membrane structure. The SLS technique also eliminates the usage of solvent, which lowers the production cost and avoids environmental issues. In this study, different processing parameters including laser power, hatch spacing and laser scan count are used to optimize the membrane performance. The laser energy density is shown to be directly linked with pure water flux and rejection. A laser energy density of 0.1J/mm2 results in membranes with the highest rejection and relatively high pure water flux. This work offers an alternative approach for fabrication of membranes for microfiltration. The findings in this exploratory study offer a perspective for optimization of membrane performance in future work.
Several water-soluble ester derivatives of acyclovir [9-[(2-hydroxyethoxy)methyl]guanine], i.e., the 2'-O-glycyl-, 2'-O-alpha-alanyl-, 2'-O-beta-alanyl- and 2'-O-3-carboxypropionyl esters, were synthesized and evaluated for their antiviral activity in cell culture. The compounds were all prepared directly from acyclovir by application of the usual esterification methods with the appropriate acyl precursors and isolated as their hydrochloride or sodium salts. When assayed in primary rabbit kidney cell cultures against various herpes simplex virus type 1 and type 2 strains, the four acyclovir esters proved almost as active as acyclovir itself, suggesting that they were readily hydrolyzed to release the parent compound.
Abstract Derivatives of TSAO-T based upon pentofuranose sugars with the L-configuration have been prepared and evaluated as inhibitors of HIV-1 induced cytopathicity.
At the high cutting speeds typical for machining with ceramics and the concomitant high temperatures generated at the cutting edge and the rake face of the tool, chemical interaction between tool and workpiece material becomes the predominant mode of tool wear. Commercial SiA1ON and YSiA1ON cutting tools are known to be unsuitable for the machining of steel because of the chemical incompatibility of these materials at elevated temperatures. In this work, the flank and crater wear behaviour in turning steel with a number of experimental ceramics, belonging to the Si3N4-SiO2-A1N-A12O3 system, are compared with that of a commercial YSiA1ON cutting tool and the influence of the workpiece composition on the wear behaviour is investigated. The relative tool wear of the different ceramics is compared with the predicted mechanical wear by abrasion, calculated from the mechanical properties of the ceramics, and the predicted chemical wear, estimated from equilibrium solubility calculations of the ceramic in pure iron. The relative crater and flank wear of the different ceramics correlates well with the predicted chemical wear. Those ceramics with a low solubility in pure iron were not sensitive towards crater formation and showed the least flank wear of the investigated ceramics, although the modest mechanical properties of these ceramics makes them more sensitive to abrasion. The relative tool wear during turning is correlated with the reactivity measured in static interaction couples.