The results of a comparative numerical study aimed at assessing the mixing performance of planar zig-zag, curvilinear, and square-wave microchannels of square cross-sections is presented in the paper. To evaluate the mixing enhancement characteristics of each geometry, suitable mixing indices are computed at different axial locations of a single repetitive module of each microchannel when fed with two equal streams of fluid having the same thermophysical properties but different solute concentrations. To separate the effects of the geometry from those of molecular diffusion, entrance flow, and channel length, the mixing in straight microchannels of the same length is also evaluated for comparison. Reynolds numbers in the range from 5 to 150 are considered. The study is performed both with reference to a fixed Péclet number, equal to 2500 and obtained by scaling the diffusion coefficient when varying the Reynolds number, and to a fixed diffusion coefficient, yielding a constant Schmidt number of 16.6. Pressure drops are also calculated. All numerical simulations are carried out using an in-house finite element code for the solution of all model equations. 相似文献
In this paper our previous researches dealing with compatibility, thermoanalytical characterization, the kinetics of thermal degradation of acetaminophen, either pure or contained in some commercial pharmaceutical formulations, have found applications outlets. In a previous investigation the possible interactions between acetaminophen and four excipients contained in the commercial pharmaceutical formulations were tested. As a continuation of this research in the present study an analytical method based on differential scanning calorimetry (DSC) was applied to determine the acetaminophen content of four commercial pharmaceutical formulations. For a fifth drug it was shown that the method is not applicable owing to observed incompatibility with one of the excipients. Finally, the analytical results obtained were compared with those derived from two UV spectrophotometric methods (one, i.e., “direct method,” recommended by the Pharmacopeia and the other based on the first-order derivative UV spectra). 相似文献
Herein we report novel pyrrole‐ and benzene‐based hydroxamates ( 8 , 10 ) and 2′‐aminoanilides ( 9 , 11 ) bearing the tert‐butylcarbamate group at the CAP moiety as histone deacetylase (HDAC) inhibitors. Compounds 8 b and 10 c selectively inhibited HDAC6 at the nanomolar level, whereas the other hydroxamates effected an increase in acetyl‐α‐tubulin levels in human acute myeloid leukemia U937 cells. In the same cell line, compounds 8 b and 10 c elicited 18.4 and 21.4 % apoptosis, respectively (SAHA: 16.9 %), and the pyrrole anilide 9 c displayed the highest cytodifferentiating effect (90.9 %). In tests against a wide range of various cancer cell lines to determine its antiproliferative effects, compound 10 c exhibited growth inhibition from sub‐micromolar (neuroblastoma LAN‐5 and SH‐SY5Y cells, chronic myeloid leukemia K562 cells) to low‐micromolar (lung H1299 and A549, colon HCT116 and HT29 cancer cells) concentrations. In HT29 cells, 10 c increased histone H3 acetylation, and decreased the colony‐forming potential of the cancer cells by up to 60 %. 相似文献
The efficiency of epoxy/CNT nanocomposites as photocatalyst on adsorbed, aqueous and gas phases is investigated. Epoxy films containing SWNTs in the range between 0.1 and 0.3 wt% are prepared by means of UV‐induced polymerization and the achieved materials are used as photocatalysts on adsorbed, aqueous, and gas phases. The activity of this new photocatalytic materials is evaluated in the adsorbed state by using the methylene blue target molecule, in the aqueous phase by following the photodegradation of phenol and 3,5‐dichlorophenol, and in the gas phase using nitrogen monoxide as probe molecule. It is demonstrated that the catalyst is suitable for both oxidative and reductive degradation reactions.
A catalytic asymmetric addition of nitroalkanes to alkylideneindolenines, generated in situ from arylsulfonylindoles, is presented. Despite the weakness of the non‐covalent H‐bond interactions between catalyst and substrates, the performance of the bifunctional organocatalyst used was found to be essentially unaffected by the polarity of the reaction medium. Nitroalkanes, mostly used in nearly stoichiometric amounts, could thus function both as solvents and reagents, resulting in a truly solvent‐free reaction. The broad substrate scope shown by the present transformation allowed the preparation of some optically active tryptamine precursors that are not accessible through the previous catalytic asymmetric methods. 相似文献
One of the most prominent alterations in cancer cells is their strict dependence on the glycolytic pathway for ATP generation. This observation led to the evaluation of glycolysis inhibitors as potential anticancer agents. The inhibition of lactate dehydrogenase (LDH) is a promising way to inhibit tumor cell glucose metabolism without affecting the energetic balance of normal tissues. However, the success of this approach depends chiefly on the availability of inhibitors that display good selectivity. We identified a compound (galloflavin, CAS 568‐80‐9) which, in contrast to other inhibitors of human LDH, hinders both the A and B isoforms of the enzyme. To determine the mechanism of action, we collected LDH‐A and ‐B inhibition data in competition reactions with pyruvate or NADH and evaluated the results using software for enzyme kinetics analysis. We found that galloflavin inhibits both human LDH isoforms by preferentially binding the free enzyme, without competing with the substrate or cofactor. The calculated Ki values for pyruvate were 5.46 μM (LDH‐A) and 15.06 μM (LDH‐B). In cultured tumor cells, galloflavin blocked aerobic glycolysis at micromolar concentrations, did not interfere with cell respiration, and induced cell death by triggering apoptosis. To our knowledge, the inhibition of LDH is, to date, the only biochemical effect described for galloflavin. Because galloflavin is not commercially available, we also describe herein a procedure for its synthesis and report its first full chemical characterization. 相似文献