Effect of oral beta-carotene supplementation on plasma human immunodeficiency virus (HIV) RNA levels and CD4+ cell counts in HIV-infected patients

We conducted a pilot, open-label study to assess the effect of short-term beta-carotene administration (180 mg/d with meals for 4 weeks) on the plasma human immunodeficiency virus (HIV) RNA levels and CD4+ lymphocyte counts in 21 HIV-infected patients. We found that plasma HIV RNA levels and CD4+ lymphocyte counts did not change following this short course of beta-carotene supplementation. Patients with lower serum concentrations of beta-carotene before supplementation were no more likely to have an increase in their CD4+ lymphocyte count or plasma HIV RNA copy number than were those with higher concentrations. No correlation was found between pre- or postsupplementation beta-carotene or vitamin A concentrations and pre- or postsupplementation CD4+ lymphocyte counts or plasma HIV RNA titers. This study provides no support for beta-carotene supplementation for HIV-infected subjects with normal baseline serum levels of beta-carotene and vitamin A.     

Active transport of nitrofurantoin across the mammary epithelium in vivo

Nitrofurantoin is a commonly used urinary tract antibiotic that has been found at high concentrations in human milk. In vivo studies in rats were carried out to determine the mechanism by which this drug crosses the mammary epithelium. Lactating rats were gavage-fed with nitrofurantoin, and their milk and plasma levels of the antibiotic were measured at intervals up to 8 hr. The average milk-to-plasma (M/P) ratio, calculated from the areas under the milk and plasma curves, respectively, was 23 compared with a ratio predicted to be about 0.3 on the basis of lipid partitioning and protein binding determinations. M/P ratios for two nitrofurantoin congeners were also calculated. The neutral compound furazolidone had a M/P ratio of about 1, as predicted, whereas the basic compound furaltadone had a M/P ratio of 3.49 compared with a predicted ratio of 1.4. These data suggest that nitrofurantoin and, to a lesser extent, furaltadone are actively transported across the mammary epithelium into milk.     

Determining robust reaction kinetics from limited data

Accurate chemical kinetics are essential for reactor design and operation. However, despite recent advances in “big data” approaches, availability of kinetic data is often limited in industrial practice. Herein, we present a comparative proof-of-concept study for kinetic parameter estimation from limited data. Cross-validation (CV) is implemented to nonlinear least-squares (LS) fitting and evaluated against Markov chain Monte Carlo (MCMC) and genetic algorithm (GA) routines using synthetic data generated from a simple model reaction. As expected, conventional LS is fastest but least accurate in predicting true kinetics. MCMC and GA are effective for larger data sets but tend to overfit to noise for limited data. LS-CV strongly outperforms these methods at much reduced computational cost, especially for significant noise. Our findings suggest that implementation of CV with conventional regression provides an efficient approach to kinetic parameter estimation with high accuracy, robustness against noise, and only minimal increase in complexity.     

Preparation of microwave‐assisted polymer‐grafted softwood kraft pulp fibers. Enhanced water absorbency

A wood pulp cellulose‐based hydrogel material was prepared with poly(methyl vinyl ether‐co‐maleic acid) (PMVEMA), polyethylene glycol (PEG), and softwood ECF kraft pulp via microwave and thermal esterification and compared via hydrogel absorption and retention of water and 0.10M NaCl. The microwave initiated reaction time was optimized to 105 s at 1600 W based on maximum water absorption of 96 g/g of the 49% PMVEMA pulp hydrogels. The influence of reaction variables such as pulp fiber size and the weight ratios of PMVEMA to pulp were investigated. The maximum water absorbency of the milled pulp fibers microwave initiated products was 151 g/g, whereas the maximum water absorbency of the milled pulp fibers thermally initiated hydrogels was 198 g/g. In addition, the microwave initiated hydrogels retained a maximum of 67% of absorbed water after centrifugation at 770 rpm for 10 min, whereas the thermally initiated hydrogels retained a maximum of 49% of water absorbed. Fourier transform infrared spectroscopy (FTIR) was used to confirm the esterification of the PMVEMA with the pulp cellulose. Microwave initiated crosslinking successfully produced a pulp hydrogel with a shorter reaction time and comparable or improved water absorption and retention properties when compared with the traditional thermally crosslinked pulp hydrogel system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Composite electrocatalysts for anodic methanol and methanol-reformate oxidation

Binary anode electrocatalyst formulations were prepared by adsorption of phthalocyanine and tetraphenylporphyrin complexes of different transition metals on a commercial carbon supported platinum catalyst. Only after pyrolyzing the complexes at 700 °C under nitrogen were catalysts of some activity obtained. A binary Pt/Ni electrocatalyst prepared by this procedure exhibits considerable anodic catalytic activity in the acidic environment of the Nafion^® electrolyte for reformate and direct methanol oxidation for more than 400 h without deterioration. Ternary electrocatalyst formulations Pt/Ru/W = 1/1/y were produced according to the Bönnemann method. The Pt/Ru/W catalyst of 1/1/1.5 (mol/mol/mol) composition is optimal. Compared to the Pt/Ru catalyst, it enhances the performance of reformate (H₂ + 150 ppm CO) fuel cells by 50% and of direct methanol fuel cells (steam/methanol vapour = 50:1 mol/mol) by 80%. Attached to a GC electrode by a thin Nafion^® film, the catalysts were also tested for methanol oxidation in aqueous methanol solutions in half cells by slow potential stepping. This procedure is useful for fast initial screening.     

Synthesis and characterization of carbon-supported Pt–Ru–WOx catalysts by spectroscopic and diffraction methods

Carbon-supported Pt–Ru–WO_x/C catalysts for application in PEMFC anodes were synthesized by a modified Bönnemann method. Their electrocatalytic activity for the oxidation of H₂/CO mixtures and CH₃OH was measured by E/i-curves in PEM single cell arrangements under working conditions. Information about composition, microstructure and nanomorphology was obtained by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence analysis (XFA) and transmission electron microscopy (TEM). X-ray diffraction data at room temperature show only one single Pt f.c.c. phase; no evidence of Ru, W and their oxides, respectively, is found. Hence, the presence of W and Ru as amorphous oxide species seems likely. Surface-sensitive XPS measurements detect Pt⁰, platinum oxide and hydroxide species, metallic Ru, ruthenium oxide, hydrous ruthenium oxide and WO₃. For the crystalline platinum phase particle sizes of less than 2 nm were determined by TEM images and XRD patterns via solving the Scherrer equation. Temperature-dependent XRD measurements were performed to show the influence of ageing on the catalyst structure.     

Chemical Defenses of the Sacoglossan Mollusk Elysia rufescens and Its Host Alga Bryopsis sp.

Sacoglossans are a group of opisthobranch mollusks that have been the source of numerous secondary metabolites; however, there are few examples where a defensive ecological role for these compounds has been demonstrated experimentally. We investigated the deterrent properties of the sacoglossan Elysia rufescens and its food alga Bryopsis sp. against natural fish predators. Bryopsis sp. produces kahalalide F, a major depsipeptide that is accumulated by the sacoglossan and that shows in vitro cytotoxicity against several cancer cell lines. Our data show that both Bryopsis sp. and Elysia rufescens are chemically protected against fish predators, as indicated by the deterrent properties of their extracts at naturally occurring concentrations. Following bioassay-guided fractionation, we observed that the antipredatory compounds of Bryopsis sp. were present in the butanol and chloroform fractions, both containing the depsipeptide kahalalide F. Antipredatory compounds of Elysia rufescens were exclusively present in the dichloromethane fraction. Further bioassay-guided fractionation led to the isolation of kahalalide F as the only compound responsible for the deterrent properties of the sacoglossan. Our data show that kahalalide F protects both Bryopsis sp. and Elysia rufescens from fish predation. This is the first report of a diet-derived depsipeptide used as a chemical defense in a sacoglossan.     

Modeling heterogeneous photocatalytic inactivation of E. coli using suspended and immobilized TiO2 reactors

A study was carried out to develop a kinetic model of the photocatalytic inactivation of Escherichia coli using different TiO₂ catalysts. The model developed is based on a reaction scheme that involves effectively coupling mass‐transfer fluxes between bacteria and catalyst surface on one hand and bacterial degradation reaction on the other. The photocatalytic results were derived from experiments led in a batch reactor under both dark and Ultra Violet (UV) irradiation conditions. Using a reference catalyst, the robustness of the developed model was tested under solar conditions. The experimental data validated the model as successfully able to reproduce evolutions in the viable bacteria concentration in the range of parameters studied without any further adjustment of the kinetic parameters. The model was used to simulate the bacterial degradation kinetics under different working conditions to describe the partitioning of both bacterial adhesion and photocatalytic reaction in the solution to be treated © 2015 American Institute of Chemical Engineers AIChE J, 61: 2532–2542, 2015     

Influence of Sr2+ on Calcium‐Deficient Hydroxyapatite Formation Kinetics and Morphology in Partially Amorphized α‐TCP

Hydration of partially amorphized α‐TCP powders with Sr²⁺ concentrations ranging from 0 to 10 mol% substitution for Ca²⁺ was analyzed by isothermal calorimetry and quantitative in‐situ XRD. Hydration of both crystalline α‐TCP and amorphous TCP (ATCP) forming CDHA was retarded to an increasing extent with increasing Sr²⁺ content. Sr²⁺ slightly reduced the crystallite size (XRD coherent scattering domains) of the CDHA formed during hydration, while the size of crystals visible under SEM was not noticeably affected. Reaction enthalpies of ΔH_{R(Sr‐α‐TCP→Sr‐CDHA)} = 122 ± 8 J/g_TCP and ΔH_{R(Sr‐ATCP→Sr‐CDHA)} = 257 ± 8 J/g_TCP were determined for the hydration of crystalline α‐TCP and ATCP containing 5 mol% Sr²⁺ substitution for Ca²⁺. This is comparable with the corresponding reaction enthalpies previously obtained for undoped samples, which are 106 ± 7 J/g_TCP for α‐TCP and 250 ± 7 J/g_TCP for ATCP.