The Rogers-Ramanujan continued fraction and a quintic iteration for

Properties of the Rogers-Ramanujan continued fraction are used to obtain a formula for calculating with quintic convergence.

     

Novel aerobic oxidation of primary sulfones to carboxylic acids

Primary alkyl aryl sulfones are converted to the corresponding carboxylic acids in fair to excellent yield through double deprotonation and exposure to atmospheric oxygen. The methodology allows for the convenient synthesis of (13)C labeled carboxylic acids.     

Effect of gender, season, and vitamin D status on bone biochemical markers in Saudi diabetes patients

Biochemical bone turnover markers (BTMs) provide important information on the diagnosis, therapy and monitoring of metabolic bone diseases. They are evident before measurable changes in bone mineral density (BMD) take place. A total of 35 adult Saudi patients (23 males; 12 females) with type 2 diabetes and diagnosed to be vitamin D deficient were recruited in this prospective study. Here we investigated the effects of gender, season, and vitamin D status on bone biochemical markers of bone remodeling. Anthropometry and blood samples were collected at different intervals. Metabolic parameters and bone biomarkers were measured routinely and by ELISA. Both males and females had a significant increase in their vitamin D status over time, but no significant changes in the bone biomarkers were observed in females. In males there was a significant increase in circulating levels of corrected calcium and OPN (p = 0.004 and 0.01 respectively) and a significant decrease in crosslaps (p = 0.005). In all subjects there was a modest but significant positive relationship between vitamin D status and OC (R = 0.34; p = 0.04). In conclusion, our study demonstrates that changes in bone remodeling markers are affected by season, gender, and possibly vitamin D status. This gender difference may well reflect the physiologic pathway responsible for the higher peak bone mass achieved in males compared to females.     

Experimental and theoretical study of the reaction of the ethynyl radical with nitrous oxide, C2H + N2O

We investigated the rate constants and reaction mechanism of the gas phase reaction between the ethynyl radical and nitrous oxide (C(2)H + N(2)O) using both experimental methods and electronic structure calculations. A pulsed-laser photolysis/chemiluminescence technique was used to determine the absolute rate coefficient over the temperature range 570 K to 836 K. In this experimental temperature range, the measured temperature dependence of the overall rate constants can be expressed as: k(T) (C(2)H + N(2)O) = 2.93 × 10(-11) exp((-4000 ± 1100) K/T) cm(3) s(-1) (95% statistical confidence). Portions of the C(2)H + N(2)O potential energy surface (PES), containing low-energy pathways, were constructed using the composite G3B3 method. A multi-step reaction route leading to the products HCCO + N(2) is clearly preferred. The high selectivity between product channels favouring N(2) formation occurs very early. The pathway corresponds to the addition of the terminal C atom of C(2)H to the terminal N atom of N(2)O. Refined calculations using the coupled-cluster theory whose electronic energies were extrapolated to the complete basis set limit CCSD(T)/CBS led to an energy barrier of 6.0 kcal mol(-1) for the entrance channel. The overall rate constant was also determined by application of transition-state theory and Rice-Ramsperger-Kassel-Marcus (RRKM) statistical analyses to the PES. The computed rate constants have similar temperature dependence to the experimental values, though were somewhat lower.     

Strategies for the Analysis of Pharmaceutical Cocrystals Using HPLC with Charged Aerosol Detection

Several active pharmaceutical ingredients are currently being developed as pharmaceutical cocrystals as these systems often have superior properties compared to traditional pharmaceutical forms. Pharmaceutical cocrystal formers typically used are polar, small molecule acids or bases which often lack a UV chromophore. Their polar nature results in almost no reversed phase retention and their detection typically cannot be done with UV. Here we discuss approaches for the analysis of pharmaceutical cocrystals using HPLC columns designed for polar retention, ion pairing chromatography (IPC), and hydrophilic interaction chromatography (HILIC) using model cocrystal formers. Corona charged aerosol detection (CAD) was used to monitor the cocrystal formers. l-alanine was used as a model basic cocrystal former, and succinic acid and glutaric acid were used as model acidic cocrystal formers. The acidic cocrystal formers were adequately retained on a C18 column. Heptafluorobutyric acid was used as the ion-pairing reagent for l-alanine as it was unretained without the ion-pairing reagent. HILIC, a newer approach for polar compound retention, was also investigated. Using the HILIC mode, all three model cocrystal formers were retained adequately. Of all the approaches studied for the analysis of the cocrystal formers, HILIC appears to be the best choice as the same column can be used for both acidic and basic cocrystal formers. With IPC, the ion-pairing reagent permanently alters the column chemistry and dedicated columns are required for each ion-pairing reagent used. CAD detection provided a linear response in the 80–100% test concentration range for the analytes studied here.     

On a linearized problem arising in the Navier–Stokes flow of a free liquid jet

In this work, we analyze a Stokes problem arising in the study of the Navier–Stokes flow of a liquid jet. The analysis is accomplished by showing that the relevant Stokes operator accounting for a free surface gives rise to a sectorial operator which generates an analytic semigroup of contractions. Estimates on solutions are established using Fourier methods. The result presented is the key ingredient in a local existence and uniqueness proof for solutions of the full nonlinear problem.     

Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

Combinatorial drug therapies emerge among the most promising strategies to treat complex pathologies such as cancer and severe infections. Biocompatible nanoparticles of mesoporous iron carboxylate metal–organic framework (nanoMOFs) are used here to address the challenging aspects related to the coincorporation of two antibiotics. Amoxicillin and potassium clavulanate, a typical example of drugs used in tandem, are efficiently coincorporated with payloads up to 36 wt%. Due to the occurrence of two distinct pore sizes/apertures within the MOF architecture, each drug is able to infiltrate the porous framework and localize within separate compartments. Molecular simulations predict drug loadings and locations consistent with experimental findings. Drug loaded nanoMOFs that are internalized by Staphylococcus aureus infected macrophages are able to colocalize with the pathogen, which in turn leads to an alleviation of bacterial infection. The data also reveal potential antibacterial properties of nanoMOFs alone as well as their ability to deliver a high payload of drugs to fight intracellular bacteria. These results pave the way toward the design of engineered “all‐in‐one” nanocarriers in which both the loaded drugs and their carrier play a role in fighting intracellular infections.     

Comparison of δ81Br and δ37Cl composition of volatiles,salt precipitates,and associated water in terrestrial evaporative saline lake systems

This study provides the first characterization of the variability of bromine and chlorine stable isotopic composition in evaporites, associated residual brines, and shoreline gases in terrestrial evaporative saline lakes. The lakes investigated here are groundwater discharge locations, and include both potash-rich alkaline lakes and sodic-dominated neutral pH lakes at a variety of salinities and evaporative stages. The chlorine and bromine isotope systems behave consistently different during evaporative salt precipitation, with ³⁷Cl more enriched in the salt than in the fluid, but ⁸¹Br more enriched in the fluid compared with the precipitated salt. The ⁸¹Br concentration of shore off-gassing was even smaller than mineral precipitate compositions. The trends observed for bromine isotopes are surprising compared with published laboratory studies, indicating that a process besides inorganic mineral precipitation is affecting δ⁸¹Br. Additional processes explored include diffusion, salt deflation, microbial and photolytic conversion to the gas phase, and oxidative bromination of organic matter.

Dedicated to Professor Peter Fritz on the occasion of his 80th birthday