Symbiotic Control in Mechanical Bond Formation

Since the advent of mechanically interlocked molecules (MIMs), many approaches to templating their formation using various different noncovalent bonding interactions have been introduced and explored. In particular, employing radical‐pairing interactions between BIPY^.+ units, the radical cationic state of 4,4′‐bipyridinium (BIPY²⁺) units, in syntheses is not only a convenient but also an attractive source of templation because of the unique properties residing in the resulting catenanes and rotaxanes. Herein, we report a copper‐mediated procedure that enables the generation, in the MIM‐precursors, of BIPY^.+ radical cations, while the metal itself, which is oxidized to Cu^I, catalyzes the azide–alkyne cycloaddition reactions that result in the efficient syntheses of two catenanes and one rotaxane, assisted by radical‐pairing interactions between the BIPY^.+ radical cations. This procedure not only provides a fillip for making and investigating the properties of Coulombically challenged catenanes and rotaxanes, but it also opens up the possibility of synthesizing artificial molecular machines which operate away from equilibrium.     

Nitro-Porphyrin Entrapped in a Silica Matrix by Sol-Gel Methodology

This work describes the preparation of the iron (III) porphyrin, FeTDCNO₂, entrapped in a silica matrix in the form of powder (FePD) or thin film using the sol-gel process. The films were obtained from sols using the dip-coating technique. The variables involved in the FePD preparation were analysed by a fractional factorial design with resolution 5, designated by 2 _V ^{5 – 1}. The variables which present a positive effect and maximise the loading of the studied ironporphyrin on the FePD material are solvent, water volume and reaction time. The utilization of pyridine or imidazole as template does not affect the preparation of the FePD material. The UV-visible absorption spectra of all prepared materials present the characteristic Soret band of ironporphyrins at 419–420 nm.The materials were analysed by thermogravimetric analysis, isotherm of nitrogen adsorption, ²⁹Si NMR and scanning electron micrograph. The catalytic performance of FePD-imidazole on the epoxidation of z-cyclooctene with iodosylbenzene is similar to that of FeTDCNO₂ in homogeneous solution (60 and 52%).     

Liquid chromatography-accurate radioisotope counting and microplate scintillation counter technologies in drug metabolism studies

The present study involves an analysis of the performance of liquid chromatography (LC)-accurate radioisotope counting (ARC) and microplate scintillation counter (TopCount) technologies in drug metabolism studies. For the purpose of evaluating these systems, biological samples resulting from the metabolism of a radiolabeled [14C] compound, known as compound B, are analyzed using LC-ARC and TopCount under similar high-performance LC conditions. Counting efficiency is 83% for LC-ARC, 77% for TopCount, and linearity is R2 of 0.9998 versus 0.9984, respectively. The limit of detection for LC-ARC is 12 disintegrations per minute (dpm) with 1-min/fraction counting, yet for TopCount it is 8.7 dpm with 5-min/fraction counting. Under optimal conditions for each, the total run time of LC-ARC is approximately half that of TopCount. These results indicate that there is no significant difference between these two systems in terms of efficiency, linearity, and limit of detection. However, the LC-ARC system does not involve any manual operations, yet TopCount requires manual sample transfer and data import. This study shows that impressive progress has been made in the technology of radioisotope counting in drug metabolism using LC-ARC. This system enhances the resolution of radiochromatograms and is able to measure volatile metabolites that TopCount cannot detect at all. The ability to acquire mass spectra online is also a major advancement. The overall results suggest that the combination of LC-ARC with radioactivity detection and mass spectrometry has great potential as a powerful tool for radioisotope measurement in metabolite identification studies during drug discovery and development.     

Flow of elasto-viscoplastic liquids through an axisymmetric expansion–contraction

In this work, we used a recently proposed constitutive model that addresses the elastic behavior of viscoplastic liquids. We used the equation in an expansion–contraction axisymmetric flow, and compared the results with experimental data found in the literature. Steady, inertialess numerical solutions were obtained by solving the balance equations of mass and momentum via the finite element method. We obtained the velocity and stress fields for different combinations of the governing parameters, and observed that elasticity leads to significant changes in the shape and position of the yield surface, affecting both the extra-stress and the rate of deformation fields in the cavity. The trends observed are in qualitative agreement with visualization results available in the literature.     

Computer geometry and encoding the information on a manifold

In this review, we try to answer the following question why should one study differential geometry? First of all, differential geometry is a Jewel of Mathematics. It is a prerequisite for theoretical physics. Secondly, in recent years, new and important applications have been discovered. Surprisingly, the structures of differential geometry are ideally suited for coding theory, information geometry and imaging process, kinematics of Robotics and computer aided geometric design, optimization and so on The main goal of the review is to establish a bridge between the theoretical aspects of modern geometry and topology on the one hand and computer experimental geometry on the other. The flood of information through various computer networks such as the internet characterizes the world situation in which we live. Information words, often called virtual spaces and cyberspace, have been formed on computer networks. The complexity of information worlds has been increasing almost exponentially through the exponential growth of computer networks. Such nonlinearity in growth and in scope characterizes information words. In other words the characterization of nonlinearity is the key to understanding, utilizing and living with the flood of information. The characterization approach is by characteristic points such as peaks, pits, and passes, according to the Morse theory on the manifold. Another approach is by singularity signs such as folds, cusps bifurcation, nodes, butterfly and swallowtail. Atoms and molecules are the other fundamental characterization approach. Topology and geometry including differential topology, serve as the framework for the characterization.     

On-line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons in seawater samples and its application to Japan Sea

An on?line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons (PAHs) in seawater was proposed. An online concentration column packed with octadecyl polyvinyl alcohol polymer, a pump and a column switching valve were introduced in the conventional HPLC with a fluorescence detector. Only 1.0-100?mL seawater sample was introduced into the concentration column at 1.0?mL?min(-1) without any other pretreatment except filtration. Then the trapped PAHs totally flew into the separation column and eluted separately to be detected fluorogenically. The proposed method had good linearity with correlation coefficients (r) ranged from 0.951 to 0.998, and limits of detection ranged from 0.002 to 0.50?ng?L(-1) for 15 PAHs as 100?mL seawater was loaded. The sensitivity of the method was 10 to 100 times higher than those reported by other works. The proposed method was applied to the determination of PAHs in the seawater samples collected in the Japan Sea with satisfactory results and to check the present benzo[a]pyrene concentration at the beaches in Noto peninsula, Japan polluted with C-heavy oil spilled from the tanker in 1997.     

Optimization and validation of an RP-HPLC method for direct determination of metformin hydrochloride in human urine and in a dosage form

A simple, selective, sensitive, accurate, and precise method was developed for determination of metformin hydrochloride (MF) in human urine using RP-HPLC. The method depends upon using an octylsilyl (C8) 5 microm particle size column at ambient temperature with mobile phase consisting of 33 mM sodium dihydrogen phosphate containing 6.38 mM hexanesulfonic acid sodium salt and adjusted to apparent pH 3.0 with phosphoric acid-acetonitrile (93 + 7, v/v) at a flow rate of 1.5 mL/min. Quantitation was achieved with UV detection at 231 nm based on peak area with a linear calibration curve over the concentration range of 0.01-50 microg/mL. The proposed method was applied to the determination of the urinary excretion pattern of MF (the cumulative amounts excreted were calculated without pretreatment of the urine sample) and for determination of the dissolution pattern of MF tablets. The proposed method was completely validated according to the U.S. Food and Drug Administration guidelines.     

Reflectance near-infrared spectroscopic method with Chemometric techniques for simultaneous determination of Chondroitin, glucosamine, and methyl sulfonyl methane

Reflectance near-IR (RNIR) spectroscopy was used for the simultaneous determination of chondroitin (CH), glucosamine (GO), and methyl sulfonyl methane (MSM) in tablets. Simple sample preparation was done by grinding, sieving, and compression of the tablets for improving RNIR spectra. Principal component regression and partial least squares (PLS-1 and PLS-2) were successfully applied to quantify the three components in the studied mixture using information included in RNIR spectra in the range of 4350-9100 cm(-1). The calibration model was developed with drug concentration ranges of 14.5-44.2% (w/w) for CH, 18.4-55.3% (w/w) for GO, and 6-18.6% (w/w) for MSM with addition of tablet excipients to the calibration set in the same ratio as in the tested tablets. The calibration models were evaluated by internal validation, cross-validation, and external validation using synthetic and pharmaceutical preparations. The proposed method was applied for analysis of six batches of the pharmaceutical product. The results of the proposed method were compared with the results of the pharmacopoeial method for the same batch of the pharmaceutical product. No significant differences between the results were found. The RNIR method is accurate and precise, and can be used for QC of pharmaceutical products.