Synthesis of Polylactide: Effect of Dispersion of the Initiator

The ring opening polymerization of L-lactide was studied in bulk using stannous octoate as initiator. In some experiments, triphenylphosphine, a Lewis base was also used as co-initiator. The polymerization was carried out at 130°C up to 29 h. The monomer was used after recrystallizing three times with dry toluene. Experiments were carried out using a wide range of monomer to initiator ratio. The averages and distributions of molar masses of resulting PLA have been determined by means of size exclusion chromatography, SEC. It is shown that the (mode, process) procedure of dispersion of the catalyst in polymerization system affects the molar mass distribution of the product as is evidenced by the bimodality or even trimodality observed in the SEC chromatograms.     

Surface modification of semiconductor photoelectrodes for better photoelectrochemical performance

The present paper describes the modification and solar hydrogen production studies employing a new semiconductor-septum (SC-SEP) photoelectrode ns-TiO₂/In₂O₃ based photoelectrochemical solar cell. The current-voltage characteristics of the above SC-SEP cell revealed that an enhancement in short-circuit current (I_SC) up to three times (5 ～ 14.6 mA cm^?2). The optimum hydrogen production rate was found to be 11.8 lh^?1 m^?2 for 5M H₂SO₄ and with a further increase in H₂SO₄ concentration, the hydrogen production rate was found to be invariant. In yet another part of our study instead of using new SC-SEP solar cell design, we used another new oxide material form such as ns-TiO₂/WO₃. The ns-TiO₂/WO₃ exhibited a high photocurrent and photo-voltage of 15.6 mA cm^?2, 960 mV, respectively. The ns-TiO₂/WO₃ electrode exhibited a higher hydrogen gas evolution rate of 13.8 lh^?1 m^?2. Evidences and arguments are put forward to show that, whereas for the bare ns-TiO₂ electrode, the improvement in the performance of this photo-electrode compared with its original form was due to the higher quantum yield. In the case of ns-TiO₂/In₂O₃ and ns-TiO₂/WO₃ photo-electrodes, the improvement is due to the improved spectral response resulting from decrease of energy band gap.     

Comparative Antioxidant Study of Stem and Stem Induced Callus of Phyllanthus fraternus Webster—An Important Antiviral and Hepatoprotective Plant

Phyllanthus fraternus is widely used in the cure of various liver diseases and possess antiviral properties especially against hepatitis virus. In the present study, evaluation of the antioxidant activity of stem and calli induced from stem has been done by different assays. Extraction was done by standard method in water and ethanol. Total antioxidant capacity was measured by 1, 1-diphenyl-2-picrylhydrazyl free radical scavenging method. Lipid peroxidation was measured in terms of thiobarbituric acid-reactive substances (TBARS) by using egg yolk homogenates as lipid-rich media, and superoxide radical scavenging activity was measured using riboflavin–light–nitro blue tetrazolium assay. Reducing power was determined on the basis of Fe³⁺–Fe²⁺ transformation in the presence of the extract. In addition to the antioxidant activity, polyphenolic compounds like total phenolics and flavonoids were also measured by spectroscopic method. Results showed that the ethanolic extract of stem is more potent in antioxidant activity than its aqueous extract and ethanolic extract of calli. A significant correlation between antioxidant capacity and polyphenolic content and reducing potential was observed, indicating that phenolic compounds and reducers present in extract are major contributors to the antioxidant potential. Thus, this plant extract could be used as a potent natural antioxidant.     

Spectrophotometric analysis of trichloroethylene in various environmental and biological samples

A simple sensitive extractive spectrophotometric method for determination of trichloroethylene is proposed. Trichloroethylene is treated with pyridine to form glutaconic aldehyde by heterolytic cleavage of the pyridine ring. Glutaconic aldehyde is further coupled with 4-aminoacetanilide to form an orange–red dye which is extractable in 3-methyl-1-butanol. The extracted dye shows absorption maximum at 520 nm. The system obeys Beer’s law in the range of 0.05–0.8 μg mL^?1. Important analytical parameters such as time, temperature, reagent concentration, acidity etc. have been optimized for complete colour reaction. Sandell’s sensitivity and molar absorptivity for the system were found to be 0.001 μg cm^?2 and 1.2 × 10⁵ L mol^?1 cm^?1, respectively. The proposed method is satisfactorily applied to micro-level determination of trichloroethylene in various environmental and biological samples.     

Conifers Phytochemicals: A Valuable Forest with Therapeutic Potential

Conifers have long been recognized for their therapeutic potential in different disorders. Alkaloids, terpenes and polyphenols are the most abundant naturally occurring phytochemicals in these plants. Here, we provide an overview of the phytochemistry and related commercial products obtained from conifers. The pharmacological actions of different phytochemicals present in conifers against bacterial and fungal infections, cancer, diabetes and cardiovascular diseases are also reviewed. Data obtained from experimental and clinical studies performed to date clearly underline that such compounds exert promising antioxidant effects, being able to inhibit cell damage, cancer growth, inflammation and the onset of neurodegenerative diseases. Therefore, an attempt has been made with the intent to highlight the importance of conifer-derived extracts for pharmacological purposes, with the support of relevant in vitro and in vivo experimental data. In short, this review comprehends the information published to date related to conifers’ phytochemicals and illustrates their potential role as drugs.     

Nanotextured multicrystalline Al‐BSF solar cells reaching 18% conversion efficiency using industrially viable solar cell processes

We report recent achievements in adapting industrially used solar cell processes on nanotextured surfaces. Nanostructures were etched into c‐Si surfaces by dry exothermic plasma‐less reaction of F species with Si in atmospheric pressure conditions and then modified using a short post‐etching process. Nanotextured multicrystalline wafers are used to prepare Al‐BSF solar cells using industrially feasible solar cell proc‐ essing steps. In comparison to the reference acidic textured solar cells, the nanostructured cells showed gain in short circuit current (J_sc) of up to 0.8 mA/cm² and absolute gain in conversion efficiency of up to 0.3%. The best nanotextured solar cell was independently certified to reach the conversion efficiency of 18.0%. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Pd(II) inhibition during hexacyanoferrate(III) oxidation of sugars: A kinetic study

An inhibition effect of PdCl₂ on the rate of oxidation of sugars by alkaline hexacyanoferrate(III) has been observed. The order of reactions in hexacyanoferrate(III) and OH⁻ is zero and unity, respectively, while that in sugars decreases from unity at higher sugar concentration. The kinetic data and spectrophotometric evidence support the formation of {Pd^II − (sugar)} and {Pd^II − sugar)₂} complexes and their resistance to react with Fe(CN)₆³⁻ © 1996 John Wiley & Sons, Inc.     

Nanocrystalline Zn1−x Ag x O y thin films evolved through electrodeposition for photoelectrochemical splitting of water

Nanocrystalline Zn_1???x Ag _x O _y (x?=?10^??3???50?×?10^??3) thin films evolved through electrodeposition over ITO substrate have been investigated for photoelectrochemical splitting of water. Samples were characterized by XRD, EDX, SEM, AFM, UV–visible optical absorption, and Mössbauer spectral analysis. Ag incorporation led to a decrease in the band gap energy and alterations in microstructural and semiconductor properties. Raising Ag concentration in samples up to 1 % at. caused a significant reduction in density and electrical resistivity, enhanced absorption along with red shift to the band gap energy, anodic shift in flat band potential, and increased charge carrier density, enabling 1 % at. Ag-incorporated ZnO films most photosensitive by yielding highest short-circuit current, photocurrent density, and applied bias photon to current efficiency. Plausible reasons have been offered.     

Hilbert functions of points on Schubert varieties in orthogonal Grassmannians

Given a point on a Schubert variety in an orthogonal Grassmannian, we compute the multiplicity, more generally the Hilbert function. We first translate the problem from geometry to combinatorics by applying standard monomial theory. The solution of the resulting combinatorial problem forms the bulk of the paper. This approach has been followed earlier to solve the same problem for Grassmannians and symplectic Grassmannians.