Distribution of uranium and thorium in fractionated sediment samples obtained from different locations across Thane Creek area (Mumbai,India)

Uranium concentration varies from 9.01 to 12.7, 8.03 to 11.5, 9.1 to 14.0 and 10.1 to 14.2 mg/kg in grab sediment, coarse sand fraction, fine sand fraction, silt and clay fraction respectively. Thorium concentration varies from 20.0 to 29.4, 17.3 to 28.6, 19.6 to 30.4 and 21.1 to 35.9 in grab sediment, coarse sand fraction, fine sand fraction, silt and clay fraction respectively. Uranium and thorium concentrations vary in different size fractionated sediment samples like silt and clay fraction > fine sand fraction > coarse sand fraction.     

Probing the Microscopic Aspects of 1-Butyl-3-Methylimidazolium Trifluoroacetate Ionic Liquid and Its Mixture with Water and Methanol: A Photophysical and Theoretical (DFT) Study

Considering the potential of mixed ionic liquid-cosolvent systems in wide range of applications, photophysical and theoretical studies on an industrially important ionic liquid, 1-butyl-3-methylimidazolium trifluoroacetate (BMIMTFA), and also its mixture with water and methanol have been investigated. Two organic dipolar solutes coumarin 153 (C153) and 2-aminonitrofluorene (ANF) have been used as the probe molecule for the present study. Steady-state absorption and emission spectral behavior of C153 has not been significantly influenced by both the cosolvents. However, excitation wavelength dependent measurements with ANF in the BMIMTFA-water and BMIMTFA-methanol show entirely different photophysical response. For BMIMTFA-methanol system the average solvation and rotational time is found to be less than that in BMIMTFA-water system. Quite interestingly, time-resolved fluorescence anisotropy measurements reveal two different solute-solvent coupling constant (C _obs ) even if same mole fraction of water and methanol is used for the mixed solvent systems. Theoretical calculations also reveal stronger intermolecular interaction between IL and methanol than that between IL and water. The present combined photophysical and theoretical calculations seem to suggest different microscopic structural organization in the two binary systems.     

High-performance thin-layer chromatographic standardization and quantification of marker compounds in an Ayurvedic polyherbal formulation: Krishnadi Churna

JPC – Journal of Planar Chromatography – Modern TLC - The present era is witnessed by the increasing demand for herbal medicine. Therefore, the preparation of herbal drugs is warranted...     

Nickel(II) chloride as an efficient and useful catalyst for chemoselective thioacetalization of aldehydes

A wide variety of acyclic and cyclic dithioacetals can be prepared chemoselectively from the corresponding aldehydes by employing a catalytic amount of nickel(II) chloride in dry CH₂Cl₂-MeOH (5:1) at room temperature in good yields. Some of the major advantages of this procedure are high chemoselectivity, ease of operation, high yields and also compatibility with other protecting groups.     

Size quantization effect in GaAs nanocrystals

GaAs nanocrystals have been synthesized by an electrochemical route from the acidic solutions of metallic gallium and arsenic oxide. Structural analysis by transmission electron microscopy (TEM), reveales the presence of orthorhombic phase, in contrast to the usual cubic phase of bulk GaAs. Well separated GaAs nanocrystals having sizes in the range of 7 to 15 nm are identified in the TEM micrograph. Optical absorption shows a strong excitonic absorption band on account of quantum size effect associated with GaAs nanocrystals. Photoluminescence, recorded at 300 K under ultraviolet excitation (369 nm), shows the HOMO-LUMO transition band as well as the red shifted bands. Micro-Raman analysis shows a phonon mode centered at 250 cm⁻¹ associated with a point defect.     

Microscopic study of low-lying collective bands in77Kr

The structure of the collective bands in⁷⁷Kr is investigated within our deformed shell model (DSM) based on Hartree-Fock states. The different levels are classified into collective bands on the basis of their B(E2) values. The calculatedK = 5/2⁺ ground band agrees reasonably well with the experiment. An attempt has been made to study the structure of the 3-quasiparticle band based on large J state in this nucleus. The calculated collective bands, the B(E2), and B(M1) values are compared with available experimental data. The nature of alignments in the low-lying bands is also analyzed.     

Preparation, characterization, and photocatalytic activity of sulfate-modified titania for degradation of methyl orange under visible light

Hydrated titania was prepared by a sol-gel method, taking tetraisopropyl orthotitanate as starting material, and then promoted with different weight percentages of sulfate by an incipient wetness impregnation method. The materials were characterized by various advanced techniques such as PXRD, BET surface area, N(2) adsorption-desorption measurements, FTIR, and SEM. Analytical results demonstrated that TiO(2) is mesoporous in nature, and sulfate modification could inhibit the phase transformation and enhance the thermal stability of TiO(2). It was also found that sulfate modification could reduce the crystallite size and increase the specific surface area of the catalysts. The degradation of methyl orange under solar radiation was investigated to evaluate the photocatalytic activity of these materials. Effects of different parameters such as pH of the solution, amount of catalyst, additives, and kinetics were investigated. At 2.5 wt% sulfate loading, the average percentage of degradation of methyl orange was nearly two times than that of neat TiO(2). The photocatalytic degradation followed first-order kinetics.     

Enantioselective formal total syntheses of Clavukerin A and isoclavukerin A via a ring-closing metathesis reaction

Enantioselective formal total syntheses of the marine trisnorsesquiterpenes clavukerin A and isoclavukerin A, starting from (R)-limonene employing an RCM reaction as the key step, are described.     

Synthesis and characterization of novel low‐bandgap triphenylamine‐based conjugated polymers with main‐chain donors and pendent acceptors for organic photovoltaics

A series of novel low‐bandgap triphenylamine‐based conjugated polymers ( PCAZCN , PPTZCN , and PDTPCN ) consisting of different electron‐rich donor main chains (N‐alkyl‐2,7‐carbazole, phenothiazine, and cyclopentadithinopyrol, respectively) as well as cyano‐ and dicyano‐vinyl electron‐acceptor pendants were synthesized and developed for polymer solar cell applications. The polymers covered broad absorption spectra of 400–800 nm with narrow optical bandgaps ranging 1.66–1.72 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of ?5.12 to ?5.32 V and ?3.45 to ?3.55 eV, respectively. Under 100 mW/cm² of AM 1.5 white‐light illumination, bulk heterojunction photovoltaic devices composing of an active layer of electron‐donor polymers ( PCAZCN , PPTZCN , and PDTPCN ) blended with electron‐acceptor [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester or [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) in different weight ratios were investigated. The photovoltaic device containing donor PCAZCN and acceptor PC₇₁BM in 1:2 weight ratio showed the highest power conversion efficiency of 1.28%, with V_oc = 0.81 V, J_sc = 4.93 mA/cm², and fill factor = 32.1%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Chiral synthons from campholenaldehyde: enantiospecific synthesis of diquinane and linear triquinanes

Enantiospecific syntheses of diquinane and linear triquinanes were accomplished, starting from the readily available α-campholenaldehyde employing a Nazarov reaction as the key step.