Effects of hypochlorite treatment on the surface morphology and mechanical properties of polyethersulfone ultrafiltration membranes

Polyethersulfone membranes are widely used for ultrafiltration and microfiltration especially in the dairy industry, but they are believed to degrade when exposed to the sodium hypochlorite solution that is used to sanitize the processing equipment. Such membranes were exposed to sodium hypochlorite for up to 25,000 ppm-day at 55 °C, and pH 9 and 12. Mechanical properties as measured by dynamic mechanical analysis and tensile strength did not change greatly, but surface properties measured by FTIR-ATR, field emission scanning electron microscopy and associated energy dispersive X-ray spectroscopy detected significant changes in the surface. Surface pitting was observed and was found to be most severe at pH 9. It was thought that pitting was the likely cause of degradation in performance of the membranes and that pits could act as stress raisers leading to cracking.     

Temperature-dependent volumetric and viscometric properties of amino acids in aqueous solutions of an antibiotic drug

Volumetric and viscometric properties of glycine and methionine (amino acids) in a 0.2 vol. % amikacin sulphate (antibiotic drug) aqueous solution with the molality range of 0.025 mol kg^?1–0.25 mol kg^?1 were measured over the temperature range of 20°C–40°C at the interval of 5°C. Different parameters like apparent molar volume (? _V), apparent molar adiabatic compression (? _κ ), isentropic compression (κ _S) along with other acoustical parameters were calculated. Parameters like viscous relaxation time (τ), free volume (V _F), internal pressure (Π _I), and molar cohesive energy (MCE) were calculated from dynamic viscosity measurements. The ? _V values are positive in both cases, but with higher magnitude observed in methionine. These positive values of ? _V are indicative of strong solute-solvent interactions at all temperatures. In case of methionine there is a sharp initial increase in the ? _V values which become almost constant with further additions of the amino acid. Structural differences in the two amino acids studied are clearly reflected in the different nature of the plots of different parameters. In case of an amino acid-drug system, dynamic viscosity increase has been attributed to the increase in the hydrophilic-ionic and hydrophilic-hydrophilic interactions with the increase in the amino acid concentration which in turn may cause more frictional resistance to the flow of the solution. All other parameters are discussed in terms of solute-solvent and solvent-solvent interactions.     

Synthesis and characterization of glycol-modified vanadium(V) oxoisopropoxide and their oximato derivatives: sol–gel transformations of [VO(OPr i )3], [VO{OCH2CH2OCH2CH2O}{OPr i }] and [VO{OCH2CH2OCH2CH2O}{ON=C(CH3)(C4H3S-2)}] to vanadia

Reaction of [VO(OPr ⁱ )₃] (1) with [O(CH₂CH₂OH)₂] in 1:1 molar ratio in anhydrous benzene yield glycol-modified precursor, [VO{OCH₂CH₂OCH₂CH₂O}{OPr ⁱ }] (2). Further reactions of (2) with internally functionalized oximes in anhydrous benzene yield heteroleptic complexes of the type [VO{OCH₂CH₂OCH₂CH₂O}{ON=C(R)(Ar)}] (3–8) {where R=CH₃, Ar=C₄H₃O-2 (3), C₄H₃S-2 (4), C₅H₄N-2 (5); and when R=H, Ar=C₄H₃O-2 (6), C₄H₃S-2 (7), C₅H₄N-2 (8)}. All these derivatives have been characterized by elemental analyses, molecular weight measurements and spectroscopic techniques. The crysoscopic molecular weight measurement as well as FAB mass study suggests dimeric nature of (2). However, FAB mass spectrum of (4), and the crysoscopic molecular weight measurements of (3), (4), (5) and (6) indicate the monomeric behavior of the oximato derivatives (3–8). Hexa-coordination around vanadium(V) has been proposed for both monomeric and dimeric derivatives. Sol–gel transformations of (1), (2) or (4) to vanadia [(a), (b) or (c), respectively] have been carried out at low sintering temperature (600 °C). The XRD patterns of (a), (b) or (c) indicate formation of a single orthorhombic phase in all the three cases. The SEM images suggest grain like [for (a) and (b)] and rod like [for (c)] morphology of the crystallites. IR, Raman spectra as well as EDX analyses indicate formation of pure vanadia. Absorption spectra of the vanadia (b) and (c) suggest energy band gaps of 2.53 and 2.65 eV, respectively.     

The effect of cesium metal clusters on the optical properties of cesium iodide thin films

Cesium metal clusters strongly affect the optical properties of cesium iodide thin films. The metal clusters are formed during film formation by thermal evaporation. The cesium cluster of 30–40 nm in the matrix of cesium iodide insulating thin films results in Surface Plasmon Resonance (SPR). The peak position of these SPR peaks showed a red shift. This was shown to be due to changes in the dielectric constant of CsI resulting from the strains in the films caused by the metal clusters themselves.     

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of acetyl-CoA and malonyl-CoA in animal tissues

A highly sensitive and specific LC‐MS/MS method was developed for simultaneous estimation of acetyl co‐enzyme A (ACoA) and malonyl co‐enzyme A (MCoA) in surrogate matrix using n‐propionyl co‐enzyme A as an internal standard (IS). LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. Simple acidification followed by dilution using an assay buffer process was used to extract ACoA, MCoA and IS from surrogate matrix and tissue samples. The total run time was 3 min and the elution of both analytes (ACoA, MCoA) and IS occurred at 1.28 min; this was achieved with a mobile phase consisting of 5 mM ammonium formate (pH 7.5)–acetonitrile (30:70, v/v) delivered at a flow rate of 1 mL/min on a monolithic RP‐18e column. A linear response function was established for the range of concentrations 1.09–2187 and 1.09–2193 ng/mL for ACoA and MCoA, respectively. The intra‐ and inter‐day precision values for ACoA and MCoA met the acceptance as per FDA guidelines. ACoA and MCoA were stable in a battery of stability studies viz. bench‐top, auto‐sampler and long‐term. The developed assay was used to quantitate ACoA and MCoA levels in various tissues of rat. Copyright © 2011 John Wiley & Sons, Ltd.     

Tetrabutylammonium fluoride (TBAF)-catalyzed addition of substituted trialkylsilylalkynes to aldehydes, ketones, and trifluoromethyl ketones

Herein we report that tetrabutylammonium fluoride (TBAF) is a very efficient catalyst for the addition of trialkylsilylalkynes to aldehydes, ketones, and trifluoromethyl ketones in THF solvent at room temperature. The reaction conditions are mild and operationally simple, and a variety of aryl functional groups, such as chloro, trifluoromethyl, bromo, and fluoro groups, are tolerated. Impressively, using our protocol, useful CF(3)-bearing tertiary propargylic alcohols can be synthesized. Product yields are generally better than or comparable to those in the literature. 1-Phenyl-2-trimethylsilyl acetylene, trimethyl ((4-(trifluoromethyl)phenyl)ethynyl)silane, 1-trimethylsilyl-1-hexyne, and trimethyl(thiophen-3-ylethynyl)silane underwent clean conversion to their corresponding propargylic alcohols as products under our conditions. Heterocyclic carbonyl compounds, such as furan-3-carboxaldehyde, thiophene-3-carboxaldehyde, and 2-pyridyl ketone, gave good yields of propargylic alcohols.     

Elastic properties of nanocrystalline forsterite under high pressure and high temperature

A simple theoretical model is developed to study the pressure–volume–temperature relationship and applied for nanocrystalline forsterite in the temperature range 300–1573 K and pressure range 0–9.6 GPa. The results obtained with the present model are in quite close agreement to the experimental values. The model is therefore extended to study the variation of bulk modulus and the coefficient of volume thermal expansion under high pressure and high temperature. The present study also reveals that the quasi-harmonic approximation, i.e., the product of bulk modulus and the coefficient of volume thermal expansion as constant, is valid at least up to the temperature 1573 K and pressure 9.6 GPa in case of nanocrystalline forsterite.     

Effects of seasonal growth on ratio dependent delayed prey predator system

The Beddington–DeAngelis ratio dependent prey predator model with time delay has been discussed. The existence of Hopf bifurcation has been established. The numerical simulations have shown that seasonal growth and delay can give rise to variety of attractors including periodic, quasi-periodic as well as chaotic oscillations. The degree of complexity in the system increases with increase in magnitude of delay, or frequency of seasonal variation. The model parameters involved in functional response can also affect the complexity of the system.     

Gold‐Iron Bimetallic Nanoparticles Impregnated Reduced Graphene Oxide Based Nanosensor for Label‐free Detection of Biomarker Related to Non‐alcoholic Fatty Liver Disease

We report for the first time a microwave assisted, one pot, direct, and facile synthesis of monodispersed iron‐gold bimetallic nanoparticles (BNP_Au‐Fe) using glucose as a reducing agent in merely 90 s. The as such synthesized BNP_Au‐Fe were thoroughly characterized using UV‐Vis, XRD, TEM, EDX, elemental mapping, and raman spectroscopy. These BNP_Au‐Fe were further impregnated with reduced graphene oxide (rGO) and coated onto glassy carbon electrode (GCE) to develop a sensor probe for label free electrochemical detection of acetaminophen, which is considered to be a most potent biomarker related to non‐alcoholic fatty liver disease. The sensor probe was systematically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BNP_Au‐Fe‐rGO nanocomposite matrix showed the sensing of acetaminophen with a wide dynamic range between 50 and 800 nM with detection limit (DL) of 0.14 nM (±0.05) nM (RSD<4.12 %) that was lower compared to previously reported acetaminophen sensors. To show the practical application of the sensor probe, acetaminophen was detected in human urine samples, which showed the percentage recovery between 86.65 % and 91.32 %. To the best of our knowledge, this is the first report where BNP_Au‐Fe impregnated rGO was used to detect acetaminophen. Interferences due to various molecules such as glucose, serum albumin, glycine, glutamic acid, alanine, citric acid, and ascorbic acid were tested individually and in mixed sample. Long‐term stability of sensor probe was examined which was found to be stable up to 12 weeks. The sensor fabricated using BNP_Au‐Fe‐rGO nanocomposite has many attractive features such as; simplicity, rapidity, and label free detection, hence it could be a method of choice for acetaminophen detection in clinical settings.