Spectroscopic investigation of the Dergaon meteorite with reference to 10 μm and 20 μm bands

Analysis of a part of the meteorite which fell at Dergaon (India) on March 2, 16.40 local time (2001) is presented with the help of FTIR, absorption and atomic spectra. The FTIR spectrum exhibits prominent absorption bands in the region 800–1100 cm⁻¹, originating from the valence vibration of SiO⁴, a basic component of the silicate lattice.     

Enzyme electrokinetics: electrochemical studies of the anaerobic interconversions between active and inactive states of Allochromatium vinosum [NiFe]-hydrogenase

The cycling between active and inactive states of the catalytic center of [NiFe]-hydrogenase from Allochromatium vinosum has been investigated by dynamic electrochemical techniques. Adsorbed on a rotating disk pyrolytic graphite "edge" electrode, the enzyme is highly electroactive: this allows precise manipulations of the complex redox chemistry and facilitates quantitative measurements of the interconversions between active catalytic states and the inactive oxidized form Ni(r) (also called Ni-B or "ready") as functions of pH, H(2) partial pressure, temperature, and electrode potential. Cyclic voltammograms for catalytic H(2) oxidation (current is directly related to turnover rate) are highly asymmetric (except at pH > 8 and high temperature) due to inactivation being much slower than activation. Controlled potential-step experiments show that the rate of oxidative inactivation increases at high pH but is independent of potential, whereas the rate of reductive activation increases as the potential becomes more negative. Indeed, at 45 degrees C, activation takes just a few seconds at -288 mV. The cyclic asymmetry arises because interconversion is a two-stage reaction, as expected if the reduced inactive Ni(r)-S state is an intermediate. The rate of inactivation depends on a chemical process (rearrangement and uptake of a ligand) that is independent of potential, but sensitive to pH, while activation is driven by an electron-transfer process, Ni(III) to Ni(II), that responds directly to the driving force. The potentials at which fast activation occurs under different conditions have been analyzed to yield the potential-pH dependence and the corresponding entropies and enthalpies. The reduced (active) enzyme shows a pK of 7.6; thus, when a one-electron process is assumed, reductive activation at pH < 7 involves a net uptake of one proton (or release of one hydroxide), whereas, at pH > 8, there is no net exchange of protons with solvent. Activation is favored by a large positive entropy, consistent with the release of a ligand and/or relaxation of the structure around the active site.     

Supercritical fluid extraction of 2,4-D from soils using derivatization and ionic modifiers

Supercritical fluid extraction (SFE) with CO(2), a clean and rapid alternative to conventional organic solvent extraction techniques, was investigated for the extraction of 2,4-D from soils using a variety of pre-extraction soil treatments to enhance extraction recoveries. Initial experiments with silylation, ion-pairing, methyl esterification, and ionic displacement are reported. Methyl esterification and ionic displacement during SFE proved to be the most promising approaches for quantitative extraction. Although the SFE procedures were not fully optimized, comparison between SFE and a standard Soxhlet extraction method demonstrated the potential for improving analytical measurement for highly polar pesticides in soil by modifying SFE-CO(2) extraction with derivatizing reagents and ionic solutions.     

First stereoselective total synthesis of triumfettamide

The first total synthesis of triumfettamide (1) is described. The asymmetric syntheses of two highly functionalized units—α-hydroxylated C17 monounsaturated fatty acid unit (2) and C26 phytosphingosine (3) have been accomplished involving Sharpless asymmetric dihydroxylation, Sharpless kinetic resolution, regioselective epoxide opening, regioselective DIBAL-H reduction of acetal, Wittig olefination as the key steps. Finally N-acylation of phytosphingosine 3 with (2R,6Z)-2-hydroxy-6-heptadecenoic acid 2 followed by DDQ deprotection of PMB, provided target compound 1.     

Volumetric and Acoustic Studies of Binary Liquid Mixtures of Dipropylene Glycol Dimethyl Ether with Methyl Acetate, Ethyl Acetate and n-Butyl Acetate in the Temperature Range T = (288.15, 293.15, 298.15, 303.15, and 308.15) K

Densities and ultrasonic speeds have been measured over the whole composition range for binary liquid mixtures of dipropylene glycol dimethyl ether, CH₃(OC₃H₆)₂OCH₃, with methyl acetate, ethyl acetate, and n-butyl acetate using an Anton Paar DSA 5000 M density and speed sound analyzer at T = (288.15, 293.15, 298.15, 303.15, and 308.15) K and atmospheric pressure in order to evaluate the behavior of these binaries. From these data excess the molar volume, $ V_{m}^{\text{E}} $ , and deviation in isentropic compressibility, ?κ _S , have been calculated. These excess properties have been fitted with the Redlich–Kister type polynomial equation to get their coefficients and standard deviations which provide a base for discussing the forces operating in solutions.     

Metabolite profiling and in-vitro colon cancer protective activity of Cycas revoluta cone extract

Abstract

The methanolic extract of Cycas revoluta cone (MECR) was analyzed by GC-MS and UHPLC for metabolite profiling and was evaluated for anti-colon cancer property by using in vitro assays like Cell Viability Assay, Colony Formation Assay, ROS Determination, Flowcytometry, DAPI staining assay, Tunel assay. GC-MS and HPLC analysis confirmed the presence of different phytochemicals in the extract of Cycas revoluta cone. In-vitro studies showed MECR extract showed significant anti-colon cancer activity by reducing proliferation and inducing apoptosis in colon cancer cell (HCT-8) line, but no such activity was seen in normal colon cell (CCD-18Co) line. The investigation confirms that MECR may be a promising candidate in colon cancer protection.     

Stability of thin film flowing down the outer surface of a rotating non-uniformly heated vertical cylinder

Nonlinear Dynamics - We investigated an incompressible viscous liquid film flow over a rotating vertical cylinder of radius R and of infinite length rotating with a uniform angular velocity...     

Comparison of different methods to measure contact angles of soil colloids

We compared five different methods, static sessile drop, dynamic sessile drop, Wilhelmy plate, thin-layer wicking, and column wicking, to determine the contact angle of colloids typical for soils and sediments. The colloids (smectite, kaolinite, illite, goethite, hematite) were chosen to represent 1:1 and 2:1 layered aluminosilicate clays and sesquioxides, and were either obtained in pure form or synthesized in our laboratory. Colloids were deposited as thin films on glass slides, and then used for contact angle measurements using three different test liquids (water, formamide, diiodomethane). The colloidal films could be categorized into three types: (1) films without pores and with polar-liquid interactions (smectite), (2) films with pores and with polar-liquid interactions (kaolinite, illite, goethite), and (3) films without pores and no polar-liquid interactions (hematite). The static and dynamic sessile drop methods yielded the most consistent contact angles. For porous films, the contact angles decreased with time, and we consider the initial contact angle to be the most accurate. The differences in contact angles among the different methods were large and varied considerably: the most consistent contact angles were obtained for kaolinite with water, and illite with diiodomethane (contact angles were within 3 degrees); but mostly the differences ranged from 10 degrees to 40 degrees among the different methods. The thin-layer and column wicking methods were the least consistent methods.     

Applications of Fruit Polyphenols and Their Functionalized Nanoparticles Against Foodborne Bacteria: A Mini Review

The ingestion of contaminated water and food is known to cause food illness. Moreover, on assessing the patients suffering from foodborne disease has revealed the role of microbes in such diseases. Concerning which different methods have been developed for protecting food from microbes, the treatment of food with chemicals has been reported to exhibit an unwanted organoleptic effect while also affecting the nutritional value of food. Owing to these challenges, the demand for natural food preservatives has substantially increased. Therefore, the interest of researchers and food industries has shifted towards fruit polyphenols as potent inhibitors of foodborne bacteria. Recently, numerous fruit polyphenols have been acclaimed for their ability to avert toxin production and biofilm formation. Furthermore, various studies have recommended using fruit polyphenols solely or in combination with chemical disinfectants and food preservatives. Currently, different nanoparticles have been synthesized using fruit polyphenols to curb the growth of pathogenic microbes. Hence, this review intends to summarize the current knowledge about fruit polyphenols as antibacterial agents against foodborne pathogens. Additionally, the application of different fruit extracts in synthesizing functionalized nanoparticles has also been discussed.     

Apparent molar volumes and transport behavior of glycine and l-valine in aqueous solutions of tripotassium citrate at T = (308.15 and 318.15) K

Densities and viscosities of glycine and l-valine have been measured at 308.15 and 318.15 K in aqueous tripotassium citrate solutions ranging from 0.2 to 0.8 mol kg^− 1 of tripotassium citrate. The viscosity data have been analyzed by Jones-Dole equation. The activation parameters of viscous flow have been obtained to throw light on the mechanism of viscous flow. The values of apparent molar volume, partial molar volume at infinite dilution and relative viscosities of each amino acid in various aqueous tripotassium citrate solutions have been evaluated from the density and viscosity data. The partial molar volumes of transfer from water to aqueous tripotassium citrate solution at infinite dilution have also been calculated. Transfer volume data have been used to calculate the pair and triplet interactions. The results have been discussed in terms of solute-solute and solute-solvent interactions and the structural changes of the solutes in solutions.