Synthesis and characterization of surrogate nuclear explosion debris: urban glass matrix

Journal of Radioanalytical and Nuclear Chemistry - We report a study of a fast radiochemical method to determine the activity of 131I via the radiochemical recovery obtained with a 129I tracer....     

Langmuir–Blodgett films of stearic acid deposited on substrates at different orientations relative to compression direction: alignment layer for nematic liquid crystal

The Langmuir monolayer at an air–water interface shows remarkably different surface pressure (π)–area (A) isotherm, when measured with the surface normal of a Wilhelmy plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir–Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid is studied using an atomic force microscope. The morphology of the LB films is found to be different due to difference in the stress in different directions. The role of such surface morphology on the alignment of a nematic liquid crystal (LC) in LC cells is studied. The granular texture of LB films of stearic acid supports the homogeneous alignment of the LC whereas the uniform texture supports the homeotropic alignment of the LC.     

Enhancement of electrical conductivity,director relaxation frequency and slope of electro-optical characteristics in the composites of single-walled carbon nanotubes and a strongly polar nematic liquid crystal

In the present work, single-walled carbon nanotubes (SWCNTs) were dispersed in a room temperature nematic liquid crystal 4-pentyl-4′-cyanobiphenyl at the concentration of 0.02 and 0.05 wt%. Differential scanning calorimetry and temperature-dependent dielectric studies suggest decrease in clearing temperature of the composite materials as compared to the pure material. Ionic conductivity increases by two orders of magnitude due to the dispersion of such a low concentration (0.05 wt%) of SWCNTs. Dielectric studies also show that the presence of the SWCNTs decreases the effective longitudinal as well as transverse components of the dielectric permittivity. For homeotropic aligned samples, a relaxation mechanism has been detected in the lower MHz region both for the pure as well as dispersed samples. Presence of SWCNTs increases the relaxation frequency corresponding to flip-flop motion of molecules around their short axes. From frequency-dependent dielectric studies, important dielectric parameters such as relaxation frequency, dielectric strength and distribution parameters have been determined. Electro-optical experiments show that the threshold voltage decreases and the steepness of the transmission voltage curve improves due to the dispersion of SWCNTs.     

Molecular Cloning and Characteristic Features of a Novel Extracellular Tyrosinase from <Emphasis Type="Italic">Aspergillus niger</Emphasis> PA2

Biofertilizers have been widely used in many countries for their benefit to soil biological and physicochemical properties. A new microbial biofertilizer containing Phanerochaete chrysosporium and Bacillus thuringiensis was prepared to decrease nicotine content in tobacco leaves by regulating soil nitrogen supply. Soil NO₃ ^?-N, NH₄ ⁺-N, nitrogen supply-related enzyme activities, and nitrogen accumulation in plant leaves throughout the growing period were investigated to explore the mechanism of nicotine reduction. The experimental results indicated that biofertilizer can reduce the nicotine content in tobacco leaves, with a maximum decrement of 16–18 % in mature upper leaves. In the meantime, the total nitrogen in mature lower and middle leaves increased with the application of biofertilizer, while an opposite result was observed in upper leaves. Protein concentration in leaves had similar fluctuation to that of total nitrogen in response to biofertilizer. NO₃ ^?-N content and nitrate reductase activity in biofertilizer-amended soil increased by 92.3 and 42.2 %, respectively, compared to those in the control, whereas the NH₄ ⁺-N and urease activity decreased by 37.8 and 29.3 %, respectively. Nitrogen uptake was improved in the early growing stage, but this phenomenon was not observed during the late growth period. Nicotine decrease is attributing to the adjustment of biofertilizer in soil nitrogen supply and its uptake in tobacco, which result in changes of nitrogen content as well as its distribution in tobacco leaves. The application of biofertilizer containing P. chrysosporium and B. thuringiensis can reduce the nicotine content and improve tobacco quality, which may provide some useful information for tobacco cultivation.     

Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

Alkaline Protease Production from <Emphasis Type="Italic">Brevibacterium luteolum</Emphasis> (MTCC 5982) Under Solid-State Fermentation and Its Application for Sulfide-Free Unhairing of Cowhides

Enzyme-based unhairing in replacement of conventional lime sulfide system has been attempted as an alternative for tackling pollution. The exorbitant cost of enzyme and the need for stringent process control need to be addressed yet. This study developed a mechanism for regulated release of protease from cheaper agro-wastes, which overcomes the necessity for stringent process control along with total cost reduction. The maximum protease activity of 1193.77 U/g was obtained after 96 h of incubation with 15% inoculum of the actinomycete strain Brevibacterium luteolum (MTCC 5982) under solid-state fermentation (SSF). The medium after SSF was used for unhairing without the downstream processing to avoid the cost involved in enzyme extraction. This also helped in the regulated release of enzyme from bran to the process liquor for controlled unhairing and avoided the problem of grain-pitting. Unhairing process parameters were standardized as 20% enzyme offer, 40% Hide-Float ratio at 5 ± 1 rpm, and process pH of 9.0. The cost of production of 1000 kU of the protease was calculated as 0.44 USD. The techno-economic feasibility studies for setting up an SSF enzyme production plant showed a high return on investment of 15.58% with a payback period of 6.4 years.     

Development of an Amperometric Biosensor Platform for the Combined Determination of <Emphasis Type="SmallCaps">l</Emphasis>-Malic,Fumaric, and <Emphasis Type="SmallCaps">l</Emphasis>-Aspartic Acid

Three amperometric biosensors have been developed for the detection of l-malic acid, fumaric acid, and l -aspartic acid, all based on the combination of a malate-specific dehydrogenase (MDH, EC 1.1.1.37) and diaphorase (DIA, EC 1.8.1.4). The stepwise expansion of the malate platform with the enzymes fumarate hydratase (FH, EC 4.2.1.2) and aspartate ammonia-lyase (ASPA, EC 4.3.1.1) resulted in multi-enzyme reaction cascades and, thus, augmentation of the substrate spectrum of the sensors. Electrochemical measurements were carried out in presence of the cofactor β-nicotinamide adenine dinucleotide (NAD⁺) and the redox mediator hexacyanoferrate (III) (HCFIII). The amperometric detection is mediated by oxidation of hexacyanoferrate (II) (HCFII) at an applied potential of + 0.3 V vs. Ag/AgCl. For each biosensor, optimum working conditions were defined by adjustment of cofactor concentrations, buffer pH, and immobilization procedure. Under these improved conditions, amperometric responses were linear up to 3.0 mM for l-malate and fumarate, respectively, with a corresponding sensitivity of 0.7 μA mM^?1 (l-malate biosensor) and 0.4 μA mM^?1 (fumarate biosensor). The l-aspartate detection system displayed a linear range of 1.0–10.0 mM with a sensitivity of 0.09 μA mM^?1. The sensor characteristics suggest that the developed platform provides a promising method for the detection and differentiation of the three substrates.     

Synthesis,characterization and antitumor activity of palladium(II) complexes of imidazolidine-2-thione

Complexes of the type cis-[PdX₂(imzt)(PPh₃)] {imzt = imidazolidine-2-thione; PPh₃ = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and ¹H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl₂(CH₃CN)₂], imidazolidine-2-thione and triphenylphosphine in CHCl₃/CH₃OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH₃OH showed that the coordination geometry around Pd^II is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by ¹H NMR spectroscopy, revealing that the coordination takes place via N7.     

Preparation,catalytical activity and crystal structure of a heptanuclear zinc acetate cluster

Reaction of [Zn₄(µ₄-O)(O₂CCH₃)₆] with one equivalent of 4-tertiary-butylpyridine leads to a nearly quantitative formation of the heptanuclear cluster [Zn₇O₂(O₂CCH₃)₁₀(^tbupy)₂] (1). Here, we present the crystal structure of 1 and first results of the examination of its catalytic activity in transesterification reactions and polymerization of lactide compared to the activity of [Zn₄(µ₄-O)(O₂CCH₃)₆] in the presence of 4-tertiary-butylpyridine.     

Effect of grinding method on the analysis of essential oil from <Emphasis Type="Italic">Baccharis articulata</Emphasis> (Lam.) Pers.

Grinding methods were evaluated aiming to determine yield and composition of essential oils (EOs) from Baccharis articulata (Lam) Pers., called as carqueja, a native plant from South Brazil. Cryogenic, knife (with and without cooling) and ball mills were used. The major constituents found in EOs were β-pinene, caryophyllene, spathulenol and caryophyllene oxide, but differences in 21 compounds were observed. All grinding processes reduced monoterpenes and oxygenated sesquiterpenes with concentration of hydrocarbon sesquiterpenes. The sesquiterpenes (hydrocarbons and oxygenated) were found from 63.55 to 86.02% while the monoterpene hydrocarbons’ concentration ranged from 13.98 to 36.45%. Plants milled with knife mill provided EOs with profile similar to those not grinded. Despite the lower working temperature, cryogenic milling resulted in smaller EO yield (0.40 ± 0.03%) in comparison to other grinding methods (yields from 0.50 ± 0.02 to 0.56 ± 0.03%) and different chromatographic profile. Microscopic analysis showed the smaller particle size provided by cryogenic grinding, which leads to glandular trichome rupture and consequently to loss of EOs. This study showed that grinding should be carefully evaluated to provide reproducible results in essential oil analysis.