Impact of lipid oxidation-derived aldehydes and ascorbic acid on the antioxidant activity of model melanoidins

As the heat-induced formation of antioxidants throughout the Maillard reaction is known, this study was undertaken to evaluate the impact of lipid oxidation-derived aldehydes and ascorbic acid in Maillard model systems on the resulting antioxidant activity. For this purpose, various fractions of melanoidin-like polycondensation products were obtained from mixtures of amino acids (glycine, lysine, arginine) and lipid oxidation-derived aldehydes (hexanal, (E)-2-hexenal), in the presence or absence of glucose or ascorbic acid. All fractions showed a significant radical scavenging capacity (DPPH assay) and ferric reducing power (FRAP assay). The activity varied according to the composition of the model system tested, although some similar trends were discovered in both assays applied. The presence of lipid oxidation products in the browning products augmented the antioxidant activity in specific cases. For instance, the combined presence of arginine, hexanal and glucose in heated model systems resulted in a significantly higher antioxidant capacity. With an exception of ascorbic acid-containing model systems, melanoidin-like polycondensation products possessed significantly stronger antioxidant activities than the corresponding unheated initial reactant mixtures. Water-soluble high molecular weight (>12kDa) and nonsoluble fractions comprised the major part of the antioxidants derived from amino acid/lipid oxidation product model systems, with or without glucose or ascorbic acid.     

Colossal Magnetoresistance Properties of La0.83Sr0.17MnO3 Thin Films Grown by MOCVD on Lucalox Substrate

The magnetoresistance (MR) of polycrystalline La_0.83Sr_0.17MnO₃ thin films have been studied in high pulsed magnetic fields up to 38 T in the temperature range 100–300 K. The lucalox substrates were used to obtain polycrystalline structures with naturally formed grain boundaries (GBs) and crystallites whose dimensions were determined by film deposition temperature. It was found that the MR value is highest in the films having smallest crystallites. The main behaviour of high-field MR was analysed using modified Mott’s hopping model assuming that the GBs might be ferromagnetic with a Curie temperature T _C being reduced in comparison with that of the crystallites interior.     

Graphene supported platinum–cobalt nanocomposites as electrocatalysts for borohydride oxidation

In the study presented herein a rapid microwave heating method was used to prepare the graphene supported PtCo catalysts with Pt:Co molar ratio 1:7, 1:22 and 1:44. The transmission electron microscopy was employed to characterize the catalysts. Inductively coupled plasma optical emission spectrometry was used for estimation of Pt and Co metal loadings. The electrocatalytic activity of the synthesized catalysts towards the oxidation of borohydride was investigated by means of cyclic voltammetry and chronoamperometry. The kinetics of the catalytic hydrolysis of NaBH₄ in the presence of the synthesized catalysts was investigated.     

The second harmonic generation in semiconductors in the DC magnetic field

The second harmonic radiation in millimeter wave region is found in semiconductors in the absence of the dc electric field. The observed resonant maximum of radiation intensity is shown to be related to the excitation of the free-electron plasma oscillations in the dc magnetic field.     

Mortality of silver eels migrating through different types of hydropower turbines in Lithuania

Hydropower plants (HPP) are considered to be one of the major threats to the survival of European eels when they migrate downstream along inland water bodies during the early part of their annual journey to the spawning area in the Sargasso Sea. There are 98 HPPs in Lithuania and thousands throughout Europe. Numerous studies describe HPP induced mortality rates among European eels as variable depending on local, environmental, and technical factors. This heterogeneity in effect complicates theoretical extrapolation to eel mortality arising from specific types of HPP, necessary for effective management of local stocks. Silver eel mortality was estimated for 4 different HPPs in Lithuania. Mortality was estimated using RFID (Radio Frequency Identification, passive integrated transponders) tags and acoustic telemetry in a large HPP (>100 MW) with Kaplan turbines, a small HPP (<1 MW) with a Kaplan turbine and a fish passage, and for the first time in two small HPPs (<1 MW) with CINK turbines. The results supported a hypothesis that the mortality rate of migrating eels depends mainly on the type and size of the turbine. HPP induced mortality varied from 100% in a small CINK turbine down to 25% in the large HPP with Kaplan turbines. The importance of simple mitigation measures was highlighted by 34% of all tagged eels bypassing one of the HPP via an adjacent fish passage constructed for upstream migration of salmonids. The observed differences in mortality provide essential information for long term strategies designed to restore depleted eel populations in Lithuania and other European countries.     

Effect of annealing on the resistivity of quench-condensed Cu and Cu(Fe) thin films

Pure Cu and Cu(Fe) thin films containing 0.1 and 1.0 at % Fe were prepared by low-temperature deposition onto a liquid-helium-cooled substrate. The Cu(Fe) films were annealed sequentially at approximately 17, 70, and 270 K. After each annealing stage the resistivity was measured down to 1.5K. The Cu(Fe) films exhibited a region in which the resistivity was proportional to ln T; in this region the logarithmic slope of the resistivity curve was only weakly affected by annealing. Below 10 K annealing produced a significant decrease in the impurity (Fe) contribution to the resistivity. The results are interpreted as due to increased interactions between Fe atoms produced by an increase in conduction-electron mean free path.This work was supported by the Materials Research Center, University of North Carolina, under Grant Number GH-33632 from the National Science Foundation.     

A graded-gap photoelectric detector for ionizing radiation

A heterostructure consisting of a graded-gap p-Al_xGa_1?xAs layer on an n-GaAs substrate is studied in relation to its role as a photoelectric-response detector of X-ray photons and α particles. It is found that the current-power sensitivity of the detector is as high as 0.13 A/W and the voltage-power sensitivity exceeds 10⁶ V/W. The effect of preliminary irradiation with 5.48-MeV α particles (²⁴¹Am) on the detector’s sensitivity is studied. It is established that the detector’s sensitivity is reduced by a factor of 1.5–2 after irradiation with α particles at a dose of 5 × 10⁹ cm^?2. A further increase in the radiation dose to 4 × 10¹⁰ cm^?2 does not affect the detector’s sensitivity.     

Comparative investigation of plain and silver impregnated activated carbons for the removal of cyanide from basic aqueous solutions in the batch process

Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO₃ were used for the removal of CN^– and Ag–CN complex from model wastewater. The formed Ag⁰ centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag⁰ participating in CN^– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN^–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The K_F values for the CN^– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN^–, and plain, removing the rest of Ag–CN.