Scattering of electrons by ionized impurities in semiconductors: quantum-mechanical approach to third body exclusion

As applied to the numerical simulation of electron transport and scattering processes in semiconductors an efficient model describing the scattering of electrons by the ionized impurities is proposed. On the example of GaAs at 77 and 300 K and Si at 300 K the dependencies of low-field electron mobility on the donor impurity concentration in the semiconductors are calculated in the framework of proposed model as well as in the framework of such most frequently used applied models as the Conwel-Weisskopf model and the Brooks-Herring one. After comparing the calculation results with the well-known experimental data it has been ascertained that the best agreement between the theory and experiment is achieved with application of the proposed model.     

DNA Comet Giemsa Staining for Conventional Bright-Field Microscopy

This study was undertaken to evaluate the compatibility of Giemsa staining protocol with the comet assay. We showed, for the first time, that DNA comets can be visualized and analyzed using Giemsa staining. We generated DNA damage dose response curves for human peripheral blood lymphocytes exposed to X-ray radiation using the comet assay with either SybrGreen I or Giemsa stain. The dose response curves were fitted by linear regressions (R² > 0.977). The SybrGreen I results showed only ~1.2-fold higher slope coefficient (method sensitivity) compared to the Giemsa results. The unexpectedly high sensitivity of Giemsa staining for the comet assay is due to the Romanowsky-Giemsa effect, the stain photo-stability and the higher resolution of bright-field imaging compared to fluorescence imaging. Our results demonstrate that Giemsa staining can effectively be used for measuring DNA damage by the comet assay. The low cost and availability of Giemsa stain makes this method affordable for any low budget research and will facilitate new applications of the comet assay in biology and medicine.     

Thermochemical stability of Fe- and co-functionalized perovskite-type SrTiO3 oxygen transport membrane materials in syngas conditions

The materials typically used for oxygen transport membranes, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) tend to decompose due to their low thermochemical stability under reducing atmosphere. Fe- and Co-doped SrTiO₃ (SrTi_1-x-yCo_xFe_yO_3-δ, x + y ≤ 0.35) (STCF) materials showing an oxygen transport comparable to LSCF have great potential for application in ion-transport-devices. In this study, the thermochemical stability of pure perovskite-structured STCF was investigated after annealing in a syngas atmosphere at 600–900 °C. The phase composition of the materials after annealing was characterized by means of X-ray diffraction (XRD). The thermodynamic activities of SrO, FeO, and CoO in the STCF materials were evaluated using Knudsen effusion mass spectrometry (KEMS). Co-doped SrTiO₃ (STC) materials were not stable after annealing in the syngas atmosphere above 5 mol% Co-substitution. Ruddlesden-Popper-like phases and SrCO₃ were detected after annealing at 600 °C. In contrast, Fe substitution (STF) showed good stability after annealing in syngas upto 35 mol% substitution.     

Morphological features of porous silicon carbide obtained via a carbothermal method

Samples of porous silicon carbide were obtained using sucrose or carbon and aerosil or silica mesoporous molecular sieves (SBA‐3, SBA‐15, KIT‐6 and MCF). Fibers content in silicon carbide samples is higher when the mesopore surface area of carbon materials derived from carbon‐silica composites is lower. Based on the found correlation between the morphology and porosity of SiC and mesopore surface area of the carbon component in the composites, a templating action of carbon in carbothermal reduction was suggested.     

Comparative Metabolomic Study of Drosophila Species with Different Lifespans

The increase in life expectancy, leading to a rise in the proportion of older people, is accompanied by a prevalence of age-related disorders among the world population, the fight against which today is one of the leading biomedical challenges. Exploring the biological insights concerning the lifespan is one of the ways to provide a background for designing an effective treatment for the increase in healthy years of life. Untargeted direct injection mass spectrometry-based metabolite profiling of 12 species of Drosophila with significant variations in natural lifespans was conducted in this research. A cross-comparison study of metabolomic profiles revealed lifespan signatures of flies. These signatures indicate that lifespan extension is associated with the upregulation of amino acids, phospholipids, and carbohydrate metabolism. Such information provides a metabolome-level view on longevity and may provide a molecular measure of organism age in age-related studies.     

Engineering of a Biomimetic Interface between a Native Dental Tissue and Restorative Composite and Its Study Using Synchrotron FTIR Microscopic Mapping

The aim of this work is to develop a biomimetic interface between the natural tooth tissue and the restorative composite and to study it on the basis of synchrotron micro-FTIR mapping and multidimensional processing of the spectral data array. Using hierarchical cluster analysis of 3D FTIR data revealed marked improvements in the formation of the dentine/adhesive/dental hybrid interface using a biomimetic approach. The use of a biomimetic strategy (application of an amino acid–modified primer, alkaline calcium and a nano-c-HAp–modified adhesive) allowed the formation of a matrix that can be structurally integrated with natural dentine and dental composite. The biomimetic hybrid layer was characterised by homogeneous chemical composition and a higher degree of conversion of the adhesive during polymerisation, which should provide optimal integration of the dental composite with the dentine.     

Effect of Salt Stress on the Expression and Promoter Methylation of the Genes Encoding the Mitochondrial and Cytosolic Forms of Aconitase and Fumarase in Maize

The influence of salt stress on gene expression, promoter methylation, and enzymatic activity of the mitochondrial and cytosolic forms of aconitase and fumarase has been investigated in maize (Zea mays L.) seedlings. The incubation of maize seedlings in 150-mM NaCl solution resulted in a several-fold increase of the mitochondrial activities of aconitase and fumarase that peaked at 6 h of NaCl treatment, while the cytosolic activity of aconitase and fumarase decreased. This corresponded to the decrease in promoter methylation of the genes Aco1 and Fum1 encoding the mitochondrial forms of these enzymes and the increase in promoter methylation of the genes Aco2 and Fum2 encoding the cytosolic forms. The pattern of expression of the genes encoding the mitochondrial forms of aconitase and fumarase corresponded to the profile of the increase of the stress marker gene ZmCOI6.1. It is concluded that the mitochondrial and cytosolic forms of aconitase and fumarase are regulated via the epigenetic mechanism of promoter methylation of their genes in the opposite ways in response to salt stress. The role of the mitochondrial isoforms of aconitase and fumarase in the elevation of respiration under salt stress is discussed.     

Synthesis and gas permeation parameters of metathesis polytricyclononenes with pendant Me3E‐groups (E = C,Si, Ge)

Metathesis polytricyclononenes were synthesized via ROMP polymerization in the presence of the 1‐st generation Grubbs catalyst and their gas‐transport properties were studied for the first time. The aim of this work was to evaluate the influence of Me₃E‐groups (E = C, Si, Ge) on gas permeation parameters of ROMP materials. New metathesis poly(3‐tert‐butyltricyclononene‐7) and poly(3‐trimethylgermyltricyclononene‐7) were obtained with high yields (up to 95%) and high‐molecular weights (M_w～3–7×10⁵ g mol^?1). The glass transition temperatures of the ROMP polytricyclononenes with Me₃E‐groups decreased when E was changed from C to Si and then to Ge. It was shown that the polytricyclononene containing Me₃Si‐groups has the highest gas permeability while the polytricyclononene containing Me₃C‐substituents has the lowest gas permeability. In addition, the gas permeation parameters were estimated for ROMP Me₃Si‐ and Me₃Ge‐substituted polytricyclonona‐3,7‐dienes. So the influence of the second double bond in the monomer units on the permeability of the polymers obtained was studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41395.