Distribution of nonequilibrium carriers in the region of a <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> junction under various photogeneration conditions

A model is described, which makes it possible to calculate the distribution of nonequilibrium carriers and an electric field near the p–n junction, which arose as a result of the internal photoeffect. Using laser illumination, the possibilities to control the properties of nanolayered structures sensitive to the concentration of free carriers are analyzed. The mutual location of the region of the intense absorption of radiation and the p–n junction itself is varied and the linear and square mechanisms of carrier recombination are analyzed.     

Vaccenic acid (<Emphasis Type="Italic">t</Emphasis>11–18∶1) is converted to <Emphasis Type="Italic">c</Emphasis>9,<Emphasis Type="Italic">t</Emphasis>11-CLA in MCF-7 and SW480 cancer cells

The aims of this study were to determine whether vaccenic acid (VA; t11–18∶1) is converted to c9,t11-CLA in human mammary (MCF-7) and colon (SW480) cancer cell lines and whether VA influences cell viability and other CLA-bioresponsive markers. When cells were incubated in the presence of VA at concentrations of 5 to 20 μg/mL, both VA and c9,t11-CLA increased in cellular lipids in a dose-dependent manner. After 4 d of incubation of SW480 and MCF-7 cells with VA (20 μg/mL), c9,t11-CLA increased from undetectable levels to 8.57 and 12.14 g/100 g FAME in cellular lipids, respectively. VA supplementation for 4 d at 5, 10, and 15 μg/mL had no effect on cell growth, whereas 20 μg/mL significantly (P<0.05) reduced cell growth in both cell lines. VA (20 μg/mL) treatment induced DNA fragmentation and significantly (P<0.05) depeleted cytosolic GSH levels in the SW480 cell line after 4 d of incubation, suggesting that apoptosis was the mode of cell death induced by VA. Both VA and c9,t11-CLA reduced (P<0.05) total ras expression in SW480 cells. ¹⁴C-Arachidonic acid uptake into the MG fraction was significantly increased (P<0.05) in both cell lines while uptake into the phospholipid fraction decreased in response to VA. VA treatment significantly (P<0.05) increased 8-epi-prostaglandin F_2α in both cell lines. The data indicate that growth suppression and cellular responses of both cells lines are likely mediated by VA desaturation to c9,t11-CLA via Δ⁹-desaturase.     

Enhancement of combustion of a hydrogen-air mixture by excitation of O<Subscript>2</Subscript> molecules to the <Emphasis Type="Italic">a</Emphasis><Superscript>1</Superscript>Δ<Subscript><Emphasis Type="Italic">g</Emphasis></Subscript> state

The possibility of increasing the laminar flame velocity in a hydrogen-air mixture by excitation of O₂ molecules into the a ¹Δ _g singlet state. The presence of 10% of O₂(a ¹Δ _g ) molecules in oxygen is demonstrated to result in noticeable (up to 50%) enhancement of mixture burning. The temperature of combustion products and also the concentrations of H₂O, NO, and other constituents increase. The greatest effect of O₂(a ¹Δ _g ) molecules is manifested in combustion of lean mixtures; the least pronounced effect is observed in rich mixtures. These effects are caused by intensification of the chain mechanism in the presence of a super-equilibrium amount of excited O₂(a ¹Δ _g ) molecules in a hydrogen-air mixture. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 3–12, July–August, 2008.     

Crystallization and melting of <Emphasis Type="Italic">α</Emphasis> and <Emphasis Type="Italic">β</Emphasis> phases in bulk syndiotactic polystyrene as monitored in situ via high-temperature wide-angle X-ray diffraction

Direct and non-intrusive observations of crystallization and melting behavior of and polymorphs in bulk syndiotactic polystyrene were made by means of temperature-programmed x-ray diffraction. Results indicated that the highest sustainable temperature identifiable via wide-angle x-ray diffraction using stepwise annealing at increasingly higher temperatures (T _a) for the perfected (with the initial crystallization temperature T _c = 245 °C, followed by annealing at stepwise increased T _a above 250 °C) phase may be at least 286 °C. In a similar manner, the highest sustainable temperature of the perfected (with T _c = 265 °C, followed by annealing at stepwise increased T _a above 275 °C) phase may be at least 280 °C. These observations suggest complete melting should occur only above the respective sustainable temperatures. It thus follows that equilibrium melting of the and the phases should occur at temperatures higher than 286 and 280 °C, respectively. Perfection of the less ordered form into the better ordered form within the family is observed to occur in the vicinity of 270 °C; no evidence of transformation between and phases is identified.     

Syntheses and optical properties of <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-cyano-poly(<Emphasis Type="Italic">p</Emphasis>-phenylene vinylene) derivatives

Two light emitting molecules with the cyano group at different positions on the vinylene i.e., 2,5-bis(2-thienyl-1-cyanovinyl)-1-(2_-ethylhexyloxy)-4-methoxybenzene (-TPT) and 2,5-bis(2-thienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene (-TPT), and corresponding polymers, i.e., poly[2,5-bis(2-thienyl-1-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P1) and poly[2,5-bis(2-ethienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P2) were synthesized. -TPT and -TPT, respectively, were blended into two host polymers, poly(methyl methacrylate (PMMA) and poly(9-vinylcarbazole) (PVK), to study the optical properties of the dopants in different host polymer matrices. Although -TPT and -TPT have the same backbone structure, their optical properties are much different. The PL emission maximum ( _max) of -TPT was found blue-shifted, compared with that of -TPT, while the PL intensity of -TPT was stronger than that of -TPT. Concentration effect in the optical properties was found, 1 wt% of -TPT in PVK had the maximum fluorescent emission.The PL maximum peak wavelengths for polymer films (P1 and P2) were found red-shifted; while their PL intensities were weaker when compared with those of blends.     

Investigation of the Meyer-Neldel rule for AC conduction in glassy Se<Subscript>100 − <Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

In many amorphous and liquid semiconductors and other class of materials, the Meyer-Neldel rule is observed in the dc conductivity, where the preexponential factor (σ₀) is found to increase exponentially with the activation energy (ΔE). In the present paper, we report on the observation of the Meyer-Neldel rule in case of ac conductivity at high temperatures (300–350 K) in bulk samples of glassy Se_{100 − x} Te _x (x = 10, 20, 30) alloys. In this temperature range, the approximate variation in ac conductivity with temperature is found to be exponential and the activation energy is found to vary with frequency. The observation of the Meyer-Neldel rule in the present study is explained in terms of the compensation effect in the relaxation time. The text was submitted by the authors in English.     

Synthesis and Properties of Alkyl <Emphasis Type="Italic">β</Emphasis>-<Emphasis Type="SmallCaps">d</Emphasis>-Galactopyranoside

A series of alkyl β-d-galactopyranosides were prepared by the trichloroacetimidate method with d-galactose and alcohols with different chain lengths as raw materials. Their solubility, surface tension, emulsification, foaming, wettability, thermotropic liquid crystalline properties, and thermal stability were investigated. Alkyl β-d-galactopyranosides are soluble in water and ethanol, and the solubility decreases with increasing alkyl chain length. Decyl β-d-galactopyranoside was insoluble in water, but soluble in ethanol. Dissolution of alkyl β-d-galactopyranoside in water is an endothermic process with dissolution enthalpies greater than zero. Nonyl β-d-galactopyranoside had an excellent emulsifying property, better foaming ability and the best foam stability. The CMC values of alkyl β-d-galactopyranosides decrease with increasing of alkyl chain length. Alkyl β-d-galactopyranosides are thermally stable up to 270 °C. Alkyl β-d-galactopyranosides show the distinctive optical texture of a thermotropic liquid crystal smectic A type phase. Decyl β-d-galactopyranoside showed the strongest wettability.     

Properties of perovskite-like phases <Emphasis Type="Italic">Ln</Emphasis>BaCuFeO<Subscript>5 + δ</Subscript> (<Emphasis Type="Italic">Ln</Emphasis> = La,Pr)

The influence of the oxygen content on the crystal chemical parameters of the LnBaCuFeO_{5 + δ} (Ln = La, Pr) ferrocuprates is investigated using X-ray powder diffraction and IR spectroscopy. The electrical conductivity of these phases is studied. The chemical expansion coefficients α_δ and the activation energies E _a for electrical conduction are calculated. It is demonstrated that, for the LnBaCuFeO_{5 + δ} (Ln = La, Pr) phases, the chemical expansion coefficients ad depend on both the ionic radius of Ln ³⁺ cations and the oxygen nonstoichiometry of the ferrocuprate, whereas the activation energies E _a for electrical conduction are predominantly determined by the oxygen content in the samples.     

Passivity and Corrosion of Cu–<Emphasis Type="BoldItalic">x</Emphasis>Zn (<Emphasis Type="BoldItalic">x</Emphasis> = 10–40 wt%) Alloys in Borate Buffer Containing Chloride Ions

The electrochemical behaviour of Cu–xZn alloys and of Cu and Zn metals was studied by cyclic voltammetry and chronopotentiometry in borate buffer, pH = 9.2, with and without the addition of chloride ions in the range from 0.01 m to 1 m. In general, the shape of voltammograms of four Cu–xZn alloys with 10 – 40 wt.% of zinc resembles that of copper more than that of zinc. With increasing zinc content several characteristics of zinc are observed. In borate buffer containing chloride anions, Cu–xZn alloys are susceptible to pitting corrosion. The breakdown potential, E_b, at which the current density in the passive region starts to increase abruptly, becomes more negative with increasing zinc content in the alloy. The general relationship E_b = a + b log c_NaCl held in all cases, with constants a and b, however, being dependent on the zinc content of the alloy and on the chloride concentration. The corrosion resistance of Cu–xZn alloys was less than that of copper metal but significantly greater than that of zinc.     

Thermal expansion and phase transitions in K<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Cs<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>BSi<Subscript>2</Subscript>O<Subscript>6</Subscript> borosilicate solid solutions

Solid solutions K_{1 − x} Cs _x BSi₂O₆ (x (atomic fraction) = 0.00, 0.20, 0.30, 0.35, 0.40, 0.80, 0.90,1.00) have been prepared by solid-phase synthesis and crystallization of glasses in the KBSi₂O₆-CsBSi₂O₆ borosilicate series. The thermal behavior of the solid solutions has been investigated using the annealing and quenching techniques, dilatometry, and high-temperature X-ray powder diffraction. It has been shown that solid solutions with x = 0.00–0.35 and 0.40–1.00 correspond to space groups I $ \bar 4 $ \bar 4 3d and I a $ \bar 3 $ \bar 3 d, respectively. The cubic-cubic phase transition I $ \bar 4 $ \bar 4 3d ai Ia $ \bar 3 $ \bar 3 d occurs in the composition range x = 0.35−0.40 at room temperature. In the series of solid solutions with x = 0−0.30, the reversible cubic-cubic polymorphic transition I $ \bar 4 $ \bar 4 3d ai ia $ \bar 3 $ \bar 3 d with an increase in the temperature has been revealed, the temperature of the polymorphic transition has been determined, and the thermal expansion in both polymorphic modifications has been studied using high-temperature X-ray diffraction and dilatometry. The solid solutions belonging to the space group Ia $ \bar 3 $ \bar 3 d are characterized by a lower thermal expansion than the solid solution belonging to the space group I $ \bar 4 $ \bar 4 3d. According to the calculations, the equivalents α/γ for the space groups I $ \bar 4 $ \bar 4 3d and Ia $ \bar 3 $ \bar 3 d are 0.03 and 0.02 (in cesium atomic fractions per degree Celsius), respectively.     

Dynamic-mechanical behavior of polyethylenes and ethene/<Emphasis Type="Italic">α</Emphasis>-olefin-copolymers: Part II. <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-relaxation

Several ethylene homopolymers and ethene/ α-olefin-copolymers with crystallinities ranging between 85 and 12% were characterized by dynamic-mechanical measurements. The occurring relaxations were correlated to the crystallinity of the polymeric materials and to morphology. The α-relaxation, being attributed to interlamellar shear, was found to be around 60 °C with activation energies of about 120 kJ/mol in samples with more than 42% crystallinity. The β-transition shows a much greater variety among the different samples characterized. Its relaxation temperatures vary between −40 and 10 °C with activation energies between 200 and 400 kJ/mol. The α- and β-relaxation of several quenched samples with crystallinities between 63 and 42% were found to overlap, thus producing bimodal maxima and different activation energies from the Arrhenius plots. A separation of these overlapping relaxations was only possible by measuring the relaxations over a frequency range of more than three orders of magnitude.     

Determination of CLA <Emphasis Type="Italic">trans</Emphasis>,<Emphasis Type="Italic">trans</Emphasis> Positional Isomerism in CLA-Rich Soy Oil by GC–MS and Silver Ion HPLC

A ~20% CLA-rich soy oil with low saturated fat and no cholesterol was produced by photoisomerizing soy oil linoleic acid. The oil is predominately trans,trans CLA, with the oil containing 17% trans,trans CLA. Recent studies have shown that trans,trans CLA-rich soy oil significantly reduces heart disease and diabetes risk factors in obese rats. However, the positional isomerism of these geometrical isomers has not been identified. The objectives of the study were to determine trans,trans CLA positional isomerism of CLA fatty acids in CLA-rich soy oil and determine the resolution of trans,trans CLA positional isomers by silver ion chromatography. GC–MS studies of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) derivatives of CLA-rich oil showed that 9,11 CLA and 10,12 CLA were the major positional isomers. These were hypothesized to be the trans,trans CLA isomers, which was confirmed by silver ion chromatography and subsequent GC–FID fatty acid and ATR-FTIR geometrical isomer analysis of the collected fractions. The identification of 9,11 trans,trans CLA and 10,12 trans,trans CLA as the major CLA isomers in CLA-rich oil then allowed the deduction of the synthetic mechanism of the photoisomerism of soy oil linoleic acid to trans,trans CLA.     

Synthesis of La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3 + δ</Subscript> manganites by pyrohydrolysis of nitrates

Single-phase finely dispersed perovskite-like manganites La_{1 ? x} Sr _x MnO_{3 + δ} (0 ≤ x ≤ 0.33) with an average particle size of approximately 3μm were synthesized by the pyrohydrolytic method from a stoichiometric mixture of the corresponding metal nitrates at a temperature of 500°C in a water vapor atmosphere. The parameter δ was changed as a result of the subsequent heat treatment. It was established that the manganite La_0.67Sr_0.33MnO_{3 + δ} synthesized by the pyrohydrolytic method is characterized by a more pronounced change in the magnetoresistance as compared to the manganite that had the same composition but was synthesized according to the conventional ceramic technique.     

A novel ∈-lysine acylase from <Emphasis Type="Italic">Streptomyces mobaraensis</Emphasis> for synthesis of <Emphasis Type="Italic">N∈</Emphasis>-acyl-<Emphasis Type="SmallCaps">l</Emphasis>-lysines

A novel ∈-lysine acylase (N ₆-acyl-l-lysine amidohydrolase; EC 3.5.1.17) was isolated from Streptomyces mobaraensis and purified to homogeneity by SDS-PAGE from the culture broth. The purified enzyme was monomeric, with a molecular mass of approximately 60 kDa. The enzyme was inactivated by the presence of 1,10-phenanthroline and activated in the presence of Co²⁺ and Zn²⁺. The enzyme showed a pH optimum of 8.0 and was stable at temperatures of up to 50°C for 1 h at pH 8.0. The enzyme specifically catalyzed the hydrolysis of the amide bond of various N∈-acyl-l-lysines. Furthermore, the enzyme efficiently catalyzed the synthesis of N∈-acyl-l-lysines with fatty and aromatic acyl groups in an aqueous buffer. In the syntheses of N∈-decanoyl-l-lysine, N∈-lauroyl-l-lysine, and N∈-myristoyl-l-lysine, the product precipitated and the yield was 90% or higher using 10 mM FA and 0.5 M l-lysine as the substrate.     

Variation of Insect Attracting Odor in Endophytic <Emphasis Type="Italic">Epichloë</Emphasis> Fungi: Phylogenetic Constrains <Emphasis Type="Italic">Versus</Emphasis> Host Influence

Odor is a key trait for pollinator attraction in flowering plants, and many studies have investigated odor evolution in the light of pollinator selection by emphasizing the importance of the plant phylogenetic history. By contrast, little is known on the evolution of odors in fungus–insect interactions. In this study, profiles of three volatile compounds that are emitted by grass-inhabiting Epichloë fungi (Clavicipitaceae, Ascomycota) and that have a confirmed or likely role in the attraction of gamete-transferring Botanophila flies were investigated. We collected headspace samples from stromata of six European Epichloë species (including various host races) that originated from different locations in Switzerland, France, Poland, and UK for conducting gas chromatography analyses. Odor profiles exhibited considerable variation, but profiles of most species overlapped and did not discriminate at the species level. The exception was Epichloë festucae, which had a profile dominated by methyl (Z)-3-methyldodec-2-enoate. Based on an Epichloë phylogeny, there was some hierarchical structuring regarding levels of chokol K, another confirmed Botanophila attractant. However, patterns of odor profiles appeared to be largely dependant on particular Epichloë–host associations. The observed variation may be the result of complex selective pressures imposed by Botanophila gametic vectors, local environment, and mycoparasites.     

RNAi-Induced Electrophysiological and Behavioral Changes Reveal two Pheromone Binding Proteins of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> Involved in the Perception of the Main Sex Pheromone Component <Emphasis Type="Italic">Z</Emphasis>11–16:Ald

Pheromone binding proteins (PBPs) are thought to play key roles in insect sex pheromone recognition; however, there is little in vivo evidence to support this viewpoint in comparison to abundant biochemical data in vitro. In the present study, two noctuid PBP genes HarmPBP1 and HarmPBP2 of the serious agricultural pest, Helicoverpa armigera were selected to be knocked down by RNA interference, and then the changes in electrophysiological and behavioral responses of male mutants to their major sex pheromone component (Z)-11-hexadecenal (Z11–16:Ald) were recorded. There were no significant electrophysiological or behavioral changes of tested male moths in response to Z11–16:Ald when either single PBP gene was knocked down. However, decreased sensitivity of male moths in response to Z11–16:Ald was observed when both HarmPBP1 and HarmPBP2 genes were silenced. These results reveal that both HarmPBP1 and HarmPBP2 are required for the recognition of the main sex pheromone component Z11–16:Ald in H. armigera. Furthermore, these findings may help clarify physiological roles of moth PBPs in the sex pheromone recognition pathway, which in turn could facilitate pest control by exploring sex pheromone blocking agents.     

Multifunctional wool fiber treated with <Emphasis Type="Italic">ɛ</Emphasis>-polylysine

A creative method for fabricating environmentally-benign multifunctional wool fibers was established and reported. Through coating the wool fibers with ɛ-polylysine, the surface morphology and biochemical properties of the fibers were altered, enhancing their antimicrobial, hygroscopic and finished properties. The process of ɛ-polylysine coating was dependent on the solution environment, which influenced the electrostatic interactions between ɛ-polylysine molecules and wool fibers. The results showed that a maximum ɛ-polylysine coating (23.60 mg/g) on the surface of wool fibers was reached when wool fibers were soaked at 50 °C for 2 h in the solution with 10% on weight of fabric (owf) ɛ-polylysine and pH 8.0. The coated wool fiber showed promising antimicrobial rates of 96.98% and 97.93% against Escherichia coli and Micrococcus luteus, respectively. The wool fiber coated with the ɛ-polylysine was more hydrophilic than the uncoated wool fabrics. The functional wool fibers after water scrubbing for two times still have good antibacterial efficiency against Escherichia coli and Micrococcus luteus, and antimicrobial rates were 96.77% and 97.33%, respectively. This study shows that wool fibers modified by the nontoxic ɛ-polylysine have a great potential to be used in constructing multifunctional textiles.     

Does the Growth Differentiation Balance Hypothesis Explain Allocation to Secondary Metabolites in <Emphasis Type="Italic">Combretum apiculatum</Emphasis><Emphasis>,</Emphasis> an African Savanna Woody Species<Emphasis>?</Emphasis>

The growth differentiation balance hypothesis (GDBH) provides a framework that predicts a trade-off between costs of secondary metabolites (SMs) relative to the demand for photosynthate by growth. However, this hypothesis was developed using empirical evidence from plant species in northern boreal and temperate systems, leaving its applicability to species under different abiotic and biotic conditions questionable and generalizations problematic. The objective of this study was to investigate whether the GDBH explains allocation to SMs in the deciduous African savanna woody species C. apiculatum along a 6-point N gradient. The cornerstone prediction of the GDBH, i.e., the parabolic response in SMs along the N gradient, was not observed, with secondary metabolism showing compound-specific responses. Quercetin, myricetin, and kaempferol glycoside concentrations, all produced via the same pathway, responded differently across the N gradient. Flavonol glycoside, cinnamic acid, and quercetin glycoside concentrations decreased as N increased, which provides partial support for the carbon nutrient balance hypothesis. Simulated herbivory had no effect on photosynthesis, decreased foliar N and consequently increased C:N ratio, but did not induce an increase in SMs, with condensed tannins and flavonol glycosides being unaffected. Defoliated plants at low N concentration compensated for lost biomass, which suggests a tolerance response, but as predicted by the limiting resource model, plants at higher N concentration were evidently C limited and thus unable to compensate. Our results show that the GDBH does not explain allocation to SMs in C. apiculatum, and suggest that mechanistic explanations of plant allocation should consider the integrative defensive effect of changed SMs.     

Cellulose–<Emphasis Type="Italic">co</Emphasis>-polyacrylonitrile blends: Properties of combined solutions in <Emphasis Type="Italic">N</Emphasis>-metylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide and the formation and thermolysis of composite fibers

Combined solutions of cellulose and an acrylonitrile-based copolymer in N-methylmorpholine-N-oxide have been prepared for the first time, new composite fibers have been formed, and the properties of the solutions and fibers under standard conditions and during thermal treatment have been studied. On the basis of studying the phase state and morphological peculiarities of combined cellulose solutions with polyacrylonitrile additives, it has been shown that the completed solutions make emulsions in the entire range of investigated concentrations. The rheological behavior of combined solutions changes with temperature. With the use of IR spectroscopy methods, it has been found that the addition of polyacrylonitrile to cellulose results in the association of nitrile groups with hydroxyl groups of cellulose, which favors the cyclization of CN groups during heating and the appearance of polyconjugated bonds in polyacrylonitrile chains. Thermal transformations of cellulose and polyacrylonitrile in the course of mixed-fiber carbonization have been studied via DSC and TGA. It has been shown that polyacrylonitrile inhibits the dehydration processes in cellulose and reduces the intensity of the peak due to the first stage of the structural rearrangement, i.e., acts as a “catalyst” of pyrolysis.