Comparative studies on electronic transport due to the reduced dimensionality at the heterojunctions of GaAs/A1xGa(1−x)As and GaxIn(1−x)As/InP systems at low temperatures

Comparative studies on ac/dc mobility due to the reduced dimensionality of spatially confined low dimensional systems, at the heterojunctions of GaAs/A1_xGa_(1−x)As and Ga_xIn_(1−x)As/InP forming quasi-two dimensional (Q2D) and quasi-one dimensional (Q1D) systems have been made. The effect of various low temperature nonphonon scattering mechanisms such as ionized impurity, alloy disorder scattering and surface roughness scattering mechanisms; and phonon scattering mechanisms such as acoustic phonon via deformation potential and piezoelectric scattering mechanisms on the systems has been studied. It is found that the surface roughness scattering mechanism dominates in Q2D system whereas acoustic phonon scattering mechanism dominates in Q1D system due to which the nature and magnitude of the temperature dependent dc/ac mobility curves shows significant variation. Whereas, it is observed that the confinement does not change the nature of the frequency dependent real and imaginary parts of ac mobility curves. However, the mobility is found to be enhanced with effective mass and also due to the confinement, i.e. the mobility for Q1D system is higher than that for Q2D system.     

Integration of Radioactive Material with Microcalorimeter Detectors

Microcalorimeter detectors with embedded radioactive material offer many possibilities for new types of measurements and applications. We will discuss the designs and methods that we are developing for precise deposition of radioactive material and its encapsulation in the absorber of transition-edge sensor (TES) microcalorimeter detectors for two specific applications. The first application is total nuclear reaction energy (Q) spectroscopy for nuclear forensics measurements of trace actinide samples, where the goal is determination of ratios of isotopes with Q values in the range of 5–7 MeV. Simplified, rapid sample preparation and detector assembly is necessary for practical measurements, while maintaining good energy resolution. The second application is electron capture spectroscopy of isotopes with low Q values, such as \(^{163}\) Ho, for measurement of neutrino mass. Detectors for electron capture spectroscopy are designed for measuring energies up to approximately 6 keV. Their smaller heat capacity and physical size present unique challenges. Both applications require precise deposition of radioactive material and encapsulation in an absorber with optimized thermal properties and coupling to the TES. We have made detectors for both applications with a variety of designs and assembly methods, and will present their development.     

Flavonoid glycosides from cowpea seeds (Vigna sinensis K.) inhibit LDL oxidation

Six flavonoid glycosides were isolated from the n-butanol fraction of cowpea seeds (Vigna sinensis K.) through silica gel (SiO₂) and octadecyl silica gel (ODS) column chromatographies. Based on their chemical structures determined via interpretation of spectroscopic data including NMR, MS, and IR, the compounds were identified as kaempferol 3-O-β-d-sophoroside (1), quercetin 3-O-β-d-sophoroside (2), isoquercitrin (3), hyperin (4), catechin 7-O-β-d-glucopyranoside (5), and quercetin 3-O-β-Dglucopyranosyl( 1→6)-O-β-d-galactopyranoside (6). This is the first report of the isolation of these flavonoids from this plant. Among these flavonoids, compound 2, 5, and 6 significantly inhibited LDL oxidation exhibiting 96.0±0.1 (IC₅₀: 3.9 μM), 96.8±1.7 (IC₅₀: 2.9 μM), and 97.4±0.1% (IC₅₀: 3.5 μM) inhibition, respectively, at a concentration of 40 μM.     

In Vitro and In Vivo Metabolism of the Radiolytic Compound 2-Dodecylcyclobutanone

ABSTRACT: Our knowledge about the metabolism of alkylcyclobutanones (2-ACBs) is limited, and the lack of literature on the metabolism of 2-ACBs causes consumers to doubt the safety of irradiated foods. The objectives of this study were to evaluate the metabolism of 2-dodecylcyclobutanone (2-DCB) and identify any possible metabolite. The 2-DCB was mixed with rat S9 (postmitochondrial supernatant fraction) and β-nicotinamide adenine dinucleotide phosphate (NADPH) in phosphate buffer (pH 7.4) and incubated for 2 h at 37 °C. Then, the incubation mixture was mixed with sodium sulfate and extracted with n-hexane by using a Soxhlet apparatus. The hexane extract was concentrated under nitrogen and injected into the gas chromatography-mass spectrometry (GC-MS) machine running in selective ion monitoring mode (SIM) to measure 2-DCB concentration. The hexane extract from the in vitro and in vivo studies was also derivatized with a silylation reagent and injected into a GC-MS running in full scan mode. The average percentage of 2-DCB recovered from the test incubations was 23%, compared with 50% from the controls. The GC-MS chromatograms of the derivatized samples showed a unique peak in the in vitro test incubations and in the hexane extract of the rat feces that were given 2-DCB. This peak was later identified as 2-doecylcyclobutanol.     

Photovoltaics literature survey (No. 115)

In order to help keep readers up‐to‐date in the field, each issue of Progress in Photovoltaics will contain a list of recently published journal articles that most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, including IEEE Journal of Photovoltaics, Solar Energy Materials and Solar Cells, Renewable Energy, Renewable and Sustainable Energy Reviews, Journal of Applied Physics, and Applied Physics Letters. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions please email Ziv Hameiri at ziv.hameiri@unsw.edu.au     

Mouse Gastric Epithelial Cells Resist CagA Delivery by the Helicobacter pylori Type IV Secretion System

The initial step in bacterial infection is adherence of the bacterium to the target cell surface. Helicobacter pylori exploits the interaction of bacterial adhesin protein HopQ with human epithelial CEACAMs (CEACAM1, 5, and 6) to stably adhere to gastric epithelial cells, which is necessary for delivery of the H. pylori CagA oncoprotein into the epithelial cells via a type IV secretion system. In contrast to human CEACAMs, however, HopQ does not interact with Ceacam1 (mouse CEACAM1) in vitro or in CHO cells ectopically expressing Ceacam1. Since the mouse genome lacks Ceacam5 and Ceacam6, no significant HopQ–Ceacam interaction may occur in mouse gastric epithelial cells. Here, we found that the mouse stomach has a much lower expression level of Ceacam1 than the expression level of CEACAM1 in the human stomach. Consistently, mouse gastric epithelial cells resist CagA delivery by cagA-positive H. pylori, and the delivery is restored by ectopic expression of human CEACAM1 or CEACAM5 in mouse gastric epithelial cells. Thus, despite the fact that mice are routinely used for H. pylori infection studies, a low expression level of Ceacam1 in the mouse stomach together with the loss or greatly reduced interaction of HopQ with Ceacams make the mouse an inappropriate model for studying the role of H. pylori-delivered CagA in gastric pathogenesis, including the development of gastric cancer.     

用QDI稳定轮胎胶料

高里程轮胎要求硫化胶具有较长的使用寿命,胶料的物理性能取决于多种因素,不仅仅是胶料中所用的橡胶、填料以及骨架材料.NR是重型轮胎(例如载重轮胎、航空轮胎和工程机械轮胎)选用的弹性体,它可以提供这些苛刻用途轮胎所需优异的强度和耐疲劳性能,兼有长疲劳寿命和良好的韧性--即抗撕裂性的弹性体需要用硫黄硫化,促进剂的品种和硫黄与促进剂的比例决定了硫交联键的特性.硫的序列,亦即每个交联键中硫原子的平均数基本上决定了所得硫化胶的特性.