Photoluminescence study of GaAs films on Si(100) grown by atomic hydrogen-assisted molecular beam epitaxy

Preliminary experimental results and analysis of photoluminescence (PL) measurements performed on GaAs heteroepitaxial films, which have been grown on Si(100) substrates by atomic hydrogen-assisted low-temperature molecular beam epitaxy technique have been presented and discussed. The results have also been compared with those obtained for GaAs homoepitaxial films. Furthermore, minority carrier lifetimes in n-GaAs on Si have been characterized by the PL decay method and an average lifetime of as high as 8.0 ns has been successfully obtained, which is the highest value ever reported to date.     

Sol–Gel Synthesis and Microstructure Analysis of Amino-Modified Hybrid Silica Nanoparticles from Aminopropyltriethoxysilane and Tetraethoxysilane

Agglomerated amino-modified silica nanoparticles were prepared from a novel Stöber-like precursor system consisting of aminopropyltriethoxysilane (APTES), tetraethoxysilane (TEOS), ethanol, and water where the molar ratio APTES/TEOS was 0, 0.1, 1.0, and 2.0, and the molar ratio H₂O/-SiOC₂H₅ was about 20 to 60, or great excess amounts of H₂O were employed. APTES catalyzed the hydrolysis and condensation of both silanes. ²⁹Si magic angle spinning nuclear magnetic resonance spectra confirmed that the particles consisted of Qⁿ species (Si(OSi) _n (OH)_{4− n} ; n =2, 3, 4) and Tⁿ species (NH₂(CH₂)₃–Si(OSi) _n (OH)_{3− n} ; n =2, 3). The APTES content in the precursor solutions controlled the agglomerating spherical particle size and morphology: 0.1 in the ratio APTES/TEOS led to almost independent spheres of 300–400 nm, while the larger ratios 1 and 2 led to ∼250 and ∼150 nm spheres, respectively, that were largely agglomerated and some were fused to look like peanut-shells. When soaked in Kokubo's simulated body fluid, those amino-modified particles deposited apatite. The mechanisms of particle formation and apatite deposition were discussed in terms of an intraparticle hydrated layer.     

A Stochastic Approach to the Detection of Receptive Fields in the Visual System

A statistical approach is developed for the detection of receptive fields of cells in the visual system. A spatiotemporal random pattern of light, composed of successive frame patterns, is used as a stimulation signal. A frame consists of N2 square elements: N rows and N columns. The brightness of each element is independent to one another and takes "light" or "dark" state. Shaped random patterns are defined in the spatiotemporal random pattern, and a list indicating the presence and absence of a defined feature pattern is made from the spatiotemporal random pattern. The receptive field is described in terms of the spatial response function based on a cross correlation between cell's reponse and feature signal (feature list). Consideration is given to feature parameters affecting on results.     

Evaluation of the effects of various factors on the serum alpha hydroxybutyrate dehydrogenase activity in young females

In this study, for determining the influence of different life style on the serum alpha hydroxybutyrate dehydrogenase activity (alpha HBD), we carried out surveys and laboratory studies on the relationships of the nutritional intake, physical activity, cigarette smoking and alcohol consumption of young females with their serum alpha HBD activity. There are significant positive correlation between alpha HBD and GOT, GPT, LDH, CPK, phospholipids, total cholesterol, and HDL-cholesterol, and significant negative correlation between alpha HBD/LDH and GOT, GPT, and gamma GTP. There are significant positive or negative correlation between alpha HBD and systolic pressure, diastolic pressure, cardiac index, stoke volume and total periperal resistance, and significant negative correlation between alpha HBD/LDH and vital capacity in young females. The serum alpha HBD activity levels of nonsmokers was significant higher than those of smokers (p < 0.05). There are significant positive correlations between serum alpha HBD activity and beverage consumption, and between alpha HBD/LDH and protein, calcium, vitamin A, B1, B2, C, pulses, vegetables and milk in young females. The finding shows that the group of serum alpha HBD activity level of 240 or more units exhibited higher level of rate of those who exercised sometimes+usually than the other group in young females. However, the serum alpha HBD activity level did not show significant correlation with energy expenditures per day. Exercise at 50 and 70% VO2 max may produce a significant increase in their serum alpha HBD activity. There is a possibility that serum alpha HBD activity may serve as an indicator for ones health condition. It is undeniable that observation of variation of serum alpha HBD activity is highly significant in health maintenance.     

English plantain and psyllium: lack of cross-allergenicity by crossed immunoelectrophoresis

BACKGROUND: English plantain (Plantago lanceolata) weed pollen and psyllium (Plantago ovata) husk dust are inhalant allergens. Because of the phylogenetic relationship between these plant species, cross-allergenicity has been a concern. OBJECTIVE: The purpose of this study was to investigate the possible cross-allergenicity of plantain and psyllium. METHODS: Homologous and heterologous crossed immunoelectrophoresis (CIE) were performed using a commercial English plantain pollen extract and an extract of psyllium seed embryo. Crossed radioimmunoelectrophoresis (CRIE) was performed using sera from subjects who were RAST positive only to plantain (group A), RAST positive only to psyllium (group B), RAST positive to both plantain and psyllium (group C), or RAST negative to both (group D). RESULTS: All of the group A plantain subjects showed IgE binding to at least one of the six plantain allergens in homologous plantain CRIEs while only one of the sera from the group B subjects reacted very weakly to these plantain allergens. In homologous psyllium CRIE, all group B subjects showed pronounced IgE binding to 2 to 7 of the seven psyllium allergens. Several of the plantain subjects demonstrated only very weak binding to psyllium allergens. Heterologous CRIEs demonstrated little relevant IgE binding. CONCLUSIONS: These results indicate that there is little cross-allergenicity between psyllium husk and English plantain pollen.     

Preparation of homo- and co-dimers of styrene derivatives using phosphate

Summary Dimers were preferably obtained in the oligomerization of styrene derivatives by diphenyl hydrogen phosphate. The reaction was assumed to proceed through the formation of esters from the monomers and diphenyl hydrogen phosphate as intermediate. This assumption was confirmed by the fact that treatment of the esters with alternative styrene derivatives gave linear codimers.     

Novel vector control system using deadbeat-controlled PWM inverter with output LC filter

This paper proposes a novel high-performance vector control system of an ac motor using a low-switching-frequency (2 kHz) pulsewidth-modulation voltage-source inverter with an output LC filter. Excellent high-speed response characteristics of the LC filter output voltage have been realized using a novel deadbeat control algorithm. As for the experimental results, the torque current response that is similar to the response of the conventional system without an LC filter has been obtained. In addition, it has been confirmed by simulation that errors of the LC filter constants within /spl plusmn/10% can be permitted.     

Scanning limitation in adaptive superresolution array

A fundamental limitation in an adaptive superresolution array, due to reciprocity between the angular resolution capability and the measurement time required, is discussed. For this purpose, a new concept for the measurement time, a scanning time concept, is introduced by considering a superresolution array consisting of an Applebaum-Howells adaptive processor with steering signal changing periodically with time. The measurement time is defined as the amount of time taken to perform one observation over the range of desired angle. Superresolution array output is defined according to the adapted angular response formulation. It is shown that the relationship between the resolution capability and the scanning time is reciprocal, i.e., the increased angular resolution is obtained at the expense of the scanning time. The relationship is discussed quantitatively for a narrow-band signal model.     

Ring-opening copolymerization of 2,4-bisphenyl-1,3,2,4-dioxadiphosphetane-2,4-dioxide with oxetane via zwitterion intermediates

Summary Copolymerization of 2,4-bisphenyl-1,3,2,4-dioxadiphosphetane-2,4-dioxide (DPO) with oxetane, a cyclic ether, was found to take place at 90 and 120°C without initiator. Copolymers obtained have a structure of phosphonate-ether units (1), which was determined by ³¹P, ¹H and ¹³C NMR, IR and elemental analysis. Oxetane was incorporated into 1 in a slight excess in all runs(m value in 1=1.5–2.1). A small amount(<15%) of a by-product (2) was always formed. Other cyclic ethers such as ethylene oxide and propylene oxide did not afford copolymers but gave 11 addition products, 10 and 11, quantitatively. The copolymerization is reasonably explained by a mechanism in which DPO behaves as an electrophilic monomer and oxetane as a nuicleophilic one. A pyrophosphonate species is considered to be a key intermediate to lead to copolymer 1 and the whole reaction course is discussed in detail.