Magnetoluminescence properties of Hg1−xCdxTe epitaxial layers and superlattice structures grown by metalorganic molecular beam epitaxy

We present a study of the electro-optical properties ofHg _1- xCd_xTe epitaxial layers and Hg_1-x Cd_xTe/CdTe (0.28 < x < 0.30) superlattice structures by x-ray diffraction, lateral transport and photo- and magneto-luminescence measurements. Systematic studies of the excitation intensity and magnetic field dependence of the photoluminescence revealed direct evidence of an excitonic contribution to the observed luminescence in Hg_{1- x}Cd_xTe epitaxial layers. Similar investigations of the superlattice structures indicated that excitonic corrections were required to adequately fit the luminescence data. Optical gains of 80 cm⁻¹ were obtained for an excitation intensity of 100 kW/cm² indicating suitable electro-optical properties for making efficient mid-infrared laser diodes.     

Modeling energy and agriculture interactions—II: Food-fodder-fuel-fertilizer relationships for biomass in Bangladesh

The model developed by Parikh¹ is applied to Bangladesh for which the situation in 1976–1977 is simulated first. This base case provides insights into the present behavior of different income groups with regard to choices of fuels and allocation of biomass for various purposes.It is shown that, due to high needs and prices of fuels, the biomass allocation for fuels takes priority over feed and fertilizers. In fact, the landless burn all, and small farmers burn 80% of animal dung rather than use it for fertilizers.The model also shows that, unless substantial amounts of fertilizers are used, the small and middle farmers would have feed and fuel shortages on adopting high-yielding varieties (HYV) that minimize straw-grain ratios. Similarly, by 1990, when the population increases further, middle farmers also become vulnerable in meeting their feed, fuel, fertilizer requirements. To mitigate these effects, improved stoves and other measures would be necessary to increase biomass use efficiencies considerably. Since Bangladesh is a very low-income and resource-scarce country, the choices of biogas, charcoal kilns, and alcohol distilleries, and the choices of mechanization, all of which require investment, play a minor role.     

Kolmogorov''s spline network

In this paper, an innovative neural-network architecture is proposed and elucidated. This architecture, based on the Kolmogorov's superposition theorem (1957) and called the Kolmogorov's spline network (KSN), utilizes more degrees of adaptation to data than currently used neural-network architectures (NNAs). By using cubic spline technique of approximation, both for activation and internal functions, more efficient approximation of multivariate functions can be achieved. The bound on approximation error and number of adjustable parameters, derived in this paper, favorably compares KSN with other one-hidden layer feedforward NNAs. The training of KSN, using the ensemble approach and the ensemble multinet, is described. A new explicit algorithm for constructing cubic splines is presented.     

Twenty years of biochemistry of human P450s: purification, expression, mechanism, and relevance to drugs

Today cytochrome P450 (P450) research is accepted as an integral part of drug development and discovery. Work leading to this point included biochemical studies on P450 in experimental animal models and application to human systems. The development of recombinant expression systems has been an important part of the progress, and in this article we describe some recently developed bacterial systems that can be used for the production of metabolites, genotoxicity testing, and screening in random mutagenesis work. Rate-limiting aspects of P450 reactions vary with particular systems, and further investigations are in order. Non-ionic detergents have been utilized widely in P450 purification work; these compounds are now shown to be substrates for P450s. These oxidations are not only of fundamental interest in expanding the repertoire of P450 substrates but have significance in light of human exposure to these compounds.     

Bias dependent microwave performance of AlGaN/GaN MODFET's up to100 V

1 μm gate-length AlGaN/GaN modulation doped field effect transistors (MODFET's) have been fabricated on an insulating GaN buffer layer for better carrier confinement. These devices demonstrate simultaneously high current levels (>500 mA/mm), excellent pinch-off and high gate-drain breakdown voltages (220 V for 3 μm gate-drain spacing). In contrast to their GaAs counterparts, the current-gain cutoff frequency of the AlGaN/GaN devices shows little degradation at high drain voltage biases. A power-gain cutoff frequency of 19 GHz is obtained at 100 V. ACW power density of 1.57 W/mm at 4 Ghz is also achieved when biased at 28 V and 205 mA/mm     

Probing the structure of the nicotinic acetylcholine receptor with the hydrophobic photoreactive probes [125I]TID-BE and [125I]TIDPC/16

The hydrophobic photoreactive compound 3-trifluoromethyl-3-(m-[125I]iodophenyl) diazirine ([125I]TID) has revealed important structural information about the pore of the ion channel and lipid-protein interface of the nicotinic acetylcholine receptor (AChR). To further characterize the structure of the AChR, we have mapped the sites of photoincorporation of a benzoic acid ester analogue of TID ([125I]TID-BE) and a phospholipid analogue ([125I]TIDPC/16). For each photoreactive probe, labeled sites were identified by amino-terminal sequencing of purified tryptic fragments of individual receptor subunits. [125I]TID-BE reacted with alphaCys-412, alphaMet-415, and alphaCys-418 in the M4 segment of the alpha-subunit and gammaCys-451 and gammaSer-460 in gammaM4. In the M1 segment of the alpha- and beta-subunits, [125I]TID-BE labeled alphaPhe-227, alphaLeu-228, and betaLeu-234, betaAla-235, respectively. The labeling pattern in the M1 and M4 segments indicate that TID and TID-BE interact with the AChR lipid-protein interface in a similar fashion, revealing the same lipid-exposed face of each transmembrane segment. In contrast to TID, there was, however, no detectable incorporation of [125I]TID-BE into the channel lining betaM2 segment when the AChR was labeled in the resting state conformation. In the presence of agonist (desensitized state), [125I]TID-BE reacted with betaLeu-257, betaVal-261, and beta-Leu-264 in betaM2; a labeling pattern which indicates that, in comparison to TID, the binding loci for TID-BE is located closer to the extracellular end of the channel. For [125I]TIDPC/16, receptor labeling was insensitive to the presence of agonist and the sites of incorporation mapped to the confines of the transmembrane segments alphaM4, alphaM1, and gammaM4, validating previous results found with small lipophilic probes.     

Role of the B cell antigen receptor in antigen processing and presentation. Involvement of the transmembrane region in intracellular trafficking of receptor/ligand complexes

To study the role of the B cell Ag receptor (membrane-bound Ig [mIg]) in Ag processing and presentation, we have generated several Ig transfectants that express transfected TEPC-15 idiotype (T15-Id) mIgM with phosphorylcholine (PC)-binding specificity. The wild-type Ig transfectant is able to present a specific Ag (e.g., PC-conjugated hen egg-white lysozyme [PC-HEL]) more efficiently than a nonspecific Ag (HEL) to a T cell hybridoma recognizing an epitope on the HEL molecule. A substitution in the entire spacer, transmembrane, and cytoplasmic region of mIg with an equivalent region of I-A alpha chain completely abolishes this mIg-enhanced Ag presentation. Experiments with the wild-type and substituted variant Ig transfectants suggest that this substitution may interfere with normal intracellular trafficking of mIg after cross-linking with specific Ag or antibodies specific for the mIg (anti-T15-Id mAb). Prolonged treatment of the wild-type Ig transfectants with specific Ag or anti-T15-Id mAb reduces the surface expression of T15-Id mIgM and leads to an accumulation of T15-Id mIgM inside the cells. The reduced surface expression and the elevated cytoplasmic accumulation of T15-Id mIgM are not observed in the variant Ig transfectant. Despite the ability of the variant to endocytose ligands similarly to the wild-type Ig transfectant, this variant displays a higher rate of recycling of the mIg/ligand complexes back to the cell surface and a lower rate of degradation of the ligands. These abnormalities may be responsible for the deficiency in mIg-mediated enhancement of Ag presentation in the variant Ig transfectant. Therefore, our results suggest that the transmembrane region of mIg is involved in intracellular trafficking of receptor/ligand complexes and that proper delivery and handling of internalized Ag are required for the enhanced presentation of specific Ag by B cells.     

Family process in health research: Extending a family typology to a new cultural context.

To describe family context in health research, the authors tested a typology of families developed in California with a sample of families in Quebec, Canada. Family scales from the California study were submitted to focus groups, translated, and standardized on a sample of 209 parents. A panel of experts then revised the scales to make them relevant to Quebec families and to health promotion. Data from the new and revised scales were collected on 509 Quebec couples (1,018 spouses) and were clustered separately by gender, using K means. The procedure classified all respondents into family types that paralleled the original typology. Discriminant analyses indicated that family profile variables significantly distinguished family types. Comparisons with family, stress, and health variables further differentiated among the types and expanded their meaning. The study demonstrates a method for redefining and extending family data in health research with different cultural groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive decision support systems

The effectiveness of decision support systems (DSS) is enhanced through dynamic adaptation of support to the needs of the decision maker, to the problem, and to the decision context. We define this enhanced DSS as adaptive decision support systems (ADSS) and propose its architecture. In an ADSS, the decision maker controls the decision process. However, the system monitors the process to match support to the needs. The proposed architecture evolves from the traditional DSS models and includes an additional intelligent‘Adaptation’ component. The ‘Adaptation’ component workd with the data, model, and interface components to provide adaptive support. The architecture also integrates enhancements proposed in the past research. In this paper, we have illustrated the proposed architecture with two examples, a prototype system, and results from a preliminary empirical investigations     

Emissivity measurements of reflective surfaces at near-millimeter wavelengths

We have developed an instrument for directly measuring the emissivity of reflective surfaces at near-millimeter wavelengths. The thermal emission of a test sample is compared with that of a reference surface, allowing the emissivity of the sample to be determined without heating. The emissivity of the reference surface is determined by one's heating the reference surface and measuring the increase in emission. The instrument has an absolute accuracy of Δε = 5 × 10(-4) and can reproducibly measure a difference in emissivity as small as Δε = 10(-4) between flat reflective samples. We have used the instrument to measure the emissivity of metal films evaporated on glass and carbon fiber-reinforced plastic composite surfaces. We measure an emissivity of (2.15 ± 0.4) × 10(-3) for gold evaporated on glass and (2.65 ± 0.5) × 10(-3) for aluminum evaporated on carbon fiber-reinforced plastic composite.