Growth of AlxGa1−x as by metalorganic chemical vapor deposition using trimethylgallium and trimethylamine alane

High-quality Al_xGa_1−xAs layers with aluminum arsenide contentx up to 0.34 have been grown in a low pressure metalorganic chemical vapor deposition (MOCVD) system using trimethylgallium (TMG), trimethylamine alane (TMAA) and arsine. The carbon content in these films depended on growth conditions but was in general lower than in those obtained with trimethylaluminum (TMA) instead of TMAA in the same reactor under similar conditions. Unlike TMA grown layers, the TMAA grown Al_xGa_1−xAs layers, (grown at much lower temperature—down to 650° C), exhibited room temperature photolu-minescence (PL). Low temperature (25 K) PL from these films showed sharp bound exciton peaks with a line width of 5.1 meV for Al_0.25Ga_0.75As. A 39 period Al_0.28Ga_0.72As (5.5 nm)/GaAs (8.0 nm) superlattice grown at 650° C showed a strong PL peak at 25 K with a line width of 5.5 meV attesting to the high quality of these layers.     

The transfer of retinol from serum retinol-binding protein to cellular retinol-binding protein is mediated by a membrane receptor

The hypothesis that the cellular uptake of retinol involves the specific interaction of a plasma membrane receptor with serum retinol-binding protein (RBP) at the extracellular surface followed by ligand transfer to cytoplasmic cellular retinol-binding protein (CRBP) has been investigated. The experimental system consisted of the [3H]retinol-RBP complex, Escherichia coli-expressed recombinant apo-CRBP containing the 10 amino acid long streptavidin-binding peptide sequence at its C terminus (designated as CRBP-Strep) and permeabilized human placental membranes. [3H]Retinol transfer from RBP to CRBP-Strep was monitored by measuring the radioactivity associated with CRBP-Strep retained by an immobilized streptavidin resin. Using this assay system, we have demonstrated that optimal retinol uptake is achieved with holo-RBP, the membrane receptor and apo-CRBP. The effects are specific: other binding proteins, including beta-lactoglobulin and serum albumin, despite their ability to bind retinol, failed to substitute for either RBP or apo-CRBP. The process is facilitated by membranes containing the native receptor suggesting that this protein is an important component in the transfer mechanism. Taken together, the data suggest that the RBP receptor, through specific interactions with the binding proteins, participates (either directly or via associated proteins) in the mechanism which mediates the transfer of retinol from extracellular RBP to intracellular CRBP.     

An expert system for wide area network component configuration

Abstract: Many organizations today have an interest in communications networks, either as users of public networks or as operators of their own private networks. Thus, the management of communications networks has become an important issue in the communications industry. The network design task is fundamental to the whole notion of network management; however, with the rapid rate of change in network technology and the emergence of highly sophisticated network users, network design has become an increasingly complex problem.
The purpose of this paper is to describe a development effort which incorporates expert systems techniques to treat one aspect of the network design problem—the initial planning and design of a network prior to implementation. The research effort was concerned with developing an expert system for Amdahl Communications Products which could be used by sales engineers in designing wide area networks to meet specified customer requirements. The system treats both the topological design problem and the component configuration problem.     

Characterization of Pt-Ru binary alloy thin films for work function tuning

This letter describes materials and electrical characterization of Pt-Ru binary alloy metal gate electrodes for control of the electrode work function. The work function of the Pt-Ru binary alloy system can be tuned over a wide range of 4.8-5.2 eV. The results indicate that the change of film properties, i.e., resistivity, work function, and crystal structure, with composition is consistent with the equilibrium phase diagram and that the work function in the face-centered cubic and hexagonal close-packed single-phase regions is only weakly dependent on composition, whereas a strong dependence is observed in the intermediate compositional range.     

Prostate-sparing effects in primates of the potent androgen 7alpha-methyl-19-nortestosterone: a potential alternative to testosterone for androgen replacement and male contraception

7alpha-Methyl-19-nortestosterone (MENT) is a potent synthetic androgen that cannot be converted to dihydrotestosterone. In this study we determined the relative androgenic, antigonadotropic, and anabolic potencies of testosterone vs. MENT in the nonhuman primate M. fascicularis. In castrated monkeys, dose-response relationships were generated for the effects of testosterone and MENT on gonadotropin levels, prostate growth, body weight, and lipid metabolism. In a pilot study, four monkeys were castrated, and magnetic resonance imaging (MRI) was used to document a 50% loss of prostate volume within 8 weeks, verifying that MRI is a reliable means to measure prostate size in this species. Two additional groups of six monkeys each were then castrated and serially administered four graded dosages of testosterone or MENT via osmotic minipumps over 20 weeks. Complete suppression of LH was achieved with a minimum of 0.3 mg/day MENT, compared to 3.0 mg/day testosterone. MENT supported body weight 10 times more potently than did testosterone. Baseline prostate volumes were maintained with 0.1-0.2 mg/day MENT vs. 0.3 mg/day testosterone. Thus, in monkeys, MENT is 10 times more potent than testosterone with regard to the clinically desirable end points of gonadotropin suppression and anabolism, but only twice as potent at stimulating prostate growth. These results suggest that MENT may have a wider therapeutic index than testosterone for human androgen replacement and male contraception.     

Microstructure-fracture toughness correlation in weld joints of Cr-Mo steel

The strength-toughness-microstructure relationship in relation to the micromechanics of a fracture process has been investigated in the weld joints of two alloys: 0.5 Mo and 2.25 Cr-1 Mo steels. These alloys are extensively used to fabricate super-heater tubes, boilers, piping, gas lines, etc., by welding. The applications require high temperature and pressure to be maintained during service. The crack initiation toughness and tearing resistance were evaluated using crack tip opening displacement/J-integral parameters at different temperatures. Quantitative analysis of micro-structure and fracture surfaces was used to study the micromechanics of fracture process in the heat-affected zone (HAZ) of the alloys. Molybdenum steel exhibited a higher percentage of ferrite and lower martensite content, while the other steel showed aligned carbide as the major constituent. The higher hardness and strength values in the HAZ and welding zone (WZ) of Cr-Mo steel, compared to molybdenum steel, may be attributed to the higher amount of martensite phase in the alloy. The higher initiation toughness at 200° C in both the alloys was reflected in the larger dimple size, compared to the size observed at room temperature. A tendency for void sheet formation was noticed in both alloys. Acicular ferrite and martensite appeared to be the most influential constituents affecting tearing resistance and initiation toughness.     

Removal of cytokine inducing substances by polymyxin-B immobilized polystyrene-derivative fibers during in vitro hemoperfusion of 10% human plasma containing Staphylococcus aureus challenge

Dietary wheat gluten has been associated with the risk of diabetes in animal models of human insulin-dependent diabetes mellitus (IDDM). To evaluate the role of wheat gluten as a T cell antigen in human IDDM, we studied the cell-mediated immune response to wheat gluten in patients with IDDM and in control subjects. The cellular response to gluten was measured by the peripheral blood mononuclear cell (PBMC) proliferation test, and the results were expressed as a stimulation index (SI). We observed an enhanced cellular immune response to gluten (SI > or = 3) in seven of 29 patients with newly diagnosed IDDM (24.1%), in six of 39 patients with a longer duration of IDDM (15.4%), and in two of 37 non-diabetic controls (5.4%). Reactivity of T cells to gluten was associated with IDDM at diagnosis (P = 0.03), whereas patients with longer duration of IDDM did not differ from controls (P = 0.16). Responses of T cells to gluten were low in general: the median SI (range) was 2.0 (1-8.6) in patients with newly diagnosed IDDM and 1.5 (1-5.8) in control subjects (P = 0.03). Cellular responsiveness to gluten was not associated with HLA-DQB1 risk alleles for IDDM in patients. Although T cell responses to gluten were slightly increased in newly diagnosed patients the responsiveness was rare, and thus our results do not support a major role of gluten in the pathogenesis of human IDDM.