Electrical characterization of homoepitaxial diamond p–n junction

Electrical properties of homoepitaxial diamond p–n⁺ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 10⁵ at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density N_i of the p–n⁺ junction is not uniform and N_i at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce N_i at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n⁺ interface and incorporating during the growth of p-type layer, which makes to reduce N_i at the vicinity of the p–n⁺ interface.     

A novel brain-derived member of the epidermal growth factor family that interacts with ErbB3 and ErbB4

The availability of an analgesic compound devoid of the side effects associated with the commonly used opioid and nonsteroidal antiinflammatory drugs would be useful during the perioperative period. Although adenosine has analgesic and anesthetic-sparing properties, it also produces dose-dependent cardiovascular depression. Inhibitors of adenosine kinase may be able to provide analgesia without producing acute cardiovascular or respiratory depression. This preliminary study investigated the effects of a novel adenosine kinase-inhibiting drug, GP683, on the minimum alveolar anesthetic concentration (MAC) of desflurane in dogs. Seven mongrel dogs were administered one of three different GP683 dose regimens (or the solvent) by intravenous infusion on separate occasions according to a cross-over study design. After determining the baseline desflurane MAC value, GP683 was infused at 75, 150, or 300 microg x kg(-1) x min(-1) for 5 min as a loading dose, followed by 15, 30, or 60 microg x kg(-1) x min(-1) for an additional 85 min to maintain a stable plasma drug level. The desflurane MAC was redetermined 30-90 min after starting the study drug or vehicle infusion, and 30-90 min and 120-180 min after termination of the infusion. Cardiovascular variables and plasma concentrations of GP683 were determined at specific intervals before, during, and after the MAC determinations. The three GP683 dose regimens produced 22%, 31%, and 50% decreases in the desflurane MAC, respectively. In addition, there was good correlation between the decrease in desflurane MAC and the plasma GP683 concentration (r = -0.78). Although the mean arterial pressure (MAP) was decreased up to 25% by the highest infusion rate of GP683, adjustments in the desflurane concentration to an equi-MAC value resulted in normalization of the MAP values. Furthermore, GP683 produced no changes in heart rate. In conclusion, the adenosine kinase-inhibiting drug, GP683, produced dose-dependent decreases in the desflurane MAC of dogs without producing untoward hemodynamic changes. IMPLICATIONS: An investigational drug (GP683) that can increase the levels of an important endogenous substance in the body (adenosine) has been found to decrease the anesthetic requirement in dogs without producing adverse effects on the cardiovascular system.     

66/77-kV C-GIS using composite insulation in SF6 gas

A second-generation model of cubicletype gas-insulated switchgear (C-GIS) with composite insulation incorporating SF₆ gas has been developed. The design does not require a gas process in field assembly; it has high reliability and its installation is more rapid; and a further reduction in size is achieved. The design principles are described in detail.     

The oxidation properties of fourth generation single-crystal nickel-based superalloys

The fourth-generation nickel-based single-crystal superalloys, which contain large amounts of refractory metals for strengthening and platinum group metals for topologically close-packed phase prevention, show excellent high-temperature strength. However, these alloying elements seem to decrease high-temperature oxidation resistance. In this study, nickel-based superalloys with various amounts of tantalum, rhenium, and ruthenium were examined in isothermal and cyclic exposures at 1,100°C to investigate the effect on the oxide growth rate and resistance to scale spallation. Ruthenium and rhenium were found to degrade the oxidation resistance by the vaporization of their oxide. Tantalum-rich oxide in the spinel layer acts to stabilize ruthenium and rhenium oxide in the scale. The addition of hafnium and yttrium is effective in improving the oxidation resistance of ruthenium-containing nickel-based superalloys.     

Swelling of hydrophilic polymers. III

The total volume change included gel and surrounded water with the swelling of five types of speherical cross-linked dextran (Sephadex) that are either nonionic (G) or possess one of four different ionic groups in the same molecular skeleton: CM: sodium carboxymethyl, SP: sodium sulphopropyl, DEAE: diethylaminoethyl chloride, and QAE: diethyl-(2-hydroxypropyl) aminoethyl chloride. All have been studied by dilatometry. The total volume decreased with the swelling of all Sephadexes. The maximum changes of total volume with the swelling in water were all negatives of CM, G, SP, (DEAE, QAE), which decrease in that order. These values did not depend on the concentration of sodium chloride and were closely related to the maximum heats of swelling. Total volume changes occurred by the dissociation of the ionic group of dextran derivatives that subtracted the total volume change due to hydration of Sephadex skeleton from the total volume change: ?21.6 ± 3.1 μL mmol^?1 for CM, ?2.8 ± 8.0 μL mmol^?1 for SP, +13.2 ± 4.4 μL mmol^?1 for DEAE, and +15.4 ± 4.6 μL mmol^?1 for QAE. These values are assumed to be reflected in the quantities of ions-water interaction of Sephadexes. © 1994 John Wiley & Sons, Inc.     

Fate of the human liver after hemihepatic portal vein embolization: cell kinetic and morphometric study

The favorable therapeutic effect of preoperative portal vein embolization (PVE) was analyzed by assessing various volumetric, cell kinetic and morphometric parameters and examining histologically the embolized and nonembolized lobes of 15 patients who underwent extended right lobectomy 2 to 3 weeks after PVE. Each lobar volume was calculated from computed tomography (CT) images, hepatocyte proliferation was evaluated by assessing proliferative cell nuclear antigen (PCNA) expression and mitosis, hepatocyte apoptosis was evaluated by the terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and the hepatocyte numerical density as well as the sinusoidal volumetric ratio (Vvs) and the mean hepatocyte volume (Cv) were calculated using morphometric methods. PVE induced hepatocyte apoptosis and atrophy of the embolized lobe (from 798 +/- 213 to 708 +/- 222 cm3; P < .05). The increased sinusoidal volume in this lobe (17.7% +/- 4.5% and 21.7% +/- 5.7%, periportal and pericentral area, respectively) may have been attributable to hepatocyte deletion. Cells in the nonembolized lobe entered a highly active phase of proliferation within 2 weeks after PVE. Further evidence of cellular proliferation was provided by the increased nonembolized lobar volume (from 379 +/- 132 to 545 +/- 130 cm3; P < .01) and numerical density of hepatocyte nuclei (Nv) (5.38 +/- 1.26 vs. 3.11 +/- 0.85 x 10(5)/mm3; P < .01, nonembolized vs. embolized lobe, respectively). In conclusion, these results indicate that the favorable effect of PVE is attributable to a net gain of functional hepatocyte mass and/or early induction of hepatocyte proliferation following hepatectomy.     

Flexural and tensile moduli of polypropylene nanocomposites and comparison of experimental data to Halpin‐Tsai and Tandon‐Weng models

This research focuses on the reinforcing efficiency of nanomateterials and the role of the reinforcement's dispersion and orientation on the nanocomposite's flexural and tensile moduli. Polypropylene‐based composites reinforced with (i) exfoliated graphite nanoplatelets, xGnP?, (ii) vapor grown carbon fibers, (iii) PAN‐based carbon fibers, (iv) highly structured carbon black and (v) montmorillonite clay were fabricated by extrusion and injection molding. It was found that graphite platelets are the best reinforcement in terms of flexural modulus whereas PAN‐based carbon fibers cause the largest improvement in the tensile modulus. The difference in the reinforcing efficiency during the flexural and tensile testing is attributed to (i) the degree of fiber alignment along the flow direction during injection molding, which is higher in the thinner tensile specimens than in the flex specimens; and (ii) the different deformation modes of the two tests. The importance of good dispersion of the reinforcements within the polymer matrix and of perfect contact between the two phases is emphasized comparing the experimental modulus data to theoretical predictions made using the Halpin‐Tsai and the Tandon‐Weng models. POLYM. ENG. SCI., 47:1796–1803, 2007. © 2007 Society of Plastics Engineers     

Intercalation and exfoliation of clay nanoplatelets in epoxy‐based nanocomposites: TEM and XRD observations

Diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) reinforced with organo‐montmorillonite clay nanoplatelets were investigated using anhydride‐ and amine‐curing agents. The sonication technique was used to process epoxy/clay nanocomposites. The basal spacing of clay nanoplatelets was observed by wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS) techniques, and transmission electron microscopy. It was found that the basal spacing of clay nanoplatelets in epoxy matrix was expanded after mixing with either DGEBA/DGEBF or methyltetrahydrophthalic‐anhydride (MTHPA) curing agent. The sonication technique provided larger d‐spacing of clay nanoplatelets. Because of the different curing temperatures, MTHPA‐cured epoxy/clay nanocomposites produced more expanded d‐spacing of clay nanoplatelets modified with methyl, tallow, bis(2‐hydroxyethyl) quaternary ammonium (MT2EtOH) than triethylenetetramine‐cured nanocomposites. Depending on the selection of curing agent and organic modification for clay nanoplatelets, the d‐spacing was expanded to be up to 8.72 nm. POLYM. ENG. SCI., 46:452–463, 2006. © 2006 Society of Plastics Engineers     

Simultaneous Perturbation Stochastic Approximation with Norm‐Limited Update Vector

This paper addresses the convergence of simultaneous perturbation stochastic approximation (SPSA) with a norm‐limited update vector. We first illustrate an unstable solution of the standard SPSA algorithm which motivates the consideration of a modified version, where the norm of the update vector is limited to a certain value. Next, a result on the almost‐sure convergence is presented by reducing the modified algorithm into the standard SPSA algorithm and restricting the probability distribution for the perturbation to a Bernoulli distribution. Finally, we apply the modified algorithm to a system identification problem to demonstrate its performance.