International Nuclear Information System (INIS)

... atp-ase azido compounds biochemical reaction kinetics endoplasmic reticulum

KoreaScience (Korea)

Full Text Available

Science.gov (United States)

Not Available

UK PubMed Central (United Kingdom)

FXYD1 (phospholemman) is a member of an evolutionarily conserved family of membrane proteins that regulate the function of the Na,K-ATPase enzyme complex in specific tissues and specific physiological...Full Text Available

KoreaScience (Korea)

Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473x10{sup 19} n {omega} cm{sup -1}. The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from -5% to 2%. In addition, the burn-up effect of the boron impurities, the residual {sup 32}P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neutron transmutation doping of the initially p-type silicon ingot was ...

Energy Technology Data Exchange (ETDEWEB)

In vivo effects of toxaphene on calcium pump activity in rat brain synaptosomes was studied. Male Sprague-Dawley rats were dosed with toxaphene at 0,25,50, and 100 mg/kg/day for 3 days and sacrificed 24 h after last dose. Ca/sup 2 +/-ATPase activity and /sup 45/Ca uptake were determined in brain P/sub 2/ fraction. Toxaphene inhibited both Ca/sup 2 +/-ATPase activity and /sup 45/Ca/sup 2 +/ uptake and the inhibition was dose dependent. Both substrate and Ca/sup 2 +/ activation kinetics of Ca/sup 2 +/-ATPase indicated non-competitive type of inhibition as evidenced by decreased catalytic velocity but not enzyme-substrate affinity. The inhibited Ca/sup 2 +/-ATPase activity and Ca/sup 2 +/ uptake were restored to normal level by exogenously added calmodulin which increased both velocity and affinity. The inhibition of Ca/sup 2 +/-ATPase activity and Ca/sup 2 +/ uptake and restoration by ...

International Nuclear Information System (INIS)

The sodium- and potassium-dependent adenosine triphosphatase (Na+,K(+)-ATPase) maintains the transmembrane Na+ gradient to which is coupled all active cellular transport systems. The R and S alleles of the gene encoding the Na+,K(+)-ATPase alpha 1 subunit isoform were identified in Dahl salt-resistant (DR) and Dahl salt-sensitive (DS) rats, respectively. Characterization of the S allele-specific Na+,K(+)-ATPase alpha 1 complementary DNA identified a leucine substitution of glutamine at position 276. This mutation alters the hydropathy profile of a region in proximity to T3(Na), the trypsin-sensitive site that is only detected in the presence of Na+. This mutation causes a decrease in the rubidium-86 influx of S allele-specific sodium pumps, thus marking a domain in the Na+,K(+)-ATPase alpha subunit important for K+ transport, and supporting the hypothesis of a putative role of these pumps in ...

British Library Electronic Table of Contents (United Kingdom)

The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473x1019ncm-1. The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from -5% to 2%. In addition, the burn-up effect of the boron impurities, the residual 32P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neut...

UK PubMed Central (United Kingdom)

Cyclophilins (Cyps), the intracellular receptors for Cyclosporine A (CsA), are responsible for peptidyl-prolyl cis-trans isomerisation and for chaperoning several membrane proteins. Those functions...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

By ab-initio calculation we show that the (Ga,Fe)N ground state may be changed from anti-ferromagnetic to ferromagnetic by acceptor defect like Ga vacancies. The electronic structures are calculated by using the Korringa-Kohn-Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that we can increase the magnetic moment of Fe in p-type GaN by oxygen co-doping. Mechanism of exchange interactions between magnetic ions in p-type (Ga,Fe)N is also studied. The effect of external magnetic field on the electronic structure of (Ga, Fe)N and p-type (Ga, Fe)N is investigated.

Energy Technology Data Exchange (ETDEWEB)

We have examined in detail the electrochemistry of both n- and p-type single crystal (100) silicon in the porous silicon formation regime using a rotating Si disk apparatus with a Ag/AgCl reference electrode. Our findings impact the use and optimization of buried n- or p-type layer anodization for silicon-on-insulator (SOI) wafer synthesis. Results are briefly discussed. 3 refs.

International Nuclear Information System (INIS)

The heavy chains of Acanthamoeba myosins, IA, IB and II, turkey gizzard myosin, and rabbit skeletal muscle myosin subfragment-1 were specifically labeled by radioactive ATP, ADP, and UTP, each of which is a substrate or product of myosin ATPase activity, when irradiated with uv light at 0"0C. With UTP, as much as 0.45 mol/mol of Acanthamoeba myosin IA heavy chain and 1 mol/mol of turkey gizzard myosin heavy chain was incorporated. Evidence that the ligands were associated with the catalytic site included the observations that reaction occurred only with nucleotides that are substrates or products of the ATPase activity; that the reaction was blocked by pyrophosphate which is an inhibitor of the ATPase activity; that ATP was bound as ADP; and that label was probably restricted to a single peptide following limited subtilisin proteolysis of labeled Acanthamoeba myosin IA heavy chain and extensive cleavage with CNBr and ...

UK PubMed Central (United Kingdom)

ATP is synthesized by ATP synthase (F_OF₁-ATPase). Its rotary electromotor (F_O) translocates protons (in some organisms sodium cations) and generates torque to drive...Full Text Available

UK PubMed Central (United Kingdom)

Thlaspi caerulescens is a heavy metal hyperaccumulator plant species that is able to accumulate extremely high levels of zinc (Zn) and cadmium (Cd) in its shoots (30,000 μg...Full Text Available

UK PubMed Central (United Kingdom)

The ntpJ gene, a cistron located at the tail end of the vacuolar-type Na⁺-ATPase (ntp) operon of Enterococcus hirae, encodes a transporter...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

This study is aimed at exploring the possible mechanism of hypnosis-enhancing effect of HgS or cinnabar (a traditional Chinese medicine containing more than 95% HgS) in mice treated with pentobarbital. We also examined whether the effect of HgS is different from that of the well-known methyl mercury (MeHg). After a short period (7 days) of oral administration to mice, a nontoxic dose (0.1 g/kg) of HgS not only significantly enhanced pentobarbital-induced hypnosis but also attenuated tolerance induction; while a higher dose (1 g/kg) of HgS or cinnabar exerted an almost irreversible enhancing effect on pentobarbital-hypnosis similar to that of MeHg (2 mg/kg) tested, which was still effective even after 10 or 35 days cessation of administration. To study comparatively the effects of different mercury forms from oral administration of MeHg and HgS on membrane ATPase activities of experimental mice, analysis of the Hg content in the cerebral cortex revealed that ...

International Nuclear Information System (INIS)

Neutron transmutation doping(NTD) for producing ntype silicon semiconductor is based on the conversion of the Si-30 isotope into phosphorus atom by neutron absorption reaction. By using this method, silicon semiconductors with extremely uniform n-type dopant distributions can be produced, and this is the dominant advantage of NTD compared with the conventional chemical doping. HANARO has two vertical holes for NTD, and the commercial NTD service for 5 and 6 inch silicon ingots has been going on at the NTD2 hole. Generally, NTD method is applied to the initially n-type silicon material. But, an initially p-type silicon material can also be used for the production of uniformly doped n-type silicon by using NTD method. Therefore, in this work, we investigated the relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material. Thereafter, we established the methodology for the neutron ...

Science.gov (United States)

of the supplier of pulled p-type silicon material. of G-6 and E 8 centers irradiated in the 1 t o 3 MeV range. tions w i l l be performed using the General ...

Energy Technology Data Exchange (ETDEWEB)

The effect of the external pH on the intracellular pH in mung bean (Vigna mungo (L.) Hepper) root-tip cells was investigated with the T P nuclear magnetic resonance (NMR) method. The T P NMR spectra showed three peaks caused by cytoplasmic G-6-P, cytoplasmic Psub(i) and vacuolar Psub(i). The cytoplasmic and vacuolar pHs could be determined by comparing the Psub(i) chemical shifts with the titration curve. When the external pH was changed over a range from pH 3 to 10, the cytoplasmic pH showed smaller changes than the vacuolar pH, suggesting that the former is regulated more strictly than the latter. The H -ATPase inhibitor, DCCD, caused the breakdown of the mechanism that regulates the intracellular pH. H -ATPase appears to have an important part in the regulation of the intracellular pH.

Energy Technology Data Exchange (ETDEWEB)

Since chlordecone (Kepone, CD) interferes with cardiac Na{sup +} ion translocases, we have studied CD effects on cardiac SR calcium pump activity. SR was isolated from heart ventricles of male Sprague-Dawley rats. Cardiac SR Ca{sup 2+}-ATPase, {sup 45}Ca-uptake and cAMP as well as calmodulin (CaM) dependent protein phosphorylation were measured. Ca{sup 2+}-ATPase was differentiated into low affinity and high affinity forms by measuring the activity using 50 and 0.7 {mu}M free Ca{sup 2+} respectively. CD in vitro inhibited {sup 45}Ca-uptake by SR in a concentration dependent manner with an IC50 value of 7 {mu}M and SR {sup 45}Ca-uptake was totally inhibited at 20-30 {mu}M CD. In agreement with this, both high affinity and low affinity Ca{sup 2+}-ATPases, which are involved in Ca{sup 2+} transport across membranes, were also inhibited by CD in a concentration dependent manner with IC50 values of 0.7 and 3.2 {mu}M ...

Energy Technology Data Exchange (ETDEWEB)

Conductivity and Hall effect measurements were made in dark and IR-photoexcited p-type ZnTe samples between 77 and 300 K. Acceptor vacancy complexes of activation energies 0.09-0.1 eV were found to be present in the photoexcited samples. Different possible scattering mobilities were considered for both samples to explain the observed hole mobility. In the photoexcited sample a scattering mobility due to vacancy complexes was suggested for the first time to explain the results. The scattering centres were associated with native vacancy complexes segregated at the dislocations sites. The expression for the complex scattering mobility has been deduced using the curve fitting method to be {mu}{sub C}=(6.6x10{sup -11})T{sup 5} e{sup 725/T}. (orig.).

Energy Technology Data Exchange (ETDEWEB)

New techniques were developed to construct Schottky barrier and homojunction solar cells on GaAs substrates. Schottky barrier metal-semiconductor solar cells were produced for the first time on p-type GaAs substrate using a sputter-deposition method to form the barrier. The sputter deposition of gold or gold/palladium is the key to the method since normal thermal evaporation of gold onto p-type GaAs produces ohmic contacts. The results of this investigation are consistent with the idea that sputter damage produces donor type surface states on GaAs. Barrier heights were measured for both p-type sputtered and n-type thermally evaporated diodes using current-voltage and capacitance-voltage methods. Deep-level transient spectroscopy was used to identify the trap center concentration and energy levels for both diodes in an effort to explain the relatively large dark current in the p-type sputtered diodes. ...

Energy Technology Data Exchange (ETDEWEB)

The effects of orthovanadate on the uptake of sucrose by Ricinus cotyledons and on sucrose-coupled proton influx were measured in order to gain insight into the relationship to the plasma membrane proton pump. Vanadate had no effect on short-term sucrose uptake. In long-term experiments (> 30 min) sucrose uptake was progressively inhibited, but only at high external sucrose concentrations. Vanadate did not affect proton efflux pumping in the absence of sucrose and neither did it change the initial rate of sucrose-coupled proton influx. However, it enhanced the maximal level of sucrose-induced alkalization of the medium at all sucrose concentrations tested. This is interpreted as an inhibiting effect of vanadate on the proton pump that recycles protons during sucrose-proton cotransport. The sensitivity towards vanadate indicates that this proton pump is an ATPase. A second proton-translocating system, that is insensitive to vanadate, is postulated to function in ...

Science.gov (United States)

Cardiac contractile function is dependent on the integrity and function of the sarcolemmal membrane. Swimming exercise training is known to increase cardiac contractile performance. The purpose of the present study was to examine whether a swimming exercise program would alter sarcolemmal enzyme activity, ion flux, and composition in rat hearts. After approximately 11 wk of exercise training, cardiac myosin and actomyosin Ca2+-adenosinetriphosphatase (ATPase) activity was significantly higher in exercised rat hearts than in sedentary control rat hearts. Glycogen content was increased in plantaris and gastrocnemius muscles from exercised animals as was succinic dehydrogenase activity in gastrocnemius muscle of exercised rats in comparison to sedentary rat preparations. Sarcolemmal vesicles were isolated from hearts of exercise-trained and control rats. Sarcolemmal Na+-K+-ATPase and K+-p-nitrophenylphosphatase activities, Na+-Ca2+ exchange, and ...

Science.gov (United States)

Surface scientists argue about the fundamental nature of Schottky barriers, or more precisely what determines the location of the Fermi level at semiconductor surfaces and interfaces. Electrical and materials engineers worry about how to make Schottky barrier diodes and gates to field effect transistors and the control of barrier heights. There is some interesting middle ground in which the location of the surface and interface Fermi level can, for example, determine semiconductor doping characteristics during crystal growth. The authors will discuss several interesting and well known examples of doping characteristics which are still somewhat mysterious. Specifically, they address the following question: (1) why is Ge doped GaAs p type when grown from Ga melts but n type when grown from Au melts (2) why is low resistivity p type ZnSe, AlAs, and AlGaInP hard to make, and more importantly, how can the ...

International Nuclear Information System (INIS)

Semiconductor properties of passive films formed on the Fe-18Cr alloy in a borate buffer solution (pH = 8.4) and 0.1 M H_2SO_4 solution were examined using a photoelectrochemical spectroscopy and an electrochemical impedance spectroscopy. Photo current reveals two photo action spectra that derived from outer hydroxide and inner oxide layers. A typical n-type semiconductor behaviour is observed by both photo current and impedance for the passive films formed in the borate buffer solution. On the other hand, a negative photo current generated, the absolute value of which decreased as applied potential increased in the sulfuric acid solution. This indicates that the passive film behaves as a p-type semiconductor. However, Mott-Schottky plot revealed the typical n-type semiconductor property. It is concluded that the passive film on the Fe-18Cr alloy formed in the borate buffer solution is composed of both n-type outer hydroxide and inner oxide layers. On the other ...

Science.gov (United States)

Metallic contamination was monitored with Surface Photovoltage (SPV) technique in integrated circuit manufacturing facilities. Conventionally, Czochralski silicon bulk materials were used as monitor wafers. However, it has been observed that the diffusion length and the `Iron' concentration measured with SPV were inconsistent from run to run in one facility. The inconsistency is believed to be due to oxygen precipitate in silicon materials during the thermal cycle. By using low oxygen concentration or Float Zone wafers, metallic contaminants can be monitored more accurately and consistently.

Science.gov (United States)

Continuous wave lasing operation with the shortest wavelength for semiconductor lasers was obtained from AlGaInP double heterostructure lasers at 77 K. The structure was grown by metalorganic vapor phase epitaxy. Lasing wavelength was 583.6 nm (yellow). Threshold current was 43 mA (1.9 kA/cm/sup 2/). Magnesium was adopted as a p-type dopant, and was proved to be preferable for a high aluminum composition AlGaInP cladding layer.

Science.gov (United States)

Environmental arsenic is a world-wide health issue, making it imperative for us to understand mechanisms of metalloid uptake and detoxification. The predominant intracellular form is the highly mephitic arsenite, which is detoxified by removal from cytosol. What prevents arsenite toxicity as it diffuses through cytosol to efflux systems? Although intracellular copper is regulated by metallochaperones, no chaperones involved in conferring resistance to other metals have been identified. In this article, we report identification of an arsenic chaperone, ArsD, encoded by the arsRDABC operon of Escherichia coli. ArsD transfers trivalent metalloids to ArsA, the catalytic subunit of an As(III)/Sb(III) efflux pump. Interaction with ArsD increases the affinity of ArsA for arsenite, thus increasing its ATPase activity at lower concentrations of arsenite and enhancing the rate of arsenite extrusion. Cells are consequently resistant to environmental concentrations of arsenic. ...

Energy Technology Data Exchange (ETDEWEB)

Passive films formed on stainless steels in a borate buffer solution (pH 9.2) have been investigated by capacitance measurements and photoelectrochemistry. The study was carried out on films formed on AISI type 304 and 316 stainless steels and high purity alloys with differing chromium, nickel, and molybdenum contents. Complementary research by Auger analysis shows that the passive films are composed essentially of an inner chromium region in contact with the metallic substrate and an outer iron oxide region developed at the film/electrolyte interface. The semiconducting properties of the passive films are determined by those of the constituent chromium and iron oxides which are of p-type and n-type, respectively. Thus the influence of the alloying elements on the semiconducting properties of the passive films is explained by changes in the electronic structure of each of these two oxide regions.

Science.gov (United States)

By applying lock-in thermography imaging, light-beam-induced current imaging, electron-beam-induced current imaging at different stages of sample preparation, and infrared light microscopy in transmission mode, the physical nature of the dominant material-induced shunts in multicrystalline solar cells made from p-type silicon material has been investigated. It turns out that these shunts are due to silicon carbide (SiC) filaments, which grow preferentially in grain boundaries and cross the whole cell. These filaments are highly n-type doped, like the emitter layer on the surface of the cells. They are electrically connected both with the emitter and with the back contact, thereby producing internal shunts in the solar cell.

British Library Electronic Table of Contents (United Kingdom)

By applying lock-in thermography imaging, light-beam-induced current imaging, electron-beam-induced current imaging at different stages of sample preparation, and infrared light microscopy in transmission mode, the physical nature of the dominant material-induced shunts in multicrystalline solar cells made from p-type silicon material has been investigated. It turns out that these shunts are due to silicon carbide (SiC) filaments, which grow preferentially in grain boundaries and cross the whole cell. These filaments are highly n-type doped, like the emitter layer on the surface of the cells. They are electrically connected both with the emitter and with the back contact, thereby producing internal shunts in the solar cell.

Energy Technology Data Exchange (ETDEWEB)

The electronic structures of platinum group elements (Ru, Os, Rh, Ir, Pd, and Pt) silicides have been calculated. Ir{sub 3}Si{sub 5} is a semiconductor with the direct gap of 1.14 eV. Among monosilicides, RuSi and OsSi with the FeSi-type structure are semiconductors with the gap values of 0.21 and 0.41 eV but RhSi, IrSi, PdSi, and PtSi with the MnP-type structure are metals. No semiconducting compounds can be found in other platinum group elements silicides other than known Ru{sub 2}Si{sub 3}, Os{sub 2}Si{sub 3}, and OsSi{sub 2}.

Energy Technology Data Exchange (ETDEWEB)

The chemical composition and the semiconducting properties of passive films formed on nickel based alloy (Alloy 600) in acidic sulphate solution, pH 2.0 at room temperature were studied using Auger analysis, voltammetric techniques and the Mott-Schottky approach. The results obtained revealed that the presence of both chromium and mixed nickel-iron oxides in the films leads to the development of a p-n heterojunction, which controls their electronic structure, similarly manner to the case of stainless steels and Alloy 600 in borate buffer solution. This behavior has been interpreted as representing of an oxide system, which has a duplex character, with an inner p-type semiconducting region, mainly formed by chromium oxide and an outer n-type semiconducting region, containing iron oxide. It could also be observed that the nickel oxide present in the films acts as a barrier layer conferring improved protection.

Energy Technology Data Exchange (ETDEWEB)

As the only non-polar plane the (110) surface has a unique role in GaAs. Together with Silicon as a dopant it is an important substrate orientation for the growth of n-type or p-type heterostructures. As a consequence, this thesis will concentrate on growth and research on that surface. In the course of this work we were able to realize two-dimensional electron systems with the highest mobilities reported so far on this orientation. Therefore, we review the necessary growth conditions and the accompanying molecular process. The two-dimensional electron systems allowed the study of a new, intriguing transport anisotropy not explained by current theory. Moreover, we were the first growing a two-dimensional hole gas on (110) GaAs with Si as dopant. For this purpose we invented a new growth modulation technique necessary to retrieve high mobility systems. In addition, we discovered and studied the metal-insulator transition in thin bulk p-type ...

International Nuclear Information System (INIS)

Cinnabar, a naturally occurring mercuric sulfide (HgS), has long been used in combination with traditional Chinese medicine as a sedative for more than 2000 years. Up to date, its pharmacological and toxicological effects are still unclear, especially in clinical low-dose and long-term use. In this study, we attempted to elucidate the effects of cinnabar on the time course of changes in locomotor activities, pentobarbital-induced sleeping time, motor equilibrium performance and neurobiochemical activities in mice during 3- to 11-week administration at a clinical dose of 10 mg/kg/day. The results showed that cinnabar was significantly absorbed by gastrointestinal (G-I) tract and transported to brain tissues. The spontaneous locomotor activities of male mice but not female mice were preferentially suppressed. Moreover, frequencies of jump and stereotype-1 episodes were progressively decreased after 3-week oral administration in male and female mice. Pentobarbital-induced sleeping time ...

International Nuclear Information System (INIS)

We have studied the correlation between the chemical state and the oxygen-sensing properties of an iron oxide thin film using a setup that allows simultaneous sensor resistance measurements and X-ray photoelectron spectroscopy (XPS) data acquisition. The gas exposures were performed at the highest operating pressure of the XPS spectrometer at a controlled sample temperature which allows direct comparison between the sensor response and the chemical state of the surface. The iron oxide film was modified by a sequence of argon ion sputtering steps and the induced changes in the chemical state, resistance, and sensitivity to oxygen were investigated. The sputtering was found to reduce the iron from the Fe"3"+ to the Fe"2"+ state and to decrease the sensor resistance. The measured sensitivity to oxygen first increased by a factor of two but then collapsed to its original level. The mechanism for oxygen sensing was found to be filling of the oxygen vacancies in the lattice. The effect of ...

British Library Electronic Table of Contents (United Kingdom)

The electrical characteristics of thin TiO2 films prepared by metal?organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO2 film of 4.7?nm on InP without and with ammonium sulfide treatment, the leakage currents are 8.8?10?2 and 1.1?10?4?A/cm2 at +2 V bias and 1.6?10?1 and 8.3?10?4?A/cm2 at ?2?V bias. The lower leakage currents of TiO2 with ammonium sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide charge number density are 33 and 2.5?1013?cm2, respectively. The lowest mid-gap interface state density is around 7.6?1011?cm?2?eV?1. The equivalent oxide thickness is 0.52?nm. The breakdown electric field increases with decreasing thickness in the range of 2.5 to 7.6?nm and reaches 9.3?MV/cm at 2.5?n...

International Nuclear Information System (INIS)

Field emitter devices are being developed for the gigatron, a high-efficiency, high frequency and high power microwave source. One approach being investigated is porous silicon, where a dense matrix of nanoscopic pores are galvanically etched into a silicon surface. In the present paper pore morphologies were used to characterize these materials. Using of Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) images of both N-type and P-type porous layers, it is found that pores propagate along the <100> crystallographic direction, perpendicular to the surface of (100) silicon. Distinct morphologies were observed systematically near the surface, in the main bulk and near the bottom of N-type (100) silicon lift-off samples. It is seen that the pores are not cylindrical but exhibit more or less approximately square cross sections. X-ray diffraction spectra and electron diffraction patterns verified that bulk porous silicon is still a ...

Energy Technology Data Exchange (ETDEWEB)

Techniques for fabricating P-type (Cu,Ag)/sub 2/Se with mesh-type bonds have been developed and are being evaluated for long-term use. In addition, methods for reducing vapor suppression by the use of coatings and/or baffling continue to show gains. The N-type alloy Gd/sub 2/Se/sub 3/ has been shown to be thermally unstable. It undergoes a sluggish cubic-to-orthorhombic phase change below 1000/sup 0/C, with an accompanying degradation in mechanical and thermoelectric properties. Fabrication studies conducted with the (Bi,Sb)/sub 2/(Se,Te)/sub 3/ alloys showed these materials to be sensitive to oxygen contamination if reproducible properties are to be obtained. Preparation of powdered material by explosive techniques was investigated. This technique appears to be useful in preparing homogeneous -325 mesh material, but it does not yield a useful amount of submicron-size powder.

Energy Technology Data Exchange (ETDEWEB)

Minority-carrier lifetime damage coefficients for 1 MeV electron, 3 MeV proton, and 6 MeV alpha particle irradiation of n-type (4.5{times}10{sup 15} and 1.3{times}10{sup 17}cm{sup {minus}3}) and p-type (2.5{times}10{sup 17}cm{sup {minus}3}) InP have been measured using time-resolved photoluminescence. These values are relatively insensitive to carrier type and show a slight increase with increasing carrier concentration. Evidence of comparable electron and hole capture lifetimes is found for the dominant recombination defect. The effect of 3 MeV proton and 6 MeV alpha particles relative to 1 MeV electrons is an increase in the lifetime damage coefficient by factors of about 10{sup 4} and 10{sup 5}, respectively. {copyright} {ital 1997 American Institute of Physics.}

Science.gov (United States)

A modified epitaxial design leads to straightforward implementation of short (1{lambda}) optical cavities and the use of C as the sole {ital p}-type dopant in AlGaInP/AlGaAs red vertical-cavity surface-emitting lasers (VCSELs). Red VCSELs fabricated into simple etched air posts operate continuous wave at room temperature at wavelengths between 670 and 690 nm, with a peak output power as high as 2.4 mW at 690 nm, threshold voltage of 2.2 V, and peak wallplug efficiency of 9%. These values are all significant improvements over previous results achieved in the same geometry with an extended optical cavity epitaxial design. The improved performance is due primarily to reduced optical losses and improved current constriction and dopant stability. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Science.gov (United States)

Ion implantation has been applied to magnesium-doped Al[sub 0.5]In[sub 0.5]P to produce high resistivity regions for the first time. Hydrogen, oxygen, and argon ions were implanted at a base dose ranging from 5[times]10[sup 12] to 5[times]10[sup 14] cm[sup [minus]2] and annealed from 400 to 900 [degree]C. Hydrogen did not appreciably compensate the In[sub 0.5]Al[sub 0.5]P layer while oxygen and argon produced sheet resistances up to 1[times]10[sup 9] [Omega]/[open square]. After annealing at 800 [degree]C, regions with high dose oxygen implants maintained a sheet resistance above 1[times]10[sup 7] [Omega]/[open square], while regions with high dose argon implants recovered most of the unimplanted conductivity.

Science.gov (United States)

Data are presented on the insulating properties and capacitance-voltage (CV) characteristics of metal-oxide-semiconductor (MOS) device-thickness (below approx. 100 nm) native oxides formed by wet thermal oxidation of thin InAlP epilayers lattice matched to GaAs. Low leakage current densities of J=1.4 x 10-9 A/cm2 and J=8.7 x 10-11 A/cm2 are observed at an applied field of 1 MV/cm for MOS capacitors fabricated with 17 nm and 48 nm oxides, respectively. TEM images show that the In-rich interfacial particles which exist in 110 nm oxides are absent in 17 nm oxide films. Quasi-static capacitance-voltage measurements of MOS capacitors fabricated on both n-type and p-type GaAs show that the InAlP oxide-GaAs interface is sufficiently free of traps to support inversion, indicating an unpinned Fermi level. These data suggest that InAlP native oxides may be a viable insulator for GaAs MOS device applications.

Science.gov (United States)

Snake envenomation employs three well integrated strategies: prey immobilization via hypotension, prey immobilization via paralysis, and prey digestion. Purines (adenosine, guanosine and inosine) evidently play a central role in the envenomation strategies of most advanced snakes. Purines constitute the perfect multifunctional toxins, participating simultaneously in all three envenomation strategies. Because they are endogenous regulatory compounds in all vertebrates, it is impossible for any prey organism to develop resistance to them. Purine generation from endogenous precursors in the prey explains the presence of many hitherto unexplained enzyme activities in snake venoms: 5'-nucleotidase, endonucleases (including ribonuclease), phosphodiesterase, ATPase, ADPase, phosphomonoesterase, and NADase. Phospholipases A(2), cytotoxins, myotoxins, and heparinase also participate in purine liberation, in addition to their better known functions. Adenosine contributes to ...

International Nuclear Information System (INIS)

Based on the results obtained for C-N and Si-C-N films, a systematic investigation of reactive magnetron sputtering of hard quaternary Si-B-C-N materials has been carried out. The Si-B-C-N films were deposited on p-type Si(100) substrates by dc magnetron co-sputtering using a single C-Si-B target (at a fixed 20% boron fraction in the target erosion area) in nitrogen-argon gas mixtures. Elemental compositions of the films, their surface bonding structure and mechanical properties, together with their oxidation resistance in air, were controlled by the Si fraction (5-75%) in the magnetron target erosion area, the Ar fraction (0-75%) in the gas mixture, the rf induced negative substrate bias voltage (from a floating potential to -500 V) and the substrate temperature (180-350 deg. C). The total pressure and the discharge current on the magnetron target were held constant at 0.5 Pa and 1 A, respectively. The energy and flux of ions bombarding the growing films were ...

International Nuclear Information System (INIS)

The valence and spin-state distributions of Co ions and the complex structure of antiferromagnetic Ba_2Co_9O_1_4 have led to the suggestion that doped Ba_2Co_9O_1_4 compounds may be good thermoelectric materials. We have checked this suggestion by measuring the magnetic properties as well as the transport properties of nominal Ba_1_._9A_0_._1Co_9O_1_4 (A=La or Na). We show that although all compounds are indicated to be single phase by powder X-ray diffraction analysis, they are all p-type polaronic conductors with low mobile-hole concentrations. Magnetic-susceptibility data of the parent and La-doped compounds give evidence of a second magnetic phase with ferromagnetic order setting in below 215 K; but this second phase is not seen in the Na-doped sample. We conclude that the structure is stabilized by oxidation and that cation exolution from the Ba_2Co_9O_1_4 structure creates cation vacancies that oxidize the high-spin (HS) Co(II) to the intermediate-spin ...

Science.gov (United States)

The authors present electric-field dependent electroreflectance and photocurrent spectra of visible-bandgap In{sub x}(Al{sub y}Ga{sub 1{minus}y}){sub 1{minus}x}P/In{sub x{prime}}(Al{sub y{prime}}Ga{sub 1{minus}y{prime}}){sub 1{minus}x{prime}}P multiple-quantum-well (MQW) structures. These structures, grown by metal-organic vapor phase epitaxy on 6{degrees}-misoriented (100) GaAs substrates, have undoped MQWs sandwiched between doped In{sub 0.5}Al{sub 0.5}P layers, forming p-i-n diodes. Quantum-well compositions in the range 0.46{le}x{le}0.52 and 0{le}y{le}0.4, corresponding to bandgaps in the red to yellow-green range, were used. The Stark shifts in these various samples were measured and found to depend on the details of the Mg p-type doping profile, confirming important diffusion effects, in agreement with secondary ion mass spectrometry and capacitance-voltage data. The results show that these new materials are promising for visible-wavelength optical modulator ...

International Nuclear Information System (INIS)

Transient enhanced diffusion (TED) and dose loss (pile-up) are investigated for phosphorus-implanted samples covered with both oxide and nitride films. P ions were implanted into p-type (1 0 0) CZ-Si (dose 5x10"1"3 cm"-"3, 100 keV) through a chemical vapor deposition (CVD) Si_3N_4 film. For a half of samples, Si_3N_4 was etched off and SiO_2 films were grown by CVD. Both samples were annealed for 20-360 min at 700 deg. C. Diffusivity of P and the dose loss were estimated based on the secondary-ion mass spectrometry (SIMS) P profiles. Both Si/Si_3N_4 and Si/SiO_2 interfaces were investigated with transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). There is no significant difference in P diffusivity between the SiO_2 and Si_3N_4 films for the present annealing condition of 700 deg. C for 20-360 min. Regarding dose loss, a distinct different behavior was observed. In case of the SiO_2 cover film, amount of dose decreases with the ...

International Nuclear Information System (INIS)

This study demonstrates amplified spontaneous emission (ASE) of the ultraviolet (UV) electroluminescence (EL) from ZnO at #lambda##approx#380 nm in the n-ZnO/ZnO nanodots-SiO_2 composite/p- Al_0_._1_2Ga_0_._8_8N heterojunction light-emitting diode. A SiO_2 layer embedded with ZnO nanodots was prepared on the p-type Al_0_._1_2Ga_0_._8_8N using spin-on coating of SiO_2 nanoparticles followed by atomic layer deposition (ALD) of ZnO. An n-type Al-doped ZnO layer was deposited upon the ZnO nanodots-SiO_2 composite layer also by the ALD technique. High-resolution transmission electron microscopy (HRTEM) reveals that the ZnO nanodots embedded in the SiO_2 matrix have diameters of 3-8 nm and the wurtzite crystal structure, which allows the transport of carriers through the thick ZnO nanodots-SiO_2 composite layer. The high quality of the n-ZnO layer was manifested by the well crystallized lattice image in the HRTEM picture and the low-threshold optically pumped stimulated ...

Energy Technology Data Exchange (ETDEWEB)

This SBIR Phase I developed neutron detectors made from gallium arsenide (GaAs) p-type/ intrinsic/n-type (P-I-N) diodes grown by metalorganic chemical vapor deposition (MOCVD) onto semi-insulating (S1) bulk GaAs wafers. A layer of isotonically enriched boron-10 evaporated onto the front surface serves to convert incoming neutrons into lithium ions and a 1.47 MeV alpha particle which creates electron-hole pairs that are detected by the GaAs diode. Various thicknesses of ''intrinsic'' (I) undoped GaAs were tested, as was use of a back-surface field (BSF) formed from a layer of Al{sub x}Ga{sub 1-x}As. Schottky-barrier diodes formed from the same structures without the p+ GaAs top layer were tested as a comparison. After mesa etching and application of contacts, devices were tested in visible light before application of the boron coating. Internal quantum efficiency (IQE) of the best diode near the GaAs bandedge is over 90%. The ...