Science.gov (United States)

Summary of personnel, commitments, and costs ... Origin of complex land-based ecosystems (W. Friedman) ...... technology has brought about the birth of lab- ..... Baross, J.A. and S.E. Hoffman, Submarine hydrothermal vents and ...

Science.gov (United States)

His talk was based on the suggestion that life on Earh has been a long but accelerating ..... a New Class of Submarine Hydrothermal System"; April 29, 2002 , ..... of media personnel, including radio, television, newspapers, and magazines. ...... "The Birth of Stars and Planets" (Denver Museum of Nature and Science ...

Science.gov (United States)

Language: English ...

Science.gov (United States)

Language: English ...

Science.gov (United States)

... as the difference between date of birth and date of ... Final model selections were based on the ... approval by the Naval Submarine Medical Research ...

Science.gov (United States)

Language: English ...

Science.gov (United States)

Language: English ...

British Library Electronic Table of Contents (United Kingdom)

A tobermorite/hydroxyapatite composite was prepared by hydrothermal treatment using diatomaceous earth, ?-tricalcium phosphate and slaked lime starting materials. The XRD patterns of the composite confirmed that tobermorite and hydroxyapatite were formed after the hydrothermal process. The bending strength of the composite reached a level higher than 9?MPa after the hydrothermal process. The development of the bending strength was due to the formation of tobermorite and hydroxyapatite during the hydrothermal process. The composite had a high specific surface area due to these newly formed crystals.

International Nuclear Information System (INIS)

The NATO Advanced Research Workshop on Nuclear Submarine Decommissioning and Related Problems was held in Moscow June 19--22, 1995. It was preceded by a visit to the Zvezdotchka Shipyard at Severodvinsk, a repair and maintenance yard for Russian nuclear submarines, for a subgroup of the workshop attendees. Most of the material in this paper is drawn directly form the workshop proceedings. Slightly less than 500 nuclear ships and submarines (the vast majority are submarines) have been constructed by the countries with nuclear navies. This includes approximately 250 by Russia, 195 by the United States, 23 by the United Kingdom, 11 by France and 6 by China. By the year 2000 it is expected that approximately one-half of these nuclear vessels will be removed from service and in various states of decommissioning. A newspaper account in June 1997 indicated that 156 Russian nuclear ...

Science.gov (United States)

hicle [UUV (essentially, a small ex- ploratory submarine robot)] of a type that has been deployed in large numbers in research pertaining to global warm- ...

Science.gov (United States)

System). From collecting terabytes of video footage to tracking the movements of the submarines, this software is essential to the science team as they explore unique structures on...

Energy Technology Data Exchange (ETDEWEB)

Microwave-hydrothermal processing was compared with conventional hydrothermal processing in the crystallization of hematite from 1M ferric nitrate and hydroxyapatite from calcium oxide and phosphoric acid. Microwave-hydrothermal processing led to the crystallization of hematite while convention-hydrothermal process led to the crystallization of a mixture of goethite and hematite under the same temperature conditions. Thus the crystallization of hematite which is the stable iron oxide phase at high temperatures has been catalyzed by microwaves. Microwave-hydrothermal processing also led to highly crystalline hydroxyapatite powders compared to the conventional hydrothermal processing which also points to the catalytic role of microwaves. The microwave induced effects may be attributed to the generation of localized high temperatures at the reaction sites which ...

UK PubMed Central (United Kingdom)

The methanogenic community in hydrothermally active sediments of Guaymas Basin (Gulf of California, Mexico) was analyzed by PCR amplification, cloning, and sequencing of methyl coenzyme M reductase...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The studies undertaken by the B.C. Hydro company at the Canada showed that the existing system of hydroelectric power plants and transport cables will not be able to satisfy the increasing energy demand on the Vancouver island after 1985, and that the best solution will be the installation of a 525 kV transfer system from the continent. THe STK participated to the development and the immersion of this new system, the first in the world comprising submarine 525 kV transport parts. This paper presents the planning, the development, the submerging and the installation of two sections of submarine cable.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

We have investigated the formation and coarsening of Ga droplets on focused-ion-beam (FIB) irradiated GaAs surfaces. To separately examine formation and coarsening, Ga droplets were fabricated by Ga"+ FIB irradiation of GaAs substrates with and without pre-patterned holes. We determined the droplet growth rate and size distribution as a function of FIB energy following irradiation. The data suggest a droplet formation mechanism that involves Ga precipitation from a Ga-rich layer, followed by droplet coarsening via a combination of diffusion and Ostwald ripening or coalescence via droplet migration (dynamic coalescence).

Energy Technology Data Exchange (ETDEWEB)

The tanning process and associated energy requirements are summarized. It appears that a significant economic impact may be possible if a shallow hydrothermal resource of approximately 150 to 170/sup 0/F (66 to 77/sup 0/C) were found, and the fluids were cascaded to produce the temperatures necessary for the various tanning operations. The hydrothermal energy would have to be cost competitive with the rapidly escalating fossil energy costs. Although one would need to thoroughly analyze the technical, environmental, and economic issues of such an application, this initial review indicates a good match between the process and potential hydrothermal resources.

Energy Technology Data Exchange (ETDEWEB)

The authors report on the nano-fabrication of GaN/AlGaN device structures using focused ion beam (FIB) etching, illustrated on a GaN/AlGaN heterostructure field effect transistor (HFET). Pillars as small as 20nm to 300nm in diameter were fabricated from the GaN/AlGaN HFET. Micro-photoluminescence and UV micro-Raman maps were recorded from the FIB-etched pattern to assess its material quality. Photoluminescence was detected from 300nm-size GaN/AlGaN HFET pillars, i.e., from the AlGaN as well as the GaN layers in the device structure, despite the induced etch damage. Properties of the GaN and the AlGaN layers in the FIB-etched areas were mapped using UV Micro-Raman spectroscopy. Damage introduced by FIB-etching was assessed. The fabricated nanometer-size GaN/AlGaN structures were found to be of good ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Science.gov (United States)

tion and the Copenhagen symposium in many regards heralded the birth of modern marine bio-optics and the .... given to conducting a pigment intercomparison based on .... assignment of personnel and equipment, so the Hout Bay deployments were suspended. ...... submarine light field. Upwelling radiance is measured at ...

Energy Technology Data Exchange (ETDEWEB)

A general calculation method for the analysis of transmission capability of a long-distance single-core ac submarine cable system is presented. The method is based on modal transformation of voltages and currents in multiconductor cable systems. Using this method, numerical calculations on 500 kV submarine cable systems have been performed with particular reference to the effect of the distance between bonds connecting metallic sheath, outer conductor and armor on the transmission capacity of the system. It was clarified that the transmission capacity of the system increased with decreasing bond intervals. Examination of the current distributions between various conductors along the length showed that this increase of transmission capacity was mainly due to the dispersion of the charging current into the metallic sheath, outer conductor and armoring at the bonding points. Analytical results for the transmission capacities of long-distance 500 ...

Science.gov (United States)

for sensitive personnel data. Based on the judgment of Task Force ...... Gunn, R ., Memorandum on Sub-Atomic Power Sources for Submarine ... Hunley, J., ed., The Birth of NASA: The Diary of T. Keith Glennan, SP-4105, ...

Energy Technology Data Exchange (ETDEWEB)

Previous models and evaluation techniques based on the Monte Carlo simulation for the reliability assessment of mixed hydrothermal generation systems are extended. Models for reservoirs on multiple rivers and pumped storage plants are developed. Operating and water management policies are extended to include the relative economical effects of operating alternative sources of generation. These effects and the benefits are described and discussed using an extended IEEE reliability test system. (Author).

Energy Technology Data Exchange (ETDEWEB)

The reactions between (100) GaAs and the near-noble metals Ni, Pd, and Pt have been investigated by application of high-resolution transmission electron microscopy (TEM), energy-dispersive analysis of x rays in the scanning TEM and Rutherford backscattering spectrometry. Emphasis is placed on the evolution of the phase distributions, film compositions, and interface morphologies during annealing at temperatures up to 480 /sup 0/C. The first phase in the Ni/GaAs reaction is shown to have the nominal composition Ni/sub 3/GaAs. Ternary phases of the type Pd/sub x/GaAs are also found to be the dominant products of the Pd/GaAs reaction. Conversely, only binary phases result from the Pt/GaAs reaction. These observations are used to construct isothermal sections of the M--Ga--As thin-film phase diagrams. The behavior of a thin (1--2 nm) native ...

Science.gov (United States)

By gas-source molecular-beam epitaxy, we obtained a device-quality GaInP epitaxial layer lattice matched to (100)-GaAs substrates, with a photoluminescence efficiency comparable to that of a crystal grown by liquid-phase epitaxy. A GaInP/AlInP double heterostructure laser with a GaInP active layer was fabricated, and pulsed lasing operation was achieved at room temperature for, we believe, the first time.

British Library Electronic Table of Contents (United Kingdom)

Abstract The Eiffel Tower edifice is situated in the Lucky Strike hydrothermal vent field at a mean depth of 1690-m on the Mid-Atlantic Ridge (MAR). At this 11-m-high hydrothermal structure, different faunal assemblages, varying in visibly dominant species (mussels and shrimp), in mussel size and in density of mussel coverage, were sampled biologically and chemically. Temperature and sulphide (-S) were measured on the different types of mussel-based assemblages and on a shrimp-dominated assemblage. Temperature was used as a proxy for calculating total concentrations of CH4. Based on the physico-chemical measurements, two microhabitats were identified, corresponding to (i) a more variable habitat featuring the greatest fluctuations in environmental variables and (ii) a second, more stable, ...

International Nuclear Information System (INIS)

This paper describes the performance of AlGaN/GaN HEMTs with 2.4 #mu#m source-drain spacing. So far these are the smallest source-drain spacing AlGaN/GaN HEMTs which have been implemented with a domestic wafer and domestic process. This paper also compares their performance with that of 4 #mu#m source-drain spacing devices. The former exhibit higher drain current, higher gain, and higher efficiency. It is especially significant that the maximum frequency of oscillation noticeably increased. (semiconductor integrated circuits)

Science.gov (United States)

... The approach is to perform noise spectral density measurements and selected materials structure measurements on GaAs detector materials, with ...

British Library Electronic Table of Contents (United Kingdom)

We report on characterization of a set of AlGaN/GaN multiple-quantum-well (MQW) photodetectors. The model structure used in the calculation is the p-i-n heterojunction with 20 AlGaN/GaN MQW structures in i-region. The MQW structures have 2nm GaN quantum well width and 15nm AlxGa1-xN barrier width. The cutoff wavelength of the MQW photodetectors can be tuned by adjusting the well width and barrier height. Including the polarization field effects, on increasing Al mole fraction, the transition energy decreases, the total noise increases, and the responsivity has a red shift, and so the detectivity decreases and has a red shift.

UK PubMed Central (United Kingdom)

Animal facilities generate a large amount of used bedding containing excrement as medical waste. We developed a recycling system for used bedding that involves soft hydrothermal processing. In this...Full Text Available

UK PubMed Central (United Kingdom)

Fatty acid biomarker analysis coupled with gas chromatography-isotope ratio mass spectrometry was used to confirm the presence of methanotrophic and thiotrophic bacterial endosymbionts in the tissues...Full Text Available

Science.gov (United States)

Photorefractives, in general, are among the most promising materials solutions to real time optical correlation. Applications include military target recognition and civilian robotic vision. Crystals of sillenite structure photorefractives, Bi12XO20, where X equals Si, Ge, or Ti, have been grown by melt techniques and in the case of bismuth silicon oxide (BSO) and bismuth titanium oxide (BTO) by the hydrothermal method of high-temperature/high-pressure solution growth. The two growth methods are discussed and crystals grown by the two methods are compared in this paper. Optical absorption and TSC studies show that hydrothermal BSO is essentially free of the native antisite Bi defect which usually acts as a donor. These studies also show that the trap density is greatly reduced in hydrothermal material. Preliminary experiments show that hydrothermal BTO crystals have improved properties over melt grown ...

Science.gov (United States)

Mar 1, 2011 ... The movement of hydrothermal fluids and/or fumarolic vapors through local rocks prior ... The Solar Energetic Particle Event of December 14, 2006 .... for measurement of non-precipitating cloud hydrometeors and aerosols, ...

Energy Technology Data Exchange (ETDEWEB)

The nature of hydrothermal resources, their associated temperatures, geographic locations, and developable capacity are described. The parties involved in development, required activities and phases of development, regulatory and permitting requirements, environmental considerations, and time required to complete development activities ae examined in detail. These activities are put in proper perspective by detailing development costs. A profile of the geothermal industry is presented by detailing the participants and their operating characteristics. The current development status of geothermal energy in the US is detailed. The work on market penetration is summarized briefly. Detailed development information is presented for 56 high temperature sites. (MHR)

International Nuclear Information System (INIS)

Striking differences in differential reflectance and carrier relaxation in In0.4Ga0.6As and In0.4Ga0.6As0.98N0.02 single quantum wells (SQWs) were studied using ultrafast time-resolved photoreflectance. Even with extremely thin SQW of only 60 A within 3000 A wide GaAs confining layers, negative and positive differential reflectance was observed for the excitation photon energy far above the bandgaps at 820 and 880 nm for both samples. Due to absorption by the GaAs confining layer, the peak differential reflectance pumped at 820 nm is an order of magnitude larger than that pumped at 880 nm; and it is larger for InGaAs SQWs than for InGaAsN SQWs. The shorter carrier lifetimes of these samples result from carrier-carrier scattering as pumped at both wavelengths. The longer carrier lifetime as pumped at 880 nm is due to hot phonon decay in ...

Energy Technology Data Exchange (ETDEWEB)

An updated review of the state of the art in the development of GaAs solar cells is provided, with emphasis on AlGaAs-GaAs cells suitable for space applications. A set of theoretically derived characteristics is given for this type of solar cell. Comparison of measured performance with theory shows excellent agreement. Data on the effects of radiation damage (high-energy electrons, protons, and neutrons) is also integrated into a form useful for evaluation purposes. Techniques for fabricating (AlGa)As-GaAs solar cells in quantities large enough for practical applications are discussed and are shown to have been demonstrated. The possibility of extending these techniques to the fabrication of very thin low-weight cells for space applications is also considered. Finally, the results obtained to date in the development of GaAs solar cells for applications requiring concentrated sunlight are reviewed, for ...

Energy Technology Data Exchange (ETDEWEB)

Since the beginning of the sixties, France has developed a fleet of nuclear powered vessels. Insofar as the ships of the 2. generation are being built, the older ones are decommissioned and enter the dismantling process. The average rate is presently one submarine decommissioned every two or three years. The overall strategy for the decommissioning of French nuclear submarines can be brought down to 3 phases: 1. Level 1 dismantling which essentially consists in: - unloading the spent fuel and storing it in a pool ; - possibly emptying the circuits which contain radioactive liquids. The level 1 is easily achieved, as it is not very different from the plant situation during ship overhaul or major refits. 2. Level 2 dismantling which consists in isolating the nuclear reactor compartment from the rest of the submarine and conditioning it for interim storage on a ground facility located inside Cherbourg Naval Dockyard. The rest ...

International Nuclear Information System (INIS)

The wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser is investigated using a microscopic theory of the semiconductor gain medium. Good agreement is found between experiment and theory for the minimum threshold lasing wavelength for a range of laser structures.

International Nuclear Information System (INIS)

Russian 2003 p. 74 Russian Federation Leksin, GA Inst. Teoreticheskoj

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)

Magneto-striction and magnetic form factors in 5f itinerant antiferromagnets UNiGa{sub 5} and UPtGa{sub 5} are studied by means of neutron scattering. Remarkable magneto-striction was observed around T{sub N}, indicating large spin-orbit coupling in the itinerant system. The orbital magnetic moment is found to be strongly suppressed due to the hybridization of uranium 5f with Ga-4p electron.

Science.gov (United States)

This request is submitted to seek interim approval to operate a chemical waste landfill for the disposal of polychlorinated biphenyl (PCB) waste. Interim approval is requested for a period not to exceed 5 years. This request covers only the disposal of sm...

Energy Technology Data Exchange (ETDEWEB)

The relations between nuclear energy availability and nuclear plant safety are analyzed in the particular cases of naval propulsion nuclear boilers (aircraft carriers, submarines): safety objectives, present and potential risk analysis, optimization of the availability-safety couple, at the design stage and during operation (procedural rules related to the boiler state, real time decisions). 6 fig., 1 tab.

Energy Technology Data Exchange (ETDEWEB)

This overview of research conducted at ORNL in 1991 presents information on the subjects of biology, physics, and the environment. Specific topics include gene mutations in kidney disease, technology assessments in thermonuclear fusion, submarine hunting technology, ozone-safe refrigerants, optical data storage via surface enhanced raman spectroscopy, and waste mitigating microbes. (GHH)

Energy Technology Data Exchange (ETDEWEB)

These documents defines the interconnection France-England rules for the 2000 MW DC submarine cable directly linking the transmission networks of England and Wales and France. Rights to use Interconnector capacity from 1 April 2001 are to be offered through competitive tenders and auctions, full details of which are set out in the Rules. The contract and a guide to the application form are provided. (A.L.B.)

Energy Technology Data Exchange (ETDEWEB)

Inductively coupled plasma etching of InGaP, AlInP and AlGaP in BI{sub 3} or BBr{sub 3} discharges was investigated as a function of source power, dc chuck bias and plasma composition. InGaP etches at the fastest rates ({gt}6000thinsp{Angstrom}thinspmin{sup {minus}1}) in both chemistries, followed by AlGaP. It is found that AlInP provides an excellent etch stop for the other two materials in both mixtures. The InGaP surface morphology improves with increasing BI{sub 3} or BBr{sub 3} content, and with increasing dc chuck bias. The etched features for this material are highly anisotropic. Etch selectivities for InGaP over SiO{sub 2} and SiN{sub x} of {ge}8 are obtained in both plasma chemistries, and there is no etch incubation time with either mixture, indicating that both can scavenge the native oxide on InGaP, AlGaP and ...

International Nuclear Information System (INIS)

The DLTS technique was employed to study deep defect centers in Si doped epitaxial layers of Al_0_._3_7Ga_0_._1_6In_0_._4_7P grown by MOCVD as a part of epitaxial structure GaAs/AlGaInP/GaAs on GaAs substrates. A high concentration of DX centers located in a region near the inverted interface GaAs/Al_0_._3_7Ga_0_._1_6In_0_._4_7P was found. The width of this region with the maximum DX center concentration ranges from 5 to 20 nm. By filling the DX centers in the whole region, the activation energy for electron emission was found to be 0.48 eV. However, it is shown for the first time, that the activation energy of the DX center increases with increasing the distance from the GaAs/Al_0_._3_7Ga_0_._1_6In_0_._4_7P inverted interface. A nonuniform of the DX center concentration on the wafers is also observed. The concentration varies in the range ...

Science.gov (United States)

The German-Russian project that is part of the G8 initiative on Global Partnership Against the Spread of Weapons and Materials of Mass Destruction focuses on the speedy construction of a land-based interim storage facility for nuclear submarine reactor compartments at Sayda Bay near Murmansk. This project includes the required infrastructure facilities for long-term storage of about 150 reactor compartments for a period of about 70 years. The interim storage facility is a precondition for effective activities of decommissioning and dismantlement of almost all nuclear-powered submarines of the Russian Northern Fleet. The project also includes the establishment of a computer-assisted waste monitoring system. In addition, the project involves clearing Sayda Bay of other shipwrecks of the Russian navy. On the German side the project is carried out by the Energiewerke Nord GmbH (EWN) on behalf of the Federal Ministry of Economics and Labour (BMWi). ...

Energy Technology Data Exchange (ETDEWEB)

The morphological aspects of ternary phase formation during the Pd-GaAs reaction have been studied by application of transmission electron microscopy (TEM) and Rutherford backscattering (RBS) techniques. The TEM images show that the first product phase, ''phase I'', forms during deposition of Pd onto (100) GaAs and exhibits the preferred orientation (0001)/sub I/ approx. // (01 anti 1)/sub GaAs/. In the presence of unreacted Pd, the second phase, ''phase II'', nucleates at large-angle grain boundaries in the phase I film as the annealing temperature increases above approx.250C. Energy dispersive analysis of x-rays and RBS suggest the nominal compositions Pd3GaAs and Pd4GaAs for phases I and II, respectively.

Energy Technology Data Exchange (ETDEWEB)

This paper reports advances in the development of solar cells made from GaAs-on-Si structures prepared by metalorganic chemical vapor deposition (MOCVD). The use of concentrator cells, operating at [similar to]200 suns, has led to the efficiency achievements of 21.3% (AM1.5D) for a GaAs-on-Si solar cell, and 27.6 (AM1.5D) for a homoepitaxial GaAs cell. The development of epitaxial multilayer dielectric mirrors (Bragg reflectors), as back-surface reflectors in thin-film GaAs cells, on both Si and GaAs substrates, is shown to lead to modest efficiency increases, over that of conventional designs.

International Nuclear Information System (INIS)

Pattern formation on GaAs by Ga"+ focused-ion-beam (FIB) irradiation and subsequent Cl_2 gas etching was carried out. A higher etch rate at the FIB-irradiated area compared with that not irradiated under Cl_2 gas allows pattern construction without a mask process. The degree of residual crystal damage was evaluated using photoluminescence (PL) intensity measurements. The PL intensity in the etched region was one order of magnitude stronger than that of FIB sputtering, and was several times stronger than that of Ga"+ FIB-assisted Cl_2 etching. Etch depths of the order of 100 nm, which is five times deeper than that obtained by FIB sputtering, were efficiently performed using moderate Ga"+-ion doses.

International Nuclear Information System (INIS)

The authors discuss several aspects of defect formation in epitax heterostructures based on solid solutions of A"3B"5 semiconductor compounds; these heterstructures were prepared by liquid phase epitaxy by cooling suitable high-temperature solutions from the initial growth temperature. An analysis shows that the regions near heterojunctions are regions of increased defect density even in compositions based on Al /SUB x/ Ga /SUB 1-x/ As-GaAs, Al /SUB x/ Ga /SUB 1-x/ P-GaP, Al /SUB x/ Ga /SUB 1-x/ Sb-GaSb, where the differences in lattice parameters of the contacting materials are a minimum.

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new approach for solving multistage decision problems in power system operation by using a new fuzzy dynamic programming technique. To investigate its validity, the hydrothermal scheduling problem is used as an example problem. Within this problem, uncertainty elements exist such as load demand and natural hydraulic inflows to reservoirs exist which can be expressed by fuzzy numbers. Two new fuzzy decision making techniques for selecting the optimal operating states at each stage are introduced. Further, the hydrothermal scheduling solution obtained had an operating band defined by upper and lower bounds. To further enhance the information that this operating band provides, a midpoint operation technique that applies both forward and backward fuzzy DP is also introduced. This allows the system operator to consider current operating conditions to determine a suitable stage by stage operation policy within the bounds of the ...

Energy Technology Data Exchange (ETDEWEB)

Semiconductive crystalline PZT powders doped with Bi and K were synthesized by hydrothermal reaction at 200{degree}C for 48 hours. The synthesis of the crystalline powders became difficult with an increase in doped amount of Bi and K, and in Zr/(Ti+Zr) ratio. Since substantial amounts of Pb remained in solution after hydrothermal reaction, the addition of Pb in excess of 25% was necessary to obtain the stoichiometric composition of the PZT solid solution. Bi contents in the powders were identical to those in starting materials, while K contents were less than expected ones. The electromechanical properties of the sintered bodies could be precisely measured by an admittance-curve-fitting method. The electromechanical coupling factor and piezoelectric coefficient of the sintered bodies varied with the Bi content like those of specimens prepared by solid state reaction, and showed the maximum values at a given Bi content. However, the change in ...

British Library Electronic Table of Contents (United Kingdom)

The features of present deposits that form in the vicinity of hot springs can provide clues to the parameters of paleowaters in places of past hydrothermal activity marked by remnant carbonate and/or siliceous sinter. We investigated a large carbonate body at the Garga hot spring developing in the Baikal zone of nitric hydrotherms in the Barguzin Rift Zone valley. The main focus was on the structure of the carbonate mound, as well as on the partitioning of radioactive elements between the cyanobacterial mat and the inorganic component of the body (the issue that has never been explored before). The cyanobacterial community of the Garga spring is an active biosorbent of 226Ra, 228Ra, 210Pb. The radionuclides accumulated by biosorption become preserved in minerals that form within the bacter...

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the results of Task 3 work that was initially discussed in our monthly reports for the period October 1, 1992 through September 30, 1993, and contained in our various papers and abstracts, both published and currently in press or in review. Our work during this period was involved (a) the continuation of studies begun prior to October, 1992, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern and Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill hole samples obtained in 1991 and 1992, and (b) new studies of veins and siliceous rocks cropping out in northwestern Yucca Mountain that provide evidence for previously unrecognized hydrothermal activity during the Crater Flat Tuff period of volcanism.

British Library Electronic Table of Contents (United Kingdom)

Hierarchical TiO2 hollow spheres had been prepared based on bubble templates by a simple one-step hydrothermal method. The diameter of hollow spheres was about 700nm and the shell thickness of them was 69nm. They were composed of similar spindle- or needle-like building units. Furthermore, hydrothermal time had an important influence on the morphology and crystallinity of hollow spheres. Moreover, the UV-Vis diffuse reflectance spectra of TiO2 hollow spheres heated at 150^oC for 10h showed the strongest absorption in the UV-Vis region and the Raman spectrum demonstrated the anatase sample. Additionally, a possible formation mechanism of TiO2 hollow spheres was proposed. So this novel and simple method would provide a development direction to fabricate all kinds of inorganic hollow spheres ...

Energy Technology Data Exchange (ETDEWEB)

Useful bipolar transistor action over the full temperature range from 78 to 823K has been demonstrated for mesa-isolated, liquid-phase epitaxial n/sup +/npn, GaP/Al/sub 0/ /sub 35/Ga/sub 0/ /sub 65/P/GaP/GaP structures. This represents both the highest temperature and the widest temperature range (745K) over which useful solid-state transistor action has ever been demonstrated in any III-V compound semiconductor system. These results imply that the GaP/Al/sub x/Ga/sub 1-x/P chemical system is an excellent materials candidate in which to base a technology for high-temperature electronics and the results also imply the very real possibility of functional solid-state devices and circuits at temperatures in excess of 500/sup 0/C.

Energy Technology Data Exchange (ETDEWEB)

The authors report a two-temperature RF bias stress test on nominal 1.2 W 7.5 GHz GaAs/AlGaAs HBT unit cell amplifiers. MTTF`s of 2020 and 1340 hours were obtained at Tj = 218{degrees}C and 245{degrees}C, respectively, under nominal input bias. An activation energy of 0.42 eV is estimated, consistent with published results for similar devices under DC bias stress.

Science.gov (United States)

Not Available

Energy Technology Data Exchange (ETDEWEB)

We report on multijunction GaInP/GaAs photovoltaic cells with total-area efficiencies of 29.5% at one-sun concentration and air mass (AM) 1.5 global and 25.7% one-sun, AM0. These values represent the highest efficiencies achieved by any solar cell under these illumination conditions. Three key areas in this technology are identified and discussed: the grid design, front surface passivation of the top cell, and bottom surface passivation of both cells. Aspects of cell design related to its operation under different solar spectra and under concentration are also discussed.

Energy Technology Data Exchange (ETDEWEB)

The theory for the general case of solar cells operating inside integrating cavity receivers is established. This is applied to the particular case of different configurations of silicon and GaAs cells. The results of the analysis show that a composite system of silicon and GaAs cells manufactured using relatively simple technology could reach an efficiency of 34%. The optimal configuration is that in which the GaAs cells are placed in the directly illuminated area of the receiver and the silicon cells are placed in the indirectly illuminated area of the receiver. (orig.).

International Nuclear Information System (INIS)

Highly reliable, practical 0.6 #mu#m-band AlGaInP visible laser diodes (LDs), using a GaInP active layer, are described. Over 10,000 hour stable operation at 50 degrees C has been achieved for 3mW light output. Characteristics for visible LDs with an AlGaInP active layer or a multi-quantum-well active layer are also presented.

Science.gov (United States)

Heterostructures based on AlGaInP alloy compounds are very attractive for visible semiconductor lasers, heterojunction bipolar transistors (HBTs), and high-electron-mobility transistors (HEMTs) lattice matched to GaAs substrates. Several wet etching solutions for AlGaP of different compositions have been studied. Al{sub 0.5}Ga{sub 0.5}P is found to etch in HF, H{sub 3}PO{sub 4}, hyphosphorous acid (HOPH{sub 2}:O), HCl, KOH, and 1% Br{sub 2}-methanol (MeOH). Etching of Al{sub 0.5}Ga{sub 0.5}P in HCl is reaction limited with an activation energy of {approximately}54.4 kJ/mol. At fixed conditions, the etch rates of Al{sub x}Ga{sub 1{minus}x}P vary exponentially with x in HF and HCl, while in 1% Br{sub 2}-MeOH and mixtures of HCl and HNO{sub 3} the etch rates follow a linear dependence on AlP mole fraction. HF has been found to be a good etchant for ...

Energy Technology Data Exchange (ETDEWEB)

We describe the growth, fabrication, and characterization of an ultraviolet (UV) photoconductive detector based on In{sub x}Al{sub y}Ga{sub 1-x-y}N quaternary alloy that is lattice matched to GaN. The detector consisted of 0.1 {mu}m In{sub x}Al{sub y}Ga{sub 1-x-y}N alloy grown on 0.5-1.0 {mu}m GaN epilayer by metalorganic chemical vapor deposition. With varying indium concentration, the cut-off wavelength of the In{sub x}Al{sub y}Ga{sub 1-x-y}N detectors could be varied to the deep UV range. The most important and intriguing result is that the responsivity of the In{sub x}Al{sub y}Ga{sub 1-x-y}N quaternary alloy exceeded that of AlGaN alloy of a comparable cutoff wavelength by a factor of five. This makes the nitride quaternary alloy very important material for solar blind UV detectors applications particularly in the deep UV range where Al ...

UK PubMed Central (United Kingdom)

Metabolism of [¹⁴C]gibberellin (GA) A₁₂ (GA₁₂) and [¹⁴C]gibberellin A₁₂-aldehyde (GA₁₂-aldehyde) was examined in cotyledons and seed...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

A modified boundary element approach was used to analyze the response of offshore piles subjected to external soil movements. The computer model employed to solve the pile-soil problem was able to model pile head and tip loading, and loading caused by lateral movement of soil. A nonlinear pile-soil interface element with the ability to represent a hardening or softening plastic response prior to reaching an ultimate state was incorporated. With the program, 4 failure modes can be determined: flow of the soil slide past an intact stationary pile; rotation of the pile with the soil at failure along the full pile length; translation of the pile with the sliding soil, resulting in failure of the supporting soil; and the long-pile mode, in which the maximum bending moment in the pile reaches the yield moment of the pile before complete development of the other 3 modes. Theoretical solutions for a realistic hypothetical offshore pile subjected to submarine slides are ...

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Hydrothermal method for preparing crystal borophosphate with zeolite structure is suggested. To increase absorption capacity and thermal stability of final product, aluminium hydroxide sol, ethylenediamine and ethyl acetate are added to the mixture of crystal boric and concentrated phosphoric acids. Thermal stability of the specimens prepared constitutes 880-950 deg, water absorption capacity is within the limits of 0.30-0.32 cmT/g. 1 table.

UK PubMed Central (United Kingdom)

In this work, porous TiO₂ hollow spheres with an average diameter of 100 nm and shell thickness of 20 nm were synthesized by a facile hydrothermal method with NH₄HCO₃...Full Text Available

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A review of the deep-level defects observed in both electron- and proton-irradiated GaAs solar cells is presented. Studies of the effects of periodic and continuous thermal annealing on the radiation-induced electron and hole traps and the recombination parameters in GaAs solar cells were made for a wide range of electron and proton energies, fluence, annealing temperature and annealing time. A refined model for numerical simulations of the displacement damage was developed for computing the defect density and the cell parameters in the electron- and proton-irradiated GaAs solar cells. Excellent agreement was obtained between the calculated values and the experimental data for the proton-irradiated GaAs solar cells. (orig.).

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Norwegian authorities regard with some disquiet the possibility of a criticality accident in a ship propulsion reactor core at the Kola coast. Along this coast, in land storages, floating storages and in submarines taken out of service, the total number of spent fuel reactor cores amount to two hundred. The total Cs-137 radioactivity in spent ship propulsion reactor fuel at the Kola peninsula can be assessed to 600,000 TBq. A worst case release may amount to more than 5,000 TBq Cs-137, a quantity which under unfavourable conditions might cause serious contamination locally and even across the border to Norway.

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The HVDC link across the English Channel, which was brought into service in 1986, has several innovative features. Techniques used in its construction together with recent developments have consolidated the viability of HVDC links for a variety of applications. Outlines the main features of the scheme, including the benefits of interconnecting the British and French 400 kV AC power systems; integration of the UK converter system to the 400 kV AC grid; the DC submarine cables; convertor equipment (particularly the UK installation); and future HVDC developments. 6 refs.

International Nuclear Information System (INIS)

The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS2-Ga2S3 glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14-15 mol% Ga2S3. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS2.14.3 mol% (1/7) Ga2S3, six-coordinated [S3Ga-X-GaS3] units (X=S or None) are well isolated by the [GeS4] structures, which contributes to the decreasing of precipitation of Ga2S3 crystals in (100-x)GeS2-xGa2S3 (x?14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range ...

Energy Technology Data Exchange (ETDEWEB)

Undoped Al /SUB 0.5/ In /SUB 0.5/ P-Ga /SUB 0.5/ In /SUB 0.5/ P double heterostructure was grown on (100) GaAs by metalorganic chemical-vapor deposition for the first time. A mirror-like grown surface was obtained. Over ten-times stronger photoluminescence-intensity was gained from the sandwiched Ga /SUB 0.5/ In /SUB 0.5/ P-layer, than that from a single epitaxially-grown Ga /SUB 0.5/ In /SUB 0.5/ P-layer on (100) GaAs, indicating that high-quality Al /SUB 0.5/ In /SUB 0.5/ P-Ga /SUB 0.5/ In /SUB 0.5/ P heterointerfaces are formed in the double heterostructure. A lasing action by optical pumping with an argon ion laser was observed in the double heterostructure at 90 K. The observed stimulated emission wavelength was 6470 A.

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A p[sup +]-Al[sub 0.3]Ga[sub 0.7]As/n[sup +]-GaAs heterojunction tunnel diode was fabricated using Atomic Layer Epitaxy (ALE) growth technique. Background carbon doping of [similar to]10[sup 20] cm[sup [minus]3] was achieved in the p-side of the diode by optimizing growth conditions such as V/III ratio, exposure times to reactant gases, and growth temperature. In the n-side of the diode GaAs was doped with silane and doping concentrations as high as 7[times]10[sup 18] cm[sup [minus]3] were also achieved. The dopants are chosen to satisfy the high levels and low diffusion requirements. The diode can be used to interconnect the high and low band-gap cells in the AlGaAs/GaAs cascade solar cell structure. The reactor used in this investigation is a commercial MOCVD system which has been specially modified for dual operation of ALE and MOCVD growth modes.

International Nuclear Information System (INIS)

Large-scale decommissioning of Russian nuclear-powered submarines (NPS) and their utilization prospects gave rise to numerous complicated scientific and technical, as well as economic, problems. Problems of handling of radioactive equipment from the reactor compartments (RC) are among the vital ones, arousing a growing concern with the public. Without solution of the problems the processes of NPS utilization can not be considered completed. It involves potential hazard, for the environment both from NPS being paid up (temporal on-float storage) with unloaded spent nuclear fuel (SNF), and RC, cut from submarine hull, containing highly radioactive equipment and materials but no SNF. Diverse variations of the concept of reactor compartment handling of NPS subject to, utilization are possible, but, in principle, there are essentially two variants: (1) RC utilization directly in the course of NPS utilization, envisaging removal of radioactive ...

Science.gov (United States)

AlGaInP double heterostructure laser diodes with a GaInP active layer constitute a basic laser structure for visible-light lasers using an AlGaInP alloy system. This paper gives a detailed description of (Al/sub x/Ga/sub 1 - x/)/sub 0.5/In/sub 0.5/P metalorganic vapor phase epitaxial growth, laser-fabrication processes, and basic device-characteristics for these lasers. The obtained pulsed-threshold-current was about 3.8 kA/cm/sup 2/(3.2 kA/cm/sup 2/ minimum) for laser diodes with an 8-10 /n//m wide and 150-300 ..mu..m long injection stripe. High characteristic-temperature T/sub o/ for the temperature dependence of pulsed threshold current was obtained and was found to be dependent on band-gap-energy differences between active layers and cladding layers. The maximum value for T/sub o/ was 222 K. The lasing wavelength of an AlGaInP double heterostructure laser diode with a ...

International Nuclear Information System (INIS)

GaAs1-xPx p-n junction structures were grown on the epi-ready n-type GaAs(100) substrate by solid source MBE system for different phosphor compositions. To obtain the lattice-match sample structure was applied graded growth procedure. The structural and optical properties of the sample structures with different P concentration were investigated by using X-ray diffraction (XRD), spectroscopic ellipsometry (SE). In addition, The range of lattice parameters in the graded epilayer and phosphorous composition were determined from the HRXRD rocking curve simulation. We analyse dielectric function spectra of disordered GaAs1-xPx junction structures measured using spectroscopic ellipsometry at room temperature in the 0.6-4.7 eV photon energy region. The critical energy points such as band gap energy and spin-orbit-split energy of these structures were determined using SE data. It is detected that E0, E1 ,E2 energies of the ...

Energy Technology Data Exchange (ETDEWEB)

Ga{sub 0.6}In{sub 0.4}P/(Al{sub 0.8}Ga{sub 0.2}){sub 0.4}In{sub 0.6}P strain-compensated multiple quantum wells (SCMQW) and Ga{sub 0.5}In{sub 0.5}P/(Al{sub 0.4}Ga{sub 0.6}){sub 0.5}In{sub 0.5}P unstrained MQW were grown by MOVPE to investigate the shift of photoluminescence (PL) peak wavelength and the carrier lifetime caused by strain effect in SCMQW. The PL peaks of SCMQW and unstrained MQW were 608 and 628 nm, respectively. From the rocking curve of SCMQW, it indicated that the active layers of SCMQW were not zero net strain. The residual strain caused the emission intensity of SCMQW to be about four times weaker than that of unstrained MQW. The carrier lifetimes of SCMQW and unstrained MQW were measured to be 3 and 6.02 ns, respectively. It was conjectured that the residual strain in SCMQW induced a decrease in the carrier lifetime by a factor of two with respect to that of unstrained MQW.

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Room-temperature cw operation for InGaP/InGaAlP double heterostructure (DH) laser diodes on GaAs substrates was achieved for the first time. The DH wafers were grown by low-pressure metalorganic chemical vapor deposition using methyl metalorganics. A lasing wavelength of 679 nm and a threshold current of 109 mA at 24C were obtained for an inner stripe structure laser diode with a 250- m-long and 7- m stripe geometry. The laser operated at up to 51C. The characteristic temperature T0 was 87 K at around room temperature. The lowest threshold current density, 5.0 kA/cmS, was obtained with a 20- m stripe width laser diode under room-temperature pulsed operation.

International Nuclear Information System (INIS)

The dependence of the photoluminescent properties of In_0_._4_8(Al_yGa_1_-_y)_0_._5_2P alloys (0#<=#y#<=#0.5) on growth temperature and substrate misorientation off GaAs(100) has been studied. Samples were grown using low-pressure metalorganic vapor phase epitaxy. By studying the dependence of ordering behavior in InGaP as a function of substrate misorientation and growth temperature simultaneously, a very large range in low-temperature photoluminescence emission energy---135 meV---has been obtained. The photoluminescence linewidth exhibits a strong, continuous dependence on the extent of atomic ordering (the emission energy) in the alloys. The results indicate that inhomogeneity in the microstructure of the material (i.e., between ''ordered'' domains and the ''disordered'' matrix) is the dominant photoluminescence broadening mechanism. This investigation has allowed a significant optimization of the optical ...

Energy Technology Data Exchange (ETDEWEB)

The characteristics of defects induced by Si and Ga focused ion beam (FIB) implantation in n-GaAs have been investigated by means of deep-level transient spectroscopy (DLTS), C--V carrier profiling, and resistance measurements. The DLTS spectra of Si and Ga FIB implanted samples annealed at temperatures up to 500 /sup 0/C are apparently identical to one another and show three different electron traps with an activation energy between 0.25 and 0.6 eV. The resistance increases by more than five orders of magnitude by Si and Ga FIB implantation due to the induced defects. However, it is restored to initial values after annealing at 600 /sup 0/C, except for a sample of Ga implantation with a dose higher than 10/sup 14/ cm/sup 2/ . For annealing of induced defects, there are no intrinsic problems for FIB implantation with a dose lower than 10/sup 13/ cm/sup 2/ .

International Nuclear Information System (INIS)

Two plasma chemistries, i.e., CH_4/H_2/Ar and Cl_2/Ar, were compared for the etching of InGaP, AlInP, and AlGaP under inductively coupled plasma (ICP) conditions. While the etching with CH_4/H_2/Ar discharges appears to be ion driven, Cl_2/Ar discharges showed an additional strong chemical enhancement. The highest etch rate (#approx#1 #mu#m/min) for InGaP was achieved at high ICP source power (#>=#750 W) with the Cl_2/Ar chemistry. Cl_2/Ar discharges provided very smooth surfaces in all three materials with root-mean-square roughness measured by atomic force microscopy around 2 nm. This result may be due to the efficient ion-assisted product desorption in this chemistry. The etched near-surface region of InGaP (#approx#100 Angstrom) with Cl_2/Ar maintained almost the same stoichiometry as that of the unetched control. By contrast, the CH_4/H_2/Ar plasma chemistry produced somewhat rougher surfaces ...

Science.gov (United States)

Stresses commonly present in AlGaAs/GaAs laser heterostructures were reduced using Molecular Beam Epitaxy grown Al/sub 0.3/Ga/sub 0.7/P/sub 0.01/As/sub 0.99/ cladding layers. The Al/sub 0.3/Ga/sub 0.7/P/sub 0.01/As/sub 0.99/ alloy was grown using an incident P/sub 2/ flux of roughly-equal1 x 10/sup 14//cm/sup 2/ indicating a sticking coefficient of 0.1 at a substrate temperature of 600 /sup 0/C. X-ray automatic Bragg angle control curvature measurements were used to monitor the residual heteroepitaxial stress. Broadened double crystal x-ray linewidths indicated the occurrence of alloy grading and broadened interfaces. The effects of P concentration and film thickness on stress and on the existence of a misfit dislocation grid are discussed.

Energy Technology Data Exchange (ETDEWEB)

The fluorescence, absorption, infrared and Raman spectra of Sm/sub 3/Ga/sub 5/O/sub 12/ have been investigated. The energy-level schemes in the energy range 3000-16000 cm/sup -1/ have been determined. The number and symmetries of the Sm/sub 3/Ga/sub 5/O/sub 12/ crystal normal mode have been obtained by the molecular site group analysis and their comparison with the experiment has been made.

Energy Technology Data Exchange (ETDEWEB)

X-ray photoemission spectroscopy has been used to measure the valence band offset {Delta}E{sub v} for the AlP/GaP (001) heterojunction interface. The heterojunction samples were prepared by molecular-beam epitaxy. A value of {triangle}E{sub v}=0.43 eV is obtained (staggered band alignment, with AlP valence band below that of GaP). 24 refs., 8 figs., 1 tab.

International Nuclear Information System (INIS)

Kinetics of decomposition of gallium and alkali metal intermetallic compounds in the systems LiGa-LiOH, LiGa-NaOH and LiGa-KON was studied in the temperature range of 40-80 deg C. It was ascertained that increase in temperature gives rise to increase in decomposition rate, whereas increase in hydroxide concentration involves the reaction deceleration. An assumption was made that the decomposition occurs with superimposing of two mechanisms, i.e. chemical and electrochemical decomposition. Basic kinetic characteristics of the process were determined - decomposition rate constant and current density

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This paper proposes the design of LQ-PSS (linear quadratic power system stabilizer) for improving power system stability using genetic algorithm(GA). We are turned weighting matrices of LQ-PSS using GA. To evaluate the usefulness of the proposed method, we performed the nonlinear simulation on a single machine infinite system. As results on a single machine infinite system. As results of the simulation, the proposed method shows the better control performance than CPSS(conventional power system stabilizer) in terms of settling time and damping effects. (author). 7 refs., 7 figs., 3 tabs.

Science.gov (United States)

This article examines problems relating to the calculation of the position of regions of limited solubility of components in the liquid state for four-component systems. An approach based on the use of criterion of stability with respect to diffusion for obtaining equations which describe the region of stratification of the liquid phase in a four-component system is used. The authors used a ES-1020 computer to analyze the critical phenomena in Al-In-P-Sb, Al-Ga-In-P, Al-Ga-In-As, and In-Ga-As-P systems. The position of the spinode in the phase diagram of a four-component system is obtained.

International Nuclear Information System (INIS)

Al, Ga and In complexing with methylthymol blue (H_6R) purified by gel filtration is studied. in the case of metal excess complexes with the ratio of components M:H_6R=2:1 with #lambda#=587(Al), 590(Ga) and 593 nm(In) appear. In the case of reacting agent excess complexes with the ratio of component 1:1 with #lambda#_m_a_x=480-490 (Al) and 480 nm(Ga, In) appear. The mechanism of complexing reactions is studied. Molar extinction coefficients and stability constants are calculated.

International Nuclear Information System (INIS)

The oxygen vacancies distribution in the rigid lattice and the thermally activated motion of oxygen atoms are studied in La1-xSrxGa1-xMgxO3-x (x=0.00; 0.05; 0.10; 0.15 and 0.20) compounds. For that 71Ga, 25Mg and 17O NMR was performed from 100 K up to 670 K, and ion conductivity measurements were carried out up to 1273 K. The comparison of the electric field gradients at the Ga- and Mg-sites evidences that oxygen vacancies appear exclusively near gallium cations as a species trapped below room temperature in local clusters, GaO5/2-#square#-GaO5/2. These clusters decay at higher temperature into mobile constituents of the structural octahedra Ga(O5/6#square#1/6)6/2. At the same time, the nearest octahedral oxygen environment of magnesium cations persists at different doping levels. The case of two adjacent vacant anion sites is found highly unlikely within the ...

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In this work, we describe the fabrication and operating characteristics of GaAs/AlGaAs thin film solar cells processed by the epitaxial liftoff (ELO) technique. This technique allows the transfer of these cells onto glass substrates. The performance of the lifted-off solar cell is demonstrated by means of electrical measurements under both dark and illuminated conditions. We have also optimized the light trapping conditions in this direct-gap material. The results show that good solar absorption is possible in active layers as thin as 0.32 {mu}m. In such a thin solar cell, the open circuit voltage would be enhanced. We believe that the combination of an epitaxial liftoff thin GaAs film, and nano-texturing can lead to record breaking performance. {copyright} {ital 1997 American Institute of Physics.}

Energy Technology Data Exchange (ETDEWEB)

Picosecond charge-collection transients measured for GaAs/AlGaAs HBTs following 3.0 MeV [alpha]-particle and 620 nm picosecond laser excitation reveal charge-collection efficiencies up to twenty-eight times smaller than for GaAs MESFETs, with [approximately]90% of the charge collected within 75 ps of the ionizing event. The small charge-collection efficiency of the HBTs is a consequence of the ultrafast charge-collection dynamics in these devices. The authors show that picosecond laser excitation reproduces nicely the ion-induced transients, providing a valuable tool for the investigation of charge-collection and SEU phenomena in these devices.

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Previous studies from this laboratory have shown that certain N-substituted phthalimides (NSPs) exhibit GA-like activity in a range of specific bioassays and that bioactive NSPs compete with ({sup 3}H)-GA{sub 4} for soluble binding sites in cucumber homogenates. As such, these compounds may prove useful in the purification and characterization of GA receptor proteins. To this end, five azido-NSPs have been synthesized and are currently being screened for biological activity and photochemical stability. Three azido-NSPs elicit {alpha}-amylase production in barley half-seeds and stimulate tissue elongation in d{sub 5} maize, lettuce, sunflower, and soybean. Further evaluations are in progress and these data as well as the utility of these compounds as photo-affinity ligands will be discussed.

Energy Technology Data Exchange (ETDEWEB)

We report the lasing characteristics of gain-guided AlGaInP/AlGaAs visible vertical-cavity surface-emitting laser diodes. At room temperature, continuous-wave operation is achieved over the wavelength range of 657--685 nm with the minimum threshold current at 670 nm. Devices with a 10-[mu]m diameter have threshold currents as low as 1.25 mA at room temperature (297 K) and 0.8 mA at 250 K. In addition, a single predetermined linear polarization state is found, independent of the lasing mode order and operating temperature.

Science.gov (United States)

Room-temperature continuous-wave (cw) operation is achieved in the MBE (molecular-beam epitaxy)-grown InGaP/InGaAlP double-heterostructure (DH) visible laser diodes with a threshold current of 110 mA. The lasing wavelength and threshold current density under pulsed operation are 666 nm and as low as 3.9 kA/cm/sup 2/, respectively. This result is achieved by the introduction of H/sub 2/ into the growth chamber during growth, the continuous growth from one layer to the next layer, and the introduction of a GaAs buffer layer. InGaP/InGaAlP quantum well structures are also grown. From photoluminescence measurements, the conduction-band discontinuity ..delta..E/sub c/ is estimated to be 0.43 of the band-gap difference ..delta..E/sub g/. Furthermore, the multiquantum-well (MQW) structure is found to be stable under thermal treatment at temperatures as high as 750 /sup 0/C. Room-temperature pulsed operation of ...

International Nuclear Information System (INIS)

(1976). USSR Lupin, VM Ramazanov, PE Tomskij Gosudarstvennyj Univ.

International Nuclear Information System (INIS)

The effects of O and C ion implantation with different implantation doses on the yellow luminescence (YL) from unintentional doped n-type GaN have been studied by the photoluminescence (PL) spectra. O and C ions were implanted in the GaN samples with different doses from 1.0 x l013 to 1.0 x l017cm-2. Post-annealing was done in a quartz open-tube furnace under flowing N2 gas for 30 min at 950 degree C. By comparing with N ion implanted samples, it is assumed that different deep-level centers involving in the YL were produced in GaN after O and C ion implantation. In addition, with a dose of 1017 cm-2, the concentration of deep C centers involving in the YL was enhanced markedly. (authors)

Energy Technology Data Exchange (ETDEWEB)

A gain-guiding tapered stripe laser was fabricated using a Ga/sub 0.5/In/sub 0.5/P/(Al/sub 0.5/Ga/sub 0.5/)/sub 0.5/In/sub 0.5/P double heterostructure wafer grown by metalorganic chemical vapor deposition. The laser showed a continuous wave (cw) threshold current of 48 mA, a maximum temperature for cw operation of 81 /sup 0/C, an aspect ratio of about 2, and an astigmatism near 25 ..mu..m. The emission wavelength was 684 nm. Thirty-two devices have been operating without significant degradation for more than 2000 h at 50 /sup 0/C with a constant output power of 3 mW.

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A new organic-inorganic hybrid membrane has been prepared with exceptional performance in dewatering applications. The only precursor used in the sol-gel synthesis of the selective layer was organically linked 1,2-bis(triethoxysilyl)ethane (BTESE). The microporous structure of this layer enables selective molecular sieving of small molecules from larger ones. In the dehydration of n-butanol with 5% of water, the membrane shows a high separation factor of over 4000 and ultra-fast water transport at a rate of more than 20 kg m{sup -2} h{sup -1} at 150C. This can be related to the high adsorption capacity of the material and the sub-micron thickness of the selective layer. The selectivity has now remained constant over almost one and a half years under continuous process testing conditions. Apart from the hydrothermal stability, the membrane exhibits a high tolerance for acid contamination. A slow performance decline in flux and separation factor is only observed at a ...

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Coal demineralization mechanism and its optimum condition were studied by hydrothermal reaction between Ca(OH)2 and quartz as a coal demineralization model. In experiment, the mixture of powder quartz and Ca(OH)2 water slurry was subjected to reaction in an autoclave under spontaneous pressure at 175-340{degree}C. After dried in N2 gas atmosphere at 105{degree}C, the reaction product was analyzed by X-ray diffraction, thermo-balance and differential thermal analysis. In measurement of quartz conversion, the specimen was analyzed by X-ray diffraction after removal of bound water by heat treatment at 850{degree}C. The mixture of clean coal deashed by NaOH and a fixed amount of quartz was also used as specimen for experiment. As the experimental result, dicalcium silicate hydrate was mainly produced at 175{degree}C, and the product changed into xonotlite through tobermorite by longer treatment at higher temperature. For complete reaction of quartz, heat treatments for ...

British Library Electronic Table of Contents (United Kingdom)

Monodisperse europium-activated titania hollow phosphors had been synthesized by a facile one-pot hydrothermal method using carbon spheres as hard templates. Samples were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive spectrometer and photoluminescence spectrum. The strongest emission intensity was observed with TiO2:Eu0.2 hollow spheres and TiO2:Eu0.2 hollow spheres calcining at 550^oC. Moreover, the strongest excitation of TiO2:Eu0.2 hollow spheres transferred from 400 to 500^oC and the effective nonradiative energy transfer from the TiO2 hollow spheres host matrix to Eu^3^+ ions crystal field states was realized due to changes of crystalline field in the environment around Eu^3^+ ions occupying Ti^4^+ site...

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A process for the production of transportation fuels from heavy hydrocarbonaceous feedstock is provided comprising a two-stage, close-coupled process, wherein the first stage comprises a hydrothermal zone into which is introduced a mixture comprising a feedstock and red mud having coke-suppressing and demetalizing activity, and hydrogen; and the second, close-coupled stage comprises a hydrocatalytic zone into which substantially all the effluent from the first stage is directly passed and processed under hydrocracking conditions.

Energy Technology Data Exchange (ETDEWEB)

A process for the production of transportation fuels from heavy hydrocarbonaceous feedstock is provided comprising a two-stage, close-coupled process, wherein the first stage comprises a hydrothermal zone into which is introduced a mixture comprising a feedstock and metals-impregnated red mud having coke-suppressing and demetalizing activity, and hydrogen; and the second, close-coupled stage comprises a hydrocatalytic zone into which substantially all the effluent from the first stage is directly passed and processed under hydrocatalytic conditions. The preferred metals for impregnation include transition metals, in particular, nickel and molybdenum.

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All power plant engineers face the problem of peak power demands. Pumped storage plants are used to generate peak load power by pumping up water utilizing off-peak energy of hydrothermal and thermonuclear plants. This is the first accessible text/reference to cover hydroelectric power generation with emphasis on engineering to meet peak power demands by means of pumped storge plants, tidal power plants, and low head power generation. Text covers hydrology, mechanical and electrical equipment, accessories such as penstocks and valves, and civil engineering considerations. Contains descriptions of several existing plants. Includes 200 diagrams and 50 photographs.

Energy Technology Data Exchange (ETDEWEB)

The most important kaolin deposits from Campo Alegre region (S C) were formed by the conjunction of at least one hydrothermal phase followed by many others weathering, supergenic, phases. Possibly deposits formed by only one of these processes exist, but these deposits shall be small and smaller than those mined today. Besides kaolinization, illitization/muscovitization and silicification, hydrothermalism also generated pyritized and propilitized zones, with quartz + chlorite. Together, hipogenic alterations related to kaolin deposits are very similar to alterations of high sulfidation epigenetic volcanogenic gold deposits. Most part of the biggest kaolin mines from the southern part of Campo Alegre Basin are distributed along a 13 Km long and 0,5 Km width bent zone that is parallel to structural alignments that point out the eastern Basin border. This zone was originated by deformation that has inclined and broken rocks, generating a fault ...

Energy Technology Data Exchange (ETDEWEB)

A fast production scheduling algorithm suitable for generation expansion studies is described in this paper. It can handle several independent rivers, thermal plants, pumped storage plants, import, export, and internal non-firm markets. Inflows and load are deterministic and a one-reservoir limit is imposed on each river. The scheduling problem is formulated as a generalized network problem which is efficiently solved by an adaption of the simplex method. The algorithm is part of a program developed by Hydro-Quebec to conduct preliminary evaluations of alternative expansion plans. The program and the scheduling algorithm are presented.

International Nuclear Information System (INIS)

Europium (Eu) ions-doped titanate nanowires were synthesized via a sol-gel-hydrothermal chemistry and they were found to be roll multilayered trititanate-type nanowires intercalated with Eu3+ and alkali ions. The average diameter was about 20 nm for nanowires synthesized in NaOH solution and about 10 nm for nanowires synthesized in KOH solution. Under ultraviolet excitation the nanowires showed bright red emission corresponding to 5D0-7Fj of Eu3+ ions at room temperature, which was attributed to the non-radiative energy transfer from the surrounding Ti-O octahedral nanosheets to the central Eu3+ ions in interlayer. The luminescent properties of nanowires were influenced by the type of co-intercalated alkali ions, doping degree, hydrothermal and annealing temperatures. The intensity ratio of 5D0-7F2 to 5D0-7F1 of titanate nanowires intercalated with Eu3+ and Na+ ions was higher than that of titanate nanowires intercalated with Eu3+ and K+ ions. ...

International Nuclear Information System (INIS)

In the report the results of the estimations of radiological risk of various stages of decommissioning of nuclear submarines are presented. At occurrence on nuclear submarine the heavy failure, relating to the class hypotetical volume of acting of radionuclides in atmosphere can reach 1.6E(15) Bq. Results of estimations probable doses on an axis of a trace of a radioactive loop show, that at distribution of radionuclides during atmospheric carry to 'agreed' settlement (500-1000 m) the maximum doses on its territory can make: about 6.0E(-3) Sv (for the whole body); 3.0E(-3) Gy for the leather (basal layer); 6.3E(-2) Gy for the lungs (acute exposure) and up to 1.8 Gy for the thyroid gland. Hypotetical failure for the estimation of the greatest possible radioecological consequences for hydrobiocenosis is considering, connected with single discharge of liquid radioactive waste (LRW) in water area. At navigating failure of the tanker with LRW in ...

Energy Technology Data Exchange (ETDEWEB)

Often oil/gas and other hydrocarbons discovered and produced offshore are transported to onshore facilities via submarine pipelines. The route of such pipelines traverses through coastal/shore approach regions. For a rational/economic design, safe installation and subsequent operation it is of utmost importance to review, evaluate and finalize various environmental hazard such as winds, waves, currents, seabed topography, seabed and sub-bottom soils, seabed erosion and soil accretion. This paper addresses the above described environmental hazards, their assessment and techniques to prepare design parameters which must be used for stability analysis, installation methods, long term operation and maintenance for the shore approaches. Additionally, various proven pipeline installation and stabilization techniques for the shore approach region are detailed. As case histories, three approaches installed in the Dutch North Sea are described.

International Nuclear Information System (INIS)

The subject is reviewed in sections, entitled: introduction (historical); sources of short-lived radionuclides; carbon-11; nitrogen-13; oxygen-15; fluorine-18; bromine-77; iodine-123; astatine-211; other radionuclides (including Ga-67, Ga-68, In-111, In-113m, Tc-99m, and Pb-203). (U.K.).

Science.gov (United States)

The (Al/sub x/Ga/sub 1-x/)/sub 0.5/In/sub 0.5/P material system, lattice matched to GaAs substrates, is useful for visible laser diodes. Here, low pressure organometallic vapor phase epitaxial growth of Ga/sub 0.5/In/sub 0.5/P and (Al/sub x/Ga/sub 1-x/)/sub 0.5/In/sub 0.5/P is examined. Epitaxial layers of bulk materials are characterized using photoluminescence, electroreflectance, Raman scattering spectroscopy, and surface morphology studies to determine lattice match and optimum growth conditions. Lattice matching at the growth temperature produces featureless growth surfaces, while lattice matching at room temperatures results in minimum photoluminescence linewidth but cracked surface due to tensile strain during growth. Raman scattering spectra of the quaternary reveal a three-mode structure, with spectral peaks due to GaP-like, in P-like, and AIP-like LO phonons. Additionally, ...

Energy Technology Data Exchange (ETDEWEB)

Three- and four-junction III-V devices are proposed for ultrahigh-efficiency solar cells using a new 1-eV material lattice-matched to GaAs, namely, GaInNAs. We demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. Under the AM1.5 direct spectrum with all the light higher in energy than the GaAs band gap filtered out, the prototypes grown with base doping of about 10{sup 17}&hthinsp;cm{sup {minus}3} have open-circuit voltages ranging from 0.35 to 0.44 V, short-circuit current densities of 1.8 mA/cm{sup 2}, and fill factors from 61{percent} to 66{percent}. To improve on the current record-efficiency tandem GaInP/GaAs solar cell by adding a GaInNAs junction, the short-circuit current density of this 1-eV cell must be significantly increased. Because these low short-circuit ...

International Nuclear Information System (INIS)

The structural changes attendant on intermartensitic transformation in a Ni-Mg-Ga shape memory alloy are considered using magneto-optical visualization with the help of ferrite-garnet monocrystalline films. It is established that on the intermartensitic transformation the complete reorganization of martensite macrostructure fails. Martensite crystals resulted from the basic transformation change somewhat their sizes on intermartensitic transition. The existence of large-scale labyrinth magnetic domain structure is revealed

International Nuclear Information System (INIS)

We have investigated the detection performance of GaAs detectors made with different thickness and contact geometries. A comparison is made between these detection capabilities and the imaging requirements for the following medical applications: digital mammography, digital chest radiography and nuclear medicine. Experimental results and preliminary images are presented and discussed. (author)

International Nuclear Information System (INIS)

We use the Generalized Quasi-Chemical Approach (GQCA) combined with ab initio ultrasoft pseudopotential calculations within density functional theory in order to obtain the structural and electronic properties of Al_xGa_yIn_1_-_x_-_yX (X=As, P or N) quaternary alloys in the zincblende structure. Results for the bond lengths show that their variations with composition are approximately linear and that they do not deviate much from the values of the corresponding binary compounds. For the variation of the band gaps, we obtain a bowing parameter b=0.26 eV for the (Ga_0_._4_7In_0_._5_3As)_z(Al_0_._4_8In_0_._5_2As)_1_-_z quaternary alloy lattice matched to InP, in very good agreement with experimental data. In the case of AlGaInN, a bowing parameter of 0.22 eV is obtained for zincblende AlGaInN lattice matched to GaN. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

British Library Electronic Table of Contents (United Kingdom)

Three field experiments were conducted at the research fields of Plant Protection Research Institute, Iran, at different locations in 2004-2005 to study the efficacy of different broadleaved herbicides to control weeds in wheat. Treatments were the full-season hand weeded and weed-infested controls, and post-emergence applications of florasulam plus flumetsulam at 8.75, 10.50, and 12.25ga.i./ha, 2,4-D plus carfentrazone-ethyl at 210, 245, 280, and 490ga.i./ha, bromoxynil plus MCPA at 75, 100, and 150ga.i./ha, 2,4-D at 560, 720, and 1120ga.i./ha, tribenuron methyl, and 2,4-D plus MCPA. Herbicides were applied at wheat tillering stage. Naturally occurring broadleaved weed populations were used in experiments. Results indicated that bromoxynil plus MCPA at 150ga.i./ha, 2,4-D plus MCPA, and 2,...

CERN Document Server

We explore a planar GaAs/AlAs photonic microcavity using pump-probe spectroscopy. Free carriers are excited in the GaAs with short pump pulses. The time-resolved reflectivity is spectrally resolved short probe pulses. We show experimentally that the cavity resonance and its width depend on the dynamic refractive index of both the lambda-slab and the lambda/4 GaAs mirrors. We clearly observe a double exponential relaxation of both the the cavity resonance and its width, which is due to the different recombination timescales in the lambda-slab and the mirrors. In particular, the relaxation time due to the GaAs mirrors approaches the photon storage time of the cavity, a regime for which nonlinear effects have been predicted. The strongly non-single exponential behavior of the resonance and the width is in excellent agreement to a transfer-matrix model taking into account two recombination times. The change ...

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 problem be fixed. In ...

International Nuclear Information System (INIS)

GaN and Al_1_-_xGa_xN films were grown by the method of ECR-MBE. Absorption constants as a function of wavelength were determined from transmission measurements. Photoconducting detectors were fabricated from these films and characterized in terms of their spectral response and photoconductive gain. Mobility-lifetime products were determined from the measurement of photoconductive gain. The resistivity and mobility-lifetime products of the films were varied from 10--10"9 ohm-cm and 10"-"3--10"-"8 cm"2/V respectively by changing the microwave power in the ECR discharge from 20--60 watts. The change in the mobility-lifetime product is attributed to change in the lifetimes of the photogenerated carriers. This assumption is supported by direct measurement of detector response times. Finally, the authors report for the first time, the detection of alpha particles using GaN detectors.

International Nuclear Information System (INIS)

The optoelectronic compounds of GaAs and ZnSe are difficult to analyze by PIXE (particle-induced X-ray emission) due to the strong absorption of the As and Se K_#alpha# X-rays. As part of a program to investigate optoelectronic materials using ion beam techniques, we have explored the possibility of using the high sensitivity of PIXE to check these materials for stoichiometry and dopant concentrations. The K_#alpha# X-ray intensity ratios of Ga to As and Zn to Se have been investigated using H beams of 0.5 to 2.5 MeV and He beams of 1.0 to 2.5 MeV. The variation in the X-ray intensity ratio with beam energy and target thickness is modelled in terms of the cross section for X-ray production and the absorption coefficients of the X-rays in the target. The results of this model show the experimental conditions that must be satisfied in order that the X-ray intensity ratios are not strongly affected by X-ray absorption; and therefore, the ...

Energy Technology Data Exchange (ETDEWEB)

The utilization of GaAs in photovoltaic (PV) applications has been hindered by the cost of substrates and processing. This paper examines the cost effectiveness of GaAs cells for use in concentrator modules when produced at the 10 to 50 MW level per year. Information on costs associated with substrates, epitaxial processing, and subsequent device fabrication will be compared to allowable costs as projected by the US Department of Energy (DOE). The high cot of GaAs solar cells can be mitigated by use of low-cost substrates or high-concentration systems. The costs then can be accommodated when the production level is sufficiently high to take advantage of economies of scale in device processing and substrate price benefits when procured at high volumes. We have found that development of processing equipment, both for the epitaxial growth and device processing, is the key to obtaining production costs consistent with DOE ...

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The properties and low pressure organometallic vapor phase epitaxy of Ga{sub x}In{sub 1{minus}x}P/(AlGa){sub 0.5}In{sub 0.5}P quantum well (QW) laser diode heterostructures with Al{sub 0.5}In{sub 0.5}P cladding layers, and having wavelength 614 < {lambda} < 690 nm, are described. At longer wavelengths ({lambda} > 660 nm), threshold current densities under 200 A/cm{sup 2} and efficiencies greater than 75% result from a biaxially-compressed GaInP QW active region. Although short wavelength laser performance is diminished by the poor electron confinement afforded by AlGaInP heterostructures, good 630 nm band performance, and extension into the 610 nm band, is achieved with strained, single QW active regions.

Energy Technology Data Exchange (ETDEWEB)

Energy from biomass is a CO{sub 2} neutral, sustainable form of energy. Anaerobic digestion is an established technology for converting biomass to biogas, which contains around 60% methane, besides CO{sub 2} and various contaminants. Most types of biomass contain material that cannot be digested; in woody biomass, this portion is particularly high. Therefore, conventional anaerobic digestion is not suited for the production of biogas from woody biomass. While wood is already being converted to energy by conventional thermal methods (gasification with subsequent methanation), dung, manure, and sewage sludge represent types of biomass whose energy potential remains largely untapped (present energetic use of manure in Switzerland: 0.4%). Conventional gas phase processes suffer from a low efficiency due to the high water content of the feed (enthalpy of vaporization). An alternative technology is the hydrothermal gasification: the water contained within the biomass ...

Science.gov (United States)

We report the first visible (657 nm) vertical-cavity surface-emitting laser. The photopumped undoped structure was grown using low-pressure metalorganic vapor-phase epitaxy in a single-growth sequence on misoriented GaAs substrates. The optical cavity consists of an In{sub 0.54}Ga{sub 0.46}P/In{sub 0.48}(Al{sub 0.7}Ga{sub 0.3}){sub 0.52} P strained quantum-well active region and a lattice-matched In{sub 0.48}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.52} P (0.7{le}{ital y}{le}1.0) graded spacer region, while the distributed Bragg reflectors are composed of Al{sub 0.5}Ga{sub 0.5}As/AlAs quarter-wave stacks. Room-temperature optically pumped lasing was achieved with a very low-threshold power, clearly demonstrating the viability of this new technology. These results provide the foundation for visible semiconductor laser-diode arrays for a number of applications including laser ...

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. ...

Science.gov (United States)

High microwave power (1,000 W) electron cyclotron resonance CH{sub 4}/H{sub 2}/Ar discharges produce etch rates for In{sub 0.5}Ga{sub 0.5}P, Al{sub 0.5}In{sub 0.5}P{sub 0.5}, and Al{sub 0.5}Ga{sub 0.5}P of {approximately} 2,000 {angstrom}/min at moderate RF power levels (150 W) and low pressure (1.5 mTorr). This is approximately a factor of five faster than for conventional reactive ion etching conditions where much higher ion energies are necessary. The etched surfaces are smooth over a wide range of CH{sub 4}-to-H{sub 2} ratios and microwave powers. AlInP is more resistant to preferential loss of P from the near-surface during etching than is InGaP. While the etching is ion-driven, pure Ar discharges produce rough surfaces and the CH{sub 4}/H{sub 2} is necessary in the achievement of acceptable morphologies. The InGaAlP/GaAs heterostructure is being increasingly utilized in diode lasers, light ...

International Nuclear Information System (INIS)

We present results from the first studies of electric-field effects on optical transitions in visible-band-gap InGaP/InAlGaP multiple-quantum-well (MQW) structures. These structures, grown at 775 degree C by metalorganic vapor phase epitaxy on (100) GaAs substrates misoriented 6 degree towards P(111)right-angle left-angle 111 right-angle A, consist of nominally undoped MQWs surrounded by doped In_0_._4_9Al_0_._5_1P cladding layers to form p-i-n diodes. The Stark shifts of various allowed and forbidden quantum-well transitions were observed in bias-dependent electroreflectance spectra of In_0_._4_9Ga_0_._5_1P/In_0_._4_9(Al_0_._5Ga_0_._5)_0_._5_1P MQW samples with 10-nm-thick layers. We find the magnitude of these shifts to depend on the details of the Mg doping profile, confirming the importance of Mg diffusion and unintentional background doping in these materials. Our results show that ...

International Nuclear Information System (INIS)

In previous work, on cooling from 300 K to 10 K the elastic moduli for both #alpha#- and #delta#-Pu dropped 30%. This large change may reflect effects of 5f-electron localization. In this work, the elastic moduli at ambient temperature of several Pu-Ga alloys were measured using resonant ultrasound spectroscopy (RUS). The strong temperature dependence of the bulk and shear modulus and the temperature independence of Poisson's ratio was confirmed and the upper temperature limit for #alpha#-Pu was extended to 360 K. Measurements of the time dependence of the shear moduli of Pu and Pu-2.36 at.% Ga were determined with high precision as a function of time and temperature. Using a model for time dependence of point defects, we determined the exponential time constant at ambient temperature for such variations. The low temperature results are consistent with Fluss .

International Nuclear Information System (INIS)

We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence '' hot '' implantation of Sb and Ga ions followed by thermal annealing. The Rutherford backscattering, transmission electron microscopy/transmission electron diffraction, Raman spectroscopy and photoluminescence were used to characterize the implanted layers. It was found that the nanocrystal size increases from 5 to 60 nm in the samples annealed at 900"oC up to 20-90 nm in those annealed at 1100"oC. For the samples annealed at 900"oC a broad band in the region of 0.75-1.05 eV is registered in the photoluminescence spectra. The nature of this photoluminescence band is discussed. (author)

Science.gov (United States)

Homogenous Al{sub x}Ga{sub 1{minus}x}P liquid phase epitaxial layers have been obtained with the temperature difference method under controlled vapor pressure (TDM-CVP). Very clear fine structures near band edge in photoluminescence spectra have been observed at 77 K for the first time. Photoluminescence measurement results confirmed that the free exciton recombination without phonon assistance plays an important role in the luminescence at 77 K and becomes dominant at room temperature. It is considered that Zero-phonon assisted free exciton recombination is intensified by some local perturbations to electrical potentials against carriers or excitons introduced by Al atoms in Al{sub x}Ga{sub 1{minus}x}P layers, which can give momentum change necessary for recombination.

International Nuclear Information System (INIS)

The highest equilibrium free-carrier doping concentration possible in a given material is limited by the ''pinning energy'' which shows a remarkable universal alignment in each class of semiconductors. Our first-principles total energy calculations reveal that equilibrium n -type doping is ultimately limited by the spontaneous formation of close-shell acceptor defects: the 3- -charged cation vacancy in AlN, GaN, InP, and GaAs and the 1- -charged DX center in AlAs, AlP, and GaP. This explains the alignment of the pinning energies and predicts the maximum equilibrium doping levels in different materials. (c) 2000 The American Physical Society

Energy Technology Data Exchange (ETDEWEB)

Today TBP and TBAs are the compounds which have the highest potential to replace the hydrides arsine and phosphine in the MOVPE process. The authors have demonstrated the entire material system Ga-In-As-P can be grown without any loss of quality using TBP and TBAs not only in one reactor, but in a complete family of reactors. These reactors range from small-scale single wafer R and D reactors to multiwafer Planetary Reactor systems. Both InP based and GaAs based materials could be grown with an excellent quality. Thus all growth processes for III-V devices--long and short wavelength lasers, LEDs, high speed transistors, etc.--can be switched to TBP and TBAs. This will drastically reduce safety hazards and lead to processes that have advantages both from the ecological and economical point of view.

International Nuclear Information System (INIS)

Efficient, low-temperature conversion of infrared light into visible light (red, orange, green) is reported at single heterojunctions and undoped quantum wells of GaAs and ordered Al_xGa_1_-_xInP_2; an increase in photon energy of 700 meV is obtained. The signal originates from the high-band-gap layers and disappears only if the excitation energy is tuned below the GaAs band gap. The intensity of the up-converted photoluminescence (PL) is found to decrease significantly slower with increasing temperature than that of the regular PL and it remains observable up to 200 K. Interface-induced cold Auger processes along with the presence of trapped states for both electrons and holes in these ordered alloys account for this nonlinear mechanism. A colinear double-beam experiment confirms this. copyright 1996 The American Physical Society.

Science.gov (United States)

AlGaInP-based quantum-well laser diodes operating at wavelengths near 680 nm have been grown by all solid source molecular beam epitaxy (SSMBE). The lowest room temperature threshold current densities obtained from shallow rid structures were 300 A/cm{sup 2} and 330 A/cm{sup 2} for pulsed and continuous wave operation, respectively. The dependences of the differential quantum efficiency and threshold current density on the cavity length were also studied in this preliminary SSMBE work. The internal quantum efficiency of 87--89% and the internal losses of 7--10 cm{sup {minus}1} were obtained.

CERN Document Server

This paper proposes the use of particle swarm optimization method (PSO) for finite element (FE) model updating. The PSO method is compared to the existing methods that use simulated annealing (SA) or genetic algorithms (GA) for FE model for model updating. The proposed method is tested on an unsymmetrical H-shaped structure. It is observed that the proposed method gives updated natural frequencies the most accurate and followed by those given by an updated model that was obtained using the GA and a full FE model. It is also observed that the proposed method gives updated mode shapes that are best correlated to the measured ones, followed by those given by an updated model that was obtained using the SA and a full FE model. Furthermore, it is observed that the PSO achieves this accuracy at a computational speed that is faster than that by the GA and a full FE model which is faster than the SA and a full FE model.

International Nuclear Information System (INIS)

This paper reports on a series of experiments performed to examine the ability of ion beam assisted thermal deposition to produce good adhesion of Au metallization on GaAs left-angle 100 right-angle substrates. A study of the influence of Ar ion-assisted thermal deposition of the Au films as well as in situ pre-sputtering of the GaAs surface with low-energy Ar ions prior to thermal deposition, shows that strong adhesion can be achieved without resorting to chemical cleaning. The substrate temperature and the relative flux of Ar ions to incident Au atoms were varied in order to correlate these parameters with film adhesion. The interfaces of films processed under these various conditions were examined by XTEM, RBS and XPS. Orientation texture was studied by x-ray diffraction (XRD).

Energy Technology Data Exchange (ETDEWEB)

This study reviews the wireline log responses of some geothermal fields in the Imperial Valley, California. The fields under study include the Heber, the East Mesa, the Brawley, and the Westmoreland. The well logs used in the study did not include all the wireline surveys obtained by the operators. The selected well logs obtained under special arrangements with the operators were chosen to maintain the anonymity of specific well locations but are only representative of each area. Analysis of the well logs indicates that on an individual field basis, the well logs are excellent for correlation purposes. The presence of extremely saline fluids in some fields precludes the monitoring of Q/sub v/ (cation exchange capacity per unit volume) profile for detection of hydrothermally altered zones. The producing sections in all the fields are characterized by low porosity and high resistivity.

British Library Electronic Table of Contents (United Kingdom)

The need for alternative energy increases steadily???especially due to the climate change and the limited availability of fossil fuels. Geothermal power uses the intrinsic heat which is stored in the accessible part of the Earth???s crust. Its importance among the renewable energy resources originates from the almost unlimited energy supply of the Earth and its independence from external influences such as seasonal or even daily climatic variability. Nevertheless, there are risks which have to be assessed. From a mathematical point of view there are four building blocks of the characterization of deep geothermal systems: seismic exploration, gravimetry, modeling transport processes, and modeling the stress field. In particular, local depletion poses a significant risk during the industrial...

British Library Electronic Table of Contents (United Kingdom)

TiO2 hollow microspheres with sea urchin-like hierarchical architectures were synthesized by a simple hydrothermal method. The as-synthesized hollow microspheres with hierarchical architectures consisting of many rhombic building units exhibit high specific surface area. Electrorheological (ER) properties of hierarchical hollow TiO2-based suspension were investigated under steady and oscillatory shear. The hollow TiO2-based suspensions show much higher yield stress and elasticity than pure TiO2 suspension at the same electric field strength. This phenomenon was elucidated well in view of their dielectric spectra analysis. The sea urchin-like architectures result in stronger interfacial polarization of hollow TiO2 suspension upon an electric field, showing higher ER activity. Also, hollow i...

British Library Electronic Table of Contents (United Kingdom)

An amphiphilic azobenzene diblock copolymer {2-[4-(4-methoxy phenyl azo)phenoxy]hexyl acrylate co-acrylic acid} was synthesized via reversible addition-fragmentation chain transfer polymerization in a hydrothermal reactor. The products were characterized by 1H-NMR, DSC, GPC and UV-Vis spectroscopy. Different self-assembly behaviors of this amphiphilic diblock copolymer in different organic solvent with different water content were investigated. In THF/H2O solution, the diblock copolymer self-assembled into spheres and the spheres would then change to vesicles with smaller size by increasing the volume of H2O. However, in DMSO/H2O solution, the sizes and morphologies of the self-assembled spheres would not change significantly with an enhanced amount of H2O. Photochromic behaviors of the am...

Energy Technology Data Exchange (ETDEWEB)

Studies of CWF preparation at laboratory scale have been carried out using the type and amount of additives and coal content as process variables. Other factors such as particle size, time and rate of stirring were kept constant. CWF with 45 wt% of dry solids, heating value of 5,475 BTU/lb, and stable without the evidence of sedimentation for 9 weeks have been obtained using carboxy methyl cellulose (CMC) as the additive. Low coal content and low heating value can be increased by hydrothermal process on the elevated temperature and pressure. By this process, CWF with dry solid of 55 wt% and a heating value of 7,125 BTU/lb could be obtained. 6 refs., 8 figs., 2 tabs.

British Library Electronic Table of Contents (United Kingdom)

SUMMARY Spontaneous potentials associated with volcanic activity are often interpreted by means of the electrokinetic potential, which is usually positive in the flow direction (i.e. Zeta potential of the rock is negative). The water-rock interactions in hydrothermal zones alter the primary minerals leading to the formation of secondary minerals. This work addresses the study of calcite precipitation in a sand composed of 98 per cent quartz and 2 per cent calcite using streaming potential measurements. The precipitation of calcite as a secondary mineral phase, inferred by high calcite saturation indices and by a fall in permeability, has a significant effect on the electrokinetic behaviour, leading to a significant reduction in the Zeta potential (in absolute value) and even a change in si...

British Library Electronic Table of Contents (United Kingdom)

The launch of the first spaceborne hyperspectral instrument, Hyperion, in 2000 has provoked further research into its capabilities with regard to mineral exploration. Our study in the remote, mountainous region of Pulang, China employed a two-step progressive approach, first to locate target areas characterized by hydrothermal mineral alteration, using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and secondly, to attempt detailed mineral mapping using Hyperion. The preliminary target detection involved principal components and broad-band spectral analysis and led to the detection of two target areas characterized by argillic alteration, iron-oxide- and sulphate-bearing minerals. A focused hyperspectral study followed using Spectral Angle Mapper (SAM) and Mixt...

Energy Technology Data Exchange (ETDEWEB)

Utilisation of geothermal energy may soon become an important factor in power supply in Germany. The contribution discusses the utilisation of hydrothermal low-pressure systems, the geological boundary conditions, the technical design of the thermal water cycle, and the current status of the hot dry rock technology. [German] Die Nutzung der Energie ausd Erdwaerme kann in naher Zukunft eine wichtige Rolle in der Energieversorgung Deutschlands spielen. Der vorliegende Artikel gibt einen Ueberblick ueber die Nutzung hydrothermaler Niederdrucksysteme, die geologischen Rahmenbedingungen, den technischen Aufbau des Thermalwasserkreislaufes sowie zum aktuellen Stand des Hot Dry Rock Verfahrens.

Energy Technology Data Exchange (ETDEWEB)

Nanosized CaSnO{sub 3} is synthesized by a hydrothermal process and characterized by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The SEM observation shows the sample has a porous flowerlike morphology. The electrochemical results exhibit that the stable and reversible capacity of 547 mAh g{sup -1} is obtained after 50 cycles at 60 mA g{sup -1} (0.1 C) and the corresponding charge capacity is determined to be 316 mAh g{sup -1} at the current density of 2.5 C. Cyclic voltammetry and electrochemical impedance spectroscopy data are analyzed to complement the galvanostatic results. The observed excellent performance is attributed to the porous structure and large surface area of flowerlike CaSnO{sub 3}.

Energy Technology Data Exchange (ETDEWEB)

Yellow-emitting pulsed laser operation of an Al/sub 0.37/Ga/sub 0.15/In/sub 0.48/P/Al/sub 0.16/Ga/sub 0.36/In/sub 0.48/P/ Al/sub 0.37/Ga/sub 0.15/In/sub 0.48/P double heterostructure laser diode was obtained at 77 K. The emission wavelength was 579 nm. The threshold current density was 5.6 kA/cm/sup 2/ for a diode with a Si/sub 3/N/sub 4/ insulated 8-..mu..m-wide and 250-..mu..m-long stripe geometry. The device was made from a DH wafer grown by conventional metalorganic chemical vapor deposition using triethyl metals and phosphine as source materials.

International Nuclear Information System (INIS)

AlGaInP epitaxial layers grown at 690 degree C by atmospheric pressure organometallic vapor phase epitaxy are investigated by transmission electron microscopy. For the first time, compositionally modulated and ordered structures are simultaneously observed in AlGaInP alloys. The ordering is of the CuPt type with ordering along the #left brace#111#right brace# directions. The ordered regions appear as plate-like microdomains, while the composition modulation takes the form of a fine columnar constrast oriented along the growth direction. In addition, from the results of (001) plan-view diffraction contrast examination, the principal strain direction associated with the modulation structures is found to be perpendicular to the growth direction and lies in the surface plane. Thus, it is concluded that the spinodal decomposition is initiated and developed on the surface during the growth of the AlGaInP epitaxial layers and, ...

International Nuclear Information System (INIS)

The electronic band structure, transport properties, and lattice dynamics in AuX_2 (X = Al, Ga and In) under high pressure have been extensively studied with full potential linearized augmented plane wave and pseudopotential plane wave methods. The theoretical results for the electronic band structure and Fermi surface reveal pressure-induced electronic topological transitions (ETTs) in AuGa_2 and AuIn_2, while they are absent in AuAl_2, in excellent agreement with the experimental observations. Moreover, calculations of the transport properties at different pressures reveal subtle changes in the band structure close to the Fermi surface of the three intermetallic compounds. It is clear that the anomalies in transport properties are due to ETTs. Interestingly, a pressure-induced soft transverse acoustic (TA) phonon mode is identified only in AuGa_2. The TA phonon instability at the Brillouin zone boundary L point might be ...

Energy Technology Data Exchange (ETDEWEB)

The temperature dependence of T/sub 1/ spin-lattice relaxation time on /sup 51/V, /sup 69/Ga, /sup 71/Ga and Knight shift on /sup 51/V and /sup 29/Si nuclei in polycrystalline V/sub 3/Si, V/sub 3/Ga, V/sub 3/Ge and in the monocrystal V/sub 3/Si in normal state is investigated. For V/sub 3/Si and V/sub 3/Ga a rapid growth (T/sub 1/T)/sup -1/ is observed with temperature decrease while for V/sub 3/Ge the maximum (T/sub 1/T)/sup -1/ at T approximately equal to 60 K has been found. The temperature dependence peculiarities have been discussed on the basis of theoretical models available and zone structure calculations for A-15 compounds. The T/sub 1/ anisotropy and possibility of its experimental discovery are considered. Anisotropic contribution in (T/sub 1/T)/sup -1/ and contributions of d states of different symmetries into the electron state density at the Fermi level are estimated for V/sub 3/Si from ...

Energy Technology Data Exchange (ETDEWEB)

A system of equations describing transient enhanced diffusion of beryllium in InGaAs due to kick-out mechanism or due to formation, migration, and dissociation of the pairs ''beryllium atom-group III self-interstitial'' is proposed and analyzed. Simulation of coupled diffusion of beryllium atoms and self-interstitials in InGaAs during rapid thermal annealing was done for the case of dual implantation. For the experiment under consideration the first ion implantation of phosphorus atoms produced the region of extended defects that led to ''uphill'' diffusion of implanted Be in the defect region and in the vicinity of the surface. The suggested reason of ''uphill'' diffusion could be related to the nonuniform distribution of group III self-interstitials that was formed due to the absorption of point defects on the extended defects and on ...

UK PubMed Central (United Kingdom)

Genetic algorithms (GA) were used to develop specific copper metal-ligand force field parameters for the MM3 force field, from a combination of crystallographic structures and ab initio...Full Text Available

Science.gov (United States)

We report the growth and fabrication of midwave infrared InAs/GaSb strain layer superlattice (SLS) detectors. Growth of alternate interfaces leads to a reduced strain between the GaSb buffer and SLS ({delta}a{sub parallel}/a=-5x10{sup -4}), enabling the growth of active regions up to 3 {mu}m (625 periods). The structural, optical, and electrical properties of the active region were characterized using x-ray crystallography and photoluminescence, respectively. p-i-n detectors were grown using 625 periods of 8 ML (monolayer) InAs/8 ML GaSb as the active region. The {lambda}{sub cutoff} for the detectors was 4.6 {mu}m with a conversion efficiency of 32% at V{sub b}=-0.2 V. Detectivity was obtained using noise power spectral density measurements under 300 K 2{pi} field of view illumination and was equal to 5.2x10{sup 10} and 3x10{sup 10} cm Hz{sup 1/2}/W (V{sub b}=-0.02 V, T=80 K) in the white noise and 1/f noise limit (at 50 ...

Science.gov (United States)

Distributed Bragg reflectors (DBRs) composed of In[sub 0.5]Al[sub 0.5]P/In[sub 0.5](Al[sub [ital y

Energy Technology Data Exchange (ETDEWEB)

GaAs material and device structure optimization studies on optical-grade, millimeter-and-less grain-size polycrystalline Ge substrates are presented. We discuss the growth of high-quality epitaxial layers across various crystalline orientations of a polycrystalline substrate; this is important for obtaining high-performance solar cells. The GaAs solar cell on n-type poly-Ge substrate is a p-on-n type, with an undoped spacer between the p-emitter and the n-base. An experimental study of dark currents in these junctions, with and without the spacer, as a function of temperature (77K to 288K) is presented; this study suggests that the spacer reduces the tunneling contribution to dark current. In addition, we describe device-structure optimization studies that have led us to achieve an open-circuit voltage (V{sub oc}) exceeding 1 Volt and an AM1.5 efficiency of {approximately}19{percent} for a 4-cm{sup 2}-area GaAs cell on ...

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Metal-Semiconductor Solar Cells," J. Appl. Phys. 46,. 1286 (1975). 12) H. B. Kim , G. G. Sweeney and I. S. Heng, "Analysis of ...

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This study focuses the granitoids of center-southern portion of Guyana Shield, southeastern Roraima, Brazil. The region is characterized by two tectonic-stratigraphic domains, named as Central Guyana (GCD) and Uatuma-Anaua (UAD) and located probably in the limits of geochronological provinces (e.g. Ventuari-Tapajos or Tapajos-Parima, Central Amazonian and Maroni-Itacaiunas or Transamazon). The aim this doctoral thesis is to provide new petrological and lithostratigraphic constraints on the granitoid rocks and contribute to a better understanding of the origin and geo dynamic evolution of Guyana Shield. The GCD is only locally studied near to the UAD boundary, and new geological data and two single zircon Pb-evaporation ages in mylonitic biotite granodiorite (1.89 Ga) and foliated hastingsite-biotite granite (1.72 Ga) are presented. These ages of the protholiths contrast with the lithostratigraphic picture in the other areas of Cd (1.96-1.93 ...

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Direct coupljng between Al and Au metal]jzations can result in an increase in gate resistance due to a metallurgical reaction. (purple plague). An RF life test on ...

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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.

International Nuclear Information System (INIS)

Samples prepared using the focused ion beam (FIB) inevitably contain the surface damage induced by energetic Ga"+ ions. An effective method of removing the surface damage is demonstrated using a plasma cleaner, a device which is widely used to minimize the surface contamination in scanning transmission electron microscopy (STEM). Surface bombardment with low-energy Ar"+ ions was induced by biasing the sample immersed in the plasma source, so as to etch off the surface materials. The etch rates of SiO_2, measured with a bias voltage of 100-300 V, were found to vary linearly with both the time and bias and were able to be controlled from 1.4 to 9 nm/min. The removal of the Ga residue was confirmed using energy dispersive spectroscopy (EDS) after the plasma processing of the FIB-prepared sample. When the FIB-prepared sample was processed via plasma etching for 10 min with a bias of 150 V, the surface Ga damage was completely ...

International Nuclear Information System (INIS)

We report a study of the physical characteristics of the pillars of C, Pt and W grown by 10-30 keV Ga focused ion beam (FIB) as a function of Ga ion flux, and present a quantitative analysis of the elements using energy-dispersive analysis of X-rays (EDAX). All the FIB grown pillars exhibit a rough morphology with whisker like protrusions on the cylindrical surface and broadening of the base as compared to the nominal size. For a constant fluence, the height of the pillar initially increases and then reduces after going through a maximum as a function of ion flux in all the cases. The compositional analysis shows good metallic quality for Pt structures but reveals significant contamination of Ga in C and Ga and C in W structures at higher ion fluxes. Explanation to all these observations has been sought in the light of secondary ion and electron effects and the different processes involved which lead to ...

International Nuclear Information System (INIS)

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III - V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned ...

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... AFM DOD AFR T. O FED DCAC MIL ANSIX AFSC JANAP DIAM GA RADC FIPS SDSP STDN AFNAG MM NORAD JSC NORADM ME NORADR ...

International Nuclear Information System (INIS)

In this work, the effects of the focus ion beam (FIB) milling process on the optical properties of semiconductor nanostructures were investigated. With this aim, a sensitive materials system based on InGaAs/GaAs quantum dots with well known and excellent optical properties was selected for the FIB treatment. The FIB technique was used to locally remove a metallic mask deposited on top of the quantum dot sample. The photoluminescence (PL) signal, collected from the circular openings, was used to infer the possible damage effects of the ion beam on the properties of the dots.

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A study was made on the effect of 3.5 MeV electron irradiation on the properties of light-emissive structure based on GaAlAs. It is shown that a considerable decrease in the emitted light intensity as a result of electron irradiation not accompanied by changes in recombination- and electric properties of the mentioned structures. It is established by the electron-microscopy and Auger-spectroscopy meazurements that electron irradiation causes the occurrence of regions of free aluminium clusters on the external surface of the structure n-layer. The number and the sizes of the regions depend on the electron doze. It was assumed that the mentioned regions can play a role of attenuation filter for the light emitted by the structure.

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The metal-semiconductor solar cell is a potential candidate for converting solar energy to electrical energy for space and terrestrial application. In this paper, a method for obtaining parameters of practical antireflection (AR) coatings for the metal-semiconductor solar cells is given. This method utilizes the measured equivalent index of refraction obtained from ellipsometry, since the surface to be AR coated has a multilayer structure. Both the experimental results and theoretical calculations of optical parameters for Ta/sub 2/O/sub 5/ AR coatings on Au-GaAs and Au-GaAs/sub 0.78/P/sub 0.22/ solar cells are presented for comparison. (AIP)

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Thirty-two patients with AIDS related complex (ARC) or acquired immunodeficiency syndrome (AIDS) underwent /sup 67/Ga scans as part of their evaluation. Three patterns of /sup 67/Ga biodistribution were found: lymph node uptake alone; diffuse pulmonary uptake; normal scan. Gallium-67 scans were useful in identifying clinically occult Pneumocystis carinii pneumonia in seven of 15 patients with ARC who were asymptomatic and had normal chest radiographs. Gallium scans are a useful ancillary procedure in the evaluation of patients with ARC or AIDS.

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This thesis dealt with the metal-organic gas phase epitaxy with nitrogen as carrier gas. For this first by means of three-dimensional modelings of the epitaxy process the influence of the carrier gas on the processes was explained. The optimization of the growth parameter for the whole light-emitting-diode structure in double-hetero arrangement resulted that an a temperature of 770 C and a V/ III-ratio of 150 layers with a high crystal quality could be reached.

International Nuclear Information System (INIS)

With the development of an array of highly-segmented germanium detectors, it now becomes possible to perform in-flight #gamma#-ray spectroscopy experiments on intermediate energy beams with unprecedented #gamma#-ray energy resolution. Presented in this report are examples of two techniques in which SeGA, the most highly-segmented operational germanium array for in-flight spectroscopy with fast beams, was used for the detection of #gamma# rays. SeGA used in conjunction with a high-resolution magnetic spectrograph (S800) to detect the reaction residues in coincidence represents a powerful combination for in-beam #gamma#-ray studies.

International Nuclear Information System (INIS)

The Gamma Physics (GaP) program of physical phenomena investigation is proposed on #gamma#p, #gamma#e and #gamma##gamma# colliders at TeV energies. The program contains specialized software (CompHEP system) created for automation of particle interaction processes calculations in the framework of various gauge models. Preliminary physical results are presented (heavy quark production, W, Z production, supersymmetry etc.), and further software development is suggested. (R.P.) 22 refs., 8 figs., 4 tabs.

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The method of aluminium metal activation by liquid eutectics Ga-In (70:30) and Ga-In-Sn-Zn (60:25:10:5) is developed. Subsequent dispersion of the obtained specimens up to a particle size of >0.5mm leads to the drastic interaction of aluminium powder and water with evolving hydrogen. In the present work the oxidation rate of activated aluminium and water is investigated depending on eutectic composition, reaction temperature, and powder particle size. The mechanism of the main eutectic's components influence on the reacting ability of aluminium is discussed. (author)

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The dependence of the photoluminescent properties of In{sub 0.48}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.52}P alloys (0{le}{ital y}{le}0.5) on growth temperature and substrate misorientation off GaAs(100) has been studied. Samples were grown using low-pressure metalorganic vapor phase epitaxy. By studying the dependence of ordering behavior in InGaP as a function of substrate misorientation and growth temperature simultaneously, a very large range in low-temperature photoluminescence emission energy---135 meV---has been obtained. The photoluminescence linewidth exhibits a strong, continuous dependence on the extent of atomic ordering (the emission energy) in the alloys. The results indicate that inhomogeneity in the microstructure of the material (i.e., between ordered'' domains and the disordered'' matrix) is the dominant photoluminescence broadening mechanism. This ...

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In order to obtain highly reliable InGaP/InGaAlP inner stripe (IS) lasers, the authors have clarified the relation between the maximum CW operation temperature and other laser characteristics, such as the pulsed threshold current, characteristic temperature, series resistance, and thermal resistance. The Al composition of the cladding layer, the carrier concentration of the p-cladding layer, and the thicknesses of the active layer and cladding layer have been optimized. It was found that an Al composition of 0.7 was the most suitable for the cladding layer, and the optimized carrier concentration was 4 x 10/sup 17/ cm/sup -3/. A maximum temperature of 90/sup 0/C was obtained for a 0.1 /mu/m active layer thickness and a 0.6 /mu/m cladding layer thickness. This is the highest value for InGaP/InGaAlP IS lasers, to our knowledge. In the case of a 0.06 /mu/m active layer thickness and a 0.8 /mu/m cladding layer thickness, a maximum temperature of ...

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Two plasma chemistries, i.e., CH{sub 4}/H{sub 2}/Ar and Cl{sub 2}/Ar, were compared for the etching of InGaP, AlInP, and AlGaP under inductively coupled plasma (ICP) conditions. While the etching with CH{sub 4}/H{sub 2}/Ar discharges appears to be ion driven, Cl{sub 2}/Ar discharges showed an additional strong chemical enhancement. The highest etch rate ({approximately}1 {mu}m/min) for InGaP was achieved at high ICP source power ({ge}750 W) with the Cl{sub 2}/Ar chemistry. Cl{sub 2}/Ar discharges provided very smooth surfaces in all three materials with root-mean-square roughness measured by atomic force microscopy around 2 nm. This result may be due to the efficient ion-assisted product desorption in this chemistry. The etched near-surface region of InGaP ({approximately}100 {Angstrom}) with Cl{sub 2}/Ar maintained almost the same stoichiometry as that of the unetched control. By contrast, the CH{sub ...

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The paper describes the work underway to adapt a former US Navy diesel electric drive ship as a 2.4 Megawatt fuel cell powered, US Coast Guard operated, demonstrator. The Project will design the new configuration, and then remove the four 600 kW diesel electric generators and auxiliaries. It will design, build and install fourteen or more nominal 180 kW diesel fueled molten carbonate internal reforming direct fuel cells (DFCs). The USCG cutter VINDICATOR has been chosen. The adaptation will be carried out at the USCG shipyard at Curtis Bay, MD. A multi-agency (state and federal) cooperative project is now underway. The USCG prime contractor, AEL, is performing the work under a Phase III Small Business Innovation Research (SBIR) award. This follows their successful completion of Phases I and II under contract to the US Naval Sea Systems (NAVSEA) from 1989 through 1993 which successfully demonstrated the feasibility of diesel fueled DFCs. The demonstrated marine propulsion of a USCG ...

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The economic feasibility of using granular activated carbon (GAC) to remove organic contaminants from industrial and municipal wastewater is contingent upon its reuse during multiple adsorption-regeneration cycles. The most common process for the regeneration of GAC is the thermal method. Drawbacks associated with thermal regeneration include a 5--10% loss of carbon due to oxidation and attrition, a decrease in adsorption capacity, and high energy costs. The purpose of this study was to investigate the regeneration of GAC using hydrothermal technology. Phenol contaminated and non-contaminated GAC samples were regenerated using supercritical water (411 deg C and 26.2 MPa) with dissolved oxygen concentrations of 0 mg/L, 5 mg/L, and 100 mg/L. For comparative purposes, GAC was regenerated using subcritical water (300 deg C and 12.4 MPa) with a dissolved oxygen concentration of 5 mg/L. Regenerated GAC samples were evaluated in terms of adsorption capacity, BET surface ...

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A number of binary geothermal cycles utilizing mixed hydrocarbon working fluids were analyzed with the overall objective of finding a working fluid which can produce low-cost electrical energy using a moderately low temperature geothermal resource. Both boiling and supercritical shell-and-tube cycles were considered. The performance of a dual-boiling isobutane cycle supplied by a 280/sup 0/F hydrothermal resource (corresponding to the 5MW pilot plant at the Raft River site in Idaho) was selected as a reference. To investigate the effect of resource temperature on the choice of working fluid, several analyses were conducted for a 360/sup 0/F hydrothermal resource, which is representative of the Heber resource in California. The hydrocarbon working fluids analyzed included methane, ethane, propane, isobutane, isopentane, hexane, heptane, and mixtures of those pure hydrocarbons. For comparison, two fluorocarbon refrigerants were also analyzed. ...

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Indium-111 is currently the radionuclide of choice for colonic transit study. However, it is expensive and not available in many hospitals. Technetium-99m has been proposed for colonic transit study but the short half-life has limited its use. Gallium-67 citrate is inexpensive and available in most countries. Most importantly, it has a suitable half-life for colonic transit study. Attempts have been made in some studies to use {sup 67}Ga citrate to label activated charcoal, but the results have not been good because of poor stability. In this study, we successfully labelled activated charcoal with {sup 67}Ga citrate by adding alcohol and 5% glucose solution. To evaluate the in vitro stability, the {sup 67}Ga-activated charcoal was incubated in a milieu mimicking the intestinal content, containing lipase, trypsin and glycochenodeoxycholate at different pH values (6.0, 7.0, 7.4 and 8.0) and for different durations (0 h, 24 h, ...

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Si and Si/P ion implantation doping of In{sub 0.5}Ga{sub 0.5}P and In{sub 0.5}Al{sub 0.5}P has been studied for several Si and P doses at energies of 90 and 100 keV, respectively. For single Si implants in InGaP a maximum Hall sheet electron concentration of 1.33{times}10{sup 13} cm{sup {minus}2} is achieved for a Si dose of 5{times}10{sup 13} cm{sup {minus}2}. When an optimum dose (2.5{times}10{sup 13} cm{sup {minus}2}) P coimplant is performed this electron concentration is increased by 65{percent}. The same dose Si implants in InAlP show a maximum effective activation of 3.9{percent} with no P coimplantation and 5.2{percent} with a P-implant dose 1.5 times the silicon dose. The apparent donor ionization energies are estimated from variable temperature Hall measurements to be 2{endash}5 meV for InGaP and {approximately}80 meV for InAlP. The deeper level in InAlP is attributed to the DX level found in the Al-containing ...

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By using a model dielectric matrix in electron self-energy evaluations the computational effort of a quasiparticle band-structure calculation for a semiconductor is greatly reduced. Applications to various systems with or without inversion symmetry, having narrow or wide band gaps, and semiconductor alloys demonstrate the reliability and accuracy of the method. Calculations have been performed for thirteen semiconducting or insulating materials: Si, LiCl, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, and the Al{sub 0.5}Ga{sub 0.5}As and In{sub 0.53}Ga{sub 0.47}As alloys. Excellent agreement with experimental results is obtained for the quasiparticle energies for these materials. The only three exceptions, {ital E}({Gamma}{sub 1{ital c}}) of AlP, {ital E}({ital L}{sub 1{ital c}}) of AlAs, and {ital E}({ital L}{sub 1{ital c}}) of AlSb are discussed and attributed to various ...

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The corrosion and passivation behaviour of bulk polycrystalline martensite Ni{sub 50}Mn{sub 30}Ga{sub 20} and austenite Ni{sub 48}Mn{sub 30}Ga{sub 22} alloys was compared in electrolytes with different pH values. Linear anodic and cyclic potentiodynamic polarisation methods and anodic current transient measurements have been conducted for the alloys and their constituents to analyze free corrosion, anodic dissolution and passive layer formation processes. Electrochemically treated alloy surfaces were characterized with scanning electron microscopy (SEM) and angle-resolved x-ray photoelectron spectroscopy (XPS). The electrochemical response of both alloys is in principal similar and is dominated by the Ni oxidation. In acidic solutions (pH 0.5 and 5) a slightly higher reactivity is detectable for the martensitic alloy which is mainly attributed to enhanced dissolution processes at the multiple twin boundaries. In weakly acidic to strongly ...

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In an earlier paper (Phys. Rev. Lett. 66, 41 (1991)), we calculated both the dielectric constant ({epsilon}{sub {infinity}}) and the nonlinear optical susceptibilities for second-harmonic generation ({chi}{sup (2)}) in the static limit for AlP, AlAs, GaP, and GaAs in the local-density approximation with and without a self-energy correction in the form of a scissors operator,'' including local-field effects. In this paper, we expand our presentation of this calculation. Agreement with experiment to within 15% for the nonlinear susceptibility is demonstrated where experiments are available (GaP and GaAs); the dielectric constants are in no worse than 4% agreement with experiment. The virtual hole'' contributions are reformulated to avoid large numerical cancellations in the case of near degeneracies. The virtual electron'' terms dominate over the ...