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Avaliação da terapia por laser de arsenito e gálio em tendinite de cavalos Puro Sangue Inglês de corrida; Evaluation of Gallium Arsenide Laser for treatment of equine tendinitis

Mikail, Solange Corrêa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/07/2008 PT
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Para avaliar a eficácia do laser de arsenito de gálio em acelerar a cicatrização tendínea em cavalos PSI de corrida com lesão no tendão flexor digital superficial, foram realizados dois experimentos, primeiro (E1) com 14 casos clínicos onde as lesões foram decorrentes do esporte em um dos membros torácicos, o segundo (E2) com cinco casos experimentais, onde as lesões foram induzidas com colagenase em ambos os membros torácicos. No E1, após a detecção da lesão no tendão flexor digital superficial por exame ultra-sonográfico, todos os animais receberam antiinflamatório não esteróide associado à dimetilsulfóxido por via intravascular, crioterapia no local da lesão, e caminharam ao passo duas vezes ao dia por 15 minutos durante os 30 dias de acompanhamento. Os membros tratados pertenceram a onze animais que receberam uma sessão diária de laser de arsenito de gálio na dose de 20 J/cm2, realizadas durante 10 dias consecutivos, após término do antiinflamatório e da crioterapia. Os membros controle pertenceram a três animais, os quais não foram tratados com laser. No E2, após identificação das lesões, foram escolhidos aleatoriamente um membro torácico controle e outro a ser tratado por laser em cada animal. Da mesma forma...

Comparação da dependência com a temperatura dos espectros de absorção de raios-X do Ge e do GaAs cristalinos

Benfatto, Vinicius Pereira
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Trabalho de Conclusão de Curso Formato: application/pdf
POR
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Neste estudo foi abordada a dependência do comprimento das ligações inter-atômicas com a temperatura para dois materiais com mesma estrutura cristalina (Germânio e Arseneto de Gálio), porém com diferenças de ionicidade de ligação. Para análise das características vibracionais utilizou-se do método de EXAFS para sondar as ligações com base em algumas aproximações, modelos e cálculo computacional, e verificou-se sua dependência com a temperatura através de características estruturais como o fator de Debye-Waller o qual descreve a desordem térmica e estrutural. Constatou-se que a taxa de expansão térmica para o germânio é maior que a do arseneto de gálio e sua ligação é mais “dura” que a GaAs.; This study addressed the dependence of the inter-atomic bond length with temperature for two materials with the same crystal structure (Germanium and Gallium Arsenide), but with differences in binding ionicity. For analysis of the vibrational characteristics we used EXAFS to probe the binding based on some approximations and computational models. We inferred the temperature dependence through structural features and the Debye-Waller factor which describes the thermal and sdisorder.tructural It was found that the rate of thermal expansion for germanium is larger than that of gallium arsenide and its binding is "harder" than GaAs.

Hydrogen influence on gallium arsenide thin films prepared by rf-magnetron sputtering technique

Vilcarromero, J.; Bustamante, R.; da Silva, J. H. D.
Fonte: Sociedade Brasileira Fisica Publicador: Sociedade Brasileira Fisica
Tipo: Artigo de Revista Científica Formato: 1035-1037
ENG
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We investigate the effect of the hydrogen intentional incorporation on the structural properties of the amorphous gallium arsenide prepared by rf-magnetron sputtering technique. The properties of the non-hydrogenated films are: band gap of 1.4 eV (E-04), Urbach energy of 110 meV, stoichiometric composition ([As]/[Ga] = 0.50), and dark conductivity of about 3.2 x 10(-5) (Omega.cm)(-1). Hydrogen was incorporated in the films by the introduction of an electronically controlled H-2 flux during deposition, keeping constant the other deposition parameters. It was observed that small hydrogen incorporation produces a great change in the structural properties of the films. The main changes result from the formation of GaAs nanocrystals with mean sizes of about 7 nm into the amorphous network.

Effect of gallium-arsenide laser, gallium-aluminum-arsenide laser and healing ointment on cutaneous wound healing in Wistar rats

Gonçalves,R.V.; Mezêncio,J.M.S.; Benevides,G.P.; Matta,S.L.P.; Neves,C.A.; Sarandy,M.M.; Vilela,E.F.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2010 EN
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This study determined the effects of gallium-aluminum-arsenide laser (GaAlAs), gallium-arsenide laser (GaAs) and Dersani® healing ointment on skin wounds in Wistar rats. The parameters analyzed were: type I and III collagen fiber concentrations as well as the rate of wound closure. Five wounds, 12 mm in diameter, were made on the animals’ backs. The depth of the surgical incision was controlled by removing the epithelial tissue until the dorsal muscular fascia was exposed. The animals were anesthetized with ketamine and xylazine via intraperitoneal injection. The rats were randomly divided into five groups of 6 animals each, according to the treatment received. Group 1 (L4): GaAs laser (4 J/cm²); group 2 (L30): GaAlAs laser (30 J/cm²); group 3 (L60): GaAlAs laser (60 J/cm²); group 4 (D): Dersani® ointment; group 5 (control): 0.9% saline. The applications were made daily over a period of 20 days. Tissue fragments were stained with picrosirius to distinguish type I collagen from type III collagen. The collagen fibers were photo-documented and analyzed using the Quantum software based on the primary color spectrum (red, yellow and blue). Significant results for wound closing rate were obtained for group 1 (L4), 7.37 mm/day. The highest concentration of type III collagen fibers was observed in group 2 (L30; 37.80 ± 7.10%)...

Hydrogen influence on gallium arsenide thin films prepared by rf-magnetron sputtering technique

Vilcarromero,J.; Bustamante,R.; Silva,J.H.D. da
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2006 EN
Relevância na Pesquisa
67.01%
We investigate the effect of the hydrogen intentional incorporation on the structural properties of the amorphous gallium arsenide prepared by rf-magnetron sputtering technique. The properties of the non-hydrogenated films are: band gap of 1.4 eV (E04), Urbach energy of 110 meV, stoichiometric composition ([As]/[Ga] = 0.50), and dark conductivity of about 3.2 x 10-5 (omega.cm)-1. Hydrogen was incorporated in the films by the introduction of an electronically controlled H2 flux during deposition, keeping constant the other deposition parameters. It was observed that small hydrogen incorporation produces a great change in the structural properties of the films. The main changes result from the formation of GaAs nanocrystals with mean sizes of about 7 nm into the amorphous network.

The selective deposition of gallium arsenide and aluminum gallium arsenide by laser-enhanced metalorganic chemical vapor deposition

Edgar, James Howard
Fonte: Universidade da Flórida Publicador: Universidade da Flórida
Tipo: Artigo de Revista Científica Formato: vii, 169 leaves : ill. ; 28 cm.
Publicado em //1987 ENGLISH
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47.34%
(Thesis) Thesis (Ph. D.)--University of Florida, 1987.; (Bibliography) Includes bibliographical references (leaves 161-168).; Typescript.; Vita.; (Statement of Responsibility) by James Howard Edgar.

Design of a very high speed dynamic RAM in gallium arsenide for an ATM switch / Michael K. McGeever.

McGeever, Michael K.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 293170 bytes; application/pdf
Publicado em //1995 EN
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This thesis analyses the design of a Dynamic RAM in gallium arsenide for use as a buffer in an ATM switch. The causes of leakage are investigated and methods to overcome or compensate the leakage are devised, resulting in a memory cell with a large storage time, high speed and low power dissipation. A 14 kbit RAM array is designed and laid out in gallium arsenide. The RAM array is designed to operate over a -25oC to +125oC temperature range using process parameters which vary by up to 2 [sigma] from typical.; Thesis (M.Eng.Sc.)--University of Adelaide, Dept. of Electrical & Electronic Engineering, 1996?; Bibliography: leaves 156-165.; xvi, 174 leaves : ill. ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Use of whispering-gallery modes and quasi TE₀np modes for broadband characterization of bulk gallium arsenide and gallium phosphide samples; Use of whispering-gallery modes and quasi TE0np modes for broadband characterization of bulk gallium arsenide and gallium phosphide samples

Krupka, J.; Mouneyrac, D.; Hartnett, J.; Tobar, M.
Fonte: IEEE-Inst Electrical Electronics Engineers Inc Publicador: IEEE-Inst Electrical Electronics Engineers Inc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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The complex permittivity of bulk crystals of semiinsulating gallium arsenide (GaAs) and gallium phosphide (GaP) were measured over the frequency range from 4 to 30 GHz and at temperatures from 30 up to 300 K employing whispering-gallery-mode (WGM) and quasi-TE0 np-mode dielectric-resonator techniques. At temperatures about 40 K, dielectric loss tangent values were below 10 -6 for GaAs and below 10 -5 for GaP. The use of several WGMs, as well as TE0 np modes excited in the same test sample enabled a broad frequency range of measurements (one decade). The real part of the permittivity of GaP and GaAs proved to be frequency independent at microwave frequencies. The dielectric loss tangents of GaAs and GaP increase with temperature and frequency.; Jerzy Krupka, David Mouneyrac, John G. Hartnett, and Michael E. Tobar

Reaction studies of gallium arsenide clusters: Models of real surfaces

Chibante, Luis Paulo Felipe
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
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As semiconductor technology continues to miniaturize, surface phenomenon become prevalent. Clusters can be considered as model compounds of the surface in free space. By performing experiments on clusters, it is equivalent to focussing on local sites of the bulk surface, and building it one atom at a time. The development of supersonic beams of clusters has proved to be one of the most powerful methods in preparing the "nano" state, the intermediate range between atomic and the macroscopic description of matter. Fourier Transform - Ion Cylcotron Resonance (FT-ICR), a mass spectrometry technique, coupled with these cluster beams was used to study gallium arsenide, a well-utilized semiconductor. The complexity of isomers and the stoichiometric distribution within a given cluster size has been simplified using mathematical methods for signal deconvolution. By studying reaction parameters with ammonia, gallium arsenide clusters proved to be an adequate comparative model for real surfaces. Furthermore, local density theoretical calculations, which are feasible on these small clusters, provided a corroborative and predictive proving ground for this system.

FT-ICR studies of gallium arsenide cluster ions

Wang, Lihong
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
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47.03%
Gallium arsenide clusters have been studied on a Fourier transform ion cyclotron resonance(FT-ICR) mass spectrometer with an external supersonic cluster source. Reaction of GaAs cluster cations with ammonia revealed that all cluster cations larger than seven atoms were most reactive near the 1/1 composition ratio of gallium/arsenic. The results suggest that even at this small size the clusters begin to adopt the alternating gallium/arsenic bonding arrangement characteristic of bulk GaAs crystal surfaces where gallium-arsenic bonding activates gallium atoms for ammonia chemisorption. With excess NH$sb3$, Ga$sb{ m x}$As$sb{ m y}$(NH$sb3$)$sb{ m z}sp+$ with the same GaAs composition (x and y) was observed with several values of z, which is explained in terms of the existence of multiple isomers of GaAs clusters. However, the anions were found to be inert toward NH$sb3$. Nitric oxide was found to etch singly charged Ga$sb{ m x}$As$sb{ m y}$(x + y = 9 to 16) clusters. A pronounced even-odd alternation in cluster ion reactivity towards NO was observed with the odd numbered cluster ions which are believed to be closed shell singlets being much less reactive than the even numbered cluster ions which are of necessity open shell species. The local density calculations of small Ga$sb{ m x}$As$sb{ m y}$(x + y $le$ 10) have been carried out. Multiple low energy structures were found and the electronic properties are in agreement with experimental results. A model which directly controls the profile width of a stored waveform inverse Fourier transform(SWIFT)...

Investigation of the Gunn effect in gallium arsenide

Slepicka, Alois Allen
Fonte: Monterey, California. U.S. Naval Postgraduate School Publicador: Monterey, California. U.S. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
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When the electric field in certain compound semiconductors exceeds a well-defined threshold value, the electrical current through the material becomes unstable. These instabilities may take the form of coherent Oscillations at microwave frequencies. The oscillations are not greatly affected by external circuit conditions. The effect was first discovered in gallium arsenide and indium phosphide by J. B. Gunn in 1963, and is now referred to as the "Gunn effect".This paper discusses some of the practical aspects of the Gunn effect in gallium arsenide. A brief theoretical explanation is given, of the intervalley electron energy transfer mechanism which is now generally accepted as the mechanism through which the effect occurs. The preparation of samples is described, and the nature of the electrical contacts to the material discussed. Ohmic contacts are necessary to prevent junction effects or carrier injection from masking the oscillations. Mounting techniques are described. Circuit considerations are discussed, and the results of various measurements reported. The value of the Gunn effect lies in its potential to directly convert pulse or DC power into microwave power, at frequencies and power levels higher than is possible with other semiconductor devices...

Speed, power consumption, and impedance in gallium arsenide IC interconnection circuits

Huck, Hugh Joseph.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
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47.01%
The goal of this project is to determine the feasibility of conserving power while maintaining reasonably high speed in Gallium Arsenide integrated circuit interconnection circuits by increasing the characteristic impedance of microstrip or stripline printed circuit board. This thesis presents the modeling and simulation of output driver and input receiver circuits for Gallium Arsenide digital ICs. Impedance controlled printed circuit board transmission lines are also studied. MATLAB is used to model and calculate the impedance that can be obtained using a microstrip and/or stripline printed circuit board interconnect. This information is then used with HSPICE to model and simulate transmission line interconnects. HSPICE is also used to model and simulate the design of the output driver and input receiver circuits for use with the printed circuit board. Finally, the IC is layed out using MAGIC to show differences in circuit size at different impedances.

Radiation tolerant, high speed, low power gallium arsenide logic

Wolfe, Kurt A.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 111 p.
EN_US
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Approved for public release; distribution is unlimited.; Gallium Arsenide (GaAs) circuits are largely immune to slowly accumulated radiation doses and therefore do not need the shielding required by complementary metal oxide semiconductor (CMOS) devices. This attribute renders GaAs circuits particularly attractive for space craft and military applications. However, it has been shown that GaAs circuits with short gate length transistors are excessively susceptible to single event upsets (SEU) due to enhanced charge collection at the edges of the gate called 'edge effect'. This thesis studies the SEU problem in two parts. Extensive computer modeling and simulation of a charged particle passing through various transistors of a low power, two-phase dynamic MESFET logic (IDFL) test chip was conducted using HSPICE in the first part. In the second part, new GaAs logic topologies are developed, simulated, and layed out in integrated circuits which require less power than directly coupled MESFET logic (DCFL) and should be less susceptible to single event upsets than TDFL circuits.; Lieutenant, United States Navy

Gallium interstitial contributions to diffusion in gallium arsenide

Schick, J. T.; Morgan, C. G.; Papoulias, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Enthalpies of formation of gallium interstitials and all the other native point defects in gallium arsenide are calculated using the same well-converged \emph{ab initio} techniques. Using these results, equilibrium concentrations of these defects are computed as a function of chemical potential from the arsenic rich limit to the gallium rich limit and as a function of the doping level from $p$-type to $n$-type. Gallium interstitial diffusion paths and migration barriers for diffusion are determined for all the interstitial charge states which are favored for Fermi levels anywhere in the gap, and the charge states which dominate diffusion as a function of Fermi level are identified. The effects of chemical potential, doping level, and non-equilibrium defect concentrations produced by ion implantation or irradiation on gallium self-diffusion are examined. Results are consistent with experimental results across the ranges of doping and stoichometry where comparisons can be made. Finally, these calculations shed some light on the complex situation for gallium diffusion in gallium arsenide that is gallium-rich and doped heavily $p$-type.; Comment: 41 pages, 20 figures

Graphene on Gallium Arsenide: Engineering the visibility

Friedemann, M.; Pierz, K.; Stosch, R.; Ahlers, F. J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.89%
Graphene consists of single or few layers of crystalline ordered carbon atoms. Its visibility on oxidized silicon (Si/SiO\_2) enabled its discovery and spawned numerous studies of its unique electronic properties. The combination of graphene with the equally unique electronic material gallium arsenide (GaAs) has up to now lacked such easy visibility. Here we demonstrate that a deliberately tailored GaAs/AlAs (aluminum arsenide) multi-layer structure makes graphene just as visible on GaAs as on Si/SiO\_2. We show that standard microscope images of exfoliated graphite on GaAs/AlAs suffice to identify mono-, bi-, and multi-layers of graphene. Raman data confirm our results.; Comment: 12 pages, 1 table, 3 figures

Spin relaxation in n-doped gallium arsenide due to impurity and electron-electron Elliot-Yafet scattering

Tamborenea, P. I.; Kuroda, M. A.; Bottesi, F. L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/03/2003
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We calculate the spin relaxation time of conduction electrons in n-doped bulk gallium arsenide. We consider the Elliot-Yafet spin-relaxation mechanism, driven by Coulombic-impurity and electron-electron scattering. We find that these two scattering mechanisms result in relaxation times of equal order of magnitude, but with disimilar dependences on doping density and temperature. Our theoretical results are compared with experimentally measured spin relaxation times in gallium arsenide.; Comment: 14 pages, 4 figures

A Review of Liquid Phase Epitaxial Grown Gallium Arsenide

Alexiev, D.; Prokopovich, D. A.; Thomson, S.; Mo, L.; Rosenfeld, A. B.; Reinhard, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/08/2004
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Liquid phase epitaxy of gallium arsenide (LPE GaAs) has been investigated intensively from the late 1960's to the present and has now a special place in the manufacture of wide band, compound semiconductor radiation detectors. Although this particular process appears to have gained prominence in the last three decades, it is interesting to note that its origins reach back to 1836 when Frankenheim made his first observations. A brief review is presented from a semiconductor applications point of view on how this subject developed. This is followed by a report on LPE GaAs growth at the Australian Nuclear Science and Technology Organisation (ANSTO).; Comment: 31 page review on Growth of Epitaxial Gallium Arsenide (GaAs). To be in 4 parts, this is parts 1&2. Part 1 is historical background, Part 2 is history of growth at ANSTO

Modified permittivity observed in bulk Gallium Arsenide and Gallium Phosphide samples at 50 K using the Whispering Gallery mode method

Hartnett, J. G.; Mouneyrac, D.; Floch, J-M. Le; Krupka, J.; Tobar, Michael E.; Cros, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/06/2009
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Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at 50 K. In both samples we observed change in permittivity under light and dark conditions. This results from a change in the polarization state of the semiconductor, which is consistent with a free electron-hole creation/recombination process. The permittivity of the semiconductor is modified by free photocarriers in the surface layers of the sample which is the region sampled by Whispering Gallery modes.; Comment: 8 pages, 3 figures

Observation of persistent photoconductivity in bulk Gallium Arsenide and Gallium Phosphide samples at cryogenic temperatures using the Whispering Gallery mode method

Hartnett, J. G.; Mouneyrac, D.; Floch, J. -M. Le; Krupka, J.; Tobar, M. E.; Cros, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/06/2009
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Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at cryogenics temperatures < 50 K. In both cases persistent photoconductivity was observed after initially exposing semiconductors to white light from a halogen lamp. Photoconductance decay time constants for GaP and GaAs were determined to be 0.900 +/- 0.081 ns and 1.098 +/- 0.063 ns, respectively, using this method.; Comment: 13 pages, 5 figures

A comparison of the carrier density at the surface of quantum wells for different crystal orientations of silicon, gallium arsenide and indium arsenide

Hatcher, Ryan; Bowen, Chris
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/08/2013
Relevância na Pesquisa
46.97%
We report the carrier densities at the surface of single-crystal quantum wells as a function of material, orientation and well width. We include wells constructed from silicon, gallium arsenide and indium arsenide with three crystal orientations, (100), (110) and (111), included for each material. We find that the D2 states in a silicon (100) quantum well have the smallest density near the surface of the slab. Inspection of the planar average of the carrier densities reveals a characteristic shape that depends on the material and orientation, which leads to a varying degree of suppression or enhancement of the density near the surface. The physics responsible for the suppression or enhancement of the density near the surface can be traced to a constraint imposed by the symmetry of quantum well wavefunction on the phases of the bulk Bloch states of the crystal from which it can be constructed.; Comment: 17 pages total, 6 figures