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Análise da precisão e acurácia de pontos georreferenciados com a técnica do código suavizado pela fase da portadora utilizando GPS de simples freqüência; Precision and accuracy analysis of georeferencing points using the carrier-smoothed-code technique with GPS single frequency receiver (L1)

Araújo Neto, João Olympio de
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 23/06/2006 Português
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A presente dissertação teve como finalidade avaliar a precisão e a discrepância das coordenadas (acurácia) obtidas por meio das observações GPS, no modo estático rápido, medidas com receptores de uma freqüência, empregando-se a técnica de suavização do código C/A pela fase da portadora para diferentes comprimentos de linha base (20, 50, 75, 100, 150, 200 e 300 Km), a partir da estação de monitoramento contínuo da EESC/USP. Essa técnica obteve boa repercussão no Brasil, a partir do momento em que foi permitida sua utilização para fins de georreferenciamento de imóveis rurais, conforme a norma técnica do INCRA, que permite a utilização da suavização do código pela fase da portadora, desde que esta apresente acurácia com valores iguais ou inferiores a 50 cm. Atualmente, trabalhos com tal técnica estão sendo desenvolvidos e aceitos para compor o banco de dados do cadastro rural nacional. Pelos resultados obtidos nesta dissertação, foi possível avaliar que a aplicação dessa técnica não atende à exigência requerida em 100% das medições e, ao mesmo tempo, verificar a diferença entre a precisão do pós-processamento, indicada pelos softwares comerciais e a acurácia dos pontos medidos comparados com os pontos de controle estabelecidos para esse fim.; The present dissertation has as objective to evaluate precision and discrepancies of coordinates (accuracy) obtained through GPS observations...

Emprego do Hamster sírio (Mesocricetus auratus) como modelo biológico para a indução de portador renal de leptospiras; The use of sirius hamster (Mesocricetus Auratus) as a biological model for inducing kidney carrier of leptospirosis

Kolber, Milton
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 02/03/2006 Português
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O emprego do hamsters (Mesocricetus auratus) como modelo biológico experimental para a reprodução da condição de portador renal de leptospiras foi investigado em machos e fêmeas jovens com 80 a 120 g de peso vivo. Os animais foram experimentalmente infectados com estirpe patogênica do sorovar Pomona caracterizada por provocar a morte por leptospirose entre o quinto e o décimo dia pós-infecção. No segundo dia pós-infecção os animais foram tratados com estolato de eritromicina, nas concentrações de 10, 20, 40 e 80 mg/kg de peso vivo. Aos 30 dias, da infecção experimental os sobreviventes foram anestesiados com isofluorano e procedeu-se a colheita de sangue para a determinação dos indicadores da função hepática e renal (Proteínas totais, Albumina, Uréia, Creatinina, Fosfatase Alcalina, Alanina Aminotransferase, Aspartato Aminotransferase, Bilirrubinas Indireta, Bilirrubinas Direta e Bilirrubinas Totais), bem como o titulo de aglutininas pela prova de soro aglutinação microscópica. A seguir, com o aprofundamento da anestesia, os animais foram submetidos a eutanásia e necropsiados para a colheita de tecido renal e hepático destinados aos exames histopatológicos pelas colorações de Hematoxilina - Eosina e Warthin- Starry...

Proteína de 18kDa de Mycobacterium leprae: um modelo de carregadora para vacinas de segunda geração; Mycobacterium leprae 18kDa protein: a carrier model to second generation vaccines

Quintilio, Wagner
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 02/06/1999 Português
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O principal problema no desenvolvimento de vacinas de segunda geração é a baixa resposta contra os antígenos, geralmente extremamente purificados. Isto tem levado à busca de novos adjuvantes que sejam mais eficientes e menos tóxicos. Este trabalho objetivava o estudo de uma proteína de choque térmico de Mycobacterium leprae - 18kDa-hsp - recombinante, produzida em levedura, veiculada em lipossomos, como modelo de proteína carregadora para antígenos fracos. Além de um estudo de estabilização de lipossomos por liofilização. A 18kDa-hsp apresenta certas características peculiares que levaram ao desenvolvimento de um método de dosagem próprio e extensível a outras proteínas com baixo teor em aminoácido cromóforos. Tendo uso potencial como proteína carregadora, a 18kDa-hsp é estável, suportando bem aquecimento, liofilização, acilação e associação com lipossomos de fosfolípides, sem perda significativa de sua atividade. Estudos paralelos de estabilização de lipossomos unilamelares mostraram que se pode usar trealose como crioprotetora no processo de liofilização-reidratação, sem perdas significativas do conteúdo dos lipossomos e com manutenção das estruturas das vesículas. Finalmente, o sistema lipossomos-18kDa-hsp mostra-se promissor como um sistema estável para veiculação de imunógenos fracos.; The major problem on development of second generation vaccines is the poor response against some immunogens. It has leading an intense research to find other substances non toxic and more efficient on enhancement of the immunological response. The aim of this work was the study of a heat-shock protein from Mycobacterium leprae - 18kDa-hsp - produced in yeast and vehiculated in liposomes...

Indução do estado de portador renal e genital pela Leptospira interrogans sorovar Canicola, estirpe LO4 em hamster (Mesocricetus auratus). Influência da concentração, da virulência da estirpe, da via de inoculação e da vacinação; Induction of renal and genital carrier for Leptospira interrogans serovar Canicola, strain LO4, in hamster (Mesocricetus auratus). Influence of concentration, strain virulence, inoculation via and vaccination

Marchiori Filho, Moacir
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/12/2007 Português
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Em decorrência da importância da leptospirose nas criações zootécnicas pelos prejuízos econômicos, principalmente pelas infecções crônicas, forma mais importante na propagação e permanência da bactéria no ambiente, este trabalho pretendeu estudar o curso da leptospirose e a formação do portador pela infecção experimental de hamsters com Leptospira interrogans sorvar Canicola, estirpe LO4, autóctone, pelas vias conjuntiva-nasal (CN) e cérvico-vaginal (CV) comparadas a via controle, intraperitonial (IP) com duas concentrações de inóculo (20-30 e 100-200 leptospiras/campo microscópico) e ainda estabelecer a eficácia conferida por cinco vacinas experimentais formuladas com dois tipos de adjuvantes (saponina e hidróxido de alumínio), pelo desafio de hamster. No preparo das vacinas foi considerada a virulência da estirpe LO4 submetida a duas e cinco passagens in vitro, que foi comparada com duas vacinas controle produzidas com a estirpe de referência, Hond Utrecht IV, com indeterminado número de passagens in vitro. Foram também avaliadas a indução de anticorpos aglutinantes e neutralizantes e as lesões histopatológicas por HE e Warthin-Starry. A detecção das leptospiras nos órgãos de hamsters mortos pela leptospirose ou eutanasiados foi realizada pela visualização direta...

Analysis of Factor VIII polymorphic markers as a means for carrier detection in Brazilian families with haemophilia A

De Carvalho, F. M.; Wolfgramm, E. de Vargas; Paneto, G. G.; Careta, F. de Paula; Perrone, A. M. Spagnol; De Paula, F.; Louro, I. D.
Fonte: Blackwell Publishing Publicador: Blackwell Publishing
Tipo: Artigo de Revista Científica Formato: 409-412
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Haemophilia A is an X-linked, recessively inherited bleeding disorder of varying severity, which results from the deficiency of procoagulant factor VIII f(8). Linkage diagnosis using polymorphic markers in the f8 gene is widely used to detect carriers. The objective of this study was to verify the informativeness of three polymorphic markers in the Brazilian population, to evaluate the usefulness of such markers in carrier detection procedures. Sixty-three unrelated healthy volunteers and 10 haemophilic families were studied. Two microsatellite repeats and one HindIII RFLP markers were used. Carrier and non-carrier status could be determined in 80% of females investigated. Intron 13 markers presented the highest heterozygosity rate (79%) followed by intron 22 (68%) and intron 19 (57%). When all three markers were used together, linkage analysis informativeness increased significantly. We conclude that these markers are suitable for carrier detection in the Brazilian population and we recommend their use in combination to maximize diagnostic efficiency.

Evaluation of experimental vaccination in chinese goose (Anser cygnoides) against newcastle disease: Investigation of the state of virus carrier

Campioni, Josie Maria; Paulillo, Antonio Carlos; Schmidt, Elizabeth Moreira dos Santos; Nishizawa, Marcia; Testi, Alan Jonathan Pereira; Denadai, Janine; Carrasco, Adriano de Oliveira Torres
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 512-514
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); This study aimed the characterization of the importance of vaccination against Newcastle disease in Chinese geese (Anser cygnoides) and to investigate the state of carrier of the virus in this species. There were used 120 Chinese geese, distributed at random into 4 groups, vaccinated or not. At 60 days of age, all groups were challenged with a pathogenic virus (NDV) suspension, EID 50= 10 8.15/0.1 mL and a group of Specific Pathogen Free (SPF) chickens were used as control of the virus. Cloacal and tracheal swabs were collected after 6, 10 and 20 days post-challenge for genome viral excretion by RT-PCR (reverse transcriptionpolymerase chain reaction). Chinese goose of all groups did not demonstrate any signs of Newcastle disease. They were refractory to the clinical disease with the NDV. In Chinese geese from control group, NDV genome was detected 20 days after challenge. It was demonstrated therefore the state of carrier of NDV by Chinese goose. In geese, from the vaccinated groups, genome viral excretion was not detected by RT-PCR. It was also demonstrated the importance of the vaccination in the suppression of the state of carrier of NDV in Chinese geese. © Asian Network for Scientific Information...

Influence of carrier concentration on the control of Galactomyces geotrichum bulking and bacterial community of biofilm reactors

Matos, M.; Pereira, M. A.; Nicolau, Ana; Rodrigues, A. L.; Brito, A. G.; Nogueira, R.
Fonte: Taylor & Francis; Desalination Publications Publicador: Taylor & Francis; Desalination Publications
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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The present work aims to evaluate a strategy to solve Galactomyces geotrichum bulking based on the incorporation of a biofilm carrier in activated sludge systems. For this study, four sequencing batch reactors (SBR) were operated without (SBR1) and with a carrier for biofilm growth (5% [SBR2], 10% [SBR3], and 20% [SBR4] of the reactor volume). As expected, G. geotrichum bulking was observed in the SBR operating just with suspended biomass, as ascertained by direct microscopic inspection. The incorporation of an optimized amount of biofilm carrier (10 and 20%) suppressed the overgrowth of the filamentous fungus probably due to the combined effect of a decreased biomass loading rate and an increased shear stress. Polymerase chain reaction—denaturing gradient gel electrophoresis (PCR–DGGE) analysis of the bacterial community suggested that the incorporation of a biofilm carrier induced increasing differences in the bacterial community structure as the concentration of carrier increased in the SBR. However, the observed differences did not seem to affect the activated sludge system since bacterial groups usually present in these systems prevailed.

Carrier detection of duchenne and becker muscular dystrophy using muscle dystrophin immunohistochemistry

Oliveira,Acary S. Bulle; Gabbai,Alberto A.; Schmidt,Beny; Hitomi Kiyomoto,Beatriz; Lima,G. Camargo; Minetti,Carlo; Bonilla,Eduardo
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1992 Português
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To ascertain whether dystrophin immunohistochemistry could improve DMD/ BMD carrier detection, we analyzed 14 muscle biopsies from 13 DMD and one BMD probable and possible carriers. All women were also evaluated using conventional methods, including genetic analysis, clinical and neurological evaluation, serum CK levels, KMG, and muscle biopsy. In 6 cases, there was a mosaic of dystrophin-positive and dystrophin-deficient fibers that allowed to make the diagnosis of a carrier state. Comparing dystrophin immunohistochemistry to the traditional methods, it was noted that this method is less sensitive than serum CK measuremens, but is more sensitive than EMG and muscle biopsy. The use of dystrophin immunohistochemistry in addition to CK, EMG and muscle biopsy improved the accuracy of carrier detection. This method is also helpful to distinguish manifesting DMD carriers from patients with other neuromuscular diseases like limb-girdle muscular dystrophy and spinal muscular atrophy.

Influence of the oxidation step on the behaviour and the performances of an oxygen carrier in fixed bed reactor

Blas,Lucia; Dorge,Sophie; Zouaoui,Nabila; Lambert,Arnold; Dutournié,Patrick
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2014 Português
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Chemical Looping Combustion is a promising technology for clean power generation with integrated CO2 capture. In this process the oxygen required for combustion is provided by a metal oxide. This work deals with the development of an experimental procedure to study performances of an oxygen carrier during oxidation/reduction cycles and the influence of the oxidation step on its behaviour. Tests were performed in a laboratory fixed bed reactor, with NiO/NiAl2O4, a promising oxygen carrier, and CO as fuel. Two different protocols of oxidation were studied. Results reveal that the oxidation step conditions can change the performances of the oxygen carrier. A significant decrease in total reduction capacity was observed using the regeneration step at high temperature due to structural changes in particles. SEM analysis reveals that particle surface contains different crystallites according to this procedure. With the second procedure (oxidation in temperature ramp), nickel is partially agglomerated.

Electronic properties of the recombination centers responsible for the light-induced carrier lifetime degradation in boron-doped Czochralski silicon

Schmidt, Jan; Cuevas, Andres
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Artigo de Revista Científica Formato: 245321 bytes; 351 bytes; application/pdf; application/octet-stream
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In order to study the electronic properties of the recombination centers responsible for the lightinduced carrier lifetime degradation commonly observed in high-purity boron-doped Czochralski (Cz) silicon, injection-level dependent carrier lifetime measurements are performed on a large number of boron-doped p-type Cz silicon wafers of various resistivities (1 – 31 Wcm) prior to and after light degradation. The measurement technique used is the contactless quasi-steady state photoconductance method, allowing carrier lifetime measurements over a very broad injection range between 1012 and 1017 cm-3. To eliminate all recombination channels not related to the degradation effect, the difference of the inverse lifetimes measured after and before light degradation is evaluated. A detailed analysis of the injection level dependence of the carrier lifetime change using the Shockley-Read-Hall theory shows that the fundamental recombination center created during illumination has an energy level between Ev + 0.35 eV and Ec - 0.45 eV and an electron/hole capture time constant ratio between 0.1 and 0.2. This deep-level center is observed in all samples and is attributed to a new type of boron-oxygen complex. Besides this fundamental defect, in some samples an additional shallow-level recombination center at 0.15 eV below Ec or above Ev is found to be activated during light exposure. This second center dominates the light-degraded carrier lifetime only under highinjection conditions and is hence only of minor importance for low-injection operated devices.; yes

Validity of Shockley-Read-Hall statistics for modeling carrier lifetimes in silicon

Macdonald, D; Cuevas, Andres
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Artigo de Revista Científica Formato: 237848 bytes; 360 bytes; application/pdf; application/octet-stream
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The Shockley-Read-Hall model, in its simplest and most common form, is often used to describe both injection- and temperature-dependent carrier lifetime measurements. Such lifetime modeling has provided the basis for novel, ultra-sensitive spectroscopic techniques for the study of recombination centers in crystalline silicon. However, this approximate model is only valid when the density of recombination centres is small enough to avoid trapping effects, which cause distortions in the excess mobile carrier concentrations. In this work, the simplified Shockley-Read-Hall model is compared with a more general solution of the continuity equations that takes account of carrier trapping. This comparison leads to an expression for the upper limit on the recombination centre density for which the simplified Shockley-Read- Hall model remains accurate. The limit depends not only on the dopant density, but also on the energy level and electron and hole capture cross-sections for a given type of recombination centre. The results allow experimental conditions that do not invalidate the use of the simplified Shockley-Read-Hall model to be determined.; yes

Deciphering chinese strategic deception: the middle kingdom's first aircraft carrier

Kong, Eu Yen; Yu, Kuei-Lin
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
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Approved for public release; distribution is unlimited; The thesis examines Chinas employment of strategic deception in the acquisition and development of its first aircraft carrier the Liaoning in 2012. By examining Chinas national goals, strategy and propensity to employ deception, this thesis aims to: 1. Explain how Chinas national goals and strategy drove it to develop an aircraft carrier. 2. Explain the aircraft carriers role in Chinas maritime strategy. 3. Explain how China employed deception in the acquisition and development of the aircraft carrier. 4. Assess the implications of Chinas use of strategic deception in developing its first aircraft carrier. 5. Assess the future role of Chinas first aircraft carrier.; Major, Republic of Singapore Navy; Lieutenant Colonel, Republic of China Marine Corps (Taiwan)

Impact of carrier profile and rear-side reflection on photoluminescence spectra in Planar Crystalline Silicon Wafers at different temperatures

Nguyen, Hieu T.; Rougieux, Fiacre E.; Baker-Finch, Simeon C.; Macdonald, Daniel
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
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The increasing use of spectral photoluminescence as an advanced and accurate diagnostic tool motivates a comprehensive assessment of the effects of some important optical and electrical properties on the photoluminescence spectra from crystalline silicon wafers. In this paper, we present both modeling results and measurements to elucidate the effects of the internal reflectance at the planar wafer surfaces, as well as the carrier profile varying across the sample thickness due to an increased rear-surface recombination velocity, as a function of temperature. These results suggest that the accuracy of existing spectral PL techniques may be improved by using higher temperatures due to the increased effect of the carrier profile at higher temperatures. They also show that changes in the photoluminescence spectrum shape caused by the addition of a rear-side specular reflector offset those caused by changes in the carrier profile due to increased rear surface recombination, and therefore, considerable care needs to be taken when changing the rear-side optics. Finally, the possible impact of variations in the rear-side reflectance on the band–band absorption coefficient and radiative recombination coefficient, which have previously been determined using the spectral photoluminescence technique...

Projeto de um par de mangas de eixo automotivas para a Fórmula SAE; Project of an automotive wheel carrier pair to Formula SAE

Flesch, Evandro Luís
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
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Este trabalho visa documentar os detalhes referentes ao projeto de um par de mangas de eixo automotivas. Tais componentes serão empregados em um veículo experimental desenvolvido por estudantes da universidade para desenvolvimento de um segundo veículo que representará a escola em uma competição de engenharia. A manga de eixo é o elo entre o conjunto de roda e pneu e os braços de suspensão do veículo, sendo responsável por sua dirigibilidade, estabilidade e comportamento. Questões relativas à sua influência no comportamento do veículo, à interferência com outros componentes e à fabricação são abordadas. Métodos de análise estrutural com auxílio computacional são empregados para estimar seu comportamento frente a suas condições de operação. Os esforços internos estimados após sucessivas iterações no desenho da geometria do componente mantiveram-se em patamares aceitáveis para o material escolhido. Os desenhos de conjunto mostraram-se adequados, de maneira a permitir a execução do componente, restando apenas a definição do conjunto de freios a ser utilizado.; The aim of this work is to register the details according to the automotive wheel carrier pair project. Such components will be employed in an experimental vehicle developed by the university students to make a second car...

The consequences of high injected carrier densities on carrier localisation and efficiency droop in InGaN/GaN quantum well structures

Hammersley, S.; Watson-Parris, D.; Dawson, P.; Godfrey, M.; Badcock, T.; Kappers, M.; McAleese, C.; Oliver, R.; Humphreys, C.
Fonte: Journal of Applied Physics Publicador: Journal of Applied Physics
Tipo: Article; submitted version
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There is a great deal of interest in the underlying causes of efficiency droop in InGaN/GaN quantum well light emitting diodes, with several physical mechanisms being put forward to explain the phenomenon. In this paper we report on the observation of a reduction in the localisation induced S-shape temperature dependence of the peak photoluminescence energy with increasing excitation power density. This S-shape dependence is a key fingerprint of carrier localisation. Over the range of excitation power density where the depth of the S shape is reduced we also observe a reduction in the integrated photoluminescence intensity per unit excitation power, i.e. efficiency droop. Hence the onset of efficiency droop occurs at the same carrier density as the onset of carrier delocalisation. We correlate these experimental results with the predictions of a theoretical model of the effects of carrier localisation due to local variations in the concentration of the randomly distributed In atoms on the optical properties of InGaN/GaN quantum wells. On the basis of this comparison of theory with experiment we attribute the reduction in the Sshape temperature dependence to the saturation of the available localised states. We propose that this saturation of the localised states is a contributory factor to efficiency droop whereby non localised carriers recombine non-radiatively.

Sensitized carrier generation in evaporated thin films and particle dispersions of benzimidazole perylene

Popovic, Zoran; Lee, Sang-Nam; Collison, Christopher; Hor, Ah-Mee; Rothberg, Lewis
Fonte: International Society for Optical Engineering Publicador: International Society for Optical Engineering
Tipo: Abstract Formato: 38660 bytes; application/pdf
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We studied photoconductivity in particle dispersions and vacuum evaporated films of benzimidazole perylene (BZP) pigment in contact with a tetraphenyldiamine (TPD) hole transport layer. Xerographic photoreceptors based on evaporated BZP photogenerator layers showed about two times higher carried generation efficiency than photoreceptors containing generator layer in the form of a particle dispersion. Time resolved fluorescence measurements were performed on these two types of structures. Fluorescence time evolution was compared in samples with and without TPD in a polycarbonate overcoat layer. Significantly larger decrease in average fluorescence lifetime was observed in structures containing thin evaporated films compared to the structures with the pigment in the form of particle dispersion. This indicates that reduced carrier generation efficiency in particle dispersion sin a consequence od exciton bulk trapping which significantly reduces the number of excitons reaching BZP/TPD interface. As carrier generation in BZP/TPD system is a result of exciton dissociation at the interface to produce electron-hole pairs. Thus a smaller number of excitons reaching the interface leads to reduction of carrier generation efficiency.

Carrier Transfer and Magneto-transport in Single Modulation-doped V-grooved Quantum Wire modified by Ion Implantation

Huang, Shao-Hua; Chen, Zhanghai H; Wang, Feng; Shen, S C; Tan, Hoe Hark; Fu, Lan; Fraser, Michael; Jagadish, Chennupati
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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A single Al0.5Ga0.5As/GaAs V-grooved quantum wire modified by selective ion implantation and rapid thermal annealing was investigated by using spatially resolved micro-photoluminescence spectroscopy and magneto-resistance measurements. The results of spatially resolved photoluminescence indicate that the ion-implantation-induced quantum well intermixing significantly raises the electronic sub-band energies in the side quantum wells (SQWs) and vertical quantum wells, and a more efficient accumulation of electrons in the quantum wires is achieved. Processes of real space carrier transfer from the SQW to the quantum wire was experimentally observed, and showed the blocking effect of carrier transfer due to the existence of the necking quantum well region. Furthermore, magneto-transport investigation on the ion-implanted quantum wire samples shows the quasi-one-dimensional intrinsic motion of electrons, which is important for the design and the optimization of one-dimensional electronic devices.

Minority Carrier Lifetime Properties of Reactive Ion Etched p-Type Float Zone Si

Deenapanray, Prakash; Horteis, M; MacDonald, Daniel; Weber, Klaus
Fonte: Electrochemical Society Inc Publicador: Electrochemical Society Inc
Tipo: Artigo de Revista Científica
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Quasi-steady-state photoconductance (QSSPC) and deep level transient spectroscopy (DLTS) were used to characterize the minority carrier lifetime properties of reactive ion etched p-type Si. The effective lifetime of the plasma-processed samples degraded after etching, with the densities of recombination centers increasing linearly with etch time. Evidence is provided for the long-range (> 2 μm) migration of defects in the plasma-etched samples. A discrete defect with energy position at (0.32 ± 0.02) eV, that could be either B- or H-related, was detected by DLTS in the etched samples. Furthermore, this energy level could be used to adequately model the injection-dependence of the measured carrier lifetimes using the Shockley-Read-Hall model. Our results show that DLTS and QSSPC is a powerful combination to characterize the electrical properties of defects that are relevant to the performance of solar cells.

Minority carrier lifetime in plasma-textured silicon wafers for solar cells

Kumaravelu, G; Alkaisi, M M; MacDonald, Daniel; Zhao, J; Rong, B; Bittar, A
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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In this work a comparison between plasma-induced defects by two different SF6 texturing techniques, reactive ion etching (RIE) and high-density plasma (HDP) is presented. It is found that without any defect-removal etching (DRE), the minority carrier lifetime is the highest for the HDP technique. After DRE, the minority carrier lifetime rises as high as 750 μs for both RIE- and HDP-textured wafers at an excess carrier density of 1×1015 cm-3. The measured lifetimes correspond to an implied one-sun open-circuit voltage of around 680 mV compared to about 640 mV before DRE for the HDP-textured wafers. FZ silicon 〈1 0 0〉 wafers were used in this study. We also noted that in the RIE process, the induced defect density was significantly lower for wafers etched at 300 K than those etched at 173 K.

Charge carrier transport in Poly(N-vinylcarbazole): CdS Quantum Dot Hybrid Nanocomposite

Choudhury, Kaushik; Samoc, Marek; Patra, Amitava; Prasad, Paras N
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
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Hybrid organic:inorganic materials have emerged as a novel class of electronic and optoelectronic media for a number of potential technological applications. However, very little fundamental understanding of charge carrier transport in such hybrid materials exists. A knowledge of the influence of nanoparticle doping on charge carrier mobility in nano composites becomes important in order to optimize properties for photorefractive and photovoltaic operations. We report here a study of the mobility of holes in a model nanoparticle-sensitized hybrid organic:inorganic system consisting of poly(N-vinylcarbazole) (PVK) doped with quantum dots of cadmium sulfide. The mobility of holes (dominant carriers in the PVK host materials) was measured using the conventional time-of-flight technique with injection of holes from a selenium layer. Though photocurrent transients exhibit features typical of dispersive transport in an amorphous semiconductor, certain deviations from the original Scher-Montroll theory are observed. Strong dependence of the carrier mobility on field and temperature indicate Poole - Frenkel-like activated hopping transport. A thickness dependence stronger than that suggested by the Scher - Montroll theory is found. Significant enhancement of the effective carrier mobility is noticed with the increase of nanoparticle concentration...