A DFT study of ethanol adsorption and decomposition on α-Al{sub 2}O{sub 3}(0 0 0 1) surface

Energy Technology Data Exchange (ETDEWEB)

Chiang, Hsin-Ni; Nachimuthu, Santhanamoorthi, E-mail: santhanamoorthi@gmail.com; Cheng, Ya-Chin; Damayanti, Nur Pradani; Jiang, Jyh-Chiang, E-mail: jcjiang@mail.ntust.edu.tw

2016-02-15

Graphical abstract: - Highlights: • Ethanol decomposition has been studied over α-Al{sub 2}O{sub 3}(0 0 0 1) surface. • EDD and DOS results confirm the stable adsorption of ethanol on the surface. • DFT calculations favor ethylene formation via C{sub β}−H bond scission. • The formation of acetaldehyde has higher energy barrier. - Abstract: Ethanol adsorption and decomposition on the clean α-Al{sub 2}O{sub 3}(0 0 0 1) surface have been systematically investigated by density functional theory calculations. The nature of the surface-ethanol bonding has studied through the density of states (DOS) and the electron density difference (EDD) contour plots. The DOS patterns confirm that the lone pair electrons of EtOH are involved in the formation of a surface Al−O dative bond and the EDD plots provide evidences for the bond weakening/forming, which are consistent with the DOS analysis. Our ethanol decomposition results indicate that ethanol dehydration to ethylene (CH{sub 3}CH{sub 2}OH{sub (a)} → C{sub 2}H{sub 4(g)} + OH{sub (a)} + H{sub (a)}), is the main reaction pathway with the energy barrier of 1.46 eV. Although the cleavage of the hydroxyl group of ethanol has lower energy barrier, the further decomposition of ethoxy owns much higher energy barrier.

Metallicity of Ca{sub 2}Cu{sub 6}P{sub 5} with single and double copper-pnictide layers

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Li, Li, E-mail: lil2@ornl.gov [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Parker, David [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Chi, Miaofang [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Tsoi, Georgiy M.; Vohra, Yogesh K. [Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294 (United States); Sefat, Athena S., E-mail: sefata@ornl.gov [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2016-06-25

We report thermodynamic and transport properties, and also theoretical calculations, for Cu-based compound Ca{sub 2}Cu{sub 6}P{sub 5} and compare with CaCu{sub 2-δ}P{sub 2}. Both materials have layers of edge-sharing copper pnictide tetrahedral CuP{sub 4}, similar to Fe–As and Fe–Se layers (with FeAs{sub 4}, FeSe{sub 4}) in the iron-based superconductors. Despite the presence of this similar transition-metal pnictide layer, we find that both Ca{sub 2}Cu{sub 6}P{sub 5} and CaCu{sub 2-δ}P{sub 2} have temperature-independent magnetic susceptibility and show metallic behavior with no evidence of either magnetic ordering or superconductivity down to 1.8 K CaCu{sub 2-δ}P{sub 2} is slightly off-stoichiometric, with δ = 0.14. Theoretical calculations suggest that unlike Fe 3d-based magnetic materials with a large density of states (DOS) at the Fermi surface, Cu have comparatively low DOS, with the majority of the 3d spectral weight located well below Fermi level. The room-temperature resistivity value of Ca{sub 2}Cu{sub 6}P{sub 5} is only 9 μΩ-cm, due to a substantial plasma frequency and an inferred electron-phonon coupling λ of 0.073 (significantly smaller than that of metallic Cu). Also, microscopy result shows that Cu–Cu distance along the c-axis within the double layers can be very short (2.5 Å), even shorter than metallic elemental copper bond (2.56 Å). The value of dρ/dT for CaCu{sub 2-δ}P{sub 2} at 300 K is approximately three times larger than in Ca{sub 2}Cu{sub 6}P{sub 5}, which suggests the likelihood of stronger electron-phonon coupling. This study shows that the details of Cu–P layers and bonding are important for their transport characteristics. In addition, it emphasizes the remarkable character of the DOS of ‘122’ iron-based materials, despite much structural similarities. - Highlights: • A comprehensive study on Cu-based compound Ca{sub 2}Cu{sub 6}P{sub 5} and compare with CaCu{sub 2-δ}P{sub 2}. • Both materials have layers of

Fatores associados ao desempenho escolar: uma análise da proficiência em matemática dos alunos do 5º ano do ensino fundamental da rede municipal do Rio de Janeiro

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Gabrielle A. Palermo

2014-12-01

Full Text Available O presente estudo está inserido na linha dos trabalhos que buscam compreender os diferentes fatores que influenciam o funcionamento das escolas da rede pública de ensino brasileira, bem como a sua qualidade, a partir da identificação de variáveis que impactam os resultados escolares, em particular o desempenho dos alunos medido pelos sistemas de avaliação utilizados pelo Inep/MEC. Os fatores que influenciam a proficiência são múltiplos e complexos, contemplando dinâmicas que atuam em diferentes níveis, desde o mais elementar, das características socioeconômicas e culturais dos indivíduos e de suas famílias, até as dinâmicas que ocorrem nas salas de aula, entre professores e alunos, e as características estruturais da escola. Alunos e seus responsáveis, diretores e professores das instituições de ensino são alguns dos atores relevantes que agem sobre o processo latente gerador de maiores ou menores rendimentos escolares. Mais especificamente, o objetivo do presente estudo é analisar os possíveis fatores que influenciam o desempenho escolar dos alunos do 5º ano do ensino fundamental, nas escolas públicas municipais da cidade do Rio de Janeiro. Para tanto, foram utilizados modelos hierárquicos com três níveis, que permitiram avaliar os efeitos de variáveis socioeconômicas e culturais e dos contextos familiares dos alunos, de práticas pedagógicas e estilos de ensinar dos docentes e, ainda, de políticas educacionais, aspectos da gestão e características das escolas. O estudo teve como fonte principal as informações provenientes da Prova Brasil 2007.

Análise do sistema de gerenciamento dos resíduos de serviços de saúde nos municípios da bacia hidrográfica do Rio dos Sinos, Rio Grande do Sul, Brasil Analysis of the management system of the healthcare waste in municipalities of Rio dos Sinos hydrographic basin, Rio Grande do Sul, Brazil

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Luciana Paulo Gomes

2012-12-01

Full Text Available Nesta pesquisa focou-se o gerenciamento dos resíduos de serviços de saúde (RSS e especificamente aqueles do tipo perfurocortantes. Foram analisadas as formas atuais de gestão implementadas na bacia hidrográfica do Rio dos Sinos (BHRS, a partir da aplicação de questionários nos estabelecimentos de saúde geradores de RSS. Os resultados indicam que 48,6% dos estabelecimentos de saúde atendem corretamente à legislação específica brasileira, verificando ainda uma melhor gestão para os estabelecimentos privados. Os estabelecimentos de saúde do tipo "laboratórios, bancos de sangue e farmácias" instalados nos municípios com mais de 20.000 habitantes e área municipal na BHRS dentro da faixa de 80 a 100% em relação à área total municipal apresentaram os piores resultados em termos de gestão de RSS. O grupo de atividades de serviços de saúde com o maior número de estabelecimentos na BHRS - "consultórios/clínicas de odontologia, clínicas veterinárias, drogarias e unidade móvel" - indicou um dos menores índices de conhecimento das exigências legais específicas relativas ao tema estudado.This research focused on the management of healthcare waste, specifically about the sharps types. The current ways of management in the Rio dos Sinos basin (BHRS were analyzed with the use of questionnaires in health establishments generators of healthcare waste. The results indicate that 48.6% of health facilities comply with the specific legislation in Brazil, also indicating a better management coming from private institutions. Health facilities of the type "labs, blood banks and pharmacies" installed in municipalities with over 20,000 inhabitants and municipal area in BHRS within the range of 80 to 100% relative to the total municipal area had the worst results in terms of healthcare waste management. The group activities of healthcare services with the highest number of establishments in BHRS - "dental offices/clinics, veterinary

O impacto do Programa Minha Casa, Minha Vida na economia brasileira: uma análise de insumo-produto

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Carlos Alberto Gonçalves Junior

Full Text Available O objetivo do presente artigo foi analisar o impacto do Programa Habitacional Minha Casa, Minha Vida na economia brasileira mediante a dinamização do setor da construção civil, utilizando a matriz de insumo-produto de 2008 para estimação dos geradores e multiplicadores de produção, renda, emprego e impostos. Os resultados mostraram que o setor da construção civil apresentou ligações para trás e para frente abaixo da média dos setores da economia. No entanto, considerando o valor de R$ 125,7 bilhões previstos para investimento no período em análise, constatou-se que haverá crescimento significativo na renda paga aos trabalhadores, serão criados cerca de 7 milhões de empregos diretos e indiretos, haverá aumento na produção de cerca de 6% do PIB em valores de 2010, e pelo menos 16% do valor dos subsídios dados nos contratos de financiamento do PMCMV voltarão aos cofres públicos.

O ENSINO DOS SABERES DA CULINÁRIA REGIONAL: experiência docente na amazônia paraense no município de Vigia

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Maraísa Andrade de Castro

2016-09-01

Full Text Available Este artigo trata-se de um relato deexperiênciadocentevivenciadanoInstituto Federal de Educação, Ciência e Tecnologia do Pará, Polo Avançado de Vigia de Nazaré, no processo de planejamento e ministração da disciplina Saberes da Culinária Regional para o Curso Técnico Subsequente em Turismo e Hospitalidade, cujo projeto pedagógico experimental, baseado na metodologia da alternância, adaptado de um modelo da educação rural, teve sua estrutura curricular organizada via temas geradores, conforme a proposta freireana de educação, que prevê a abordagem do conhecimento cientí co através dos saberes empíricos dos estudantes. Por meio do levantamento dos hábitos alimentares dos discentes e de entrevistas com idosos da comunidade, o conteúdo central da disciplina foi desenvolvido, e após leituras de textos, visitas técnicas e atividades práticas e lúdicas, os futuros técnicos sugeriram proposições para valorização da culinária típica da região, e posteriormente realizaram um evento objetivando sensibilizar o empresariado sobre essa questão. O artigo tem como objetivo apresentar uma abordagem de ensino temática diferenciada que pode contribuir para o aprimoramento das práticas de ensino em qualquer instância, assim como inspirar docentes para elaboração de planos de aula criativos. Dentre os resultados obtidos, destaca-se a re exão sobre as modi cações nos hábitos alimentares da comunidade. Palavras-chave: Ensino técnico. Hábitos alimentares. Culinária regional.

Enhanced thermoelectric performance with participation of F-electrons in β-Zn{sub 4}Sb{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Liu, Mian; Qin, Xiaoying, E-mail: xyqin@issp.ac.cn; Liu, Changsong; Li, Xiyu; Yang, Xiuhui

2014-01-25

Highlights: • Find an effective route to enhance the thermoelectric figure of merit of β-Zn{sub 4}Sb{sub 3}. • Provide the corresponding theoretical predictions. • Investigated the effects of doping Ce and Pr in β-Zn{sub 4}Sb{sub 3}. -- Abstract: The effects of rare-earth element impurities Ce and Pr on the electronic structure and thermoelectric properties of β-Zn{sub 4}Sb{sub 3} were investigated by performing self-consistent ab initio electronic structure calculations within density functional theory and solving the Boltzmann transport equations within the relaxation time approximation. The results demonstrated that these rare-earth element impurities with f orbitals could introduce giant sharp resonant peaks in the density of states (DOS) near the host valence band maximum in energy. And these deliberately engineered DOS peaks result in a sharp increase of the room-temperature Seebeck coefficient and power factor from those of impurity-free system by a factor of 100 and 22, respectively. Additionally, with the simultaneous declining of carrier thermal conductivity, a potential 5-fold increase at least with Ce doping and more than 3 times increase with Pr doping in the thermoelectric figure of merit of β-Zn{sub 4}Sb{sub 3} at room temperature are achieved. The effective DOS restructuring strategy opens up new opportunities for thermoelectric power generation and waste heat recovery at large scale.

CoMAprend – a experiência da construção de um corpus de aprendizes para estudos

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Stella Esther Ortweiler Tagnin

2011-02-01

Full Text Available O objetivo deste artigo é mostrar o processo de construção de um site na Internet especialmente criado para reunir textos escritos por alunos dos cursos de línguas inglesa, francesa, alemã, italiana e espanhola numa universidade brasileira para formar um corpus (ou corpora para pesquisadores. Os aprendizes inserem suas redações no site e o professor/pesquisador pode, então, construir um subcorpus de aprendizes (de acordo com a língua, por exemplo para estudos específicos e pesquisar o mesmo com ferramentas de análise disponíveis no site (gerador de listas de palavras, concordanciador, gerador de n-gramas ou exportá-lo para investigação com outras ferramentas de análise lexical off-line.

O processo de gestão da marca “Vinho do Porto”: relevância da marca-país e dos aglomerados produtivos

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Caio Miralles de Araújo

2008-01-01

Full Text Available http://dx.doi.org/10.5007/2175-8069.2008v10n20p182 No mundo dos negócios é incontestável o valor das marcas, relacionando-se muito estreitamente com os objetivos organizacionais e implementação de estratégias de negócio. Este artigo tem como objetivo analisar características inerentes à gestão da marca “Vinho do Porto”, destacando a perspectiva da “marca-país” e relevância da gestão desta como vantagem competitiva, para o produto e país de modo geral. A coleta de dados baseou-se na observação - durante período de vivência em Portugal por um dos autores -, informações levantadas em institutos relacionados ao Vinho do Porto, empresas comerciantes, e obras publicadas sobre o Vinho. A análise baseou-se em referencial relacionado à gestão de marcas, publicidade, posicionamento e clusters. Destacam-se os esforços das empresas na divulgação da marca no mercado global, institutos envolvidos e até mesmo do governo, por se tratar de um produto não só gerador de muitos empregos diretos e indiretos, mas um embaixador português mundialmente.

Anisotropic electrical, thermal and magnetic properties of Al{sub 13}Ru{sub 4} decagonal quasicrystalline approximant

Energy Technology Data Exchange (ETDEWEB)

Wencka, Magdalena [Polish Academy of Sciences, Poznan (Poland). Inst. of Molecular Physics; Vrtnik, Stanislav; Kozelj, Primoz; Dolinsek, Janez [Ljubljana Univ. (Slovenia). Faculty of Mathematics and Physics; Jozef Stefan Institute, Ljubljana (Slovenia); Jaglicic, Zvonko [Ljubljana Univ. (Slovenia). Inst. of Mathematics, Physics and Mechanics; Gille, Peter [Muenchen Univ. (Germany). Crystallography Section

2017-09-01

We present measurements of the anisotropic electrical and thermal transport coefficients (the electrical resistivity, the thermoelectric power, the thermal conductivity), the magnetization and the specific heat of the Al{sub 13}Ru{sub 4} monoclinic approximant to the decagonal quasicrystal, in comparison to the isostructural Al{sub 13}Fe{sub 4}. The electrical and thermal transport parameters of Al{sub 13}Ru{sub 4} were found to exhibit significant anisotropy, qualitatively similar to that found previously in the Al{sub 13}Fe{sub 4} (P. Popcevic, et al., Phys. Rev. B 2010, 81, 184203). The crystallographic b direction, corresponding to the stacking direction of the (a,c) atomic planes, is the most conducting direction for the electricity and heat. The thermopower is strongly anisotropic with a complicated temperature dependence, exhibiting maxima, minima, crossovers and sign change. The electronic density of states (DOS) at the Fermi energy is reduced to 35% of the DOS of Al metal. The magnetic susceptibility is diamagnetic and the diamagnetism is by a factor of 2 stronger for the magnetic field along the stacking b direction.

GERENCIAMENTO DE EFLUENTES DE SERVIÇO DE RADIOLOGIA: INQUÉRITO REALIZADO EM TRÊS CENTROS DE SAÚDE DA REGIÃO DOS LAGOS ESTADO DO RIO DE JANEIRO

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João Marcos Rodrigues dos SANTOS

2017-07-01

Full Text Available A radiologia é uma área muito importante para as ciências biomédicas. Apesar dos benefícios que os exames radiológicos oferecem, muito têm se discutido sobre o destino dos efluentes gerados por este tipo de atividade. Os problemas ambientais ocasionados por essas substâncias são diversos: contaminação de rios, lagos e lençóis freáticos além da ausência de um tratamento adequado dos resíduos por parte dos geradores. O objetivo desta pesquisa foi realizar um diagnóstico sobre o gerenciamento dos resíduos em serviços de radiologia em três centros de saúde da Região dos Lagos estado do Rio de Janeiro. As informações foram obtidas através de entrevistas realizadas por questionário semiestruturado direcionado aos responsáveis técnicos. Foram obtidas informações sobre: o volume total de líquido produzido, a forma de armazenamento, os métodos de descarte, dentre outras. Após o tratamento dos dados, os mesmos foram confrontados com a literatura, mantendo-se a imparcialidade para o melhor conhecimento possível sobre o tema. Os dados da pesquisa revelaram uma não conformidade com a legislação e parâmetros estabelecidos pelas instituições fiscalizadoras. De uma forma mais específica, observou-se uma certa dificuldade em relação ao gerenciamento dos líquidos residuais, evidenciando a possibilidade de riscos para a saúde e meio ambiente. Uma preocupação evidenciada na pesquisa está relacionada ao destino das películas inutilizadas, observou-se pouca preocupação em relação a este tipo de descarte. Conclui-se que o diagnóstico realizado sinaliza pontos preocupantes sobre o gerenciamento dos resíduos nos serviços de radiologia. A pesquisa deixa uma contribuição para futuras discussões sobre o tema.     

Conversion degree of SO{sub 2} into SO{sub 3} and SO{sub x} emissions in steam generators; Grado de conversion de SO{sub 2} en SO{sub 3} y emisiones de SO{sub x} en generadores de vapor

Energy Technology Data Exchange (ETDEWEB)

Espinoza Garza, Jesus; Penna Garcia, Adriana; Huerta Espino, Mario [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1996-12-31

A large part of the electric energy produced in this country is obtained burning fossil fuels as primary energy source. These fuels are mainly coal, fuel oil, and natural gas. The first two have high percentages of sulfur, therefore producing and emitting to the air different amounts of sulfur dioxide (SO{sub 2}) and sulfur trioxide (SO{sub 3}). The relationship between this two contaminants varies depending on the type of steam generator, the rated capacity, and most of all on the sulfur content in the fuel and on the combustion system operating conditions. [Espanol] Una gran parte de la energia electrica generada en el pais se obtiene utilizando combustibles fosiles como fuente primaria de energia. Estos combustibles son principalmente carbon, combustoleo y gas natural. Los dos primeros tienen altos porcentajes de azufre, con lo cual se producen y emiten a la atmosfera diferentes cantidades de dioxido de azufre (SO{sub 2}) y trioxido de azufre (SO{sub 3}). La relacion entre estos dos contaminantes varia dependiendo del tipo de generador de vapor, la capacidad nominal y, sobre todo, de la concentracion de azufre en el combustible y de las condiciones de operacion del sistema de combustion.

Conversion degree of SO{sub 2} into SO{sub 3} and SO{sub x} emissions in steam generators; Grado de conversion de SO{sub 2} en SO{sub 3} y emisiones de SO{sub x} en generadores de vapor

Energy Technology Data Exchange (ETDEWEB)

Espinoza Garza, Jesus; Penna Garcia, Adriana; Huerta Espino, Mario [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1997-12-31

A large part of the electric energy produced in this country is obtained burning fossil fuels as primary energy source. These fuels are mainly coal, fuel oil, and natural gas. The first two have high percentages of sulfur, therefore producing and emitting to the air different amounts of sulfur dioxide (SO{sub 2}) and sulfur trioxide (SO{sub 3}). The relationship between this two contaminants varies depending on the type of steam generator, the rated capacity, and most of all on the sulfur content in the fuel and on the combustion system operating conditions. [Espanol] Una gran parte de la energia electrica generada en el pais se obtiene utilizando combustibles fosiles como fuente primaria de energia. Estos combustibles son principalmente carbon, combustoleo y gas natural. Los dos primeros tienen altos porcentajes de azufre, con lo cual se producen y emiten a la atmosfera diferentes cantidades de dioxido de azufre (SO{sub 2}) y trioxido de azufre (SO{sub 3}). La relacion entre estos dos contaminantes varia dependiendo del tipo de generador de vapor, la capacidad nominal y, sobre todo, de la concentracion de azufre en el combustible y de las condiciones de operacion del sistema de combustion.

Evaluación de absentismo dos enfermeria profesional en una unidad de cuidados intensivos neonatal

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Carolina Sampaio OLIVEIRA

2011-04-01

Full Text Available O absenteísmo é um problema que para os trabalhadores de enfermagem da área hospitalar gera graves conseqüências, como a queda na qualidade da assistência prestada ao cliente e o aumento do estresse e ansiedade nos membros da equipe de trabalho. Este artigo busca identificar os fatores geradores de absenteísmo apresentados por funcionários de enfermagem alocados em uma UTIN de um hospital escola do município de Cuiabá- MT, no período de janeiro de 2009 a janeiro de 2011. Trata-se de pesquisa quantitativa com abordagem descritiva, exploratória e documental. Foi realizado um levantamento do absenteísmo, e registros de 35 profissionais de enfermagem. Pode-se concluir que houve a predominância do sexo feminino (90,33% e (45,16% dos profissionais possuíam mais de um vínculo empregatício. Em relação às ausências (54, 84% confirmam já ter se ausentado do trabalho por motivo doença sendo as mais prevalentes relacionadas ao aparelho respiratório totalizando 17,32% seguido pelas doenças osteomusculares em 12,59%%. O absenteísmo-doença na unidade de escolha foi considerável, elevado, indicando, ações que favoreçam o controle da saúde do trabalhador

Sustentabilidade na indústria da construção: uma logística para reciclagem dos resíduos de pequenas obras

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Joel Vieira Baptista Junior

2013-12-01

Full Text Available Neste trabalho são discutidos os principais aspectos relacionados à geração de resíduos da construção civil, sob ponto de vista de sustentabilidade das edificações. Esse conceito exige, das novas construções, a adoção de projetos criativos e eficientes, com soluções adequadas para as diversas fases de vida da obra, incluindo a previsão do reaproveitamento e descarte de materiais ao fim de sua vida útil. Um dos problemas atuais da gestão de resíduos da construção civil é que a segregação dos materiais por classe, visando à sua posterior reciclagem ou descarte, só acontece na cidade do Rio de Janeiro em grandes obras com canteiros instalados, embora mais da metade da quantidade produzida seja proveniente de pequenas obras com resíduos descartados em caçambas de rua ou simplesmente lançados em vias públicas ou terrenos baldios. É sugerido um plano de gestão circular, especialmente voltado para os pequenos geradores, com obrigatoriedade de segregação dos materiais, instalação de pontos de recolhimento pelos bairros da cidade e implantação de centros de tratamento de resíduos da construção civil, operados por associações de catadores, com objetivo de produção de materiais reciclados. O sucesso da proposta depende da efetiva participação de todos os agentes envolvidos no processo, como o poder público, proprietários, empresas e demais profissionais da indústria da construção civil.

Promoção à saúde e educação: diagnóstico de saneamento através da pesquisa participante articulada à educação popular (Distrito São João dos Queiróz, Quixadá, Ceará, Brasil

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Mello Dalva A.

1998-01-01

Full Text Available Este trabalho foi desenvolvido em uma comunidade rural ­ vila de São João dos Queiróz, Distrito do Município de Quixadá, Ceará, através da pesquisa participante articulada à educação popular, tendo como referencial a promoção à saúde de acordo com os princípios da Carta de Ottawa, 1986. Participaram do projeto representantes das diversas instituições públicas do distrito e entidades associativas ligadas ao movimento popular. O tema gerador, definido em assembléia da associação comunitária, foi o diagnóstico de saneamento, e o ponto de partida, o levantamento da condição situacional. Os resultados obtidos mostraram as precárias condições locais de saneamento, escolaridade, renda e trabalho. As sugestões para resoluções dos problemas foram organizadas para subsidiar a agenda de planejamento das políticas locais de saúde. A avaliação foi processual e enriquecida com práticas do cotidiano da pesquisa. A pedagogia problematizadora, desenvolvida durante o processo educativo, contribuiu para a construção e a reconstrução crítica dos conceitos de promoção à saúde e de saneamento, assim como para a efetivação da construção, apropriação e socialização dos conhecimentos produzidos.

Comparative study of the core level photoemission of the ZrB{sub 2} and ZrB{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Huerta, L. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 Mexico D.F. (Mexico); Duran, A. [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, Ensenada, Baja California 22800 (Mexico); Falconi, R. [Division Academica de Ciencias Basicas, Universidad Juarez Autonoma de Tabasco, Cunduacan, Tabasco, CP 86690, AP 24 (Mexico); Flores, M. [Departamento de Ingenieria de Proyectos, CUCEI, Universidad de Guadalajara, AP 307, Zapopan Jal 45101 (Mexico); Escamilla, R., E-mail: rauleg@servidor.unam.m [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 Mexico D.F. (Mexico)

2010-05-01

X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) were used to investigate the binding energies and valence band for ZrB{sub 2} and ZrB{sub 12}. The Zr 3d and B 1s core levels were identified. The Zr 3d core level shows a spin-orbit split 3d{sub 5/2} and 3d{sub 3/2} while that for B 1s core level exhibited a single symmetric peak, these being typical of zirconium and boride signals. Comparing the Zr 3d and B 1s core levels with metallic Zr, B{sub 2}O{sub 3} and ZrO{sub 2} reference materials only a negative chemical shift for Zr 3d associated to ZrB{sub 2} was observed, which suggests that the charge transfer model based on the concept of electronegativity was not applicable to explain the superconductivity in the ZrB{sub 12} sample. The measured valence band using UPS is consistent with the band-structure calculations indicating a higher density of states (DOS) at E{sub F} for ZrB{sub 12} respect to ZrB{sub 2}. Finally, we found that the weak mixed B-p and Zr-d states for ZrB{sub 12} is crucial for the superconductivity due to the state population increased the DOS at the E{sub F}.

GERAÇÃO E DESTINO DOS RESÍDUOS ELETRÔNICOS DE INFORMÁTICA NAS INSTITUIÇÕES DE ENSINO SUPERIOR DE NATAL-RN

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Ricardo Teixeira Gregório Andrade

2010-07-01

Full Text Available Os produtos eletrônicos, hodiernamente tão imiscuídos em nosso cotidiano e cultura, e confeccionados para nos trazerem comodidade e conforto, são responsáveis por gerar severos prejuízos (econômicos, sociais, ambientais, desde a produção ao descarte, a despeito de sua aparente inofensibilidade. A expansividade do uso de equipamentos e as constantes trocas de versões, motivados pela febre de consumo imposta e obsolescência programada, geram um montante de resíduos colossal e praticamente imensurável. A destinação final incorreta destes materiais, os resíduos eletroeletrônicos (ou chamados ‘lixo digital’, pode em pouco tempo se agravar em grandes desastres ambientais, caso não sejam tomadas as providências necessárias. Na cidade de Natal, em similaridade ao contexto nacional, não existe ainda uma política de tratamento do lixo digital. O presente estudo objetiva traçar um breve e inicial panorama da geração e destinação dos resíduos eletrônicos de informática de algumas das principais instituições de ensino superior de Natal–RN. Os dados levantados, através de entrevistas e bancos de dados institucionais, evidenciam a parca consciência quanto ao lixo digital e quão incipiente ainda é a gestão desses resíduos, apesar de serem as instituições de ensino superior os grandes pólos geradores e distribuidores de conhecimentos científicos que possam criar/aplicar as soluções devidas à fiel execução sustentável dos processos produtivos.

Alocação ótima de dispositivos limitadores de corrente de curto-circuito usando representação no nível de subestação

OpenAIRE

Duarte, Isabel Schvabe

2013-01-01

Resumo: O constante crescimento do parque gerador e transmissor exige a realização contínua do cálculo.dos níveis de corrente de curto-circuito que circulam pelos disjuntores instalados nas subestações a fim de se sinalizar os que estão superadosNo entanto, as metodologias existentes para cálculo das correntes de curto-circuito utilizam o convencional modelo barra-ramo que impede a análise dos componentes internos às subestações, e que quando necessários devem ser feitos a parte, num processo...

Análise da carga de trabalho de analistas de sistemas e dos distúrbios osteomusculares

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Bruno Maia de Guimarães

Full Text Available OBJETIVOS: O objetivo desta pesquisa foi realizar avaliação das condições ergonômicas de analistas de sistemas, com a finalidade de conhecer os fatores geradores de sobrecargas físicas e cognitivas, suas repercussões sobre os trabalhadores e propor melhorias para a diminuição dessas sobrecargas. METODOLOGIA: Foram utilizados o método SHTM (sistema homem-tarefa-máquina de avaliação ergonômica; o diagrama de Corlett, para a avaliação do desconforto corporal; o questionário de avaliação do mobiliário; e o NASA-TLX, para a avaliação de carga mental de trabalho. RESULTADOS: Foram encontradas as prevalências de dor na coluna lombar (71% e na coluna cervical (64% dos entrevistados. Após a avaliação da carga mental de trabalho, foi observado que a demanda mental foi a mais exigida entre os analistas de sistemas e a média da carga global foi de 13,23. CONCLUSÃO: Pode-se concluir que a alta prevalência de dor musculoesquelética pode ser causada pela presença de mobiliário inadequado, pela adoção de posturas incorretas e pela alta exigência mental das atividades desenvolvidas.

Impactos decorrentes da implantação de pólos geradores de viagens na estrutura espacial das cidades

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Erika Cristine Kneib

2010-11-01

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Resumo:Em meio às alterações que ocorrem nas cidades, com ênfase no uso e ocupação do solo e nos deslocamentos, este trabalho tem por objetivo avaliar os possíveis impactos decorrentes da implantação de Polos Geradores de Viagens (PGVs na estrutura espacial das cidades, conformada pelo conjunto de centros e subcentros urbanos. Como conclusão, a partir do método desenvolvido, corroborase a relação entre os PGVs e os impactos decorrentes destes na estrutura espacial da cidade objeto do estudo. Assim como, identificamse as atividades que mais contribuem para tal relação.

Abstract: Among the changes that take place in the cities, especially those related to trips and to land use and occupation, this paper aims at assessing the possible impacts caused by the implantation of trip generating developments in their spatial structure, shaped by urban centres and subcentres. In conclusion, from the method developed in the work, the relationship is confirmed between trip generating developments and their impacts on the spatial structure of the city studied, as well as the activities that most contribute to that relationship are identified.

Mapeamento da produção científica e participação dos autores nos anais do ENANCIB: uma análise a partir da correlação entre as redes de coautoria e redes de participação nos grupos de trabalho

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Dalton Lopes Martins

2014-03-01

Full Text Available Os eventos científicos são importantes espaços de articulação dos pesquisadores em suas áreas do conhecimento. Relações sociais de coautoria na produção científica e participação em determinados grupos de trabalho na apresentação oral e divulgação em painéis representam tipos de relação que podemos modelar como redes sociais e analisar seus padrões em busca de entender como uma comunidade científica se articula. O presente trabalho analisa os anais do Encontro Nacional de Pesquisa em Ciência da Informação (ENANCIB, propondo um estudo de análise de redes que integre o mapeamento dos principais padrões das redes de coautoria e participação de pesquisadores em grupos de trabalho. Utilizamos a análise de redes sociais e a correlação de indicadores de centralidade com os dados descritivos dos anais para identificar possíveis características e eventos geradores dessas redes. Resultados apontam que a articulação entre pesquisadores se dá mais em âmbito local em seus componente de rede do que no âmbito de seus pares presentes nos grupos de trabalho por onde circulam.

Evaluación del Progreso de Selección Masal en Dos Sub-Poblaciones de Maíz

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Arboleda R. Fernando

1974-04-01

Full Text Available Resumen. En la Estación Experimental de la Universidad de Nebraska, se llevó a cabo un estudio del progreso de selección masal en dos sub-poblaciones de la variedad de maíz Hays Golden. Los objetivos y resultados fueron: 1.Estimar la ganancia total en rendimiento después de ocho ciclos de selección masal en las dos sub-poblaciones. El octavo ciclo de selección en la sub-población "control" rindió 46% más que la variedad original. El mismo octavo ciclo de la sub-población "irradiada" fue 10% superior a Hays Golden. 2.Estudiar el comportamiento de los cruzamientos entre las generaciones de ciclos con la variedad original. Hubo aumentos progresivos de 6, 17, 18, Y 19% sobre la variedad original en el rendimiento de los ciclos 2, 4, 6, Y 8 respectivamente, en la sub-población "control". En la sub-población "irradiada" las correspondientes respuestas fueron 8, 4, 20 y 18%. 3. Estudiar el comportamiento y la respuesta heterótica cuando se intercruzaron los ciclos de ambas sub-poblaciones. Hubo un progreso continuo del rendimiento de 11, 13, 15, Y 22% sobre la variedad original para los cruzamientos de ciclos comparables en ambas subpoblaciones: Sin embargo, no hubo respuesta heterótica en esos cruzamientos. De los resultados se concluyó que la selección resultó en un aumento de homocigocidad de loci para rendimiento, que se tradujo en más productividad en los cruzamientos entre ciclos y entre éstos con la variedad original, aunque con un efecto heterótico bajo que sugiere que la selección practicada por separado en ambas sub-poblaciones (hasta el octavo ciclo no resultó en diversidad genética. /abstract. The objectives of the present study were: (a to estimate the total gain in grain yield through eight cycles of mass selection in two subpopulations of Hays Golden variety; (b to compare the gains and behavior between these two selected subpopulations; (c to study the behavior of the crosses of the cycled

Photophysical electronic structure of double-perovskites A{sub 2}GdTaO{sub 6} (A = Ba and Sr)

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Binita, E-mail: ghosh.binita@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)

2015-11-05

X-ray photoemission spectroscopy (XPS) measurements of double perovskite oxides, Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} are performed in the energy window of 0–1300 eV. Density functional theory calculations are initiated with the Vienna ab initio Simulation Package to understand the electronic structure of the systems. The calculated DOS has been compared with the experimental valence band XPS spectra. It has been observed that the Ta-5d and O-2p states are hybridized in the valence band. The chemical shifts of these compounds suggest a mixed ionic and covalent character of the bonds, which has been used to explain the electrical conduction mechanism of the systems. The calculated ratio of the spin-orbit interaction energy for Ba 3d and 4d states matches well with the observed experimental results. - Highlights: • DFT calculations of Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} have been performed with VASP. • XPS measurements are performed in the energy window of 0–1300 eV. • The calculated DOS has been compared with the valence band XPS spectra. • Chemical shifts from XPS spectra have been used to explain the conduction mechanism.

Custo da eletricidade gerada em conjunto motor gerador utilizando biogás da suinocultura - DOI: 10.4025/actascitechnol.v26i2.1510

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Samuel Nelson Melegari de Souza

2004-03-01

Full Text Available Uma das maiores fontes de energia disponíveis nas áreas rurais e agroindustriais é a biomassa. A mesma aparece na forma de resíduos vegetais e animais, tais como restos de colheita, esterco animal, plantações energéticas e efluentes agroindustriais. Estes resíduos podem ser utilizados pelo produtor rural ou agroindústria para a queima direta, visando a produção de calor ou produção de biogás em biodigestores. Nas propriedades agrícolas, onde há a atividade de suinocultura, ocorre a disponibilidade desses resíduos, caracterizando-se num grande potencial energético. No presente trabalho objetivou-se determinar o custo e viabilidade de produção de eletricidade gerada a partir do biogás EM uma propriedade rural, utilizando-se como equipamentos de conversão de biogás em eletricidade, um motor de combustão interna acoplado a um gerador elétrico

Classificação dos pesquisadores/consultores da área de enfermagem no CNPq: contribuição para um banco de dados

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Isabel Amélia Costa Mendes

2003-10-01

Full Text Available Trata-se de análise das temáticas e sub-áreas de conhecimento nas quais pesquisadores de enfermagem do CNPq estão incluídos, tomando por base os projetos julgados no período 2002/ 2003. Os objetivos foram apresentar a distribuição dos pesquisadores de acordo com a atual classificação da área de Enfermagem adotada pelo CNPq e discutir a representatividade dos pesquisadores por sub-área de conhecimento. Os resultados evidenciaram as sub-áreas predominantes de pesquisa da categoria: fundamentos dos processos de cuidar, seguido da área de assistência em enfermagem do adulto. Revela ainda a concentração dos pesquisadores e aponta para necessidade de estabelecimento de estratégias de inclusão e de incentivo à demanda por financiamento à pesquisa por eles desenvolvida. Ressalta, por fim, a importância de atualização das sub-áreas em consonância com o fortalecimento da produção científica.

Subsídios norteadores para uma prática educacional da consciência corporal e postural de alunos dos anos iniciais do ensino fundamental

OpenAIRE

Viel, Greice de Barba

2015-01-01

A presente dissertação tem como objetivo principal apresentar aos professores subsídios para uma prática educacional, enfocando o cuidado com a postura corporal de alunos dos anos iniciais do Ensino Fundamental, baseada em conhecimentos científicos e fisioterapêuticos, com vistas à prevenção de saúde. Trata-se de uma pesquisa teórica de caráter interdisciplinar, cujas fontes bibliográficas são de autores clássicos com diferentes abordagens, estudos e conceitos acerca de questões como corpo, e...

Fiber-optic components for optical communicatios and sensing =

Science.gov (United States)

Marques, Carlos Alberto Ferreira

Nos ultimos anos, a Optoelectronica tem sido estabelecida como um campo de investigacao capaz de conduzir a novas solucoes tecnologicas. As conquistas abundantes no campo da optica e lasers, bem como em comunicacoes opticas tem sido de grande importancia e desencadearam uma serie de inovacoes. Entre o grande numero de componentes opticos existentes, os componentes baseados em fibra optica sao principalmente relevantes devido a sua simplicidade e a elevada de transporte de dados da fibra optica. Neste trabalho foi focado um destes componentes opticos: as redes de difraccao em fibra optica, as quais tem propriedades opticas de processamento unicas. Esta classe de componentes opticos e extremamente atraente para o desenvolvimento de dispositivos de comunicacoes opticas e sensores. O trabalho comecou com uma analise teorica aplicada a redes em fibra e foram focados os metodos de fabricacao de redes em fibra mais utilizados. A inscricao de redes em fibra tambem foi abordado neste trabalho, onde um sistema de inscricao automatizada foi implementada para a fibra optica de silica, e os resultados experimentais mostraram uma boa aproximacao ao estudo de simulacao. Tambem foi desenvolvido um sistema de inscricao de redes de Bragg em fibra optica de plastico. Foi apresentado um estudo detalhado da modulacao acustico-optica em redes em fibra optica de silica e de plastico. Por meio de uma analise detalhada dos modos de excitacao mecanica aplicadas ao modulador acustico-optico, destacou-se que dois modos predominantes de excitacao acustica pode ser estabelecidos na fibra optica, dependendo da frequencia acustica aplicada. Atraves dessa caracterizacao, foi possivel desenvolver novas aplicacoes para comunicacoes opticas. Estudos e implementacao de diferentes dispositivos baseados em redes em fibra foram realizados, usando o efeito acustico-optico e o processo de regeneracao em fibra optica para varias aplicacoes tais como rapido multiplexador optico add-drop, atraso de grupo

Games, indicadores e geradores de possibilidades educacionais

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José Antônio Baêta Zille

2012-05-01

Full Text Available Esse estudo teve o objetivo de avaliar parte do universo do adolescente e suas relações, priorizando a educação e os games. Foi de interesse primordial considerar o posicionamento dos jovens frente ao ensino formal e as potencialidades construtivas do ambientes dos games. Os dados foram levantados ao fim de 2009 e início de 2010, em Belo Horizonte – MG, junto a alunos de escolas das redes particular e pública e em LAN houses, com participantes da etapa mineira do World Cyber Games 2009 e em um campeonato local. Foram entrevistados 104 adolescentes, escolhidos aleatória e proporcionalmente ao total de indivíduos de cada escola e evento. Com relação aos jogos, foram analisados os três mais jogados em PC na ocasião: World of Warcraft, Call of Duty 4: Modern Warfare e Halo: Combat Evolved. Constatou-se que os games permitem ao usuário ação, diálogo, intervenção, utilização das capacidades criativa e análise, e acesso a informações em redes, tudo envolvido por elementos lúdicos. Os games se estabelecem em processos de criação e difusão de inovações tecnológicas; possibilitam novos conhecimentos; permitem potencializações nos âmbitos cognitivo, prático e social e, como função psicossociocultural, são instâncias favoráveis à construção e consolidação de identidades. Verificou-se, ainda, que para esses adolescentes, a escola é algo importante para a vida, no entanto, constatou-se uma demanda para que a escola seja: mais dinâmica, divertida e menos monótona; mais prática, criativa e interativa; mais próxima da realidade, atual e fora do contexto exclusivo da sala de aula.

Microgeneration of electricity with producer gas in dual fuel mode operation Microgeração de eletricidade com gás de gaseificação num motor gerador dual

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Marcelo J. Silva

2011-10-01

Full Text Available Among the alternatives to meet the increasing of world demand for energy, the use of biomass as energy source is one of the most promising as it contributes to reducing emissions of carbon dioxide in the atmosphere. Gasification is a technological process of biomass energy production of a gaseous biofuel. The fuel gas has a low calorific value that can be used in Diesel engine in dual mode for power generation in isolated communities. This study aimed to evaluate the reduction in the consumption of oil Diesel an engine generator, using gas from gasification of wood. The engine generator brand used was a BRANCO, with direct injection power of 7.36 kW (10 HP coupled to an electric generator 5.5 kW. Diesel oil mixed with intake air was injected, as the oil was injected via an injector of the engine (dual mode. The fuel gas was produced in a downdraft gasifier. The engine generator was put on load system from 0.5 kW to 3.5 kW through a set of electrical resistances. Diesel oil consumption was measured with a precision scale. It was concluded that the engine converted to dual mode when using the gas for the gasification of wood decreased Diesel consumption by up to 57%.Dentre as alternativas à crescente demanda energética mundial, o uso da biomassa como fonte de energia é uma das formas mais promissoras, pois contribui para a redução das emissões de dióxido de carbono na atmosfera. A gaseificação é uma tecnologia de transformação energética da biomassa num biocombustível gasoso. O gás de gaseificação é um combustível de baixo poder calorífico que pode ser utilizado em motor ciclo Diesel no modo dual para geração de energia elétrica em comunidades isoladas. Este trabalho teve por objetivo avaliar a redução no consumo de Diesel num motor gerador, com a utilização de gás da gaseificação da madeira. O motor avaliado foi da marca BRANCO, com injeção direta e potência de 7,36 kW (10 cv acoplado a um gerador elétrico de 5

Perfil dos trabalhadores por conta própria no Brasil

OpenAIRE

Kon, Anita

2001-01-01

O objetivo global desta pesquisa foi contribuir com subsídios para a análise das características do trabalhador brasileiro por conta própria ou autônomo, particularmente no que se refere ao padrão de distribuição setorial, ocupacional e dos rendimentos da população ocupada, tendo em vista os novos requisitos demandados pelos atuais processos produtivos e organizacionais, dentro e fora das empresas. Estas características são retratadas pela representatividade ocupacional dos trabalhadores deta...

FORMA DE DESCARTE DE PILHAS E BATERIAS DE CELULARES USADAS POR MORADORES DO MUNICÍPIO DE CAMPOS DOS GOYTACAZES E CONSCIÊNCIA AMBIENTAL QUANTO O DESCARTE ADEQUADO

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FORMA DE DESCARTE DE PILHAS E BATERIAS DE CELULARES USADAS POR MORADORES DO MUNICÍPIO DE CAMPOS DOS GOYTACAZES E CONSCIÊNCIA AMBIENTAL QUANTO O DESCARTE ADEQUADO

2015-12-01

Full Text Available O descarte de pilhas e baterias é um problema que não envolve somente órgãos responsáveis, mas também a população como um todo. A cooperação da comunidade pode contribuir para a diminuição dos impactos causados por resíduos perigosos no meio ambiente. O objetivo do presente trabalho é analisar as formas de descarte de pilhas e baterias usadas pelos moradores dos bairros Calabouço, Jardim Carioca e Parque Guarus do município de Campos dos Goytacazes – RJ. Foi elaborado um questionário de seis perguntas fechadas, sendo duas perguntas sobre informações pessoais dos participantes e quatro perguntas sobre o descarte de pilhas e baterias. O mesmo foi aplicado a um total de 308 moradores (numero de pessoas alcançadas num período de seis meses dos bairros selecionados, sendo 98 do calabouço, 107 do Jardim Carioca e 103 do Parque Guarus. O resultado dos questionários foi tabulado, devidamente analisado e discutido com base no objetivo proposto pelo presente trabalho. Analisando os dados de modo geral é possível dizer que, embora a população não apresente conhecimento sobre os problemas ocasionados pelo descarte indevido, é necessário que haja por parte dos órgãos governamentais a implementação de políticas públicas que viabilizem o descarte correto e responsável uma vez que segundo a lei 12.305/2010 (que trata da Política Nacional de Resíduos Sólidos a responsabilidade pelo gerenciamento de resíduos sólidos, incluindo os perigosos é dos geradores, do poder público e dos instrumentos econômicos aplicáveis (Sistema de Gestão Integrada. Os fabricantes de pilhas e baterias ainda de acordo com a lei 12.305/2010 devem estruturar e implementar sistemas de logística reversa, ou seja, o retorno dos produtos após o uso pelo consumidor. Esse sistema quando colocado em prática traz benefícios como: o retorno de alguns materiais para o processo produtivo e redução do volume de resíduos despejados em aterros, no

ECONOMIA DOS RECURSOS HUMANOS: TEORIA E EVIDÊNCIAS

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Andre Carraro

2014-12-01

Full Text Available Este trabalho tem como objetivo discutir as diversas contribuições dadas ao longo das últimas décadas à economia dos recursos humanos, uma área de crescente destaque tanto entre a comunidade acadêmica, quanto entre empresários e trabalhadores. Discutem-se os diversos tópicos que compõem as abrangentes relações empresariais, estabelecidos na literatura em quatro tópicos principais: treinamento, incentivos, organização e seleção de pessoas. É feita uma análise dos principais artigos e autores de cada uma dessas subáreas, com o intuito principal de facilitar o acesso à informação, apontar caminhos para novas pesquisas e incentivar potenciais pesquisadores.

Microstructure of two phases alloy Al{sub 3}Ti/Al{sub 3}Ti{sub 0.75}Fe{sub 0.25}; Microestructura de una aleacion de dos fases Al{sub 3}Ti/Al{sub 3}Ti{sub 0.75}Fe{sub 0.25}

Energy Technology Data Exchange (ETDEWEB)

Angeles, C; Rosas, G; Perez, R [Instituto Nacional de Investigaciones Nucleares, Departamento de Sintesis y Caracterizacion de Materiales, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

1998-07-01

The titanium-aluminium system presents three intermetallic compounds from those Al{sub 3}Ti is what less attention has received. The objective of this work is to generate and characterize the microstructure of multiphase alloys nearby to Al{sub 3}Ti compound through Fe addition as alloying. This is because it has been seen that little precipitates of Al{sub 2}Ti phase over Al{sub 3}Ti intermetallic compound increases its ductility. (Author)

Synthesis, physical properties and band structure of non-magnetic Y{sub 3}AlC

Energy Technology Data Exchange (ETDEWEB)

Ghule, S.S. [Bharati Vidyapeeth Deemed University College of Engineering, Pune-Satara Road, Pune 411043 (India); Garde, C.S., E-mail: gardecs@gmail.com [Vishwakarma Institute of Information Technology, S. no. 2/3/4, Kondhwa(Bk), Pune 411048 (India); Ramakrishnan, S. [Tata Institute of Fundamental Research, Navynagar, Mumbai 400005 (India); Singh, S. [Indian Institute of Science Education and Research, Dr Homi Bhabha Road, Pashan, Pune 411008 (India); Rajarajan, A.K. [Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Laad, Meena [Symbiosis Institute of Technology (SIT), Symbiosis International University (SIU), Lavale, Pune 412115 (India)

2016-10-01

Y{sub 3}AlC has been synthesized by arc melting and subsequent annealing. Rietveld analysis of the powder x-ray diffraction (XRD) data confirms cubic Pm-3m structure. Electrical resistivity (ρ) of Y{sub 3}AlC exhibits metallic behaviour. No sign of superconductivity is observed down to the lowest measurement temperatures of 4.2 K in ρ, and 2 K in magnetic susceptibility (χ) and specific heat (C{sub p}) measurements. The value of the electronic specific heat coefficient γ is 1.36 mJ/K{sup 2} mol from which the density of states (DOS) at the Fermi energy (E{sub F}) is obtained as 0.57 states/eV.unit cell. The value of Debye temperature θ{sub D} is estimated to be 315 K. Electronic band structure calculations of Y{sub 3}AlC reveal a pseudo-gap in the DOS at E{sub F} leading to a small value of 0.5 states/eV unit cell which matches quite well with that obtained from γ. Non-zero value of the DOS indicates metallic behaviour as confirmed by our ρ data. Covalent and ionic bonding seem to co-exist with metallic bonding in Y{sub 3}AlC as indicated by van Arkel- Ketelaar triangle for Zintl-like systems.

Transa: Arquitectura brasileira entre o Modernismo e o Tropicalismo

OpenAIRE

Maria João Trigo Moutinho Rito

2015-01-01

Brasil do "terceiro mundo", déspota, paternalista mas tropical. Assim seria o Brasil,dos anos 60, percepcionado por aqueles que, conscientes da realidade politica e social dopaís, não aceitavam a sua desvalorização, condenando os estereótipos e criando uma posiçãoanti-colonialista. Por entre as palavras imagéticas de Oswald de Andrade, fixavam-se registosreferenciais geradores de um caminho ao encontro da felicidade do Brasil anterior à chegada dosportugueses. A necessidade de fugir ao provin...

Effect of Si substitution on structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds

Energy Technology Data Exchange (ETDEWEB)

Maurya, Dinesh Kumar; Saini, Sapan Mohan, E-mail: smsaini.phy@nitrr.ac.in

2016-10-15

We employed first principle calculations for investigation of structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. These properties are studied first time on YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} compounds. The exchange and correlation potential is treated by the Coulomb corrected local spin density approximation (LSDA+U) method for better accounting of the correlation between the 4f electrons. The optimized lattice constants and internal cell parameters are in agreement with the available data. Self consistence band structure calculations show that Ni-3d states remains in valance band and dominant below the E{sub F}, while Dy-5d and 4f states mainly contributes above Fermi Energy (E{sub F}) in DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. We also find that when silicon for nickel substitution takes place (DyNi{sub 4}Si), there is a gradual hybridization of Ni-3d and Si-3p states results, nickel moments decrease rapidly in agreement with the experiment. Optical spectra shows the main absorption peak around 4 eV depends on the substituent concentration and could be due to transition from hybridized band (Ni-3d and Si-3p), below E{sub F} to free Dy-4d states. Frequency-dependent refractive index, n(ω), and the extinction coefficient, k(ω), of DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) are also calculated for the radiation up to 14 eV. - Highlights: • Calculated DOS revels that Ni-3d states are dominated below Fermi level (E{sub F}). • Spin down Dy-4f states show significant contribution to DOS above E{sub F.} • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Most significant peak is found around 7eV in optical conductivity. • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Peak indicates the possibility of transitions from Ni-3d states to empty spin down Dy-4f states.

Incômodo causado pelo ruído urbano à população de Curitiba, PR

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Paulo Henrique Trombetta Zannin

2002-08-01

Full Text Available Descreve-se a reação da população de Curitiba, PR -- cidade com aproximadamente 1,6 milhões de habitantes --, ao ruído ambiental . Os dados foram coletados por meio de questionários distribuídos aleatoriamente a moradores da cidade. Dos 1.000 questionários distribuídos, 860 (86% foram avaliados. As principais fontes de ruído causadoras de incômodo identificadas foram o tráfego de veículos (73% e os vizinhos (38%, sendo que estes foram classificados como a principal fonte de desconforto. Todos os respondentes apontaram pelo menos um dos seguintes itens como geradores de ruído: vizinhos, animais, sirenes, construção civil, templos religiosos, casas noturnas, brinquedos e aparelhos domésticos. As principais reações ao ruído foram: irritabilidade (58%, baixa concentração (42%, insônia (20% e dores de cabeça (20%.

Study of gels of molybdenum with cerium in the preparation of generators of 99Mo - 99mTc

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Vanessa Moraes

2005-10-01

Full Text Available 99mTc has ideal nuclear properties for organ imaging in nuclear medicine, and it is obtained from the 99Mo-99mTc generator. Four different types of generators are available: chromatographic that uses 99Mo from fission of uranium; MEK solvent extraction; Tc2O7 sublimation; gel chromatographic. This work presents the preparation of gel generators of molybdenum with cerium and characterization of the gels: mass ratio between molybdenum and cerium, structure, size of particles and elution percentage of 99mTc after irradiating the gels. Eight gels were prepared at the same temperature of 50 ºC with concentrations of NaOH of 2 and 4 mol/L, mass ratio of 0.31 and 0.38 and final pH of 3.5 and 4.5. The analysis of the results proved that these gels are not adequate for preparation of the generators of 99Mo-99mTc, since the elution percentages are low, when compared with the gel of molybdenum with zirconium.O 99mTc é o radiofármaco mais utilizado em Medicina Nuclear. Ele é obtido do gerador de 99Mo-99mTc e existem quatro tipos diferentes de geradores: cromatográfico que utiliza 99Mo de fissão; extração por solvente com MKT; sublimação do heptaóxido de tecnécio; cromatográfico tipo gel. Este trabalho apresenta a preparação de geradores tipo gel de molibdênio com cério, a caracterização desses géis com relação à quantidade de molibdênio e de cério, sua estrutura, tamanho das partículas e porcentagem de eluição do 99mTc após o gel ser irradiado. Foram preparados oito géis na temperatura de 50ºC com concentração de NaOH de 2 e 4 mol/L, relação de massa de 0,31 e 0,38 e pH final de 3,5 e 4,5. A análise dos resultados comprovou que esses géis não são adequados para preparação dos geradores de 99Mo-99mTc, já que as porcentagens de eluição são baixas, quando comparadas com o gel de molibdênio com zircônio.

Electronic, magnetic and optical properties of reduced hybrid layered complex Ni(pyz)V{sub 4}O{sub 10} (pyz=C{sub 4}H{sub 4}N{sub 2}) by first-principles

Energy Technology Data Exchange (ETDEWEB)

Munir, Junaid; Mat Isa, Ahmad Radzi [Physics Department, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Yousaf, Masood [IBS Center for Multidimensional Carbon Materials, Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Aliabad, H.A. Rahnamaye [Department of Physics, Hakim Sabzevari University (Iran, Islamic Republic of); Ain, Qurat-ul [Key Laboratory for Laser Plasamas (MOE) & Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Saeed, M.A., E-mail: saeed@utm.my [Physics Department, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia)

2016-10-15

This article reports the electronic, structure, magnetic and optical properties of reduced hybrid layered complex Ni(pyz)V{sub 4}O{sub 10} (pyz=C{sub 4}H{sub 4}N{sub 2}) studied by employing density functional theory with local density approximation (LDA), generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof-96 (PBE) and modified Becke–Johnson (mBJ) exchange-correlation potential and energy. The band structure and density of states of these compounds are also presented. The total density of states (DOS) for up and down spin states clearly split, which means that the exchange interaction causes the ordered spin arrangement. PBE-mBJ calculation reveals a wider band gap in spin down state, which shows a half-metallic electronic character at the equilibrium state. The spin-polarized calculations indicate metallic nature in orthorhombic crystalline phase. It is also noted that the optical conductivity for PBE-mBJ is larger than that of LDA and PBE-GGA. Furthermore, the results show a half-metallic ferromagnetic ground state for Ni(pyz)V{sub 4}O{sub 10} in PBE-mBJ potential. The present results suggest Ni(pyz)V{sub 4}O{sub 10} compound as a potential candidate for the future optoelectronic and spintronic applications. - Highlights: • First study of the electronic, structure, magnetic and optical properties of reduced hybrid layered complex Ni(pyz)V{sub 4}O{sub 10} (pyz=C{sub 4}H{sub 4}N{sub 2}) by first principles. • PBE-mBJ calculation reveals a wider band gap in spin down state indicating its half-metallic electronic character. • The large spin magnetic moment on Ni and V cations indicates the ferromagnetic interaction which makes this compound suitable candidate for spintronics applications. • An optical band gap reveals that this compound is also useful for the application in optoelectronics.

Metáforas e imagens dos formadores de professores na área da informática aplicada à educação Teacher educators' metaphors and images in the field of computing applied to education

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Joana Peixoto

2007-12-01

Full Text Available O ponto de partida desta pesquisa é a preocupação com a lacuna existente entre a formação dos professores na área da informática educativa (IE e sua experiência ulterior. A hipótese principal é que existe, entre os formadores dos professores desta área, uma certa representação do modelo de formação que se transferiria automaticamente para a futura prática dos professores. Foi realizada uma enquete com 21 professores da disciplina "Informática e Educação", da Universidade Católica de Goiás, utilizando-se as técnicas de associação livre de palavras, entrevista semi-estruturada e grupo focal. O núcleo figurativo das representações identificadas mostra o computador como um instrumento gerador de transformações educacionais e a informática educativa como o agente promotor das transformações pedagógicas. Esta analogia torna-se uma referência importante que dá forma ao discurso dos formadores por meio de metáforas que constituem o seu imaginário.The focus of this research is the gap between the formation of educational computing (EC teachers and their further experience. The main hypothesis is that, among EC teacher formers, there is a certain representation of the educational model and a conception on the beneficial aspects of digital technologies that would be automatically transferred to the future teachers' practice. An investigation was carried out with the 21 teachers of the discipline "Computing and Education" at the Catholic University of Goiás, with the use of techniques of free word association, semi-structured interviews and focus groups. The nucleus of the identified representations shows the computer as a generator of educational changes, and educational computing as the agent of pedagogical changes. This analogy becomes an important reference that shapes formers' discourse by means of metaphors which constitute their imagination.

Treinamento desportivo: perfil acadêmico dos líderes de grupos de estudo brasileiros

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Hudson Fabricius Peres Nunes

Full Text Available Resumo Este estudo objetivou caracterizar o perfil acadêmico dos professores líderes de grupos de estudo brasileiros que desenvolvem pesquisas na subárea de treinamento desportivo. A metodologia usada foi a pesquisa descritiva dos currículos acadêmicos encontrados no banco de dados da Plataforma Lattes, tendo em vista que os dados quantitativos foram interpretados a partir da análise qualitativa das informações. Os resultados revelam que os grupos estão vinculados principalmente a universidades da Região Sudeste, a maioria dos líderes é doutor e a prevalência da produção científica está relacionada à preparação orgânica, pedagógica, psicológica e desportiva dos atletas.

Uma contribuição ao estudo da adição de resíduos de poliuretano expandido na confecção de blocos de concreto leve

OpenAIRE

Siqueira, Ligia Vieira Maia

2006-01-01

Atualmente, a produção de resíduos em quantidades cada vez maiores tem exigido soluções mais eficazes e investimentos mais elevados por parte de seus geradores e da sociedade de uma forma geral. Além do controle e a minimização das fontes de poluição e do encaminhamento correto dos resíduos gerados, a responsabilidade social inerente ao setor industrial, faz com que as empresas promovam o desenvolvimento sustentável, remodelando seu processo produtivo. O desenvolvimento de novos materiais pod...

Estressores no trabalho das enfermeiras em centro cirúrgico: conseqüências profissionais e pessoais

OpenAIRE

Jael Maria de Aquino

2005-01-01

O estresse tem sido um tema bastante discutido, nos últimos anos, pela comunidade científica. Vários estudos têm apresentado o estresse como causador de doenças, sendo considerado o “mal do século”. O centro cirúrgico é um dos ambientes mais complexos do hospital, pois concentra os recursos humanos e materiais necessários ao ato cirúrgico e, freqüentemente, as suas atividades são desenvolvidas em um clima de tensão, pela existência de procedimentos estressantes geradores de ansiedade, quer pe...

ConsciÃncia Corporal e Ancestralidade Africana: Conceitos SociopoÃticos Produzidos por Pessoas de Santo

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Norval Batista Cruz

2009-01-01

Este estudo apresenta os conceitos sociopoÃticos produzidos por uma comunidade de terreiro de candomblÃ, Ilà Axà Omo TifÃ, localizada no bairro de Jangurussu, na periferia de Fortaleza-Ce. O tema gerador da pesquisa à consciÃncia corporal e ancestralidade africana. Noto que, apesar dos terreiros de candomblÃ, em principio estarem mais conectados com a cultura de matriz africana, nem sempre se encontra uma prÃtica de consciÃncia corporal associada à ancestralidade africana e Ãs vezes, hà uma d...

Crystal electric field splitting of R{sup 3+}-ions in pure and Co- and Cu-doped RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm)

Energy Technology Data Exchange (ETDEWEB)

Gasser, U.; Allenspach, P.; Henggeler, W.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-09-01

From the crystal-electric-field (CEF) splitting of the R{sup 3+}-ions, the CEF parameters of RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm) were deduced. In order to get information about the influence of the variation of the density of states (DOS) at the Fermi level (E{sub F}), CEF spectroscopy measurements with Co- and Cu-doped ErNi{sub 2}B{sub 2}C-samples were performed. (author) 1 fig., 1 tab., 1 ref.

Study on adsorption of O{sub 2} on LaFe{sub 1-x}Mg{sub x}O{sub 3} (0 1 0) surface by density function theory calculation

Energy Technology Data Exchange (ETDEWEB)

Liu, Xing, E-mail: liuxing0108@mail.sdu.edu.cn [Civil Engineer Department, Qingdao Technological University (Linyi), Easter Outer Ring Road 1, Linyi, 273400 (China); Cheng, Bin [Civil Engineer Department, Qingdao Technological University (Linyi), Easter Outer Ring Road 1, Linyi, 273400 (China); Hu, Jifan; Qin, Hongwei [State Key Laboratory of Crystal Material, Department of Physics, Shandong University, Hongjialou 5, Jinan, 250100 (China)

2012-09-01

Highlights: Black-Right-Pointing-Pointer Mg-doping can change the electronic properties of LaFeO{sub 3} (0 1 0) surface by decreasing the band gap. Black-Right-Pointing-Pointer The position and content of Mg-doping can both affect the ability to adsorb O{sub 2}. Black-Right-Pointing-Pointer The strong hybridization between O{sub 2} p and Fe d orbital is the origin of binding mechanism. - Abstract: The adsorption of O{sub 2} on the clean and Mg doped LaFeO{sub 3} (0 1 0) surface has been investigated using the density functional theory (DFT) method. Calculation results show that Mg-doping can change the electronic properties of LaFeO{sub 3} (0 1 0) surface by decreasing the band gap. When Mg ions were not on the first layer of the surface, with increasing Mg content the adsorption of O{sub 2} was enhanced. When Mg ions were on the first layer, the adsorption of O{sub 2} was weakened with the increase of Mg content. The analysis results of the DOS indicated that the Mg ion and adsorbed O{sub 2} had no strong hybridization, and the bonding mechanism was originated from the strong hybridization between the O p and Fe d orbital. Referring to all the calculation results, it was found that except for the increase of stability of oxygen adsorption, the Mg doping could not improve the sensitivity to O{sub 2}.

First-principles study of electronic properties of FeSe{sub 1-x}S{sub x} alloys

Energy Technology Data Exchange (ETDEWEB)

Kumar, Sandeep, E-mail: sandeep@phy.iitb.ac.in; Singh, Prabhakar P. [Department of Physics, Indian Institute of Technology-Bombay, Mumbai-400076 (India)

2016-05-06

We have studied the electronic and superconducting properties of FeSe{sub 1-x}S{sub x} (x = 0.0, 0.04) alloys by first-principles calculations using the Korringa-Kohn-Rostoker Atomic Sphere Approximation within the coherent potential approximation (KKR-ASA-CPA). The electronic structure calculations show the ground states of S-doped FeSe to be nonmagnetic. We present the results of our unpolarized calculations for these alloys in terms of density of states (DOS), band structures, Fermi surfaces and the superconducting transition temperature of FeSe and FeSe{sub 0.96}S{sub 0.04} alloys. We find that the substitution of S at Se site into FeSe exhibit the subtle changes in the electronic structure with respect to the parent FeSe. We have also estimated bare Sommerfeld constant (γ{sub b}), electron-phonon coupling constant (λ) and the superconducting transition temperature (T{sub c}) for these alloys, which were found to be in good agreement with experiments.

COMPORTAMENTO DOS PREÇOS NOS MERCADOS BRASILEIROS DE SUINOS, MILHO E SOJA

OpenAIRE

Rosado, Patricia Lopes; Gomes, Marilia Fernandes Maciel; Figueiredo, Adelson Martins

2006-01-01

O comportamento das séries históricas de preços de suínos e dos principais insumos usados no seu processo produtivo como, milho e soja, pode apresentar oscilações que o produtor, geralmente, não consegue prever, o que contribui para elevar o risco da atividade. Destarte, como forma de fornecer subsídios teóricos e empíricos aos agentes econômicos envolvidos em operações com suínos, milho e soja, buscou-se, neste trabalho, detectar a existência dos componentes estocásticos e, ou, determinístic...

O legado de Cabanis: hipótese sobre raízes da educação médica no Brasil

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Naomar Almeida-Filho

Full Text Available Georges Cabanis foi um reformador da prática clínica e do ensino médico que, na Revolução Francesa, lançou as bases conceituais do modelo de educação implantado na França no decorrer do século XIX. Tal modelo, por sua vez, marcou a organização dos sistemas educacionais de muitos países latino-americanos. Este artigo tem como objetivo apresentar e justificar uma hipótese: o modelo de educação médica ainda hoje hegemônico no Brasil ainda hoje se baseia na reforma cabasiana, mantendo uma perspectiva conceitual linear e cartesiana, com matriz curricular disciplinar, formatos tradicionais de prática pedagógica e submissão à lógica profissional corporativa. Para melhor compreensão do contexto social e político dos processos históricos geradores desse anacronismo, em primeiro lugar, apresento uma súmula da biografia e do conjunto pensamento-obra de Georges Cabanis, introduzindo-o como personagem central em seu contexto histórico. Em segundo lugar, destaco os principais elementos estruturais do modelo cabanisiano, com foco especial no ensino médico, tomando alguns dos seus textos autorais como fonte documental. Finalmente, em breves traços, apresento o projeto de reforma do ensino médico elaborado por Cabanis e seus colaboradores como subsídio para avaliação preliminar da hipótese proposta.

Experimental investigation of electronic and magnetic properties of LaAlO{sub 3}-SrTiO{sub 3} interfaces

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Richter, Christoph

2013-02-08

This thesis is an experimental study of the interface between LaAlO{sub 3} (LAO) and SrTiO{sub 3} (STO). Both materials are non-magnetic insulators. LAO-STO interfaces, however, can be conducting, and even superconducting at millikelvin temperatures. Moreover, using cantilever-based torque magnetometry we have found a ferromagnetic-like ordering at such interfaces that coexists with the superconductivity. To gain insight into the underlying electronic structure I have developed and built solid-state planar tunnel devices with LAO-STO interfaces as one tunneling electrode. Using these devices the electronic density of states (DOS) of normal- and superconducting LAO-STO interfaces was mapped with tunneling spectroscopy. Since the charge carrier density at LAO-STO interfaces is highly tunable with electrostatic gating, the spectral DOS of the 2D-superconductor could be explored across a wide T,n-phase diagram. The main result bears a striking resemblance to the pseudogap-phase of high-temperature cuprate superconductors. The appendix reports on possible technical applications of LAO-STO interfaces in field-effect transistors and integrated circuits. Furthermore, it contains extensive experimental results concerning alternative growth procedures and related material systems. The LAO-STO interface is established as a representative of a broader class of conducting oxide interfaces. In particular, a conducting oxide interface without SrTiO{sub 3}, the LaAlO{sub 3}-CaTiO{sub 3} interface, is investigated.

DOS.

Science.gov (United States)

Traven, Bill

1988-01-01

Discusses using the DOS PATH command (for MS-DOS) to enable the microcomputer user to move from directory to directory on a hard drive. Lists the commands to be programed, gives examples, and explains the use of each. (MVL)

Wearing mechanisms of Al{sub 2} O{sub 3}-Si C-C for torpedo car; Mecanismos de desgate dos refratarios de Al{sub 2}O{sub 3}-SiC-C para carro-torpedo

Energy Technology Data Exchange (ETDEWEB)

Quintela, Marco Antonio; Correa Filho, Gerson [USIMINAS, Ipatinga, MG (Brazil). Centro de Pesquisa e Desenvolvimento; Correa Filho, Joao Rodrigues [USIMINAS, Ipatinga, MG (Brazil). Gerencia de Manutencao de Refratarios e Civil

1995-12-31

Recently, with the improvement in the hot metal pretreatment practice in the torpedo car at USIMINAS, refractory linings were subjected to severe working conditions resulting in a considerable change in the performance of Al{sub 2} O{sub 3}-Si C-C bricks. A Post Mortem study of the torpedo car linings was carried out using ceramographic analysis and scanning electron microscopy. It was found that the wear mechanisms of Al{sub 2} O{sub 3}-Si C-C bricks comprise mainly the development of dense and secondary phases around Al{sub 2} O{sub 3} particles, together with the formation of low refractoriness phases on the slag and refractory interface. (author) 5 figs.

Quaternary rare-earth sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE=La–Nd, Sm; M=Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Iyer, Abishek K. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Yin, Wenlong [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900 (China); Lee, Emma J. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Lin, Xinsong [Centre for Oil Sands Sustainability, Northern Alberta Institute of Technology, Edmonton, Alberta, Canada T6N 1E5 (Canada); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)

2017-06-15

The two metal-deficient series of quaternary Ge-containing sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE = La–Nd, Sm; M = Co, Ni), as well as the related Si-containing sulfide Y{sub 3}Pd{sub 0.5}SiS{sub 7}, were prepared by reactions of the elements at 1050 °C. Single-crystal X-ray diffraction analysis performed on all compounds confirmed noncentrosymmetric hexagonal structures (space group P6{sub 3}, Z =2) with cell parameters in the ranges of a =10.0–10.3 Å and c =5.7–5.8 Å for RE{sub 3}Co{sub 0.5}GeS{sub 7} and RE{sub 3}Ni{sub 0.5}GeS{sub 7}, or a =9.7891(3) Å and c =5.6840(4) Å for Y{sub 3}Pd{sub 0.5}SiS{sub 7}. They are classified as La{sub 3}Mn{sub 0.5}SiS{sub 7}-type structures, with M atoms centred within octahedra (in contrast to La{sub 3}CuSiS{sub 7}-type structures in which M atoms occupy trigonal planar sites) and Ge atoms centred within tetrahedra, both types of polyhedra being arranged in one-dimensional stacks aligned along the c-direction. Charge balance requirements dictate half-occupancy of the M sites. However, bond valence sum arguments indicated that the M atoms are somewhat underbonded within these octahedral sites, so that there is evidence that in some compounds, they can also enter the trigonal planar site at low occupancy (~5%). Magnetic measurements on RE{sub 3}Co{sub 0.5}GeS{sub 7} (RE = Ce, Pr, Sm) revealed paramagnetic behaviour for the Ce and Pr members and apparent antiferromagnetic ordering (T{sub N} =14 K) for the Sm member; fitting to the Curie-Weiss law gave effective magnetic moments consistent with the presence of RE{sup 3+} and Co{sup 2+} species. Band structure calculations on ordered models of La{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) showed that the Fermi level cuts through M 3d states in the DOS curve and supported the presence of strong M–S and Ge–S bonding interactions. - Graphical abstract: RE{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7} contain M atoms partially occupying

Strain effects on electronic structure of Fe{sub 0.75}Ru{sub 0.25}Te

Energy Technology Data Exchange (ETDEWEB)

Winiarski, M.J., E-mail: M.Winiarski@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław (Poland); Samsel-Czekała, M. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław (Poland); Ciechan, A. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668, Warsaw (Poland)

2017-01-15

Structural and electronic properties of a hypothetical Fe{sub 0.75}Ru{sub 0.25}Te alloy and the parent FeTe compound have been investigated from first principles within the density functional theory (DFT). For both systems the double-stripe antiferromagnetic ground state is predicted at ambient pressure. The incorporation of Ru atoms into FeTe in the nonmagnetic phase leads to a deep valley of density of states in the vicinity of the Fermi level and the DOS at the Fermi level is significantly diminished in the considered solid solution. The single-stripe antiferromagnetic phase in Fe{sub 0.75}Ru{sub 0.25}Te may be induced by tensile strain. These findings suggest that strained thin films of Fe{sub 1−x}Ru{sub x}Te are good candidates for new superconducting Fe-based materials. - Highlights: • Ru-doped FeTe systems are investigated by density-functional theory methods. • Structural and electronic properties of Fe{sub 0.75}Ru{sub 0.25}Te and parent FeTe are studied. • The double-stripe antiferromagnetic ground state is predicted for both systems. • The single-stripe antiferromagnetic phase may be induced by tensile strain. • Tensile strained Fe{sub 0.75}Ru{sub 0.25}Te is a candidate for a new Fe-based superconductor.

A influência dos processos que buscam a autoformação: uma leitura através da fenomenologia e da Semiótica Social The influence of processes that involve self-formation: a reading through the Fenomenology and the Social Semiotics

Directory of Open Access Journals (Sweden)

Silvia Regina Quijadas Aro Zuliani

2009-01-01

Full Text Available Os Estágios Supervisionados são disciplinas integradoras entre o conhecimento específico e os conhecimentos pedagógicos. Neste trabalho, apresentamos resultados de uma pesquisa realizada com Licenciandos em Química utilizando a Metodologia Investigativa. O objetivo foi buscar as percepções dos sujeitos a respeito da própria aprendizagem e sua transferência ao processo de ensino. Utilizou-se o referencial proposto pela Fenomenologia e Semiótica Social para a análise dos dados. Confirmaram-se o potencial da metodologia no desenvolvimento metacognitivo dos sujeitos e na evolução de suas concepções. Estes valorizam a construção de estratégias de aprendizagem como um processo pessoal e profissional. A reflexão levou-os a reconhecer a complementaridade entre ensinar e aprender, como processos indissociáveis, e geradores de conhecimentos aplicáveis à atividade profissional.Teaching Practices are integrative discipline between the specific knowledge and the pedagogical knowledge. In this work, we present the results of a research carried through with future teachers in Chemistry, using the Investigative Methodology. The objective was to seek the perceptions of the students about their own learning and its transference to the educational process. We used the benchmark proposed by the Phenomenology and Social Semiotic for the data analysis. It has confirmed the potential of the methodology in the students metacognitive development and in the evolution of their conceptions. They value the construction of learning strategies as a personal process and professional knowledge. The reflection led them to recognize the complementarity between teaching and learning processes inseparable, and its application to the professional activity.

Conflitos socioambientais no extrativismo da aroeira (Schinus terebebinthifolius Raddi), Baixo São Francisco - Sergipe/Alagoas

OpenAIRE

Jesus, Nádia Batista de; Gomes, Laura Jane

2012-01-01

Esta pesquisa analisou os conflitos socioambientais envolvidos no extrativismo da aroeira no Baixo São Francisco, Sergipe e Alagoas. A pesquisa aconteceu entre os anos de 2001 e 2011, por meio da realização de entrevistas com os atores envolvidos e pesquisa documental. As informações foram analisadas quanto à conduta diante do extrativismo e tipificação dos conflitos. A ausência de normatização para o manejo da espécie é o fator central gerador do conflito que se dá pela apropriação e acesso ...

First-principles energy band calculation of Ruddlesden–Popper compound Sr{sub 3}Sn{sub 2}O{sub 7} using modified Becke–Johnson exchange potential

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Kamimura, Sunao, E-mail: kamimura-sunao@che.kyutech.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, 1-1 Sensuicho, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan); National Institute of Advanced Industrial Science and Technology (AIST), 807-1 Shuku-machi, Tosu, Saga 841-0052 (Japan); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1 Kasuga Kouen, Kasuga, Fukuoka 816-8580 Japan (Japan); Obukuro, Yuki [Interdisciplinary Graduate School of Agriculture and Engineering, University of Miyazaki, 1-1 Gakuenkibanadai-nishi, Miyazaki 889-2192 (Japan); Matsushima, Shigenori, E-mail: smatsu@kct.ac.jp [Department of Creative Engineering, National Institute of Technology, Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, Fukuoka 802-0985 (Japan); Nakamura, Hiroyuki [Department of Creative Engineering, National Institute of Technology, Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, Fukuoka 802-0985 (Japan); Arai, Masao [Computational Materials Science Unit (CMSU), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Xu, Chao-Nan, E-mail: cn-xu@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), 807-1 Shuku-machi, Tosu, Saga 841-0052 (Japan); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-1 Kasuga Kouen, Kasuga, Fukuoka 816-8580 Japan (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

2015-12-15

The electronic structure of Sr{sub 3}Sn{sub 2}O{sub 7} is evaluated by the scalar-relativistic full potential linearized augmented plane wave (FLAPW+lo) method using the modified Becke–Johnson potential (Tran–Blaha potential) combined with the local density approximation correlation (MBJ–LDA). The fundamental gap between the valence band (VB) and conduction band (CB) is estimated to be 3.96 eV, which is close to the experimental value. Sn 5s states and Sr 4d states are predominant in the lower and upper CB, respectively. On the other hand, the lower VB is mainly composed of Sn 5s, 5p, and O 2p states, while the upper VB mainly consists of O 2p states. These features of the DOS are well reflected by the optical transition between the upper VB and lower CB, as seen in the energy dependence of the dielectric function. Furthermore, the absorption coefficient estimated from the MBJ–LDA is similar to the experimental result. - Graphical abstract: Calculated energy band structure along the symmetry lines of the first BZ of Sr{sub 3}Sn{sub 2}O{sub 7} crystal obtained using the MBJ potential. - Highlights: • Electronic structure of Sr{sub 3}Sn{sub 2}O{sub 7} is calculated on the basis of MBJ–LDA method for the first time. • Band gap of Sr{sub 3}Sn{sub 2}O{sub 7} is determined accurately on the basis of MBJ–LDA method. • The experimental absorption spectrum of Sr{sub 3}Sn{sub 2}O{sub 7} produced by MBJ–LDA is more accurate than that obtained by GGA method.

Study of the structure of H<sub>2sub>SO>4sub>-amine Primene 81R and Fe(III-amine Primene 81R sulphate compounds by infrared spectroscopy

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Alguacil, F. J.

1999-08-01

Full Text Available The primary amine Primene 81R extracts sulphuric acid from aqueous solutions to form the corresponding sulphate and bisulphate salts. The infrared study shows that in the sulphate salt, the sulphate group presents a T<sub>d> symmetry, whereas the amine bisulphate presents a C<sub>3vsub> symmetry for the bisulphate group. The former of the above compounds, the amine sulphate, is complexed to Fe(III in sulphate media, and two complexes are extracted depending on temperature. At 8°C or lower temperatures a complex with the stoichiometric formula 4(RNH<sub>3sub>>2sub>SO>4sub> (Fe(OHSO<sub>4sub>>2sub> is formed, whereas at 50°C or higher temperatures the complex with the stoichiometric formula 3(RNH<sub>3sub>>2sub>SO>4sub> (Fe(OHSO<sub>4sub>>2sub> is formed. The infrared spectrum of both complexes is very similar and it is consistent with a weaker interaction between the protons associated with the amine group and the anion, and with a change in the symmetry of the sulphate group respect to the symmetry presented in the amine sulphate salt.

La amina primaria Primene 81R extrae al ácido sulfúrico de los medios acuosos para formar las sales sulfato y bisulfato. El estudio IR muestra que en la sal sulfato, el grupo sulfato presenta una simetría T<sub>d>, mientras que en la sal bisulfato este grupo presenta una simetría C<sub>3vsub>. La sal sulfato compleja al Fe(III, formando dos compuestos en función de la temperatura de reacción. A temperaturas iguales a 8°C o inferiores se forma el compuesto de estequiometría 4(RNH<sub>3sub>>2sub>SO>4sub> (Fe(OHSO<sub>4sub>>2sub>, mientras que a temperaturas iguales o superiores a 50°C la estequiometría del compuesto extraído es 3(RNH<sub>3sub>>2sub>SO>4sub> (Fe(OHSO<sub>4sub>>2sub>. El espectro infrarrojo de ambos compuestos es muy parecido y es consistente, tanto con una interacción d

Half-metallic and insulating natures in Ru-based ordered double perovskite oxides Ba{sub 2}X{sup III}Ru{sup V}O{sub 6} (X = V, Cr) induced by 3d-t{sub 2g}{sup n} orbital filling

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Saad, H.-E.M. Musa, E-mail: musa.1964@gmail.com; Althoyaib, S.S.

2017-04-01

In this paper, we present results of a comprehensive systemic study of the crystal, electronic and magnetic structures on two members of Ru-based ordered double perovskite oxides Ba{sub 2}XRuO{sub 6} (X = V, Cr). For the corporate compound, the analysis of density of states (DOS) results suggests that the 3d-t{sub 2g} orbital filling plays a major role in governing the conduction mechanism in these systems. The DOS and magnetic results show that Ba{sub 2}XRuO{sub 6} exhibits half-metallic (HM) nature as X = V, where the electronic structure of Ba{sub 2}V{sup III}Ru{sup V}O{sub 6} with 3d-t{sub 2g}{sup 2} behaves like that of HM ferrimagnetic (FI), switches to compensate FI insulating behavior as X = Cr, with an extra electron filled 3d-t{sub 2g}{sup 3} in Ba{sub 2}Cr{sup III}Ru{sup V}O{sub 6}. We find, on consideration of electron correlation (LSDA+U) and spin-orbital coupling (SOC) effects that the electronic structure of Ba{sub 2}XRuO{sub 6} takes a HM nature, whereas it is completely transformed to insulating nature once an extra electron filled the 3d-t{sub 2g} orbitals in X = Cr case. Such tuning is accompanied by spin-state hopping of one electron from half-filled spin-state in Ru{sup V} (t{sub 2g}{sup 3} e{sub g}{sup 0}) to two and three occupied spin-state in V{sup III} (t{sub 2g}{sup 2} e{sub g}{sup 0}) and Cr{sup III} (t{sub 2g}{sup 3} e{sub g}{sup 0}), respectively. The charge distribution results show that this extra electron occupies chiefly the spin-down of conduction orbitals and plays a major role in determining the electronic and magnetic structures of Ba{sub 2}XRuO{sub 6} system. - Highlights: • Half-metallic and insulating natures are observed in Ba{sub 2}XRuO{sub 6} (X = V, Cr). • 3d-t{sub 2g}{sup n} orbitals filling plays a major role in governing the conduction mechanism. • LSDA+U method under density functional theory (DFT) is considered. • HM ferrimagnetic (FI) (X = V) switch to compensate FI insulating (X = Cr).

Subúrbios e veredas - apontamentos para uma leitura comparada dos narradores em Dom Casmurro e Grande sertão: veredas

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Wilson Madeira Filho

2000-03-01

Full Text Available Dois grandes autores, verdadeira unanimidade da crítica literária nacional, Machado de Assis e Guimarães Rosa representam a elaboração de uma escrita repleta de sutilezas, cuja metalinguagem permite desdobramentos na própria interação entre as esferas do autor e a do leitor. A questão da autoria, apresentada com picardia na abertura do Dom Casmurro, refrata-se em jogos interpretativos. No capítulo inicial, o narrador sugere uma bifurcação: de um lado, a biografia possível, de outro lado, a crônica histórico-social com a redação de uma Históriados subúrbios. No fundo, trata-se de um mesmo projeto, posto que ambos, o cidadão e a cidade, projetam-se em suas face tas ocultas; no centro urbano, as vias de acesso via trem da Central do Brasil, articulandoas a rtérias da polis; no homem, os recônditos da alma, a irromper no fluxo de uma memória que se quer centralizadora. Por sua vez, herdandoa perplexidade e tentativa de "atar as pontas da vida", a ascese de Riobaldo confunde-se com a de um grande sertão cujas trilhas compõema trajetória hermética de desvendamento dos contrários, da revelação do Tudo no Nada. A obra de Machado é permeada pelo pessimismode Schopenhauer, narrando-se o desespero de uma vida onde tudo tornou-se vão. A de Rosa, enlaça a admiração inicial de Nietzsche por Schopenhauer para, contudo, reverter esse pessimismo através da teoria do eterno retorno e dos aforismos de Zarathustra, com a alternânciada alegria e do desespero, da criação e da destru ição, do bem e do mal.

Study of half-metallic ferromagnetism and elastic properties of Cd{sub 1-x}Cr{sub x}Z (Z=S, Se)

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Rani, Anita [Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab (India); Kumar, Ranjan [Panjab University Chandigarh, Department of Physics, Chandigarh (India)

2016-12-15

We have studied the structural, electronic and magnetic properties of Cd{sub 1-x}Cr{sub x}S and Cd{sub 1-x}Cr{sub x}Se diluted magnetic semiconductors in zinc blende (B3) phase at x = 0.25, 0.125 and 0.0625. The calculations have been performed using DFT (density functional theory) as implemented in SIESTA code using LDA (local density approximation) as exchange-correlation (XC) potential. Study of band structures and DOS (density of states) shows HMF (half-metallic ferromagnetic) nature of Cd{sub 1-x}Cr{sub x}S and Cd{sub 1-x}Cr{sub x}Se alloys. The calculated values of s-d exchange constant Nα and p-d exchange constant Nβ show the magnetic behavior of these compounds. Moreover, both DMSs retain their half-metallic nature at 0.25, 0.125 and 0.0625 concentrations with 100% spin polarization at Fermi level (E{sub F}). Total magnetic moment of these compounds is due to 3d states of Cr atom and also existence of small induced magnetic moment on other non-magnetic atoms as well. HM robustness is also calculated as a function of lattice constants. (orig.)

Grain boundary engineering of La{sub 0.7} Sr{sub 0.3} MnO{sub 3} films on silicon substrate: Scanning Tunneling Microscopy-Spectroscopy study

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Joshi, Anupama [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411025 (India); Nori, Rajashree [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology (IIT Bombay), Mumbai 400076 (India); Dhobale, Sandip [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411025 (India); Ramgopal Rao, V. [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology (IIT Bombay), Mumbai 400076 (India); Kale, S.N., E-mail: sangeetakale2004@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411025 (India); Datar, Suwarna, E-mail: suwarna.datar@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411025 (India)

2014-09-01

We employed a Scanning Tunnelling Microscope (STM) to study the surface topography and spatially resolved local electronic properties like local density of states (LDOS) of nanostructured films of La{sub 0.7} Sr{sub 0.3} MnO{sub 3} (LSMO). The nanostructured thin films of LSMO on silicon substrate were prepared using Pulsed Laser Deposition (PLD) technique. The deposition conditions were tuned to yield two different morphologies; one with uniform columnar closely packed islands and other with larger grain distribution in random fashion. The Scanning Tunnelling Spectroscopy (STS) revealed the extent of variation of density of states (DOS) near the Fermi level. From the spectroscopic features obtained we found the occurrence of phase separation between conducting and semiconducting domains and its possible correlation with the properties of the system. Semiconducting nature was observed at the grain boundaries, which could be extremely promising in futuristic nano-devices.

Quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) - a new coloring variant of the aristotype AlB{sub 2}

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Hoffmann, Rolf-Dieter; Vosswinkel, Daniel; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Matar, Samir F. [CNRS, Universite de Bordeaux, ICMCB, UPR 9048, 33600 Pessac (France)

2016-09-15

The quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce{sub 3}TaRh{sub 4}Ge{sub 4} was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR{sub 2} = 0.0678, 1004 F{sup 2} values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce{sub 3}TaRh{sub 4}Ge{sub 4} is a new superstructure variant of the aristotype AlB{sub 2} with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh{sub 4}Ge{sub 4}] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce{sub 3}TaRh{sub 4}Ge{sub 4} structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh{sub 4}Ge{sub 4}] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce{sub 3}TaRh{sub 4}Ge{sub 4}. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge

Electronic structure and thermoelectricity of filled skutterudite CeRu{sub 4}Sb{sub 12}

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Shankar, A., E-mail: amitshan2009@gmail.com [Department of Physics, University of North Bengal, Darjeeling, 734013 (India); Rai, D.P. [Department of Physics, Pachhunga University College, Aizawl, 796001 (India); Sandeep [Condensed Matter Theory Research Group, Department of Physics, Mizoram University, Aizawl, 796004 (India); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique (LPQ3M), Département de Technologie, Université de Mascara, 29000 (Algeria); Thapa, R.K. [Condensed Matter Theory Research Group, Department of Physics, Mizoram University, Aizawl, 796004 (India); Mandal, P.K. [Department of Physics, University of North Bengal, Darjeeling, 734013 (India)

2016-07-05

First-principles calculations of the energy band structure and density of states of filled skutterudite CeRu{sub 4}Sb{sub 12} have been performed to understand the origin of thermoelectricity. The calculations are carried out using the full potential linear augmented plane wave (FP-LAPW) method within a framework of LDA approach. CeRu{sub 4}Sb{sub 12} is a metal with bands crossing Fermi energy level more than twice with indirect energy band gap of ∼0.09 eV above the Fermi energy level. The study of the elastic properties suggests the ductile nature of the material with covalent contribution in the atomic bonding. Our calculations performed for the density of electronic states near the Fermi energy level show that the large thermo-power at room temperature originates from the hybridized Ru-d and Sb-p orbitals. The study of the thermal transport properties suggests the high value of Seebeck coefficient with figure of merit (ZT) = 0.12, which is consistent to the values obtained for the analogous compounds. - Highlights: • CeRu{sub 4}Sb{sub 12} is ductile material with covalent contribution in bonding. • An indirect energy bandgap of 0.09 eV is present above the Fermi energy level. • The crossing of E{sub F} by the energy bands increases the number of DOS at E{sub F}. • Fermi level is situated within the valence region. • The thermal efficiency of the material is 0.12 at room temperature.

The ‘sub’ metallide oxide hydrides Sr{sub 21}Si{sub 2}O{sub 5}H{sub 12+x} and Ba{sub 21}M{sub 2}O{sub 5}H{sub 12+x} (M = Zn, Cd, Hg, In, Tl, Si, Ge, Sn, Pb, As, Sb, Bi)

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Jehle, Michael; Hoffmann, Anke [Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, D-79104 Freiburg (Germany); Kohlmann, Holger [Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, D-04103 Leipzig (Germany); Scherer, Harald [Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, D-79104 Freiburg (Germany); Röhr, Caroline, E-mail: caroline@ruby.chemie.uni-freiburg.de [Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, D-79104 Freiburg (Germany)

2015-02-25

interpenetrating diamond-like networks: Network A consists of suboxide-like clusters [O{sub 5}A{sub 18}] (4{sup ¯}3m, 8a) and icosahedra [MA{sub 12}], i.e. isolated M anions (3{sup ¯}m, 16c). Network B, within which the H/D ions are interspersed in octahedral and tetrahedral coordination by Sr/Ba, contains FK-16 polyhedra [A(1)A{sub 16}] (4{sup ¯}3m, 8b) and bicapped hexagonal prisms [A(2)A{sub 14}] (3{sup ¯}m, 16d). For the tetrelides, the observed hydrogen content of 14 H/f.u. is in best accordance with the presence of the suboxide cluster [O{sub 5}A{sub 18}], the results of the FP-LAPW band structure calculations, the physical and chemical properties as well as with the NMR chemical shifts and dipolar coupling motifs. The range of suitable elements M (encompassing transition metals and pentelides too) also support the derived model for the H atom distribution inside the network B. The distinct minima at 90 (Zn: 88) v.e./f.u. in the tDOS of all calculated model compounds Ba{sub 21}M{sub 2}O{sub 5}H{sub 12} suggest hydrogen contents of 12 H/f.u. for Zn, Cd, Hg and the triels and 16 H/f.u. for the pentels.

Thermal expansion of mullite-type Bi{sub 2}Al{sub 4}O{sub 9}: A study by X-ray diffraction, vibrational spectroscopy and density functional theory

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Mangir Murshed, M., E-mail: murshed@uni-bremen.de [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany); Mendive, Cecilia B.; Curti, Mariano [Departamento de Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Dean Funes 3350, B7600AYL Mar del Plata (Argentina); Šehović, Malik [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany); Friedrich, Alexandra [Institut für Geowissenschaften, Abteilung Kristallographie, Goethe-Universität Frankfurt, Altenhöferallee 1, D-60438 Frankfurt am Main (Germany); Fischer, Michael [Kristallographie, FB Geowissenschaften, Universität Bremen, Klagenfurter Straße, D-28359 Bremen (Germany); Gesing, Thorsten M. [Chemische Kristallographie fester Stoffe, Institut für Anorganische Chemie, Universität Bremens, Leobener Straße, D-28359 Bremen (Germany)

2015-09-15

Polycrystalline Bi{sub 2}Al{sub 4}O{sub 9} powder samples were synthesized using the glycerine method. Single crystals were produced from the powder product in a Bi{sub 2}O{sub 3} melt. The lattice thermal expansion of the mullite-type compound was studied using X-ray diffraction, Raman spectroscopy and density functional theory (DFT). The metric parameters were modeled using Grüneisen approximation for the zero pressure equation of state, where the temperature-dependent vibrational internal energy was calculated from the Debye characteristic frequency. Both the first-order and second-order Grüneisen approximations were applied for modeling the volumetric expansion, and the second-order approach provided physically meaningful axial parameters. The phonon density of states as well as phonon dispersion guided to set the characteristic frequency for simulation. The experimental infrared and Raman phonon bands were compared with those calculate from the DFT calculations. Selective Raman modes were analyzed for the thermal anharmonic behaviors using simplified Klemens model. The respective mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. - Graphical abstract: Crystal structure of mullite-type Bi{sub 2}Al{sub 4}O{sub 9} showing the edge-sharing AlO{sub 6} octahedra running parallel to the c-axis. - Highlights: • Thermal expansion of Bi{sub 2}Al{sub 4}O{sub 9} was studied using XRD, FTIR, Raman and DFT. • Metric parameters were modeled using Grüneisen approximation. • Phonon DOS and phonon dispersion helped to set the Debye frequency. • Mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. • Anharmonicity was analyzed for some selective Raman modes.

Electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) Heusler alloys: First-principles calculations

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Guezlane, M. [Department of Physics, Faculty of Science, University of Batna, 05000 Batna (Algeria); Baaziz, H., E-mail: baaziz_hakim@yahoo.fr [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); El Haj Hassan, F., E-mail: hassan.f@ul.edu.lb [Université Libanaise, Faculté des Sciences (I), Laboratoire de Physique et d’Electronique (LPE), Elhadath, Beirut (Lebanon); Charifi, Z. [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); Djaballah, Y. [Laboratoire d’étude Physico-Chimique des Matériaux, Département de Physique, Faculté des Sciences, Université de Batna, Rue Chahid Boukhlouf, 05000 Batna (Algeria)

2016-09-15

Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) full Heusler alloys, with L2{sub 1} structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel–Vosko generalized gradient approximation (EVGGA) and modified Becke–Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co{sub 2}Cr{sub x}Fe{sub 1−x}X that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions. - Highlights: • We present electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) Heusler alloys. • The calculated phase diagram indicates a significant phase miscibility gap. • The computed band structures of ternary compounds using GGA, EVGGA and mBJ schemes indicate an indirect band gap (Γ-X) for the ternary compounds Co{sub 2}FeAl, Co{sub 2}CrAl, Co{sub 2}FeSi and Co{sub 2}CrSi while both alloys have a direct band gap. • The quasi-harmonic Debye model is successfully applied to determine the thermal properties.

SUBSÍDIOS PARA ELABORAÇÃO DE PLANO MUNICIPAL PARA GESTÃO DA FRAÇÃO ORGÂNICA DE RESÍDUOS SÓLIDOS DOMICILIARES PARA O MUNICÍPIO DE RIO CLARO-SP

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Elisa Fonseca Horta

2017-01-01

Full Text Available A pesquisa propôs subsídios para elaboração de plano municipal para a gestão dos resíduos orgânicos. O universo da pesquisa foram os estabelecimentos da tipologia hortifrútis, compostos por mercados e verdurões. A partir da seleção da amostra foram obtidos os seguintes dados em campo: quantidade gerada, destino dos resíduos, segregação dos resíduos e frequência de coleta. A partir destes dados, estimou-se a geração total de resíduos orgânicos deste segmento no município, os custos para implantação e operação de uma central de compostagem, e as formas de cobrança dos geradores para a sustentabilidade financeira do sistema. De acordo com os resultados, cada estabelecimento gera, em média, 105 t/mês de resíduos, sendo 35 t/mês de orgânicos. Dos estabelecimentos entrevistados, 94% fazem a segregação na fonte dos resíduos, sinalizando que a proposta de gestão dos resíduos orgânicos pode ser aplicada sem muitas alterações na rotina já existente nos estabelecimentos. O custo de implantação da central de compostagem foi estimado em R$165 mil e o de operação em R$10 mil/mês. Foram desenvolvidos dois modelos de cobrança, um que tem como base o número de caixas registradoras (check-outs e outro baseado no número de recipientes (cestas coletados de resíduo por estabelecimento, ambos consideram o porte do estabelecimento. Os resultados sinalizam que o número de check-outs existentes nos estabelecimentos pode ser utilizado para formular os valores do sistema de cobrança. Assim, o custo mensal para ambos modelos está entre as faixas: Pequeno de R$75,44/mês a R$334,88/mês; Pequeno/Médio de R$295,04/mês a R$898,88/mês; e Médio de R$357,44/mês a R$1462,88/mês.

Synthesis and characterization particles of Ba{sub 0,50}Sr{sub 0,50}Co{sub 0,80}Fe{sub 0,20}O{sub 3} obtained by the citrate-EDTA technique; Sintese e caracterizacao de particulados de Ba{sub 0,50}Sr{sub 0,50}Co{sub 0,80}Fe{sub 0,20}O{sub 3} obtidos pela tecnica dos citratos-EDTA

Energy Technology Data Exchange (ETDEWEB)

Bonturim, E; Vargas, R A; Andreoli, M; Seo, E S.M., [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

2010-07-01

The Ba{sub (1-x)}Sr{sub (x)}Co{sub (1-y)}Fe{sub (y)}O{sub (3)} (BSCF) has been studied as a cathode material for Intermediate Temperature Solid Oxide Fuel Cell, due to its better ion and electron conduction. This work aims to study the synthesis of the compound obtained from the citrate-EDTA technique. Thermogravimetric analysis indicated the formation of the compound above 800 deg C. The materials calcined at temperatures of 700, 800 and 900 deg C for 5 h showed cubic pseudo-perovskite structure, according to the literature. By analysis of X-ray fluorescence were obtained powders with nominal chemical composition in the temperature range studied. The micrographs obtained by SEM and particle size distribution analysis showed the formation of particle with diameters below 1 micron. (author)

Tempo e Trânsito na Experiência Subjetiva de Motoristas

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Ana Inez Oka Elvas de Lima

2015-03-01

Full Text Available Esta pesquisa investiga como são percebidos e vivenciados o tempo e a pressa no trânsito por motoristas de Fortaleza, identificando e analisando seus estados subjetivos e comportamentos associados a essa experiência. Para a coleta de dados, organizaram-se quatro grupos focais, a partir dos quais emergiram diversos elementos relacionados ao tempo e à pressa e à incidência de comportamentos inadequados no trânsito, segundo o sexo e a idade dos participantes. Para analisar os dados obtidos nas discussões grupais utilizaram-se os critérios da Análise Clássica de Conteúdo. Os resultados levaram à conclusão de que a questão do tempo e da pressa constitui um potencial gerador de erros e violações na condução de veículos, pois exerce influência decisiva sobre os comportamentos dos motoristas e configura uma realidade importante para se compreender os fatores humanos envolvidos na dinâmica do trânsito e do ambiente urbano como um todo.

Os organismos geneticamente modificados e a rotulagem dos alimentos - uma análise a partir dos direitos dos consumidores

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Marcello Vitor Rocha Cota

2015-11-01

Full Text Available Ao longo do presente trabalho serão analisados os organismos geneticamente modificados (OGMs frente aos riscos à saúde alimentar e ao meio ambiente, sobretudo o princípio da precaução e a rotulagem dos produtos. A partir de uma dimensão comparativa de três realidades distintas, isto é, a estadunidense, a europeia, com ênfase mercado ao português, e a brasileira – sob um prisma ambiental, a rotulagem dos produtos será confrontada com os direitos dos consumidores, embora em determinadas ocasiões, diante da inexistência de informações adequadas e claras dos produtos, que estão sendo ofertados e consumidos, os consumidores não sabem o que estão consumindo.

Promoção à saúde e educação: diagnóstico de saneamento através da pesquisa participante articulada à educação popular (Distrito São João dos Queiróz, Quixadá, Ceará, Brasil Health promotion and education: a diagnosis of sanitation conditions using participatory research and community education (São João dos Queiróz, Quixadá, Ceará, Brazil

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Dalva A. Mello

1998-07-01

Full Text Available Este trabalho foi desenvolvido em uma comunidade rural ­ vila de São João dos Queiróz, Distrito do Município de Quixadá, Ceará, através da pesquisa participante articulada à educação popular, tendo como referencial a promoção à saúde de acordo com os princípios da Carta de Ottawa, 1986. Participaram do projeto representantes das diversas instituições públicas do distrito e entidades associativas ligadas ao movimento popular. O tema gerador, definido em assembléia da associação comunitária, foi o diagnóstico de saneamento, e o ponto de partida, o levantamento da condição situacional. Os resultados obtidos mostraram as precárias condições locais de saneamento, escolaridade, renda e trabalho. As sugestões para resoluções dos problemas foram organizadas para subsidiar a agenda de planejamento das políticas locais de saúde. A avaliação foi processual e enriquecida com práticas do cotidiano da pesquisa. A pedagogia problematizadora, desenvolvida durante o processo educativo, contribuiu para a construção e a reconstrução crítica dos conceitos de promoção à saúde e de saneamento, assim como para a efetivação da construção, apropriação e socialização dos conhecimentos produzidos.This study was conducted in a rural community, São João dos Queiróz, a township in the county of Quixadá, Ceará, Brazil, using a combination of participatory research and community education in compliance with the health promotion reference and principles of the 1986 Ottawa Charter. The project was joined by representatives of several local government institutions and organizations from the grassroots community movement. The theme generating the research, as defined by an assembly meeting of the community association, was a diagnosis of sanitation conditions in the community. The starting point was the assessment of local conditions. Results showed adverse local conditions in sanitation, literacy, income, and employment

Autonomia profissional dos professores

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Guerra, Teresa P.; Veiga, Feliciano

2007-01-01

Este estudo pretendeu analisar as representações dos professores acerca da sua autonomia em contexto escolar, com recurso a uma amostra de 203 professores de ambos os sexos, pertencentes a escolas dos distritos de Lisboa, Setúbal, Leiria e Aveiro. Utilizou-se a Escala de Autonomia Profissional dos Professores (EAPP).

Carta de fragilidade ambiental da bacia do rio Keller, Estado do Paraná: subsídio ao estudo dos processos erosivos

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Myriam da Silveira Reis Nakashima

2001-05-01

Full Text Available Este trabalho desenvolvido na bacia do rio Keller, Estado do Paraná objetiva divulgar a metodologia para o estudo da fragilidade ambiental da relação relevo-solo e dos graus de proteção pertinentes ao uso da terra/vegetação. Pretende também demonstrar a sua repercussão sobre os processos erosivos em áreas com substrato basáltico, sob interferência de clima mesotérmico úmido do (tipo cfa, cfah, da classificação de Köeppen. Fundamentada nestas constatações, propõe-se a classificação da fragilidade ambiental para a bacia do rio Keller, apoiada nas análises laboratoriais efetuadas nos horizontes dos diferentes tipos de solos, bem como nos ensaios de campo, utilizando o penetrômetro de bolso (que mede a resistência à penetração de cada um destes horizontes e o infiltrômetro de superfície e sub-superfície. Tais procedimentos levam à compreensão da fragilidade ambiental (relação relevo-solo, uso da terra/vegetação evidenciando e localizando as classes com maior potencial erosivo (mais “instáveis” e as menos susceptíveis ao desencadeamento desses processos (mais “estáveis”. Os resultados alcançados com a pesquisa demonstram: Baixa fragilidade ambiental inerente aos altos topos esculpidos no basalto amigdaloidal (0%-6% de declividade, que abrigam Latossolo Vermelho, textura argilosa, café ou cultivo temporário. Sua vinculação com as classes texturais compreendendo argila e argila pesada, com índices de infiltração muito rápidos a rápidos, que podem ocasionar processos erosivos voltados para a erosão laminar. Fragilidade média nas vertentes (de 0%-12%, 12%-20%, de declividade, detentoras de basalto amigdaloidal, com Nitossolo Vermelho ou de basalto de estrutura maciça com Neossolo Litótico. O uso da terra é caracterizado por cultivos temporários ou pastagem. Classe textural franco-argila-siltosa, franco-siltosa e índice do infiltrômetro de subsuperfície muito rápido (Neossolo Lit

Two anhydrous zeolite X crystal structures, Pd sub 1 sub 8 Tl sub 5 sub 6 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4 and Pd sub 2 sub 1 Tl sub 5 sub 0 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4

CERN Document Server

Yoon, B Y; Lee, S H; Kim, Y

2001-01-01

The crystal structures of fully dehydrated Pd sup 2 sup + - and Tl sup + -exchanged zeolite X, Pd sub 1 sub 8 Tl sub 5 sub 6 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4 (Pd sub 1 sub 8 Tl sub 5 sub 6 X, a = 24.935(4) A) and Pd sub 2 sub 1 Tl sub 5 sub 0 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4 (Pd sub 2 sub 1 Tl sub 5 sub 0 -X, a = 24.914(4) A), have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at 21(1) .deg. C. The crystals were prepared using an exchange solution that had a Pd(NH sub 3) sub 4 Cl sub 2 : TINO sub 3 mole ratio of 50 : 1 and 200 : 1, respectively, with a total concentration of 0.05 M for 4 days. After dehydration at 360 .deg. C and 2 x 10 sup - sup 6 Torr in flowing oxygen for 2 days, the crystals were evacuated at 21(1) .deg. C for 2 hours. They were refined to the final error indices R sub 1 = 0.045 and R sub 2 = 0.038 with 344 reflections for Pd sub 1 sub 8 Tl sub 5 sub 6 -X, and R sub 1 = 0.043 and R sub 2 = 0.045 with ...

Microstructure study of the rare-earth intermetallic compounds R<sub>5sub>(Si_xGe>1-xsub>)>4sub> and R<sub>5sub>(Si_xGe>1-xsub>)>3sub>

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Cao, Qing [Iowa State Univ., Ames, IA (United States)

2012-01-01

The unique combination of magnetic properties and structural transitions exhibited by many members of the R<sub>5sub>(Si_xGe>1-xsub>)>4sub> family (R = rare earths, 0 ≤ x ≤ 1) presents numerous opportunities for these materials in advanced energy transformation applications. Past research has proven that the crystal structure and magnetic ordering of the R<sub>5sub>(Si_xGe>1-xsub>)>4sub> compounds can be altered by temperature, magnetic field, pressure and the Si/Ge ratio. Results of this thesis study on the crystal structure of the Er<sub>5sub>Si>4sub> compound have for the first time shown that the application of mechanical forces (i.e. shear stress introduced during the mechanical grinding) can also result in a structural transition from Gd<sub>5sub>Si>4sub>-type orthorhombic to Gd<sub>5sub>Si>2sub>Ge>2sub>-type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 °C.

Structural and Magnetothermal Properties of Compounds: Yb<sub>5sub>Si_xGe>4-xsub>,Sm>5sub>Si_xGe>4-xsub>, EuO, and Eu<sub>3sub>O>4sub>

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Ahn, Kyunghan [Iowa State Univ., Ames, IA (United States)

2007-01-01

The family of R<sub>5sub>Si_xGe>4-xsub> alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R<sub>5sub>Si_xGe>4-xsub> systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R<sub>5sub>Si_xGe>4-xsub> pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R<sub>5sub>Si_xGe>4-xsub> systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb<sub>5sub>Si_xGe>4-xsub>and Sm<sub>5sub>Si_xGe>4-xsub> pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb<sub>5sub>Si_xGe>4-xsub> alloys with 0 ≤ x ≤ 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R<sub>5sub>Si_xGe>4-xsub> systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd<sub>5sub>Si>4sub>-type structure. The magnetic properties of Yb<sub>5sub>Si_xGe>4-xsub> materials are nearly composition

ANÁLISE EXERGÉTICA DE UM SISTEMA DE REFRIGERAÇÃO POR ABSORÇÃO DE SIMPLES EFEITO OPERANDO COM O PAR LiBr/H2O

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Igor Marcel Gomes Almeida

2010-09-01

Full Text Available A segunda lei da termodinâmica trata da qualidade da energia. Mais especificamente, trata da degradação de energia durante um processo, a geração de entropia, e as perdas de oportunidade da realização de trabalho, o que oferece muita margem para melhorias. O objetivo deste trabalho é identificar os principais fatores que afetam o desempenho de um sistema de refrigeração por absorção de simples efeito (chiller que utiliza o par água/brometo de lítio como fluidos refrigerantes e tem como fonte térmica rejeitos provenientes de um grupo motor/gerador elétrico, constituinte de uma planta de cogeração. O sistema tem capacidade de refrigeração entre 4 a 16 TR. A análise exergética foi realizada de modo que a eficácia dos componentes do sistema pôde ser estimada e classificada, permitindo direcionar os esforços no sentido de melhorar e identificar os principais pontos de perda de eficiência no ciclo. As análises revelaram que o gerador e o absorvedor apresentam as maiores fontes de perdas no sistema e os esforços devem ser direcionados de modo a aprimorar o desempenho destes componentes.

Magnetic signature of charge ordering in Li[Mn sub 1 sub . sub 9 sub 6 Li sub 0 sub . sub 0 sub 4]O sub 4 and Li sub 0 sub . sub 2 [Mn sub 1 sub . sub 9 sub 6 Li sub 0 sub . sub 0 sub 4]O sub 4

CERN Document Server

Verhoeven, V W J; Mulder, F M

2002-01-01

The stoichiometric compound LiMn sub 2 O sub 4 is known to show charge ordering with well-defined Mn sup 3 sup + and Mn sup 4 sup + sites just below room temperature (RT). Above RT the electrons are hopping rapidly between sites. For lithium-ion batteries the material Li[Mn sub 1 sub . sub 9 sub 6 Li sub 0 sub . sub 0 sub 4]O sub 4 is technologically relevant. Due to the small amount of Li on the Mn site, the low-T regular ordering of the Mn charge appears to be destroyed completely, as is evidenced by neutron diffraction in the magnetically ordered state. However, the charges are still fixed in an irregular fashion, as can also be deduced from sup 7 Li nuclear magnetic resonance measurements. In the lithium-extracted compound Li sub 0 sub . sub 2 [Mn sub 1 sub . sub 9 sub 6 Li sub 0 sub . sub 0 sub 4]O sub 4 , predominantly Mn sup 4 sup + is present. Neutron diffraction in the magnetically ordered state shows a well-defined antiferromagnetic ordering, with doubling of the unit cell in three directions. Clear...

A química no ensino médio e a contextualização: a fabricação dos sabões e detergentes como tema gerador de ensino aprendizagem

OpenAIRE

Oliveira, Ana Maria Cardoso de

2006-01-01

O Conhecimento químico é fundamental à compreensão de processos físicos e químicos que nos cercam, para fazer opção por uma vida com qualidade, promover e acompanhar o desenvolvimento tecnológico. Porém, a formação de um pensamento químico fruto de uma aprendizagem significativa, tem sido um desafio para educadores em química de todo o país. Estudos apontam para a contextualização dos conteúdos químicos como recurso para promover uma inter-relação entre conhecimentos escolares e fatos/situ...

Electronic properties of CdWO{sub 4}: Use of hybrid exchange and correlation functionals

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Meena, B. S., E-mail: bsmphysics@gmail.com; Mund, H. S.; Ahuja, B. L. [Department of Physics, University College of Science, M. L. Sukhadia University, Udaipur-313001 (India); Heda, N. L. [Department of Pure and Applied Physics, University of Kota, Kota-324010 (India)

2016-05-23

Energy bands, density of states (DOS), Mulliken population (MP) and electron momentum densities (EMDs) of CdWO{sub 4} are presented using hybrid exchange and correlation functionals namely B3LYP, B3PW and PBE0. To validate the present hybrid potentials, theoretical EMDs have been compared with the experimental Compton profile. It is found that LCAO-B3LYP based Compton profile gives a better agreement with experiment than other theoretical profiles. The energy bands and DOS show a wide band gap semiconducting nature of CdWO{sub 4}. The theoretical band gap obtained using B3LYP scheme reconciles well with the available experimental data. In addition, we have also presented the anisotropies in EMDs along [100], [110] and [001] directions and the bonding effects using the MP data.

Perfil dos discentes ingressos do Centro de Ciências da Saúde UFPE

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Ludmila Galindo França Gurgel

Full Text Available A busca pelo conhecimento das características e da opinião dos estudantes do nível superior fornece importantes subsídios para o planejamento e reorganização do desenvolvimento acadêmico. Com o objetivo de traçar o perfil do aluno do Centro de Ciências da Saúde da Universidade Federal de Pernambuco (UFPE, foram distribuídos formulários aos acadêmicos do 2º período, contendo perguntas referentes aos seus aspectos socioeconômicos e pessoais. O perfil dos estudantes (n = 210 caracterizou-se por um predomínio feminino, com idades entre 19 e 21 anos, provenientes de escolas privadas e classes sociais economicamente mais favorecidas, que receberam grande influência do núcleo familiar na escolha da profissão. A maioria dos estudantes não estava matriculada nos cursos de primeira opção, porém possuía alta expectativa com relação ao curso, considerando-o correspondente às suas expectativas. Após formados pretendem realizar algum curso de pós-graduação e trabalhar no serviço público. No entanto, persiste um problema relativo à escolha da profissão, regulada pela condição socioeconômica e influência familiar.

Optoelectronic behavior of Quaternary Uranium Chalcogenides Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se): A first principle study

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Din, Haleem Ud [Department of Physics, Hazara University, Mansehra (Pakistan); Azam, Sikander; Khan, Saleem Ayaz [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modélisation Mathématique (LPQ3M), Département de Technologie, Université de Mascara, Mascara 29000 (Algeria)

2014-12-05

Highlights: • The Fermi surface and optoelectronic properties for Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se) compounds are investigated for the first time. • The electronic band structure calculations reveal a metallic nature for the herein studied compounds. • The bonding nature between different atoms is discussed. • Considerable anisotropy was found between the principal complex tensor components for the two compounds. - Abstract: First principle calculations of electronic, Fermi surface, electronic charge density and optical properties of Quaternary Uranium Chalcogenides Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se) are performed using full potential linear augmented plane wave (FP-LAPW) method within the frame work of density functional theory. Using mBJ method, the electronic band curves overlap at Fermi level and show metallic band structure for both compounds. The calculated densities of states (DOS) spectra show that the valence band is mainly attributed to Rb-p, Pd-d and S-s/p or Se-s/p states; conduction band is mainly attributed to Pd-d, U-f and S-p or Se-p/d states. From the electronic charge density spectrum, it is revealed that a strong covalent bond exists between Pd and S, and Pd or Se while charge transfer between U and S, U and Se, Rb and S, and Rb and Se atoms results in ionic bond nature. It is noted from Fermi surface calculations that both compounds comprise same number of fast velocity electrons but differs in slow or intermediate velocity of electrons. The calculated frequency dependent dielectric function, energy loss function and reflectivity show a considerable anisotropy for both compounds.

Regionalizando as instituições da sociedade internacional: uma leitura dos novos debates

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Maria Beatriz Bonna Nogueira

2015-04-01

Full Text Available Estudos recentes têm revisado a tradição universalista da Escola Inglesa de Relações Internacionais e aplicado seus principais conceitos ao plano sub-global. O presente ensaio analisa as tentativas de aplicação dos conceitos de sociedade internacional e de instituições às regiões e discute as contribuições que esse esforço traz ao campo de estudos.      Recent studies have revised the English School’s long universalist tradition by applying some of its main concepts to the sub-global level. The present essay analyzes the attempts to employ the concepts of international society and institutions to regions and discusses the contributions that this effort brings to the field.

Mechanism of superconductivity in Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub O sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta

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Anvekar, T S; Sarode, P R; Kamat-Dalal, V N; Narlikar, Anant V

2002-01-01

EXAFS, X-ray Rietveld refinement and infra-red absorption measurements have been made on Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub 0 sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta in order to understand the effect of Ca doping on the local structure of planar Cu ion. The study indicates that restoration of superconductivity is due to oxidation of copper ions in the CuO sub 2 planes. (author)

The new mixed cluster trielide K{sub 3}Ga{sub 11-x}In{sub x} (x = 1.16-1.36). Synthesis, crystal chemistry, and chemical bonding

Energy Technology Data Exchange (ETDEWEB)

Falk, Martha; Meyer, Carolin; Roehr, Caroline [Institut fuer Anorganische und Analytische Chemie, Universitaet Freiburg (Germany)

2017-12-13

The new cluster compound K{sub 3}Ga{sub 11-x}In{sub x}, which exhibits a very small In/Ga phase width of x = 1.16 to 1.36 only, was obtained in the course of a systematic synthetic, crystallographic and bond theoretical investigation of mixed potassium trielides of the ternary system K-In-Ga. The compound, which was synthesized from nearly stoichiometric amounts of the elements at a maximum temperature of 500 C, crystallizes in a new orthorhombic crystal structure type [space group Cmmm, a = 1577.9(5), b = 3355.1(8), c = 655.2(2) pm, Z = 10, R{sub 1} = 0.0471]. In the complex polyanion, the triels form two crystallographically different [Ga{sub 12}] icosahedra, which are present in a 1:2 ratio, and a previously unknown [M{sub 13}] ''double-cluster'' consisting of two vertex-sharing [M{sub 7}] pentagonal bipyramids. All clusters are connected among each other and via a four-bonded pure In and Ga atom [In(1), Ga(1)]. The polyanion of the compound with the overall formula K{sub 15}M{sub 55} can thus be split up according to [Ga(1X){sub 12}][Ga(2X){sub 12}]{sub 2}[M(3X){sub 13}]In(1){sub 4}Ga(1){sub 2}. Herein, the all-exo bonded closo icosahedra carry a charge of -2, the six four-bonded In/Ga contribute with a charge of -6 and the new [M{sub 13}] ''double-cluster'' thus carries a charge of -3. Under the reasonable assumption of an ''intermediate'' interaction between the two cluster fragments, this charge, i.e. the presence of 15 skeleton electron pairs, is in accordance with the mno electron counting rules. FP-LAPW DFT band structure calculations of two ordered model compounds support this interpretation: The tDOS exhibits a small bandgap and the electron density map suggests a limited additional interaction between the Ga{sub 5} bases of the two bipyramidal cluster fragments. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

FATORES CONTROLADORES DA EVOLUÇÃO DO RELEVO NO FLANCO NNW DO RIFT CONTINENTAL DO SUDESTE DO BRASIL: UMA ANÁLISE BASEADA NA MENSURAÇÃO DOS PROCESSOS DENUDACIONAIS DE LONGO-TERMO

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Éric Andrade Rezende

2013-03-01

Full Text Available O presente trabalho tem como objetivo estudar os fatores controladores da evolução do relevo de um trecho do interflúvio entre a bacia interiorana do rio Grande, um dos formadores do rio Paraná, e a bacia do rio Paraíba do Sul. Este divisor hidrográfico está contido em uma das porções mais elevadas da Serra da Mantiqueira e coincide com o flanco NNW do Rift Continental do Sudeste do Brasil. Para este estudo foram selecionadas nove sub-bacias localizadas no extremo sul de Minas Gerais, entre os municípios de Itamonte e Bocaina de Minas. Essas sub-bacias tiveram suas taxas denudacionais estimadas pela mensuração da produção do isótopo cosmogênico 10Be em sedimentos fluviais. Os resultados mostram que a taxa média de denudação das sub-bacias do rio Paraíba do Sul, voltadas para o gráben (17,39 m/Ma, é superior a das sub-bacias dos rios Grande e Aiuruoca, voltadas para o interior continental (12,24 m/Ma. Entre os fatores controladores das taxas de denudação, se destaca a boa correlação existente entre as taxas e dois parâmetros morfométricos: amplitude de relevo e declividade média das sub-bacias. A influência da litologia também se mostra importante, já que a resistência dos granitos frente aos processos erosivos é um dos fatores que condiciona taxas denudacionais bastante baixas na área. Os resultados indicam que o granito Maromba é a unidade litológica mais resistente entre aquelas presentes nas sub-bacias amostradas. As baixas taxas mensuradas, referentes às últimas dezenas de milhares de anos, contrastam com o relevo rejuvenescido e com as elevadas altitudes desse setor da Mantiqueira, onde há um reconhecido papel da neotectônica na morfogênese. Deste modo, é provável que tenha havido uma atenuação da atividade tectônica no Quaternário Superior, com a consequente estabilização dos níveis de base e diminuição dos processos denudacionais.

Ternary rhombohedral Laves phases RE{sub 2}Rh{sub 3}Ga (RE = Y, La-Nd, Sm, Gd-Er)

Energy Technology Data Exchange (ETDEWEB)

Seidel, Stefan; Benndorf, Christopher; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Oldenburg Univ. (Germany). Inst. fuer Chemie; Mausolf, Bernhard [RWTH Aachen (Germany). Inst. fuer Anorganische Chemie; Haarmann, Frank [RWTH Aachen (Germany). Inst. fuer Anorganische Chemie; Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany); Eckert, Hellmut [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Sao Paulo Univ., Sao Carlos (Brazil). Inst. of Physics

2017-06-01

The ordered Laves phases RE{sub 2}Rh{sub 3}Ga (RE=Y, La-Nd, Sm, Gd-Er) were synthesized by arc-melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction (XRD). They crystallize with the rhombohedral Mg{sub 2}Ni{sub 3}Si type structure, space group R3m. Three structures were refined from single crystal X-ray diffractometer data: a=557.1(1), c=1183.1(2), wR2=0.0591, 159 F{sup 2} values, 10 variables for Y{sub 2}Rh{sub 3}Ga, a=562.5(2), c=1194.4(2) pm, wR2=0.0519, 206 F{sup 2} values, 11 variables for Ce{sub 2}Rh{sub 3}Ga and a=556.7(2), c=1184.1(3) pm, wR2=0.0396, 176 F{sup 2} values, 11 variables for Tb{sub 2}Rh{sub 3}Ga. The Rh{sub 3}Ga tetrahedra are condensed via common corners and the large cavities left by the network are filled by the rare earth atoms. The RE{sub 2}Rh{sub 3}Ga Laves phases crystallize with a translationengleiche subgroup of the cubic RERh{sub 2} Laves phases with MgCu{sub 2} type. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y{sub 2}Rh{sub 3}Ga and La{sub 2}Rh{sub 3}Ga. Ce{sub 2}Rh{sub 3}Ga shows intermediate cerium valence while all other RE{sub 2}Rh{sub 3}Ga phases are Curie-Weiss paramagnets which order magnetically at low temperatures. The {sup 89}Y and {sup 71}Ga solid state nuclear magnetic resonance (NMR) spectra of the diamagnetic representative Y{sub 2}Rh{sub 3}Ga show well-defined single resonances in agreement with an ordered bulk phase. In comparison to the binary Laves phase YRh{sub 2} a strongly increased {sup 89}Y resonance frequency is observed owing to a higher s-electron spin density at the {sup 89}Y nuclei as proven by density of states (DOS) calculations.

Comunicação transnacional mediada por computador: uma análise discursiva das identidades de futuros professores de inglês no Facebook

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Bárbara Cristina Gallardo

2014-06-01

Full Text Available Tomando potencialmente inovadoras as oportunidades de Comunicação Mediada por Computador no âmbito da formação de professores de inglês, o objetivo deste artigo é analisar as representações da identidade nacional constituídas em um contexto virtual. Duas estudantes de Letras estabeleceram contato com estrangeiros no Facebook e com eles interagiram em língua inglesa. Utilizou-se a Análise Crítica do Discurso para desvendar a organização linguística e ideológica dos discursos nacionais acionados na transição para o contexto transnacional online. Os resultados sugerem a hibridação de estratégias do discurso de contextos offline com os recursos multimodais dos contextos online. Os sujeitos adotaram estereótipos oriundos de centros geradores das dinâmicas de globalização, tanto em escala regional (sudeste do Brasil como mundial (os EUA.

Crystallographic and electronic structure of the Ca{sub 2}TiMnO{sub 6} double perovskite

Energy Technology Data Exchange (ETDEWEB)

López, J.P. Garzón [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Cardona, R. [Grupo de Estudios de Materiales – GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Santos, A. Sarmiento [Grupo de Superficies, Electroquímica y Corrosión, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Téllez, D.A. Landínez [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

2014-12-15

In this work, we report synthesis and crystalline structure study of the Ca{sub 2}TiMnO{sub 6} complex perovskite, by X-ray diffraction experiments and through the application of the Rietveld refinement using the GSAS code. Results revealed the crystallization of the system in a tetragonal perovskite with the characteristic structure given by I4/m (#87) space group and lattice parameters a=5.339(4) Å and c=7.736(6) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system, by the Density Functional Theory (DFT) and using the Full-potential Linearized Augmented Plane Waves (FP-LAPW) method. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. For the up spin orientation the compound has a semiconducting behavior and for down spin polarization it behaves like a conductor. The calculated effective magnetic moment in cell was 4.02 μ{sub B}, which is close to the expected value calculated from Hund's rules.

Análise de sensibilidade dos parâmetros do modelo SWAT e simulação dos processos hidrossedimentológicos em uma bacia no agreste nordestino

Directory of Open Access Journals (Sweden)

Ricardo de Aragão

2013-08-01

Full Text Available O processo erosivo constitui-se na principal causa de degradação dos solos e é acelerado por intervenções humanas nas bacias hidrográficas, resultando em prejuízos ao setor agrícola e ao meio ambiente. Para a previsão dos impactos de ações antrópicas ou de mudanças climáticas sobre os processos hidrossedimentológicos, os modelos distribuídos e de base física têm sido bastante eficazes. Neste estudo, aplicou-se o modelo SWAT à sub-bacia do Rio Japaratuba Mirim, em Sergipe, nas seções de medição das estações Fazenda Pão de Açúcar (PA e Fazenda Cajueiro (CJ, com áreas de contribuição respectivamente de 137,3 e 277,8 km², visando à parametrização das duas bacias aninhadas por meio dos processos de calibração e de validação. Foram realizadas simulações do escoamento na bacia menor (PA, a partir dos parâmetros calibrados na bacia maior (CJ, e, reciprocamente, do escoamento na bacia maior (CJ. Em seguida, foram também realizadas simulações do escoamento e da produção de sedimentos para o período de dados de vazão disponíveis (1985 a 2000, para a seção CJ. Os resultados evidenciaram que o modelo calibrado simulou bem o escoamento superficial e conseguiu prever, de forma coerente, a produção de sedimentos com base nos 12 parâmetros mais sensíveis do modelo. A transposição dos parâmetros da bacia maior para a menor e, vice-versa, resultou em índices de Eficiência de Nash-Sutcliffe (NSE e de Tendência Percentual (PBIAS, considerados satisfatórios para o primeiro caso e insatisfatório para o segundo.

Caracterização do nível tecnológico dos apicultores do estado do Rio de Janeiro

Directory of Open Access Journals (Sweden)

Niraldo José Ponciano

2013-09-01

Full Text Available O estudo analisa e busca subsídios para gerar e transferir tecnologias compatíveis com o nível socioeconômico dos apicultores. Os dados foram extraídos a partir do Censo Apícola, englobando 75 municípios com atividade apícola representativa. Foi utilizada a Análise Fatorial para caracterizar o nível tecnológico dos apicultores. Os resultados evidenciaram baixo nível tecnológico. Por meio dos escores fatoriais calculou-se o índice bruto de desenvolvimento. Com valores mais altos desse índice, destacaram-se os municípios de Conceição de Macabu, Areal, Duas Barras, Rio Claro, Cardoso Moreira, Cachoeiras de Macacu, Campos dos Goytacazes, Natividade e Nova Iguaçu. Constatou-se que o grau de escolaridade influenciou positivamente o desenvolvimento dos apicultores. Esse desenvolvimento também foi afetado pela assistência técnica, pelo manejo da troca de rainha e pela prática da apicultura migratória. Dessa forma, a modernização dos apicultores no sentido de melhorar o nível tecnológico, expandir a produtividade e diversificar a produção passa necessariamente pelo nível de conhecimento do apicultor e pela situação socioeconômica.

Ni{sub 0,5}Zn{sub 0,5}Fe{sub 2}O{sub 3} ferrite synthesized by combustion and Pechini method for use in nanomedicine: methods evaluation; Ferrita Ni{sub 0,5}Zn{sub 0,5}Fe{sub 2}O{sub 3} sintetizada por reacao de combustao e metodo Pechini para uso na nanomedicina: avaliacao dos metodos

Energy Technology Data Exchange (ETDEWEB)

Albuquerque, I.L.T. de; Nascimento, A.L.C.; Costa, A.C.F.M., E-mail: allana.layla@gmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

2016-07-01

The objective of this work was to synthesize the Ni0.5Zn0.5Fe2O3 ferrite by combustion reaction and Pechini method, and to evaluate structural characteristics and magnetic behavior for its use in nanomedicine. The synthesized ferrite was characterized by DRX, BET, TG and magnetic properties. According to the results of XRD, the Ni{sub 0,5}Zn{sub 0,5}Fe{sub 2}O{sub 3} ferrite synthesized by both methods presented nano crystallite sizes, high crystallinity, surface area, stable at high temperatures and with high saturation magnetization, being higher in the ferrite synthesized by combustion reaction. Both methods produced materials that could be used in nanomedicine.

Thermal Annealing of Paramagnetic Defects Induced by Gamma Irradiation in (NH{sub 4}){sub 2}SO{sub 4} and (ND{sub 4}){sub 2}SO{sub 4} Single Crystals: Experimental Verification of the Theory of Fletcher and Brown; Recuit Thermique des Defauts Paramagnetiques Induits par Irradiation Gamma dans des Monocristaux de (NH{sub 4}){sub 2}SO{sub 4} et (ND{sub 4}){sub 2}SO{sub 4}: Verification Experimentale de la Theorie de Fletcher et Brown; 0422 0415 0420 041c 0414 ; Regeneracion Termica de los Defectos Paramagneticos Inducidos por Irradiacion Gamma en Monocristales de (NH{sub 4}){sub 2}SO{sub 4} y (ND{sub 4}){sub 2}SO{sub 4}: Verificacion Experimental de la Teoria de Fletcher y Brown

Energy Technology Data Exchange (ETDEWEB)

Calusaru, A.; Barbur, I.; Ursu, I. [Institut de Physique Atomique, Bucarest (Romania); Universite ' Babes' , Cluj (Romania)

1965-04-15

second 2,020, pour le sulfate d'ammonium avec hydrogene; les memes constantes pour le cristal deutere sont 1,9996 et 2,0032. L'etude du recuit du premier radical pour des temperatures comprises entre 60 Degree-Sign et 170 Degree-Sign C a montre qu'il y a dans ce cas une cinetique a un seul plateau correspondant a une recombinaison totale des radicaux. Il a ete possible d'etablir une equation pour chaque isotherme, en utilisant la fonction des erreurs deduite par Fletcher et Brown, et en prenant pour modele la recombinaison, selon un processus aleatoire (random-walk process), des paires initialement conelees, puis liberees. L'accord entre cette fonction et l'experience a ete obtenu apres correction de cette fonction par un facteur a. La courbe de recuit ainsi etablie verifie tres bien la fonction des erreurs corrigee. En appliquant la methode phenomenologique de Fletcher et Brown pour le calcul de l'energie d'activation, on a trouve la valeur 1,594 eV, qui correspond au premier radical en (NH{sub 4}){sub 2}SO{sub 4}. En utilisant la variation du coefficient de diffusion en fonction de la temperature, on a obtenu pour la meme energie d'activation la valeur 1,592 eV. Par la methode de Vand-Primack on a trouve la valeur 1,45 eV, qui est plus petite que les deux precedentes. On a considere, en conclusion, que le modele de la recombinaison des paires correlees d'apres un processus aleatoire est applicable dans la forme donnee par la theorie lorsqu'il y a une assez faible interaction entre le reseau et les especes formees-, de cette maniere les paires initialement correlees peuvent se liberer. (author) [Spanish] En cristales de (NH{sub 4}){sub 2}SO{sub 4} y (ND{sub 4}){sub 2}SO{sub 4}, sometidos a irradiacion, se han identificado dos especies paramagneticas aplicando el metodo de resonancia del espfn electronico. La constante g del primer radical es de 2,014 y la del segundo de 2,020, para el (NH{sub 4}){sub 2}SO{sub 4}; en el caso del cristal deuterado, dichas constantes son 1

N–Mg dual-acceptor co-doping in CuCrO{sub 2} studied by first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Xu, Ying, E-mail: 1080071@hnust.edu.cn [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Nie, Guo-Zheng [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Zou, Daifeng [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shenzhen 518055 (China); Tang, Jing-Wu [School of Physics, Hunan University of Science and Technology, Xiangtan 411201 (China); Ao, Zhimin, E-mail: Zhimin.Ao@gdut.edu.cn [Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

2016-11-25

In this paper, N–Mg dual-acceptor co-doping in CuCrO{sub 2} is investigated by first-principles calculations. The electronic structure and formation energies of Mg substituting Cr-site, N substituting O-site, and co-doping of both Mg on Cr-site and N on O-site in CuCrO{sub 2} are calculated. It is found that the structure with N and Mg codoped at the nearest sites has the lowest energy due to a modest attractive interaction between the two dopants. Compared with single N or Mg doped CuCrO{sub 2}, the N–Mg codoped CuCrO{sub 2} has a lower formation energy and shallower transition level. In addition, the total density of states (DOS) analysis shows that more hole states appear above the Fermi level and higher DOS for N–Mg co-doping is obtained in the N–Mg codoped CuCrO{sub 2}, which is good to enhance the p-type conductivity in CuCrO{sub 2}. - Highlights: • N–Mg dual-acceptor co-doping in CuCrO{sub 2} is investigated. • N–Mg complex has a lower formation energy and shallower transition level. • More hole states appear above the Fermi level for N–Mg co-doping. • N–Mg co-doping in CuCrO{sub 2} can be expected to have more stable p-type conductivity.

Crystallization of Zr<sub>2sub>Pd_xCu>1-xsub> and Zr<sub>2sub>Ni_xCu>1-xsub> Metallic Glass

Energy Technology Data Exchange (ETDEWEB)

Xu, Min [Iowa State Univ., Ames, IA (United States)

2008-01-01

One interesting aspect of rretallic glasses is the numerous instances of the deviation of the phase selection from the amorphous state to thermodynamically stable phases during the crystallization process. Their devitrification pathways allow us to study the relationship between the original amorphous structure and their crystalline counter parts. Among the various factors of phase selections, size and electronic effects have been most extensively studied. Elucidating the phase selection process of a glassy alloy will be helpful to fill in the puzzle of the changes from disordered to ordered structures. In this thesis, Two model Zr<sub>2sub>Pd_xCu>1-xsub> and Zr<sub>2sub>Ni_xCu>1-xsub> (x = 0, 0.25, 0.5, 0.75 and 1) glassy systems were investigated since: (1) All of the samples can be made into a homogenous metallic glass; (2) The atomic radii differ from Pd to Cu is by 11%, while Ni has nearly the identical atomic size compare to Cu. Moreover, Pd and Ni differ by only one valence electron from Cu. Thus, these systems are ideal to test the idea of the effects of electronic structure and size factors; (3) The small number of components in these pseudo binary systems readily lend themselves to theoretical modeling. Using high temperature X-ray diffraction (HTXRD) and thermal analysis, topological, size, electronic, bond and chemical distribution factors on crystallization selections in Zr<sub>2sub>Pd_xCu>1-xsub> and Zr<sub>2sub>Ni_xCu>1-xsub> metallic glass have been explored. All Zr<sub>2sub>Pd_xCu>1-xsub> compositions share the same Cu11b phase with different pathways of meta-stable, icosahedral quasicrystalline phase (i-phase), and C16 phase formations. The quasicrystal phase formation is topologically related to the increasing icosahedral short range order (SRO) with Pd content in Zr<sub>2sub>Pd_xCu>1-xsub> system. Meta-stable C16 phase is competitive with

DOS cones along atomic chains

International Nuclear Information System (INIS)

Kwapiński, Tomasz

2017-01-01

The electron transport properties of a linear atomic chain are studied theoretically within the tight-binding Hamiltonian and the Green’s function method. Variations of the local density of states (DOS) along the chain are investigated. They are crucial in scanning tunnelling experiments and give important insight into the electron transport mechanism and charge distribution inside chains. It is found that depending on the chain parity the local DOS at the Fermi level can form cone-like structures (DOS cones) along the chain. The general condition for the local DOS oscillations is obtained and the linear behaviour of the local density function is confirmed analytically. DOS cones are characterized by a linear decay towards the chain which is in contrast to the propagation properties of charge density waves, end states and Friedel oscillations in one-dimensional systems. We find that DOS cones can appear due to non-resonant electron transport, the spin–orbit scattering or for chains fabricated on a substrate with localized electrons. It is also shown that for imperfect chains (e.g. with a reduced coupling strength between two neighboring sites) a diamond-like structure of the local DOS along the chain appears. (paper)

DOS cones along atomic chains

Science.gov (United States)

Kwapiński, Tomasz

2017-03-01

The electron transport properties of a linear atomic chain are studied theoretically within the tight-binding Hamiltonian and the Green’s function method. Variations of the local density of states (DOS) along the chain are investigated. They are crucial in scanning tunnelling experiments and give important insight into the electron transport mechanism and charge distribution inside chains. It is found that depending on the chain parity the local DOS at the Fermi level can form cone-like structures (DOS cones) along the chain. The general condition for the local DOS oscillations is obtained and the linear behaviour of the local density function is confirmed analytically. DOS cones are characterized by a linear decay towards the chain which is in contrast to the propagation properties of charge density waves, end states and Friedel oscillations in one-dimensional systems. We find that DOS cones can appear due to non-resonant electron transport, the spin-orbit scattering or for chains fabricated on a substrate with localized electrons. It is also shown that for imperfect chains (e.g. with a reduced coupling strength between two neighboring sites) a diamond-like structure of the local DOS along the chain appears.

The uranium(VI) oxoazides [UO{sub 2}(N{sub 3}){sub 2}.CH{sub 3}CN], [(bipy){sub 2}(UO{sub 2}){sub 2}(N{sub 3}){sub 4}], [(bipy)UO{sub 2}(N{sub 3}){sub 3}]{sup -}, [UO{sub 2}(N{sub 3}){sub 4}]{sup 2-}, and [(UO{sub 2}){sub 2}(N{sub 3}){sub 8}]{sup 4-}

Energy Technology Data Exchange (ETDEWEB)

Haiges, Ralf; Christe, Karl O. [Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA (United States); Vasiliu, Monica; Dixon, David A. [Department of Chemistry, The University of Alabama, Tuscaloosa, AL (United States)

2017-01-12

The reaction between [UO{sub 2}F{sub 2}] and an excess of Me{sub 3}SiN{sub 3} in acetonitrile solution results in fluoride-azide exchange and the uranium(VI) dioxodiazide adduct [UO{sub 2}(N{sub 3}){sub 2}.CH{sub 3}CN] was isolated in quantitative yield. The subsequent reaction of [UO{sub 2}(N{sub 3}){sub 2}.CH{sub 3}CN] with 2,2{sup '}-bipyridine (bipy) resulted in the formation of the azido-bridged binuclear complex [(bipy){sub 2}(UO{sub 2}){sub 2}(N{sub 3}){sub 4}]. The triazido anion [(bipy)UO{sub 2}(N{sub 3}){sub 3}]{sup -} was obtained by the reaction of [UO{sub 2}(N{sub 3}){sub 2}.CH{sub 3}CN] with stoichiometric amounts of bipy and the ionic azide [PPh{sub 4}][N{sub 3}]. The reaction of [UO{sub 2}(N{sub 3}){sub 2}] with two equivalents of the [PPh{sub 4}][N{sub 3}] resulted in the formation of the mononuclear tetraazido anion [UO{sub 2}(N{sub 3}){sub 4}]{sup 2-} as well as the azido-bridged binuclear anion [(UO{sub 2}){sub 2}(N{sub 3}){sub 8}]{sup 4-}. The novel uranium oxoazides were characterized by their vibrational spectra and in the case of [(bipy){sub 2}(UO{sub 2}){sub 2}(N{sub 3}){sub 4}].CH{sub 3}CN, [PPh{sub 4}][(bipy)UO{sub 2}(N{sub 3}){sub 3}], [PPh{sub 4}]{sub 2}[UO{sub 2}(N{sub 3}){sub 4}], [PPh{sub 4}]{sub 2}[UO{sub 2}(N{sub 3}){sub 4}].2CH{sub 3}CN, and [PPh{sub 4}]{sub 4}[(UO{sub 2}){sub 2}(N{sub 3}){sub 8}].4CH{sub 3}CN by their X-ray crystal structures. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Phase composition and superconducting properties of (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z

CERN Document Server

Balchev, N; Kunev, B; Souleva, A; Tsacheva, T

2001-01-01

The effect of Sn-doping in (Pb sub 0 sub . sub 6 Sn sub y Cu sub 0 sub . sub 4 sub - sub y)Sr sub 2 (Y sub 1 sub - sub x Ca sub x)Cu sub 2 O sub z for 0 <= y <= 0.3 and 0 <= x <= 0.7 was investigated. It was established that a nearly pure 1212 phase could be obtained at 0 <= y <= 0.1 and 0 <= x <= 0.3. The obtained X-ray diffraction (XRD) patterns as well as the results of the inductively coupled plasma atomic emission spectrometry (ICP-AES) and energy-dispersive X-ray (EDX) analysis showed that the Sn-substitution was possible in the (Pb,Cu)-1212 phase. Superconductivity was observed at 0.4 <= x <= 0.7. The onset of the diamagnetic transitions varied from 10 to 30 K. The influence of the strong Pb deficiency on the superconducting properties of the samples was discussed. (authors)

Thermal analysis and phase diagrams of the LiF BiF{sub 3} e NaF BiF{sub 3} systems; Analise termica e diagramas de fase dos sistemas LiF-BiF{sub 3} e NaF-BiF{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Gerson Hiroshi de Godoy

2013-07-01

Investigations of the binary systems LiF-BiF{sub 3} and NaF-BiF{sub 3} were performed with the objective of clarifying the thermal behavior and phase equilibria of these systems and their intermediary phases, an important requisite for high-quality crystal growth. Several samples in the entire range of compositions (0 to 100 mol% BiF{sub 3}) of both systems were subjected to experiments of differential thermal analysis (DTA) and thermogravimetry (TG), and also of differential scanning calorimetry (DSC). A few specific compositions were selected for X-ray diffraction to supplement the experimental data. Due to the high vulnerability of BiF{sub 3} to oxygen contamination, its volatility and propensity to destroy metal parts upon heating, it was necessary to determine the optimal conditions for thermal analysis before investigating the systems themselves. Phase relations in the system LiF-BiF{sub 3} were completely clarified and a phase diagram was calculated and evaluated via the commercial software Factsage. The diagram itself consists in a simple peritectic system in which the only intermediary compound, LiBiF{sub 4}, decomposes into LiF and a liquid phase. The NaF-BiF{sub 3} system could not be completely elucidated and the phase relations in the NaF poor side (> 50% BiF{sub 3}) are still unknown. In the NaF rich side, however, the possible peritectoid decomposition of the compound NaBiF{sub 4} was identified. In both systems X-ray diffraction yielded crystal structures discrepant with the literature for the intermediary phases, LiBiF{sub 4}, NaBiF{sub 4} and a solid solution of NaF and BiF{sub 3} called {sup I.} The observed structures remain unknown and explanations for the discrepancies were proposed. (author)

Experimental and theoretical investigations for site preference and anisotropic size change of RE{sub 11}Ge{sub 4}In{sub 6−x}M{sub x} (RE = La, Ce; M = Li, Ge; x = 1, 1.96)

Energy Technology Data Exchange (ETDEWEB)

Jeon, Beom-Yong; Jeon, Jieun [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Lee, Junseong [Department of Chemistry, Chonnam National University, Gwangju, Chonnam 500-757 (Korea, Republic of); Kim, Jongsik [Department of Chemistry, Dong-A University, Pusan 604-714 (Korea, Republic of); You, Tae-Soo [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of)

2015-01-25

particular site preference, which can be understood by QVAL values. Theoretical investigations using tight-binding linear muffin-tin orbital (LMTO) method provide rationales for the anisotropic size change of the unit cell of La{sub 11}Ge{sub 4}In{sub 5.00(1)}Li{sub 1.00} using the various crystal orbital Hamilton population (COHP) curves and the possible short-range anionic ordering based on total electronic energy comparisons. Density of states (DOS) curves are also analyzed to explain the orbital interactions among components in the given crystal structure.

Effects of hole doping on the electronic transport properties of PrBa sub 1 sub . sub 8 Sr sub 0 sub . sub 2 Cu sub 3 O sub y and PrSr sub 2 Cu sub 2 sub . sub 7 Mo sub 0 sub . sub 3 O sub y

CERN Document Server

Yang, C F; Zhang, H

2002-01-01

We investigate the effect of Ca doping on the electronic transport properties and superconductivity of Pr sub 1 sub - sub x Ca sub x Ba sub 1 sub . sub 8 Sr sub 0 sub . sub 2 Cu sub 3 O sub y and Pr sub 1 sub - sub x Ca sub x Sr sub 2 Cu sub 2 sub . sub 7 Mo sub 0 sub . sub 3 O sub y systems. It is found that when PrBa sub 2 Cu sub 3 O sub y (Pr123) is in a highly localized state, the Ca doping mainly decreases the 4f-2p hybridized states and thus releases the holes into the CuO sub 2 planes. Whereas when Pr123 is in a less localized state, the Ca doping not only introduces holes into the CuO sub 2 planes, but also induces dramatic charge transfer. Our results suggest that only when the hole concentration in both the CuO chain and the CuO sub 2 planes reaches a proper value, can the superconductivity be restored in the Pr123 system.

Comparison among structural characteristics of Ce{sub 1-x}Cu{sub x}O{sub 2} nanocatalysts obtained by two methods of distinct synthesis; Comparacao entre as caracteristicas estruturais dos nanocatalisadores Ce{sub 1-x}Cu{sub x}O{sub 2} obtidos por dois metodos de sintese distintos

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Bispo, A.; Santos, P.T.A.; Costa, A.C.F.M.; Gama, L., E-mail: lucianna@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia de Materiais; Mascarenhas, A.J.S. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Quimica

2009-07-01

The objective this work is to synthesize nano catalysts Ce{sub 1-x}Cu{sub x}O{sub 2} type by the synthesis methods of the combustion reaction and Pechini. The value of the concentration (x) of the element dope (Cu) varies between 0,1 and 0,5 mols. It intends evaluate that form the synthesis method influences in the physical structural characteristics of this material. nano catalysts were characterized by ray- X diffraction. The results showed nano catalysts formation with a formed structure for the most part by the phase CeO{sub 2}, as it was expected, since this is the hostess matrix of the element dope (Cu). Nano catalysts obtained by the method Pechini presents crystallinity larger deg, according with patterns of ray-X. Thus, it was concluded that synthesis employee method the kind in the methodology, as well as the value of the concentration of the element dope has influence on the final structural characteristics of the developed material. (author)

Spatially resolved analytical electron microscopy at grain boundaries of {alpha}-Al{sub 2}O{sub 3}; Ortsaufgeloeste analytische Elektronenmikroskopie an Korngrenzen in {alpha}Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Nufer, S.

2001-10-01

Aluminum oxide, {alpha}-Al{sub 2}O{sub 3}, is a common structural ceramic material. The most technologically important properties are either determined or strongly influenced by the polycrystalline microstructure. For instance, the grain boundaries control the mechanical behavior (e.g. plasticity, creep, and fracture) or various transport phenomena (e.g. ion diffusion, segregation, and electrical resistivity). In order to understand the structure-properties relationships, it is therefore important to characterize the structure and chemistry of grain boundaries, both experimentally and theoretically. In this work the electronic structure of the basal and rhombohedral twin grain boundaries and the impurity excess at different tilt grain boundaries in bicrystals were investigated, using electron energy-loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). The electronic structure of the rhombohedral twin grain boundary was determined by comparing spatially resolved EELS measurements of the O-K ionisation edge with the theoretical density of states (DOS), obtained from local density functional theory (LDFT) calculations. The interface excess of impurities was quantitatively analysed at grain boundaries with and without Y-doping. (orig.)

Phase diagram and EXAFS study of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 sub - sub x Ba sub x MnO sub 3 manganites

CERN Document Server

Ulyanov, A N; Yang, D S

2003-01-01

The phase diagram and local structure of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 sub - sub x Ba sub x MnO sub 3 (x=0; 0.03; 0.06; ... 0.3) lanthanum manganites were studies. The Curie temperature, T sub c , of the compositions showed a sharp change near the concentrational structural orthorhombic-rhombohedral phase transition. Maximums of dispersion, sigma sub M sub n sub - sub O sup 2 , and asymmetry, sigma M sub n sub - sub O sup 3 , of pair distribution function for the Mn-O bond distances of MnO sub 6 octahedron on x-dependence were observed by extended X-ray absorption fine structure (EXAFS) analysis. The maximum of sigma sub M sub n sub - sub O sup 2 is caused by increase of dynamic rms displacements of Mn-O bond distances near the T sub c. The observed x dependence of sigma sub M sub n sub - sub O sup 3 reflects the reduction of charge carriers mobility at approaching to T sub c. (author)

REDUÇÃO DOS CUSTOS DA QUALIDADE COM MELHORIA DOS PROCESSOS: UM ESTUDO DE CASO

OpenAIRE

Oliveira, Gabriel Rech; Universidade de Caxias do Sul; Motta, Marta Elisete Ventura; Universidade de Caxias do Sul; Camargo, Maria Emilia; Universidade de Caxias do Sul; Tondolo, Vilmar Antonio Gonçalves; Universidade Federal de Rio Grande; Zanadrea, Gabriela; Universidade de Caxias do Sul; Russo, Suzana Leitão; Universidade Federal de Sergipe

2016-01-01

Com o objetivo de se tornarem competitivas, as empresas impulsionam a redução dos custos dos processos que impactam diretamente no preço do produto, destacando-se os custos de qualidade. Neste cenário, a busca pela qualidade total torna-se o caminho para a sobrevivência, devido ao fato da crescente exigência dos clientes para produtos com qualidade superior e preços baixos. Dentre os principais gastos que contribuem para o aumento dos custos da qualidade destacam-se a sucata e retrabalho de p...

Structural and magnetic properties and superconductivity in Ba(Fe<sub>1-xsub>TM_x)>2sub>As>2sub>

Energy Technology Data Exchange (ETDEWEB)

Thaler, Alexander [Iowa State Univ., Ames, IA (United States)

2012-01-01

We studied the effects on structural and magnetic phase transitions and the emergence of superconductivity in transition metal substituted BaFe<sub>2sub>As>2sub>. We grew four series of Ba(Fe<sub>1-xsub>TM>2sub>)>2sub>As>2sub> (TM=Ru, Mn, Co+Cr and Co+Mn) and characterized them by crystallographic, magnetic and transport measurements. We also subjected Ba(Fe<sub>1-xsub>Cr_x)>2sub>As>2sub> and Ba(Fe<sub>1-xsub>Co_x)>2sub>As>2sub> to heat treatment to explore what changes might be induced.

Self-regulating the effortful "social dos".

Science.gov (United States)

Cortes, Kassandra; Kammrath, Lara K; Scholer, Abigail A; Peetz, Johanna

2014-03-01

In the current research, we explored differences in the self-regulation of the personal dos (i.e., engaging in active and effortful behaviors that benefit the self) and in the self-regulation of the social dos (engaging in those same effortful behaviors to benefit someone else). In 6 studies, we examined whether the same trait self-control abilities that predict task persistence on personal dos would also predict task persistence on social dos. That is, would the same behavior, such as persisting through a tedious and attentionally demanding task, show different associations with trait self-control when it is framed as benefitting the self versus someone else? In Studies 1-3, we directly compared the personal and social dos and found that trait self-control predicted self-reported and behavioral personal dos but not social dos, even when the behaviors were identical and when the incentives were matched. Instead, trait agreeableness--a trait linked to successful self-regulation within the social domain--predicted the social dos. Trait self-control did not predict the social dos even when task difficulty increased (Study 4), but it did predict the social don'ts, consistent with past research (Studies 5-6). The current studies provide support for the importance of distinguishing different domains of self-regulated behaviors and suggest that social dos can be successfully performed through routes other than traditional self-control abilities. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

First-principles study of electronic and elastic properties of LuAl{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Shukla, Pushplata, E-mail: pujashukla50@gmail.com; Shrivastava, Deepika; Sanyal, Sankar P. [Department of Physics, Barkatullah university, Bhopal 462026 (India)

2016-05-06

A systematic theoretical study of electronic structure of rare earth intermetallic LuAl{sub 3} has been carried out using full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation(GGA) for exchange and correlation potential. The ground state properties such as lattice constant (a{sub o}), bulk modulus (B) and pressure derivative of bulk modulus (B′) were evaluated. LuAl{sub 3} has the cubic AuCu{sub 3} type crystal structure. The electronic properties of this compound have been analyzed quantatively from band structure and DOS. It is clear from band structure that this compound is metallic in nature. The calculated elastic constants infer that this compound is mechanically stable.

Crystal structures of Ni sup 2 sup + -and Tl sup + -exchanged zeolite X, Ni sub 1 sub 7 Tl sub 5 sub 8 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4 and Ni sub 1 sub 2 Tl sub 6 sub 8 Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4

CERN Document Server

Song, M K; Kim, Y

2001-01-01

The crystal structures of fully dehydrated Ni sup 2 sup + - and Tl sup + -exchanged zeolite X (Ni sub 1 sub 7 Tl sub 5 sub 8 -X, and Ni sub 1 sub 2 Tl sub 6 sub 8 -X; X=Si sub 1 sub 0 sub 0 Al sub 9 sub 2 O sub 3 sub 8 sub 4) have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1) .deg. C (a=24.380(4) A, 24.660(4) A, respectively). Their structures have been refined to the final error indices R sub 1 =0.037 and R sub 2 =0.043 with 485 reflections, and R sub 1 =0.039 and R sub 2 =0.040 with 306 reflections, respectively, for which I>3 sigma(I). In Ni sub 1 sub 7 Tl sub 5 sub 8 -X, 17 Ni sup 2 sup + ions per unit cell were found at only two sites: 15 at site I at the center of the hexagonal prism (Ni-O=2.203(9) A). and the remaining 2 at site II near single six-oxygen rings in the supercage (Ni-O=2.16(3) A). Fifty-eight Tl sup + ions were found at five crystallographic sites: 28 at site II (Tl-O=2.626(8) A, 2 at site I' in the sodalite cavity near the hexagonal ...

Structural and morphological characterization of TiO{sub 2}-ZrO{sub 2} powders obtained by the polymeric precursors method; Caracterizacao estrutural e morfologica de pos de TiO{sub 2}-ZrO{sub 2} obtidos pelo metodo dos precursores polimericos

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, M.A.; Gama, L.; Bispo, A.; Neiva, L.S., E-mail: m_aparecidaribeiro@yahoo.com.b [Universidade Federal de Campina Grande (DEMa/UFCG), PB (Brazil). Dept. de Engenharia de Materiais; Bernardi, M.I.B. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

2010-07-01

This work aims to characterize the structure and morphology of TiO{sub 2}-ZrO{sub 2} powders obtained by polymeric precursor method. For this we studied the following compositions: 0.25, 0.5 and 0.75 moles of Zr and calcined at 800 deg C for one hour. The powders obtained were characterized by XRD, SEM and nitrogen adsorption (BET). The analysis of X-ray diffraction showed that the powders had a phase of TiO{sub 2} in the anatase form and a tetragonal phase of ZrO{sub 2}. The crystallite size was between 8, 13 and 11 nm respectively. The analysis of scanning electron microscopy showed the growth of ZrO{sub 2} nanoparticles and that these comprise spherical agglomerates of less than 100 nm. Particle size determined by the BET ranging 28.1-29.5 nm, showing thereby the character of nanosized powders. (author)

Moessbauer studies of single crystal Pr sub 1 sub / sub 3 Sr sub 2 sub / sub 3 FeO sub 3

CERN Document Server

Uhm, Y R; Kim, C S; Tomioka, Y; Tokura, Y

2000-01-01

Single crystal Pr sub 1 sub / sub 3 Sr sub 2 sub / sub 3 FeO sub 3 was synthesized by using the floating zone method and the relation of magnetic properties and charge ordering transition with lattice dynamics was systematically investigated. Moessbauer spectra of Pr sub 1 sub / sub 3 sub S r sub 2 sub / sub 3 FeO sub 3 were taken at various temperatures ranging from 20 K to room temperature. The charge disproportionation, in which iron with valence states Fe sup 3 sup + and Fe sup 5 sup + was found in a ratio of 2:1, was detected in Pr sub 1 sub / sub 3 Sr sub 2 sub / sub 3 FeO sub 3 below 190+-3 K. Iron with valence state Fe sup 4 sup + coexisted in Pr sub 1 sub / sub 3 sub S r sub 2 sub / sub 3 FeO sub 3 at and above 150 K, and its ratio increased from 13 to 66 % with increasing temperature. This result means that charge-ordered and -disordered phases co-exist in Pr sub 1 sub / sub 3 Sr sub 2 sub / sub 3 FeO sub 3.

Tunable White-Light Emission in Single-Cation-Templated Three-Layered 2D Perovskites (CH <sub>3sub> CH <sub>2sub> NH <sub>3sub> ) <sub>4sub> Pb <sub>3sub> Br <sub>10–xsub> Cl <sub>x>

Energy Technology Data Exchange (ETDEWEB)

Mao, Lingling; Wu, Yilei; Stoumpos, Constantinos C.; Traore, Boubacar [Institut; Katan, Claudine [Institut; Even, Jacky [Fonctions; Wasielewski, Michael R.; Kanatzidis, Mercouri G.

2017-08-16

Two-dimensional (2D) hybrid halide perovskites come as a family (B)<sub>2sub>(A)>n-1sub>PbnX>3n+1sub> (B and A= cations; X= halide). These perovskites are promising semiconductors for solar cells and optoelectronic applications. Among the fascinating properties of these materials is white-light emission, which has been mostly observed in single-layered 2D lead bromide or chloride systems (n = 1), where the broad emission comes from the transient photoexcited states generated by self-trapped excitons (STEs) from structural distortion. Here we report a multilayered 2D perovskite (n = 3) exhibiting a tunable white-light emission. Ethylammonium (EA+) can stabilize the 2D perovskite structure in EA<sub>4sub>Pb>3sub>Br>10–xsub>Cl_x> (x = 0, 2, 4, 6, 8, 9.5, and 10) with EA⁺ being both the A and B cations in this system. Because of the larger size of EA, these materials show a high distortion level in their inorganic structures, with EA4Pb3Cl10 having a much larger distortion than that of EA<sub>4sub>Pb>3sub>Br>10sub>, which results in broadband white-light emission of EA<sub>4sub>Pb>3sub>Cl>10sub> in contrast to narrow blue emission of EA4Pb3Br10. The average lifetime of the series decreases gradually from the Cl end to the Br end, indicating that the larger distortion also prolongs the lifetime (more STE states). The band gap of EA<sub>4sub>Pb>3sub>Br>10–xsub>Cl_x> ranges from 3.45 eV (x = 10) to 2.75 eV (x = 0), following Vegard’s law. First-principles density functional theory calculations (DFT) show that both EA<sub>4sub>Pb>3sub>Cl>10sub> and EA<sub>4sub>Pb>3sub>Br>10sub> are direct band gap semiconductors. The color rendering index (CRI) of the series improves from 66 (EA<sub>4sub>Pb>3sub>Cl>10sub>) to 83 (EA<sub>4sub>Pb>3sub>Br>0.5sub>Cl>9.5sub>), displaying high tunability and versatility of the

Properties of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub y superconductor prepared by different processes in air

CERN Document Server

Giovannelli, F; Monot-Laffez, I

2003-01-01

Bars and pellets of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub x superconductor were processed in air, using the floating zone method and the top-seeded melt-textured growth method, respectively. The samples were prepared using different experimental conditions, i.e. maximal processing temperature, translation rate or cooling rate. Their physical properties and their microstructure were studied. All the samples exhibit a satisfying superconducting transition whereas the critical current density greatly depends on the processing parameters. The sample prepared by the floating zone method at 1070 deg C with a translation rate of 2 mm h sup - sup 1 exhibits a very high J sub c value of 70000 A cm sup - sup 2 in the self-field and more than 30000 A cm sup - sup 2 at 1.7 T. The pellet processed at 1080 deg C with a cooling rate of 2 deg C h sup - sup 1 has a high J sub c reaching about 56000 A cm sup - sup 2 in the self-field and more than 32000 A ...

Magnetostructural Phase Diagram of Multiferroic (ND<sub>4sub>)>2sub>FeCl>5sub>.H>2sub>O

Energy Technology Data Exchange (ETDEWEB)

Clune, A. [Univ. of Tennessee, Knoxville, TN (United States); Hughey, K. [Univ. of Tennessee, Knoxville, TN (United States); Musfeldt, J. L. [Univ. of Tennessee, Knoxville, TN (United States); Tian, W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fernandez-Baca, J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Singleton, John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-02-13

Spin and polarization flop transitions are fascinating, especially when controlled by external stimuli like magnetic and electric field and accompanied by large material responses involving multiple degrees of freedom. Multiferroics like MnWO<sub>4sub>, TbMnO<sub>3sub>, and Ni<sub>3sub>TeO>6sub> are flagship examples and owe their remarkable properties, for instance field control of polarization and polarization flops combined with spin helix reorientation, to the anisotropy and heavy centers that bring in spin-orbit coupling. The family of A<sub>2sub>FeX>5sub>.H>2sub>O erythrosiderites (A = K, Rb, NH<sub>4sub>; B = Fe, Mn, Co; X = Cl, Br, H<sub>2sub>O) drew our attention due to the rich chemical tuning possibilities, complex phase diagrams, and topological similarities to oxide multiferroics.1 (NH<sub>4sub>)>2sub>FeCl>5sub>.H>2sub>O is the flagship example (Fig. 1(a)). It displays a high temperature order-disorder transition involving long-range hydrogen bonding of the NH<sub>4sub>⁺ group and two successive low temperature magnetic transitions below which non-collinear magnetic order and ferroelectricity are established.1 In addition to the magnetically-induced electric polarization that arises below 6.9 K (P = 3 μC/m<sub>2sub> along a and a smaller component along b), applied field reveals a peculiar hysteretic spin flop transition near 4.5 T above which polarization flops from the a- to the c-axis. There are elastic components as well. Taken together, these findings raise questions about the interactions that induce this behavior and whether additional non-equilibrium phases might be accessed under even higher magnetic fields.

Gerenciamento de resíduos odontológicos no serviço público

Directory of Open Access Journals (Sweden)

Lídia Regina da Costa Hidalgo

Full Text Available OBJETIVO: Verificar o processo de gerenciamento dos resíduos odontológicos do serviço público de saúde em 11 municípios brasileiros. MATERIAL E MÉTODO: Uma única pesquisadora realizou as visitas e as observações foram anotadas em um roteiro previamente elaborado e testado. RESULTADO: Foram visitadas 50 unidades de saúde, sendo que nenhuma apresentou cópia do plano de gerenciamento de resíduos. Do total de estabelecimentos, 62% realizavam a correta segregação dos resíduos no momento da sua geração. A presença de recipientes adequados a cada tipo de resíduo gerado no consultório odontológico foi observada em 74% dos estabelecimentos e, destes, 94% apresentavam capacidade adequada ao tipo de resíduo gerado. A identificação do tipo de resíduo nas embalagens plásticas bem como anotações identificando o estabelecimento gerador dos resíduos foram encontradas em 8% e 6%, respectivamente. Somente 21% dos estabelecimentos apresentavam locais apropriados, de acordo com as normas vigentes, para o armazenamento dos resíduos até que fosse feita a coleta externa. CONCLUSÃO: Constatou-se na presente pesquisa que a rotina adotada pela rede pública de saúde bucal, no que tange ao gerenciamento de resíduos de saúde, apresentou falhas.

Systems Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O at 25 deg C. Sistemy Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O pri 25 grad S

Energy Technology Data Exchange (ETDEWEB)

Skvortsov, V G; Sadetdinov, Sh V; Akimov, V M; Mitrasov, Yu N; Petrova, O V; Klopov, Yu N [Chuvashskij Gosudarstvennyj Pedagogicheskij Inst., Cheboksary (Russian Federation) Universitet Druzhby Narodov, Moscow (Russian Federation)

1994-02-01

Phase equilibriums in the Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O systems were investigated by methods of isothermal solubility, refractometry and PH-metry at 25 deg C for the first time. Lithium and sodium tetraborates was established to form phases of changed composition mM[sub 2]B[sub 4]O[sub 7][center dot]nN[sub 2]H[sub 3]C[sub 2]H[sub 4]OH[center dot]XH[sub 2]O, where M=Li, Na with hydrazine ethanol. K[sub 2]B[sub 4]O[sub 7][center dot]4H[sub 2]O precipitates in solid phase in the case of potassium salt. Formation of isomorphous mixtures was supported by X-ray diffraction and IR spectroscopy methods.

C60 and U ion irradiation of Gd<sub>2sub>Ti_xZr>2-xsub>O>7sub> pyrochlore

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jiaming; Toulemonde, Marcel; Lang, Maik; Costantini, Jean Marc; Della-Negra, Serge; Ewing, Rodney C.

2015-08-01

Gd<sub>2sub>Ti_xZr>2-xsub>O>7sub> (x = 0 to 2) pyrochlore was irradiated by 30 MeV C<sub>60sub> clusters, which provide an extremely high ionizing energy density. Here, high-resolution transmission electron microscopy revealed a complex ion-track structure in Gd<sub>2sub>Ti>2sub>O>7sub> and Gd<sub>2sub>TiZrO>7sub>, consisting of an amorphous core and a shell of a disordered, defect-fluorite structure.

A first principles study of Nd doped cubic LaAlO{sub 3} perovskite: mBJ+U study

Energy Technology Data Exchange (ETDEWEB)

Sandeep, E-mail: sndp.chettri@gmail.com [Dept. of Physics, Mizoram University, Aizawl 796004 (India); Rai, D.P. [Dept. of Physics, Pachhunga University College, Aizawl, Mizoram 796001 (India); Shankar, A. [Department of Physics, University of North Bengal, Darjeeling 734013 (India); Ghimire, M.P. [Condensed Matter Physics Research Center, Butwal-13, Rupandehi, Lumbini (Nepal); Khenata, R. [Laboratoire de Physique Quantique et de Modlisation Mathmatique (LPQ3M), Dpartement de Technologie, Universit de Mascara, 29000 Mascara (Algeria); Thapa, R.K. [Dept. of Physics, Mizoram University, Aizawl 796004 (India)

2016-11-01

The structural, electronic and magnetic properties of Nd-doped Rare earth aluminate, La{sub 1−x}Nd{sub x}AlO{sub 3} (x=0–100%) are studied using the full potential linearized augmented plane-wave (FP-LAPW) method within the density functional theory. The effects of Nd substitution in LaAlO{sub 3} are studied using super-cell calculations. The electronic structures were computed using modified Beck Johnson (mBJ) potential based approximation with the inclusion of Coulomb energy (U) for Nd-4f state electrons. The La{sub 1−x}Nd{sub x}AlO{sub 3} may possess half metallic behavior on Nd doping with finite density of states at E{sub F}. The direct and indirect band gaps were studied as a function of Nd concentration in LaAlO{sub 3}. The calculated magnetic moments in La{sub 1−x}Nd{sub x}AlO{sub 3} were found to arise mainly from the Nd-4f state electrons. A probable half-metallic nature is suggested for these systems with supportive integral magnetic moments and high spin polarized electronic structures in these doped cases at E{sub F}. The controlled decrease in band gap with increase in concentration of Nd doping is a suitable technique for harnessing useful spintronic and magnetic devices. - Highlights: • Electronic and magnetic properties of La{sub 1−x}Nd{sub x}AlO{sub 3} to study the effect of doping (x=0%, 25%, 50%, 75% and 100%) is carried out using DFT. • Theoretically calculated U was used in the mBJ+U approximation in order to stress accuracy in band-gap determination along with electron correlation effects in rare earth ions. • A high DOS at E{sub F} for certain doping concentrations in one spin channel with insulting DOS in the other channel supported their probable use as spintronic devices. • The change in doping concentration was found suitable for rare earth aluminates for desirable properties through band-gap tuning.

NMR Studies of the Vanadium Spin Dynamics and Spin Structure in LiV<sub>2sub>O>4sub>, CaV<sub>2sub>O>4sub>, and (Li<sub>xV>1-xsub>)>3sub>BO>5sub> (x ≈ 0.33, 0.40)

Energy Technology Data Exchange (ETDEWEB)

Zong, Xiaopeng [Iowa State Univ., Ames, IA (United States)

2007-01-01

Strong electron correlation is believed to be an essential and unifying factor in diverse properties of condensed matter systems. Ground states that can arise due to electron correlation effects include Mott insulators, heavy fermion, ferromagnetism and antiferromagnetism, spin glasses, and high-temperature superconductivity. The electronic systems in transition metal oxide compounds are often highly correlated. In this thesis, the author presents experimental studies on three strongly correlated vanadium oxide compounds: LiV<sub>2sub>O>4sub>, (Li<sub>xV>1-xsub>)>3sub>BO>5sub>, and CaV<sub>2sub>O>4sub>, which have completely different ground states.

The seeding effect of floating zone growth on Nd sub 1 sub . sub 8 sub 5 Ce sub 0 sub . sub 1 sub 5 CuO sub 4 and Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 sub - subdelta single crystals

CERN Document Server

Lin, C T; Liang, B

2002-01-01

Single crystals with the [100] orientation were selected and used as seeds to investigate the effect of travelling solvent floating zone growth on superconducting oxides of Nd sub 1 sub . sub 8 sub 5 Ce sub 0 sub . sub 1 sub 5 CuO sub 4 and Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 sub - subdelta. The number of nuclei was remarkably reduced and random nuclei could be eased when the seeding was applied during the growth of Nd sub 1 sub . sub 8 sub 5 Ce sub 0 sub . sub 1 sub 5 CuO sub 4 single crystals, compared to the crystals grown without seed. The crystal could preferentially grow on the seed although some additional nuclei occurred at the solid-liquid interface during the initial growth process. In consequence, the crystal ingot obtained is a large single grain having dimensions of 5 mm in diameter and 40 mm in length. The orientation of the seeded growth crystal was found to be 5deg off the [100] seed identified by an x-ray Laue pattern. For the growth of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 sub - subdelta, it...

Giant Magneto-Resistance in Epitaxial (La<sub>0.7sub>Sr>0.3sub>MnO>3sub>)>0.5sub>: (ZnO)<sub>0.5sub> Nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Pan, Wei [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Jiang, Y. X. [Georgia Inst. of Technology, Atlanta, GA (United States); Ihlefeld, Jon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lu, Ping [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lee, Stephen R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-12-01

A great deal of research has been carried out in oxide material systems. Among them, ZnO and La<sub>0.7sub>Sr>0.3sub>MnO>3sub> (LSMO) are of particular interest due to their superb optical properties and colossal magneto-resistive effect. Here, we report our recent results of magneto-transport studies in self-assembled, epitaxial (ZnO)0.5:(La<sub>0.7sub>Sr>0.3sub>MnO>3sub>)>0.5sub> nanocomposite films.

Diagramas de Voronoi para a definição de áreas de abrangência de hospitais públicos no Município do Rio de Janeiro

Directory of Open Access Journals (Sweden)

Flavio Astolpho Vieira Souto Rezende

2000-06-01

Full Text Available No planejamento de recursos em saúde é importante o conhecimento da área de abrangência de uma unidade. Os Diagramas de Voronoi constituem uma técnica para tal; são polígonos construídos de tal forma que as bordas de polígonos adjacentes encontram-se eqüidistantes de seus respectivos pontos geradores. Uma modificação nas áreas de abrangência assim definidas é sua ponderação (Diagramas de Voronoi ponderados, representando a capacidade da unidade de forma mais real. No presente trabalho foram utilizados, como pontos geradores, 21 hospitais gerais públicos no Rio de Janeiro, RJ. Inicialmente foram criados os Diagramas de Voronoi sem ponderação, e, a partir destes, os diagramas ponderados, empregando-se como variável de ponderação as estimativas de internação anual para cada unidade. Na divisão clássica, áreas de abrangência similares foram atribuídas a hospitais com características diferenciadas, problema esse contornado no método ponderado. O método é de simples implementação e visualização, utiliza dados de fácil acesso e independe de parâmetros arbitrários ou geopolíticos. Portanto, esses diagramas podem fornecer, a gerentes de saúde, uma visão mais realista para o planejamento da demanda de suas unidades.

Characterization of dispersion of a nano composites PP/TiO{sub 2} non modified; Caracterizacao da dispersao dos nanocompositos de PP/TiO{sub 2} nao modificados

Energy Technology Data Exchange (ETDEWEB)

Soares, Igor L.; Tavares, Maria I.B.; Silva, Vanessa A. da; Legramanti, Cintia, E-mail: igorl@ima.ufrj.br [Universidade Federal do Rio de Janeiro - UFRJ, Instituto de Macromoleculas - IMA (Brazil); Luetkmeyer, Leandro [Universidades Federais do Mato Grosso - UFMT, Escritorio de Inovacao Tecnologica - EIT (Brazil)

2011-07-01

Polymeric nano composites are composite materials where an inorganic particle, which has a dimension in the nanometer range, is dispersed in a polymer matrix. Nano composites, using polypropylene (PP) as matrix polymer and titanium dioxide (TiO{sub 2}) as filler, have great versatility in marketing applications, this factor is inherent in the PP and the inherent ability photo degraded TiO{sub 2} particles. This combination can lead to a widely used material and a degradation time after discharge reduced, there by becoming, a residue of low environmental impact. This study aimed to evaluate the dispersion and particle distribution of TiO{sub 2}, non modified, in PP matrix, using the process of preparation by melt extrusion pathway and characterization of the materials obtained: on the molecular dynamics, using low field NMR solid state, measures the relaxation time spin-network (T{sub 1}H); morphology using XRD technique, and thermal analysis technique with the TGA of pure PP and nano composites PP/TiO{sub 2}. (author)

First-principles study of electronic properties of Si doped FeSe{sub 0.9} alloys

Energy Technology Data Exchange (ETDEWEB)

Kumar, Sandeep, E-mail: sandeep@phy.iitb.ac.in; Singh, Prabhakar P. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

2016-05-23

We have performed first-principles study of electronic and superconducting properties of FeSe{sub 0.9-x}Si{sub x} (x = 0.0, 0.05) alloys using Korringa-Kohn-Rostoker Atomic Sphere Approximation within the coherent potential approximation (KKR-ASA-CPA). In our calculations, we used the local density approximation (LDA) for the exchange correlation potential. Our calculations show that these alloys are nonmagnetic in nature. We found that the substitution of Si at Se site into FeSe{sub 0.9} made subtle affects in the electronic structure with respect to the parent FeSe. The results have been analyzed in terms of changes in the density of states (DOS), band structures, Fermi surfaces and the superconducting transition temperature of FeSe{sub 0.9} and FeSe{sub 0.85}Si{sub 0.05} alloys.

Representações e expectativas dos profissionais dos serviços de pediatria do Hospital de Braga relativamente à intervenção dos "Doutores Palhaços"

OpenAIRE

Almeida, Isabel Cristina Ferreira de

2012-01-01

Dissertação de mestrado em Estudos da Criança (área de especialização em Intervenção Psicossocial com Crianças, Jovens e Famílias) Neste estudo são dadas a conhecer as representações e expetativas dos profissionais de saúde dos serviços de pediatria do Hospital de Braga, relativamente ao trabalho dos palhaços profissionais da Operação Nariz Vermelho: os “Doutores Palhaços” (DP). A recolha dos dados realizou-se cerca de um mês antes do início da intervenção dos DP naquela unidad...

Local study of the Mg{sub 1-x}Al{sub x}B{sub 2} single crystals by scanning tunneling spectroscopy in magnetic field up to 3 Tesla

Energy Technology Data Exchange (ETDEWEB)

Giubileo, F. [CNR-INFM Laboratorio Regionale SUPERMAT, Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, via Salvador Allende, 84081 Baronissi, SA (Italy)], E-mail: giubileo@sa.infn.it; Bobba, F.; Scarfato, A.; Cucolo, A.M. [CNR-INFM Laboratorio Regionale SUPERMAT, Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, via Salvador Allende, 84081 Baronissi, SA (Italy); Kohen, A.; Roditchev, D. [Institut des Nanosciences de Paris, INSP, Universite P. et M. Curie Paris 6, CNRS, UMR 75-88, Paris (France); Zhigadlo, N.D.; Karpinski, J. [Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich (Switzerland)

2008-04-01

We have performed local tunneling spectroscopy on high quality Mg{sub 1-x}Al{sub x}B{sub 2} single crystals by means of variable temperature scanning tunneling spectroscopy in magnetic field up to 3 Tesla. Single gap conductance spectra due to c-axis tunneling were extensively measured, probing different amplitudes of the three-dimensional {delta}{sub {pi}} as a function of Al content (i.e. as a function of the critical temperature T{sub C}). Temperature and magnetic field dependences of the conductance spectra were studied in S-I-N configuration: the effect of the doping resulted in a monotonous reduction of the locally measured T{sub C} down to 24 K for x = 0.2. The magnetic field dependence was studied in a local way: An estimation for upper critical field H{sub c2} was inferred from the evolution of the tunneling spectra with the field perpendicular to the sample surface, for different doping levels. The high spatial resolution of the STS technique allowed us to evidence possible non-homogeneities of the superconducting properties on the sample surface with variation of in the same sample depending on different local levels of doping. The locally measured upper critical field resulted to vary for different dopings, and the maximum value H{sub c2}{approx_equal}3T was found for samples with T{sub C}=33 K. The evolution of the density of states (DOS) was found to be characterized by two distinct regimes separated by a crossover region. Our results indicate a rapid suppression of the intrinsic term in {pi}-band superconductivity for 0 T < B < 0.5 T. At high fields (0.8 T < B < 3 T) the superconductivity in the {pi}-band survives uniquely due to the coupling to the {sigma}-band. The shape of tunneling spectra suggests an important role played by the quasiparticle inter-band scattering.

Investigations of the R<sub>5sub>(Si_xGe>1-xsub>)>4sub> Intermetallic Compounds by X-Ray Resonant Magnetic Scattering

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Tan, Lizhi [Iowa State Univ., Ames, IA (United States)

2008-08-18

The XRMS experiment on the Gd<sub>5sub>Ge>4sub> system has shown that, below the Neel temperature, T<sub>N> = 127 K, the magnetic unit cells is the same as the chemical unit cell. From azimuth scans and the Q dependence of the magnetic scattering, all three Gd sites in the structure were determined to be in the same magnetic space group Pnma. The magnetic moments are aligned along the c-axis and the c-components of the magnetic moments at the three different sites are equal. The ferromagnetic slabs are stacked antiferromagnetically along the b-direction. They found an unusual order parameter curve in Gd<sub>5sub>Ge>4sub>. A spin-reorientation transition is a possibility in Gd<sub>5sub>Ge>4sub>, which is similar to the Tb<sub>5sub>Ge>4sub> case. Tb<sub>5sub>Ge>4sub> possesses the same Sm<sub>5sub>Ge>4sub>-type crystallographic structure and the same magnetic space group as Gd<sub>5sub>Ge>4sub> does. The difference in magnetic structure is that Tb<sub>5sub>Ge>4sub> has a canted one but Gd<sub>5sub>Ge>4sub> has nearly a collinear one in the low temperature antiferromagnetic phase. The competition between the magneto-crystalline anisotropy and the nearest-neighbor magnetic exchange interactions may allow a 3-dimensional canted antiferromagnetic structure in Tb<sub>5sub>Ge>4sub>. The spin-reorientation transition in both Gd<sub>5sub>Ge>4sub> and Tb<sub>5sub>Ge>4sub> may arise from the competition between the magnetic anisotropy from the spin-orbit coupling of the conduction electrons and the dipolar interactions anisotropy.

Modification of the stability of polymorph nanometric TiO{sub 2} by surface excess of SnO{sub 2}; Modificacao da estabilidade dos polimorfos de TiO{sub 2} nanometrico pelo excesso de superficie de SnO{sub 2}

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Matioli, A.; Miagava, J.; Gouvea, D., E-mail: dgouvea@usp.br [Laboratorio de Processos Ceramicos, Departamento de Engenharia Metalurgica e de Materiais, Escola Politecnica da Universidade de Sao Paulo, SP (Brazil)

2012-01-15

Some oxides present stable polymorph forms only for nanometric size. Anatase (TiO{sub 2}) is stable in nanosized particles while the rutile phase is stable for larger ones. This results from the surface energies contribution, which modifies the total energy of the system and the phase stability. In turn, surface energy can be altered by the heterogeneous additives distribution, such as surface segregation or surface excess. This study investigated the action of the SnO{sub 2} on the polymorph stability of nanosized TiO{sub 2} prepared by polymeric precursor derived from the Pechini method. It appears that there is a strong effect on the stability of anatase and rutile with the SnO{sub 2} concentration while various surface properties are altered as well as a strong change in particle size, indicating that even though there are no large differences in the charge and size between the two cations, a surface phenomenon may underlie the stability of crystalline phases (author)

O conhecimento tático declarativo dos levantadores campeões de voleibol The tactical declarative knowledge of the volleyball champions setters

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Cristino Julio Alves da Silva Matias

2013-03-01

Full Text Available O objetivo do estudo consistiu em analisar o conhecimento tático declarativo do levantador de voleibol, expert, dos Escalões Iniciais ao Adulto. Como voluntários a amostra teve dezoito levantadores. Dois levantadores, um de cada sexo, campeões estaduais (SP-MG dos escalões: Mirim (sub-14, Infantil (sub-15, Infanto (sub-17 e Juvenil (sub-20. Houve também a participação dos campeões do escalão Adulto (Superliga, um masculino e outro feminino. Empregou-se como instrumento o Teste de Conhecimento Tático Declarativo do Levantador (MATIAS; GRECO, 2009. Os resultados demonstraram a expertise tática declarativa dos levantadores, pois todos foram capazes de tomar a decisão correta e justificar com exatidão a decisão. Para tal, aplicou-se o teste de correlação de Spearman que demonstrou uma associação significativa em todos os escalões (p=0,000. Por meio da aplicação do teste de Kruskall-Wallis e Mann-Whitney verificou-se a diferença do escalão Adulto perante os demais, em ambos os sexo, pois o valor de significância dos testes foram inferiores a 0,05. Os resultados apurados sugerem que equipes campeãs possuem, como responsável pela organização ofensiva, levantadores com compreensão declarativa das ações inerentes a distribuição de jogo.The aim of this study consisted of the volleyball setter's (expert declarative knowledge analysis. The sample counted on eighteen setters as volunteers. Two of them, each one of a different gender, distributed equally among categories of competition: 14 under division, 15 under division, 17 under division and 20 under division. All champions for the state of SP or MG. There was also a participation of two setters that were champions in the Adult category (Professional National Championship: Superliga, each one of a different gender. It was employed the Setter's Tactical Declarative Knowledge Test (MATIAS; GRECO, 2009. The results showed the setter's tactical declarative expertise, because

Hydrothermal synthesis and crystal structures of Na{sub 2}Be{sub 3}(SeO{sub 3}){sub 4}.H{sub 2}O and Cs{sub 2}[Mg(H{sub 2}O){sub 6}]{sub 3}(SeO{sub 3}){sub 4}

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Shen, Chen; Mei, Dajiang; Sun, Chuanling; Liu, Yunsheng; Wu, Yuandong [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science (China)

2017-09-04

The selenites, Na{sub 2}Be{sub 3}(SeO{sub 3}){sub 4}.H{sub 2}O and Cs{sub 2}[Mg(H{sub 2}O){sub 6}]{sub 3}(SeO{sub 3}){sub 4}, were synthesized under hydrothermal conditions. The crystal structures of Na{sub 2}Be{sub 3}(SeO{sub 3}){sub 4}.H{sub 2}O and Cs{sub 2}[Mg(H{sub 2}O){sub 6}]{sub 3}(SeO{sub 3}){sub 4} were determined by single-crystal X-ray diffractions. Na{sub 2}Be{sub 3}(SeO{sub 3}){sub 4}.H{sub 2}O crystallizes in the triclinic space group P1 (no. 2) with unit cell parameters a = 4.8493(9), b = 12.013(2), c = 12.077(2) Aa, and Z = 2, whereas Cs{sub 2}[Mg(H{sub 2}O){sub 6}]{sub 3}(SeO{sub 3}){sub 4} crystallizes in the monoclinic space group C2/m (no. 12) with lattice cell parameters a = 12.596(6), b = 7.297(4), c = 16.914(8) Aa, and Z = 2. Na{sub 2}Be{sub 3}(SeO{sub 3}){sub 4}.H{sub 2}O features a three-dimensional open framework structure formed by BeO{sub 4} tetrahedra and SeO{sub 3} trigonal pyramids. Na cations and H{sub 2}O molecules are located in different tunnels. Cs{sub 2}[Mg(H{sub 2}O){sub 6}]{sub 3}(SeO{sub 3}){sub 4} has a structure composed of isolated [Mg(H{sub 2}O){sub 6}] octahedra and SeO{sub 3} trigonal pyramids interacted by hydrogen bonds, and Cs cations are resided in-between. Both compounds were characterized by thermogravimetric analysis and FT-IR spectroscopy. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Em defesa dos direitos da criança no ambiente hospitalar: o exercício da advocacia em saúde pelos enfermeiros

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Bruna Ruoso da Silva Neutzling

Full Text Available Resumo Objetivo: Conhecer as ações dos enfermeiros na defesa dos direitos das crianças hospitalizadas. Métodos: Pesquisa qualitativa, desenvolvida em duas instituições hospitalares do Sul do Brasil, com 12 enfermeiros, - por meio de entrevistas semiestruturadas, em junho de 2014. Resultados: Foi possível perceber que os enfermeiros exercem a defesa dos direitos das crianças hospitalizadas através de ações que visam garantir o direito à vida, à dignidade e à saúde. Conclusões: As ações dos enfermeiros na defesa dos direitos das crianças hospitalizadas, foram realizadas, principalmente, por meio de orientações que possibilitam a participação da criança nos seus cuidados e a promoção da autonomia dos pais ou responsáveis para a tomada de decisões quanto aos cuidados com a saúde da criança. Implicações para a prática: O reconhecimento das ações de advocacia em saúde constitui um avanço para a prática da enfermagem, pois oportuniza aos enfermeiros subsídios para o enfrentamento de futuras vivências no contexto pediátrico.

The Nature of the Distinctive Microscopic Features in R<sub>5sub>(Si_xGe>1-xsub>)>4sub> Magnetic Refrigeration Materials

Energy Technology Data Exchange (ETDEWEB)

Ugurlu, Ozan [Iowa State Univ., Ames, IA (United States)

2006-01-01

Magnetic refrigeration is a promising technology that offers a potential for high energy efficiency. The giant magnetocaloric effect of the R<sub>5sub>(Si<sub>x>, Ge<sub>1-xsub>)>4sub> alloys (where R=rare-earth and O ≤ x ≤ 1), which was discovered in 1997, make them perfect candidates for magnetic refrigeration applications. In this study the microstructures of Gd<sub>5sub>(Six>, Ge<sub>1-xsub>)>4sub> alloys have been characterized using electron microscopy techniques, with the focus being on distinctive linear features first examined in 1999. These linear features have been observed in R<sub>5sub>(Six>, Ge<sub>1-xsub>)>4sub> alloys prepared from different rare-earths (Gd, Tb, Dy and Er) with different crystal structures (Gd<sub>5sub>Si>4sub>-type orthorhombic, monoclinic and Gd<sub>5sub>Ge>4sub>-type orthorhombic). Systematic scanning electron microscope studies revealed that these linear features are actually thin-plates, which grow along specific directions in the matrix material. The crystal structure of the thin-plates has been determined as hexagonal with lattice parameters a=b=8.53 Å and c=6.40 Å using selected area diffraction (SAD). Energy dispersive spectroscopy analysis, carried out in both scanning and transmission electron microscopes, showed that the features have a composition approximating to R<sub>5sub>Six,Ge>1-xsub>)>3sub>.phase. Orientation relationship between the matrix and the thin-plates has been calculated as [- 1010](1-211)<sub>p>//[010](10-2)<sub>m>. The growth direction of the thin plates are calculated as (22 0 19) and (-22 0 19) by applying the Ag approach of Zhang and Purdy to the SAD patterns of this system. High Resolution TEM images of the Gd_{5sub>Ge>4sub> were used to study the crystallographic relationship. A terrace-ledge structure was observed at the interface and a 7° rotation of the reciprocal lattices}

Observation of the strain-driven charge-ordered state in La sub 0 sub . sub 7 sub C a sub 0 sub . sub 3 MnO sub 3 sub - sub d elta thin film with oxygen deficiency

CERN Document Server

Prokhorov, V G; Kaminsky, G G; Svetchnikov, V L; Zandbergen, H W; Lee, Y P; Park, J S; Kim, K W

2003-01-01

The magnetic and transport properties of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 sub - sub d elta films with an oxygen deficiency (delta approx 0.1) and a La sub 0 sub . sub 9 Ca sub 0 sub . sub 1 MnO sub 3 film with the stoichiometric oxygen content are investigated in a wide temperature range. It is shown that the charge-ordered insulating (COI) state is observed for a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with thickness d <= 30 nm, which manifests mainly a cubic crystal structure with an anomalously small lattice parameter for this composition. An increase in the film thickness (d approx 60 nm) leads to a structural transition from the lattice-strained cubic to the relaxed rhombohedral phase, is accompanied by a shift of the Curie point (T sub C) to lower temperature and a frustration of the COI state. The magnetic and transport properties of the La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with d approx 60 nm are similar to those exhibi...

Anisotropy of superconducting transformation in magnetic fields in Nd sub 1 sub . sub 8 sub 5 Ce sub 0 sub . sub 1 sub 5 CuO sub 4 monocrystal

CERN Document Server

Panova, G K; Chernoplekov, N A; Emelchenko, G A; Malyuk, A N; Lin, S T

2002-01-01

The anisotropy of the superconducting properties of the Nd sub 1 sub . sub 8 sub 5 Ce sub 0 sub . sub 1 sub 5 CuO sub 4 monocrystal is studied by resistance within the temperature range of 2-30 K in the 0, 1, 2, 4, 6 Tl magnetic fields in the a-b plane. The T sub c (H) and H sub c sub 2 (T) strong anisotropy was observed by the magnetic field different orientation in the a-b plane. The zero direction in the gap of the order parameter is determined. The analysis of the experimental data shows, that such a result may be related to the change in the symmetry in the copper atoms surrounding, leading to its reduction from the tetragonal to orthorhombic one in the low-temperature area. The comparison with the La sub 1 sub . sub 8 sub 5 Sr sub 0 sub . sub 1 sub 5 CuO sub 4 gives all grounds to suppose, that the superconductivity mechanism in the electron- and hole-doped superconductor is similar and the observed difference is connected with the structure peculiarities

Raman spectra of the solid-solution between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 and RbCa sub 2 Nb sub 3 O sub 1 sub 0

CERN Document Server

Kim, H J; Yun, H S

2001-01-01

A site preference of niobium atom in Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) and RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0), which are the solid-solutions between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 are RbCa sub 2 Nb sub 3 O sub 1 sub 0 , has been investigated by Raman spectroscopy. The Raman spectra of Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0) showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed onl...

Methanesulfonates of high-valent metals. Syntheses and structural features of MoO{sub 2}(CH{sub 3}SO{sub 3}){sub 2}, UO{sub 2}(CH{sub 3}SO{sub 3}){sub 2}, ReO{sub 3}(CH{sub 3}SO{sub 3}), VO(CH{sub 3}SO{sub 3}){sub 2}, and V{sub 2}O{sub 3}(CH{sub 3}SO{sub 3}){sub 4} and their thermal decomposition under N{sub 2} and O{sub 2} atmosphere

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Betke, Ulf; Neuschulz, Kai; Wickleder, Mathias S. [Carl von Ossietzky University of Oldenburg, Institute of Pure and Applied Chemistry (Germany)

2011-11-04

Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO{sub 3}, UO{sub 2}(CH{sub 3}COO){sub 2}.2 H{sub 2}O, Re{sub 2}O{sub 7}(H{sub 2}O){sub 2}, and V{sub 2}O{sub 5} with CH{sub 3}SO{sub 3}H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO{sub 2}(CH{sub 3}SO{sub 3}){sub 2} (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm{sup 3}, Z=8) contains [MoO{sub 2}] moieties connected by [CH{sub 3}SO{sub 3}] ions to form layers parallel to (100). UO{sub 2}(CH{sub 3}SO{sub 3}){sub 2} (P2{sub 1}/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, β=112.80(1) {sup circle}, V=1.8937(3) nm{sup 3}, Z=8) consists of linear UO{sub 2}{sup 2+} ions coordinated by five [CH{sub 3}SO{sub 3}] ions, forming a layer structure. VO(CH{sub 3}SO{sub 3}){sub 2} (P2{sub 1}/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, β=113.66(1) {sup circle}, V=0.8290(2) nm{sup 3}, Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO{sub 3}(CH{sub 3}SO{sub 3}) (P anti 1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), β=96.11(2), γ=99.04(2) {sup circle}, V=1.1523(4) nm{sup 3}, Z=8) a chain structure exhibiting infinite O-[ReO{sub 2}]-O-[ReO{sub 2}]-O chains is formed. Each [ReO{sub 2}]-O-[ReO{sub 2}] unit is coordinated by two bidentate [CH{sub 3}SO{sub 3}] ions. V{sub 2}O{sub 3}(CH{sub 3}SO{sub 3}){sub 4} (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, β=102.58(3), V=1.5637(5) pm{sup 3}, Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH{sub 3}SO{sub 3}] ligands. Additional methanesulfonate ions connect the [V{sub 2}O{sub 3}] groups along [001]. Thermal decomposition of the compounds was monitored under N{sub 2} and O{sub 2} atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N{sub 2} the decomposition proceeds

Identification of Raman peaks of high-T{sub c} cuprates in normal state through density of states

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Bishoyi, K.C. [P.G. Department of Physics, F.M. College (Auto.), Balasore 756 001 (India)]. E-mail: bishoyi@iopb.res.in; Rout, G.C. [Condensed Matter Physics Group, Govt. Science College, Chatrapur 761 020, Orissa (India); Behera, S.N. [Physics Enclave, H.I.G.-23/1, Housing Board Phase-I, Chandrasekharpur, Bhubaneswar 7510016 (India)

2007-05-31

We present a microscopic theory to explain and identify the Raman spectral peaks of high-T{sub c} cuprates R{sub 2-x}M{sub x}CuO{sub 4} in the normal state. We used electronic Hamiltonian prescribed by Fulde in presence of anti-ferromagnetism. Phonon interaction to the hybridization between the conduction electrons of the system and the f-electrons has been incorporated in the calculation. The phonon spectral density is calculated by the Green's function technique of Zubarev at zero wave vector and finite (room) temperature limit. The four Raman active peaks (P{sub 1}-P{sub 4}) representing the electronic states of the atomic sub-systems of the cuprate system are identified by the calculated quasi-particle energy bands and electron density of states (DOS). The effect of interactions on these peaks are also explained.

Electronic phase separation in the rare-earth manganates (La sub 1 sub - sub x Ln sub x) sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 (Ln = Nd, Gd and Y)

CERN Document Server

Sudheendra, L

2003-01-01

Electron transport and magnetic properties of three series of manganates of the formula (La sub 1 sub - sub x Ln sub x) sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 with Ln = Nd, Gd and Y, wherein only the average A-site cation radius (r sub A ) and associated disorder vary, without affecting the Mn sup 4 sup + /Mn sup 3 sup + ratio, have been investigated in an effort to understand the nature of phase separation. All three series of manganates show saturation magnetization characteristic of ferromagnetism, with the ferromagnetic T sub c decreasing with increasing x up to a critical value of x, x sub c (x sub c = 0.6, 0.3, 0.2 respectively for Nd, Gd, Y). For x > x sub c , the magnetic moments are considerably smaller, showing a small increase around T sub M , the value of T sub M decreasing slightly with increase in x or decrease in (r sub A ). The ferromagnetic compositions (x x sub c are insulating. The magnetic and electrical resistivity behaviour of these manganates is consistent with the occurrence...

Thermoelectric power measurements in Fe doped La sub 0 sub . sub 6 sub 5 Ca sub 0 sub . sub 3 sub 5 MnO sub 3

CERN Document Server

Aslam, A; Zubair, M; Akhtar, M J; Nadeem, M

2002-01-01

We report measurements of the thermoelectric power (TEP) on the La sub 0 sub . sub 6 sub 5 Ca sub 0 sub . sub 3 sub 5 Mn sub 1 sub - sub x Fe sub x O sub 3 system for 0.00 <= x <= 0.07. The ferromagnetic and metallic transition temperatures are lowered and the TEP shows an increasingly positive trend with the addition of Fe. We also observe a clear magnetic contribution that manifests itself as a peak in the TEP close to the critical temperature. The activation energies determined from the TEP are seen to be insensitive to the Fe content. The data are interpreted firstly as showing a decrease in the density of active holes, i.e. holes that can participate in the hopping process, with increasing Fe content. Secondly the data suggest the role of magnetic scattering due to the clusters formed by the antiferromagnetically coupled Fe. Abrupt changes in the variation of the TEP are observed at the concentration region x approx 0.04 consistent with the hole density variation and with previously reported transp...

OS SACRAMENTAIS, SACRAMENTOS DOS POBRES

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Victor Codina

1990-01-01

Full Text Available Basta ter tido um pouco de experiência pastoral com setores populares, concretamente na América Latina, para constatar a importância dos sacramentais na vida cristã do povo. Além das manifestações de piedade popular que se costuma estudar sob a rubrica de religiosidade popular (peregrinações, festas de padroeiro, procissões..., gostaria de destacar aqui outros elementos mais estreitamente ligados ao mundo dos sacramentos, ainda que não formem parte dos sete sacramentos tridentinos.

Camponeses e esquecimento na Antiguidade Tardia: as revoltas dos bagaudas e dos circunceliões

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Uiran Gebara da Silva

2016-12-01

Full Text Available Esse artigo apresenta alguns dos problemas com os quais eu tive de lidar ao realizar um estudo comparativo entre dois conjuntos de revoltas rurais do Império Romano tardio: as revoltas dos bagaudas na Gália e dos circunceliões na África. O artigo toma como eixo articulador a hipótese lançada por E. A. Thompson sobre o papel do esquecimento na produção dos relatos antigos sobre os bagaudas e a problematiza. Num segundo momento o artigo trata do problema relacionado à compreensão do caráter social de ambos os grupos, levando em consideração os múltiplos relatos presentes nas fontes antigas e as divergentes interpretações modernas sobre eles, enfatizando a necessidade de se reconhecer a tópica da inversão social como um elemento que diferencia os relatos sobre os revoltosos daqueles sobre a bandidagem. Outro elemento importante é o reconhecimento da heterogeneidade dos discursos cristãos com relação às classes subalternas e aos revoltosos, que apontam não para um fortalecimento do patronato rural, mas para o enfraquecimento ou para a crise dessas relações no campo tardo-romano.

EDUCAÇÃO AMBIENTAL NA ESCOLA BÁSICA: REFLEXÕES SOBRE A PRÁTICA DOS PROFESSORES

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Marília Freitas de Campos Tozoni-Reis

2012-12-01

Full Text Available A inserção quantitativa de práticas educativas ambientais nas escolas de educação básica no Brasil já é uma realidade, embora os estudos indiquem sua fragilidade qualitativa. Entre os aspectos a serem compreendidos em busca dessa qualidade, está a prática profissional dos professores. São muitas as questões que se pode colocar para essa análise, mas este artigo selecionou a formação e a atuação dos professores nas escolas públicas - e a questão da autonomia -, buscando subsídios teóricos nos estudos sobre esses temas já consolidados na área da educação, para pensar sua contribuição para a educação ambiental como processo educativo consistente.

The borosulfates K{sub 4}[BS{sub 4}O{sub 15}(OH)], Ba[B{sub 2}S{sub 3}O{sub 13}], and Gd{sub 2}[B{sub 2}S{sub 6}O{sub 24}

Energy Technology Data Exchange (ETDEWEB)

Gross, Peter; Kirchhain, Arno; Hoeppe, Henning A. [Universitaet Augsburg, Institut fuer Physik (Germany)

2016-03-18

K{sub 4}[BS{sub 4}O{sub 15}(OH)], Ba[B{sub 2}S{sub 3}O{sub 13}], and Gd{sub 2}[B{sub 2}S{sub 6}O{sub 24}] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid H[B(HSO{sub 4}){sub 4}] which is subsequently reacted in an open system with anhydrous chlorides of K, Ba, and Gd to the respective borosulfates and a volatile molecule (HCl). Furthermore, protonated borosulfates should be accessible by appropriate stoichiometry of the starting materials, particularly in closed systems, which inhibit deprotonation of H[B(HSO{sub 4}){sub 4}] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (Ba[B{sub 2}S{sub 3}O{sub 13}] with band-silicate topology and Gd{sub 2}[B{sub 2}S{sub 6}O{sub 24}] with cyclosilicate topology) and the first hydrogen borosulfate K{sub 4}[BS{sub 4}O{sub 15}(OH)]. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Exploration of R<sub>2sub>XM>2sub> (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd<sub>2sub>AlGe>2sub> and Analysis of the U<sub>3sub>Si>2sub> and Zr<sub>3sub>Al>2 sub>Structure Types

Energy Technology Data Exchange (ETDEWEB)

McWhorter, Sean William [Iowa State Univ., Ames, IA (United States)

2006-01-01

In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> several new compounds were synthesized with different crystal structures, but similar structural features. In Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> can be thought of as being formed from two 3²434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd<sub>2sub>MgGe>2sub> and Gd<sub>2sub>InGe>2sub> both possess the same 3²434 nets of Gd atoms as Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>, but these nets are connected differently, forming the Mo<sub>2sub>FeB>2sub> crystal structure. A search of the literature revealed that compounds with the composition R<sub>2sub>XM>2sub> (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo<sub>2sub>FeB>2sub>, Zr<sub>3sub>Al>2sub>, Mn<sub>2sub>AlB>2sub> and W<sub>2sub>CoB>2sub> crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd<sub>2sub>AlGe>2sub> forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

Cation composition and oxygen content dependence of crystal structure and T sub c for Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y

CERN Document Server

Idemoto, Y; Koura, N; Kamiyama, T; Oikawa, K; Izumi, F

2003-01-01

Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y (Tl-2223 system) superconducting oxides with various Tl contents and Cu contents were prepared. We investigated the relation between crystal structure and superconducting property dependence of Tl and Cu content. First, we obtained an almost single-phase material at a Tl content 2-x = 1.7 and the Tl-2223 phase remained the main phase in the region of 2 - x >= 0.631 of Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 O sub y. T sub c was about 120 K for the Tl-2223 in a wide range of 0.631 <= 2 - x <= 1.761. Second, we obtained a single-phase at 2 - x = 1.777 and Cu content 3 + z = 3.284 of Tl sub 2 sub - sub x Ba sub 2 Ca sub 2 Cu sub 3 sub + sub z O sub y. The T sub c (zero) dependence of Cu/Tl ratio, showed a maximum value of 122 K at Cu/Tl ratio = 2.026. Based on results of crystal structure refinements by powder neutron diffraction, it was found that the change in bond length and angle dependence of average Cu valence were similar fo...

Pressure-induced instability of magnetic order in Kondo-lattice system. Neutron diffraction study of the pseudo-binary alloy system Ce(Ru sub 0 sub . sub 9 sub 0 Rh sub 0 sub . sub 1 sub 0) sub 2 (Si sub 1 sub - sub y Ge sub y) sub 2

CERN Document Server

Watanabe, K; Kanadani, C; Taniguchi, T; Kawarazaki, S; Uwatoko, Y; Kadowaki, H

2003-01-01

Neutron diffraction experiments have been carried out to study the nature of the magnetic order of the pseudo-binary alloy system Ce(Ru sub 0 sub . sub 9 sub 0 Rh sub 0 sub . sub 1 sub 0) sub 2 (Si sub 1 sub - sub y Ge sub y) sub 2. Response of the ordered atomic magnetic moment, mu, the transition temperature, T sub N , and the magnitude of the magnetic modulation vector, q, to the chemical pressure and also to the applied hydrostatic pressure, P, were examined at low temperatures. When y changes, all of mu, T sub N and q show a sudden alteration of the manner of the y-dependence at around y - 0.08. The P-dependence of q shows quite different features for different y's of 0.0, 0.2 and 0.25. On the basis of these observations the possibility of a pressure-induced alternation of the magnetic regime of the order is discussed. (author)

Unidirectional spin density wave state in metallic (Sr<sub>1-xsub>Lax)>2sub>IrO>4sub>

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiang; Schmehr, Julian L.; Islam, Zahirul; Porter, Zach; Zoghlin, Eli; Finkelstein, Kenneth; Ruff, Jacob P. C.; Wilson, Stephen D.

2018-01-09

Materials that exhibit both strong spin–orbit coupling and electron correlation effects are predicted to host numerous new electronic states. One prominent example is the J<sub>eff> = 1/2 Mott state in Sr<sub>2sub>IrO>4sub>, where introducing carriers is predicted to manifest high temperature superconductivity analogous to the S=1/2 Mott state of La<sub>2sub>CuO>4sub>. While bulk super- conductivity currently remains elusive, anomalous quasiparticle behaviors paralleling those in the cuprates such as pseudogap formation and the formation of a d-wave gap are observed upon electron-doping Sr<sub>2sub>IrO>4sub>. Here we establish a magnetic parallel between electron-doped Sr<sub>2sub>IrO>4sub> and hole-doped La<sub>2sub>CuO>4sub> by unveiling a spin density wave state in electron-doped Sr<sub>2sub>IrO>4sub>. Our magnetic resonant X-ray scattering data reveal the presence of an incom- mensurate magnetic state reminiscent of the diagonal spin density wave state observed in the monolayer cuprate (La<sub>1-xsub>Sr_x)>2sub>CuO>4sub>. This link supports the conjecture that the quenched Mott phases in electron-doped Sr<sub>2sub>IrO>4sub> and hole-doped La<sub>2sub>CuO>4sub> support common competing electronic phases.

CONSIDERAÇÕES SOBRE RESÍDUOS SÓLIDOS DE SERVIÇOS DE SAÚDE

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Maria Auxiliadora Gomes de Mello Brito

2000-12-01

Full Text Available O presente estudo trata da situação dos resíduos sólidos de serviços de saúde ( RSSS e aborda a coleta seletiva de resíduos como uma alternativa para a redução do volume de lixo enviado para deposição ao solo. O trabalho lança uma discussão a respeito do "lixo" sob a ótica da educação ambiental e insere os RSSS nesse contexto. Pretende, através de abordagens educativas, despertar nas pessoas envolvidas com a geração de resíduos, e em especial os resíduos de serviços de saúde, uma consciência crítica sobre a sua responsabilidade como gerador de "lixo" e poluidor do meio ambiente. A mudança de atitudes resultará em combate ao desperdício e diminuição da geração dos diferentes tipos de resíduos com destino ao aterro sanitário.

A utilização de mapas conceituais como recurso didático para a construção e inter-relação de conceitos

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Valter Carabetta Júnior

Full Text Available Os mapas conceituais, criados por Novak com base na teoria de Ausubel, podem constituir para os alunos uma estratégia pedagógica de grande relevância para a construção de conceitos científicos, ajudando-os a integrar e relacionar informações e atribuir significado ao que estão estudando. Este artigo descreve o trabalho realizado com alunos de um curso de Medicina usando mapas conceituais, tomando por base os "temas geradores" criados na disciplina de Atenção Básica em Saúde a partir da constatação dos principais problemas de saúde da região em que está localizada a escola médica. A utilização dos mapas constituiu um recurso metodológico relevante por se alinhar a uma formação teórica adequada às necessárias intervenções na realidade estudada e por facilitar a apropriação de conceitos científicos pelos alunos.

O contencioso do algodão: cenários para mudança na política de subsídios dos EUA The cotton dispute: scenarios for change in the U.S. subsidies policy

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Thiago Lima

2006-06-01

Full Text Available Neste artigo se examina a não adequação dos EUA ao parecer da OMC no contencioso do algodão. Argumenta-se que tal atitude é irracional do ponto de vista do Estado unitário e racional, mas que pode ser explicada por meio de uma perspectiva fragmentada do Estado. Assim, embora a administração desejasse a adequação, cotonicultores e congressistas potencializados por instituições políticas constrangeram as mudanças necessárias. Ao final são projetados cenários para a modificação da política de subsídios agrícolas dos EUA.The article examines the non compliance of the United States with the WTO report on the cotton dispute. It is argued that that attitude is not rational from the unitary and rational State point of view, but it can be explained through a fragmented perspective of the State. Thus, although the administration desired to comply, cotton growers and congressists, strengthened by political institutions, constrained the needed changes. In the end, scenarios about possible changes in the U.S. agriculture subsidy policy are projected.

Magnetic properties and inhomogeneous phase transition in (Fe sub x Co sub 0 sub . sub 5 sub - sub x)Pt sub 0 sub . sub 5 films

CERN Document Server

Jang, P W; Na, J G; Lee, S R

1999-01-01

(Fe sub x Co sub 0 sub . sub 5 sub - sub x)Pt sub 0 sub . sub 5 ternary thin films were deposited on glass substrates by using a dc sputtering method at room temperature and were subsequently annealed at 700 .deg. C in a high vacuum. A high degree of the (111) preferred orientation could be obtained in all the as-deposited films and was not destroyed, even though post annealing. The CoPt and the FePt binary alloys were completely mixed and had a L1 sub o -type ordered structure, as confirmed by single (222) peaks and by the linear variation of the lattice constant a sub o. The ordered structure of the FePt alloy was thought to have formed from the disordered structure by an inhomogeneous process, which was confirmed by the asymmetric peak shapes. The lattice parameter a sub o varied linearly with the Fe content while the coercivity showed a minimum value at the equiatomic composition of the Fe and the Co atoms.

Stabilization of MgCr<sub>2sub>O>4sub> spinel in slags of the
SiO<sub>2sub>-CaO-MgO-Cr>2sub>O>3sub> system

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Arredondo-Torres, V.

2006-12-01

Full Text Available El objetivo de este estudio es analizar el efecto del contenido de MgO y la basicidad de la escoria sobre la estabilidad de las especies mineralógicas del sistema de escoria SiO<sub>2sub>-CaOMgO-
Cr<sub>2sub>O>3sub>. Se realizaron ensayos al equilibrio a 1600 °C bajo condiciones reductoras (pO2=10^-9atm. El contenido de MgO fue de 0 a 12 % masa, el Cr<sub>2sub>O>3sub> de 10% y la basicidad de 1 y 1,5. También se realizó un análisis termodinámico para determinar las fases mineralógicas más estables en la escoria. Los resultados experimentales y calculados muestran que el Cr<sub>2sub>O>3sub> se encuentra principalmente ligado en una fase espinela MgCr<sub>2sub>O>4sub>, incluso a bajos contenidos de MgO. Los resultados obtenidos por microscopia electrónica de barrido (MEB-EDS, muestran la evidencia de tres estructuras cristalinas: (A Octaedros, los cuales
corresponden a la espinela MgCr<sub>2sub>O>4sub>, (B Cristales alargados que corresponden a la formación de silicatos cálcicos y (C Matriz de silicatos cálcicos con impurezas de Mg y Cr que no cristalizaron por completo.

El objetivo de este estudio es analizar el efecto del contenido de MgO y la basicidad de la escoria sobre la estabilidad de las especies mineralógicas del sistema de escoria SiO<sub>2sub>-CaOMgO-Cr>2sub>O>3sub>. Se realizaron ensayos al equilibrio a 1600 °C bajo condiciones reductoras (pO<sub>2sub>=10^-9atm. El contenido de MgO fue de 0 a 12 % masa, el Cr<sub>2sub>O>3sub> de 10% y la basicidad de 1 y 1,5. También se realizó un análisis termodinámico para determinar las fases mineralógicas más estables en la escoria. Los resultados experimentales y calculados muestran que el Cr<sub>2sub>O>3sub> se encuentra principalmente ligado en una fase espinela MgCr<sub>2sub>O>4sub>, incluso a bajos contenidos de MgO. Los resultados obtenidos por

X-ray and NQR studies of bromoindate(III) complexes. [C{sub 2}H{sub 5}NH{sub 3}]{sub 4}InBr{sub 7}, [C(NH{sub 2}){sub 3}]{sub 3}InBr{sub 6}, and [H{sub 3}NCH{sub 2}C(CH{sub 3}){sub 2}CH{sub 2}NH{sub 3}]InBr{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Iwakiri, Takeharu; Ishihara, Hideta [Saga Univ. (Japan). Faculty of Culture and Education; Terao, Hiromitsu [Tokushima Univ. (Japan). Faculty of Integrated Arts and Sciences; Lork, Enno; Gesing, Thorsten M. [Bremen Univ. (Germany). Inst. of Inorganic Chemistry and Crystallography

2017-03-01

The crystal structures of [C{sub 2}H{sub 5}NH{sub 3}]{sub 4}InBr{sub 7}(1), [C(NH{sub 2}){sub 3}]{sub 3}InBr{sub 6}(2), and [H{sub 3}NCH{sub 2}C(CH{sub 3}){sub 2}CH{sub 2}NH{sub 3}]InBr{sub 5}(3) were determined at 100(2) K: monoclinic, P2{sub 1}/n, a=1061.94(3), b=1186.40(4), c=2007.88(7) pm, β= 104.575(1) , Z=4 for 1; monoclinic, C2/c, a=3128.81(12), b=878.42(3), c=2816.50(10) pm, β=92.1320(10) , Z=16 for 2; orthorhombic, P2{sub 1}2{sub 1}2{sub 1}, a=1250.33(5), b=1391.46(6), c=2503.22(9) pm, Z=4 for 3. The structure of 1 contains an isolated octahedral [InBr{sub 6}]{sup 3-} ion and a Br{sup -} ion. The structure of 2 contains three different isolated octahedral [InBr{sub 6}]{sup 3-} ions. The structure of 3 has a corner-shared double-octahedral [In{sub 2}Br{sub 11}]{sup 5-} ion and an isolated tetrahedral [InBr{sub 4}]{sup -} ion. The {sup 81}Br nuclear quadrupole resonance (NQR) lines of the terminal Br atoms of the compounds are widely spread in frequency, and some of them show unusual positive temperature dependence. These observations manifest the N-H..Br-In hydrogen bond networks developed between the cations and anions to stabilize the crystal structures. The {sup 81}Br NQR and differential thermal analysis (DTA) measurements have revealed the occurrence of unique phase transitions in 1 and 3. When the bond angles were estimated from the electric field gradient (EFG) directions calculated by the molecular orbital (MO) methods, accurate values were obtained for [InBr{sub 6}]{sup 3-} of 1 and for [In{sub 2}Br{sub 11}]{sup 5-} and [InBr{sub 4}]{sup -} of 3, except for several exceptions in those for the latter two ions. On the other hand, the calculations of {sup 81}Br NQR frequencies have produced up to 1.4 times higher values than the observed ones.

Effect of substitutional defects on Kambersky damping in L1{sub 0} magnetic materials

Energy Technology Data Exchange (ETDEWEB)

Qu, T. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Victora, R. H., E-mail: victora@umn.edu [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2015-02-16

Kambersky damping, representing the loss of magnetic energy from the electrons to the lattice through the spin orbit interaction, is calculated for L1{sub 0} FePt, FePd, CoPt, and CoPd alloys versus chemical degree of order. When more substitutional defects exist in the alloys, damping is predicted to increase due to the increase of the spin-flip channels allowed by the broken symmetry. It is demonstrated that this corresponds to an enhanced density of states (DOS) at the Fermi level, owing to the rounding of the DOS with loss of long-range order. Both the damping and the DOS of the Co-based alloy are found to be less affected by the disorder. Pd-based alloys are predicted to have lower damping than Pt-based alloys, making them more suitable for high density spintronic applications.

REDUÇÃO DOS CUSTOS DA QUALIDADE COM MELHORIA DOS PROCESSOS: UM ESTUDO DE CASO

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Gabriel Rech Oliveira

2016-06-01

Full Text Available Com o objetivo de se tornarem competitivas, as empresas impulsionam a redução dos custos dos processos que impactam diretamente no preço do produto, destacando-se os custos de qualidade. Neste cenário, a busca pela qualidade total torna-se o caminho para a sobrevivência, devido ao fato da crescente exigência dos clientes para produtos com qualidade superior e preços baixos. Dentre os principais gastos que contribuem para o aumento dos custos da qualidade destacam-se a sucata e retrabalho de produtos durante o processo produtivo. Devido à ocorrência desses fatores, este trabalho tem como finalidade analisar os custos da qualidade e propor melhorias no processo produtivo utilizando ferramentas da qualidade para reduzir os desperdícios com sucata. As fases do projeto envolvem o comprometimento e dedicação de equipes para levantar as principais causas dos principais problemas do processo de produção de tubos capilares em cobre, resultando na redução dos gastos com sucata e aumento da produtividade. As metodologias utilizadas para atingir os objetivos foram baseadas pesquisa exploratória e estudo de caso. A partir da redução de custo e aumento da produtividade alcançada, constata-se a importância deste trabalho envolvendo equipes responsáveis para a obtenção de resultados em curto prazo.

Thio-, selenido-, and telluridogermanates(III): K/sub 6/Ge/sub 2/S/sub 6/, K/sub 6/Ge/sub 2/Se/sub 6/, and Na/sub 6/Ge/sub 2/Te/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Eisenmann, B; Kieselbach, E; Schaefer, H; Schrod, H [Technische Hochschule Darmstadt (Germany, F.R.). Fachbereich Anorganische Chemie und Kernchemie

1984-09-01

The new compounds K/sub 6/Ge/sub 2/S/sub 6/ and K/sub 6/Ge/sub 2/Se/sub 6/ crystallize in the monoclinic system, space group C2/m (No 12). The compounds are isotypic and form the K/sub 6/Si/sub 2/Te/sub 6/ structure. Na/sub 6/Ge/sub 2/Te/sub 6/ crystallizes in the K/sub 6/Sn/sub 2/Te/sub 6/ structure, monoclinic, space group P2/sub 1//c (No 14). The lattice constants are given.

Proton glass behaviour in a solid solution of gamma-irradiated deuterated betaine phosphate sub 0 sub . sub 1 sub 5 betaine phosphite sub 0 sub . sub 8 sub 5

CERN Document Server

Banys, J; Klimm, C; Voelkel, G; Kloepperpieper, A

1997-01-01

Measurements of the dielectric permittivity are reported for a deuterated solid solution of gamma-irradiated antiferroelectric (betainephosphate) sub 0 sub . sub 1 sub 5 ferroelectric (betainephosphite) sub 0 sub . sub 8 sub 5 at frequencies 20 H sub Z sub z. The freezing phenomena in DPB sub 0 sub . sub 1 sub 5 DBPI sub 0 sub . sub 8 sub 5 revealed the characteristics of a transition into a dipolar glass state. The activation energy was found to be E sub b = 311.6 K (0.027 eV). The Kutnjak model showed a non-typical glass behaviour with an estimated glass temperature of 55.4 K. (author). Letter-to-the-editor

TENDÊNCIAS TEMÁTICAS DOS GRADUANDOS EM BIBLIOTECONOMIA: UM ESTUDO A PARTIR DOS TRABALHOS DE CONCLUSÃO DE CURSO DA UFRN

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Arthur Ferreira Campos

2015-12-01

Full Text Available Apresenta uma análise sobre os trabalhos de conclusão de curso dos graduandos do Curso de Biblioteconomia da Universidade Federal do Rio Grande do Norte, no período de 2010 a 2014. Objetivou-se verificar se há alguma tendência temática ou um ‘modismo temático’ em relação aos temas pesquisados pelos alunos, verificando-se também se há lacunas temáticas demandadas pelos graduandos do Curso de Biblioteconomia, uma vez que é um dos critérios de avaliação final para se obter o diploma para exercer a profissão. Nessa perspectiva, definiu-se quatro grandes subáreas temáticas da área de Biblioteconomia: Fundamentos Teóricos, Recursos e Serviços de Informação, Gestão de Unidades de Informação e Organização e Tratamento da Informação. Para tanto, realizou-se uma análise dos trabalhos de conclusão de curso, defendidos no período de 2010 a 2014. A amostra foi realizada no Núcleo Temático da Seca (NUT – SECA, o qual equivale a um centro de documentação arquivístico localizado na própria Universidade, e na Biblioteca Digital de Monografias da Universidade, que é o repositório digital institucional. A metodologia de natureza qualiquantitativa, do tipo descritivo exploratório, propiciou a coleta de dados, sua análise e elaboração de gráficos, a partir da problemática do estudo. Como resultado verificou-se grande tendência temática no que tange às tecnologias de informação, bem como uma lacuna em relação aos temas tradicionais como, por exemplo, Organização e Tratamento da Informação.

Pt{sub X}Ru{sub Y}Ir{sub Z} as a bifunctional electrocatalyst for oxygen reduction reaction in a PEM fuel cell; Pt{sub X}Ru{sub Y}Ir{sub Z} como electrocatalizador bifuncional para la reaccion redox del oxigeno en una celda tipo PEM

Energy Technology Data Exchange (ETDEWEB)

Morales, L.; Fernandez, A.M. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico)]. E-mail: limos@cie.unam.mx; Cano, U. [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

2009-09-15

This work presents the synthesis and characterization of the ternary material Pt{sub X}Ru{sub Y}Ir{sub Z}, obtained by chemical reduction with NaBH{sub 4}. Two different atomic compositions were developed (sample A and B) in order to observe the kinetic effect, as suggested by the combinatorial libraries. The main objective of this synthesis is to study the oxygen reduction reaction (ORR and OER) and its potential use in the construction of a bifunctional catalyst. In addition, each of the metals are synthesized separately using the same technique in order to make the corresponding comparison. The compounds obtained were characterized by sweep electron microscopy, x-ray diffraction and composition using fluorescence and energy-dispersive x-ray spectroscopy. The results showed a displacement of the x-ray diffraction peaks for Ir and Pt in sample A, and displacement in sample B for Ru and Ir peaks. These changes suggest the possible formation of a solid solution substitution. Separate cyclic and linear voltamperometry studies were performed for the oxygen reduction and release reactions. The electrochemical analysis showed improved kinetic behavior when combining the three metals according to the composition of sample B. [Spanish] En este trabajo se presenta la sintesis y caracterizacion del material ternario Pt{sub X}Ru{sub Y}Ir{sub Z}, elaborado por la tecnica de Reduccion Quimica utilizando al NaBH{sub 4}. Se elaboraron dos composiciones atomicas diferentes (Muestra A y B) con el fin de observar el efecto cinetico, como lo sugieren las librerias combinatorias. El objetivo principal de esta sintesis es para el estudio de la Reaccion Redox del Oxigeno (RRO y REO) y su potencial uso para la construccion de un catalizador bifuncional. Asi mismo, se realiza la sintesis de cada uno de los metales por separado empleando la misma tecnica, con el proposito de realizar la comparacion correspondiente. Los compuestos obtenidos se caracterizaron por Microscopia Electronica de

Magnetic phase transitions in the anion-deficient La sub 1 sub - sub x Ba sub x MnO sub 3 sub - sub x sub / sub 2 (0 <= x <= 0.50) manganites

CERN Document Server

Trukhanov, S V; Bushinsky, M V; Troyanchuk, I O; Szymczak, H

2003-01-01

The crystal structure, magnetization and electrical resistivity properties of the anion-deficient La sub 1 sub - sub x Ba sub x MnO sub 3 sub - sub x sub / sub 2 (0 = 0.03) being a mixture of antiferromagnetic and ferromagnetic phases. At x >= 0.12 competition between antiferromagnetic and ferromagnetic interactions leads to a cluster spin glass state appearance with a magnetic moment freezing temperature of approx 45 K. The dominant magnetic phase for x >= 0.22 is supposed to be antiferromagnetic. All the reduced samples are semiconductors and show considerable magnetoresistance over a wide temperature range in a magnetically ordered state. The largest magnetoresistance (approx 34% in a 9 kOe field at liquid nitrogen temperatures) is observed for an x = 0.30 sample. The magnetic phase diagram of La sub 1 sub - sub x sup 3 sup + Ba sub x sup 2 sup + Mn sup 3 sup + O sub 3 sub - sub x sub / sub 2 sup 2 sup - manganites has been established by combining the results of magnetic and electrical measurements. The r...

Influence of structural disorder on the optical and transport properties of Co sub 0 sub . sub 5 sub 0 Ti sub 0 sub . sub 5 sub 0 alloy films

CERN Document Server

Kim, K W; Rhee, J Y; Kudryavtsev, Y V; Ri, H C

2000-01-01

Co sub 0 sub . sub 5 sub 0 Ti sub 0 sub . sub 5 sub 0 alloy films with a total thickness of about 100 nm were prepared by flash evaporation of the crushed alloy powders onto heated (730 K for the ordered state) and LN sub 2 -cooled (150 K for the disordered state) substrates. Structural analysis of the films was performed by suing transmission electron microscopy. The optical conductivity (OC) of the samples was measured at room temperature in a spectral range of 265 -2500 nm (4.7 - 0.5 eV). The resistivity measurements were carried out by using the four-probe technique in a temperature range of 4.2 - 300 K. The experimental OC spectra for the Co sub 0 sub . sub 5 sub 0 Ti sub 0 sub . sub 5 sub 0 alloys show the most significant change in the infrared region upon the order-disorder transformation. The structural disorder in the Co sub 0 sub . sub 5 sub 0 Ti sub 0 sub . sub 5 sub 0 alloy film leads to a change in the sign of the temperature coefficient of the resistivity from positive to negative. The observed...

Electronic properties of new superconductors based on Ca(Al sub x Si sub 1 sub - sub x) sub 2 and Sr(Ga sub x Si sub 1 sub - sub x) sub 2 in crystal and nanotubular states

CERN Document Server

Shein, I R; Medvedeva, N I; Ivanovskij, A L

2002-01-01

The zone structures of the new Ca(Al sub x Si sub 1 sub - sub x) sub 2 and Sr(Ga sub x Si sub 1 sub - sub x) sub 2 layered superconductors (AlB sub 2 -type) are studied through the LMTO first-principle full-potential method. It is shown that the superconducting properties of the ternary silicides is conditioned by high density of the (Ca, Sr)d-states near the Fermi level, whereas the T sub C growth by the Sr(Ga sub x Si sub 1 sub - sub x) sub 2 -> Ca(Al sub x Si sub 1 sub - sub x) sub 2 transition is related to the increase in the photon frequencies due to the atoms mass decrease. Modeling the electron properties of the hypothetical (11, 11) and (20, 0) CaAlSi and SrGaSi nanotubes is accomplished. The silicide systems by transition from the crystalline to nanotubular state retain the metal-like properties. The template and film convolution methods may become the methods for obtaining the silicide nanotubes

Self-referencing thermometry in the nanoscale =

Science.gov (United States)

Brites, Carlos Antonio Delgado Sousa

Na ultima decada emergiu uma linha de investigacao muito activa em termometros nao invasivos e precisos que possam determinar temperatura a escala nanometrica. Esta investigacao foi fortemente estimulada pelas numerosas solicitacoes da nanotecnologia e da biomedicina, por exemplo. Uma das abordagens mais promissoras propoe o uso de ioes trivalentes de lantanideos que apresenta propriedades fotoluminescentes que dependem da temperatura. Neste trabalho demonstra-se que esta tecnica combina as vantagens de te um limite de deteccao de 0.5 graus com sensibilidade ate 4.5 % K-1. Este termometro molecular pode ser processado em filmes finos ou nanoparticulas, abrindo os campos de aplicacao a diferentes utilizacoes. As nanoparticulas de silica produzidas sao caracterizadas na presenca e na ausencia de ioes lantanideos. Sem o metal, as nanoparticulas de APTES/TEOS demonstram ser luminescentes sob excitacao UV sem necessidade de utilizar qualquer tratamento termico. O rendimento quantico de emissao depende apenas da proporcao dos silanos e pode atingir o valor de 0.15 +/- 0.02. A co-dopagem destas nanoparticulas com Eu3+ e Tb3+ permite obter sondas com resposta raciometrica, com a possibilidade de ajustar a gama de temperaturas de operacao e a sensibilidade, via desenho inteligente da matriz de suporte e dos ligandos de beta-dicetona que estao coordenados ao iao metalico. Quando processados como filmes, este termometro permite o mapeamento de temperaturas com resolucao espacial 1.8 mum. A racionalizacao da dependencia de temperatura e uma ferramenta util para desenvolver termometros que operam em gamas de temperatura especificos (e.g. gama de temperatura fisiologica, 290-340 K) com sensibilidade acima de 0.5 % K-1. A combinacao de esforcos de um grande numero de diversas disciplinas ira previsivelmente permitir o surgimento de termometros moleculares novos e sofisticados, preenchendo os principais requisitos das nanociencias.

Crystallographic orientations and electrical properties of Bi sub 3 sub . sub 4 sub 7 La sub 0. sub 8 sub 5 Ti sub 3 O sub 1 sub 2 thin films on Pt/Ti/SiO sub 2 /Si and Pt/SiO sub 2 /Si substrates

CERN Document Server

Ryu, S O; Lee, W J

2003-01-01

We report on the crystallization and electrical properties of Bi sub 3 sub . sub 4 sub 7 La sub 0 sub . sub 8 sub 5 Ti sub 3 O sub 1 sub 2 (BLT) thin films for possible ferroelectric non-volatile memory applications. The film properties were found to be strongly dependent on process conditions especially on the intermediate heat treatment conditions. The crystallographic orientation of the films showed sharp changes at the intermediate rapid thermal annealing (RTA) temperature of 450degC. Below 450degC, BLT thin films have (117) orientation while they have preffered c-axis orientation above 450degC. We found that RTA conditions of the first coating layer play a major role in determining the entire crystallographic orientation of the films. The films also showed of ferroelectric hysterisis behavior strongly dependent on RTA treatment. In fact, the remanent polarization of Bi sub 3 sub . sub 4 sub 6 sub 5 La sub 0 sub . sub 8 sub 5 Ti sub 3 O sub 1 sub 2 thin films having (001) preferred crystallographic orient...

Effect of external magnetic field on superconducting and spin density wave gaps of high-T{sub c} superconductors

Energy Technology Data Exchange (ETDEWEB)

Pradhan, B., E-mail: brunda@iopb.res.i [Govt. Science College, Malkangiri 764 048 (India); Raj, B.K. [B.J.B. College, Bhubaneswar 751 014 (India); Rout, G.C., E-mail: gcr@iopb.res.i [Condensed Matter Physics Group P.G. Dept. of Applied Physics and Ballistics, F.M. University, Balasore 756 019 (India)

2009-07-01

A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev's technique of Green's functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at +-(z+z{sub 1}) and +-(z-z{sub 1}). The applied magnetic field further induces Zeeman splitting which is explained on the basis of spin-filter effect of tunneling experiment.

Systems of Na/sup +/NO/sub 3/, Na/sub 2/SO/sub 4/, RbNO/sub 3/, Rb/sub 2/SO/sub 4/-H/sub 2/O and NaNO/sub 3/, Na/sub 2/SO/sub 4/, CsNO/sub 3/, Cs/sub 2/SO/sub 4/-H/sub 2/O at 25 and 75 deg C

Energy Technology Data Exchange (ETDEWEB)

Poletaev, I F; Krasnenkova, L V

1975-08-01

Quaternary Na/sup +/, Rb/sup +///NO/sub 3/-, SO/sub 4//sup 2 -/-H/sub 2/O and Nsub(+), Cs/sup +///NO/sub 3/-, SO/sub 4//sup 2 -/-H/sub 2/O mutual systems have been studied isothermally. The following six fields of crystallization have been revealed in these systems at 25 deg C: Cs/sub 2/SO/sub 4/, Na/sub 2/SO/sub 4/, Na/sub 2/SO/sub 4/x10H/sub 2/O, NaNO/sub 3/xNa/sub 2/SO/sub 4/x2H/sub 2/O, NaNO/sub 3/, and CsNO/sub 3/.

Synthesis, crystal and electronic structures and optical properties of (HIm)<sub>2sub> Hg<sub>3sub>Cl>8sub> and (HIm)HgI<sub>3sub> (HIm = imidazolium)

Energy Technology Data Exchange (ETDEWEB)

Nhalil, Hariharan [Univ. of Oklahoma, Norman, OK (United States). Dept. of Chemistry and Biochemistry; Whiteside, Vincent R. [Univ. of Oklahoma, Norman, OK (United States). Homer L. Dodge Dept. of Physics & Astronomy; Sellers, Ian R. [Univ. of Oklahoma, Norman, OK (United States). Homer L. Dodge Dept. of Physics & Astronomy; Ming, Wenmei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Du, Mao-Hua [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Saparov, Bayrammurad [Univ. of Oklahoma, Norman, OK (United States). Dept. of Chemistry and Biochemistry

2017-11-22

Here, we report synthesis, crystal and electronic structures, and optical properties of two new Hg-based zero-dimensional hybrid organic-inorganic halides (HIm)2Hg3Cl8 and (HIm)HgI3 (HIm = imidazolium). (HIm)<sub>2sub>Hg>3sub>Cl>8sub> crystallizes in the triclinic P-1 space group with a pseudo-layered structure made of organic imidazolium cation layers and anionic inorganic layers containing [Hg<sub>2sub>Cl>6sub>]^2- units and linear [HgCl<sub>2sub>]⁰ molecules. (HIm)HgI<sub>3sub> crystallizes in the monoclinic P2<sub>1sub>/c space group featuring anionic [HgI<sub>3sub>]- units that are surrounded by imidazolium cations. Based on density functional theory calculations, (HIm)<sub>2sub>Hg>3sub>Cl>8sub> has an indirect band gap, whereas (HIm)HgI<sub>3sub> has a direct band gap with the measured onsets of optical absorption at 3.43 and 2.63 eV, respectively. (HIm)<sub>2sub>Hg>3sub>Cl>8sub> and (HIm)HgI<sub>3sub> are broadband light emitters with broad photoluminescence peaks centered at 548 nm (2.26 eV) and 582 nm (2.13 eV), respectively. In conclusion, following the crystal and electronic structure considerations, the PL peaks are assigned to self-trapped excitons.

Nonlinear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) phosphate glasses

International Nuclear Information System (INIS)

Senin, H.B.; Sidek, H.A.A.; Saunders, G.A.

1994-01-01

From measurements of changes in transit time of 10 MHz of ultrasonic wave as a function of temperature and hydrostatic pressure, the linear and non-linear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses with compositions near to that corresponding to the metaphosphate have been determined. For each glass the second order elastic stiffness tensor components C sub ijs (SOEC) continue to increase down to 10K in a manner consistent with phonons interactions with two level systems. Measurements of the effects of hydrostatic pressure on the ultrasonic wave velocities have been used to determine the hydrostatic pressure derivatives (dC sub ij/dP) sub T,P=0 of the SOEC and (dB0 sup s)/dP) sub T,P=0 of the bulk modulus B0 sup s at room temperature (293K). For the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses, (dC sub 11/dP), (dC sub 44/dP), and (dBo/dP), are small but positives; these glasses stiffen under pressure. The elastic behaviour of these ternary glasses lies intermediate between those of (Sm sub 2 O sub 3)(P sub 2 O sub 5) sub (1-x) and (La sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses. Replacement of the Sm sup 3+ by La sup 3+ in the ternary phosphate glasses negates the acoustic mode softening. Possible sources of the different effects of La sub 3+ and Sm sub 3+ modifiers on the nonlinear acoustic properties of metaphosphate glasses are discussed

Oxygen diffusion in Y sub 1 sub - sub x Pr sub x Ba sub 2 Cu sub 3 O sub 7 sub - subdelta observed by resistivity measurements

CERN Document Server

Diosa, J E; Mellander, B E

1997-01-01

In situ resistivity measurements have been used to monitor the oxygen uptake and removal for the ceramic system Y sub 1 sub - sub x Pr sub x Ba sub 2 Cu sub 3 O sub 7 sub - subdelta (YPBCO) in the temperature range 300 - 1000 K. The study of the out-diffusion of oxygen was performed by annealing the oxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen concentration O sub 7 sub - subdelta is preserved up to 600 K, and that oxygen diffuses out of the oxides at temperatures higher than 600 K. However, the rate of oxygen removal from PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta (PBCO) is greatly reduced as compared to the rate for pure YBa sub 2 Cu sub 3 O sub 7 sub - subdelta (YBCO), and decreases with increasing x in YPBCO. The study of the in-diffusion of oxygen was performed by annealing the deoxygenated samples in ambient air at constant heating rates. We found that, independently of x, the oxygen uptake takes place in the temperature range 550 - 750 K, whe...

The influence of the cations Cu{sup +2}/Co{sup +2}/Nd{sup +3} at the ferrite Mi{sub 0,2}Y{sub 0,3}Zn{sub 0,5}Fe{sub 2}O{sub 4} at different temperatures; Estudo da influencia dos cations Cu{sup +2}/Co{sup +2}/Nd{sup +3} na ferrita Mi{sub 0,2}Y{sub 0,3}Zn{sub 0,5}Fe{sub 2}O{sub 4} em diferentes temperaturas

Energy Technology Data Exchange (ETDEWEB)

Lima, U.R., E-mail: ulisandra.lima@ifrn.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia do Rio Grande do Norte (IFRN), Sao Paulo do Potengi, RN (Brazil); Nasar, R.S.; Nasar, M.C.; Silva, J.E.M. da [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Programa de Pos-Grduacao em Quimica

2016-07-01

The work consisted of Ni{sub 0,2}Y{sub 0,3}Zn{sub 0,5}Fe{sub 2}O{sub 4} composition ferrites synthesis ranging copper ions (Cu{sup +2}), cobalt (Co{sup +2}) and neodymium (Nd{sup +3}) whose objective is to evaluate the particle size by the method citrate precursor. After synthesis, the samples were calcined at 350° C and subsequently sintered at 1000° for 3 hours, with controlled heating and cooling rate. The calcined materials were characterized by XRD and SEM showed that the method of the precursor citrate is an effective method. The X-ray diffraction spectra and refinement show good agreement between the experimental peaks and the theoretical spectrum. In Scanning Electron Microscopy (SEM), the samples to 350° C/3h, have dimensions in the micrometer order in all compositions. The average size of the crystals are consistent with the higher definition and intensity of peaks of X-rays, that is, there is high correlation with those obtained by refining method. (author)

Magnetic and transport properties of the (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} systems

Energy Technology Data Exchange (ETDEWEB)

Granovsky, S.A. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation) and TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany)]. E-mail: ser@plms.phys.msu.ru; Gaidukova, I.Yu. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation); Doerr, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Loewenhaupt, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Markosyan, A.S. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation)

2005-04-15

Magnetic and transport characteristics of pseudo-ternary compounds (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} have been studied. The role of the 4f-3d exchange and Mn-Mn distances in the formation of the magnetic structure of these compounds is discussed.

Charge/orbital ordering structure in ordered perovskite Sm sub 1 sub / sub 2 Ba sub 1 sub / sub 2 MnO sub 3

CERN Document Server

Uchida, M; Akahoshi, D; Kumai, R; Tomioka, Y; Tokura, Y; Arima, T H

2002-01-01

In an A-site ordered perovskite manganite Sm sub 1 sub / sub 2 Ba sub 1 sub / sub 2 MnO sub 3 , a new charge/orbital ordering pattern was found at room temperature. Electron diffraction studies revealed a series of superlattice reflections with modulation vectors at q sub 2 =(1/2, 1/2, 1/2) as well as at q sub 1 =(1/4, 1/4, 0) in the tetragonal setting (a sub p x a sub p x 2a sub p , a sub p being the cubic perovskite lattice parameter). Together with the results of the resonant X-ray scattering and the charge-transport and magnetization measurements, a new model for the three-dimensional charge/orbital ordering in the ordered perovskite is proposed. (author)

Magnetic ordering of Hf{sub 3}Ni{sub 2}Si{sub 3}-type {Sm, Tb, Er}{sub 3}Co{sub 2}Ge{sub 3} and {Tb, Ho}{sub 3}Ni{sub 2}Ge{sub 3} compounds

Energy Technology Data Exchange (ETDEWEB)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow, GSP-1, 119991 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil); Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Isnard, O. [CNRS, Institut. Néel, 25 rue des Martyrs BP166 x, F-38042 Grenoble (France); Université Grenoble Alpes, Inst. Néel, F-38042 Grenoble (France)

2017-02-15

The magnetic ordering of Hf{sub 3}Ni{sub 2}Si{sub 3}-type {Sm, Tb, Er}{sub 3}Co{sub 2}Ge{sub 3} and {Tb, Ho}{sub 3}Ni{sub 2}Ge{sub 3} compounds (space group Cmcm, oC32) was investigated via magnetization measurements and neutron diffraction study in a zero-applied field. {Sm, Tb, Er}{sub 3}Co{sub 2}Ge{sub 3} and Ho{sub 3}Ni{sub 2}Ge{sub 3} exhibit field sensitive complex antiferromagnetic orderings with T{sub N}=51 K, T{sub m}=10 K for Sm{sub 3}Co{sub 2}Ge{sub 3}, T{sub N}=34 K, T{sub m}=13 K for Tb{sub 3}Co{sub 2}Ge{sub 3}, T{sub N}=7 K for Er{sub 3}Co{sub 2}Ge{sub 3} and T{sub N}=11 K for Ho{sub 3}Ni{sub 2}Ge{sub 3}. At 2 K and above the critical field of ~5 kOe, 20 kOe, 4 kOe and 7 kOe for Sm{sub 3}Co{sub 2}Ge{sub 3}, Tb{sub 3}Co{sub 2}Ge{sub 3}, Er{sub 3}Co{sub 2}Ge{sub 3} and Ho{sub 3}Ni{sub 2}Ge{sub 3}, respectively, saturation magnetizations per rare-earth atom are 6.5 μ{sub B} for Tb{sub 3}Co{sub 2}Ge{sub 3}, 7.0 μ{sub B} for Er{sub 3}Co{sub 2}Ge{sub 3} and 8.0 μ{sub B} for Ho{sub 3}Ni{sub 2}Ge{sub 3} in the field of 140 kOe, whereas magnetization of Sm{sub 3}Co{sub 2}Ge{sub 3} has an antiferromagnetic behaviour. The isothermal magnetic entropy change, ΔS{sub m}, indicates a field-induced ferromagnetic ordering in Sm{sub 3}Co{sub 2}Ge{sub 3}, Tb{sub 3}Co{sub 2}Ge3, Er{sub 3}Co{sub 2}Ge{sub 3} and Ho{sub 3}Ni{sub 2}Ge{sub 3} with a maximal ΔS{sub m} value of −10.9 J/kg K for Ho{sub 3}Ni{sub 2}Ge{sub 3} at 11 K for a field change of 50 kOe. In a zero-applied magnetic field, below T{sub N}=33 K and down to T{sub m}{sup ND}=15 K Tb{sub 3}Ni{sub 2}Ge{sub 3} shows an ac-antiferromagnetic ordering with the C2′/c magnetic space group, a K{sub 0}=[0, 0, 0] propagation vector and a a{sub Tb3Ni2Ge3}×b{sub Tb3Ni2Ge3}×c{sub Tb3Ni2Ge3} magnetic unit cell. Below T{sub m}{sup ND}=15 K, its magnetic structure is a sum of the ac-antiferromagnetic component with the C2′/c magnetic space group of the K{sub 0} vector and a sine-modulated a

Neurobiologia dos transtornos do controle dos impulsos The neurobiology of impulse control disorders

Directory of Open Access Journals (Sweden)

Wendol A Williams

2008-05-01

Full Text Available OBJETIVO: Revisar os artigos sobre substratos neurobiológicos dos transtornos do controle dos impulsos. O jogo patológico é o foco central desta revisão na medida em que a maioria dos estudos biológicos dos formalmente classificados como transtornos do controle dos impulsos examinou este transtorno. MÉTODO: Foi feita uma busca no banco de dados Medline de artigos publicados de 1966 até o presente para identificar aqueles relevantes para serem revisados neste artigo. DESFECHOS: Estudos pré-clínicos sugerem que a neuromodulação das monoaminas cerebrais está associada à tomada de decisões impulsivas e aos comportamentos de risco. Os estudos clínicos implicam diversos sistemas de neurotransmissores (serotoninérgico, dopaminérgico, adrenérgico e opióide na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. Estudos de neuroimagem preliminares têm indicado o córtex pré-frontal ventromedial e o estriato ventral como atuantes na fisiopatologia do jogo patológico e de outros transtornos do controle dos impulsos. As contribuições genéticas para o jogo patológico parecem substanciais e os estudos iniciais têm relacionado esse transtorno a polimorfismos alélicos específicos, ainda que os achados de varredura genômica ainda tenham que ser publicados. CONCLUSÃO: Mesmo que tenham sido logrados avanços significativos em nossa compreensão sobre os transtornos do controle dos impulsos, mais pesquisas são necessárias para ampliar o conhecimento existente e traduzir esses achados em avanços clínicos.OBJECTIVE: To review the neurobiological substrates of impulse control disorders. Pathological gambling is a main focus of the review in that most biological studies of the formal impulse control disorders have examined this disorder. METHOD: The medical database Medline from 1966 to present was searched to identify relevant articles that were subsequently reviewed to generate this manuscript

Pinning in high performance MgB{sub 2} thin films and bulks: Role of Mg-B-O nano-scale inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Prikhna, Tatiana, E-mail: prikhna@mail.ru [Institute for Superhard Materials of the National Academy of Sciences of Ukraine , 2, Avtozavodskaya Str. , Kiev 07074 (Ukraine); Shapovalov, Andrey [Institute for Superhard Materials of the National Academy of Sciences of Ukraine , 2, Avtozavodskaya Str. , Kiev 07074 (Ukraine); Eisterer, Michael [Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Vienna (Austria); Shaternik, Vladimir [G.V. Kurdyumov Institute for Metal Physics of the National Academy of Sciences of Ukraine, 36 Academician Vernadsky blvd., Kiev, 03680 (Ukraine); Goldacker, Wilfried [Karlsruhe Institute of Technology (KIT), 76344 Eggenstein (Germany); Weber, Harald W. [Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Vienna (Austria); Moshchil, Viktor; Kozyrev, Artem; Sverdun, Vladimir [Institute for Superhard Materials of the National Academy of Sciences of Ukraine , 2, Avtozavodskaya Str. , Kiev 07074 (Ukraine); Boutko, Viktor [Donetsk Institute for Physics and Engineering named after O.O. Galkin of the National Academy of Sciences of Ukraine, R. Luxemburg str.72, Donetsk-114, 83114 (Ukraine); Grechnev, Gennadiy [B. Verkin Institute for Low Temperature Physics of the National Academy of Sciences of Ukraine, 47, Prospekt Nauky, Kharkiv 61103 (Ukraine); Gusev, Alexandr [Donetsk Institute for Physics and Engineering named after O.O. Galkin of the National Academy of Sciences of Ukraine, R. Luxemburg str.72, Donetsk-114, 83114 (Ukraine); Kovylaev, Valeriy; Shaternik, Anton [Institute for Superhard Materials of the National Academy of Sciences of Ukraine , 2, Avtozavodskaya Str. , Kiev 07074 (Ukraine)

2017-02-15

Highlights: • Pinning in MgB{sub 2} depends on the Mg-B-O nano-scaled inhomogeneities. • Finer oxygen-enriched inhomogeneities is the reason of the higher J{sub c} in MgB{sub 2} thin films as compared to bulk. • The results of DOS calculations for MgB{sub 2-x}O{sub x} compounds demonstrate that they have metal-like behavior. • Ordered oxygen distribution in MgB{sub 2} (in pairs or zigzags) reduces binding energy. - Abstract: The comparison of nano-crystalline MgB{sub 2} oxygen-containing thin film (140 nm) and highly dense bulk materials showed that the critical current density, J{sub c}, depends on the distribution of Mg-B-O nano-scale inhomogeneities. It has been shown that MgB{sub 2} bulks with high J{sub c} in low (∼10{sup 6} A/cm{sup 2} in 0-1 T at 10 K) and medium magnetic fields contain MgB{sub 0.6-0.8}O{sub 0.8-0.9} nano-inclusions, where δT{sub c} or a combined δT{sub c} (dominant) / δ{sub l} pinning mechanism prevails, while in bulk MgB{sub 2} with high J{sub c} in high magnetic fields (B{sub irr}(18.5 K) = 15 T, B{sub c2}(0 K) = 42.1 T) MgB{sub 1.2-2.7}O{sub 1.8-2.5} nano-layers are present and δ{sub l} pinning prevails. The structure of oxygen-containing films with high J{sub c} in low and high magnetic fields (J{sub c} (0 T) = 1.8 × 10{sup 7} A/cm{sup 2} and J{sub c} (5 T) = 2 × 10{sup 6} A/cm{sup 2} at 10 K) contains very fine oxygen-enriched Mg-B-O inhomogeneities and δ{sub l} pinning is realized. The results of DOS calculations in MgB{sub 2-x}O{sub x} cells for x = 0, 0.125, 0.25, 0.5, 1 demonstrate that all compounds are conductors with metal-like behaviour. In the case of ordered oxygen substitution for boron the binding energy, E{sub b}, does not increase sufficiently as compared with that for MgB{sub 2}, while when oxygen atoms form zigzag chains the calculated E{sub b} is even lower (E{sub b} = −1.15712 Ry).

Participação dos Pais na Psicoterapia da Criança: Práticas dos Psicoterapeutas

Directory of Open Access Journals (Sweden)

Luiz Ronaldo Freitas de Oliveira

Full Text Available Resumo A participação dos pais na psicoterapia de crianças é um tema controverso na literatura. Há autores a favor de uma abordagem mais intervencionista em relação aos pais e outros que circunscrevem seu papel à manutenção do tratamento e provimento de informações sobre a criança. O objetivo deste estudo exploratório, de levantamento, transversal, foi identificar experiências de psicoterapeutas de crianças brasileiros quanto às formas de inclusão dos pais no tratamento. Participaram 76 psicólogos, que responderam a um questionário on-line e as análises contemplaram estatística descritiva e análise de conteúdo. De acordo com os resultados, os respondentes foram predominantemente mulheres (89,5%, residentes na Região Sul (86,8%, entre 26 e 35 anos (53,9% e com até três anos de experiência clínica (43,4%. De maneira geral, os participantes incluem os pais na psicoterapia (76,3%; em entrevistas específicas (90,8%; coleta de informações (88,2%, para aconselhamento/orientação (72,4%; e para fortalecer a aliança terapêutica (61,8%. Riscos e benefícios da participação dos pais foram reportados e constituíram seis categorias: a criança como sintoma dos conflitos familiares; resistência dos pais à psicoterapia e às mudanças; cumprimento do contrato pelos pais; aliança terapêutica; compreensão da dinâmica familiar e dos sintomas da criança; e fortalecimento dos vínculos pais-filhos. Conclui-se que há tendência de inclusão dos pais, por parte dos psicoterapeutas, no processo de psicoterapia de crianças.

The first quinary rare earth thiophosphates. Cs{sub 5}Ln{sub 3}X{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) (Ln = La, Ce, X = Br, Cl) and the quasi-quaternary Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3}

Energy Technology Data Exchange (ETDEWEB)

Schoop, Leslie Mareike; Eger, Roland; Nuss, Juergen; Pielnhofer, Florian [Max Planck Institute for Solid State Research, Stuttgart (Germany); Lotsch, Bettina Valeska [Max Planck Institute for Solid State Research, Stuttgart (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience, Muenchen (Germany)

2017-12-13

We report the first examples of quinary rare earth thiophosphates with a fully ordered cation and anion distribution, Cs{sub 5}Ln{sub 3}X{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}), (Ln = La, Ce and X = Br, Cl) as well as the quasi-quaternary Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3}. These four new compounds crystallize in three different, unknown structure types. The yellowish, transparent, brittle Cs{sub 5}Ce{sub 3}Br{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) crystallizes in the orthorhombic space group Pnma (no. 62) with a = 13.276(3), b = 14.891(3), c = 19.593(4) Aa, and V = 3873(1) Aa{sup 3} in a novel structure type. Colorless crystals of Cs{sub 5}La{sub 3}Br{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) and Cs{sub 5}La{sub 3}Cl{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) are isotypic and were obtained in the monoclinic space group P2{sub 1}/m (no. 11) with a = 9.715(2), b = 14.310(3), c = 13.685(3) Aa, β = 100.16(3) and V = 1873(1) Aa{sup 3} and a = 9.513(2), b = 14.182(3), c = 13.699(3) Aa, β = 99.39(3) and V = 1823(1) Aa{sup 3}, respectively. Both structures contain isolated hexathiohypodiphosphate(IV) [P{sub 2}S{sub 6}]{sup 4-} and thiophosphate [PS{sub 4}]{sup 3-} units that are arranged alternately in layers. Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3} crystallizes in colorless transparent platelets in the orthorhombic space group Pnnm (no. 58) with a = 13.153(3), b = 28.964(6), c = 7.780(2) Aa, and V = 2964(1) Aa{sup 3}. The structure is composed of isolated [P{sub 4/2}S{sub 6}]{sup 4-} octahedra containing four half occupied P positions surrounded octahedrally by sulfur. We show with Raman scattering that this disordered thiophosphate anion shows a Raman spectrum that is distinct from spectra published for other literature-known thiophosphate anions. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation, crystallography, magnetic and magnetothermal properties of Ce<sub>5sub>Si_xGe>4-xsub> alloys

Energy Technology Data Exchange (ETDEWEB)

Vijayaraghavan, Rangarajan [Iowa State Univ., Ames, IA (United States)

2005-01-01

An investigation of the crystal structure and the phase relationships in the Ce<sub>5sub>Si>4-xsub>Ge_x> system has been carried out. The crystal structures of the single phase intermetallics were characterized using X-ray powder diffraction and subsequent refinement employing the Rietveld analysis technique was performed. The intermetallic system was found to crystallize in three distinct crystal structures. The Ce<sub>5sub>Si>4sub>-based solid solution extends from x = 0 to x = 2.15 and it was found to crystallize in the well-known Zr<sub>5sub>Si>4sub>-type tetragonal structure. The germanium rich alloys, where 3.1 ≤} x ≤ 4, crystallized in the Sm<sub>5sub>Ge>4sub>-type orthorhombic structure. The crystal structure of the intermediate phase, when 2.35 ≤ x ≤ 2.8, was found out to be of the Gd<sub>5sub>Si>2sub>Ge>2sub>-type monoclinic structure. Microhardness tests were conducted on the samples in order to probe the trend in mechanical properties in this alloy system as a function of Ge concentration. The magnetic, thermal and magnetocaloric properties of the Ce<sub>5sub>Si>4-xsub>Ge_x> alloy system have been investigated for x = 0, 1.0, 1.8, 2.5, 2.8, 3.5, 3.8 and 4.0. The phases with x = 0, 1.0 and 1.8 crystallize in the tetragonal Zr<sub>5sub>Si>4sub> structure and those with x = 2.5, 2.8 form in the Gd<sub>5sub>Si>2sub>Ge>2sub>-type monoclinic structure. The alloys with x = 3.5, 3.8 and 4.0 crystallize in the Sm<sub>5sub>Ge>4sub>-type orthorhombic structure. The Curie temperature of the tetragonal phases increases with increasing Ge content. The ordering temperatures of the monoclinic and orthorhombic phases remain nearly unaffected by the composition, with the Curie temperatures of the latter slightly higher than those of the former. All the alloys display evidence of antiferromagnetic interactions in the ground state. The orthorhombic and the

The Dopants and Doping Level Dependence of the Structure and Magnetic Properties of the Eu (BA<sub>1-xsub>LR_x)>2sub>Cu>3sub>O>7+δsub>

Energy Technology Data Exchange (ETDEWEB)

Lin, Yu [Iowa State Univ., Ames, IA (United States)

2002-12-31

Eu(Ba<sub>1-xsub>LR_x)>2sub>Cu>3sub>O>7+δsub> were systematically studied in order to understand how the valence of the rear earth elements, ionic sizes and magnetic moment affect the crystal structure and magnetic and electrical properties. Differential thermal analyses were carried out to check the phase purity, X-ray data were least-squares fitted to determine the lattice parameters, and DC-SQUID magnetometry was used to characterize the superconducting properties. These results showed that the crystallography is consistent with other EuLR123ss series, LR = La, Pr, Eu. The lattice parameters vary with the ionic radii of the rare earth ions. Unlike the uniform change in lattice parameter, the superconducting transition did not vary systematically with the ionic size of the dopants. Although the general trend was for T<sub>c> to decrease with decreasing ionic size of the dopant, for the same doping level, Pr was anomalous, depressing T<sub>c> faster. Although the exact mechanism is not clear, this result is consistent with the depression of T<sub>c> for Pr substitution for the rare earth in R123. The critical current J<sub>c> was determined using the Bean model from magnetization versus field measurements as a function of temperature and field. The effect of the dopants on J<sub>c> with the increasing of temperature or applied field was determined. For T < 77 K and small values of x, the value of J<sub>c> was increased over that of the x = 0 sample. In addition, the smaller the substituting atom, the higher the J<sub>c> becomes. For instance, at x = 0.025, Eu123 < EuLa.025 < EuPr.025 < EuNd.025 < EuEu.025. The enhancement of J<sub>c> disappears for x > 0.05 and T > 0.5T<sub>c>.

Synthesis, characterization and comparison of Li{sub 1,05}M{sub 0,02}Mn{sub 1,98}O{sub 4} (M = Al{sup 3+} or + Ga{sup 3+}) obtained by calcination in muffle and microwave; Sintese, caracterizacao e comparacao dos Li{sub 1,05}Mn{sub 1,98}M{sub 0,02}O{sub 4} (M= Al{sup 3+} ou GA{sup 3+}) obtidos por calcinacao em mufla e microondas

Energy Technology Data Exchange (ETDEWEB)

Santana, L.K.; Canobre, S.C.; Amaral, F.A., E-mail: fabioamaral@yahoo.com.br [Universidade Federal de Uberlandia (UFU), MG (Brazil). Instituto de Quimica. Laboratorio de Armazenamento de Energia e Tratamento de Efluentes

2014-07-01

Due to the economic and environmental importance of using LiMn{sub 2}O{sub 4} as cathode batteries, the goal of this work was to synthesize LiMn{sub 2}O{sub 4} doped and undoped, comparing methods of calcination kiln and microwave. The precursors were obtained by Pechini method. The resulting samples were structurally characterized by XRD, morphology by SEM and area by B.E.T. XRD results were compared to card JCPDS 35-0782 regarding the pure LiMn{sub 2}O{sub 4}. The DRX results indicate that the calcination furnace was more efficient for obtaining doped oxides. However, the use of microwave was effective for rapid attainment of non-doped spinel close to those found for the pure spinel structural features. The surface area values confirm the existence of clusters and particles with nanometric features. Oxides synthesized in both procedures showed small, organized and highly crystalline particles, demonstrating the efficiency of the methodology and Pechini methods of calcination compared. (author)

Syntheses, crystal structures, and properties of the isotypic pair [Cr(H{sub 2}O){sub 6}]{sub 2}[B{sub 12}H{sub 12}]{sub 3}.15H{sub 2}O and [In(H{sub 2}O){sub 6}]{sub 2}[B{sub 12}H{sub 12}]{sub 3}.15H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Van, Nguyen-Duc; Kleeberg, Fabian M.; Schleid, Thomas [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)

2015-11-15

Single crystals of [Cr(H{sub 2}O){sub 6}]{sub 2}[B{sub 12}H{sub 12}]{sub 3}.15H{sub 2}O and [In(H{sub 2}O){sub 6}]{sub 2}[B{sub 12}H{sub 12}]{sub 3}.15H{sub 2}O were obtained by reactions of aqueous solutions of the acid (H{sub 3}O){sub 2}[B{sub 12}H{sub 12}] with chromium(III) hydroxide and indium metal shot, respectively. The title compounds crystallize isotypically in the trigonal system with space group R anti 3c (a = 1157.62(3), c = 6730.48(9) pm for the chromium, a = 1171.71(3), c = 6740.04(9) pm for the indium compound, Z = 6). The arrangement of the quasi-icosahedral [B{sub 12}H{sub 12}]{sup 2-} dianions can be considered as stacking of two times nine layers with the sequence..ABCCABBCA.. and the metal trications arrange in a cubic closest packed..abc.. stacking sequence. The metal trications are octahedrally coordinated by six water molecules of hydration, while another fifteen H{sub 2}O molecules fill up the structures as zeolitic crystal water or second-sphere hydrating species. Between these free and the metal-bonded water molecules, bridging hydrogen bonds are found. Furthermore, there is also evidence of hydrogen bonding between the anionic [B{sub 12}H{sub 12}]{sup 2-} clusters and the free zeolitic water molecules according to B-H{sup δ-}..{sup δ+}H-O interactions. Vibrational spectroscopy studies prove the presence of these hydrogen bonds and also show slight distortions of the dodecahydro-closo-dodecaborate anions from their ideal icosahedral symmetry (I{sub h}). Thermal decomposition studies for the example of [Cr(H{sub 2}O){sub 6}]{sub 2}[B{sub 12}H{sub 12}]{sub 3}.15H{sub 2}O gave no hints for just a simple multi-stepwise dehydration process. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Fabrication and characterization of Ba sub x Sr sub 1 sub - sub x TiO sub 3 /YBa sub 2 Cu sub 3 O sub x /SrTiO sub 3 structure

CERN Document Server

Choi, J; Park, S Y; Lee Jae Sik; No, K; Sung, T H; Park, Y

2002-01-01

Ba sub x Sr sub 1 sub - sub x TiO sub 3 (BST)/YBa sub 2 Cu sub 3 O sub x (YBCO)/SrTiO sub 3 (STO) structures were deposited, and the microstructure, orientation and electrical characteristics were investigated. (00l) oriented YBCO thin films were deposited on STO substrates using pulsed laser deposition, and (h00) oriented BST thin films were deposited on YBCO/STO substrates using electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapor deposition (MOCVD). A new phase was formed at the interface between YBCO and BST films and was speculated to be (Ba sub x Y sub 1 sub - sub x)(Ti sub y Y sub 1 sub - sub y)O sub 3. Ba-rich BST films showed a higher dielectric loss than Sr-rich BST films did, which indicates that Sr-rich BST films are more suited for application to microwave devices. The dielectric loss of the films was reduced as temperature decreased, which may be due to the conductivity change of YBCO film and the formation of a conduction path rather than a dielectric property change ...

Suppressed oxygen extraction and degradation of LiNi<sub>xMn_yCo_zO>2sub> cathodes at high charge cut-off voltages

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jianming; Yan, Pengfei; Zhang, Jiandong; Engelhard, Mark H.; Zhu, Zihua; Polzin, Bryant J.; Trask, Steve; Xiao, Jie; Wang, Chongmin; Zhang, Jiguang

2017-09-01

The capacity degradation mechanism in lithium nickel–manganese–cobalt oxide (NMC) cathodes (LiNi<sub>1/3sub>Mn>1/3sub>Co>1/3sub>O>2sub> (NMC<sub>333sub>) and LiNi<sub>0.4sub>Mn>0.4sub>Co>0.2sub>O>2sub> (NMC<sub>442sub>)) during high-voltage (cut-off of 4.8 V) operation has been investigated. In contrast to NMC<sub>442sub>, NMC<sub>333sub> exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interfacial stability of NMC<sub>333sub> was found to be correlated to its high Co content and the significant overlap between the Co^3+/4+ t<sub>2gsub> and O^2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems.

Structural study of U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 at high pressure

CERN Document Server

Sikolenko, V V; Pomjakushina, E V; Pomjakushin, V Y; Balagurov, A M; Keller, L; Glazkov, V P; Gribanov, A V; Goncharenko, I N; Savenko, B N

2003-01-01

The crystal structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with Fe content x = 0- 0.03 and the crystal and magnetic structure of U(Pd sub 0 sub . sub 9 sub 8 Fe sub 0 sub . sub 0 sub 2) sub 2 Ge sub 2 at high external pressures up to 4.5 GPa were studied by means of powder neutron diffraction in the temperature range 1.5-300 K. With increasing Fe content the values of the lattice parameters and interatomic distances change only slightly, but it is known from previous experiments that the magnetic structure changes drastically for x >= 0.015. In contrast to this, high external pressure modifies the crystal structure more significantly while the magnetic structure remains unchanged. The results obtained allow one to infer that drastic changes in the magnetic structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with increasing Fe content are a consequence of modification of the RKKY-type (RKKY standing for Ruderman, Kittel, Kasuya and Yosida) indirect exchange in...

Caracterização da condutividade hidráulica dos solos e estudo da vulnerabilidade à contaminação dos aquíferos da sub-bacia do Córrego Palmital Viçosa/MG

OpenAIRE

Betim, Luiza Silva

2013-01-01

A crescente importância e utilização das águas subterrâneas torna fundamental a avaliação da vulnerabilidade à contaminação de aquíferos, a qual pode constituir uma ótima ferramenta de planejamento ambiental. Tal avaliação exige uma caracterização do meio físico, especialmente relacionada às propriedades físicas dos solos e aquíferos, dentre as quais destaca-se a condutividade hidráulica. Nesse contexto, a presente pesquisa tem como objetivos o estudo da condutividade hidráulica dos solos e a...

Synthesis and performance of Li{sub 3}(V{sub 1-x}Mg{sub x}){sub 2}(PO{sub 4}){sub 3} cathode materials

Energy Technology Data Exchange (ETDEWEB)

Dai, Changsong; Chen, Zhenyu; Jin, Haizu; Hu, Xinguo [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China)

2010-09-01

In order to search for cathode materials with better performance, Li{sub 3}(V{sub 1-x}Mg{sub x}){sub 2}(PO{sub 4}){sub 3} (0, 0.04, 0.07, 0.10 and 0.13) is prepared via a carbothermal reduction (CTR) process with LiOH.H{sub 2}O, V{sub 2}O{sub 5}, Mg(CH{sub 3}COO){sub 2}.4H{sub 2}O, NH{sub 4}H{sub 2}PO{sub 4}, and sucrose as raw materials and investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM) and electrochemical impedance spectrum (EIS). XRD shows that Li{sub 3}(V{sub 1-x}Mg{sub x}){sub 2}(PO{sub 4}){sub 3} (x = 0.04, 0.07, 0.10 and 0.13) has the same monoclinic structure as undoped Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} while the particle size of Li{sub 3}(V{sub 1-x}Mg{sub x}){sub 2}(PO{sub 4}){sub 3} is smaller than that of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} according to SEM images. EIS reveals that the charge transfer resistance of as-prepared materials is reduced and its reversibility is enhanced proved by the cyclic votammograms. The Mg{sup 2+}-doped Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} has a better high rate discharge performance. At a discharge rate of 20 C, the discharge capacity of Li{sub 3}(V{sub 0.9}Mg{sub 0.1}){sub 2}(PO{sub 4}){sub 3} is 107 mAh g{sup -1} and the capacity retention is 98% after 80 cycles. Li{sub 3}(V{sub 0.9}Mg{sub 0.1}){sub 2}(PO{sub 4}){sub 3}//graphite full cells (085580-type) have good discharge performance and the modified cathode material has very good compatibility with graphite. (author)

Electronic structures of (Pb sub 2 Cu)Sr sub 2 Eu sub x Ce sub n sub - sub x Cu sub 2 O sub 2 sub n sub + sub 6 (n=2, 3): Effect of fluorite blocks between adjacent CuO sub 2 layers

CERN Document Server

Arai, M

2003-01-01

The electronic structures of (Pb sub 2 Cu)Sr sub 2 Eu sub x Ce sub n sub - sub x Cu sub 2 O sub 2 sub n sub + sub 6 (n = 2, 3) compounds which have fluorite blocks between two adjacent CuO sub 2 layers have been studied by using ab-initio method. It is found that the anisotropy is enhanced by inserting the fluorite blocks. The Fermi velocity perpendicular to the CuO sub 2 layers decreases as the thickness of fluorite blocks increases. The Eu substitution is found to affect both the atomic positions and electronic structures. The distance between apical oxygen and copper becomes shorter by the Eu substitution. The energy bands derived from oxygens in the fluorite blocks approach Fermi energy as the content of Eu substitution increases. (author)

Um estudo sobre os processos de aprendizagem dos trabalhadores que não exercem função gerencial

Directory of Open Access Journals (Sweden)

Patricia Kinast de Camillis

2010-04-01

Full Text Available Os processos de aprendizagem que ocorrem no local de trabalho constituem o foco deste estudo. O objetivo é identificar e analisar os processos de aprendizagem no local de trabalho de indivíduos que não exercem a função gerencial. No plano teórico, adota-se a abordagem social da aprendizagem organizacional. No plano metodológico, realiza-se um estudo qualitativo básico junto a duas equipes administrativas pertencentes a uma empresa de fertilizantes químicos. Os resultados evidenciam a importância dos processos informais de aprendizagem a partir das contribuições das experiências obtidas no contexto de trabalho dos pesquisados. Identificaram-se os objetivos, aspectos facilitadores, obstáculos e resultados dos processos de aprendizagem. A relevância da interação social, do aprender pela prática e do contexto organizacional foi destaque nos processos de aprendizagem. O estudo adiciona subsídios aos profissionais de recursos humanos na elaboração de uma análise crítica sobre as atuais práticas e políticas de desenvolvimento dos indivíduos nas organizações.

The Pr sub 0 sub . sub 5 Ca sub 0 sub . sub 5 Mn sub 1 sub - sub x Cr sub x O sub 3 series (0 <= x <= 0.5): evidence of steps in the magnetic and transport properties for a narrow composition range

CERN Document Server

Pi, L; Yaicle, C; Martin, C; Maignan, A; Raveau, B

2003-01-01

The Pr sub 0 sub . sub 5 Ca sub 0 sub . sub 5 Mn sub 1 sub - sub x Cr sub x O sub 3 series has been investigated up to x = 0.5. For low doping content (x 0.04-0.06, is completely different from the low-x side.

Formation of Self-Assembled Ba<sub>2sub>YNbO>6sub> Nanocolumns and their Contribution to Flux-Pinning and J<sub>c> in Nb-doped YBa<sub>2sub>Cu>3sub>O>7- sub> Films

Energy Technology Data Exchange (ETDEWEB)

Wee, Sung Hun [ORNL; Goyal, Amit [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Specht, Eliot D [ORNL

2010-01-01

Ba{sub 2}RENbO{sub 6} (RE = rare earth elements including Y) compounds are considered new additives for superior flux-pinning in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films due to their excellent chemical inertness to and large lattice mismatches with YBCO. Simultaneous laser ablation of a YBCO target and a Nb metal foil attached to the surface of the target resulted in epitaxial growth of YBCO films having columnar defects comprised of self-aligned Ba{sub 2}YNbO{sub 6} (BYNO) nanorods parallel to the c-axis of the film. Compared to pure YBCO, YBCO+BYNO films exhibited no T{sub c} reduction as well as superior J{sub c} performance with higher self- and in-field J{sub c} by a factor of 1.5-7 and also exhibited a strong J{sub c} peak for H {parallel} c indicative of strong c-axis correlated flux-pinning.

Low field magnetoresistance effects in fine particles of La sub 0 sub . sub 6 sub 7 Ca sub 0 sub . sub 3 sub 3 MnO sub 3 perovskites

CERN Document Server

Rivas, J; Fondado, A; Rivadulla, F; López-Quintela, M A

2000-01-01

In this work magnetic and magnetotransport experimental data in well-characterized small particles of La sub 0 sub . sub 6 sub 7 Ca sub 0 sub . sub 3 sub 3 MnO sub 3 are presented. Grain size reduction leads to a larger resistivity and a decrease in metal-insulator transition temperature. Intrinsic colossal magnetoresistance (CMR) is destroyed while intergranular one is promoted to larger values. This low field MR can be explained taking into account magnetization data through spin-polarized tunneling model, which ensures an acceptable first-order fit between both magnitudes. Finally, low-temperature resistivity upturn present in small particle size samples can be understood in terms of an electrostatic barrier between grains.

“Ni{sub 5}TiO{sub 7}” is Ni{sub 5}TiO{sub 4}(BO{sub 3}){sub 2}

Energy Technology Data Exchange (ETDEWEB)

Nalbandyan, V.B.

2017-05-15

It is shown that the compound known as Ni{sub 5}TiO{sub 7} and considered as a promising catalyst and oxidation product of alloys does not exist and its XRD pattern actually corresponds to Ni{sub 5}TiO{sub 4}(BO{sub 3}){sub 2} - Graphical abstract: XRD pattern of “Ni{sub 5}TiO{sub 7}” (top) is identical to that for Ni{sub 5}TiO{sub 4}(BO{sub 3}){sub 2} (bottom) based on single-crystal structural data. - Highlights: • Popular catalyst known as Ni{sub 5}TiO{sub 7} is actually Ni{sub 5}TiO{sub 4}(BO{sub 3}){sub 2}. • B{sub 2}O{sub 3} came from the flux used for crystal growth. • Some authors reporting this phase did not use any boron compounds.

Ílion, a Pátria dos Ventos: O uso da Meteorologia e da Astronomia na Ilíada * Ilion, la Patrie des Vents: l'utilisation de la Meteorologie et l'Astronomie dans l'Iliade

Directory of Open Access Journals (Sweden)

RAFAEL VIRGILIO DE CARVALHO

2014-01-01

Full Text Available Resumo: Na Grécia Antiga o céu era personificado como um dos deuses primordiais do panteão helênico. Como gerador de tudo o que existe, Urano (Céu abrigava em seu bojo as forças naturais que indicavam a presença dos deuses e dos titãs. Nessa direção, a observação de seus objetos - os metéoroi - era de inestimável valor para a cultura homérica. Homero iluminou as ações dos heróis da Ilíada por meio de analogias com os objetos celestes, os quais mais tarde no século IV a.C. mobilizariam os olhares de Platão e de Aristóteles. Os meteóroi, "objetos naturais suspensos no ar", foram descritos pelo poeta através de certas funções narrativas da epopeia, estruturando assim uma protometeorologia homérica. O presente trabalho procura então levantar certos padrões expressivos encontrados durante a leitura da Ilíada e algumas considerações que os problematizam de modo a iluminar o entendimento sobre tema.Palavras-chave: Mundo homérico – Meteorologia e astronomia – Crença – Mecanismos de linguagem. Résumé: Dans la Grèce antique, le ciel était personnifié comme l'un des dieux primordiaux du panthéon hellénique. Comme un générateur de tout ce qui existe, Uranus (le Ciel logé en elle les forces naturelles qui indiquaient la présence des dieux et des Titans. De cette façon, l'observation des ses objets - les meteóroi - a été d'une valeur inestimable à la culture homèrique. Homère éclarait les actions de l'Iliade grâce a des analogies avec les objets célestes, qui, plus tard dans l'IVe siècle av. J.-C., mobiliseraient les regards de Platon et d'Aristote. Les meteóroi, "les objets naturels en suspension dans l'air", ont été décrits par le poète à travers des certaines fonctions narratives de l'histoire, structurant ainsi une proto-météorologie homérique. Cet article cherche alors à soulever certaines normes de description trouvés au cours de la lecture de l'Iliade et quelques consid

Scintillation characteristics of nonstoichiometric phases formed in MF sub 2 -GdF sub 3 -CeF sub 3 systems Part III. Dense Gd sub 1 sub - sub x sub - sub y M sub x Ce sub y F sub 3 sub - sub x tysonite-related crystals (M=Ca, Sr)

CERN Document Server

Kobayashi, M; Sobolev, B P; Zhmurova, Z I; Krivandina, E A; Nikl, M

1999-01-01

We evaluated the scintillation characteristics and the radiation hardness of Gd sub 1 sub - sub x Ca sub x F sub 3 sub - sub x and Gd sub 1 sub - sub x Sr sub x F sub 3 sub - sub x tysonite-type solid solutions (close to 6.6 g/cm sup 3 in density) doped with Ce which were grown from the congruent melt. As the Ce concentration increased, the Ce sup 3 sup + emission at 345 nm increased to a level comparable with the Gd sup 3 sup + emission at 310 nm. Both emissions, however, were slow with the decay constant in the order of ms. The radiation hardness, which was roughly 10 sup 4 rad, tends to degrade as the wavelength decreases and/or the Ce concentration increases. Both spontaneous recovery and UV annealing of the radiation damages were significant. The intensity of the gamma-ray excited luminescence, integrated over time, was as large as 50% of that in BaF sub 2 (12% of that in CdWO sub 4). When the Ce concentration is nil or only small, the yellow-green luminescence for UV excitation was as intense as in CdWO...

Levantamento das condições de funcionamento dos serviços de radiologia de hospitais públicos e universitários do Rio de Janeiro Evaluation of working conditions of radiology departments of public and university hospitals in Rio de Janeiro, Brazil

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Marcos Otaviano da Silva

2004-08-01

Full Text Available Foram realizados testes de controle de qualidade, descritos na Portaria 453/98 do Ministério da Saúde, em sete hospitais públicos do Rio de Janeiro, em um total de 29 tubos de raios X, 30 chassis e 20 vestimentas de proteção individual. Os testes avaliaram o desempenho do gerador de raios X e a geometria do feixe. Foram verificados, também, chassis, "écrans" e negatoscópios, assim como as câmaras claras e escuras. Alguns dos resultados encontrados foram: 55% dos tubos foram reprovados em exatidão e 15% em reprodutibilidade de kVp; 53% foram reprovados em exatidão e 31% em reprodutibilidade de tempo de exposição; 30% foram reprovados em camada semi-redutora; 18% foram reprovados no alinhamento do feixe central; 30% foram reprovados em coincidência de campos; 40% foram reprovados na linearidade de exposição; 64% foram rejeitados no teste de ponto focal. Foram verificadas a guarda inadequada e a falta de recomendação para uso dos aventais plumbíferos. Os resultados dos testes sugerem a necessidade da implementação sistemática de controle de qualidade por um profissional qualificado. A relação de custo-benefício reforça a implantação e a manutenção dos procedimentos contidos e executados neste trabalho, pois tais procedimentos garantiriam a diminuição do custo final do serviço e da dose nos pacientes.Quality control tests, according to "Portaria 453/98" of the Brazilian Health Ministry, were applied in seven public hospitals of Rio de Janeiro including 29 X-ray tubes, 30 cassettes and 20 individual protection garments. These tests evaluate mainly the X-ray generator and system geometry. Other tests in the accessories were also performed, such as: cassettes, screens, viewing boxes, darkrooms and clear rooms. In the kVp tests, 55% of the equipments were disapproved in exactitude and 15% in reproducibility. Time exactitude and reproducibility were not approved in 53% and 31% of the equipments, respectively. The

Experimental Determination of Solubilities of Tri-calcium Di-Citrate Tetrahydrate [Ca<sub>3sub>[C>3sub>H>5sub>O(COO)>3sub>]>2sub>•4H<sub>2sub>O] Earlandite in NaCl and MgCl<sub>2sub> Solutions to High Ionic Strengths and Its Pitzer Model: Applications to Nuclear Waste Isolation and Other Low Temperature Environments

Energy Technology Data Exchange (ETDEWEB)

Xiong, Yongliang [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Kirkes, Leslie Dawn [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Westfall, Terry [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Marrs, Cassandra [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Knox, Jandi [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group; Burton, Heather Lynn [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Carlsbad Programs Group

2017-09-01

In this study, solubility measurements on tri-calcium di-citrate tetrahydrate [Ca<sub>3sub>[C>3sub>H>5sub>O(COO)>3sub>]2•4H<sub>2sub>O, abbreviated as Ca<sub>3sub>[Citrate]>2sub>•4H<sub>2sub>O] as a function of ionic strength are conducted in NaCl solutions up to I = 5.0 mol•kg^–1 and in MgCl<sub>2sub> solutions up to I = 7.5 mol•kg^–1, at room temperature (22.5 ± 0.5°C). The solubility constant (log K$0\\atop{sp}$) for Ca<sub>3sub>[Citrate]>2sub>•4H<sub>2sub>O and formation constant (logβ$0\\atop{1}$) for Ca[C<sub>3sub>H>5sub>O(COO)>3sub>]^–Ca>3sub>[C>3sub>H>5sub>O(COO)>3sub>]>2sub>•4H<sub>2sub>O (earlandite) = 3Ca²⁺ + 2[C<sub>3sub>H>5sub>O(COO)>3sub>]^3– + 4H<sub>2sub>O (1) Ca²⁺ + [C<sub>3sub>H>5sub>O(COO)>3sub>]^3– = Ca[C<sub>3sub>H>5sub>O(COO)>3sub>]^– (2) are determined as –18.11 ± 0.05 and 4.97 ± 0.05, respectively, based on the Pitzer model with a set of Pitzer parameters describing the specific interactions in NaCl and M<sub>gCl>2sub> media.

Possible martensitic transformation in Heusler alloy Mn{sub 2}PdSn from first principles

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Feng, L., E-mail: author.fenglin@tyut.edu.cn [Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education, Computational Condensed Matter Physics Laboratory, Department of Physics, Taiyuan University of Technology, Taiyuan 030024 (China); Feng, X. [Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education, Computational Condensed Matter Physics Laboratory, Department of Physics, Taiyuan University of Technology, Taiyuan 030024 (China); Liu, E.K.; Wang, W.H.; Wu, G.H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Hu, J.F.; Zhang, W.X. [Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education, Computational Condensed Matter Physics Laboratory, Department of Physics, Taiyuan University of Technology, Taiyuan 030024 (China)

2016-12-01

The tetragonal distortion, electronic structure and magnetic property of Mn{sub 2}PdSn have been systematically investigated by first-principles calculations. The results indicate that the total energy of tetragonal martensitic phase is lower than cubic austenitic phase for Mn{sub 2}PdSn. The corresponding c/a ratio and energy difference are 1.23 and 41.62 meV/f.u., respectively. This suggests that there is a great possibility for martensitic transformation to occur in Mn{sub 2}PdSn with temperature decreasing. The electronic structure shows that there are sharp DOS peaks originating from p–d hybridization in the vicinity of Fermi level in the cubic phase. And these peaks disappear or become more flat in the martensitic phase. - Highlights: • The martensitic transformation is prone to occur with temperature decreasing in Mn{sub 2}PdSn. • Electronic structure and magnetic property of Mn{sub 2}PdSn are investigated. • Both the austenitic and martensitic phases of Mn{sub 2}PdSn are ferrimagnetic.

Syntheses and structural characterization of vanado-tellurites and vanadyl-selenites: SrVTeO{sub 5}(OH), Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}, Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O and Ba{sub 2}VSe{sub 3}O{sub 10}

Energy Technology Data Exchange (ETDEWEB)

Konatham, Satish; Vidyasagar, Kanamaluru, E-mail: kvsagar@iitm.ac.in

2017-05-15

Four new quaternary vanado-tellurites and vanadyl-selenites, namely, SrVTeO{sub 5}(OH)(1), Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}(2), Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O(3) and Ba{sub 2}VSe{sub 3}O{sub 10}(4) have been synthesized and structurally characterized by single crystal X-ray diffraction. The oxidation state of vanadium is +5 in tellurites 1 and 2 and +4 in selenites 3 and 4. The structures of SrVTeO{sub 5}(OH)(1) and Cd{sub 2}V{sub 2}Te{sub 2}O{sub 11}(2) compounds consist of (VTeO{sub 5}(OH)){sup 2-} and (V{sub 2}Te{sub 2}O{sub 11}){sup 4-}anionic chains respectively, which are built from tetrahedral VO{sub 4} and disphenoidal TeO{sub 4} moieties. Similarly the structures of Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O(3) and Ba{sub 2}VSe{sub 3}O{sub 10}(4) respectively contain (VSe{sub 2}O{sub 7}){sup 2-} and (VSe{sub 3}O{sub 10}){sup 4-} anionic chains, which are made up of octahedral VO{sub 6} and pyramidal SeO{sub 3} units. Compounds 1 and 3 have been characterized by thermogravimetric and infrared spectroscopic methods. Compounds 1 and 2 are wide band gap semiconductors. - Graphical abstract: Ca{sub 3}VSe{sub 4}O{sub 13}·H{sub 2}O and Ba{sub 2}VSe{sub 3}O{sub 10} compounds contain (VSe{sub 2}O{sub 7}){sup 2-} and (VSe{sub 3}O{sub 10}){sup 4-} chains. - Highlights: • Four new vanado-tellurites and vanadyl-selenites are synthesized. • Their structural features are different. • The vanado-tellurites are wide band gap semiconductors.

Chemistry through cocrystals: pressure-induced polymerization of C<sub>2sub>H>2sub>·C>6sub>H>6sub> to an extended crystalline hydrocarbon

Energy Technology Data Exchange (ETDEWEB)

Ward, Matthew D. [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA; Huang, Haw-Tyng [Department of Materials Science and Engineering; Pennsylvania State University; University Park; USA; Zhu, Li [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA; Biswas, Arani [Department of Chemistry; Pennsylvania State University; University Park; USA; Popov, Dmitry [High Pressure Collaborative Access Team (HPCAT); Geophysical Laboratory; Carnegie Institution of Washington; Argonne; USA; Badding, John V. [Department of Materials Science and Engineering; Pennsylvania State University; University Park; USA; Department of Chemistry; Strobel, Timothy A. [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA

2018-01-01

The 1 : 1 acetylene–benzene cocrystal, C<sub>2sub>H>2sub>·C>6sub>H>6sub>, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

Chemistry through cocrystals: pressure-induced polymerization of C<sub>2sub>H>2sub>·C <sub>6sub>H>6sub> to an extended crystalline hydrocarbon

Energy Technology Data Exchange (ETDEWEB)

Ward, Matthew D. [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA; Huang, Haw-Tyng [Department of Materials Science and Engineering; Pennsylvania State University; University Park; USA; Zhu, Li [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA; Biswas, Arani [Department of Chemistry; Pennsylvania State University; University Park; USA; Popov, Dmitry [High Pressure Collaborative Access Team (HPCAT); Geophysical Laboratory; Carnegie Institution of Washington; Argonne; USA; Badding, John V. [Department of Materials Science and Engineering; Pennsylvania State University; University Park; USA; Department of Chemistry; Strobel, Timothy A. [Geophysical Laboratory; Carnegie Institution of Washington; Washington; USA

2018-01-01

The 1:1 acetylene–benzene cocrystal, C<sub>2sub>H>2sub>·C>6sub>H>6sub>, was synthesized under pressure in a diamond anvil cell (DAC) and its evolution under pressure was studied with single-crystal X-ray diffraction and Raman spectroscopy.

Ab initio study of the structural, electronic, elastic and thermal properties of RMn{sub 2}Ge{sub 2} (R = Ca, Nd and Y) intermetallic compounds

Energy Technology Data Exchange (ETDEWEB)

Miloud Abid, O.; Yakoubi, A. [Laboratoire d’Etudes des Matériaux et Instrumentations Expérimentales, Université Djilali Liabes de Sidi Bel-Abbes, 22000 (Algeria); Tadjer, A. [Modeling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, Sidi Bel-Abbes (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique de la Modélisation Mathématique (LPQ3M), Université de Mascara, 29000 (Algeria); Ahmed, R. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Murtaza, G. [Materials Modeling Laboratory, Department of Physics, Islamia College University, Peshawar (Pakistan); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Azam, Sikander [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic)

2014-12-15

Highlights: • The calculated structural parameters of RMn{sub 2}Ge{sub 2} (R = Ca, Nd and Y) compounds are found in good agreement with the experimental data. • The structural and band structure calculation reveals that these compounds are ferromagnetic brittle metals. • The elastic and thermodynamic properties for the herein studied compounds are investigated for the first time. - Abstract: Intermetallic RMn{sub 2}Ge{sub 2} ternary compounds have attracted considerable attention from researchers in recent years because they show strong indications for novel magnetic characteristics and they have the potential to reveal the mechanism of superlattices. The study of the paramagnetic, ferromagnetic and antiferromagnetic phases affirms the strong dependence to the distance between atomic species in these compounds. In this study, we investigated the structural, elastic, electronic and thermodynamic properties of the intermetallic RMn{sub 2}Ge{sub 2} (R = Ca, Nd and Y) compounds. To carry out this study, we used the full potential (FP) linearized (L) augmented plane wave plus local orbitals (APW + lo), a scheme of calculations developed within the frame work of density functional theory (DFT). To incorporate the exchange correlation (XC) energy and corresponding potential into the total energy calculations, local density approximation (LDA) parameterized by Perdew and Wang is taken into account. Analysis of the density of states (DOS) profile illustrates the conducting nature of these intermetallic compounds; with a predominantly contribution from the R and Mn-d states. At ambient conditions, calculations for elastic constants (C{sub 11}, C{sub 12}, C{sub 13}, C{sub 44}, C{sub 33} and C{sub 66}) are also performed, which point to their brittle character. In addition, the quasi harmonic Debye model was used to predict the thermal properties, together with relative expansion coefficients and heat capacity.

Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yahia, H. Ben [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. Box 5825 Doha (Qatar); Essehli, R., E-mail: ressehli@qf.org.qa [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. Box 5825 Doha (Qatar); Avdeev, M. [Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights NSW 2234 (Australia); Park, J-B.; Sun, Y-K. [Department of Energy Engineering Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Al-Maadeed, M.A. [Center for Advanced Materials (CAM), Qatar University, 2713 Doha (Qatar); Belharouak, I., E-mail: ibelharouak@qf.org.qa [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. Box 5825 Doha (Qatar)

2016-06-15

The new compounds NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} crystallize with a stuffed α-CrPO{sub 4}-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} a statistical disorder Ni{sup 2+}/Cr{sup 3+} was observed on both the 8g and 4a atomic positions, whereas in NaCoCr{sub 2}(PO{sub 4}){sub 3} the statistical disorder Co{sup 2+}/Cr{sup 3+} was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} delivered specific capacities of 352, 385, and 368 mA h g{sup −1}, respectively, which attests to the electrochemical activity of sodium in these compounds. - Highlights: • NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method. • The crystal structures were determined by using neutron powder diffraction data. • The three compounds crystallize with a stuffed α-CrPO{sub 4}-type structure. • The three compounds were tested as anodes in sodium-ion batteries. • Relatively high specific capacities were obtained for these compounds.

Room Temperature Radiolytic Synthesized Cu@CuAlO<sub>2sub>-Al>2sub>O>3sub> Nanoparticles

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Nayereh Soltani

2012-09-01

Full Text Available Colloidal Cu@CuAlO<sub>2sub>-Al>2sub>O>3sub> bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a ⁶⁰Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO<sub>2sub>-Al>2sub>O>3sub> nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM, energy dispersive X-ray spectrometry (EDX, and X-ray diffraction (XRD showed that Cu@CuAlO<sub>2sub>-Al>2sub>O>3sub> nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation.

Deposition of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films on the lithium-ion conductor of Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet

Energy Technology Data Exchange (ETDEWEB)

Wu, Xian Ming, E-mail: xianmingwu@163.com [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China); Xiangxi Minerals and New Materials Research and Service Center, Jishou Hunan 416000 (China); Chen, Shang [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China); Xiangxi Minerals and New Materials Research and Service Center, Jishou Hunan 416000 (China); He, Ze Qiang; Chen, Shou Bin; Li, Run Xiu [College of Chemistry and Chemical Engineering, Jishou University, Jishou Hunan 416000 (China)

2015-08-31

LiMn{sub 2}O{sub 4} and Li{sub 4}Ti{sub 5}O{sub 12} films were deposited on the lithium-ion conductor of Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet by spray technique. The effect of annealing temperature, annealing time, Li:Ti and Li:Mn molar ratio on the phase and crystallization of the films were investigated with X-ray diffraction. The LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3}/Li{sub 4}Ti{sub 5}O{sub 12} thin-film lithium-ion battery using Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet as both electrolyte and substrate was also studied. The results show that the effect of annealing temperature, annealing time, Li:Ti and Li:Mn molar ratio has great effect on the phase and crystallization of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films deposited on the Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet. The optimal Li:Ti and Li:Mn molar ratio for the deposition of Li{sub 4}Ti{sub 5}O{sub 12} and LiMn{sub 2}O{sub 4} films on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet are 7.2:5 and 1.05:2, respectively. The optimal annealing temperature and time for the deposition of LiMn{sub 2}O{sub 4} film on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet are 650 °C and 10 min. While those for Li{sub 4}Ti{sub 5}O{sub 12} film are 700 °C and 10 min. The LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3}/Li{sub 4}Ti{sub 5}O{sub 12} thin-film battery offers a working voltage about 2.25 V and can be easily cycled. - Highlights: • LiMn{sub 2}O{sub 4} and Li{sub 4}Ti{sub 5}O{sub 12} films spray deposited on Li{sub 1.3}Al{sub 0.3}Ti{sub 1.7}(PO{sub 4}){sub 3} sintered pellet • Film crystal phase depends on the spray solution composition and annealing conditions. • Prepared thin-film lithium-ion battery employs sintered pellet as electrolyte and substrate. • LiMn{sub 2}O{sub 4}/Li{sub 1.3}Al{sub 0.3}Ti{sub 1

Influência do nível de ruídos na percepção do estresse em pacientes cardíacos The influence of noise levels on the perception of stress in heart disease patients

Directory of Open Access Journals (Sweden)

Aline Maria Heidemann

2011-03-01

Full Text Available OBJETIVO: Identificar os principais fatores geradores de estresse em pacientes internados em unidade coronariana e a influência do nível de ruídos na percepção de estresse dos mesmos. MÉTODOS: Estudo prospectivo, descritivo e quantitativo, realizado de junho a novembro de 2009 na Unidade Coronariana do Hospital de Clínicas da Unicamp. Para identificar os fatores estressantes foi utilizada a Escala de Estressores em Unidade de Terapia Intensiva (Intensive Care Unit Environmental Stressor Scale ICUESS no primeiro, segundo e terceiro dias de internação. Na primeira e segunda noite de internação, foi mensurado o nível de ruído pelo decibelímetro marca Instrutherm - modelo DEC-460. RESULTADOS: Participaram do estudo 32 pacientes cardiopatas clínicos. A mediana para a Escala de Estressores em Unidade de Terapia Intensiva foi de 67,5, 60,5 e 59,5, no primeiro, segundo e terceiro dias respectivamente, não apresentando diferença estatisticamente significante entre os valores. O maior valor de nível de ruídos foi às 21 horas, da segunda noite com mediana de 58,7dB, e o me-nor, de 51,5dB à zero hora da primeira noite. Quando feita a regressão linear múltipla, o nível de ruídos da primeira noite teve correlação de 33% com a Escala de Estressores do segundo dia, e o nível de ruídos da segunda noite teve correlação de 32,8% com a Escala de Estressores do terceiro dia, com p=0,001. CONCLUSÃO: Pacientes internados em Unidade Coronariana apresentam maior percepção de estresse. O elevado nível de ruídos também é responsável pela percepção do estresse dos pacientes.OBJECTIVES: To identify the main causes of stress in patients staying in a coronary unit and to assess the influence of noise levels on their perception of stress. METHODS: This was a prospective, descriptive and quantitative study conducted between June and November 2009 in the Coronary Unit of the Hospital de Clínicas da Universidade Estadual de Campinas. The

Os subsídios à agricultura no comércio internacional: as políticas da União Europeia e dos Estados Unidos da América The agricultural subsidies in international trade: the policies adopted by the European Union and the United States of America

Directory of Open Access Journals (Sweden)

Flávio Marcelo Rodrigues Bruno

2012-04-01

Full Text Available O presente artigo analisa a prática de subsídios à agricultura no comércio internacional, tendo como principal objetivo dimensionar a sua prática enquanto instrumento econômico estratégico para o setor agrícola, especialmente para os Estados Unidos e a União Europeia. Uma completa proibição dos subsídios não é desejável porque sua prática, em essência, constitui uma alternativa à busca do bem-estar social da nação. Contudo, a utilização dos subsídios agrícolas, na forma como vêm sendo praticados, constituem-se em intervenções de cunho protecionista que provocam distorções no comércio internacional. Sendo os Estados Unidos e a União Europeia as nações que mais os utilizam no comércio internacional, tem-se gerado preocupações sobre sua própria eficiência enquanto instrumento de política comercial estratégica para o comércio internacional.This study examines the practice of agricultural subsidies in international trade, aiming at scaling its practice as a strategic economic tool primarily for the agricultural sector, especially to the United States and the European Union. A complete ban on subsidies is not desirable because its practice, in essence, is a path to improve the welfare of the nation. However, the way the agricultural subsidies have been employed, constitute protectionist interventions that distort international trade. The United States and the European Union are the major users of this instrument in international trade, a factor that has raised concerns about their own efficiency as a strategic trade policy for international trade.

Projeto pró-ABEn: subsídios e reflexões para o marketing da associação

Directory of Open Access Journals (Sweden)

Isília Aparecida Silva

2002-08-01

Full Text Available No presente estudo, procedemos a análise interna da ABEn, diante dos objetivos: conhecer as representações dos enfermeiros membros das Diretorias das Seções e Diretoria Nacional sobre a ABEn e fornecer subsídios para o planejamento e implementação do projeto de fortalecimento institucional. Os cenários de obtenção dos dados foram as diretorias das Seções e a Diretoria Nacional e os sujeitos constituídos por todos os membros disponíveis de cada Diretoria de seção e dois membros da ABEn Nacional. Para a captação dos dados foi utilizado um formulário, que foi respondido por 15 Seções, no período de 1997 a 2000. A análise dos dados do material empírico foi feita em duas vertentes, sendo aprimeira fundamentada no Discurso do Sujeito Coletivo-DSC e a segunda na Análise Institucional. Os resultados permitiram evidenciar as representações desses sujeitos sobre a ABEn, de modo a possibilitar que estratégias de marketing possam ser viabilizadas.

The new Zintl phases Eu{sub 21}Cd{sub 4}Sb{sub 18} and Eu{sub 21}Mn{sub 4}Sb{sub 18}

Energy Technology Data Exchange (ETDEWEB)

Wang, Yi; Darone, Gregory M.; Bobev, Svilen, E-mail: bobev@udel.edu

2016-06-15

Crystals of two new Zintl compounds, Eu{sub 21}Mn{sub 4}Sb{sub 18} and Eu{sub 21}Cd{sub 4}Sb{sub 18} have been synthesized using the molten metal flux method, and their structures have been established by single-crystal X-ray diffraction. Both compounds are isotypic and crystallize in the monoclinic space group C2/m (No. 12, Z=4). The structures are based on edge- and corner-shared MnSb{sub 4} or CdSb{sub 4} tetrahedra, which make octameric [Mn{sub 8}Sb{sub 22}] or [Cd{sub 8}Sb{sub 22}] polyanions. Homoatomic Sb–Sb bonds are present in both structures. The Eu atoms take the role of Eu{sup 2+}cations with seven unpaired 4f electrons, as suggested by the temperature-dependent magnetization measurements. The magnetic susceptibilities of Eu{sub 21}Mn{sub 4}Sb{sub 18} and Eu{sub 21}Cd{sub 4}Sb{sub 18} indicate that both phases order anti-ferromagnetically with Néel temperatures of ca. 7 K and ca. 10 K, respectively. The unpaired 3d electrons of the Mn atoms in Eu{sub 21}Mn{sub 4}Sb{sub 18} do contribute to the magnetic response, however, the bulk magnetization measurements do not provide evidence for long-range ordering of the Mn spins down to 5 K. Electrical resistivity measurements suggest that both compounds are narrow band gap semiconductors. - Graphical abstract: Eu{sub 21}Mn{sub 4}Sb{sub 18} and Eu{sub 21}Cd{sub 4}Sb{sub 18} have complex monoclinic structures, based on MnSb{sub 4} and CdSb{sub 4} tetrahedra, both edge- and corner-shared. A perspective of the crystal structure is shown, as viewed along the b axis. Display Omitted - Highlights: • Eu{sub 21}Mn{sub 4}Sb{sub 18} and Eu{sub 21}Cd{sub 4}Sb{sub 18} are novel compounds in the respective ternary phase diagrams. • For both structures, the Zintl-Klemm rules are followed, and both are small gap semiconductors. • Eu{sub 21}Mn{sub 4}Sb{sub 18} and Eu{sub 21}Cd{sub 4}Sb{sub 18} are air-stable Zintl phases and could be new thermoelectric materials.

The quaternary arsenide oxides Ce{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} and Pr{sub 9}Au{sub 5-x}As{sub 8}O{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Bartsch, Timo; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie

2016-07-01

The quaternary gold arsenide oxides Ce{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} and Pr{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} were synthesized from the rare earth elements (RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F{sup 2} values, 160 variables for Ce{sub 9}Au{sub 4.91(4)}As{sub 8}O{sub 6} and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F{sup 2} values, 160 variables for Pr{sub 9}Au{sub 4.75(1)}As{sub 8}O{sub 6}. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au{sub 5}As{sub 8}]{sup 15-} (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O rate at RE{sub 4/4} and O rate at RE{sub 4/3} tetrahedra ([RE{sub 4}O{sub 3}]{sub 2}{sup 12+}) as well as RE{sup 3+} cations in cavities.

A comparative study of low-field magnetoresistance for La sub 2 sub / sub 3 Ca sub 1 sub / sub 3 Mn sub 1 sub - sub x Cu sub x O sub 3 (x = 0% and 4%) synthesized at different temperatures

CERN Document Server

Yuan, S L; Xia, Z C; Zhao, L F; Liu, L; Chen, W; Zhang, G H; Zhang, L J; Feng, W; Zhong, Q H; Liu, S

2003-01-01

Polycrystalline samples of nominal La sub 2 sub / sub 3 Ca sub 1 sub / sub 3 Mn sub 1 sub - sub x Cu sub x O sub 3 (x 0% and 4%) were fabricated by a sol-gel method following sintering treatments at temperature T sub s ranging between 1000 deg. C and 1300 deg. C. Experiments indicate that doping Cu does not cause a change in crystalline structure, but strongly affects transport and magnetoresistance (MR) properties. For lower T sub s , when a low magnetic field of H = 0.3 T, is applied, the x = 0 samples show typical intergrain MR behaviour with a monotonic increase in MR sub 0 (ident to DELTA rho/rho(H = 0)) on cooling; while for the x = 4% samples, in addition to intergrain MR, a characteristic feature similar to colossal MR (CMR) is observed near the insulator-metal transition. The maximum MR with a value approx 80% of that for H = 0.3 T is obtained in the sample prepared at 1100 deg. C, which is comparable to the intrinsic CMR response usually observed in large fields of the order of several teslas.

Electronic structure of Ti/sub 2/O/sub 3/, V/sub 2/O/sub 3/, and Cr/sub 2/O/sub 3/

Energy Technology Data Exchange (ETDEWEB)

Bondarenko, T N; Zhurakovskii, E A; Dzeganovskii, V P [AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya

1975-11-01

Electronic structure of oxides Ti/sub 2/O/sub 3/, V/sub 2/O/sub 3/, Cr/sub 2/O/sub 3/ was elucidated by means of X-ray and ESCA methods and the results were compared with the data obtained by other methods and with the available models of electronic structures. Energy diagram of V/sub 2/O/sub 3/ and common energy scale of X-ray spectra of Ti and Cr in Ti/sub 2/O/sub 3/ and Cr/sub 2/O/sub 3/ are presented. X-ray spectra show that these oxides possess the states which are related genetically to the M4p-states i.e. the X-ray data complement essentially to the result of optical and electrophysical measurements. MO and M/sub 2/O/sub 3/ compounds in the region of Fermi level have overlapping emission and absorption spectra which is specific to the matters with the metallic type of bonding. Actually TiO, VO, Ti/sub 2/O/sub 3/ and V/sub 2/O/sub 3/ have metallic type of bonding. However such overlap was observed in Cr/sub 2/O/sub 3/ as well whose forbidden zone according to photoconductivity measurments is about 3 eV. Absence of energy gap between emission and absorption spectra in Cr/sub 2/O/sub 3/ may be explained by traces of impurities which convert dielectrics conductors - impurities act as agents caus:ng filling or generation of vacancies rather than independent allowing additives. On the other hand this may be due to the defects in Cr/sub 2/O/sub 3/ lattice which may cause appearance of excited states in forbidden zone. These investigations enable to draw energy diagram of V/sub 2/O/sub 3/ and to combine the spectra of M in Ti/sub 2/O/sub 3/ into common energy scheme. Analysis of the diagram and combined spectra revealed great similarity in the electronic structures of M/sub 2/O/sub 3/ oxides (M - Ti, V, Cr) .

UMA ANÁLISE DAS REPRESENTAÇÕES DOS AFRODESCENDENTES NAS PROPAGANDAS DE JORNAIS PAULISTAS

Directory of Open Access Journals (Sweden)

Sibele Gomes de Santana Faria

2014-05-01

Full Text Available A preocupação com a sub-representação do afrodescendente verificada no marketing e em outras manifestações da mídia gera reflexões sociais e acadêmicas. Esta categoria de personagens é presença invariável em papeis subalternos em peças, novelas, filmes e mensagens de propaganda. Tal evidência aponta para estigmas, estereótipos negativos e a transmissão de ideologia racista, explícita ou implícita. No entanto, a literatura, liderada pelo modelo de evolução de Clark (1969 aponta para uma mudança cronológica no tratamento dos afrodescendentes na propaganda e em outras mídias. O objetivo desta pesquisa é analisar o modelo cronológico de representações dos afrodescendentes em propagandas de mídia impressa no Brasil que identifica quatro fases: não reconhecimento, ridicularização, regulamentação e respeito. Esta perspectiva nunca foi aplicada ao caso brasileiro, o que é feito agora. O material de pesquisa é constituído da propaganda veiculada nos jornais Folha de São Paulo e Estado de São Paulo (Estadão, ambos de grande circulação durante três décadas.  Para este tipo de pesquisa as atitudes sociais, em permanente evolução em função de pressões socioeconômicas dos seus principais atores, resultam na aceitação e no respeito às minorias, o que vai se refletir na classificação cronológica proposta. A apreciação crítica dos dados segue a análise de conteúdo de Kassarjian (1976. Os resultados apontam para a inadequação parcial do modelo de Clark ao universo abordado pela pesquisa para o caso brasileiro onde persiste uma eternização do não reconhecimento dos afrodescendentes na mídia impressa.

Triangular Zn{sub 3} and Ga{sub 3} units in Sr{sub 2}Au{sub 6}Zn{sub 3}, Eu{sub 2}Au{sub 6}Zn{sub 3}, Sr{sub 2}Au{sub 6}Ga{sub 3}, and Eu{sub 2}Au{sub 6}Ga{sub 3}. Structure, magnetism, {sup 151}Eu Moessbauer and {sup 69;71}Ga solid state NMR spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Gerke, Birgit; Niehaus, Oliver; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Korthaus, Alexander; Haarmann, Frank [RWTH Aachen Univ. (Germany). Inst. fuer Anorganische Chemie

2016-08-01

The gold-rich intermetallic compounds Sr{sub 2}Au{sub 6}Zn{sub 3}, Eu{sub 2}Au{sub 6}Zn{sub 3}, Sr{sub 2}Au{sub 6}Ga{sub 3}, and Eu{sub 2}Au{sub 6}Ga{sub 3} were synthesized from the elements in sealed tantalum ampoules in induction or muffle furnaces. The europium compounds are reported for the first time and their structures were refined from single crystal X-ray diffractometer data: Sr{sub 2}Au{sub 6}Zn{sub 3} type, R anti 3c, a = 837.7(1), c = 2184.5(4) pm, wR2 = 0.0293, 572 F{sup 2} values for Eu{sub 2}Au{sub 6.04}Zn{sub 2.96} and a = 838.1(2), c = 2191.7(5) pm, wR2 = 0.0443, 513 F{sup 2} values for Eu{sub 2}Au{sub 6.07}Ga{sub 2.93} with 20 variables per refinement. The structures consist of a three-dimensional gold network with a 6R stacking sequence, similar to the respective diamond polytype. The cavities of the network are filled in a ratio of 2:1 by strontium (europium) atoms and Ga{sub 3} (Zn{sub 3}) triangles in an ordered manner. Sr{sub 2}Au{sub 6}Zn{sub 3} and Sr{sub 2}Au{sub 6}Ga{sub 3} are diamagnetic with room temperature susceptibilities of -3.5 x 10{sup -4} emu mol{sup -1}. Temperature dependent susceptibility and {sup 151}Eu Moessbauer spectroscopic measurements show a stable divalent ground state for both europium compounds. Eu{sub 2}Au{sub 6}Zn{sub 3} and Eu{sub 2}Au{sub 6}Ga{sub 3} order antiferromagnetically below Neel temperatures of 16.3 and 12.1 K, respectively. Anisotropic electrical conductivity of Sr{sub 2}Au{sub 6}Ga{sub 3} is proven by an alignment of the crystallites in the magnetic field. Orientation-dependent {sup 69;71}Ga NMR experiments combined with quantum mechanical calculations (QM) give evidence for a highly anisotropic charge distribution of the Ga atoms.

Low-field tunnel-type magnetoresistance properties of polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 thin films

CERN Document Server

Shim, I B; Choi, S Y

2000-01-01

The low-field tunnel-type magnetoresistance (TMB) properties of sol-gel derived polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 (LSMO) thin films were investigated. The polycrystalline thin films were fabricated on Si (100) with a thermally oxidized SiO sub 2 layer while the epitaxial thin films were grown on LaAlO sub 3 (001) single-crystal substrates. The epitaxial thin films displayed both typical intrinsic colossal magnetoresistance (CMR) and abnormal extrinsic tunnel-type magnetoresistance behaviors. Tunnel-type MR ratio as high as 0.4% were observed in the polycrystalline thin films at a field of 120 Oe at room temperature (300 K) whereas the ratios were less than 0.1% for the epitaxial films in the same field range. The low-field tunnel-type MR of polycrystalline LSMO/SiO sub 2 ?Si (100) thin films originated from the behaviors of the grain-boundary properties.

Ternary gallides RE{sub 4}Rh{sub 9}Ga{sub 5}, RE{sub 5}Rh{sub 12}Ga{sub 7} and RE{sub 7}Rh{sub 18}Ga{sub 11} (RE=Y, La-Nd, Sm, Gd, Tb). Intergrowth structures with MgCu{sub 2} and CaCu{sub 5} related slabs

Energy Technology Data Exchange (ETDEWEB)

Seidel, Stefan; Rodewald, Ute C.; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Oldenburg (Germany). Inst. fuer Chemie

2017-07-01

Fourteen ternary gallides RE{sub 4}Rh{sub 9}Ga{sub 5}, RE{sub 5}Rh{sub 12}Ga{sub 7} and RE{sub 7}Rh{sub 18}Ga{sub 11} (RE=Y, La-Nd, Sm, Gd, Tb) were synthesized from the elements by arc-melting, followed by different annealing sequences either in muffle or induction furnaces. The samples were characterized through Guinier powder patterns and the crystal structures of Ce{sub 4}Rh{sub 9}Ga{sub 5}, Ce{sub 5}Rh{sub 12}Ga{sub 7}, Ce{sub 7}Rh{sub 18}Ga{sub 11}, Nd{sub 5}Rh{sub 10.44(4)}Ga{sub 8.56(4)}, Nd{sub 4}Rh{sub 9}Ga{sub 5} and Gd{sub 4}Rh{sub 9}Ga{sub 5} were refined from single crystal X-ray diffractometer data. The new gallides are the n=2, 3 and 5 members of the RE{sub 2+n} Rh{sub 3+3n} Ga{sub 1+2n} structure series in the Parthe intergrowth concept. The slabs of these intergrowth structures derive from the cubic Laves phase MgCu{sub 2} (Mg{sub 2}Ni{sub 3}Si as ternary variant) and CaCu{sub 5} (CeCo{sub 3}B{sub 2} as ternary variant). Only the Nd{sub 5}Rh{sub 10.44(4)}Ga{sub 8.56(4)} crystal shows Rh/Ga mixing within the Laves type slabs. Magnetic susceptibility measurements reveal Pauli paramagnetism for Y{sub 4}Rh{sub 9}Ga{sub 5} and Curie-Weiss paramagnetism for Gd{sub 4}Rh{sub 9}Ga{sub 5} and Tb{sub 4}Rh{sub 9}Ga{sub 5}. Low-temperature data show ferromagnetic ordering at T{sub C}=78.1 (Gd{sub 4}Rh{sub 9}Ga{sub 5}) and 55.8 K (Tb{sub 4}Rh{sub 9}Ga{sub 5}).

Cubic-tetragonal phase transition in Ca sub 0 sub . sub 0 sub 4 Sr sub 0 sub . sub 9 sub 6 TiO sub 3 a combined specific heat and neutron diffraction study

CERN Document Server

Gallardo, M C; Romero, F J; Cerro, J D; Seifert, F; Redfern, S A T

2003-01-01

The specific heat corresponding to the tetragonal-to-cubic transition in Ca sub 0 sub . sub 0 sub 4 Sr sub 0 sub . sub 9 sub 6 TiO sub 3 perovskite has been measured by conduction calorimetry. The order parameter of the transition has been obtained by means of neutron diffraction at low temperatures. Comparison of calorimetric data with the evolution of the order parameter indicates that this transition seems to follow a mean field Landau potential as in SrTiO sub 3. The linear behaviour of the excess of entropy versus temperature suggests that a 2-4 Landau potential is sufficient to describe the transition.

Comparative study between traditional and modified Pechini synthesis methods in the preparation of LaNiO{sub 3} and LaNi{sub 0,8}Co{sub 0,2}O{sub 3} catalysts; Estudo comparativo entre os metodos de sintese Pechini tradicional e modificado na confeccao dos catalisadores LaNiO{sub 3} e LaNi{sub 0,8}Co{sub 0,2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Silva, F.E.F.; Aquino, F.M.; Silva, M.C.M.F., E-mail: fabio@cear.ufpb.br [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Departamento de Engenharia de Energias Renovaveis

2016-07-01

One of the ways of obtaining hydrogen is from the methane reforming reaction, which is an endothermic and non-spontaneous reaction. In order to minimize this energy, nickel catalysts are used. This work aims to synthesize and characterize the catalysts LaNiO{sub 3} and LaNi{sub 0,8}Co{sub 0,2}O{sub 3} using the Pechini method, making use of citric acid and ethylene glycol and modified Pechini, using the edible gelatin as a chelating and polymerizing agent. The obtained materials were characterized by X-Ray Diffraction (XRD), where the formation of peaks characteristic of perovskite and monophasic structures was observed. Scanning Electron Microscopy (SEM) showed that porosity and powders with few agglomerates were observed by both methods. In the analysis of determination of the specific surface area (BET) the materials were shown with areas that are according to the literature.

Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>

Energy Technology Data Exchange (ETDEWEB)

Han, Mangui [Iowa State Univ., Ames, IA (United States)

2004-01-01

Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> for x 0 ~ 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd<sub>5sub>(Si>0.15sub>Ge>3.85sub>), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd<sub>5sub>(Si>2.3sub>Ge>1.7sub>) and Gd<sub>5sub>(Si>3sub>Ge>1sub>), it was a second order transformation between the paramagnetic and ferromagnetic state, because no ΔT have been found. Giant magnetostriction was only found on Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally

Pressure dependence of the elastic constants and vibrational anharmonicity of Pd sub 3 sub 9 Ni sub 1 sub 0 Cu sub 3 sub 0 P sub 2 sub 1 bulk metallic glass

CERN Document Server

Wang Li; Sun, L L; Wang, W H; Wang, W K

2003-01-01

The pressure dependence of the acoustic velocities of a Pd sub 3 sub 9 Ni sub 1 sub 0 Cu sub 3 sub 0 P sub 2 sub 1 bulk metallic glass have been investigated up to 0.5 GPa at room temperature with the pulse echo overlap method. Two independent second-order elastic coefficients C sub 1 sub 1 and C sub 4 sub 4 and their pressure derivatives are yielded. The vibrational anharmonicity is shown by calculating both the acoustic mode Grueneisen parameters in the long-wavelength limit and the thermal Grueneisen parameter, and this result is compared with that for the Pd sub 4 sub 0 Ni sub 4 sub 0 P sub 2 sub 0 bulk glass.

London penetration depth measurements in Ba (Fe<sub>1-xsub>T_x)>2sub>As>2sub>(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

Energy Technology Data Exchange (ETDEWEB)

Gordon, Ryan T. [Iowa State Univ., Ames, IA (United States)

2011-01-01

The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe<sub>1-xsub>T_x)>2sub>As>2sub> (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλ<sub>ab>(T) = CTⁿ, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe<sub>1-xsub>T_x)>2sub>As>2sub> (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared to results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λ<sub>ab>(0), by using TDR frequency shifts. By using this technique, the doping dependence of λ<sub>ab>(0) has been measured in the Ba(Fe<sub>1-xsub>Co_x)>2sub>As>2sub> series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρ<sub>s>(T) = [λ(0)/λ(T)]². By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.

Controllable solvothermal synthesis and photocatalytic properties of complex (oxy)fluorides K{sub 2}TiOF{sub 4}, K{sub 3}TiOF{sub 5}, K{sub 7}Ti{sub 4}O{sub 4}F{sub 7} and K{sub 2}TiF{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Sheng Jie [Division of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, Hefei, Anhui 230026 (China); Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Tang Kaibin, E-mail: kbtang@ustc.edu.cn [Division of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, Hefei, Anhui 230026 (China); Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Cheng Wei; Wang Junli; Nie Yanxiang; Yang Qing [Division of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at Microscale, Hefei, Anhui 230026 (China); Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2009-11-15

Complex (oxy)fluorides K{sub 2}TiF{sub 6}, K{sub 2}TiOF{sub 4}, K{sub 3}TiOF{sub 5} and K{sub 7}Ti{sub 4}O{sub 4}F{sub 7} have been successfully synthesized for the first time through a controllable solvothermal route involving different solvents, for example, methanol, methanol-H{sub 2}O and methanol-H{sub 2}O{sub 2}. The as-prepared products were characterized by X-ray powder diffraction, N{sub 2} surface area adsorption, scanning electron microscope, Fourier transform infrared spectroscopy, UV-vis absorption spectra and X-ray fluorescence. The influences of reaction conditions such as the ratio of methanol to H{sub 2}O{sub 2} or methanol to H{sub 2}O, reaction temperature on the phase, crystallizability and purity of the (oxy)fluorides products were discussed in detail. Meanwhile, the photocatalytic behaviors of the as-prepared K{sub 2}TiF{sub 6}, K{sub 2}TiOF{sub 4}, K{sub 3}TiOF{sub 5} and K{sub 7}Ti{sub 4}O{sub 4}F{sub 7} were evaluated by degradation of rhodamine B molecules, and the results showed that all of the products possessed photocatalytic activities in the order of K{sub 2}TiOF{sub 4} > K{sub 2}TiF{sub 6} > K{sub 7}Ti{sub 4}O{sub 4}F{sub 7} > K{sub 3}TiOF{sub 5} at room temperature under the UV light.

A [Mo{sub 2}O{sub 2}S{sub 2}]-based ring system incorporating tartrate as the bridging ligand. Synthesis, structure and catalytic activity of Cs{sub 4}[Mo{sub 2}O{sub 2}(μ-S){sub 2}]{sub 2}(μ{sub 4}-tart){sub 2} (tart=[C{sub 4}H{sub 2}O{sub 6}]{sup 4-})

Energy Technology Data Exchange (ETDEWEB)

Qian, Ting-Ting; Cui, Yu-Jie; Xin, Zhifeng; Jia, Ai-Quan; Zhang, Qian-Feng [Anhui Univ. of Technology, Anhui (China). Inst. of Molecular Engineering and Applied Chemistry and Anhui Province Key Lab. of Metallurgy Engineering and Resources Recycling

2017-08-01

Treatment of [Mo{sub 2}S{sub 2}O{sub 2}(H{sub 2}O){sub 6}]{sup 2+} with racemic tartaric acid (tartH{sub 4}) in the presence of sodium hydroxide and cesium chloride in aqueous solution led to the isolation of a new tetra-molybdenum ring cluster Cs{sub 4}[Mo{sub 2}O{sub 2}(μ-S){sub 2}]{sub 2}(μ{sub 4}-tart){sub 2}. The cyclic cluster polyanion consists of two dinuclear [Mo{sub 2}O{sub 2}(μ-S){sub 2}]{sup 2+} moieties and two bridging tart{sup 4-} ligands. The cyclic polyoxothiomolybdate cluster, supported on the mesoporous silica SBA-15, was tested for heterogenerous catalysis in thiophene hydrodesulfurization.

Unveiling the Structural Evolution of Ag<sub>1.2sub>Mn>8sub>O>16sub> under Coulombically Controlled (De)Lithiation

Energy Technology Data Exchange (ETDEWEB)

Huang, Jianping [Department; Hu, Xiaobing [Energy; Brady, Alexander B. [Department; Wu, Lijun [Energy; Zhu, Yimei [Energy; Takeuchi, Esther S. [Department; Energy; Department; Marschilok, Amy C. [Department; Department; Takeuchi, Kenneth J. [Department; Department

2018-01-02

MnO<sub>2sub> materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesium batteries due to their earth abundance and environmental friendliness. One polymorph of MnO<sub>2sub>, α-MnO<sub>2sub>, has 2 × 2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver-ion-containing α-MnO<sub>2sub> (Ag<sub>1.2sub>Mn>8sub>O>16sub>) is examined as a candidate cathode material for Li based batteries. Electrochemical stability of Ag<sub>1.2sub>Mn>8sub>O>16sub> is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7%) and atomic distances (~4.8%) are observed when x in Li<sub>xAg>1.2sub>Mn>8sub>O>16sub> is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn–O framework. In contrast, lattice a only expands by 2.2% and Mn–O/Mn-Mn distances show minor changes (~1.4%) at x < 2. The structural deformation (tunnel breakage) at x > 4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag⁰, and long-term cycle stability for this silver-containing α-MnO<sub>2sub> type material at both low and high lithiation levels.

Description and crystal structure of albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Mereiter, K. [Vienna Univ. of Technology (Austria). Inst. of Chemical Technologies and Analytics

2013-04-15

Albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O, triclinic, space group P anti 1, a = 13.569(2), b = 13.419(2), c = 11.622(2) Aa, α = 115.82(1), β = 107.61(1), γ = 92.84(1) (structural unit cell, not reduced), V = 1774.6(5) Aa{sup 3}, Z = 2, Dc = 2.69 g/cm{sup 3} (for 17.5 H{sub 2}O), is a mineral that was found in small amounts with schroeckingerite, NaCa{sub 3}F[UO{sub 2}(CO{sub 3}){sub 3}](SO{sub 4}).10H{sub 2}O, on a museum specimen of uranium ore from Joachimsthal (Jachymov), Czech Republic. The mineral forms small grain-like subhedral crystals (= 0.2 mm) that resemble in appearance liebigite, Ca{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]. ∝ 11H{sub 2}O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2V = 65(1) (λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO{sub 2} and H{sub 2}O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO{sub 2}(CO{sub 3}){sub 3}]{sup 4-} anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF{sub 2}(O{sub carbonate}){sub 3}(H{sub 2}O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO{sub 6}, CaF{sub 2}O{sub 2}(H{sub 2}O){sub 4}, CaFO{sub 3}(H{sub 2}O){sub 4} and CaO{sub 2}(H{sub 2}O){sub 6} coordination polyhedra. The crystal structure is built up from MgCa{sub 3}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].8H{sub 2}O layers parallel to (001) which

La{sub 3}Cu{sub 4}P{sub 4}O{sub 2} and La{sub 5}Cu{sub 4}P{sub 4}O{sub 4}Cl{sub 2}. Synthesis, structure and {sup 31}P solid state NMR spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Bartsch, Timo; Eul, Matthias; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Benndorf, Christopher; Eckert, Hellmut [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Sao Paulo Univ., Sao Carlos, SP (Brazil). Inst. of Physics

2016-04-01

The phosphide oxides La{sub 3}Cu{sub 4}P{sub 4}O{sub 2} and La{sub 5}Cu{sub 4}P{sub 4}O{sub 4}Cl{sub 2} were synthesized from lanthanum, copper(I) oxide, red phosphorus, and lanthanum(III) chloride through a ceramic technique. Single crystals can be grown in a NaCl/KCl flux. Both structures were refined from single crystal X-ray diffractometer data: I4/mmm, a = 403.89(4), c = 2681.7(3) pm, wR2 = 0.0660, 269 F{sup 2} values, 19 variables for La{sub 3}Cu{sub 4}P{sub 4}O{sub 2} and a = 407.52(5), c = 4056.8(7) pm, wR2 = 0.0905, 426 F{sup 2} values, 27 variables for La{sub 5}Cu{sub 4}P{sub 4}O{sub 4}Cl{sub 2}. Refinement of the occupancy parameters revealed full occupancy for the oxygen sites in both compounds. The structures are composed of cationic (La{sub 2}O{sub 2}){sup 2+} layers and covalently bonded (Cu{sub 4}P{sub 4}){sup 5-} polyanionic layers with metallic characteristics, and an additional La{sup 3+} between two adjacent (Cu{sub 4}P{sub 4}){sup 5-} layers. The structure of La{sub 5}Cu{sub 4}P{sub 4}O{sub 4}Cl{sub 2} comprises two additional LaOCl slabs per unit cell. Temperature-dependent magnetic susceptibility studies revealed Pauli paramagnetism. The phosphide substructure of La{sub 3}Cu{sub 4}P{sub 4}O{sub 2} was studied by {sup 31}P solid state NMR spectroscopy. By using a suitable dipolar re-coupling approach the two distinct resonances belonging to the P{sub 2}{sup 4-} and the P{sup 3-} units could be identified.

Electron spin resonance study of a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 single crystal

CERN Document Server

Joh, K W; Lee, C E; Hur, N H; Ri, H C

2003-01-01

Comprehensive measurements of electron spin resonance were carried out on a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 single crystal over a wide temperature range covering the ferromagnetic as well as the paramagnetic phases. Our analysis of the asymmetric lineshapes indicates that the phase segregation of good and poor conducting regions persists far above the ferromagnetic-paramagnetic phase transition temperature.

CeNi{sub 3}-type rare earth compounds: crystal structure of R{sub 3}Co{sub 7}Al{sub 2} (R=Y, Gd–Tm) and magnetic properties of {Gd–Er}{sub 3}Co{sub 7}Al{sub 2}, {Tb, Dy}{sub 3}Ni{sub 8}Si and Dy{sub 3}Co{sub 7.68}Si{sub 1.32}

Energy Technology Data Exchange (ETDEWEB)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-1, Moscow 119991 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600 036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil)

2017-03-15

The crystal structure of new CeNi{sub 3}-type {Y, Gd–Tm}{sub 3}Co{sub 7}Al{sub 2} (P63/mmc. N 194, hP24) compounds has been established using powder X-ray diffraction studies. The magnetism of Tb{sub 3}Ni{sub 8}Si and Dy{sub 3}Ni{sub 8}Si is dominated by rare earth sublattice and the magnetic properties of R{sub 3}Co{sub 7}Al{sub 2} (R =Gd–Er) and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} are determined by both rare earth and cobalt sublattices. Magnetization data indicate ferromagnetic ordering of {Tb, Dy}{sub 3}Ni{sub 8}Si at 32 K and 21 K, respectively. Gd{sub 3}Co{sub 7}Al{sub 2} and Tb{sub 3}Co{sub 7}Al{sub 2} exhibit ferromagnetic ordering at 309 K and 209 K, respectively, whereas Dy{sub 3}Co{sub 7}Al{sub 2}, Ho{sub 3}Co{sub 7}Al{sub 2}, Er{sub 3}Co{sub 7}Al{sub 2} and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} show a field dependent ferromagnetic-like ordering at 166 K, 124 K, 84 K and 226 K, respectively followed by a low temperature transition at 34 K for Dy{sub 3}Co{sub 7}Al{sub 2}, 18 K for Ho{sub 3}Co{sub 7}Al{sub 2}, 56 K for Er{sub 3}Co{sub 7}Al{sub 2}, 155 K and 42 K for Dy{sub 3}Co{sub 7.68}Si{sub 1.32}. Among these compounds, Dy{sub 3}Ni{sub 8}Si shows largest magnetocaloric effect (isothermal magnetic entropy change) of −11.6 J/kg·K at 18 K in field change of 50 kOe, whereas Tb{sub 3}Co{sub 7}Al{sub 2}, Dy{sub 3}Co{sub 7}Al{sub 2} and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} exhibit best permanent magnet properties in the temperature range of 2–5 K with remanent magnetization of 11.95 μ{sub B}/fu, 12.86 μ{sub B}/fu and 14.4 μ{sub B}/fu, respectively and coercive field of 3.0 kOe, 1.9 kOe and 4.4 kOe, respectively. - Highlights: • {Y, Gd–Tm}{sub 3}Co{sub 7}Al{sub 2} compounds crystallize in the CeNi{sub 3}-type structure. • {Gd-Er}{sub 3}Co{sub 7}Al{sub 2} show ferrimagnetic ordering at 309 K, 209 K, 166 K, 124 K and 84 K. • Dy{sub 3}Co{sub 7.68}Si{sub 1.32} exhibits magnetic transitions at 226 K, 155 K and 42 K. • {Tb-Er}{sub 3}Co{sub 7}Al{sub 2

First principles study of the structural and electronic properties of double perovskite Ba{sub 2}YTaO{sub 6} in cubic and tetragonal phases

Energy Technology Data Exchange (ETDEWEB)

Deluque Toro, C.E., E-mail: deluquetoro@gmail.com [Grupo de Nuevos Materiales, Universidad Popular del Cesar, Valledupar (Colombia); Rodríguez M, Jairo Arbey [Grupo de Estudios de Materiales—GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Moreno Salazar, N.O. [Departamento de Física, Universidade Federal de Sergipe (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

2014-12-15

The Ba{sub 2}YTaO{sub 6} double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba{sub 2}YTaO{sub 6} in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba{sub 2}YTaO{sub 6} (I4/m) phase is the most stable one. {sup ©} 2013 Elsevier Science. All rights reserved.

Explaining R{sub D}{sup {sub (}{sub *}{sub )}} with leptoquarks and flavor symmetries

Energy Technology Data Exchange (ETDEWEB)

Schoenwald, Kay [TU Dortmund (Germany)

2016-07-01

Recently LHCb confirmed the anomalies in R{sub D}{sup {sub (}{sub *}{sub )}} previously measured by BaBar and Belle. We use flavor symmetries capable of explaining the observed mixing in the quark and lepton sector to constrain leptoquark couplings and study whether this models can explain the anomalies in R{sub D}{sup {sub (}{sub *}{sub )}}.

Site-selective doping and superconductivity in (La/sub 1-//sub y/Pr/sub y/)(Ba/sub 2-//sub x/La/sub x/)Cu3O/sub 7+//sub δ/

International Nuclear Information System (INIS)

Mitzi, D.B.; Feffer, P.T.; Newsam, J.M.; Webb, D.J.; Klavins, P.; Jacobson, A.J.; Kapitulnik, A.

1988-01-01

Samples in the quaternary system (La/sub 1-//sub y/Pr/sub y/)(Ba/sub 2-//sub x/La/sub x/)Cu 3 O/sub 7+//sub δ/ have been prepared and characterized using x-ray and neutron diffraction, thermogravimetric analysis, and transport and magnetic measurements. Pr substitutes on the oxygen-depleted La layers for y>0.0, while La substitutes on the Ba sites for x>0.0. The effect of doping on each site is inferred to be primarily local, affecting immediately adjacent Cu-O layers. The similar suppression of superconductivity that accompanies doping on each of the two distinct sites apparently correlates with the degree of oxidation of the Cu-O sheets (and not the chains), indicating that the sheets support the high temperature superconductivity. Comparison of orthorhombic and tetragonal samples with similar Ba:La ratios (and y = 0) demonstrates that the orthorhombic phase yields the largest Meissner signals and highest transition temperatures in the La(Ba/sub 2-//sub x/La/sub x/)Cu 3 O/sub 7+//sub δ/ system

Informatividade dos lucros contábeis e divulgação dos ativos biológicos: evidências brasileiras

OpenAIRE

Holanda, Allan Pinheiro

2013-01-01

A pesquisa tem o objetivo de investigar a influência exercida pela divulgação dos ativos biológicos na informatividade dos lucros contábeis nas firmas brasileiras listadas na BM&FBovespa, considerando-se o período de 2010 a 2011. Para a investigação da informatividade dos ativos biológicos foi utilizada a adaptação dos modelos propostos por Easton e Harris (1991) e Francis e Schipper (1999). Os ativos biológicos, por sua vez, foram mensurados de duas maneiras, pela simples existência da c...

Molecular field analysis for melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys (18<=60)

CERN Document Server

Yano, K

2000-01-01

The magnetic properties for the melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys were analyzed using the molecular field theory (MFT). A concentration dependence of three exchange interaction constants was derived over a wide concentration range (18=T sub c sub o sub m sub p. Curvature of the Arrott plot in Gd-rich region was qualitatively simulated.

Photochemistry of U(BH/sub 4/)/sub 4/ and U(BD/sub 4/)/sub 4/

Energy Technology Data Exchange (ETDEWEB)

Paine, R T; Schonberg, P R; Light, R W [New Mexico Univ., Albuquerque (USA). Dept. of Chemistry; Danen, W C; Freund, S M

1979-01-01

U(BH/sub 4/)/sub 4/ and U(BD/sub 4/)/sub 4/ are observed to undergo complex degradation reactions promoted by broadband UV radiation. The primary products of these reactions appear to be U(BH/sub 4/)/sub 3/, B/sub 2/H/sub 6/, H/sub 2/, U(BD/sub 4/)/sub 3/, B/sub 2/D/sub 6/ and D/sub 2/. Further, U(BD/sub 4/)/sub 4/ undergoes a related decomposition reaction under the influence of CO/sub 2/ laser irradiation at 924.97 cm/sup -1/.

Synthesis and structural characterization of Li{sub 3}K{sub 3}Eu{sub 7}(BO{sub 3}){sub 9}

Energy Technology Data Exchange (ETDEWEB)

Braeuchle, Sebastian; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Seibald, Markus [OSRAM GmbH, Schwabmuenchen (Germany). Corporate Innovation

2017-07-01

Li{sub 3}K{sub 3}Eu{sub 7}(BO{sub 3}){sub 9} was prepared by high-temperature solid state synthesis at 900 C in a platinum crucible from lithium carbonate, potassium carbonate, boric acid, and europium(III) oxide. The title compound crystallizes in the orthorhombic space group Pca2{sub 1} (no. 29) (Z = 4). The structure was refined from single-crystal X-ray diffraction data: a = 21.126(2), b = 6.502(2), c = 17.619(2) Aa, V = 2420.1(2) Aa{sup 3}, R1 = 0.0183 and wR2 = 0.0412 for all data. The crystal structure of Li{sub 3}K{sub 3}Eu{sub 7}(BO{sub 3}){sub 9} is isotypic to Li{sub 3}K{sub 3}Y{sub 7}(BO{sub 3}){sub 9} featuring isolated BO{sub 3} units and LiO{sub 6} octahedra forming [Li{sub 3}B{sub 4}O{sub 21}] units in the ac plane, which are linked by additional BO{sub 3} units. The K{sup +} and Eu{sup 3+} cations are arranged in the cavities of the structure.

Quasi-homoepitaxial growth of a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta thick film on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal

CERN Document Server

Sato, M; Morishita, T

2003-01-01

The structural characterizations of the quasi-homoepitaxial growth of a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta thick film grown on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal were investigated in comparison with those of the film grown on (001) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal. The a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films, expected to be a barrier layer, were prepared using a dc-95 MHz hybrid plasma sputtering on (100) and (001) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystals that are superconducting ground planes. The atomic force microscopy image revealed that the surfaces of 700-nm-thick a-axis PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystals were smooth with a mean roughness of 2.8 nm. X-ray diffraction scans showed that a-axis PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films deposited on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single cry...

Persistence of slow fluctuations in the overdoped regime of Ba(Fe<sub>1-xsub>Rh_x)>2sub>As>2sub> superconductors

Energy Technology Data Exchange (ETDEWEB)

Bossoni, L. [Univ. of Pavia (Italy); Leiden Univ. (Netherlands); Moroni, M. [Univ. of Pavia (Italy); Julien, M. H. [Leiden Univ. (Netherlands); Canfield, Paul C. [Ames Lab. and Iowa State Univ., Ames, IA (United States); Mayaffre, H. [Leiden Univ. (Netherlands); Reyes, A. [National High Magnetic Field Lab., Tallahassee, FL (United States); Halperin, W. P. [Northwestern Univ., Evanston, IL (United States); Carretta, P. [Univ. of Pavia (Italy)

2016-04-15

We present nuclear magnetic resonance evidence that very slow (1 MHz) spin fluctuations persist into the overdoped regime of Ba(Fe<sub>1-xsub>Rh_x)>2sub>As>2sub> superconductors. Measurements of the ⁷⁵As spin echo decay rate, obtained both with Hahn Echo and Carr Purcell Meiboom Gill pulse sequences, show that the slowing down of spin uctuations can be described by short-range diffusive dynamics, likely involving domain walls motions separating (π/a, 0) from (0, π/a) correlated regions. This slowing down of the fluctuations is weakly sensitive to the external magnetic field and, although fading away with doping, it extends deeply into the overdoped regime.

AOI [3] High-Temperature Nano-Derived Micro-H<sub>2sub> and - H<sub>2sub>S Sensors

Energy Technology Data Exchange (ETDEWEB)

Sabolsky, Edward M. [West Virginia Univ., Morgantown, WV (United States)

2014-08-01

The emissions from coal-fired power plants remain a significant concern for air quality. This environmental challenge must be overcome by controlling the emission of sulfur dioxide (SO<sub>2sub>) and hydrogen sulfide (H<sub>2sub>S) throughout the entire coal combustion process. One of the processes which could specifically benefit from robust, low cost, and high temperature compatible gas sensors is the coal gasification process which converts coal and/or biomass into syngas. Hydrogen (H<sub>2sub>), carbon monoxide (CO) and sulfur compounds make up 33%, 43% and 2% of syngas, respectively. Therefore, development of a high temperature (>500°C) chemical sensor for in-situ monitoring of H<sub>2sub>, H<sub>2sub>S and SO2<sub>2sub> levels during coal gasification is strongly desired. The selective detection of SO<sub>2sub>/H>2sub>S in the presence of H<sub>2sub>, is a formidable task for a sensor designer. In order to ensure effective operation of these chemical sensors, the sensor system must inexpensively function within harsh temperature and chemical environment. Currently available sensing approaches, which are based on gas chromatography, electrochemistry, and IR-spectroscopy, do not satisfy the required cost and performance targets. This work focused on the development microsensors that can be applied to this application. In order to develop the high- temperature compatible microsensor, this work addressed various issues related to sensor stability, selectivity, and miniaturization. In the research project entitled “High-Temperature Nano-Derived Micro-H<sub>2sub> and -H<sub>2sub>S Sensors”, the team worked to develop micro-scale, chemical sensors and sensor arrays composed of nano-derived, metal-oxide composite materials to detect gases like H<sub>2sub>, SO<sub>2sub>, and H<sub>2sub>S within high-temperature environments (>500°C). The research was completed in collaboration with NexTech Materials, Ltd. (Lewis Center, Ohio). Nex

Structure and physical properties of Cr{sub 5}B{sub 3}-type Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yuan, Fang; Forbes, Scott [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Ramachandran, Krishna Kumar [Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2 (Canada); Mozharivskyj, Yurij, E-mail: mozhar@mcmaster.ca [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada)

2015-11-25

The Cr{sub 5}B{sub 3}-type Ta{sub 5}Si{sub 3} phase was prepared by arc-melting, while the Cr{sub 5}B{sub 3}-type Ta{sub 5}Ge{sub 3} one was synthesized through sintering at 1000 °C. X-ray single crystal diffraction was employed to elucidate their structure. According to the magnetization measurements, both Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3} are Pauli paramagnets, with Ta{sub 5}Ge{sub 3} showing a Curie-Weiss-like paramagnetic behavior at low temperatures likely due to presence of paramagnetic impurity. Both Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3} display a very low electrical resistivity from 2 to 300 K. The resistivity is constant below 20 K, but displays a positive temperature coefficient above 20 K. Electronic structure calculations with the TB-LMTO-ASA method support the metallic character of the two phases and suggest that the bonding is optimized in both phases. - Highlights: • Synthesis of Cr{sub 5}B{sub 3}-type Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3} phases with high purity by arc-melting and sintering, respectively. • Magnetization data and electrical resistivity of the Cr{sub 5}B{sub 3}-type Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3} phases. • Crystal and electronic structure analysis for Ta{sub 5}Si{sub 3} and Ta{sub 5}Ge{sub 3} phase by X-ray diffraction and TB-LMTO-ASA calculations.

In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7} heterostructured nanoparticles with enhanced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Xing, Yonglei [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, School of Electronic and Information Engineering, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, School of Electronic and Information Engineering, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Yin, Xingtian; He, Zuoli; Liu, Xiaobin; Yang, Yawei; Shao, Jinyou [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, School of Electronic and Information Engineering, State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Kong, Ling Bing, E-mail: ELBKong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

2016-11-30

Highlights: • Visible-light photocatalytic activities of the nanostructured In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7} heterostructures were studied. • Effect of In{sub 2}O{sub 3} content on the photocatalytic activity of the In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7} heterostructure was evaluated. • 0.1In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7} heterostructure photocatalyst shows a superior photocatalytic activity. • Based on Mott-Schottky analysis and active species detection, a mechanism for the separation of photogenerated carriers is proposed. • The effective separation process of the photogenerated electron-hole pairs was testified by photocurrent test. - Abstract: In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7} composite photocatalysts with various contents of cubic In{sub 2}O{sub 3} nanoparticles were fabricated by using impregnation method. A thriving modification of Bi{sub 2}Sn{sub 2}O{sub 7} by an introduction of In{sub 2}O{sub 3} was confirmed by using X-ray diffraction, UV–vis diffuse reflectance spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The samples composed of hybrids of In{sub 2}O{sub 3} and Bi{sub 2}Sn{sub 2}O{sub 7} exhibited a much higher photocatalytic activity for the degradation of Rhodamine B under visible light, as compared with pure In{sub 2}O{sub 3} and Bi{sub 2}Sn{sub 2}O{sub 7} nanoparticles. Optimized composition of the composite photocatalysts was 0.1In{sub 2}O{sub 3}/Bi{sub 2}Sn{sub 2}O{sub 7}, which shows a rate constant higher than those of pure In{sub 2}O{sub 3} and Bi{sub 2}Sn{sub 2}O{sub 7} by 4.06 and 3.21 times, respectively. Based on Mott-Schottky analysis and active species detection, the photoexcited electrons in the conduction band of In{sub 2}O{sub 3} and the holes in the valence band of Bi{sub 2}Sn{sub 2}O{sub 7} participated in reduction and oxidation reactions, respectively. Hence, ·OH, ·O{sub 2}{sup −} and h

Ammonothermal synthesis of alkali-alkaline earth metal and alkali-rare earth metal carbodiimides. K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}

Energy Technology Data Exchange (ETDEWEB)

Mallmann, Mathias; Haeusler, Jonas; Cordes, Niklas; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU) (Germany)

2017-12-13

Alkali-alkaline earth metal and alkali-rare earth metal carbodiimides, namely K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (x = 0 - 1) (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}, were synthesized under ammonothermal conditions in high-pressure autoclaves. The structures of the three compounds can be derived from homeotypic K{sub 5}H(CN{sub 2}){sub 3} and Na{sub 5}H(CN{sub 2}){sub 3} by partial substitution of K{sup +} or Na{sup +}by Sr{sup 2+} or Eu{sup 2+}. The reactions were carried out in two step syntheses (T{sub 1} = 673 K, T{sub 2} = 823 K) starting from sodium or potassium azide, dicyandiamide and strontium or Eu(NH{sub 2}){sub 2}, respectively. The crystal structures were solved and refined from single-crystal X-ray diffraction data [K{sub 4.16}Sr{sub 0.84}(CN{sub 2}){sub 2.84}(HCN{sub 2}){sub 0.16}: space group Im3m (no. 229), a = 7.8304(5) Aa, Z = 2, R{sub 1} = 0.024, wR{sub 2} = 0.052; K{sub 4.40}Eu{sub 0.60}(CN{sub 2}){sub 2.60}(HCN{sub 2}){sub 0.40}: space group Im anti 3m (no. 229), a = 7.8502(6) Aa, Z = 2, R{sub 1} = 0.022, wR{sub 2} = 0.049]. In contrast to the potassium carbodiimides, the sodium-strontium carbodiimide was only synthesized as microcrystalline powder. The crystal structure was determined by powder X-ray diffraction and refined by the Rietveld method [Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}: space group Im3m (no. 229), a = 7.2412(1) Aa, Z = 2, R{sub wp} = 0.050]. The presence of hydrogencyanamide units ([HNCN]{sup -}) next to carbodiimide units ([CN{sub 2}]{sup 2-}) in all compounds was confirmed by FT-IR spectroscopy. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

High-efficiency Thin-film Fe<sub>2sub>SiS>4sub> and Fe<sub>2sub>GeS>4sub>-based Solar Cells Prepared from Low-Cost Solution Precursors. Final Report

Energy Technology Data Exchange (ETDEWEB)

Radu, Daniela Rodica [Delaware State Univ., Dover, DE (United States); Univ. of Delaware, Newark, DE (United States); Liu, Mimi [Delaware State Univ., Dover, DE (United States); Hwang, Po-yu [Delaware State Univ., Dover, DE (United States); Berg, Dominik [Rowan Univ., Glassboro, NJ (United States); Dobson, Kevin [Univ. of Delaware, Newark, DE (United States). Inst. of Energy Conversion (IEC)

2017-12-28

The project aimed to provide solar energy education to students from underrepresented groups and to develop a novel, nano-scale approach, in utilizing Fe<sub>2sub>SiS>4sub> and Fe<sub>2sub>GeS>4sub> materials as precursors to the absorber layer in photovoltaic thin-film devices. The objectives of the project were as follows: 1. Develop and implement one solar-related course at Delaware State University and train two graduate students in solar research. 2. Fabricate and characterize high-efficiency (larger than 7%) Fe<sub>2sub>SiS>4sub> and Fe<sub>2sub>GeS>4sub>-based solar devices. The project has been successful in both the educational components, implementing the solar course at DSU as well as in developing multiple routes to prepare the Fe<sub>2sub>GeS>4sub> with high purity and in large quantities. The project did not meet the efficiency objective, however, a functional solar device was demonstrated.