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A distância e o conteúdo estelar da região HII gigante G333.1-0.4 - vínculos para a taxa de formação estelar da galáxia

NASA Astrophysics Data System (ADS)

Figuerêdo, E.; Damineli, A.; Blum, R.; Conti, P.

2003-08-01

Neste trabalho apresentamos imagens de alta resolução angular da região HII gigante G333.1-0.4 obtidas através dos filtros J, H e K no telescópio de 4-m do CTIO. Este trabalho faz parte de um estudo de regiões HII gigantes no infravermelho próximo que tem por objetivo estudar a natureza da formação de estrelas massivas e traçar a estrutura espiral de nossa galáxia. Nossa determinação da distância é baseada no método da paralaxe espectroscópica de estrelas OB localizadas na seqüência principal de idade zero (ZAMS) do Diagrama HR. No caso de G333.1-0.4, a magnitude aparente das estrelas localizadas na ZAMS indica que a distância não pode ser maior do que o limite inferior determinado por técnica rádio (2,8 kpc). Resultados semelhantes foram encontrados para regiões estudadas anteriormente, reforçando a idéia de que a taxa de formação estelar na Via Láctea é menor do que o determinado a partir de dados rádio. Nossos resultados mais recentes sobre o conteúdo estelar de G333.1-0.4 revelaram vários objetos que possuem cores bastante avermelhadas (H-K > 2,0). Nós identificamos estes objetos usando os diagramas cor-cor e cor-magnitude dos aglomerados. Estes objetos apresentam um forte excesso em emissão na banda K e possivelmente se tratam de estrelas do tipo OB envolvidas por um disco/envelope circumestelar espesso. O estudo da função de massa inical desta região, em conjunto com resultados de nossos trabalhos anteriores, aponta para uma IMF independente da posição galática. A contagem de estrelas nos fornece um valor para o número de fótons no contínuo de Lyman que corrobora com a afirmação de que G333.1-0.4 se encontra mais próxima da menor distância determinada por rádio.
Qual o Papel da Escola e da Mídia na Obtenção dos Conhecimentos Astronômicos?

NASA Astrophysics Data System (ADS)

da Cunha, W. S.; Voelzke, M. R.; Amaral, L. H.

2007-08-01

É amplamente reconhecido que as pessoas em geral têm grande fascínio e interesse pela Astronomia. Por outro lado, o conteúdo dessa área incluído no ensino formal está longe de ser abrangente e suficiente para suprir a demanda. Esse interesse permite aperfeiçoar a divulgação e o ensino não formal de Astronomia através da mídia aliando a adequação do conteúdo à expectativa das pessoas. A reforma do Currículo Básico da Escola Pública da maioria dos Estados brasileiros tem introduzido Astronomia desde a pré-escola até o Ensino Médio. Num estudo realizado com 1180 alunos do Ensino Médio de seis escolas estaduais, revelou-se através da aplicação de um formulário contendo questões que abordavam conhecimentos básicos em Astronomia, como foram adquiridos tais conhecimentos e à infra-estrutura da escola. Para 66,1% dos entrevistados o professor já fez alguma apresentação a respeito de Astronomia. O presente estudo revelou também que 54,4% dos alunos entrevistados adquiriram seus conhecimentos astronômicos na escola, 18,4% através da televisão e 27,1% afirmaram que seus conhecimentos foram obtidos através de outros tipos de mídia (internet, livros didáticos, filmes e revistas). Embora o estudo revele claramente que há certo equilíbrio no meio em que os alunos obtiveram seus conhecimentos astronômicos, a mídia busca não somente sua difusão, mas a disponibilização desse conhecimento de maneira correta, que às vezes, não é atingido, apresentando conceitos sem fundamentação e incorretos. Por outro lado, no dia-a-dia escolar, é comum encontrar professores que vêm para as aulas com concepções prévias, que podem diferir substancialmente das idéias a serem ensinadas, dificultando o aprendizado de futuros conceitos científicos. Uma avaliação criteriosa, avaliando as dificuldades dos professores em determinar o sentido correto dos conceitos e observando a metodologia que utilizam no ensino, poderá proporcionar uma melhor
Percepção Astronômica de Alunos do Ensino Médio da Rede Estadual de São Paulo

NASA Astrophysics Data System (ADS)

de Oliveira, E. F.; Voelzke, M. R.; Amaral, L. H.

2005-08-01

Embora a astronomia seja uma das ciências mais antigas da humanidade e muitos dos conceitos astronômicos serem populares, principalmente nesta época de alta globalização do conhecimento por intermédio de eficientes meios de comunicação e de obtenção da informação, notadamente através da internet, observa-se que uma parcela significativa dos estudantes encontra-se à margem dessas informações. O presente trabalho visa analisar o nível de conhecimento básico dos alunos de Ensino Médio da rede estadual da cidade de Suzano quanto aos fenômenos astronômicos que os rodeiam, tais como a sucessão dos dias e das estações do ano, além de questioná-los sobre fatos genéricos tais como: quais são os astros que se encontram mais próximos do planeta Terra, o que vem a ser o Sol, o Big Bang, um ano-luz, uma estrela cadente, a estrela de Bélem e o que ocasionou a extinção dos dinossauros. Para tanto foi elaborado um formulário constando de questões de múltipla escolha, o qual foi aplicado no primeiro colegial noturno da Escola Estadual Batista Renzi. Num espaço amostral de 34 alunos constatou-se que apenas 29,4% compreendiam a sucessão dos dias da semana, que apenas 20,6% explicaram corretamente as estações do ano, que apenas 20,6% tinham idéia de quais são os objetos celestes mais próximos da Terra, em contraposição 67,6% sabiam classificar corretamente o Sol como estrela, 55,9% relacionavam o Big Bang à origem do universo, apenas 20,6% identificavam um ano-luz como unidade de distância, 32,4% reconheciam uma estrela cadente como meteoro, 41,2% consideravam a estrela de Belém como um cometa e 50,0% explicaram corretamente a extinção dos dinossauros. A presente análise será expandida para as demais classes de primeiro colegial, não somente do período noturno, mas também do diurno da Escola Estadual Batista Renzi, bem como o formulário será devidamente ampliado. Já nesta primeira fase nota-se claramente o pequeno discernimento
Centro de Divulgação da Astronomia - o Observatório de São Carlos

NASA Astrophysics Data System (ADS)

Dias, W. S.; Hönel, J.; Líbero, V. L.; Anderlini, A.; de Andrade, D.; Scatena, E.; Lazo, M. J.; Trevisan, M.; de Castro, V.

2005-07-01

Apresentamos as principais características do Centro de Divulgação da Astronomia, que é constituído e um observatório cujo objetivo é a divulgação da Astronomia junto à comunidade, através de palestras e de observação direta dos astros. Descrevemos, neste trabalho, as atividades desenvolvidas desde sua fundação em 1986, e mostramos sua importância na região através de números anuais das atividades realizadas.
A estabilidade dos PAHS em função da energia da radiação interestelar nas faixas UV e raios-X

NASA Astrophysics Data System (ADS)

Pinotti, R.; Costa, R. K.; Boechat-Roberty, H. M.; Lago, A.; Souza, G. B.

2003-08-01

A nebulosa CRL 618, uma proto-nebulosa planetária cuja nuvem molecular espessa envolve uma estrela B0, contém uma grande quantidade de C2H2 e CH4. Estas moléculas são consideradas os tijolos da criação de grandes moléculas carbonadas como os Hidrocarbonetos Policíclicos Aromáticos (PAHs). Esta nebulosa, por estar exposta a intensos campos de UV e Raios-X, é uma região de fotodissociação molecular que propicia a formação de novas moléculas, confirmada pela presença de C4H2 e C6H6 (Benzeno), que é a unidade básica dos PAHs. Atribui-se a esta família de moléculas orgânicas duas propriedades fundamentais, a resistência para sobreviver ao campo de radiação UV interestelar e a geração das bandas de emissão não identificadas (UIR) observadas no infravermelho. No entanto, alguns autores questionam a resistência dos PAHs ao campo de radiação UV interestelar. Empregando a técnica de Espectrometria de Massas por Tempo de Vôo, no modo de coincidência fotoelétron-fotoíon, estudamos a ionização e fragmentação das seguintes moléculas: Benzeno, Benzeno deuterado, Naftaleno, Antraceno e Fenantreno. Utilizamos uma fonte de Hélio monocromática em 21,21 eV (584,5 Å) e a radiação Síncroton do Laboratório Nacional de Luz Síncroton (LNLS) em diferentes energias nas proximidades da borda do C 1s ( 290 eV). Comprovamos a estabilidade dos PAHs sob ação de UV (21,21 eV), onde eles apresentam um baixo nível de fotodissociação, produzindo fragmentos ionizados com rendimento total na ordem de 5 por cento em relação ao íon molecular pai. Entretanto, em altas energias, na faixa de Raios-X, a quebra destas moléculas torna-se mais intensa, com a produção de muitos fragmentos. Como uma das rotas de fragmentação do Naftaleno é [(C10H8) = > (C6H6+) + (C4H2) + (e-)], e como temos as evidências observacionais da existência do C4H2 e C6H6 na nebulosa CRL 618, sugerimos que este ambiente também possui o Naftaleno.
Investigação dos perfís temporais de alta resolução de explosões solares tipo-III decimétricas

NASA Astrophysics Data System (ADS)

Cecatto, J. R.; Fernandes, F. C. R.; Sawant, H. S.; Madsen, F. R. H.

2003-08-01

Explosões solares tipo-III indicam a presença de feixes de elétrons acelerados durante "flares" solares. Sua investigação fornece informações tanto sobre os processos de aceleração de partículas quanto das características do agente causador e do local de aceleração. Explosões tipo-III decimétricas são geradas por feixes de elétrons viajando através de arcos magnéticos densos da baixa coroa solar. Os perfís temporais destes fenômenos, quando tomados com alta resolução, informam sobre os mecanismos de aceleração de partículas do feixe e o meio de transporte da energia liberada a partir da região de aceleração. Usando o Brazilian Solar Spectroscope (BSS), em operação no INPE, foram registradas dezenas de explosões tipo-III decimétricas, dentro da faixa de 2050-2250 MHz com alta resolução temporal (20 ms), em 13 de setembro de 2001, entre 13:00 e 16:10 UT. Foram selecionadas 10 explosões isoladas para uma investigação estatística detalhada de seus perfís temporais, em todos os cerca de 50 canais de freqüência. Os resultados indicam que cerca de 70% dos perfís temporais são complexos tanto durante a subida quanto descida. Os 30% restantes indicam que os perfís da subida podem ser bem representados, na maioria dos casos, por um processo não-linear e uma parcela significativa por processos lineares. Os perfís temporais da descida são dominados por um decaimento não-linear. Neste trabalho, será efetuada uma análise dos perfís temporais, tanto durante a subida quanto descida do fluxo, para as explosões selecionadas, em termos dos prováveis mecanismos de aceleração e relaxamento. 2
Efeitos do binarismo não resolvido na determinação da função de massa de aglomerados

NASA Astrophysics Data System (ADS)

Kerber, L. O.; Santiago, B. X.

2003-08-01

Através de simulações numéricas buscamos quantificar os efeitos que o binarismo não resolvido causa na determinação da função de massa (MF) de aglomerados estelares. Geramos diagramas cor-magnitude (CMDs) artificiais simulando uma população única, caracterizada por estrelas de mesma idade e composição quí mica, com uma fração de binárias não resolvidas e distribuição em massa das estrelas dada por uma MF do tipo lei de potência. A presença de pares de estrelas não resolvidos faz com que a MF obtida da função de luminosidade (LF) tenha a têndencia de ser mais plana do que a MF que gerou o CMD artificial. Propomos um tratamento de correção para tal efeito. Outro efeito relacionado diz respeito ao alargamento do CMD, que apresenta-se como um indicador do número total de estrelas no domí nio de baixas massas (m < 0.6M¤). Todos os resultados acima possuem uma forte dependência com os erros fotométricos e estão baseados na hipótese de que ambas estrelas do par não resolvido são sorteadas de uma mesma MF de forma independente. O objetivo final é aplicarmos o tratamento aqui desenvolvido para implementarmos a análise da nossa amostra de aglomerados ricos da Grande Nuvem de Magalhães.
Detecção da fase impulsiva de uma explosão solar gigante até 405 GHz

NASA Astrophysics Data System (ADS)

Raulin, J.-P.; Makhmutov, V.; Kaufmann, P.; Pacini, A. A.; Luethi, T.; Hudson, H. S.; Gary, D. E.; Yoshimori, M.

2003-08-01

A explosão ocorrida no dia 25/08/2001 foi uma das mais intensas do presente ciclo solar em ondas de rádio de altas frequências. Foram medidas em ondas milimétricas e submilimétricas, aproximadamente, 105 e vários milhares de unidades de fluxo solar, respectivamente. Apresentamos um estudo deste evento em múltiplas frequências, desde microondas (1GHz), até ondas submilimétricas (405 GHz) detectadas pelo Telescópio Solar para ondas Submilimétricas (SST). Esta base de dados foi complementada utilizando-se o experimento Yohkoh, incluindo a emissão em raios-X duros e raios-g (até 100 MeV), e imagens em raios-X moles da região ativa envolvida. Enfocamos e discutimos principalmente os seguintes aspectos da fase impulsiva do evento: (i) as implicações deduzidas do espectro eletromagnético, obtido pela primeira vez até 405 GHz; (ii) a dinâmica da região ativa. Os resultados mostram que para explicar o espectro rádio observado, são necessários entre 3.5×1037 e 1.5×1039 elétrons acelerados acima de 20 keV em uma região de campo magnético entre 300 e 800 Gauss. A estimativa do fluxo de fótons que seria produzido por estes elétrons, mostra que grande parte deles não precipitou na baixa atmosfera. A evolução temporal da emissão em raios-X moles revela que a configuração magnética da região ativa foi muito dinâmica durante a fase impulsiva da explosão. Em particular, mostramos que a produção dos elétrons altamente energéticos foi iniciada junto com a aparição, na baixa coroa solar, de um novo sistema compacto de estruturas magnéticas. Este fato sugere que os locais de aceleração estão localizados na baixa atmosfera do Sol, como resultado da interação entre o novo sistema compacto e o campo magnético ambiente da região ativa.
A Influência da Escola e da Mídia na Obtenção dos Conhecimentos Astronômicos

NASA Astrophysics Data System (ADS)

da Cunha, W. S.; Voelzke, M. R.; Amaral, L. H.

2006-08-01

O universo em que vivemos possui segredos jamais imaginados pelo homem, fruto da pequena proporção que ocupamos diante de um cosmos infinito. A astronomia funciona como um instrumento que sacia a sede humana em desvendar esses segredos, estudando as galáxias, quasares, pulsares além da existência de todos os elementos que preenchem o espaço cósmico, o vácuo, não mais vazio como se pensou em outros tempos. A mídia explora esse campo de forma mística e também científica. A difusão adequada e dentro dos padrões educacionais vigentes, de conceitos astronômicos, se faz necessária, devido sua presença nos conteúdos escolares, centros de ciência e na mídia, de modo geral. A reforma do Currículo Básico da Escola Pública da maioria dos Estados brasileiros introduziu conceitos astronômicos desde a pré-escola até o Ensino Médio. Num estudo realizado com 1.032 alunos do Ensino Médio de seis escolas estaduais, revelou-se através da aplicação de um questionário que abordava conheciment os básicos em astronomia, como estes foram adquiridos e qual era a infra-estrutura oferecida pela escola: para 66,2% dos entrevistados o professor já fez alguma apresentação a respeito de astronomia. O presente estudo revelou também que 44,5% dos alunos entrevistados adquiriram seus conhecimentos astronômicos na escola, 28,1% através da televisão e 27,4% afirmaram que seus conhecimentos foram obtidos através de outros tipos de mídia (internet, filmes e revistas). Embora o estudo revele claramente que há certo equilíbrio na forma em que os alunos obtiveram seus conhecimentos astronômicos, a mídia ainda explora e muitas vezes desperta o interesse pela astronomia com assuntos que não fazem parte de nosso cotidiano como, por exemplo, o homem na Lua, os projetos espaciais e a primeira viagem de um astronauta brasileiro no espaço. Porém, em certos casos, a mídia pode promover conhecimentos incompletos ou mesmo equivocados sobre os conceitos que envolvam
Desenvolvimento de modelo clínico para predição da possibilidade de identificação da artéria de Adamkiewicz por angiotomografia

PubMed Central

Amato, Alexandre Campos Moraes; Parga, José Rodrigues; Stolf, Noedir Antônio Groppo

2018-01-01

Resumo Contexto Diferenças morfológicas da artéria de Adamkiewicz (AKA) entre a população portadora e não portadora de doença aórtica têm importância clínica, influenciando as complicações neuroisquêmicas da medula espinhal em procedimentos operatórios. Ainda não é conhecida a correlação entre parâmetros clínicos e a previsibilidade da identificação dessa artéria pela angiotomografia. Objetivo Desenvolver um modelo matemático que, através de parâmetros clínicos correlacionados com aterosclerose, possa prever a probabilidade de identificação da AKA em pacientes submetidos a angiotomografias. Método Estudo observacional transversal utilizando banco de imagens e dados de pacientes. Foi feita análise estatística multivariada e criado modelo matemático logit de predição para identificação da AKA. Variáveis significativas foram utilizadas na montagem da fórmula para cálculo da probabilidade de identificação. O modelo foi calibrado, e a discriminação foi avaliada pela curva receiver operating characteristic (ROC). A seleção das variáveis explanatórias foi guiada pela maior área na curva ROC (p = 0,041) e pela significância combinada das variáveis. Resultados Foram avaliados 110 casos (54,5% do sexo masculino, com idade média de 60,97 anos e etnia com coeficiente B -2,471, M -1,297, N -0,971), com AKA identificada em 60,9%. Índice de massa corporal: 27,06 ± 0,98 (coef. -0,101); fumantes: 55,5% (coef. -1,614/-1,439); diabéticos: 13,6%; hipertensos: 65,5% (coef. -1,469); dislipidêmicos: 58,2%; aneurisma aórtico: 38,2%; dissecção aórtica: 12,7%; e trombo mural: 24,5%. Constante de 6,262. Fórmula para cálculo da probabilidade de detecção: (e−(Coef. Etnia+(Coef. IMC×IMC)+Coef.fumante+Coef.HAS+Coef.dislip+Constante)+1)−1 . O modelo de predição foi criado e disponibilizado no link https://vascular.pro/aka-model . Conclusão Com as covariáveis etnia, índice de massa corporal, tabagismo, hipertensão
Tão perto de casa, tão longe de nós: etnografia das novas margens no centro da urbe

PubMed Central

Fernandes, Por Luís

2011-01-01

Philippe Bourgois é, desde 2007, “Richard Perry University professor” no Departamento de Antropologia e de Medicina Familiar e de Práticas Comunitárias na Universidade da Pensilvânia. Esteve durante largos anos ligado ao Departamento de Antropologia, História e Medicina Social da Universidade da Califórnia, São Francisco. A publicação, em 1995, de In Search of Respect: Selling Crack in El Barrio1 projectaria o seu nome muito para além dos Estados Unidos: uma etnografia no coração porto-riquenho do Harlem, em torno dos actores e dos ambientes da venda de crack. Seguir-se-ia um longo trabalho de terreno em acampamentos de dependentes de heroína em São Francisco, orientando o seu trabalho para as formas mais radicais da pobreza e da marginalidade nos EUA. É deste trabalho de terreno que sai o seu último livro, Righteous Dopefiend2. Em Junho de 2007 esteve em Lisboa para participar na 3.a edição do “Ethnografeast”. Foi então que aproveitámos a oportunidade para ouvir um percurso invulgar contado pelo próprio: uma longa conversa no Hotel Zurique, cujo nome só vem ao caso por evocar o país onde passou uma parte da infância. PMID:22013286
Trombose induzida pelo calor endovenoso: relato de dois casos tratados com rivaroxabana e revisão da literatura

PubMed Central

de Araujo, Walter Junior Boim; Timi, Jorge Rufino Ribas; Erzinger, Fabiano Luiz; Caron, Filipe Carlos

2016-01-01

Resumo Define-se trombose induzida pelo calor endovenoso como a propagação do trombo a partir de uma veia superficial em direção a uma veia mais profunda. Em geral, é considerada clinicamente insignificante quando não há propagação do trombo para o sistema venoso profundo. Essa condição pode ser tratada com terapia anticoagulante, embora a observação pareça ser suficiente, principalmente para graus menores. Neste estudo, relatamos dois casos de trombose induzida pelo calor endovenoso que teriam indicação de heparina de baixo peso molecular até a resolução do quadro. Porém, optou-se pelo uso da rivaroxabana (15 mg de 12 em 12h), com resolução completa do trombo em 4 semanas (caso 1) e em 7 dias (caso 2). A rivaroxabana pode ser uma alternativa promissora no tratamento da trombose induzida pelo calor endovenoso avançada, pela simplicidade da posologia, sem comprometimento da eficácia ou da segurança. São necessários estudos prospectivos, randomizados e controlados que possibilitem melhor entendimento da condição e o desenvolvimento de recomendações mais definitivas sobre opções de prevenção e tratamento.
Bimetallic-organic framework derived porous Co3O4/Fe3O4/C-loaded g-C3N4 nanocomposites as non-enzymic electrocatalysis oxidization toward ascorbic acid, dopamine acid, and uric acid

NASA Astrophysics Data System (ADS)

Hu, Bin; Liu, Yongkang; Wang, Zhuo-Wei; Song, Yingpan; Wang, Minghua; Zhang, Zhihong; Liu, Chun-Sen

2018-05-01

We report on the synthesis of Co- and Fe-based bimetallic nanocatalysts embedded in mesoporous carbon and g-C3N4 nanosheets (denoted as Co3O4/Fe3O4/mC@g-C3N4) for selectively simultaneous determination of ascorbic acid (AA), dopamine acid (DA), and uric acid (UA). These electrocatalysts consisting of bimetallic Co-Fe alloy nanoparticles encapsulated in N-doped carbon matrix were prepared via pyrolysis of Co/Fe-MOFs after grinding with high amounts of melamine. Chemical/crystal structures suggest high contents of mesoporous carbon in calcinated Co3O4/Fe3O4/mC nanocomposites, which exhibited enhanced electrocatalytic activity toward small biomolecules. The intrinsic performances of Co/Fe-MOFs with large specific surface area and regular nodes in the two-dimensional nanostructured g-C3N4 nanosheets endowed the as-prepared series of Co3O4/Fe3O4/mC@g-C3N4 nanocomposites with remarkable electrocatalytic activities and high adsorption ability toward oxidation of AA, DA, and UA. The developed biosensors also showed long-term stability and high selectivity for targeted analytes, with satisfactory results on actual samples in human urine. The results indicate that the as-synthesized Co3O4/Fe3O4/mC@g-C3N4 nanostructure exhibits good electrocatalytic activity and potential applications in clinical diagnosis and biosensing.
Estudo de não gaussianidade nas anisotropias da RCF medidas Wmap

NASA Astrophysics Data System (ADS)

Andrade, A. P. A.; Wuensche, C. A.; Ribeiro, A. L. B.

2003-08-01

A investigação do campo de flutuações da Radiação Cósmica de Fundo (RCF) pode oferecer um importante teste para os modelos cosmológicos que descrevem a origem e a evolução das flutuações primordiais. De um lado, apresenta-se o modelo inflacionário que prevê um espectro de flutuações adiabáticas distribuídas segundo uma gaussiana e, de outro, os modelos de defeitos topológicos (dentre outros) que descrevem um mecanismo para a geração de flutuações de isocurvatura que obedecem a uma distribuição não gaussiana. Este trabalho tem como objetivo caracterizar traços do modelo não gaussiano de campo misto (entre flutuações adiabáticas e de isocurvatura) nos mapas do Wilkinson Microwave Anisotropy Probe (WMAP). Simulações das anisotropias da RCF no contexto de mistura indicam traços marcantes na distribuição das flutuações de temperatura, mesmo quando consideradas pequenas contribuições do campo de isocurvatura (da ordem de 0.001). O efeito da mistura entre os campos resulta na transferência de potência de flutuações em escalas angulares intermediárias para flutuações em pequenas escalas angulares. Este efeito pode ser caracterizado pela relação entre as amplitudes dos primeiros picos acústicos no espectro de potência da RCF. Neste trabalho, investigamos a contribuição do campo de isocurvatura, no contexto de mistura, sobre as observações recentes da RCF realizadas pelo WMAP. As previsões do modelo de campo misto, uma vez confrontadas com as observações em pequenas escalas angulares, podem ajudar a revelar a natureza das flutuações primordiais.
Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetrahydrate {di-μ-aqua-bis(triaquadiperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nonahydrate {heptaaquadiperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetrahydrate consist of Sr2+ cations coordinated by five water molecules and four O atoms of four perchlorate tetrahedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water molecules and thus forming chains parallel to [100]. In the tetrahydrate, dimers of two [SrO9] polyhedra connected by two sharing water molecules are formed. The structure of the nonahydrate contains one Sr2+ cation coordinated by seven water molecules and by two O atoms of two perchlorate tetrahedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water molecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water molecules as donor and ClO4 tetrahedra and water molecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures. PMID:25552979
Exosome purification based on PEG-coated Fe3O4 nanoparticles.

PubMed

Chang, Ming; Chang, Yaw-Jen; Chao, Pei Yu; Yu, Qing

2018-01-01

Cancer cells secrete many exosomes, which facilitate metastasis and the later growth of cancer. For early cancer diagnosis, the detection of exosomes is a crucial step. Exosomes exist in biological fluid, such as blood, which contains various proteins. It is necessary to remove the proteins in the biological fluid to avoid test interference. This paper presented a novel method for exosome isolation using Fe3O4 magnetic nanoparticles (MNPs), which were synthesized using the chemical co-precipitation method and then coated with polyethylene glycol (PEG). The experimental results showed that the diameter of the PEG-coated Fe3O4 nanoparticles was about 20 nm, while an agglomerate of MNPs reached hundreds of nanometers in size. In the protein removal experiments, fetal bovine serum (FBS) was adopted as the analyte for bioassays of exosome purification. PEG-coated Fe3O4 MNPs reduced the protein concentration in FBS to 39.89% of the original solution. By observing a particle size distribution of 30~200 nm (the size range of various exosomes), the exosome concentrations were kept the same before and after purification. In the gel electrophoresis experiments, the bands of CD63 (~53 kDa) and CD9 (~22 kDa) revealed that exosomes existed in FBS as well as in the purified solution. However, the bands of the serum albumins (~66 kDa) and the various immunoglobulins (around 160 ~ 188 kDa) in the purified solution's lane explained that most proteins in FBS were removed by PEG-coated Fe3O4 MNPs. When purifying exosomes from serum, protein removal is critical for further exosome investigation. The proposed technique provides a simple and effective method to remove proteins in the serum using the PEG-coated Fe3O4 MNPs.
Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, calcium perchlorate tetrahydrate and calcium perchlorate hexahydrate, were crystallized at low temperatures according to the solid–liquid phase diagram. The structure of the tetrahydrate consists of one Ca2+ cation eightfold coordinated in a square-antiprismatic fashion by four water molecules and four O atoms of four perchlorate tetrahedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetrahedra. The structure of the hexahydrate contains two different Ca2+ cations, each coordinated by six water molecules and two O atoms of two perchlorate tetrahedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetrahedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetrahedra. O—H⋯O hydrogen bonds between the water molecules as donor and ClO4 tetrahedra and water molecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures. PMID:25552974
Projeto do sistema anti-ressonante da fiação dos transdutores para o detector Mario Schenberg

NASA Astrophysics Data System (ADS)

Vieira, S. J.., Jr.; Melo, J. L.

2003-08-01

O detector de ondas gravitacionais Mario Schenberg está sendo projetado e construído pelo grupo Gráviton. Sua construção está ocorrendo no Laboratório de Estado Sólido e Baixas Temperaturas (LESBT) da Universidade de São Paulo, na cidade de São Paulo. Esse detector possui uma massa ressonante esférica de cobre-alumínio, com 65 cm de diâmetro, pesando aproximadamente 1150 Kg, suspensa por um sistema de isolamento vibracional, que se encontra em fase de testes preliminares. A real eficácia desse sistema, entretanto, só poderá ser comprovada quando o detector estiver aparelhado com, pelo menos, um transdutor eletromecânico de altíssima sensibilidade acoplado à massa ressonante. Neste momento, não só este sistema de isolamento vibracional será posto em teste, como o do projeto da fiação que transporta os sinais de microondas até os transdutores e destes para a pré-amplificação. Apesar dessa fiação ter sido projetada para não apresentar nenhum contato com a superfície esférica da antena, de maneira a não haver nenhuma transmissão de ruído vibracional do laboratório para esta, deve-se minimizar o ruído microfônico produzido nessa fiação por oscilações mecânicas, uma vez que ela não utiliza nenhum sistema de isolamento vibracional. Com o intuito de resolver este problema, projetamos uma estrutura, formada por pequenos cilindros conectados por barras, a qual não terá nenhuma ressonância mecânica na faixa de freqüências de interesse para detecção (3000 - 3400 Hz). Desta forma, as vibrações nessa faixa não serão amplificadas. O projeto foi feito usando iterativamente, de maneira a otimizar os resultados obtidos, o programa de elementos finitos Msc/Nastran. Através de simulações feitas neste programa, determinamos os parâmetros geométricos ideais a serem utilizados, os quais proporcionam a maior região espectral de interesse livre de ressonâncias.
Conhecimento Científico e Cotidiano em Astronomia: Uma Investigação com Alunos da Educação Básica

NASA Astrophysics Data System (ADS)

Vieira, J. B.; Longhini, M. D.

2011-12-01

Este texto apresenta resultados de uma investigação que teve como objetivo, investigar como os conhecimentos científicos e do cotidiano relacionados a essa área de conhecimento apresentam na escola de Educação Básica, especialmente, em alunos do Ensino Médio prestes a deixar Educação Básica. Para realização da pesquisa, utilizamos como recurso metodológico a aplicação de um questionário estruturado contendo 47 questões, organizadas em duas categorias: Conhecimento Cotidiano e Conhecimento Científico. As questões da categoria “Conhecimento Cotidiano” possuíam afirmações relacionadas a crendices, contos populares, especulações e temáticas do gênero, as quais, geralmente, estão fora do círculo de discussão da comunidade científica, talvez por não serem consideradas como objeto de estudo da ciência. As questões da categoria “Conhecimento Científico” são relacionadas a conteúdos específicos de Astronomia, as quais são compartilhadas pela comunidade científica e aceitas, pelo menos provisoriamente, como possuindo fundamentação científica. Concluímos que, possuem ainda concepções de temas Astronômicos persistentes à mudança, por exemplo, fases da Lua relacionadas à melhor período para corte de cabelo e também para plantio; estrela cadente e ocasião perfeita para se fazer um pedido. Entretanto, podemos observar no que diz respeito a mitos e superstições, que quase não existe influência destes entre os alunos. Portanto, ao trabalharmos com os alunos determinados conceitos científicos, é importante lembrarmos que o professor não opera no vazio; os alunos são sujeitos de saberes, práticas e, dessa forma constroem e reconstroem saberes. Cabe ao professor ouvir os estudantes reconstruindo junto deles conceitos científicos. Acreditamos que o ensino de Ciências na Educação Básica deve lidar criticamente com o conhecimento cotidiano e científico e, assim, efetivar a Ciência como disciplina educativa
Construção de um catálogo de aglomerados abertos para estudo da dinâmica da estrutura espiral da Galáxia

NASA Astrophysics Data System (ADS)

Carlos, I. M.; Lépine, J. R. D.

2003-08-01

Os aglomerados abertos são objetos de grande valor para o estudo da dinâmica da Galáxia devido esses objetos terem uma faixa de idade relativamente ampla. O trabalho visa estudar a dinâmica da estrutura espiral da Galáxia principalmente através do uso desses aglomerados, uma vez que o estudo da cinemática desses objetos é fundamental para esse objetivo. Nosso grupo trabalha no sentido de construir uma base de dados de aglomerados abertos contendo coordenadas, distância, idade, movimentos próprios e velocidades radiais e já disponibiliza uma nova versão do catálogo de aglomerados abertos o qual é uma compilação de edições anteriores, principalmente Lynga (1987), Mermilliod (1995) e ESO-B (Lauberts 1982). Nossa amostra possui cerca de 1630 aglomerados, mas nem todos os parâmetros acima citados foram determinados em sua totalidade. Para determinarmos esses parâmetros, derivamos as cores intrínsecas das estrelas membro de cada aglomerado a partir de seus tipos espectrais (busca feita no SIMBAD) obtendo assim o excesso de cor individual. A distribuição dos excessos de cor foi então utilizada para derivarmos o avermelhamento médio para cada aglomerado. De maneira similar, os tipos espectrais foram usados para estimar as magnitudes absolutas, e com as magnitudes absolutas e aparentes determinamos a respectiva distribuição do módulo de distância e finalmente a distância. Para determinar as idades foram confeccionados os diagramas cor-magnitude das estrelas de cada aglomerado onde foram superpostas a Seqüência Principal de Idade Zero (ZAMS). Superpomos a ZAMS de Schmidt-Kaler e isócronas de composição solar. Essas isócronas foram usadas para determinação das idades dos aglomerados. Uma vez que não temos ainda resultados finais, apresentamos então alguns diagramas cor-magnitude os quais foram usados para determinação, principalmente, da distância e idade dos aglomerados.

Análise da medição do raio solar em ultravioleta

NASA Astrophysics Data System (ADS)

Saraiva, A. C. V.; Giménez de Castro, C. G.; Costa, J. E. R.; Selhorst, C. L.; Simões, P. J. A.

2003-08-01

A medição acurada do raio solar em qualquer banda do espectro eletromagnético é de relevância na formulação e calibração de modelos da estrutura e atmosfera solar. Esses modelos atribuem emissão do contínuo do Sol calmo em microondas à mesma região da linha Ha do Hell. Apresentamos a medição do raio solar em UV com imagens do EIT (Extreme Ultraviolet Image Telescope) entre 1996 e 2002, no comprimento de onda 30,9 nm (Ha do Hell), que se forma na região de transição/cromosfera solar. A técnica utilizada para o cálculo do raio UV foi baseada na transformada Wavelet B3spline. Fizemos um banco de dados com 1 imagem por dia durante o período citado. Obtivemos como resultado o raio médio da ordem de 975.61" e uma diminuição do mesmo para o período citado variando em média -0,45" /ano. Comparamos estes dados com os valores obtidos pelo ROI (Radio Observatório de Itapetinga) em 22/48 GHz e Nobeyama Radio Heliograph em 17 GHz mostrando que os raios médios são muito próximos o que indica que a região de formação nessas freqüências é a mesma conforme os modelos. Comparamos os resultados também com outros índices de atividade solar.
Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

NASA Astrophysics Data System (ADS)

Glassell, M.; Robles, J.; Das, R.; Phan, M. H.; Srikanth, H.

Iron oxide nanoparticles especially Fe3O4, γ-Fe2O3 have been extensively studied for magnetic hyperthermia because of their tunable magnetic properties and stable suspension in superparamagnetic regime. However, their relatively low heating capacity hindered practical application. Recently, a large improvement in heating efficiency has been reported in exchange-coupled nanoparticles with exchange coupling between soft and hard magnetic phases. Here, we systematically studied the effect of core and shell size on the heating efficiency of the Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) showed formation of spherical shaped Fe3O4 and Fe3O-/CoFe2O4 nanoparticles. Magnetic measurements showed high magnetization (≅70 emu/g) and superparamagnetic behavior for the nanoparticles at room temperature. Magnetic hyperthermia results showed a large increase in specific absorption rate (SAR) for 8nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of the same size. The heating efficiency of the Fe3O4/CoFe2O4 with 1 nm CoFe2O4 (shell) increased from 207 to 220 W/g (for 800 Oe) with increase in core size from 6 to 8 nm. The heating efficiency of the Fe3O4/CoFe2O4 with 2 nm CoFe2O4 (shell) and core size of 8 nm increased from 220 to 460 W/g (for 800 Oe). These exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.
XPS and EELS characterization of Mn2SiO4, MnSiO3 and MnAl2O4

NASA Astrophysics Data System (ADS)

Grosvenor, A. P.; Bellhouse, E. M.; Korinek, A.; Bugnet, M.; McDermid, J. R.

2016-08-01

X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn2SiO4, MnSiO3, and MnAl2O4 by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn2SiO4, MnSiO3 and MnAl2O4 were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn2SiO4, MnSiO3 and MnAl2O4 standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.
Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles.

PubMed

Wang, Liying; Sun, Ying; Wang, Jing; Wang, Jian; Yu, Aimin; Zhang, Hanqi; Song, Daqian

2011-06-01

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively. Copyright © 2011 Elsevier B.V. All rights reserved.
Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

NASA Astrophysics Data System (ADS)

Robles, J.; Das, R.; Glassell, M.; Phan, M. H.; Srikanth, H.

2018-05-01

We report a systematic study of the effects of core and shell size on the magnetic properties and heating efficiency of exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) confirmed the formation of spherical Fe3O4 and Fe3O4/CoFe2O4 nanoparticles. Magnetic measurements showed high saturation magnetization for the nanoparticles at room temperature. Increasing core diameter (6.4±0.7, 7.8±0.1, 9.6±1.2 nm) and/or shell thickness (˜1, 2, 4 nm) increased the coercive field (HC), while an optimal value of saturation magnetization (MS) was achieved for the Fe3O4 (7.8±0.1nm)/CoFe2O4 (2.1±0.1nm) nanoparticles. Magnetic hyperthermia measurements indicated a large increase in specific absorption rate (SAR) for 8.2±1.1 nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of same size. The SAR of the Fe3O4/CoFe2O4 nanoparticles increased from 199 to 461 W/g for 800 Oe as the thickness of the CoFe2O4 shell was increased from 0.9±0.5 to 2.1±0.1 nm. The SAR enhancement is attributed to a combination of the large MS and the large HC. Therefore, these Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.
Transparent Cu4O3/ZnO heterojunction photoelectric devices

NASA Astrophysics Data System (ADS)

Kim, Hong-Sik; Yadav, Pankaj; Patel, Malkeshkumar; Kim, Joondong; Pandey, Kavita; Lim, Donggun; Jeong, Chaehwan

2017-12-01

The present article reports the development of flexible, self-biased, broadband, high speed and transparent heterojunction photodiode, which is essentially important for the next generation electronic devices. We grow semitransparent p-type Cu4O3 using the reactive sputtering method at room temperature. The structural and optical properties of the Cu4O3 film were investigated by using the X-ray diffraction and UV-visible spectroscopy, respectively. The p-Cu4O3/n-ZnO heterojunction diode under dark condition yields rectification behavior with an extremely low saturation current value of 1.8 × 10-10 A and a zero bias photocurrent under illumination condition. The transparent p-Cu4O3/n-ZnO heterojunction photodetector can be operated without an external bias, due to the light-induced voltage production. The metal oxide heterojunction based on Cu4O3/ZnO would provide a route for the transparent and flexible photoelectric devices, including photodetectors and photovoltaics.
Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles

NASA Astrophysics Data System (ADS)

Polishchuk, Dmytro; Nedelko, Natalia; Solopan, Sergii; Ślawska-Waniewska, Anna; Zamorskyi, Vladyslav; Tovstolytkin, Alexandr; Belous, Anatolii

2018-03-01

Two sets of core/shell magnetic nanoparticles, CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4, with a fixed diameter of the core ( 4.1 and 6.3 nm for the former and latter sets, respectively) and thickness of shells up to 2.5 nm were synthesized from metal chlorides in a diethylene glycol solution. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. The analysis of the results of magnetic measurements shows that coating of magnetic nanoparticles with the shells results in two simultaneous effects: first, it modifies the parameters of the core-shell interface, and second, it makes the particles acquire combined features of the core and the shell. The first effect becomes especially prominent when the parameters of core and shell strongly differ from each other. The results obtained are useful for optimizing and tailoring the parameters of core/shell spinel ferrite magnetic nanoparticles for their use in various technological and biomedical applications.
Density Functional Study of Structures and Electron Affinities of BrO4F/BrO4F−

PubMed Central

Gong, Liangfa; Xiong, Jieming; Wu, Xinmin; Qi, Chuansong; Li, Wei; Guo, Wenli

2009-01-01

The structures, electron affinities and bond dissociation energies of BrO4F/BrO4F− species have been investigated with five density functional theory (DFT) methods with DZP++ basis sets. The planar F-Br…O2…O2 complexes possess 3A′ electronic state for neutral molecule and 4A′ state for the corresponding anion. Three types of the neutral-anion energy separations are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The EAad value predicted by B3LYP method is 4.52 eV. The bond dissociation energies De (BrO4F → BrO4-mF + Om) (m = 1–4) and De− (BrO4F− → BrO4-mF− + Om and BrO4F− → BrO4-mF + Om−) are predicted. The adiabatic electron affinities (EAad) were predicted to be 4.52 eV for F-Br…O2…O2 (3A′←4A′) (B3LYP method). PMID:19742128
Thermal conversion of Cu4O3 into CuO and Cu2O and the electrical properties of magnetron sputtered Cu4O3 thin films

NASA Astrophysics Data System (ADS)

Murali, Dhanya S.; Aryasomayajula, Subrahmanyam

2018-03-01

Among the three oxides of copper (CuO, Cu2O, and Cu4O3), Cu4O3 phase (paramelaconite is a natural, and very scarce mineral) is very difficult to synthesize. It contains copper in both + 1 and + 2 valence states, with an average composition Cu2 1+Cu2 2+O3. We have successfully synthesized Cu4O3 phase at room temperature (300 K) by reactive DC magnetron sputtering by controlling the oxygen flow rate (Murali and Subrahmanyam in J Phys D Appl Phys 49:375102, 2016). In the present communication, Cu4O3 thin films are converted to CuO phases by annealing in the air at 680 K and to Cu2O phase when annealed in argon at 720 K; these phase changes are confirmed by temperature-dependent Raman spectroscopy studies. Probably, this is the first report of the conversion of Cu4O3-CuO and Cu2O by thermal annealing. The temperature-dependent (300-200 K) electrical transport properties of Cu4O3 thin films show that the charge transport above 190 K follows Arrhenius-type behavior with activation energy of 0.14 eV. From photo-electron spectroscopy and electrical transport measurements of Cu4O3 thin films, a downward band bending is observed at the surface of the thin film, which shows its p-type semiconducting nature. The successful preparation of phase pure p-type semiconducting Cu4O3 could provide opportunities to further explore its potential applications.
Porous nanocubic Mn3O4-Co3O4 composites and their application as electrochemical supercapacitors.

PubMed

Pang, Huan; Deng, Jiawei; Du, Jimin; Li, Sujuan; Li, Juan; Ma, Yahui; Zhang, Jiangshan; Chen, Jing

2012-09-14

A simple approach has been developed to fabricate ideal supercapacitors based on porous Mn(3)O(4)-Co(3)O(4) nanocubic composite electrodes. We can easily obtain porous corner-truncated nanocubic Mn(3)O(4)-Co(3)O(4) composite nanomaterials without any subsequent complicated workup procedure for the removal of a hard template, seed or by using a soft template. In such a composite, the porous Mn(3)O(4)-Co(3)O(4) enables a fast and reversible redox reaction to improve the specific capacitance. The porous nanocubic Mn(3)O(4)-Co(3)O(4) composite electrode can effectively transport electrolytes and shorten the ion diffusion path, which offers excellent electrochemical performance. These results suggest that such porous Mn(3)O(4)-Co(3)O(4) composite nanocubes are very promising for next generation high-performance supercapacitors.
High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds.

PubMed

Ishii, Takayuki; Sakai, Tsubasa; Kojitani, Hiroshi; Mori, Daisuke; Inaguma, Yoshiyuki; Matsushita, Yoshitaka; Yamaura, Kazunari; Akaogi, Masaki

2018-06-04

We have investigated high-pressure, high-temperature phase transitions of spinel (Sp)-type MgV 2 O 4 , FeV 2 O 4 , and MnCr 2 O 4 . At 1200-1800 °C, MgV 2 O 4 Sp decomposes at 4-7 GPa into a phase assemblage of MgO periclase + corundum (Cor)-type V 2 O 3 , and they react at 10-15 GPa to form a phase with a calcium titanite (CT)-type structure. FeV 2 O 4 Sp transforms to CT-type FeV 2 O 4 at 12 GPa via decomposition phases of FeO wüstite + Cor-type V 2 O 3 . MnCr 2 O 4 Sp directly transforms to the calcium ferrite (CF)-structured phase at 10 GPa and 1000-1400 °C. Rietveld refinements of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 confirm that both the CT- and CF-type structures have frameworks formed by double chains of edge-shared B 3+ O 6 octahedra (B 3+ = V 3+ and Cr 3+ ) running parallel to one of orthorhombic cell axes. A relatively large A 2+ cation (A 2+ = Mg 2+ , Fe 2+ , and Mn 2+ ) occupies a tunnel-shaped space formed by corner-sharing of four double chains. Effective coordination numbers calculated from eight neighboring oxygen-A 2+ cation distances of CT-type MgV 2 O 4 and FeV 2 O 4 and CF-type MnCr 2 O 4 are 5.50, 5.16, and 7.52, respectively. This implies that the CT- and CF-type structures practically have trigonal prism (six-coordinated) and bicapped trigonal prism (eight-coordinated) sites for the A 2+ cations, respectively. A relationship between cation sizes of VIII A 2+ and VI B 3+ and crystal structures (CF- and CT-types) of A 2+ B 2 3+ O 4 is discussed using the above new data and available previous data of the postspinel phases. We found that CF-type A 2+ B 2 3+ O 4 crystallize in wide ionic radius ranges of 0.9-1.4 Å for VIII A 2+ and 0.55-1.1 Å for VI B 3+ , whereas CT-type phases crystallize in very narrow ionic radius ranges of ∼0.9 Å for VIII A 2+ and 0.6-0.65 Å for VI B 3+ . This would be attributed to the fact that the tunnel space of CT-type structure is geometrically less flexible due to the smaller coordination
Syntheses and structures of [UO2( L)5](ClO4)2 and [U( L')4(H2O)4](ClO4)4 ( L is dimethylformamide, L' is N,N-dimethylcarbamide)

NASA Astrophysics Data System (ADS)

Serezhkin, V. N.; Vologzhanina, A. V.; Pushkin, D. V.; Astashkina, D. A.; Savchenkov, A. V.; Serezhkina, L. B.

2017-09-01

The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [UVIO2(C3H7NO)5](ClO4)2 ( I) and [UIV(C3H8N2O)4(H2O)4](ClO4)4 ( II), where C3H7NO is N,N-dimethylformamide ( Dmfa) and C3H8N2O is N,N-dimethylcarbamide ( a-Dmur), were studied by X-ray diffraction. Complex II and the complex UIV( s-Dmur)4(H2O)4(ClO4)4 ( III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO2( Dmfa)5]2+ and [U( Dmur)4(H2O)4]4+ groups as uranium-containing structural units belonging to the crystal-chemical groups AM 7 1 ( A = UVI, M 1 = O2- and Dmfa) and AM 8 1 ( A = UIV, M 1 = Dmur and H2O) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.
Comparação entre cirurgia aberta e endovascular no tratamento do aneurisma da artéria poplítea: uma revisão

PubMed Central

Gonçalves, Ana Fernanda Fagundes; Pelek, Carlos Augusto; Nogueira, Lorena Slusarz; de Carvalho, Renan Francisco; Stumpf, Matheo Augusto Morandi; Gomes, Ricardo Zanetti; Kluthcovsky, Ana Claudia Garabeli Cavalli

2018-01-01

Resumo Os aneurismas de artéria poplítea correspondem a 70% dos aneurismas periféricos e o tratamento é cirúrgico, com controvérsias sobre os resultados da via endovascular. Este estudo objetivou realizar uma revisão da literatura sobre a comparação entre cirurgia aberta e endovascular no tratamento dos aneurismas da artéria poplítea. A pesquisa foi realizada utilizando os termos apropriados nos portais de periódicos LILACS e MEDLINE, com a seleção de 15 artigos. Um total de 5.166 procedimentos cirúrgicos foram comparados, sendo 3.930 cirurgias abertas e 1.236 cirurgias endovasculares. A cirurgia aberta com bypass venoso continua sendo o padrão-ouro. A cirurgia endovascular apresenta menor tempo de internação e é uma opção viável em pacientes eletivos, com baixa expectativa de vida, alto risco cirúrgico, comorbidades e mais idosos, desde que tenham anatomia favorável para o procedimento. Contudo, são necessários estudos de longo prazo para estabelecer os reais benefícios e indicações das duas técnicas, como o ensaio clínico randomizado controlado.
Fe{sub 3}O{sub 4}/CuO/ZnO/Nano graphene platelets (Fe{sub 3}O{sub 4}/CuO/ZnO/NGP) composites prepared by sol-gel method with enhanced sonocatalytic activity for the removal of dye

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendry, Tju; Taufik, Ardiansyah; Saleh, Rosari, E-mail: rosari.saleh@gmail.com, E-mail: rosari.saleh@ui.ac.id

2016-04-19

In this study, an attempt has been made to synthesize nanographene platelets coupled with Fe3O4/CuO/ZnO (Fe3O4/CuO/ZnO/NGP) with various ZnO loadings using a two step methods, sol-gel followed by hydrothermal method. Characterization was carried out by X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometer. The sonocatalytic performance was evaluated by degradation of methylene blue under ultrasonic irradiation.The Fe3O4/CuO/ZnO/NGP showed superior sonocatalytic activity than the Fe3O4/CuO/ZnO materials. They also showed high stability and can be easily separated from the reaction system for recycling process.
Water oxidation catalyzed by the tetranuclear Mn complex [Mn(IV)4O5(terpy)4(H2O)2](ClO4)6.

PubMed

Gao, Yunlong; Crabtree, Robert H; Brudvig, Gary W

2012-04-02

The tetranuclear manganese complex [Mn(IV)(4)O(5)(terpy)(4)(H(2)O)(2)](ClO(4))(6) (1; terpy = 2,2':6',2″-terpyridine) gives catalytic water oxidation in aqueous solution, as determined by electrochemistry and GC-MS. Complex 1 also exhibits catalytic water oxidation when adsorbed on kaolin clay, with Ce(IV) as the primary oxidant. The redox intermediates of complex 1 adsorbed on kaolin clay upon addition of Ce(IV) have been characterized by using diffuse reflectance UV/visible and EPR spectroscopy. One of the products in the reaction on kaolin clay is Mn(III), as determined by parallel-mode EPR spectroscopic studies. When 1 is oxidized in aqueous solution with Ce(IV), the reaction intermediates are unstable and decompose to form Mn(II), detected by EPR spectroscopy, and MnO(2). DFT calculations show that the oxygen in the mono-μ-oxo bridge, rather than Mn(IV), is oxidized after an electron is removed from the Mn(IV,IV,IV,IV) tetramer. On the basis of the calculations, the formation of O(2) is proposed to occur by reaction of water with an electrophilic manganese-bound oxyl radical species, (•)O-Mn(2)(IV/IV), produced during the oxidation of the tetramer. This study demonstrates that [Mn(IV)(4)O(5)(terpy)(4)(H(2)O)(2)](ClO(4))(6) may be relevant for understanding the role of the Mn tetramer in photosystem II.
Subluxação da mandíbula para abordagem de bifurcação carotídea alta em paciente com parotidite por contraste iodado: relato de caso e revisão de literatura

PubMed Central

dos Santos, Reinaldo Benevides; Queiroz, André Brito; Fidelis, Ronald José Ribeiro; Lopes, Cicero Fidelis; de Araújo, José Siqueira

2017-01-01

Resumo A doença aterosclerótica das carótidas extracranianas pode resultar em complicações com alta morbidade e mortalidade. A avaliação pré-operatória com exames contrastados de imagem é associada a complicações como a parotidite, além das já bem conhecidas reações alérgicas e da disfunção renal. A bifurcação carotídea alta e a doença aterosclerótica de extensão cranial costumam ser fatores limitantes para o tratamento cirúrgico convencional. Entretanto, quando há contraindicação ao uso de contraste iodado ou impossibilidade do tratamento endovascular, há a necessidade do conhecimento de técnicas cirúrgicas que permitam a realização da endarterectomia com segurança. A subluxação da mandíbula se mostrou uma técnica adjuvante segura e efetiva, de fácil execução e reprodutibilidade, possibilitando o acesso a bifurcações carotídeas altas com boa exposição do campo cirúrgico e permitindo a realização da endarterectomia conforme a técnica padrão. Apresentamos o caso de uma paciente com bifurcação carotídea alta e com limitações para uso do contraste iodado que foi submetida a endarterectomia carotídea após subluxação de mandíbula. PMID:29930669
Assembly of flexible CoMoO4@NiMoO4·xH2O and Fe2O3 electrodes for solid-state asymmetric supercapacitors

PubMed Central

Wang, Jing; Zhang, Leipeng; Liu, Xusong; Zhang, Xiang; Tian, Yanlong; Liu, Xiaoxu; Zhao, Jiupeng; Li, Yao

2017-01-01

In this work, CoMoO4@NiMoO4·xH2O core-shell heterostructure electrode is directly grown on carbon fabric (CF) via a feasible hydrothermal procedure with CoMoO4 nanowires (NWs) as the core and NiMoO4 nanosheets (NSs) as the shell. This core-shell heterostructure could provide fast ion and electron transfer, a large number of active sites, and good strain accommodation. As a result, the CoMoO4@NiMoO4·xH2O electrode yields high-capacitance performance with a high specific capacitance of 1582 F g−1, good cycling stability with the capacitance retention of 97.1% after 3000 cycles and good rate capability. The electrode also shows excellent mechanical flexibility. Also, a flexible Fe2O3 nanorods/CF electrode with enhanced electrochemical performance was prepared. A solid-state asymmetric supercapacitor device is successfully fabricated by using flexible CoMoO4@NiMoO4·xH2O as the positive electrode and Fe2O3 as the negative electrode. The asymmetric supercapacitor with a maximum voltage of 1.6 V demonstrates high specific energy (41.8 Wh kg−1 at 700 W kg−1), high power density (12000 W kg−1 at 26.7 Wh kg−1), and excellent cycle ability with the capacitance retention of 89.3% after 5000 cycles (at the current density of 3A g−1). PMID:28106170
Crystal structure of bis-[tetra-kis-(tetra-hydro-furan-κO)lithium] bis[μ-2,2',2''-methanetriyltris(4,6-di-tert-butylphenolato)-κ4O,O':O',O'']-dimagnesiate.

PubMed

Zhou, Hongyan; Wang, Lei

2017-07-01

The title ion-association metal complex, [Li(C 4 H 8 O) 4 ] 2 [Mg 2 (C 43 H 61 O 3 ) 2 ], has been synthesized from the tridentate phenolic ligand tris-(3,5-di- tert -butyl-2-hy-droxy-phen-yl)methane in tetra-hydro-furan (THF). The aryl-oxo magnesiate complex anion is binuclear with each Mg 2 O 4 complex unit inversion-related and bridged through the two tridentate chelating phenolate O-donors of the ligand. The complex centres have a distorted tetra-hedral stereochemistry [Mg-O range 1.8796 (17)-2.0005 (16) Å] and an Mg⋯Mg separation of 2.9430 (14) Å]. The LiO 4 coodination sphere of the cation comprises four THF O-donor atoms and has a slightly distorted tetra-hedral conformation [Li-O range 1.899 (5)- 1.953 (5) Å]. In the crystal, a number of stabilizing intra-anion C-H⋯O hydrogen-bonding inter-actions are present but no inter-species associations are found.
High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer
Interfaces in La2NiO4- La2CuO4 superlattices

NASA Astrophysics Data System (ADS)

Smadici, S.; Lee, J. C. T.; Wang, S.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

2009-03-01

Ni substitution on Cu sites in underdoped La2-xSrxCuO4 quickly restores Neel order. This was attributed to strong interaction between the Ni and doped holes. An open question was whether the additional Ni empty orbital or the different spin on Ni sites was at the origin of this strong interaction. We have addressed this problem with resonant soft x-ray scattering on a La2NiO4- La2CuO4 heterostructure. La2NiO4 and La2CuO4 have close lattice structures and electronic configurations. However, the x-ray scattering contrast between superlattice layers is greatly enhanced at soft x-ray resonant energies. Based on our measurements at the O K, La M, Cu L and Ni L edges a model of the charge, orbital and spin structures in these superlattices will be presented with a special emphasis on the interface region. This work was supported by Grants. DE-FG02- 06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.

Nafion covered core-shell structured Fe3O4@graphene nanospheres modified electrode for highly selective detection of dopamine.

PubMed

Zhang, Wuxiang; Zheng, Jianzhong; Shi, Jiangu; Lin, Zhongqiu; Huang, Qitong; Zhang, Hanqiang; Wei, Chan; Chen, Jianhua; Hu, Shirong; Hao, Aiyou

2015-01-01

Nafion covered core-shell structured Fe3O4@graphene nanospheres (GNs) modified glassy carbon electrode (GCE) was successfully prepared and used for selective detection dopamine. Firstly, the characterizations of hydro-thermal synthesized Fe3O4@GNs were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Then Fe3O4@GNs/Nafion modified electrode exhibited excellent electrocatalytic activity toward the oxidations of dopamine (DA). The interference test showed that the coexisted ascorbic acid (AA) and uric acid (UA) had no electrochemical interference toward DA. Under the optimum conditions, the broad linear relationship was obtained in the experimental concentration from 0.020 μM to 130.0 μM with the detection limit (S/N=3) of 0.007 μM. Furthermore, the core-shell structured Fe3O4@GNs/Nafion/GCE was applied to the determination of DA in real samples and satisfactory results were got, which could provide a promising platform to develop excellent biosensor for detecting DA. Copyright © 2014 Elsevier B.V. All rights reserved.
Determinação da composição química em nebulosas planetárias na direção do anticentro galáctico

NASA Astrophysics Data System (ADS)

Costa, R. D. D.; Uchida, M. M. M.; Maciel, W. J.

2003-08-01

Existe um gradiente radial de abundâncias no disco galáctico, cujo comportamento é razoavelmente bem conhecido para distâncias galactocêntricas entre 3 e 10 kpc. Foi obtido a partir de resultados derivados de nebulosas planetárias, regiões HII e estrelas, como as estrelas quentes de tipo O, B e aglomerados abertos. Com o objetivo de investigar o comportamento deste gradiente radial na região externa do disco, conhecida como anticentro galáctico, reportamos aqui os resultados finais da análise de uma amostra de nebulosas planetárias na direção do anticentro, observadas no LNA e no ESO entre 1995 e 2000. O uso de nebulosas planetárias permite o cálculo das abundâncias de elementos traçadores da evolução química do disco como oxigênio, argônio e neônio com o uso de técnicas de espectroscopia nebular. Os resultados indicam uma distribuição de abundâncias distinta daquela encontrada na vizinhança solar, mostrando que o gradiente radial diminui sensivelmente para distâncias galactocêntricas maiores que 10 kpc. Este resultado está de acordo com os mais recentes modelos de evolução química do disco, que prevêem uma diminuição ou mesmo um desaparecimento do gradiente radial no bordo externo do disco galáctico. (FAPESP/CNPq)
Análise da aplicação e dos resultados do modelo OPM3® para a área da saúde

PubMed Central

Augusto dos Santos, Luis; de Fátima Marin, Heimar

2015-01-01

Esta pesquisa procurou analisar se um modelo de questionário criado por uma comunidade internacional de gerenciamento de projetos e se é aplicavél a organizações voltadas a área de saúde. O modelo OPM3® (Organizational Project Management Maturity Model) foi criado para que organizações de qualquer área ou porte pudessem identificar a presença, ou ausência, de boas práticas de gerenciamento. O objetivo da aplicação desse modelo é avaliar sempre a organização e não o entrevistado. No presente artigo, são apresentados os resultados da aplicação desse modelo em uma organização que possuía produtos e serviços de tecnologia da informação aplicados à área de saúde. Este estudo verificou que o modelo é aplicável de forma rápida e que a organização analisada possuía um número expressivo de boas práticas. PMID:26924862
Projeto educação em ciências com observatórios virtuais: a participação da Escola Moppe no período 2000-2003

NASA Astrophysics Data System (ADS)

Wuensche, C. A.; Gavioli, E.; Oliveira, A. L. P. R. S.; da Silva, C.; Cardoso, H. P.; Estácio, S.

2003-08-01

O projeto Educação em Ciências com Observatórios Virtuais foi concebido pelo Instituto Astronômico e Geofísico da USP, agregando diversas instituições de ensino e pesquisa no país para desenvolver competências diversas na educação fundamental, média e superior utilizando a astronomia como ferramenta multidisciplinar. Este trabalho descreve a participação da MOPPE, escola-piloto do INPE no projeto, no período de 2000-2003. Serão apresentadas 1) a criação de um clube de ciências (1999 a 2001) cujo tema foi a colonização de Marte e 2) a ementa de astronomia trabalhada com as 7a. e 8a. séries do ensino fundamental. A proposta do projeto Colonizando Marte foi estudar diversos aspectos de uma missão interplanetária e construir experiementos que permitissem quantificar esses aspectos. Os resultados obtidos incluiram apresentações nas SBPC Jovem em 2000 e 2001. Discutiremos também as ementas de astronomia trabalhadas desde 2001 e o envolvimento dos alunos com atividades ligadas a astronomia, fora da aula de ciências. A inclusão de astronomia no currículo das últimas séries motivou a participação de mais alunos culminando com a conquista de duas medalhas para alunos da 7a. série na Olimpiada Brasileira de Astronomia em 2002. Houve também um aumento no número de participantes na OBA 2003 e nos projetos de astronomia mais elaborados nas Feira de Ciências de 2001 e 2002. Destacamos em 2003 a inclusão da MOPPE no projeto TIE - Telescopes in Education - da NASA, que utiliza o telescópio do Observatório de Mount Wilson (EUA) para observações remotas em projetos pedagógicos para o ensino de astronomia.
CoFe2O4-TiO2 and CoFe2O4-ZnO thin film nanostructures elaborated from colloidal chemistry and atomic layer deposition.

PubMed

Clavel, Guylhaine; Marichy, Catherine; Willinger, Marc-Georg; Ravaine, Serge; Zitoun, David; Pinna, Nicola

2010-12-07

CoFe(2)O(4)-TiO(2) and CoFe(2)O(4)-ZnO nanoparticles/film composites were prepared from directed assembly of colloidal CoFe(2)O(4) in a Langmuir-Blodgett monolayer and atomic layer deposition (ALD) of an oxide (TiO(2) or ZnO). The combination of these two methods permits the use of well-defined nanoparticles from colloidal chemistry, their assembly on a large scale, and the control over the interface between a ferrimagnetic material (CoFe(2)O(4)) and a semiconductor (TiO(2) or ZnO). Using this approach, architectures can be assembled with a precise control from the Angstrom scale (ALD) to the micrometer scale (Langmuir-Blodgett film). The resulting heterostructures present well-calibrated thicknesses. Electron microscopy and magnetic measurement studies give evidence that the size of the nanoparticles and their intrinsic magnetic properties are not altered by the various steps involved in the synthesis process. Therefore, the approach is suitable to obtain a layered composite with a quasi-monodisperse layer of ferrimagnetic nanoparticles embedded in an ultrathin film of semiconducting material.
Phase and Physicochemical Properties Diagrams of Quaternary System Li2B4O7 + Na2B4O7 + Mg2B6O11 + H2O

NASA Astrophysics Data System (ADS)

Wang, Shi-qiang; Du, Xue-min; Jing, Yan; Guo, Ya-fei; Deng, Tian-long

2017-12-01

The phase and physicochemical properties diagrams of the quaternary system (Li2B4O7 + Na2B4O7 + Mg2B6O11) at 288.15 K and 0.1 MPa were constructed using the solubilities, densities, and refractive indices measured. In the phase diagrams of the system there are one invariant point, three univariant isothermic dissolution curves, and three crystallization regions corresponding to Li2B4O7 · 3H2O, Na2B4O7 · 10H2O, and Mg2B6O11 · 15H2O, respectively. The solution density, refractive index of the quaternary system changes regularly with the increasing of Li2B4O7 concentration. The calculated values of density and refractive index using empirical equations of the quaternary system are in good agreement with the experimental values.
Investigating the Structural, Thermal, and Electronic Properties of the Zircon-Type ZrSiO4, ZrGeO4 and HfSiO4 Compounds

NASA Astrophysics Data System (ADS)

Chiker, Fafa; Boukabrine, Fatiha; Khachai, H.; Khenata, R.; Mathieu, C.; Bin Omran, S.; Syrotyuk, S. V.; Ahmed, W. K.; Murtaza, G.

2016-11-01

In the present study, the structural, thermal, and electronic properties of some important orthosilicate dielectrics, such as the ZrSiO4, ZrGeO4, and HfSiO4 compounds, have been investigated theoretically with the use of first-principle calculations. We attribute the application of the modified Becke-Johnson exchange potential, which is basically an improvement over the local density approximation and the Perdew-Burke-Ernzerhof exchange-correlation functional, for a better description of the band gaps of the compounds. This resulted in a good agreement with our estimated values in comparison with the reported experimental data, specifically for the ZrSiO4, and HfSiO4 compounds. Conversely, for the ZrGeO4 compound, the calculated electronic band structure shows a direct band gap at the Γ point with the value of 5.79 eV. Furthermore, our evaluated thermal properties that are calculated by using the quasi-harmonic Debye model indicated that the volume variation with temperature is higher in the ZrGeO4 compound as compared to both the ZrSiO4 and HfSiO4 compounds, which is ascribed to the difference between the electron shells of the Si and Ge atoms. Therefore, these results also indicate that while the entropy ( S) and enthalpy ( U) parameters increase monotonically, the free energy ( G), in contrast, decreases monotonically with increasing temperature, respectively. Moreover, the pressure and temperature dependencies of the Debye temperature Θ, thermal expansion coefficient, and heat capacities C V were also predicted in our study.
Determinação de regiões de órbitas diretas estáveis ao redor da Lua

NASA Astrophysics Data System (ADS)

de Melo, C. F.; Winter, O. C.; Vieira Neto, E.

2003-08-01

Neste Trabalho estamos investigando regiões do sistema Terra-Lua que contêm órbitas diretas estáveis ao redor da Lua visando a utilização destas órbitas em futuras missões de veículos espaciais como alternativas de trajetórias com baixo custo de manutenção. Adotando-se o problema restrito de três corpos, Terra-Lua-partícula, a localização e a extensão destas regiões de estabilidade foram investigadas numericamente considerando como estável toda órbita que permanece ao redor a Lua por, no mínimo, 1000 dias com energia de dois corpos da partícula em relação à Lua negativa. A estabilidade de tais regiões está associada a duas famílias de órbitas periódicas simples H1 e H2 e a órbitas quase-periódicas associadas a elas. Uma vez identificadas as regiões de estabilidade passamos a analisá-las introduzindo, paulatinamente, outras interações relevantes ao sistema como as perturbações do Sol (via problema restrito de quatro corpos), das marés, da pressão de radiação e do achatamento terrestre. Os resultados encontrados até o momento mostram que a perturbação do Sol é a única que reduz significativamente o tamanho das regiões de estabilidade. Também estamos investigando o comportamento de tais regiões quando características intrínsecas do sistema como as excentricidades das órbitas da Terra e da Lua e a inclinação da órbita Lua são consideradas. Com este estudo estamos reunindo informações que nos permitirão compreender a evolução das regiões de estabilidade no sistema Terra-Lua, bem como estabelecer parâmetros adequados para a utilização das trajetórias estáveis em futuras missões espaciais. Agradecimentos: Este projeto conta com o apoio do CNPq, da Capes e da Fapesp.
Preparation, Characterization, and Structure of Two Layered Molybdenum(VI) Phosphates: KMo(H 2O)O 2PO 4 and NH 4Mo(H 2O)O 2PO 4

NASA Astrophysics Data System (ADS)

Millini, Roberto; Carati, Angela

1995-08-01

New layered Mo(VI) compounds, KMo(H 2O)O 2PO 4 (I) and NH 4Mo(H 2O)O 2PO 4 (II), were synthesized hydrothermally and their structures were determined from single-crystal X-ray analysis. Compounds (I) and (II) are isostructural and crystallize in the monoclinic P2 1/ n space group with a = 12.353(3), b = 8.623(2), c = 5.841(1) Å, β = 102.78(1)°, V = 606.8(2) Å 3, Z = 4, and R = 0.027 ( Rw = 0.030) for compound (I) and a = 12.435(3), b = 8.761(2), c = 6.015(1), β = 103.45(1)°, V = 637.3(2) Å 3, Z = 4, and R = 0.040 ( Rw = 0.041) for compound (II). The structure consists of layers built up of eight- and four-membered rings resulting from the alternation of corner-sharing [MoO 6] octahedra and [PO 4] tetrahedra. The layers stack along the (1¯01) direction by intercalating K and NH 4 ions.
Undulated oxo-centered layers in PbLn3O4(VO4) (Ln= La and Nd) and relationship with Nd4O4(GeO4)

NASA Astrophysics Data System (ADS)

Colmont, Marie; Mentré, Olivier; Henry, Natacha; Pautrat, Alain; Leclercq, Bastien; Capet, Frédéric; Djelal, Nora; Roussel, Pascal

2018-04-01

Single crystals of PbLa3O4(VO4) have been synthesized using the flux growth technique and characterized by X-ray diffraction. The crystal structure of the tittle phase was solved by charge flipping and refined to R1 = 0.024 (wR2 = 0.031) for 2777 reflections [I>3σ(I)]. The compound is orthorhombic and crystallized in the space group Cmcm: a = 5.8686(6)Å, b = 17.898(2)Å, c = 7.9190(7)Å, V = 831.8(1)Å3, Z = 4. The structure is built on [PbLa3O4]3+ layers with zig-zag cross-sections, surrounded by isolated (VO4)3- tetrahedra. Its crystal structure shows direct relationship with the isoformular Nd4O4(GeO4) compound which crystallized in the primitive non centrosymmetric Pb21m sub-group. Its stability in temperature and under air was checked as well as optical properties. In a second part, lanthanum was substituted by neodymium giving rise to a paramagnet and f→ f electronic excitations superposed to the broad absorption front below 3.05 eV related to the presence of VO4 groups.
Magnetic studies of SiO2 coated CoFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Abyaneh, Majid K.; Kulkarni, Sulabha K.

2017-11-01

Oleic acid capped CoFe2O4 nanoparticles which exhibit a high coercivity of ∼9.47 kOe at room temperature were coated with a robust coating of SiO2. We have used chemical synthesis method to obtain SiO2 coated CoFe2O4 nanoparticles with different weight percentages of CoFe2O4 in SiO2 (1.5, 3.1 and 4.8 wt.%). The morphological investigation of the coated nanoparticles by transmission electron microscopy shows that the particles are spherical with average size ∼160 nm. Infrared spectroscopy reveals that oleic acid capping on the surface of CoFe2O4 nanoparticles is retained after silica coating process. The complete coating of SiO2 on CoFe2O4 nanoparticles is confirmed by X-ray photoelectron spectroscopy as there is no signature of cobalt or iron ions on the surface. Magnetic measurements show that coercivity of SiO2 coated CoFe2O4 particles remains more or less unaffected as in CoFe2O4 nanoparticles at room temperature. In addition, the temperature dependent magnetic measurements show that at 5 K the CoFe2O4 and SiO2 coated 1.5 wt.% CoFe2O4 samples exhibit a very high value of coercivity (∼20 kOe) which is more than twice as compared to room temperature coercivity value (∼9.47 kOe). We conclude that silica coating in our study does not significantly affect the coercivity of CoFe2O4 nanoparticles.
Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

PubMed

Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

2016-11-15

Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources. Copyright © 2016 Elsevier Inc. All rights reserved.
On Ensino de Astronomia nas Cidades de Ribeirão Pires e Rio Grande da Serra

NASA Astrophysics Data System (ADS)

Faria, R. Z.; Voelzke, M. R.

2007-08-01

Apesar da astronomia ser um dos temas indicados pelos Parâmetros Curriculares Nacionais, observa-se que poucas mudanças ocorreram desde a implementação do mesmo em sala de aula. A presente pesquisa diz respeito sobre como os tópicos de astronomia estão sendo abordados pelos professores no ensino médio. Optou-se por aplicar um questionário com os professores que ministram a disciplina de física. Os mesmos trabalham em escolas estaduais situadas nas cidades de Ribeirão Pires e Rio Grande da Serra, ambas subordinadas a Diretoria de Ensino de Mauá, no Estado de São Paulo. O questionário foi aplicado durante o 2° semestre de 2006. Até o momento os resultados são preliminares. Dos 82,0% dos professores que responderam ao questionário no município de Rio Grande da Serra, 66,7% não aplicaram nenhum tópico de astronomia, 77,8% não utilizaram qualquer tipo de programa computacional, 66,7% não utilizaram laboratório, que 77,8% nunca levaram os alunos a museus e ou planetários e que 66,7% não indicaram qualquer tipo de revista ou livro sobre astronomia aos seus alunos. No município de Ribeirão Pires, 53,3% dos professores responderam ao questionário, destes 75,0% não aplicaram nenhum tópico de astronomia, 93,8% não utilizaram qualquer tipo de programa computacional, 75,0% não utilizaram laboratório, 81,3% nunca levaram os alunos a museus e ou planetário e 56,3% não indicaram qualquer tipo de revista ou livro sobre astronomia ao seus alunos. Apesar da maioria dos professores reconhecerem que o conteúdo de astronomia influi na formação do jovem, os mesmos não incluem o tema em seus planejamentos escolares.
Removal of nitrate and phosphate using chitosan/Al2O3/Fe3O4 composite nanofibrous adsorbent: Comparison with chitosan/Al2O3/Fe3O4 beads.

PubMed

Bozorgpour, Farahnaz; Ramandi, Hossein Fasih; Jafari, Pooya; Samadi, Saman; Yazd, Shabnam Sharif; Aliabadi, Majid

2016-12-01

In the present study the chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibrous adsorbent was prepared by electrospinning process and its application for the removal of nitrate and phosphate were compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite bead adsorbent. The influence of Al 2 O 3 /Fe 3 O 4 composite content, pH, contact time, nitrate and phosphate initial concentrations and temperature on the nitrate and phosphate sorption using synthesized bead and nanofibrous adsorbents was investigated in a single system. The reusability of chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers after five sorption-desorption cycles were carried out. The Box-Behnken design was used to investigate the interaction effects of adsorbent dosage, nitrate and phosphate initial concentrations on the nitrate and phosphate removal efficiency. The pseudo-second-order kinetic model and known Freundlich and Langmuir isotherm models were used to describe the kinetic and equilibrium data of nitrate and phosphate sorption using chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers. The influence of other anions including chloride, fluoride and sulphate on the sorption efficiency of nitrate and phosphate was examined. The obtained results revealed the higher potential of chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibers for nitrate and phosphate compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite beads. Copyright © 2016 Elsevier B.V. All rights reserved.
Fabrication and tritium release property of Li2TiO3-Li4SiO4 biphasic ceramics

NASA Astrophysics Data System (ADS)

Yang, Mao; Ran, Guangming; Wang, Hailiang; Dang, Chen; Huang, Zhangyi; Chen, Xiaojun; Lu, Tiecheng; Xiao, Chengjian

2018-05-01

Li2TiO3-Li4SiO4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li2TiO3 and Li4SiO4. Wet method was developed for the pebble fabrication and Li2TiO3-Li4SiO4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li2TiO3-Li4SiO4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H2 and tritium, the addition of 0.1%H2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li2TiO3-Li4SiO4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles.
Oxygen potentials in Ni + NiO and Ni + Cr2O3 + NiCr2O4 systems

NASA Astrophysics Data System (ADS)

Kale, G. M.; Fray, D. J.

1994-06-01

The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr2O3 + NiCr2O4 equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu2O // (Y2O3)ZrO2 // Ni + NiO, Pt (-) and (+) Pt, Ni + NiO // (Y2O3)ZrO2 // Ni + Cr2O3 + NiCr2O4, Pt (-) in the temperature range of 800 to 1300 K and 1100 to 1460 K, respectively. The electromotive force (emf) of both the cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. For the coexistence of the two-phase mixture of Ni + NiO, δΜO 2(Ni + NiO) = -470,768 + 171.77T (±20) J mol-1 (800 ≤ T ≤ 1300 K) and for the coexistence of Ni + Cr2O3 + NiCr2O4, δΜO 2(Ni + Cr2O3 + NiCr2O4) = -523,190 + 191.07T (±100) J mol-1 (1100≤ T≤ 1460 K) The “third-law” analysis of the present results for Ni + NiO gives the value of ‡H{298/o} = -239.8 (±0.05) kJ mol-1, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.
Implementação de um algoritmo para a limpeza de mapas da RCFM

NASA Astrophysics Data System (ADS)

Souza, C. L.; Wuensche, C. A.

2003-08-01

A Radiação Cósmica de Fundo em Microondas (RCFM), descoberta por Penzias e Wilson em 1965, é uma das ferramentas mais poderosas para o estudo da cosmologia. Com a descoberta de flutuações de temperatura na RCFM, da ordem de uma parte em 105, pelo COBE (1992), uma nova era teve início. Nos últimos onze anos, diversos instrumentos fizeram novas medidas de alta precisão, refinando os resultados apresentados pelo COBE, culminando com os resultados recentes do satélite WMAP. A análise de dados da RCFM, especialmente no caso de experimentos com pequena cobertura do céu, apresenta uma série de dificuldades devido a emissões de contaminantes externos, tais como a emissão da Galáxia e de fontes pontuais, e de ruídos intrínsecos tanto ao sistema de detecção quanto à estratégia de observação do céu. Uma das soluções típicas para a filtragem de dados brutos de um experimento para medir flutuações de temperatura é aplicar um gabarito (template) e um filtro passa alta ao produzir mapas simplificados (sem considerar matrizes de correlação ou covariância). No caso de experimentos que utilizam detectores HEMT, essa combinação de filtros remove, satisfatoriamente, ruídos do tipo 1/f gerados pela instabilidade no ganho do detector acoplado ao movimento do instrumento, definido pela estratégia de observação. Entretanto, o sinal resultante medido, tanto em simulações quanto em séries temporais reais, sugere que parte do sinal cosmológico pode estar sendo removido junto com o ruído dos detectores. Este trabalho descreve as etapas para a produção de um mapa típico (simulado) e os testes preliminares de um algoritmo para remover ruídos do tipo 1/f introduzidos pela estratégia de observação sem prejudicar a qualidade do sinal cosmológico presente no mapa.
Facile transformation of FeO/Fe3O4 core-shell nanocubes to Fe3O4 via magnetic stimulation

NASA Astrophysics Data System (ADS)

Lak, Aidin; Niculaes, Dina; Anyfantis, George C.; Bertoni, Giovanni; Barthel, Markus J.; Marras, Sergio; Cassani, Marco; Nitti, Simone; Athanassiou, Athanassia; Giannini, Cinzia; Pellegrino, Teresa

2016-09-01

Here, we propose the use of magnetic hyperthermia as a means to trigger the oxidation of Fe1-xO/Fe3-δO4 core-shell nanocubes to Fe3-δO4 phase. As a first relevant consequence, the specific absorption rate (SAR) of the initial core-shell nanocubes doubles after exposure to 25 cycles of alternating magnetic field stimulation. The improved SAR value was attributed to a gradual transformation of the Fe1-xO core to Fe3-δO4, as evidenced by structural analysis including high resolution electron microscopy and Rietveld analysis of X-ray diffraction patterns. The magnetically oxidized nanocubes, having large and coherent Fe3-δO4 domains, reveal high saturation magnetization and behave superparamagnetically at room temperature. In comparison, the treatment of the same starting core-shell nanocubes by commonly used thermal annealing process renders a transformation to γ-Fe2O3. In contrast to other thermal annealing processes, the method here presented has the advantage of promoting the oxidation at a macroscopic temperature below 37 °C. Using this soft oxidation process, we demonstrate that biotin-functionalized core-shell nanocubes can undergo a mild self-oxidation transformation without losing their functional molecular binding activity.
Evolução temporal da explosão solar de 06 de junho de 2000 apresentando estruturas finas em rádio freqüências

NASA Astrophysics Data System (ADS)

Fernandes, F. C. R.; Sawant, H. S.; Cecatto, J. R.; Caracini, A. G.; Vats, H. O.; Karlický, M.; Meszarosova, H.

2003-08-01

Em 06 de junho de 2000 (~15: 00-17: 00 UT), o Brazilian Solar Spectroscope (BSS) registrou uma explosão solar intensa no intervalo de freqüência de (1000-2000) MHz, com alta resolução temporal (100 ms) e espectral (5 MHz). A atividade solar relacionada a esta explosão associada à região ativa (AR) 9026 e classificada como X2.3 foi grande. O Ondrejov Observatory registrou rádio emissões até 4,5 GHz. O satélite SOHO registrou uma série de erupções solares, incluindo uma Ejeção de Massa Coronal (CME) tipo "full-halo" (~15: 54 UT). Explosões tipo II/IV também foram registradas. Na faixa de ondas decimétricas, este evento apresentou dois picos distintos (~15: 21 UT e ~16: 42 UT). O primeiro pico coincide com a explosão registrada em raios-X moles (GOES) e em raios-X duros (Yohkoh). Os espectros dinâmicos com alta resolução do BSS revelaram várias estruturas finas, principalmente emissões tipo "zebra" e "fibra", rádio pulsações, emissões tipo III e do único caso de emissões "zebra" harmônicas observado na faixa decimétrica. Neste trabalho, analisamos a evolução temporal e o comportamento global do evento de 06 de junho de 2000, com ênfase na identificação e associação da ocorrência de cada tipo de estrutura fina registrada em rádio com cada etapa da explosão. Resultados preliminares mostraram que, na fase pré-flare, as estruturas finas apresentaram taxa de deriva negativa (~ 70-190 MHz/s). As emissões tipo "zebra" concentram-se na fase de descida do primeiro pico impulsivo e na de subida do segundo pico. Enquanto que as emissões tipo "fibra" ocorrem em ambas fases, mas preferivelmente durante a fase de descida. Os resultados serão apresentados e discutidos.
A V(IV) Hydroxyhydrogenomonophosphate with an Intersecting Tunnel Structure: HK 4[V 10O 10(H 2O) 2(OH) 4(PO 4) 7]·9H 2O

NASA Astrophysics Data System (ADS)

Berrah, F.; Guesdon, A.; Leclaire, A.; Borel, M. M.; Provost, J.; Raveau, B.

1999-12-01

A V(IV) hydroxyhydrogenomonophosphate HK4[V10O10(H2O)2(OH)4(PO4)7]·9H2O has been obtained, using hydrothermal conditions. Its structure, closely related to that of (CH3)2NH2K4[V10O10(H2O)2(OH)4(PO4)7]·4H2O, differs from the latter by its I41/a space group (instead of P43). This difference corresponds to a "disordering" of the vanadium atoms, with respect to the dimethyl ammonium phase. It is shown that this disorder, which appears in the form of "V5O22" units distributed at random, does not affect the oxygen framework. The analysis of this complex structure shows that it can be described from the stacking along c of [V8P7O38(OH)4(H2O)2]∞ layers interconnected through layers of isolated VO6 octahedra. In this structure, built up of VO6, VO5OH, and VO4(OH)(H2O) octahedra, of VO4OH pyramids, and of PO4 tetrahedra, large "toffee" tunnels and smaller ones with a tulip-shape section are running along a (or b). The first ones are stuffed with H2O molecules forming aquo tubes, where protons are likely "delocalized," whereas the second ones are occupied by K+ cations.

Preparation of SiO2/(PMMA/Fe3O4) from monolayer linolenic acid modified Fe3O4 nanoparticles via miniemulsion polymerization.

PubMed

He, Lei; Li, Zhiyang; Fu, Jing; Deng, Yan; He, Nongyue; Wang, Zhifei; Wang, Hua; Shi, Zhiyang; Wang, Zunliang

2009-10-01

SiO2/(PMMA/Fe3O4) composite particles were prepared from linolenic acid (LA) instead of oleic acid (OA) modified Fe3O4 nanoparticles by miniemulsion polymerization. LA has three unsaturated double bonds with which it can polymerizate more easily than OA. And coating Fe3O4 with polymethyl methacrylate (PMMA) polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. Finally, the resulting PMMA/Fe3O4 nanoparticles were coated with silica, forming SiO2/(PMMA/Fe3O4) core-shell structure particles. The sizes of nanoparticles with core-shell structure were in the range from 300 to 600 nm. The nanoparticles were spherical particles and had consistent size. The result of magnetic measurement showed that the composite particles had superparamagnetic property.
Influência da termoablação com baixa e alta densidade de energia na junção safeno-femoral, utilizando laser endovenoso 1470 nm

PubMed Central

de Araujo, Walter Junior Boim; Erzinger, Fabiano Luiz; Caron, Filipe Carlos; Nejm, Carlos Seme; Timi, Jorge Rufino Ribas

2017-01-01

Resumo Contexto Faz-se importante o conhecimento técnico dos ajustes de potência e de densidade de energia linear endovenosa (linear endovenous energy density, LEED) adequados para atingir o objetivo final da termoablação endovenosa (endovenous laser ablation, EVLA). Objetivos Avaliar a influência de diferentes LEEDs em termos de patência e presença de refluxo, bem como determinar a evolução clínica. Métodos Foram incluídas 60 veias safenas magnas (VSM). Os pacientes foram randomizados em dois grupos: EVLA com baixa potência (7 W e LEED de 20-40 J/cm) e com alta potência (15 W e LEED de 80-100 J/cm). O acompanhamento com eco-Doppler e escore de severidade clínica venoso (VCSS) foi realizado nos intervalos de 3-5 dias, 30 dias, 180 dias e 1 ano após o procedimento. Resultados Dezoito pacientes (29 membros) tratados com 7W de potência e 13 pacientes (23 membros) com 15 W completaram o estudo. Não houve diferença significativa considerando idade, tempo de cirurgia e o uso de analgésicos, lateralidade, gênero e presença de comorbidades. O LEED médio foi de 33,54 J/cm no grupo de 7 W e de 88,66 J/cm no de 15 W. Ambos apresentaram melhora no VCSS, redução significativa dos diâmetros da JSF e ausência de diferença significativa quanto ao aumento do comprimento do coto da VSM e de refluxo após o tratamento. Conclusões A utilização de maior densidade de energia mostrou-se mais efetiva em relação à estabilização do comprimento do coto da VSM e do refluxo em 6 meses. Fazem-se necessários estudos com um período de acompanhamento maior para fundamentar essa hipótese. PMID:29930650
Mechanism of thermal decomposition of K2FeO4 and BaFeO4: A review

NASA Astrophysics Data System (ADS)

Sharma, Virender K.; Machala, Libor

2016-12-01

This paper presents thermal decomposition of potassium ferrate(VI) (K2FeO4) and barium ferrate(VI) (BaFeO4) in air and nitrogen atmosphere. Mössbauer spectroscopy and nuclear forward scattering (NFS) synchrotron radiation approaches are reviewed to advance understanding of electron-transfer processes involved in reduction of ferrate(VI) to Fe(III) phases. Direct evidences of Fe V and Fe IV as intermediate iron species using the applied techniques are given. Thermal decomposition of K2FeO4 involved Fe V, Fe IV, and K3FeO3 as intermediate species while BaFeO3 (i.e. Fe IV) was the only intermediate species during the decomposition of BaFeO4. Nature of ferrite species, formed as final Fe(III) species, of thermal decomposition of K2FeO4 and BaFeO4 under different conditions are evaluated. Steps of the mechanisms of thermal decomposition of ferrate(VI), which reasonably explained experimental observations of applied approaches in conjunction with thermal and surface techniques, are summarized.
Three-Dimensional NiCo2O4@MnMoO4 Core-Shell Nanoarrays for High-Performance Asymmetric Supercapacitors.

PubMed

Yuan, Yuliang; Wang, Weicheng; Yang, Jie; Tang, Haichao; Ye, Zhizhen; Zeng, Yujia; Lu, Jianguo

2017-10-10

Design of new materials with sophisticated nanostructure has been proven to be an efficient strategy to improve their properties in many applications. Herein, we demonstrate the successful combination of high electron conductive materials of NiCo 2 O 4 with high capacitance materials of MnMoO 4 by forming a core-shell nanostructure. The NiCo 2 O 4 @MnMoO 4 core-shell nanoarrays (CSNAs) electrode possesses high capacitance of 1169 F g -1 (4.24 F cm -2 ) at a current density of 2.5 mA cm -2 , obviously larger than the pristine NiCo 2 O 4 electrode. The asymmetric supercapacitors (ASCs), assembled with NiCo 2 O 4 @MnMoO 4 CSNAs as binder-free cathode and active carbon (AC) as anode, exhibit high energy density of 15 Wh kg -1 and high power density of 6734 W kg -1 . Cycle performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs, conducted at current density of 20 mA cm -2 , remain 96.45% of the initial capacitance after 10,000 cycles, demonstrating its excellent long-term cycle stability. Kinetically decoupled analysis reveals that the capacitive capacitance is dominant in the total capacitance of NiCo 2 O 4 @MnMoO 4 CSNAs electrode, which may be the reason for ultra long cycle stability of ASCs. Our assembled button ASC can easily light up a red LED for 30 min and a green LED for 10 min after being charged for 30 s. The remarkable electrochemical performance of NiCo 2 O 4 @MnMoO 4 CSNAs//AC ASCs is attributed to its enhanced surface area, abundant electroactive sites, facile electrolyte infiltration into the 3D NiCo 2 O 4 @MnMnO 4 nanoarrays and fast electron and ion transport path.
K0.78Na0.22MoO2AsO4

PubMed Central

Jouini, Raja; Bouzidi, Chahira; Zid, Mohamed Faouzi; Driss, Ahmed

2013-01-01

The title compound, potassium sodium dioxidomolybdenum(VI) arsenate, K0.78Na0.22MoO2AsO4, was synthesized by a solid-state reaction route. The structure is built up from corner-sharing MoO6 octahedra and AsO4 tetrahedra, creating infinite [MoAsO8]∞ chains running along the b-axis direction. As, Mo and all but one O atom are on special positions (4c) with m symmetry and K (occupancy 0.78) is on a position (4a) of -1 in the tunnels. The possible motion of the alkali cations has been investigated by means of the bond-valance sum (BVS) model. The simulation shows that the Na+ motion appears to be easier mainly along the b-axis direction. Structural relationships between the different compounds of the AMoO2AsO4 (A = Ag, Li, Na, K, Rb) series and MXO8 (M = V; X = P, As) chains are discussed. PMID:24109253
Polyoxometal cations within polyoxometalate anions. Seven-coordinate uranium and zirconium heteroatom groups in [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14-

NASA Astrophysics Data System (ADS)

Gaunt, Andrew J.; May, Iain; Collison, David; Travis Holman, K.; Pope, Michael T.

2003-08-01

Two new composite polyoxotungstate anions with unprecedented structural features, [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- (1) and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14- (2) contain polyoxo-uranium and -zirconium clusters as bridging units. The anions are synthesized by reaction of Na12[P2W15O56] with solutions of UO2(NO3)2 and ZrCl4. The structure of 1 in the sodium salt contains four [P2W15O56]12- anions assembled into an overall tetrahedral cluster by means of trigonal bridging groups formed by three equatorial-edge-shared UO7 pentagonal bipyramids. The structure of anion 2 consists of a centrosymmetric assembly of two [P2W16O59]12- anions linked by a {Zr4O2(OH)2(H2O)4}10+ cluster. Both complexes in solution yield the expected two-line 31P-NMR spectra with chemical shifts of -2.95, -13.58 and -6.45, -13.69 ppm, respectively.
Mössbauer Studies of Core-Shell FeO/Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Kamzin, A. S.; Valiullin, A. A.; Khurshid, H.; Nemati, Z.; Srikanth, H.; Phan, M. H.

2018-02-01

FeO/Fe3O4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical shape with an average size of 20 nm. It was found that the obtained FeO/Fe3O4 nanoparticles had exchange coupling. The effect of anisotropy on the efficiency of heating (hyperthermic effect) of FeO/Fe3O4 nanoparticles by an external alternating magnetic field was examined. The specific absorption rate (SAR) of the studied nanoparticles was 135 W/g in the experiment with an external alternating magnetic field with a strength of 600 Oe and a frequency of 310 kHz. These data led to an important insight: the saturation magnetization is not the only factor governing the SAR, and the efficiency of heating of magnetic FeO/Fe3O4 nanoparticles may be increased by enhancing the effective anisotropy. Mössbauer spectroscopy of the phase composition of the synthesized nanoparticles clearly revealed the simultaneous presence of three phases: magnetite Fe3O4, maghemite γ-Fe2O3, and wustite FeO.
Preparation and photocatalytic properties of nanometer-sized magnetic TiO2/SiO2/CoFe2O4 composites.

PubMed

Li, Hansheng; Zhang, Yaping; Wu, Qin; Wang, Xitao; Liu, Changhao

2011-11-01

Magnetic TiO2/SiO2/CoFe2O4 nanoparticles (TiO2/SCFs) were prepared by a sol-gel process in a reverse microemulsion combined with solvent-thermal technique. TiO2/SCFs were characterized by Fourier transform infrared spectrometry, thermogravimetric analysis-differential scanning calorimetry, X-ray diffraction, Raman spectrometry, TEM, BET specific surface area measurement, and magnetic analysis. Structure analyses indicated that TiO2/SCFs presented a core-shell structure with TiO2 uniformly coating on SiO2/CoFe2O4 nanomagnets (SCFs) and typical ferromagnetic hysteresis. TiO2/SCFs showed larger specific surface area and better photocatalytic activities than TiO2 and TiO2/CoFe2O4 photocatalysts prepared by the same method. The doping interaction between TiO2 and CoFe2O4 reduced thanks to the inert SiO2 mesosphere.
ANÁLISE DA INSERÇÃO DOS TEMAS DE HUMANIDADES E ÉTICA, COM METODOLOGIA DE APRENDIZAGEM BASEADA EM PROBLEMAS, EM CURRICULO MÉDICO INTEGRADO EM ESCOLA PÚBLICA NO DISTRITO FEDERAL, BRASIL

PubMed Central

Novaes, Maria Rita Carvalho Garbi; Novaes, Luiz Carlos Garcez; Guilhem, Dirce; Lolas, Fernando; Silveira, Carla; Guiotti, Murilo

2009-01-01

Objetivo Realizar uma análise da inserção da ética e humanidades no currículo do Curso de Medicina da Escola Superior em Ciências da Saúde - ESCS, escola pública do Distrito Federal, Brasil, de forma a contribuir com o processo de gestão curricular. Metodologia O Estudo é de coorte e documental. Foram pesquisados 37 termos relacionados à ética e 36 referentes à humanização nos objetivos educacionais e conteúdo dos módulos temáticos, habilidades e atitudes e interação ensino-serviço-comunidade, de 1a a 4a série e no programa do internato no currículo (ano 2006) e no projeto pedagógico do Curso de Medicina (2001). Resultados Maior inserção da humanização, ética e bioética na 1a e 2a série, quando comparado à inserção na 3a e 4a série e no internato, (IC95%-α=0,034, pvalue=0,007). Unidade de habilidades e atitudes: freqüência das 3 temáticas no currículo da 1a a 4a séries (IC95%-α=0,026, pvalue=0,013). Quando comparada a inserção entre o internato e as quatro primeiras séries, observa-se que nestas a inserção da temática humanização é superior (IC95%-α=0,042, pvalue=0,029). Conclusão O currículo desenvolvido no ano de 2006 na ESCS apresentou correlação com o projeto pedagógico do curso e contemplou a temática de forma abrangente, em todas as séries e internato. PMID:20396594
Experimental heat capacities, excess entropies, and magnetic properties of bulk and nano Fe3O4-Co3O4 and Fe3O4-Mn3O4 spinel solid solutions

NASA Astrophysics Data System (ADS)

Schliesser, Jacob M.; Huang, Baiyu; Sahu, Sulata K.; Asplund, Megan; Navrotsky, Alexandra; Woodfield, Brian F.

2018-03-01

We have measured the heat capacities of several well-characterized bulk and nanophase Fe3O4-Co3O4 and Fe3O4-Mn3O4 spinel solid solution samples from which magnetic properties of transitions and third-law entropies have been determined. The magnetic transitions show several features common to effects of particle and magnetic domain sizes. From the standard molar entropies, excess entropies of mixing have been generated for these solid solutions and compared with configurational entropies determined previously by assuming appropriate cation and valence distributions. The vibrational and magnetic excess entropies for bulk materials are comparable in magnitude to the respective configurational entropies indicating that excess entropies of mixing must be included when analyzing entropies of mixing. The excess entropies for nanophase materials are even larger than the configurational entropies. Changes in valence, cation distribution, bonding and microstructure between the mixing ions are the likely sources of the positive excess entropies of mixing.
Three new d10 transition metal selenites containing PO4 tetrahedron: Cd7(HPO4)2(PO4)2(SeO3)2, Cd6(PO4)1.34(SeO3)4.66 and Zn3(HPO4)(SeO3)2(H2O)

NASA Astrophysics Data System (ADS)

Ma, Yun-Xiang; Gong, Ya-Ping; Hu, Chun-li; Mao, Jiang-Gao; Kong, Fang

2018-06-01

Three new d10 transition metal selenites containing PO4 tetrahedron, namely, Cd7(HPO4)2(PO4)2(SeO3)2 (1), Cd6(PO4)1.34(SeO3)4.66 (2) and Zn3(HPO4)(SeO3)2(H2O) (3), have been synthesized by hydrothermal reaction. They feature three different structural types. Compound 1 exhibits a novel 3D network composed of 3D cadmium selenite open framework with phosphate groups filled in the 1D helical tunnels. The structure of compound 2 displays a new 3D framework consisted of 2D cadmium oxide layers bridged by SeO3 and PO4 groups. Compound 3 is isostructural with the reported solids of Co3(SeO3)3-x(PO3OH)x(H2O) when x is equal to 1.0. Its structure could be viewed as a 3D zinc oxide open skeleton with SeO3 and HPO4 polyhedra attached on the wall of the tunnels. They represent the only examples in metal selenite phosphates in addition to the above cobalt compounds. Optical diffuse reflectance spectra revealed that these solids are insulators, which are consistent with the results of band structure computations based on DFT algorithm.
Cu@Fe3O4 core-shell nanoparticle-catalyzed oxidative degradation of the antibiotic oxytetracycline in pre-treated landfill leachate.

PubMed

Pham, Van Luan; Kim, Do-Gun; Ko, Seok-Oh

2018-01-01

Novel Cu@Fe 3 O 4 core-shell nanoparticles prepared via a simple reduction method were evaluated for degradation of oxytetracycline (OTC) in pre-treated leachate (L p-TREA ) (leachate treated by conventional methods). Changes in the characteristics of dissolved organic matter (DOM) in the leachate were also investigated to gain a better understanding of the effects of DOM on the performance of Cu@Fe 3 O 4 . An excellent OTC degradation of >99% was achieved within 30 min under conditions of 1 g/L Cu@Fe 3 O 4 , 20 mg/L OTC, 20 mM H 2 O 2 , and initial pH 3.0, which was similar to the efficiency obtained in deionized water (90% even at pH 9.05). Humic acid (HA) and fulvic acid (FA) were completely degraded at initial pH 3, while aromatic protein (AP) with 32.7% of 1-3 kDa constituents were totally transformed to 0.5-1 kDa compounds, and 17% < 0.5 kDa material was degraded. The OTC removal rate decreased gradually as Cu@Fe 3 O 4 was repeatedly used, but it was significantly enhanced when Cu@Fe 3 O 4 was washed after five uses to remove the organic matter on its surface. The results suggest that Cu@Fe 3 O 4 is a promising and effective catalyst for pharmaceutical and personal care product degradation in landfill leachates. Copyright © 2017 Elsevier Ltd. All rights reserved.
Multifunctional Fe3O4/ZnO nanocomposites with magnetic and optical properties.

PubMed

Zou, Peng; Hong, Xia; Chu, Xueying; Li, Yajun; Liu, Yichun

2010-03-01

Multifunctional Fe3O4/ZnO nanocomposites were successfully synthesized through two-step solution-based methods. Fe3O4 nanoparticles were used as seeds for the deposit and growth of ZnO nanocrystals. Transmission electron microscopy (TEM) images, X-ray diffraction (XRD) patterns, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were employed to observe the morphology, size, structure, and crystalline phase of the nanocomposites and confirm their chemical composition. The results of magnetization curves, resonant Raman scattering, and photoluminescence spectra revealed that the nanocomposites simultaneously possessed the super-paramagnetism of Fe3O4 and the multiphonon resonant Raman scattering and photoluminescence (PL) properties of ZnO. Compared with that of pure Fe3O4, the saturation magnetization of the Fe3O4 component within the nanocomposites was enhanced. The Raman spectroscopic fingerprint of ZnO component was preserved, and the fluorescent background was efficiently reduced. The interfacial effect was found to play an important role in modulating or improving the properties of the nanocomposites.
Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals.

PubMed

Martynyuk-Lototska, Irina; Mys, Oksana; Dudok, Taras; Adamiv, Volodymyr; Smirnov, Yevgen; Vlokh, Rostyslav

2008-07-01

Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.
Resultados a longo prazo da angioplastia de artérias renais com stent na doença aterosclerótica: revisão sistemática

PubMed Central

Siqueira, Daniel Emilio Dalledone; Guillaumon, Ana Terezinha

2017-01-01

Resumo A doença renovascular aterosclerótica é a principal causa de hipertensão secundária. A história natural da doença demonstra taxas de progressão de 4 a 12% ao ano. Entre os métodos de tratamento existe a angioplastia com stent de artérias renais; porém, poucos estudos clínicos demonstraram seus resultados a longo prazo. Esta revisão sistemática da literatura se propõe a apresentar os resultados a longo prazo (acima de 24 meses) da angioplastia com stent de artérias renais na doença aterosclerótica em relação à função renal e aos níveis pressóricos no controle da hipertensão. Foi realizada uma ampla pesquisa, utilizando os termos apropriados, nas bases de dados LILACS, EMBASE, SCIELO, Cochrane Library e MEDLINE. De um total de 2.170 referências, apenas sete artigos contemplavam todos os critérios de inclusão. Conclui-se que, a longo prazo, há uma estabilização da função renal, redução dos níveis pressóricos e diminuição do número de classes de medicamentos anti-hipertensivos. PMID:29930639
SOLID SOLUTION EFFECTS ON THE THERMAL PROPERTIES IN THE MgAl2O4-MgGa2O4

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Hara, Kelley; Smith, Jeffrey D; Sander, Todd P.

Solid solution eects on thermal conductivity within the MgO-Al2O3-Ga2O3 system were studied. Samples with systematically varied additions of MgGa2O4 to MgAl2O4 were prepared and the laser ash technique was used to determine thermal diusivity at temperatures between 200C and 1300C. Heat capacity as a function of temperature from room temperature to 800C was also determined using dierential scanning calorimetry. Solid solution in the MgAl2O4-MgGa2O4 system decreases the thermal conductivity up to 1000C. At 200C thermal conductivity decreased 24% with a 5 mol% addition of MgGa2O4 to the system. At 1000C the thermal conductivity decreased 13% with a 5 mol% addition.more » Steady state calculations showed a 12.5% decrease in heat ux with 5 mol% MgGa2O4 considered across a 12 inch thickness.« less
Framework 'interstitial' oxygen in La(10)(GeO(4))(5-)(GeO(5))O(2) apatite electrolyte.

PubMed

Pramana, Stevin S; Klooster, Wim T; White, T J

2007-08-01

Oxygen conduction at low temperatures in apatites make these materials potentially useful as electrolytes in solid-oxide fuel cells, but our understanding of the defect structures enabling ion migration is incomplete. While conduction along [001] channels is dominant, considerable inter-tunnel mobility has been recognized. Using neutron powder diffraction of stoichiometric 'La(10)(GeO(4))(6)O(3)', it has been shown that this compound is more correctly described as an La(10)(GeO(4))(5-)(GeO(5))O(2) apatite, in which high concentrations of interstitial oxygen reside within the channel walls. It is suggested that these framework interstitial O atoms provide a reservoir of ions that can migrate into the conducting channels of apatite, via a mechanism of inter-tunnel oxygen diffusion that transiently converts GeO(4) tetrahedra to GeO(5) distorted trigonal bipyramids. This structural modification is consistent with known crystal chemistry and may occur generally in oxide apatites.
Photopyroelectric spectroscopic studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) ceramics.

PubMed

Rizwan, Zahid; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

2011-01-01

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.
Photopyroelectric Spectroscopic Studies of ZnO-MnO2-Co3O4-V2O5 Ceramics

PubMed Central

Rizwan, Zahid; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

2011-01-01

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO2 + 0.4Co3O4 + xV2O5), x = 0–1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300–800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (Eg) was 2.11 eV for 0.3 mol% V2O5 at a sintering temperature of 1025 °C as determined from the plot (ρhυ)2 versus hυ. With a further increase in V2O5, the value of Eg was found to be 2.59 eV. Steepness factor ‘σA’ and ‘σB’, which characterize the slope of exponential optical absorption, is discussed with reference to the variation of Eg. XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively. PMID:21673911
Crystal structure of poly[diaqua(μ2-benzene-1,4-dicarboxylato-κ2 O 1:O 4)(μ2-benzene-1,4-dicarboxylato-κ4 O 1,O 1′:O 4,O 4′)bis(μ2-3,3′,5,5′-tetramethyl-4,4′-bipyrazole-κ2 N:N′)dinickel(II)

PubMed Central

Wu, Chao; Cao, Peng

2015-01-01

The asymmetric unit of the polymeric title compound, [Ni(C8H4O4)(C10H14N4)(H2O)]n, contains one Ni2+ cation, one coordinating water molecule, one 3,3′,5,5′-tetramethyl-4,4′-bipyrazole ligand and half each of two benzene-1,4-dicarboxylate anions, the other halves being generated by inversion symmetry. The Ni2+ cation exhibits an octahedral N2O4 coordination sphere defined by the O atoms of the water molecule and two different anions and the N atoms of two symmetry-related N-heterocycles. The N-heterocycles and both anions bridge adjacent Ni2+ cations into a three-dimensional network structure, with one of the anions in a bis-bidentate and the other in a bis-monodentate bridging mode. N—H⋯O and O—H⋯O hydrogen bonds between the N-heterocycles and water molecules as donor groups and the carboxylate O atoms as acceptor groups consolidate the crystal packing. PMID:26090165

Electron excitation cross sections for the 2s(2)2p(3)4S(O) -- 2s(2)2p(3)2D(O) (forbidden) and 4S(O) -- 2s2p(4) 4P (resonance) transitions in O II

NASA Technical Reports Server (NTRS)

Zuo, M.; Smith, Steven J.; Chutjian, A.; Williams, I. D.; Tayal, S. S.; Mclaughlin, Brendan M.

1995-01-01

Experimental and theoretical excitation cross sections are reported for the first forbidden transition 4S(O) -- 2S(2)2p(3) 2D(O) (lambda-lambda 3726, 3729) and the first allowed (resonance) transition 4S(O) -- 2s2p(4) 4P(lambda-833) in O II. Use is made of electron energy loss and merged-beams methods. The electron energy range covered is 3.33 (threshold) to 15 eV for the S -- D transition, and 14.9 (threshold) to 40 eV for the S -- P transition. Care was taken to assess and minimize the metastable fraction of the O II beam. An electron mirror was designed and tested to reflect inelastically backscattered electrons into the forward direction to account for the full range of polar scattering angles. Comparisons are made between present experiments and 11-state R-matrix calculations. Calculations are also presented for the 4S(O) -- 2s(2)2p(3)2P(O) (lambda-2470) transition.
Synthesis and Characterization of Photocatalytic TiO 2 -ZnFe 2 O 4 Nanoparticles

DOE PAGES

Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

2006-01-01

A new coprecipimore » tation/hydrolysis synthesis route is used to create a TiO 2 -ZnFe 2 O 4 nanocomposite that is directed towards extending the photoresponse of TiO 2 from UV to visible wavelengths ( > 400 nm ). The effect of TiO 2 's accelerated anatase-rutile phase transformation due to the presence of the coupled ZnFe 2 O 4 narrow-bandgap semiconductor is evaluated. The transformation's dependence on pH, calcinations temperature, particle size, and ZnFe 2 O 4 concentration has been analyzed using XRD, SEM, and UV-visible spectrometry. The requirements for retaining the highly photoactive anatase phase present in a ZnFe 2 O 4 nanocomposite are outlined. The visible-light-activated photocatalytic activity of the TiO 2 -ZnFe 2 O 4 nanocomposites has been compared to an Aldrich TiO 2 reference catalyst, using a solar-simulated photoreactor for the degradation of phenol.« less
Fabrication by Electrophoretic Deposition of Nano-Fe3O4 and Fe3O4@SiO2 3D Structure on Carbon Fibers as Supercapacitor Materials

NASA Astrophysics Data System (ADS)

Hajalilou, Abdollah; Abouzari-Lotf, Ebrahim; Etemadifar, Reza; Abbasi-Chianeh, Vahid; Kianvash, Abbas

2018-05-01

Core-shell nanostructured magnetic Fe3O4@SiO2 with particle size ranging from 3 nm to 40 nm has been synthesized via a facile precipitation method. Tetraethyl orthosilicate was employed as surfactant to prepare core-shell structures from Fe3O4 nanoparticles synthesized from pomegranate peel extract using a green method. X-ray diffraction analysis, Fourier-transform infrared and ultraviolet-visible (UV-Vis) spectroscopies, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy were employed to characterize the samples. The prepared Fe3O4 nanoparticles were approximately 12 nm in size, and the thickness of the SiO2 shell was 4 nm. Evaluation of the magnetic properties indicated lower saturation magnetization for Fe3O4@SiO2 powder ( 11.26 emu/g) compared with Fe3O4 powder ( 13.30 emu/g), supporting successful wrapping of the Fe3O4 nanoparticles by SiO2. As-prepared powders were deposited on carbon fibers (CFs) using electrophoretic deposition and their electrochemical behavior investigated. The rectangular-shaped cyclic voltagrams of Fe3O4@CF and Fe3O4@C@CF samples indicated electrochemical double-layer capacitor (EDLC) behavior. The higher specific capacitance of 477 F/g for Fe3O4@C@CF (at scan rate of 0.05 V/s in the potential range of - 1.13 to 0.45 V) compared with 205 F/g for Fe3O4@CF (at the same scan rate in the potential range of - 1.04 to 0.24 V) makes the former a superior candidate for use in energy storage applications.
The effect of Fe2NiO4 and Fe4NiO4Zn magnetic nanoparticles on anaerobic digestion activity.

PubMed

Chen, Jian Lin; Steele, Terry W J; Stuckey, David C

2018-06-11

Two types of magnetic nanoparticles (MNPs), i.e. Ni ferrite nanoparticles (Fe 2 NiO 4 ) and Ni Zn ferrite nanoparticles (Fe 4 NiO 4 Zn) containing the trace metals Ni and Fe, were added to the anaerobic digestion of synthetic municipal wastewater at concentrations between 1 and 100 mg Ni L -1 in order to compare their effects on biogas (methane) production and sludge activity. Using the production of methane over time as a measure, the assays revealed that anaerobic digestion was stimulated by the addition of 100 mg Ni L -1 in Fe 2 NiO 4 NPs, while it was inhibited by the addition of 1-100 mg Ni L -1 in Fe 4 NiO 4 Zn NPs. Especially at 100 mg Ni L -1 , Fe 4 NiO 4 Zn NPs resulted in a total inhibition of anaerobic digestion. The metabolic activity of the anaerobic sludge was tested using the resazurin reduction assay, and the assay clearly revealed the negative effect of Fe 4 NiO 4 Zn NPs and the positive effect of Fe 2 NiO 4 NPs. Re-feeding fresh synthetic medium reactivated the NPs added to the anaerobic sludge, except for the experiment with 100 mg Ni L -1 addition of Fe 4 NiO 4 Zn NPs. The findings in this present study indicate a possible new strategy for NPs design to enhance anaerobic digestion. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.
Photoelectron spectroscopy of B4O4 (-): Dual 3c-4e π hyperbonds and rhombic 4c-4e o-bond in boron oxide clusters.

PubMed

Tian, Wen-Juan; Zhao, Li-Juan; Chen, Qiang; Ou, Ting; Xu, Hong-Guang; Zheng, Wei-Jun; Zhai, Hua-Jin; Li, Si-Dian

2015-04-07

Gas-phase anion photoelectron spectroscopy (PES) is combined with global structural searches and electronic structure calculations at the hybrid Becke 3-parameter exchange functional and Lee-Yang-Parr correlation functional (B3LYP) and single-point coupled-cluster with single, double, and perturbative triple excitations (CCSD(T)) levels to probe the structural and electronic properties and chemical bonding of the B4O4 (0/-) clusters. The measured PES spectra of B4O4 (-) exhibit a major band with the adiabatic and vertical detachment energies (ADE and VDE) of 2.64 ± 0.10 and 2.81 ± 0.10 eV, respectively, as well as a weak peak with the ADE and VDE of 1.42 ± 0.08 and 1.48 ± 0.08 eV. The former band proves to correspond to the Y-shaped global minimum of Cs B4O4 (-) ((2)A″), with the calculated ADE/VDE of 2.57/2.84 eV at the CCSD(T) level, whereas the weak band is associated with the second lowest-energy, rhombic isomer of D2h B4O4 (-) ((2)B2g) with the predicted ADE/VDE of 1.43/1.49 eV. Both anion structures are planar, featuring a B atom or a B2O2 core bonded with terminal BO and/or BO2 groups. The same Y-shaped and rhombic structures are also located for the B4O4 neutral cluster, albeit with a reversed energy order. Bonding analyses reveal dual three-center four-electron (3c-4e) π hyperbonds in the Y-shaped B4O4 (0/-) clusters and a four-center four-electron (4c-4e) π bond, that is, the so-called o-bond in the rhombic B4O4 (0/-) clusters. This work is the first experimental study on a molecular system with an o-bond.
A teoria da percolação aplicada às galáxias aneladas peculiares

NASA Astrophysics Data System (ADS)

Poppe, P. C. R.; Martin, V. A. F.; de Medeiros, N. G. F.; Faúndez-Abans, M.; Oliveira-Abans, M.

2003-08-01

Formulado no final da década de 50, o modelo de percolação concentra-se em descrever o meio poroso, que será visto neste trabalho como uma rede de canais aleatórios, por onde escoa um fluido determinístico. Se o número de canais for suficientemente grande, então eles estarão ligados e o meio se tornará permeável à passagem do fluido. Neste caso, dizemos que houve a percolação do fluido. Reformulando o modelo acima, podemos escrever um código particularmente adaptado para simulações em Galáxias, onde iremos supor que os canais formam um reticulado, e que cada sítio da rede representa um poro que será interpretado como uma região ativa de formação estelar. Para cada elo teremos um pequeno canal ligando dois sítios vizinhos, que poderá, após um tempo "t", induzir ou não a formação de uma região ativa no poro vizinho. Para simular a passagem desta região ativa através dos poros, diremos que um elo está aberto com probabilidade p e fechado com probabilidade 1-p. Dessa forma, passamos a imaginar configurações de elos abertos e fechados, onde cada configuração ocorre com uma certa probabilidade, dada por p|A|(1-p)|F|, onde |A| é o número de elos abertos e |F| o número de elos fechados da configuração. A expressão anterior só tem importância física se |A| e |F| forem ambos finitos, pois, caso contrário, a probabilidade de ocorrência de uma dada configuração será sempre nula. Neste trabalho, foram considerados dados cinemáticos publicados na literatura bem como aqueles obtidos pelos autores a partir de observações fotométricas realizadas no Observatório de Las Campanãs, em 1994, para a Galáxia Anelada Peculiar HRG 03401. Mostraremos que para certos valores de p, situados entre 0,5 e 0,6, os clusters assim formados irão simular, de maneira coerente, o referido objeto.
β-K3Fe(MoO4)2Mo2O7

PubMed Central

Souilem, Amira; Zid, Mohamed Faouzi; Driss, Ahmed

2014-01-01

The title compound, tripotassium iron(III) bis(orthomolybdate) dimolybdate, was obtained by a solid-state reaction. The main structural building units are one FeO6 octahedron, two MoO4 tetrahedra and one Mo2O7 dimolybdate group, all with point group symmetries m. These units are linked via corner-sharing to form ribbons parallel to [010]. The three K+ cations are located between the ribbons on mirror planes and have coordination numbers of 10 and 12. Two O atoms of one of the MoO4 tetrahedra of the dimolybdate group are disordered over two positions in a 0.524 (11):0.476 (11) ratio. The structure of the title compound is compared briefly with that of Rb3FeMo4O15. PMID:25161509
Degradation of sulfamethazine using Fe3O4-Mn3O4/reduced graphene oxide hybrid as Fenton-like catalyst.

PubMed

Wan, Zhong; Wang, Jianlong

2017-02-15

In this paper, Fe 3 O 4 -Mn 3 O 4 /reduced graphene oxide (RGO) hybrid was synthesized through polyol process and impregnation method and used as heterogeneous Fenton-like catalyst for degradation of sulfamethazine (SMT) in aqueous solution. The hybrid catalyst had higher catalytic efficiency compared with Fe 3 O 4 -Mn 3 O 4 and Mn 3 O 4 as catalyst for degradation of SMT . The effects of pH value, H 2 O 2 concentration, catalyst dosage, initial SMT concentration and temperature on SMT degradation were investigated. The removal efficiency of SMT was about 98% at following optimal conditions: pH=3, T=35°C, Fe 3 O 4 /Mn 3 O 4 -RGO composites=0.5g/L, H 2 O 2 =6mM. The inhibitor experiments indicated that the main active species was hydroxyl radicals (·OH) on catalyst surface. At last, the possible catalytic mechanism was proposed. Copyright © 2016 Elsevier B.V. All rights reserved.
Popcorn balls-like ZnFe2O4-ZrO2 microsphere for photocatalytic degradation of 2,4-dinitrophenol

NASA Astrophysics Data System (ADS)

Chen, Xi; Liu, Yutang; Xia, Xinnian; Wang, Longlu

2017-06-01

In this paper, novel popcorn balls-like ZnFe2O4-ZrO2 composite microspheres were successfully fabricated by a simple hydrothermal method. The morphology, structure and optical property of the microspheres were characterized. The microspheres were used as the photocatalysts to degrade 2,4-dinitrophenol, and exhibited superior photocatalytic performance. Under simulated solar visible light irradiation, the degradation rate of ZnFe2O4-ZrO2 photocatalyst (mass ratio of ZnFe2O4/ZrO2 = 2:1) was almost 7.4 and 2.4 times higher than those of pure ZnFe2O4 and ZrO2. The enhancement could attribute to stronger light absorption, lower carrier recombination and multi-porous structure of the microspheres. Moreover, the popcorn balls-like photocatalysts can be easily separated, because of the magnetism of the samples. After five times runs, the photocatalyst still showed 90% of its photocatalytic degradation efficiency. This work demonstrated a good prospect for removing organic pollutants in water.
Photoelectron spectroscopy of B4O4-: Dual 3c-4e π hyperbonds and rhombic 4c-4e o-bond in boron oxide clusters

NASA Astrophysics Data System (ADS)

Tian, Wen-Juan; Zhao, Li-Juan; Chen, Qiang; Ou, Ting; Xu, Hong-Guang; Zheng, Wei-Jun; Zhai, Hua-Jin; Li, Si-Dian

2015-04-01

Gas-phase anion photoelectron spectroscopy (PES) is combined with global structural searches and electronic structure calculations at the hybrid Becke 3-parameter exchange functional and Lee-Yang-Parr correlation functional (B3LYP) and single-point coupled-cluster with single, double, and perturbative triple excitations (CCSD(T)) levels to probe the structural and electronic properties and chemical bonding of the B4O40/- clusters. The measured PES spectra of B4O4- exhibit a major band with the adiabatic and vertical detachment energies (ADE and VDE) of 2.64 ± 0.10 and 2.81 ± 0.10 eV, respectively, as well as a weak peak with the ADE and VDE of 1.42 ± 0.08 and 1.48 ± 0.08 eV. The former band proves to correspond to the Y-shaped global minimum of Cs B4O4- (2A″), with the calculated ADE/VDE of 2.57/2.84 eV at the CCSD(T) level, whereas the weak band is associated with the second lowest-energy, rhombic isomer of D2h B4O4- (2B2g) with the predicted ADE/VDE of 1.43/1.49 eV. Both anion structures are planar, featuring a B atom or a B2O2 core bonded with terminal BO and/or BO2 groups. The same Y-shaped and rhombic structures are also located for the B4O4 neutral cluster, albeit with a reversed energy order. Bonding analyses reveal dual three-center four-electron (3c-4e) π hyperbonds in the Y-shaped B4O40/- clusters and a four-center four-electron (4c-4e) π bond, that is, the so-called o-bond in the rhombic B4O40/- clusters. This work is the first experimental study on a molecular system with an o-bond.
The electron affinities of C{sub 3}O and C{sub 4}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rienstra-Kiracofe, J.C.; Ellison, G.B.; Hoffman, B.C.

The authors predict the adiabatic electron affinities of C{sub 3}O and C{sub 4}O based on electronic structure calculations, using a large triple-{zeta} basis set with polarization and diffuse functions (TZ2Pf+diff) with the SCF, CCSD, and CCSD(T) methods as well as with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. The results imply electron affinities for C{sub 3}O and C{sub 4}O; EA(C{sub 3}O) = 0.93 eV {+-} 0.10 and EA(C{sub 4}O) = 2.99 {+-} 0.10. The EA(C{sub 3}O) is 0.41 eV lower than the experimental value of 1.34 {+-} 0.15 eV, while the EA(C{sub 4}O) is 0.94 eV higher than the experimental valuemore » of 2.05 {+-} 0.15 eV. Optimized geometries for all species at each level of theory are given, and harmonic vibrational frequencies are reported at the SCF/TZ2Pf+diff and CCSD/aug-cc-pVDZ levels.« less
The Phase Relations in the In 2O 3-Al 2ZnO 4-ZnO System at 1350°C

NASA Astrophysics Data System (ADS)

Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko; Isobe, Mitsumasa

1993-08-01

Phase relations in the In 2O 3-Al 2ZnO 4-ZnO system at 1350°C are determined by a classical quenching method. This system consists of In 2O 3, Al 2ZnO 4, ZnO, and homologous phases InAlO 3(ZnO) m ( m = 2, 3, …) having solid solutions with LuFeO 3(ZnO) m-type crystal structures. These solid solution ranges are as follows: In 1+ x1Al 1- x1O 3(ZnO) 2 ( x1 = 0.70)-In 1+ x2Al 1- x2O 3(ZnO) 2 ( x2 = 0.316-0.320), In 2O 3(ZnO) 3-In 1+ xAl 1- xO 3(ZnO) 3 ( x = 0.230), In 2O 3(ZnO) 4-In 1+ xAl 1- xO 3(ZnO) 4 ( x = 0.15-0.16), In 2O 3(ZnO) 5-In 1+ xAl 1- xO 3(ZnO) 5 ( x = 0.116-0.130), In 2O 3(ZnO) 6-In 1+ xAl 1- xO 3(ZnO) 6 ( x = 0.000-0.111), In 2O 3(ZnO) 7-In 1+ xAl 1- xO 3(ZnO) 7 ( x = 0.08), In 2O 3(ZnO) 8-In 1+ xAl 1- xO 3(ZnO) 8 ( x: undetermined), and In 2O 3(ZnO) m-InAlO 3(ZnO) m ( m = 9, 10, 11, 13, 15, 17, and 19). The space groups of these homologous phases belong to R3¯ m for m = odd or P6 3/ mmc for m = even. Their crystal structures, In 1+ xAl 1- xO 3(ZnO) m (0 < x < 1), consist of three kinds of layers: an InO 1.5 layer, an (In xAl 1- xZn)O 2.5 layer, and ZnO layers. A comparison of the phase relations in the In 2O 3- M2ZnO 4-ZnO systems ( M = Fe, Ga, or Al) is made and their characteristic features are discussed in terms of the ionic radii and site preferences of the M cations.
Magnetically separable mesoporous Fe{sub 3}O{sub 4}/silica catalysts with very low Fe{sub 3}O{sub 4} content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grau-Atienza, A.; Serrano, E.; Linares, N.

2016-05-15

Two magnetically separable Fe{sub 3}O{sub 4}/SiO{sub 2} (aerogel and MSU-X) composites with very low Fe{sub 3}O{sub 4} content (<1 wt%) have been successfully prepared at room temperature by co-condensation of MPTES-functionalized Fe{sub 3}O{sub 4} nanoparticles (NPs) with a silicon alkoxide. This procedure yields a homogeneous incorporation of the Fe{sub 3}O{sub 4} NPs on silica supports, leading to magnetic composites that can be easily recovered using an external magnetic field, despite their very low Fe{sub 3}O{sub 4} NPs content (ca. 1 wt%). These novel hybrid Fe{sub 3}O{sub 4}/SiO{sub 2} materials have been tested for the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) withmore » hydrogen peroxide showing an enhancement of the stability of the NPs in the Fe{sub 3}O{sub 4}/silica aerogel as compared to the Fe{sub 3}O{sub 4} NPs alone, even after five catalytic cycles, no leaching or agglomeration of the Fe{sub 3}O{sub 4}/SiO{sub 2} systems. - Graphical abstract: Novel magnetically separable mesoporous silica-based composites with very low magnetite content. - Highlights: • An innovative way to prepare magnetically separable composites with <1 wt% NPs. • The Fe{sub 3}O{sub 4}/silica composites are readily magnetized/demagnetized. • The Fe{sub 3}O{sub 4}/silica composites can be easily recovered using an external magnetic field. • Excellent catalytic performance and recyclability despite the low Fe{sub 3}O{sub 4} NPs content.« less
Water activities of NaClO4, Ca(ClO4)2, and Mg(ClO4)2 brines from experimental heat capacities: Water activity >0.6 below 200 K

NASA Astrophysics Data System (ADS)

Toner, J. D.; Catling, D. C.

2016-05-01

Perchlorate salts found on Mars are extremely hygroscopic and form low eutectic temperature aqueous solutions, which could allow liquid water to exist on Mars despite cold and dry conditions. The formation, dynamics, and potential habitability of perchlorate salt solutions can be broadly understood in terms of water activity. Water activity controls condensation and evaporation of water vapor in brines, deliquescence and efflorescence of crystalline salts, and ice formation during freezing. Furthermore, water activity is a basic parameter defining the habitability of aqueous solutions. Despite the importance of water activity, its value in perchlorate solutions has only been measured at 298.15 K and at the freezing point of water. To address this lack of data, we have determined water activities in NaClO4, Ca(ClO4)2, and Mg(ClO4)2 solutions using experimental heat capacities measured by Differential Scanning Calorimetry. Our results include concentrations up to near-saturation and temperatures ranging from 298.15 to 178 K. We find that water activities in NaClO4 solutions increase with decreasing temperature, by as much as 0.25 aw from 298.15 to 178 K. Consequently, aw reaches ∼0.6-0.7 even for concentrations up to 15 molal NaClO4 below 200 K. In contrast, water activities in Ca(ClO4)2 and Mg(ClO4)2 solutions generally decrease with decreasing temperature. The temperature dependence of water activity indicates that low-temperature NaClO4 solutions will evaporate and deliquesce at higher relative humidity, crystallize ice at higher temperature, and potentially be more habitable for life (at least in terms of water activity) compared to solutions at 298.15 K. The opposite effects occur in Ca(ClO4)2 and Mg(ClO4)2 solutions.
Percepção astronómica de um grupo de alunos do ensino médio de uma escola da rede estadual de São Paulo

NASA Astrophysics Data System (ADS)

de Oliveria, E. F.; Voelzke, M. R.

2009-03-01

Sendo a Astronomia uma das cièncias mais antigas da humanidade, e considerando sua importáncia histórica e cultural, é de extrema releváncia que tópicos relacionados a ela sejam tratados nas escolas. Embora os Parámetros Curriculares Nacionais do Ensino Médio (PCN-EM) e as Orientaçiacute;es Complementares aos Parámetros (PCN+) apontem a importáncia de uma abordagem significativa de conceitos relacionados à Astronomia nas aulas de Física, muitos estudantes terminam o Ensino Médio (EM) sem compreender a razão de certos acontecimentos de origem celeste, ainda que estes façam parte de seu cotidiano e sejam alvos da curiosidade natural dos jovens. Da observação dessa curiosidade em alunos de uma escola pública paulista, na cidade de Suzano, surgiu o interesse em investigar os conhecimentos básicos em Astronomia dos alunos do Ensino Médio desta escola, constituindo-se este como principal objetivo desta pesquisa. Para tanto foi elaborado um questionário de múltipla escolha aplicado inicialmente a 34 alunos do primeiro ano e, posteriormente, a mais 310, distribuídos entre as très séries do Ensino Médio dos períodos matutino e noturno. Dessa forma, observou-se que 73,9% dos estudantes identificaram o Sol como sendo uma estrela, 67,1% mostraram compreender a sucessão entre dia e noite e 52,3% relacionaram o Big Bang à origem do Universo. Em contrapartida, apenas 34,5% relacionaram as estaçíes do ano à inclinação do eixo de rotação da Terra, 21,3% indicaram a influència gravitacional simultánea da Lua e do Sol como responsável pelo fenòmeno das marés, 24,5% indicaram corretamente quais são os objetos celestes mais próximos da Terra, 36,1% identificaram ano-luz como uma medida de distáncia e 34,2% reconheceram as estrelas cadentes como meteoros, evidenciando-se assim o pequeno discernimento dos estudantes quanto aos fenòmenos e termos astronòmicos do cotidiano. Além disso, foram comparadas as respostas de alun! os de diferentes s
Porous ZnO-Coated Co3O4 Nanorod as a High-Energy-Density Supercapacitor Material.

PubMed

Gao, Miao; Wang, Wei-Kang; Rong, Qing; Jiang, Jun; Zhang, Ying-Jie; Yu, Han-Qing

2018-06-27

Co 3 O 4 with a high theoretical capacitance has been widely recognized as a promising electrode material for supercapacitor, but its poor electrical conductivity and stability limit its practical applications. Here, we developed an effective synthetic route to synthesize one-dimensional (1D) porous ZnO/Co 3 O 4 heterojunction composites. Benefiting from the heterostructure to promote the charge transfer and protect Co 3 O 4 from corrosion and the 1D porous structure to improve ion diffusion and prevent structural collapse in charge and discharge process, the as-prepared ZnO/Co 3 O 4 composites exhibited an excellent capacitive performance and good cycling stability. The specific capacitance of the ZnO/Co 3 O 4 -450 (1135 F g -1 at 1 A g -1 ) was 1.4 times higher than that of Co 3 O 4 (814 F g -1 ), and the high-rate performance for ZnO/Co 3 O 4 -450 was 4.9 times better than that of Co 3 O 4 . Also, approximately 83% of its specific capacitance was retained after 5000 cycles at 10 A g -1 . Most importantly, the as-fabricated asymmetric supercapacitor, with a ZnO/Co 3 O 4 -450 positive electrode and an activated carbon negative electrode, delivered a prominent energy density of 47.7 W h kg -1 and a high power density of 7500 W kg -1 . Thus, the ZnO/Co 3 O 4 composites could serve as a high-activity material for supercapacitor and the preparation method also offers an attractive strategy to enhance the capacitive performance of Co 3 O 4 .
Controllable synthesis and enhanced microwave absorbing properties of Fe3O4/NiFe2O4/Ni heterostructure porous rods

NASA Astrophysics Data System (ADS)

Li, Yana; Wu, Tong; Jin, Keying; Qian, Yao; Qian, Naxin; Jiang, Kedan; Wu, Wenhua; Tong, Guoxiu

2016-11-01

We developed a coordinated self-assembly/precipitate transfer/sintering method that allows the controllable synthesis of Fe3O4/NiFe2O4/Ni heterostructure porous rods (HPRs). A series of characterizations confirms that changing [Ni2+] can effectively control the crystal size, internal strain, composition, textural characteristics, and properties of HPRs. Molar percentages of Ni and NiFe2O4 in HPRs increase with [Ni2+] in various Boltzmann function modes. Saturation magnetization Ms and coercivity Hc show U-shaped change trends because of crystal size, composition, and interface magnetic coupling. High magnetic loss is maintained after decorating NiFe2O4 and Ni on the surface of Fe3O4 PRs. Controlling the NiFe2O4 interface layers and Ni content can improve impedance matching and dielectric losses, thereby leading to lighter weight, stronger absorption, and broader absorption band of Fe3O4/NiFe2O4/Ni HPRs than Fe3O4 PRs. An optimum EM wave absorbing property was exhibited by Fe3O4/NiFe2O4/Ni HPRs formed at [Ni2+] = 0.05 M. The maximum reflection loss (RL) reaches -58.4 dB at 13.68 GHz, which corresponds to a 2.1 mm matching thickness. The absorbing bandwidth (RL ≤ -20 dB) reaches 14.4 GHz with the sample thickness at 1.6-2.4 and 2.8-10.0 mm. These excellent properties verify that Fe3O4/NiFe2O4/Ni HPRs are promising candidates for new and effective absorptive materials.
Fabrication and photocatalytic property of magnetic NiFe2O4/Cu2O composites

NASA Astrophysics Data System (ADS)

He, Zuming; Xia, Yongmei; Tang, Bin; Su, Jiangbin

2017-09-01

Magnetically separable NiFe2O4/Cu2O composites were successfully synthesized by a two-step method. The samples were characterized by XRD, XPS, SEM and VSM as well as their PL spectra and UV-vis adsorption spectra. The results showed that the NiFe2O4/Cu2O composites were composed of cubic-structured Cu2O and spinel-structured NiFe2O4, were able to absorb a large amount of visible light, exhibited excellent photocatalytic activity under simulated solar light irradiation and could be easily separated by an external magnetic field. The NiFe2O4/Cu2O composites exhibited higher photocatalytic performance than that of a single semiconductor. It was found that the prominently enhanced photocatalytic performance of NiFe2O4/Cu2O composites was ascribed to the effective separation of photo-generated electron-hole pairs and the effective generation of the hydroxyl radical •OH.
Identificação de radiofontes puntiformes presentes na região observada pelo telescópio BEAST

NASA Astrophysics Data System (ADS)

Oliveira, M. S.; Wuensche, C. A.; Leonardi, R.; Tello, C.

2003-08-01

Radiofontes extragalácticas são um dos principais contaminantes nas medidas da Radiação Cósmica de Fundo (RCF) em freqüências abaixo de 200 GHz. O estudo de seu comportamento espectral permite determinar a contribuição destas fontes às anisotropias intrísincas da RCF. Um dos experimentos recentes concebidos para estudar a RCF é o BEAST (Background Emission Anisotropy Scanning Telescope), cujos primeiros resultados foram publicados em fevereiro de 2003. Nos últimos meses, geramos mapas do céu nas freqüências de 30 GHz e 41 GHz, para um total de 648 horas de observação entre julho e outubro de 2002. Identificamos 4 fontes puntiformes extragalácticas na região do céu situada entre 0h < RA < 24 h e +32° < DEC < +42°, com relação S/R > 4,3 e situadas a pelo menos 25° acima do Plano Galáctico. Suas contrapartidas em 5 GHz, segundo o catálogo GB6, são: J1613+3412, J1635+3808, J0927+3902 e J1642+3948. Estas fontes também foram identificadas pelo satélite WMAP sendo que três coincidem com as observadas pelo BEAST dentro da incerteza do feixe do telescópio e a quarta encontra-se bastante próxima (J1613+3412), embora não seja coincidente. As estimativas preliminares de fluxos obtidas para esses objetos são, respectivamente, 0,51; 0,97; 1,08 e 1,6 Jy em 41 GHz. Usando estes resultados e medidas de fluxos em outras frequências existentes na literatura, apresentamos uma estimativa dos índices espectrais destes objetos no intervalo de frequências entre 4,85 GHz e 41 GHz.
Hierarchical Heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) as an Electrode Material for High-Performance Supercapacitors.

PubMed

Hu, Jiyu; Qian, Feng; Song, Guosheng; Wang, Linlin

2016-12-01

Hierarchical heterostructures of NiCo2O4@XMoO4 (X = Ni, Co) were developed as an electrode material for supercapacitor with improved pseudocapacitive performance. Within these hierarchical heterostructures, the mesoporous NiCo2O4 nanosheet arrays directly grown on the Ni foam can not only act as an excellent pseudocapacitive material but also serve as a hierarchical scaffold for growing NiMoO4 or CoMoO4 electroactive materials (nanosheets). The electrode made of NiCo2O4@NiMoO4 presented a highest areal capacitance of 3.74 F/cm(2) at 2 mA/cm(2), which was much higher than the electrodes made of NiCo2O4@CoMoO4 (2.452 F/cm(2)) and NiCo2O4 (0.456 F/cm(2)), respectively. Meanwhile, the NiCo2O4@NiMoO4 electrode exhibited good rate capability. It suggested the potential of the hierarchical heterostructures of NiCo2O4@CoMoO4 as an electrode material in supercapacitors.

Identifying Planetary Biosignature Impostors: Spectral Features of CO and O4 Resulting from Abiotic O2/O3 Production

NASA Astrophysics Data System (ADS)

Schwieterman, Edward W.; Meadows, Victoria S.; Domagal-Goldman, Shawn D.; Deming, Drake; Arney, Giada N.; Luger, Rodrigo; Harman, Chester E.; Misra, Amit; Barnes, Rory

2016-03-01

O2 and O3 have been long considered the most robust individual biosignature gases in a planetary atmosphere, yet multiple mechanisms that may produce them in the absence of life have been described. However, these abiotic planetary mechanisms modify the environment in potentially identifiable ways. Here we briefly discuss two of the most detectable spectral discriminants for abiotic O2/O3: CO and O4. We produce the first explicit self-consistent simulations of these spectral discriminants as they may be seen by James Webb Space Telescope (JWST). If JWST-NIRISS and/or NIRSpec observe CO (2.35, 4.6 μm) in conjunction with CO2 (1.6, 2.0, 4.3 μm) in the transmission spectrum of a terrestrial planet it could indicate robust CO2 photolysis and suggest that a future detection of O2 or O3 might not be biogenic. Strong O4 bands seen in transmission at 1.06 and 1.27 μm could be diagnostic of a post-runaway O2-dominated atmosphere from massive H-escape. We find that for these false positive scenarios, CO at 2.35 μm, CO2 at 2.0 and 4.3 μm, and O4 at 1.27 μm are all stronger features in transmission than O2/O3 and could be detected with S/Ns ≳ 3 for an Earth-size planet orbiting a nearby M dwarf star with as few as 10 transits, assuming photon-limited noise. O4 bands could also be sought in UV/VIS/NIR reflected light (at 0.345, 0.36, 0.38, 0.445, 0.475, 0.53, 0.57, 0.63, 1.06, and 1.27 μm) by a next generation direct-imaging telescope such as LUVOIR/HDST or HabEx and would indicate an oxygen atmosphere too massive to be biologically produced.
Identifying Planetary Biosignature Impostors: Spectral Features of CO and O4 Resulting from Abiotic O2/O3 Production

NASA Technical Reports Server (NTRS)

Schwieterman, Edward W.; Meadows, Victoria S.; Domagal-Goldman, Shawn D.; Deming, Drake; Arney, Giada N.; Luger, Rodrigo; Harman, Chester E.; Misra, Amit; Barnes, Rory

2016-01-01

O2 and O3 have been long considered the most robust individual biosignature gases in a planetary atmosphere, yet multiple mechanisms that may produce them in the absence of life have been described. However, these abiotic planetary mechanisms modify the environment in potentially identifiable ways. Here we briefly discuss two of the most detectable spectral discriminants for abiotic O2/O3: CO and O4. We produce the first explicit self-consistent simulations of these spectral discriminants as they may be seen by James Webb Space Telescope (JWST). If JWST-NIRISS (Near InfraRed Imager and Slitless Spectrograph) and/or NIRSpec (Near InfraRed Spectograph) observe CO (2.35, 4.6 micrometers) in conjunction with CO2 (1.6, 2.0, 4.3 micrometers) in the transmission spectrum of a terrestrial planet it could indicate robust CO2 photolysis and suggest that a future detection of O2 or O3 might not be biogenic. Strong O4 bands seen in transmission at 1.06 and 1.27 micrometers could be diagnostic of a post-runaway O2-dominated atmosphere from massive H-escape. We find that for these false positive scenarios, CO at 2.35 micrometers, CO2 at 2.0 and 4.3 micrometers, and O4 at 1.27 micrometers are all stronger features in transmission than O2/O3 and could be detected with sigal to noise ratios greater than or approximately 3 for an Earth-size planet orbiting a nearby M dwarf star with as few as 10 transits, assuming photon-limited noise. O4 bands could also be sought in UV/VIS/NIR reflected light (at 0.345, 0.36, 0.38, 0.445, 0.475, 0.53, 0.57, 0.63, 1.06, and 1.27 micrometers) by a next generation direct imaging telescope such as LUVOIR (Large Ultraviolet Visible Infrared)/HDST (High-Definition Space Telescope) or HabEx (Habitable-Exoplanet Imaging Mission) and would indicate an oxygen atmosphere too massive to be biologically produced.
Thermodynamic data from redox reactions at high temperatures. II. The MnO-0Mn3O4 oxygen buffer, and implications for the thermodynamic properties of MnO and Mn3O4

NASA Astrophysics Data System (ADS)

O'Neill, Hugh St. C.; Pownceby, Mark I.

1993-09-01

Theμ _{O_2 } defined by the reaction 6 MnO+O2 =2 Mn3O4 has been determined from 917 to 1,433 K using electrochemical cells (with calcia-stabilized zirconta, CSZ) of the type: MediaObjects/410_2005_BF01046534_f2.tif Steady emfs were achieved rapidly at all temperatures on both increasing and decreasing temperature, indicating that the MnO-Mn3O4 oxygen buffer equilibrates relatively easily. It therefore makes a useful alternative choice in experimental petrology to Fe2O3-Fe3O4 for buffering oxygen potentials at oxidized values. The results are (in J/mol, temperature in K, reference pressure 1 bar);μ _{O_2 } (±200)=-563,241+1,761.758 T-220.490 T in T+0.101819 T 2 with an uncertainty of ±200 J/mol. Third law analysis of these data, including a correction for the deviations in stoichiometry of MnO, implies S 298.15 for Mn3O4 of 166.6 J/K · mol, which is 2.5 J/K · mol higher than the calorimetric determination of Robie and Hemingway (1985). The low value of the calorimetric entropy may be due to incomplete ordering of the magnetic spins. The third law value of Δ r H {298.15/0} is-450.09 kJ/mol, which is significantly different from the calorimetric value of-457.5±3.4 kJ/mol, calculated from Δ f H {298.15/0} of MnO and Mn3O4, implying a small error in one or both of these latter.
Effects of TiO2 and Co3O4 Nanoparticles on Circulating Angiogenic Cells

PubMed Central

Spigoni, Valentina; Cito, Monia; Alinovi, Rossella; Pinelli, Silvana; Passeri, Giovanni; Zavaroni, Ivana; Goldoni, Matteo; Campanini, Marco; Aliatis, Irene; Mutti, Antonio

2015-01-01

Background and Aim Sparse evidence suggests a possible link between exposure to airborne nanoparticles (NPs) and cardiovascular (CV) risk, perhaps through mechanisms involving oxidative stress and inflammation. We assessed the effects of TiO2 and Co3O4 NPs in human circulating angiogenic cells (CACs), which take part in vascular endothelium repair/replacement. Methods CACs were isolated from healthy donors’ buffy coats after culturing lymphomonocytes on fibronectin-coated dishes in endothelial medium for 7 days. CACs were pre-incubated with increasing concentration of TiO2 and Co3O4 (from 1 to 100 μg/ml) to test the effects of NP – characterized by Transmission Electron Microscopy – on CAC viability, apoptosis (caspase 3/7 activation), function (fibronectin adhesion assay), oxidative stress and inflammatory cytokine gene expression. Results Neither oxidative stress nor cell death were associated with exposure to TiO2 NP (except at the highest concentration tested), which, however, induced a higher pro-inflammatory effect compared to Co3O4 NPs (p<0.01). Exposure to Co3O4 NPs significantly reduced cell viability (p<0.01) and increased caspase activity (p<0.01), lipid peroxidation end-products (p<0.05) and pro-inflammatory cytokine gene expression (p<0.05 or lower). Notably, CAC functional activity was impaired after exposure to both TiO2 (p<0.05 or lower) and Co3O4 (p<0.01) NPs. Conclusions In vitro exposure to TiO2 and Co3O4 NPs exerts detrimental effects on CAC viability and function, possibly mediated by accelerated apoptosis, increased oxidant stress (Co3O4 NPs only) and enhancement of inflammatory pathways (both TiO2 and Co3O4 NPs). Such adverse effects may be relevant for a potential role of exposure to TiO2 and Co3O4 NPs in enhancing CV risk in humans. PMID:25803285
3D coordination polymers with nitrilotriacetic and 4,4'-bipyridyl mixed ligands: structural variation based on dinuclear or tetranuclear subunits assisted by Na-O and/or O-H...O interactions.

PubMed

Lü, Xing-Qiang; Jiang, Ji-Jun; Chen, Chun-Long; Kang, Bei-Sheng; Su, Cheng-Yong

2005-06-27

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4'-bipyridyl (4,4'-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4'-bpy)]ClO4 x 5H2O (1) and [Cu2(NTA) (4,4'-bpy)2]ClO4 x 4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4'-bpy)]2- dinuclear unit which was further assembled via multiple Na-O and O-H...O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4'-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O-H...O hydrogen bonds into a 3D structure with several channels running in different directions.
A Utilização da Astronomia como Tema Interdisciplinar e Aplicações de Objetos de Aprendizagem

NASA Astrophysics Data System (ADS)

da Silva, L. A.; Voelzke, M. R.

2008-09-01

Este trabalho visa analisar a possibilidade de relacionar conteúdos aplicados no ensino fundamental e médio de forma interdisciplinar por intermédio da astronomia, com a intervenção de objetos de aprendizagem que possam integrar as disciplinas e a utilização de recursos tecnológicos. Em uma pesquisa prévia com 20 professores de uma escola estadual situada na cidade de Guarulhos foi observado que apenas 25% dos professores utilizam algum recurso tecnológico para o desenvolvimento de conteúdos pertinentes à sua disciplina, tais como sites e softwares educativos, sendo que a maioria absoluta continua ensinando apenas com livros didáticos. A maior parte dos professores apresenta dificuldades em trabalhar sua disciplina de forma interdisciplinar, ou seja, 75% dos professores preferem aplicar os conteúdos seguindo uma hierarquia linear de tópicos, evitando a discussão de temas que de alguma forma estão relacionados. A astronomia pode vir à fascinar o ser humano e despertar sua curiosidade promovendo um maior interesse no aprendizado, podendo favorecer análises interdisciplinares de forma lógica e objetiva, desta forma colocar a astronomia como tema motivador interdisciplinar, pode ser relevante no que se refere ao distanciamento da fragmentação dos conteúdos. No Estado de São Paulo, a implantação da proposta curricular no ensino fundamental e médio mostra claramente a inserção da astronomia na maior parte das séries, principalmente na 6Âª série em que todo o bimestre se fala de astronomia.
Preparation of Fe3O4/SiO2-guanidine organobase catalyst for 1,5-diphenylpenta-2,4-dien-1-one synthesis

NASA Astrophysics Data System (ADS)

Cahyana, A. H.; Fitria, D.; Ardiansah, B.; Rahayu, D. U. C.

2017-04-01

A novel heterogeneous organobase catalyst of Fe3O4/SiO2-guanidine was prepared in three stages. First, Fe3O4 nanoparticle was obtained by co-precipitation method using seaweed Sargassum Sp. as natural reductant. Fe3O4 was then coated by SiO2 using TEOS as silica source, resulting Fe3O4/SiO2. Finally, Fe3O4/SiO2-Guanidine was obtained by modifying Fe3O4/SiO2 with guanidine in the suitable reaction condition. This organobase catalyst was characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Particle Size Analyzer (PSA). The material was then used as a highly active catalyst in aldol condensation reaction between acetophenone and cinnamaldehyde to produce 1,5-diphenylpenta-2,4-dien-1-one. The structure elucidation of the organic product was confirmed by UV-Vis, FTIR, and LC-MS.
The crystal structure of ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5: a possible phase for Pu 4+ incorporation during the oxidation of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Burns, Peter C.; Finch, Robert J.; Hawthorne, Frank C.; Miller, Mark L.; Ewing, Rodney C.

1997-10-01

Ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5, is the only known uranyl oxide hydrate mineral that contains U 4+, and it has been proposed that ianthinite may be an important Pu 4+-bearing phase during the oxidative dissolution of spent nuclear fuel. The crystal structure of ianthinite, orthorhombic, a = 0.7178(2), b = 1.1473(2), c = 3.039(1) nm, V = 2.5027 nm 3Z = 4, space group P2 1cn, has been solved by direct methods and refined by least-squares methods to an R index of 9.7% and a wR index of 12.6% using 888 unique observed [| F| ≥ 5 σ | F|] reflections. The structure contains both U 4+. The U 6+ cations are present as roughly linear (U 6+O 2) 2+ uranyl ion (Ur) that are in turn coordinated by five O 2- and OH - located at the equatorial positions of pentagonal bipyramids. The U 4+ cations are coordinated by O 2-, OH - and H 2O in a distorted octahedral arrangement. The Ur φ5and U 4+| 6 (φ: O 2-, OH -, H 2O) polyhedra l sharing edges to for two symmetrically distinct sheets at z ≈ 0.0 and z ≈ 0.25 that are parallel to (001). The sheets have the β-U 3O 8 sheet anion-topology. There are five symmetrically distinct H 2O groips located at z ≈ 0.125 between the sheets of U φn polyhedra, and the sheets of U φn polyhedra are linked together only by hydrogen bonding to the intersheet H 2O groups. The crystal-chemical requirements of U 4+ and Pu 4+ are very similar, suggesting that extensive Pu 4+ ↔ U 4+ substitution may occur within the sheets of U φn polyhedra in trh structure of ianthinine.
Encapsulation of superparamagnetic Fe 3 O 4 @SiO 2 core/shell nanoparticles in MnO 2 microflowers with high surface areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yu-Gang; Truong, Tu T.; Liu, Yu-Zi

2015-02-01

Microflowers made of interconnected MnO2 nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO4 with aqueous HCl at elevated temperatures in the presence of superparamagnetic Fe3O4@SiO2 core-shell nanoparticles. Due to the chemical compatibility between SiO2 and MnO2, the heterogeneous reaction leads to the spontaneous encapsulation of the Fe3O4@SiO2 core-shell nanoparticles in the MnO2 microflowers. The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO2 nanosheets and superparamagnetism originated from the Fe3O4@SiO2 core-shell nanoparticles, which are beneficial for applications requiring both high surface area and magnetic separation. (C) 2014 Yu-Gangmore » Sun.« less
Oxothiomolybdenum derivatives of the superlacunary crown heteropolyanion {P8W48}: structure of [K4{Mo4O4S4(H2O)3(OH)2}2(WO2)(P8W48O184)]30– and studies in solution.

PubMed

Korenev, Vladimir S; Floquet, Sébastien; Marrot, Jérôme; Haouas, Mohamed; Mbomekallé, Israël-Martyr; Taulelle, Francis; Sokolov, Maxim N; Fedin, Vladimir P; Cadot, Emmanuel

2012-02-20

Reaction of the cyclic lacunary [H(7)P(8)W(48)O(184)](33-) anion (noted P(8)W(48)) with the [Mo(2)S(2)O(2)(H(2)O)(6)](2+) oxothiocation led to two compounds, namely, [K(4){Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(WO(2))(P(8)W(48)O(184))](30-) (denoted 1) and [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) (denoted 2), which were characterized in the solid state and solution. In the solid state, the structure of [K(4){Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(WO(2))(P(8)W(48)O(184))](30-) reveals the presence of two disordered {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) "handles" connected on both sides of the P(8)W(48) ring. Such a disorder is consistent with the presence of two geometrical isomers where the relative disposition of the two {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) handles are arranged in a perpendicular or parallel mode. Such an interpretation is fully supported by (31)P and (183)W NMR solution studies. The relative stability of both geometrical isomers appears to be dependent upon the nature of the internal alkali cations, i.e., Na(+) vs K(+), and increased lability of the two {Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2+) handles, compared to the oxo analogous, was clearly identified by significant broadening of the (31)P and (183)W NMR lines. Solution studies carried out by UV-vis spectroscopy showed that formation of the adduct [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) occurs in the 1.5-4.7 pH range and corresponds to a fast and quantitative condensation process. Furthermore, (31)P NMR titrations in solution reveal formation of the "monohandle" derivative [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(P(8)W(48)O(184))](38-) as an intermediate prior to formation of the "bishandle" derivatives. Furthermore, the electrochemical behavior of [{Mo(4)O(4)S(4)(H(2)O)(3)(OH)(2)}(2)(P(8)W(48)O(184))](36-) was studied in aqueous medium and compared with the parent anion P(8)W(48).
Syntheses and characterization of phosphonates and diphosphonates of molybdenum, A4[(MoO3)5(O3PR)2]·xH2O, A2[Mo2O5(O3PR)2] and A2[Mo2O5(O3P-R-PO3)] (A = K, Rb, Cs, Tl, NH4).

PubMed

Elias Jesu Packiam, D; Vidyasagar, Kanamaluru

2017-11-28

Twenty new molybdenum phosphonates and diphosphonates have been synthesized and structurally characterized by single crystal and powder X-ray diffraction, CHN analyses, spectroscopic and thermal studies. Four of them are molecular phenyl- and benzyl-phosphonates containing discrete [(MoO 3 ) 5 (O 3 PR) 2 ] 4- (R = Ph or CH 2 Ph) cyclic anions. The sixteen non-molecular compounds are layered isostructural phenylphosphonates, A 2 [Mo 2 O 5 (O 3 PPh) 2 ] (A = NH 4 , Tl, Rb, Cs) and K 1.5 (H 3 O) 0.5 [Mo 2 O 5 (O 3 PPh) 2 ] and the corresponding diphosphonate compounds with pillared anionic layers, A 2 [Mo 2 O 5 (O 3 P(CH 2 ) 3 PO 3 )], A 2 [Mo 2 O 5 (O 3 P(CH 2 ) 4 PO 3 )] and A 2 [Mo 2 O 5 (O 3 P(C 6 H 4 )PO 3 )]. The A + ions reside in the interlayer region as well as in the cavities within the anionic layers.
Crystal structure of BaMn2(AsO4)2 containing discrete [Mn4O18]28- units.

PubMed

Alcantar, Salvador; Ledbetter, Hollis R; Ranmohotti, Kulugammana G S

2017-12-01

In our attempt to search for mixed alkaline-earth and transition metal arsenates, the title compound, barium dimanganese(II) bis-(arsenate), has been synthesized by employing a high-temperature RbCl flux. The crystal structure of BaMn 2 (AsO 4 ) 2 is made up of MnO 6 octa-hedra and AsO 4 tetra-hedra assembled by sharing corners and edges into infinite slabs with composition [Mn 2 (AsO 4 ) 2 ] 2- that extend parallel to the ab plane. The barium cations reside between parallel slabs maintaining the inter-slab connectivity through coordination to eight oxygen anions. The layered anionic framework comprises weakly inter-acting [Mn 4 O 18 ] 28- tetra-meric units. In each tetra-mer, the manganese(II) cations are in a planar arrangement related by a center of inversion. Within the slabs, the tetra-meric units are separated from each other by 6.614 (2) Å (Mn⋯Mn distances). The title compound has isostructural analogues amongst synthetic Sr M 2 ( X O 4 ) 2 compounds with M = Ni, Co, and X = As, P.
New vanadium tellurites: Syntheses, structures, optical properties of noncentrosymmetric VTeO{sub 4}(OH), centrosymmetric Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Ming-Li; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002; Marsh, Matthew

Two new vanadium tellurites, VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2), have been synthesized successfully with the use of hydrothermal reactions. The crystal structures of the two compounds were determined by single-crystal X-ray diffraction. Compound 1 crystallizes in the polar space group Pca2{sub 1} (No. 29) while compound 2 crystallizes in the centrosymmetric space group C2/c (No. 15). The topography of compound 1 reveals a two-dimensional, layered structure comprised of VO{sub 6} octahedral chains and TeO{sub 3}(OH) zig-zag chains. Compound 2, on the contrary, features a three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic framework withmore » Ba{sup 2+} ions filled into the 10-member ring helical tunnels. The [V{sub 4}O{sub 8}(Te{sub 3}O{sub 10})]{sup 4-} anionic network is the first 3D vanadium tellurite framework to be discovered in the alkaline-earth vanadium tellurite system. Powder second harmonic generation (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.3×KDP (KH{sub 2}PO{sub 4}) under 1064 nm laser radiation. Infrared spectroscopy, elemental analysis, thermal analysis, and dipole moment calculations have also been carried out. - Graphical abstract: VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} (No. 29) while Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) crystallizes in the centrosymmetric space group C2/c (No. 15). - Highlights: • VTeO{sub 4}(OH) (1) and Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) have been synthesized successfully with the use of hydrothermal reactions. • VTeO{sub 4}(OH) (1) crystallizes in the noncentrosymmetric space group Pca2{sub 1} and displays a weak SHG response. • VTeO{sub 4}(OH) (1) represents only the fourth SHG-active material found in vanadium tellurite systems. • Ba{sub 2}V{sub 4}O{sub 8}(Te{sub 3}O{sub 10}) (2) exhibits a novel three-dimensional [V{sub 4}O{sub 8}(Te{sub 3}O
A comparative study of the Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15

NASA Astrophysics Data System (ADS)

Tellier, J.; Boullay, Ph.; Manier, M.; Mercurio, D.

2004-06-01

The room temperature structures of the four-layer Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15 are determined by means of single crystal X-ray diffraction. Regarding the CaBi 4Ti 4O 15 phase, in agreement with the tolerance factor, a significant deformation of the perovskite blocks is observed. The rotation system of the octahedra is typical from even layer Aurivillius phases and leads to the use of the space group A2 1am. For the BaBi 4Ti 4O 15 phase, only a weak variation with respect to the F2 mm space group can be suggested from single crystal X-ray diffraction. A significant presence of Ba atoms in the [ M2O 2] slabs is confirmed in agreement with the previous works but specific Ba 2+ and Bi 3+ sites have to be considered due to the large difference in bounding requirement of these cations. Possible origins for the ferroelectric relaxor behavior of the Ba-based compound are discussed in view of the presented structural analyses.
Photoelectrochemical Properties and Photostabilities of High Surface Area CuBi 2O 4 and Ag-Doped CuBi 2O 4 Photocathodes

DOE PAGES

Kang, Donghyeon; Hill, James C.; Park, Yiseul; ...

2016-06-09

Here, electrochemical synthesis methods were developed to produce CuBi 2O 4, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi 2O 4 at 450°C in air. Ag-doped CuBi 2O 4 electrodes were also prepared by adding a trace amount of Ag+ in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi 2O 4, Ag+ ions substitutionally replaced Bi3+ ions andmore » increased the hole concentration in CuBi 2O 4. As a result, photocurrent enhancements for both O 2 reduction and water reduction were achieved. Furthermore, while undoped CuBi 2O 4 electrodes suffered from anodic photocorrosion during O 2 reduction due to poor hole transport, Ag-doped CuBiO 4 effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi 2O 4 and Ag-doped CuBi 2O 4 electrodes prepared in this study were found to be more positive than 1.3 V vs RHE in a 0.1 M NaOH solution (pH 12.8), which make these photocathodes highly attractive for use in solar hydrogen production. The optimized CuBi 2O 4/Ag-doped CuBi 2O 4 photocathode showed a photocurrent onset for water reduction at 1.1 V vs RHE, achieving a photovoltage higher than 1 V for water reduction. The thermodynamic feasibility of photoexcited electrons in the conduction band of CuBi 2O 4 to reduce water was also confirmed by detection of H 2 during photocurrent generation. This study provides new understanding for constructing improved CuBi 2O 4 photocathodes by systematically investigating photocorrosion as well as photoelectrochemical properties of high-quality CuBi 2O 4 and Ag-doped CuBi 2O 4 photoelectrodes for photoreduction of both O 2 and water.« less
Photoelectrochemical Properties and Photostabilities of High Surface Area CuBi 2O 4 and Ag-Doped CuBi 2O 4 Photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Donghyeon; Hill, James C.; Park, Yiseul

Here, electrochemical synthesis methods were developed to produce CuBi 2O 4, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi 2O 4 at 450°C in air. Ag-doped CuBi 2O 4 electrodes were also prepared by adding a trace amount of Ag+ in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi 2O 4, Ag+ ions substitutionally replaced Bi3+ ions andmore » increased the hole concentration in CuBi 2O 4. As a result, photocurrent enhancements for both O 2 reduction and water reduction were achieved. Furthermore, while undoped CuBi 2O 4 electrodes suffered from anodic photocorrosion during O 2 reduction due to poor hole transport, Ag-doped CuBiO 4 effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi 2O 4 and Ag-doped CuBi 2O 4 electrodes prepared in this study were found to be more positive than 1.3 V vs RHE in a 0.1 M NaOH solution (pH 12.8), which make these photocathodes highly attractive for use in solar hydrogen production. The optimized CuBi 2O 4/Ag-doped CuBi 2O 4 photocathode showed a photocurrent onset for water reduction at 1.1 V vs RHE, achieving a photovoltage higher than 1 V for water reduction. The thermodynamic feasibility of photoexcited electrons in the conduction band of CuBi 2O 4 to reduce water was also confirmed by detection of H 2 during photocurrent generation. This study provides new understanding for constructing improved CuBi 2O 4 photocathodes by systematically investigating photocorrosion as well as photoelectrochemical properties of high-quality CuBi 2O 4 and Ag-doped CuBi 2O 4 photoelectrodes for photoreduction of both O 2 and water.« less
Depolarization currents in Al 2O 3 and MgAl 2O 4 oxides

NASA Astrophysics Data System (ADS)

Carvalhaes, R. P. M.; Rocha, M. S.; de Souza, S. S.; Blak, A. R.

2004-06-01

In the present work, dipole defects in γ-irradiated and thermally treated samples of Al 2O 3 and MgAl 2O 4 oxides are investigated, applying the thermally stimulated depolarisation currents technique (TSDC). The TSDC spectra of MgAl 2O 4 doped with Fe 2+, Fe 3+, Co 2+, Cr 3+ and Mn 2+ show four bands at 130 K, 160 K, 250 K and 320 K, and the spectra of Al 2O 3 doped with Mg 2+, Cr 3+ and Fe 3+ show bands between 230 K and 260 K. It has been observed that the bands at 130 K, 160 K and 250 K in MgAl 2O 4 spinel and that the 230 K and 240 K bands in Al 2O 3 are related to dipole defects. The other bands are possibly related to different types of charge storage mechanisms (space-charge and interfacial polarisation) or deal with distributions in activation energies and/or in relaxation times. A thermal decrease of the TSDC bands for heat treatments above 1000 K has been observed. In MgAl 2O 4 spinel, the 250 K band could be recovered after γ-irradiation and the two dipole peaks in Al 2O 3 were partially recovered. Thermal treatments affect the dipole aggregation processes in both oxides. Optical absorption (AO) results indicate that the presence of bands of water molecules in the infrared region obstructs the appearance of the TSDC bands in both Al 2O 3 and MgAl 2O 4. The 250 K peak in MgAl 2O 4 was correlated to V-type centres and the 250 K peak in Al 2O 3 to a substitutional Mg 2+ ion near a trapped hole localised on an adjacent oxygen ion.
Facile synthesis and paramagnetic properties of Fe3O4@SiO2 core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Yang, Lili; Zou, Ping; Cao, Jian; Sun, Yunfei; Han, Donglai; Yang, Shuo; Chen, Gang; Kong, Xiangwang; Yang, Jinghai

2014-12-01

The Fe3O4@SiO2 core-shell nanoparticles (NPs) had been successfully fabricated via direct decomposition of tetraethyl orthosilicate (TEOS) in solution under the presence of as-synthesized Fe3O4 NPs prepared by chemical coprecipitation method. The structure and magnetic properties of Fe3O4@SiO2 NPs were characterized and the result indicated that Fe3O4@SiO2 NPs are about 12 nm in size with paramagnetic property. The possible growth and magnetic mechanism was discussed in detail.
Seaurchin-like hierarchical NiCo2O4@NiMoO4 core-shell nanomaterials for high performance supercapacitors.

PubMed

Zhang, Qiang; Deng, Yanghua; Hu, Zhonghua; Liu, Yafei; Yao, Mingming; Liu, Peipei

2014-11-14

A novel electrode material of the three-dimensional (3D) multicomponent oxide NiCo2O4@NiMoO4 core-shell was synthesized via a facile two-step hydrothermal method using a post-annealing procedure. The uniform NiMoO4 nanosheets were grown on the seaurchin-like NiCo2O4 backbone to form a NiCo2O4@NiMoO4 core-shell material constructed by interconnected ultrathin nanosheets, so as to produce hierarchical mesopores with a large specific surface area of 100.3 m(2) g(-1). The porous feature and core-shell structure can facilitate the penetration of electrolytic ions and increases the number of electroactive sites. Hence, the NiCo2O4@NiMoO4 material exhibited a high specific capacitance of 2474 F g(-1) and 2080 F g(-1) at current densities of 1 A g(-1) and 20 A g(-1) respectively, suggesting that it has not only a very large specific capacitance, but also a good rate performance. In addition, the capacitance loss was only 5.0% after 1000 cycles of charge and discharge tests at the current density of 10 A g(-1), indicating high stability. The excellent electrochemical performance is mainly attributed to its 3D core-shell and hierarchical mesoporous structures which can provide unobstructed pathways for the fast diffusion and transportation of ions and electrons, a large number of active sites and good strain accommodation.
Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

NASA Astrophysics Data System (ADS)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Magnetic domain interactions of Fe3O4 nanoparticles embedded in a SiO2 matrix.

PubMed

Fuentes-García, J A; Diaz-Cano, A I; Guillen-Cervantes, A; Santoyo-Salazar, J

2018-03-23

Currently, superparamagnetic functionalized systems of magnetite (Fe 3 O 4 ) nanoparticles (NPs) are promising options for applications in hyperthermia therapy, drug delivery and diagnosis. Fe 3 O 4 NPs below 20 nm have stable single domains (SSD), which can be oriented by magnetic field application. Dispersion of Fe 3 O 4 NPs in silicon dioxide (SiO 2 ) matrix allows local SSD response with uniaxial anisotropy and orientation to easy axis, 90° <001> or 180° <111>. A successful, easy methodology to produce Fe 3 O 4 NPs (6-17 nm) has been used with the Stöber modification. NPs were embedded in amorphous and biocompatible SiO 2 matrix by mechanical stirring in citrate and tetraethyl orthosilicate (TEOS). Fe 3 O 4 NPs dispersion was sampled in the range of 2-12 h to observe the SiO 2 matrix formation as time function. TEM characterization identified optimal conditions at 4 h stirring for separation of SSD Fe 3 O 4 in SiO 2 matrix. Low magnetization (M s ) of 0.001 emu and a coercivity (H c ) of 24.75 Oe indicate that the embedded SSD Fe 3 O 4 in amorphous SiO 2 reduces the M s by a diamagnetic barrier. Magnetic force microscopy (MFM) showed SSD Fe 3 O 4 of 1.2 nm on average embedded in SiO 2 matrix with uniaxial anisotropy response according to Fe 3+ and Fe 2+ electron spin coupling and rotation by intrinsic Neél contribution.
Spatially-controlled NiCo2O4@MnO2 core–shell nanoarray with hollow NiCo2O4 cores and MnO2 flake shells: an efficient catalyst for oxygen evolution reaction

NASA Astrophysics Data System (ADS)

Xue, Hairong; Yu, Hongjie; Li, Yinghao; Deng, Kai; Xu, You; Li, Xiaonian; Wang, Hongjing; Wang, Liang

2018-07-01

Control of structures and components of the nanoarray catalysts is very important for electrochemical energy conversion. Herein, unique NiCo2O4@MnO2 core–shell nanoarray with hollow NiCo2O4 Cores and MnO2 flake shells is in situ fabricated on carbon textile via a two-step hydrothermal treatment followed by a subsequent annealing. The as-made nanoarray is highly active and durable catalyst for oxygen evolution reaction in alkaline media attribute to the synergetic effect derived from spatially separated nanoarray with favorable NiCo2O4 and MnO2 compositions.
Spatially-controlled NiCo2O4@MnO2 core-shell nanoarray with hollow NiCo2O4 cores and MnO2 flake shells: an efficient catalyst for oxygen evolution reaction.

PubMed

Xue, Hairong; Yu, Hongjie; Li, Yinghao; Deng, Kai; Xu, You; Li, Xiaonian; Wang, Hongjing; Wang, Liang

2018-07-13

Control of structures and components of the nanoarray catalysts is very important for electrochemical energy conversion. Herein, unique NiCo 2 O 4 @MnO 2 core-shell nanoarray with hollow NiCo 2 O 4 Cores and MnO 2 flake shells is in situ fabricated on carbon textile via a two-step hydrothermal treatment followed by a subsequent annealing. The as-made nanoarray is highly active and durable catalyst for oxygen evolution reaction in alkaline media attribute to the synergetic effect derived from spatially separated nanoarray with favorable NiCo 2 O 4 and MnO 2 compositions.
Infrared and TPD studies of nitrates adsorbed on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, BaO, and MgO/{gamma}-Al{sub 2}O{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chi, Y.; Chuang, S.S.C.

2000-05-18

NO and O{sub 2} coadsorption on {gamma}-Al{sub 2}O{sub 3}-supported Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, BaO, and MgO has been investigated by in situ infrared spectroscopy coupled with temperature-programmed decomposition and desorption. BaO/{gamma}-Al{sub 2}O{sub 3} and MgO/{gamma}-Al{sub 2}O{sub 3} possess a higher NO{sub x} storage capability than Tb{sub 4}O{sub 7}/{gamma}-Al{sub 2}O{sub 3} and La{sub 2}O{sub 3}/{gamma}-Al{sub 2}O{sub 3}. NO/O{sub 2} coadsorbed on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO in the form of bridging bidentate, chelating bidentate, and monodentate nitrates, and on MgO in the form of bridging bidentate and monodentate nitrates via the reaction of adsorbed NO withmore » adsorbed oxygen at 298 K. NO/O{sub 2} coadsorbed as a chelating bidentate nitrate on Tb{sub 4}O{sub 7} and La{sub 2}O{sub 3}, and as a distinctive bridging bidentate nitrate on BaO and MgO via the reaction of adsorbed NO with surface lattice oxygen at 523 K. These various forms of adsorbed nitrate differ in structure and reactivity from Tb(NO{sub 3}){sub 3}, La(NO{sub 3}){sub 3}, Ba(NO{sub 3}){sub 2}, and Mg(NO{sub 3}){sub 2}, the precursor used to prepare metal oxides for NO/O{sub 2} coadsorption. Temperature-programmed desorption (TPD) of chelating bidentate nitrate on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO produced primarily NO and O{sub 2}, with maxima at 640 and 670 K, respectively. TPD of bridging bidentate nitrate and monodentate nitrate on Tb{sub 4}O{sub 7}, La{sub 2}O{sub 3}, and BaO produced NO and O{sub 2} as major products and N{sub 2} and N{sub 2}O as minor products, at 320--500 K. Decomposition of bridging bidentate on MgO produced NO as a major product and N{sub 2}O as a minor product at a peak temperature of 690 K. Peak temperatures for Tb(NO{sub 3}){sub 3}, La(NO{sub 3}){sub 3}, Ba(NO{sub 3}){sub 2}, and Mg(NO{sub 3}){sub 2} decomposition occurred between those for bridging and chelating nitrates. The difference in stability between
Enterocin F4-9, a Novel O-Linked Glycosylated Bacteriocin

PubMed Central

Maky, Mohamed Abdelfattah; Ishibashi, Naoki; Zendo, Takeshi; Perez, Rodney Honrada; Doud, Jehan Ragab; Karmi, Mohamed

2015-01-01

Enterococcus faecalis F4-9 isolated from Egyptian salted-fermented fish produces a novel bacteriocin, termed enterocin F4-9. Enterocin F4-9 was purified from the culture supernatant by three steps, and its molecular mass was determined to be 5,516.6 Da by mass spectrometry. Amino acid and DNA sequencing showed that the propeptide consists of 67 amino acid residues, with a leader peptide containing a double glycine cleavage site to produce a 47-amino-acid mature peptide. Enterocin F4-9 is modified by two molecules of N-acetylglucosamine β-O-linked to Ser37 and Thr46. The O-linked N-acetylglucosamine moieties are essential for the antimicrobial activity of enterocin F4-9. Further analysis of the enterocin F4-9 gene cluster identified enfC, which has high sequence similarity to a glycosyltransferase. The antimicrobial activity of enterocin F4-9 covered a limited range of bacteria, including, interestingly, a Gram-negative strain, Escherichia coli JM109. Enterocin F4-9 is sensitive to protease, active at a wide pH range, and moderately resistant to heat. PMID:25956765
Enterocin F4-9, a Novel O-Linked Glycosylated Bacteriocin.

PubMed

Maky, Mohamed Abdelfattah; Ishibashi, Naoki; Zendo, Takeshi; Perez, Rodney Honrada; Doud, Jehan Ragab; Karmi, Mohamed; Sonomoto, Kenji

2015-07-01

Enterococcus faecalis F4-9 isolated from Egyptian salted-fermented fish produces a novel bacteriocin, termed enterocin F4-9. Enterocin F4-9 was purified from the culture supernatant by three steps, and its molecular mass was determined to be 5,516.6 Da by mass spectrometry. Amino acid and DNA sequencing showed that the propeptide consists of 67 amino acid residues, with a leader peptide containing a double glycine cleavage site to produce a 47-amino-acid mature peptide. Enterocin F4-9 is modified by two molecules of N-acetylglucosamine β-O-linked to Ser37 and Thr46. The O-linked N-acetylglucosamine moieties are essential for the antimicrobial activity of enterocin F4-9. Further analysis of the enterocin F4-9 gene cluster identified enfC, which has high sequence similarity to a glycosyltransferase. The antimicrobial activity of enterocin F4-9 covered a limited range of bacteria, including, interestingly, a Gram-negative strain, Escherichia coli JM109. Enterocin F4-9 is sensitive to protease, active at a wide pH range, and moderately resistant to heat. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Synthesis and characterization of SiO2/(PMMA/Fe3O4) magnetic nanocomposites.

PubMed

Wang, Zhifei; Guo, Yafei; Li, Song; Sun, Yueming; He, Nongyue

2008-04-01

Magnetic silica nanocomposites (magnetic nanoparticles core coated by silica shell) have the wide promising applications in the biomedical field and usually been prepared based on the famous Stöber process. However, the flocculation of Fe3O4 nanoparticles easily occurs during the silica coating, which limits the amount of magnetic silica particles produced in the Stöber process. In this paper, PMMA/Fe3O4 nanoparticles were used in the Stöber process instead of the "nude" Fe3O4 nanoparticles. And coating Fe3O4 with PMMA polymer beforehand can prevent magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of tetraethoxysilane (TEOS) by the steric hindrance. The results show that the critical concentration of magnetic nanoparticles can increase from 12 mg/L for "nude" Fe3O4 nanoparticles to 3 g/L for PMMA/Fe3O4 nanoparticles during the Stöber process. And before the deposition of silica shell, the surface of PMMA/FeO4 nanoparticles had to be further modified by hydrolyzing them in CH3OH/NH3 x H2O mixture solution, which provides the carboxyl groups on their surface to react further with the silanol groups of silicic acid.
Evaluation of the SO(2) and NH(3) gas adsorption properties of CuO/ZnO/Mn(3)O(4) and CuO/ZnO/NiO ternary impregnated activated carbon using combinatorial materials science methods.

PubMed

Romero, Jennifer V; Smith, Jock W H; Sullivan, Braden M; Macdonald, Landan; Croll, Lisa M; Dahn, J R

2013-02-11

Impregnated activated carbons (IAC) are widely used materials for the removal of toxic gases in personal respiratory protection applications. The combinatorial method has been employed to prepare IACs containing different types of metal oxides in various proportions and evaluate their adsorption performance for low molecular weight gases, such as SO(2) and NH(3), under dry conditions. Among the metal oxides used for the study, Mn(3)O(4) was found to have the highest capacity for retaining SO(2) gas under dry conditions. NiO and ZnO were found to have similar NH(3) adsorption capacities which are higher than the NH(3) capacities observed for the other metal oxide impregnants used in the study. Although Cu- or Zn-based impregnants and their combinations have been extensively studied and used as gas adsorbents, neither Mn(3)O(4) nor NiO have been incorporated in the formulations used. In this study, ternary libraries of IACs with various combinations of CuO/ZnO/Mn(3)O(4) and CuO/ZnO/NiO were studied and evaluated for their adsorption of SO(2) and NH(3) gases. Combinations of CuO, ZnO, and Mn(3)O(4) were found to have the potential to be multigas adsorbents compared to formulations that contain NiO.
Single Crystalline Co3O4 Nanocrystals Exposed with Different Crystal Planes for Li-O2 Batteries

PubMed Central

Su, Dawei; Dou, Shixue; Wang, Guoxiu

2014-01-01

Single crystalline Co3O4 nanocrystals exposed with different crystal planes were synthesised, including cubic Co3O4 nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co3O4 enclosed by {100} and {110} crystal planes, Co3O4 nanosheets exposed by {110} crystal planes, hexagonal Co3O4 nanoplatelets exposed with {111} crystal planes, and Co3O4 nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co3O4 nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O2 batteries shows that Co3O4 nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co3O4 nanocrystals, namely, crystal planes-dependent process. The correlation between different Co3O4 crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}. PMID:25169737
Single crystalline Co3O4 nanocrystals exposed with different crystal planes for Li-O2 batteries.

PubMed

Su, Dawei; Dou, Shixue; Wang, Guoxiu

2014-08-29

Single crystalline Co3O4 nanocrystals exposed with different crystal planes were synthesised, including cubic Co3O4 nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co3O4 enclosed by {100} and {110} crystal planes, Co3O4 nanosheets exposed by {110} crystal planes, hexagonal Co3O4 nanoplatelets exposed with {111} crystal planes, and Co3O4 nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co3O4 nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O2 batteries shows that Co3O4 nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co3O4 nanocrystals, namely, crystal planes-dependent process. The correlation between different Co3O4 crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}.
Tuning optical properties of magic number cluster (SiO2)4O2H4 by substitutional bonding with gold atoms.

PubMed

Cai, Xiulong; Zhang, Peng; Ma, Liuxue; Zhang, Wenxian; Ning, Xijing; Zhao, Li; Zhuang, Jun

2009-04-30

By bonding gold atoms to the magic number cluster (SiO(2))(4)O(2)H(4), two groups of Au-adsorbed shell-like clusters Au(n)(SiO(2))(4)O(2)H(4-n) (n = 1-4) and Au(n)(SiO(2))(4)O(2) (n = 5-8) were obtained, and their spectral properties were studied. The ground-state structures of these clusters were optimized by density functional theory, and the results show that in despite of the different numbers and types of the adsorbed Au atoms, the cluster core (SiO(2))(4)O(2) of T(d) point-group symmetry keeps almost unchanged. The absorption spectra were obtained by time-dependent density functional theory. From one group to the other, an extension of absorption wavelength from the UV-visible to the NIR region was observed, and in each group the absorption strengths vary linearly with the number of Au atoms. These features indicate their advantages for exploring novel materials with easily controlled tunable optical properties. Furthermore, due to the weak electronic charge transfer between the Au atoms, the clusters containing Au(2) dimers, especially Au(8)(SiO(2))(4)O(2), absorb strongly NIR light at 900 approximately 1200 nm. Such strong absorption suggests potential applications of these shell-like clusters in tumor cells thermal therapy, like the gold-coated silica nanoshells with larger sizes.
Relatedness of the O-polysaccharide structures of Escherichia coli O123 and Salmonella enterica O58, both containing 4,6-dideoxy-4-{N-[(S)-3-hydroxybutanoyl]-D-alanyl}amino-D-glucose; revision of the E. coli O123 O-polysaccharide structure.

PubMed

Perepelov, Andrei V; Liu, Bin; Shevelev, Sergei D; Senchenkova, Sof'ya N; Shashkov, Alexander S; Feng, Lu; Knirel, Yuriy A; Wang, Lei

2010-04-19

O-Polysaccharides were isolated by mild acid degradation of the lipopolysaccharides of Escherichia coli O123 and Salmonella enterica O58 and studied by chemical methods and 2D (1)H and (13)C NMR spectroscopy, including experiments in a H(2)O/D(2)O mixture, which enabled observation of correlations for nitrogen-linked protons. The following structure of the O-polysaccharide of E. coli O123 was established: -->3)-beta-D-Quip4NAlaHb-(1-->6)-alpha-D-GlcpNAc-(1-->3)-alpha-L-QuipNAc-(1-->3)-alpha-D-Glcp (6)(approx. 30% OAc)NAc-(1--> where L-QuipNAc stands for 2-acetamido-2,6-dideoxy-L-glucose and D-Qui4NAlaHb for 4-{N-[(S)-3-hydroxybutanoyl]-D-alanyl}amino-4,6-dideoxy-D-glucose. The latter was isolated as an ethylene glycol glycoside by three sequential Smith degradations of the O-deacetylated O-polysaccharide. The structure established in this work is at variance with the E. coli O123-polysaccharide structure reported earlier [Clark, C. G.; Kropinski, A. M.; Parolis, H.; Grant, C. C.; Trout-Yakel, K. M.; Franklin, K.; Ng, L. K.; Paramonov, N. A.; Parolis, L. A.; Rahn, K.; Tabor, H. J. Med. Microbiol.2009, 58, 884-894]. In accordance with the genetic data, the O-polysaccharide of S. enterica O58 has the same structure, except for it lacks the O-acetylation. Copyright (c) 2010 Elsevier Ltd. All rights reserved.
Two-photon momentum density in La2-xSrxCuO4 and Nd2-xCexCuO4

NASA Astrophysics Data System (ADS)

Blandin, P.; Massidda, S.; Barbiellini, B.; Jarlborg, T.; Lerch, P.; Manuel, A. A.; Hoffmann, L.; Gauthier, M.; Sadowski, W.; Walker, E.; Peter, M.; Yu, Jaejun; Freeman, A. J.

1992-07-01

We present calculations of the electron-positron momentum density for the high-Tc superconductors La2-xSrxCuO4 and Nd2-xCexCuO4, together with experimental two-dimensional angular correlation of annihilation radiation (2D-ACAR) for Nd2-xCexCuO4. The calculations are based on first-principles electronic structure obtained using the full-potential linearized augmented-plane-wave and the linear muffin-tin orbital methods. Our results indicate a non-negligible overlap of the positron wave function with the CuO2 plane electrons responsible for the Fermi surfaces in these compounds. Therefore, these compounds may be well suited for investigating Fermi-surface-related effects. After the folding of umklapp terms according to Lock, Crisp, and West, the predicted Fermi-surface breaks are mixed with strong effects induced by the positron wave function in La2-xSrxCuO4, while their resolution is better in Nd2-xCexCuO4. A comparison of our calculations with the most recent experimental results for La2-xSrxCuO4 shows good agreement. For Nd2-xCexCuO4 good agreement is observed between theoretical and experimental 2D-ACAR profiles.
The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C

NASA Astrophysics Data System (ADS)

Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko

1990-05-01

The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C are determined by means of a classical quenching method. There are a series of homologous solid solutions, In 1.28Fe 0.72O 3(ZnO)InFeO 3(ZnO), In 1.69Fe 0.31O 3(ZnO) 2InFeO 3(ZnO) 2In 0.85Fe 1.15O 3(ZnO) 2, In 2O 3(ZnO) 3InFeO 3(ZnO) 3In 0.78Fe 1.22O 3(ZnO) 3, In 2O 3(ZnO) 4InFeO 3(ZnO) 4In 0.62Fe 1.38O 3(ZnO) 4, In 2O 3(ZnO) 5InFeO 3(ZnO) 5In 0.67Fe 1.33O 3(ZnO) 5, In 2O 3(ZnO) 6InFeO 3(ZnO) 6In 0.60Fe 1.40O 3(ZnO) 6, In 2O 3(ZnO) 7InFeO 3(ZnO) 7In 0.51Fe 1.49O 3(ZnO) 7, In 2O 3(ZnO) 8InFeO 3(ZnO) 8In 1- xFe 1+ xO 3(ZnO) 8 (0.44 ≦ x ≦ 0.64), In 2O 3(ZnO) 9InFeO 3(ZnO) 9In 0.20Fe 1.80O 3(ZnO) 9, In 2O 3(ZnO) 10InFeO 3(ZnO) 10In 1- xFe 1+ xO 3(ZnO) 10 (0.74 ≦ x ≦ 0.89), In 2O 3(ZnO) 11InFeO 3(ZnO) 11In 1- xFe 1+ xO 3(ZnO) 11 (0.60 ≦ x < 1.00), and In 2O 3(ZnO) 13InFeO 3(ZnO) 13Fe 2O 3(ZnO) 13 having the layered structures with space group R overline3m (m = odd) or {P6 3}/{mmc} (m = even) for m in the InFeO 3(ZnO) m. We conclude that there are a series of homologous phases, (Fe 2O 3)(ZnO) m (m ≧ 12) , in the binary ZnOFe 2O 3 system. The lattice constants for these solid solutions are presented as a hexagonal crystal system. It is also concluded that the crystal structures for each solid solution consist of three kinds of layers which are stacked perpendicular to the c-axis in the hexagonal crystal system. In 1+ xFe 1- xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of the InO 1.5, (In xFe 1- xZn)O 2.5, and ZnO layers, and In 1- xFe 1+ xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of (In 1- xFe x)O 1.5, (FeZn)O 2.5, and ZnO layers, respectively. The solid solution range between Fe 2ZnO 4 and In xFe 2- xZnO 4 ( x = 0.40 ± 0.02) with a spinel structure is observed.
Preparation, characterization, and antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite

NASA Astrophysics Data System (ADS)

Allafchian, Alireza; Jalali, Seyed Amir Hossein; Bahramian, Hamid; Ahmadvand, Hossein

2016-04-01

We have described a facile fabrication of silver deposited on the TiO2, Poly Acrylonitrile Co Maleic Anhydride (PAMA) polymer and nickel ferrite composite (NiFe2O4/PAMA/Ag-TiO2) through a three-step procedure. A pre-synthesized NiFe2O4 was first coated with PAMA polymer and then Ag-TiO2 was deposited on the surface of PAMA polymer shell. After the characterization of this three-component composite by various techniques, such as FTIR, XRD, FESEM, BET, TEM and VSM, it was impregnated in standard antibiotic discs. The antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite was investigated against some gram positive and gram negative bacteria by employing disc diffusion assay and then compared with that of naked NiFe2O4, NiFe2O4/Ag, AgNPs and NiFe2O4/PAMA. The results demonstrated that the AgNPs, when embedded in TiO2 and combined with NiFe2O4/PAMA, became an excellent antibacterial agent. The NiFe2O4/PAMA/Ag-TiO2 nanocomposite could be readily separated from water solution after the disinfection process by applying an external magnetic field.
Origin of Active Oxygen in a Ternary CuO x /Co 3O 4–CeO 2 Catalyst for CO Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhigang; Wu, Zili; Peng, Xihong

2014-11-14

In this paper, we have studied CO oxidation over a ternary CuO x/Co 3O 4-CeO 2 catalyst and employed the techniques of N 2 adsorption/desporption, XRD, TPR, TEM, in situ DRIFTS and QMS (Quadrupole mass spectrometer) to explore the origin of active oxygen. DRIFTS-QMS results with labeled 18O2 indicate that the origin of active oxygens in CuO x/Co 3O 4-CeO 2 obeys a model, called as queue mechanism. Namely gas-phase molecular oxygens are dissociated to atomic oxygens and then incorporate in oxygen vacancies located at the interface of Co 3O 4-CeO 2 to form active crystalline oxygens, and these activemore » oxygens diffuse to the CO-Cu + sites thanks to the oxygen vacancy concentration magnitude and react with the activated CO to form CO 2. This process, obeying a queue rule, provides active oxygens to form CO 2 from gas-phase O 2 via oxygen vacancies and crystalline oxygen at the interface of Co 3O 4-CeO 2.« less
Band alignment of atomic layer deposited SiO2 and HfSiO4 with (\\bar{2}01) β-Ga2O3

NASA Astrophysics Data System (ADS)

Carey, Patrick H., IV; Ren, Fan; Hays, David C.; Gila, Brent P.; Pearton, Stephen J.; Jang, Soohwan; Kuramata, Akito

2017-07-01

The valence band offset at both SiO2/β-Ga2O3 and HfSiO4/β-Ga2O3 heterointerfaces was measured using X-ray photoelectron spectroscopy. Both dielectrics were deposited by atomic layer deposition (ALD) onto single-crystal β-Ga2O3. The bandgaps of the materials were determined by reflection electron energy loss spectroscopy as 4.6 eV for Ga2O3, 8.7 eV for Al2O3 and 7.0 eV for HfSiO4. The valence band offset was determined to be 1.23 ± 0.20 eV (straddling gap, type I alignment) for ALD SiO2 on β-Ga2O3 and 0.02 ± 0.003 eV (also type I alignment) for HfSiO4. The respective conduction band offsets were 2.87 ± 0.70 eV for ALD SiO2 and 2.38 ± 0.50 eV for HfSiO4, respectively.
High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

NASA Astrophysics Data System (ADS)

Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

2016-04-01

In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.
A novel synthesis method for TiO2 particles with magnetic Fe3O4 cores.

PubMed

Dong, Qi; Zhang, Keqiang; An, Yi

2014-01-01

TiO2@(AC/Fe3O4) (AC is activated carbon) was prepared by using AC and Fe3O4 as joint support. The morphological features, crystal structure, and magnetism of the final product were characterized. The results indicate that TiO2 particles formed on the surface of AC and Fe3O4; the sizes of TiO2 and Fe3O4 were 0.5 and 0.7 μm respectively, and that of AC fell within a wide range. The highly crystalline cubic structures of the TiO2 particles was in accord with the standard X-ray diffractometry spectrum of magnetite and anatase. The maximum saturation magnetization of TiO2@(AC/Fe3O4) was 75 emu g(-1), which was enough to support magnetic recovery. The rate of methylene blue (MB) removal photocatalyzed by TiO2@(AC/Fe3O4) was higher by 50% than that achieved with AC/Fe3O4 photocatalysis, and similar to that achieved with TiO2@AC. The removal rate (kobs) decreased drastically from 1.77 × 10(-2) to 9.36 × 10(-3)min(-1) when the initial concentration of MB solution increased from 2.0 to 5.0 mg L(-1). The kobs value increased from 9.41 × 10(-3) to 1.34 × 10(-2)min(-1) with increasing photocatalyst dosage from 0.2 to 1.0 g, then slightly decreased to 1.33 × 10(-2)min(-1) at 2.0 g dosage.
Feasibility study of Fe3O4/TaO x nanoparticles as a radiosensitizer for proton therapy

NASA Astrophysics Data System (ADS)

Ahn, Sang Hee; Lee, Nohyun; Choi, Changhoon; Shin, Sung Won; Han, Youngyih; Park, Hee Chul

2018-06-01

We investigated the feasibility of using multifunctional Fe3O4/TaO x (core/shell) nanoparticles, developed for use in contrast agents for computed tomography (CT) and magnetic resonance imaging (MRI), as dose-enhancing radiosensitizers. First, to verify the detectability of Fe3O4/TaO x nanoparticles in imaging, in vivo tests were conducted. Approximately 600 mg kg‑1 of 19 nm-diameter Fe3O4/TaO x nanoparticles dispersed in phosphate-buffered saline was injected into the tail vein of six Balb/c mice used as tumour (4T1 mammary carcinoma cell) models. Three mice underwent MRI (BioSpec 70/20 USR, Bruker, Billerica, MA, USA) and micro-CT (Inveon, Siemens Preclinical, Knoxville, TN, USA) before and after the injection. The difference between the pre- and post-injection images was quantified by finding the correlation coefficient. The aorta, blood vessel, and liver were clearly seen in the MRI and micro-CT images 60 min after intravenous injection of Fe3O4/TaO x nanoparticles, but the tumour region was not visible in the CT images until after 24 h. There were large differences between the pre- and post-injection images. Second, the therapeutic enhancement dose of nanomaterials was computed via Monte Carlo simulation. Monoenergetic 70- and 150 MeV proton beams irradiated x-ray contrast agent (iodine, BaSO4), MRI contrast agent (gadolinium, Fe3O4), Au, Fe3O4/TaO x (core/shell) nanoparticles and water located at the centre of a 4 × 4 × 4 µm3 water phantom, upon which the dose enhancement ratio (DER) (dose with/without nanoparticles) was computed. When 70 MeV protons irradiated the Au, gadolinium, Fe3O4/TaO x , Fe3O4, iodine, and BaSO4 nanoparticles, the DERs at 1 nm were 15.76, 7.68, 7.82, 6.17, 4.85, and 5.51, respectively. Fe3O4/TaO x nanoparticles have the potential to be used as a multifunctional agent that enhances tumour detection and increases the dose. Dose enhancement with Fe3O4/TaO x was half that with Au. However, Fe3O4/TaO x is

Synthesis of KMnO4-treated magnetic graphene oxide nanocomposite (Fe3O4@GO/MnO x ) and its application for removing of Cu2+ ions from aqueous solution

NASA Astrophysics Data System (ADS)

Zhang, Huining; Chang, Qing; Jiang, Yu; Li, Huili; Yang, Yahong

2018-04-01

A magnetic KMnO4-treated graphene-oxide-based nanocomposite, Fe3O4@GO/MnO x , was synthesized through a facile hydrothermal technique. The properties of the Fe3O4@GO/MnO x nanocomposite were characterized by SEM, XRD and FTIR. Batch experiments showed that the maximum adsorption capacity calculated by the Langmuir model for Cu2+ was 62.65 mg g-1 at T = 303.15 K. Kinetics and XPS analysis also revealed that the mechanism of Cu2+ removal was mainly a chemical adsorption process involving both the MnO x particles and oxygen functional groups. The prepared Fe3O4@GO/MnO x was found to be an ideal adsorbent for the removal of Cu2+ ions due to the MnO x particle coating, and was easily separated using a magnetic field after utilization. Reusability studies imply that Fe3O4@GO/MnO x is a suitable material for heavy metal ion removal from aqueous solutions in real applications.
Magnetically Separable Fe3O4/SnO2/Graphene Adsorbent for Waste Water Removal

NASA Astrophysics Data System (ADS)

Paramarta, V.; Taufik, A.; Saleh, R.

2017-05-01

Our previous study conducted the SnO2 and SnO2/graphene adsorption efficiency in Methylene Blue removal from aqueous solution, however, the difficulty of adsorbent separation from the methylene blue solution limits its efficiency. Therefore, in this work, SnO2 and SnO2/graphene was combined with Fe3O4 to improve the separation process and adsorption performance for removing the organic dyes. Fe3O4/SnO2/grapheme were synthesized by using the co-precipitation method. The graphene content was varied from 1, 3, and 5 weight percent (wt%). The crystalline phase and thermal stability of the samples were characterized by using X- ray Diffraction (XRD) and Thermal Gravimetric Analysis (TGA). The adsorption ability of the samples was investigated by using significant adsorption degradation of MB observed when the graphene in Fe3O4/SnO2 nanocomposite was added. The other parameters such as pH and initial concentration have also been investigated. The reusability was also investigated to study the stability of the samples. The fitting of equilibrium adsorption capacity result indicates that the adsorption mechanism of Fe3O4/SnO2 nanocomposite with graphene tends to follow the Langmuir adsorption isotherm model.
MnTiO3-driven low-temperature oxidative coupling of methane over TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst

PubMed Central

Wang, Pengwei; Zhao, Guofeng; Wang, Yu; Lu, Yong

2017-01-01

Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process. PMID:28630917
Como os Alunos do Ensino Médio da Rede Estadual de São Paulo obtém Conhecimentos Astronômicos?

NASA Astrophysics Data System (ADS)

da Cunha, W. S.; Voelzke, M. R.; Amaral, L. H.

2005-08-01

Atualmente vivencia-se um mundo globalizado onde os computadores e a internet permitiram um acesso rápido e seguro a todo tipo de informação e conhecimento. O presente trabalho visa analisar a maneira pela qual alunos de segundo grau da rede estadual da cidade de São Paulo obtiveram, caso tenham, conhecimentos básicos de astronomia quanto aos fenômenos celestes que os rodeiam, tais como a sucessão dos dias e das estações do ano, além de questioná~los sobre fatos genéricos tais como: o que vem a ser o Sol, o Big Bang, o que ocasionou a extinção dos dinossauros. Para tanto foi elaborado um formulário constando de questões de múltipla escolha, o qual foi aplicado no primeiro colegial diurno da Escola Estadual Guilherme de Almeida. Num espaço amostral de 44 alunos constatou-se que 41% dos alunos adquiriram seus conhecimentos astronômicos na escola e 59% através da mídia em geral. Neste mesmo espaço amostral apenas 11% dos alunos usaram computadores na escola, 41% na residência, 5% no trabalho e 43% não utilizaram. O presente estudo revelou também que para 50% dos alunos o professor jamais utilizou um programa de computador a respeito de astronomia ou fez alguma apresentação sobre o tema. Embora em sua fase inicial este estudo revela claramente que a maioria dos alunos não obtém na escola seus conhecimentos astronômicos, estes provém de fontes não especificamente didático-pedagógicas tais como filmes e revistas populares que não raramente geram conhecimentos incompletos e em muitos casos inclusive falhos.
A promising tritium breeding material: Nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles

NASA Astrophysics Data System (ADS)

Dang, Chen; Yang, Mao; Gong, Yichao; Feng, Lan; Wang, Hailiang; Shi, Yanli; Shi, Qiwu; Qi, Jianqi; Lu, Tiecheng

2018-03-01

As an advanced tritium breeder material for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER), Li2TiO3-Li4SiO4 biphasic ceramic has attracted widely attention due to its merits. In this paper, the uniform precursor powders were prepared by hydrothermal method, and nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles were fabricated by an indirect wet method at the first time. In addition, the composition dependence (x/y) of their microstructure characteristics and mechanical properties were investigated. The results indicated that the crush load of biphasic ceramic pebbles was better than that of single phase ceramic pebbles under identical conditions. The 2Li2TiO3-Li4SiO4 ceramic pebbles have good morphology, small grain size (90 nm), satisfactory crush load (37.8 N) and relative density (81.8 %T.D.), which could be a promising breeding material in the future fusion reactor.
Synthesis and characterization of Fe3O4-SiO2-AgCl photocatalyst

NASA Astrophysics Data System (ADS)

Husni, H. N.; Mahmed, N.; Ngee, H. L.

2016-07-01

Magnetite-silica-silver chloride (Fe3O4-SiO2-AgCl) coreshell particles with AgCl crystallite size of 117 nm was prepared by a wet chemistry method at ambient temperature. The magnetite-core was synthesized by using iron (II) sulfate heptahydrate (FeSO4•7H2O) and iron (III) sulfate hydrate (Fe2(SO4)3) with ammonium hydroxide (NH4OH) as the precipitating agent. The silica-shell was synthesized by using a modified Stöber process. The silver ions (Ag+) was adsorbed onto the silica surface after Söber process, followed by the addition of Cl- and polyvinylpyrrolidone (PVP) for the formation of Fe3O4-SiO2-AgCl coreshell particles. The effectiveness of the synthesized photocatalyst was investigated by monitoring the degradation of the methylene blue (MB) under sunlight for five cycles. About 90 % of the MB solution can be degraded after 2 hours. The degradation of MB solution by the Fe3O4-SiO2-AgCl particles is highly efficient for first three cycles according to the MB concentration recorded by the UV-Visible spectroscopy (UV-Vis). Nevertheless, the synthesized particles could be a promising material for photocatalytic applications.
Co3(PO4)2·4H2O

PubMed Central

Lee, Young Hoon; Clegg, Jack K.; Lindoy, Leonard F.; Lu, G. Q. Max; Park, Yu-Chul; Kim, Yang

2008-01-01

Single crystals of Co3(PO4)2·4H2O, tricobalt(II) bis[orthophosphate(V)] tetrahydrate, were obtained under hydrothermal conditions. The title compound is isotypic with its zinc analogue Zn3(PO4)2·4H2O (mineral name hopeite) and contains two independent Co2+ cations. One Co2+ cation exhibits a slightly distorted tetrahedral coordination, while the second, located on a mirror plane, has a distorted octahedral coordination environment. The tetrahedrally coordinated Co2+ is bonded to four O atoms of four PO4 3− anions, whereas the six-coordinate Co2+ is cis-bonded to two phosphate groups and to four O atoms of four water molecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O—H⋯O are present throughout the crystal structure. PMID:21200978
Hydrothermal Syntheses and Structures of Three-Dimensional Oxo-fluorovanadium Phosphates: [H 2N(C 2H 4) 2NH 2] 0.5[(VO) 4V(HPO 4) 2(PO 4) 2F 2(H 2O) 4] · 2H 2O and K 2[(VO) 3(PO 4) 2F 2(H 2O)] · H 2O

NASA Astrophysics Data System (ADS)

Bonavia, Grant; Haushalter, R. C.; Zubieta, Jon

1996-11-01

The hydrothermal reactions of FPO3H2with vanadium oxides result in the incorporation of fluoride into V-P-O frameworks as a consequence of metal-mediated hydrolysis of the fluorophosphoric acid to produce F-and PO3-4. By exploiting this convenient source of F-, two 3-dimensional oxo-fluorovanadium phosphate phases were isolated, [H2N(C2H4)2NH2]0.5[(VO)4V(HOP4)2(PO4)2F2(H2O)4) · 2H2O (1 · 2H2O) and K2[(VO)3(PO4)2F2(H2O)] · H2O (2 · H2O). Both anionic frameworks contain (VIVO)-F--phosphate layers, with confacial bioctahedral {(VIVO)2FO6} units as the fundamental motif. In the case of 1, the layers are linked through {VIIIO6} octahedra, while for 2 the interlayer connectivity is provided by edge-sharing {(VIVO)2F2O6} units. Crystal data are 1 · 2H2O, CH10FN0.5O13P2V2.5, monoclinicC2/m,a= 18.425(4) Å,c= 8.954(2) Å, β = 93.69(2)0,V= 1221.1(4) Å3,Z= 4,Dcalc= 2.423 g cm-3; 2 · H2O, H4F2K2O13P2V3, triclinicPoverline1,a= 7.298(1) Å,b= 8.929(2) Å,c = 10.090(2) Å, α = 104.50(2)0, β = 100.39(2)0, δ = 92.13(2)0,V= 623.8(3) Å3,Z= 2,Dcalc= 2.891 g cm-3.
Mössbauer study and magnetic properties of MgFe2O4 crystallized from the glass system B2O3/K2O/P2O5/MgO/Fe2O3

NASA Astrophysics Data System (ADS)

Shabrawy, S. El; Bocker, C.; Miglierini, M.; Schaaf, P.; Tzankov, D.; Georgieva, M.; Harizanova, R.; Rüssel, C.

2017-01-01

An iron containing magnesium borate glass with the mol% composition 51.7 B2O3/9.3 K2O /1 P2O5/27.6MgO/10.4Fe2O3was prepared by the conventional melts quenching method followed by a thermal treatment process at temperatures in the range from 530 to 604 °C.The thermally treated samples were characterized by X-ray diffraction, scanning and transmission electron microscopy. It was shown that superparamagnetic MgFe2O4 nanoparticles were formed during thermal treatment. The size of the spinel type crystals was in the range from 6 to 15 nm. Mössbauer spectra of the powdered glass ceramic samples and the extracted nanoparticles after dissolving the glass matrix in diluted acid were recorded at room temperature. The deconvolution of the spectra revealed the crystallization of two spinel phases MgFe2O4 (as a dominant phase) and superparamagnetic maghemite, γ-Fe2O3 (as a secondary phase). Room temperature magnetic measurements showed that, increasing the crystallization temperature changed the superparamagnetic behavior of the samples to ferrimagnetic behavior. The Curie temperatures of the samples were measured and showed a higher value than that of the pure bulk MgFe2O4.
Pyrolysis reaction networks for lignin model compounds: unraveling thermal deconstruction of β-O-4 and α-O-4 compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Yong S.; Singh, Rahul; Zhang, Jing

2016-01-01

Although lignin is one of the main components of biomass, its pyrolysis chemistry is not well understood due to complex heterogeneity. To gain insights into this chemistry, the pyrolysis of seven lignin model compounds (five ..beta..-O-4 and two ..alpha..-O-4 linked molecules) was investigated in a micropyrolyzer connected to GC-MS/FID. According to quantitative product mole balance for the reaction networks, concerted retro-ene fragmentation and homolytic dissociation were strongly suggested as the initial reaction step for ..beta..-O-4 compounds and ..alpha..-O-4 compounds, respectively. The difference in reaction pathway between compounds with different linkages was believed to result from thermodynamics of the radical initiation.more » The rate constants for the different reaction pathways were predicted from ab initio density functional theory calculations and pre-exponential literature values. The computational findings were consistent with the experiment results, further supporting the different pyrolysis mechanisms for the ..beta..-ether linked and ..alpha..-ether linked compounds. A combination of the two pathways from the dimeric model compounds was able to describe qualitatively the pyrolysis of a trimeric lignin model compound containing both ..beta..-O-4 and ..alpha..-O-4 linkages.« less
Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

NASA Astrophysics Data System (ADS)

Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

2015-01-01

Fe3O4@SiO2-graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2-NH2. Fe3O4@SiO2-GO composites were synthesized by linking of Fe3O4@SiO2-NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2-GO composite has potential applications in the production of bioethanol.
Collision cross sections and transport coefficients of O-, O2 -, O3 - and O4 - negative ions in O2, N2 and dry air for non-thermal plasmas modelling

NASA Astrophysics Data System (ADS)

Hennad, Ali; Yousfi, Mohammed

2018-02-01

The ions interaction data such as interaction potential parameters, elastic and inelastic collision cross sections and the transport coefficients (reduced mobility and diffusion coefficients) have been determined and analyzed in the case of the main negative oxygen ions (O-, O2 -, O3 - and O4 -) present in low temperature plasma at atmospheric pressure when colliding O2, N2 and dry air. The ion transport has been determined from an optimized Monte Carlo simulation using calculated elastic and experimentally fitted inelastic collision cross sections. The elastic momentum transfer collision cross sections have been calculated from a semi-classical JWKB approximation based on a ( n-4) rigid core interaction potential model. The cross sections sets involving elastic and inelastic processes were then validated using measured reduced mobility data and also diffusion coefficient whenever available in the literature. From the sets of elastic and inelastic collision cross sections thus obtained for the first time for O3-/O2, O2 -/N2, O3 -/N2, and O4 -/N2 systems, the ion transport coefficients were calculated in pure gases and dry air over a wide range of the density reduced electric field E/N.
Massa do gás e das estrelas em aglomerados: eficiência da formação estelar

NASA Astrophysics Data System (ADS)

Laganá, T. F.; Lima Neto, G. B.

2003-08-01

Os aglomerados de galáxias apresentam um interesse especial para a cosmologia observacional. Eles são as maiores estruturas ligadas pela gravitação no Universo e relaxadas na região central. A comparação entre a massa do gás intra-aglomerado (responsável por ~25% da massa total, inferida a partir de observações em raios-X), a massa contida nas estrelas (i.e., nas galáxias) e a massa total (incluindo a matéria escura não bariônica), nos dá informações importantes sobre os processos de formação e evolução de aglomerados. Por exemplo, a razão entre a massa do gás e a massa total é uma medida da fração de bárions no Universo (razão entre a matéria bariônica e matéria escura) e, utilizando a densidade de bárions predita pela nucleosíntese primordial, podemos deduzir a densidade de matéria escura no Universo (cf. White et al. 1993). O objetivo deste trabalho é obter as razões entre as massas do gás, estelar (contida nas galáxias), e a total (massa dinâmica). As massas do gás e total são obtidas a partir das análises fotométrica e espectroscópica em raios-X enquanto que a massa estelar é obtida pela análise fotométrica das galáxias. Esta análise foi aplicada ao aglomerado Abell 496 observado pelo satélite XMM-Newton. A massa contida nas galáxias foi estimada a partir da função de luminosidade obtida por Durret et al. (2002). Para determinar as massas dinâmica e do gás nos precisamos determinar os perfis radiais de densidade e temperatura. Nós apresentaremos aqui estes resultados e suas implicações na eficiência da formação estelar em Abell 496.
Magnetic anisotropy modulation of epitaxial Fe3O4 films on MgO substrates

NASA Astrophysics Data System (ADS)

Chichvarina, O.; Herng, T. S.; Xiao, W.; Hong, X.; Ding, J.

2015-05-01

Fe3O4 has been widely studied because of its great potential in spintronics and other applications. As a magnetic electrode, it is highly desired if magnetic anisotropy can be controlled. Here, we report the results from our systematic study on the magnetic properties of magnetite (Fe3O4) thin films epitaxially grown on various MgO substrates. Strikingly, we observed a prominent perpendicular magnetic anisotropy in Fe3O4 film deposited on MgO (111) substrate. When measured in out-of-plane direction, the film (40 nm thick) exhibits a well-defined square hysteresis loop with coercivity (Hc) above 1 kOe, while much lower coercivity was obtained in the in-plane orientation. In sharp contrast, the films deposited onto MgO (100) and MgO (110) substrates show in-plane magnetic anisotropy. These films exhibit a typical soft magnet characteristic—Hc lies within the range of 200-400 Oe. All the films showed a clear Verwey transition near 120 K—a characteristic of Fe3O4 material. In addition, a series of magnetoresistance (MR) measurements is performed and the MR results are in good agreement with the magnetic observations. The role of the substrate orientation and film thickness dependency is also investigated.
New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

NASA Astrophysics Data System (ADS)

Weng, Sheng-Feng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-04-01

Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La(1a), Ce(1b)) and [Ce2(C2O4)(C6H6O7)2] . 4H2O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1¯ (No. 2); compound 2 crystallized in monoclinic space group P21/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of CuII ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d1 excited state and two levels of the 4f1 ground state (2F5/2 and 2F7/2). Compounds 1b and 2 containing CeIII ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers.
PREPARATION OF FLOWER-LIKE Co3O4/Fe3O4 MAGNETIC MICROSPHERES FOR PHOTODEGRADATION OF RhB UNDER UV LIGHT

NASA Astrophysics Data System (ADS)

Zhang, Baoliang; Zhang, Hepeng; Zhou, Lunwei; Ali, Nisar; Geng, Wangchang; Zhang, Qiuyu

2013-07-01

Flower-like Co3O4/Fe3O4 magnetic microspheres were prepared by coprecipitation of Fe2+ and Fe3+ in presence of flower-like Co3O4 microspheres as template. The preparation process included three steps: preparation of flower-like Co3O4 microspheres by hydrothermal method; immersion of Fe2+ and Fe3+ ions; coprecipitation in the presence of OH-. Rhodamine B (RhB) was chosen as model pollutants to investigate the photodegradation capacities of Co3O4/Fe3O4 magnetic microspheres. The results showed that the microspheres exhibited excellent degradation property and can be recycled to use again. After four times use the degradation efficiency was still above 90%.
Spin dynamics and magnetoelectric coupling mechanism of C o4N b2O9

NASA Astrophysics Data System (ADS)

Deng, Guochu; Cao, Yiming; Ren, Wei; Cao, Shixun; Studer, Andrew J.; Gauthier, Nicolas; Kenzelmann, Michel; Davidson, Gene; Rule, Kirrily C.; Gardner, Jason S.; Imperia, Paolo; Ulrich, Clemens; McIntyre, Garry J.

2018-02-01

Neutron powder diffraction experiments reveal that C o4N b2O9 forms a noncollinear in-plane magnetic structure with C o2 + moments lying in the a b plane. The spin-wave excitations of this magnet were measured by using inelastic neutron scattering and soundly simulated by a dynamic model involving nearest- and next-nearest-neighbor exchange interactions, in-plane anisotropy, and the Dzyaloshinskii-Moriya interaction. The in-plane magnetic structure of C o4N b2O9 is attributed to the large in-plane anisotropy, while the noncollinearity of the spin configuration is attributed to the Dzyaloshinskii-Moriya interaction. The high magnetoelectric coupling effect of C o4N b2O9 in fields can be explained by its special in-plane magnetic structure.
Influence of the Organic Species and Oxoanion in the Synthesis of two Uranyl Sulfate Hydrates, (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 (H 2 O)]·7H 2 O and (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 (H 2 O)]·4H 2 O, and a Uranyl Selenate-Selenite [C 5 H 6 N][(UO 2 )(SeO 4 )(HSeO 3 )

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J.; Wylie, Ernest M.; Burns, Peter C.

2012-08-08

Two uranyl sulfate hydrates, (H3O)2[(UO2)2(SO4)3(H2O)]·7H2O (NDUS) and (H3O)2[(UO2)2(SO4)3(H2O)]·4H2O (NDUS1), and one uranyl selenate-selenite [C5H6N][(UO2)(SeO4)(HSeO3)] (NDUSe), were obtained and their crystal structures solved. NDUS and NDUSe result from reactions in highly acidic media in the presence of L-cystine at 373 K. NDUS crystallized in a closed vial at 278 K after 5 days and NDUSe in an open beaker at 278 K after 2 weeks. NDUS1 was synthesized from aqueous solution at room temperature over the course of a month. NDUS, NDUS1, and NDUSe crystallize in the monoclinic space group P21/n, a = 15.0249(4) Å,b = 9.9320(2) Å, c = 15.6518(4)more » Å, β = 112.778(1)°, V = 2153.52(9) Å3,Z = 4, the tetragonal space group P43212, a = 10.6111(2) Å,c = 31.644(1) Å, V = 3563.0(2) Å3, Z = 8, and in the monoclinic space group P21/n, a = 8.993(3) Å, b = 13.399(5) Å, c = 10.640(4) Å,β = 108.230(4)°, V = 1217.7(8) Å3, Z = 4, respectively.The structural units of NDUS and NDUS1 are two-dimensional uranyl sulfate sheets with a U/S ratio of 2/3. The structural unit of NDUSe is a two-dimensional uranyl selenate-selenite sheets with a U/Se ratio of 1/2. In-situ reaction of the L-cystine ligands gives two distinct products for the different acids used here. Where sulfuric acid is used, only H3O+ cations are located in the interlayer space, where they balance the charge of the sheets, whereas where selenic acid is used, interlayer C5H6N+ cations result from the cyclization of the carboxyl groups of L-cystine, balancing the charge of the sheets.« less
Immobilization of Alkali Metal Fluorides via Recrystallization in a Cationic Lamellar Material, [Th(MoO4)(H2O)4Cl]Cl·H2O.

PubMed

Lin, Jian; Bao, Hongliang; Qie, Meiying; Silver, Mark A; Yue, Zenghui; Li, Xiaoyun; Zhu, Lin; Wang, Xiaomei; Zhang, Linjuan; Wang, Jian-Qiang

2018-06-05

Searching for cationic extended materials with a capacity for anion exchange resulted in a unique thorium molybdate chloride (TMC) with the formula of [Th(MoO 4 )(H 2 O) 4 Cl]Cl·H 2 O. The structure of TMC is composed of zigzagging cationic layers [Th(MoO 4 )(H 2 O) 4 Cl] + with Cl - as interlamellar charge-balancing anions. Instead of performing ion exchange, alkali thorium fluorides were formed after soaking TMC in AF (A = Na, K, and Cs) solutions. The mechanism of AF immobilization is elucidated by the combination of SEM-EDS, PXRD, FTIR, and EXAFS spectroscopy. It was observed that four water molecules coordinating with the Th 4+ center in TMC are vulnerable to competition with F - , due to the formation of more favorable Th-F bonds compared to Th-OH 2 . This leads to a single crystal-to-polycrystalline transformation via a pathway of recrystallization to form alkali thorium fluorides.
Sodium citrate functionalized reusable Fe3O4@TiO2 photocatalyst for water purification

NASA Astrophysics Data System (ADS)

Li, Wenyu; Wu, Haoyi

2017-10-01

Easy-recycle photocatalysts are new materials for water treatment technologies. In order to improve the recyclable ability, we employed Fe3O4 particles, which were functionalized by sodium citrate, to serve as a substrate core to attract the deposition of a shell of TiO2 particles. When compared to the calcining process for preparing the composite, the TiO2 distributed homogeneously on the sodium citrate treated Fe3O4, forming a mesoporous shell layer. Due to the mesoporous structure, this Fe3O4@TiO2 exhibited high photocatalytic degradation activity to Rhodamine B, and it was easily recycled using a magnetic field to recover the catalyst from solution.

Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents.

PubMed

Wang, Chongwen; Zhang, Kehan; Zhou, Zhe; Li, Qingjun; Shao, Liting; Hao, Rong Zhang; Xiao, Rui; Wang, Shengqi

2017-01-01

Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe 3 O 4 @SiO 2 @Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe 3 O 4 @SiO 2 @Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe 3 O 4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe 3 O 4 @SiO 2 @Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus , with minimum inhibitory concentrations of 10 and 20 μg mL -1 , respectively. The microflowers also showed enhanced effect compared with bare Fe 3 O 4 @SiO 2 @Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe 3 O 4 @SiO 2 @Ag microflowers exhibit promising applications in the antibacterial fields.
A Visão do Universo Segundo a Concepção de um Grupo de Alunos do Ensino Médio de São Paulo

NASA Astrophysics Data System (ADS)

Araújo, M. A. A.; Elias, D. C. N.; Amaral, L. H.; Araújo, M. S. T.; Voelzke, M. R.

2005-12-01

Nesse trabalho foi identificada por meio de um questionário a visão de mundo sobre o Universo espaço e tempo entre 270 estudantes de Ensino Médio de três escolas de São Paulo. Constatou-se pouco conhecimento dos temas investigados sendo que apenas 20% dos alunos relacionaram as semanas com as fases da lua enquanto 28% associaram as estações do ano à inclinação do eixo de rotação da Terra e 23% tinham noções das distâncias entre objetos celestes próximos da Terra. Enquanto 56% conseguiram relacionar o Big Bang com a origem do Universo verificou-se que 37% reconheciam ano-luz como unidade de distância e 60% reconheciam o Sol como uma estrela. Apesar de 60% dos alunos indicarem a escola como principal fonte dos conhecimentos de astronomia seus conceitos ainda são inadequados havendo necessidade de aprimoramento da abordagem desses conteúdos pois apesar de popular a astronomia é veiculada de maneira pouco esclarecedora e com imprecissões.
Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation

NASA Astrophysics Data System (ADS)

Zhu, Hua-Yue; Jiang, Ru; Fu, Yong-Qian; Li, Rong-Rong; Yao, Jun; Jiang, Sheng-Tao

2016-04-01

Novel multifunctional NiFe2O4/ZnO hybrids were prepared by a hydrothermal method and their physicochemical properties were characterized by XRD, SEM, TEM, TGA, VSM, BET and UV-vis DRS. The adsorption and photocatalytic performance of NiFe2O4/ZnO hybrids were systematically investigated using congo red as a model contaminant. With the introduction of NiFe2O4, NiFe2O4/ZnO hybrids can absorb the whole light from 300 nm to 700 nm. The adsorption capacity (221.73 mg g-1) of NiFe2O4/ZnO hybrids is higher than those of NiFe2O4, ZnO and mechanically mixed NiFe2O4/ZnO hybrids. The removal of congo red solution (20 mg L-1) by NiFe2O4/ZnO hybrids was about 94.55% under simulated solar light irradiation for 10 min. rad OH and h+ play important roles in the decolorization of congo red solution by NiFe2O4/ZnO hybrids under simulated solar light irradiation. The decolorization efficiency of congo red solution is 97.23% for the fifth time by NiFe2O4/ZnO hybrids under simulate solar light irradiation, indicating the high photostability and durability. NO3- and Cl- anions which are ubiquitous components in dye-containing wastewater have negligible influence on the effectiveness of NiFe2O4/ZnO hybrids. Moreover, the magnetic NiFe2O4/ZnO hybrids can be easily separated from the reacted solution by an external magnet.
Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.
Attikaite, Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O, a new mineral species

NASA Astrophysics Data System (ADS)

Chukanov, N. V.; Pekov, I. V.; Zadov, A. E.

2007-12-01

Attikaite, a new mineral species, has been found together with arsenocrandalite, arsenogoyazite, conichalcite, olivenite, philipsbornite, azurite, malachite, carminite, beudantite, goethite, quartz, and allophane at the Christina Mine No. 132, Kamareza, Lavrion District, Attiki Prefecture (Attika), Greece. The mineral is named after the type locality. It forms spheroidal segregations (up to 0.3 mm in diameter) consisting of thin flexible crystals up to 3 × 20 × 80 μm in size. Its color is light blue to greenish blue, with a pale blue streak. The Mohs’ hardness is 2 to 2.5. The cleavage is eminent mica-like parallel to {001}. The density is 3.2(2) g/cm3 (measured in heavy liquids) and 3.356 g/cm3 (calculated). The wave numbers of the absorption bands in the infrared spectrum of attikaite are (cm-1; sh is shoulder; w is a weak band): 3525 sh, 3425, 3180, 1642, 1120 w, 1070 w, 1035 w, 900 sh, 874, 833, 820, 690 w, 645 w, 600 sh, 555, 486, 458, and 397. Attikaite is optically biaxial, negative, α = 1.642(2), β = γ = 1.644(2) ( X = c) 2 V means = 10(8)°, and 2 V calc = 0°. The new mineral is microscopically colorless and nonpleochroic. The chemical composition (electron microprobe, average over 4 point analyses, wt %) is: 0.17 MgO, 17.48 CaO, 0.12 FeO, 16.28 CuO, 10.61 Al2O3, 0.89 P2O5, 45.45 As2O5, 1.39 SO3, and H2O (by difference) 7.61, where the total is 100.00. The empirical formula calculated on the basis of (O,OH,H2O)22 is: Ca2.94Cu{1.93/2+} Al1.97Mg0.04Fe{0.02/2+} [(As3.74S0.16P0.12)Σ4.02O16.08](OH)3.87 · 2.05H2 O. The simplified formula is Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O. Attikaite is orthorhombic, space group Pban, Pbam or Pba2; the unit-cell dimensions are a = 10.01(1), b = 8.199(5), c = 22.78(1) Å, V = 1870(3) Å3, and Z = 4. In the result of the ignition of attikaite for 30 to 35 min at 128 140°, the H2O bands in the IR spectrum disappear, while the OH-group band is not modified; the weight loss is 4.3%, which approximately corresponds to two H2O
Metabolism of aspirin and procaine in mice pretreated with O-4-nitrophenyl methyl(phenyl)phosphinate or O-4-nitrophenyl diphenylphosphinate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joly, J.M.; Brown, T.M.

Concentrations of (carboxyl-/sup 14/C)procaine in blood of mice were increased threefold for 27 min by exposure to O-4-nitrophenyl diphenylphosphinate 2 hr prior to (carboxyl-/sup 14/C)procaine injection ip, while there was no effect of O-4-nitrophenyl methyl(phenyl)phosphinate pretreatment. There was no effect of either organophosphinate on the primary hydrolysis of (acetyl-l-/sup 14/C)aspirin when assessed by the expiration of (/sup 14/C)carbon dioxide; however, O-4-nitrophenyl diphenylphosphinate pretreatment produced transient increases in blood concentrations of both (carboxyl-/sup 14/C)aspirin and (carboxyl-/sup 14/C)salicylic acid following administration of (carboxyl-/sup 14/C)aspirin. Liver carboxylesterase activity in O-4-nitrophenyl diphenylphosphinate pretreated mice was 11% of control activity. These results indicate the potentialmore » for drug interaction with O-4-nitrophenyl diphenylphosphinate but not with O-4-nitrophenyl methyl(phenyl)phosphinate. It appears that liver carboxylesterase activity has a minor role in hydrolysis of aspirin in vivo, but may be more important in procaine metabolism.« less
Crystal Chemical Substitution at Ca and La Sites in CaLa4(SiO4)3O To Design the Composition Ca1- xM xLa4-xRE x(SiO4)3O for Nuclear Waste Immobilization and Its Influence on the Thermal Expansion Behavior.

PubMed

Ravikumar, Ramya; Gopal, Buvaneswari; Jena, Hrudananda

2018-06-04

The oxysilicate apatite host CaLa 4 (SiO 4 ) 3 O has been explored for immobilization of radioactive nuclides. Divalent ion, trivalent rare earth ion, and combined ionic substitutions in the silicate oxyapatite were carried out to optimize the simulated wasteform composition. The phases were characterized by powder X-ray diffraction, FT-IR, TGA, SEM-EDS, and HT-XRD techniques. The results revealed the effect of ionic substitutions on the structure and thermal expansion behavior. The investigation resulted in the formulation of simulated wasteforms such as La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (WF-1) and Ca 0.8 Sr 0.1 Pb 0.1 La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (WF-2). In comparison to the average axial thermal expansion coefficients of the hexagonal unit cell of the parent CaLa 4 (SiO 4 ) 3 O measured in the temperature range 298-1073 K (α' a = 9.74 × 10 -6 K -1 and α' c = 10.10 × 10 -6 K -1 ), rare earth ion substitution decreases the thermal expansion coefficients, as in the case of La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (α' a = 8.67 × 10 -6 K -1 and α' c = 7.94 × 10 -6 K -1 ). However, the phase Ca 0.8 Sr 0.1 Pb 0.1 La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O shows an increase in the values of thermal expansion coefficients: α' a = 11.74 × 10 -6 K -1 and α' c = 11.70 × 10 -6 K -1 .
Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

DOE PAGES

Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.; ...

2017-11-14

The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less
Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.

The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less
Hybrid supercapacitor devices based on MnCo2O4 as the positive electrode and FeMn2O4 as the negative electrode

NASA Astrophysics Data System (ADS)

Nagamuthu, Sadayappan; Vijayakumar, Subbukalai; Lee, Seong-Hun; Ryu, Kwang-Sun

2016-12-01

MnCo2O4 nanosheets and FeMn2O4 nanospheres were synthesized using a hydrothermal method. Choline chloride was used as the capping agent during the preparation of the nanoparticles. XRD patterns confirmed the spinel structure of MnCo2O4 and FeMn2O4. XPS measurements were used to determine the oxidation state of the prepared spinel metal oxides. HRTEM images revealed the formation of hexagonal nanosheets of MnCo2O4 and nanospheres of FeMn2O4. Electrochemical measurements were made for both positive and negative electrodes using three electrode systems. MnCo2O4 Exhibits 282C g-1 and FeMn2O4 yields 110C g-1 at a specific current of 1 A g-1. Hybrid supercapacitor device was fabricated using MnCo2O4 as the positive and FeMn2O4 as the negative electrode material. The hybrid supercapacitor device was delivered a maximum power of 37.57 kW kg-1.
Novel high-efficiency visible-light responsive Ag 4(GeO 4) photocatalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Xianglin; Wang, Peng; Li, Mengmeng

A novel high-efficiency visible-light responsive Ag 4(GeO 4) photocatalyst was prepared by a facile hydrothermal method. The photocatalytic activity of as-prepared Ag 4(GeO 4) was evaluated by photodegradation of methylene blue (MB) dye and water splitting experiments. The photodegradation efficiency and oxygen production efficiency of Ag 4(GeO 4) were detected to be 2.9 and 1.9 times higher than those of Ag 2O. UVvis diffuse reflectance spectroscopy (DRS), photoluminescence experiment and photoelectric effect experiments prove that the good light response and high carrier separation efficiency facilitated by the internal electric field are the main reasons for Ag 4(GeO 4)'s excellent catalyticmore » activity. Radical-trapping experiments reveal that the photogenerated holes are the main active species. Lastly, first-principles theoretical calculations provide more insight into understanding the photocatalytic mechanism of the Ag 4(GeO 4) catalyst.« less
Novel high-efficiency visible-light responsive Ag 4(GeO 4) photocatalyst

DOE PAGES

Zhu, Xianglin; Wang, Peng; Li, Mengmeng; ...

2017-04-25

A novel high-efficiency visible-light responsive Ag 4(GeO 4) photocatalyst was prepared by a facile hydrothermal method. The photocatalytic activity of as-prepared Ag 4(GeO 4) was evaluated by photodegradation of methylene blue (MB) dye and water splitting experiments. The photodegradation efficiency and oxygen production efficiency of Ag 4(GeO 4) were detected to be 2.9 and 1.9 times higher than those of Ag 2O. UVvis diffuse reflectance spectroscopy (DRS), photoluminescence experiment and photoelectric effect experiments prove that the good light response and high carrier separation efficiency facilitated by the internal electric field are the main reasons for Ag 4(GeO 4)'s excellent catalyticmore » activity. Radical-trapping experiments reveal that the photogenerated holes are the main active species. Lastly, first-principles theoretical calculations provide more insight into understanding the photocatalytic mechanism of the Ag 4(GeO 4) catalyst.« less
Experimental and first-principles calculation study of the pressure-induced transitions to a metastable phase in GaP O4 and in the solid solution AlP O4-GaP O4

NASA Astrophysics Data System (ADS)

Angot, E.; Huang, B.; Levelut, C.; Le Parc, R.; Hermet, P.; Pereira, A. S.; Aquilanti, G.; Frapper, G.; Cambon, O.; Haines, J.

2017-08-01

α -Quartz-type gallium phosphate and representative compositions in the AlP O4-GaP O4 solid solution were studied by x-ray powder diffraction and absorption spectroscopy, Raman scattering, and by first-principles calculations up to pressures of close to 30 GPa. A phase transition to a metastable orthorhombic high-pressure phase along with some of the stable orthorhombic C m c m CrV O4 -type material is found to occur beginning at 9 GPa at 320 ∘C in GaP O4 . In the case of the AlP O4-GaP O4 solid solution at room temperature, only the metastable orthorhombic phase was obtained above 10 GPa. The possible crystal structures of the high-pressure forms of GaP O4 were predicted from first-principles calculations and the evolutionary algorithm USPEX. A predicted orthorhombic structure with a P m n 21 space group with the gallium in sixfold and phosphorus in fourfold coordination was found to be in the best agreement with the combined experimental data from x-ray diffraction and absorption and Raman spectroscopy. This method is found to very powerful to better understand competition between different phase transition pathways at high pressure.
Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

PubMed Central

Wang, Chongwen; Zhang, Kehan; Zhou, Zhe; Li, Qingjun; Shao, Liting; Hao, Rong Zhang; Xiao, Rui; Wang, Shengqi

2017-01-01

Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 μg mL−1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields. PMID:28450783
Fe doped BaTiO3 sensitized by Fe3O4 nanoparticles for improved photoelectrochemical response

NASA Astrophysics Data System (ADS)

Upadhyay, Rishibrind Kumar; Sharma, Dipika

2018-01-01

Nanostructured powders of pristine Fe3O4, BaTiO3, and Fe-BaTiO3 were synthesized using hydrothermal method and BaTiO3/Fe3O4 and Fe-BaTiO3/Fe3O4 composite sample were also prepared by mixing the appropriate amount of pristine powders. All samples were characterized using x-ray diffraction, SEM and UV-vis spectrometry. Photoelectrochemical properties were investigated in a three-electrode cell system. Maximum photocurrent density of 2.1 mA cm-2 at 0.95 V/SCE was observed for Fe-BaTiO3/Fe3O4 composite sample. Increased photocurrent density offered by composite may be attributed to improved conductivity and better separation of the photogenerated charge carriers at interface.
Magnetically addressable fluorescent Fe3O4/ZnO nanocomposites: Structural, optical and magnetization studies

NASA Astrophysics Data System (ADS)

Roychowdhury, A.; Pati, S. P.; Mishra, A. K.; Kumar, S.; Das, D.

2013-06-01

Fe3O4/ZnO nanocomposites (NCs) are prepared by a wet chemical route. X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy studies confirm the coexistence of Fe3O4 and ZnO phases in the NCs. The UV-vis absorption spectra show a red shift of the absorption peak with increase in Fe3O4 content indicating a modification of the band structure of ZnO in the NCs. Photoluminescence emission spectra of the NCs display strong excitonic emission in the UV region along with weak emission bands in the visible range caused by electronic transitions involving defect-related energy levels in the band gap of ZnO. Positron annihilation lifetimes indicate that cation vacancies in the ZnO structure are the strong traps for positrons and the overall defect concentration in the NCs decreases with increase in Fe3O4 content. Dc magnetization measurements reveal an anomalous temperature dependence of the coercivity of the NCs that is argued to be due to the anomalous variation of magnetocrystalline anisotropy at lower temperature. The irreversibility observed in the temperature dependent ZFC-FC magnetization points to the presence of a spin-glass phase in the NCs.
Core/shell structure NiCo2O4@MnCo2O4 nanofibers fabricated by different temperatures for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Qing; Qin, Xuefeng; Jiang, Pengcheng; Dai, Jianfeng; Li, Weixue; Gao, Haoran

2018-03-01

Core/shell structure NiCo2O4@MnCo2O4 nanofibers (NiCo2O4@MnCo2O4 NFs) were prepared by a facile co-electrospinning method and heat treatment. The composites annealed at 500 °C have a complete, continuously obvious core/shell structure, and clear interface of composites with good morphology, while annealed at 600 °C were stacked on each other and were unable to sustain three-dimensional network structures and 700 °C calcination have completely lost one-dimensional structure. The core NiCo2O4 is about 70 nm in diameter and the MnCo2O4 shell behaves a thickness about 60 nm. When investigated as an electrode material for supercapacitors, the NiCo2O4@MnCo2O4 NFs annealed at 500 °C exihibited the specific capacitance of 463 F g-1 (0.926 F cm-2) at 1 A g-1, higher than that annealed at 600 °C 362 F g-1, 1 A g-1 (0.724 F cm-2, 1 A g-1) and 700 °C 283 F g-1, 1 A g-1 (0.566 F cm-2, 1 A g-1). These results suggest that core/shell NiCo2O4@MnCo2O4 NFs annealed at 500 °C have formed a good morphology with continuously complete core/shell structure which lead to good properties would be potential electrodes for supercapacitors.
Monazite-type SrCr O 4 under compression

DOE PAGES

Gleissner, J.; Errandonea, Daniel; Segura, A.; ...

2016-10-20

We report a high-pressure study of monoclinic monazite-type SrCrO 4 up to 26 GPa. Therein we combined x-ray diffraction, Raman, and optical-absorption measurements with ab initio calculations, to find a pressure-induced structural phase transition of SrCrO 4 near 8-9 GPa. Evidence of a second phase transition was observed at 10-13 GPa. The crystal structures of the high-pressure phases were assigned to the tetragonal scheelite-type and monoclinic AgMnO 4-type structures. Both transitions produce drastic changes in the electronic band gap and phonon spectrum of SrCrO 4. We determined the pressure evolution of the band gap for the low- and high-pressure phasesmore » as well as the frequencies and pressure dependencies of the Raman-active modes. In all three phases most Raman modes harden under compression, however the presence of low-frequency modes which gradually soften is also detected. In monazite-type SrCrO 4, the band gap blueshifts under compression, but the transition to the scheelite phase causes an abrupt decrease of the band gap in SrCrO 4. Calculations showed good agreement with experiments and were used to better understand the experimental results. From x-ray-diffraction studies and calculations we determined the pressure dependence of the unit-cell parameters of the different phases and their ambient-temperature equations of state. The results are compared with the high-pressure behavior of other monazites, in particular PbCrO 4. A comparison of the high-pressure behavior of the electronic properties of SrCrO 4 (SrWO 4) and PbCrO 4 (PbWO 4) will also be made. Lastly, the possible occurrence of a third structural phase transition is discussed.« less
Formation of self-organized Mn3O4 nanoinclusions in LaMnO3 films

NASA Astrophysics Data System (ADS)

Pomar, Alberto; Konstantinović, Zorica; Bagués, Nuria; Roqueta, Jaume; López-Mir, Laura; Balcells, Lluis; Frontera, Carlos; Mestres, Narcis; Gutiérrez-Llorente, Araceli; Šćepanović, Maja; Lazarević, Nenad; Popović, Zoran; Sandiumenge, Felip; Martínez, Benjamín; Santiso, José

2016-09-01

We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favourable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behaviour. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight ( 9º) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions.
Evaluation of simultaneous organic matters and nutrients removal from municipal wastewater using a novel bioreactor (D-A2O) system.

PubMed

Ye, Changbing; Zhou, Zhiming; Li, Ming; Liu, Qin; Xu, Tiantian; Li, Jia

2018-07-15

A novel bioreactor, the divisional influent dual-anaerobic-anoxic/oxic (D-A 2 O) system, was applied to treat municipal wastewater. This new system improved the removal efficiency of simultaneous organic matters and nutrients, and provided a reduction in the system's energy costs and sludge yield. Results from the reactor's 18 months of operation demonstrated the following optimal conditions for the 4 key parameters of the system: (1) a divisional ratio (DR) of 8:2 between the influent flow volumes fed into the anaerobic and anoxic tanks, (2) a hydraulic retention time (HRT) of 6 h, (3) a R:r ratio of 200%:100% between the mixed liquor return ratio (R) and the return activated sludge ratio (r), and (4) an alternative operating time (t A/B ) of 1 h for the A/B anaerobic-anoxia series. Under optimal conditions, the system showed a high removal efficiency for the chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH 3 -N), and total phosphorus (TP) removals, with the average removal efficiencies (with a standard deviation of less than 3%) being 95.23%, 80.64%, 90.42%, and 90.03%, respectively. The final concentration ranges of COD, TN, NH 3 -N, and TP in the effluent were 26-48 mg L -1 , 6.11-11.03 mg L -1 , 2.93-4.04 mg L -1 , and 0.21-0.45 mg L -1 , respectively. The concentrations of the pollutants in the effluent from the D-A 2 O system were lower than those required for Level 1A (Chinese quality of wastewater discharge standard GB18918-2002). According to the results, we concluded that the divisional influent dual-anaerobic-anoxic system (which integrated the A 2 O and sequencing batch reactor (SBR) process) was successfully provided sufficient carbon sources for denitrification and phosphorus uptake without external carbon addition. Compared to the conventional anaerobic-anoxic/oxic (A 2 O) process, the D-A 2 O system offers a high removal efficiency, simple operation, and significant energy saving of about 0.276 kWh m -3

Catalytic performance of Mn 3O 4 and Co 3O 4 nanocrystals prepared by sonochemical method in epoxidation of styrene and cyclooctene

NASA Astrophysics Data System (ADS)

Askarinejad, Azadeh; Bagherzadeh, Mojtaba; Morsali, Ali

2010-09-01

A simple sonochemical method was developed to synthesis uniform sphere-like Co 3O 4 and Mn 3O 4 nanocrystals. Epoxidation of styrene and cyclooctene by anhydrous tert-butyl hydroperoxide over the prepared Co 3O 4 and Mn 3O 4 nanocatalysts was investigated. The results of conversion activity were compared with bulk Co 3O 4 and Mn 3O 4. Under optimized reaction conditions, the nanocatalysts showed a superior catalytic performance as compared to the bulk catalysts. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area, were used to characterize and investigate the nanocatalysts.
Photo-thermal characteristics of water-based Fe3O4@SiO2 nanofluid for solar-thermal applications

NASA Astrophysics Data System (ADS)

Khashan, Saud; Dagher, Sawsan; Omari, Salahaddin Al; Tit, Nacir; Elnajjar, Emad; Mathew, Bobby; Hilal-Alnaqbi, Ali

2017-05-01

This work proposes and demonstrates the novel idea of using Fe3O4@SiO2 core/shell structure nanoparticles (NPs) to improve the solar thermal conversion efficiency. Magnetite (Fe3O4) NPs are synthesized by controlled co-precipitation method. Fe3O4@SiO2 NPs are prepared based on sol-gel approach, then characterized. Water-based Fe3O4@SiO2 nanofluid is prepared and usedto illustrate the photo-thermal conversion characteristics of a solar collector under solar simulator. The temperature rise characteristics of the nanofluids are investigated at different heights of the solar collector, for duration of 300 min, under a solar intensity of 1000 W m-2. The experimental results show that Fe3O4@SiO2 NPs have a core/shell structure with spherical morphology and size of about 400 nm. Fe3O4@SiO2/H2O nanofluid enhances the photo-thermal conversion efficiency compared with base fluid and Fe3O4/H2O nanofluid, since the silica coating improves both the thermodynamic stability of the nanofluid and the light absorption effectiveness of the NPs. At a concentration of 1 mg/1 ml of Fe3O4@SiO2/H2O, and with the utilization of kerosene into the solar collector, and exposure for radiation for 5 min, the photo-thermal conversion efficiency has shown an enhancement at the bottom of the collector of about 32.9% compared to the base fluid.
Photoelectron spectroscopy of B{sub 4}O{sub 4}{sup −}: Dual 3c-4e π hyperbonds and rhombic 4c-4e o-bond in boron oxide clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Wen-Juan; Chen, Qiang; Ou, Ting

2015-04-07

Gas-phase anion photoelectron spectroscopy (PES) is combined with global structural searches and electronic structure calculations at the hybrid Becke 3-parameter exchange functional and Lee-Yang-Parr correlation functional (B3LYP) and single-point coupled-cluster with single, double, and perturbative triple excitations (CCSD(T)) levels to probe the structural and electronic properties and chemical bonding of the B{sub 4}O{sub 4}{sup 0/−} clusters. The measured PES spectra of B{sub 4}O{sub 4}{sup −} exhibit a major band with the adiabatic and vertical detachment energies (ADE and VDE) of 2.64 ± 0.10 and 2.81 ± 0.10 eV, respectively, as well as a weak peak with the ADE and VDEmore » of 1.42 ± 0.08 and 1.48 ± 0.08 eV. The former band proves to correspond to the Y-shaped global minimum of C{sub s} B{sub 4}O{sub 4}{sup −} ({sup 2}A″), with the calculated ADE/VDE of 2.57/2.84 eV at the CCSD(T) level, whereas the weak band is associated with the second lowest-energy, rhombic isomer of D{sub 2h} B{sub 4}O{sub 4}{sup −} ({sup 2}B{sub 2g}) with the predicted ADE/VDE of 1.43/1.49 eV. Both anion structures are planar, featuring a B atom or a B{sub 2}O{sub 2} core bonded with terminal BO and/or BO{sub 2} groups. The same Y-shaped and rhombic structures are also located for the B{sub 4}O{sub 4} neutral cluster, albeit with a reversed energy order. Bonding analyses reveal dual three-center four-electron (3c-4e) π hyperbonds in the Y-shaped B{sub 4}O{sub 4}{sup 0/−} clusters and a four-center four-electron (4c-4e) π bond, that is, the so-called o-bond in the rhombic B{sub 4}O{sub 4}{sup 0/−} clusters. This work is the first experimental study on a molecular system with an o-bond.« less
Thermogravimetric, Calorimetric, and Structural Studies of the Co3 O4 /CoO Oxidation/Reduction Reaction

NASA Astrophysics Data System (ADS)

Unruh, Karl; Cichocki, Ronald; Kelly, Brian; Poirier, Gerald

2015-03-01

To better assess the potential of cobalt oxide for thermal energy storage (TES), the Co3O4/CoO oxidation/reduction reaction has been studied by thermogravimetric (TGA), calorimetric (DSC), and x-ray diffraction (XRD) measurements in N2 and atmospheric air environments. TGA measurements showed an abrupt mass loss of about 6.6% in both N2 and air, consistent with the stoichiometric reduction of Co3O4 to CoO and structural measurements. The onset temperature of the reduction of Co3O4 in air was only weakly dependent on the sample heating rate and occurred at about 910 °C. The onset temperature for the oxidation of CoO varied between about 850 and 875 °C for cooling rates between 1 and 20 °C/min, but complete re-conversion to Co3O4 could only be achieved at the slowest cooling rates. Due to the dependence of the rate constant on the oxygen partial pressure, the oxidation of Co3O4 in a N2 environment occurred at temperatures between about 775 and 825 °C for heating rates between 1 and 20 °C/min and no subsequent re-oxidation of the reduced Co3O4 was observed on cooling to room temperature. In conjunction with a measured transition heat of about 600 J/g of Co3O4, these measurements indicate that cobalt oxide is a viable TES material.
Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

PubMed Central

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-01-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040
Comparison of Photocatalytic Performance of Different Types of Graphene in Fe3O4/SnO2 Composites

NASA Astrophysics Data System (ADS)

Paramarta, Valentinus; Taufik, Ardiansyah; Saleh, Rosari

2017-03-01

We have reported the role of annealing temperature Fe3O4/SnO2 nanocomposites as a photocatalyst for remove methylene blue (MB) dye from aqueous solution. However, how to enhanced the degradation performance of Fe3O4/SnO2 nanocomposites is important to its photocatalytic application. Therefore, in this work Fe3O4/SnO2 nanocomposites was combined with two different types of graphene materials (NGP and grahene) to improve the photocatalytic performance for remove methylene blue (MB) dye. Fe3O4/SnO2/NGP and Fe3O4/SnO2/graphene have been successfully synthesized by co-precipitation method. The influence of two types graphene on Fe3O4/SnO2 nanocomposites properties were systematically investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). Degradation of methylene Blue (MB) in aqueous solution was studied in detail under photocatalytic process. Effect of catalyst dosage (0.1-0.4 g/L) and scavengers on dye degradation were carried out to check the efficiency of photocatalyst. The results indicated Fe3O4/SnO2/graphene displayed higher photocatalytic activity than other catalyst. The reusability tests have also been done to ensure the stability of the used photocatalyst.
Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

PubMed Central

Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J.G.

2013-01-01

Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081
Synthesis and luminescence studies of Tb-doped MgO-MgAl2O4-Mg2SiO4 ceramic for use in radiation dosimetry.

PubMed

Gugliotti, C; Moriya, K; Tatumi, S; Mittani, J

2018-05-01

In the present work, MgO ceramic samples with different terbium concentrations were produced and the Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties analyzed and discussed, aiming the use in radiation dosimetry. The samples were produced using MgO, Mg(NO 3 ) 2 ·6H 2 O, Al 2 O 3 , SiO 2 and Tb(NO 3 ) 3 ·6H 2 O precursors in stoichiometric concentrations with five different terbium concentrations between 0.1 and 0.5 mol% and after, heat-treated at high temperature ~1500 °C. X-ray diffraction measurements on samples showed the formation of MgO as principal phase, and others in low concentration due to MgAl 2 O 4 , Mg 2 SiO 4 and Tb 4 O 7 phases. The TL glow curve of samples showed an intense and well-defined peak having the maximum at ~210 °C and other less intense at ~350 °C. The sample with 0.1 mol% of terbium concentration presented highest luminescence peak when compared to the other samples. The relationship between 210 °C TL peak intensity and dose was linear to doses between 1 and 20 Gy and the minimum detectable dose obtained by interpolation taking into account three times the standard deviation of the zero dose reading, was ~40 μGy. A fading of ~20% during the first 5 hours after irradiation of 210 °C peak was observed. TL emission spectra showed strong emission lines due to Tb 3+ ion. The OSL signal presented a linear behavior to doses between 1 and 10 Gy using 532 nm wavelength stimulation. Copyright © 2018 Elsevier Ltd. All rights reserved.
Evaluation to the effect of B2O3-La2O3-SrO-Na2O-Al2O3 bonding agent on Ti6Al4V-porcelain bonding.

PubMed

Zhao, C Q; Wu, S Q; Lu, Y J; Gan, Y L; Guo, S; Lin, J J; Huang, T T; Lin, J X

2016-10-01

Low-fusing bonding agents have been widely applied in Ti-ceramics restorations. As an important category, borate bonding agents have great potentials in increasing Ti-porcelain bonding. The purpose of this study is to evaluate the effect of borate bonding agent with addition of Na2O and Al2O3 on Ti6Al4V-porcelain bonding. The thermal properties of borate bonding agent, such as glass transition temperature (Tg) and crystallization peak temperature (Tp), were investigated to establish the sintering process. And the coefficient of thermal expansion (CTE) was to evaluate the matching effect of porcelain to Ti6Al4V. The bond strength was analyzed by the three point bending test. The microscopic morphology of the borate bonding agent surface after sintering, the interface of Ti-borate bonding agent-porcelain, and the fracture mode after porcelains fracture, were studied to assess the influence of borate bonding agent on Ti6Al4V-ceramics. With the addition of Na2O and Al2O3, the porcelain residues were observed increased indication on the Ti6Al4V surface after porcelain fracture and the bond strength was acquired the maximum (49.45MPa) in the bonding agent composition of 75.70B2O3-5.92La2O3-11.84SrO-4.67Na2O-1.87Al2O3. Those results suggest that borate bonding agent is an effective way to improve the Ti6Al4V-ceramics bond strength. And the addition of Na2O and Al2O3 strengthen this effect. Copyright © 2016 Elsevier Ltd. All rights reserved.
IDENTIFYING PLANETARY BIOSIGNATURE IMPOSTORS: SPECTRAL FEATURES OF CO AND O{sub 4} RESULTING FROM ABIOTIC O{sub 2}/O{sub 3} PRODUCTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwieterman, Edward W.; Meadows, Victoria S.; Arney, Giada N.

O{sub 2} and O{sub 3} have been long considered the most robust individual biosignature gases in a planetary atmosphere, yet multiple mechanisms that may produce them in the absence of life have been described. However, these abiotic planetary mechanisms modify the environment in potentially identifiable ways. Here we briefly discuss two of the most detectable spectral discriminants for abiotic O{sub 2}/O{sub 3}: CO and O{sub 4}. We produce the first explicit self-consistent simulations of these spectral discriminants as they may be seen by James Webb Space Telescope (JWST). If JWST-NIRISS and/or NIRSpec observe CO (2.35, 4.6 μm) in conjunction withmore » CO{sub 2} (1.6, 2.0, 4.3 μm) in the transmission spectrum of a terrestrial planet it could indicate robust CO{sub 2} photolysis and suggest that a future detection of O{sub 2} or O{sub 3} might not be biogenic. Strong O{sub 4} bands seen in transmission at 1.06 and 1.27 μm could be diagnostic of a post-runaway O{sub 2}-dominated atmosphere from massive H-escape. We find that for these false positive scenarios, CO at 2.35 μm, CO{sub 2} at 2.0 and 4.3 μm, and O{sub 4} at 1.27 μm are all stronger features in transmission than O{sub 2}/O{sub 3} and could be detected with S/Ns ≳ 3 for an Earth-size planet orbiting a nearby M dwarf star with as few as 10 transits, assuming photon-limited noise. O{sub 4} bands could also be sought in UV/VIS/NIR reflected light (at 0.345, 0.36, 0.38, 0.445, 0.475, 0.53, 0.57, 0.63, 1.06, and 1.27 μm) by a next generation direct-imaging telescope such as LUVOIR/HDST or HabEx and would indicate an oxygen atmosphere too massive to be biologically produced.« less
NO2 Gas Sensing Properties of Multiple Networked ZnGa2O4 Nanorods Coated with TiO2.

PubMed

An, Soyeon; Park, Sunghoon; Ko, Hyunsung; Jin, Changhyun; Lee, Chongmu

2015-01-01

The NO2 gas sensing properties of ZnGa2O4-TiO2 heterostructure nanorods was examined. ZnGa2O4-core/TiO2-shell nanorods were fabricated by the thermal evaporation of a mixture of Zn and GaN powders and the sputter deposition of TiO2. Multiple networked ZnGa2O4-core/TiO2-shell nanorod sensors showed the response of 876% at 10 ppm NO2 at 300 degrees C. This response value at 10 ppm NO2 is approximately 4 times larger than that of bare ZnGa2O4 nanorod sensors. The response values obtained by the ZnGa2O4-core/TiO2-shell nanorods in this study are more than 13 times higher than those obtained previously by the SnO2-core/ZnO-shell nanofibers at 5% NO2. The significant enhancement in the response of ZnGa2O4 nanorods to NO2 gas by coating them with TiO2 can be explained based on the space-charge model.
Synthesis and properties of 2'-O-methyl-4'-thioRNA.

PubMed

Takahashi, Mayumi; Inoue, Naonori; Minakawa, Noriaki; Matsuda, Akira

2005-01-01

In this presentation, we will discuss the synthesis and properties of 2'-O-methyl-4'-thioRNA, an RNA molecule consisting of 2'-O-methyl-4'-thionucleosides. We first synthesized 2'-O-methyl-4'-thiouridine and -cytidine derivatives via 2,2'-O-anhydro-4'-thiouridine. The RNA consisting of 2'-O-methyl-4'-thiopyrimidine nucleosides and 2'-O-methylpurine nucleosides, 2'-OMe-4'-thioRNA, was synthesized on a DNA synthesizer according to the standard phosphoramidite protocol.
Enhanced photodegradation of 2,4-dichlorophenoxyacetic acid using a novel TiO2@MgFe2O4 core@shell structure.

PubMed

Huy, Bui The; Jung, Da-Som; Kim Phuong, Nguyen Thi; Lee, Yong-Ill

2017-10-01

A novel TiO 2 @MgO-Fe 2 O 3 core-shell structure has been synthesized via a hydrolysis and co-precipitation method followed by calcination at 500 °C and has proven to be an efficient photocatalyst. The obtained TiO 2 @MgO-Fe 2 O 3 core-shell was characterized by scanning electron microscopy, X-ray diffraction, and UV-Vis diffused reflectance techniques. Its photocatalytic activity toward 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated in aqueous solutions with and without visible light irradiation in the presence and absence of hydrogen peroxide. It was revealed that a strong electronic coupling exists between two components within the TiO 2 @MgO-Fe 2 O 3 core-shell structure. The present findings clearly highlight that TiO 2 @MgO-Fe 2 O 3 exhibits excellent photocatalytic activity under visible light irradiation in the presence of H 2 O 2 . More than 83% degradation of 2,4-D was observed within 240 min, at an initial concentration of 100 mg L -1 with 0.5 g of catalyst per liter. Moreover, the material showed high chemical stability after four consecutive experiments with no significant difference in the rate of photocatalytic degradation. Therefore, the results reported herein offer a green, low cost and highly efficient photocatalyst for environmental remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.
From {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} to {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite chains in A{sub 6}U{sub 2}Mo{sub 4}O{sub 21} (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagoubi, S.; Groupe de Radiochimie, Institut de Physique Nucleaire d'Orsay, Universite Paris-Sud XI, 91406 Orsay Cedex; Obbade, S., E-mail: said.obbade@phelma.grenoble-inp.f

2011-05-15

A new caesium uranyl molybdate belonging to the M{sub 6}U{sub 2}Mo{sub 4}O{sub 21} family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A{sub 6}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}], the caesium compound Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 21} should be written Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] crystallizes in the triclinic symmetry withmore » space group P1-bar and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, {alpha}=70.72(1){sup o}, {beta}=80.38(1){sup o} and {gamma}=86.39(1){sup o}, V=2604.7(6) A{sup 3}, Z=4, {rho}{sub mes}=5.02(2) g/cm{sup 3} and {rho}{sub cal}=5.08(3) g/cm{sup 3}. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R{sub 1}=0.0464 and wR{sub 2}=0.0950 for 596 parameters with 6964 independent reflections with I{>=}2{sigma}(I) collected on a BRUKER AXS diffractometer with Mo(K{alpha}) radiation and a CCD detector. The crystal structure of Cs compound is characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} parallels chains built from U{sub 2}O{sub 13} dimeric units, MoO{sub 4} tetrahedra and MoO{sub 5} square pyramids, whereas, Na, K and Rb compounds are characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} parallel chains formulated simply of U{sub 2}O{sub 13} units and MoO{sub 4} tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610
Liquid-phase deposition of TiO2 nanoparticles on core-shell Fe3O4@SiO2 spheres: preparation, characterization, and photocatalytic activity

NASA Astrophysics Data System (ADS)

Ma, Jian-Qi; Guo, Shao-Bo; Guo, Xiao-Hua; Ge, Hong-Guang

2015-07-01

To prevent and avoid magnetic loss caused by magnetite core phase transition involving in high-temperature crystallization of amorphous sol-gel TiO2, core-shell Fe3O4@SiO2@TiO2 composite spheres were synthesized via non-thermal process of TiO2. First, core-shell Fe3O4@SiO2 particles were synthesized through a solvothermal method followed by a sol-gel process. Second, anatase TiO2 nanoparticles (NPs) were directly coated on Fe3O4@SiO2 surface by liquid-phase deposition method, which uses (NH4)2TiF6 as Ti source for TiO2 and H3BO3 as scavenger for F- ions at 50 °C. The morphology, structure, composition, and magnetism of the resulting composites were characterized and their photocatalytic activities were also evaluated. The results demonstrate that TiO2 NPs with an average size of 6-8 nm were uniformly deposited on the Fe3O4@SiO2 surface. Magnetic hysteresis curves indicate that the composite spheres exhibit superparamagnetic characteristics with a magnetic saturation of 32.5 emu/g at room temperature. The magnetic TiO2 composites show high photocatalytic performance and can be recycled five times by magnetic separation without major loss of activity, which meant that they can be used as efficient and conveniently renewable photocatalyst.
Magnetic properties of mixed spinel BaTiO{sub 3}-NiFe{sub 2}O{sub 4} composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

2014-03-28

Solid solution of nickel ferrite (NiFe{sub 2}O{sub 4}) and barium titanate (BaTiO{sub 3}), (100-x)BaTiO{sub 3}–(x) NiFe{sub 2}O{sub 4} has been prepared by solid state reaction. Compressive strain is developed in NiFe{sub 2}O{sub 4} due to mutual structural interaction across the interface of NiFe{sub 2}O{sub 4} and BaTiO{sub 3} phases. Quantitative analysis of X-ray diffraction and X-ray photo electron spectrum suggest mixed spinel structure of NiFe{sub 2}O{sub 4}. A systematic study of composition dependence of composite indicates BaTiO{sub 3} causes a random distribution of Fe and Ni cations among octahedral and tetrahedral sites during non-equilibrium growth of NiFe{sub 2}O{sub 4}. Themore » degree of inversion decreases monotonically from 0.97 to 0.75 with increase of BaTiO{sub 3} content. Temperature dependence of magnetization has been analyzed by four sublattice model to describe complex magnetic exchange interactions in mixed spinel phase. Curie temperature and saturation magnetization decrease with increase of BaTiO{sub 3} concentration. Enhancement of strain and larger occupancy of Ni{sup 2+} at tetrahedral site increase coercivity up to 200 Oe. Magnetostructual coupling induced by BaTiO{sub 3} improves coercivity in NiFe{sub 2}O{sub 4}. An increase in the demagnetization and homogeneity in magnetization process in NiFe{sub 2}O{sub 4} is observed due to the interaction with diamagnetic BaTiO{sub 3}.« less
Highly visible-light-responsive Cu2O/rGO decorated with Fe3O4@SiO2 nanoparticles as a magnetically recyclable photocatalyst

NASA Astrophysics Data System (ADS)

Liu, Shou-Heng; Lu, Jun-Sheng; Yang, Sheng-Wei

2018-07-01

The rhombic dodecahedral cuprous oxide-reduced graphene oxide/core–shell Fe3O4@SiO2 composites (denoted as rCu2O-rGO/Fe3O4@SiO2) are successfully synthesized facilely via a wet-chemical route. The resulting rCu2O-rGO/Fe3O4@SiO2 combines the unique structure of Cu2O, electronic characteristics of reduced graphene oxide (rGO) and magnetic property of Fe3O4@SiO2 to be an effective and recoverable photocatalyst for the degradation of methyl orange (MO). The obtained results show that rCu2O-rGO/Fe3O4@SiO2 is capable of completely degrading MO in the presence of a very low catalyst concentration (0.125 g l‑1) within a short time (60 min) under visible light compared to the reported catalysts. The observations may be due to the distinctive interfacial structures of rhombic dodecahedral Cu2O nanoparticles connected to rGO sheets that can enhance the separation of photogenerated electron–hole pairs, stabilize the Cu2O and increase MO adsorption, as evidenced by a variety of spectroscopic analyses (transmission electron microscopy, x-ray photoelectron spectroscopy and photoluminescence). More importantly, these efficient photocatalysts can easily be recovered under a magnetic field and remain highly photoactive towards the degradation of MO after cyclic tests, and may be promising photocatalysts for practical applications in the solar-energy purification of wastewater.
Highly visible-light-responsive Cu2O/rGO decorated with Fe3O4@SiO2 nanoparticles as a magnetically recyclable photocatalyst.

PubMed

Liu, Shou-Heng; Lu, Jun-Sheng; Yang, Sheng-Wei

2018-07-27

The rhombic dodecahedral cuprous oxide-reduced graphene oxide/core-shell Fe 3 O 4 @SiO 2 composites (denoted as rCu 2 O-rGO/Fe 3 O 4 @SiO 2 ) are successfully synthesized facilely via a wet-chemical route. The resulting rCu 2 O-rGO/Fe 3 O 4 @SiO 2 combines the unique structure of Cu 2 O, electronic characteristics of reduced graphene oxide (rGO) and magnetic property of Fe 3 O 4 @SiO 2 to be an effective and recoverable photocatalyst for the degradation of methyl orange (MO). The obtained results show that rCu 2 O-rGO/Fe 3 O 4 @SiO 2 is capable of completely degrading MO in the presence of a very low catalyst concentration (0.125 g l -1 ) within a short time (60 min) under visible light compared to the reported catalysts. The observations may be due to the distinctive interfacial structures of rhombic dodecahedral Cu 2 O nanoparticles connected to rGO sheets that can enhance the separation of photogenerated electron-hole pairs, stabilize the Cu 2 O and increase MO adsorption, as evidenced by a variety of spectroscopic analyses (transmission electron microscopy, x-ray photoelectron spectroscopy and photoluminescence). More importantly, these efficient photocatalysts can easily be recovered under a magnetic field and remain highly photoactive towards the degradation of MO after cyclic tests, and may be promising photocatalysts for practical applications in the solar-energy purification of wastewater.
Understanding the role of Co3O4 on stability between active hierarchies and scaffolds: An insight into NiMoO4 composites for supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Yuanyuan; Zhang, Peng; Fu, Wenbin; Ma, Xiangwen; Zhou, Jinyuan; Zhang, Xiaojuan; Li, Jian; Xie, Erqing; Pan, Xiaojun

2017-09-01

It is often reported that pseudocapacitive electrodes' mechanical stability seriously limited their cycling performances in supercapacitors due to their quick fall off the electrode matrix during frequent fast charge/discharge process. In this work, we have demonstrated the mechanical enhancement in hierarchical NiMoO4 nanosheet arrays (NSAs) on free-standing substrates after introducing Co3O4 hierarchies. Under sonication vibration environment, the mechanical stability of Co3O4@NiMoO4 NSAs was enhanced by ∼70% compared to that of the pure NiMoO4 ones. Moreover, the Co3O4@NiMoO4 NSAs can display a high specific capacitance of 1476 F g-1 at the current density of 1 A g-1, and an excellent rate capability (keeping 81% at 20 A g-1). And after 2000 cycles, high capacitance retention of 96% was achieved for the Co3O4@NiMoO4 core/shell NSAs, while only 70% for the pure NiMoO4 ones.
Selectivity shifting behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires sensors

NASA Astrophysics Data System (ADS)

Arafat, M. M.; Ong, J. Y.; Haseeb, A. S. M. A.

2018-03-01

In this research, the gas sensing behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires were investigated. The Zn2SnO4/ZnO nanowires were grown on Au interdigitated alumina substrate by carbon assisted thermal evaporation process. Pd nanoparticles were loaded on the Zn2SnO4/ZnO nanowires by wet reduction process. The nanowires were characterized by X-ray diffractometer, field emission scanning electron microscope and energy dispersive X-ray spectroscope. The Zn2SnO4/ZnO and Pd nanoparticles loaded Zn2SnO4/ZnO nanowires were investigated for detecting H2, H2S and C2H5OH gases in N2 background. Results revealed that the average diameter and length of as-grown Zn2SnO4/ZnO nanowires were 74 nm and 30 μm, respectively. During wet reduction process,Pd particles having size of 20-60 nm were evenly distributed on the Zn2SnO4/ZnO nanowires. The Zn2SnO4/ZnO nanowires based sensors showed selective response towards C2H5OH whereas Pd nanoparticles loaded Zn2SnO4/ZnO nanowires showed selective response towards H2. The recovery time of the sensors reduced with Pd loading on Zn2SnO4/ZnO nanowires. A mechanism is proposed to elucidate the gas sensing mechanism of Pd nanoparticles loaded Zn2SnO4/ZnO nanowires.

Examination of the magnetic hyperthermia and other magnetic properties of CoFe2O4@MgFe2O4 nanoparticles using external field Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Park, Jeongho; Choi, Hyunkyung; Kim, Sam Jin; Kim, Chul Sung

2018-05-01

CoFe2O4@MgFe2O4 core/shell nanoparticles were synthesized by high temperature thermal decomposition with seed-mediated growth. The crystal structure and magnetic properties of the nanoparticles were investigated using X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and Mössbauer spectrometry. The magnetic hyperthermia properties were investigated using a MagneTherm device. Analysis of the XRD patterns showed that CoFe2O4@MgFe2O4 had a cubic spinel crystal structure with space group Fd-3m and a lattice constant (a0) of 8.3686 Å. The size and morphology of the CoFe2O4@MgFe2O4 nanoparticles were confirmed by HR-TEM. The VSM measurements showed that the saturation magnetization (MS) of CoFe2O4@MgFe2O4 was 77.9 emu/g. The self-heating temperature of CoFe2O4@MgFe2O4 was 37.8 °C at 112 kHz and 250 Oe. The CoFe2O4@MgFe2O4 core/shell nanoparticles showed the largest saturation magnetization value, while their magnetic hyperthermia properties were between those of the CoFe2O4 and MgFe2O4 nanoparticles. In order to investigate the hyperfine interactions of CoFe2O4, MgFe2O4, and CoFe2O4@MgFe2O4, we performed Mössbauer spectrometry at various temperatures. In addition, Mössbauer spectrometry of CoFe2O4@MgFe2O4 was performed at 4.2 K with applied fields of 0-4.5 T, and the results were analyzed with sextets for the tetrahedral A-site and sextets for the octahedral B-site.
Synergistic operation of photocatalytic degradation and Fenton process by magnetic Fe3O4 loaded TiO2

NASA Astrophysics Data System (ADS)

Sun, Qiong; Hong, Yong; Liu, Qiuhong; Dong, Lifeng

2018-02-01

The magnetic Fe3O4 loaded anatase TiO2 photocatalysts with different mass ratios were successfully synthesized by a one-step convenient calcining method. The morphology and structure analysis revealed that Fe3O4 was formed in TiO2 with very fine-grained particles. After a small amount of Fe3O4 loaded onto TiO2, the photocatalytic property enhanced obviously for the degradation of organic dye. Furthermore, the photo-Fenton-like catalysis of the iron-containing samples could also be induced after the addition of hydrogen peroxide. The apparent kinetic constant of the reaction that catalyzed by Fe-TiO2 was about 5.3 and 8.3 times of that catalyzed by TiO2 or Fe3O4 only, respectively, proving an effective synergistic contribution of the photocatalysis and Fenton reaction in the composite. Compared with Fe3O4 or free Fe3+ ions, only 13% of iron in TiO2 dissolved into acidic solution (25% for Fe3O4 and 100% for Fe3+) after the reaction, which confirmed the iron had been well immobilized onto TiO2. In addition, the extremely stable photocatalytic activity in cycling experiments proved the immobilized iron had been tightly attached onto TiO2, indicating the great potential of the catalyst for practical applications.
Na7Cr4(P2O7)4PO4

PubMed Central

Bourguiba Fakhar, Noura; Zid, Mohamed Faouzi; Driss, Ahmed

2013-01-01

The title compound, heptasodium tetrachromium(III) tetrakis(diphosphate) orthophosphate, was synthesized by solid-state reaction. Its structure is isotypic with that of Na7 M 4(P2O7)4PO4 (M = In, Al) compounds and is made up from a three-dimensional [(CrP2O7)4PO4]7− framework with channels running along [001]. The three Na+ cations are located in the voids of the framework. One of the cations is situated on a general position, one is equally disordered around a twofold rotation axis and one is on a fourfold rotoinversion axis. The isolated PO4 tetrahedron of the anionic framework is also situated on the -4 axis. Structural relationships between the title compound and different diphosphates containing MP2O11 units (M = Mo, V) are discussed. PMID:23723751
Preparation of Fe3O4/TiO2 magnetic mesoporous composites for photocatalytic degradation of organic pollutants.

PubMed

Zhang, Hongfeng; He, Xiu; Zhao, Weiwei; Peng, Yu; Sun, Donglan; Li, Hao; Wang, Xiaocong

2017-04-01

Fe 3 O 4 /TiO 2 magnetic mesoporous composites were synthesized through a sol-gel method with tetra-n-butyl titanate as precursor and surfactant P123 as template. The as-prepared Fe 3 O 4 /TiO 2 composites were characterized by X-ray diffraction, diffuse reflectance spectroscopy, nitrogen adsorption-desorption isotherm and pore size distribution. The as-synthesized products were applied as photocatalysis for the degradation of Acid Black ATT and tannery wastewater under UV lamp irradiation. Fe 3 O 4 /TiO 2 -8 composites containing Fe 3 O 4 of 8 wt% were selected as model catalysts. The optimal catalyst dosage was 3 g/L in this photocalytic system. The magnetic Fe 3 O 4 /TiO 2 composites possessed good photocatalytic stability and durability. This approach may provide a platform to prepare a magnetic composite to optimize the catalytic ability.
Zn0-CNTs-Fe3O4 catalytic in situ generation of H2O2 for heterogeneous Fenton degradation of 4-chlorophenol.

PubMed

Yang, Zhao; Gong, Xiao-Bo; Peng, Lin; Yang, Dan; Liu, Yong

2018-06-04

A novel Zn 0 -CNTs-Fe 3 O 4 composite was synthesized by the chemical co-precipitation combined with high sintering process at nitrogen atmosphere. The as-prepared composite was characterized by SEM, EDS, XRD, XPS, VSM and N 2 adsorption/desorption experiments. A novel heterogeneous Fenton-like system, composed of Zn 0 -CNTs-Fe 3 O 4 composite and dissolved oxygen (O 2 ) in solution, which can in situ generate H 2 O 2 and OH, was used for the degradation of 4-chlorophenol (4-CP). The influences of various operational parameters, including the initial pH, dosage of Zn 0 -CNTs-Fe 3 O 4 and initial concentration of 4-CP on the removal of 4-CP were investigated. The removal efficiencies of 4-CP and total organic carbon (TOC) were 99% and 57%, respectively, at the initial pH of 1.5, Zn 0 -CNTs-Fe 3 O 4 dosage of 2 g/L, 4-CP initial concentration of 50 mg/L and oxygen flow rate of 400 mL/min. Based on the results of the radical scavenger effect study, the hydroxyl radical was considered as the main reactive oxidants in Zn 0 -CNTs-Fe 3 O 4 /O 2 system and a possible degradation pathway of 4-CP was proposed. Copyright © 2018. Published by Elsevier Ltd.
Hilarionite, Fe{2/3+}(SO4)(AsO4)(OH) · 6H2O, a new supergene mineral from Lavrion, Greece

NASA Astrophysics Data System (ADS)

Pekov, I. V.; Chukanov, N. V.; Yapaskurt, V. O.; Rusakov, V. S.; Belakovsky, D. I.; Turchkova, A. G.; Voudouris, P.; Magganas, A.; Katerinopoulos, A.

2014-12-01

A new mineral, hilarionite, ideally Fe{2/3+} (SO4)(AsO4)(OH) · 6H2O, has been found in the Hilarion Mine, Agios Konstantinos, Kamariza, Lavrion district, Attiki Prefecture, Greece. It was formed in the oxidation zone of a sulfide-rich orebody in association with goethite, gypsum, bukovskyite, jarosite, melanterite, chalcanthite, allophane, and azurite. Hilarionite occurs as light green (typically with an olive or grayish tint) to light yellowish green spherulites (up to 1 mm in size) and bunches of prismatic to acicular "individuals" up to 0.5 mm long that are in fact near-parallel or divergent aggregates of very thin, curved fibers up to 0.3 mm long and usually lesser than 2 μm thick. The luster is silky to vitreous. The Mohs' hardness is ca. 2. Hilarionite is ductile, its "individuals" are flexible and inelastic; fracture is uneven or splintery. D(meas) = 2.40(5), D(calc) = 2.486 g/cm3. IR spectrum shows the presence of arsenate and sulfate groups and H2O molecules in significant amounts. The Mössbauer spectrum indicates the presence of Fe3+ at two six-fold coordinated sites and the absence of Fe2+. Hilarionite is optically biaxial (+), α = 1.575(2), γ = 1.64(2), 2 V is large. The chemical composition (electron microprobe, average of 7 point analyses; H2O determined by modified Penfield method) is as follows, wt %: 0.03 MnO, 0.18 CuO, 0.17 ZnO, 33.83 Fe2O3, 0.22 P2O5, 18.92 As2O5, 22.19 SO3, 26.3 H2O, total is 101.82%. The empirical formula calculated on the basis of 15 O is: (Fe{1.90/3+}Cu0.01Zn0.01)Σ1.92[(SO4)1.24(AsO4)0.74(PO4)0.01]Σ1.99(OH)1.01 · 6.03H2O. The X-ray powder diffraction data show close structural relationship of hilarionite and kaňkite, Fe{2/3+}(AsO4)2 · 7H2O. Hilarionite is monoclinic, space group C2/ m, Cm or C2, a = 18.53(4), b = 17.43(3), c = 7.56(1) Å, β = 94.06(15)°, V = 2436(3) Å3, Z = 8. The strongest reflections in the X-ray powder diffraction pattern ( d, Å- I[ hkl]) are: 12.66-100[110], , 5.00-10[22l], , 4
A study of Na(x)Pt3O4 as an O2 electrode bifunctional electrocatalyst

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph

1991-01-01

The present study suggests that polytetrafluoroethylene (PTFE) bonded Na(X)Pt3O4 gas porous diffusion electrodes may be a viable candidate for bifunctional O2 reduction and evolution activity. The electrodes exhibited Tafel slopes of about 0.06 V/decade for both O2 reduction an evolution. For O2 reduction, the 0.06 slope doubled to 0.12 V/decade at larger current densities. Preliminary stability testing at 24 C suggest that the Na(x)Pt3O4 electrodes were relatively stable at reducing and oxidizing potentials typically encountered at the O2 electrodes in a regenerative fuel cell.
Electronic structures of C u 2 O , C u 4 O 3 , and CuO: A joint experimental and theoretical study

DOE PAGES

Wang, Y.; Lany, S.; Ghanbaja, J.; ...

2016-12-14

We present a joint experimental and theoretical study for the electronic structures of copper oxides including Cu 2O, CuO, and the metastable mixed-valence oxide Cu 4O 3. The optical band gap is determined by experimental optical absorption coefficient, and the electronic structure in valence and conduction bands is probed by photoemission and electron energy loss spectroscopies, respectively. Furthermore, we compare our experimental results with many-body GW calculations utilizing an additional on-site potential for d-orbital energies that facilitates tractable and predictive computations. The side-by-side comparison between the three oxides, including a band insulator (Cu2O) and two Mott/charge-transfer insulators (CuO, Cu 4Omore » 3) leads to a consistent picture for the optical and band-structure properties of the Cu oxides, strongly supporting indirect band gaps of about 1.2 and 0.8 eV in CuO and Cu 4O 3, respectively. This comparison also points towards surface oxidation and reduction effects that can complicate the interpretation of the photoemission spectra.« less
Uniform Fe3O4 coating on flower-like ZnO nanostructures by atomic layer deposition for electromagnetic wave absorption.

PubMed

Wan, Gengping; Wang, Guizhen; Huang, Xianqin; Zhao, Haonan; Li, Xinyue; Wang, Kan; Yu, Lei; Peng, Xiange; Qin, Yong

2015-11-21

An elegant atomic layer deposition (ALD) method has been employed for controllable preparation of a uniform Fe3O4-coated ZnO (ZnO@Fe3O4) core-shell flower-like nanostructure. The Fe3O4 coating thickness of the ZnO@Fe3O4 nanostructure can be tuned by varying the cycle number of ALD Fe2O3. When serving as additives for microwave absorption, the ZnO@Fe3O4-paraffin composites exhibit a higher absorption capacity than the ZnO-paraffin composites. For ZnO@500-Fe3O4, the effective absorption bandwidth below -10 dB can reach 5.2 GHz and the RL values below -20 dB also cover a wide frequency range of 11.6-14.2 GHz when the coating thickness is 2.3 mm, suggesting its potential application in the treatment of the electromagnetic pollution problem. On the basis of experimental observations, a mechanism has been proposed to understand the enhanced microwave absorption properties of the ZnO@Fe3O4 composites.
Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

NASA Astrophysics Data System (ADS)

Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

2015-06-01

Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.
Fabrication of Fe3O4@CuO core-shell from MOF based materials and its antibacterial activity

NASA Astrophysics Data System (ADS)

Rajabi, S. K.; Sohrabnezhad, Sh.; Ghafourian, S.

2016-12-01

Magnetic Fe3O4@CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe3O4@HKUST-1 in air atmosphere. The morphology, structure, magnetic and porous properties of the as-synthesized nano composites were characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and vibration sample magnetometer (VSM). The results showed that the nanocomposite material included a Fe3O4 core and a CuO shell. The Fe3O4@CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe3O4-CuO core-shell was investigated against gram-positive and gram-negative bacteria. A new mechanism was proposed for inactivation of bacteria over the prepared sample. It was demonstrated that the core-shell exhibit recyclable antibacterial activity, acting as an ideal long-acting antibacterial agent.
Chemoselectivity-induced multiple interfaces in MWCNT/Fe3O4@ZnO heterotrimers for whole X-band microwave absorption.

PubMed

Wang, Zhijiang; Wu, Lina; Zhou, Jigang; Jiang, Zhaohua; Shen, Baozhong

2014-11-07

A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band.
Thermodynamic Properties of α-Fe 2O 3 and Fe 3O 4 Nanoparticles

DOE PAGES

Spencer, Elinor C.; Ross, Nancy L.; Olsen, Rebecca E.; ...

2015-04-21

Here we comprehansively assessed the thermodynamic properties of hydrated α-Fe 2O 3 (hematite) and Fe 3O 4 (magnetite) nanoparticles. In addition to 9 nm Fe 3O 4, three α-e 2O 3nanoparticles samples of different sizes (11, 14, and 25 nm) and bulk α-e 2O 3 have been evaluated by inelastic neutron scattering methods. The contribution of the two-level magnetic spin flip transition to the heat capacity of the α-e 2O 3 particles has been determined. The isochoric heat capacity of the water confined on the surface of these two types of iron oxide particles have been calculated from their INSmore » spectra, and is affected by the chemical composition of the underlying particle. Furthermore, the heat capacity and dynamics of the particle hydration layers appear to be influenced by a complex array of factors including particle size, water coverage, and possibly the magnetic state of the particle itself.« less
Spin-Coating and Characterization of Multiferroic MFe2O4 (M=Co, Ni) / BaTiO3 Bilayers

NASA Astrophysics Data System (ADS)

Quandt, Norman; Roth, Robert; Syrowatka, Frank; Steimecke, Matthias; Ebbinghaus, Stefan G.

2016-01-01

Bilayer films of MFe2O4 (M=Co, Ni) and BaTiO3 were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO3. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm-3 for the CoFe2O4/BaTiO3 and 188 emu cm-3 for the NiFe2O4/BaTiO3 bilayer, respectively were found. For the CoFe2O4/BaTiO3 bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe2O4/BaTiO3 bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems.
TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater.

PubMed

Santiago, Dunia E; Pastrana-Martínez, Luisa M; Pulido-Melián, Elisenda; Araña, Javier; Faria, Joaquim L; Silva, Adrián M T; González-Díaz, Óscar; Doña-Rodríguez, José M

2018-03-02

Magnetite (Fe 3 O 4 ), a core-shell material (SiO 2 @Fe 3 O 4 ), and reduced graphene oxide-Fe 3 O 4 (referred as rGO-MN) were used as supports of a specific highly active TiO 2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N 2 ), and TiO 2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO 2 @Fe 3 O 4 material-or a N 2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO 2 -based catalysts (the magnetic properties being preserved). The materials treated with N 2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L -1 , i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO 2 @Fe 3 O 4 , an intermediate TiO 2 :support ratio (1.5), and treated at 200 °C under N 2 atmosphere (i.e., SiO 2 @Fe 3 O 4 -EST-1.5-200-N 2 ). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH 0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO 2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L -1 ), added H 2 O 2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO 2 .
Enhanced electrical properties of SrBi4Ti4O15 ceramic with addition of ZrO2

NASA Astrophysics Data System (ADS)

Mamatha, B.; Rani, G. Neeraja; Shankar, J.

2018-04-01

Polycrystalline SrBi4Ti3.95Zr0.05O15 (SBZT) ceramic was prepared by solid-state double sintering method. It was characterized by X-Ray Diffraction (XRD) and Scanning Electron Micrograph (SEM). With the increased addition of ZrO2, the electrical properties as dielectric, ferroelectric and piezoelectric were studied. From XRD, single-phase formation with orthorhombic structure was identified by the increase of ZrO2. The remnant polarization (Pr) and dielectric constant was found to be increased with the increase of ZrO2. With the increase of ZrO2, Curie temperature (Tc) was found to be decreased. The planar electromechanical coupling coefficient (Kp = 0.57) and Piezoelectric coefficient (d33 = 18 pC/N) was found to be increased with the increase of ZrO2.
Surface modification of layered perovskite Sr2TiO4 for improved CO2 photoreduction with H2O to CH4.

PubMed

Kwak, Byeong Sub; Do, Jeong Yeon; Park, No-Kuk; Kang, Misook

2017-11-27

Layered perovskite Sr 2 TiO 4 photocatalyst was synthesized by using sol-gel method with citric acid. In order to increase the surface area of layered perovskite Sr 2 TiO 4 , and thus to improve its photocatalytic activity for CO 2 reduction, its surface was modified via hydrogen treatment or exfoliation. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping analysis, energy-dispersive X-ray spectroscopy, N 2 adsorption-desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electrophoretic light scattering. CO 2 photoreduction was performed in a closed reactor under 6 W/cm 2 UV irradiation. The gaseous products were analyzed using a gas chromatograph equipped with flame ionization and thermal conductivity detectors. The exfoliated Sr 2 TiO 4 catalyst (E-Sr 2 TiO 4 ) exhibited a narrow band gap, a large surface area, and high dispersion. Owing to these advantageous properties, E-Sr 2 TiO 4 photocatalyst showed an excellent catalytic performance for CO 2 photoreduction reaction. The rate of CH 4 production from the photoreduction of CO 2 with H 2 O using E-Sr 2 TiO 4 was about 3431.77 μmol/g cat after 8 h.
Electrochemical performance of La2O3/Li2O/TiO2 nano-particle coated cathode material LiFePO4.

PubMed

Wang, Hong; Yang, Chi; Liu, Shu-Xin

2014-09-01

Cathode material, LiFePO4 was modified by coating with a thin layer of La2O3/Li2O/TiO2 nano-particles for improving its performance for lithium ion batteries. The morphology and structure of the modified cathode material were characterized by powder X-ray diffraction, scanning electron microcopy and AES. The performance of the battery with the modified cathode material, including cycling stability, C-rate discharge was examined. The results show that the battery composed of the coated cathode materials can discharge at a large current density and show stable cycling performance in the range from 2.5 to 4.0 V. The rate of Li ion diffusion increases in the battery with the La2O3/Li2O/TiO2-coated LiFePO4 as a cathode and the coating layer may acts as a faster ion conductor (La(2/3-x)Li(3x)TiO3).
Astronomical Perception of the Secondary School's Students in São Paulo's State School in Suzano City. (Spanish Title: Percepción Astronómica de Alumnos de la Enseñanza Media de la Red Estatal de San Pablo en la Ciudad de Suzano.) Percepção Astronômica de um Grupo de Alunos do Ensino Médio da Rede Estadual de São Paulo da Cidade de Suzano

NASA Astrophysics Data System (ADS)

França de Oliveira, Edilene; Voelzke, Marcos Rincon; Amaral, Luis Henrique

2007-12-01

año y 20,6% tenían la idea de cuales son los objetos celestes más cercanos de la Tierra. En contraposición, 67,6% clasificaron correctamente el Sol como una estrella; 55,9% relacionaron el Big Bang al origen del Universo; solamente 20,6% identificaron un año-luz como unidad de distancia y 32,4% reconocieron una estrella fugaz como meteoro. El presente análisis fue expandido para otros grupos de la Enseñanza Media, no solamente del período nocturno, sino también diurno de la misma escuela. En esta primera fase se nota el pequeño conocimiento de los alumnos sobre eventos astronómicos y principalmente la gran confusión sobre el significado correcto de los términos astronómicos populares. Embora a Astronomia seja uma das ciências mais antigas da humanidade e muitos dos conceitos astronômicos serem populares, observa-se que uma parcela significativa dos estudantes encontra-se à margem dessas informações. O presente trabalho visa analisar o nível de conhecimento básico dos alunos do Ensino Médio da Rede Estadual da cidade de Suzano quanto aos fenômenos astronômicos que os rodeiam. Para tanto foi elaborado um formulário constando de questões de múltipla escolha, aplicado no primeiro ano noturno da Escola Estadual Batista Renzi. Num espaço amostral de 34 alunos constatou-se que apenas 29,4% compreendiam a sucessão dos dias; 20,6% explicaram corretamente as estações do ano e 20,6% tinham idéia de quais são os objetos celestes mais próximos da Terra. Em contraposição, 67,6% classificaram corretamente o Sol como estrela; 55,9% relacionaram o Big Bang à origem do Universo; apenas 20,6% identificaram um ano-luz como unidade de distância e 32,4% reconheceram uma estrela cadente como meteoro. A presente análise foi expandida para mais 310 alunos de outras classes de Ensino Médio, não somente do período noturno, mas também diurno da mesma escola. Nesta primeira fase nota-se o pequeno discernimento dos alunos sobre eventos astronômicos e
Folate conjugated Mn{sub 3}O{sub 4}@SiO{sub 2} nanoparticles for targeted magnetic resonance imaging in vivo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xinyi; Zhou, Zhiguo, E-mail: zgzhou@shnu.edu.cn; Wang, Li

2014-09-15

Graphical abstract: The Mn{sub 3}O{sub 4}@SiO{sub 2}(PEG)–FA has been used as a T{sub 1}-MRI probe for in vivo. - Highlights: • The PEG and FA modified Mn{sub 3}O{sub 4}@SiO{sub 2} nanoparticles (Mn{sub 3}O{sub 4}@SiO{sub 2}–FA) were prepared. • Mn{sub 3}O{sub 4}@SiO{sub 2}–FA exhibited the good colloidal stability in the simulated biological medium. • Mn{sub 3}O{sub 4}@SiO{sub 2}–FA showed the targeting ability to HeLa cells overexpressed the FA receptor. • The T{sub 1}-weighted magnetic resonance (MR) imaging demonstrated the targeting ability of Mn{sub 3}O{sub 4}@SiO{sub 2}–FA in vivo tumor. - Abstract: The monodisperse silica-coated manganese oxide nanoparticles (Mn{sub 3}O{sub 4}@SiO{sub 2}more » NPs) were synthesized via the high temperature pyrolysis approach and were aminated through silanization. The amine-functionalized Mn{sub 3}O{sub 4} NPs enabled the covalent conjugation of hydrophilic methoxypoly(ethylene glycol) (PEG) and the targeting ligand of folate (FA) onto their surface. The formed PEG and FA modified Mn{sub 3}O{sub 4} NPs (Mn{sub 3}O{sub 4}@SiO{sub 2}(PEG)–FA) exhibited the good colloidal stability in the simulated biological medium and the targeting ability to HeLa cells overexpressed the FA receptor. The T{sub 1}-weighted magnetic resonance (MR) imaging and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis of Mn{sub 3}O{sub 4}@SiO{sub 2}(PEG)–FA NPs further demonstrated their targeting ability in tumor.« less

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

NASA Astrophysics Data System (ADS)

Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.
Exploring the Neither in João Pedro Rodrigues and João Rui Guerra Da Mata's "A ultima vez que vi Macau"

ERIC Educational Resources Information Center

ten Haaf, Rachel

2017-01-01

Torn between two colonial powers, Macau has long existed as a peripheral region in Lusophone studies. This current study explores João Pedro Rodrigues and João Rui Guerra da Mata's 2012 film "A ultima vez que vi Macau". With a focus on a contemporary Macau that seeks to resolve its fundamental duality through investigation of gender,…
Construction of viscosity diagrams for CaO-SiO2-Al2O3-8% MgO-4% B2O3 slags by the simplex lattice method

NASA Astrophysics Data System (ADS)

Babenko, A. A.; Istomin, S. A.; Zhuchkov, V. I.; Sychev, A. V.; Ryabov, V. V.; Upolovnikova, A. G.

2017-05-01

The simplex lattice method of planning experiments is used to study the viscosities of CaO-SiO2-Al2O3-8% MgO-4% B2O3 slags in a wide chemical composition range. For each viscosity, we developed an adequate mathematical model in the form of a reduced third-order polynomial. The results of mathematical simulation are presented in composition-viscosity diagrams. Composition regions with a high fluidity of slags, the viscosities of which are 0.8-1.2 Pa s in the temperature range 1500-1600°C, are indicated in the diagrams.
Polar materials with isolated V 4+ S = 1/2 Triangles: NaSr 2V 3O 3(Ge 4O 13)Cl and KSr 2V 3O 3(Ge 4O 13)Cl

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanjeewa, Liurukara D.; McGuire, Michael A.; McMillen, Colin D.

Here, crystals of ASr 2V 3O 3(Ge 4O 13)Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V 4+ ( S = 1/2) trimer magnetic clusters. The structures consist of a trimeric V 3O 13 unit based on V 4+ ( S = 1/2), having rigorous 3-fold symmetry with a short V–V separation of 3.325(3) Å. The trinuclear V 4+ units are formed by three edge shared VO 6 octahedra sharing a centralmore » μ3-oxygen atom, which also imparts a polar sense on the structure. The V 3O 13 units are isolated from one another by tetranuclear Ge 4O 13 units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular d 1 system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V 3 trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure–property relationships via chemistry involving unconventional solvents and reaction conditions.« less
Polar materials with isolated V 4+ S = 1/2 Triangles: NaSr 2V 3O 3(Ge 4O 13)Cl and KSr 2V 3O 3(Ge 4O 13)Cl

DOE PAGES

Sanjeewa, Liurukara D.; McGuire, Michael A.; McMillen, Colin D.; ...

2017-01-03

Here, crystals of ASr 2V 3O 3(Ge 4O 13)Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V 4+ ( S = 1/2) trimer magnetic clusters. The structures consist of a trimeric V 3O 13 unit based on V 4+ ( S = 1/2), having rigorous 3-fold symmetry with a short V–V separation of 3.325(3) Å. The trinuclear V 4+ units are formed by three edge shared VO 6 octahedra sharing a centralmore » μ3-oxygen atom, which also imparts a polar sense on the structure. The V 3O 13 units are isolated from one another by tetranuclear Ge 4O 13 units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular d 1 system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V 3 trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure–property relationships via chemistry involving unconventional solvents and reaction conditions.« less
Facile synthesis of CuFe2O4-Fe2O3 composite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Khan, Rashid; Habib, Muhammad; Gondal, Mohammed A.; Khalil, Adnan; Rehman, Zia Ur; Muhammad, Zahir; Haleem, Yasir A.; Wang, Changda; Wu, Chuan Qiang; Song, Li

2017-10-01

We report the synthesis of CuFe2O4-Fe2O3 composite material for efficient and highly stable supercapacitor electrode by using eco-friendly low-temperature co-precipitation method. The CuFe2O4-Fe2O3 composite demonstrated the highest specific capacitance of 638.24 F g-1 and excellent stability up to 2000 charge/discharge cycles. The achieved capacitance value is 16 times higher than that of pure CuFe2O4. The results revealed the extraordinary performance of CuFe2O4-Fe2O3 composite as supercapacitor electrode with excellent retention in comparison to CuFe2O4. The enhanced electrochemical activity of CuFe2O4-Fe2O3 composite is attributed to the synergistic effect which is responsible for redox coupling between Cu2+ and Fe3+ that has never been achieved by single component before.
Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Kamran, M.; Ullah, Asmat; Mehmood, Y.; Nadeem, K.; Krenn, H.

2017-02-01

Effect of silica (SiO2) coating concentration on structural and magnetic properties of multiferroic cobalt chromite (CoCr2O4) nanoparticles have been studied. The nanoparticles with average crystallite size in the range 19 to 28 nm were synthesised by sol-gel method. X-ray diffraction (XRD) analysis has verified the composition of single-phase cubic normal spinel structure of CoCr2O4 nanoparticles. The average crystallite size and cell parameter decreased with increasing SiO2 concentration. TEM image revealed that the shape of nanoparticles was non-spherical. Zero field cooled/field cooled (ZFC/FC) curves revealed that nanoparticles underwent a transition from paramagnetic (PM) state to collinear short-range ferrimagnetic (FiM) state, and this PM-FiM transition temperature decreased from 101 to 95 K with increasing SiO2 concentration or decreasing crystallite size. A conical spin state at Ts = 27 K was also observed for all the samples which decreased with decreasing average crystallite size. Low temperature lock-in transition was also observed in these nanoparticles at 12 K for uncoated nanoparticles which slightly shifted towards low temperature with decreasing average crystallite size. Saturation magnetization (Ms) showed decreasing trend with increasing SiO2 concentration, which was due to decrease in average crystallite size of nanoparticles and enhanced surface disorder in smaller nanoparticles. The temperature dependent AC-susceptibility also showed the decrease in the transition temperature (Tc), broadening of the Tc peak and decrease in magnetization with increasing SiO2 concentration or decreasing average crystallite size. In summary, the concentration of SiO2 has significantly affected the structural and magnetic properties of CoCr2O4 nanoparticles.
Production of nearly monodisperse Fe3O4 and Fe@Fe3O4 nanoparticles in aqueous medium and their surface modification for biomedical applications

NASA Astrophysics Data System (ADS)

Tegafaw, Tirusew; Xu, Wenlong; Lee, Sang Hyup; Chae, Kwon Seok; Chang, Yongmin; Lee, Gang Ho

2017-02-01

Iron (Fe)-based nanoparticles are extremely valuable in biomedical applications owing to their low toxicity and high magnetization values at room temperature. In this study, we synthesized nearly monodisperse iron oxide (Fe3O4) and Fe@Fe3O4 (core: Fe, shell: Fe3O4) nanoparticles in aqueous medium under argon flow and then, coated them with various biocompatible ligands and silica. In this study, eight types of surface-modified nanoparticles were investigated, namely, Fe3O4@PAA (PAA = polyacrylic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PAA-FA (FA = folic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PEI-fluorescein (PEI = polyethylenimine; Mw of PEI = 1300 amu), Fe@Fe3O4@PEI (Mw of PEI = 10,000 amu), Fe3O4@SiO2 and Fe@Fe3O4@SiO2 nanoparticles. We characterized the prepared surface-modified nanoparticles using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) absorption spectroscopy, a superconducting quantum interference device (SQUID), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and confocal microscopy. Finally, we measured the cytotoxicity of the samples. The results indicate that the surface-modified nanoparticles are biocompatible and are potential candidates for various biomedical applications.
Mesoporous Cu2O-CeO2 composite nanospheres with enhanced catalytic activity for 4-nitrophenol reduction

NASA Astrophysics Data System (ADS)

Pang, Juanjuan; Li, Wenting; Cao, Zhenhao; Xu, Jingjing; Li, Xue; Zhang, Xiaokai

2018-05-01

In this paper, mesoporous Cu2O-CeO2 nanospheres were fabricated via a facile, low-temperature solution route in the presence of poly(2-vinylpyridine)-b-poly(ethylene Oxide) (P2VP-b-PEO) block copolymers. The prepared mesoporous Cu2O-CeO2 nanospheres were characterized systematically by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption. The formation mechanism of mesoporous Cu2O-CeO2 nanospheres was discussed. The results show that the molar ratios of Ce3+/Cu2+ and the reaction time have an important influence on the nanostructure of Cu2O-CeO2 composite spheres. The resultant Cu2O-CeO2 nanospheres exhibit superior catalytic activities in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. The activity factor (K = k/m) for the Cu2O-CeO2 nanospheres prepared with the molar ratio of Ce3+/Cu2+ of 5/1 is 3006.6 s-1 g-1, which is much higher than reported values. This paper demonstrates a highly controllable approach to the production of mesoporous Cu2O-CeO2 nanospheres, which have potential applications in the areas of catalysis, adsorption, sensors and so on.
Enhanced ferromagnetic order in Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} featuring canted [MnO{sub 4}]{sub ∞} spin chains of mixed-valent Mn(III)/Mn(IV). Aliovalent substitution of the Sr{sub 4−x}Ln{sub x}Mn{sup III}{sub 2+x}Mn{sup IV}{sub 1−x}O{sub 3}(GeO{sub 4}){sub 3} solid-solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, J. Palmer; Sulejmanovic, Dino; Becht, Gregory

2013-10-15

Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{submore » 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1�
Tailoring the nickel nanoparticles anchored on the surface of Fe3O4@SiO2 spheres for nanocatalysis.

PubMed

Ding, Lei; Zhang, Min; Zhang, Yanwei; Yang, Jinbo; Zheng, Jing; Hayat, Tasawar; Alharbi, Njud S; Xu, Jingli

2017-08-25

Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured Fe 3 O 4 @SiO 2 @C-Ni hybrid composite. Firstly, the Fe 3 O 4 cores were synthesized by hydrothermal reaction, and sequentially coated with SiO 2 and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni 2+ ) using an extended Stöber method. This was followed by carbonization to produce the Fe 3 O 4 @SiO 2 @C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO 2 spacer layer between RF-Ni 2+ and Fe 3 O 4 plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of Fe 3 O 4 @SiO 2 nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO 2 spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO 2 layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).
Synthesis of scaly Sn3O4/TiO2 nanobelt heterostructures for enhanced UV-visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Chen, Guohui; Ji, Shaozheng; Sang, Yuanhua; Chang, Sujie; Wang, Yana; Hao, Pin; Claverie, Jerome; Liu, Hong; Yu, Guangwei

2015-02-01

A novel scaly Sn3O4/TiO2 nanobelt heterostructured photocatalyst was fabricated via a facile hydrothermal route. The scaly Sn3O4 nanoflakes can be synthesized in situ and assembled on surface coarsened TiO2 nanobelts through a hydrothermal process. The morphology and distribution of Sn3O4 nanoflakes can be well-controlled by simply tuning the Sn/Ti molar ratio of the reactants. Compared with single phase nanostructures of Sn3O4 and TiO2, the scaly hybrid nanobelts exhibited markedly enhanced photoelectrochemical (PEC) response, which caused higher photocatalytic hydrogen evolution even without the assistance of Pt as a co-catalyst, and enhanced the degradation ability of organic pollutants under both UV and visible light irradiation. In addition to the increased exposure of active facets and broad light absorption, the outstanding performance is ascribed to the matching energy band structure between Sn3O4 and TiO2 at the two sides of the heterostructure, which efficiently reduces the recombination of photo-excited electron-hole pairs and prolongs the lifetime of charge carriers. Both photocatalytic assessment and PEC tests revealed that Sn3O4/TiO2 heterostructures with a molar ratio of Sn/Ti of 2/1 exhibited the highest photocatalytic activity. This study provides a facile and low-cost method for the large scale production of Sn3O4 based materials in various applications.A novel scaly Sn3O4/TiO2 nanobelt heterostructured photocatalyst was fabricated via a facile hydrothermal route. The scaly Sn3O4 nanoflakes can be synthesized in situ and assembled on surface coarsened TiO2 nanobelts through a hydrothermal process. The morphology and distribution of Sn3O4 nanoflakes can be well-controlled by simply tuning the Sn/Ti molar ratio of the reactants. Compared with single phase nanostructures of Sn3O4 and TiO2, the scaly hybrid nanobelts exhibited markedly enhanced photoelectrochemical (PEC) response, which caused higher photocatalytic hydrogen evolution even without the
A rapid procedure for the detection and isolation of enterohaemorrhagic Escherichia coli (EHEC) serogroup O26, O103, O111, O118, O121, O145 and O157 strains and the aggregative EHEC O104:H4 strain from ready-to-eat vegetables.

PubMed

Tzschoppe, Markus; Martin, Annett; Beutin, Lothar

2012-01-03

Human infections with Enterohaemorrhagic Escherichia coli strains (EHEC) as agents of Haemorrhagic Colitis (HC) and Haemolytic Uraemic Syndrome (HUS) are frequently associated with the consumption of EHEC contaminated foodstuffs of different origins. EHEC O26, O103, O111, O118, O121, O145 and O157 strains are responsible for the majority of HC and HUS cases worldwide. In May 2011, the emerging aggregative EHEC O104:H4 strain caused a large outbreak with high HUS incidence in northern Germany. Contaminated sprouted seeds were suspected to be the vehicles of transmission. The examination of vegetables retailed for raw consumption revealed low numbers of E. coli (<100 cfu/g) together with high titres of Enterobacteriaceae and Pseudomonas (approx. 5.6 × 10⁷ cfu/g). Specific methods of EHEC detection adapted to vegetables are not yet published. Therefore, we have developed a rapid and sensitive method for detecting low EHEC contamination in vegetables (1-10 cfu/25 g) with artificially EHEC contaminated ready-to-eat salads. A 6-hour enrichment period in BRILA-broth was sufficient to detect 1-10 EHEC from spiked samples after plating 0.1 ml portions of enrichment culture on selective TBX-agar and CHROMagar STEC plates that were incubated at 44 °C overnight. Unlike EHEC strains, the growth of bacteria of the plant flora was substantially inhibited at 44 °C. DNA for real-time PCR detection of EHEC characteristic genes (stx(1), stx(2), eae, ehxA, and O-antigen associated) was prepared with bacteria grown on TBX-agar plates. The storage of EHEC inoculated salad samples for 72 h at 6 °C resulted in a significant reduction (mean value 14.6%) of detectable EHEC, suggesting interference of EHEC with the resident plant microflora. CHROMagar STEC was evaluated as a selective medium for the detection of EHEC strains. Growth on CHROMagar STEC was closely associated with EHEC O26:[H11], O111:[H8], O118:H16, O121:[H19], O145:[H28], O157:[H7] and aggregative EHEC O104:H4 strains
Corrosion Behavior of Alloy 625 in PbSO4-Pb3O4-PbCl2-ZnO-10 Wt Pct CdO Molten Salt Medium

NASA Astrophysics Data System (ADS)

Mohammadi Zahrani, E.; Alfantazi, A. M.

2012-08-01

Corrosion behavior and degradation mechanisms of alloy 625 under a 47.288 PbSO4-12.776 Pb3O4-6.844PbCl2-23.108ZnO-10CdO (wt pct) molten salt mixture under air atmosphere were studied at 873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C). Electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) measurements, and potentiodynamic polarization techniques were used to evaluate the degradation mechanisms and characterize the corrosion behavior of the alloy. Morphology, chemical composition, and phase structure of the corrosion products and surface layers of the corroded specimens were studied by scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) and X-ray map analyses. Results confirmed that during the exposure of alloy 625 to the molten salt, chromium was mainly dissolved through an active oxidation process as CrO3, Cr2O3, and CrNbO4, while nickel dissolved only as NiO in the system. Formation of a porous and nonprotective oxide layer with low resistance is responsible for the weak protective properties of the barrier layer at high temperatures of 973 K and 1073 K (700 °C and 800 °C). There were two kinds of attack for INCONEL 625, including general surface corrosion and pitting. Pitting corrosion occurred due to the breakdown of the initial oxide layer by molten salt dissolution of the oxide or oxide cracking.
Low-temperature molar heat capacities and entropies of MnO2 (pyrolusite), Mn3O4 (hausmanite), and Mn2O3 (bixbyite)

USGS Publications Warehouse

Robie, R.A.; Hemingway, B.S.

1985-01-01

Pyrolusite (MnO2), hausmanite (Mn3O4), and bixbyite (Mn2O3), are important ore minerals of manganese and accurate values for their thermodynamic properties are desirable to understand better the {p(O2), T} conditions of their formation. To provide accurate values for the entropies of these important manganese minerals, we have measured their heat capacities between approximately 5 and 380 K using a fully automatic adiabatically-shielded calorimeter. All three minerals are paramagnetic above 100 K and become antiferromagnetic or ferrimagnetic at lower temperatures. This transition is expressed by a sharp ??-type anomaly in Cpmo for each compound with Ne??el temperatures TN of (92.2??0.2), (43.1??0.2), and (79.45??0.05) K for MnO2, Mn3O4, and Mn2O3, respectively. In addition, at T ??? 308 K, Mn2O3 undergoes a crystallographic transition, from orthorhombic (at low temperatures) to cubic. A significant thermal effect is associated with this change. Hausmanite is ferrimagnetic below TN and in addition to the normal ??-shape of the heat-capacity maxima in MnO2 and Mn2O3, it has a second rounded maximum at 40.5 K. The origin of this subsidiary bump in the heat capacity is unknown but may be related to a similar "anomalous bump" in the curve of magnetization against temperature at about 39 K observed by Dwight and Menyuk.(1) At 298.15 K the standard molar entropies of MnO2, Mn3O4, and Mn2O3, are (52.75??0.07), (164.1??0.2), and (113.7??0.2) J??K-1??mol-1, respectively. Our value for Mn3O4 is greater than that adopted in the National Bureau of Standards tables(2) by 14 per cent. ?? 1985.
Surface characterization of ZnO/ZnMn{sub 2}O{sub 4} and Cu/Mn{sub 3}O{sub 4} powders obtained by thermal degradation of heterobimetallic complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barrault, Joeel, E-mail: joel.barrault@univ-poitiers.fr; Makhankova, Valeriya G., E-mail: leram@univ.kiev.ua; Khavryuchenko, Oleksiy V.

2012-03-15

From the selective transformation of the heterometallic (Zn-Mn or Cu-Mn) carboxylate complexes with 2,2 Prime -bipyridyl by thermal degradation at relatively low (350 Degree-Sign C) temperature, it was possible to get either well defined spinel ZnMn{sub 2}O{sub 4} over zinc oxide or well dispersed copper particles surrounded by a manganese oxide (Mn{sub 3}O{sub 4}) in a core-shell like structure. Morphology of the powder surface was examined by scanning electron microscopy with energy dispersive X-ray microanalysis (SEM/EDX). Surface composition was determined by X-ray photoelectron spectroscopy (XPS). Specific surface of the powders by nitrogen adsorption was found to be 33{+-}0.2 and 9{+-}0.06more » m{sup 2} g{sup -1} for Zn-Mn and Cu-Mn samples, respectively, which is comparable to those of commercial products. - Graphical abstract: From the selective transformation of heterometallic (Zn-Mn or Cu-Mn) carboxylate complexes, it was possible to get either well defined spinel ZnMn{sub 2}O{sub 4} over zinc oxide or well dispersed copper particles surrounded by a manganese oxide (Mn{sub 3}O{sub 4}) in a core-shell like structure. Highlights: Black-Right-Pointing-Pointer Thermal degradation of heterometallic complexes results in fine disperse particles. Black-Right-Pointing-Pointer Core-shell Cu/Mn{sub 3}O{sub 4} particles are obtained. Black-Right-Pointing-Pointer ZnMn{sub 2}O{sub 4} spinel layer covers ZnO particles.« less
Bulk superconductivity in bismuth oxysulfide Bi4O4S3.

PubMed

Singh, Shiva Kumar; Kumar, Anuj; Gahtori, Bhasker; Shruti; Sharma, Gyaneshwar; Patnaik, Satyabrata; Awana, Veer P S

2012-10-10

A very recent report on the observation of superconductivity in Bi(4)O(4)S(3) [Mizuguchi, Y.; http://arxiv.org/abs/1207.3145] could potentially reignite the search for superconductivity in a broad range of layered sulfides. We report here the synthesis of Bi(4)O(4)S(3) at 500 °C by a vacuum encapsulation technique and its basic characterizations. The as-synthesized Bi(4)O(4)S(3) was contaminated with small amounts of Bi(2)S(3) and Bi impurities. The majority phase was found to be tetragonal (space group I4/mmm) with lattice parameters a = 3.9697(2) Å and c = 41.3520(1) Å. Both AC and DC magnetization measurements confirmed that Bi(4)O(4)S(3) is a bulk superconductor with a superconducting transition temperature (T(c)) of 4.4 K. Isothermal magnetization (M-H) measurements indicated closed loops with clear signatures of flux pinning and irreversible behavior. The lower critical field (H(c1)) at 2 K for the new superconductor was found to be ~15 Oe. Magnetotransport measurements showed a broadening of the resistivity (ρ) and a decrease in T(c) (ρ = 0) with increasing magnetic field. The extrapolated upper critical field H(c2)(0) was ~31 kOe with a corresponding Ginzburg-Landau coherence length of ~100 Å . In the normal state, the ρ ~ T(2) dependence was not indicated. Hall resistivity data showed a nonlinear magnetic field dependence. Our magnetization and electrical transport measurements substantiate the appearance of bulk superconductivity in as-synthesized Bi(4)O(4)S(3). On the other hand, Bi heat-treated at the same temperature is not superconducting, thus excluding the possibility of impurity-driven superconductivity in the newly discovered superconductor Bi(4)O(4)S(3).
Synthesis and X-ray crystal structure of (OsO(3)F(2))(2)2XeOF(4) and the Raman spectra of (OsO(3)F(2))(infinity), (OsO(3)F(2))(2), and (OsO(3)F(2))(2)2XeOF(4).

PubMed

Hughes, Michael J; Mercier, Hélène P A; Schrobilgen, Gary J

2009-05-18

The adduct, (OsO(3)F(2))(2)2XeOF(4), was synthesized by dissolution of the infinite chain polymer, (OsO(3)F(2))(infinity), in XeOF(4) solvent at room temperature followed by removal of excess XeOF(4) under dynamic vacuum at 0 degrees C. Continued pumping at 0 degrees C resulted in removal of associated XeOF(4), yielding (OsO(3)F(2))(2), a new low-temperature phase of OsO(3)F(2). Upon standing at 25 degrees C for 1(1)/(2) h, (OsO(3)F(2))(2) underwent a phase transition to the known monoclinic phase, (OsO(3)F(2))(infinity). The title compounds, (OsO(3)F(2))(infinity), (OsO(3)F(2))(2), and (OsO(3)F(2))(2)2XeOF(4) have been characterized by low-temperature (-150 degrees C) Raman spectroscopy. Crystallization of (OsO(3)F(2))(2)2XeOF(4) from XeOF(4) solution at 0 degrees C yielded crystals suitable for X-ray structure determination. The structural unit contains the (OsO(3)F(2))(2) dimer in which the OsO(3)F(3) units are joined by two Os---F---Os bridges having fluorine bridge atoms that are equidistant from the osmium centers (2.117(5) and 2.107(4) A). The dimer coordinates to two XeOF(4) molecules through Os-F...Xe bridges in which the Xe...F distances (2.757(5) A) are significantly less than the sum of the Xe and F van der Waals radii (3.63 A). The (OsO(3)F(2))(2) dimer has C(i) symmetry in which each pseudo-octahedral OsO(3)F(3) unit has a facial arrangement of oxygen ligands with XeOF(4) molecules that are only slightly distorted from their gas-phase C(4v) symmetry. Quantum-chemical calculations using SVWN and B3LYP methods were employed to calculate the gas-phase geometries, natural bond orbital analyses, and vibrational frequencies of (OsO(3)F(2))(2), (OsO(3)F(2))(2)2XeOF(4), XeOF(4), OsO(2)F(4), and (mu-FOsO(3)F(2))(2)OsO(3)F(-) to aid in the assignment of the experimental vibrational frequencies of (OsO(3)F(2))(2), (OsO(3)F(2))(2)2XeOF(4), and (OsO(3)F(2))(infinity). The vibrational modes of the low-temperature polymeric phase, (OsO(3)F(2))(infinity), have been
Highly efficient and recyclable triple-shelled Ag@Fe3O4@SiO2@TiO2 photocatalysts for degradation of organic pollutants and reduction of hexavalent chromium ions

NASA Astrophysics Data System (ADS)

Su, Jianwei; Zhang, Yunxia; Xu, Sichao; Wang, Shuan; Ding, Hualin; Pan, Shusheng; Wang, Guozhong; Li, Guanghai; Zhao, Huijun

2014-04-01

Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2 (P25), pure TiO2 microspheres, Fe3O4@SiO2@TiO2 and annealed Ag@Fe3O4@SiO2@TiO2 nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe3O4@SiO2@TiO2 hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe3O4@SiO2@TiO2 photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues.Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2
Roymillerite, Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)10(OH)14O4, a new mineral: mineralogical characterization and crystal chemistry

NASA Astrophysics Data System (ADS)

Chukanov, Nikita V.; Jonsson, Erik; Aksenov, Sergey M.; Britvin, Sergey N.; Rastsvetaeva, Ramiza K.; Belakovskiy, Dmitriy I.; Van, Konstantin V.

2017-11-01

The new mineral roymillerite Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)10(OH)14O4, related to britvinite and molybdophyllite, was discovered in a Pb-rich assemblage from the Kombat Mine, Grootfontein district, Otjozondjupa region, Namibia, which includes also jacobsite, cerussite, hausmannite, sahlinite, rhodochrosite, barite, grootfonteinite, Mn-Fe oxides, and melanotekite. Roymillerite forms platy single-crystal grains up to 1.5 mm across and up to 0.3 mm thick. The new mineral is transparent, colorless to light pink, with a strong vitreous lustre. Cleavage is perfect on (001). Density calculated using the empirical formula is equal to 5.973 g/cm3. Roymillerite is optically biaxial, negative, α = 1.86(1), β ≈ γ = 1.94(1), 2 V (meas.) = 5(5)°. The IR spectrum shows the presence of britvinite-type tetrahedral sheets, {CO}3^{2 - }, {BO}3^{3 - }, and OH- groups. The chemical composition is (wt%; electron microprobe, H2O and CO2 determined by gas chromatography, the content of B2O3 derived from structural data): MgO 4.93, MnO 1.24, FeO 0.95, PbO 75.38, B2O3 0.50, Al2O3 0.74, CO2 5.83, SiO2 7.90, H2O 1.8, total 99.27. The empirical formula based on 83 O atoms pfu (i.e. Z = 1) is Pb24.12Mg8.74Mn1.25Fe0.94B1.03Al1.04C9.46Si9.39H14.27O83. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is triclinic, space group P \\bar{1}, with a = 9.315(1), b = 9.316(1), c = 26.463(4) Å, α = 83.295(3)°, β = 83.308(3)°, γ = 60.023(2)°, V = 1971.2(6) Å3. The crystal structure of roymillerite is based built by alternating pyrophyllite-type TOT-modules Mg9(OH)8[(Si,Al)10O28] and I-blocks Pb24(OH)6O4(CO3)10(BO3,SiO4). The strongest lines of the powder X-ray diffraction pattern [ d, Å (I, %) ( hkl)] are: 25.9 (100) (001), 13.1 (11) (002), 3.480 (12) (017, 107, -115, 1-15), 3.378 (14) (126, 216), 3.282 (16) (-2-15, -1-25), 3.185 (12) (-116, 1-16), 2.684 (16) (031, 301, 030, 300, 332, -109, 0-19, 1-18), 2.382 (11) (0.0.-11). Roymillerite is

Epoxy composites coating with Fe3O4 decorated graphene oxide: Modified bio-inspired surface chemistry, synergistic effect and improved anti-corrosion performance

NASA Astrophysics Data System (ADS)

Zhan, Yingqing; Zhang, Jieming; Wan, Xinyi; Long, Zhihang; He, Shuangjiang; He, Yi

2018-04-01

To obtain graphene or graphene derivatives based epoxy composite coatings with high anti-corrosion performance, the morphology of nanostructures, dispersion, and interfacial adhesion are key factors that need to be considered. We here demonstrated the bio-inspired co-modification of graphene oxide/Fe3O4 hybrid (GO-Fe3O4@ poly (DA+KH550)) and its synergistic effect on the anti-corrosion performance of epoxy coating. For this purpose, graphene oxide/Fe3O4 hybrid obtained from hydrothermal route was modified by self-polymerization between dopamine and secondary functional monomer (KH550), which led to the modified bio-inspired surface functionalization. This novel modified bio-inspired functionalization was quite distinct from conventional surface modification or decoration. Namely, abundant amino groups were introduced by modified bio-inspired functionalization, which allowed the graphene oxide/Fe3O4 hybrid to disperse well in epoxy resin and enhanced the interfacial adhesion between modified nanofiller and epoxy resin through chemical crosslinking reaction. The electrochemical impedance spectroscopy (EIS) test revealed that anti-corrosive performance of epoxy coatings was significantly enhanced by addition of 0.5 wt% modified bio-inspired functionalized GO-Fe3O4 hybrid compared with neat epoxy and other nanofillers/epoxy composite coatings. Moreover, the micro-hardness of epoxy coating was enhanced by 71.8% compared with pure epoxy coating at the same loading content. In addition, the anticorrosion mechanism of GO-Fe3O4@poly (DA+KH550) was tentatively discussed.
Structural, optical and magnetic studies of CuFe2O4, MgFe2O4 and ZnFe2O4 nanoparticles prepared by hydrothermal/solvothermal method

NASA Astrophysics Data System (ADS)

Kurian, Jessyamma; Mathew, M. Jacob

2018-04-01

In this paper we report the structural, optical and magnetic studies of three spinel ferrites namely CuFe2O4, MgFe2O4 and ZnFe2O4 prepared in an autoclave under the same physical conditions but with two different liquid medium and different surfactant. We use water as the medium and trisodium citrate as the surfactant for one method (Hydrothermal method) and ethylene glycol as the medium and poly ethylene glycol as the surfactant for the second method (solvothermal method). The phase identification and structural characterization are done using XRD and morphological studies are carried out by TEM. Cubical and porous spherical morphologies are obtained for hydrothermal and solvothermal process respectively without any impurity phase. The optical studies are carried out using FTIR and UV-Vis reflectance spectra. In order to elucidate the nonlinear optical behaviour of the prepared nanomaterial, open aperture z-scan technique is used. From the fitted z-scan curves nonlinear absorption coefficient and the saturation intensity are determined. The magnetic characterization of the samples is performed at room temperature using vibrating sample magnetometer measurements. The M-H curves obtained are fitted using theoretical equation and the different components of magnetization are determined. Nanoparticles with high saturation magnetization are obtained for MgFe2O4 and ZnFe2O4 prepared under solvothermal reaction. The magnetic hyperfine parameters and the cation distribution of the prepared materials are determined using room temperature Mössbauer spectroscopy. The fitted spectra reveal the difference in the magnetic hyperfine parameters owing to the change in size and morphology.
Rational construction of three dimensional hybrid Co3O4@NiMoO4 nanosheets array for energy storage application

NASA Astrophysics Data System (ADS)

Hong, Wei; Wang, Jinqing; Gong, Peiwei; Sun, Jinfeng; Niu, Lengyuan; Yang, Zhigang; Wang, Zhaofeng; Yang, Shengrong

2014-12-01

Electrodes with rationally designed hybrid nanostructures can offer many opportunities for the enhanced performance in electrochemical energy storage. In this work, the uniform 2D Co3O4-based building blocks have been prepared through a facile chemical etching assistant approach and a following treatment of thermal annealing. The obtained nanosheets array has been directly employed as 2D backbone for the subsequent construction of hybrid nanostructure of Co3O4@NiMoO4 by a simple hydrothermal synthesis. As a binder-free electrode, the constructed 3D hybrid nanostructures exhibit a high specific capacitance of 1526 F g-1 at a current density of 3 mA cm-2 and a capacitance retention of 72% with the increase of current density from 3 mA cm-2 to 30 mA cm-2. Moreover, an asymmetric supercapacitor based on this hybrid Co3O4@NiMoO4 and activated carbon can deliver a maximum energy density of 37.8 Wh kg-1 at a power density of 482 W kg-1. The outstanding electrochemical behaviors presented here suggest that this hybrid nanostructured material has potential applications in energy storage.
Interface magnetism and electronic structure: ZnO(0001)/Co3O4 (111)

NASA Astrophysics Data System (ADS)

Kupchak, I. M.; Serpak, N. F.; Shkrebtii, A.; Hayn, R.

2018-03-01

We have studied the structural, electronic, and magnetic properties of spinel Co3O4 (111) surfaces and their interfaces with ZnO(0001) using density functional theory within the generalized gradient approximation with the on-site Coulomb repulsion term. Two possible forms of spinel surface, containing Co2 + or Co3 + ions and terminated with either cobalt or oxygen ions, were considered, as well as their interface with zinc oxide. Our calculations demonstrate that Co3 + ions attain nonzero magnetic moments at the surface and interface, in contrast to the bulk, where they are not magnetic, leading to the ferromagnetic ordering. Since heavily Co doped ZnO samples can contain a Co3O4 secondary phase, such magnetic ordering at the interface might explain the origin of the magnetism in such diluted magnetic semiconductors.
Oxygen evolution from BF3/MnO4-.

PubMed

Yiu, Shek-Man; Man, Wai-Lun; Wang, Xin; Lam, William W Y; Ng, Siu-Mui; Kwong, Hoi-Ki; Lau, Kai-Chung; Lau, Tai-Chu

2011-04-14

MnO(4)(-) is activated by BF(3) to undergo intramolecular coupling of two oxo ligands to generate O(2). DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO(2)(OBF(3))(2)](-) to the O···O coupling transition state.
Ni doped Fe3O4 magnetic nanoparticles.

PubMed

Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J

2012-03-01

In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.
Synthesis of ZnFe2O4/SiO2 composites derived from a diatomite template.

PubMed

Liu, Zhaoting; Fan, Tongxiang; Zhou, Han; Zhang, Di; Gong, Xiaolu; Guo, Qixin; Ogawa, Hiroshi

2007-03-01

A novel porous ZnFe2O4/SiO2 composite product has been generated with a template-directed assembly method from porous diatomite under different synthesis conditions, such as precursor concentrations (metallic nitrates), calcination temperature and diatomite type. The phase composition and morphology of all the materials were examined by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results indicated that an inherited hierarchical porous structure from the diatomite template can be obtained, and the synthesis conditions were found to have clear effects on the formation of the ZnFe2O4/SiO2 composite. The ideal composite of ZnFe2O4/SiO2 can be obtained through optimization of diatomite template type, precursor solution and calcination temperature. Furthermore, the adsorption abilities of two types of diatomites were analyzed in detail using FTIR spectra and nitrogen adsorption measurements etc, which proved that A-diatomite (Shengzhou-diatomite) is better than B-diatomite (Changbai-diatomite) on the aspect of adsorbing Zn and Fe ions, and of forming the ZnFe2O4.
Avaliação dos efeitos do subgalato de bismuto na proliferação de miofibroblastos

PubMed Central

de Lima, Rubianne Ligório; Sampaio, Cláudia Paraguaçu; Seidel, Karin Caroline; Branco, Melina; Sobreiro, Rafaela Mabile

2016-01-01

Resumo Contexto O subgalato de bismuto é um metal pesado e insolúvel, utilizado por suas propriedades adstringentes e hemostáticas. Objetivo Avaliar os efeitos do subgalato de bismuto na cicatrização mediante observação de miofibroblastos em pele de ratos. Métodos Foram utilizados 60 ratos da linhagem Wistar, que receberam uma ferida no dorso da pele. Os animais foram divididos em dois grupos: controle (aplicação diária de cloreto de sódio a 0,9%) e experimental (aplicação diária de 0,5 mg de subgalato de bismuto). Cada grupo foi subdividido em três subgrupos, que foram reoperados para retirada da ferida em 3, 7 e 14 dias. Foi realizada coloração de hematoxilina eosina, picrosirius e imuno-histoquímica para avaliar contagem de miofibroblastos, resposta inflamatória e síntese de colágeno. Resultados Não foi encontrada diferença entre os grupos controle e experimento com relação ao processo inflamatório – subgrupos 3 dias (p = 1), 7 dias (p = 0,474) e 14 dias (p = 303). A avaliação dos colágenos tipo I e III no grupo-controle não demonstrou benefícios de cicatrização – 3 dias (p = 0,436), 7 dias (p = 0,853) e 14 dias (p = 0,436); já no grupo experimental, houve aumento dos colágenos tipos I e III nos subgrupos 3 e 14 dias (p = 0,005). A imuno-histoquímica confirmou os resultados encontrados na coloração hematoxilina eosina, na qual a área de miofibroblastos entre os subgrupos, nos grupos experimental (p = 0,4) e controle (p = 0,336), foi indiferente. Conclusão A utilização do subgalato de bismuto em ferida de pele de ratos não evidenciou benefícios na cicatrização, ou seja, não houve diferença na fibroplasia quando comparados os grupos experimental e controle. PMID:29930592
[An in vivo DNA adduct database for carcinogens: O6-alkylguanine, O4-alkylthymine and 8-hydroxyguanine].

PubMed

Morimoto, K; Kimura, M; Murata, T; Imai, Y; Ookami, N; Igarashi, T; Kanoh, N; Kaminuma, T; Hayashi, Y

1994-01-01

Many carcinogens react with DNA and form critical DNA adducts, such as O6-alkylguanine (O6-AG), O4-alkylthymine (O4-AT), and 8-hydroxyguanine (8-OHG). This study provides a database that can be used for molecular dosimetry of these DNA adducts. A literature survey on DNA binding in vivo was done by the Dialog search from the MEDLINE database. We propose a Critical Covalent Binding Index (CCBI) for the assessment of in vivo DNA binding level (expressed as micro mol chemical bound per mol G or T/mmol chemical administered per kg body weight). The number of records and compounds in parenthesis of O6-AG, O4-AT, and 8-OHG were 245(13), 54(4), 79(15), respectively. Since the CCBI values for N-nitrosamine in target organ were higher than for non-target organ, they may provide a useful index for estimation of target organ site and carcinogenic potency. As a case example, CCBI values for O4-AT from animal data were applied for diethylnitrosamine human exposure estimation by diethylnitrosamine.
Magnetic and magnetocaloric properties of CuMn2O4 and Mn3O4 composite system

NASA Astrophysics Data System (ADS)

Vinod, K.; Satya, A. T.; Radhikesh Ravindran, N.; Mani, Awadhesh

2018-05-01

Polycrystalline CuMn2O4 is synthesized by solid state reaction method. Structural and magnetization studies reveal that the sample is multiphase with CuMn2O4 as primary phase and Mn3O4 as secondary phase. Magnetocaloric properties such as isothermal magnetic entropy change (‑ΔS M ) and refrigerant capacity (RC) are evaluated from isothermal magnetization data. Value of isothermal magnetic entropy change (| {{Δ }}{S}M| ) in the 40–80 K temperature range is 3.5–4.6 J kg‑1K‑1, for a field change of ΔH = 70 kOe. Value of refrigeration capacity (RC) evaluated for the same field change (ΔH = 70 kOe) is ∼190 J/kg for the T cold and T hot pair of 40 and 90 K respectively. Also value of | {{Δ }}{S}M| remains almost constant over a broad temperature range of 60–80 K.
Determination of 3-O- and 4-O-methylated monosaccharide constituents in snail glycans.

PubMed

Stepan, Herwig; Bleckmann, Christina; Geyer, Hildegard; Geyer, Rudolf; Staudacher, Erika

2010-07-02

The N- and O-glycans of Arianta arbustorum, Achatina fulica, Arion lusitanicus and Planorbarius corneus were analysed for their monosaccharide pattern by reversed-phase HPLC after labelling with 2-aminobenzoic acid or 3-methyl-1-phenyl-2-pyrazolin-5-one and by gas chromatography-mass spectrometry. Glucosamine, galactosamine, mannose, galactose, glucose, fucose and xylose were identified. Furthermore, three different methylated sugars were detected: 3-O-methyl-mannose and 3-O-methyl-galactose were confirmed to be a common snail feature; 4-O-methyl-galactose was detected for the first time in snails. Copyright 2010 Elsevier Ltd. All rights reserved.
Solution based synthesis of mixed-phase materials in the Li2TiO3-Li4SiO4 system

NASA Astrophysics Data System (ADS)

Hanaor, Dorian A. H.; Kolb, Matthias H. H.; Gan, Yixiang; Kamlah, Marc; Knitter, Regina

2015-01-01

As candidate tritium breeder materials for use in the ITER helium cooled pebble bed, ceramic multiphasic compounds lying in the region of the quasi-binary lithium metatitanate-lithium orthosilicate system may exhibit mechanical and physical advantages relative to single phase materials. Here we present an organometallic solution-based synthesis procedure for the low-temperature fabrication of compounds in the Li2TiO3-Li4SiO4 region and investigate phase stability and transformations through temperature varied X-ray diffraction and scanning calorimetry. Results demonstrate that the metatitanate and metasilicate phases Li2TiO3 and Li2SiO3 readily crystallise in nanocrystalline form at temperatures below 180 °C. Lithium deficiency in the region of 5% results from Li sublimation from Li4SiO4 and/or from excess Li incorporation in the metatitanate phase and brings about a stoichiometry shift, with product compounds exhibiting mixed lithium orthosilicate/metasilicate content towards the Si rich region and predominantly Li2TiO3 content towards the Ti rich region. Above 1150 °C the transformation of monoclinic to cubic γ-Li2TiO3 disordered solid-solution occurs while the melting of silicate phases indicates a likely monotectic type system with a solidus line in the region 1050-1100 °C. Synthesis procedures involving a lithium chloride precursor are not likely to be a viable option for breeder pebble synthesis as this route was found to yield materials with a more significant Li-deficiency exhibiting the crystallisation of the Li2TiSiO5 phase at intermediate compositions.
Determination of O:4 antigen-antibody affinity level in O:5 antigen positive and negative variants of Salmonella enterica serovar Typhimurium.

PubMed

Nakai, Yuka; Ito, Akihisa; Ogawa, Yohsuke; Aribam, Swarmistha Devi; Elsheimer-Matulova, Marta; Shiraiwa, Kazumasa; Kisaka, Stevens M B; Hikono, Hirokazu; Nishikawa, Sayaka; Akiba, Masato; Kawahara, Kazuyoshi; Shimoji, Yoshihiro; Eguchi, Masahiro

2017-04-01

Salmonella enterica serovar Typhimurium (S. Typhimurium) has two serological variants: one that expresses the O:5 antigen (1,4,5,12:i:1,2) and one that lacks O:5 antigen (1,4,12:i:1,2). For serotyping, S. Typhimurium is agglutinated by diagnostic O:4 antigen serum. This study was carried out to compare the antigen-antibody affinity of O:4 antigen in S. Typhimurium χ3306 O:5-positive and S. Typhimurium χ3306 O:5-negative strains. The affinity of O:4 antigen with O:4 antigen serum was found to be stronger in the O:5-negative strains compared to O:5-positive strains. Next, we investigated the antigen-antibody affinity of O:4 antigen with O:4 antigen serum in field strains of S. Typhimurium, which showed the same tendency in affinity as seen with S. Typhimurium χ3306 O:5-positive and negative strains. This study suggests that the presence or absence of O:5 antigen causes differences in O:4 agglutination reactions with different field strains of S. Typhimurium. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Efficient removal of arsenite through photocatalytic oxidation and adsorption by ZrO2-Fe3O4 magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Sun, Tianyi; Zhao, Zhiwei; Liang, Zhijie; Liu, Jie; Shi, Wenxin; Cui, Fuyi

2017-09-01

Bifunctional ZrO2-Fe3O4 magnetic nanoparticles were synthesized and characterized, to remove As(III) through photocatalyic oxidation and adsorption. With a saturation magnetization of 27.39 emu/g, ZrO2-Fe3O4 nanoparticles with size of 10-30 nm could be easily separated from solutions with a simple magnetic process. Under UV light, As(III) could be completely oxidized to less toxic As(V) by ZrO2-Fe3O4 nanoparticles within 40 min in the photocatalytic reaction. Simultaneously, As(V) could be adsorbed onto the surface of nanoparticles with high efficiency. The adsorption of As(V) was well fitted by the pseudo-second-order model and the Freundlich isotherm model, respectively, and the maximum adsorption capacities of the nanoparticles was 133.48 mg/g at pH 7.0. As(III) could be effectively removed by ZrO2-Fe3O4 nanoparticles at initial pH range from 4 to 8. Among all the common coexisting ions investigated, except for chloride and sulfate, carbonate, silicate and phosphate decreased the As(III) removal by competing with arsenic species for adsorption sites. The synthesized magnetic ZrO2-Fe3O4 combined the photocatalytic oxidation property of ZrO2 and the high adsorption capacity of both ZrO2 and Fe3O4, which make it have significant potential applications in the As(III)-contaminated water treatment.
Melting relations of model lherzolite in the system CaO-MgO-Al2O3-SiO2 at 2.4-3.4 GPa and the generation of komatiites

NASA Astrophysics Data System (ADS)

Gudfinnsson, Gudmundur H.; Presnall, Dean C.

1996-12-01

Isobarically invariant phase relations in the CaO-MgO-Al2O3-SiO2 system (CMAS) involving the lherzolite phase assemblage in equilibrium with liquid have been determined at 2.4-3.4 GPa. These phase relations form the solidus of model lherzolite in the CMAS system. Our data, which include determinations of all phase compositions, are in excellent agreement with the 3.0 and 4.0 GPa points of Milholland and Presnall [1991] and Davis and Schairer [1965], respectively. The invariant transition on the P-T solidus curve from spinel- to garnet-lherzolite at 3.0 GPa, 1575°C [Milholland and Presnall, 1991], is confirmed, but we observe that the theoretically required temperature depression on the solidus curve at this point is not experimentally detectable. Composition trends along the solidus take a sharp turn at the transition. In the spinel-lherzolite stability field, melt compositions become increasingly Fo-normative and less En-normative with increasing pressure, but become less Fo-normative and more pyroxenitic as pressure increases in the garnet-lherzolite stability field. Calculated melting reactions indicate that forsterite is in reaction relationship with the melt up to 3.0 GPa. Orthopyroxene is also in reaction relationship at pressures higher than just over 2.8 GPa and is the only phase in reaction relationship with the melt in the garnet-lherzolite stability field. Comparison of the normative compositions and the CaO/Al2O3 values of the komatiites of Gorgona Island and of the Reliance Formation in Zimbabwe with the compositions of liquids along the solidus of model lherzolite in the CMAS system indicates that the former komatiites were generated at pressures close to 3.7 GPa and the latter at close to 4.5 GPa, assuming that the melt generation occurred in the presence of the complete garnet-lherzolite assemblage.
Ti n O2n-1-Coated Li4Ti5O12 Composite Anode Material for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Zhang, Xiaoyan; Xu, Wen; Liu, Wanying; Li, Xing; Zhong, Xiaoxi; Lin, Yuanhua

2018-01-01

In an effort to enhance the rate capability of Li4Ti5O12, the Ti n O2n-1-coated Li4Ti5O12 (Li4Ti5O12-Ti n O2n-1, 3 < n < 10) composite has been synthesized through a sol-gel process followed by heat treatment in H2 atmosphere. Compared with pure Li4Ti5O12, Li4Ti5O12-Ti n O2n-1 composite shows higher specific capacity, better rate capability and cycle stability. The initial discharge capacity of the Li4Ti5O12-Ti n O2n-1 composite electrode is 171.2 mAh g-1 at 0.2°C, and 103.8 mAh g-1 at 20°C. Moreover, the discharge capacity remains 79.5 mAh g-1 after 100 cycles at 20°C with a capacity loss of 23.4%. The improved rate capacity and cycling stability clarify the positive effects of Ti n O2n-1 coating layer in Li4Ti5O12-Ti n O2n-1 composite as an anode material for lithium ion batteries.
Radiation-induced amorphization of Ce-doped Mg2Y8(SiO4)6O2 silicate apatite

NASA Astrophysics Data System (ADS)

Zhou, Jianren; Yao, Tiankai; Lian, Jie; Shen, Yiqiang; Dong, Zhili; Lu, Fengyuan

2016-07-01

Ce-doped Mg2Y8(SiO4)6O2 silicate apatite (Ce = 0.05 and 0.5) were irradiated with 1 MeV Kr2+ ion beam irradiation at different temperatures and their radiation response and the cation composition dependence of the radiation-induced amorphization were studied by in situ TEM. The two Ce-doped Mg2Y8(SiO4)6O2 silicate apatites are sensitive to ion beam induced amorphization with a low critical dose (0.096 dpa) at room temperature, and exhibits significantly different radiation tolerance at elevated temperatures. Ce concentration at the apatite AI site plays a critical role in determining the radiation response of this silicate apatite, in which the Ce3+ rich Mg2Y7.5Ce0.5(SiO4)6O2 displays lower amorphization susceptibility than Mg2Y7.95Ce0.05(SiO4)6O2 with a lower Ce3+ occupancy at the AI sites. The critical temperature (Tc) and activation energy (Ea) change from 667.5 ± 33 K and 0.162 eV of Mg2Y7.5Ce0.5(SiO4)6O2 to 963.6 ± 64 K and 0.206 eV of Mg2Y7.95Ce0.05(SiO4)6O2. We demonstrate that the radiation tolerance can be controlled by varying the chemical composition, and enhanced radiation tolerance is achieved by increasing the Ce concentration at the AI site.
Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors

PubMed Central

Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

2016-01-01

Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm−2 at 2 mA cm−2 and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm−2. The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure. PMID:27515274
Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors.

PubMed

Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

2016-08-12

Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm(-2) at 2 mA cm(-2) and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm(-2). The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure.
Hierarchical core-shell NiCo2O4@NiMoO4 nanowires grown on carbon cloth as integrated electrode for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Huang, Liang; Zhang, Wei; Xiang, Jinwei; Xu, Henghui; Li, Guolong; Huang, Yunhui

2016-08-01

Hierarchical core-shell NiCo2O4@NiMoO4 nanowires were grown on carbon cloth (CC@NiCo2O4@NiMoO4) by a two-step hydrothermal route to fabricate a flexible binder-free electrode. The prepared CC@NiCo2O4@NiMoO4 integrated electrode was directly used as an electrode for faradaic supercapacitor. It shows a high areal capacitance of 2.917 F cm-2 at 2 mA cm-2 and excellent cycling stability with 90.6% retention over 2000 cycles at a high current density of 20 mA cm-2. The superior specific capacitance, rate and cycling performance can be ascribed to the fast transferring path for electrons and ions, synergic effect and the stability of the hierarchical core-shell structure.

Magneto electric effects in BaTiO3-CoFe2O4 bulk composites

NASA Astrophysics Data System (ADS)

Agarwal, Shivani; Caltun, O. F.; Sreenivas, K.

2012-11-01

Influence of a static magnetic field (HDC) on the hysteresis and remanence in the longitudinal and transverse magneto electric voltage coefficients (MEVC) observed in [BaTiO3]1-x-[CoFe2O4]x bulk composites are analyzed. Remanence in MEVC at zero bias (HDC=0) is stronger in the transverse configuration over the longitudinal case. The observed hysteretic behavior in MEVC vs. HDC is correlated with the changes observed in the magnetostriction characteristics (λ and dλ/dH) reported for [BaTiO3]1-x-[CoFe2O4]x bulk composites.
Construction of g-C3N4/CeO2/ZnO ternary photocatalysts with enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Yuan, Yuan; Huang, Gui-Fang; Hu, Wang-Yu; Xiong, Dan-Ni; Zhou, Bing-Xin; Chang, Shengli; Huang, Wei-Qing

2017-07-01

Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis. In this work, binary g-C3N4/CeO2 nanosheets are first prepared by pyrolysis and subsequent exfoliation method, then decorated with ZnO nanoparticles to construct g-C3N4/CeO2/ZnO ternary nanocomposites with multi-heterointerfaces. Notably, the type-II staggered band alignments existing between any two of the constituents, as well as the efficient three-level transfer of electron-holes in unique g-C3N4/CeO2/ZnO ternary composites, leads to the robust separation of photoexcited charge carriers, as verified by its photocurrent increased by 8 times under visible light irradiation. The resulting g-C3N4/CeO2/ZnO ternary nanocomposites unveil appreciably increased photocatalytic activity, faster than that of pure g-C3N4, ZnO and g-C3N4/CeO2 by a factor of 11, 4.6 and 3.7, respectively, and good stability toward methylene blue (MB) degradation. The remarkably enhanced photocatalytic activity of g-C3N4/CeO2/ZnO ternary heterostructures can be interpreted in terms of lots of active sites of nanosheet shapes and the efficient charge separation owing to the resulting type-II band alignment with more than one heterointerface and the efficient three-level electron-hole transfer. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photogenerated holes and •OH radicals play a crucial role in photodegradation reaction under visible light irradiation. This work suggest that the rational design and construction of type II multi-heterostructures is powerful for developing highly efficient and reusable visible-light photocatalysts for environmental purification and energy conversion.
Magnetic ordered mesoporous Fe3O4/CeO2 composites with synergy of adsorption and Fenton catalysis

NASA Astrophysics Data System (ADS)

Li, Keyan; Zhao, Yongqin; Song, Chunshan; Guo, Xinwen

2017-12-01

Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L-1 and cerium 0.63 mg L-1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.
Análise sobre o Conhecimento de um Grupo de Alunos do Ensino Médio da Rede Estadual de São Paulo sobre Termos e Fenômenos Astronômicos do Cotidiano

NASA Astrophysics Data System (ADS)

de Oliveira, E. F.; Voelzke, M. R.; Amaral, L. H.

2007-08-01

Embora os Parâmetros Curriculares Nacionais do Ensino Médio (PCN-EM) e as orientações complementares a esses Parâmetros (PCN+) apontem a importância de uma abordagem significativa de conceitos relacionados à astronomia nas aulas de Física, muitos estudantes terminam o Ensino Médio (EM) sem compreender a razão de certos acontecimentos de origem celeste, ainda que estes façam parte de seu cotidiano. Este trabalho tem por objetivo analisar os conhecimentos básicos em astronomia dos alunos de EM da escola estadual Batista Renzi, bem como investigar os meios através dos quais estes conhecimentos foram adquiridos. Para tanto foi elaborado um questionário de múltipla escolha aplicado a 310 alunos distribuídos entre as três séries do EM dos períodos matutino e noturno. Dessa forma, observou-se que apenas 34,5% relacionaram as estações do ano à inclinação do eixo de rotação da Terra, 21,3% indicaram a influência gravitacional da Lua e do Sol como responsáveis pelo fenômeno das marés, 24,5% indicaram corretamente quais são os objetos celestes mais próximos da Terra, 36,1% identificaram ano-luz como uma medida de distância e 34,2% reconheceram uma estrela cadente como meteoro. Em contrapartida, 67,1% compreendiam a sucessão entre dia e noite, 73,9% identificaram o Sol como estrela e 52,3% relacionaram o Big Bang à origem do Universo. Além disso, foram comparadas as respostas de alunos de diferentes séries e períodos, observando-se, dentre outras coisas, que os estudantes do terceiro ano apresentam um percentual de acertos semelhante ao dos alunos do primeiro, caracterizando que a abordagem de tópicos relacionados à astronomia no EM não tem contribuído para uma maior compreensão dos fenômenos e conceitos.
Magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles for visible light photodegradation of methyl orange

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulkarni, Suresh D., E-mail: suresh.dk@manipal.edu; Kumbar, Sagar; Menon, Samvit G.

Highlights: • Phase pure, magnetic ZnFe{sub 2}O{sub 4}@ZnO nanoparticles synthesized with excellent yield. • ZnFe{sub 2}O{sub 4}@ZnO displayed higher UV photocatalytic efficiency than ZnO nanoparticles. • First report on visible light photodegradation of methyl orange by ZnFe{sub 2}O{sub 4}@ZnO. • Excellent reusability of ZnFe{sub 2}O{sub 4}@ZnO nanoparticles observed for azo dye removal. - Abstract: Visible light photodegradation of aqueous methyl orange using magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported. A combination of low temperature (190 °C) microwave synthesis and hydrothermal method were used to prepare phase pure material with excellent yield (95%). The magnetic separability, surface area ofmore » 41 m{sup 2}/g and visible light absorption make ZnFe{sub 2}O{sub 4}@ZnO nanoparticles a good solar photocatalyst. ZnFe{sub 2}O{sub 4}@ZnO displayed greater UV photocatalytic efficiency than ZnO owing to the generation of large number of electron-hole pairs. Visible light photodegradation of MO using ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported for the first time. Higher first order rate constants under both UV and visible light for core-shell nanoparticles suggested their superiority over its individual oxides. The ZnFe{sub 2}O{sub 4}@ZnO showed excellent reusability with high photocatalytic efficiencies suggesting its suitability for solar photocatalytic applications.« less
Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

NASA Astrophysics Data System (ADS)

Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

2018-04-01

Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.
In situ loading of gold nanoparticles on Fe3O4@SiO2 magnetic nanocomposites and their high catalytic activity.

PubMed

Zheng, Jinmin; Dong, Yalei; Wang, Weifeng; Ma, Yanhua; Hu, Jing; Chen, Xiaojiao; Chen, Xingguo

2013-06-07

In this work, a facile approach was successfully developed for in situ catalyzing Au nanoparticles loaded on Fe3O4@SiO2 magnetic nanospheres via Sn(2+) linkage and reduction. After the Fe3O4@SiO2 MNPs were first prepared via a sol-gel process, only one step was needed to synthesize the Fe3O4@SiO2-Au magnetic nanocomposites (Fe3O4@SiO2-Au MNCs), so that both the synthesis step and the reaction cost were remarkably decreased. Significantly, the as-synthesized Fe3O4@SiO2-Au MNCs showed high performance in the catalytic reduction of 4-nitrophenol to 4-aminophenol and could be reused for several cycles with convenient magnetic separability. This approach provided a useful platform based on Fe3O4@SiO2 MNPs for the fabrication of Au or other noble metal magnetic nanocatalysts, which would be very useful in various catalytic reductions.
New metal oxides of the family Am[( TO) q]: ALiMn 3O 4 and ALiZn 3O 4 ( A = K, Rb)

NASA Astrophysics Data System (ADS)

Hoppe, R.; Seipp, E.; Baier, R.

1988-01-01

The new compounds KLiMn 3O 4 ( I), RbLiMn 3O 4 ( II), KLiZn 3O 4 ( III) and RbLiZn 3O 4 ( IV) have been prepared by solid state reaction of A2O ( A = K, Rb), Li 2O, and MO ( M = Mn, Zn). The isomorphous compounds are tetragonal, space group {I4}/{m}, Z = 2 , with lattice constants a = 838.32(4) pm, c = 341.88(3) pm for I; a = 840.66(8) pm, c = 344.85(4) pm for II; a = 819.27(9) pm, c = 334.20(7) pm for III,a = 823.62(9) pm, c = 339.73(7) pm for IV, as determined from Guinier X-ray powder patterns. The orange-colored manganates and colorless zincates are sensitive to moisture. The crystal structures of II and III have been determined by single-crystal X-ray techniques and refined to R = 0.09 ( II) and R = 0.06 ( III). The structure is built up from chains of face-shared cubes, 1∞[A O{8}/{2}] (A = K, Rb) , running parallel to the c axis. These are connected by Li + and M2+ ( M = Mn, Zn), statistically distributed on tetrahedral positions between the chains.
Anti-arthritic activity of 11-O-(4'-O-methyl galloyl)-bergenin and Crassula capitella extract in rats.

PubMed

El-Hawary, Seham S; Mohammed, Rabab; Abouzid, Sameh; Ali, Zeinab Y; Elwekeel, Ahlam

2016-06-01

Isolation and identification of phytochemicals of Crassula capitella (Thunberg), evaluation of the anti-arthritic potential of the extract and the major isolated compound; 11-O-(4'-O-methyl galloyl)-bergenin and underlying their mechanism on rat model of rheumatoid arthritis (RA). Different fractions were subjected to column chromatography giving fourteen compound identified by mass and NMR spectroscopic techniques. RA was induced by intraplantar injection of complete Freund's adjuvant into the right hind paw of rats. Influence of tested samples in comparable to methotrexate on paw oedema, body weight gain, serum diagnostic markers, cartilage and bone degeneration enzymes, pro-inflammatory mediators and oxidative stress biomarkers in arthritic rats. Fourteen phenolic compounds were isolated and identified for the first time from C. capitella. The major compound identified as 11-O-(4'-O-methyl galloyl)-bergenin. Treatment of arthritic rats with extract or 11-O-(4'-O-methyl galloyl)-bergenin with the tested doses can reduce the progression and severity of RA. Crassula capitella is a new natural and abundant source for 11-O-(4'-O-methyl galloyl)-bergenin for resolving chronic inflammatory diseases as RA through antioxidant, anti-inflammatory and membrane stabilizing mechanism. © 2016 Royal Pharmaceutical Society.
Mixed-metal uranium(VI) iodates: hydrothermal syntheses, structures, and reactivity of Rb[UO(2)(CrO(4))(IO(3))(H(2)O)], A(2)[UO(2)(CrO(4))(IO(3))(2)] (A = K, Rb, Cs), and K(2)[UO(2)(MoO(4))(IO(3))(2)].

PubMed

Sykora, Richard E; McDaniel, Steven M; Wells, Daniel M; Albrecht-Schmitt, Thomas E

2002-10-07

The reactions of the molecular transition metal iodates A[CrO(3)(IO(3))] (A = K, Rb, Cs) with UO(3) under mild hydrothermal conditions provide access to four new, one-dimensional, uranyl chromatoiodates, Rb[UO(2)(CrO(4))(IO(3))(H(2)O)] (1) and A(2)[UO(2)(CrO(4))(IO(3))(2)] (A = K (2), Rb (3), Cs (4)). Under basic conditions, MoO(3), UO(3), and KIO(4) can be reacted to form K(2)[UO(2)(MoO(4))(IO(3))(2)] (5), which is isostructural with 2 and 3. The structure of 1 consists of one-dimensional[UO(2)(CrO(4))(IO(3))(H(2)O)](-) ribbons that contain uranyl moieties bound by bridging chromate and iodate anions as well as a terminal water molecule to create [UO(7)] pentagonal bipyramidal environments around the U(VI) centers. These ribbons are separated from one another by Rb(+) cations. When the iodate content is increased in the hydrothermal reactions, the terminal water molecule is replaced by a monodentate iodate anion to yield 2-4. These ribbons can be further modified by replacing tetrahedral chromate anions with MoO(4)(2)(-) anions to yield isostructural, one-dimensional [UO(2)(MoO(4))(IO(3))(2)](2)(-) ribbons. Crystallographic data: 1, triclinic, space group P(-)1, a = 7.3133(5) A, b = 8.0561(6) A, c = 8.4870(6) A, alpha = 88.740(1) degrees, beta = 87.075(1) degrees, gamma = 71.672(1) degrees, Z = 2; 2, monoclinic, space group P2(1)/c, a = 11.1337(5) A, b = 7.2884(4) A, c = 15.5661(7) A, beta = 107.977(1) degrees, Z = 4; 3, monoclinic, space group P2(1)/c, a = 11.3463(6) A, b = 7.3263(4) A, c = 15.9332(8) A, beta = 108.173(1) degrees, Z = 4; 4, monoclinic, space group P2(1)/n, a = 7.3929(5) A, b = 8.1346(6) A, c = 22.126(2) A, beta = 90.647(1) degrees, Z = 4; 5, monoclinic, space group P2(1)/c, a = 11.3717(6) A, b = 7.2903(4) A, c = 15.7122(8) A, beta = 108.167(1) degrees, Z = 4.
Potential of SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles in achieving integrated magneto-optical isolators

NASA Astrophysics Data System (ADS)

Zamani, Mehdi; Hocini, Abdesselam

2017-05-01

We have investigated the potential of the SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles in order to overcome the problem of integration of the magneto-optical isolators (MOIs). In this way, we have performed a theoretical study for the case of designing perfect and adjustable MOIs based on magnetophotonic crystals (MPCs) containing SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles as a magnetic medium. Despite the existence the attenuation coefficient for SiO2/ZrO2 matrix at wavelength 1550 nm that leads to a non-perfect transmittance, we could introduce an MPC structure having no reflectance; therefore, an ideal MOI for eliminating unwanted back-reflection could be achieved.
Crystal structures of lazulite-type oxidephosphates Ti IIITi IV3O 3(PO 4) 3 and MIII4Ti IV27O 24(PO 4) 24 ( MIII=Ti, Cr, Fe)

NASA Astrophysics Data System (ADS)

Schöneborn, M.; Glaum, R.; Reinauer, F.

2008-06-01

Single crystals of the oxidephosphates Ti IIITi IV3O 3(PO 4) 3 (black), Cr III4Ti IV27O 24(PO 4) 24 (red-brown, transparent), and Fe III4Ti IV27O 24(PO 4) 24 (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2 dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti IIITi IV3O 3(PO 4) 3: Z=24, a=7.3261(9) Å, b=22.166(5) Å, c=39.239(8) Å, R1=0.029, w R2=0.084, 6055 independent reflections, 301 variables; Cr III4Ti IV27O 24(PO 4) 24: Z=1, a=7.419(3) Å, b=21.640(5) Å, c=13.057(4) Å, R1=0.037, w R2=0.097, 1524 independent reflections, 111 variables; Fe III4Ti IV27O 24(PO 4) 24: Z=1, a=7.4001(9) Å, b=21.7503(2) Å, c=12.775(3) Å, R1=0.049, w R2=0.140, 1240 independent reflections, 112 variables). For Ti IIITi IVO 3(PO 4) 3 a well-ordered structure built from dimers [Ti III,IV2O 9] and [Ti IV,IV2O 9] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr 4Ti 27O 24(PO 4) 24 and Fe 4Ti 27O 24(PO 4) 24, consisting of dimers [ MIIITi IVO 9] and [Ti IV,IV2O 9], monomeric [Ti IVO 6] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti III4Ti IV27O 24(PO 4) 24 ( a=7.418(2) Å, b=21.933(6) Å, c=12.948(7) Å) is isotypic to the oxidephosphates MIII4Ti IV27O 24(PO 4) 24 ( MIII: Cr, Fe). The UV/vis spectrum of Cr 4Ti 27O 24(PO 4) 24 reveals a rather small ligand-field splitting Δ o=14,370 cm -1 and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr IIIO 6] within the dimers [Cr IIITi IVO 9].
Phase relations in the system Cu-Gd-O and Gibbs energy of formation of CuGd[sub 2]O[sub 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacob, K.T.; Mathews, T.; Hajra, J.P.

1993-07-01

The phase relations in the system Cu-Gd-O have been determined at 1,273 K by X-ray diffraction, optical microscopy, and electron microprobe analysis of samples equilibrated in quartz ampules and in pure oxygen. Only one ternary compound, CuGd[sub 2]O[sub 4], was found to be stable. The Gibbs free energy of formation of this compound has been measured using the solid-state cell Pt, Cu[sub 2]O + CuGd[sub 2]O[sub 4] + Gd[sub 2]O[sub 3]//(Y[sub 2]O[sub 3])ZrO[sub 2]//CuO + Cu[sub 2]O, Pt in the temperature range of 900 to 1,350 K. For the formation of CuGd[sub 2]O[sub 4] from its binary component oxides, CuOmore » (s) + Gd[sub 2]O[sub 3] (s) [r arrow] CuGd[sub 2]O[sub 4] (s) [Delta]G[degree] = 8230 - 11.2T([plus minus]50)J/mol. Since the formation is endothermic, CuGd[sub 2]O[sub 4] becomes thermodynamically unstable with respect to CuO and Gd[sub 2]O[sub 3] below 735 K. When the oxygen partial pressure over CuGd[sub 2]O[sub 4] is lowered, it decomposes according to the reaction 4CuGd[sub 2]O[sub 4] (s) [r arrow] 4Gd[sub 2]O[sub 3] (s) + 2Cu[sub 2]O (s) + O[sub 2] (g) for which the equilibrium oxygen potential is given by [Delta][mu][sub o][sub 2] = [minus]227,970 + 143.2T([plus minus]500)J/mol. An oxygen potential diagram for the system Cu-Gd-O at 1,273 is presented.« less
RNA adducts with Na 2SeO 4 and Na 2SeO 3 - Stability and structural features

NASA Astrophysics Data System (ADS)

Nafisi, Shohreh; Manouchehri, Firouzeh; Montazeri, Maryam

2011-12-01

Selenium compounds are widely available in dietary supplements and have been extensively studied for their antioxidant and anticancer properties. Low blood Se levels were found to be associated with an increased incidence and mortality from various types of cancers. Although many in vivo and clinical trials have been conducted using these compounds, their biochemical and chemical mechanisms of efficacy are the focus of much current research. This study was designed to examine the interaction of Na 2SeO 4 and Na 2SeO 3 with RNA in aqueous solution at physiological conditions, using a constant RNA concentration (6.25 mM) and various sodium selenate and sodium selenite/polynucleotide (phosphate) ratios of 1/80, 1/40, 1/20, 1/10, 1/5, 1/2 and 1/1. Fourier transform infrared, UV-Visible spectroscopic methods were used to determine the drug binding modes, the binding constants, and the stability of Na 2SeO 4 and Na 2SeO 3-RNA complexes in aqueous solution. Spectroscopic evidence showed that Na 2SeO 4 and Na 2SeO 3 bind to the major and minor grooves of RNA ( via G, A and U bases) with some degree of the Se-phosphate (PO 2) interaction for both compounds with overall binding constants of K(Na 2SeO 4-RNA) = 8.34 × 10 3 and K(Na 2SeO 3-RNA) = 4.57 × 10 3 M -1. The order of selenium salts-biopolymer stability was Na 2SeO 4-RNA > Na 2SeO 3-RNA. RNA aggregations occurred at higher selenium concentrations. No biopolymer conformational changes were observed upon Na 2SeO 4 and Na 2SeO 3 interactions, while RNA remains in the A-family structure.
Template-etching route to construct uniform rattle-type Fe3O4@SiO2 hollow microspheres as drug carrier.

PubMed

Cheng, Lin; Liu, Yuanyuan; Zou, Bingfang; Yu, Yong; Ruan, Weimin; Wang, Yongqiang

2017-06-01

Template-etching strategy was put forward to synthesize rattle-type magnetic silica (Fe 3 O 4 @SiO 2 ) hollow microspheres in a controlled way. During the experiment, monodisperse Fe 2 O 3 microspheres were fabricated as physical template to generate uniform Fe 2 O 3 @SiO 2 with controlled shell thicknesses through sol-gel method, and the subsequent Fe 2 O 3 template etching process created variable space between Fe 2 O 3 core and SiO 2 shell, and the final calcination process transformed rattle-type Fe 2 O 3 @SiO 2 hollow microspheres into corresponding Fe 3 O 4 @SiO 2 product in hydrogen/nitrogen atmosphere. Compared with traditional physical template, here template-etching synthesis of rattle-type hollow microspheres saved the insertion of middle shells and their removal, which simplified the synthesis process with controllable core size and shell thickness. The rattle-type Fe 3 O 4 @SiO 2 hollow microspheres as drug carrier show efficient doxorubicin (DOX) loading, and the release rate of DOX loaded the rattle-type Fe 3 O 4 @SiO 2 hollow microspheres exhibit a surprising shell-thickness-dependent and a pH responsive drug release features. Additionally, MTT assays in HeLa cells demonstrated that the Fe 3 O 4 @SiO 2 nanocarriers were non-toxic even at the concentration of 250µgmL -1 for 48h. Thus, our results revealed that the Fe 3 O 4 @SiO 2 -DOX could play an important role in the development of intracellular delivery nanodevices for cancer therapy. Copyright © 2017. Published by Elsevier B.V.
(CaO)nIrO2 (n = 1, 2, 4) family: Chemical scissors effects of CaO on structural characteristics correlated to physical properties. Ab initio study

NASA Astrophysics Data System (ADS)

Matar, Samir F.; Etourneau, Jean

2017-11-01

Based on crystal chemistry analysis within Ca-Ir-O ternary, the generic (CaO)nIrO2 formula leading to CaIrO3 for n = 1, Ca2IrO4 for n = 2 and Ca4IrO6 for n = 4 actual chemical compounds show significant structural changes regarding the spatial arrangement of IrO6 octahedra whereby increasing amounts of CaO act as 'chemical scissor' decreasing the dimensionality of stacking octahedra from 3D (IrO2) to 0D (Ca4IrO6). This is accompanied by changes in the electronic structure investigated within density functional theory. Such changes are particularly exhibited by linear increase of Ir density of states at the Fermi level revealing increasing localization of d states with crystal field effects. Eventually only for Ca4IrO6 a magnetic instability occurs in non magnetic configuration. Spin polarized calculations lead to development of small magnitude but finite magnetization on Ir with M 0.50 μB totally polarized along minority spin channel ↓.
Synthesis, characterization, and antibacterial activities of ZnLaFe2O4/NiTiO3 nanocomposite

NASA Astrophysics Data System (ADS)

Sobhani-Nasab, Ali; Zahraei, Zohreh; Akbari, Maryam; Maddahfar, Mahnaz; Hosseinpour-Mashkani, S. Mostafa

2017-07-01

In this research, for the first time, ZnLaFe2O4/NiTiO3 nanocomposites have been synthesized through a polyol assistant sol-gel method. To investigate the effect of different surfactants on the morphology and particle size of ZnLaFe2O4 nanostructure, cetrimonium bromide, sodium dodecyl sulfate, polyvinylpyrrolidone, polyvinyl alcohol, and oleic acid were used as surfactant agents. Based on the SEM results, it was found that morphology and particle size of the products could be affected by these surfactants. Furthermore, study on antibacterial effect of ZnLaFe2O4/NiTiO3 nanocomposites by colony forming unit (CFU) reduction assay showed that ZnLaFe2O4/NiTiO3 nanocomposites have antibacterial activity against Gram-negative Escherchia coli (ATCC 10536) and Gram-positive Staphylococcus aureus (ATCC 29737). Antibacterial results demonstrate that nanocomposite significantly reduced the growth rate of E. coli bacteria and S. aureus after 120 min. The structure and morphology of the resulting particles were characterized by XRD, FT-IR, EDX, and SEM analysis.
Fabrication of Fe{sub 3}O{sub 4}@CuO core-shell from MOF based materials and its antibacterial activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajabi, S.K.; Sohrabnezhad, Sh., E-mail: sohrabnezhad@guilan.ac.ir; Ghafourian, S.

Magnetic Fe{sub 3}O{sub 4}@CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe{sub 3}O{sub 4}@HKUST-1 in air atmosphere. The morphology, structure, magnetic and porous properties of the as-synthesized nano composites were characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and vibration sample magnetometer (VSM). The results showed that the nanocomposite material included a Fe{sub 3}O{sub 4} core and a CuO shell. The Fe{sub 3}O{sub 4}@CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe{sub 3}O{sub 4}-CuO core-shell was investigated againstmore » gram-positive and gram-negative bacteria. A new mechanism was proposed for inactivation of bacteria over the prepared sample. It was demonstrated that the core-shell exhibit recyclable antibacterial activity, acting as an ideal long-acting antibacterial agent. - Graphical abstract: Fe{sub 3}O{sub 4}@CuO core-shell release of copper ions. These Cu{sup 2+} ions were responsible for the exhibited antibacterial activity. - Highlights: • The Fe{sub 3}O{sub 4}@CuO core-shell was prepared by MOF method. • This is the first study of antibacterial activity of core-shell consist of CuO and Fe{sub 3}O{sub 4}. • The core-shell can be reused effectively. • Core-shell was separated from the reaction solution by external magnetic field.« less
Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

PubMed

Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

2017-09-20

Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo 2 O 4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo 2 O 4 /C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo 2 O 4 /C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo 2 O 4 /C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo 2 O 4 /C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo 2 O 4 /C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo 2 O 4 /C nanocages.
A Concepção de Universo entre Alunos do Ensino Médio de São Paulo e suas Fontes de Aquisição

NASA Astrophysics Data System (ADS)

Araújo, M. A. A.; Elias, D. C. N.; Amaral, L. H.; Araújo, M. S. T.; Voelzke, M. R.

2006-08-01

Nesse trabalho procurou-se identificar por meio de um questionário as concepções de Universo, de espaço e tempo que sustentam a visão de mundo de um grupo de 270 estudantes de Ensino Médio, pertencentes a três escolas de São Paulo. As questões relacionadas aos conhecimentos prévios dos estudantes permitiram constatar que há pouco conhecimento acerca dos temas investigados, destacando-se que apenas 20% dos alunos foram capazes de relacionar as semanas com as fases da lua, enquanto 28% associaram as estações do ano à inclinação do eixo de rotação da Terra e 23% tinham noções das distâncias entre objetos celestes próximos da Terra. Enquanto 56% conseguiram relacionar o Big Bang com a origem do Universo, verificou-se que 37% reconheciam ano-luz como unidade de distância e 60% concebiam o Sol como uma estrela. No que se refere às fontes de aquisição que proporcionaram esses conhecimentos, apesar de 60% dos alunos indicarem a escola como principal fonte dos conhecimentos de Ast! ronomia, verificou-se claramente que para a maioria dos alunos seus conceitos ainda são inadequados, havendo necessidade de aprimoramento da abordagem desses conteúdos, pois apesar de popular, a Astronomia ainda é veiculada de maneira pouco esclarecedora e com imprecisões. Nesse contexto, são discutidas algumas possíveis contribuições que podem ser dadas para o ensino de Astronomia pelo uso das ferramentas computacionais nas escolas.

Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO 4· nH 2O

NASA Astrophysics Data System (ADS)

Eda, Kazuo; Kato, Yasuyuki; Ohshiro, Yu; Sugitani, Takamitu; Whittingham, M. Stanley

2010-06-01

The synthesis and crystal structure of NiMoO 4· nH 2O were investigated. The hydrate crystallized in the triclinic system with space group P-1, Z=4 with unit cell parameters of a=6.7791(2) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO 4·3/4H 2O rather than NiMoO 4·1H 2O. Under hydrothermal conditions the hydrate turned directly into α-NiMoO 4 above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature.
Interaction mechanisms between α-Fe2O3, γ-Fe2O3 and Fe3O4 nanoparticles and Citrus maxima seedlings.

PubMed

Li, Junli; Hu, Jing; Xiao, Lian; Wang, Yunqiang; Wang, Xilong

2018-06-01

The interactions between α-Fe 2 O 3 , γ-Fe 2 O 3 , and Fe 3 O 4 nanoparticles (NPs) and Citrus maxima seedlings were examined so as to better understand possible particle applications as an Fe source for crop plants. NPs toxicity to the exposed plant was investigated as well. The α- and γ-Fe 2 O 3 NPs were accumulated by plant root cells through diapirism and endocytosis, respectively, but translocation to the shoots was negligible. Analysis of malondialdehyde (MDA), soluble protein content, and antioxidant enzyme activity revealed that Fe deficiency induced strong oxidative stress in Citrus maxima seedlings, which followed an order of Fe deficiency>Fe 3+ >α-Fe 2 O 3 , γ-Fe 2 O 3 NPs>Fe 3 O 4 NPs. However, the chlorophyll leaf content of plants exposed to α-Fe 2 O 3 , γ-Fe 2 O 3 , Fe 3 O 4 NPs and Fe 3+ were significantly reduced by 31.1%, 14.8%, 18.8% and 22.0%, respectively, relative to the control. Furthermore, RT-PCR analysis revealed no up-regulation of AHA and Nramp3 genes in Citrus maxima roots; however, the relative FRO2 gene expression upon exposure to iron oxide NPs was 1.4-2.8-fold higher than the control. Ferric reductase activity was consistently enhanced upon iron oxide NPs exposure. These findings advance understanding of the interaction mechanisms between metal oxide NPs and plants, and provide important knowledge need for the possible application of these materials in agriculture. Copyright © 2017 Elsevier B.V. All rights reserved.
Fe4Nb2O9 : A magnetoelectric antiferromagnet

NASA Astrophysics Data System (ADS)

Maignan, Antoine; Martin, Christine

2018-04-01

The structural, magnetic, and electrical properties of a Fe4Nb2O9 polycrystalline sample have been characterized. It is found that this compound crystallizes in the P 3 ¯c 1 space group of the α -A l2O3 structure and is thus isostructural to Co4Nb2O9 and Mn4Nb2O9 , two linear magnetoelectric oxides. But in marked contrast, its ɛ'(T ) curve reveals two broad transitions at TN 1≅90 K and TN 2≅77 K , the former corresponding to the antiferromagnetic ordering temperature. Below TN 1, the M(H ) magnetization curves reveal the existence of spin flop at about 6 T. In this temperature region, a H-induced electric polarization for μ0H >6 T is evidenced by both sets of Ip(T) H and P (H) T curves. All these results point towards Fe4Nb2O9 being a magnetoelectric member of the A4B2O9 family (A =Mn , Fe, Co and B =Nb , Ta).
Synthesis and crystal structures of new oxyapatites BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, V.D., E-mail: zhvd@ihim.uran.ru; Tyutyunnik, A.P.; Zubkov, V.G.

2012-10-15

New germanate-vanadates with the general formula BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3, have been synthesized by the nitrate-citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa{sub 4}(VO{sub 4}){sub 3}O (space group P6{sub 3}/m (N 176), Z=2, a=9.8327-9.8755(3), and c=7.1203-7.2133(2) ). They may be viewed as continuous series of solid solutions where Ca{sup 2+} and V{sup 5+} cations in the crystal lattice of vanadate BiCa{sub 4}(VO{sub 4}){sub 3}O are replaced by La{sup 3+} and Ge{sup 4+} cations. In the process of substitution, the La{sup 3+} cations occupy mainlymore » the 4f lattice sites of the germanate-vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa{sub 3}(GeO{sub 4}){sub 3} is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO{sub 4} and VO{sub 4} are separated from each other, and the (V/Ge)O{sub 4} tetrahedra exhibit a quasi-independent behavior. - Graphical abstract: Schematic drawing of the BiCa{sub 3}La(VO{sub 4}){sub 2}(GeO{sub 4})O structure in projection on the ac plane. Green-V and Ge, red-Ca(1) and La(1), yellow-Ca(2), La(2) and Bi, dark-blue-O(1)-O(4), blue-O(5). Highlights: Black-Right-Pointing-Pointer The citrate synthesis of germanate-vanadate oxyapatites. Black-Right-Pointing-Pointer The synthesized compounds crystallize in the hexagonal symmetry. Black-Right-Pointing-Pointer A single series of solid solutions BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, (x=0-3). Black-Right-Pointing-Pointer IR an Raman spectra of mixed crystals.« less
Electrochemical properties and structures of the mixed-valence lithium cuprates Li 3Cu 2O 4 and Li 2NaCu 2O 4

NASA Astrophysics Data System (ADS)

Raekelboom, E. A.; Hector, A. L.; Weller, M. T.; Owen, J. R.

The electrochemical performances of Li 3Cu 2O 4 and Li 2NaCu 2O 4 as cathode materials in lithium coin type batteries have been studied. In Li 3Cu 2O 4, the copper was oxidised to the III level when cycling. The replacement of the lithium by the sodium ions in the octahedral sites in Li 2NaCu 2O 4 might have an effect on the pathway of the lithium ions during the (de)intercalations.
Highly efficient and porous TiO2-coated Ag@Fe3O4@C-Au microspheres for degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Shen, Mao; Chen, Suqing; Jia, Wenping; Fan, Guodong; Jin, Yanxian; Liang, Huading

2016-12-01

In this paper, we reported a novel hierarchical porous Ag@Fe3O4@C-Au@TiO2 core@shell microspheres with a highly photocatalytic activity and magnetically separable properties. The synthesis method is included of a Fe3O4 magnetic embedded Ag core (Ag@Fe3O4), an interlayer of carbon modified by PEI to form sufficient amounts of amine functional groups (Ag@Fe3O4@C-PEI), the grafting of Au nanoparticles on the surface of Ag@Fe3O4@C-PEI (Ag@Fe3O4@C-Au), and an ordered porous TiO2 structured shell. As an example of the applications, the photocatalytic activities of the samples were investigated by the reduction of Rhodamine B (RhB) under visible-light irradiation. The results show that the porous Ag@Fe3O4@C-Au@TiO2 core@shell microspheres display higher adsorption and photocatalytic activities compared to the pure porous TiO2 and Ag@Fe3O4@C@TiO2 microspheres, which are attributed to the local surface plasmon resonance (LSPR) by the Ag and Au nanoparticles and the high specific surface area.
In situ stratospheric measurements of CH4, (C-13)H4, N2O, and OC(O-18) using the BLISS tunable diode laser spectrometer

NASA Technical Reports Server (NTRS)

Webster, Christopher R.; May, Randy D.

1992-01-01

Simultaneous in situ measurements of stratospheric CH4, (C-13)H4, N2O, OC(O-18), pressure, and temperature have been made from Palestine, Texas (32 deg N) in September 1988 with the JPL Balloon-borne Laser In Situ Sensor. Measurements of CH4 and N2O in the altitude range 30-35 km agree well with other measurements, except for an anomalously high value for the N2O at 31 km. Measurements of CH4 support earlier observations of fold in the vertical profile. A ratio for stratospheric (C-13)H4/CH4 of 0.0105 +/- 0.0010 implies an enrichment of delta(C-13) = -45 +/- 92 parts per thousand over the PDB value, in agreement with previous measurements in the troposphere. A large mixing ratio of 1.9 +/- 0.2 ppmv for OC(O-18) is measured, corresponding to an enrichment of delta(O-18) = 280 +/- 50 parts per thousand for the (O-18) isotopic species over the SMOW value.
First-Principles Study of Electronic Structure, Mechanical, and Thermoelectric Properties of Ternary Palladates CdPd3O4 and TlPd3O4

NASA Astrophysics Data System (ADS)

Khan, Amin; Ali, Zahid; Khan, Imad; Ahmad, Iftikhar

2018-03-01

Ternary palladates CdPd3O4 and TlPd3O4 have been studied theoretically using the generalized gradient approximation (GGA), modified Becke-Johnson, and spin-orbit coupling (GGA-SOC) exchange-correlation functionals in the density functional theory (DFT) framework. From the calculated ground-state properties, it is found that SOC effects are dominant in these palladates. Mechanical properties reveal that both compounds are ductile in nature. The electronic band structures show that CdPd3O4 is metallic, whereas TlPd3O4 is an indirect-bandgap semiconductor with energy gap of 1.1 eV. The optical properties show that TlPd3O4 is a good dielectric material. The dense electronic states, narrow-gap semiconductor nature, and Seebeck coefficient of TlPd3O4 suggest that it could be used as a good thermoelectric material. The magnetic susceptibility calculated by post-DFT treatment confirmed the paramagnetic behavior of these compounds.
Estudo da região HII galática NGC 2579

NASA Astrophysics Data System (ADS)

Riffel, R.; Copetti, M. V. F.

2003-08-01

Desde a descoberta dos gradientes de abundância química em galáxias espirais, as regiões HII galáticas têm sido intensamente estudadas com o objetivo de determinar a forma do gradiente de abundância química na Via-Láctea. Entretanto, a forma do gradiente galático continua controversa e existem muitas regiões HII que continuam inexploradas. A região HII galática NGC 2579 é um objeto que aparece em imagens Ha, como uma pequena mancha brilhante de aproximadamente 2 segundos de arco de diâmetro a 20 segundos de arco ao leste de RCW 20, sendo NGC 2579 muitas vezes confundida com esta última. Apesar de seu alto brilho superficial, NGC 2579 é um objeto pouco estudado provavelmente por problemas de identificação deste objeto. Como parte de um projeto de reavaliação dos gradientes de abundância química das regiões HII na Via-Láctea, estamos realizando um estudo extensivo das propriedades físicas básicas como temperatura eletrônica, densidade eletrônica e composição química da região HII galática NGC 2579. Analisamos dados espectrofotométricos de fenda longa na faixa de 3700Å a 7750Å obtidos com o telescópio de 1.52 m do ESO, Chile, em 2002. Determinamos a temperatura eletrônica usando a razão entre as linhas do [OIII] (l4959+l5007/l4363) e a densidade eletrônica pela razão entre as linhas do [SII] (l6716/l6731). As abundâncias químicas do O, N, Cl, S, Ne e He foram determinadas. Realizamos um estudo de imagens fotométricas nas bandas UBVRI obtidas em 2000 no observatório astronômico San Pedro Mártir, México, para identificar e classificar as estrelas ionizantes de NGC 2579 e determinar a distância deste objeto.
Biocompatible polyurethane/thiacalix[4]arenes functionalized Fe3O4 magnetic nanocomposites: Synthesis and properties.

PubMed

Mohammadi, Abbas; Barikani, Mehdi; Lakouraj, Moslem Mansour

2016-09-01

In this study, a series of magnetic polyurethane/Fe3O4 elastomer nanocomposites were prepared by covalently embedding novel thiacalix[4]arenes (TC4As) functionalized Fe3O4 nanoparticles (TC4As-Fe3O4) which contain macrocycles with reactive hydroxyl groups. Surface functionalization of Fe3O4 nanoparticles with TC4As macrocycles as unique reactive surface modifier not only gives specific characteristics to Fe3O4 nanoparticles but also improves the interphase interaction between nanoparticles and the polyurethane matrices through covalent attachment of polymer chains to nanoparticle surfaces. The novel synthesized TC4As-Fe3O4 nanoparticles were characterized by FTIR, XRD, TGA, VSM and SEM analysis. Furthermore, the effect of functionalization of Fe3O4 nanoparticles on the various properties of resulting nanocomposites was studied by XRD, TGA, DMTA, SEM, and a universal tensile tester. It was found that the functionalization of nanoparticles with TC4As affords better mechanical and thermal properties to polyurethane nanocomposites in comparison with unmodified nanoparticles. The SEM analysis showed finer dispersion of TC4As-Fe3O4 nanoparticles than unmodified Fe3O4 nanoparticles within the polyurethane matrices, which arising from formation of covalent bonding between TC4As functionalized Fe3O4 nanoparticles and polyurethane matrices. Moreover, the investigation of in vitro biocompatibility of novel nanocomposites showed that these samples are excellent candidate for biomedical use. Copyright © 2016 Elsevier B.V. All rights reserved.
Synthesis, structure, optical, photoluminescence and magnetic properties of K2[Co(C2O4)2(H2O)2]·4H2O

NASA Astrophysics Data System (ADS)

Narsimhulu, M.; Hussain, K. A.

2018-06-01

The synthesis, crystal structure, optical, photoluminescence and magnetic behaviour of potassium bis(oxalato)cobaltate(II)tertrahydrate{K2[Co(C2O4)2(H2O)2]·4H2O} are described. The compound was grown at room temperature from mixture of aqueous solutions by slow evaporation method. The X-ray crystallographic data showed that the compound belongs to the monoclinic crystal system with P21/n space group and Z = 4. The UV-visible diffuse absorbance spectra exhibited bands at 253, 285 and 541 nm in the visible and ultraviolet regions. The optical band gap of the compound was estimated as 3.4 eV. At room temperature, an intense photoluminescence was observed from this material around 392 nm when it excited at 254 nm. The variable temperature dc magnetic susceptibility measurements exposed paramagnetic behaviour at high temperatures and antiferromagnetic ordering at low temperatures.
Difference between blocking and Néel temperatures in the exchange biased Fe3O4/CoO system.

PubMed

van der Zaag, P J; Ijiri, Y; Borchers, J A; Feiner, L F; Wolf, R M; Gaines, J M; Erwin, R W; Verheijen, M A

2000-06-26

The blocking temperature T(B) has been determined as a function of the antiferromagnetic layer thickness in the Fe3O4/CoO exchange biased system. For CoO layers thinner than 50 A, T(B) is reduced below the Néel temperature T(N) of bulk CoO (291 K), independent of crystallographic orientation or film substrate ( alpha-Al2O3, SrTiO3, and MgO). Neutron diffraction studies show that T(B) does not track the CoO ordering temperature and, hence, that this reduction in T(B) does not arise from finite-size scaling. Instead, the ordering temperature of the CoO layers is enhanced above the bulk T(N) for layer thicknesses approximately less than or equal to 100 A due to the proximity of magnetic Fe3O4 layers.
Determinação da massa de júpiter a partir das órbitas de seus satélites: um experimento didático

NASA Astrophysics Data System (ADS)

Schlickmann, M. S.; Saito, R. K.; Becker, D. A.; Rezende, M. F., Jr.; Cid Fernandes, R.

2003-08-01

Este trabalho apresenta o roteiro piloto de uma prática observacional em astronomia, junto com os primeiros resultados obtidos nesta fase de implementacão. O projeto, que será executado em duas etapas, visa introduzir noções de Astronomia a alunos do Ensino Médio e iniciantes nos cursos de Física. O experimento consiste em medir as órbitas dos satélites Galileanos e, a partir da análise dos dados coletados, verificar a validade da Lei das órbitas de Kepler, determinando a massa do planeta Júpiter. Em uma primeira etapa, as observações serão feitas utilizando um telescópio Meade LX200 10" e câmera CCD para obter uma seqüência de imagens do planeta, que possibilitará medir o movimento de seus satélites. A segunda etapa terá início a partir do funcionamento do telescópio em modo robótico, com a possibilidade de observações via internet por instituições de ensino. Para o desenvolvimento deste experimento foram inicialmente coletadas várias imagens de Júpiter obtidas com os instrumentos citados acima. Estas imagens serviram como base para confecção dos roteiros para a experiência no nível médio e superior. Os roteiros serão inicialmente apresentados em uma home-page. Nela também se buscará uma contextualização histórica da experiência bem como o estabelecimento de relações com professores e alunos, propostas metodológicas e a disponibilização dos programas computacionais necessários para a utilização "on-line" pelos usuários. O projeto conta com apoio da Fundação VITAE.
Excitação e fotoabsorção de moléculas interestelares no ultra violeta

NASA Astrophysics Data System (ADS)

Rodrigues, A. M. F.; Boechat-Roberty, H. M.; Souza, G. B.; Turci, C. C.

2003-08-01

O estudo dos processos de excitação, fotoabsorção e ionização molecular nas nuvens interestelar, permite a análise dos processos químicos, como a formação e destruição de moléculas, até mesmo daquelas que dão origem à vida. Acredita-se que as moléculas como CS2, NH3, CO2 e N2O estão presentes nas nuvens onde são formadas as estrelas e seus sistemas planetários. Estas moléculas são congeladas na superfície de objetos densos, como aqueles encontrados na Nuvem de Oort do nosso Sistema Solar. Quando esses objetos (cometas) desprendem-se dessa região, aproximam-se do Sol, sofrem a interação da radição Ultra Violeta (UV), passam à fase gasosa e são bombardeados por íons e elétrons presentes nos ventos solares. Obtivemos os espectros de fotoabsorção do CS2, NH3 e N2O na faixa do UV, convertendo espectros de Perda de Energia de Elétrons, medidos no menor ângulo de espalhamento e na energia de impacto de 1000 eV. Destes espectros determinamos os valores de força de oscilador (f) e de seção de choque absolutas na faixa de 500 a 2000 Å. Para tal, estudamos e comparamos dois diferentes métodos de conversão. Neste trabalho também geramos muitos dados moleculares como, valores absolutos de seção de choque elástica em função do ângulo de espalhamento e a distribuição de força do oscilador generalizada (df/dE) em função da energia de excitação para diversos ângulos de espalhamento. Comparando nossos espectros de fotoabsorção com o espectro da atmosfera de Júpiter, obtido pelo Telescópio Espacial Hubble, logo após o impacto do cometa Shoemaker-Levy 9, confirmamos a presença do CS2 e da amônia.
First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

NASA Astrophysics Data System (ADS)

Kahlenberg, Volker; Mayerl, Michael Jean-Philippe; Schmidmair, Daniela; Krüger, Hannes; Tribus, Martina

2018-04-01

In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/ c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.
Nanofibrillated Cellulose-Assisted Synthesis of Fiber-Like ZnO-ZnFe2O4 Composites with Enhanced Visible-Light-Driven Photocatalytic Activity

NASA Astrophysics Data System (ADS)

Cai, Aijun; Guo, Aiying; Du, Liqiang; Chang, Yongfang; Wang, Xiuping

2018-05-01

In this article, fiber-like ZnO-ZnFe2O4 composites are obtained by using nanofibrillated cellulose as a biotemplate. The as-prepared composites exhibit strong absorbance in the visible-light region. The ZnO-ZnFe2O4 composites exhibit a similar bandgap (1.88 eV) compared with the ZnFe2O4 (1.85 eV). The ZnO-ZnFe2O4 composites can be easily collected by an external magnet, which contributes to improving the utilization efficiency of the photocatalysts. The photocatalytic activity of the ZnO-ZnFe2O4 catalysts was evaluated by photodegrading rhodamine B (RhB) under visible-light irradiation. Compared with ZnO and ZnFe2O4, the ZnO-ZnFe2O4 catalysts show higher photocatalytic activity due to the efficient electron-hole separation.
Synthesis of polycrystalline CoFe2O4 and NiFe2O4 powders by auto-combustion method using a novel amino-based gel

NASA Astrophysics Data System (ADS)

Jiang, Linwen; Yang, Shanshan; Zheng, Mengyao; Wu, Anhua; Chen, Hongbing

2017-12-01

Polycrystalline CoFe2O4/NiFe2O4 powders were prepared by auto-combustion method using a novel amino-based gel. The thermal evolution of gel precursors, as well as the microstructure, morphology and magnetic properties of as-synthesized powders were studied in detail. Energy dispersive x-ray spectroscopy indicated that the ratios of Ni:Fe was close to the theoretical value (Ni:Fe = 1:2), suggesting high purity of synthesized NiFe2O4 powders. The saturated magnetization (M s) and residual magnetization (M r) of CoFe2O4 were highly dependent upon the annealed temperatures. The M s increased from 77.5 to 84.7 emu g-1, and M r increased from 37.7 emu g-1 to 42.5 emu g-1 by annealing from room temperature to 600 °C. The M s of NiFe2O4 was 38.7 emu g-1, much lower than that of CoFe2O4. The experimental results indicated that this auto-combustion method using amino-based gel was a suitable method for synthesizing high-quality CoFe2O4/NiFe2O4 powders.
Facile preparation of magnetic mesoporous MnFe2O4@SiO2-CTAB composites for Cr(VI) adsorption and reduction.

PubMed

Li, Na; Fu, Fenglian; Lu, Jianwei; Ding, Zecong; Tang, Bing; Pang, Jiabin

2017-01-01

Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe 2 O 4 @SiO 2 -CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area, and vibrating sample magnetometer were used to characterize MnFe 2 O 4 @SiO 2 -CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe 2 O 4 nanoparticles, which ensured the easy separation by an external magnetic field. The performance of MnFe 2 O 4 @SiO 2 -CTAB composites in Cr(VI) removal was far better than that of bare MnFe 2 O 4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe 2 O 4 @SiO 2 -CTAB composites: (1) mesoporous silica shell with abundant CTA + significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe 2 O 4 , followed by Cr(III) immobilized on MnFe 2 O 4 @SiO 2 -CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe 2 O 4 @SiO 2 -CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe 2 O 4 @SiO 2 -CTAB composites exhibited a great potential for the removal of Cr(VI) from water. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Synthesis of magnetic Bi2O2CO3/ZnFe2O4 composite with improved photocatalytic activity and easy recyclability

NASA Astrophysics Data System (ADS)

Liu, Yumin; Ren, Hao; Lv, Hua; Guang, Jing; Cao, Yafei

2018-03-01

Magnetic Bi2O2CO3/ZnFe2O4 heterojunction photocatalysts with varying content of ZnFe2O4 were constructed by modifying Bi2O2CO3 nanosheets with mesoporous ZnFe2O4 nanoparticles. The photoactivity of the products was investigated by decomposing RhodamineB (RhB) and it was found that the photoactivity of Bi2O2CO3/ZnFe2O4 composite was closely related to the loading amount of ZnFe2O4. Under simulant sunlight irradiation, the optimum photoactivity of Bi2O2CO3/ZnFe2O4 composite was almost 2.3 and 2.1 times higher than that by bare ZnFe2O4 and Bi2O2CO3, respectively. The improved photoactivity resulted from the synergistic effect of Bi2O2CO3 and ZnFe2O4, which not only extended the photoabsorption region but also significantly facilitated the interfacial charge transfer. Besides the high photocatalytic performance, Bi2O2CO3/ZnFe2O4 composite also exhibited excellent stable and recycling properties, which enabled it have great potential in a long-term practical use.
Formation of Fe3O4@SiO2@C/Ni hybrids with enhanced catalytic activity and histidine-rich protein separation.

PubMed

Zhang, Yanwei; Zhang, Min; Yang, Jinbo; Ding, Lei; Zheng, Jing; Xu, Jingli; Xiong, Shenglin

2016-09-21

In this paper, we have developed an extended Stöber method to construct a Ni(2+)-polydopamine (PDA) complex thin coating on Fe3O4@SiO2 spheres, which can be carbonized to produce hybrid composites with metallic nickel nanoparticles embedded in a PDA-derived thin graphitic carbon layer (named Fe3O4@SiO2@C/Ni). Interestingly, by introducing a thin SiO2 spacer layer between PDA-Ni(2+) and Fe3O4, the reverse electron transfer from PDA to Fe3O4 is probably able to be suppressed in the calcination process, which leads to the in situ reduction of only Ni(2+) by PDA instead of Fe3O4 and Ni(2+). Consequently, the size and density of nickel nanoparticles on the surface of SiO2@Fe3O4 can be finely adjusted. Moreover, it is found that the ability of tuning nickel nanoparticles is mainly dependent on the thickness of the spacer layer. When the thickness of the SiO2 spacer is beyond the electron penetration depth, the size and density of nickel nanoparticles can be exactly tuned. The as-prepared Fe3O4@SiO2@C/Ni was employed as the catalyst to investigate the catalytic performance in the reduction of 4-nitrophenol (4-NP); furthermore, nickel nanoparticles decorated on Fe3O4@SiO2@C spheres display a strong affinity to His-tagged proteins (BHb and BSA) via a specific metal affinity force between polyhistidine groups and nickel nanoparticles.

Nano-sized Fe2O3/Fe3O4 facilitate anaerobic transformation of hexavalent chromium in soil-water systems.

PubMed

Zhang, Yaxian; Li, Hua; Gong, Libo; Dong, Guowen; Shen, Liang; Wang, Yuanpeng; Li, Qingbiao

2017-07-01

The purpose of this study is to investigate the effects of nano-sized or submicro Fe 2 O 3 /Fe 3 O 4 on the bioreduction of hexavalent chromium (Cr(VI)) and to evaluate the effects of nano-sized Fe 2 O 3 /Fe 3 O 4 on the microbial communities from the anaerobic flooding soil. The results indicated that the net decreases upon Cr(VI) concentration from biotic soil samples amended with nano-sized Fe 2 O 3 (317.1±2.1mg/L) and Fe 3 O 4 (324.0±22.2mg/L) within 21days, which were approximately 2-fold of Cr(VI) concentration released from blank control assays (117.1±5.6mg/L). Furthermore, the results of denaturing gradient gel electrophoresis (DGGE) and high-throughput sequencing indicated a greater variety of microbes within the microbial community in amendments with nano-sized Fe 2 O 3 /Fe 3 O 4 than the control assays. Especially, Proteobacteria occupied a predominant status on the phylum level within the indigenous microbial communities from chromium-contaminated soils. Besides, some partial decrease of soluble Cr(VI) in abiotic nano-sized Fe 2 O 3 /Fe 3 O 4 amendments was responsible for the adsorption of nano-sized Fe 2 O 3 /Fe 3 O 4 to soluble Cr(VI). Hence, the presence of nano-sized Fe 2 O 3 /Fe 3 O 4 could largely facilitate the mobilization and biotransformation of Cr(VI) from flooding soils by adsorption and bio-mediated processes. Copyright © 2017. Published by Elsevier B.V.
Avaliação da influência de alterações cardíacas na ultrassonografia vascular periférica de idosos

PubMed Central

Ribeiro, Alcides José Araújo; Ribeiro, Andréa Campos de Oliveira; Rodrigues, Márcia Marisia Maciel; Negreiros, Sandra de Barros Cobra; Nogueira, Ana Cláudia Cavalcante; Almeida, Osório Luís Rangel; Silva, José Carlos Quináglia e; de Paula, Ana Patrícia

2016-01-01

Resumo Contexto As cardiopatias podem causar alterações no formato das ondas da ultrassonografia vascular (UV) em vasos periféricos. Essas alterações, tipicamente bilaterais e sistêmicas, são pouco conhecidas e estudadas. Objetivo Avaliar as ondas periféricas da UV de pacientes idosos para identificar alterações decorrentes de cardiopatias. Métodos Foram estudados 183 pacientes idosos submetidos a UV periférica no ano de 2014. Resultados Foram avaliados 102 mulheres (55,7%) e 81 homens (44,3%) com idade entre 60 e 91 anos (média de 70,4±7,2 anos). Encontraram-se alterações pela UV em 84 pacientes (45,9%). Foram identificadas 138 alterações de oito dos 13 tipos descritos na literatura: arritmia, onda bisferiens de pico sistólico, baixa velocidade de pico sistólico, pulsatilidade em veias femorais, bradicardia, taquicardia, onda de pulso parvus tardus e onda de pulso alternans. Houve baixa concordância entre a presença e a não presença de alterações na UV e na avaliação cardiológica. Na análise específica das alterações, os exames tiveram uma concordância variável, que foi boa para o achado de taquicardia, moderada para arritmia e baixa para bradicardia. Não houve concordância entre a UV e os exames cardiológicos para as demais alterações. Conclusões É possível identificar determinadas alterações cardíacas em idosos por meio da análise do formato das ondas periféricas da UV. É importante reconhecer e relatar a presença dessas alterações, pela possibilidade de alertar para um diagnóstico ainda não identificado nesses pacientes. Entretanto, mais estudos são necessários para que seja definida a importância das alterações no formato das ondas Doppler periféricas no reconhecimento de cardiopatias. PMID:29930591
MWCNT-MnFe2O4 nanocomposite for efficient hyperthermia applications

NASA Astrophysics Data System (ADS)

Seal, Papori; Hazarika, Monalisa; Paul, Nibedita; Borah, J. P.

2018-04-01

In this work we present synthesis of multi-walled carbon nanotube (MWCNT)-Manganese ferrite (MnFe2O4) nanocomposite and its probable application in hyperthermia. MnFe2O4 nanoparticles were synthesized by co-precipitation method. X ray diffractogram (XRD) confirms the formation of cubic phase of MnFe2O4 with preferred crystallographic orientation along (311) plane. High resolution electron microscope (HRTEM) image of the composites confirms the presence of MnFe2O4 spherical nanoparticles on the surface of CNT which are bound strongly to the surface. MWCNT-MnFe2O4 nanocomposite were prepared after acid functionalization of MWCNT. Vibrational features of the synthesized samples were confirmed through Fourier transformed infra-red spectroscopy (FTIR). FTIR spectra of acid functionalized MWCNT shows a peak positioned at ˜1620cm-1 which corresponds to C=O functional group of carboxylic acid. Prepared MnFe2O4 nanoparticles and MWCNT-MnFe2O4 nanocomposites were subjected to hyperthermia studies.
17O NMR studies on 4- and 4'-substituted chalcones and p-substituted β-nitrostyrenes

NASA Astrophysics Data System (ADS)

Boykin, D. W.; Baumstark, A. L.; Balakrishnan, P.; Perjéssy, A.; Hrnc˜iar, P.

The 17O NMR chemical shift data for 17O-enriched 4- and 4'-chalcones in toluene at 90°C and for p-substituted β-nitrostyrenes (natural abundance) in acetonitrile at 70°C are reported. The SCS (substituent chemical shift) range for the 4-chalcones p-CH 3O to p-NO 2 is 16.3 ppm; the range for the 4'-chalcones p-CH 3O to p-NO 2 is 32.4 ppm. The SCS range for the p-substituted-β-nitrostyrenes p-CH 3O to p-NO 2 is 13.2 ppm. The data for the three series gave good correlations with σ + constants, while the Dual Substitutent Parameter treatment only slightly improved the correlations using σ R+ constants. Plots of the 17O chemical shifts for both 4- and 4'-chalcones with 17O data for acetophenones and correlation of 17O chemical shift data for the β-nitrostyrenes with that of nitrobenzenes gave good correlations. Plots of the 17O data for all the three series with their respective functional group stretching frequencies gave fair correlations.
Heterogeneous UV/Fenton degradation of bisphenol A catalyzed by synergistic effects of FeCo2O4/TiO2/GO.

PubMed

Bai, Xue; Lyu, Lingling; Ma, Wenqiang; Ye, Zhengfang

2016-11-01

A new method for bisphenol A (BPA) degradation in aqueous solution was developed. The characteristics of BPA degradation in a heterogeneous ultraviolet (UV)/Fenton reaction catalyzed by FeCo 2 O 4 /TiO 2 /graphite oxide (GO) were studied. The properties of the synthesized catalysts were characterized using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry. FeCo 2 O 4 and TiO 2 were grown as spherical shape, rough surface, and relatively uniform on the surface of GO (FeCo 2 O 4 /TiO 2 /GO). Batch tests were conducted to evaluate the effects of the initial pH, FeCo 2 O 4 /TiO 2 /GO dosage, and H 2 O 2 concentration on BPA degradation. In a system with 0.5 g L -1 of FeCo 2 O 4 /TiO 2 /GO and 10 mmol L -1 of H 2 O 2 , approximately 90 % of BPA (20 mg L -1 ) was degraded within 240 min of UV irradiation at pH 6.0. The reused FeCo 2 O 4 /TiO 2 /GO catalyst retained its activity after three cycles, which indicates that it is stable and reusable. The heterogeneous UV/Fenton reaction catalyzed by FeCo 2 O 4 /TiO 2 /GO is a promising advanced oxidation technology for treating wastewater that contains BPA.
Spectroscopic properties of Sm3+ and V4+ ions in Na2O-SiO2-ZrO2 glasses

NASA Astrophysics Data System (ADS)

Neeraja, K.; Rao, T. G. V. M.; Kumar, A. Rupesh; Uma Lakshmi, V.; Veeraiah, N.; Rami Reddy, M.

2013-12-01

Na2O-SiO2-ZrO2 glasses of Sm3+ ions with and without V2O5 are characterized by spectroscopic and optical properties. The XRD and EDS spectra of the glass samples reveal an amorphous nature with different compositions within the glass matrix. The Infrared and Raman spectral studies are carried out and the existence of conventional structural units are analyzed in the glass network. The ESR spectra of the glass samples have indicating that a considerable proportion of vanadium ion exists in V4+ state. The optical absorption spectra of these glasses are recorded at room temperature, from the measured intensities of various absorption bands the Judd-Ofelt parameters Ω2, Ω4 and Ω6 are calculated. The photo-luminescence spectra recorded with excited wavelength 400 nm, five emission bands are observed; in this the energy transfer probability takes place between Sm3+ and V4+ ions.
Binder-free NiFe2O4/C nanofibers as air cathodes for Li-O2 batteries

NASA Astrophysics Data System (ADS)

Zhang, Xin; Wang, Chengyi; Chen, Ya-Nan; Wang, Xin-Gai; Xie, Zhaojun; Zhou, Zhen

2018-02-01

Rechargeable Li-O2 batteries have aroused much attention for their high energy density. However, the poor rechargeability and low efficiency hinder their practical applications. To solve these issues, free-standing carbon films combined with high-activity NiFe2O4 catalysts are prepared by electrospinning method, and directly used as air cathodes for Li-O2 batteries. The obtained films have 3D networks formed by stacking and interlacing massive nanofibers with uniformly dispersed NiFe2O4 nanoparticles on them. The Li-O2 batteries with such binder-free air cathodes show low charging overpotential even comparable to precious metal cathodes, and can sustain excellent discharge/charge cyclic stability. The unique structure and binder-free superiority greatly facilitates the Li+ and O2 diffusion, accelerates the decomposition of Li2O2, and avoid the disturbance of polymer binders.
Fabrication and Characterization of Luminescent Magnetic Bifunctional Nanocomposite Based on TbPO4·H2O Nanowires and Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Huong, Nguyen Thanh; Hung, Nguyen Manh; Lien, Pham Thi; Van, Nguyen Duc; Nam, Pham Hong; Binh, Nguyen Thanh; Minh, Le Quoc

2016-07-01

The fabrication and properties of luminescent magnetic bifunctional nanocomposites comprised of TbPO4·H2O nanowires as a core and magnetite nanoparticles as a shell are presented. TbPO4·H2O nanowires were synthesized by a microwave-assisted method while the grafting process of freshly-formed superparamagnetic magnetite nanoparticles on the surface of luminescent nanowires was carried out by a co-precipitate method. The effects of the Fe3O4/TbPO4·H2O mass ratio on the luminescent and magnetic properties of the obtained nanocomposite were also investigated. The results showed that, for the optimized bifunctional nanocomposites, green luminescent emissions at 488 nm, 542 nm, 585 nm, 620 nm and superparamagnetic behavior with saturation magnetization M s of 6 emu/g were achieved. With a hyperthermia temperature of ~43.5°C under an alternating current (AC) magnetic field, the obtained TbPO4·H2O/Fe3O4 nanocomposite was expected to be used for both optical probing and hyperthermia cancer treatments in biomedical applications.
Synthesis, crystal structures and ionic conductivities of Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85}. Two members of the series Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} (M=P, V) related to the fluorite-type structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauvy, F.; Launay, J.C.; Darriet, J.

2005-06-15

The two hitherto unknown compounds Bi{sub 14}P{sub 4}O{sub 31} and Bi{sub 50}V{sub 4}O{sub 85} were prepared by the direct solid-state reaction of Bi{sub 2}O{sub 3} and (NH{sub 4})H{sub 2}PO{sub 4} or V{sub 2}O{sub 5}, respectively. Bi{sub 14}P{sub 4}O{sub 31} crystallizes in a C-centred monoclinic symmetry (C2/c space group) with the unit-cell parameters: a=19.2745(2)A, b=11.3698(1)A, c=52.4082(2)A and {beta}=93.63(1){sup o} (Z=16). The symmetry of Bi{sub 50}V{sub 4}O{sub 85} is also monoclinic (I2/m space group) with lattice parameters of a=11.8123(3)A, b=11.7425(2)A, c=16.5396(2)A and {beta}=90.14(1){sup o} (Z=2). Both structures correspond to a fluorite-type superstructure where the Bi and P or V atoms are orderedmore » in the framework. An idealized structural model is proposed where the structures result of the stacking of mixed atomic layers of composition [Bi{sub 14}M{sub 4}O{sub 31}] and [Bi{sub 18}O{sub 27}] respectively. This new family can be formulated Bi{sub 18-4m}M{sub 4m}O{sub 27+4m} with M=P, V and where the parameter m (0=4}O{sub 31}] layers to the total number of layers in the sequence. Bi{sub 14}P{sub 4}O{sub 31} corresponds to m=1 when Bi{sub 50}V{sub 8}O{sub 85} corresponds to m=1/3. In this last case, the structural sequence is simply one [Bi{sub 14}V{sub 4}O{sub 31}] layer to two [Bi{sub 18}O{sub 27}] layers. As predicted by the proposed structural building principle, Bi{sub 14}P{sub 4}O{sub 31} is not a good ionic conductor. The conductivity at 650 deg. C is 4 orders of magnitude lower from those found in Bi{sub 46}M{sub 8}O{sub 89} (M=P, V) (m=2/3) and Bi{sub 50}V{sub 4}O{sub 85} (m=1/3)« less
Oxygen electrode bifunctional electrocatalyst NiCo2O4 spinel

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph

1988-01-01

A significant increase in energy density may be possible if a two-unit alkaline regenerative H2-O2 fuel cell is replaced with a single-unit system that uses passive means for H2O transfer and thermal control. For this single-unit system, new electrocatalysts for the O2 electrode will be required which are not only bifunctionally active but also chemically and electrochemically stable between the voltage range of about 0.7 and 1.5 V. NiCo2O4 spinel is reported to have certain characteristics that make it useful for a study of electrode fabrication techniques. High surface area NiCo2O4 powder was fabricated into unsupported, bifunctional, PTFE-bonded, porous gas fuel cell electrodes by commercial sources using varying PTFE contents and sintering temperatures. The object of this study is to measure the bifunctional activities of these electrodes and to observe what performance differences might result from different commercial electrode fabricators. O2 evolution and O2 reduction data were obtained at 80 C (31 percent KOH). An irreversible reaction (i.e., aging) occurred during O2 evolution at potentials greater than about 1.5 V. Anodic Tafel slopes of 0.06 and 0.12 V/decade were obtained for the aged electrodes. Within the range of 15 to 25 percent, the PTFE content was not a critical parameter for optimizing the electrode for O2 evolution activity. Sintering temperatures between 300 and 340 C may be adequate but heating at 275 C may not be sufficient to properly sinter the PTFE-NiCo2O4 mixture. Electrode disintegration was observed during O2 reduction. Transport of O2 to the NiCo2O4 surface became prohibitive at greater than about -0.02 A/sq cm. Cathodic Tafel slopes of -0.6 and -0.12 V/decade were assumed for the O2 reduction process. A PTFE content of 25 percent (or greater) appears to be preferable for sintering the PTFE-NiCo2O4 mixture.
Phase transitions in (NH4)2MoO2F4 crystal

NASA Astrophysics Data System (ADS)

Krylov, Alexander; Laptash, Natalia; Vtyurin, Alexander; Krylova, Svetlana

2016-11-01

The mechanisms of temperature and high pressure phase transitions have been studied by Raman spectroscopy. Room temperature (295 K) experiments under high hydrostatic pressure up to 3.6 GPa for (NH4)2 MoO2 F4 have been carried out. Experimental data indicates a phase transition into a new high-pressure phase for (NH4)2 MoO2 F4 at 1.2 GPa. This phase transition is related to the ordering anion octahedron groups [MoO2 F4]2- and is not associated with ammonium group. Raman spectra of small non-oriented crystals ranging from 10 to 350 K have been observed. The experiment shows anion groups [MoO2 F4]2- and ammonium in high temperature phase are disordered. The phase transition at T1 = 269.8 K is of the first-order, close to the tricritical point. The first temperature phase transition is related to the ordering anion octahedron groups [MoO2 F4]2-. Second phase transitions T2 = 180 K are associated with the ordering of ammonium. The data presented within this study demonstrate that 2D correlation analysis combined with traditional Raman spectroscopy are powerful tool to study phase transitions in the crystals.
Uma Visão do Universo Segundo um Grupo de Alunos do Ensino Médio de São Paulo

NASA Astrophysics Data System (ADS)

Elias, D. S.; Araújo, M.; Amaral, L. H.; Voelzke, M. R.; Araújo, M.

2005-08-01

A astronomia, embora seja uma ciência popular, com inúmeras descobertas de interesse público, ainda é apresentada desconsiderando-se os aspectos históricos e científicos relacionados ao seu desenvolvimento, sendo geralmente veiculada nos meios de comunicação de maneira pouco esclarecedora e não raro com imprecisões. Neste trabalho analisou-se a concepção de um grupo de estudantes de Ensino Médio sobre conceitos de astronomia, visando identificar sua visão de mundo a respeito do Universo, envolvendo idéias sobre espaço e tempo. Para issso, foi aplicado um questionário em três escolas da grande São Paulo em um espaço amostral de 270 alunos. Constatou-se que, embora o ensino de astronomia esteja previsto nos PCNEM, os resultados obtidos na pesquisa mostram que há grande deficiência no conhecimento dos temas investigados. Nesse sentido, verificou-se que apenas 20% dos alunos eram capazes de relacionar a sucessão das semanas com as fases da lua, enquanto 28% associaram as estações do ano à inclinação do eixo de rotação da Terra. Por outro lado, somente 23% dos alunos tinham noções das distâncias entre os objetos celestes próximos da Terra e 56% conseguiram relacionar o Big Bang com a origem do Universo. Finalmente, constatou-se que 37% reconheciam o ano-luz como uma unidade de distância e 60% reconheciam o Sol como sendo uma estrela. Apesar de 60% dos alunos indicarem que a escola é a principal fonte para aquisição dos conhecimentos de astronomia, conclui-se que seus conceitos nessa área ainda são inadequados, havendo necessidade de ampliação e aprimoramento da abordagem desses conteúdos nos ambientes escolares.
Monoclinic modification of bis(μ2-pyridine-2,6-dicarboxylato)-κ4 O 2,N,O 6:O 6;κ4 O 2:O 2,N,O 6-bis[aquadibutyltin(IV)

PubMed Central

Ng, Seik Weng

2011-01-01

The SnIV atom in the centrosymmetric dinuclear title compound, [Sn2(C4H9)4(C7H3NO4)2(H2O)2], exists in a trans-C2SnNO4 pentagonal–bipyramidal geometry. There are two half-molecules in the asymmetric unit that are completed by inversion symmetry. The crystal studied was a non-merohedral twin with a ratio of 47.3 (1)% for the minor twin component. Bond dimensions are similar to those found in the tetragonal polymorph [Huber et al. (1989 ▶). Acta Cryst. C45, 51–54]. O—H⋯O hydrogen-bonding interactions stabilize the crystal packing. PMID:21522924
Efficient solar light-driven degradation of Congo red with novel Cu-loaded Fe3O4@TiO2 nanoparticles.

PubMed

Arora, Priya; Fermah, Alisha; Rajput, Jaspreet Kaur; Singh, Harminder; Badhan, Jigyasa

2017-08-01

In this work, Cu-loaded Fe 3 O 4 @TiO 2 core shell nanoparticles were prepared in a single pot by coating of TiO 2 on Fe 3 O 4 nanoparticles followed by Cu loading. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), thermogravimetric analysis (TGA), Brunauer-Emmett- Teller (BET), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and valence band X-ray photoelectron spectroscopy (VB XPS) techniques were used for characterization of as prepared nanoparticles. Synergism between copper and titania was evaluated by studying the solar light-driven photodegradation of Congo red dye solution in the presence of Fe 3 O 4 @TiO 2 nanoparticles on one side and Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles on the other side. The latter performed better than the former catalyst, indicating the enhanced activity of copper-loaded catalyst. Further photodegradation was studied by three means, i.e., under ultraviolet (UV), refluxing, and solar radiations. Cu-loaded Fe 3 O 4 @TiO 2 enhanced the degradation efficiency of Congo red dye. Thus, Cu act possibly by reducing the band gap of TiO 2 and widening the optical response of semiconductor, as a result of which solar light could be used to carry out photocatalysis. Graphical abstract Photodegradation of congo red over Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles.
Operando identification of the point of [Mn- 2]O- 4 spinel formation during gamma-MnO 2 discharge within batteries

DOE PAGES

Gallaway, Joshua W.; Hertzberg, Benjamin J.; Zhong, Zhong; ...

2016-05-07

The rechargeability of γ-MnO 2 cathodes in alkaline batteries is limited by the formation of the [Mn 2]O 4 spinels ZnMn 2O 4 (hetaerolite) and Mn 3O 4 (hausmannite). However, the time and formation mechanisms of these spinels are not well understood. Here we directly observe γ-MnO 2 discharge at a range of reaction extents distributed across a thick porous electrode. Coupled with a battery model, this reveals that spinel formation occurs at a precise and predictable point in the reaction, regardless of reaction rate. Observation is accomplished by energy dispersive X-ray diffraction (EDXRD) using photons of high energy andmore » high flux, which penetrate the cell and provide diffraction data as a function of location and time. After insertion of 0.79 protons per γ-MnO 2 the α-MnOOH phase forms rapidly. α-MnOOH is the precursor to spinel, which closely follows. ZnMn 2O 4 and Mn 3O 4 form at the same discharge depth, by the same mechanism. The results show the final discharge product, Mn 3O 4 or Mn(OH) 2, is not an intrinsic property of γ-MnO 2. While several studies have identified Mn(OH) 2 as the final γ-MnO 2 discharge product, we observe direct conversion to Mn 3O 4 with no Mn(OH) 2.« less
Porous Co3O4 nanorods anchored on graphene nanosheets as an effective electrocatalysts for aprotic Li-O2 batteries

NASA Astrophysics Data System (ADS)

Yuan, Mengwei; Yang, Yan; Nan, Caiyun; Sun, Genban; Li, Huifeng; Ma, Shulan

2018-06-01

The large over-potential during the battery operation is a great obstacle for the application of Li-O2 batteries. The porous structure and electrical conductivity of the electrocatalysts are significant for the electrocatalytic performance of Li-O2 batteries. In this work, a porous Co3O4/GN nanocomposite (Co3O4 nanorods anchored on graphene nanosheets) is prepared via a facile hydrothermal method assisted with heat treatment. The unique structure of Co3O4/GN endows efficient electrocatalystic activity for Li-O2 batteries. In comparison to the Co3O4, the Co3O4/GN demonstrates a better cycle performance showing more than 40 cycles with a 1500 mAh g-1 capacity limit strategy at a current density of 300 mA g-1, and a reduced over-potential of 110 mV at high current density (1200 mA g-1). The Co3O4/GN also displays a high initial specific capacity (7600 mAh g-1) and a good reversibility in full cycle with a coulombic efficiency of 99.8% in the first cycle. The impressed cyclability, specific capacity, rate performance, and low over-potentials indicate that the as-prepared Co3O4/GN nanocomposite is a promising catalyst candidate for reversible Li-O2 batteries.
Phosphoinnelite, Ba4Na3Ti3Si4O14(PO4,SO4)2(O,F)3, a new mineral species from peralkaline pegmatite of the Kovdor pluton, Kola Peninsula

NASA Astrophysics Data System (ADS)

Pekov, I. V.; Chukanov, N. V.; Kulikova, I. M.; Belakovsky, D. I.

2007-12-01

Phosphoinnelite, an analogue of innelite with P > S, has been found in a peralkaline pegmatite vein crosscutting calcite carbonatite at the phlogopite deposit, Kovdor pluton, Kola Peninsula. Cancrinite (partly replaced with thomsonite-Ca), orthoclase, aegirine-augite, pectolite, magnesioarfvedsonite, golyshevite, and fluorapatite are associated minerals. Phosphoinnelite occurs as lath-shaped crystals up to 0.2 × 1 × 6 mm in size, which are combined typically in bunch-, sheaf-, and rosettelike segregations. The color is yellow-brown, with vitreous luster on crystal faces and greasy luster on broken surfaces. The mineral is transparent. The streak is pale yellowish. Phosphoinnelite is brittle, with perfect cleavage parallel to the {010} and good cleavage parallel to the {100}; the fracture is stepped. The Mohs hardness is 4.5 to 5. Density is 3.82 g/cm3 (meas.) and 3.92 g/cm3 (calc.). Phosphoinnelite is biaxial (+), α = 1.730, β = 1.745, and γ = 1.764, 2V (meas.) is close to 90°. Optical orientation is Z^c ˜ 5°. Chemical composition determined by electron microprobe is as follows (wt %): 6.06 Na2O, 0.04 K2O, 0.15 CaO, 0.99 SrO, 41.60 BaO, 0.64 MgO, 1.07 MnO, 1.55 Fe2O3, 0.27 Al2O3, 17.83 SiO2, 16.88 TiO2, 0.74 Nb2O5, 5.93 P2O5, 5.29 SO3, 0.14 F, -O=F2 = -0.06, total is 99.12. The empirical formula calculated on the basis of (Si,Al)4O14 is (Ba3.59Sr0.13K0.01)Σ3.73(Na2.59Mg0.21Ca0.04)Σ3.04(Ti2.80Fe{0.26/3+}Nb0.07)Σ3.13[(Si3.93Al0.07)Σ4O14(P1.11S0.87)Σ1.98O7.96](O2.975F0.10)Σ3.075. The simplified formula is Ba4Na3Ti3Si4O14(PO4,SO4)2(O,F)3. The mineral is triclinic, space group P overline 1 or P1. The unit cell dimensions are a = 5.38, b = 7.10, c = 14.76 Å; α = 99.00°, β = 94.94°, γ = 90.14°; and V = 555 Å3, Z = 1. The strongest lines of the X-ray powder pattern [ d, Å in ( I)( hkl)] are: 14.5(100)(001), 3.455(40)(103), 3.382(35)(0overline 2 2), 2.921(35)(005), 2.810(40)(1overline 1 4), 2.683(90)(200, overline 2 01), 2.133(80)(overline 2 overline
The Niño1+2 region and the Niño4 region predictability.

NASA Astrophysics Data System (ADS)

Miguel, Tasambay-Salazar; Jose, Ortizbevia Maria; Francisco Jose, Alvarez-Garcia; Antonio, Ruizdeelvira

2016-04-01

The El Niño-Southern Oscillation variability is monitored basically by the the Niño3.4 Index. In addition, the Niño1+2 and the Niño4 Indexes are also used to characterise ENSO variability, by reason of their relationships with some of the variability of the neighboring regions, like the air temperature in South America or Australia. However, with the increased length of the available instrumental ENSO records, the need of considering the two different ENSO types identified, Eastern Pacific (EP) or Central Pacific (CP), has become more evident. (Yu and Kim 2013). While the Nino3.4 Index is used to monitor the EP events, the CP events are currently identified by removing from the Niño4 Index the variability associated to the Niño1+2 Index (Kao and Yu 2009). Therefore there is a renewed interest on the predictability of both Indexes. In this study we focus on the predictability of the Niño1+2 region variability and those of the Niño4 region, in the recent post-satellital period. We develop a methodology to identify potential predictors among climate modes, represented by their respective indexes. Among the tropical predictors tested we include the most commonly used,like the Southern Oscillation Index or the Warm Water Volume in the equatorial Pacific (WWV) Index, but also some whose part in the ENSO generation and evolution has been pointed only recently, like the Pacific Meridional Mode (PMM) Index or the North Tropical Zonal Gradient and South Tropical Zonal Gradient Indexes.We also include in our study some other tropical Indexes outside the Pacific basin, like the Tropical North Atlantic, the Tropical South Atlantic and the Indian Ocean Dipole Indexes. We use a seasonal approach, based in a linear statistical relationship and focus on leads going from one season to one year. In the case of the Niño1+2 Index, the number of potential predictors is much higher in spring, followed by winter and summer and last of all autumn. The potential predictor most
Morphological Control of Mesoporosity and Nanoparticles within Co3O4-CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance.

PubMed

Pradhan, Amaresh C; Uyar, Tamer

2017-10-18

The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co 3 O 4 -CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co 3 O 4 -CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co 3 O 4 -CuO NFs but also single mesoporous Co 3 O 4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co 3 O 4 nanofibers framework (Co 3 O 4 -CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co 3 O 4 -CuO NFs is due to the internal charge transfer between Co 2+ to Co 3+ and Cu 2+ , proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co 3 O 4 also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co 3 O 4 -CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co 3 O 4 -CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co 3 O 4 NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic
Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.

PubMed

Villani, M; Rimoldi, T; Calestani, D; Lazzarini, L; Chiesi, V; Casoli, F; Albertini, F; Zappettini, A

2013-04-05

A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

Unique and hierarchically structured novel Co3O4/NiO nanosponges with superior photocatalytic activity against organic contaminants

NASA Astrophysics Data System (ADS)

Raja, Vahini; Puvaneswaran, Senthil Kumar; Swaminathan, Karuthapandian

2017-12-01

In the present study, novel Co3O4/NiO nanosponges designed for the photocatalytic degradation of organic contaminants were synthesized by a simple precipitation technique. The formation of sponge-like nanostructures was clearly evident through the TEM analysis. The photocatalytic efficiency was tested against rhodamine B (RhB) and congo red (CR) dye solutions. Co3O4/NiO nanosponges showed excellent and enhanced photocatalytic efficacy compared to those of Co3O4, NiO nanoparticles, and standards like TiO2 and ZnO. The influence of paramount important operational parameters was explored and the conditions for the best photocatalytic efficiency were optimized. The trapping experiment revealed that the reactive oxygen species (ROS) identified was OH radical. These findings certainly open up a new way for synthesizing a morphology dependent photocatalyst.
Influence of O-Co-O layer thickness on the thermal conductivity of Na{sub x}Co{sub 2}O{sub 4} studied by positron annihilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, H. Q.; Zhao, B.; Zhang, T.

2015-07-21

Nominal stoichiometric Na{sub x}Co{sub 2}O{sub 4} (x = 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0) polycrystals were synthesized by a solid-state reaction method. They were further pressed into pellets by the spark plasma sintering. The crystal structure and morphology of Na{sub x}Co{sub 2}O{sub 4} samples were characterized by X-ray diffraction and scanning electron microscopy measurements. Good crystallinity and layered structures were observed for all the samples. Positron annihilation measurements were performed for Na{sub x}Co{sub 2}O{sub 4} as a function of Na content. Two lifetime components are resolved. τ{sub 1} is attributed mainly to positron annihilation in the O-Co-O layers and shifts tomore » Na layers only in the H3 phase. The second lifetime τ{sub 2} is due to positron annihilation in vacancy clusters which may exist in the Na layers or grain boundary region. The size of vacancy clusters grow larger but their concentration decreases with increasing Na content in the range of 1.0 < x < 1.8. The thickness of O-Co-O layer also shows continuous increase with increasing Na content, which is reflected by the increase of τ{sub 1}. The thermal conductivity κ, on the other hand, shows systematic decrease with increasing Na content. This suggests that the increasing spacing of O-Co-O layer could effectively reduce the thermal conductivity of Na{sub x}Co{sub 2}O{sub 4}.« less
Characterization of Fe3O4/SiO2/Gd2O(CO3)2 core/shell/shell nanoparticles as T1 and T2 dual mode MRI contrast agent.

PubMed

Yang, Meicheng; Gao, Lipeng; Liu, Kai; Luo, Chunhua; Wang, Yiting; Yu, Lei; Peng, Hui; Zhang, Wen

2015-01-01

Core/shell/shell structured Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles were successfully synthesized. Their properties as a new type of T1-T2 dual model contrast agent for magnetic resonance imaging were investigated. Due to the introduce of a separating SiO2 layer, the magnetic coupling between Gd2O(CO3)2 and Fe3O4 could be modulated by the thickness of SiO2 layer and produce appropriate T1 and T2 signal. Additionally, the existence of Gd(3+) enhances the transverse relaxivity of Fe3O4 possibly because of the magnetic coupling between Gd(3+) and Fe3O4. The Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles exhibit good biocompatibility, showing great potential for biomedical applications. Copyright © 2014 Elsevier B.V. All rights reserved.
Synthesis of nanocrystalline α - Zn 2SiO 4 at ZnO-porous silicon interface: Phase transition study

NASA Astrophysics Data System (ADS)

Singh, R. G.; Singh, Fouran; Mehra, R. M.; Kanjilal, D.; Agarwal, V.

2011-05-01

Thermal annealing induced formation of nanocrystalline Zinc silicate (α-Zn 2SiO 4) at the interface of ZnO-porous silicon (PSi) nanocomposites is reported. The PSi templates were formed by electrochemical anodization of p-type (100) Si and ZnO crystallites were deposited on the PSi surface by a Sol-gel spin coating process. The formation of α-Zn 2SiO 4 is confirmed by glancing angle X-ray diffraction and Fourier transform infrared spectroscopy studies. The presence of intense yellow-green emission also confirms the formation of α-Zn 2SiO 4. The mechanism of silicate phase formation at the ZnO-PSi interface and the origin of various photoluminescence (PL) bands are discussed in view of its potential applications in advanced optoelectronic devices.
Improving low-temperature performance of spinel LiNi0.5Mn1.5O4 electrode and LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell by coating solid-state electrolyte Li-Al-Ti-P-O

NASA Astrophysics Data System (ADS)

Bi, Kun; Zhao, Shi-Xi; Huang, Chao; Nan, Ce-Wen

2018-06-01

Octahedral cathode materials LiNi0.5Mn1.5O4 (LNMO), with primary particles size of 300-600 nm are prepared through one-step co-precipitation. Then solid-state electrolyte Li2O-Al2O3-TiO2-P2O5 (LATP) was coated on LNMO to form continuous surface-modification layer. There is no obviously difference of structure, morphology between coated LATP LiNi0.5Mn1.5O4 (LATP-LNMO) and pristine LiNi0.5Mn1.5O4 (P-LNMO). Low-temperature electrochemical performance of P-LNMO and LATP-LNMO electrodes, including charge-discharge capacity, cycle performance, middle discharge voltage and electrochemical impedance spectra (EIS), were measured systematically with three electrode. The results reveal that LATP-LNMO electrode presents superior electrochemical performance at low temperature, compared to P-LNMO electrode. At -20 °C, the capacity retention of LATP-LNMO (61%) is much higher than that of P-LNMO (39%). According to EIS, the enhancement of performance of LATP-LNMO cathode at low temperature can be attribute to LATP coating, which not only promotes lithium-ion diffusion at electrode/electrolyte interface but also decreases the charge transfer resistance. Finally, the electrochemical performances of full cell of LATP-LNMO or P-LNMO cathode vs Li4Ti5O12 anode are investigated. The energy density can be achieved to 270 Wh·Kg-1 at -20 °C if using LATP-LNMO, which is much better than that of P-LNMO.
Spin orientations of the spin-half Ir 4+ ions in Sr 3NiIrO 6, Sr 2IrO 4 and Na 2IrO 3: Density functional, perturbation theory and Madelung potential analyses

DOE PAGES

Gordon, Elijah E.; Xiang, Hongjun; Koehler, Jurgen; ...

2016-03-01

The spins of the low-spin Ir 4+ (S = 1/2, d 5) ions at the octahedral sites of the oxides Sr 3NiIrO 6, Sr 2IrO 4 and Na 2IrO 3 exhibit preferred orientations with respect to their IrO6 octahedra. We evaluated the magnetic anisotropies of these S = 1/2 ions on the basis of DFT calculations including spin-orbit coupling (SOC), and probed their origin by performing perturbation theory analyses with SOC as perturbation within the LS coupling scheme. The observed spin orientations of Sr 3NiIrO 6 and Sr 2IrO 4 are correctly predicted by DFT calculations, and are accounted formore » by the perturbation theory analysis. As for the spin orientation of Na 2IrO 3, both experimental studies and DFT calculations have not been unequivocal. Our analysis reveals that the Ir 4+ spin orientation of Na 2IrO 3 should have nonzero components along the c- and a-axes directions. The spin orientations determined by DFT calculations are sensitive to the accuracy of the crystal structures employed, which is explained by perturbation theory analyses when interactions between adjacent Ir 4+ ions are taken into consideration. There are indications implying that the 5d electrons of Na 2IrO 3 are less strongly localized compared with those of Sr 3NiIrO 6 and Sr 2IrO 4. This implication was confirmed by showing that the Madelung potentials of the Ir 4+ ions are less negative in Na 2IrO 3 than in Sr 3NiIrO 6, Sr 2IrO 4. Most transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC induces interactions among their crystal-field split d-states, and the associated mixing of the states modifies only the orbital parts of the states. This finding cannot be mimicked by a spin Hamiltonian because this model Hamiltonian lacks the orbital degree of freedom, thereby leading to the spin-half syndrome. As a result, the spin-orbital entanglement for the 5d spin-half ions Ir 4+ is not as strong as has been assumed lately.« less
Spin orientations of the spin-half Ir4+ ions in Sr3NiIrO6, Sr2IrO4, and Na2IrO3: Density functional, perturbation theory, and Madelung potential analyses

NASA Astrophysics Data System (ADS)

Gordon, Elijah E.; Xiang, Hongjun; Köhler, Jürgen; Whangbo, Myung-Hwan

2016-03-01

The spins of the low-spin Ir4+ (S = 1/2, d5) ions at the octahedral sites of the oxides Sr3NiIrO6, Sr2IrO4, and Na2IrO3 exhibit preferred orientations with respect to their IrO6 octahedra. We evaluated the magnetic anisotropies of these S = 1/2 ions on the basis of density functional theory (DFT) calculations including spin-orbit coupling (SOC), and probed their origin by performing perturbation theory analyses with SOC as perturbation within the LS coupling scheme. The observed spin orientations of Sr3NiIrO6 and Sr2IrO4 are correctly predicted by DFT calculations, and are accounted for by the perturbation theory analysis. As for the spin orientation of Na2IrO3, both experimental studies and DFT calculations have not been unequivocal. Our analysis reveals that the Ir4+ spin orientation of Na2IrO3 should have nonzero components along the c- and a-axis directions. The spin orientations determined by DFT calculations are sensitive to the accuracy of the crystal structures employed, which is explained by perturbation theory analyses when interactions between adjacent Ir4+ ions are taken into consideration. There are indications implying that the 5d electrons of Na2IrO3 are less strongly localized compared with those of Sr3NiIrO6 and Sr2IrO4. This implication was confirmed by showing that the Madelung potentials of the Ir4+ ions are less negative in Na2IrO3 than in Sr3NiIrO6 and Sr2IrO4. Most transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC induces interactions among their crystal-field split d-states, and the associated mixing of the states modifies only the orbital parts of the states. This finding cannot be mimicked by a spin Hamiltonian because this model Hamiltonian lacks the orbital degree of freedom, thereby leading to the spin-half syndrome. The spin-orbital entanglement for the 5d spin-half ions Ir4+ is not as strong as has been assumed.
Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

NASA Astrophysics Data System (ADS)

Ahmad, Bhat Zahoor; Want, Basharat

2016-04-01

We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau- Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.
Synthesis and catalytic activity of electrospun NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation

NASA Astrophysics Data System (ADS)

Kim, Il Hee; Lee, Hyerim; Yu, Areum; Jeong, Jae Hwan; Lee, Youngmi; Kim, Myung Hwa; Lee, Chongmok; Dok Kim, Young

2018-04-01

NiO/NiCo2O4 nanotubes with a diameter of approximately 100 nm are synthesized using Ni and Co precursors via electro-spinning and subsequent calcination processes. The tubular structure is confirmed via transmission electron microscopy imaging, whereas the structures and elemental compositions of the nanotubes are determined using x-ray diffraction, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. N2 adsorption isotherm data reveal that the surface of the nanotubes consists of micropores, thereby resulting in a significantly higher surface area (˜20 m2 g-1) than expected for a flat-surface structure (<15 m2 g-1). Herein, we present a study of the catalytic activity of our novel NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation. The catalytic activity of NiO/NiCo2O4 is superior to Pt below 100 °C for CO oxidation. For acetaldehyde oxidation, the total oxidation activity of NiO/NiCo2O4 for acetaldehyde is comparable with that of Pt. Coexistence of many under-coordinated Co and Ni active sites in our structure is suggested be related to the high catalytic activity. It is suggested that our novel NiO/NiCo2O4 tubular structures with surface microporosity can be of interest for a variety of applications, including the catalytic oxidation of harmful gases.
Synthesis and catalytic activity of electrospun NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation.

PubMed

Kim, Il Hee; Lee, Hyerim; Yu, Areum; Jeong, Jae Hwan; Lee, Youngmi; Kim, Myung Hwa; Lee, Chongmok; Kim, Young Dok

2018-04-27

NiO/NiCo 2 O 4 nanotubes with a diameter of approximately 100 nm are synthesized using Ni and Co precursors via electro-spinning and subsequent calcination processes. The tubular structure is confirmed via transmission electron microscopy imaging, whereas the structures and elemental compositions of the nanotubes are determined using x-ray diffraction, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. N 2 adsorption isotherm data reveal that the surface of the nanotubes consists of micropores, thereby resulting in a significantly higher surface area (∼20 m 2 g -1 ) than expected for a flat-surface structure (<15 m 2 g -1 ). Herein, we present a study of the catalytic activity of our novel NiO/NiCo 2 O 4 nanotubes for CO and acetaldehyde oxidation. The catalytic activity of NiO/NiCo 2 O 4 is superior to Pt below 100 °C for CO oxidation. For acetaldehyde oxidation, the total oxidation activity of NiO/NiCo 2 O 4 for acetaldehyde is comparable with that of Pt. Coexistence of many under-coordinated Co and Ni active sites in our structure is suggested be related to the high catalytic activity. It is suggested that our novel NiO/NiCo 2 O 4 tubular structures with surface microporosity can be of interest for a variety of applications, including the catalytic oxidation of harmful gases.
Passage of Magnetic Tat-Conjugated Fe3O4@SiO2 Nanoparticles Across In Vitro Blood-Brain Barrier

NASA Astrophysics Data System (ADS)

Zhao, Xueqin; Shang, Ting; Zhang, Xiaodan; Ye, Ting; Wang, Dajin; Rei, Lei

2016-10-01

Delivery of diagnostic or therapeutic agents across the blood-brain barrier (BBB) remains a major challenge of brain disease treatment. Magnetic nanoparticles are actively being developed as drug carriers due to magnetic targeting and subsequently reduced off-target effects. In this paper, we developed a magnetic SiO2@Fe3O4 nanoparticle-based carrier bound to cell-penetrating peptide Tat (SiO2@Fe3O4 -Tat) and studied its fates in accessing BBB. SiO2@Fe3O4-Tat nanoparticles (NPs) exhibited suitable magnetism and good biocompatibility. NPs adding to the apical chamber of in vitro BBB model were found in the U251 glioma cells co-cultured at the bottom of the Transwell, indicating that particles passed through the barrier and taken up by glioma cells. Moreover, the synergistic effects of Tat and magnetic field could promote the efficient cellular internalization and the permeability across the barrier. Besides, functionalization with Tat peptide allowed particles to locate into the nucleus of U251 cells than the non-conjugated NPs. These results suggest that SiO2@Fe3O4-Tat NPs could penetrate the BBB through the transcytosis of brain endothelial cells and magnetically mediated dragging. Therefore, SiO2@Fe3O4-Tat NPs could be exploited as a potential drug delivery system for chemotherapy and gene therapy of brain disease.
Structural and electronic investigations of PbTa4O11 and BiTa7O19 constructed from α-U3O8 types of layers

NASA Astrophysics Data System (ADS)

Boltersdorf, Jonathan; Maggard, Paul A.

2015-09-01

The PbTa4O11 and BiTa7O19 phases were prepared by ion-exchange and solid-state methods, respectively, and their structures were characterized by neutron time-of-flight diffraction and Rietveld refinement methods (PbTa4O11, R 3 (No. 146), a=6.23700(2) Å, c=36.8613(1) Å; BiTa7O19, P 6 bar c 2 (No. 188), a=6.2197(2) Å, c=20.02981(9) Å). Their structures are comprised of layers of TaO6 octahedra surrounded by three 7-coordinate Pb(II) cations or two 8-coordinate Bi(III) cations. These layers alternate down the c-axis with α-U3O8 types of single and double TaO7 pentagonal bipyramid layers. In contrast to earlier studies, both phases are found to crystallize in noncentrosymmetric structures. Symmetry-lowering structural distortions within PbTa4O11, i.e. R 3 bar c →R3, are found to be a result of the displacement of the Ta atoms within the TaO7 and TaO6 polyhedra, towards the apical and facial oxygen atoms, respectively. In BiTa7O19, relatively lower reaction temperatures leads to an ordering of the Bi/Ta cations within a lower-symmetry structure, i.e., P63/mcm→ P 6 bar c 2 . In the absence of Bi/Ta site disorder, the Ta-O-Ta bond angles decrease and the Ta-O bond distances increase within the TaO7 double layers. Scanning electron microscopy images reveal two particle morphologies for PbTa4O11, hexagonal rods and finer irregularly-shaped particles, while BiTa7O19 forms as aggregates of irregularly-shaped particles. Electronic-structure calculations confirm the highest-energy valence band states are comprised of O 2p-orbitals and the respective Pb 6s-orbital and Bi 6s-orbital contributions. The lowest-energy conduction band states are composed of Ta 5d-orbital contributions that are delocalized over the TaO6 octahedra and layers of TaO7 pentagonal bipyramids. The symmetry-lowering distortions in the PbTa4O11 structure, and the resulting effects on its electronic structure, lead to its relatively higher photocatalytic activity compared to similar structures without
Synthesis, characterization, and magnetic properties of ZnO-ZnFe2O4 nanoparticles with high photocatalytic activity

NASA Astrophysics Data System (ADS)

Falak, P.; Hassanzadeh-Tabrizi, S. A.; Saffar-Teluri, A.

2017-11-01

In the present research, a magnetic ZnO-ZnFe2O4 binary nanocomposite was synthesized by a one-step microemulsion method. The characteristics of the synthesized powders were characterized using various analytical instruments including X-ray diffraction, scanning electron microscope, transmission electron microscope, thermogravimetric and differential thermal analysis, vibrating sample magnetometer, and ultraviolet-visible spectroscopy. The results of transmission electron microscope proved that the synthesized nanoparticles have irregular morphologies and the average particle size is about 20 nm. The photocatalytic investigation of ZnO-ZnFe2O4 nanoparticles was carried out using methylene blue solution under UV light. The synthesized nanoparticles showed enhanced photocatalytic performance in comparison with the ZnO nanoparticles more than 40%. The magnetization saturation value of ZnO-ZnFe2O4 nanoparticles was about 5.8 emu/g, which was high enough to be magnetically removed by applying a magnetic field. The results showed that the magnetization and coercivity of the samples reduced by increasing calcination temperature.
Spinel, YbFe2O4, and Yb2Fe3O7 types of structure for compounds in the In2O3 and Sc2O3-A2O3-BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, Cu, or Zn) at temperatures over 1000C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimizuka, N.; Mohri, T.

In the Sc2O3-Ga2O3-CuO, Sc2O3-Ga2O3-ZnO, and Sc2O3-Al2O3-CuO systems, ScGaCuO4, ScGaZnO4, and ScAlCuO4 with the YbFe2O4-type structure and Sc2Ga2CuO7 with the Yb2Fe3O7-type structure were obtained. In the In2O3-A2O3-BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO4, InGaNiO4, and InFeT MgO4 with the spinel structure, InGaZnO4, InGaMgO4, and InAl-CuO4 with the YbFe2O4-type structure, and In2Ga2MnO7 and In2Ga2ZnO7 with the Yb2Fe3O7-type structure were obtained. InGaMnO4 and InFe2O4 had both the YbFe2O4-type and spinel-type structures. The revised classification for the crystal structures of AB2O4 compounds is presented, based upon the coordination numbers of constituent A and B cations. 5more » references, 2 tables.« less
Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

NASA Astrophysics Data System (ADS)

Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

2016-07-01

(1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.
Fe3O4 and MnO2 assembled on honeycomb briquette cinders (HBC) for arsenic removal from aqueous solutions.

PubMed

Zhu, Jin; Baig, Shams Ali; Sheng, Tiantian; Lou, Zimo; Wang, Zhuoxing; Xu, Xinhua

2015-04-09

In this study, a novel composite adsorbent (HBC-Fe3O4-MnO2) was synthesized by combining honeycomb briquette cinders (HBC) with Fe3O4 and MnO2 through a co-precipitation process. The purpose was to make the best use of the oxidative property of MnO2 and the adsorptive ability of magnetic Fe3O4 for enhanced As(III) and As(V) removal from aqueous solutions. Experimental results showed that the adsorption capacity of As(III) was observed to be much higher than As(V). The maximum adsorption capacity (2.16 mg/g) was achieved for As(III) by using HBC-Fe3O4-MnO2 (3:2) as compared to HBC-Fe3O4-MnO2 (2:1) and HBC-Fe3O4-MnO2 (1:1). The experimental data of As(V) adsorption fitted well with the Langmuir isotherm model, whereas As(III) data was described perfectly by Freundlich model. The pseudo-second-order kinetic model was fitted well for the entire adsorption process of As(III) and As(V) suggesting that the adsorption is a rate-controlling step. Aqueous solution pH was found to greatly affect the adsorption behavior. Furthermore, co-ions including HCO3(-) and PO4(3-) exhibited greater influence on arsenic removal efficiency, whereas Cl(-), NO3(-), SO4(2-) were found to have negligible effects on arsenic removal. Five consecutive adsorption-regeneration cycles confirmed that the adsorbent could be reusable for successive arsenic treatment and can be used in real treatment applications. Copyright © 2015 Elsevier B.V. All rights reserved.
[{(Mo)Mo5O21(H2O)3(SO4)}12(VO)30(H2O)20]36-: a molecular quantum spin icosidodecahedron.

PubMed

Botar, Bogdan; Kögerler, Paul; Hill, Craig L

2005-07-07

Self-assembly of aqueous solutions of molybdate and vanadate under reducing, mildly acidic conditions results in a polyoxomolybdate-based {Mo72V30} cluster compound Na8K16(VO)(H2O)5[K10 subset{(Mo)Mo5O21(H2O)3(SO4)}12(VO)30(H2O)20].150H2O, 1, a quantum spin-based Keplerate structure.
Preparation and characterization of chain-like and peanut-like Fe3O4@SiO2 core-shell structure.

PubMed

Shi, Haowei; Huang, Yan; Cheng, Chao; Ji, Guoyuan; Yang, Yuxiang; Yuan, Hongming

2013-10-01

The size- and shape-controlled Fe3O4@SiO2 nanocomposites were successfully synthesized via the sol-gel method. The results showed that the size, shape, and property of the products were directly influenced by the amount of TEOS, and the concentration of water-based magnetic fluid in the coating process. The morphology and properties of the products were characterized by TEM, SEM, X-ray powder diffraction, IR and EDS. The Fe3O4@SiO2 composites with easily-controlled size arranged from 58 to 835 nm could be synthesized by adjusting the experimental parameters. When TEOS amount is 1 mL and the concentration of magnetic fluid were 30.0 and 10.0 mg/mL respectively, chain-like and peanuts-like well-dispersed Fe3O4@SiO2 particles with clear core-shell structure were obtained. These size- and shape-controlled Fe3O4@SiO2 composites may have potential application in the field of targeted drug delivery and MRI contrast agent.
Rapid removal of uranium from aqueous solutions using magnetic Fe3O4@SiO2 composite particles.

PubMed

Fan, Fang-Li; Qin, Zhi; Bai, Jing; Rong, Wei-Dong; Fan, Fu-You; Tian, Wei; Wu, Xiao-Lei; Wang, Yang; Zhao, Liang

2012-04-01

Rapid removal of U(VI) from aqueous solutions was investigated using magnetic Fe(3)O(4)@SiO(2) composite particles as the novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time and initial U(VI) concentrations on uranium sorption efficiency as well as the desorbing of U(VI). The sorption of uranium on Fe(3)O(4)@SiO(2) composite particles was pH-dependent, and the optimal pH was 6.0. In kinetics studies, the sorption equilibrium can be reached within 180 min, and the experimental data were well fitted by the pseudo-second-order model, and the equilibrium sorption capacities calculated by the model were almost the same as those determined by experiments. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 20-200 mg/L. The maximum uranium sorption capacity onto magnetic Fe(3)O(4)@SiO(2) composite particles was estimated to be about 52 mg/g at 25 °C. The highest values of uranium desorption (98%) was achieved using 0.01 M HCl as the desorbing agent. Fe(3)O(4)@SiO(2) composite particles showed a good selectivity for uranium from aqueous solution with other interfering cation ions. Present study suggested that magnetic Fe(3)O(4)@SiO(2) composite particles can be used as a potential adsorbent for sorption uranium and also provided a simple, fast separation method for removal of heavy metal ion from aqueous solution. Copyright © 2011 Elsevier Ltd. All rights reserved.
A new SrBi4Ti4O15/CaBi4Ti4O15 thin-film capacitor for excellent electric stability.

PubMed

Noda, Minoru; Nomura, Shuhei; Uchida, Hiroshi; Yamashita, Kaoru; Funakubo, Horoshi

2012-09-01

SrBi(4)Ti(4)O(15) (SBTi) and CaBi(4)Ti(4)O(15) (CBTi) dielectric films of bismuth layered-structure dielectrics (BLSD) are prepared on Pt(100) film for constructing stacked-type dielectric capacitors; it is observed that they are c-axis singleoriented crystalline films. Compared with the perovskite barium titanate family of (Ba,Sr)TiO(3) (BST), it is observed that the SBTi film keeps a low leakage of 10(-7) A/cm(2) at 250 kV/ cm, which is smaller by an order of magnitude than the BST film, even with thinner SBTi film. The temperature coefficient of capacitance (TCC) of the SBTi or CBTi film is about 100 to 250 ppm/K and is much smaller than that of the perovskite BST film. Because the SBTi and CBTi films have opposite polarities of TCC in this experiment, they are expected to cancel out the temperature dependence in the SBTi/CBTi composite capacitor. These results indicate that the BLSD films of SBTi and CBTi are effective for application in high-temperature and high-permittivity capacitors with the practical barium perovskite oxide family.

MnMoO4 nanolayers : Synthesis characterizations and electrochemical detection of QA

NASA Astrophysics Data System (ADS)

Muthamizh, S.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V.

2018-04-01

MnMoO4 nanolayers were prepared by precipitation method. The MnMoO4 nanolayers were synthesized by using commercially available (CH3COO)2Mn.4H2O and Na2WO4.2H2O. The XRD pattern reveals that the synthesized MnMoO4 has monoclinic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MnMoO4 nanolayers. DRS-UV analysis shows that MnMoO4 has a band gap of 2.59 eV. FE-SEM and HR-TEM analysis along with EDAX confirms the material morphology in stacked layers like structure in nano scale. Synthesized nanolayers were utilized for the detection of biomolecule quercetin (QA).
Application of Sawdust modified with m-DMDHEU/Choline chloride for the removal of CrO4 2- and H2AsO4 - in water

NASA Astrophysics Data System (ADS)

Dang, N. T.; Quan, P. T.; Sang, P. H. P.

2017-06-01

This article studies the use of acacia auriculiformis wood sawdust modified with 4,5-dihydroxy-1,3-bis (methoxymethyl) imidazolidin-2-one (m-DMDHEU) and choline chloride for separating CrO4 2- and H2AsO4 - ions in water. NaOH 0.2N/ethanol 70° solution was used to remove lignin from the raw material, the material was then immersed in m-DMDHEU/choline chloride aqueous solution for 24 hours, after that the material was activated at 140oC for one hour. The ability to adsorb and exchange ions of the material was examined using solutions containing CrO4 2- and H2AsO4 - ions in different conditions. The results suggested that the ability to separate CrO4 2- and H2AsO4 - ions of the modified material was better than that of anion resin at pH = 7.0; the chromate adsorption capacity was the highest in acidic condition; the presence of arsenate (V) anions had no effect on the ability to remove chromate. Lastly, the modified material was used to treat water samples containing concentrations of arsenic similar to groundwater in several arsenic-contaminated areas of Vietnam.
Electromagnetic Wave Absorption Property of Graphene with FeO4 Nanoparticles.

PubMed

Yang, Cheng; Dai, Shenglong; Zhang, Xiaoyan; Zhao, Tianyu; Yan, Shaojiu; Zhao, Xiuying

2016-02-01

Nanomaterials consisting of various ratios of Fe3O4 and graphene (defined C-Fe3O4/GR) were pre- pared by an in situ coordination complex hydro-thermal synthesis method. The structure and morphology of the nanomaterials C-Fe3O4/GR obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). It was found that the Fe3O4 nanoparticles distributed on the surfaces of graphene, and had a spinel structure and a uniform chemical phase when the weight ratios of Fe3O4 to graphene oxide (GO) were 9:1 or 9:2. It was suggested that GO had been successfully reduced to graphene and the Fe3O4 nanoparticles were chemically bonded to graphene. The SQUID vibrating sample magnetometer (SQUID-VSM) indicated that the maximum of the saturation magnetization was 83.6 emmicro g(-1) when the mass ratio of Fe3O4 to GO was 9:2. Electromagnetic wave absorption showed that the chemical compound of Fe3O4 and graphene had a better electromagnetic property than the mechanical blend of Fe3O4 and graphene (M-Fe3O4/GR). The C-Fe3O4/GR had a reflection loss larger than -10 dB in the frequency range 12.9-17.0 GHz for an absorber thickness of 3 mm, and a maximum reflection loss of -12.3 dB at 14.8 GHz and a maximum reflection loss of -31.2 dB at 10.5 GHz for an absorber thickness of 10 mm. Theoretical analysis showed that the electromagnetic wave absorption behavior obeyed the quarter-wave principles. These results showed that the C-Fe3O4/GR nanomaterials can meet the requirements for some engineering applications, showing great application potential in electromagnetic wave absorption.
UV Light-Driven Photodegradation of Methylene Blue by Using Mn0.5Zn0.5Fe2O4/SiO2 Nanocomposites

NASA Astrophysics Data System (ADS)

Indrayana, I. P. T.; Julian, T.; Suharyadi, E.

2018-04-01

The photodegradation activity of nanocomposites for 20 ppm methylene blue solution has been investigated in this work. Nanocomposites Mn0.5Zn0.5Fe2O4/SiO2 have been synthesized using coprecipitation method. The X-ray diffraction (XRD) pattern confirmed the formation of three phases in sample Mn0.5Zn0.5Fe2O4/SiO2 i.e., Mn0.5Zn0.5Fe2O4, Zn(OH)2, and SiO2. The appearance of SiO2 phase showed that the encapsulation process has been carried out. The calculated particles size of Mn0.5Zn0.5Fe2O4/SiO2 is greater than Mn0.5Zn0.5Fe2O4. Bonding analysis via vibrational spectra for Mn0.5Zn0.5Fe2O4/SiO2 confirmed the formation of bonds Me-O-Si stretching (2854.65 cm-1) and Si-O-Si asymmetric stretching (1026.13 cm-1). The optical gap energy of Mn0.5Zn0.5Fe2O4/SiO2 was smaller (2.70 eV) than Mn0.5Zn0.5Fe2O4 (3.04 eV) due to smaller lattice dislocation and microstrain that affect their electronic structure. The Mn0.5Zn0.5Fe2O4/SiO2 showed high photodegradation ability due to smaller optical gap energy and the appearance of SiO2 ligand that can easily attract dye molecules. The Mn0.5Zn0.5Fe2O4/SiO2 also showed high degradation activity even without UV light radiation. The result showed that photodegradation reaction doesn’t follow pseudo-first order kinetics.
Modification of YNbO4 and YNbTiO6 photoluminescence by nitrogen doping

NASA Astrophysics Data System (ADS)

Pei, H.; Su, L. M.; Cai, G. M.; Jin, Z. P.

2018-04-01

Niobates as multifunctional materials were of vital importance in the industry production and daily life. In present work, niobates YNbO4 and YNbTiO6 are investigated as luminescence materials. The compounds have self-activated luminescence, and it is discussed how nitrogen doping affects their electronic structure and optical properties. Various analytical techniques, including x-ray diffraction, nitrogen-content analysis, x-ray photoelectron spectroscopy, scanning electron microscopy, UV-vis absorption spectroscopy and vacuum ultraviolet emission spectroscopy at variable temperature, were used to characterize the structure, composition, crystallinity and optical performance of these niobates. By considering the luminescence mechanisms in YNbO4 and YNbTiO6, the enhanced luminescence obtained upon nitrogen doping is attributed to the presence of oxygen vacancies and nitrogen levels, which changes the band gaps of the materials. Present work demonstrates the use of nitrogen doping for improving the photoluminescence properties of self-activated niobates.
Synthesis of double-shelled sea urchin-like yolk-shell Fe3O4/TiO2/Au microspheres and their catalytic applications

NASA Astrophysics Data System (ADS)

Li, Jie; Tan, Li; Wang, Ge; Yang, Mu

2015-03-01

Double-shelled sea urchin-like yolk-shell Fe3O4/TiO2/Au microspheres were successfully synthesized through loading Au nanoparticles on the Fe3O4/TiO2 support by a in situ reduction of HAuCl4 with NaBH4 aqueous solution. These microspheres possess tunable cavity size, adjustable shell layers, high structural stability and large specific surface area. The Au nanoparticles of approximately 5 nm in diameter were loaded both on the TiO2 nanofibers and inside the cavities of sea urchin-like yolk-shell Fe3O4/TiO2 microspheres. The sea urchin-like structure composed of TiO2 nanofibers ensure the good distribution of the Au nanoparticles, while the novel double-shelled yolk-shell structure guarantees the high stability of the Au nanoparticles. Furthermore, the Fe3O4 magnetic core facilitates the convenient recovery of the catalyst by applying an external magnetic field. The Fe3O4/TiO2/Au microspheres display excellent activities and recycling properties in the catalytic reduction of 4-nitrophenol (4-NP): the rate constant is 1.84 min-1 and turnover frequency is 5457 h-1.
A study of Pd/SO4/ZrO2/Al2O3 catalysts in n-hexane isomerization

NASA Astrophysics Data System (ADS)

Dzhikiya, O. V.; Smolikov, M. D.; Kazantsev, K. V.; Yablokova, S. S.; Kireeva, T. V.; Paukshtis, E. A.; Gulyaeva, T. I.; Belyi, A. S.

2017-08-01

The effect of palladium concentration in a range from 0.02 to 1.6 wt.% on characteristics of n-hexane isomerization was studied. The (O2-Hchem) titration and O2 chemisorption study revealed that palladium in Pd/SO4/ZrO2/Al2O3 systems adsorbs hydrogen in a ratio H/Pds = 1.13-1.65 at./at. Investigation of the charge state of the metal by IR spectroscopy of adsorbed CO showed the presence of both the metallic (Pd0) and charged palladium species. Pd/SO4/ZrO2/Al2O3 catalysts with charged palladium atoms exhibit high activity and selectivity in n-hexane isomerization.
Rapid Detection of Tetrodotoxin Using Surface-Enhanced Raman Spectroscopy and Fe3O4/SiO2/Au Gold/Magnetic Nanoparticles

NASA Astrophysics Data System (ADS)

Neng, Jing; Wang, Xujun; Jia, Kan; Sun, Peilong

2018-03-01

Fe3O4 nanoparticles were first modified with tetraethoxylsilane to form Fe3O4/SiO2 nanoparticles, followed by the addition of 3-aminopropyltriethoxysilane and 3-thiolpropyltriethoxysilane to introduce -NH2 and -SH groups to the surface of Fe3O4/SiO2 nanoparticles. Gold nanoparticles were further assembled on the surface of Fe3O4/SiO2 via the electrostatic adsorption of -NH2 and the Au-S bond to produce stable core-shell Fe3O4/SiO2/Au gold/magnetic nanoparticles. These Fe3O4/SiO2/Au gold/magnetic nanoparticles were characterized by a variety of techniques such as transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX), and afterwards conjugated with tetrodotoxin antibodies (Ab) and used as a Raman active substrate (Fe3O4/SiO2/Au-Ab) with Rhodamine B (RhB)-labeled tetrodotoxin antibody as a Raman reporter (Ab-RhB). Upon mixing these reagents with tetrodotoxin (TTX), a sandwich complex [Fe3O4/SiO2/Au-Ab···TTX···Ab-RhB] was generated due to the specific antibody-antigen interactions. The immunocomplex was subsequently separated by an externally applied magnetic source and concentrated into a pellet point, where the laser interrogation of the pellet produced a strong signal characteristic of RhB. The logarithmic intensity of the signal was found to be proportional to the concentration of TTX with a limit of detection of 0.01 μg/mL and a detection linearity range of 0.01-0.5 μg/mL. The established method eliminates the complicated procedures of traditional centrifuging, column separation, and incubation and achieves a rapid detection of tetrodotoxin with improved detection sensitivity.
Characterization and application of the hetero-junction ZnFe2O4/TiO2 for Cr(VI) reduction under visible light

NASA Astrophysics Data System (ADS)

Rekhila, G.; Trari, M.; Bessekhouad, Y.

2017-06-01

The spinel ZnFe2O4 prepared by nitrate route is used as dispersed photons collector capable to sensitize TiO2 under visible light and to reduce Cr(VI) into trivalent state. The transport properties, optical and photo-electrochemical characterizations are correlated, to build the energetic diagram of the hetero-system ZnFe2O4/TiO2/CrO4 - solution. A gap of 1.97 eV is obtained for the spinel from the diffuse reflectance. The conduction band of ZnFe2O4 (-1.47 V SCE) favors the electrons injection into TiO2, permitting a physical separation of the charge carriers. The oxidation of oxalic acid by photoholes prevents the corrosion of the spinel. The best configuration ZnFe2O4 (75 %)/TiO2 (25 %) is used to catalyze the downhill reaction (2HCrO4 - + 3C2H4O4 + 1.5O2 + 8H+ → 2Cr3+ + 6CO2 + 11 H2O, Δ G° = -557 kcal mol-1). 60 % of Cr(VI) are reduced after 3 h of visible light illumination and the photoactivity follows a first-order kinetic with a half-life of 70 min. The water reduction competes with the HCrO4 - reduction which is the reason in the regression of the photoactivity; a hydrogen evolution rate of 24 µmol mg-1 h-1 is obtained.
On the existence of a high-temperature polymorph of Na2Ca6Si4O15—implications for the phase equilibria in the system Na2O-CaO-SiO2

NASA Astrophysics Data System (ADS)

Kahlenberg, Volker; Maier, Matthias

2016-12-01

Singe crystals of a new high-temperature polymorph of Na2Ca6Si4O15 have been obtained from solid state reactions performed at 1300 °C. The basic crystallographic data of this so-called β-phase at ambient conditions are as follows: space group P1 c1, a = 9.0112(5) Å, b = 7.3171(5) Å, c = 10.9723(6) Å, β = 107.720(14)°, V = 689.14(7) Å3, Z = 2. The crystals showed twinning by reticular merohedry (mimicking an orthorhombic C-centred unit cell) which was accounted for during data processing and structure solution. Structure determination was accomplished by direct methods. Least-squares refinements resulted in a residual of R(|F|) = 0.043 for 5811 observed reflections with I > 2σ(I). From a structural point of view β-Na2Ca6Si4O15 can be attributed to the group of mixed-anion silicates containing [Si2O7]-dimers as well as isolated [SiO4]-tetrahedra in the ratio 1:2, i.e. more precisely the formula can be written as Na2Ca6[SiO4]2[Si2O7]. The tetrahedral groups are arranged in layers parallel to (100). Sodium and calcium cations are located between the silicate anions for charge compensation and are coordinated by six to eight nearest oxygen ligands. Alternatively, the structure can be described as a mixed tetrahedral-octahedral framework based on kröhnkite-type [Ca(SiO4)2O2]-chains in which the CaO6-octahedra are corner-linked to bridging SiO4-tetrahedra. The infinite chains are running parallel to [001] and are concentrated in layers parallel to (010). Adjacent layers are shifted relative to each other by an amount of +δ or -δ along a*. Consequently, a …ABABAB… stacking sequence is created. A detailed comparison with related structures such as α-Na2Ca6Si4O15 and other A2B6Si4O15 representatives including topological as well as group theoretical aspects is presented. There are strong indications that monoclinic Na2Ca3Si2O8 mentioned in earlier studies is actually misinterpreted β-Na2Ca6Si4O15. In addition to the detailed crystallographic analysis of
μ-Carbonato-κ(4) O,O':O',O''-bis-{[2'-(di-tert-butyl-phosphan-yl)biphenyl-2-yl-κ(2) P,C (1)]palladium(II)} dichloro-methane monosolvate.

PubMed

Muller, Alfred; Holzapfel, Cedric W

2012-12-01

The title compound, [(μ2-CO3){Pd(P(t-C4H9)2(C12H8)}2]·CH2Cl2, the first CO3-bridged palladium dimer complex reported to date, was obtained while preparing the Pd(0) complex with (2-biphen-yl)P( (t) Bu)2. In the crystal, each palladium dimer is accompanied by a dichloro-methane solvent mol-ecule. Coordination of the carbonate and chelated phosphane ligands gives distorted square-planar environments at the Pd atoms. Important geometrical parameters include Pd-P(av.) = 2.2135 (4) Å, Pd-C(av.) = 1.9648 (16) Å and P-Pd-C = 84.05 (5) and 87.98 (5)°, and O-Pd-O' = 60.56 (4) and 61.13 (4)°. Bonding with the carbonate O atoms shows values of 2.1616 (11) and 2.1452 (11) Å for the Pd-O-Pd bridge, whereas other Pd-O distances are slightly longer at 2.2136 (11) and 2.1946 (11) Å. One of the tert-butyl groups is disordered over two set of sites with an occupancy ratio of 0.723 (6):0.277 (6). Weak C-H⋯O interactions are observed propagating the molecules along the [100] direction.
Rietveld refinement, electronic structure and ionic conductivity of Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boughzala, Khaled, E-mail: khaledboughzala@gmail.com; Preparatory Institute for Engineering Studies, 5000 Monastir; Debbichi, Mourad

In this paper, we report the effect of the tunnel anions on the ionic conductivity of Strontium-Lanthanum silicate apatites. The Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics were prepared by the solid state reaction method. X-ray diffraction, NMR spectroscopy and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Moreover, the electronic structures of the crystals were evaluated by the first-principles quantum mechanical calculation based on the density functional theory. Finally, the ionic conductivity was studied according to the complex impedance method. - Graphical abstract: The relaxed primitive unit cellmore » for Sr{sub 4}La{sub 6}Fap. Display Omitted.« less
Synthesis, crystal structure, thermal analysis and dielectric properties of Rb4(SO4)(HSO4)2(H3AsO4) compound

NASA Astrophysics Data System (ADS)

Belhaj Salah, M.; Nouiri, N.; Jaouadi, K.; Mhiri, T.; Zouari, N.

2018-01-01

A new inorganic Rb4(SO4)(HSO4)2(H3AsO4) compound was prepared. It was found to crystallize in the monoclinic system (P21 space group) with the following lattice parameters: a = 5868 (1) Å, b = 13,579(2) Å, c = 11,809 (3) Å and β = 94,737 (1)°. The structure is characterized by SO42-, HSO4- and H3AsO4 tetrahedra connected by hydrogen bridge to form two types of dimmer (H(8)S(2)O4- … S(1)O42- and H(12)S(2)O4- … H3AsO4). These dimmers are interconnected by both hydrogen bonds O(14)sbnd H(14)· · ·O(4) and O(15)sbnd H(15)· · ·O(2). They are also linked by the hydrogen bridge assured by the hydrogen atoms H(2), H(3) and H(4) of the H3AsO4 group to build the chain S(1)O4⋯H3AsO4 which are parallel to the ''a'',direction. The rubidium cations are coordinated by eight oxygen atoms with Rbsbnd O distance ranging from 2893(8) to 3.415(6) Å. The existence of Osbnd H and (S/As)sbnd O bonds in the structure at room temperature has been confirmed by IR and Raman spectroscopy in the frequency ranges 4000-400 cm-1and 1200 - 50 cm-1, respectively. Thermal analysis of Rb4(HSO4)(HSO4)2(H3AsO4) showed that the transformation to high temperature phase occurs at 407 K by one-step process. Thermal decomposition of the product takes place at much higher temperatures, with an onset of approximately 522 K. The first transition detected by differential scanning calorimetry (DSC) was also analyzed by dielectric and conductivity measurements using the impedance spectroscopy techniques. The conductivity in the high temperature phase at 428 K is 1.04 × 10-3 Ω-1 cm-1, and the activation energy for the proton transport is 0.36 eV. The conductivity relaxation parameters associated with the high disorder protonic conduction have been examined from analysis of the M"/M"max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to the proton hopping mechanism. The obtained results show that this transition is protonic by nature.
A facile growth process of CeO2-Co3O4 composite nanotubes and its catalytic stability for CO oxidation

NASA Astrophysics Data System (ADS)

Oh, Hyerim; Kim, Il Hee; Lee, Nam-Suk; Dok Kim, Young; Kim, Myung Hwa

2017-08-01

Hybrid cerium dioxide (CeO2)-cobalt oxide (Co3O4) composite nanotubes were successfully prepared by a combination of electrospinning and thermal annealing using CeO2 and Co3O4 precursors for the first time. Electrospun CeO2-Co3O4 composite nanotubes represent relatively porous surface texture with small dimensions between 80 and 150 nm in the outer diameter. The microscopic investigations indicate that the nanoparticle like crystalline structures of CeO2 and Co3O4 are homogenously distributed and continuously connected to form the shape of nanotube in the length of a few micrometers during thermal annealing. It is expected that the different evaporation behaviors of solvents and matrix polymer between the core and the shell in as-spun nanofibers in the course of thermal annealing could be reasonably responsible for the formation of well-defined CeO2/Co3O4 hybrid nanotubes. Additionally, the general catalytic activities of electrospun CeO2/Co3O4 hybrid nanotubes toward the oxidation of carbon monoxide (CO) were carefully examined by a continuous flow system, resulting in favorable catalytic activity as well as catalytic stability for CO oxidation between 150 °C and 200 °C without the deactivation of the catalyst with time stems from accumulation of reaction intermediates such as carbonate species.
SCP4 Promotes Gluconeogenesis Through FoxO1/3a Dephosphorylation.

PubMed

Cao, Jin; Yu, Yi; Zhang, Zhengmao; Chen, Xi; Hu, Zhaoyong; Tong, Qiang; Chang, Jiang; Feng, Xin-Hua; Lin, Xia

2018-01-01

FoxO1 and FoxO3a (collectively FoxO1/3a) proteins regulate a wide array of cellular processes, including hepatic gluconeogenesis. Phosphorylation of FoxO1/3a is a key event that determines its subcellular location and transcriptional activity. During glucose synthesis, the activity of FoxO1/3a is negatively regulated by Akt-mediated phosphorylation, which leads to the cytoplasmic retention of FoxO1/3a. However, the nuclear phosphatase that directly regulates FoxO1/3a remains to be identified. In this study, we discovered a nuclear phosphatase, SCP4/CTDSPL2 (SCP4), that dephosphorylated FoxO1/3a and promoted FoxO1/3a transcription activity. We found that SCP4 enhanced the transcription of FoxO1/3a target genes encoding PEPCK1 and G6PC, key enzymes in hepatic gluconeogenesis. Ectopic expression of SCP4 increased, while knockdown of SCP4 inhibited, glucose production. Moreover, we demonstrated that gene ablation of SCP4 led to hypoglycemia in neonatal mice. Consistent with the positive role of SCP4 in gluconeogenesis, expression of SCP4 was regulated under pathophysiological conditions. SCP4 expression was induced by glucose deprivation in vitro and in vivo and was elevated in obese mice caused by genetic (A vy ) and dietary (high-fat) changes. Thus, our findings provided experimental evidence that SCP4 regulates hepatic gluconeogenesis and could serve as a potential target for the prevention and treatment of diet-induced glucose intolerance and type 2 diabetes. © 2017 by the American Diabetes Association.
Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

PubMed Central

Zhang, Guo-Fang; Cai, Mei-Yu; Jing, Ping; He, Chong; Li, Ping; Zhao, Feng-Qi; Li, Ji-Zhen; Fan, Xue-Zhong; Ng, Seik Weng

2010-01-01

Two transition-metal compounds derived from 2,4-dinitroimidazole, {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O, 1, and Pb(DNI)2(H2O)4, 2, were characterized by elemental analysis, FT-IR, TG-DSC and X-ray single-crystal diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 26.826(3), b = 7.7199(10), c = 18.579(2) Å, β = 111.241(2)° and Z = 4; 2: monoclinic, space group C2/c, a = 6.5347(6), b = 17.1727(17), c = 14.1011(14) Å, β = 97.7248(10) and Z = 4. Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon. PMID:20526419
Snynthesis and magnetization of BaLn2O4 (Ln = lanthanide)

NASA Astrophysics Data System (ADS)

Lundberg, Matthew

The BaLn2O4 family has been synthesized successfully as single crystals by the flux-growth method. The phases crystallize in the CaV2O4 structure prototype in space group Pnma (# 62). The structure has been studied using single-crystal x-ray diffraction, and stoichiometry confirmed with EDS, and the unit cell parameters and atomic positions have been determined for the whole lanthanide series (with the exception of the Lu compound). The effects of the lanthanide ionic radius on the atomic positions in the unit cell has been studied in terms of fractional atomic coordinates, bond lengths and angles, and bond valence sums. Magnetic measurements have been performed on the series with the exception of the La, Eu, and Lu members in the form of susceptibility versus temperature. The crystals all show signs of geometric antiferromagnetic frustration with the Neel temperatures significantly below the temperature predicted by the Weiss constant. Additionally some members of the family, namely BaCe2O4, BaNd2O4, BaPr 2O4, BaSm2O4, BaTb2O 4, and BaYb2O4 show significant crystal field splitting, that causes deviation from Currie-Weiss behavior.
Solid state reactions of CeO 2, PuO 2, (U,Ce)O 2 and (U,Pu)O 2 with K 2S 2O 8

NASA Astrophysics Data System (ADS)

Keskar, Meera; Kasar, U. M.; Mudher, K. D. Singh; Venugopal, V.

2004-09-01

Solid state reactions of CeO 2, PuO 2 and mixed oxides (U,Ce)O 2 and (U,Pu)O 2 containing different mol.% of Ce and Pu, were carried out with K 2S 2O 8 at different temperatures to identify the formation of various products and to investigate their dissolution behaviour. X-ray, chemical and thermal analysis methods were used to characterise the products formed at various temperatures. The products obtained by heating two moles of K 2S 2O 8 with one mole each of CeO 2, PuO 2, (U,Ce)O 2 and (U,Pu)O 2 at 400 °C were identified as K 4Ce(SO 4) 4, K 4Pu(SO 4) 4, K 4(U,Ce)(SO 4) 4 and K 4(U,Pu)(SO 4) 4, respectively. K 4Ce(SO 4) 4 further decomposed to form K 4Ce(SO 4) 3.5 at 600 °C and mixture of K 2SO 4 and CeO 2 at 950 °C. Thus the products formed during the reaction of 2K 2S 2O 8 + CeO 2 show that cerium undergoes changes in oxidation state from +4 to +3 and again to +4. XRD data of K 4Ce(SO 4) 4 and K 4Ce(SO 4) 3.5 were indexed on triclinic and monoclinic system, respectively. PuO 2 + 2K 2S 2O 8 reacts at 400 °C to form K 4Pu(SO 4) 4 which was stable upto 750 °C and further decomposes to form K 2SO 4 + PuO 2 at 1000 °C. The products formed at 400 °C during the reactions of the oxides and mixed oxides were found to be readily soluble in 1-2 M HNO 3.
Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH 3 ) 4 ](ReO 4 ) 2 on γ-Al 2 O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Simon T.; Lamb, H. Henry

The double complex salt [Pd(NH3)4](ReO4)2 was employed as precursor of supported bimetallic catalysts for selective hydrogenation of furfural. Direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 in flowing H2 at 400 °C yields bimetallic nanoparticles 1–2 nm in size that exhibit significant interaction between the metals, as evidenced by temperature-programmed hydride decomposition (complete suppression of β-PdHx formation), extended X-ray absorption fine structure spectroscopy at the Pd K and Re LIII edges (PdRe distance = 2.72 Å), and scanning transmission electron microscopy with energy dispersive X-ray analysis. In contrast, calcination of [Pd(NH3)4](ReO4)2 on γ-Al2O3 at 350 °C in air and subsequent reduction inmore » H2 at 400 °C results in metal segregation and formation of large (>50 nm) supported Pd particles; Re species cover the Pd particles and γ-Al2O3 support. A PdRe 1:2 catalyst prepared by sequential impregnation and calcination using HReO4 and [Pd(NH3)4](NO3)2 has a similar morphology. The catalyst derived by direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 exhibits remarkably high activity for selective hydrogenation of furfural to furfuryl alcohol (FAL) at 150 °C and 1 atm. Suppression of H2 chemisorption via elimination of Pd threefold sites, as evidenced by CO diffuse-reflectance infrared Fourier transform spectroscopy, correlates with increased FAL selectivity.« less
Rapid degradation of methylene blue in a novel heterogeneous Fe3O4 @rGO@TiO2-catalyzed photo-Fenton system.

PubMed

Yang, Xiaoling; Chen, Wei; Huang, Jianfei; Zhou, Ying; Zhu, Yihua; Li, Chunzhong

2015-05-22

Herein, a ternary nanocomposite with TiO2 nanoparticles anchored on reduced graphene oxide (rGO)-encapsulated Fe3O4 spheres (Fe3O4@rGO@TiO2) is presented as a high efficient heterogeneous catalyst for photo-Fenton degradation of recalcitrant pollutants under neutral pH. Fe3O4@rGO@TiO2 was synthesized by depositing TiO2 nanoparticles on the surface of the Fe3O4 spheres wrapped by graphene oxide (GO) which was obtained by an electrostatic layer-by-layer method. This as-prepared catalyst reflected good ferromagnetism and superior stability which makes it convenient to be separated and recycled. Due to the synergic effects between the different components composed the catalyst, swift reduction of Fe(3+) can be achieved to regenerate Fe(2+). Fe3O4@rGO@TiO2 exhibited enhancing catalytic activity for the degradation of azo-dyes compared with Fe3O4, Fe3O4@SiO2@TiO2 or SiO2@rGO@TiO2, further conforming the rapid redox reaction between Fe(2+) and Fe(3+). All these merits indicate that the composite catalyst possesses great potential for visible-light driven destruction of organic compounds.

Rapid degradation of methylene blue in a novel heterogeneous Fe3O4 @rGO@TiO2-catalyzed photo-Fenton system

PubMed Central

Yang, Xiaoling; Chen, Wei; Huang, Jianfei; Zhou, Ying; Zhu, Yihua; Li, Chunzhong

2015-01-01

Herein, a ternary nanocomposite with TiO2 nanoparticles anchored on reduced graphene oxide (rGO)-encapsulated Fe3O4 spheres (Fe3O4@rGO@TiO2) is presented as a high efficient heterogeneous catalyst for photo-Fenton degradation of recalcitrant pollutants under neutral pH. Fe3O4@rGO@TiO2 was synthesized by depositing TiO2 nanoparticles on the surface of the Fe3O4 spheres wrapped by graphene oxide (GO) which was obtained by an electrostatic layer-by-layer method. This as-prepared catalyst reflected good ferromagnetism and superior stability which makes it convenient to be separated and recycled. Due to the synergic effects between the different components composed the catalyst, swift reduction of Fe3+ can be achieved to regenerate Fe2+. Fe3O4@rGO@TiO2 exhibited enhancing catalytic activity for the degradation of azo-dyes compared with Fe3O4, Fe3O4@SiO2@TiO2 or SiO2@rGO@TiO2, further conforming the rapid redox reaction between Fe2+ and Fe3+. All these merits indicate that the composite catalyst possesses great potential for visible-light driven destruction of organic compounds. PMID:26000975
Solid-State Synthesis and Structure of the Enigmatic Ammonium Octaborate: (NH4)2[B7O9(OH)5]·3/4B(OH)3·5/4H2O.

PubMed

Neiner, Doinita; Sevryugina, Yulia V; Schubert, David M

2016-09-06

The compound known since the 19th century as ammonium octaborate was structurally characterized revealing the ammonium salt of the ribbon isomer of the heptaborate anion, [B7O9(OH)5](2-), with boric acid and water molecules. Of composition (NH4)2B7.75O12.63·4.88H2O, it approximates the classical ammonium octaborate composition (NH4)2B8O13·6H2O and has the structural formula {(NH4)2[B7O9(OH)5]}4·3B(OH)3·5H2O. It spontaneously forms at room temperature in solid-state mixtures of ammonium tetraborate and ammonium pentaborate. It crystallizes in the monoclinic space group P21/c with a = 11.4137(2) Å, b = 11.8877(2) Å, c = 23.4459(3) Å, β = 90.092(1)°, V = 3181.19(8) Å(3), and Z = 2 and contains well-ordered ammonium cations and [B7O9(OH)5](2-) anions and disordered B(OH)3 and H2O molecules linked by extensive H bonding. Expeditious solid-state formation of the heptaborate anion under ambient conditions has important implications for development of practical syntheses of industrially useful borates.
Mesoporous Pd/Co3O4 nanosheets nanoarrays as an efficient binder/carbon free cathode for rechargeable Li-O2 batteries

NASA Astrophysics Data System (ADS)

Ren, Yanbiao; Zhang, Shichao; Li, Honglei; Wei, Xin; Xing, Yanlan

2017-10-01

In this work, two shapes of mesoporous Co3O4 nanoarrays (i.e., nanosheets, nanowires) were synthesized through a facile hydrothermal method on nickel foam (Ni foam) substrates and tested as the Li-O2 cathodes. The comparison of these two shapes of Co3O4 nanoarrays revealed that the single crystalline feature of Co3O4 nanosheets with a predominant high reactivity {112} exposed crystal plane, favorable nanostructure and high specific area displayed better catalytic performance. Furthermore, a new binder/carbon-free Pd nanoparticles (PdNPs) decorated Co3O4 nanosheets cathode was also fabricated through the chemical reduction method. The presence of PdNPs effectively promotes the uniform growth of a fluffy, porous discharge product Li2O2 layer on the surface of Pd/Co3O4 electrode. The Pd/Co3O4 electrode catalyzed Li-O2 battery exhibited a higher specific capacity (1551 mAh g-1 at 50 mA g-1), lower over-potential and longer cycle life over 72 cycles at 100 mA g-1 with the capacity limited at 300 mAh g-1. The superior catalytic performance for Li-O2 batteries is ascribed to the unique design in both component and architecture of Pd/Co3O4 electrode.
Misfit paradox on nucleation potency of MgO and MgAl{sub 2}O{sub 4} for Al

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, D.; Wang, L.

MgO and MgAl{sub 2}O{sub 4} are believed to be effective heterogeneous nuclei for Al based alloys due to their small lattice misfits with Al. However, there is a strong evidence to suggest that liquid Al reacts with MgO and MgAl{sub 2}O{sub 4} phases but the heterogeneous nucleation behavior of such phases is rarely discussed. In order to identify the nucleation mechanism of Al, under the interference of the chemical reaction, the heterogeneous nucleation process is systematically investigated through thermal analysis and high resolution transmission electron microscopy (HRTEM). The observed multi-nucleation interfaces (Al/MgO, Al/MgAl{sub 2}O{sub 4} and Al/Al{sub 2}O{sub 3}) andmore » scattered experimental undercooling data indicate an independent multi-phase nucleation process in these systems. - Highlights: •Theoretical lattice misfit doesn’t always disclose nucleation potency. •The nucleation of liquid can be triggered by multi-nucleation interfaces. •An independent multi-agents nucleation was verified in the study.« less
Artificial Metalloproteins Containing Co 4O 4Cubane Active Sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olshansky, Lisa; Huerta-Lavorie, Raul; Nguyen, Andy I.

Artificial metalloproteins (ArMs) containing Co 4O 4 cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co III-OH 2 moieties are observed crystallographically in a series of immobilized cubane sites. Solution electrochemistry provided correlations of oxidation potential and pH. For variants containing Ser and Phe adjacent to the metallocofactor, 1e -/1H + chemistry predominates until pH 8, above which the oxidation becomes pH-independent. Installation of Tyr proximal to the Co 4O 4 active site provided a single H-bond to one of a set of cofacial Co III-OH 2 groups. With this variant, multi-emore » - /multi-H + chemistry is observed, along with a change in mechanism at pH 9.5 that is consistent with Tyr deprotonation. Finally, with structural similarities to both the oxygen-evolving complex of photosystem II (H-bonded Tyr) and to thin film water oxidation catalysts (Co 4O 4 core), these findings bridge synthetic and biological systems for water oxidation, highlighting the importance of secondary sphere interactions in mediating multi-e - /multi-H + reactivity.« less
Artificial Metalloproteins Containing Co 4O 4Cubane Active Sites

DOE PAGES

Olshansky, Lisa; Huerta-Lavorie, Raul; Nguyen, Andy I.; ...

2018-02-05

Artificial metalloproteins (ArMs) containing Co 4O 4 cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co III-OH 2 moieties are observed crystallographically in a series of immobilized cubane sites. Solution electrochemistry provided correlations of oxidation potential and pH. For variants containing Ser and Phe adjacent to the metallocofactor, 1e -/1H + chemistry predominates until pH 8, above which the oxidation becomes pH-independent. Installation of Tyr proximal to the Co 4O 4 active site provided a single H-bond to one of a set of cofacial Co III-OH 2 groups. With this variant, multi-emore » - /multi-H + chemistry is observed, along with a change in mechanism at pH 9.5 that is consistent with Tyr deprotonation. Finally, with structural similarities to both the oxygen-evolving complex of photosystem II (H-bonded Tyr) and to thin film water oxidation catalysts (Co 4O 4 core), these findings bridge synthetic and biological systems for water oxidation, highlighting the importance of secondary sphere interactions in mediating multi-e - /multi-H + reactivity.« less
Neutron scattering study on cathode LiMn2O4 and solid electrolyte 5(Li2O)(P2O5)

NASA Astrophysics Data System (ADS)

Kartini, E.; Putra, Teguh P.; Jahya, A. K.; Insani, A.; Adams, S.

2014-09-01

Neutron scattering is very important technique in order to investigate the energy storage materials such as lithium-ion battery. The unique advantages, neutron can see the light atoms such as Hydrogen, Lithium, and Oxygen, where those elements are negligible by other corresponding X-ray method. On the other hand, the energy storage materials, such as lithium ion battery is very important for the application in the electric vehicles, electronic devices or home appliances. The battery contains electrodes (anode and cathode), and the electrolyte materials. There are many challenging to improve the existing lithium ion battery materials, in order to increase their life time, cyclic ability and also its stability. One of the most scientific challenging is to investigate the crystal structure of both electrode and electrolyte, such as cathodes LiCoO2, LiMn2O4 and LiFePO4, and solid electrolyte Li3PO4. Since all those battery materials contain Lithium ions and Oxygen, the used of neutron scattering techniques to study their structure and related properties are very important and indispensable. This article will review some works of investigating electrodes and electrolytes, LiMn2O4 and 5(Li2O)(P2O5), by using a high resolution powder diffraction (HRPD) at the multipurpose research reactor, RSG-Sywabessy of the National Nuclear Energy Agency (BATAN), Indonesia.
Structure and electrical properties of intergrowth bismuth layer-structured Bi4Ti3O12-CaBi4Ti4O15 ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Choi, Gi Ppeum; Cho, Sam Yeon; Bu, Sang Don

2016-09-01

Pb-free ferroelectric Bi4Ti3O12-CaBi4Ti4O15 (BIT-CBT) ceramics were manufactured using a solid-state reaction method. Structural analysis by using X-ray diffraction confirmed the presence of a second phase of Bi2Ti2O7, and the surface depth X-ray diffraction analysis revealed that this phase existed only on the surface. This second phase appears to have been caused by the volatilization of Bi ions at high sintering temperatures. For resolution of the issue of volatilization of Bi ions and manufacture of BIT-CBT ceramics with a single phase, Bi2O3 powder was added to the BIT-CBT mixture, and a powder-bed method, in which pellets were covered with BIT-CBT powder, was used to manufacture the ceramic. The piezoelectric coefficient of the single-phase BIT-CBT ceramics was 12.4 pC/N while the residual polarization and the coercive electric field were 11.3 μC/cm2, and 125 kV/cm, respectively. The results suggest that single-phase BIT-CBT ceramics are suitable for the manufacture of elements incorporating these electrical characteristics.
Orthorhombic YBaCo{sub 4}O{sub 8.4} crystals as a result of saturation of hexagonal YBaCo{sub 4}O{sub 7} crystals with oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podberezskaya, N. V., E-mail: podberez@niic.nsc.ru; Bolotina, N. B., E-mail: nb-bolotina@mail.ru; Komarov, V. Yu., E-mail: komarov-v-y@niic.nsc.ru

Hexagonal YBaCo{sub 4}O{sub 7} crystals (sp. gr. P6{sub 3}mc, a{sub h} = 6.3058(4) Å, c{sub h} = 10.2442(7) Å, Z = 2) are saturated with oxygen to the YBaCo{sub 4}O{sub 8.4} composition and studied by X-ray diffraction (XRD) analysis. The saturation is completed by a structural first-order phase transition to orthorhombic crystals (sp. gr. Pbc2{sub 1}, a{sub o} = 31.8419(2) Å, b{sub o} = 10.9239(5) Å, c{sub o} = 10.0960(5) Å, Z = 20). The connection of two lattices is expressed in terms of the action of matrix (500/120/001) on the hexagonal basis. Five structural fragments of the same typemore » but with different degrees of order alternate along the long axis of the oxygen-saturated orthorhombic structure. The XRD data on single crystals differ from the results obtained by other researchers on ceramic samples; possible causes of these differences are discussed.« less
Magnetically induced ferroelectricity in Bi2CuO4

NASA Astrophysics Data System (ADS)

Zhao, L.; Guo, H.; Schmidt, W.; Nemkovski, K.; Mostovoy, M.; Komarek, A. C.

2017-08-01

The tetragonal copper oxide Bi2CuO4 has an unusual crystal structure with a three-dimensional network of well separated CuO4 plaquettes. The spin structure of Bi2CuO4 in the magnetically ordered state below TN˜43 K remains controversial. Here we present the results of detailed studies of specific heat, magnetic, and dielectric properties of Bi2CuO4 single crystals grown by the floating zone technique, combined with the polarized neutron scattering and high-resolution x-ray measurements. Down to 3.5 K our polarized neutron scattering measurements reveal ordered magnetic Cu moments which are aligned within the a b plane. Below the onset of the long range antiferromagnetic ordering we observe an electric polarization induced by an applied magnetic field, which indicates inversion symmetry breaking by the ordered state of Cu spins. For the magnetic field applied perpendicular to the tetragonal axis, the spin-induced ferroelectricity is explained in terms of the linear magnetoelectric effect that occurs in a metastable magnetic state. A relatively small electric polarization induced by the field parallel to the tetragonal axis may indicate a more complex magnetic ordering in Bi2CuO4 .
Chemistry of CCl 4 on Fe 3O 4(1 1 1)-(2 × 2) surfaces in the presence of adsorbed D 2O studied by temperature programmed desorption

NASA Astrophysics Data System (ADS)

Adib, K.; Totir, G. G.; Fitts, J. P.; Rim, K. T.; Mueller, T.; Flynn, G. W.; Joyce, S. A.; Osgood, R. M.

2003-07-01

Temperature programmed desorption (TPD) was used to study surface reactions of Fe 3O 4(1 1 1)-(2 × 2) sequentially exposed, at ˜100 K, to vapor-phase D 2O and CCl 4. Previous TPD and XPS results have indicated that in the absence of D 2O, CCl 4 dissociatively adsorbs on Fe 3O 4(1 1 1) producing chemisorbed Cl and CCl 2. Subsequent heating of the surface results in abstraction of lattice iron and oxygen atoms and causes them to desorb as FeCl 2 and OCCl 2, respectively. This study shows that when this Fe 3O 4 surface is exposed only to D 2O, TPD measures a rich surface chemistry with multiple desorption events extending as high as ˜800 K, indicating dissociative adsorption of D 2O on the Fe 3O 4(1 1 1) surface. After sequential exposure to D 2O and then CCl 4, the production of FeCl 2 and OCCl 2 from adsorbed CCl 4 is suppressed, indicating that D 2O fragments block the surface reactive sites.
Observação do abrilhantamento de limbo solar e de estruturas filamentares em 48 ghz utilizando a técnica de regularização adaptativa

NASA Astrophysics Data System (ADS)

Machado, W. R. S.; Mascarenhas, N.; Costa, J. E. R.; Silva, A. V. R.

2003-08-01

O radiotelescópio do Itapetinga tem sido utilizado em campanhas de observações de explosões solares gerando um grande número de mapas diários em 48 GHz como sub-produto destas observações. A resolução espacial do telescópio de 14m do Itapetinga nesta freqüência é de aproximadamente dois minutos de arco. Estruturas de interesse para análise da atmosfera solar quiescente tais como os filamentos e o anel de abrilhantamento do limbo são de dimensão angular moderada da ordem ou ligeiramente menores que a resolução do telescópio. É conhecido que a convolução da função de espalhamento do telescópio, PSF (padrão de ganho do feixe) borra as estruturas de dimensão angular abaixo do HPBW (largura a meia potência do feixe) e portanto é comum a busca por técnicas de restauração que eliminem pelo menos em parte este borramento. Estudamos a restauração destas radioimagens usando a técnica de regularização adaptativa e os resultados ressaltam estas estruturas espaciais de pequeno contraste. O algoritmo da regularização adaptativa faz uso de k imagens, chamadas protótipos, obtidas através da variação de parâmetros de um filtro de regularização. Para controle da qualidade da restauração utilizamos uma imagem de alta resolução espacial obtida na linha H-a e a PSF do Itapetinga para borrá-la. Pequenos desvios, entre a PSF utilizada para o borramento e a PSF utilizada na restauração, produziram alguns desvios notáveis na imagem restaurada porém a adição de ruído nas simulações de restauração foram mais influentes no cálculo da rugosidade da imagem e portanto mais limitante para a restauração. Apresentamos como nosso primeiro resultado uma imagem em 48 GHz com a presença clara do abrilhantamento de limbo que não estava evidente na imagem original e traços de estruturas filamentares, porém ainda sem grande evidência.
Dissecção aórtica de tipo B de Stanford: relato de caso e revisão de literatura

PubMed Central

Michaelis, Wilson; Santos, Antônio Lacerda; Yokohama, Rogério Akira; Andretta, Marianne Ariely; Delazari, Mariana Vieira; Vieira, Luciano; Seguro, Erick Fernando; Sarquis, Lucas Mansano

2017-01-01

Resumo O complexo tratamento de dissecção da aorta ainda apresenta controvérsias devido à gravidade do caso e à necessidade de individualização da terapêutica. A gravidade relaciona-se ao difícil diagnóstico pelas queixas inespecíficas e pelas graves complicações inerentes à evolução da doença (ruptura aórtica, síndrome de má perfusão, dissecção retrógrada, dor ou hipertensão refratária). Este relato apresenta um homem de 61 anos, tabagista e hipertenso mal controlado, que evoluiu para dissecção aórtica de tipo B de Stanford. Foi abordado através de técnica endovascular com uso de endoprótese com stent para tratamento do caso após falha do tratamento medicamentoso. O tratamento endovascular mostrou-se uma ferramenta eficaz para o tratamento definitivo, com boa taxa de sobrevida ao final do primeiro ano após o procedimento.
Stereospecificity of {beta}-O-4 lignin oligomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faulon, J.L.; Pohl, P.I.

1995-12-01

Lignin, a complex macromolecule of vascular plants is a cross-linked polymer of glyceryl methoxyphenol units. The major type of linkage between the monomers is the {beta}-O-4 bond. We have studied the conformations of {beta}-O-4 lignin oligomers in a vacuum, and in the presence of water, cations, and cellulosic materials. There are several stereoisomers of {beta}-O-4 lignin oligomers because lignin monomers contain chiral atoms. We have constructed the stereoisomers using a stochastic chemical structure generator (the SIGNATURE program). The potential energies of the resulting structures were calculated using several force fields (MM2, DREIDING, CVFF), and several semiempirical codes (AM1, PM3). Themore » conformational space of the stereoisomers were investigated using Monte Carlo and simulated annealing modeling techniques. It was observed that the lowest energies were obtained for the stereospecific all-three and all-erythro isomers independently of the degree of polymerization.« less
3- and 4-O-sulfoconjugated and methylated dopamine: highly reduced binding affinity to dopamine D2 receptors in rat striatal membranes.

PubMed

Werle, E; Lenz, T; Strobel, G; Weicker, H

1988-07-01

The binding properties of 3- and 4-O-sulfo-conjugated dopamine (DA-3-O-S, DA-4-O-S) as well as 3-O-methylated dopamine (MT) to rat striatal dopamine D2 receptors were investigated. 3H-spiperone was used as a radioligand in the binding studies. In saturation binding experiments (+)butaclamol, which has been reported to bind to dopaminergic D2 and serotoninergic 5HT2 receptors, was used in conjunction with ketanserin and sulpiride, which preferentially label 5HT2 and D2 receptors, respectively, in order to discriminate between 3H-spiperone binding to D2 and to 5HT2 receptors. Under our particular membrane preparation and assay conditions, 3H-spiperone binds to D2 and 5HT2 receptors with a maximal binding capacity (Bmax) of 340 fmol/mg protein in proportions of about 75%:25% with similar dissociation constants KD (35 pmol/l; 43 pmol/l). This result was verified by the biphasic competition curve of ketanserin, which revealed about 20% high (KD = 24 nmol/l) and 80% low (KD = 420 nmol/l) affinity binding sites corresponding to 5HT2 and D2 receptors, respectively. Therefore, all further competition experiments at a tracer concentration of 50 pmol/l were performed in the presence of 0.1 mumol/l ketanserin to mask the 5HT2 receptors. DA competition curves were best fitted assuming two binding sites, with high (KH = 0.12 mumol/l) and low (KL = 18 mumol/l) affinity, present in a ratio of 3:1. The high affinity binding sites were interconvertible by 100 mumol/l guanyl-5-yl imidodiphosphate [Gpp(NH)p], resulting in a homogenous affinity state of DA receptors (KD = 2.8 mumol/l).2+ off
Porous MnCo2O4 as superior anode material over MnCo2O4 nanoparticles for rechargeable lithium ion batteries

NASA Astrophysics Data System (ADS)

Baji, Dona Susan; Jadhav, Harsharaj S.; Nair, Shantikumar V.; Rai, Alok Kumar

2018-06-01

Pyro synthesis is a method to coat nanoparticles by uniform layer of carbon without using any conventional carbon source. The resultant carbon coating can be evaporated in the form of CO or CO2 at high temperature with the creation of large number of nanopores on the sample surface. Hence, a porous MnCo2O4 is successfully synthesized here with the same above strategy. It is believed that the electrolyte can easily permeate through these nanopores into the bulk of the sample and allow rapid access of Li+ ions during charge/discharge cycling. In order to compare the superiority of the porous sample synthesized by pyro synthesis method, MnCo2O4 nanoparticles are also synthesized by sol-gel synthesis method at the same parameters. When tested as anode materials for lithium ion battery application, porous MnCo2O4 electrode shows high capacity with long lifespan at all the investigated current rates in comparison to MnCo2O4 nanoparticles electrode.
High-pressure synthesis, crystal structure, and electromagnetic properties of CdRh2O4: an analogous oxide of the postspinel mineral MgAl2O4.

PubMed

Wang, Xia; Guo, Yanfeng; Shi, Youguo; Belik, Alexei A; Tsujimoto, Yoshihiro; Yi, Wei; Sun, Ying; Shirako, Yuichi; Arai, Masao; Akaogi, Masaki; Matsushita, Yoshitaka; Yamaura, Kazunari

2012-06-18

The postspinel mineral MgAl(2)O(4) exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh(2)O(4) exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 °C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl(2)O(4) are absent in CdRh(2)O(4). X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe(2)O(4) structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl(2)O(4). Replacement of Mg(2+) with Cd(2+) appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO(3). In addition, Rh(3+) could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched from lower-pressure conditions.
Low temperature magnetization and anomalous high temperature dielectric behaviour of (1-x) YMnO3/xZnFe2O4 composites

NASA Astrophysics Data System (ADS)

Kumar, Virendra; Gaur, Anurag

2018-04-01

We synthesized YMnO3 and ZnFe2O4 composites, (1-x)YMnO3/x(ZnFe2O4) with x = 0, 0.05, 0.10, and 0.15 by high temperature sintering. X-ray diffraction (XRD) patterns indicate the successful formation of composites. Weak ferromagnetism is manifested below Néel temperature (TN) for pristine YMnO3, according to (M-H) study performed at 10 K. For (1-x)YMnO3/xZnFe2O4 (x = 0.05, 0.10, 0.15) a thin coercivity is observed in all compositions, due to short range magnetic ordering at low temperature after the insertion of ZnFe2O4. For pristine YMnO3 explicit divarication between FC-ZFC curves is observed, with crimps observed in both FC and ZFC curves at 75 K, which is the TN of YMnO3. For 1-x(YMnO3)/x ZnFe2O4 composites (x = 0.05, 0.10, 0.15) crimps are perceived only in ZFC curves at slightly varying values of 39.8, 42.32 and 45.63 K respectively. Anomalous peaks are observed in high temperature dielectric curves above 400 K for 1-x(YMnO3)/xZnFe2O4 (x = 0, 0.05, 0.10, 0.15) composites due to Maxwell-Wagner relaxation effect.
Lesion Orientation of O4-Alkylthymidine Influences Replication by Human DNA Polymerase η.

PubMed

O'Flaherty, D K; Patra, A; Su, Y; Guengerich, F P; Egli, M; Wilds, C J

2016-08-01

DNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases. O 4 -Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4- O 4 bond on processing by human DNA polymerase η (hPol η ) was studied for oligonucleotides containing O 4 -methylthymidine, O 4 -ethylthymidine, and analogs restricting the O 4 -methylene group in an anti -orientation. Primer extension assays revealed that the O 4 -alkyl orientation influences hPol η bypass. Crystal structures of hPol η •DNA•dNTP ternary complexes with O 4 -methyl- or O 4 -ethylthymidine in the template strand showed the nucleobase of the former lodged near the ceiling of the active site, with the syn - O 4 -methyl group engaged in extensive hydrophobic interactions. This unique arrangement for O 4 -methylthymidine with hPol η , inaccessible for the other analogs due to steric/conformational restriction, is consistent with differences observed for nucleotide incorporation and supports the concept that lesion conformation influences extension across DNA damage. Together, these results provide mechanistic insights on the mutagenicity of O 4 MedT and O 4 EtdT when acted upon by hPol η .
On Ensino de Astronomia: Desafios para Implantação

NASA Astrophysics Data System (ADS)

Faria, R. Z.; Voelzke, M. R.

2008-09-01

Em 2002 o ensino de Astronomia foi proposto como um dos temas estruturadores pelos Parâmetros Curriculares Nacionais e sugerido como facilitador para que o aluno compreendesse a Física como construção humana e parte do seu mundo vivencial, mas raramente seus conceitos foram ensinados. A presente pesquisa discute dois aspectos relacionados à abordagem de Astronomia. O primeiro aspecto é se ela está sendo abordada pelos professores do Ensino Médio e o segundo, aborda a maneira como ela está sendo ensinada. Optou-se pela aplicação de um questionário a partir do 2° semestre de 2006 e durante o ano de 2007 com professores que ministram a disciplina de Física, os quais trabalham em escolas estaduais em Rio Grande da Serra, Ribeirão Pires e Mauá no estado São Paulo. Dos 66,2% dos professores que responderam ao questionário nos municípios de Rio Grande da Serra, Ribeirão Pires e Mauá, 57,4% não aplicaram nenhum tópico de astronomia, 70,2% não utilizaram laboratório, 89,4% não utilizaram qualquer tipo de programa computacional, 83,0% nunca fizeram visitas com alunos a museus e planetários e 38,3% não indicaram qualquer tipo de livro ou revista referente à astronomia aos seus alunos. Mesmo considerando a Astronomia um conteúdo potencialmente significativo, esta não fez parte dos planejamentos escolares. Portanto são necessárias propostas que visem estratégias para a educação continuada dos professores como, por exemplo, cursos específicos sobre o ensino em Astronomia.

K-shell photoionization of O4 + and O5 + ions: experiment and theory

NASA Astrophysics Data System (ADS)

McLaughlin, B. M.; Bizau, J.-M.; Cubaynes, D.; Guilbaud, S.; Douix, S.; Shorman, M. M. Al; Ghazaly, M. O. A. El; Sakho, I.; Gharaibeh, M. F.

2017-03-01

Absolute cross-sections for the K-shell photoionization of Be-like (O4 +) and Li-like (O5 +) atomic oxygen ions were measured for the first time (in their respective K-shell regions) by employing the ion-photon merged-beam technique at the SOLEIL synchrotron-radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E/ΔE ≈ 3200 (≈170 meV, full width at half-maximum) was achieved with photon energy from 550 to 670 eV. Rich resonance structure observed in the experimental spectra is analysed using the R-matrix with pseudo-states (RMPS) method. Results are also compared with the screening constant by unit nuclear charge (SCUNC) calculations. We characterize and identify the strong 1s → 2p resonances for both ions and the weaker 1s → np resonances (n ≥ 3) observed in the K-shell spectra of O4 +.
Reduction of chromium (VI) on the hetero-system CuBi2O4/TiO2 under solar light

NASA Astrophysics Data System (ADS)

Lahmar, H.; Benamira, M.; Akika, F. Z.; Trari, M.

2017-11-01

The CuBi2O4/TiO2 heterojunction was tested with success for the photo-catalytic reduction of chromate ions under sunlight. CuBi2O4, prepared by nitrate process, was characterised photo-electrochemically. The oxide is stable against photo corrosion by consumption of holes in presence of oxalic acid. The light absorption promotes electrons in the conduction band of the sensitizer (CuBi2O4) with a very negative potential (-1.74 VSCE) to participate in the exchange of the electron with HCrO4-. The enhanced activity is due to electron injection of activated CuBi2O4 into TiO2-CB (-0.97 VSCE). The band gap of the semiconductor CuBi2O4 is 1.50 eV with a direct optical transition. This compound is a p-type semiconductor with a flat band potential of -0.39 VSCE and activation energy of 0.18 eV. The electrochemical impedance spectroscopy was undertaken to study the semiconductor/electrolyte interfacial phenomena. The photoactivity on the heterojunction is strongly enhanced. A remarkable performance is obtained in less than 4 h for a concentration of 30 mg in (Cr (VI)) at pH ∼ 4 and a dose of 1 mg/mL; a 98% reduction has been obtained. The kinetic of chromate photoreduction is well described by the Langmuir-Hinshelwood model. The chromate elimination obeys to a pseudo-first order kinetic with an apparent rate constant of 0.014 min-1.
Laboratory Studies of FeO and NiO Chemiluminescence

NASA Astrophysics Data System (ADS)

Kalogerakis, K. S.; Bartlett, N. C.; Copeland, R. A.; Slanger, T. G.

2013-12-01

Although the terrestrial nightglow spectrum has been studied for over a century, new identifications of spectral features continue to be made. Recently, FeO* continuum emissions in the mesosphere were identified by comparison of results from the OSIRIS spectrometer to existing laboratory spectra [1]. This discovery has sparked a renewal of interest in the reactions of meteoric metals with mesospheric gases [2,3], and has motivated the current study. We report laboratory-based chemiluminescence spectra from the reactions Fe + O3 and Ni + O3 produced under various conditions. Iron and nickel vapor was prepared in a vacuum cell using laser ablation at 248 and 800 nm in the presence of ozone. Emission spectra from FeO* and NiO* were recorded in the region of 450-700 nm using a commercial fiber-coupled spectrometer and compared to previous results using different methods. Knowledge of the excited-state production efficiency of Fe + O3 → FeO* + O2 and the analogous reaction with Ni is critical in modeling upper atmospheric dynamics of meteoric metal layers. The only relevant experimental study in the literature for iron oxide is from West and Broida [4], who reported a yield of approximately 2% at around 1 Torr, in stark contrast with the 100% efficiency used in relevant model calculations [5]. This work was supported by the National Science Foundation's Aeronomy Program under grant AGS-0637433. References 1. W.F.J. Evans, R.L. Gattinger, T.G. Slanger, D.V. Saran, D.A. Degenstein, and E.J. Llewellyn, Geophys. Res. Lett., 37, L22105 (2010). 2. D.V. Saran, T.G. Slanger, W. Feng, and J.M.C. Plane, J. Geophys. Res. 116, D12303 (2011). 3. R.L. Gattinger, W.F.J. Evans, and E.J. Llewellyn, Canadian Journal of Physics 89, 869 (2011). 4. J.B. West and H.P. Broida, J. Chem. Phys. 62, 2566 (1975 ). 5. C.S. Gardner, J.M.C. Plane, W.L. Pan, T. Vondrak, B.J. Murray, and X.Z. Chu, J. Geophys. Res. 110, D10302 (2005).
Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

NASA Astrophysics Data System (ADS)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.
Monodisperse Fe3O4 and γ-Fe2O3 magnetic mesoporous microspheres as anode materials for lithium-ion batteries.

PubMed

Xu, Jing-San; Zhu, Ying-Jie

2012-09-26

Monodisperse Fe(3)O(4) and γ-Fe(2)O(3) magnetic mesoporous microspheres are prepared via a surfactant-free solvothermal combined with precursor thermal transformation method. The as-prepared Fe(3)O(4) and γ-Fe(2)O(3) magnetic mesoporous microspheres have a relatively high specific surface area of 122.3 and 138.6 m(2)/g, respectively. The Fe(3)O(4) and γ-Fe(2)O(3) magnetic mesoporous microspheres are explored as the anode materials for lithium-ion batteries, and they have a high initial discharge capacity of 1307 and 1453 mA h/g, respectively, and a good reversible performance (450 mA h/g for Fe(3)O(4) and 697 mA h/g for γ-Fe(2)O(3) after 110 cycles) at the current density of 0.2C.
Molecular cloning and characterization of genistein 4'-O-glucoside specific glycosyltransferase from Bacopa monniera.

PubMed

Ruby; Santosh Kumar, R J; Vishwakarma, Rishi K; Singh, Somesh; Khan, Bashir M

2014-07-01

Health related benefits of isoflavones such as genistein are well known. Glycosylation of genistein yields different glycosides like genistein 7-O-glycoside (genistin) and genistein 4'-O-glycoside (sophoricoside). This is the first report on isolation, cloning and functional characterization of a glycosyltransferase specific for genistein 4'-O-glucoside from Bacopa monniera, an important Indian medicinal herb. The glycosyltransferase from B. monniera (UGT74W1) showed 49% identity at amino acid level with the glycosyltransferases from Lycium barbarum. The UGT74W1 sequence contained all the conserved motifs present in plant glycosyltransferases. UGT74W1 was cloned in pET-30b (+) expression vector and transformed into E. coli. The molecular mass of over expressed protein was found to be around 52 kDa. Functional characterization of the enzyme was performed using different substrates. Product analysis was done using LC-MS and HPLC, which confirmed its specificity for genistein 4'-O-glucoside. Immuno-localization studies of the UGT74W1 showed its localization in the vascular bundle. Spatio-temporal expression studies under normal and stressed conditions were also performed. The control B. monniera plant showed maximum expression of UGT74W1 in leaves followed by roots and stem. Salicylic acid treatment causes almost tenfold increase in UGT74W1 expression in roots, while leaves and stem showed decrease in expression. Since salicylic acid is generated at the time of injury or wound caused by pathogens, this increase in UGT74W1 expression under salicylic acid stress might point towards its role in defense mechanism.
Kinetic study of Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y superconductor in water

NASA Astrophysics Data System (ADS)

Wang, C. M.; Wei, T. P.; Kao, H.-C. I.

1993-10-01

The reaction of Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y powder in water was studied quantitatively. It was found that the [H 3O +] ion would act as a catalyst in this reaction and the initial rate equation was R 0 = - {d[A] 0}/{dt } = k[A] 0[ H3O+] 0.20, where [ A] represented the surface area of the superconducting powder. The rate constant, k, obtained at 10, 25 and 40°C was 3.98, 8.8 and 19.6 × 10 -4 mol min -1 cm -2 M 0.8, respectively. The activation energy and pre-exponential factor calculated from the Arrhenius equation were respectively 39.1 kJ mol -1 and 6.4 × 10 3 mol min -1 cm -2 M 0.8.
Hydrothermal synthesis and photocatalytic activities of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} composite micro-platelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Wei, E-mail: zhaowei2004@tsinghua.org.cn; Wang, Hongxing; Feng, Xiangning

2015-10-15

Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} composite was fabricated by combining hydrothermal reaction and molten salt method. • Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} exhibits higher photocatalytic activity than pure Bi{sub 4}Ti{sub 3}O{sub 12}. • The absorption light of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} has been broadened to visible light. - Abstract: In this study, Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} micro-platelets were successfully synthesized by using hydrothermal and molten salt methods, and the morphology and photocatalytic degradation performance of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} was characterized. The results indicated a much higher degradation rate of methylene blue and methylene orange,more » reaching more than 90% and 65%, respectively, within 3 h under visible-light irradiation. Compared with pure Bi{sub 4}Ti{sub 3}O{sub 12}, the photocatalytic activity of Bi{sub 4}Ti{sub 3}O{sub 12}/SrTiO{sub 3} was significantly better, due to the micron–submicron heterojunction with SrTiO{sub 3} reducing the band gap of Bi{sub 4}Ti{sub 3}O{sub 12}. In addition, the perovskite structure layer facilitates the mobility of the photogenerated carriers and hampers their recombination, which were affected the photocatalytic properties.« less
Thermal conductivity of ZrO2-4mol%Y2O3 thin coatings by pulsed thermal imaging method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Byung-Koog; Sun, Jiangang; Kim, Seongwon

Thin ZrO2-4mol% Y2O3 coatings were deposited onto ZrO2 substrates by electron beam-physical vapor deposition. The coated samples revealed a feather-like columnar microstructure. The main phase of the ZrO2-4mol% Y2O3 coatings was the tetragonal phase. To evaluate the influence of the coating’s thickness on the thermal conductivity of thin ZrO2-4mol% Y2O3 coatings, the pulsed thermal imaging method was employed to obtain the thermal conductivity of the coating layer in the two-layer (coating and substrate) samples with thickness between 56 and 337 micrometers. The thermal conductivity of the coating layer was successfully evaluated and compared well with those obtained by the lasermore » flash method for similar coatings. The thermal conductivity of coatings shows an increasing tendency with an increase in the coating’s thickness.« less
Infrared and Raman spectroscopic characterization of the silicate-carbonate mineral carletonite - KNa4Ca4Si8O18(CO3)4(OH,F)·H2O

NASA Astrophysics Data System (ADS)

Frost, Ray L.; Xi, Yunfei; Scholz, Ricardo; López, Andrés; Belotti, Fernanda Maria

2013-06-01

An assessment of the molecular structure of carletonite a rare phyllosilicate mineral with general chemical formula given as KNa4Ca4Si8O18(CO3)4(OH,F)·H2O has been undertaken using vibrational spectroscopy. Carletonite has a complex layered structure. Within one period of c, it contains a silicate layer of composition NaKSi8O18·H2O, a carbonate layer of composition NaCO3·0.5H2O and two carbonate layers of composition NaCa2CO3(F,OH)0.5. Raman bands are observed at 1066, 1075 and 1086 cm-1. Whether these bands are due to the CO32- ν1 symmetric stretching mode or to an SiO stretching vibration is open to question. Multiple bands are observed in the 300-800 cm-1 spectral region, making the attribution of these bands difficult. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate and carbonate surfaces.
Preparation and electrochemical properties of NiO-Co3O4 composite as electrode materials for supercapacitors

NASA Astrophysics Data System (ADS)

Wang, X. W.; Zheng, D. L.; Yang, P. Z.; Wang, X. E.; Zhu, Q. Q.; Ma, P. F.; Sun, L. Y.

2017-01-01

The precursor of NiO-Co3O4 composites was synthesized via a simple hydrothermal process. After that, the precursor was calcined at 300 °C for 3 h to obtain the composite powders. The powders calcined at 300 °C showed amorphous, and the powders calcined at 400 °C and 500 °C for comparison showed the composite phase of NiO and Co3O4. The composite products showed a microstructure of micro-spheres. For the samples calcined at 300 °C for 3 h, the specific capacitance reached 801 F g-1 at a current density of 1 A g-1.
Bobjonesite, V4+ O (SO4) (H2O 3, a new mineral species from Temple Mountain, Emery County, Utah, U.S.A

USGS Publications Warehouse

Schindler, M.; Hawthorne, F.C.; Huminicki, D.M.C.; Haynes, P.; Grice, Joel D.; Evans, H.T.

2003-01-01

Bobjonesite, V4+ O (SO4) (H2O 3, is a new mineral species from Temple Mountain, Emery County, Utah, U.S.A. It occurs as blue-green crusts and efflorescences in fractures in a fossil (Triassic) tree: individual crystals are ??1 mm and are intimately intergrown. Bobjonesite hydrates very easily, and is unstable in all but the driest atmosphere. Its structure was determined on a crystal of bobjonesite: however, the physical properties, optical properties and X-ray powder-diffraction pattern were recorded on the synthetic equivalent, and an electron-microprobe analysis was not possible. Bobjonesite has a pale blue streak, a vitreous luster and no observable fluorescence under ultraviolet light. It has no cleavage or parting. The Mohs hardness is ???1, and the calculated density is 2.28 g/cm3. Bobjonesite is biaxial positive, with ?? 1.555(2 , ?? 1.561(1), ?? 1.574(2), 2V(obs.) = 72(1)??, 2V(calc.) = 69??; it is non-pleochroic, X = b, Y ??? 19?? (in ?? obtuse). Bobjonesite is monoclinic, space group P21/n, cell dimensions from single-crystal data: a 7.3940(5), b 7.4111(3), c 12.0597(9) A??, ?? 106.55(1)??, V 633.5(1) A??3, Z=4. The strongest seven lines in the X-ray powder-diffraction pattern [d in A??(I)(hkl)] are as follows: 5.795(100)(002), 3.498(90)(112), 3.881(48)(1??03), 5.408(37) (101), 4.571(20)(012), 6.962(11 (1??01) and 6.254(11)(011). The chemical formula was derived from crystal-structure analysis; the end-member formula is V O (SO4) (H2O)3. The crystal structure of bobjonesite was refined to an R index of 3.6% for 1105 observed (Fo> 5??F) reflections measured with an automated four-circle X-ray diffractometer using MoK?? X-radiation. There is one V site occupied by V4+ and surrounded by three O atoms and three (H2O) groups in an octahedral arrangement, with one short vanadyl bond (1.577 A??), four similar equatorial bonds (<2.022 A??), and one longer V-O bond (2.278 A??) trans to the vanadyl bond. The structure consists of isolated [V4+2 O2 (H2O)6 (SO4
Synthesis and photocatalytic activity of p–n junction CeO2/Co3O4 photocatalyst for the removal of various dyes from wastewater

NASA Astrophysics Data System (ADS)

Tang, Yuanzheng; Zhang, Meng; Wu, Zhengying; Chen, Zhigang; Liu, Chengbao; Lin, Yun; Chen, Feng

2018-04-01

CeO2, Co3O4, and Co3O4/CeO2 composites are successfully synthesized by a simple coprecipitation method. X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) results indicate that the CeO2, Co3O4, and Co3O4/CeO2 precursors sintered at 500 °C has good crystallization. The cerium nitrate introduced into cobalt nitrate precursor solution improved the surface morphology and photocatalytic activity of Co3O4 significantly. The photo-degradation of methylene blue (MB), xylenol orange (XO), methyl orange (MO), and methyl red (MR) catalyzed by prepared nanocomposites were studied under visible light irradiation. Photocatalytic experiment results indicate that the photocatalytic activity of Co3O4/CeO2 composites for degradation of various dyes highly depend on pH value. The optimum conditions for the photocatalytic experiments of Co3O4/CeO2 composites were determined to be as follows: dye concentration, 50 mg L‑1, and catalyst concentration, 50 mg L‑1. The excellent photocatalytic activity of the p–n junction Co3O4/CeO2 composites can be ascribed to the ·O2‑ radicals and h+.
Cosmoeducação: uma proposta para o ensino de astronomia

NASA Astrophysics Data System (ADS)

Medeiros, L. A. L.; Jafelice, L. C.

2003-08-01

Entende-se por cosmoeducação o desenvolvimento vivencial da unidade homem-cosmo. Este conceito é norteado pela psicologia transpessoal, que estuda o ser humano em sua totalidade, onde suas relações ecológicas e cósmicas são de grande importância. Constata-se uma necessidade latente no ser humano moderno em resgatar uma relação holística com o Universo. Neste trabalho exploramos meios de cultivar a consciência de que o ser humano constitui parte integrante do cosmo e se relaciona com este com o objetivo de promover em si uma percepção ambiental mais ampla. Nossa hipótese de trabalho inicial foi que o ensino de conteúdos básicos em astronomia realizado através de uma abordagem holística, que incorpore práticas vivenciais correlacionadas àqueles conteúdos, pode despertar no indivíduo sua identidade cósmica. O método que utilizamos é o fenomenológico e o universo desta pesquisa é um grupo de estudantes da disciplina de Astronomia (Curso de Licenciatura em Geografia/UFRN), onde realizamos observação participante, entrevistas, depoimentos e as práticas vivenciais mencionadas. Neste caso estamos desenvolvendo e adaptando exercícios de algumas técnicas terapêuticas de psicologia transpessoal, que um de nós (LALM) tem aplicado no contexto clínico, para trabalhar aspectos cognitivos envolvidos naquele processo de conscientização cósmica. Resultados parciais claramente referendam a hipótese inicial. Um resultado a destacar é fruto de uma dinâmica de representação corporal interiorizada do eclipse lunar, envolvendo um pequeno grupo daqueles estudantes, na qual conteúdos míticos afloraram de maneira espontânea e contundente para todos, sugerindo ressonância, ou pelo menos isomorfismo, entre o macro e o microcosmo. Este e outros resultados são discutidos em detalhe neste trabalho. (PPGECNM/UFRN; PRONEX/FINEP; NUPA/USP; Temáticos/FAPESP).
Synthesis of Co3O4/TiO2 composite by pyrolyzing ZIF-67 for detection of xylene

NASA Astrophysics Data System (ADS)

Bai, Shouli; Tian, Ke; Tian, Ye; Guo, Jun; Feng, Yongjun; Luo, Ruixian; Li, Dianqing; Chen, Aifan; Liu, Chung Chiun

2018-03-01

Co3O4/TiO2 composites with p-n heterojunction have been successfully prepared by pyrolyzing sacrificial template of Ti ion loaded Co-based Zeolitic imidazolate framework (ZIF-67). The structure and morphology of composite have been characterized by means of the analysis of XRD, FESEM, HRTEM and XPS spectra. The composite with a Co/Ti molar ratio of 4:1 exhibits the maximum sensing response of 6.17-50 ppm xylene, which is 5 times higher than pristine Co3O4. Moreover, Co3O4/TiO2 composite also shows good selectivity, long-term stability and rapid response and recovery. Such excellent sensing performances are attributed to material porous structure, high specific surface and the formation of abundant p-n heterojunction that permits the gas adsorption, diffusion and surface reaction and then improve the gas sensing performance. This work develops a promising synthesized approach of metal oxide composites for broader MOFs application in gas sensor field.
Improving antiproliferative effect of the anticancer drug cytarabine on human promyelocytic leukemia cells by coating on Fe3O4@SiO2 nanoparticles.

PubMed

Shahabadi, Nahid; Falsafi, Monireh; Mansouri, Kamran

2016-05-01

In this study, Fe3O4@SiO2-cytarabine magnetic nanoparticles (MNPs) were prepared via chemical coprecipitation reaction and coating silica on the surface of Fe3O4 MNPs by Stöber method via sol-gel process. The surface of Fe3O4@SiO2 MNPs was modified by an anticancer drug, cytarabine. The structural properties of the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Zetasizer analyzer, and transmission electron microscopy (TEM). The results indicated that the crystalline phase of iron oxide NPs was magnetite (Fe3O4) and the average sizes of Fe3O4@SiO2-cytarabine MNPs were about 23 nm. Also, the surface characterization of Fe3O4@SiO2-cytarabine MNPs by FT-IR showed that successful coating of Fe3O4 NPs with SiO2 and binding of cytarabine drug onto the surface of Fe3O4@SiO2 MNPs were through the hydroxyl groups of the drug. The in vitro cytotoxic activity of Fe3O4@SiO2-cytarabine MNPs was investigated against cancer cell line (HL60) in comparison with cytarabine using MTT colorimetric assay. The obtained results showed that the effect of Fe3O4@SiO2-cytarabine magnetic nanoparticles on the cell lines were about two orders of magnitude higher than that of cytarabine. Furthermore, in vitro DNA binding studies were investigated by UV-vis, circular dichroism, and fluorescence spectroscopy. The results for DNA binding illustrated that DNA aggregated on Fe3O4@SiO2-cytarabine MNPs via groove binding. Copyright © 2016 Elsevier B.V. All rights reserved.
Isomerization of 1-O-indol-3-ylacetyl-beta-D-glucose. Enzymatic hydrolysis of 1-O, 4-O, and 6-O-indol-3-ylacetyl-beta-D-glucose and the enzymatic synthesis of indole-3-acetyl glycerol by a hormone metabolizing complex

NASA Technical Reports Server (NTRS)

Kowalczyk, S.; Bandurski, R. S.

1990-01-01

The first compound in the series of reactions leading to the ester conjugates of indole-3-acetic acid (IAA) in kernels of Zea mays sweet corn is the acyl alkyl acetal, 1-O-indol-3-ylacetyl-beta-D-glucose (1-O-IAGlu). The enzyme catalyzing the synthesis of this compound is UDP-glucose:indol-3-ylacetate glucosyl-transferase (IAGlu synthase). The IAA moiety of the high energy compound 1-O-IAGlu may be enzymatically transferred to myo-inositol or to glycerol or the 1-O-IAGlu may be enzymatically hydrolyzed. Alternatively, nonenzymatic acyl migration may occur to yield the 2-O, 4-O, and 6-O esters of IAA and glucose. The 4-O and 6-O esters may then be enzymatically hydrolyzed to yield free IAA and glucose. This work reports new enzymatic activities, the transfer of IAA from 1-O-IAGlu to glycerol, and the enzyme-catalyzed hydrolysis of 4-O and 6-O-IAGlu. Data is also presented on the rate of non-enzymatic acyl migration of IAA from the 1-O to the 4-O and 6-O positions of glucose. We also report that enzymes catalyzing the synthesis of 1-O-IAGlu and the hydrolysis of 1-O, 4-O, and 6-O-IAGlu fractionate as a hormone metabolizing complex. The association of synthetic and hydrolytic capabilities in enzymes which cofractionate may have physiological significance.
Synthesis, characterization and electrochemical performance of graphene decorated with 1D NiMoO4.nH2O nanorods

NASA Astrophysics Data System (ADS)

Ghosh, Debasis; Giri, Soumen; Das, Chapal Kumar

2013-10-01

One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg-1 accompanied with long term cyclic stability.One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene
The effect of calcination temperature on the performance of Co3O4-Bi2O3 as a heterogeneous catalyst of peroxymonosulfate

NASA Astrophysics Data System (ADS)

Zhang, Guangshan; Hu, Limin; Wang, Peng; Yuan, Yixing

2017-11-01

In this work, a time-saving microwave-assisted method for synthesis of Co3O4-Bi2O3 was reported. The synthesized Co3O4-Bi2O3 samples were characterized with different techniques to probe their crystalline structures and morphologies. The catalytic performances of synthesized Co3O4-Bi2O3 as peroxymonosulfate activator were evaluated by the degradation of bisphenol A. The effect of calcination temperature on Co3O4-Bi2O3 products was explored and the result showed that the sample calcined at 400 °C possessing superior catalytic activity.
Self-assembly and electrical characteristics of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles on SiO2/n-Si

NASA Astrophysics Data System (ADS)

Baharuddin, Aainaa Aqilah; Ang, Bee Chin; Wong, Yew Hoong

2017-11-01

A novel investigation on a relationship between temperature-influential self-assembly (70-300 °C) of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles (NPs) on SiO2/n-Si with electrical properties was reported with the interests for metal-oxide-semiconductor applications. X-ray diffractometer (XRD) analysis conveyed that 8 ± 1 nm of the NPs were assembled. Increasing heating temperature induced growth of native oxide (SiO2). Raman analysis confirmed the coexistence of Fe3O4-γ-Fe2O3. Attenuated Total Reflectance Infrared (ATR-IR) spectra showed that self-assembly occurred via Sisbnd Osbnd C linkages. While Sisbnd Osbnd C linkages were broken down at elevated temperatures, formations of Si-OH defects were amplified; a consequence of physisorbed surfactants disintegration. Atomic force microscopy (AFM) showed that sample with more physisorbed surfactants exhibited the highest root-mean-square (RMS) roughness (18.12 ± 7.13 nm) whereas sample with lesser physisorbed surfactants displayed otherwise (12.99 ± 4.39 nm RMS roughness). Field Emission Scanning Electron Microscope (FE-SEM) analysis showed non-uniform aggregation of the NPs, deposited as film (12.6 μm thickness). The increased saturation magnetization (71.527 A m2/kg) and coercivity (929.942 A/m) acquired by vibrating sample magnetometer (VSM) of the sample heated at 300 °C verified the surfactants' disintegration. Leakage current density-electric field (J-E) characteristics showed that sample heated at 150 °C with the most aggregated NPs as well as the most developed Sisbnd Osbnd C linkages demonstrated the highest breakdown field and barrier height at 2.58 × 10-3 MV/cm and 0.38 eV respectively. Whereas sample heated at 300 °C with the least Sisbnd Osbnd C linkages as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08 × 10-3 MV/cm and 0.19 eV respectively. This study opens up better understandings on how formation and breaking down of covalent

Ensino de astronomia no 1o. e 2o. ciclos do nível fundamental e na educação de jovens e adultos: exemplos e discussões

NASA Astrophysics Data System (ADS)

Queiroz, A. S. B.; Jafelice, L. C.

2003-08-01

Tem-se constatado uma preocupante carência no ensino de astronomia nos diversos níveis de escolaridade. Neste trabalho discutimos várias práticas didático-pedagógicas que vimos desenvolvendo para crianças, jovens e adultos em processo de alfabetização, visando contribuir para reparar aquela carência. Propomos uma metodologia que incorpora as recentes exigências das políticas públicas educacionais, estimula o desenvolvimento de textos e materiais instrucionais, é compatível com a realidade desse público e é adaptável às respectivas faixas etárias. A observação do céu sempre esteve presente na vida de nossos antepassados, dando suporte à compreensão do ser humano como integrante da natureza. Visamos com este trabalho suprir a deficiência encontrada para se tratar a relação do ser humano com o céu, no ambiente escolar. Os resultados são animadores e envolvem práticas e textos que desenvolvemos e atividades realizadas pelos alunos. No primeiro grupo destacamos o desenvolvimento de várias práticas: "viagem aos planetas" (construímos o "foguete", os planetas em escala, contamos história e redigimos texto de orientação para os professores); "gnômon humano" (os próprios corpos dos alunos são usados para registrar o movimento aparente do Sol); "crateras da Lua" (concretização de "meteoritos" e "solo lunar" de gesso e exploração da relação entre energia cinética do bólido e tamanho da cratera formada); etc. No segundo grupo, produções de desenhos e redações e discussões dos alunos após a realização de cada prática, revelam que estas têm se mostrado muito eficientes, tanto para estimular a imaginação e a fantasia dos envolvidos, como para trabalhar-se habilidades, competências e conteúdos relacionados à astronomia, segundo uma perspectiva interdisciplinar contextualizada. (PPGECNM/UFRN; NUPA/USP; Temáticos/FAPESP)
High-performance Ti/Sb-SnO(2)/Pb(3)O(4) electrodes for chlorine evolution: preparation and characteristics.

PubMed

Shao, Dan; Yan, Wei; Cao, Lu; Li, Xiaoliang; Xu, Hao

2014-02-28

Chlorine evolution via electrochemical approach has wide application prospects in drinking water disinfection and wastewater treatment fields. Dimensional stable anodes used for chlorine evolution should have high stability and adequate chlorine evolution efficiency. Thus a novel and cost-effective Ti/Sb-SnO(2)/Pb(3)O(4)electrode was developed. The physicochemical and electrochemical properties as well as the chlorine evolution performances of the electrodes were investigated. The electrocatalytic activity and deactivation course of the electrodes were also explored. Results showed that this novel electrode had strong chlorine evolution ability with high current efficiency ranging from 87.3% to 93.4% depending on the operational conditions. The accelerated service life of Ti/Sb-SnO(2)/Pb(3)O(4) electrode could reach 180 h at a current density of 10,000 A m(-2) in 0.5 molL(-1) H(2)SO(4). During the electrolysis process, it was found that the conversion of Pb(3)O(4) into β-PbO(2) happened gradually on the electrode surface, which not only inhibited the leakage of hazardous Pb(2+) ion but also increased the anti-corrosion capacity of the electrode effectively. Copyright © 2014 Elsevier B.V. All rights reserved.
Nanoscale PdO Catalyst Functionalized Co3O4 Hollow Nanocages Using MOF Templates for Selective Detection of Acetone Molecules in Exhaled Breath.

PubMed

Koo, Won-Tae; Yu, Sunmoon; Choi, Seon-Jin; Jang, Ji-Soo; Cheong, Jun Young; Kim, Il-Doo

2017-03-08

The increase of surface area and the functionalization of catalyst are crucial to development of high-performance semiconductor metal oxide (SMO) based chemiresistive gas sensors. Herein, nanoscale catalyst loaded Co 3 O 4 hollow nanocages (HNCs) by using metal-organic framework (MOF) templates have been developed as a new sensing platform. Nanoscale Pd nanoparticles (NPs) were easily loaded on the cavity of Co based zeolite imidazole framework (ZIF-67). The porous structure of ZIF-67 can restrict the size of Pd NPs (2-3 nm) and separate Pd NPs from each other. Subsequently, the calcination of Pd loaded ZIF-67 produced the catalytic PdO NPs functionalized Co 3 O 4 HNCs (PdO-Co 3 O 4 HNCs). The ultrasmall PdO NPs (3-4 nm) are well-distributed in the wall of Co 3 O 4 HNCs, the unique structure of which can provide high surface area and high catalytic activity. As a result, the PdO-Co 3 O 4 HNCs exhibited improved acetone sensing response (R gas /R air = 2.51-5 ppm) compared to PdO-Co 3 O 4 powders (R gas /R air = 1.98), Co 3 O 4 HNCs (R gas /R air = 1.96), and Co 3 O 4 powders (R gas /R air = 1.45). In addition, the PdO-Co 3 O 4 HNCs showed high acetone selectivity against other interfering gases. Moreover, the sensor array clearly distinguished simulated exhaled breath of diabetics from healthy people's breath. These results confirmed the novel synthesis of MOF templated nanoscale catalyst loaded SMO HNCs for high performance gas sensors.
Mechanical properties and in vitro bioactivity of Ca5(PO4)2SiO4 bioceramic.

PubMed

Lu, Wenhao; Duan, Wei; Guo, Yaping; Ning, Congqin

2012-02-01

Pure Ca(5)(PO(4))(2)SiO(4) bioceramic was first prepared by a sol-gel method using triethyl phosphate, tetraethoxysilane, and calcium nitrate tetrahydrate as original materials. Simulated body fluid (SBF) immersion tests revealed that Ca(5)(PO(4))(2)SiO(4) samples had a greater in vitro apatite-forming ability than hydroxyapatite (HA). After soaking Ca(5)(PO(4))(2)SiO(4) samples in the SBF for 1 day, bone-like apatite precipitated on the surfaces and the apatite layer became thicker with increasing the soaking time. However, few bone-like apatites precipitated on the HA samples even after soaking in the SBF for 7 days. The good in vitro bioactivity of Ca(5)(PO(4))(2)SiO(4) samples was attributed to the silanol (Si-OH) groups and greater solubility of Ca(5)(PO(4))(2)SiO(4). In addition, hot-pressed Ca(5)(PO(4))(2)SiO(4) ceramic exhibited lower bending strength and elastic modulus than hot-pressed HA, since the former had a lower relative density than the latter. The results have shown that Ca(5)(PO(4))(2)SiO(4) is a potential candidate material for bone repair. © The Author(s), 2010.
Orbital engineering near La2 NiO 4- La2 CuO 4 superlattice interfaces

NASA Astrophysics Data System (ADS)

Smadici, S.; Lee, J. C. T.; Morales, J.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

2011-03-01

Orbital states of transition metal oxides present the opportunity of adjusting material properties to a specific purpose (orbital engineering). A comparison of the resonant soft x-ray reflectivity of La 2 Ni O4 - La 2 Cu O4 superlattices at Ni L and Cu L edges shows different spatial distributions of the occupation of Ni d x 2 -y 2 and d 3z 2 -r 2 orbitals in the LNO layers. This modulation of the Ni valence is possible through a pronounced modulation of the density of oxygen interstitial dopants within the structure which does not follow exactly the structure itself. This is the first observation of orbital engineering in a 214 oxide. This work was supported by Grants DE-FG02-06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.
Two actinide-organic frameworks constructed by a tripodal flexible ligand: Occurrence of infinite {(UO2)O2(OH)3}4n and hexanuclear {Th6O4(OH)4} motifs

NASA Astrophysics Data System (ADS)

Liang, Lingling; Zhang, Ronglan; Zhao, Jianshe; Liu, Chiyang; Weng, Ng Seik

2016-11-01

Two new actinide metal-organic frameworks were constructed by using a tripodal flexible ligand tris (2-carboxyethyl) isocyanurate (H3tci) under hydrothermal condition. The combination of H3tci and uranyl nitrate hexahydrate in aqueous solution leads to the isolation of [(UO2)2(H2O)4]0.5(tci)2(UO2)4(OH)4·18H2O (1), which contains two distinct UO22+ coordination environments. Four uranyl cations, linked through μ3-OH respectively, result in the edge-sharing ribbons. Then, the layer structure is constructed by U-O clusters linked through other eight-coordinated uranyl unions, giving rise to a porous structure in the space. Topological analysis reveals that complex 1 belongs to a (4, 8)-connected net with a schläfli symbol of (34.26.3)2(34.46.56.68.73.8). Th3(tci)2O2(OH)2(H2O)3·12H2O (2) generated by the reaction of H3tci and thorium nitrate tetrahydrate, possesses nine-fold coodinated Th(IV) centers with a monocapped square antiprismatic geometry. The hexamers "Th6O4(OH)4" motifs are connected together by the carboxylate groups, showing a three-dimensional structures. Complex 2 takes on an 8-connected architecture and the point symbol is (424.64).
Acetic Acid Ketonization over Fe3O4/SiO2 for Pyrolysis Bio-Oil Upgrading.

PubMed

Bennett, James A; Parlett, Christopher M A; Isaacs, Mark A; Durndell, Lee J; Olivi, Luca; Lee, Adam F; Wilson, Karen

2017-05-10

A family of silica-supported, magnetite nanoparticle catalysts was synthesised and investigated for continuous-flow acetic acid ketonisation as a model pyrolysis bio-oil upgrading reaction. The physico-chemical properties of Fe 3 O 4 /SiO 2 catalysts were characterised by using high-resolution transmission electron microscopy, X-ray absorption spectroscopy, X-ray photo-electron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis and porosimetry. The acid site densities were inversely proportional to the Fe 3 O 4 particle size, although the acid strength and Lewis character were size-invariant, and correlated with the specific activity for the vapour-phase acetic ketonisation to acetone. A constant activation energy (∼110 kJ mol -1 ), turnover frequency (∼13 h -1 ) and selectivity to acetone of 60 % were observed for ketonisation across the catalyst series, which implies that Fe 3 O 4 is the principal active component of Red Mud waste.
Full synergistic effect of hydrothermal NiCo2O4 nanosheets/CuCo2O4 nanocones supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Bai, Hongye; Shao, Rong; Xu, Wei; Shi, Weidong

2018-06-01

In this work, a series of NiCo2O4/CuCo2O4 composites were prepared by a two-step hydrothermal method. The optimized NiCo2O4/CuCo2O4 electrode shows more than 5 times area capacitance (4.97 F cm-2) than pure NiCo2O4 at the current density of 1 mA cm-2. The best performance of sample assembled an asymmetric supercapacitor could reach up to 42 F g-1 at the current density of 1 A g-1. In addition, the maximum energy density of 15 W h kg-1 was achieved with the power density of 814 W kg-1. The as-prepared active electrode material also reveals excellent cycling stability with 90.6% capacitance retention after 5000 cycles. These results indicate potential application in developing energy storage devices with high energy density power density.
Profilaxia de tromboembolismo venoso na gestação

PubMed Central

de Oliveira, André Luiz Malavasi Longo; Marques, Marcos Arêas

2016-01-01

Resumo O tromboembolismo venoso é importante causa de morbidade e mortalidade obstétrica. Durante a gestação, o risco de sua ocorrência aumenta entre cinco e dez vezes quando comparado ao de mulheres não gestantes de mesma idade. Associado a esse fato, a gestante apresenta algumas limitações para o diagnóstico clínico (alta frequência de dor e edema nos membros inferiores), ecográfico (menor sensibilidade e especificidade no diagnóstico de trombose venosa de ilíaca com a evolução da gestação) e laboratorial (o D-dímero apresenta aumento progressivo no decorrer da gravidez). Uma estratificação criteriosa de risco de tromboembolismo venoso de cada mulher antes da gestação pode diminuir a incidência dessa doença, frequente e de difícil diagnóstico na gravidez, e suas complicações. PMID:29930607
Synthesis and characterization of Cr doped CoFe2O4

NASA Astrophysics Data System (ADS)

Verma, Kavita; Patel, K. R.; Ram, Sahi; Barbar, S. K.

2016-05-01

Polycrystalline samples of pure and Cr-doped cobalt ferrite (CoFe2O4 and CoCrFeO4) were prepared by solid state reaction route method. X-ray diffraction pattern infers that both the samples are in single phase with Fd3m space group. Slight reduction in the lattice parameter of CoCrFeO4 has been observed as compared to CoFe2O4. The dielectric dispersion has been explained on the basis of Fe2+ ↔ Fe3+ hopping mechanism. The polarizations at lower frequencies are mainly attributed to electronic exchange between Fe2+ ↔ Fe3+ ions on the octahedral site in the ferrite lattice. In the present system a part from n-type charge carrier (Fe3+/Fe2+), the presence of (Co3+/Co2+) ions give rise to p-type charge carrier. Therefore in addition to n-type charge carrier, the local displacement of p-type charge carrier in direction of external electric field also contributes to net polarization. However, the dielectric constant and loss tangent of CoCrFeO4 are found to be lower than CoFe2O4 and is attributed to the availability of ferrous ion. CoCrFeO4 have less amount of ferrous ion available for polarization as compared to that of CoFe2O4. The impedance spectra reveal a grain interior contribution to the conduction process.
Efficient one-pot sonochemical synthesis of thickness-controlled silica-coated superparamagnetic iron oxide (Fe3O4/SiO2) nanospheres

NASA Astrophysics Data System (ADS)

Abbas, Mohamed; Abdel-Hamed, M. O.; Chen, Jiangang

2017-12-01

A facile and eco-friendly efficient sonochemical approach was designed for the synthesis of highly crystalline Fe3O4 and Fe3O4/SiO2 core/shell nanospheres in single reaction. The generated physical properties (shock waves, microjets, and turbulent flows) from ultrasonication as a consequence of the collapse of microbubbles and polyvinylpyrrolidone (PVP) as a chemical linker were found to play a crucial role in the successful formation of the core/shell NPs within short time than the previously reported methods. Transmission electron microscopy revealed that a uniform SiO2 shell is successfully coated over Fe3O4 nanospheres, and the thickness of the silica shell could be easily controlled in the range from 5 to 15 nm by adjusting the reaction parameters. X-ray diffraction data were employed to confirm the formation of highly crystalline and pure phase of a cubic inverse spinel structure for magnetite (Fe3O4) nanospheres. The magnetic properties of the as-synthesized Fe3O4 and Fe3O4/SiO2 core/shell nanospheres were measured at room temperature using vibrating sample magnetometer, and the results demonstrated a high magnetic moment values with superparamagnetic properties.
Enhancement of ferromagnetic properties in composites of BaSnO3 and CoFe2O4

NASA Astrophysics Data System (ADS)

Manju, M. R.; Ajay, K. S.; D'Souza, Noel M.; Hunagund, Shivakumar; Hadimani, R. L.; Dayal, Vijaylakshmi

2018-04-01

In this paper, we report structural and magnetic properties of BaSnO3(BSO)(1-x)-CoFe2O4 (CFO)(x) composite (with x = 0%, 1% (C1), 2% (C2) and 5% (C3) in molar ratio) synthesized using nitrate precursor method. The X-ray diffraction (XRD) pattern of the composite powder confirmed presence of both BaSnO3 with the cubic perovskite structure and CoFe2O4 with the cubic spinel structure. No signature of any other phases in pure BaSnO3, CoFe2O4 and composites have been detected either in XRD or energy dispersive X-ray (EDS) analysis. The temperature dependent zero field cooled (ZFC) & field cooled (FC) magnetization and magnetic field dependence magnetization measurements have been carried at room temperature of the pure BaSnO3. We observe a weak ferromagnetic (FM) behavior at room temperature in pure BaSnO3 even though it is non-magnetic in nature. The room temperature Raman spectroscopy and electron spin resonance measurements of the sample confirm the presence of oxygen vacancy and formation of F-center, which is responsible for the FM behavior. The oxidation state and elemental analysis have been carried out using X-ray photoelectron spectroscopy (XPS). The magnetic field dependence of magnetization of the composite samples reveal increase of saturation magnetization (Ms), remanence magnetization (Mr) and coercivity (Hc) with increase in ferrite content in the composite. Significant enhancement in FM components is observed with lowering of temperature.
Variação temporal do gradiente radial de o/h a partir de uma amostra de nebulosas planetárias

NASA Astrophysics Data System (ADS)

Maciel, W. J.; Costa, R. D. D.; Uchida, M. M. M.

2003-08-01

Gradientes radiais de abundância são observados no disco de nossa Galáxia e também em outras galáxias espirais. No caso da Galáxia, o principal problema relativo aos gradientes é sua variação temporal, que constitui um dos principais vínculos aos modelos de evolução química da Galáxia. As nebulosas planetárias são particularmente interessantes no estudo dos gradientes e suas variações, tanto espaciais como temporais. São objetos brilhantes, podendo ser observadas a grandes distâncias, e têm abundâncias relativamente precisas de diversos elementos químicos. Além disso, sendo originadas de estrelas com massas entre 0.8 e 8 massas solares na sequência principal, incluem objetos com idades e populações diferentes, o que as torna especialmente interessantes ao estudo da variação temporal dos gradientes. Neste trabalho, apresentamos resultados recentes sobre a variação temporal do gradiente de O/H a partir de uma amostra contendo cerca de 200 nebulosas, para as quais obtivemos distâncias por métodos estatísticos. As abundâncias foram parcialmente obtidas a partir de observações em Itajubá e La Silla, sendo as restantes obtidas da literatura. Os resultados mostram, pela primeira vez, evidências de um achatamento do gradiente de O/H, de -0.11 dex/kpc para -0.06 dex/kpc nos últimos 9 giga-anos ou de -0.08 dex/kpc para -0.06 dex/kpc nos últimos 5 giga-anos. Esses valores apresentam um bom acordo com alguns modelos recentes para a evolução química da Galáxia. (FAPESP/CNPq)
Photospheres of hot stars. IV - Spectral type O4

NASA Technical Reports Server (NTRS)

Bohannan, Bruce; Abbott, David C.; Voels, Stephen A.; Hummer, David G.

1990-01-01

The basic stellar parameters of a supergiant (Zeta Pup) and two main-sequence stars, 9 Sgr and HD 46223, at spectral class O4 are determined using line profile analysis. The stellar parameters are determined by comparing high signal-to-noise hydrogen and helium line profiles with those from stellar atmosphere models which include the effect of radiation scattered back onto the photosphere from an overlying stellar wind, an effect referred to as wind blanketing. At spectral class O4, the inclusion of wind-blanketing in the model atmosphere reduces the effective temperature by an average of 10 percent. This shift in effective temperature is also reflected by shifts in several other stellar parameters relative to previous O4 spectral-type calibrations. It is also shown through the analysis of the two O4 V stars that scatter in spectral type calibrations is introduced by assuming that the observed line profile reflects the photospheric stellar parameters.
Large magnetoresistance in Fe3O4/molecule nanoparticles

NASA Astrophysics Data System (ADS)

Wang, S.; Yue, F. J.; Lin, L.; Shi, Y. J.; Wu, D.

2010-08-01

In this work, we successfully fabricate Fe3O4 nanoparticles self-assembled with molecules to explore a new approach of studying the molecular spintronics. Fourier transform infrared spectroscopy measurements indicate that one monolayer molecules chemically bonds to the Fe3O4 nanoparticles and the physically absorbed molecules do not exist in the samples. The magnetoresistance (MR) of molecule fully coated ~10 nm size nanoparticles is up to 7.3% at room temperature and 17.5% at 115 K under a field of 5.8 kOe. And the MR ratio is more than two times larger than that of pure Fe3O4 nanoparticles. This enhanced MR is likely arising from weak spin scattering while carriers transport through the molecules. Moreover, a very large low field magnetoresistance is also observed with ~500nm ferromagnetic Fe3O4 nanoparticles coated with acetic acid molecules. Those features open a door for the development of future spin-based molecular electronics.
Raman spectroscopy of the multi-anion mineral schlossmacherite (H 3O,Ca)Al 3(AsO 4,PO 4,SO 4) 2(OH) 6

NASA Astrophysics Data System (ADS)

Frost, Ray L.; Palmer, Sara J.; Xi, Yunfei

2012-02-01

The mineral schlossmacherite (H 3O,Ca)Al 3(AsO 4,PO 4,SO 4) 2(OH) 6, a multi-cation-multi-anion mineral of the beudantite mineral subgroup has been characterised by Raman spectroscopy. The mineral and related minerals functions as a heavy metal collector and is often amorphous or poorly crystalline, such that XRD identification is difficult. The Raman spectra are dominated by an intense band at 864 cm -1, assigned to the symmetric stretching mode of the AsO 43- anion. Raman bands at 809 and 819 cm -1 are assigned to the antisymmetric stretching mode of AsO 43-. The sulphate anion is characterised by bands at 1000 cm -1 ( ν1), and at 1031, 1082 and 1139 cm -1 ( ν3). Two sets of bands in the OH stretching region are observed: firstly between 2800 and 3000 cm -1 with bands observed at 2850, 2868, 2918 cm -1 and secondly between 3300 and 3600 with bands observed at 3363, 3382, 3410, 3449 and 3537 cm -1. These bands enabled the calculation of hydrogen bond distances and show a wide range of H-bond distances.
Structure disordering and thermal decomposition of manganese oxalate dihydrate, MnC2O4·2H2O

NASA Astrophysics Data System (ADS)

Puzan, Anna N.; Baumer, Vyacheslav N.; Lisovytskiy, Dmytro V.; Mateychenko, Pavel V.

2018-04-01

It is found that the known regular structures of MnC2O4·2H2O (I) do not allow to refine the powder X-ray pattern of (I) properly using the Rietveld method. Implementation of order-disorder scheme [28] via the including of appropriate displacement vector improves the refinement results. Also it is found that in the case of (I) the similar improvement may be achieved using the data on two phases of (I) obtained as result of decomposition MnC2O4·3H2O single crystal in the mother solution after growth. Thermal decomposition of (I) produce the anhydrous γ-MnC2O4 (II) the structure of which is differ from the known α- and β-modifications of VIIIb transition metal oxalates. The solved ab initio from the powder pattern structure (II) (space group Pmna, a = 7.1333 (1), b = 5.8787 (1), c = 9.0186 (2) Å, V = 378.19 (1) Å3, Z = 4 and Dx = 2.511 Mg m-3) contains seven-coordinated Mn atoms with Mn-O distances of 2.110-2.358 Å, and is not close-packed. Thermal decomposition of (II) in air flows via forming of amorphous MnO, the heating of which up to 723 K is accompanied by oxidation of MnO to Mn2O3 and further recrystallization of the latter.
Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

PubMed

Lee, Sungho; Ueda, Kyosuke; Narushima, Takayuki; Nakano, Takayoshi; Kasuga, Toshihiro

2017-01-01

Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.
A Co3O4-embedded porous ZnO rhombic dodecahedron prepared using zeolitic imidazolate frameworks as precursors for CO2 photoreduction

NASA Astrophysics Data System (ADS)

Wang, Tao; Shi, Li; Tang, Jing; Malgras, Victor; Asahina, Shunsuke; Liu, Guigao; Zhang, Huabin; Meng, Xianguang; Chang, Kun; He, Jianping; Terasaki, Osamu; Yamauchi, Yusuke; Ye, Jinhua

2016-03-01

Metal-organic frameworks (MOFs) are attracting considerable attention for their use as both the precursor and the template to prepare metal oxides or carbon-based materials. For the first time in this paper, the core-shell ZIF-8@ZIF-67 crystals are thermally converted into porous ZnO@Co3O4 composites by combining a seed-mediated growth process with a two-step calcination. The designed porous ZnO@Co3O4 composites exhibited the highest photocatalytic activity with an excellent stability for the reduction of CO2 among the commonly reported composite photocatalysts. Their superior photocatalytic performance is demonstrated to be resulting from the unique porous structure of ZnO@Co3O4 and the co-catalytic function of Co3O4 which can effectively suppress the photocorrosion of ZnO.Metal-organic frameworks (MOFs) are attracting considerable attention for their use as both the precursor and the template to prepare metal oxides or carbon-based materials. For the first time in this paper, the core-shell ZIF-8@ZIF-67 crystals are thermally converted into porous ZnO@Co3O4 composites by combining a seed-mediated growth process with a two-step calcination. The designed porous ZnO@Co3O4 composites exhibited the highest photocatalytic activity with an excellent stability for the reduction of CO2 among the commonly reported composite photocatalysts. Their superior photocatalytic performance is demonstrated to be resulting from the unique porous structure of ZnO@Co3O4 and the co-catalytic function of Co3O4 which can effectively suppress the photocorrosion of ZnO. Electronic supplementary information (ESI) available: Additional TG and DTA curves, XRD patterns, SEM images, TEM images, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy and GC-MS spectra of the samples. See DOI: 10.1039/c5nr08747c
Tuning the optical bandgap in multi-cation compound transparent conducting-oxides: The examples of In2ZnO4 and In4Sn3O12

NASA Astrophysics Data System (ADS)

Sabino, Fernando P.; Oliveira, Luiz N.; Wei, Su-Huai; Da Silva, Juarez L. F.

2018-02-01

Transparent conducting oxides such as the bixbyite In2O3 and rutile SnO2 systems have large disparities between the optical and fundamental bandgaps, ΔEgO F , because selection rules forbid dipolar transitions from the top of the valence band to the conduction-band minimum; however, the optical gaps of multi-cation compounds with the same chemical species often coincide with their fundamental gaps. To explain this conundrum, we have employed density-functional theory to compute the optical properties of multi-cation compounds, In2ZnO4 and In4Sn3O12, in several crystal structures. We show that a recently proposed mechanism to explain the disparity between the optical and fundamental gaps of M2O3 (M = Al, Ga, and In) applies also to other binary systems and to multi-compounds. Namely, a gap disparity will arise if the following three conditions are satisfied: (i) the crystal structure has inversion symmetry; (ii) the conduction-band minimum is formed by the cation and O s-orbitals; and (iii) there is strong p-d coupling and weak p-p in the vicinity of the valence-band maximum. The third property depends critically on the cationic chemical species. In the structures with inversion symmetry, Zn (Sn) strengthens (weakens) the p-d coupling in In2ZnO4 (In4Sn3O12), enhancing (reducing) the gap disparity. Furthermore, we have also identified a In4Sn3O12 structure that is 31.80 meV per formula unit more stable than a recently proposed alternative model.

Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 Systems

NASA Astrophysics Data System (ADS)

Kang, Youn-Bae; Jung, In-Ho

2017-06-01

A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2SiO4-Mn2SiO4) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3-FeSiO3) and braunite (Mn7SiO_{12} with excess Mn2O3) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3O4) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.
Solid phase extraction of magnetic carbon doped Fe3O4 nanoparticles.

PubMed

Yang, Jing; Li, Jia-yuan; Qiao, Jun-qin; Lian, Hong-zhen; Chen, Hong-yuan

2014-01-17

Carbon decorated Fe3O4 nanoparticles (Fe3O4/C) are promising magnetic solid-phase extraction (MSPE) sorbents in environmental and biological analysis. Fe3O4/C based MSPE method shows advantages of easy operation, rapidness, high sensitivity, and environmental friendliness. In this paper, the MSPE mechanism of Fe3O4/C nanoparticles has been comprehensively investigated, for the first time, through the following three efforts: (1) the comparison of extraction efficiency for polycyclic aromatic hydrocarbons (PAHs) between the Fe3O4/C sorbents and activated carbon; (2) the chromatographic retention behaviors of hydrophobic and hydrophilic compounds on Fe3O4/C nanoparticles as stationary phase; (3) related MSPE experiments for several typical compounds such as pyrene, naphthalene, benzene, phenol, resorcinol, anisole and thioanisole. It can be concluded that there are hybrid hydrophobic interaction and hydrogen bonding interaction or dipole-dipole attraction between Fe3O4/C sorbents and analytes. It is the existence of carbon and oxygen-containing functional groups coated on the surface of Fe3O4/C nanoparticles that is responsible for the effective extraction process. Copyright © 2013 Elsevier B.V. All rights reserved.
Facile synthesis of hierarchical Co3O4@MnO2 core-shell arrays on Ni foam for asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Huang, Ming; Zhang, Yuxin; Li, Fei; Zhang, Lili; Wen, Zhiyu; Liu, Qing

2014-04-01

Hierarchical Co3O4@MnO2 core-shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors. Owing to the high conductivity of the well-defined mesoporous Co3O4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co3O4@MnO2 core-shell arrays on Ni foam have exhibited a high specific capacitance (560 F g-1 at a current density of 0.2 A g-1), good rate capability, and excellent cycling stability (95% capacitance retention after 5000 cycles). An asymmetric supercapacitor with Co3O4@MnO2 core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide activated graphene (MEGO) as the negative electrode yielded an energy density of 17.7 Wh kg-1 and a maximum power density of 158 kW kg-1. The rational design of the unique core-shell array architectures demonstrated in this work provides a new and facile approach to fabricate high-performance electrode for supercapacitors.
Separation of vitexin-4″-O-glucoside and vitexin-2″-O-rhamnoside from hawthorn leaves extracts using macroporous resins.

PubMed

Li, Hongjuan; Liu, Ying; Jin, Haizhu; Liu, Sujing; Fang, Shengtao; Wang, Chunhua; Xia, Chuanhai

2015-12-15

Vitexin-4″-O-glucoside and vitexin-2″-O-rhamnoside are the major flavonoids of hawthorn leaves. In this work, the adsorption and desorption characteristics of vitexin-4″-O-glucoside and vitexin-2″-O-rhamnoside on seven macroporous resins were evaluated. Among the tested resins, the HPD-400 resin showed the best adsorption and desorption capacities. Adsorption isotherms were constructed for the HPD-400 resin and well fitted to Langmuir and Freundlich models. Dynamic adsorption and desorption tests were performed on column packed with the HPD-400 resin to optimize the chromatographic parameters. After one run treatment with the HPD-400 resin, the contents of vitexin-4″-O-glucoside and vitexin-2″-O-rhamnoside in the product were increased 8.44-fold and 8.43-fold from 0.720% and 2.63% to 6.08% and 22.2% with recovery yields of 79.1% and 81.2%, respectively. These results show that the developed method is a promising basis for the large-scale purification of vitexin-4″-O-glucoside and vitexin-2″-O-rhamnoside from hawthorn leaves and other plant materials. Copyright © 2015 Elsevier B.V. All rights reserved.
Revisiting the ground state of CoAl 2 O 4 : Comparison to the conventional antiferromagnet MnAl 2 O 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDougall, Gregory J.; Aczel, Adam A.; Su, Yixi

The A-site spinel material CoAl 2O 4 is a physical realization of the frustrated diamond-lattice antiferromagnet, a model in which unique incommensurate or “spin-spiral-liquid” ground states are predicted. Our previous single-crystal neutron scattering study instead classified it as a “kinetically inhibited” antiferromagnet, where the long-ranged correlations of a collinear Néel ground state are blocked by the freezing of domain-wall motion below a first-order phase transition at T*=6.5 K. This study provides new data sets from a number of experiments, which support and expand this work in several important ways. We show that the phenomenology leading to the kinetically inhibited ordermore » is unaffected by sample measured and instrument resolution, while new low-temperature measurements reveal spin correlations are unchanging between T=2 K and 250 mK, consistent with a frozen state. Polarized diffuse neutron measurements show several interesting magnetic features, which can be entirely explained by the existence of short-ranged Néel order. Finally, and crucially, this paper presents some neutron scattering studies of single crystalline MnAl 2O 4, which acts as an unfrustrated analog to CoAl 2O 4 and shows all the hallmarks of a classical antiferromagnet with a continuous phase transition to Néel order at T N=39 K. Direct comparison between the two compounds indicates that CoAl 2O 4 is unique, not in the nature of high-temperature diffuse correlations, but rather in the nature of the frozen state below T*. Finally, the higher level of cation inversion in the MnAl 2O 4 sample indicates that this behavior is primarily an effect of greater next-nearest-neighbor exchange.« less
Revisiting the ground state of CoAl 2 O 4 : Comparison to the conventional antiferromagnet MnAl 2 O 4

DOE PAGES

MacDougall, Gregory J.; Aczel, Adam A.; Su, Yixi; ...

2016-11-17

The A-site spinel material CoAl 2O 4 is a physical realization of the frustrated diamond-lattice antiferromagnet, a model in which unique incommensurate or “spin-spiral-liquid” ground states are predicted. Our previous single-crystal neutron scattering study instead classified it as a “kinetically inhibited” antiferromagnet, where the long-ranged correlations of a collinear Néel ground state are blocked by the freezing of domain-wall motion below a first-order phase transition at T*=6.5 K. This study provides new data sets from a number of experiments, which support and expand this work in several important ways. We show that the phenomenology leading to the kinetically inhibited ordermore » is unaffected by sample measured and instrument resolution, while new low-temperature measurements reveal spin correlations are unchanging between T=2 K and 250 mK, consistent with a frozen state. Polarized diffuse neutron measurements show several interesting magnetic features, which can be entirely explained by the existence of short-ranged Néel order. Finally, and crucially, this paper presents some neutron scattering studies of single crystalline MnAl 2O 4, which acts as an unfrustrated analog to CoAl 2O 4 and shows all the hallmarks of a classical antiferromagnet with a continuous phase transition to Néel order at T N=39 K. Direct comparison between the two compounds indicates that CoAl 2O 4 is unique, not in the nature of high-temperature diffuse correlations, but rather in the nature of the frozen state below T*. Finally, the higher level of cation inversion in the MnAl 2O 4 sample indicates that this behavior is primarily an effect of greater next-nearest-neighbor exchange.« less
Raman spectroscopic study of the minerals apophyllite-(KF) KCa4Si8O20F·8H2O and apophyllite-(KOH) KCa4Si8O20(F,OH)·8H2O

NASA Astrophysics Data System (ADS)

Frost, Ray L.; Xi, Yunfei

2012-11-01

Raman spectroscopy complimented with infrared spectroscopy has been used to study the variation in molecular structure of two minerals of the apophyllite mineral group, namely apophyllite-(KF) KCa4Si8O20F·8H2O and apophyllite-(KOH) KCa4Si8O20(F,OH)·8H2O. apophyllite-(KF) and apophyllite-(KOH) are different minerals only because of the difference in the percentage of fluorine to hydroxyl ions. The Raman spectra are dominated by a very intense sharp peak at 1059 cm-1. A band at around 846 cm-1 is assigned to the water librational mode. It is proposed that the difference between apophyllite-(KF) and apophyllite-(KOH) is the observation of two Raman bands in the OH stretching region at around 3563 and 3625 cm-1. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate surfaces.
Co3O4-x-Carbon@Fe2-yCoyO3 Heterostructural Hollow Polyhedrons for the Oxygen Evolution Reaction.

PubMed

Xu, Wangwang; Xie, Weiwei; Wang, Ying

2017-08-30

Hollow heterostructured nanomaterials have received tremendous interest in new-generation electrocatalyst applications. However, the design and fabrication of such materials remain a significant challenge. In this work, we present Co 3 O 4-x -carbon@Fe 2-y Co y O 3 heterostructural hollow polyhedrons that have been fabricated by facile thermal treatment followed by solution-phase growth for application as efficient oxygen evolution reaction (OER) electrocatalysts. Starting from a single ZIF-67 hollow polyhedron, a novel complex structured composite material constructed from Co 3 O 4-x nanocrystallite-embedded carbon matrix embedded with Fe 2-y Co y O 3 nanowires was successfully prepared. The Co 3 O 4-x nanocrystallite with oxygen vacancies provides both heterogeneous nucleation sites and growth platform for Fe 2-y Co y O 3 nanowires. The resultant heterostructure combines the advantages of Fe 2-y Co y O 3 nanowires with the large surface area and surface defects of Co 3 O 4-x nanocrystallite, resulting in improved electrocatalytic activity and electrical conductivity. As a result, such novel heterostructured OER electrocatalysts exhibit much lower onset potential (1.52 V) and higher current density (70 mA/cm 2 at 1.7 V) than Co 3 O 4-x -carbon hollow polyhedrons (onset 1.55 V, 35 mA/cm 2 at 1.7 V) and pure Co 3 O 4 hollow polyhedrons (onset 1.62 V, 5 mA/cm 2 at 1.7 V). Furthermore, the design and synthesis of metal-organic framework (MOF)-derived nanomaterials in this work offer new opportunities for developing novel and efficient electrocatalysts in electrochemical devices.
Growth and interface engineering in thin-film Ba0.6Sr0.4TiO3 /SrMoO3 heterostructures

NASA Astrophysics Data System (ADS)

Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert; Komissinskiy, Philipp

2017-04-01

Epitaxial heterostructures of ferroelectric Ba0.6Sr0.4TiO3 and highly conducting SrMoO3 were grown by pulsed laser deposition on SrTiO3 (0 0 1) substrates. Surface oxidation of the SrMoO3 film is suppressed using a thin cap interlayer of Ba0.6Sr0.4TiO3-δ grown in reduced atmosphere. As shown by X-ray photoelectron spectroscopy, the Mo4+ valence state of the SrMoO3 films is stable upon annealing of the sample in oxygen up to 600 °C. The described oxygen interface engineering enables utilization of the highly conducting material SrMoO3 in multilayer oxide ferroelectric varactors.
Magnetic structure of Ba (TiO ) Cu4(PO4)4 probed using spherical neutron polarimetry

NASA Astrophysics Data System (ADS)

Babkevich, P.; Testa, L.; Kimura, K.; Kimura, T.; Tucker, G. S.; Roessli, B.; Rønnow, H. M.

2017-12-01

The antiferromagnetic compound Ba (TiO ) Cu4(PO4)4 contains square cupola of corner-sharing CuO4 plaquettes, which were proposed to form effective quadrupolar order. To identify the magnetic structure, we have performed spherical neutron polarimetry measurements. Based on symmetry analysis and careful measurements, we conclude that the orientation of the Cu2 + spins form a noncollinear in-out structure with spins approximately perpendicular to the CuO4 motif. Strong Dzyaloshinskii-Moriya interaction naturally lends itself to explain this phenomenon. The identification of the ground-state magnetic structure should serve well for future theoretical and experimental studies into this and closely related compounds.
Hierarchical honeycomb-like Co3O4 pores coating on CoMoO4 nanosheets as bifunctional efficient electrocatalysts for overall water splitting

NASA Astrophysics Data System (ADS)

Pei, Zhihao; Xu, Li; Xu, Wei

2018-03-01

Efficient electrocatalytic water splitting is one of the most effective ways to solve the global energy crisis. In this paper, we report on a novel self-assembled hierarchical structure of Co3O4/CoMoO4 grown in situ on a bare nickel foam. The unique, three-dimensional honeycomb-like Co3O4 pores were constructed from one-dimensional nanowires and coated on two-dimensional CoMoO4 nanosheets structures grown on nickel foam. The synthesis involved a step-wise solvothermal method followed by an annealing treatment. Benefiting from the synergistic effect of the hierarchical nanostructures, the materials had more reaction active sites and a smaller electron transfer impedance, and they exhibited excellent electrocatalytic performances for the HER and OER of 143 and 244 mV, respectively, at 10 mA cm-2 in an alkaline solution. Furthermore, the materials remained stable during the long electrolysis period, over 10 h, presenting promising application prospects in the field of electrocatalytic water splitting.
Porous Fe3O4-SiO2 core-shell nanorods as high-performance MRI contrast agent and drug delivery vehicle

NASA Astrophysics Data System (ADS)

Beg, Muhammad Shahbaz; Mohapatra, Jeotikanta; Pradhan, Lina; Patkar, D.; Bahadur, D.

2017-04-01

A high-performance MRI contrast agent and a drug nanocarrier have been realized in porous Fe3O4@SiO2 nanorods (NRs). The Fe3O4@SiO2 NRs of length 520 nm and diameter 180 nm are synthesized by annealing FeOOH@SiO2 nanorods at a temperature of 300 ℃ under continuous flow of forming gas. The magnetic measurement confirms that the Fe3O4@SiO2 NRs is ferrimagnetic in nature with magnetization of 20 emu/g and coercivity HC 450 Oe. The aqueous suspension of the NRs is stable over a time frame of one month and exhibits a high R2 relaxivity value of 192 mM-1 s-1. The R2 darkening effect is also observed in HeLa cells incubated with NRs in comparison to untreated control cells. The porous Fe3O4@SiO2 NRs further work as an excellent carrier for doxorubicin (DOX) drug with loading efficiency of 65%. The drug release study shows a pH-dependent behavior and is higher in acidic pH (4.3) as compared to the physiological pH (7.4). After 72 h, the cumulative DOX release is found to be 58% at pH 4.3 and 17% at pH 7.4. The induction heating studies of the NRs exhibit a sharp increasing trend of SAR value with the increase of magnetic field.
Sonochemical approach to the synthesis of Fe(3)O(4)@SiO(2) core-shell nanoparticles with tunable properties.

PubMed

Morel, Anne-Laure; Nikitenko, Sergei I; Gionnet, Karine; Wattiaux, Alain; Lai-Kee-Him, Josephine; Labrugere, Christine; Chevalier, Bernard; Deleris, Gerard; Petibois, Cyril; Brisson, Alain; Simonoff, Monique

2008-05-01

In this study, we report a rapid sonochemical synthesis of monodisperse nonaggregated Fe(3)O(4)@SiO(2) magnetic nanoparticles (NPs). We found that coprecipitation of Fe(II) and Fe(III) in aqueous solutions under the effect of power ultrasound yields smaller Fe(3)O(4) NPs with a narrow size distribution (4-8 nm) compared to the silent reaction. Moreover, the coating of Fe(3)O(4) NPs with silica using an alkaline hydrolysis of tetraethyl orthosilicate in ethanol-water mixture is accelerated many-fold in the presence of a 20 kHz ultrasonic field. The thickness of the silica shell can be easily controlled in the range of several nanometers during sonication. Mossbauer spectra revealed that nonsuperparamagnetic behavior of obtained core-shell NPs is mostly related to the dipole-dipole interactions of magnetic cores and not to the particle size effect. Core-shell Fe(3)O(4)@SiO(2) NPs prepared with sonochemistry exhibit a higher magnetization value than that for NPs obtained under silent conditions owing to better control of the deposited silica quantities as well as to the high speed of sonochemical coating, which prevents the magnetite from oxidizing.
Chemical and structural evolution in the Th-SeO3(2-)/SeO4(2-) system: from simple selenites to cluster-based selenate compounds.

PubMed

Xiao, Bin; Langer, Eike; Dellen, Jakob; Schlenz, Hartmut; Bosbach, Dirk; Suleimanov, Evgeny V; Alekseev, Evgeny V

2015-03-16

While extensive success has been gained in the structural chemistry of the U-Se system, the synthesis and characterization of Th-based Se structures are widely unexplored. Here, four new Th-Se compounds, α-Th(SeO3)2, β-Th(SeO3)2, Th(Se2O5)2, and Th3O2(OH)2(SeO4)3, have been obtained from mild hydrothermal or low-temperature (180-220 °C) flux conditions and were subsequently structurally and spectroscopically characterized. The crystal structures of α-Th(SeO3)2 and β-Th(SeO3)2 are based on ThO8 and SeO3 polyhedra, respectively, featuring a three-dimensional (3D) network with selenite anions filling in the Th channels along the a axis. Th(Se2O5)2 is a 3D framework composed of isolated ThO8 polyhedra interconnected by [Se2O5](2-) dimers. Th3O2(OH)2(SeO4)3 is also a 3D framework constructed by octahedral hexathorium clusters [Th6(μ3-O)4(μ3-OH)4](12+), which are interlinked by selenate groups SeO4(2-). The positions of the vibrational modes associated with both Se(IV)O3(2-) and Se(VI)O4(2-) units, respectively, were determined for four compounds, and the Raman spectra of α- and β-Th(SeO3)2 are compared and discussed in detail.
A neodymium(III)-ammonium complex involving oxalate and carbonate ligands: (NH4)2[Nd2(C2O4)3(CO3)(H2O)].H2O.

PubMed

Trombe, Jean-Christian; Galy, Jean; Enjalbert, Renée

2002-10-01

The title compound, diammonium aqua-mu-carbonato-tri-mu-oxalato-dineodymium(III) hydrate, (NH(4))(2)[Nd(2)(CO(3))(C(2)O(4))(3)(H(2)O)].H(2)O, involving the two ligands oxalate and carbonate, has been prepared hydrothermally as single crystals. The Nd atoms form a tetranuclear unit across the inversion centre at (1/2, 1/2, 1/2). Starting from this tetranuclear unit, the oxalate ligands serve to develop a three-dimensional network. The carbonate group acts as a bis-chelating ligand to two Nd atoms, and is monodentate to a third Nd atom. The oxalate groups are all bis-chelating. The two independent Nd atoms are ninefold coordinated and the coordination polyhedron of these atoms is a distorted monocapped antiprism.
A Scalable Strategy To Develop Advanced Anode for Sodium-Ion Batteries: Commercial Fe3O4-Derived Fe3O4@FeS with Superior Full-Cell Performance.

PubMed

Hou, Bao-Hua; Wang, Ying-Ying; Guo, Jin-Zhi; Zhang, Yu; Ning, Qiu-Li; Yang, Yang; Li, Wen-Hao; Zhang, Jing-Ping; Wang, Xin-Long; Wu, Xing-Long

2018-01-31

A novel core-shell Fe 3 O 4 @FeS composed of Fe 3 O 4 core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial Fe 3 O 4 as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared Fe 3 O 4 @FeS combines the merits of FeS and Fe 3 O 4 with high Na-storage capacity and superior cycling stability, respectively. The optimized Fe 3 O 4 @FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g -1 after 750 cycles at 0.2 A g -1 and 151 mAh g -1 at a high current density of 2 A g -1 , which is about 7.5 times in comparison to the Na-storage capacity of commercial Fe 3 O 4 . More importantly, the prepared Fe 3 O 4 @FeS also exhibits excellent full-cell performance. The assembled Fe 3 O 4 @FeS//Na 3 V 2 (PO 4 ) 2 O 2 F sodium-ion full battery gives a reversible capacity of 157 mAh g -1 after 50 cycles at 0.5 A g -1 with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.
Light-induced structural changes and the site of O=O bond formation in PSII caught by XFEL.

PubMed

Suga, Michihiro; Akita, Fusamichi; Sugahara, Michihiro; Kubo, Minoru; Nakajima, Yoshiki; Nakane, Takanori; Yamashita, Keitaro; Umena, Yasufumi; Nakabayashi, Makoto; Yamane, Takahiro; Nakano, Takamitsu; Suzuki, Mamoru; Masuda, Tetsuya; Inoue, Shigeyuki; Kimura, Tetsunari; Nomura, Takashi; Yonekura, Shinichiro; Yu, Long-Jiang; Sakamoto, Tomohiro; Motomura, Taiki; Chen, Jing-Hua; Kato, Yuki; Noguchi, Takumi; Tono, Kensuke; Joti, Yasumasa; Kameshima, Takashi; Hatsui, Takaki; Nango, Eriko; Tanaka, Rie; Naitow, Hisashi; Matsuura, Yoshinori; Yamashita, Ayumi; Yamamoto, Masaki; Nureki, Osamu; Yabashi, Makina; Ishikawa, Tetsuya; Iwata, So; Shen, Jian-Ren

2017-03-02

Photosystem II (PSII) is a huge membrane-protein complex consisting of 20 different subunits with a total molecular mass of 350 kDa for a monomer. It catalyses light-driven water oxidation at its catalytic centre, the oxygen-evolving complex (OEC). The structure of PSII has been analysed at 1.9 Å resolution by synchrotron radiation X-rays, which revealed that the OEC is a Mn 4 CaO 5 cluster organized in an asymmetric, 'distorted-chair' form. This structure was further analysed with femtosecond X-ray free electron lasers (XFEL), providing the 'radiation damage-free' structure. The mechanism of O=O bond formation, however, remains obscure owing to the lack of intermediate-state structures. Here we describe the structural changes in PSII induced by two-flash illumination at room temperature at a resolution of 2.35 Å using time-resolved serial femtosecond crystallography with an XFEL provided by the SPring-8 ångström compact free-electron laser. An isomorphous difference Fourier map between the two-flash and dark-adapted states revealed two areas of apparent changes: around the Q B /non-haem iron and the Mn 4 CaO 5 cluster. The changes around the Q B /non-haem iron region reflected the electron and proton transfers induced by the two-flash illumination. In the region around the OEC, a water molecule located 3.5 Å from the Mn 4 CaO 5 cluster disappeared from the map upon two-flash illumination. This reduced the distance between another water molecule and the oxygen atom O4, suggesting that proton transfer also occurred. Importantly, the two-flash-minus-dark isomorphous difference Fourier map showed an apparent positive peak around O5, a unique μ 4 -oxo-bridge located in the quasi-centre of Mn1 and Mn4 (refs 4,5). This suggests the insertion of a new oxygen atom (O6) close to O5, providing an O=O distance of 1.5 Å between these two oxygen atoms. This provides a mechanism for the O=O bond formation consistent with that proposed previously.
40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...
40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...
40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...

40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...
40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214, CAS...
ZnO supported CoFe2O4 nanophotocatalysts for the mineralization of Direct Blue 71 in aqueous environments.

PubMed

Sathishkumar, Panneerselvam; Pugazhenthiran, Nalenthiran; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M; Anandan, Sambandam

2013-05-15

In this study, an attempt was made to render both the magnetic and photocatalytic properties in a semiconductor material to enhance the efficiency of degradation and recycling possibility of magnetic nanophotocatalysts. CoFe2O4 and CoFe2O4 loaded ZnO nanoparticles were prepared by a simple co-precipitation method and characterized using various analytical tools and in addition to check its visible light assisted photocatalytic activity. CoFe2O4/ZnO nanocatalyst coupled with acceptor, peroxomonosulphate (PMS) showed 1.69-fold enhancement in Direct Blue 71 (triazo dye; DB71) mineralization within 5h. The accomplished enrichment in decolorization was due to the production of more number of non-selective and active free radicals at the catalyst surface. Copyright © 2013 Elsevier B.V. All rights reserved.
Fe3O4@Au@mSiO2 as an enhancing nanoplatform for Rose Bengal photodynamic activity.

PubMed

Rosa-Pardo, I; Roig-Pons, M; Heredia, A A; Usagre, J V; Ribera, A; Galian, R E; Pérez-Prieto, J

2017-07-27

A novel nanoplatform composed of three types of materials with different functionalities, specifically core-shell Fe 3 O 4 @Au nanoparticles encapsulated near the outer surface of mesoporous silica (mSiO 2 ) nanoparticles, has been successfully synthesised and used to enhance the efficiency of a photosensitiser, namely Rose Bengal, in singlet oxygen generation. Fe 3 O 4 is responsible for the unusual location of the Fe 3 O 4 @Au nanoparticle, while the plasmonic shell acts as an optical antenna. In addition, the mesoporous silica matrix firmly encapsulates Rose Bengal by chemical bonding inside the pores, thus guaranteeing its photostability, and in turn making the nanosystem biocompatible. Moreover, the silica surface of the nanoplatform ensures further functionalisation on demand.
Synthesis of palm-based polyurethane-LiClO{sub 4} via prepolymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sien, Jason Wong Chee; School of Biosciences, Taylor’s University, Subang Jaya; Badri, Khairiah Haji

2015-09-25

Palm-based polyurethane (pPU) with varying lithium salt (LiClO{sub 4}) content was synthesized. Higher loading percentage of LiClO{sub 4} in the pPU led to the inhibition of prepolymerization process from taking place. Hydrogen bonded C=O was detected in the FTIR spectrum indicating the hydrogen bonding between the urethane bonds. Ordered complexed C=O was observed in the FTIR spectrum confirming the complex formation between urethane bond and Li{sup +} ion. DSC thermogram showed the increase in the LiClO{sub 4} content could increase the glass transition temperature. SEM micrographs exhibited that more bubbles were formed when the LiClO{sub 4} increased from 10 tomore » 30wt% indicating the reaction between free isocyanate groups with moisture presence in the salt due to the hygroscopic properties of LiClO{sub 4}.« less
O-GlcNAc regulates NEDD4-1 stability via caspase-mediated pathway.

PubMed

Jiang, Kuan; Bai, Bingyang; Ta, Yajie; Zhang, Tingling; Xiao, Zikang; Wang, Peng George; Zhang, Lianwen

2016-03-18

O-GlcNAc modification of cytosolic and nuclear proteins regulates essential cellular processes such as stress responses, transcription, translation, and protein degradation. Emerging evidence indicates O-GlcNAcylation has a dynamic interplay with ubiquitination in cellular regulation. Here, we report that O-GlcNAc indirectly targets a vital E3 ubiquitin ligase enzyme of NEDD4-1. The protein level of NEDD4-1 is accordingly decreased following an increase of overall O-GlcNAc level upon PUGNAc or glucosamine stimulation. O-GlcNAc transferase (OGT) knockdown, overexpression and mutation results confirm that the stability of NEDD4-1 is negatively regulated by cellular O-GlcNAc. Moreover, the NEDD4-1 degradation induced by PUGNAc or GlcN is significantly inhibited by the caspase inhibitor. Our study reveals a regulation mechanism of NEDD4-1 stability by O-GlcNAcylation. Copyright © 2016 Elsevier Inc. All rights reserved.
Investigation on charge transfer bands of Ce 4+ in Sr 2CeO 4 blue phosphor

NASA Astrophysics Data System (ADS)

Li, Ling; Zhou, Shihong; Zhang, Siyuan

2008-03-01

Bulk and nano-materials Sr2CeO4 were prepared by solid-state reaction and sol-gel technique, respectively. Photoluminescence shows that luminescence has the characteristic of a ligand-to-metal charge transfer (CT) emission. Compared with bulk Sr2CeO4, the nano-material exhibits stronger emission intensity, longer decay time, and higher CT excitation energy. Three CT excitation peaks were observed in both bulk and nano samples. Based on the theoretical calculations of the average energy gap of the chemical bond using the dielectric theory of complex crystal, the highest and the lowest energy CT bands were assigned to the transitions O1 → Ce4+ and O2 → Ce4+, respectively. The middle bands were due to the superposition of the transitions Ce-O1 and Ce-O2.
MnFe2O4: Synthesis, morphology and electrochemical properties

NASA Astrophysics Data System (ADS)

Kulkarni, Shrikant; Thombare, Balu; Patil, Shankar

2017-05-01

MnFe2O4 has been synthesized by simple ammonia assisted co-precipitation method to obtain nanocrystalline powder. X-ray diffraction studies confirmed its crystallinity and phase purity. The MnFe2O4 calcined at 1000°C for 4 h has spinel crystal structure with Fd3m space group and lattice constant 8.511 Å. The electrode was prepared by dip coating method on stainless steel substrate and fired at 600°C for 2 h. Random shape grains of 0.2 to 1.5 micron with pores of 1-2 micron dimensions were observed in SEM images. The electrochemical studies of MnFe2O4 were carried out with 1 mole Na2SO4 electrolyte. The MnFe2O4 electrode shows highest specific capacitance of 27.53 F.g-1 and interfacial capacitance of 0.83 F.cm-2.
Cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles: a highly efficient SERS substrate for pesticide detection

NASA Astrophysics Data System (ADS)

Sun, Mei; Zhao, Aiwu; Wang, Dapeng; Wang, Jin; Chen, Ping; Sun, Henghui

2018-04-01

As a novel surface-enhanced Raman spectroscopic (SERS) nanocomposite, cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles (NPs) were synthesized for the first time. Cube-like α-Fe2O3 NPs with uniform size were achieved by optimizing reaction temperature and time. Firstly, the cube-like Fe3O4@SiO2 with good dispersity was achieved by calcining α-Fe2O3@SiO2 NPs in hydrogen atmosphere at 360 °C for 2.5 h, followed by self-assembling a PEI shell via sonication. Furthermore, the Au@Ag particles were densely assembled on the Fe3O4@SiO2 NPs to form the Fe3O4@SiO2@Au@Ag composite structure via strong Ag-N interaction. The obtained nanocomposites exhibited an excellent SERS behavior, reflected by the low detection of limit (p-ATP) at the 5 × 10-14 M level. Moreover, these nanocubes were used for the detection of thiram, and the detection limit can reach 5 × 10-11 M. Meanwhile, the U.S. Environmental Protection Agency specifies that the residue in fruit must be lower than 7 ppm. Hence, the resulting substrate with high SERS activity has great practical potential applications in the rapid detection of chemical, biological, and environment pollutants with a simple portable Raman instrument at trace level.
Preparation and Electrochemical Performance of Li4Mn5O12 Nanorods using β-MnO2 Nanorods as Precursor

NASA Astrophysics Data System (ADS)

Zhao, Yan; Wang, Li; Mu, Yanlin; Zhang, Chongwei; Zhu, Fan; Liu, Mengjiao; Lai, Qiongyu; Bi, Jian; Gao, Daojiang

2018-03-01

Li4Mn5O12 nanorods were successfully prepared by using β-MnO2 nanorod precursors as self-templates. The obtained Li4Mn5O12 nanorods were approximately 0.8-1.5 μm in length and 0.15 μm in width, and were employed as electrode materials and applied in supercapacitors. The results show that Li4Mn5O12 nanorods can deliver 211 F g-1 within the potential range of 0-1.4 V at a scan rate of 5 mV s-1 in 1 mol L-1 Li2SO4 solution, which presents a good electrochemical performance.
Hierarchically porous MnO2 microspheres doped with homogeneously distributed Fe3O4 nanoparticles for supercapacitors.

PubMed

Zhu, Jian; Tang, Shaochun; Xie, Hao; Dai, Yuming; Meng, Xiangkang

2014-10-22

Hierarchically porous yet densely packed MnO2 microspheres doped with Fe3O4 nanoparticles are synthesized via a one-step and low-cost ultrasound assisted method. The scalable synthesis is based on Fe(2+) and ultrasound assisted nucleation and growth at a constant temperature in a range of 25-70 °C. Single-crystalline Fe3O4 particles of 3-5 nm in diameter are homogeneously distributed throughout the spheres and none are on the surface. A systematic optimization of reaction parameters results in isolated, porous, and uniform Fe3O4-MnO2 composite spheres. The spheres' average diameter is dependent on the temperature, and thus is controllable in a range of 0.7-1.28 μm. The involved growth mechanism is discussed. The specific capacitance is optimized at an Fe/Mn atomic ratio of r = 0.075 to be 448 F/g at a scan rate of 5 mV/s, which is nearly 1.5 times that of the extremely high reported value for MnO2 nanostructures (309 F/g). Especially, such a structure allows significantly improved stability at high charging rates. The composite has a capacitance of 367.4 F/g at a high scan rate of 100 mV/s, which is 82% of that at 5 mV/s. Also, it has an excellent cycling performance with a capacitance retention of 76% after 5000 charge/discharge cycles at 5 A/g.
O-GlcNAc transferase regulates transcriptional activity of human Oct4.

PubMed

Constable, Sandii; Lim, Jae-Min; Vaidyanathan, Krithika; Wells, Lance

2017-10-01

O-linked β-N-acetylglucosamine (O-GlcNAc) is a single sugar modification found on many different classes of nuclear and cytoplasmic proteins. Addition of this modification, by the enzyme O-linked N-acetylglucosamine transferase (OGT), is dynamic and inducible. One major class of proteins modified by O-GlcNAc is transcription factors. O-GlcNAc regulates transcription factor properties through a variety of different mechanisms including localization, stability and transcriptional activation. Maintenance of embryonic stem (ES) cell pluripotency requires tight regulation of several key transcription factors, many of which are modified by O-GlcNAc. Octamer-binding protein 4 (Oct4) is one of the key transcription factors required for pluripotency of ES cells and more recently, the generation of induced pluripotent stem (iPS) cells. The action of Oct4 is modulated by the addition of several post-translational modifications, including O-GlcNAc. Previous studies in mice found a single site of O-GlcNAc addition responsible for transcriptional regulation. This study was designed to determine if this mechanism is conserved in humans. We mapped 10 novel sites of O-GlcNAc attachment on human Oct4, and confirmed a role for OGT in transcriptional activation of Oct4 at a site distinct from that found in mouse that allows distinction between different Oct4 target promoters. Additionally, we uncovered a potential new role for OGT that does not include its catalytic function. These results confirm that human Oct4 activity is being regulated by OGT by a mechanism that is distinct from mouse Oct4. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Enhancement of the physical properties of novel (1- x) NiFe2O4 + ( x) Al2O3 nanocomposite

NASA Astrophysics Data System (ADS)

Mansour, S. F.; Ahmed, M. A.; El-Dek, S. I.; Abdo, M. A.; Kora, H. H.

2017-07-01

NiFe2O4, Al2O3 and their nanocomposites; (1- x) NiFe2O4 + ( x) Al2O3, 0.0 ≤ x ≤ 1; were synthesized using the citrate-nitrate technique. The crystal structure was examined by X-ray diffraction, the microstructure was observed by transmission electron microscopy. The Curie temperature T C grows until reaching more than 1100 K with increasing alumina content ( x), while the saturation magnetization ( M s) decreased. The large improvement of room temperature resistivity which achieved two orders of magnitude from x = 0 to x = 70% was interpreted from the fact that the NiFe2O4 grains become electrically isolated and the conduction path is broken by the insulating Al2O3 nanoparticulates in the composite. The electrical properties of the nanocomposite could thus be tuned easily by adjusting the Al2O3 ratio to realize the targeted value of losses and resistivity at any temperature and frequency.
Ambiente e formação estelar em galáxias

NASA Astrophysics Data System (ADS)

Mateus, A., Jr.; Sodré, L., Jr.

2003-08-01

Estudamos o ambiente de galáxias com formação estelar inicialmente a partir de uma amostra limitada em volume proveniente do 2dF Galaxy Redshift Survey. Discriminamos as galáxias com formação estelar com base em distintas classes espectrais, utilizando para esta classificação as larguras equivalentes das linhas [OII]l3727 e Hd. O ambiente é caracterizado pela densidade espacial local de galáxias. Mostramos que a fração de galáxias com formação estelar é bastante reduzida em ambientes densos, enquanto a de galáxias passivas aumenta nestas regiões. Por outro lado, quando analisamos a fração de galáxias que apresentam um surto recente de formação estelar, notamos que ela independe do ambiente, sendo que em regiões mais densas alguns destes objetos apresentam distorções em sua morfologia. Estes resultados são confrontados com a análise da dependência ambiental da taxa de formação estelar, estimada pela emissão em Ha, de uma amostra extraída do Sloan Digital Sky Survey. Um declínio gradual da formação estelar também é observado nesta análise, sugerindo que as interações por efeitos de maré sejam responsáveis pela redução da formação estelar em ambientes densos através da remoção do reservatório de gás das galáxias. No entanto, estas interações também podem induzir surtos de formação estelar nas galáxias, além de peculiaridades morfológicas observadas nos objetos que habitam regiões mais densas.
Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23}: A new alkali and alkaline-earth metal mixed borate with [B{sub 10}O{sub 18}]{sup 6-} network and isolated [B{sub 2}O{sub 5}]{sup 4-} unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Min; Graduate University of Chinese Academy of Sciences, Beijing 100049; Pan Shilie, E-mail: slpan@ms.xjb.ac.cn

2012-06-15

A novel ternary lithium strontium borate Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23} crystal with size up to 20 mm Multiplication-Sign 10 mm Multiplication-Sign 4 mm has been grown via the top-seeded solution growth method below 730 Degree-Sign C. Single-crystal XRD analyses showed that Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23} crystallizes in the monoclinic space group P2{sub 1}/c with a=6.4664(4) A, b=8.4878(4) A, c=15.3337(8) A, {beta}=102.02(3) Degree-Sign , Z=2. The crystal structure is composed of [B{sub 10}O{sub 18}]{sup 6-} network and isolated [B{sub 2}O{sub 5}]{sup 4-} unit. The IR spectrum further confirmed the presence of both BO{sub 3} and BO{sub 4} groups. TG-DSCmore » and Transmission spectrum were reported. Band structures and density of states were calculated. - Graphical abstract: A new phase, Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23}, has been discovered in the ternary M{sub 2}O-M Prime O-B{sub 2}O{sub 3} (M=alkali-metal, M Prime =alkalineearth metal) system. The crystal structure consists of [B{sub 10}O{sub 18}]{sup 6-} network and isolated [B{sub 2}O{sub 5}]{sup 4-} unit. Highlights: Black-Right-Pointing-Pointer Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23} is a a novel borate discovered in the M{sub 2}O-M Prime O-B{sub 2}O{sub 3} (M=alkali-metal, M Prime =alkaline-earth metal) system. Black-Right-Pointing-Pointer Li{sub 2}Sr{sub 4}B{sub 12}O{sub 23} crystal structure has a three-dimensional crystal structure with [B{sub 10}O{sub 18}]{sup 6-} network and isolated [B{sub 2}O{sub 5}]{sup 4-} unit. Black-Right-Pointing-Pointer Sr{sub 1} and Sr{sub 2} are located in two different channels constructed by {sup 3}{sub {infinity}}[B{sub 10}O{sub 18}] network.« less
β-Li0.37Na0.63Fe(MoO4)2

PubMed Central

Souilem, Amira; Zid, Mohamed Faouzi; Driss, Ahmed

2014-01-01

The title compound, lithium/sodium iron(III) bis[orthomolybdate(VI)], was obtained by a solid-state reaction. The main structure units are an FeO6 octahedron, a distorted MoO6 octahedron and an MoO4 tetrahedron sharing corners. The crystal structure is composed of infinite double MoFeO11 chains along the b-axis direction linked by corner-sharing to MoO4 tetrahedra so as to form Fe2Mo3O19 ribbons. The cohesion between ribbons via mixed Mo—O—Fe bridges leads to layers arranged parallel to the bc plane. Adjacent layers are linked by corners shared between MoO4 tetrahedra of one layer and FeO6 octahedra of the other layer. The Na+ and Li+ ions partially occupy the same general position, with a site-occupancy ratio of 0.631 (9):0.369 (1). A comparison is made with AFe(MoO4)2 (A = Li, Na, K and Cs) structures. PMID:24764805
Enhanced photoelectrochemical and photocatalytic behaviors of MFe2O4 (M = Ni, Co, Zn and Sr) modified TiO2 nanorod arrays

PubMed Central

Gao, Xin; Liu, Xiangxuan; Zhu, Zuoming; Wang, Xuanjun; Xie, Zheng

2016-01-01

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications. In this research, various ferrites, incorporated with various cations (MFe2O4, M = Ni, Co, Zn, and Sr), are utilized to modify the well aligned TiO2 nanorod arrays (NRAs), which is synthesized by hydrothermal method. It is found that all MFe2O4/TiO2 NRAs show obvious red shift into the visible light region compared with the TiO2 NRAs. In particular, NiFe2O4 modification is demonstrated to be the best way to enhance the photoelectrochemical and photocatalytic activity of TiO2 NRAs. Furthermore, the separation and transfer of charge carriers after MFe2O4 modification are clarified by electrochemical impedance spectroscopy measurements. Finally, the underlying mechanism accounting for the enhanced photocatalytic activity of MFe2O4/TiO2 NRAs is proposed. Through comparison among different transition metals modified TiO2 with the same synthesis process and under the same evaluating condition, this work may provide new insight in designing modified TiO2 nanomaterials as visible light active photocatalysts. PMID:27464888
Enhanced photoelectrochemical and photocatalytic behaviors of MFe2O4 (M = Ni, Co, Zn and Sr) modified TiO2 nanorod arrays

NASA Astrophysics Data System (ADS)

Gao, Xin; Liu, Xiangxuan; Zhu, Zuoming; Wang, Xuanjun; Xie, Zheng

2016-07-01

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications. In this research, various ferrites, incorporated with various cations (MFe2O4, M = Ni, Co, Zn, and Sr), are utilized to modify the well aligned TiO2 nanorod arrays (NRAs), which is synthesized by hydrothermal method. It is found that all MFe2O4/TiO2 NRAs show obvious red shift into the visible light region compared with the TiO2 NRAs. In particular, NiFe2O4 modification is demonstrated to be the best way to enhance the photoelectrochemical and photocatalytic activity of TiO2 NRAs. Furthermore, the separation and transfer of charge carriers after MFe2O4 modification are clarified by electrochemical impedance spectroscopy measurements. Finally, the underlying mechanism accounting for the enhanced photocatalytic activity of MFe2O4/TiO2 NRAs is proposed. Through comparison among different transition metals modified TiO2 with the same synthesis process and under the same evaluating condition, this work may provide new insight in designing modified TiO2 nanomaterials as visible light active photocatalysts.
Excess charge driven dissociative hydrogen adsorption on Ti2O4.

PubMed

Song, Xiaowei; Fagiani, Matias R; Debnath, Sreekanta; Gao, Min; Maeda, Satoshi; Taketsugu, Tetsuya; Gewinner, Sandy; Schöllkopf, Wieland; Asmis, Knut R; Lyalin, Andrey

2017-08-30

The mechanism of dissociative D 2 adsorption on Ti 2 O 4 - , which serves as a model for an oxygen vacancy on a titania surface, is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations and a recently developed single-component artificial force induced reaction method. Ti 2 O 4 - readily reacts with D 2 under multiple collision conditions in a gas-filled ion trap held at 16 K forming a global minimum-energy structure (DO-Ti-(O) 2 -Ti(D)-O) - . The highly exergonic reaction proceeds quasi barrier-free via several intermediate species, involving heterolytic D 2 -bond cleavage followed by D-atom migration. We show that, compared to neutral Ti 2 O 4 , the excess negative charge in Ti 2 O 4 - is responsible for the substantial lowering of the D 2 dissociation barrier, but does not affect the molecular D 2 adsorption energy in the initial physisorption step.
Inauguração do Telescópio SOAR

NASA Astrophysics Data System (ADS)

Steiner, João

2004-04-01

A comunidade astronômica brasileira de há muito almeja ter a sua disposição um instrumento científico com o qual possa fazer pesquisa de vanguarda e manter a competitividade científica a nível internacional. Hoje este sonho se torna uma realidade. O Brasil tem tido uma política de pesquisa e de pós-graduação bem sucedida. Estamos formando 7000 doutores por ano e produzimos 1,5% da ciência mundial. Nosso desafio, hoje, é associar a esta capacidade de gerar conhecimento também a capacidade de usar o conhecimento em beneficio da sociedade. A Astronomia não é exceção. Temos 7 programas de pós-graduação em nível de doutorado e 11 em nível de mestrado. O telescópio SOAR será o principal instrumento que sustentará estes programas nas próximas décadas. A inauguração do telescópio SOAR simboliza de forma concreta e decidida o apoio do MCT, do CNPq e da FAPESP para o financiamento à pesquisa básica em nosso país. O Laboratório Nacional de Astrofísica, criado a cerca de 20 anos pelo CNPq, a par do Laboratório Nacional de Luz Sincrotron, são até hoje, os únicos laboratórios nacionais do Brasil e ambos voltados basicamente ao avanço do conhecimento. Os vinte anos de existência do LNA foram decisivos para a estruturação da comunidade astronômica no Brasil e para a construção das parcerias como o SOAR.

Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

NASA Astrophysics Data System (ADS)

Wang, Hai; Huang, Jun; Wang, Chao; Li, Dapeng; Ding, Liyun; Han, Yun

2011-04-01

Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.
Oxygen-atom transfer chemistry and thermolytic properties of a di-tert-butylphosphate-ligated Mn4O4 cubane.

PubMed

Van Allsburg, Kurt M; Anzenberg, Eitan; Drisdell, Walter S; Yano, Junko; Tilley, T Don

2015-03-16

[Mn4O4{O2P(OtBu)2}6] (1), an Mn4O4 cubane complex combining the structural inspiration of the photosystem II oxygen-evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen-atom acceptor (PEt3), to give the butterfly complex [Mn4O2{O2P(OtBu)2}6(OPEt3)2]. The cubane structure is restored by reaction of the latter complex with the O-atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X-ray absorption spectroscopy to determine the fate of the Mn4O4 unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn(II) species. Finally, the related butterfly complex [Mn4O2{O2P(pin)}6(bpy)2] (pin = pinacolate) is described. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effects of TiO2 addition on microwave dielectric properties of Li2MgSiO4 ceramics

NASA Astrophysics Data System (ADS)

Rose, Aleena; Masin, B.; Sreemoolanadhan, H.; Ashok, K.; Vijayakumar, T.

2018-03-01

Silicates have been widely studied for substrate applications in microwave integrated circuits owing to their low dielectric constant and low tangent loss values. Li2MgSiO4 (LMS) ceramics are synthesized through solid-state reaction route using TiO2 as an additive to the pure ceramics. Variations in dielectric properties of LMS upon TiO2 addition in different weight percentages (0.5, 1.5, 2) are studied by keeping the sintering parameters constant. Crystalline structure, phase composition, and microstructure of LMS and LMS-TiO2 ceramics were studied using x-ray diffraction spectrometer and High Resolution Scanning electron microscope. Density was measured through Archimedes method and the microwave dielectric properties were examined by Cavity perturbation technique. LMS achieved relative permittivity (ε r) of 5.73 and dielectric loss (tan δ) of 5.897 × 10‑4 at 8 GHz. In LMS-TiO2 ceramics, 0.5 wt% TiO2 added LMS showed comparatively better dielectric properties than other weight percentages where ε r = 5.67, tan δ = 7.737 × 10‑4 at 8 GHz.
Non-enzymatic detection of glucose in fruits using TiO2-Mn3O4 hybrid nano interface

NASA Astrophysics Data System (ADS)

Jayanth Babu, K.; Sasya, Madhurantakam; Nesakumar, Noel; Shankar, Prabakaran; Gumpu, Manju Bhargavi; Ramachandra, Bhat Lakshmishri; Kulandaisamy, Arockia Jayalatha; Rayappan, John Bosco Balaguru

2017-08-01

Consumption of fruits leads to increase in glucose level in blood for diabetic patients, which in turn leads to peripheral, vascular, ocular complications and cardiac diseases. In this context, a non-enzymatic hybrid glucose biosensor was fabricated for the first time to detect glucose by immobilizing titanium oxide-manganese oxide (TiO2-Mn3O4) nanocomposite and chitosan membrane on to the surface of Pt working electrode (Pt/TiO2-Mn3O4/chitosan). TiO2-Mn3O4 nanocomposite catalyzed the oxidation of glucose to gluconolactone in the absence of glucose oxidase enzyme with high electron transfer rate, good biocompatibility and large surface coverage. Electrochemical measurements revealed the excellent sensing response of the developed biosensor towards glucose with a high sensitivity of 7.073 µA mM-1, linearity of 0.01-0.1 mM, low detection limit of 0.01 µM, reproducibility of 1.5% and stability of 98.8%. The electrochemical parameters estimated from the anodic process were subjected to linear regression models for the detection of unknown concentration of glucose in different fruit samples.
Self-Template Synthesis of Hybrid Porous Co3 O4 -CeO2 Hollow Polyhedrons for High-Performance Supercapacitors.

PubMed

Wei, Chengzhen; Liu, Kangfei; Tao, Jing; Kang, Xiaoting; Hou, Haiyan; Cheng, Cheng; Zhang, Daojun

2018-01-04

In this work, hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons have been successfully obtained via a simple cation-exchange route followed by heat treatment. In the synthesis process, ZIF-67 polyhedron frameworks are firstly prepared, which not only serve as a host for the exchanged Ce3 + ions but also act as the template for the synthesis of hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons. When utilized as electrode materials for supercapacitors, the hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons delivered a large specific capacitance of 1288.3 F g -1 at 2.5 A g -1 and a remarkable long lifespan cycling stability (<3.3 % loss after 6000 cycles). Furthermore, an asymmetric supercapacitor (ASC) device based on hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons was assembled. The ASC device possesses an energy density of 54.9 W h kg -1 , which can be retained to 44.2 W h kg -1 even at a power density of 5100 W kg -1 , indicating its promising application in electrochemical energy storage. More importantly, we believe that the present route is a simple and versatile strategy for the preparation of other hybrid metal oxides with desired structures, chemical compositions and applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dianionic Titanyl and Vanadyl (Cation+ )2 [MIV O(Pc4- )]2- Phthalocyanine Salts Containing Pc4- Macrocycles.

PubMed

Konarev, Dmitri V; Kuzmin, Alexey V; Khasanov, Salavat S; Litvinov, Alexey L; Otsuka, Akihiro; Yamochi, Hideki; Kitagawa, Hiroshi; Lyubovskaya, Rimma N

2018-06-18

In this study, the titanyl and vanadyl phthalocyanine (Pc) salts (Bu 4 N + ) 2 [M IV O(Pc 4- )] 2- (M=Ti, V) and (Bu 3 MeP + ) 2 [M IV O(Pc 4- )] 2- (M=Ti, V) with [M IV O(Pc 4- )] 2- dianions were synthesized and characterized. Reduction of M IV O(Pc 2- ) carried out with an excess of sodium fluorenone ketyl in the presence of Bu 4 N + or Bu 3 MeP + is exclusive to the phthalocyanine centers, forming Pc 4- species. During reduction, the metal +4 charge did not change, implying that Pc is an non-innocent ligand. The Pc negative charge increase caused the C-N(pyr) bonds to elongate and the C-N(imine) bonds to alternate, thus increasing the distortion of Pc. Jahn-Teller effects are significant in the [eg(π*)] 2 dianion ground state and can additionally distort the Pc macrocycles. Blueshifts of the Soret and Q-bands were observed in the UV/Vis/NIR when M IV O(Pc 2- ) was reduced to [M IV O(Pc . 3- )] . - and [M IV O(Pc 4- )] 2- . From magnetic measurements, [Ti IV O(Pc 4- )] 2- was found to be diamagnetic and (Bu 4 N + ) 2 [V IV O(Pc 4- )] 2- and (Bu 3 MeP + ) 2 [V IV O(Pc 4- )] 2- were found to have magnetic moments of 1.72-1.78 μ B corresponding to an S=1/2 spin state owing to V IV electron spin. As a result, two latter salts show EPR signals with V IV hyperfine coupling. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
X-ray fluorescence analysis of Cr(6+) component in mixtures of Cr(2)O(3) and K(2)CrO(4).

PubMed

Tochio, Tatsunori; Sakakura, Shusuke; Oohashi, Hirofumi; Mizota, Hirohisa; Zou, Yanhui; Ito, Yoshiaki; Fukushima, Sei; Tanuma, Shigeo; Shoji, Takashi; Fujimura, Hajime; Yamashita, Michiru

2010-01-01

X-ray fluorescence analysis using Cr K(alpha) spectra was applied to the determination of the mixing ratio of Cr(6+) to (Cr(6+) + Cr(3+)) in several mixtures of K(2)CrO(4) and Cr(2)O(3). Because the powder of K(2)CrO(4) contained large particles that were more than 50 microm in diameter, it was ground between a pestle and a mortar for about 8 h. The coarse particles still remaining were removed by using a sieve with 325-mesh (44 microm) in order to reduce the difference in absorption effects between emissions from Cr(6+) and those from Cr(3+). The mixing ratio, K(2)CrO(4)/(K(2)CrO(4) + Cr(2)O(3)), of the five mixtures investigated is 0.50, 0.40, 0.20, 0.10, and 0.05 in weight, respectively. Each spectrum obtained was analyzed by decomposing it into two reference spectra, those of the two pure materials, K(2)CrO(4) and Cr(2)O(3), with a constant background. The results for the mixtures containing K(2)CrO(4) of more than 20 wt% are that the relative deviation from the true value is less than approximately 5%. On the other hand, when the content of K(2)CrO(4) decreases to less than 10 wt%, the relative deviation gets so large as 20 - 25%. The error coming from a peak separation of spectrum involved in our results were estimated by applying our method to five sets of data for each mixture computationally generated, taking into account the uncertainty in total counts of real measurements.
Implantation of Fe3O4 Nanoparticles in Shells of Au@m-SiO2 Yolk@Shell Nanocatalysts with Both Improved Recyclability and Catalytic Activity.

PubMed

Li, Yanan; Jin, Chenjing; Yuan, Ganyin; Han, Jie; Wang, Minggui; Guo, Rong

2017-08-01

Multifunctional nanocatalysts of Au@Fe 3 O 4 /m-SiO 2 yolk@shell hybrids had been developed through a template-assisted synthesis, where Fe 3 O 4 nanoparticles (∼12 nm) and m-SiO 2 shells were sequentially assembled on surfaces of Au/SiO 2 core/shell templates, followed by selective etching of the inner SiO 2 cores, leading to the formation of Au@Fe 3 O 4 /m-SiO 2 yolk@shell hybrids. The Fe 3 O 4 nanoparticles were implanted in the inner surfaces of m-SiO 2 shells with partially exposed surfaces to the inner cavity. The novel design not only ensures a high surface area (540.0 m 2 /g) and saturation magnetization (48.6 emu/g) of the hybrids but also enables interaction between Au and Fe 3 O 4 nanoparticles. Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH 4 indicated that Au@Fe 3 O 4 /m-SiO 2 yolk@shell nanocatalysts not only showed high stability and recyclability but also maintained improved catalytic activity as a result of the synergetic effect resulting from Au and Fe 3 O 4 interactions.
Direct ultrasonic-assisted synthesis of sphere-like nanocrystals of spinel Co3O4 and Mn3O4.

PubMed

Askarinejad, Azadeh; Morsali, Ali

2009-01-01

A simple sonochemical method was developed to synthesize uniform sphere-like or cubic Co(3)O(4) and Mn(3)O(4) nanocrystals by using acetate salts and sodium hydroxide or tetramethylammonium hydroxide (TMAH) as precursors. Influence of some parameters such as time of reaction, alkali salts, and power of the ultrasound and the molar ratio of the starting materials on the size, morphology and degree of crystallinity of the products was studied. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FTIR spectroscopy, Thermal gravimetry analysis and differential thermal analysis (TGA/DTA) were used to characterize the nanocrystals.
A Fe3O4/FeAl2O4 composite coating via plasma electrolytic oxidation on Q235 carbon steel for Fenton-like degradation of phenol.

PubMed

Wang, Jiankang; Yao, Zhongping; Yang, Min; Wang, Yajing; Xia, Qixing; Jiang, Zhaohua

2016-08-01

The Fe3O4/FeAl2O4 composite coatings were successfully fabricated on Q235 carbon steel by plasma electrolytic oxidation technique and used to degrade phenol by Fenton-like system. XRD, SEM, and XPS indicated that Fe3O4 and FeAl2O4 composite coating had a hierarchical porous structure. The effects of various parameters such as pH, phenol concentration, and H2O2 dosage on catalytic activity were investigated. The results indicated that with increasing of pH and phenol content, the phenol degradation efficiency was reduced significantly. However, the degradation rate was improved with the addition of H2O2, but dropped with further increasing of H2O2. Moreover, 100 % removal efficiency with 35 mg/L phenol was obtained within 60 min at 303 K and pH 4.0 with 6.0 mmol/L H2O2 on 6-cm(2) iron oxide coating. The degradation process consisted of induction period and rapid degradation period; both of them followed pseudo-first-order reaction. Hydroxyl radicals were the mainly oxidizing species during phenol degradation by using n-butanol as hydroxyl radical scavenger. Based on Fe leaching and the reaction kinetics, a possible phenol degradation mechanism was proposed. The catalyst exhibited excellent stability.
Large exchange bias effect in NiFe2O4/CoO nanocomposites

NASA Astrophysics Data System (ADS)

Mohan, Rajendra; Prasad Ghosh, Mritunjoy; Mukherjee, Samrat

2018-03-01

In this work, we report the exchange bias effect of NiFe2O4/CoO nanocomposites, synthesized via chemical co-precipitation method. Four samples of different particle size ranging from 4 nm to 31 nm were prepared with the annealing temperature varying from 200 °C to 800 °C. X-ray diffraction analysis of all the samples confirmed the presence of cubic spinel phase of Nickel ferrite along with CoO phase without trace of any impurity. Sizes of the particles were studied from transmission electron micrographs and were found to be in agreement with those estimated from x-ray diffraction. Field cooled (FC) hysteresis loops at 5 K revealed an exchange bias (HE) of 2.2 kOe for the sample heated at 200 °C which decreased with the increase of particle size. Exchange bias expectedly vanished at 300 K due to high thermal energy (kBT) and low effective surface anisotropy. M-T curves revealed a blocking temperature of 135 K for the sample with smaller particle size.
Spin-Coating and Characterization of Multiferroic MFe{sub 2}O{sub 4} (M=Co, Ni) / BaTiO{sub 3} Bilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quandt, Norman; Roth, Robert; Syrowatka, Frank

2016-01-15

Bilayer films of MFe{sub 2}O{sub 4} (M=Co, Ni) and BaTiO{sub 3} were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO{sub 3}. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm{sup −3} for the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} and 188 emu cm{sup −3} for the NiFe{sub 2}O{sub 4}/BaTiO{submore » 3} bilayer, respectively were found. For the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems. - Graphical abstract: The SEM image of the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer on Pt–Si-substrate (left), magnetization as a function of the magnetic field perpendicular and parallel to the film plane (right top) and P–E and I–V hysteresis loops of the bilayer at room temperature. - Highlights: • Ferrite and perovskite oxides grown on platinum using spin coating technique. • Columnar growth of cobalt ferrite particle on the substrate. • Surface investigation showed a homogenous and smooth surface. • Perpendicular and parallel applied magnetic field revealed a magnetic anisotropy. • Switching peaks and saturated P–E hysteresis loops show ferroelectricity.« less
A eficiência de formação estelar em Musca

NASA Astrophysics Data System (ADS)

Hickel, G. R.; Vilas-Boas, J. W. S.; Roberto, A. J.., Jr.; Khan, R. P.

2003-08-01

Apresentamos os resultados de um survey no infravermelho próximo (bandas J e H), executado no Laboratório Nacional de Astrofísica, na direção da nuvem escura em forma de filamento de Musca (observamos ao longo de todo o filamento, além de todas as fontes pontuais IRAS e/ou fontes ROSAT brilhantes a uma distância de 2o da nuvem). Nosso objetivo é determinar a eficiência de formação estelar para esta nuvem escura (massa de estrelas formadas/massa da nuvem), procurando por objetos estelares jovens de pequena massa no seu interior e/ou evoluídos o suficiente para estarem afastados do local de nascimento, mas ainda mostrando características de objetos pré-seqüência principal como emissão de raios-X e excesso de emissão no infravermelho próximo. Este survey não estabeleceu nenhum viés na seleção de fontes pontuais IRAS ou fontes ROSAT, uma vez que a imensa maioria das fontes pontuais IRAS nesta região têm qualidade de fluxo ruim. Os candidatos a objetos estelares jovens foram selecionados pelo excesso no índice de cor (J-H), descontados os efeitos da extinção interestelar na linha de visada, determinada através da emissão estendida no infravermelho distante (IRAS). Estimativas de massa foram feitas para estes candidatos, através da relação massa-luminosidade, para calcular a eficiência de formação estelar de Musca.
Site Occupancies, Luminescence, and Thermometric Properties of LiY9(SiO4)6O2:Ce3+ Phosphors.

PubMed

Zhou, Weijie; Pan, Fengjuan; Zhou, Lei; Hou, Dejian; Huang, Yan; Tao, Ye; Liang, Hongbin

2016-10-04

In this work, we report the tunable emission properties of Ce 3+ in an apatite-type LiY 9 (SiO 4 ) 6 O 2 compound via adjusting the doping concentration or temperature. The occupancies of Ce 3+ ions at two different sites (Wyckoff 6h and 4f sites) in LiY 9 (SiO 4 ) 6 O 2 have been determined by Rietveld refinements. Two kinds of Ce 3+ f-d transitions have been studied in detail and then assigned to certain sites. The effects of temperature and doping concentration on Ce 3+ luminescence properties have been systematically investigated. It is found that the Ce 3+ ions prefer occupying Wyckoff 6h sites and the energy transfer between Ce 3+ at two sites becomes more efficient with an increase in doping concentration. In addition, the charge-transfer vibronic exciton (CTVE) induced by the existence of free oxygen ion plays an important role in the thermal quenching of Ce 3+ at 6h sites. Because of the tunable emissions from cyan to blue with increasing temperature, the phosphors LiY 9 (SiO 4 ) 6 O 2 :Ce 3+ are endowed with possible thermometric applications.
Structural and genetic relationships of closely related O-antigens of Cronobacter spp. and Escherichia coli: C. sakazakii G2594 (serotype O4)/E. coli O103 and C. malonaticus G3864 (serotype O1)/E. coli O29.

PubMed

Shashkov, Alexander S; Wang, Min; Turdymuratov, Eldar M; Hu, Shaohui; Arbatsky, Nikolay P; Guo, Xi; Wang, Lei; Knirel, Yuriy A

2015-03-02

O-Antigen (O-polysaccharide) variation is the basis for bacterial serotyping and is important in bacterial virulence and niche adaptation. In this work, we present structural and genetic evidences for close relationships between the O-antigens of the Cronobacter spp. and Escherichia coli. Cronobacter sakazakii G2594 (serotype O4) and Cronobacter malonaticus G3864 (serotype O1) are structurally related to those of E. coli O103 and O29, respectively, and some other members of the Enterobacteriaceae family differing in the patterns of lateral glucosylation (C. sakazakii G2594) or O-acetylation (C. malonaticus G3864). The O-antigen gene clusters of the corresponding Cronobacter and E. coli strains contain the same genes with high-level similarity, and the structural differences within both O-antigen pairs were suggested to be due to modification genes carried by prophages. Copyright © 2014 Elsevier Ltd. All rights reserved.
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}

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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)more » 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.« less
Thermal equation of state of CaFe 2O 4-type MgAl 2O 4

NASA Astrophysics Data System (ADS)

Sueda, Yuichiro; Irifune, Tetsuo; Sanehira, Takeshi; Yagi, Takehiko; Nishiyama, Norimasa; Kikegawa, Takumi; Funakoshi, Ken-ichi

2009-05-01

In situ X-ray diffraction measurements of CaFe 2O 4-type MgAl 2O 4 have been conducted at pressures up to 42 GPa and temperatures to 2400 K using Kawai-type multianvil apparatus with sintered diamond anvils. Additional measurements have also been conducted at pressures to 12 GPa using diamond anvil cell with helium as a pressure medium at room temperature, and at temperatures to 836 K at the ambient pressure using a high-temperature X-ray diffractometer. The analysis of room-temperature data yielded V0 = 240.1(2) Å 3, K0 = 205(6) GPa, and K0=4.1(3). A fit of the present data to high-temperature Birch-Murnaghan equation of state (EOS) yielded (∂ K0/∂ T) P = -0.030(2) GPa/K and α0 = a0 + b0T with values of a0 = 1.96(13) × 10 -5 K -1 and b0 = 1.64(24) × 10 -8 K -2. The present data set was also fitted to Mie-Grüneisen-Debye (MGD) EOS and we obtained γ0 = 1.73(7), q = 2.03(37), and θ0 = 1546(104) K. Density changes of MORB have been estimated using the newly obtained thermoelastic parameters, assuming that the Al-rich phase in this composition possesses the CaFe 2O 4-type structure under the lower mantle P, T conditions. The calculated densities along geotherms for the normal mantle and subducting cold slabs are both significantly higher than those of typical seismological models, confirming the conclusion of some recent results on MORB by laser-heated diamond anvil cell experiments.
Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy.

PubMed

Zhang, Wei; Chen, Xianchun; Liao, Xiaoming; Huang, Zhongbing; Dan, Xiuli; Yin, Guangfu

2011-10-01

The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved.
A moderate method for preparation DMSA coated Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Song, L. N.; Gu, N.; Zhang, Y.

2017-01-01

A moderate way to prepare water soluble magnetic Fe3O4 nanoparticles has been developed. Firstly, oleic acid coated Fe3O4 is prepared by coprecipitation. Second, oleic acid were replaced by 2,3-dimercaptosuccinnic acid (DMSA) to prepare DMSA/Fe3O4 in the mixed solution of n-hexane and acetone. After dialysis and filtration the DMSA/Fe3O4 can be transferred into distilled water to form stable Fe3O4 nanoparticle solutions. The TEM images indicated that the particles had spherical shape and the nanoparticles were found to be 12 nm with a relatively narrow size distribution with the hydrodynamic size of 30 nm. And the result of VSM shows that DMSA/Fe3O4 nanoparticles have a saturation magnetization of 31 emu/g. The IR spectra indicated that the iron oxide was located by carboxyl matrix.
Dielectric and Energy Storage Properties of Ba0.65Sr0.35TiO3 Ceramics Modified by BiNbO4

NASA Astrophysics Data System (ADS)

Zheng, Yi; Zhang, Jihua; Wei, Meng; Dong, Xiangxiang; Huang, Jiapeng; Wu, Kaituo; Chen, Hongwei

2018-02-01

(1 - x) (Ba0.65Sr0.35TiO3)-xBiNbO4 (x = 0.0-0.15) ceramic were prepared by solid-state reaction method. The phase composition, microstructure, dielectric properties, polarization-electric field, breakdown strength and energy storage behaviors for the BiNbO4-modified Ba0.65Sr0.35TiO3 ceramics were investigated. With the addition of BiNbO4, the remnant polarization and saturation polarization decreased and the nonlinearity was suppressed. When x = 0.07, the maximum recoverable energy storage achieved was 0.5 J/cm3, 1.5 times that of un-doped Ba0.65Sr0.35TiO3 ceramics, with an efficiency of 96.89% and a breakdown electric field reaching 15.3 kV/mm. Therefore, BiNbO4 doping could improve the energy storage properties of Ba0.65Sr0.35TiO3 for high-energy pulse capacitor application.

Soft-template-synthesis of hollow CuO/Co3O4 composites for pseudo-capacitive electrode: A synergetic effect on electrochemical performance

NASA Astrophysics Data System (ADS)

Wang, Kuaibing; Lv, Bo; Wu, Hua; Luo, Xuefei; Xu, Jiangyan; Geng, Zhirong

2016-12-01

Hollow CuO/Co3O4 hybrids, which inherited from its coordination polymer precursor consisting of sheets layer and nanoparticles layer composites, were synthesized and characterized by SEM, EDX, XRD and XPS. To assess its electrochemical capacitive performances, cyclic voltammetry, galvanostatic charging-discharging measurements and A.C. impedance tests were performed successively. The CuO/Co3O4 hybrids had higher capacitance and lower charge transfer resistance than bare Co3O4 nanostructures, revealing that it provided a protection layer and produced a synergistic effect due to the existence of CuO layer. The distinct synergistic effect could be further confirmed by endurance cycling tests. The capacitance of the CuO/Co3O4 hybrids was 111% retained after 500 cycles at a charging rate of 1.0 A g-1 and remained an intense growth trend after 2000 cycles at scan rate of 200 mV s-1.
A unique polysaccharide containing 3-O-methylarabinose and 3-O-methylgalactose from Tinospora sinensis.

PubMed

Nagar, Shipra; Hensel, Andreas; Mischnick, Petra; Kumar, Vineet

2018-08-01

Tinospora sinensis (Lour.) Merrill is of great therapeutic significance in Indian traditional medicine. Crude polysaccharides were isolated from methanol pre-extracted stems of dried material by successive extractions with cold water, hot water and NaOH (0.25 mol/L) in 0.98, 0.55 and 0.70 % yields respectively. Cold water soluble polysaccharides (CWSP) were purified and fractionated by ion exchange chromatography on DEAE-Sephacel. Neutral polysaccharides were further fractionated on Sepharose CL6B to yield three fractions TW1, TW2, TW3. The study further focuses on structural elucidation of TW1. TW1 was obtained in 0.8 % yield relative to CWSP, with MW of 1.6 × 10 5  Da. It was composed of 3-O-methyl-arabinose, 3-O-methyl-galactose and galactose in molar ratio of 1.0:6.3:0.9 respectively. Based on per-deuteromethylation, NMR and ESI-MS analyses, TW1 was composed of 1,4-linked 3-O-methyl-β-d-galactopyranose and β-d-galactopyranose backbone with branching at O-6 of 3-O-methyl-β-d-galactosyl residues by 1,5-linked 3-O-methyl-α-l-arabinofuranoside chains. 3-O-methyl-arabinose and 3-O-methyl-galactose have first ever been reported in any polysaccharide and Tinospora genus, respectively. Copyright © 2018 Elsevier Ltd. All rights reserved.
Comparison of catalytic activities for photocatalytic and sonocatalytic degradation of organic dye in the presence of ternary Fe{sub 3}O{sub 4}/ZnO/CuO magnetic heteregenous nanocatalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taufik, Ardiansyah; Saleh, Rosari, E-mail: rosari.saleh@gmail.com, E-mail: rosari.saleh@ui.ac.id; Integrated Laboratory of Energy and Environment, Fakultas MIPA-Universitas Indonesia, 16424 Depok

2016-04-19

The Fe{sub 3}O{sub 4}/ZnO/CuO nanocatalyst with various CuO loading were synthesized by sol-gel method and were characterized by powder X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV-Vis spectroscopy, and vibrating sample magnetometry. The findings demonstrate that all samples exhibit ferromagnetic behavior at room temperatureand containa well-crystalline ternary oxide nanocatalyst. Methylene blue was taken as the model of organic dye to evaluate its photocatalytic and sonocatalytic degradation in the presence of Fe{sub 3}O{sub 4}/ZnO/CuO nanocatalyst. The observed degradation activity indicate that the order of degradation of methylene blue issonocatalysis> photocatalysis. Fe{sub 3}O{sub 4}/ZnO/CuO nanocatalyst with the lowest CuOmore » loading exhibit the highest rate of degradation of methylene blue during the sono- and photocatalytic processes. The experimental data shows that holes are the predominant oxidative species involved in the sono- and photodegradation of methylene blue.« less
Metal-Organic Frameworks Derived Porous Core/Shell Structured ZnO/ZnCo2O4/C Hybrids as Anodes for High-Performance Lithium-Ion Battery.

PubMed

Ge, Xiaoli; Li, Zhaoqiang; Wang, Chengxiang; Yin, Longwei

2015-12-09

Metal-organic frameworks (MOFs) derived porous core/shell ZnO/ZnCo2O4/C hybrids with ZnO as a core and ZnCo2O4 as a shell are for the first time fabricated by using core/shell ZnCo-MOF precursors as reactant templates. The unique MOFs-derived core/shell structured ZnO/ZnCo2O4/C hybrids are assembled from nanoparticles of ZnO and ZnCo2O4, with homogeneous carbon layers coated on the surface of the ZnCo2O4 shell. When acting as anode materials for lithium-ion batteries (LIBs), the MOFs-derived porous ZnO/ZnCo2O4/C anodes exhibit outstanding cycling stability, high Coulombic efficiency, and remarkable rate capability. The excellent electrochemical performance of the ZnO/ZnCo2O4/C LIB anodes can be attributed to the synergistic effect of the porous structure of the MOFs-derived core/shell ZnO/ZnCo2O4/C and homogeneous carbon layer coating on the surface of the ZnCo2O4 shells. The hierarchically porous core/shell structure offers abundant active sites, enhances the electrode/electrolyte contact area, provides abundant channels for electrolyte penetration, and also alleviates the structure decomposition induced by Li(+) insertion/extraction. The carbon layers effectively improve the conductivity of the hybrids and thus enhance the electron transfer rate, efficiently prevent ZnCo2O4 from aggregation and disintegration, and partially buffer the stress induced by the volume change during cycles. This strategy may shed light on designing new MOF-based hybrid electrodes for energy storage and conversion devices.
Discos de acresção em sistemas Be-X

NASA Astrophysics Data System (ADS)

Lopes de Oliveira, R.; Janot-Pacheco, E.

2003-08-01

Alguns fenômenos de outbursts em Be-X sugerem a existência, mesmo que temporária, de um disco de acresção quando da passagem do objeto compacto pelo periastro orbital. Neste trabalho avaliamos a possibilidade de formação do disco de acresção em sistemas Be+estrela de neutrons e Be+anã branca, e a influência da excentricidade orbital na ocorrência deste fenômeno. Utilizamos a expressão analítica para o momento angular específico da matéria constituinte de um meio em expansão lenta, como é o caso do disco circunstelar das estrelas Be, proposta por Wang(1981), sob a condição básica de que o raio de circularização deva ser maior do que o raio de Alfvén. Concluímos que existe um limite para o período orbital do sistema acima do qual não é possível a formação do disco de acresção, e que este valor aumenta para sistemas com excentricidade orbital maior.
Synthesis, crystal structure, and spectroscopic characterization of trans-bis[(mu-1,3-bis(4-pyridyl)propane)(mu-(3-thiopheneacetate-O))(3-thiopheneacetate-O)]dicopper(II), [[Cu2(O2CCH2C4H3S)4mu-(BPP)2

PubMed

Marinho, Maria Vanda; Yoshida, Maria Irene; Guedes, Kassilio J; Krambrock, Klaus; Bortoluzzi, Adailton J; Hörner, Manfredo; Machado, Flávia C; Teles, Wagner M

2004-02-23

From the reaction between a dinuclear paddle-wheel carboxylate, namely [Cu2mu-(O2CCH2C4H3S)4] (1), and the flexible ligand 1,3-bis(4-pyridyl)propane (BPP) a neutral 2-D coordination polymer [[Cu2(O2CCH2C4H3S)4mu-(BPP)2
Olivine-modified spinel-spinel transitions in the system Mg2SiO4-Fe2SiO4: Calorimetric measurements, thermochemical calculation, and geophysical application

NASA Astrophysics Data System (ADS)

Akaogi, Masaki; Ito, Eiji; Navrotsky, Alexandra

1989-11-01

The olivine(α)-modified spinel(β)-spinel (γ) transitions in the system Mg2SiO4-Fe2SiO4 were studied by high-temperature solution calorimetry. Enthalpies of the β-γ and a α-γ transitions in Mg2SiO4 at 975 K and of the α-γ transition in Fe2SiO4 at 298 K were measured. The γ solid solution showed a positive enthalpy of mixing. Phase relations at high pressures and high temperatures were calculated from these thermochemical data including correction for the effect of nonideality of α, β, and γ solid solutions. The calculated phase diagrams agree well with those determined experimentally by Katsura and Ito very recently. The α - (Mg0.89, Fe0.11)2SiO4 transforms to β through a region of α+β without passing through the α+γ phase field at around 400 km depth in the mantle with an interval of about 18(±5) km. Temperatures at 390 and 650 km depths are estimated to be about 1673 and 1873 K, respectively, assuming an adiabatic geotherm.
Degradation of 4-nitrophenol (4-NP) using Fe-TiO2 as a heterogeneous photo-Fenton catalyst.

PubMed

Zhao, Binxia; Mele, Giuseppe; Pio, Iolanda; Li, Jun; Palmisano, Leonardo; Vasapollo, Giuseppe

2010-04-15

Photocatalytic degradation of 4-nitrophenol was investigated using Fe-doped (1, 3, 5 and 8 wt.% Fe) TiO(2) catalysts under UV light irradiation in aqueous dispersions in the presence of H(2)O(2). Photocatalysts with the lowest Fe content (1%) showed a considerably better behavior with respect to the unloaded TiO(2) and the catalysts with higher Fe contents. Photocatalytic degradation was studied under different conditions such as amounts of 1% Fe-TiO(2) catalyst, H(2)O(2) dose and initial pH of 4-NP solution. The results indicated that about 67.53% total organic carbon of a solution containing 20 mg L(-1) 4-NP was removed at pH 6.17 by using 4.9 mM of H(2)O(2) and 0.4 g L(-1) of the catalyst in a 2-L batch photo-reactor, the complete degradation of 4-NP occurring after 60 min. It was also observed that catalytic behavior could be reproduced in consecutive experiments without a considerable decrease of the UV/Fe-TiO(2)/H(2)O(2) process efficiency. 2009 Elsevier B.V. All rights reserved.
Crystal structures of NiSO4·9H2O and NiSO4·8H2O: magnetic properties, stability with respect to morenosite (NiSO4·7H2O), the solid-solution series (Mg x Ni1-x )SO4·9H2O

NASA Astrophysics Data System (ADS)

Fortes, A. D.; Knight, K. S.; Gibbs, A. S.; Wood, I. G.

2018-02-01

Since being discovered initially in mixed-cation systems, a method of forming end-member NiSO4·9H2O and NiSO4·8H2O has been found. We have obtained powder diffraction data from protonated analogues (with X-rays) and deuterated analogues (using neutrons) of these compounds over a range of temperatures, allowing us to determine their crystal structures—including all H-atoms—and to characterise the transitions on warming from 220 to 278 K; glass → 9-hydrate → 8-hydrate + ice → 7-hydrate + ice → partial melt (7-hydrate + liquid). NiSO4·8D2O is triclinic, space-group P\\bar {1} , Z = 2, with unit cell parameters at 150 K, a = 6.12463(8) Å, b = 6.8401(1) Å, c = 12.5339(2) Å, α = 92.846(1)°, β = 97.822(1)°, γ = 96.627(1)° and V = 515.58(1) Å3. The structure consists of two symmetry-inequivalent Ni(D2O)6 octahedra on sites of \\bar {1} symmetry. These are directly joined by a water-water H-bond to form chains of octahedra parallel with the c-axis at x = 0. Two interstitial water molecules serve both to bridge the Ni(D2O)6 octahedral chains in the b-c plane and also to connect with the SO4 2- tetrahedral oxyanion. These tetrahedra are linked by the two interstitial water molecules in a reticular motif to form sheets perpendicular to c. NiSO4·9D2O is monoclinic, space-group P21/c, Z = 4, with unit-cell parameters at 150 K, a = 6.69739(6) Å, b = 11.8628(1) Å, c = 14.5667(1) Å, β = 94.9739(8)° and V = 1152.96(1) Å3. The structure is isotypic with the Mg analogue described elsewhere (Fortes et al., Acta Cryst B 73:47‒64, 2017b). It shares the motif of H-bonded octahedral chains with NiSO4·8D2O, although in the enneahydrate these run parallel with the b-axis at x = 0. Three interstitial water molecules bridge the Ni(D2O)6 octahedra to the SO4 2- tetrahedral oxyanion. The tetrahedra sit at x ≈ 0.5 and are linked by two of the three interstitial water molecules in a pentagonal motif to form ribbons parallel with b. A solid-solution series
Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

NASA Astrophysics Data System (ADS)

Lu, Huafei; Lin, Yuanhua; Yuan, Jiancong; Nan, Cewen; Chen, Kexin

2013-02-01

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb-and-Co doped ZnO and TiO2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol-gel methods respectively, and then obtained the TCCTO/ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of 210(1 kHz) with a nonlinear coefficient of 11. The dielectric behavior of TCCTO/ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.
Rich structural chemistry in new alkali metal yttrium tellurites: three-dimensional frameworks of NaYTe4O10, KY(TeO3)2, RbY(TeO3)2, and a novel variant of hexagonal tungsten bronze, CsYTe3O8.

PubMed

Kim, Youngkwon; Lee, Dong Woo; Ok, Kang Min

2015-01-05

Pure polycrystalline phases and single crystals of four new quaternary alkali metal yttrium tellurites, NaYTe4O10, KY(TeO3)2, RbY(TeO3)2, and CsYTe3O8, have been prepared by solid-state and hydrothermal reactions using A2CO3 (A = Na, K, Rb, and Cs), Y(NO3)3·6H2O, Y2O3, and TeO2 as starting reagents. X-ray diffraction analyses suggest that NaYTe4O10 exhibits a highly symmetric three-dimensional (3D) framework consisting of YO8 square antiprisms and chains of TeO4 polyhedra. Within the framework, six- (6-) and eight-membered ring (8-MR) channels are observed. KY(TeO3)2 and RbY(TeO3)2 are isostructural to each other and reveal another 3D framework with structures containing YO6 octahedra and TeO3 trigonal pyramids with 4-MR and 12-MR channels. CsYTe3O8 shows a hexagonal tungsten bronze (HTB)-like topology composed of hexagonal tungsten oxide-like layers of TeO4 polyhedra and YO6 octahedral linkers with 3-MR and 6-MR channels. Thermal analyses, elemental analyses, and spectroscopic characterizations, such as UV-vis diffuse reflectance and infrared spectra, are presented, as are local dipole moment calculations for the constituent asymmetric polyhedra TeO3 and TeO4.
Heat of formation of petalite, LiAlSi4O10

NASA Astrophysics Data System (ADS)

Faßhauer, D. W.; Cemič, L.

The enthalpy of formation of petalite, LiAlSi4O10, has been measured using high-temperature solution calorimetry. The measurements were carried out in a Calvet-type twin micro calorimeter at 728°C. A 2PbO.B2O3 melt was used as a solvent. Tabulated heats of formation of the components and tabulated heat capacities of the reactants and the product (Robie and Hemingway 1995) were used to calculate the standard heat of formation of petalite from the measured heats of solution. The calculations yielded a mean value of ΔfHpet298.15=-4872+/-5.4 kJ mol-1. This value may be compared to the heat of formation of ΔfHpet298.15= -4886.5+/-6.3 kJ mol-1 determined by the HF solution calorimetry by Bennington etal. (1980). Faßhauer etal. (1998) combined thermodynamic data with phase-equilibrium results to obtain best-fit thermodynamic results using the Bayes method, in order to derive an internally consistent dataset for phases in the NaAlSiO4- LiAlSiO4-Al2O3-SiO2-H2O system. They determined -4865.6+/-0.8kJmol-1 as the enthalpy of formation of petalite, a value that is appreciably closer to the enthalpy found in this work.
48 CFR 47.305-4 - F.o.b. destination solicitations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false F.o.b. destination... CONTRACT MANAGEMENT TRANSPORTATION Transportation in Supply Contracts 47.305-4 F.o.b. destination solicitations. (a) When preparing f.o.b destination solicitations, the contracting officer shall refer to 47.303...
48 CFR 47.305-4 - F.o.b. destination solicitations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... CONTRACT MANAGEMENT TRANSPORTATION Transportation in Supply Contracts 47.305-4 F.o.b. destination solicitations. (a) When preparing f.o.b destination solicitations, the contracting officer shall refer to 47.303... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false F.o.b. destination...
Metallic Nanoparticle (TiO2 and Fe3O4) Application Modifies Rhizosphere Phosphorus Availability and Uptake by Lactuca sativa.

PubMed

Zahra, Zahra; Arshad, Muhammad; Rafique, Rafia; Mahmood, Arshad; Habib, Amir; Qazi, Ishtiaq A; Khan, Saud A

2015-08-12

Application of engineered nanoparticles (NPs) with respect to nutrient uptake in plants is not yet well understood. The impacts of TiO2 and Fe3O4 NPs on the availability of naturally soil-bound inorganic phosphorus (Pi) to plants were studied along with relevant parameters. For this purpose, Lactuca sativa (lettuce) was cultivated on the soil amended with TiO2 and Fe3O4 (0, 50, 100, 150, 200, and 250 mg kg(-1)) over a period of 90 days. Different techniques, such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and Fourier transform infrared spectroscopy (FTIR) were used to monitor translocation and understand the possible mechanisms for phosphorus (P) uptake. The trends for P accumulation were different for roots (TiO2 > Fe3O4 > control) and shoots (Fe3O4 > TiO2 > control). Cystine and methionine were detected in the rhizosphere in Raman spectra. Affinities of NPs to adsorb phosphate ions, modifications in P speciation, and NP stress in the rhizosphere had possibly contributed to enhanced root exudation and acidification. All of these changes led to improved P availability and uptake by the plants. These promising results can help to develop an innovative strategy for using NPs for improved nutrient management to ensure food security.
Conduction Mechanisms in Multiferroic Multilayer BaTiO3/NiFe2O4/BaTiO3 Memristors

NASA Astrophysics Data System (ADS)

Samardzic, N.; Bajac, B.; Srdic, V. V.; Stojanovic, G. M.

2017-10-01

Memristive devices and materials are extensively studied as they offer diverse properties and applications in digital, analog and bio-inspired circuits. In this paper, we present an important class of memristors, multiferroic memristors, which are composed of multiferroic multilayer BaTiO3/NiFe2O4/BaTiO3 thin films, fabricated by a spin-coating deposition technique on platinized Si wafers. This cost-effective device shows symmetric and reproducible current-voltage characteristics for the actuating voltage amplitude of ±10 V. The origin of the conduction mechanism was investigated by measuring the electrical response in different voltage and temperature conditions. The results indicate the existence of two mechanisms: thermionic emission and Fowler-Nordheim tunnelling, which alternate with actuating voltage amplitude and operating temperature.
Electrospun Fe3O4/TiO2 hybrid nanofibers and their in vitro biocompatibility: prospective matrix for satellite cell adhesion and cultivation.

PubMed

Amna, Touseef; Hassan, M Shamshi; Van Ba, Hoa; Khil, Myung-Seob; Lee, Hak-Kyo; Hwang, I H

2013-03-01

We report the fabrication of novel Fe3O4/TiO2 hybrid nanofibers with the improved cellular response for potential tissue engineering applications. In this study, Fe3O4/TiO2 hybrid nanofibers were prepared by facile sol-gel electrospinning using titanium isopropoxide and iron(III) nitrate nonahydrate as precursors. The obtained electrospun nanofibers were vacuum dried at 80 °C and then calcined at 500 °C. The physicochemical characterization of the synthesized composite nanofibers was carried out by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray diffraction pattern. To examine the in vitro cytotoxicity, satellite cells were treated with as-prepared Fe3O4/TiO2 and the viability of cells was analyzed by Cell Counting Kit-8 assay at regular time intervals. The morphological features of unexposed satellite cells and exposed to Fe3O4/TiO2 composite were examined with a phase contrast microscope whereas the quantification of cell viability was carried out via confocal laser scanning microscopy. The morphology of the cells attached to hybrid matrix was observed by Bio-SEM. Cytotoxicity experiments indicated that the satellite cells could attach to the Fe3O4/TiO2 composite nanofibers after being cultured. We observed that Fe3O4-TiO2 composite nanofibers could support cell adhesion and growth. Results from this study therefore suggest that Fe3O4/TiO2 composite scaffold with small diameters (approximately 200 nm) can mimic the natural extracellular matrix well and provide possibilities for diverse applications in the field of tissue engineering and regenerative medicine. Copyright © 2012 Elsevier B.V. All rights reserved.
Thermally activated rotational disorder in CaMoO 4 nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Culver, Sean P.; Brutchey, Richard L.

2016-04-12

In this study, a dual-space approach, combining Rietveld and pair distribution function (PDF) analyses, has been applied to temperature-dependent synchrotron X-ray total scattering data collected on vapor diffusion sol–gel derived CaMoO 4 nanocrystals. A sharp transition in Ca–O bond distances in the range of 151–163 K was identified by PDF analysis, which is attributed to the thermal activation of rotational disorder associated with the rigid MoO 4 tetrahedra.
Trapping {BW12}2 tungstoborate: synthesis and crystal structure of hybrid [{(H2BW12O42)2O}{Mo6O6S6(OH)4(H2O)2}]14- anion.

PubMed

Korenev, V S; Abramov, P A; Vicent, C; Mainichev, D A; Floquet, S; Cadot, E; Sokolov, M N; Fedin, V P

2012-12-28

Reaction between monolacunary {BW(11)} tungstoborate and oxothiocationic building block, {Mo(2)O(2)S(2)}, results in the formation of a new polyoxothiometalate with a unique architecture in which two [H(2)BW(12)O(43)](9-) tungstoborate subunits are linked together with a hexamolybdate [Mo(V)(6)O(6)S(6)(OH)(4)(H(2)O)(2)](2+) bridge.
Calcinaksite, KNaCa(Si4O10) H2O, a new mineral from the Eifel volcanic area, Germany

NASA Astrophysics Data System (ADS)

Chukanov, Nikita V.; Aksenov, Sergey M.; Rastsvetaeva, Ramiza K.; Blass, Günter; Varlamov, Dmitry A.; Pekov, Igor V.; Belakovskiy, Dmitry I.; Gurzhiy, Vladislav V.

2015-08-01

The new mineral calcinaksite, ideally KNaCa(Si4O10) · H2O, the first hydrous and Ca-dominant member of the litidionite group, is found in a xenolith of metamorphosed carbonate-rich rock from the southern lava flow of the Bellerberg volcano, Eastern Eifel region, Rheinland-Pfalz, Germany. It is associated with wollastonite, gehlenite, brownmillerite, Ca2SiO4 (larnite or calcio-olivine), quartz, aragonite, calcite, jennite, tobermorite and ettringite. Calcinaksite occurs as clusters of colourless to light-grey subhedral prismatic crystals. The mineral is brittle, with Mohs' hardness of 5; Dmeas is 2.62(2) g/cm3 and Dcalc is 2.623 g/cm3. The IR spectrum shows the presence of H2O molecules forming three different H-bonds. Calcinaksite is optically biaxial (+), α = 1.542(2), β = 1.550(2), γ = 1.565(3), 2 V meas = 75(10). The chemical composition (electron-microprobe data, H2O determined by the Alimarin method, wt%) is: Na2O 6.69, K2O 12.01, CaO 15.04, FeO 0.59, SiO2 61.46, H2O 4.9, total 100.69. The empirical formula is H2.11 K0.99Na0.84Ca1.04Fe0.03Si3.98O11. The crystal structure was solved and refined to R 1 = 0.053, wR 2 = 0.075 based upon 3057 reflections having I > 3σ( I). Calcinaksite is triclinic, space group P , a = 7.021(2), b = 8.250(3), c = 10.145(2) Å. α = 102.23(2)°, β = 100.34(2)°, γ = 115.09(3)°, V = 495.4(3) Å3, Z = 2. The strongest reflections of the X-ray powder pattern [ d, Å ( I,%) ( hkl)] are: 3.431 (70) (-121, -211, -210, 012, 0-22), 3.300 (67) (-031), 3.173 (95) (-103, -201, -220, 003, 111), 3.060 (100) (-212, 2-11, -221, 200, -1-13, 021, -202), 2.851 (83) (0-23, -122, 1-13, 1-31), 2.664 (62) (1-23, -222, 201).

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