Nanocrystalline semiconductors: synthesis, properties, and perspectives

The preparation of hollow particles of ZnO by calcination of hydrozincite coated poly(styrene) beads is reported. Synthetic studies have been performed on such polymer/inorganic composite precursors in order to establish the optimum conditions for the preparation of the ZnO particles. The morphological properties of the powders were characterised by optical microscopy and scanning electron microscopy. The micrometric ZnO particles show morphological characteristics related to the template used in their preparation

The first dinuclear zinc(II) dithiocarbarnate complex with butyl substituent groups

The crystal structure of the title compound, bis( -N,N- dibutyldithiocarbamato- 2S:S0)bis[(N,N-dibutyldithiocarba\- forcelb]mato- 2S,S0)zinc(II)], [Zn2(C9H18NS2)4], has been determined at 180 K. The structure contains two crystallographically unique Zn2+ metal centres, showing almost identical slightly distorted tetrahedral coordination environments, and forming a dinuclear complex with two skew-bridging syn-N,N-dibutyldithiocarbamate ligands. Two other dithiocarbamate ligands are connected to the Zn2+ centres in a syn,syn-chelate coordination mode

Aerosol-assisted metallo-organic chemical vapour deposition of Bi2Se3 films using single-molecule precursors: the crystal structure of bismuth(m) dibutyldiselenocarbamate

The complexes [Bi{Se2CN(C2H5)2}3], [Bi{Se2CN(C4H9)2}3], [Bi{Se2CN(CH3)(C4H9)}3] and [Bi{Se2CN(CH3)(C6H13)}3] have been synthesized and characterized structurally using IR, 1H and 13C NMR. In addition, the crystal structure of [Bi{Se2CN(C4H9)2}3] was determined by single-crystal X-ray diffraction, showing the bismuth centre coordinated to three dialkyldiselenocarbamate ligands through the selenium donor atoms. The Bi(III) compounds were used as precursors for the deposition of Bi2Se3 films on glass substrates through aerosol-assisted metallo-organic chemical vapour deposition (AA-MOCVD)

Sistema de gestão da qualidade e ambiental na Embrapa Arroz e Feijão.

O presente documento relata o histórico dessa mudança de filosofia institucional e mostra a interface existente entre a Gestão da Qualidade e Ambiental, para identificar e desenvolver estratégias para aplicação de modelos de planejamento integrado, que ofereçam subsídios para a sustentabilidade da empresa.bitstream/CNPAF/26654/1/doc_215.pd

Polymer based nanocomposites: synthetic strategies for hybrid materials

Associating the well known advantages of hybrid materials to the wide potential of nanomaterials, the new and featuring class of polymer nanocomposites turned into one of the most intensively researched areas. This review highlights recent developments in the field of the synthesis of polymer based nanocomposites. Important issues related to the surface modification of fillers, in order to promote the compatibility between the inorganic/organic components, are also reported. The enhancement of the physical properties and the potential applications of polymer nanocomposites are considered in typical examples, given for each synthetic method describe

Melhoria da produtividade da clementina ‘Fina’, no Algarve.

A clementina ‘Fina’ é uma das tangerineiras mais cultivadas no Algarve. A baixa produtividade e o pequeno tamanho dos frutos deste cultivar, limitam os rendimentos do citricultor. Na tentativa de melhorar a produtividade desta clementina, foi realizado um ensaio, num pomar comercial, onde se estudou o efeito de aplicações hormonais de GA3 e de GA3+2,4-D. A aplicação de GA3 em plena floração aumentou o número de frutos vingados e provocou uma pequena redução do seu tamanho. O tratamento com GA3 +2,4-D reduziu o número de frutos vingados, em relação ao tratamento com GA3, mas estimulou o crescimento do fruto e aumentou o seu tamanho final. Podemos concluir que, no nosso ensaio, a aplicação conjunta de GA3 e 2,4-D constituiu o tratamento mais eficaz, na melhoria da produtividade da clementina ‘Fina’

Biased cosmological parameter estimation with galaxy cluster counts in the presence of primordial non-Gaussianities

The redshift dependence of the abundance of galaxy clusters is very sensitive to the statistical properties of primordial density perturbations. It can thus be used to probe small deviations from Gaussian initial conditions. Such deviations constitute a very important signature of many inflationary scenarios, and are thus expected to provide crucial information on physical processes which took place in the very early Universe. We have determined the biases which may be introduced in the estimation of cosmological parameters by wrongly assuming the absence of primordial non-Gaussianities. Although we find that the estimation of the present-day dark energy density using cluster counts is not very sensitive to the non-Gaussian properties of the density field, we show that the biases can be considerably larger in the estimation of the dark energy equation of state parameter $w$ and of the amplitude of the primordial density perturbations. Our results suggest that a significant level of non-Gaussianity at cluster scales may be able to reconcile the constraint on the amplitude of the primordial perturbations obtained using galaxy cluster number counts from the Planck Sunyaev-Zeldovich Catalog with that obtained from the primary Cosmic Microwave Background anisotropies measured by the Planck satellite.Comment: 4 pages, 1 figur

A prematuridade em Portugal

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