Non-Zeeman splitting for a spin-resolved STM with a Kondo adatom in a spin-polarized two-dimensional electron gas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Produção de biscoitos extrusados de polvilho azedo com fibras: efeito de parâmetros operacionais sobre as propriedades físicas

Neste trabalho buscou-se avaliar o efeito de parâmetros operacionais do processo de extrusão no desenvolvimento de biscoitos de polvilho com fibras, utilizando como matérias-primas o polvilho azedo e o farelo de mandioca. O processamento foi realizado em um extrusor mono-rosca, sendo considerados parâmetros variáveis: temperatura na 3ª zona de extrusão, umidade e porcentagem de fibras na mistura. Para analisar o efeito combinado das variáveis independentes nas características tecnológicas dos extrusados, utilizou-se o delineamento 'central composto rotacional' para três fatores. Os resultados obtidos mostraram efeitos significativos da umidade e porcentagem de fibras sobre o volume específico, sendo que a temperatura afetou os índices de solubilidade e absorção de água dos produtos extrusados. Condições de baixa temperatura (65 °C), baixa umidade (12%) e baixo teor de fibras (<4%), nas condições de processo utilizadas, produzem biscoitos com boas características tecnológicas.

Haematological response and growth performance of Nile tilapia (Oreochromis niloticus L.) fed diets containing folic acid

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliações sensoriais, bioquímicas e microbiológicas do guacamole, um produto à base de abacate, sob armazenamento a frio e com adição de ácido ascórbico

The elaboration of avocado products for commercialization keeping their characteristics of fresh product has been limited. The cut avocado darkens quickly and their sensorial characteristics are modified with the storage. In the present research, the sensorial parameters, microbiological stability, and peroxidase and polyphenoloxidase activity were evaluated in guacamole added with ascorbic acid and conserved under low temperature, by using avocado variety Hass. Products were conditioned in polyethylene+nylon packages with and without vacuum application; then, they were subjected to the slow and fast freezing (-18 degrees C) and stored in freezer (-18 degrees C). Evaluations were performed at the moment of elaboration of the product (t0) and at 3, 7 and 30 days post-storage. At t30, samples were kept under refrigeration (4 +/- 1 degrees C) and evaluated at 3, 5 and 7 days. After the 30 days of storage, -18 degrees C under freezing, followed by thawing and keeping at 4 +/- 1 degrees C for 7 days, the notes for the sensorial parameters decreased. The peroxidase activity was totally inhibited in the elaborated product and the polifenol oxidase activity considerably decreased in the guacamole (20.07 mM catechol/g fresh matter) relative to those in the fruit (58.31 mM catechol/g fresh matter), however with no significant variation during storage (at -18 degrees C). The samples were microbiologically stable under the conditions of the present study. The addition of ascorbic acid contributed to the conservation of the frozen avocado product by decreasing the enzymatic activity. However, the sensorial parameters are prejudiced under thawing and storage at 4 +/- 1 degrees C.

Growth and reproductive dynamics of the South American red shrimp, Pleoticus muelleri (Crustacea: Solenoceridae), from the southeastern coast of Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bose-Einstein condensates in 2D with time-periodic scattering length

We discuss two-dimensional Bose-Einstein Condensates (BEC) under time-periodic variation of the scattering length. In particular we argue that for high-frequency variation there exist stable self-confined condensates without an external trap, when the do component of the scattering length is negative. Our results are based on a variational approximation, on direct averaging of the Gross-Pitaevskii equation and on numerical simulations.

Spin-orbit coupling in the superconducting phase and DDW states of high-T-c cuprates

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of annealing time on morphological characteristics of Ba(Zr,Ti)O-3 thin films

Ba(Zr0.50Ti0.50)O-3 thin films were prepared by the polymeric precursor method using the annealing low temperature of 300 degrees C for 8, 16, 24, 48, 96 and 192 It in a furnace tube with oxygen atmosphere. The X-ray diffraction patterns revealed that the film annealed for 192 h presented some crystallographic planes (1 0 0), (1 1 0) and (2 0 0) in its crystalline lattice. Fourier transformed infrared presented the formation of metal-oxygen stretching at around 756 cm(-1). The atomic force microscopy analysis presented the growth of granules in the Ba(Zr0.50Ti0.50)O-3 films annealed from 8 to 96 h. The crystalline film annealed for 192 h already presents grains in its perovskite structure. It evidenced a reduction in the thickness of the thin films with the increase of the annealing time. (C) 2006 Elsevier B.V. All rights reserved.

Ferroelectric characteristics of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by the soft chemical method

Ferroelectric SrBi4Ti4O15 thin films were successfully prepared on a Pt(111)/Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. X-ray diffraction patterns of the films indicate that they are polycrystalline in nature. Atomic force microscopy (AFM) analyses showed that the surface of these films is smooth, dense and crack-free with low surface roughness (6.4 nm). At room temperature and at a frequency of 1 MHz, the dielectric constant and the dissipation factor were, respectively, 150 and 0.022. The C-V characteristics of perovskite thin film prepared at low temperature show normal ferrolectric behaviour. The remanent polarization and coercive field for the films deposited were 5.4 mu C/cm(2) and 8 5 kV/cm, respectively. All the capacitors showed good polarization fatigue characteristics at least up to 1 x 10(10) bipolar pulse cycles indicating that SrBi4Ti4O15 thin films can be a promising material for use in nonvolatile memories. (c) 2005 Elsevier B.V. All rights reserved.

Note on the germination of Vochysia tucanorum seeds treated with growth regulators

(Nota sobre a germinação de sementes de Vochysia tucanorum tratadas com reguladores vegetais). O objetivo deste trabalho foi avaliar a resposta germinativa sob luz branca e escuro de sementes de Vochysia tucanorum Mart. tratadas com GA3 e CEPA. Sementes recém-coletadas de uma área de Cerrado foram armazenadas durante 14 dias em duas temperaturas (25 ± 2 °C e 7 ± 1 °C). Após o período de armazenamento, as sementes foram pré-tratadas com água destilada (controle), ácido giberélico (GA3), ácido 2-cloroetilfosfônico (CEPA) e uma mistura de GA3 + CEPA; em seguida, as sementes foram semeadas em placas de Petri sobre papel filtro umedecido com água destilada e colocadas para germinar em escuro e sob luz branca. Os resultados sugerem que as sementes não são fotoblásticas nem dormentes, no entanto um comportamento fotoblástico emerge quando as sementes foram previamente armazenadas em baixa temperatura e embebidas em soluções de GA3 e CEPA. em geral, não houve diferença entre as temperaturas de armazenamento de 7 °C e 25 °C. A germinação sob luz branca de sementes pré-tratadas com CEPA + GA3 e CEPA foi antecipada, em comparação com o controle de água destilada, sendo que o efeito da mistura CEPA + GA3 foi mais pronunciado do que o de CEPA sozinho. Assim, a taxa de germinação de sementes de V. tucanorum, sob luz branca, pode ser melhorada pela embebição das mesmas em soluções de CEPA ou de CEPA + GA3.

Influência das temperaturas mínima e máxima em características de qualidade industrial e em rendimentos de grãos de trigo

Na região tritícola sul-brasileira predominam invernos com temperatura baixa (mínima absoluta, em dias com geada, de até - 8,0ºC). No entanto, a incidência de elevada temperatura (máxima absoluta, em dias isolados entre outubro e novembro, de até 41,0ºC) pode ser encontrada durante todo o período de enchimento de grãos e na maturação fisiológica. Este trabalho teve por objetivos verificar a influência das temperaturas mínima e máxima na qualidade industrial e no rendimento de grãos. Foram usados dados de experimentos com trigo Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) 16, conduzidos nos anos de 1990 a 1998, em sete locais do Rio Grande do Sul e em quatro locais de Santa Catarina. A análise estatística realizada foi correlações múltiplas. Verificou-se que, nos diferentes períodos analisados: a) o aumento da temperatura máxima média resultou em acréscimo do peso de mil grãos, do rendimento de grãos, da força geral de glúten, da microssedimentação com dodecil sulfato de sódio e do número de queda: b) o peso do hectolitro (exceção feita ao período final de maturação fisiológica), o peso de mil grãos, o número de queda e a extração experimental de farinha foram influenciados negativamente pela temperatura mínima média; c) a temperatura mínima média influenciou positivamente a força geral de glúten, a relação P/L e a microssedimentação com dodecil sulfato de sódio.

Estudo da germinação de sementes de espécies arbóreas pioneiras: Tibouchina pulchra Cogn. e Tibouchina granulosa Cogn. (Melastomataceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface morphology and optical characterization of OC1 OC6-PPV films

We report optical and morphological properties of poly(2-methoxy-5-hexyloxy-p-phenylenevinylene) (OC1OC6-PPV) films processed by casting, spin-coating (SC) and Langmuir-Blodgett (LB) techniques. The absorption spectra are practically the same, with an absorption maximum at approximately at 500 nm. For the photoluminescence (PL) spectra at low temperature (T=10K), a small but significant difference was noted in the cast film, in comparison with the LB and SC films. The zero-phonon transition shifted from 609 nm for the LB film to 615 and 621 nm for the SC and cast films, respectively. At room temperature, the PL spectra are similar for all films, and blue shifted by ca. 25 nm in comparison with the spectra at low temperature due to thermal disorder. Using atomic force microscopy (AFM) we inferred that the distinctive behavior of the cast film, probably associated with structural defects, is related to the large thickness of this film. The surface roughness, which was surprisingly higher for the LB film, apparently played no role in the emission properties of OC1OC6-PPV films.

Spectroscopic investigation of a new hybrid glass formed by the interaction between croconate ion and calcium polyphosphate

In this work, a new organic-inorganic hybrid material has been synthesized by the incorporation of croconate ion into a calcium polyphosphate coacervate. The hybrid so obtained was characterized by means of electronic and vibrational spectroscopies. The material is a homogeneous mixture described by a structural model, which includes helical chains of polyphosphate ions, where the calcium ion occupies the internal vacancies of the structure. The croconate ion appears to be occupying the regions outside the polymeric structure, surrounded by several water molecules. The electronic spectrum of the incorporated material shows a broad band peaking at the same wavelength region (363 nm) observed for the aqueous solution of croconate ion, and manifesting the Jahn-Teller effect as evidenced by the doublet structure of the band. The infrared spectrum is widely dominated by the absorption bands of the polyphosphate ion and the appearance of the carbonyl stretching band at ca. 1550 cm(-1) indicates the presence of croconate ion incorporated in the structure. The Raman spectrum of the material shows several vibrational bands related to the oxocarbon moiety; most of them are shifted in comparison with the free ion. These shifts can be understood in terms of strong hydrogen bonding interactions between water molecules and the oxocarbon moiety. The low temperature methodology proposed here can be well used in the preparation of new phosphate glasses containing organic moieties opening the route to an entirely new class of hybrid glasses. (c) 2004 Elsevier B.V All rights reserved.

Effect of the type of environmental stress on the emergence of sunflower (Helianthus annus L.), soybean (Glycine max (L.) Merril) and maize (Zea mays L.) seeds with different levels of vigor

Sowing is a critical time in the cycle of a crop and the seeds are frequently exposed to adverse conditions that may compromise the establishment of seedlings in the field. on this basis, the objective of the present study was to determine the effect of types of environmental stress on the emergence of sunflower, maize and soybean seeds with different levels of vigor. High vigor seeds were artificially aged in order to obtain medium and low vigor seeds and then they were sown in clay soil in plastic boxes and submitted to the following types of environmental stress during the germination process : 1) high temperature (35degreesC), 2) low temperature (15 or 18degreesC), 3) water excess (Psi > -0.0001 MPa), 4) water deficiency (Psi approximately equal to -1.1; -1.2 and -0.6 MPa for sunflower, maize and soybean, respectively), 5) sowing at a depth of 7 cm and 6) pathogenic infection of sunflower seeds with Alternaria helianthi, of maize seeds with Fusarium moniliforme and of soybean seeds with Colletotrichum dematium, var. truncata. The results were compared to those obtained with controls sown under optimal condition. It was concluded that: 1) the effect of seed vigor on emergence depends on the type of enviromental stress to which the seeds are exposed, 2) the stress to which the the seeds demonstrated highest sensitivity varied with species and 3) high temperature stress was the one that most impaired the emergence of the three species.