Low-temperature synthesis of single-phase Co7Sb2O12

Polycrystalline Co7Sb2O12 compounds have been synthesized by a chemical route, which is based on a modified polymeric precursor method. In order to study the physical properties of the samples, X-ray diffraction (XRD), thermal analyses (TG and DSC), infrared spectroscopy (IR), specific surface area (BET), and magnetization measurements were performed on these materials. Characterization through XRD revealed that the samples are single-phase after a heat-treatment at 1100degreesC for 2h, while the X-ray patterns of the samples heat-treated at lower temperatures revealed the presence of additional Bragg reflections belonging to the Co6Sb2O6 phase. These data were analyzed by means of Rietveld refinement and further analyze showed that Co7Sb2O12 displays an inverse spinel crystalline structure. In this structure, the Co2+ ions occupy the eight tetrahedral positions, and the sixteen octahedral positions are randomly occupied by the Sb5+ and Co2+ ions. IR studies disclosed two strong absorption bands, v(1) and v(2), in the expected spectral range for a spinel-type binary oxide with space group Fd3m. Exploratory studies concerning the magnetic properties indicated that this sample presents a spin-glass transition at T-f similar to 64 K. (C) 2004 Elsevier B.V. All rights reserved.

Study of the alkaline earth metals with 8-hydroxyquinolinate derivatives - Calcium complexes

Metal complexes of calcium with 5,7-dibromo, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinolate were precipitated in aqueous ammonia and acetone medium, except for the solid state compound with 5,7-dichloro-8-hydroxyquinoline which hasn't been obtained under these conditions. The complexes obtained through the mentioned precipitation are Ca[(C9H4ONBr2)(2)](3).H2O, Ca[(C9H5ONI)(2)].2H(2)O and Ca[(C9H4ONICl)(2)].2.5H(2)O. Their intermediate from the thermal decomposition found through TG/DTA curves in air indicated the presence of different kinds of calcium carbonates related to the reversibility and crystalline structure, depending on the original compounds. The initial compounds and the intermediate from the thermal decomposition were also characterized through IR spectra and X-ray diffraction.

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO2 nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl2 . 2H(2)O in ethylene glycol at 195 degrees C for 4 h under vigorous stirring in air. The as-prepared SnO2 nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g(-1) beyond 100 cycles. (c) 2006 Elsevier B.V. All rights reserved.

Dinâmica espaço-temporal de taxocenoses de crisopídeos (Neuroptera: Chrysopidae) em ecossistemas naturais

In order to study the interactions of green lacewings toxocenosis on natural ecossystems, samplings were carried out in the Parque Ecologic Quedas do Rio Bonito, located in Lavras, Alto Rio Grande region, South of Minas Gerais, Brazil. The species inventory was accomplished in two vegetation types: semi-evergreen forest and open field formations, including areas of montane grassland, rocky montane grassland and "cerrado". Insects were captured with a butterfly net during 2h, walking through each vegetation formation. Sampling resulted in 1,948 specimens belonging to 30 species, of which 14 were Chrysopini and 16 Leucochrysini. Representatives of these tribes were observed both in forest and in open field formations. Species of the genera Ceraeochrysa, Chrysoperla, Chrysopodes, Plesiochrysa and Leucochrysa were found in forests and in open field formations, except for Plesiochrysa. The highest richness and diversity of species were observed in the forest. The similarity index among the communities of green lacewings in the studied areas was 27%.

Static electric fields interfere in the viability of cells exposed to ionising radiation

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

Microwave-assisted hydrothermal synthesis of nanocrystalline SnO powders

Tin oxide (SnO) powders were obtained by the microwave-assisted hydrothermal synthesis technique using SnCl2 center dot 2H(2)O as a precursor. By changing the hydrothermal processing time, temperature, the type of mineralizing agent (NaOH, KOH or NH4 OH) and its concentration, SnO crystals having different sizes and morphologies could be achieved. The powders were characterized by X-ray diffraction (X-ray), Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM) and Selected Area Electron Diffraction (SAED). The results showed that plate-like form is the characteristic morphology of growth and the TEM analyses indicate the growth direction as (200). (c) 2007 Elsevier B.V. All rights reserved.

Biodegradable Nanoparticles Containing Benzopsoralens: An Attractive Strategy for Modifying Vascular Function in Pathological Skin Disorders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dielectric properties of pure and lanthanum modified bismuth titanate thin films

We investigated the dielectric properties of pure and lanthanum modified bismuth titanate thin films obtained by the polymeric precursor method. X-ray diffraction of the film annealed at 300 degrees C for 2h indicates a disordered structure. Lanthanum addition increases gradually the dielectric permittivity of films, keeping unchanged their loss tangent. From C-V curve we can see no hysteresis behavior indicating the absence of domain structure. The decrease in the conductivity for the heavily doped Bi4Ti3O12 (BIT) must be associated to the unidentified crystal defects. For comparison, dielectric properties of crystalline BIT film were also investigated. (C) 2007 Published by Elsevier B.V.

Ebselen and cytokine-induced nitric oxide synthase expression in insulin-producing cells

Interleukin-1 (IL-1) may be a mediator of β-cell damage in insulin-dependent diabetes mellitus (IDDM). The IL-1 mechanism of action on insulin-producing cells probably includes activation of the transcription nuclear factor κB (NF-κB), increased transcription of the inducible form of nitric oxide synthase (iNOS) and the subsequent production of nitric oxide (NO). Reactive oxygen intermediates, particularly H2O2, have been proposed as second messengers for NF-κB activation. In the present study, we tested whether ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a glutathione peroxidase mimicking compound, could counteract the effects of IL-1β, H2O2 and alloxan in rat pancreatic islets and in the rat insulinoma cell line RINm5F (RIN cells). Some of these experiments were also reproduced in human pancreatic islets. Ebselen (20 μM) prevented the increase in nitrite production by rat islets exposed to IL-1β for 6 hr and induced significant protection against the acute inhibitory effects of alloxan or H2O2 exposure, as judged by the preserved glucose oxidation rates. However, ebselen failed to prevent the increase in nitrite production and the decrease in glucose oxidation and insulin release by rat islets exposed to IL-1β for 24 hr. Ebselen prevented the increase in nitrite production by human islets exposed for 14 hr to a combination of cytokines (IL-1β, tumor necrosis factor-α and interferon-γ). In RIN cells, ebselen counteracted both the expression of iNOS mRNA and the increase in nitrite production induced by 6 hr exposure to IL-β but failed to block IL-1β-induced iNOS expression following 24 hr exposure to the cytokine. Moreover, ebselen did not prevent IL-1β-induced NF-κB activation. As a whole, these data indicate that ebselen partially counteracts cytokine-induced NOS activation in pancreatic β-cells, an effect not associated with inhibition of NF-κB activation.

Phenolics from Brazilian propolis

The main phenolic constituents from Brazilian propolis, originating from Sao Paulo State, were isolated and identified: three flavonoids, a prenylated coumaric acid and two new benzopyranes, E and Z 2,2-dimethyl-6-carboxyethenyl-8-prenyl-2H-benzopyranes.

Highly excited states for the helium atom in the hyperspherical adiabatic approach

The hyperspherical adiabatic approach is used to obtain the highly excited series 1sns 1S e and 1s(n + 1)p 1P o of the helium atom. The introduction of appropriate asymptotic conditions at large values of the hyperspherical radius results in a stable algorithm that allows the calculation of the full atomic spectrum with precision of a few parts per million. Comparison with the variational calculations available in the literature shows that the accuracy of the results improves with increasing principal quantum number. We present the energies up to n = 31 which is the typical value used in multiphoton excitation experiments.

Preparation and characterization of BaBi2Nb2O9(BBN) ceramics synthetized by polymeric precursors method

Pure BBN powders and with addition of 1 and 2 wt% in excess of bismuth were obtained by Pechini Method. The powders calcined at 300°C/4h were analyzed by TG/DTA to study the temperature of organic matter decomposition. A systematic study of calcination temperature and time to the formation of the BBN phase was performed and the phase formation was accompanied by XRD. The calcined powders at 800°C during 2h were analyzed by infrared spectroscopy and by BET. The powders were isostaticaly pressed and sintered at temperatures ranging from 900°C to 1000°C. The ceramics were characterized by XRD to control the crystalline phase and by SEM to analyze the microstructure.

Infrared-to-visible frequency upconversion in transparent glass ceramics containing trivalent-rare-earth-doped nanocrystals

In this work we report on visible upconversion emission in Er 3+-, and Ho3+-doped PbGeO3-PbF 2-CdF2-based transparent glass ceramics under 980 nm infrared excitation. In erbium-doped vitroceramic samples, blue(410 ran), green(530, and 550 nm) and red(660 nm) emission signals were generated, which were identified as due to the 2H9/2, 2H 11/2, 4S3/2, and 4F9/2 transitions to the 4I15/2 ground-state, respectively. Intense red(650 nm) upconversion emission corresponding to the 5F5 - 5I8 transition and very small blue(490 nm) and green(540 nm) signals assigned to the 5F 2,3 - 5I8 and 4S2, 5F4 - 5I8 transitions, respectively, were observed in the holmium-doped samples. The 540 nm is the dominant upconversion signal in Ho3+-doped vitroceramics under 850 nm excitation. The dependence of the upconversion processes upon pump power and doping concentration are also investigated, and the main routes for the upconversion excitation processes are also identified. The comparison of the upconversion process in transparent glass ceramics and the precursor glass was also examined and the results revealed that the former present higher upconversion efficiencies.

Chorismate synthase: An attractive target for drug development against orphan diseases

The increase in incidence of infectious diseases worldwide, particularly in developing countries, is worrying. Each year, 14 million people are killed by infectious diseases, mainly HIV/AIDS, respiratory infections, malaria and tuberculosis. Despite the great burden in the poor countries, drug discovery to treat tropical diseases has come to a standstill. There is no interest by the pharmaceutical industry in drug development against the major diseases of the poor countries, since the financial return cannot be guaranteed. This has created an urgent need for new therapeutics to neglected diseases. A possible approach has been the exploitation of the inhibition of unique targets, vital to the pathogen such as the shikimate pathway enzymes, which are present in bacteria, fungi and apicomplexan parasites but are absent in mammals. The chorismate synthase (CS) catalyses the seventh step in this pathway, the conversion of 5-enolpyruvylshikimate-3-phosphate to chorismate. The strict requirement for a reduced flavin mononucleotide and the anti 1,4 elimination are both unusual aspects which make CS reaction unique among flavin-dependent enzymes, representing an important target for the chemotherapeutic agents development. In this review we present the main biochemical features of CS from bacterial and fungal sources and their difference from the apicomplexan CS. The CS mechanisms proposed are discussed and compared with structural data. The CS structures of some organisms are compared and their distinct features analyzed. Some known CS inhibitors are presented and the main characteristics are discussed. The structural and kinetics data reviewed here can be useful for the design of inhibitors. © 2007 Bentham Science Publishers Ltd.

Antimicrobial activity of coffee-based solutions and their effects on Streptococcus mutans adherence

The aim of this study was to evaluate the antimicrobial activity of different coffee solutions and their effects on the adherence of Streptococcus mutans to glass surface. Coffee solutions were prepared with three commercial products (Pilao, Mellita and Café do Ponto) by two different methods (simple and boiled) (n=15). A control group was also included in the study. For antimicrobial activity testing, tubes containing coffee solution and culture medium were inoculated with a suspension of S. mutans ATCC 35688 and incubated for 1 min 1h, 2h and 4h. Serial dilutions and plating on BHI agar were performed. S, mutans adherence to glass in presence of different coffee solutions was also tested. The number of adhered bacteria (CFU/mL) was determined by plating method. The results were statistically analyzed by ANOVA and Turkey's test. The tested coffee solutions did not reduce the number of colony forming units of S. mutans in relation to the control at all evaluation periods. All the solutions reduced significantly the adherence of S. mutans to the glass surface in relation to control. The tested coffee solutions did not present any antimicrobial effect on Streptococcus mutans, however, all the coffee solutions reduced significantly the adherence of S mutans to the glass surface.