Water splitting is a promising process to produce hydrogen from friendly feedstock and solar energy. In this work we have evaluated binary (GO-CdS) and ternary (Pt-GO-CdS) hybrid photocatalysts for hydrogen production assisted by visible light irradiation. Cadmium sulfide and composites with GO were prepared by sonochemical and thermal methods. GO addition took place by different strategies: during the synthesis or by mechanical mixture. A variety of configurations was tested and the best performance in hydrogen production among all materials was the ternary photocatalyst named Pt(GO/CdSTT), whose hydrogen production rate was 651 µmol gcat-1 h-1. Such material was obtained by thermal method with GO addition during the synthesis. Additionally, the XRD and Raman analyses have confirmed the GO photoreduction during photocatalytic hydrogen evolution.

This paper deals with the solubility and reactivity of gases, especially in water, covering the main aspects that influence the dissolution process, namely polarizability of atoms or molecules in gas phase and their ability to react with the solvent. The discussion highlights the importance of solubility of gases in several biological processes, such as respiration and photosynthesis, hydrogen storage and industrial processes, as the production of carbonated beverages. The discussion also addresses the importance of gas solubility in atmospheric chemistry and aquatic environments.

O diagnóstico de infecção assintomática por Leishmania (Leishmania) chagasi tem assumido crescente importância nos últimos anos. A expansão da leishmaniose visceral pode estar associada a outras vias de transmissão tais como transfusional, congênita, ou mesmo vetorial, sendo os indivíduos com infecção assintomática, potenciais reservatórios. Ademais, a identificação da infecção poderia auxiliar na condução dos pacientes com condições de imunossupressão (HIV, transplante, uso de imunomoduladores) e na avaliação da efetividade das medidas de controle. Neste estudo, foram avaliados clinicamente 149 indivíduos residentes em área endêmica de leishmaniose visceral e realizada a reação em cadeia da polimerase (PCR) gênero-específica, testes sorológicos e teste de Montenegro. Destes, 49 (32,9%) apresentaram PCR positiva, dos quais nenhum evoluiu com clínica de leishmaniose visceral nos três anos subsequentes. Não houve associação entre o resultado da PCR, dos exames sorológicos e do teste cutâneo. A positividade da PCR em indivíduos da área endêmica estudada não indicou risco de progressão para leishmaniose visceral e também não foi associada à maior positividade dos testes sorológicos.

The diagnosis of asymptomatic infection with Leishmania (Leishmania) chagasi has become more important over recent years. Expansion of visceral leishmaniasis might be associated with other routes of transmission such as transfusion, congenital or even vector transmission, and subjects with asymptomatic infection are potential reservoirs. Moreover, the identification of infection may contribute to the management of patients with immunosuppressive conditions (HIV, transplants, use of immunomodulators) and to the assessment of the effectiveness of control measures. In this study, 149 subjects living in a visceral leishmaniasis endemic area were evaluated clinically and submitted to genus-specific polymerase chain reaction (PCR), serological testing, and the Montenegro skin test. Forty-nine (32.9%) of the subjects had a positive PCR result and none of them developed the disease within a follow-up period of three years. No association was observed between the results of PCR, serological and skin tests. A positive PCR result in subjects from the endemic area did not indicate a risk of progression to visceral leishmaniasis and was not associated with a positive result in the serological tests.

Hidrogênio é considerado o vetor energético do futuro por ser não poluente e muito flexível quanto à conversão a diferentes formas de energia, como calor por combustão ou energia elétrica via células a combustível. Tradicionalmente, o hidrogênio é produzido a partir da reforma a vapor de gás natural de origem fóssil, o que torna a implantação efetiva da economia de hidrogênio insustentável do ponto de vista ambiental. Para contornar esse problema, diversas rotas de produção de hidrogênio a partir de fontes renováveis estão sendo propostas. Pesquisas recentes apontam a reforma foto-induzida de biomassa como uma possibilidade promissora, uma vez que utiliza radiação solar, fonte inesgotável de energia e matérias primas renováveis como derivados de biomassa e água. Os trabalhos nesse campo são ainda muito incipientes, porém bastante animadores. O processo consiste na combinação da decomposição fotocatalítica da água com a reação de fotodecomposição de substâncias orgânicas mediadas por um semicondutor irradiado. Neste processo, a reação de oxidação da água é suprimida pela presença de um doador de elétrons de sacrifício (biomassa), assim como a formação de radical superóxido quando a reação é realizada em condições anaeróbicas. Os resultados de reforma foto-induzida apontam para rendimentos semelhantes ou superiores a outros processos de produção de hidrogênio a partir de biomassa como hidrólise enzimática e reforma catalítica em fase aquosa. No entanto, os trabalhos desenvolvidos até o momento estão focados no TiO2, o que limita a porção absorvida da radiação solar à luz UV. Deste modo, o grande desafio atual nesta área é o desenvolvimento de semicondutores de banda estreita capazes de conduzir a reação de reforma foto-induzida de biomassa com luz visível, que consiste de cerca de 40% da radiação solar.

Hydrogen is considered the energy carrier of the future because of its clean and very flexible conversion into different forms of energy, e.g., into heat via combustion or electricity via fuel cells. Traditionally, hydrogen is produced from natural gas steam reforming from fossil fuels making the effective implementation of hydrogen economically and environmentally unsustainable. To overcome this problem, several routes are being proposed for hydrogen production from renewable sources. Recent research points to the photoinduced reforming of biomass as a promising possibility, since it uses solar radiation, an inexhaustible source of energy, and raw materials derived from renewable sources such as biomass and water. Studies in this field are still incipient but quite encouraging. The process combines photocatalytic water splitting with the photodecomposition of organic compounds mediated by an irradiated semiconductor. In this process, the water oxidation reaction is suppressed by a sacrificial electron donor (biomass), as well as the formation of superoxide radicals when the reaction is carried out under anaerobic conditions. The hydrogen production rates from photoinduced reforming are similar or superior to other processes, including biomass hydrolysis and aqueous phase reforming. However, the major researches into hydrogen production by photoinduced reforming of biomass derivatives have focused on TiO2, which limits the portion of solar radiation absorbed as UV light. Thus, the current challenge in this field is the development of narrow band gap semiconductors that are able to drive the photoinduced reform of biomass with visible light, which corresponds to about 43% of solar radiation.

The solubility of sulfides is discussed in this article based on the factors that can influence this property, such as predominant type of chemical bonds and structures formed in many compounds. For soluble sulfides, considerations are made on the thermodynamic parameters and the acid-base equilibrium, since the sulfide anion is extensively hydrolyzed in aqueous solutions. On the other hand, for the insoluble sulfides, the discussion concerned the influence of structural factors that will be determinant for the low solubility.

The water content in seafoods is very important since it affects their sensorial quality, microbiological stability, physical characteristics and shelf life. In this study, thermoanalytical techniques were employed to develop a simple and accurate method to determine water content (moisture) by thermogravimetry (TG) and water activity from moisture content values and freezing point depression using differential scanning calorimetry (DSC). The precision of the results suggests that TG is a suitable technique to determine moisture content in biological samples. The average water content values for fish samples of Lutjanus synagris and Ocyurus chrysurus species were 76.4 ± 5.7% and 63.3 ± 3.9%, respectively, while that of Ulva lactuca marine algae species was 76.0 ± 4.4%. The method presented here was also successfully applied to determine water activity in two species of fish and six species of marine algae collected in the Atlantic coastal waters of Bahia, in Brazil. Water activity determined in fish samples ranged from 0.946 - 0.960 and was consistent with values reported in the literature, i.e., 0.9 - 1.0. The water activity values determined in marine algae samples lay within the interval of 0.974 - 0.979.

The solubility rules presented in the majority of introductory texts of chemistry usually do not comprise a systematic analysis of the dissolution processes, neither from a microscopic nor from a macroscopic point of view. The solubility of nitrates in aqueous solution is discussed in this article, focusing on the thermodynamic data and the properties of the nitrate ion.

O quadro clínico da toxoplasmose adquirida em pacientes imunocompetentes habitualmente não inclui manifestações neurológicas focais, o que é freqüente em pacientes imunodeprimidos, como aqueles com síndrome da imunodeficiência adquirida. Este trabalho tem como objetivo relatar o caso de uma paciente adulta que apresentou abscessos cerebrais por Toxoplasma gondii, sem evidência de qualquer fator causador de imunossupressão.

The clinical manifestations of acquired toxoplasmosis in the immunocompetent patient rarely include localized neurological signs, which are frequent in the immunosuppressed patient (Aids). The objective of this paper is to report the case of a woman with Toxoplasma gondii brain abscess, without an identified cause of immunosuppression.

The metal-catalyzed autooxidation of S(IV) has been studied for more than a century without a consensus being obtained as to reaction rates, rate laws or mechanisms. The main objective in this work was to explore the reaction between Cu(II) and SO2 in the presence of M(II), paying special attention to the formation of double sulfites like Cu2SO3.M(II)SO3.2H 2O. The two principal aspects studied were: i) a new way to prepare double sulfites with high purity degree and the selectivity in the M(II) incorporation during the salt formation.