Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Three samples of hydrotalcite-like materials (HTC) were synthesized and their structural characteristics were compared with two HTCs obtained commercially. Thermal analyses, FT-IR, PXRD and textural analyses were used to investigate the structural differences between commercial and synthetic samples. Particularly, the memory effect was observed at temperature higher than 600 ºC. The Rietveld refinements were obtained with expressive accuracy and the statistical parameters of goodness of fit are quite satisfactory. In conclusion, the procedures adopted in synthesis of HTC produced crystalline materials with high surface area materials.

Health knowledge of prostitutes in Saigon, Vietnam: a study of health attitudes and habits relating to venereal diseases taken from a group of prostitutes

A study of health knowledge and practices of prostitutes is presented here. The study took place at the V. D. Center in Saigon, Vietnam. It was designed with the objective of obtaining information to be used in preparing an educational program to be offered to the prostitutes at the Center, and for using, in preparing educational materials with focus on V. D. prevention. The outline of a course is also presented.

Development of natural products as drugs acting on central nervous system

We have recenty studied several natural product constituents which have effects on the CNS. (1) Tetrahydropalmatine (THP) and its analogues were isolated from Corydalis ambigua and various species of Stephania. (+)-THP and (-)-THP posses not only analgesic activity, but also exert sedative-tranquillizing and hypnotic actions. Results of receptor binding assay and their pre-and post-synaptic effects on dopaminergic system indicate that (-)-THP and (-)-stepholidine are dopamine receptor antagonists while (+)-THP is a selective dopamine depletor. (2) 3-Acetylaconitine (AAC) is an alkaloid isolated from Aconitum flavum. The relative potency of analgesic action of AAC was 5.1-35.6 and 1250-3912 times that of morphine and aspirin, respectively. The analgesic effect of AAC was antagonized by naloxone, but was eliminated by reserpine. In monkeys, after AAC was injected for 92 days, no abstinence syndrome was seen after sudden AAC withdrawal or when challenged with nalorphine. (3) Huperzine A (Hup-A) is an alkaloid isolated from Huperzia serrata which was found to be a selective ChE inhibitor and could improve learning and retrieval process. Preliminary clinical studies showed that Hup-A improve short-and long-term memory in patients of cerebral arteriosclerosis with memory impairment. (4) Ranamargarin is a new tetradecapeptide isolated from the skin of the Chines frog Rana margaratae. This peptide may mainly act on NK-1 receptor.

LAYERED DOUBLE HYDROXIDES: NANOMATERIALS FOR APPLICATIONS IN AGRICULTURE

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

Soybean cultivar BR-16-AHAS tolerance to the herbicide imazapyr

The objective of this work was to evaluate the effect of the transgenic soybean BR-16-AHAS genetic constitution on the tolerance to the herbicide imazapyr. BR-16-AHAS was crossed with ten other genotypes. The experimental design was a complete randomized block, in a 2x12x3 factorial arrangement, with two sowing periods (winter and summer), twelve crossing groups and three plant positions (upper, mid and lower), with three replicates. The plants were treated with 100 g ha-1 a.i. of imazapyr at the V3/V4 stage. For each position of the plant (upper, mid and lower), the following variables were assessed: number of pods, number of seeds, seed weight, number of seeds per pod and the 100 seeds weight. The effect of the herbicide varied according to the more affected plant position (upper, mid and lower) of each genotype. The use of the same gene ahas of BR-16-AHAS, in various genotypes, results in materials with good tolerance to imazapyr; tolerance levels depend not only on the ahas gene, but also on the presence of other genes.

Transdutores potenciométricos a base de polímeros condutores: aplicações analíticas

A review is given about the most relevant advances on the analytical applications of conducting polymers in potentiometric sensors. These organic polymers represent a new class of materials with conducting properties due to its doping by ions. Several polymers already were synthesized such as polypyrrole, polyaniline, polythiophene, among others. Particular attention is devoted to the main advantages supplied by ion selective electrodes and gas sensors using conducting polymers, as well as the incorporation of bioactive elements in these polymers for the construction of biosensors. The correlation between structure, stability and ability to ion exchange of some conducting polymers applied as potentiometric transducers, is discussed.

Síntese de poli(p-xililenos)

Poly(p-xylylenes), PPX, are a class of high performance insulating materials with many applications in the electronic component industry. We review herewith the most important synthetic routes to these polymers, described in the literature, since 1904.

Decomposição de precursores metalorgânicos: uma técnica química de obtenção de filmes finos

This review focus the more relevant foundations and applications of the Metallo-Organic Decomposition (MOD) technique, mainly within the last decade. The technique has grown significantly, mainly due to the good results concerning the preparation of multicomponent oxide systems with composition, structural and morphologic control, in a relatively simple way. This opened new opportunities to obtain materials with well-defined electrical and optical properties.

Resistência química de vitro-cerâmicos pertencentes a sistemas Li2O-ZrO2-BaO-SiO2 frente ao tratamento com soluções ácidas e básicas

The chemical durability of the Li2O-ZrO2-BaO-SiO2 system was examined by determination of the Vickers hardness. The dependence of hardness and of the chemical resistance with BaO addition was investigated. The experimental results indicate that the hardness increases with the BaO content. The samples surface's morphology submitted to the chemical treatment in acidic (H2SO4) and basic (KOH) solution was accompanied by scanning electron microscopy. The chemical durability of the materials with BaO showed better than the glass ceramic without this content. These materials treated with H2SO4 solution showed a preferential attack to the silica rich sites.

Desenvolvimento de um dispositivo para obtenção de monocristais de ligas à base de cobre

This paper describes the drawing, construction and optimization of a device, which can be used to obtain single crystals of different metallic materials with melting point from 550 to 1050 ºC. Components of ease obtaining and of low cost were used. The device was based on the modified Bridgman technique and it was used to obtain single crystals of copper-based alloys. The temperature axial profiles and a difference less then 1% in the temperature between the wall and the center of the ceramic tube in the critical region for obtaining single crystals of good quality indicated that the oven presents a good thermal stability. Single crystals of CuZnAl and CuAlAg alloys of good quality were growth and characterized using optical microscopy and Laüe X-ray back reflection.

Influência do agente precipitante na preparação do óxido de nióbio (V) hidratado pelo método da precipitação em solução homogênea

This work reports the preparation, characterization and study of the ion exchange behavior of hydrous niobium oxide prepared by a homogeneous precipitation method. The precipitating agent was obtained in aqueous solution by thermal decomposition of urea or ammonium carbonate. The compounds were chemically and physically characterized by X-ray diffractometry, thermal analysis (TG/DTG), surface area measurements and ion exchange behavior with sodium. The materials prepared with ammonium carbonate presented a higher degree of crystallinity and better ion exchange capacity with sodium than materials prepared with urea. In the homogeneous precipitation method, materials were obtained with specific surface area of 123 - 224 m² g-1. A variation of the preparation process produced hydrous niobium oxide with a different degree of hydration and specific surface area. This provided materials with different physico-chemical properties.

Estratégia supramolecular para a nanotecnologia

Brazilian science is evolving rapidly and steadly in the last 10 years, reaching the 15º place in the international ranking. Research in nanotechnology is following a similar way generating new scientific and technological knowledge in several frontiers but specially in the interfaces of two or more areas, where Chemistry is consolidating itself as a central science. In this context, the supramolecular approach is a very promissing one because it allows the build-up of a chemical inteligence using all the sistematized knowledge for the design and development of new nanomaterials and products. The great challenge of Chemistry is not decrease the dimensionality of the materials but instead find ways to increase the dimensionality and structural complexity keeping strict control on the interactions between the components, in order to generate materials with new properties and functionalities. Unfortunately, the current vigorous advancement of scientific research has not been followed by the transformation of such know-how into patents and produts. Therefore much efforts should be devoted to build a national science and technology program, joining all the segments of the society involved in the technological development (university, institutes of technological research, industry and government) in order to promote the furtherance of the Brazilian technological base. Only in this way it is possible to evolve to a technological society capable to transform the scientific knowledge into wealthy, thus sustaining the socioeconomic development of the country.

Produção de matéria seca e de grãos por plantas de feijoeiro (Phaseolus vulgaris L.) cultivadas em solos tratados com metais pesados

This work aimed at evaluating the contents of extractable Cd, Pb, Zn and Cu with a solution of DTPA (diethyleneaminopentacetic acid) and to relate them with the production of dry material and grain production of bean plants under two conditions of experimentally contaminated soil materials with Cd, Pb, Cu and Zn: (i) samples of distrofic red latosol and (ii) humic yellow-red latosol. A decrease in the yield of dry matter was observed for all treatments, if compared with the zero-dose control sample; the grain yield was affected for the soil samples treated with Cd and Cu but only slightly for those treated with Pb and Zn.

Óleos essenciais no Brasil: aspectos gerais, desenvolvimento e perspectivas

Essential oils are extracted by steam distillation of plants or cold pressing of citrus fruit pericarp. They are used in food, cosmetic, personal care and pharmaceutical industries. In Brazil, oils from orange and related products contribute to near 97% to the positive commercial performance of the sector. Predatory exploitation and the availability of new sources of raw materials, with more attracting prices, changed the paradigm. Prospective studies, sustainable use of Brazilian biodiversity, domestication of exotic species with commercial relevance, the use of breeding techniques and the development of new applications for essential oils are thematic lines, usually multidisciplinary, which have been prompting the expansion of the research on essential oils. This paper presents an analysis on essential oils balance trade from 2005 to 2008 and some historical data on research and production of essential oils in Brazil.

Materiais híbridos à base de sílica obtidos pelo método sol-gel

This review deals with silica based hybrid materials obtained by the sol-gel method. It involves concepts, classifications and important definitions regarding the sol-gel method that allows obtaining materials with organic and inorganic components dispersed in a molecular or nanometric level. We discuss the properties and characteristics of hybrid materials related to experimental synthesis conditions. We devote a special attention to the nanostructured materials, where the self-organization is imposed by the organic component. Finally, we present some important applications of these materials based on their specific properties.