O efeito SERS na análise de traços: o papel das superfícies nanoestruturadas

Surface-Enhanced Raman Scattering - SERS - underwent huge advances since a single-molecule Raman spectrum was obtained in 1997. New theoretical and experimental approaches emerged since then leading to a better understanding of the enhancement mechanisms and to a significant improvement in the Raman signal. This review presents the current status of the SERS effect and the promising ways of designing and preparing high performance SERS-active substrates.

Composição química de um resíduo alcalino da indústria de papel e celulose (DREGS)

Dregs is an alkaline solid by-product generated in the cellulose manufacturing industry that could be used to correct soil acidity. The present study aimed to evaluate the chemical composition of this product and some of its properties. The dregs presented 354 g kg-1 of calcium, neutralization capacity of 80.3%, and pH 10.7, besides low concentration of sodium (10.2 g kg-1), lead (62.9 mg kg-1) and cadmium (5.6 mg kg-1). Thus, it is a product that can safely be used to increase the soil pH.

O fabrico e uso da pólvora no Brasil colonial: o papel de alpoim na primeira metade do século XVIII

Gunpowder played a significant role in colonial Brazil. This reached a climax in the eighteenth century, when the country's large gold output enticed the greed of many. The French invasion of Rio de Janeiro in 1711 made the city's defense even more pressing to the metropolis. Brigadier Alpoim symbolized this reaction. He was a leading Luso-Brazilian engineer of that century, whose multiple activities set him apart in colonial life. These activities included a pioneer role in teaching the manufacture and use of gunpowder, about which he wrote extensively during the first half of the eighteenth century. His work is thus among the first to treat chemical technology in the colony at such an early age.

Glutationa e enzimas relacionadas: papel biológico e importância em processos patológicos

Glutathione (GSH) and related enzymes are pivotal for the normal functioning of several important biological processes. In this review we discuss the biosynthesis and the catalytic cycles of glutathione as well as the major GSH-related enzymes. We also present how glutathione and enzymes are involved in cancer and the chromatographic and non-chromatographic methods used to analyze glutathione and/or its derivatives.

Considerações sobre o papel da comunicação científica na educação em química

In the present work, we provide some considerations about the role of scientific communication in Chemistry Education. Such considerations may subsidize the development of communication in scientific language by Chemistry students. These considerations are based on information collected during a participatory research for the production of didactic material about scientific communication. The meetings were audio recorded and the contents of the participants' speeches were divided into categories. The category analysis supported the elaboration of the considerations.

O papel governamental como ator essencial para a P&D de medicamentos: um estudo de casos

The importance of natural products as a source of new high value-added drugs has, no doubt, transformed Brazilian megadiversity into one of the country's most valuable and strategic assets. Thus the rational exploration of the Brazilian flora on an economic basis should be considered as part of a national development strategy. In this respect, governmental mechanisms to stimulate regulation on the access, bioprospection and industrial use of natural products represent a crucial issue. The aim of this paper is to show how the incentives and institutional arrangements that led to one of the greatest breakthroughs in the pharmaceutical industry, the development and commercialization of the anti-cancer agent Taxol, could be applied to the Brazilian case.

Formação de micelas mistas entre o sal biliar colato de sódio e o surfactante aniônico dodecanoato de sódio

Mixed-micelle formation between sodium chlolate (NaC) and the anionic surfactant sodium dodecanoate (SDoD) in Tris-HCl buffer solutions, pH 9.00, varying the molar fraction of the surfactants, was investigated by means of electrical conductivity and steady-state fluorescence of pyrene. The critical micelar concentration (cmc) was measured from the equivalent conductance versus the square root of the molar surfactant concentration plots and the regular solution theory (RST) was used to predict the mixing behavior. The I1/I3 pyrene ratio-surfactant concentration plots were used as an additional technique to follow the behavior and the changes in the micropolarity of the mixed micelles.

O papel dos sulfetos volatilizados por acidificação no controle do potencial de biodisponibilidade de metais em sedimentos contaminados de um estuário tropical, no sudeste do Brasil

Measurements of acid volatile sulfide (AVS) and simultaneously extracted metals (SEM) were combined in order to verify the ecological hazard of contaminated sediments from the Santos-Cubatão Estuarine System (SE Brazil), which is located in one of the most industrialized areas in the Latin America. Intertidal sediments from the Morrão River estuary were collected seasonally in short cores. The redox conditions, organic matter contents and grain-size were the main controlling factors on SEM distribution. However, clear relationships among these variables and AVS were not observed. The molar SEM/AVS ratios were frequently > 1 especially in the summer, suggesting major metal bioavailability hazard in this humid hot season.

Previsão das propriedades físicas do papel kraft por espectroscopia no infravermelho próximo (NIR) e regressão por mínimos quadrados parciais (PLS)

The main objective of the present work is represented by the characterization of the physical properties of industrial kraft paper (i.e. transversal and longitudinal tear resistance, transversal traction resistance, bursting or crack resistance, longitudinal and transversal compression resistance (SCT (Compressive Strength Tester) and compression resistance (RCT-Ring Crush Test)) by near infrared spectroscopy associated to partial least squares regression. Several multivariate models were developed, many of them with high prevision capacity. In general, low prevision errors were observed and regression coefficients that are comparable with those provided by conventional standard methodologies.

Comparação entre um trocador aniônico de sal de amônio quaternário de quitosana e um trocador comercial na extração de fósforo disponível em solos

The present work aimed modify chemically the chitosan (QTS) surface to obtain a reticulate chitosan quaternary ammonium salt (SAQQR), and compare this anionic exchanger with an commercial ion exchanger in the extraction of available phosphorus in soils. The results showed that the two exchangers are identical, extracting similar and proportional quantities of available phosphorus in the studied soils, and the anionic exchanger of SAQQR provides a high chemical stability, not affected by the pH difference of soils.

Caracterização cromatográfica de compostos orgânicos presentes nos resíduos sólidos provenientes de indústria de reciclagem de papel e sua aplicação na produção de briquetes de carvão vegetal

Recycling of paper in industrial scale has become an established practice worldwide. In this work, organic compositions of three different kinds of sludge generated in recycle paper industry were studied, and the incorporation of one of those sludge in briket was also investigated. The characterization of organic compounds in sludge samples and briket was performed using Gas Chromatography coupled with Mass Spectrometry after a Soxhlet extraction. Different chemical classes were identified in each type of sludge, but just the sludge composed by cellulose residue did not presented polyaromatic hydrocarbons. Four formulations of sludge incorporated with charcoal for briket production were evaluated.

Influencia de variables de formulación en la viscosidad de emulsiones de surfactante aniónico-aceite-agua

Phase transition and viscosity behavior of emulsified systems were studied after modifying their physicochemical formulation. Effects of concentration and nature of salts and n-alcohols, and water/oil relation on the rheological properties of emulsions were also studied. Pre-equilibrated systems were emulsified according to an agitation procedure, and the viscosity (cP) was measured at different shear rates ranging from 1 to 300 s-1. The phase behavior, as well as the emulsion type based on electrolytic conductivity, was observed. Several interpretations of the flow and viscosity curves of emulsions were made through the estimation of rheological parameters such as consistency index "k" and behavior index "n".

Determinação simultânea de carbamazepina, fenitoína e fenobarbital em sangue seco em papel por cromatografia líquida de alta eficiência

Carbamazepine, phenobarbital and phenytoin were determined in dried blood spots (DBS) by high performance liquid chromatography, after extraction of 8 mm DBS using a mixture of acetonitrile and methanol. Analytes were separated by reversed-phase chromatography, with a run time of 17 minutes. Intra-assay and inter-assay precisions were in the 5.3 to 8.4% and 3.3 to 5.2% ranges, respectively. Accuracy was in the 98.8 to 104.3% range. The method had sensitivity to detect all analytes at levels below minimum therapeutic concentrations. The analytes were stable at 4 ºC and room temperature for up to 12 days and at 45 ºC for 9 days. The method was applied to 14 paired clinical samples of blood serum and DBS.

MOTIVAÇÃO PARA A CARREIRA DOCENTE E CONSTRUÇÃO DE IDENTIDADES: O PAPEL DOS PESQUISADORES EM ENSINO DE QUÍMICA

This research aims to identify the reasons that lead students to pursue a specific course of chemistry teacher training, i.e., their perspectives on the course and the teaching career, and if they are motivated by trainers to become basic education (BE) teachers. It was concluded that most students did not want to be teachers of BE. They identified through the social context of the course that the teachers focused on the area of chemistry teaching sought to motivate them for this career, whereas the teachers of these specific areas of chemistry encouraged them to seek other career opportunities.