L'efecte del canvi climàtic sobre els precursos de les aromes minoritàries del raïm

Aquest treball forma part d'un macroprojecte que pretén centrar-se en l'estudi de l'evolució dels precursos de les aromes minoritàries a la zona de la Rioja. Neix d'una inquietud que intenta esbrinar quins efectes globals té el canvi climàtic sobre les propietats químiques del raïm. Per tal de que es desenvolupi aquest projecte, prèviament es disposa d’un seguit de dades històriques i analítiques que permetran analitzar diferents paràmetres dels anys considerats com a anys d'estudi, que són 2009, 2010 i 2011. Els principals paràmetres que s'estudiaran són el GDD (Growing Degree Day) i la pluviometria, analitzant-los en tres collites diferents pels tres anys d’estudi , primer per separat i després junts per veure el seu efecte. Posteriorment, es farà un estudi més acurat de les diferents famílies químiques que hi ha, quina és la seva evolució així com, quines són les propietats químiques dels seus precursors minoritaris.

Líquidos iônicos contendo o cátion dialquilimidazólio: estrutura, propriedades físico-químicas e comportamento em solução

Ionic liquids, in specially those based on the 1,3-dialkylimidazolium cation, have been receiving special attention in differents areas due to their interesting physical-chemical properties. In this work, some aspects of their structure (in both solid and liquid state) and its relationships with their properties are reviewed.

Aquecimento em forno de microondas / desenvolvimento de alguns conceitos fundamentais

The microwave oven became a common domestic equipment, due mainly to the short time spent to heat foods. One of the most interesting characteristics of the microwave oven is the selective heating. Different from the conventional oven, where the heating is not selective, the heating by microwave depends on the chemical nature of the matter. Many Students of Chemistry have no knowledge of the principles involved in this selective heating, in spite of the daily microwave oven use. The heating by microwave is feasible for chemistry courses. In discussions about the microwave absorption by the matter it is possible to explore chemical properties like: heat capacity, chemical bound, molecular structure, dipole moments, polarization and dielectric constant. This paper presents the basic principles involved in the microwave heating. It is proposed a simple and inexpensive experiment that could be developed in general chemistry courses, to illustrate the relationship between heating and the chemical properties of some solvents. Experiments to check the power of the microwave oven are also proposed.

Preparação de compostos de alumínio a partir da bauxita: considerações sobre alguns aspectos envolvidos em um experimento didático

Aluminum metal and aluminum compounds have many applications in several branches of the industry and in our daily lives. The most important raw material for aluminum and its manufactured compounds is bauxite, a rock constituted mainly by aluminum hydroxides minerals. In this work, a didactic experiment aiming the preparation of alumina and potassium alum starting from bauxite is proposed for undergraduate students. Both compounds are of great commercial, scientific and historical interest. The experiment involves applications of important chemical principles such as acid-base and precipitation. Some chemical properties and uses of aluminum compounds are also illustrated.

Avaliando a contaminação por elementos traço em atividades de maricultura: resultados parciais de um estudo de caso realizado na ilha de Santa Catarina, Brasil

Adopting the perspective of human health risk assessment, an interdisciplinary research group has been investigating since 1998 the quality of mussels and oysters cultivated in coastal zones of Santa Catarina State. Evaluation of physico-chemical parameters considered relevant in measuring the degree of eutrophication showed values compatible with the dynamics of well balanced environmental systems. Concentrations of metallic and semi-metallic elements in seawater and bivalves were found to be similar to or lower than those found in Chile, Greenland and the USA. Further investigations focusing upon sediments will provide new and useful data for the management of sustainable mariculture strategies in Brazil.

Caracterização e estabilidade físico-química de sistemas poliméricos nanoparticulados para administração de fármacos

Polymeric nanoparticle systems such as nanocapsules and nanospheres present potential applications for the administration of therapeutic molecules. The physico-chemical characteristics of nanoparticle suspensions are important pre-requisites of the success of any dosage form development. The purpose of this review is to present the state of the art regarding the physico-chemical characterization of these drug carriers, in terms of the particle size distribution, the morphology, the polymer molecular weight, the surface charge, the drug content and the in vitro drug release profiles. Part of the review is devoted to the description of the techniques to improve the stability of colloidal systems.

NMR investigation and theoretical calculations of the effect of solvent on the conformational analysis of 4',7-di-hydroxy-8-prenylflavan

The NMR conformational study of 4',7-di-hydroxy-8-prenylflavan 1 was carried out in acetone-d6, DMSO-d6 and CDCl3 which enabled the proposition of three conformations, namely 1a, 1b and 1c, differing in the position of the prenyl group. Geometry optimizations performed using AM1 method showed that 1a (deltaHf = -86.2 kcal/mol) is as stable as 1b (deltaHf = -85.1 kcal/mol) and 1c (deltaHf = -85.4 kcal/mol). When the solvent was included, the calculations showed that the solute-solvent interactions could be explained either in the light of the electronic intermolecular delocalization or the electrostatic character between solute and solvent. Theoretical calculations (HF/6-31G*, deltaFT/BLYP/6-31G*, and deltaFT/B3LYP/6-31G*) showed that the combination of these types of interactions present in each solute-solvent system, dependent on the chemical properties of the solvent, lead to different spatial arrangements of the prenyl group, which in turn determined the conformation of 1.

Quantifying seasonality along a latitudinal gradient: from stream temperature to growth of invasive mosquitofish

Most ecosystems undergo substantial variation over the seasons, ranging from changes in abiotic features, such as temperature, light and precipitation, to changes in species abundance and composition. How seasonality varies along latitudinal gradients is not well known in freshwater ecosystems, despite being very important in predicting the effects of climate change and in helping to advance ecological understanding. Stream temperature is often well correlated with air temperature and influences many ecosystem features such as growth and metabolism of most aquatic organisms. We evaluated the degree of seasonality in ten river mouths along a latitudinal gradient for a set of variables, ranging from air and water temperatures, to physical and chemical properties of water and growth of an invasive fish species (eastern mosquitofish, Gambusia holbrooki ). Our results show that although most of the variation in air temperature was explained by latitude and season, this was not the case for water features, including temperature, in lowland Mediterranean streams, which depended less on season and much more on local factors. Similarly, although there was evidence of latitude-dependent seasonality in fish growth, the relationship was nonlinear and weak and the significant latitudinal differences in growth rates observed during winter were compensated later in the year and did not result in overall differences in size and growth. Our results suggest that although latitudinal differences in air temperature cascade through properties of freshwater ecosystems, local factors and complex interactions often override the water temperature variation with latitude and might therefore hinder projections of species distribution models and effects of climate change

A destilação simulada na indústria do petróleo

One of the most widely used physico-chemical characterizations of hydrocarbon mixtures is the determination of their boiling point distribution. Knowledge of the boiling range of crude oils and petroleum products is essential to ensure the correct specification of final products and to control refinery processes. Simulated distillation, a GC based process, has been playing this role for the past decades in the petroleum industry. The main purpose of this work is to show the fundamentals of this technique as well as its present trends.

Óxido nítrico: propriedades e potenciais usos terapêuticos

Nitric oxide (•NO) is a substance that acts as a second-messenger and is associated with a number of important physiological functions such as regulation of the vascular tonus, immune modulation and neurotransmission. As a physiological mediator, alteration of its concentration level may cause pathophysiological disfunctions such as hypertension, septic shock and impotence. Possible therapeutic approaches are being developed to control NO levels in vivo. We review herein the main physical and chemical properties of •NO, its biological functions and available chemical interventions to reduce and increment its physiological concentration levels. Recent developments in the field are also highlighted.

Filmes de nanodiamantes para aplicações em sistemas eletroquímicos e tecnologia aeroespacial

The goal of this work is to show the use of undoped nanodiamond films as a new material for electrochemical and aerospace applications. Correlation between the applications and physico-chemical features of nano and conventional CVD polycrystalline diamond films are presented. An important and innovative application of these nanodiamonds is organic electrosynthesis, including pharmaceutical and water disinfection products, as well as electroanalytical applications, for example, development of biosensors for detection of glucose, glutamate and dopamine. In aeronautics and space developments, these nanodiamonds could be used as electrodes in rechargable batteries and in tribological investigations.

Cinética e caracterização físico-química do fermentado do pseudofruto do caju (Anacardium occidentale L.)

The production of cashew apple wine has the purpose of minimizing the wastage in the Brazilian cashew production. Knowing that the cashew apple fermentation produces a good cashew wine, a study of alcoholic fermentation kinetics of the cashew apple and the physico-chemical characterization of the product were made. The cashew wine was produced in an stirred batch reactor. The results of the physico-chemical analysis of volatiles, residual sugars, total acidity and pH of cashew wine showed that their concentrations were within the standard limits established by the Brazilian legislation for fruit wines.

Aspectos físico-químicos e biológicos relacionados à ocorrência de Biomphalaria glabrata em focos litorâneos da esquistossomose em Pernambuco

This study analyzes the physico-chemical and biological parameters of freshwater aquatic environments in coastal areas of the State of Pernambuco, Brazil, where snail vector foci and cases of schistosomiasis have been recorded. The tests were carried out using standard methods and sediments were analyzed using the X-ray fluorescence technique. The micro-algae were analyzed using conventional microscopy. The most abundant chemical elements in the sediments were Fe, Ca, Si and Al and there were high concentrations of electrolytes in comparison with data published in the literature. The mean values for salinity (7.7 g/L) and sulfate (489 mg/L) were much higher than normal for freshwater environments. The micro-algae identified are those that inhabit environments with higher levels of salinity. The snail Biomphalaria glabrata seems, therefore, to be more tolerant to salty environments and this constitutes a risk of spread of schistosomiasis.

Argilas especiais: argilas quimicamente modificadas - uma revisão

The simultaneous use of the specific values of some structural and chemical properties of clay minerals, such as kaolinite, montmorillonite and talc, allows the development of new properties for these materials, especially in relation to the external and internal microcrystal surfaces. These developments are very diversified for montmorillonite, due to the high specific surface area, expansible basal spacings, easy intercalation inside the 2:1 structural layers and a reversible and high cation exchance capacity. The review presents examples of chemical modifications on kaolins, montmorillonites (bentonites) and talcs.

Cucurbiturilas

This review article describes the properties and the main applications of the glicol[n]urils. These compounds are cavitands made of n glycolurilic units arranged in circles, giving rise to extremely symmetric toroidal molecules. The cucurbit[n]urils create this way variable-sized hydrophobic cavities and the glycolurilic carbonyles delimit two portals on these cavities, slightly narrower than their internal radii. Their structure, physical and chemical properties favor the formation of inclusion compounds, and turn them into important building blocks for supramolecular chemistry and nanotechnology.