Aspectos técnicos envolvidos na construção de um "cluster beowulf"

Beowulf cluster is perhaps the cheapest way to construct a high performance computers. The strategy of reaching a high power computing isn't so difficult, but buying and configurating should be done carefully. Technical aspects of hardware components and message-passing libraries are considered, with some results given as examples.

Aspectos regio- e estereoquímicos da adição de Michael assimétrica via iminas quirais com centros estereogênicos pré-existentes

The asymmetric Michael addition reactions using chiral imines, under neutral conditions (deracemizing alkylation process), constitute one of the main methods for the stereocontrolled elaboration of quaternary carbon centers. This protocol is based on the conjugate addition of secondary chiral enamines to electron-deficient alkenes. The focus of this report deals with the discussion of regio- and stereochemical aspects of the deracemizing alkylation process concerning enamines bearing a resident chiral center.

Queijos: aspectos químicos, bioquímicos e microbiológicos

This article presents a brief historical outline of cheese manufacture. Chemical, biochemical and microbiological aspects are presented: the main constituents of curd, the reactions involved in the development of flavour, and the role of micro-organisms and enzymes in the fermentation and maturation processes. A brief description of the characteristics of some cheeses is also given.

Gênero Baccharis (Asteraceae): aspectos químicos, econômicos e biológicos

The Baccharis genus is represented by more than 500 species distributed mainly in the tropical areas of South America. Many of them are extensively used in folk medicine in the treatment or prevention of anemias, inflammations, diabetes and stomach, liver and prostate diseases. Phytochemical and biological investigations in about 120 species resulted mainly in the isolation of clerodane and labdane diterpenes and flavonoid aglicones with the flavone unit being the most frequent.

Aspectos e fatores da produtividade em pesquisa, desenvolvimento e inovação

Comparison of national budgets for R&D is often made but it should consider the relative productivity and their factors. In Brazil, inefficiency factors as well as their causes have been diagnosed since the late 60's and solutions have been proposed within various governmental organisms, from CNPq to the strategy think tanks. Problems that hinder R&D and innovation in Brazil are reviewed from a historical perspective together with the proposed solutions providing a detailed analysis of the difficulties that have to be overcome to achieve a more effective innovation environment, adequate for the present times, challenges and opportunities.

Aspectos terapêuticos de compostos da planta Cannabis sativa

Several cannabinoid compounds present therapeutic properties, but also have psychotropic effects, limiting their use as medicine. Nowadays, many important discoveries on the compounds extracted from the plant Cannabis sativa (cannabinoids) have contributed to understand the therapeutic properties of these compounds. The main discoveries in the last years on the cannabinoid compounds were: the cannabinoid receptors CB1 and CB2, the endogenous cannabinoids and the possible mechanisms of action involved in the interaction between cannabinoid compounds and the biological receptors. So, from the therapeutical aspects presented in this work, we intended to show the evolution of the Cannabis sativa research and the possible medicinal use of cannabinoid compounds.

Cloreto isocianúrico e cloreto cianúrico: aspectos gerais e aplicações em síntese orgânica

The aromatic six-membered heterocycles having three nitrogen atoms are denominated triazines. Among these heterocycles, isocyanuric chloride and cyanuric chloride are inexpensive and readily available 1,3,5-triazine derivatives, which have been attracting significant attention of organic chemists due to their different kinds of applications, which vary from pharmaceuticals to explosives. This short overview explores their uses in synthetic methods, as chlorinating and oxidating agents and some procedures for their preparation.

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.

Aspectos estruturais relacionados ao processo de troca iônica no niobato lamelar K4Nb6O17

The niobate with formula K4Nb6O17 has a layered structure formed by stacked negative sheets and exchangeable cations in the interlayer region. In this study we discuss some structural aspects related to the ion exchange in layered hexaniobate based on X-ray diffractometry and vibrational Raman spectroscopy data. Hexaniobate has two distinct interlayer regions and the potassium ions of one interlayer in particular are preferably exchanged by other cations, leading to an interstratified material.

Aspectos químicos, biológicos e etnofarmacológicos do gênero Cassia

Species of Cassia are widely distributed in tropical and subtropical regions throughout the world, and have been extensively investigated chemically and pharmacologically.They are known to be a rich source of phenolic derivatives, most of them with important biological and pharmacological properties. Some Asian, African and Indian tribes use these species as a laxative, purgative, antimicrobial, antipyretic, antiviral and anti-inflammatory agent. Among a number of other classes of secondary metabolites, such as anthracene derivatives, antraquinones, steroids and stilbenoids, biologically active piperidine alkaloids are an especially important bioactive class of compounds that showed to be restricted to a small group of Cassia species. In this paper we present an overview of the chemical, biological and ethnopharmacological data on Cassia piblished in the literature.

Espectroscopia optogalvânica: alguns aspectos relevantes

In this work we present the optogalvanic effect in ionized gases in an historical perspective. This effect was observed for the first time by Foote and Mohler in 1925, and explained by Penning in 1928 for mixtures (Ne-Ar) and pure gases (or vapours) in 1937. Also, we show some aspects of the contributions of Romenian authors for the development of optogalvanic spectroscopy, which was used as a new technique only after 1964.

Aspectos toxicológicos e químicos da Anatoxina-a e seus análogos

Anatoxin-a and its analogues are azabicyclic alkaloids that represent one of the most powerful nicotinic agonists known for the nicotinic acetylcholine receptor (nAChR). Because of this potent mechanism of action, anatoxin-a and its derivatives represent a target for the discovery of novel drugs. Their syntheses are useful for environmental monitoring and also for pharmacokinetic/pharmacodynamic and toxicological studies. Some strategies for the synthesis of anatoxin-a and analogous compounds are described herein, covering the period from 1996 to the present date. In this review, emphasis is given to the chemical and toxicological aspects of some variants of anatoxin-a, including homoanatoxin-a and anatoxin-a(s).

A síntese da amônia: alguns aspectos históricos

The ammonia synthesis from its elements plays an important role in the survival of humankind. A short historical development of discoveries of the nitrogen cycle, the nitrogen sources for agriculture and the ammonia synthesis (in laboratory and industry) are presented. Some brief aspects of nitrogen chemistry are described. Short biographies of Fritz Haber and Carl Bosch, the main persons in this epopee, are also presented.

Biodiversidade flavonoídica e aspectos farmacológicos em espécies dos gêneros Ouratea e Luxemburgia (Ochnaceae)

This work describes the flavonoids and biflavonoids found in species of Ouratea and Luxemburgia as chemical markers that serve to detect the difference between these taxa according to the linkage between the flavonoidal units. A rational nomenclature is proposed and the pharmacological potencial is discussed.

Reações de acoplamento cruzado de organossilanos catalisadas por paládio: aspectos históricos, sintéticos e mecanísticos

The development of the palladium catalyzed cross-coupling reactions employing organosilicon compounds is described. Important synthetic methods utilized to prepare organosilicons and different types of cross-coupling reactions involving these compounds are presented. Mechanistic aspects are also discussed.