Resumo em Inglês:

Al-pillared clay was prepared with a Brazilian bentonite from the Campina Grande region (Paraíba, BRAZIL). It was intercalated at 298 K, during 48 hours, with a solution containing [Al3+] = 0.10 mol/L and molar ratio OH/Al = 2.0 prepared at 333 K, and was calcined at 773K. The catalytic activity was evaluated by alkylation of benzene with 1-dodecene. The characterization methods were: X-ray fluorescence and diffraction analysis; 27Al, 29Si and 23Na MAS NMR and textural analysis by N2 adsorption. The thermal stability of the natural clay was improved by the pillaring procedure, as well as the catalytic activity. The intercalated clay presented the highest initial rate of reaction among the systems tested.

Resumo em Inglês:

The present work proposes the application of the 4-Hidroxy-3-(2-hydroxynaphtylazo)-benzenesulphonic acid (C.I. 15670), Alizarine Violet N (AVN), as a reagent for direct aluminium determination using molecular absorption spectrophotometry in the presence of tensoatives. Al(III) cation reacts with AVN in pH 9.4, forming a red complex, stable for at least 24 hours, with absorption minimum at 607nm and, against a reagent blank, (epsiloncomplex - epsilonreagent) = -2.71x10(4) L.mol-1.cm-1. The reaction occurs in the presence of a Triton-X100 and CTAB tensoatives mixture, in the presence of EDTA. Al(III) determination is possible in the linear range of 50 up to 400ng.mL-1, with a detection limit of 41 ng.mL-1.

Resumo em Inglês:

Multicomponent ( Al2O3, CaO, SiO2, MgO) calcium aluminate-based glasses containing Nd3+ were prepared in order to evaluate their possibilities as laser host materials. The refractive index, UV-visible-near IR absorption spectrum, IR and visible luminescence spectra, and fluorescence decay time were measured. Judd-Ofelt model was used to obtain experimental intensity parameters ( omega2, omega4 and omega6), emission cross-section, radiative lifetimes, emission branching ratios and quantum efficiency.

Resumo em Inglês:

A flow injection spectrophotometric method was developed for determining aspartame in sweeteners. Sample was dissolved in water and 250 µL of the solution was injected into a carrier stream of 5.0 x 10-5 mol L-1 sodium borate solution. The sample flowed through a column (14 cm x 2.0 mm) packed with Zn3(PO4)2 immobilized in a polymeric matrix of polyester resin and Zn(II) ions were released from the solid-phase reactor by formation of the Zn(II)-aspartame complex. The mixture merged with a stream of borate buffer solution (pH 9.0) containing 0.030 % (m/v) alizarin red S and the Zn(II)-alizarin red complex formed was measured spectrophotometrically at 540 nm. The calibration graph for aspartame was linear in the concentration range from 10 to 80 µg mL-1 with a detection limit of 4 µg mL-1 of aspartame. The RSD was 0.3 % for a solution containing 40 µg mL-1 aspartame (n = 10) and seventy results were obtained per hour. The proposed method was applied for determining aspartame in commercial sweeteners.

Resumo em Inglês:

The aim of this work was to evaluate the availability of the toxic heavy metals: cadmium, lead and chromium, in soybean, from some fertilizers. Five fertilizers and soluble salts contend Cd, Pb and Cr were used. All the treatments were accomplished in vases of 2,5 L with application of two doses, 50 and 100 kg.ha-1 for the fertilizers and 25 and 50 kg.ha-1 for the salts.

Resumo em Inglês:

Combinatorial chemistry has emerged as a tool to circumvent a major problem of pharmaceutical industries to discover new lead compounds. A rapid and massive evaluation of a myriad of newly synthesised compounds can be carried out. Combinatorial synthesis leads to high throughput screening en masse towards another myriad of biological targets. The design of a set of compounds based upon combinatorial chemistry may be envisaged by using of QSPR-SIMCA and QSAR-SIMCA as tools for classification purposes. This work deals with the definition and establishment of a spanned substituent space (SSS) that reduces the analogue numbers with no exclusion of global content. The chemical diversity may be set properly within a specified pharmacological field. This allows a better use of its potentiality without loosing information.

Resumo em Inglês:

A fast and direct method for the determination of Cr in milk and cane sugar suspensions using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction is described. No sample pre-treatment was necessary, minimizing the risk of contamination. The concentration of chromium in cane sugar was evaluated using Cr reference solutions prepared in 1% v/v HNO3 solution. The milk samples were introduced into the furnace with a mixture of amines for avoiding the autosampler blockage and foaming of milk. Chromium determination in milk was based on the standard additions method (SAM). The limit of detection and characteristic mass for cane sugar sample (30 muL) were 0,13 ng/ml and 4,3 pg, and for milk sample (10 muL) were 0,23 ng/ml and 7,8 pg, respectively. The graphite tube lifetime was 300 firings for sugar-cane sample and 100 firings for milk sample. The heating program was implemented in 68 s.

Resumo em Inglês:

In this work we present the synthesis and characterization of some organolanthanide compounds [LnCp2Cl.PPh3], Ln = La, Nd, Eu, Yb and Lu. The catalytic activity of these compounds has been verified in cyclohexene hydrogenation. Cyclohexane was identified by¹H NMR analysis in the reaction products.

Resumo em Inglês:

This review is about the aliphatic, alicyclic and aromatic compounds (non-heterocyclic compounds) that are present in the volatile fractions of roasted coffees. Herein, the contents, aroma precursors and the sensorial properties of volatile phenols, aldehydes, ketones, alcohols, ethers, hydrocarbons, carboxylic acids, anhydrides, esters, lactones, amines and sulphur compounds are discussed. Special attention is given to the compounds of these groups that are actually important to the final aroma of roasted coffees.

Resumo em Inglês:

This review discusses the methods used to prepare conductive polymers in confined environments. This spatial restriction causes formation of defect-free polymer chains in the interlayer as porous cavities of inorganic hosts. The properties of the different composites obtained are a synergist combination of the characteristics of the inorganic host and the polymer. This opens new perspectives for the preparation of these materials and widens its potential applications.

Resumo em Inglês:

Thallium(III) salts promote a number of different reactions useful in organic synthesis. In this paper, the ring contraction of ketones and olefins, mediated by thallium(III) salts, is exhaustively reviewed.

Resumo em Inglês:

Rules for the occurence of the ambergris odor is presented and discussed in terms of the relationship between chemical structure and odor. A general overview of the major approaches in the synthesis of Ambrox® , the key ambergris-type compound, is also presented.

Resumo em Inglês:

A view of the general aspects involving the 2D NMR spectroscopy using inverse detection and field gradient techniques is presented through the analysis of a sesquiterpene.

Resumo em Inglês:

Photodynamic Therapy (PDT) has been designated as a promising new modality in the treatment of cancer and other diseases since the early 1980s. It has been used with success for the treatment of a variety of tumours, and attempts are being made to extend this treatment modality to other clinical conditions (as example, the inactivation of viruses in blood and blood components). This can be partly attributed to the very attractive basic concept of PDT: the combination of a photosensitizing drug and light, which are relatively harmless by themselves but combined (in the presence of oxygen) ultimately cause more or less selective tumour destruction.

Resumo em Inglês:

Anodic electrodissolution procedure in a flow injection system for determination of constituents in alloys is discussed. This approach implement sample preparation procedure by using a chamber and a DC power supply with constant direct current. Solid sample was attached to chamber as anode. In this review a general overview of these procedure is presented. The procedure presented a good performance characterized by a high sample throughput determinations, good accuracy and relative standard deviation.

Resumo em Inglês:

Unusual chemical phenomenon associated with ultrasound is on account of cavitation effect. The ultrasound increase the rate and yield of chemical reaction on account of its ability to emulsify liquids. When the ultrasound is used in metallic catalyst reaction the activity of catalyst is increased because the ultrasound clean the surface of catalyst. Sonogels have a fine porosity and large specific surface improving different properties. This paper deals with ultrasound phenomenon and gives some examples of reactions and properties where this radiation takes an important role.

Resumo em Inglês:

In this work we first introduce the reader to the basic concepts of biology, bioenergetics and biochemistry, concerning the area of cell biology. Then we explain what diauxism is and an example of this phenomenon, applied to S. cerevisiae, is presented. Finally, thermograms obtained by microcalorimetry, from S. cerevisiae that undergo diauxism, are discussed from a biochemical point of view.

Resumo em Inglês:

This work considers mainly the problem of environmental pollution due to the production of energy by burning fossil fuels, particularly in urban vehicles. Electrochemical energy conversion is proposed as a partial solution to this problem, through the use of hydrogen in fuel cells. In both the production of hydrogen by electrolysis and in the electrochemical processes in fuel cells, the key factor is electrocatalysis. The concept of electrocatalysis, the production of catalysts and supported catalysts and their use in practical systems for the conversion of energy is discussed.

Resumo em Inglês:

Though Free Radicals is one of the most frequently explored scientific subjects in mass communication media, the topic is absent of many Biochemistry introductory courses, especially those in which the students do not have a good chemical background. To overcome this contradictory situation we have developed a software treating this topic in a very simple way. The software is divided in four sections: (1) definition and description of free radicals, (2) production pathways, (3) mechanism of action and (4) enzymatic and non enzymatic protection. The instructional capacity of the software has been both qualitative and quantitatively evaluated through its application in undergraduate courses. The software is available in the INTERNET at the site: http://www.unicamp.br/ib/bioquimica/ensino.

Resumo em Inglês:

A procedure for the nitration of phenol in a semi-micro scale, followed by separation of the formed orto- and para-nitrophenol isomers by column chromatography, is described. All the experiment, including determination of the melting point of the isolated products, require a period of 4 hours, and it is suitable for organic chemistry laboratory undergraduate courses.

Resumo em Inglês:

This article presents the basic ideas that oriented the elaboration of the new Chemistry Curriculum for the High Schools in the State of Minas Gerais, Brazil. The main features of traditional Brazilian Chemistry Curriculum are critically discussed, namely, the excessive number of concepts, the overemphasis in procedures and rituals instead of chemical principles and the lack of relationship between the concepts and the social, technological and environmental contexts. Trying to overcome these features, the proposed curriculum deals with a fewer number of concepts, clearly related in a conceptual structure, opening space to a balanced emphasis on phenomena, theory and representation, and on conceptual and contextual aspects of chemical knowledge.

Resumo em Inglês:

This paper proposes a model for visual communication, conservation, and maintenance of the collection "Chemical Abstracts". It describes the various steps for its implementation and makes considerations about the whole reference work.