Alguns aspectos históricos da classificação periódica dos elementos químicos

A history of the periodic table of the elements is presented, from the first tentative classifications, passing through Meyer and Mendeleev, up to recent speculations on super-heavy elements still to be synthesized. Many of the discussions and discoveries related to chemical elements and their proper periodic classification are also presented.

Alguns aspectos da política nacional de ciência e tecnologia

The Brazilian industrialisation process, which occurred from World War II up to the early eighties, was almost totally based on imported technology and has thus not demanded local S&T capability. National S&T expenditures were limited to 0.7 % of the GNP, covering mainly expenses with basic research and training of scientists and engineers. Federal Government was then responsible for 90% of the national S&T expenditures. The globalisation of the economy, associated with the reduction of tariff barriers, has, since the early nineties, exposed Brazilian industries to international competition and, thus, forced them to invest in research and development. S&T policy fosters research activities, provides research infrastructure and human resources training. The goal is to raise national expenditures to 1.5% of GDP by 1999, with a share of the private sector of about 40%. In 1996, national S&T expenditures have already attained 1.1% of the GDP and private sector investments in this area reached a share of 30%.

Aspectos mecanísticos da adição de Michael

The Michael addition reaction has been reported as a conventional nucleophilic process. However, more recently, alternative mechanisms involving electron transfer between acceptor and donnor species have been proposed.

O emprego de lipases como agentes de resolução cinética de enantiômeros em síntese orgânica: aspectos gerais sobre a influência do solvente

In organic synthesis, lipases are the most frequently used biocatalysts. They are efficient stereoselective catalysts in the kinetic resolution of a wide variety of chiral compounds. The discovery that enzymes possess catalytic activity in organic solvents has made it possible to address the question of reaction medium influence on enzymatic specificity. Perhaps the most exciting and significant development in this emerging area is the discovery that enzyme specificity, in particular enantioselectivity, can be affected by changing from one organic solvent to another. This article discusses the scope and possible mechanistic models of this phenomenon in hydrolases, specially lipases, as well as directions of future research in the area.

Alguns aspectos de imunoensaios aplicados à química analítica

In the last years, the use of antibody-antigen interactions, has earned attention not only for clinical analysis, but also for food industry and environmental control. Since the scope and diversity of immunoassay technology have shown a wide development. Continuous advances in order to analyse complex matrices, to improve reliability, simplicity (nonseparation) and to get multiple simultaneous assays, and extreme sensitivity (lower than zeptomole detection limits) are increasing. Many strategies have been investigated including chemiluminescent enzyme immunoassays, DNA as label and development of flow injection and immunosensors techniques. This subject became very usefull and important in nowadays that are taught in the undergraduate courses of chemistry in the european universities. However in our country are still ignored in the chemistry course.

O ensino de aspectos históricos e filosóficos da Química e as teorias ácido-base do século XX

In this paper, an overview about philosophy of science, the concept of "theory" and some characteristics of a"good"theory (1- ordination and explanation of the facts, 2- proposal of problems, and 3- simplicity and funcionality) are initialy introduced. Following, some historical landmarks of acidity and basicity and a summary of the main acid-base theories of the XX century (Arrhenius, solvent systems, protonic, electronic, Lux, Usanovich and ionotropic) are presented. Historical and conceptual relations between these theories are discussed and the three characteristics of a "good" theory are applied. The results showed that the protonic and eletronic theories are the "best". Some discussion of the implications to chemical education are presented too.

La retorica delle sarabandes : ricerca retorica nelle prime tre sarabandes delle Sechs Partiten für klavier di J. S. Bach

La presente tesi di ricerca si propone di studiare la danza della sarabanda come capolavoro di musica, retorica e poesia in tre delle Sechs Partiten für klavier di J. S. Bach (BWV 825-830). Lo studio svolto è fondamentalmente di tipo retorico: permette di individuare e interpretare la struttura oratorialepoetica del discorso letterario-musicale nelle tre danze scelte e di imarcarne i suoi aspetti più salienti di ritmica e ornatus. L’approccio permette di osservare, con uno sguardo di comparazione, la presenza di un percorso retorico comune alle tre sarabande, che evolve con gradualità, differenziandole nettamente: ciò riesce a valorizzare a pieno la danza nella sua forza ed efficacia espressiva, che la rende di fatto il movimento di massima commozione di ogni Partita.

Trompa interestelar : el color sonoro de la trompa en la "llamada interestelar" de O. Messiaen

Mi trabajo versa sobre la obra de O. Messiaen "Des Canyons aux etoiles" (De los cañones a las estrellas), y en particular de uno de los movimientos de la obra: "Appel Interestellaire" -N.VI- (Llamada Interestelar) -para trompa sola-. Se estructura en dos partes. La primera se centra en su contexto histórico -como, cuando y para quien fue compuesta-; análisis formal, armónico, melódico, rítmico; y aspectos estéticos. La segunda parte está vinculada con la interpretación de la obra. Se realiza un análisis para la interpretación -técnica de la trompa, efectos sonoros, timbres-; se hace una comparación entre la interpretación de 2 diferentes trompistas, y por último, aporto mi propuesta de interpretación. El trabajo se cierra con una conclusión, bibliografía, y un extracto con anexos (esquema, partitura y datos o imágenes de interés).

Estudo da adsorção de hidrogênio e sulfeto na superfície de paládio: aspectos experimentais (eletroquímica) e teóricos (ab initio e Teoria do Funcional da Densidade)

The adsorption of H and S2- species on Pd (100) has been studied with ab initio, density-functional calculations and electrochemical methods. A cluster of five Pd atoms with a frozen geometry described the surface. The computational calculations were performed through the GAUSSIAN94 program, and the basis functions adapted to a pseudo-potential obtained by using the Generator Coordinate Method adapted to the this program. Using the cyclic voltammetry technique through a Model 283 Potentiostat/Galvanostat E.G.&G-PAR obtained the electrochemical results. The calculated chemisorption geometry has a Pd-H distance of 1.55Ã…, and the potential energy surface was calculated using the Becke3P86//(GCM/DFT/SBK) methodology. The adsorption of S2- ions on Pd surface obtained both through comparison between the experimental and theoretical results, at MP2 level, suggest a S2- absorption into the metallic cluster. The produced Pd-(S2-) system was show to be very stable under the employed experimental conditions. The paper has shows the powerful aid of computational methods to interpret adsorption experimental data.

Consideraciones sobre la fundamentación psicopedagógica del ABP : aspectos esenciales

La metodología ABP respeta la tendencia innata al crecimiento y la autorrealización defendida desde la psicología humanista, y permite crear el contexto de desarrollo idóneo para satisfacer las necesidades psicológicas básicas propuestas desde la teoría de la autodeterminación. Por su contribución al desarrollo de las competencias personales y sociales, está indicada tanto para universitarios como para alumnado de niveles preuniversitarios

Aspectos práticos relacionados ao uso do Rincoforol, o feromônio de agregação da Broca-do-olho-do-coqueiro Rhynchophorus palmarum L. (Coleopterate: Curculionidae) no controle de pragas do coqueiro: análise de sua eficiência em campo

Rhynchophorol (6-Methyl-2-hepten-4-ol) is the major constituent of the aggregation pheromone of Rhynchophorus palmarum L. (Coleoptera: Curculionidae), which is released by males of this species. The racemic mixture has been produced in one step-simplified preparation. The pheromone is placed into ampoules and furnished to coconut farmers. In the field, traps baited with Rhynchophorol and pieces of sugarcane attract both males and females, reducing the population of R. palmarum. The best conditions for field application are showed.

Aspectos relacionados à utilização da equação logística quadrática em processos eletroquímicos

The concepts of dissipation and feedback are contained in the behavior of many natural dynamical systems. They have been used to predict the evolution of populations leading to the formulation of the quadratic logistic equation (QLE). More recently, the QLE has been used to provide a better understanding of physicochemical systems with promising results. Many physical, chemical and biological dynamic phenomena can be understood on the basis of the QLE and this work describes the main aspects of this equation and some recent applications, with emphasis on electrochemical systems. Also, it is illustrated the concept of potential energy as a convenient way of describing the stability of the fixed points of the QLE.

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.

Terapia fotodinâmica: aspectos farmacológicos, aplicações e avanços recentes no desenvolvimento de medicamentos

Photodynamic Therapy (PDT) is a clinical procedure, which utilize a photosensitive compound and light. This is a new modality of treatment for cancer, aged related macular degenerescence (AMD), psoriasis, arthritis, arterial restenosis, etc which exhibits efficiency, less traumatic effects, low recovery time and few co-lateral effects. The first officially approved drug for PDT by the Food and Drug Administration (EUA) is Photofrin<FONT FACE=Symbol>â</FONT>, which is applied for cancer. A new generation drug for PDT, Visudyne<FONT FACE=Symbol>â</FONT> was recently approved to treat AMD; its photoactive compound is BPDMA, a benzoporphyrin mono-acid derivative (chlorin-type molecule). A concise history, technical information and some drugs for PDT are reported.

Aportaciones del Comunicado de Londres en el Proceso de Bolonia: conclusiones sobre los programas de doctorado y otros aspectos destacables

[spa] El pasado 18 de mayo de 2007, tuvo lugar en Londres el último de los encuentros bienales del Proceso de Bolonia, en el que se reunieron los ministros responsables de la educación superior de los países participantes. En el consiguiente London Communiqué se resumieron las valoraciones de los ministros sobre el estado en el que dicho proceso se halla. Así, se pasó revista a los avances consolidados, a aquellas deficiencias que aún no han recibido la atención necesaria, y a las medidas y estrategias urgentes para su definitiva conclusión. El presente texto da noticia de todas estas cuestiones y, con motivo de ofrecer al lector referencias adicionales sobre el contexto general, incluye una breve síntesis de otros documentos directamente relacionados con los temas más destacados en Londres 2007: los programas de doctorado y la figura del doctorando.