491 resultados para Pesquisa computacional


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The aim of this work is to establish a program for the treatment of chemical residues and waste waters at the Centro de Energia Nuclear na Agricultura (CENA/USP), for environmental preservation and training of staff. Five tons of stored residues and the ones currently generated in the laboratories have to be treated. Rational use of water is also part of the program. The traditional purification by distillation has been replaced by purification with ion exchange resins. Lower energy consumption and better water quality were achieved.

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Technology companies created from University research are known as "Academic Spin-Off" (ASO). These innovative companies play an important role for the technological, economical and social development of a country. This work discusses some aspects of ASO companies and their importance to Universities. It is also presented a fictitious history of Prof. João, a chemical researcher who will create an ASO company from his academic research work illustrating the basic steps involved in this process.

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As technological information is published mainly as a patent, it is fundamental for the country development to know the patent system. In this article it is presented basic information on intellectual property, in special on patent. It is showed the structure of the patent documents, and it is given notions on International Classification and patent data banks.

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This article provides some aspects that allow making a current reading of the situation of the Brazilian Chemistry that permit us considerate it as a strategic area. They are still presented some initial proposals related to the organization of the research as well as to win the challenges of the relationship with the other areas of the knowledge.

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Nanotechnology can be viewed as a powerful tool, capable of shaping the chemistry of atoms and molecules, converting them into exciting nanosized and nanostructured materials, devices and machines. However, in pursuing this task, an exceptional ability is required to deal with complex inter- and multidisciplinary approaches, as imposed by the nanoscale. A new research organization framework, capable of promoting cooperative interactions in many complementary areas, including the industries, is demanded. In this sense, an interesting example are the nanotechnology networks and millenium institutes recently created in Brazil. The highlights and weakness of such cooperative research networks are discussed, in addition to relevant nanotechnology themes focusing on the special needs and resources from the developing nations.

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Chemical research in Brazil has grown significantly in the past 20 years, largely thanks to the Brazilian S&T Development Program of the federal government (PADCT). However, the newly achieved levels of highly qualified manpower and research infra-structure require new research organization frameworks to make science, technology and innovation really useful and meaningful for the citizens. The current requirements for creating viable networks of academic and industry researchers are presented and discussed as well as some structural and procedural bottlenecks that have to be eliminated, to achieve maximum high-quality science, technology and relevant innovation output.

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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.

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As the Chemical Science is an experimental one a Chemical Industry require technical people in all its staff level: from Directors and Managers to Operators. This chemical and chemical engineering based education is the foundation of the innovate process and motivation. The paper discusses this and the role of Public Policies to improve the R&D and innovation in the Brazilian Chemical Industry.

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Environmental concern is growing in the current days and there is global agreement to banish production and use of persistent organic pollutants (POP). The synthetic insecticides chlordecone and mirex, classified as POPs, have similar structures and they are potentially toxic. This work uses properties and physicochemical constants related to the pesticides and computational simulation to evaluate the leach phenomenon and persistency in soil. The largest tendency of persistence of the compound is found to be in the surface of soil, but even low concentration in water represents a high risk due to bioaccumulation in adipose tissue.

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A computational quantum chemistry experiment is described of Diels-Alder reactions between 2-cycloenones and cyclopentadiene. The effects of FMO-Frontier Molecular Orbitals (HOMO-LUMO) and of the withdrawing nature of substituents at the C=C bond of cycloenones were evaluated. The calculations were made using HF/STO-3G and B3LYP/6-31+G(d,p) methods. The FMO based indexes are in agreement with the experimentally observed reactivity order. NBO - Natural Bond Orbitals - analysis was used to ascertain the effect of C=C substituents on the dienophile reactivity.

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This paper presents an overview of the Natural Products Research in Brazil in the last five years (2002-2006), and also discusses how some relevant aspects of the Chemical Biology area could create new research opportunities and challenges for the natural product chemists. In addition, some aspects of the scientific policies and their impact on current projects are discussed.

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Enzymes are extremely efficient catalysts. Here, part of the mechanisms proposed to explain this catalytic power will be compared to quantitative experimental results and computer simulations. Influence of the enzymatic environment over species along the reaction coordinate will be analysed. Concepts of transition state stabilisation and reactant destabilisation will be confronted. Divided site model and near-attack conformation hypotheses will also be discussed. Molecular interactions such as covalent catalysis, general acid-base catalysis, electrostatics, entropic effects, steric hindrance, quantum and dynamical effects will also be analysed as sources of catalysis. Reaction mechanisms, in particular that catalysed by protein tyrosine phosphatases, illustrate the concepts.

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The field of application of mass spectrometry (MS) has increased considerably due to the development of ionization techniques. Other factors that have stimulated the use of MS are the tandem mass spectrometry (MS/MS) and sequential mass spectrometry (MSn) techniques. However, the interpretation of the MS/MS and MSn data may lead to speculative conclusions. Thus, various quantum chemical methods have been applied for obtaining high quality thermochemical data in gas phase. In this review, we show some applications of computational quantum chemistry to understand the formation and fragmentation of gaseous ions of organic compounds in a MS analysis.

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The objective of this work was to evaluate the environmental distribution of benzo(a)pirene, a polycyclic aromatic hydrocarbon, by the EQC model. The modeling of the contaminant distribution was accomplished by means of the fugacity model applied to a hypothetical scenario constituted by air, water, soil and sediment. The modeling and simulations revealed that the soil is the preferential compartment. We also discuss the implications of the results about fate and ecological risks associated with benzo(a)pirene. We concluded that the emissions of HPAs can not be ignored and bioaccumulation among others risks can be induced.

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Basic concepts that play an important role in some organic reactions are revisited in this paper, which reports a pedagogical experience involving undergraduate and graduate students. A systematic procedure has been applied in order to use widespread available computational tools. This paper aims to discuss the use of computers in teaching electrophilic addition reactions to alkenes. Two classical examples have been investigated: addition to non-conjugated alkenes and addition to conjugated dienes. The results were compared with those normally discussed in organic textbooks. Several important concepts, such as conformational analysis and energy control (kinetic and thermodynamic) involved in reaction mechanisms can be taught more efficiently if one connects theoretical and practical tools.