Experimental and theoretical investigation of molecular structure and conformation of the 4-isopropylthioxanthone

In this study, the molecular structure and conformational analyses of the 4-isopropylthioxanthone (4-ITX) are reported according to experimental and theoretical results. The compound crystallizes in the centrosymmetric P (1) over bar space group with only one molecule in the asymmetric unit, presenting the most stable conformation, in which the three fused-rings adopt a planar geometry, and the isopropyl group assumes a torsional angle with less sterical hindrance. The structural and conformational analyses were performed using theoretical calculations such as Hartree-Fock (HF), DFT method in combination with 6-311G(d,p) and 6-31++G(d,p) and the results were compared with infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The supramolecular assembly of 4-ITX is kept by non-classical C-H center dot center dot center dot O hydrogen bonds and weak interactions such as pi-pi stacking. 4-ITX was also studied by (1)H and (13)C NMR spectroscopy. UV-Vis absorption spectroscopic properties of the 4-ITX showed the long-wavelength maximum shifts towards high energy when the solvent polarity increases. (C) 2011 Elsevier B.V. All rights reserved.

Crystal structure and statistical coupling analysis of highly glycosylated peroxidase from royal palm tree (Roystonea regia)

Royal palm tree peroxidase (RPTP) is a very stable enzyme in regards to acidity, temperature, H(2)O(2), and organic solvents. Thus, RPTP is a promising candidate for developing H(2)O(2)-sensitive biosensors for diverse applications in industry and analytical chemistry. RPTP belongs to the family of class III secretory plant peroxidases, which include horseradish peroxidase isozyme C, soybean and peanut peroxidases. Here we report the X-ray structure of native RPTP isolated from royal palm tree (Roystonea regia) refined to a resolution of 1.85 angstrom. RPTP has the same overall folding pattern of the plant peroxidase superfamily, and it contains one heme group and two calcium-binding sites in similar locations. The three-dimensional structure of RPTP was solved for a hydroperoxide complex state, and it revealed a bound 2-(N-morpholino) ethanesulfonic acid molecule (MES) positioned at a putative substrate-binding secondary site. Nine N-glycosylation sites are clearly defined in the RPTP electron-density maps, revealing for the first time conformations of the glycan chains of this highly glycosylated enzyme. Furthermore, statistical coupling analysis (SCA) of the plant peroxidase superfamily was performed. This sequence-based method identified a set of evolutionarily conserved sites that mapped to regions surrounding the heme prosthetic group. The SCA matrix also predicted a set of energetically coupled residues that are involved in the maintenance of the structural folding of plant peroxidases. The combination of crystallographic data and SCA analysis provides information about the key structural elements that could contribute to explaining the unique stability of RPTP. (C) 2009 Elsevier Inc. All rights reserved.

Structured minimal-memory inexact quasi-Newton method and secant preconditioners for augmented Lagrangian optimization

Augmented Lagrangian methods for large-scale optimization usually require efficient algorithms for minimization with box constraints. On the other hand, active-set box-constraint methods employ unconstrained optimization algorithms for minimization inside the faces of the box. Several approaches may be employed for computing internal search directions in the large-scale case. In this paper a minimal-memory quasi-Newton approach with secant preconditioners is proposed, taking into account the structure of Augmented Lagrangians that come from the popular Powell-Hestenes-Rockafellar scheme. A combined algorithm, that uses the quasi-Newton formula or a truncated-Newton procedure, depending on the presence of active constraints in the penalty-Lagrangian function, is also suggested. Numerical experiments using the Cute collection are presented.

Efficient solutions to robust, semi-implicit discretizations of the immersed boundary method

The immersed boundary method is a versatile tool for the investigation of flow-structure interaction. In a large number of applications, the immersed boundaries or structures are very stiff and strong tangential forces on these interfaces induce a well-known, severe time-step restriction for explicit discretizations. This excessive stability constraint can be removed with fully implicit or suitable semi-implicit schemes but at a seemingly prohibitive computational cost. While economical alternatives have been proposed recently for some special cases, there is a practical need for a computationally efficient approach that can be applied more broadly. In this context, we revisit a robust semi-implicit discretization introduced by Peskin in the late 1970s which has received renewed attention recently. This discretization, in which the spreading and interpolation operators are lagged. leads to a linear system of equations for the inter-face configuration at the future time, when the interfacial force is linear. However, this linear system is large and dense and thus it is challenging to streamline its solution. Moreover, while the same linear system or one of similar structure could potentially be used in Newton-type iterations, nonlinear and highly stiff immersed structures pose additional challenges to iterative methods. In this work, we address these problems and propose cost-effective computational strategies for solving Peskin`s lagged-operators type of discretization. We do this by first constructing a sufficiently accurate approximation to the system`s matrix and we obtain a rigorous estimate for this approximation. This matrix is expeditiously computed by using a combination of pre-calculated values and interpolation. The availability of a matrix allows for more efficient matrix-vector products and facilitates the design of effective iterative schemes. We propose efficient iterative approaches to deal with both linear and nonlinear interfacial forces and simple or complex immersed structures with tethered or untethered points. One of these iterative approaches employs a splitting in which we first solve a linear problem for the interfacial force and then we use a nonlinear iteration to find the interface configuration corresponding to this force. We demonstrate that the proposed approach is several orders of magnitude more efficient than the standard explicit method. In addition to considering the standard elliptical drop test case, we show both the robustness and efficacy of the proposed methodology with a 2D model of a heart valve. (C) 2009 Elsevier Inc. All rights reserved.

Simple Method to Evaluate and to Predict Flash Points of Organic Compounds

Flash points (T(FP)) of organic compounds are calculated from their flash point numbers, N(FP), with the relationship T(FP) = 23.369N(FP)(2/3) + 20.010N(FP)(1/3) + 31.901. In turn, the N(FP) values can be predicted from boiling point numbers (Y(BP)) and functional group counts with the equation N(FP) = 0.974Y(BP) + Sigma(i)n(i)G(i) + 0.095 where G(i) is a functional group-specific contribution to the value of N(FP) and n(i) is the number of such functional groups in the structure. For a data set consisting of 1000 diverse organic compounds, the average absolute deviation between reported and predicted flash points was less than 2.5 K.

Extraction of structured programs from specification proofs

We present a method using an extended logical system for obtaining programs from specifications written in a sublanguage of CASL. These programs are “correct” in the sense that they satisfy their specifications. The technique we use is to extract programs from proofs in formal logic by techniques due to Curry and Howard. The logical calculus, however, is novel because it adds structural rules corresponding to the standard ways of modifying specifications: translating (renaming), taking unions, and hiding signatures. Although programs extracted by the Curry-Howard process can be very cumbersome, we use a number of simplifications that ensure that the programs extracted are in a language close to a standard high-level programming language. We use this to produce an executable refinement of a given specification and we then provide a method for producing a program module that maximally respects the original structure of the specification. Throughout the paper we demonstrate the technique with a simple example.

The Potential Of Kohonen Method For Classifying Rivers Focused On Regional Environmental Flow Determination With ELOHA

This article highlights the potential benefits that the Kohonen method has for the classification of rivers with similar characteristics by determining regional ecological flows using the ELOHA (Ecological Limits of Hydrologic Alteration) methodology. Currently, there are many methodologies for the classification of rivers, however none of them include the characteristics found in Kohonen method such as (i) providing the number of groups that actually underlie the information presented, (ii) used to make variable importance analysis, (iii) which in any case can display two-dimensional classification process, and (iv) that regardless of the parameters used in the model the clustering structure remains. In order to evaluate the potential benefits of the Kohonen method, 174 flow stations distributed along the great river basin “Magdalena-Cauca” (Colombia) were analyzed. 73 variables were obtained for the classification process in each case. Six trials were done using different combinations of variables and the results were validated against reference classification obtained by Ingfocol in 2010, whose results were also framed using ELOHA guidelines. In the process of validation it was found that two of the tested models reproduced a level higher than 80% of the reference classification with the first trial, meaning that more than 80% of the flow stations analyzed in both models formed invariant groups of streams.

A impossível simetria : distinção, interdependência e poder na relação entre agricultores ecologistas e mediadores sociais

Esta dissertação analisa a relação entre agricultores ecologistas organizados em uma associação e mediadores sociais vinculados a uma ONG do Rio Grande do Sul. Parte-se da hipótese de que a construção da simetria pretendida nesta relação encobre interesses sobre os quais não se fala, mas que compõe as bases de uma disputa velada estruturada no espaço social no qual interagem agricultores e mediadores, entre outros agentes. Busca-se, a partir de dados empíricos, problematizar alguns elementos que estão ocultos ou que não são considerados relevantes, exatamente por estarem subjacentes à doxa que configura a relação em questão. Para isso, foram empregados conceitos como espaço social, capital, participação, mediação, interdependência e identidade. Trata-se, portanto, de evidenciar como se processa a relação de poder existente entre estes agentes dotados de volume e estrutura de capital diferenciados e de compreender como são constituídas as identidades do agricultor ecologista e do mediador social que estão envolvidos com esta proposta distinta de se fazer agricultura. Nesse sentido, a trajetória destes grupos, os agentes influentes nessa constituição, as disputas estabelecidas no campo das diferentes propostas de se fazer agricultura e os contextos onde se desenvolvem as relações são algumas das dimensões empíricas que foram consideradas para o desenvolvimento das análises contidas nessa dissertação. Assim, verificou-se que a pretensão, anunciada por certos agentes, de uma horizontalidade entre os agricultores ecologistas e os mediadores sociais é ilusória. A diversidade de interesses e de atuações que os mobilizam ao redor da agricultura ecológica geram disputas e, ao mesmo tempo, uma interdependência entre eles. Porém, a lógica desse jogo social está, em grande medida, determinada pelo agente de maior poder e, ainda que haja variações, são os mediadores sociais que mais produzem interferência no curso desse jogo. Ficou constatado, finalmente, que é nesse cenário de posições e contraposições, ação e reação, que vão se constituindo as fronteiras das identidades desses agentes e a realidade de suas relações.

Análise teórico-metodológica das monografias do curso de turismo da UFMA que abordam o assunto da gestão de negócios turísticos no período de 2001 a 2005.

Este trabalho tem por finalidade analisar as características teóricas e metodológicas das monografias defendidas no curso de turismo da Universidade Federal do Maranhão – UFMA, que tratam de assuntos voltados para a temática em Gestão de Negócios turísticos no período de 2001/2005. Trabalham-se as principais definições e conceitos relacionados à pesquisa, mostrando ser a pesquisa um ato não isolado, processual e sistematizado. Apresenta a importância e as funções da pesquisa afirmando que a mesma vem conquistando um certo espaço na vida acadêmica por melhorar as práticas educativas bem como contribuindo para melhoria de vida dos cidadãos, quando unida à tecnologia, além de apresentar a importância dos métodos de investigação nos vários níveis e fases. Aborda sobre a pesquisa nas diversas concepções na universidade de forma contextualizada. Aborda sobre a função social da pesquisa estimulando a divulgação científica, vinculando esta responsabilidade como débito social do pesquisador para com a comunidade científica. A pesquisa configura-se como um método descritivo - exploratório analisado segundo três matrizes: paradigmática, tipológica e o mapa conceitual que serviram como critério orientador, onde as monografias foram metodicamente analisadas em sua estrutura no nível teórico, apresentando as principais temáticas trabalhadas, as críticas e as propostas, bem como os autores mais citados e os tipos de documento mais pesquisados. No nível técnico são analisados a característica das pesquisas, as técnicas, instrumentos e procedimentos utilizados na coleta e analise dos dados. No nível epistemológico foram observados os critérios de validação, as concepções de causalidade e de ciência, e os pressupostos lógico – gnosiológicos. Os dados obtidos, analisados a luz do referencial teórico apontam para necessidade de um maior rigor científico e espírito crítico por parte dos pesquisadores.

O processo decisório do empreendedor frente à transição da pequena para a média empresa: casos do setor hoteleiro na cidade Curitiba-PR

O presente estudo buscou entender como as mudanças ocasionadas pelo crescimento da empresa afetam o processo decisório, com foco na transição de pequena para média empresa. Buscou-se preencher o gap existente sobre esse período de transição entre pequenas e médias empresas, principalmente sob os aspectos abordados pelas lógicas Effectuation e Causation, descritas por Sarasvathy (2001). Esta pesquisa parte do princípio de que as pequenas empresas possuem poucos níveis hierárquicos e geralmente as decisões estão centralizadas no empreendedor-proprietário. Já quando a empresa cresce e torna-se média empresa, há um aumento nas formalizações dos processos e nas hierarquias. Com isso, há uma necessidade de modificar o processo decisório, que pode ser descentralizada ou envolver mais pessoas, se comparado às pequenas empresas. O referencial teórico da pesquisa, teve como base temas relativos à pequenas e médias empresas; setor hoteleiro, estrutura organizacional; ciclo de vida das organizações; processo decisório; e, por fim, o uso das lógicas causation e effectuation, com foco nas características do processo decisório do empreendedor. A pesquisa teve de caráter qualitativo e exploratório e faz uso do método de estudos de casos, através de entrevistas em profundidade com empreendedores do setor hoteleiro, que é um setor de serviços que tem tido grande visibilidade e crescimento nos últimos anos. Foram analisados dois casos no setor hoteleiro de Curitiba- PR, que passaram recentemente pela fase de transição de pequena para média empresa. Em cada um dos casos foram entrevistados os proprietários-fundadores, os seus sucessores diretos e o gerente-geral. Também levantou-se depoimentos de clientes em sites de avalizações de hospedagem. Para análise dos dados foram atribuídas categorias analíticas, e foi realizada a análise do conteúdo, (contrapondo com o referencial teórico apresentado) e cross-case analysis (comparativo das informações obtidas em cada caso). Ao finalizar a pesquisa, concluiu-se que a transição de pequena para média empresa afeta as decisões no sentido de aumentar a formalização de processos, há uma delegação de pequenos poderes, um maior distanciamento dos funcionários e a cúpula administrativa, há uma preocupação maior com a capacitação dos funcionários, são consideração de aspectos racionais na decisão, há uma equipe de suporte para tomada de decisões, há uma preocupação com o longo prazo, as responsabilidades tornam-se mais claras, e mais autonomia é delegada aos funcionários. Pode-se dizer que não mudou o fato da administração permanecer familiar, o foco das decisões ainda mantém-se no curto prazo, as decisões permanecem flexíveis, mantém-se a centralização do poder de decisões estratégicas; há ainda uma dificuldade em separar o pessoal do profissional, definição de metas e objetivos não muito claras, investimentos em um projeto por vez, e o uso de rede de contatos ainda é importante para o desenvolvimento da empresa.

KittyCat: a cognitive model of structure-form discovery

Cognition is a core subject to understand how humans think and behave. In that sense, it is clear that Cognition is a great ally to Management, as the later deals with people and is very interested in how they behave, think, and make decisions. However, even though Cognition shows great promise as a field, there are still many topics to be explored and learned in this fairly new area. Kemp & Tenembaum (2008) tried to a model graph-structure problem in which, given a dataset, the best underlying structure and form would emerge from said dataset by using bayesian probabilistic inferences. This work is very interesting because it addresses a key cognition problem: learning. According to the authors, analogous insights and discoveries, understanding the relationships of elements and how they are organized, play a very important part in cognitive development. That is, this are very basic phenomena that allow learning. Human beings minds do not function as computer that uses bayesian probabilistic inferences. People seem to think differently. Thus, we present a cognitively inspired method, KittyCat, based on FARG computer models (like Copycat and Numbo), to solve the proposed problem of discovery the underlying structural-form of a dataset.

A new method to quantify macroalgae and a practical sampler for experimentation in lotic habitats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of Etching on Zircon Grains and Its Implications for the Fission Track Method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Topliss method in the optimization of salicylic acid derivatives as potential antimycobacterial agents

The Topliss method was used to guide a synthetic path in support of drug discovery efforts toward the identification of potent antimycobacterial agents. Salicylic acid and its derivatives, p-chloro, p-methoxy, and m-chlorosalicylic acid, exemplify a series of synthetic compounds whose minimum inhibitory concentrations for a strain of Mycobacterium were determined and compared to those of the reference drug, p-aminosalicylic acid. Several physicochemical descriptors (including Hammett's sigma constant, ionization constant, dipole moment, Hansch constant, calculated partition coefficient, Sterimol-L and -B-4 and molecular volume) were considered to elucidate structure-activity relationships. Molecular electrostatic potential and molecular dipole moment maps were also calculated using the AM1 semi-empirical method. Among the new derivatives, m-chlorosalicylic acid showed the lowest minimum inhibitory concentration. The overall results suggest that both physicochemical properties and electronic features may influence the biological activity of this series of antimycobacterial agents and thus should be considered in designing new p-aminosalicylic acid analogs.

Structural characterization of Ti-15Mo alloy used as biomaterial by Rietveld method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)