Theoretical study of the competition between folding and contact interactions on the properties of polymers using self-avoid random walk algorithm

The self-avoid random walk algorithm has been extensively used in the study of polymers. In this work we study the basic properties of the trajectories generated with this algorithm when two interactions are added to it: contact and folding interaction. These interactions represent the internal forces of the polymer as well as the effect of the solvent. When independently added to the algorithm, the contact interaction creates the compact phase while the folding one creates the extended phase. These are the consequences of the typical event of each interaction. On the other hand, when this typical event is avoided there is no established phase on the system. When simultaneously added, there is a competition between the interactions and the folding one is dominant over the contact one. The resulting phase is always the extended one with and without the contact interaction.Comment: 8 pages, 7 figure

Consolidation problem solution with a coupled hydro-mechanical formulation considering fluid compressibility

There are two principles which may be referred to as essentials to describing soil and rock behavior. The mechanical behavior is associated to the law of conservation of linear momentum, allowing forces balance analysis and the hydraulic behavior is characterized by mass conservation. These phenomena are related: stress-strain state is affected by fluid pressures and vice-versa. Therewith, it is intuitive the understanding of the importance of coupled analyses, which are certainly a more precise manner of describing how mechanical and hydraulic behavior are connected. Given certain difficulties related to the modeling process, porous media numerical model representation is usually simplified. In certain cases, simplifications do not imply on losses in results and behavior prediction. However, some situations require more comprehensive approaches, with development of previously neglected conditions. The main objective of this paper is to present a formulation for fully coupled hydro-mechanical analyses considering fluid and solids compressibility. This formulation, implemented in Finite Element program ALLFINE [1,2,3], was tested for a one-dimensional consolidation case. A sensitivity analyses for the fluid compressibility parameter using modified Cam-clay constitutive model showed that this consideration affects fluid pressure responses significantly, with a delay in fluid pressure dissipation during consolidation process. The simulations results were compared to Terzaghi’s analytical solution for the onedimensional consolidation problem. Also, the comparison of the simulation results to the analytical responses clearly shows the differences between using linear elastic and elastoplastic models. In simulations for different stress levels with the modified Cam-clay model, it is possible to capture a flow induction effect due to high stress levels

Atributos microbiológicos do solo de sistemas de manejo em condições de Cerrado.

FERTBIO 2010

Métodos de apoio à decisão em experimentação agrícola: o caso de sistemas consorciados.

Este artigo teve como objetivo avaliar o desempenho de sistemas consorciados de cenoura e alface e indicar o melhor para o manejo dos recursos ambientais em relação a produtividade e indicadores econômicos. O modelo DEA CCR e o método multicritério ordinal de Copeland foram usados na análise. No primeiro, as variáveis foram as produtividades da alface e da cenoura e o índice de lucratividade. Na segunda abordagem, os critérios de decisão foram o índice de uso eficiente da terra e o índice de lucratividade. Observaram-se maiores v alores de eficiência DEA nos sistemas consorciados que tinham a cenoura "Brasília" como cultura componente, e aqueles baseados nas alfaces "Maravilha das 4 estações" ou "Verônica". A ordenação obtida do método de Copeland ratificou os resultados do modelo DEA

Avaliação multicritério das opções de ligação aérea Rio-São Paulo.

O artigo apresenta uma análise das opções existentes na ligação aérea Rio-São Paulo. As opções existentes no mercado são descritas e avaliadas. A abordagem de avaliação escolhida é o Apoio Multicritério à Decisão. No caso investigado os critérios de decisão são preço, rota, frequência de voos, serviço de bordo, modelo de aeronave e características do programa de milhagem, avaliados segundo duas óticas, a do turista e a do executivo. Os critérios são agregados em um único critério síntese, com o uso de uma soma ponderada. Os critérios subjetivos e os pesos da soma ponderada são quantificados com o auxílio do método MACBETH

Índices de desempenho de sistemas agrícolas consorciados: uso eficiente da terra, indicadores econômicos e eficiência DEA.

Este artigo teve como objetivo avaliar o desempenho de sistemas consorciados de cenoura e alface e indicar qual sistema é melhor para o manejo dos recursos ambientais em relação a produtividade e indicadores econômicos. Foram avaliados o ínndice de uso eficiente da terra - UET, o índice de eficiência produtiva - IEP (via modelos DEA), além de indicadores econômicos (renda bruta, renda líquida, vantagem monetária, taxa de retorno e índice de lucratividade). Observaram-se maiores valores de eficiência agronômica e dos indicadores econômicos nos sistemas consorciados que tinham a cenoura ?Brasília? como cultura componente, e aqueles baseados no grupo de alface crespa

Dinâmica populacional da Eugenia tapacumensis Berg em uma floresta secundária de terra-firme ao longo de 12 anos no município de Bragança-PA.

As ações antrópicas sobre o ecossistema acarretam sérios problemas ao meio ambiente, um dos principais é a retirada total ou parcial da vegetação primária para o cultivo agrícola ou atividades pastoril, cedendo espaço para florestas secundárias. Desse modo o presente trabalho buscou analisar a fitossociologia da Eugenia tapacumensis Berg nos anos: 1999 2003 e 2011. O trabalho foi realizado em uma floresta secundária no município de Bragança nordeste do Pará, Brasil. Em 1999 instalaram-se parcelas permanentes, possibilitando acompanhar a floresta durante esses anos. Para avaliar a fitossociologia de Eugenia tapacumensis, foi verificado as espécies mais abundantes, no que resultou nas três espécies com maior número de indivíduos: Eugenia tapacumensis, Maprounea guianensis e Neea guianensis. Inicialmente (ano de 1999) a Eugenia tapacumensis se concentrou nas menores classes de diâmetro 1(5cm- 6,3cm) com 159 indivíduos, 2(6,4cm ? 7,7cm) com 118 indivíduos e classe 3(7,8cm ? 9,1cm) com 86 indivíduos, A espécie apresentou um alto desenvolvimento durante esses anos, pois em 2003 pode-se perceber um ganho considerável no diâmetro. De 2003 para 2011 a Eugenia tapacumensis aumentou o número de indivíduos para 15 na classe 6 e 5 indivíduos na classe 7, mostrando que essa espécie tem um papel importante na dinâmica de uma floresta secundária. Com a análise feita pode-se aumentar o conhecimento sobre a Eugenia tapacumensis e mostrar que apesar dessa espécie não ter valor econômico, ela exercer papel fundamental em aumentar o incremento de biomassa para a floresta secundária e, além disso, é um consumidor de carbono, compensando parcialmente as emissões

Use of chemometrics to characterize tropical wines from different vintages and grape cultivars according to the 1H NMR spectroscopy data.

Resumo

Use of chemometrics to characterize tropical wines from different vintages and grape cultivars according to the 1H NMR spectroscopy data.

Tropical wines have been produced in Northeast of Brazil since 1980's, between the 8° and 9° S latitude, in a region called Sub-rniddle São Francisco river Valley. This area presents an intra-annual climate variability and wines can be elaborated in different months of the year, according to the winery, with different analytical characteristics due to the climatic conditions. NMR spectroscopy is an interesting tool that allows to determine in a single analysis many analytical compounds of the wines. PCA and PLS rnultivariate statistical analyses applied on NMR data allow to discriminate samples and to identify the responsible compounds for the clustering. The aim of this work was to use chemometrics, PCA and PLS, applied on IH NMR spectroscopy data, to characterize tropical wines from different vintages and grape cultivars, in Northeast of Brazil. Wines were elaborated by using traditional winemaking process with control of the fermentations temperature and use of antioxidants. Before statistical analyses, IHNMR spectra were segmented, normalized, converted to Excel software format and further processed for PCA and PLS analyses. Statistical analyses applied on NMR spectra data were not satisfactory to discriminate between different vintages of white and red wines together, but they were able to separate each one according to different vintages and cultivars. Metabolic compounds were found to explain wine clusters, and fingerprints are discussed

Global gene expression under nitrogen starvation in Xylella fastidiosa: contribution of the σ54 regulon

<p>Abstract</p> <p>Background</p> <p><it>Xylella fastidiosa</it>, a Gram-negative fastidious bacterium, grows in the xylem of several plants causing diseases such as citrus variegated chlorosis. As the xylem sap contains low concentrations of amino acids and other compounds, <it>X. fastidiosa </it>needs to cope with nitrogen limitation in its natural habitat.</p> <p>Results</p> <p>In this work, we performed a whole-genome microarray analysis of the <it>X. fastidiosa </it>nitrogen starvation response. A time course experiment (2, 8 and 12 hours) of cultures grown in defined medium under nitrogen starvation revealed many differentially expressed genes, such as those related to transport, nitrogen assimilation, amino acid biosynthesis, transcriptional regulation, and many genes encoding hypothetical proteins. In addition, a decrease in the expression levels of many genes involved in carbon metabolism and energy generation pathways was also observed. Comparison of gene expression profiles between the wild type strain and the <it>rpoN </it>null mutant allowed the identification of genes directly or indirectly induced by nitrogen starvation in a σ⁵⁴-dependent manner. A more complete picture of the σ⁵⁴regulon was achieved by combining the transcriptome data with an <it>in silico </it>search for potential σ⁵⁴-dependent promoters, using a position weight matrix approach. One of these σ⁵⁴-predicted binding sites, located upstream of the <it>glnA </it>gene (encoding glutamine synthetase), was validated by primer extension assays, confirming that this gene has a σ⁵⁴-dependent promoter.</p> <p>Conclusions</p> <p>Together, these results show that nitrogen starvation causes intense changes in the <it>X. fastidiosa </it>transcriptome and some of these differentially expressed genes belong to the σ⁵⁴regulon.</p