Long Range Bond-Bond Correlations in Dense Polymer Solutions

The scaling of the bond-bond correlation function $C(s)$ along linear polymer chains is investigated with respect to the curvilinear distance, $s$, along the flexible chain and the monomer density, $\rho$, via Monte Carlo and molecular dynamics simulations. % Surprisingly, the correlations in dense three dimensional solutions are found to decay with a power law $C(s) \sim s^{-\omega}$ with $\omega=3/2$ and the exponential behavior commonly assumed is clearly ruled out for long chains. % In semidilute solutions, the density dependent scaling of $C(s) \approx g^{-\omega_0} (s/g)^{-\omega}$ with $\omega_0=2-2\nu=0.824$ ($\nu=0.588$ being Flory's exponent) is set by the number of monomers $g(\rho)$ contained in an excluded volume blob of size $\xi$. % Our computational findings compare well with simple scaling arguments and perturbation calculation. The power-law behavior is due to self-interactions of chains on distances $s \gg g$ caused by the connectivity of chains and the incompressibility of the melt. %Comment: 4 pages, 4 figure

Desempenho inicial de sementes de milho tratadas com biorreguladores submetidas a déficit hídrico.

Edição Especial contendo os Anais do XVIII Congresso Brasileiro de Sementes, Florianópolis, set. 2013

Velocidade de embebição de sementes de soja submetidas a diferentes recobrimentos.

O tratamento de sementes de soja é uma prática utilizada para aumentar o desempenho das sementes, especialmente durante as fases iniciais do ciclo. A utilização do tratamento de sementes com polímeros tem sido uma alternativa para os agricultores por permitir melhor fi xação dos princípios ativos utilizados no tratamento químico. Entretanto, esses produtos não devem afetar as propriedades fisiológicas e físicas das sementes, como a velocidade de embebição. Assim, o objetivo do trabalho foi estudar o efeito de diferentes recobrimentos na velocidade de embebição das sementes de soja. Foram utilizados dois lotes de sementes de soja das cultivares SYN1263 RR e BMX Potência RR, as quais foram submetidas a seis diferentes recobrimentos: 1: Testemunha (ausência de fungicida, inseticida e polímero); 2: Fungicida + Inseticida; 3: Fungicida + Inseticida + Polímero A; 4: Fungicida + Inseticida + Polímero B; 5: Polímero A; 6: Polímero B. O fungicida e o inseticida utilizados foram Derosal Plus (carbendazim + thiram) e Cropstar FloRite 1197 (Nitral Urbana (imidacloprido + tiodicarbe), respectivamente, e os polímeros ) (A) e Laborsan (Laborsan) (B). Para a determinação da velocidade de embebição, as sementes foram dispostas sobre papel germitest umedecido 2,25 vezes o peso do papel seco e incubadas àtemperatura de 20°C, mensurando-se a massa das sementes em intervalos regularesde 1h, durante um período de 24h. De acordo com os resultados, o recobrimento das sementes de soja com os polímeros FloRite1197 (Nitral Urbana) e Laborsan (Laborsan) isolados ou em associação com o fungicida e inseticida não retardam a velocidade de absorção de água

Single chain structure in thin polymer films: Corrections to Flory's and Silberberg's hypotheses

Conformational properties of polymer melts confined between two hard structureless walls are investigated by Monte Carlo simulation of the bond-fluctuation model. Parallel and perpendicular components of chain extension, bond-bond correlation function and structure factor are computed and compared with recent theoretical approaches attempting to go beyond Flory's and Silberberg's hypotheses. We demonstrate that for ultrathin films where the thickness, $H$, is smaller than the excluded volume screening length (blob size), $\xi$, the chain size parallel to the walls diverges logarithmically, $R^2/2N \approx b^2 + c \log(N)$ with $c \sim 1/H$. The corresponding bond-bond correlation function decreases like a power law, $C(s) = d/s^{\omega}$ with $s$ being the curvilinear distance between bonds and $\omega=1$. % Upon increasing the film thickness, $H$, we find -- in contrast to Flory's hypothesis -- the bulk exponent $\omega=3/2$ and, more importantly, an {\em decreasing} $d(H)$ that gives direct evidence for an {\em enhanced} self-interaction of chain segments reflected at the walls. Systematic deviations from the Kratky plateau as a function of $H$ are found for the single chain form factor parallel to the walls in agreement with the {\em non-monotonous} behaviour predicted by theory. This structure in the Kratky plateau might give rise to an erroneous estimation of the chain extension from scattering experiments. For large $H$ the deviations are linear with the wave vector, $q$, but are very weak. In contrast, for ultrathin films, $H<\xi$, very strong corrections are found (albeit logarithmic in $q$) suggesting a possible experimental verification of our results.Comment: 16 pages, 7 figures. Dedicated to L. Sch\"afer on the occasion of his 60th birthda

Distribuição espacial de danos de percevejo em campos de produção de sementes de soja.

RESUMO: Estudos tem demonstrado que a qualidade fisiológica de sementes de soja nos campos de produção apresenta variabilidade espacial. Uma das possíveis causas dessa variabilidade, pode ser o ataque localizado de pragas, principalmente percevejos. O objetivo do trabalho foi determinar a distribuição espacial dos danos de percevejos em sementes de soja nos campos de produção de sementes e o seu efeito na qualidade fisiológica. O trabalho foi desenvolvido em quatro campos de produção de sementes na safra 2011/12, na região central do Estado do Rio Grande do Sul, Brasil. Para a coleta das amostras, foi estabelecida uma malha de amostragem com densidade de 1:0,10; 1:0,25; 1:0,10 e 1:0,25 pontos/ha, sendo a área total dos campos de 4,3; 11,4; 5,9 e 12,7ha e as cultivares NA 5909 RG, BMX Turbo RR, NA 5909 RG e NA 4725 RG, respectivamente. Foram realizadas as seguintes determinações: produtividade, teste de germinação, primeira contagem, emergência de plântulas e teste de tetrazólio. Os dados gerados foram utilizados para a elaboração de modelos digitais (mapas) através do software ?Sistema Agropecuário CR - Campeiro 7?. Os danos causados por percevejos em sementes de soja apresentam variabilidade espacial nos campos de produção e os dados são correlacionados a uma distância mínima de 200m. Os ataques de percevejos reduzem a viabilidade e o vigor de sementes de soja em diferentes intensidades dentro dos campos de produção. ABSTRACT: Studies have shown that the physiological quality of soybean seed production fields presents spatial variability. One of the possible causes of this variability can be localized attack of pests, especially stink bugs. The goal of this study was to determine the spatial distribution of stink bug damage in soybean seeds in seed production fields and their effect on physiological quality. The study was conducted in four seed production fields in the 2011/12 season, in the central region of Rio Grande do Sul, Brazil. For sample collection, a sampling grid with density of 1:0.10, 1:0.25, 1:0.10, 1:0.25 points/ ha was established, with total area of the fields of 4.3, 11.4, 5.9 and 12.7ha and cultivars NA 5909 RG, BMX Turbo RR, NA 5909 RG and NA 4725 RG, respectively. The following determinations were made: productivity, germination test, first count, seedling emergence and tetrazolium test. The generated data were used for the development of digital models (maps) using the ?System Agricultural CR - Campeiro 7? software. Damage caused by stink bugs in soybean seeds exhibit spatial variability in production fields and the data are correlated at a minimum distance of 200m. The attacks of stink bug reduce the viability and vigor of soybean seeds at different intensities within the fields of production. RESUMEN: Estudios anteriores han demostrado que la calidad fisiológica de las semillas de soya en los campos de producción presenta variabilidad espacial. Una de las causas posibles de tal variabilidad puede ser el ataque localizado de plagas, principalmente de chinches. El objetivo del presente trabajo fue determinar la distribución espacial de los daños por chinches en semillas de soya en los campos de producción de semillas y su efecto en la calidad fisiológica. El trabajo fue llevado a cabo en cuatro campos de producción de semillas en la zafra 2011/2012, en la región central del estado de Rio Grande del Sur, Brasil. Para la recolección de muestras se estableció una malla de muestreo con densidades de 1:0,10; 1:0,25; 1:0,10 y 1:0,25 puntos/ha, siendo el área total de los campos de 4,3; 11,4; 5,9 e 12,7ha y los cultivares NA 5909 RG, BMX Turbo RR, NA 5909 RG e NA 4725 RG, respectivamente. Fueron realizadas las siguientes determinaciones: productividad, prueba de germinación, primer contaje, emergencia de plántulas y test de tetrazolio. Los datos obtenidos fueron utilizados para la elaboración de modelos digitales (mapas) por medio del logicial ? Sistema Agropecuario CR - Campeiro 7?. Los daños causados por chinches en semillas de soya presentan variabilidad espacial en los campos de producción y los datos se correlacionan una distancia mínima de 200m. Los ataques de chinches reducen la viabilidad y el vigor de las semillas de soya en diversos grados en los campos de producción

Individual electrical conductivity test for the assessment of soybean seed germination.

ABSTRACT: Soybean seed quality is affected by many factors, which may occur during the production, processing, and storage phases. To ensure the quality of seeds, the adoption of fast and efficient methods to estimate seed viability in quality control programs is important. This study aimed to determine a partition point of the individual electrical conductivity test to predict soybean seed germination. Three lots each of five different soybean cultivars (Fundacep 57 RR, BMX Potência RR, BMX Força RR, BMX Turbo RR, and Nidera 7321 RG) were used. Seed quality was assessed through the mass of 1,000 seeds (MTS), moisture content (MC), germination test (G), bulk electrical conductivity (BEC), individual electrical conductivity (IEC), accelerated ageing (AA), and field seedling emergence (FSE). To determine a partition point in the IEC test for predicting germination, seeds were subjected to the germination test in the same position used for the IEC test. The accuracy of the partition point was tested by comparing predicted germination with the standard germination test. The partition point obtained for normal seeds was 130 ?S .cm-1.seed-1. The IEC test, however, had limitations in predicting soybean seed germination. The data for predicted germination were different from those obtained by the standard test, because the characteristics of each lot led to differences in the electrical conductivity values. RESUMO: A qualidade das sementes de soja pode ser afetada por inúmeros fatores que podem ocorrer em qualquer etapa da produção. Para garantir a qualidade das sementes é necessária a adoção testes rápidos e eficientes em estimar a viabilidade das sementes. O objetivo desse estudo foi determinar o ponto de partição do teste de condutividade elétrica individual (CEI) para estimar a germinação de sementes de soja. Foram utilizados 15 lotes pertencentes a diferentes cultivares (Fundacep 57 RR, BMX Potência RR, BMX Força RR, BMX Turbo RR, e Nidera 7321 RG). A caracterização dos lotes foi efetuada pelo peso de mil sementes, teor de água, germinação, condutividade elétrica massal e individual, envelhecimento acelerado e emergência a campo. Para determinação do ponto de partição as sementes foram submetidas ao teste padrão de germinação, respeitando-se a posição utilizada na leitura da CEI. A veracidade do ponto de partição foi testada através de comparação entre a germinação estimada e a obtida no teste padrão. O ponto de partição da CEI é 130 ?S .cm-1.semente-1. Entretanto o método mostrou limitação em estimar a germinação de sementes de soja. Características de cada lote influenciaram na CEI levando a diferenças entre a germinação estimada e o teste padrão

Scale-free static and dynamical correlations in melts of monodisperse and Flory-distributed homopolymers: A review of recent bond-fluctuation model studies

It has been assumed until very recently that all long-range correlations are screened in three-dimensional melts of linear homopolymers on distances beyond the correlation length $\xi$ characterizing the decay of the density fluctuations. Summarizing simulation results obtained by means of a variant of the bond-fluctuation model with finite monomer excluded volume interactions and topology violating local and global Monte Carlo moves, we show that due to an interplay of the chain connectivity and the incompressibility constraint, both static and dynamical correlations arise on distances $r \gg \xi$. These correlations are scale-free and, surprisingly, do not depend explicitly on the compressibility of the solution. Both monodisperse and (essentially) Flory-distributed equilibrium polymers are considered.Comment: 60 pages, 49 figure

Cell Cycle-Dependent Induction of Homologous Recombination by a Tightly Regulated I-SceI Fusion Protein

Double-strand break repair is executed by two major repair pathways: non-homologous end joining (NHEJ) and homologous recombination (HR). Whereas NHEJ contributes to the repair of ionizing radiation (IR)-induced double strand breaks (DSBs) throughout the cell cycle, HR acts predominantly during the S and G2 phases of the cell cycle. The rare-cutting restriction endonuclease, I-SceI, is in common use to study the repair of site-specific chromosomal DSBs in vertebrate cells. To facilitate analysis of I-SceI-induced DSB repair, we have developed a stably expressed I-SceI fusion protein that enables precise temporal control of I-SceI activation, and correspondingly tight control of the timing of onset of site-specific chromosome breakage. I-SceI-induced HR showed a strong, positive linear correlation with the percentage of cells in S phase, and was negatively correlated with the G1 fraction. Acute depletion of BRCA1, a key regulator of HR, disrupted the relationship between S phase fraction and I-SceI-induced HR, consistent with the hypothesis that BRCA1 regulates HR during S phase

GA4GH: International policies and standards for data sharing across genomic research and healthcare.

The Global Alliance for Genomics and Health (GA4GH) aims to accelerate biomedical advances by enabling the responsible sharing of clinical and genomic data through both harmonized data aggregation and federated approaches. The decreasing cost of genomic sequencing (along with other genome-wide molecular assays) and increasing evidence of its clinical utility will soon drive the generation of sequence data from tens of millions of humans, with increasing levels of diversity. In this perspective, we present the GA4GH strategies for addressing the major challenges of this data revolution. We describe the GA4GH organization, which is fueled by the development efforts of eight Work Streams and informed by the needs of 24 Driver Projects and other key stakeholders. We present the GA4GH suite of secure, interoperable technical standards and policy frameworks and review the current status of standards, their relevance to key domains of research and clinical care, and future plans of GA4GH. Broad international participation in building, adopting, and deploying GA4GH standards and frameworks will catalyze an unprecedented effort in data sharing that will be critical to advancing genomic medicine and ensuring that all populations can access its benefits

Session 17 Ecophysiology

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