Dynamic multifactor hubs interact transiently with sites of active transcription in Drosophila embryos.

The regulation of transcription requires the coordination of numerous activities on DNA, yet how transcription factors mediate these activities remains poorly understood. Here, we use lattice light-sheet microscopy to integrate single-molecule and high-speed 4D imaging in developing Drosophila embryos to study the nuclear organization and interactions of the key transcription factors Zelda and Bicoid. In contrast to previous studies suggesting stable, cooperative binding, we show that both factors interact with DNA with surprisingly high off-rates. We find that both factors form dynamic subnuclear hubs, and that Bicoid binding is enriched within Zelda hubs. Remarkably, these hubs are both short lived and interact only transiently with sites of active Bicoid-dependent transcription. Based on our observations, we hypothesize that, beyond simply forming bridges between DNA and the transcription machinery, transcription factors can organize other proteins into hubs that transiently drive multiple activities at their gene targets.Editorial noteThis article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)

Past terrestrial water storage (1980–2008) in the Amazon Basin reconstructed from GRACE and in situ river gauging data

Terrestrial water storage (TWS) composed of surface waters, soil moisture, groundwater and snow where appropriate, is a key element of global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) space gravimetry mission provides a new tool to measure large-scale TWS variations. However, for the past few decades, direct estimate of TWS variability is accessible from hydrological modeling only. Here we propose a novel approach that combines GRACE-based TWS spatial patterns with multi-decadal-long in situ river level records, to reconstruct past 2-D TWS over a river basin. Results are presented for the Amazon Basin for the period 1980–2008, focusing on the interannual time scale. Results are compared with past TWS estimated by the global hydrological model ISBA-TRIP. Correlations between reconstructed past interannual TWS variability and known climate forcing modes over the region (e.g., El Niño-Southern Oscillation and Pacific Decadal Oscillation) are also estimated. This method offers new perspective for improving our knowledge of past interannual TWS in world river basins where natural climate variability (as opposed to direct anthropogenic forcing) drives TWS variations

Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids

We study both experimentally and theoretically the rheological behavior of isotropic bidisperse suspensions of noncolloidal particles in yield stress fluids. We focus on materials in which noncolloidal particles interact with the suspending fluid only through hydrodynamical interactions. We observe that both the elastic modulus and yield stress of bidisperse suspensions are lower than those of monodisperse suspensions of same solid volume fraction. Moreover, we show that the dimensionless yield stress of such suspensions is linked to their dimensionless elastic modulus and to their solid volume fraction through the simple equation of Chateau et al.[J. rheol. 52, 489-506 (2008)]. We also show that the effect of the particle size heterogeneity can be described by means of a packing model developed to estimate random loose packing of assemblies of dry particles. All these observations finally allow us to propose simple closed form estimates for both the elastic modulus and the yield stress of bidisperse suspensions: while the elastic modulus is a function of the reduced volume fraction $\phi/\phi_m$ only, where $\phi_m$ is the estimated random loose packing, the yield stress is a function of both the volume fraction $\phi$ and the reduced volume fraction

Avaliação de genótipos de soja em área de rotação com a cultura de arroz irrigado no município de Capão do Leão na safra 2013/14.

O objetivo deste trabalho foi avaliar o comportamento de genótipos de soja nas condições edafoclimáticas de áreas de rotação com a cultura do arroz irrigado no RS

Plla Synthesis And Nanofibers Production: Viability By Human Mesenchymal Stem Cell From Adipose Tissue

The absorbable polyacid is one of the most used and studied materials in tissue engineering. This work synthesized a poly (L-lactic acid) (PLLA) through ring-opening polymerization and produced with it nanofibers by the electrospinning process. The PLLA was analyzed by FTIR and its cytotoxicity was evaluated by the MTT assay and Live/Dead (R) (Molecular Probes). The tests were performed in contact with human mesenchymal cells at varying times. The high rates of viability and proliferation of cells in contact with the PLLA shown by MTT and Live/Dead (R) tests demonstrate that this PLLA is a biocompatible material. There was also the successful production of electrospinning nanofibers, which can be converted for specific biomedical applications in the future. (C) 2015 The Authors. Published by Elsevier B.V.492132212nd CIRP Conference on Biomanufacturing (CIRP-BioM)JUL 29-31, 2015Manchester, ENGLAN

Universality in Bacterial Colonies

The emergent spatial patterns generated by growing bacterial colonies have been the focus of intense study in physics during the last twenty years. Both experimental and theoretical investigations have made possible a clear qualitative picture of the different structures that such colonies can exhibit, depending on the medium on which they are growing. However, there are relatively few quantitative descriptions of these patterns. In this paper, we use a mechanistically detailed simulation framework to measure the scaling exponents associated with the advancing fronts of bacterial colonies on hard agar substrata, aiming to discern the universality class to which the system belongs. We show that the universal behavior exhibited by the colonies can be much richer than previously reported, and we propose the possibility of up to four different sub-phases within the medium-to-high nutrient concentration regime. We hypothesize that the quenched disorder that characterizes one of these sub-phases is an emergent property of the growth and division of bacteria competing for limited space and nutrients.Comment: 12 pages, 5 figure

The effect of thresholding on temporal avalanche statistics

We discuss intermittent time series consisting of discrete bursts or avalanches separated by waiting or silent times. The short time correlations can be understood to follow from the properties of individual avalanches, while longer time correlations often present in such signals reflect correlations between triggerings of different avalanches. As one possible source of the latter kind of correlations in experimental time series, we consider the effect of a finite detection threshold, due to e.g. experimental noise that needs to be removed. To this end, we study a simple toy model of an avalanche, a random walk returning to the origin or a Brownian bridge, in the presence and absence of superimposed delta-correlated noise. We discuss the properties after thresholding of artificial timeseries obtained by mixing toy avalanches and waiting times from a Poisson process. Most of the resulting scalings for individual avalanches and the composite timeseries can be understood via random walk theory, except for the waiting time distributions when strong additional noise is added. Then, to compare with a more complicated case we study the Manna sandpile model of self-organized criticality, where some further complications appear.Comment: 15 pages, 12 figures, submitted to J. Stat. Mech., special issue of the UPoN2008 conferenc

Vicious walkers, friendly walkers and Young tableaux II: With a wall

We derive new results for the number of star and watermelon configurations of vicious walkers in the presence of an impenetrable wall by showing that these follow from standard results in the theory of Young tableaux, and combinatorial descriptions of symmetric functions. For the problem of $n$-friendly walkers, we derive exact asymptotics for the number of stars and watermelons both in the absence of a wall and in the presence of a wall.Comment: 35 pages, AmS-LaTeX; Definitions of n-friendly walkers clarified; the statement of Theorem 4 and its proof were correcte

Alteração na fotossíntese causada pela mancha de alternaria (Alternaria helianthi) em girassol.

A mancha de Alternaria (Alternaria helianthi) diminui a área fotossintética da planta, devido à formação de manchas foliares que podem coalescer, formando áreas extensas de tecido necrosado, provocando seca prematura da folha. Objetivou-se avaliar as alterações na fotossíntese causada pela mancha de Alternaria em quatro genótipos de girassol (BRS 324, BRS 321, BRS 323 e HLA 887). O delineamento experimental foi inteiramente casualizado com 4 tratamentos e 6 repetições. Plantas de girassol cultivadas em vaso foram inoculadas com o fungo, no estágio V8 (oito folhas verdadeiras). Após 32 horas, foi feita a leitura da fotossíntese líquida nas folhas 3 e 4, utilizando o analisador de fotossíntese LI-6400XT. A taxa líquida de fotossíntese foi relacionada à severidade da doença por meio do modelo Px/Po=(1-x)b, onde Px representa a taxa fotossintética líquida de folhas com severidade de doença x (em proporção), Po representa a taxa fotossintética líquida média de folhas sadias e b representa a relação entre a lesão virtual (área foliar sem sintomas mas com fotossíntese nula) e a lesão visual (área foliar coberta por sintomas). Os valores de b determinados por regressão não-linear (R2 de 0,35 a 0,52 para os diferentes materiais) variaram entre 0,77 a 2,18. Observou-se diferença na taxa de fotossíntese líquida para os genótipos BRS 324 (1,93), BRS 321 (2,15) e BRS 323 (2,17), que apresentaram b maior que 1. Esta alteração na atividade fotossintética pode ser causada por redução na interceptação da radiação (RI), resultante da perda de área foliar fotossintetizante nas áreas próximas à região necrosada