The XMM Cluster Survey: the interplay between the brightest cluster galaxy and the intracluster medium via AGN feedback

Using a sample of 123 X‐ray clusters and groups drawn from the XMM Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole and the intracluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant active galactic nuclei (AGN) feedback, gas cooling dominates in those with T X > 2 keV while AGN feedback dominates below. This may be understood through the subunity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 10 13 < M 500 < 10 15  M ⊙ and the lack of correlation between radio luminosity and cluster mass, such that BCG AGN in groups can have relatively more energetic influence on the ICM. The L X – T X relation for systems with the most massive BCGs, or those with BCGs co‐located with the peak of the ICM emission, is steeper than that for those with the least massive and most offset, which instead follows self‐similarity. This is evidence that a combination of central gas cooling and powerful, well fuelled AGN causes the departure of the ICM from pure gravitational heating, with the steepened relation crossing self‐similarity at T X = 2 keV. Importantly, regardless of their black hole mass, BCGs are more likely to host radio‐loud AGN if they are in a massive cluster ( T X ≳ 2 keV) and again co‐located with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of ‘cluster’ and ‘group’, delineated at 2 keV.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91324/1/j.1365-2966.2012.20764.x.pd

Extracellular Matrix Aggregates from Differentiating Embryoid Bodies as a Scaffold to Support ESC Proliferation and Differentiation

Embryonic stem cells (ESCs) have emerged as potential cell sources for tissue engineering and regeneration owing to its virtually unlimited replicative capacity and the potential to differentiate into a variety of cell types. Current differentiation strategies primarily involve various growth factor/inducer/repressor concoctions with less emphasis on the substrate. Developing biomaterials to promote stem cell proliferation and differentiation could aid in the realization of this goal. Extracellular matrix (ECM) components are important physiological regulators, and can provide cues to direct ESC expansion and differentiation. ECM undergoes constant remodeling with surrounding cells to accommodate specific developmental event. In this study, using ESC derived aggregates called embryoid bodies (EB) as a model, we characterized the biological nature of ECM in EB after exposure to different treatments: spontaneously differentiated and retinoic acid treated (denoted as SPT and RA, respectively). Next, we extracted this treatment-specific ECM by detergent decellularization methods (Triton X-100, DOC and SDS are compared). The resulting EB ECM scaffolds were seeded with undifferentiated ESCs using a novel cell seeding strategy, and the behavior of ESCs was studied. Our results showed that the optimized protocol efficiently removes cells while retaining crucial ECM and biochemical components. Decellularized ECM from SPT EB gave rise to a more favorable microenvironment for promoting ESC attachment, proliferation, and early differentiation, compared to native EB and decellularized ECM from RA EB. These findings suggest that various treatment conditions allow the formulation of unique ESC-ECM derived scaffolds to enhance ESC bioactivities, including proliferation and differentiation for tissue regeneration applications. © 2013 Goh et al

Parâmetros genéticos de características de carcaça em bovinos da raça Nelore.

A necessidade de melhoria das carcaças bovinas produzidas torna necessário o estudo de características que permitam rapidez na identificação de genótipos superiores. Considerando a grande representatividade da raça Nelore no rebanho brasileiro, estimou-se parâmetros genéticos para conformação frigorífica ao sobreano (CFS), área de olho de lombo (AOL), espessura de gordura subcutânea (EGS) e marmoreio (MAR). Adotou-se modelo animal em análise univariada. As estimativas de herdabilidade para as características de CFS, AOL, EGS e MAR foram de 0,21; 0,18; 0,15 e 0,33, respectivamente. Características de carcaça avaliadas por ultrassonografia podem ser incluídas nos processos de seleção, esperando-se respostas satisfatórias. A conformação frigorífica ao sobreano pode ser adotada como critério de seleção de fácil adoção e baixo custo para melhoria das carcaças produzidas na raça Nelore

Repeated pulses of vertical methane flux recorded in glacial sediments from the southeast Bering Sea

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 26 (2011): PA2210, doi:10.1029/2010PA001993.There is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glacial period of intense methane flux reaching the seafloor. Within the uncertainty of the radiocarbon age model, the episodes are contemporaneous in the two cores and have similar timing and duration as Dansgaard-Oeschger events. The episodes are marked by horizons of sediment containing 13C-depleted authigenic carbonate minerals; 13C-depleted archaeal and bacterial lipids, which resemble those found in ANME-1 type anaerobic methane oxidizing microbial consortia; and changes in the abundance and species distribution of benthic foraminifera. The similar timing and isotopic composition of the authigenic carbonates in the two cores is consistent with a region-wide increase in the upward flux of methane bearing fluids. This study is the first observation outside Santa Barbara Basin of pervasive, repeated methane flux in glacial sediments. However, contrary to the “Clathrate Gun Hypothesis” (Kennett et al., 2003), these coring sites are too deep for methane hydrate destabilization to be the cause, implying that a much larger part of the ocean's sedimentary methane may participate in climate or carbon cycle feedback at millennial timescales. We speculate that pulses of methane in these opal-rich sediments could be caused by the sudden release of overpressure in pore fluids that builds up gradually with silica diagenesis. The release could be triggered by seismic shaking on the Aleutian subduction zone caused by hydrostatic pressure increase associated with sea level rise at the start of interstadials.Support for this project was from the National Science Foundation Office of Polar Programs, United States Department of Energy, Oak Foundation, and MARUM at University of Bremen