AGN effect on cooling flow dynamics

We analyzed the feedback of AGN jets on cooling flow clusters using three-dimensional AMR hydrodynamic simulations. We studied the interaction of the jet with the intracluster medium and creation of low X-ray emission cavities (Bubbles) in cluster plasma. The distribution of energy input by the jet into the system was quantified in its different forms, i.e. internal, kinetic and potential. We find that the energy associated with the bubbles, (pV + gamma pV/(gamma-1)), accounts for less than 10 percent of the jet energy.Comment: "Accepted for publication in Astrophysics & Space Science

The lifecycle of powerful AGN outflows

During the course of this conference, much evidence was presented that points to an intimate connection between the energetic outflows driven by AGN and the energy budget and quite possibly also the evolution of their gaseous environments. However, it is still not clear if and how the AGN activity is triggered by the cooling gas, how long the activity lasts for and how these effects give rise to the observed distribution of morphologies of the outflows. In this contribution we concentrate on the high radio luminosity end of the AGN population. While most of the heating of the environmental gas may be due to less luminous and energetic outflows, these more powerful objects have a very profound influence on their surroundings. We will describe a simple model for powerful radio galaxies and radio-loud quasars that explains the dichotomy of their large-scale radio morphologies as well as their radio luminosity function.Comment: 6 pages, contribution to 'Heating vs. coooling in galaxies and galaxy clusters', Garching 2006, proceedings to be published by Springer (ESO Astrophysics Symposia), eds. H. Boehringer, P. Schuecker, G.W. Pratt & A. Finogueno

The impact of firms’ social media initiatives on operational efficiency and innovativeness

Social media have been increasingly adopted for organizational purposes but their operational implications are not well understood. Firms’ social media initiatives might facilitate information flow and knowledge sharing within and across organizations, strengthening firm‐customer interaction, and improving internal and external collaboration. In this research we empirically examine the impact of social media initiatives on firms’ operational efficiency and innovativeness. Taking the resource‐based view of firms’ information capability, we consider firms’ social media initiatives as strategic resources for operational improvement. We posit that firms’ social media initiatives enhance dynamic knowledge‐sharing routines through an information‐rich social network, leading to both operational efficiency and innovativeness. Collecting secondary data in a longitudinal setting from multiple sources, we construct dynamic panel data (DPD) models. Based on system generalized method of moments (GMM) estimation, we show that firms’ social media initiatives improve operational efficiency and innovativeness. We identify the importance of an information‐rich social network to the creation of knowledge‐based advantage through firms’ social media initiatives, and discuss the theoretical and managerial implications from the perspective of operations management

Satisfaction of hydrogen-bonding potential influences the conservation of polar sidechains

Although polar amino acids tend to be found on the surface of proteins due to their hydrophilic nature, their important roles within the core of proteins are now becoming better recognized. It has long been understood that a significant number of mainchain functions will not achieve hydrogen bond satisfaction through the formation of secondary structures; in these circumstances, it is generally buried polar residues that provide hydrogen bond satisfaction. Here, we describe an analysis of the hydrogen-bonding of polar amino acids in a set of structurally aligned protein families. This allows us not only to calculate the conservation of each polar residue but also to assess whether conservation is correlated with the hydrogen-bonding potential of polar sidechains. We show that those polar sidechains whose hydrogen-bonding potential is satisfied tend to be more conserved than their unsatisfied or nonhydrogen-bonded counterparts, particularly when buried. Interestingly, these buried and satisfied polar residues are significantly more conserved than buried hydrophobic residues. Forming hydrogen bonds to mainchain amide atoms also influences conservation, with those satisfied buried polar residues that form two hydrogen bonds to mainchain amides being significantly more conserved than those that form only one or none. These results indicate that buried polar residues whose hydrogen-bonding potential is satisfied are likely to have important roles in maintaining protein structure

Structural and functional constraints in the evolution of protein families

High-throughput genomic sequencing has focused attention on understanding differences between species and between individuals. When this genetic variation affects protein sequences, the rate of amino acid substitution reflects both Darwinian selection for functionally advantageous mutations and selectively neutral evolution operating within the constraints of structure and function. During neutral evolution, whereby mutations accumulate by random drift, amino acid substitutions are constrained by factors such as the formation of intramolecular and intermolecular interactions and the accessibility to water or lipids surrounding the protein. These constraints arise from the need to conserve a specific architecture and to retain interactions that mediate functions in protein families and superfamilies

Meet me halfway: when genomics meets structural bioinformatics

The DNA sequencing technology developed by Frederick Sanger in the 1970s established genomics as the basis of comparative genetics. The recent invention of next-generation sequencing (NGS) platform has added a new dimension to genome research by generating ultra-fast and high-throughput sequencing data in an unprecedented manner. The advent of NGS technology also provides the opportunity to study genetic diseases where sequence variants or mutations are sought to establish a causal relationship with disease phenotypes. However, it is not a trivial task to seek genetic variants responsible for genetic diseases and even harder for complex diseases such as diabetes and cancers. In such polygenic diseases, multiple genes and alleles, which can exist in healthy individuals, come together to contribute to common disease phenotypes in a complex manner. Hence, it is desirable to have an approach that integrates omics data with both knowledge of protein structure and function and an understanding of networks/pathways, i.e. functional genomics and systems biology; in this way, genotype-phenotype relationships can be better understood. In this review, we bring this 'bottom-up' approach alongside the current NGS-driven genetic study of genetic variations and disease aetiology. We describe experimental and computational techniques for assessing genetic variants and their deleterious effects on protein structure and function