645 research outputs found

    More on the Tensor Response of the QCD Vacuum to an External Magnetic Field

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    In this Letter we discuss a few issues concerning the magnetic susceptibility of the quark condensate and the Son-Yamamoto (SY) anomaly matching equation. It is shown that the SY relation in the IR implies a nontrivial interplay between the kinetic and WZW terms in the chiral Lagrangian. It is also demonstrated that in a holographic framework an external magnetic field triggers mixing between scalar and tensor fields. Accounting for this, one may calculate the magnetic susceptibility of the quark condensate to all orders in the magnetic field.Comment: 20 pages, 2 figure

    On the stationary vibrations of a rectangular plate subjected to stress prescribed partially at the circumference

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    The stationary periodical problem of a vibrating rectangular plate, stressed at a segment while fixed elsewhere at one of its edges, is considered. Using the finite Fourier transformation, the problem is converted to a singular integral equation that in turn can be reduced to an infinite system of algebraic equations. The truncation of the algebraic system is justified

    Picard satellite for solar astrometry

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    The Picard solar satellite has been launched on June 15, 2010. This mission is dedicated to the measurement of the solar diameter with an expected accuracy of milliarcseconds of arc. The radiometer onboard is to measure the total solar irradiance. The final goal is the evaluation of the W, the logarithmic ratio of radius and luminosity. This parameter will help the climatologists to recover past values of the solar luminosity when the radius is available from ancient eclipses data.Comment: 5 pages, 2 figures, Proc. 2nd Galileo-Xu Guangqi Meeting, Ventimiglia - Villa Hanbury, Italy, 11-16 July 201

    PNAS plus: plasmodium falciparum responds to amino acid starvation by entering into a hibernatory state

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    The human malaria parasite Plasmodium falciparum is auxotrophic for most amino acids. Its amino acid needs are met largely through the degradation of host erythrocyte hemoglobin; however the parasite must acquire isoleucine exogenously, because this amino acid is not present in adult human hemoglobin. We report that when isoleucine is withdrawn from the culture medium of intraerythrocytic P. falciparum, the parasite slows its metabolism and progresses through its developmental cycle at a reduced rate. Isoleucine-starved parasites remain viable for 72 h and resume rapid growth upon resupplementation. Protein degradation during starvation is important for maintenance of this hibernatory state. Microarray analysis of starved parasites revealed a 60% decrease in the rate of progression through the normal transcriptional program but no other apparent stress response. Plasmodium parasites do not possess a TOR nutrient-sensing pathway and have only a rudimentary amino acid starvation-sensing eukaryotic initiation factor 2α (eIF2α) stress response. Isoleucine deprivation results in GCN2-mediated phosphorylation of eIF2α, but kinase-knockout clones still are able to hibernate and recover, indicating that this pathway does not directly promote survival during isoleucine starvation. We conclude that P. falciparum, in the absence of canonical eukaryotic nutrient stress-response pathways, can cope with an inconsistent bloodstream amino acid supply by hibernating and waiting for more nutrient to be provided

    Expanding Duplication of Free Fatty Acid Receptor-2 (GPR43) Genes in the Chicken Genome

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    International audienceFree fatty acid receptors (FFAR) belong to a family of five G-protein coupled receptors that are involved in the regulation of lipidmetabolism, so that their loss of function increases the risk of obesity. The aim of this study was to determine the expansion of genesencoding paralogs of FFAR2 in the chicken, considered as amodel organism for developmental biology and biomedical research. Byestimating the gene copy number using quantitative polymerase chain reaction, genomic DNA resequencing, and RNA sequencingdata, we showed the existence of 23 ±1.5 genes encoding FFAR2 paralogs in the chicken genome. The FFAR2 paralogs shared anidentity from 87.2%up to 99%. Extensive gene conversion was responsible for this high degree of sequence similarities betweenthese genes, and this concerned especially the four amino acids known to be critical for ligand binding. Moreover, elevated nonsynonymous/synonymous substitutionratios onsomeamino acids withinor inclose-vicinity of the ligand-bindinggroove suggest thatpositive selectionmay have reduced the effective rate of gene conversion in this region, thus contributing to diversify the function ofsome FFAR2 paralogs. All the FFAR2 paralogs were located on a microchromosome in a same linkage group. FFAR2 genes wereexpressed in different tissues and cells such as spleen, peripheral blood mononuclear cells, abdominal adipose tissue, intestine, andlung, with the highest rate of expression in testis. Further investigations are needed to determine whether these chicken-specificevents along evolution are the consequence of domestication and may play a role in regulating lipid metabolism in this species

    The BAH domain of Rsc2 is a histone H3 binding domain

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    Bromo-adjacent homology (BAH) domains are commonly found in chromatin-associated proteins and fall into two classes; Remodels the Structure of Chromatin (RSC)-like or Sir3-like. Although Sir3-like BAH domains bind nucleosomes, the binding partners of RSC-like BAH domains are currently unknown. The Rsc2 subunit of the RSC chromatin remodeling complex contains an RSC-like BAH domain and, like the Sir3-like BAH domains, we find Rsc2 BAH also interacts with nucleosomes. However, unlike Sir3-like BAH domains, we find that Rsc2 BAH can bind to recombinant purified H3 in vitro, suggesting that the mechanism of nucleosome binding is not conserved. To gain insight into the Rsc2 BAH domain, we determined its crystal structure at 2.4 Ă… resolution. We find that it differs substantially from Sir3-like BAH domains and lacks the motifs in these domains known to be critical for making contacts with histones. We then go on to identify a novel motif in Rsc2 BAH that is critical for efficient H3 binding in vitro and show that mutation of this motif results in defective Rsc2 function in vivo. Moreover, we find this interaction is conserved across Rsc2-related proteins. These data uncover a binding target of the Rsc2 family of BAH domains and identify a novel motif that mediates this interaction
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