899 research outputs found
Polyphosphate Loss Promotes SNF/SWI- and Gcn5-Dependent Mitotic Induction of PHO5
Approximately 800 transcripts in Saccharomyces cerevisiae are cell cycle regulated. The oscillation of ∼40% of these genes, including a prominent subclass involved in nutrient acquisition, is not understood. To address this problem, we focus on the mitosis-specific activation of the phosphate-responsive promoter, PHO5. We show that the unexpected mitotic induction of the PHO5 acid phosphatase in rich medium requires the transcriptional activators Pho4 and Pho2, the cyclin-dependent kinase inhibitor Pho81, and the chromatin-associated enzymes Gcn5 and Snf2/Swi2. PHO5 mitotic activation is repressed by addition of orthophosphate, which significantly increases cellular polyphosphate. Polyphosphate levels also fluctuate inversely with PHO5 mRNA during the cell cycle, further substantiating an antagonistic link between this phosphate polymer and PHO5 mitotic regulation. Moreover, deletion of PHM3, required for polyphosphate accumulation, leads to premature onset of PHO5 expression, as well as an increased rate, magnitude, and duration of PHO5 activation. Orthophosphate addition, however, represses mitotic PHO5 expression in a phm3Δ strain. Thus, polyphosphate per se is not necessary to repress PHO transcription but, when present, replenishes cellular phosphate during nutrient depletion. These results demonstrate a dynamic mechanism of mitotic transcriptional regulation that operates mostly independently of factors that drive progression through the cell cycle
Specific heat and high-temperature series of lattice models: interpolation scheme and examples on quantum spin systems in one and two dimensions
We have developed a new method for evaluating the specific heat of lattice
spin systems. It is based on the knowledge of high-temperature series
expansions, the total entropy of the system and the low-temperature expected
behavior of the specific heat as well as the ground-state energy. By the choice
of an appropriate variable (entropy as a function of energy), a stable
interpolation scheme between low and high temperature is performed. Contrary to
previous methods, the constraint that the total entropy is log(2S+1) for a spin
S on each site is automatically satisfied. We present some applications to
quantum spin models on one- and two- dimensional lattices. Remarkably, in most
cases, a good accuracy is obtained down to zero temperature.Comment: 10 pages (RevTeX 4) including 11 eps figures. To appear in Phys. Rev.
Deciphering Human Heat Shock Transcription Factor 1 Regulation via Post-Translational Modification in Yeast
Heat shock transcription factor 1 (HSF1) plays an important role in the cellular response to proteotoxic stresses. Under normal growth conditions HSF1 is repressed as an inactive monomer in part through post-translation modifications that include protein acetylation, sumoylation and phosphorylation. Upon exposure to stress HSF1 homotrimerizes, accumulates in nucleus, binds DNA, becomes hyper-phosphorylated and activates the expression of stress response genes. While HSF1 and the mechanisms that regulate its activity have been studied for over two decades, our understanding of HSF1 regulation remains incomplete. As previous studies have shown that HSF1 and the heat shock response promoter element (HSE) are generally structurally conserved from yeast to metazoans, we have made use of the genetically tractable budding yeast as a facile assay system to further understand the mechanisms that regulate human HSF1 through phosphorylation of serine 303. We show that when human HSF1 is expressed in yeast its phosphorylation at S303 is promoted by the MAP-kinase Slt2 independent of a priming event at S307 previously believed to be a prerequisite. Furthermore, we show that phosphorylation at S303 in yeast and mammalian cells occurs independent of GSK3, the kinase primarily thought to be responsible for S303 phosphorylation. Lastly, while previous studies have suggested that S303 phosphorylation represses HSF1-dependent transactivation, we now show that S303 phosphorylation also represses HSF1 multimerization in both yeast and mammalian cells. Taken together, these studies suggest that yeast cells will be a powerful experimental tool for deciphering aspects of human HSF1 regulation by post-translational modifications
Large- expansion of the specific heat for the two-dimensional -state Potts model
We have calculated the large- expansion for the specific heat at the phase
transition point in the two-dimensional -state Potts model to the 23rd order
in using the finite lattice method. The obtained series allows us
to give highly convergent estimates of the specific heat for on the first
order transition point. The result confirm us the correctness of the conjecture
by Bhattacharya et al. on the asymptotic behavior of the specific heat for .Comment: 7 pages, LaTeX, 2 postscript figure
Mechanical design, materials selection, fabrication and assembly of ultraclean, high-gain, Nd: glass disk laser amplifiers
Particulate contamination in disk amplifiers with high flashlamp fluxes (which can generate particles) causes three types of laser beam obscuration, which cause small-scale self-focusing. Methods for obtaining disk amplifiers that stay clean are described. (auth
The Three Dimensions of Archaeology - Introduction
This volume brings together presentations from two sessions organized for the XVII World UISPP Conference that was held from 1-7 September 2014 in Burgos (Spain). The sessions are: The scientific value of 3D archaeology, organised by Hans Kamermans, Chiara Piccoli and Roberto Scopigno, and Detecting the Landscape(s) – Remote Sensing Techniques from Research to Heritage Management, organised by Axel Posluschny and Wieke de Neef. The common thread amongst the papers presented here is the application of digital recording techniques to enhance the documentation and analysis of the spatial component intrinsically present in archaeological data. For a long time the capturing of the third dimension, the depth, the height or z-coordinate, was problematic. Traditionally, excavation plans and sections were documented in two dimensions. Objects were also recorded in two dimensions, often from different angles. Remote sensing images like aerial photographs were represented as flat surfaces. Although depth could be visualized with techniques such as stereoscopes, analysis of relief was troublesome. All this changed at the end of the last century with the introduction of computer based digitization technologies, 3D software, and digital near-surface sampling devices. The spatial properties of the multi-scale archaeological dataset can now be accurately recorded, analysed and presented. Relationships between artefacts can be clarified by visualizing the records in a three dimensional space, computer-based simulations can be made to test hypotheses on the past use of space, remote sensing techniques help in detecting previously hidden features of landscapes, thus shedding light on bygone land uses.
 Digital Archaeolog
Kondo Effect in a Metal with Correlated Conduction Electrons: Diagrammatic Approach
We study the low-temperature behavior of a magnetic impurity which is weakly
coupled to correlated conduction electrons. To account for conduction electron
interactions a diagrammatic approach in the frame of the 1/N expansion is
developed. The method allows us to study various consequences of the conduction
electron correlations for the ground state and the low-energy excitations. We
analyse the characteristic energy scale in the limit of weak conduction
electron interactions. Results are reported for static properties (impurity
valence, charge susceptibility, magnetic susceptibility, and specific heat) in
the low-temperature limit.Comment: 16 pages, 9 figure
A multidisciplinary study of an exceptional prehistoric waste dump in the mountainous inland of Calabria (Italy):Implications for reconstructions of prehistoric land use and vegetation in Southern Italy
A multidisciplinary study of an exceptional prehistoric waste dump in the mountainous inland of Calabria (Italy):Implications for reconstructions of prehistoric land use and vegetation in Southern Italy
Stakeholder participation in agricultural research projects: a conceptual framework for reflection and decision-making
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