1,979 research outputs found
The Baryon Oscillation Spectroscopic Survey: Precision measurements of the absolute cosmic distance scale
BOSS, the Baryon Oscillation Spectroscopic Survey, is a 5-year program to
measure the absolute cosmic distance scale and expansion rate with
percent-level precision at redshifts z<0.7 and z~2.5. BOSS uses the "standard
ruler" provided by baryon acoustic oscillations (BAO). BOSS will achieve a near
optimal measurement of the BAO scale at z<0.7, with a redshift survey of 1.5
million luminous galaxies. It will pioneer a new method of BAO measurement at
high redshift, using the LyA forest to 160,000 QSOs in the redshift range
2.1<z<3.0. The forecast measurement precision for angular diameter distance d_A
is 1.0%, 1.0%, and 1.5% at z=0.35, 0.6, and 2.5, respectively, and the forecast
precision for the Hubble parameter H(z) is 1.8%, 1.7%, and 1.2% at the same
redshifts. These measurements will provide powerful constraints on the nature
of dark energy and the curvature of space, complementing the constraints
obtained from other probes. BOSS will also provide a superb data set for
studying large- and small-scale clustering, the evolution of massive galaxies
and the luminosity function and clustering of QSOs at 2.3 < z < 6.5. BOSS is
one of four surveys that comprise SDSS-III (the Sloan Digital Sky Survey III),
a 6-year program that will use highly multiplexed spectrographs on the 2.5-m
Sloan Foundation Telescope to investigate cosmological parameters, the history
and structure of the Milky Way galaxy, and the population of giant planet
systems.Comment: Unpublished SDSS-III white paper for the US Decadal Survey. See
http://www.sdss3.org for details of the international SDSS-III projec
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Fitting Interatomic Potentials to Reproduce Phase Transitions
Due to the high computational demand of quantum mechanical simulations, researchers still rely on models for atomic interactions to simulate a large number of atoms. These so called “interatomic potentials” take a variety of forms ranging from the simple Lennard-Jones potential to machine learning potentials. They are usually fitted for specific structures as well as pressure and temperature realms and do not necessarily reproduce the full experimentally known solid and liquid phase diagram. There have been limited trials of fitting the parameters of interatomic potentials to phase transitions. In this work, I present improvements upon two already existing potentials from the literature – a CuAu potential and a Ti potential. These potentials are modified so that they reproduce experimental phase transitions better than before. For the CuAu potential, I fit the eutectic melting curve using my own implementation of the Nelder-Mead algorithm. The Ti potential is modified to predict a triple point which is in qualitative agreement with experimental predictions. To calculate phase transitions, I use the nested sampling algorithm which was already established in the literature. The Ti nested sampling results are verified with thermodynamic integration. My Nelder-Mead implementation allows for semi-automatic submission and analysis of the nested sampling runs. Both potentials are improved considerably. The new CuAu potential now accurately reproduces the melting curve for the alloy compositions used in the fitting procedure. The new Ti potential now – as opposed to before the modifications – predicts a triple point which is in qualitative accordance with experimental predictions. My work demonstrates how the transferability of potentials can be improved by just slight modifications to the original parameters using experimental data of the phase diagram. The Nelder-Mead implementation used for the CuAu potential could be used to improve other potentials. To fit more complex systems, the way the objective function is calculated could be upgraded in future.EPSRC Centre for Doctoral Training in Computational Methods for Materials Science under grant number EP/L015552/1. Computing time on the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk) via the UKCP consortium funded by EPSRC grants ref EP/K013564/1 and ref EP/P022561/1. Additional funding from King's College (Cambridge) after the third year of the PhD
Alignments of mitochondrial genome arrangements: Applications to metazoan phylogeny
Mitochondrial genomes provide a valuable dataset for phylogenetic studies, in particular of metazoan phylogeny because of the extensive taxon sample that is available. Beyond the traditional sequence-based analysis it is possible to extract phylogenetic information from the gene order. Here we present a novel approach utilizing these data based on cyclic list alignments of the gene orders. A progressive alignment approach is used to combine pairwise list alignments into a multiple alignment of gene orders. Parsimony methods are used to reconstruct phylogenetic trees, ancestral gene orders, and consensus patterns in a straightforward approach. We apply this method to study the phylogeny of protostomes based exclusively on mitochondrial genome arrangements. We, furthermore, demonstrate that our approach is also applicable to the much larger genomes of chloroplasts
Convergent evolution of heat-inducibility during subfunctionalization of the Hsp70 gene family
Background: Heat-shock proteins of the 70 kDa family (Hsp70s) are essential chaperones required for key cellular functions. In eukaryotes, four subfamilies can be distinguished according to their function and localisation in different cellular compartments: cytosol, endoplasmic reticulum, mitochondria and chloroplasts. Generally, multiple cytosol-type Hsp70s can be found in metazoans that show either constitutive expression and/or stress-inducibility, arguing for the evolution of different tasks and functions. Information about the hsp70 copy number and diversity in microbial eukaryotes is, however, scarce, and detailed knowledge about the differential gene expression in most protists is lacking. Therefore, we have characterised the Hsp70 gene family of Paramecium caudatum to gain insight into the evolution and differential heat stress response of the distinct family members in protists and to investigate the diversification of eukaryotic hsp70s focusing on the evolution of heat-inducibility.
Results: Eleven putative hsp70 genes could be detected in P. caudatum comprising homologs of three major Hsp70-subfamilies. Phylogenetic analyses revealed five evolutionarily distinct Hsp70-groups, each with a closer relationship to orthologous sequences of Paramecium tetraurelia than to another P. caudatum Hsp70-group. These highly diverse, paralogous groups resulted from duplications preceding Paramecium speciation, underwent divergent evolution and were subject to purifying selection. Heat-shock treatments were performed to test for differential expression patterns among the five Hsp70-groups as well as for a functional conservation within Paramecium. These treatments induced exceptionally high mRNA up-regulations in one cytosolic group with a low basal expression, indicative for the major heat inducible hsp70s. All other groups showed comparatively high basal expression levels and moderate heat-inducibility, signifying constitutively expressed genes. Comparative EST analyses for P. tetraurelia hsp70s unveiled a corresponding expression pattern, which supports a functionally conserved evolution of the Hsp70 gene family in Paramecium.
Conclusions: Our analyses suggest an independent evolution of the heat-inducible cytosol-type hsp70s in Paramecium and in its close relative Tetrahymena, as well as within higher eukaryotes. This result indicates convergent evolution during hsp70 subfunctionalization and implies that heat-inducibility evolved several times during the course of eukaryotic evolution
Jahresbericht der Research Academy Leipzig 2008
Jahresbericht der Research Academy Leipzig 2008:Inhalt
-Die Research Academy Leipzig
-Vorwort Research Academy Leipzig im Aufwind
-Die Arbeit der RAL-Doktorandenvertretung 2008
-Fächerübergreifendes Qualifikationsprogramm Die Veranstaltungen der Research Academy Leipzig 2008
-Seminar „Junge Wissenschaft und Praxis“
-Präsentation in der Öffentlichkeit
-Kleinkindbetreuung fĂĽr Kinder der Doktorandinnen und Doktoranden
-Das Graduiertenzentrum Mathematik/Informatik und Naturwissenschaften
-Graduiertenschule Leipzig School of Natural Sciences – Building with Molecules and Nano-objects BuildMoNa
-International Max Planck Research School Mathematics in the Sciences
-Deutsch-Französisches Doktorandenkollegium/Collège Doctoral Franco-Allemand Statistische Physik in komplexen Systemen
-International Research Training Group Diffusion in Porous Materials
-Graduiertenkolleg Analysis, Geometrie und ihre Verbindung zu den Naturwissenschaften
-Graduiertenkolleg Wissensrepräsentation
-Internationales Promotionsprogramm Forschung in Grenzgebieten der Chemie
-Das Graduiertenzentrum Lebenswissenschaften
-Graduiertenkolleg Interdisziplinäre Ansätze in den Neurowissenschaften InterNeuro
-Graduiertenkolleg Funktion von Aufmerksamkeit bei kognitiven Prozessen Attention
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-International Max Planck Research School The Leipzig School of Human Origins
-MD-PhD-Programm der Universität Leipzig
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-Bericht zur 6. International Sommerschule fĂĽr Doktorandinnen und Doktoranden World Orders Revisited
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-Internationales Promotionsprogramm Transnationalisierung und Regionalisierung vom 18. Jahrhundert bis zur Gegenwart
-Graduiertenkolleg Bruchzonen der Globalisierung
-Deutsch als Fremdsprache Transcultural German Studies
-Kultureller Austausch Altertumswissenschaftliche, historische und ethnologische Perspektiven
-Entwicklung der Doktorandenzahlen
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-Impressu
Jahresbericht der Research Academy Leipzig 2013
Jahresbericht der Research Academy Leipzig 201
Jahresbericht der Research Academy Leipzig 2009
Jahresbericht der Research Academy Leipzig 2009:Inhalt
-Die Research Academy Leipzig
-Vorwort RAL feiert 3. Geburtstag
-Die Arbeit der RAL-Doktorandenvertretung 2009
-Fächerübergreifendes Qualifikationsprogramm Die Veranstaltungen der Research Academy Leipzig 2009
-Seminar „Junge Wissenschaft und Praxis“
-Präsentation in der Öffentlichkeit
-Kleinkindbetreuung fĂĽr Kinder der Doktorandinnen und Doktoranden
-Das Graduiertenzentrum Mathematik/Informatik und Naturwissenschaften
-Graduiertenschule Leipzig School of Natural Sciences – Building with Molecules and Nano-objects BuildMoNa
-Deutsch-Französisches Doktorandenkollegium/Collège Doctoral Franco-Allemand Statistische Physik komplexer Systeme
-International Max Planck Research School Mathematics in the Sciences
-International Research Training Group Diffusion in Porous Materials
-Graduiertenkolleg Analysis, Geometrie und ihre Verbindung zu den Naturwissenschaften
-Graduiertenkolleg Wissensrepräsentation
-Internationales Promotionsprogramm Forschung in Grenzgebieten der Chemie
-Das Graduiertenzentrum Lebenswissenschaften
-Graduiertenkolleg Interdisziplinäre Ansätze in den Neurowissenschaften
-Graduiertenkolleg Funktion von Aufmerksamkeit bei kognitiven Prozessen
-Internationales Promotionsprogramm Von der Signalverarbeitung zum Verhalten
-International Max Planck Research School The Leipzig School of Human Origins
-MD-PhD-Programm der Universität Leipzig
-Integriertes Graduiertenkolleg Proteinwissenschaften
-International Max Planck Research School Neuroscience of Communication: Function, Structure and Plasticity
-Integriertes Graduiertenkolleg Matrixengineering
-Das Graduiertenzentrum Geistes- und Sozialwissenschaften
-Bericht zur 7. Internationalen Sommerschule fĂĽr Doktorandinnen und Doktoranden Erinnerungskulturen in transkultureller und transnationaler Perspektive
-Jahresbericht 2009 der Doktorandenvertreter/innen des Graduiertenzentrums Geistes- und Sozialwissenschaften
-Ehemaliger Doktorand fĂĽr Forschungen nach Leipzig zurĂĽckgekehrt
-Internationales Promotionsprogramm Transnationalisierung und Regionalisierung vom 18. Jahrhundert bis zur Gegenwart
-Graduiertenkolleg Bruchzonen der Globalisierung
-Deutsch als Fremdsprache Transcultural German Studies
-Kultureller Austausch Altertumswissenschaftliche, historische und ethnologische Perspektiven
-Graduiertenkolleg Religiöser Non-Konformismus und kulturelle Dynamik
-Entwicklung der Doktorandenzahlen
-Bildnachweise
-Impressu
Jahresbericht der Research Academy Leipzig 2010
Jahresbericht der Research Academy Leipzig 2010:Research Academy Leipzig – Jahresbericht 2010
-Vorwort – Research Academy fit für die Evaluierung 7
-Die Arbeit der Doktorandenvertretung 2010 8
-Fächerübergreifende Qualifizierung für Doktorandinnen und Doktoranden der Universität
-Vernetzung und Kooperation – die Öffentlichkeitsarbeit
-Ăśber die Kompetenzschule ELSYS
-GleichstellungsmaĂźnahmen
-Graduiertenzentrum Mathematik / Informatik und Naturwissenschaften
-Die Arbeit des Graduiertenzentrums
-Graduiertenschule „Leipzig School of Natural Sciences – Building with Molecules and Nano-objects“ (BuildMoNa)
-Deutsch-Französisches Doktorandenkollegium (DFDK) / Collège Doctoral Franco-Allemand (CDFA) „Statistische Physik komplexer Systeme“
-Graduiertenkolleg „Analysis, Geometrie und ihre Verbindungen zu den Naturwissenschaften“
-International Max Planck Research School „Mathematics in the Sciences“ -International Research Training Group (IRTG) “Diffusion in Porous Materials” -Internationales Promotionsprogramm (IPP) „Forschung in Grenzgebieten der Chemie”
-Graduiertenzentrum Lebenswissenschaften
-Die Arbeit des Graduiertenzentrums
-Internationales Promotions programm (IPP) „Von der Signal verarbeitung zum Verhalten“
-Graduiertenkolleg „Interdisziplinäre Ansätze in den Neurowissenschaften“ (InterNeuro)
-Graduiertenkolleg „Funktion von Aufmerksamkeit bei kognitiven Prozessen“
MD / PhD-Programm der Universität Leipzig
-International Max Planck Research School “The Leipzig School of Human Origins”
Integriertes Graduiertenkolleg (IGK) „Proteinwissenschaften“
-International Max Planck Research School “Neuroscience of Communication: Function, Structure, and Plasticity” (NeuroCom)
-Integriertes Graduiertenkolleg „Matrixengineering“
-Graduiertenzentrum Geistes- und Sozialwissenschaften
-Die Arbeit des Graduiertenzentrums
-VIII. Internationalen Sommerschule „Transnationale Akteure – Akteure der Transnationalisierung“
-Doktorandenvertreter organisieren Workshop „Publikationsstrategien“ Internationales Promotionsprogramm (IPP) „Transnationalisierung und Regionalisierung vom 18. Jahrhundert bis zur Gegenwart“
-Graduiertenkolleg „Bruchzonen der Globalisierung“
-Deutsch als Fremdsprache / Transcultural German Studies
-„Kultureller Austausch – Altertumswissenschaftliche, historische und ethnologische Perspektiven“
-Graduiertenkolleg „Religiöser Nonkonformismus und kulturelle Dynamik“ -Volkswirtschaftliches Doktorandenprogramm Dresden-Halle-Leipzig (Central-German Doctoral Program Economics, CGDE)
-Kontakte
-Finanzen der Graduiertenzentren 2010
-Ăśberblick Doktorandenzahle
- …