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  • 1
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    Simulating radiative feedback and star cluster formation in GMCs - I. Dependence on gravitational boundedness (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-15
    Description: Radiative feedback is an important consequence of cluster formation in giant molecular clouds (GMCs) in which newly formed clusters heat and ionize their surrounding gas. The process of cluster formation, and the role of radiative feedback, has not been fully explored in different GMC environments. We present a suite of simulations which explore how the initial gravitational boundedness, and radiative feedback, affect cluster formation. We model the early evolution (〈5 Myr) of turbulent, 10 6 M clouds with virial parameters ranging from 0.5 to 5. To model cluster formation, we use cluster sink particles, coupled to a raytracing scheme, and a custom subgrid model which populates a cluster via sampling an initial mass function (IMF) with an efficiency of 20 per cent per free-fall time. We find that radiative feedback only decreases the cluster particle formation efficiency by a few per cent. The initial virial parameter plays a much stronger role in limiting cluster formation, with a spread of cluster formation efficiencies of 37–71 per cent for the most unbound to the most bound model. The total number of clusters increases while the maximum mass cluster decreases with an increasing initial virial parameter, resulting in steeper mass distributions. The star formation rates in our cluster particles are initially consistent with observations but rise to higher values at late times. This suggests that radiative feedback alone is not responsible for dispersing a GMC over the first 5 Myr of cluster formation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Type IV collagens regulate BMP signalling in Drosophila (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-08-15
    Description: Dorsal-ventral patterning in vertebrate and invertebrate embryos is mediated by a conserved system of secreted proteins that establishes a bone morphogenetic protein (BMP) gradient. Although the Drosophila embryonic Decapentaplegic (Dpp) gradient has served as a model to understand how morphogen gradients are established, no role for the extracellular matrix has been previously described. Here we show that type IV collagen extracellular matrix proteins bind Dpp and regulate its signalling in both the Drosophila embryo and ovary. We provide evidence that the interaction between Dpp and type IV collagen augments Dpp signalling in the embryo by promoting gradient formation, yet it restricts the signalling range in the ovary through sequestration of the Dpp ligand. Together, these results identify a critical function of type IV collagens in modulating Dpp in the extracellular space during Drosophila development. On the basis of our findings that human type IV collagen binds BMP4, we predict that this role of type IV collagens will be conserved.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, Xiaomeng -- Harris, Robin E -- Bayston, Laura J -- Ashe, Hilary L -- BBS/B/11672/Biotechnology and Biological Sciences Research Council/United Kingdom -- Biotechnology and Biological Sciences Research Council/United Kingdom -- England -- Nature. 2008 Sep 4;455(7209):72-7. doi: 10.1038/nature07214.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18701888" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Body Patterning ; Bone Morphogenetic Proteins/genetics/*metabolism ; Cell Count ; Collagen Type IV/genetics/*metabolism ; Drosophila Proteins/genetics/*metabolism ; Drosophila melanogaster/embryology/genetics/*metabolism ; Female ; Male ; Ovary/cytology/metabolism ; Protein Binding ; *Signal Transduction ; Transforming Growth Factor beta/genetics/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Does the dose make the poison? (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-04-12
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harris, Randall E -- New York, N.Y. -- Science. 2005 Apr 8;308(5719):203.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15821073" target="_blank"〉PubMed〈/a〉
    Keywords: Celecoxib ; Colonic Polyps/prevention & control ; Cyclooxygenase 2 ; Cyclooxygenase 2 Inhibitors ; Cyclooxygenase Inhibitors/adverse effects ; *Dose-Response Relationship, Drug ; Humans ; Lactones/adverse effects ; Membrane Proteins ; Prostaglandin-Endoperoxide Synthases ; Pyrazoles/adverse effects ; *Randomized Controlled Trials as Topic/standards ; Research Design ; Sulfonamides/adverse effects ; Sulfones/adverse effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Cluster formation in molecular clouds - I. Stellar populations, star formation rates and ionizing radiation (2014)
    Oxford University Press
    Details
    Publication Date: 2014-01-29
    Description: We present a model for the radiative output of star clusters in the process of star formation suitable for use in hydrodynamical simulations of radiative feedback. Gas in a clump, defined as a region whose density exceeds 10 4  cm –3 , is converted to stars via the random sampling of the Chabrier initial mass function. A star formation efficiency controls the rate of star formation. We have completed a suite of simulations which follow the evolution of accretion-fed clumps with initial masses ranging from 0 to 10 5 M and accretion rates ranging from 10 –5 to 10 –1 M  yr –1 . The stellar content is tracked over time which allows the aggregate luminosity, ionizing photon rate, number of stars and star formation rate (SFR) to be determined. For a fiducial clump of 10 4 M , the luminosity is ~4 10 6 L with an SFR of roughly 3 10 –3 M  yr –1 . We identify two regimes in our model. The accretion-dominated regime obtains the majority of its gas through accretion and is characterized by an increasing SFR, while the reservoir-dominated regime has the majority of its mass present in the initial clump with a decreasing SFR. We show that our model can reproduce the expected number of O stars, which dominate the radiative output of the cluster. We find a nearly linear relationship between SFR and mass as seen in observations. We conclude that our model is an accurate and straightforward way to represent the output of clusters in hydrodynamical simulations with radiative feedback.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Frontiers and route-ways from Europe: the Early Middle Palaeolithic of Britain (2018)
    Wiley
    Details
    Publication Date: 2018-02-01
    Description: ABSTRACT Britain has a rich and well-documented earlier Palaeolithic record, which provides a unique resource to investigate population dynamics and the cultural and geographical links with north-west Europe during the Middle Pleistocene. This paper examines a newly enhanced dataset for the distribution of finds locations and their geological context. Using artefact types as proxies for different populations it contrasts the Lower Palaeolithic and Early Middle Palaeolithic records. New methods are devised to mitigate for the clear bias towards handaxes in collection history. Taking account of this bias, the results suggest differences in distribution between Lower Palaeolithic and Early Middle Palaeolithic populations, with the latter more heavily concentrated in the lower reaches of large southern and eastern rivers. Drawing on recent studies on the palaeogeography of the Channel and southern North Sea Basin, the paper suggests that this restricted distribution reflects short-lived occupation by small groups of early Neanderthals in late MIS 8, who eventually became locally extinct because of isolation caused by rising sea levels in the first warm sub-stage of MIS 7.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of organic additives in rubber vulcanizates using mass spectrometry (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 3188-3195 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00127a059
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Capillary Condensation in Adsorption by Powders (1958)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 62 (1958), S. 655-657 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150564a005
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio MO-SCF calculation on a model of anomalous water (1970)
    Springer
    Theoretical chemistry accounts 18 (1970), S. 235-238 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden ab initio-Rechnungen für das planare Hexamer-Modell von anomalem Wasser unter Verwendung mehrerer BasissÄtze durchgeführt. Die Ergebnisse werden mit Resultaten Ähnlicher Rechnungen über freies Wasser und Wasser in der I-Eis Ähnlichen Konfiguration verzerrter Ringe verglichen.
    Abstract: Résumé Calculs ab initio sur le modèle hexamérique plan de l'eau anormale en utilisant différentes bases. Les résultats sont comparés à ceux de calculs similaires sur l'eau libre et sur l'eau dans une configuration cyclique compacte analogue à celle de la glace I.
    Notes: Abstract Ab initio calculations are carried out on the planar hexamer model of anomalous water using a variety of basis sets. The results are compared to results of similar calculations on free water and water in the ice I-like puckered ring configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527337
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  • 9
    Electronic Resource
    Electronic Resource
    Assessment of biological nitrogen fixation in grassland and associated sites (1973)
    Springer
    Plant and soil 38 (1973), S. 637-649 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The extent of nitrogen fixation in native grassland on clay soil was measured using the C2H2 reduction assay. Undisturbed soil cores incubated in microcanopies in the field indicated fixation rates of 2 kg N/ha per season. Less nitrogen fixation activity was found in associated cultivated soils. Other sites on different soil associations were found capable of fixing 1 kg·N/ha or less per growing season. The fixation by several legumes and nodulated nonlegumes ranged up to 1.8 μg/cm2. h. Phyllosphere samples of a moss, Ceratodon purpureus Brid reduced appreciable amounts of C2H2. An equivalent of 25 to 110 ng N fixation per hour was found per gram of organic material. C2H2 reduction in the materials used was related to the availability of light and Nostoc spp. were found to be associated with the moss. The major asymbiotic bacteria in the grassland soil were Clostridia although the relationship between numbers of this organism and nitrogen fixation was not significant. Klebsiella spp. were isolated and nitrogen fixation measured with C2H2 reduction and Kjeldahl methods. Both techniques indicated that the isolated bacteria fixed 30 mg N per litre of media during an 8-day incubation period. re]19720704
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010702
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  • 10
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    Superconductor‐insulator‐superconductor quasiparticle junctions as microwave photon detectors (1980)
    American Institute of Physics
    Details
    Publication Date: 1980-03-15
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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