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  • 1
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    Accelerated modern human-induced species losses: Entering the sixth mass extinction (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2015-06-21
    Beschreibung: The oft-repeated claim that Earth’s biota is entering a sixth "mass extinction" depends on clearly demonstrating that current extinction rates are far above the "background" rates prevailing in the five previous mass extinctions. Earlier estimates of extinction rates have been criticized for using assumptions that might overestimate the severity of the extinction crisis. We assess, using extremely conservative assumptions, whether human activities are causing a mass extinction. First, we use a recent estimate of a background rate of 2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY), which is twice as high as widely used previous estimates. We then compare this rate with the current rate of mammal and vertebrate extinctions. The latter is conservatively low because listing a species as extinct requires meeting stringent criteria. Even under our assumptions, which would tend to minimize evidence of an incipient mass extinction, the average rate of vertebrate species loss over the last century is up to 114 times higher than the background rate. Under the 2 E/MSY background rate, the number of species that have gone extinct in the last century would have taken, depending on the vertebrate taxon, between 800 and 10,000 years to disappear. These estimates reveal an exceptionally rapid loss of biodiversity over the last few centuries, indicating that a sixth mass extinction is already under way. Averting a dramatic decay of biodiversity and the subsequent loss of ecosystem services is still possible through intensified conservation efforts, but that window of opportunity is rapidly closing.
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Topological control of cytokine receptor signaling induces differential effects in hematopoiesis (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2019
    Beschreibung: 〈p〉Although tunable signaling by G protein–coupled receptors can be exploited through medicinal chemistry, a comparable pharmacological approach has been lacking for the modulation of signaling through dimeric receptors, such as those for cytokines. We present a strategy to modulate cytokine receptor signaling output by use of a series of designed C2-symmetric cytokine mimetics, based on the designed ankyrin repeat protein (DARPin) scaffold, that can systematically control erythropoietin receptor (EpoR) dimerization orientation and distance between monomers. We sampled a range of EpoR geometries by varying intermonomer angle and distance, corroborated by several ligand-EpoR complex crystal structures. Across the range, we observed full, partial, and biased agonism as well as stage-selective effects on hematopoiesis. This surrogate ligand strategy opens access to pharmacological modulation of therapeutically important cytokine and growth factor receptor systems.〈/p〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Hoatzin nestling locomotion: Acquisition of quadrupedal limb coordination in birds (2019)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2019
    Beschreibung: 〈p〉The evolution of flight in birds involves (i) decoupling of the primitive mode of quadrupedal locomotor coordination, with a new synchronized flapping motion of the wings while conserving alternating leg movements, and (ii) reduction of wing digits and loss of functional claws. Our observations show that hoatzin nestlings move with alternated walking coordination of the four limbs using the mobile claws on their wings to anchor themselves to the substrate. When swimming, hoatzin nestlings use a coordinated motion of the four limbs involving synchronous or alternated movements of the wings, indicating a versatile motor pattern. Last, the proportions of claws and phalanges in juvenile hoatzin are radically divergent from those in adults, yet strikingly similar to those of 〈i〉Archaeopteryx.〈/i〉 The locomotor plasticity observed in the hoatzin suggests that transitional forms that retained claws on the wings could have also used them for locomotion.〈/p〉
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Receptor and betagamma binding sites in the alpha subunit of the retinal G protein transducin (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 1997-01-17
    Beschreibung: Transmembrane receptors for hormones, neurotransmitters, light, and odorants mediate their cellular effects by activating heterotrimeric guanine nucleotide-binding proteins (G proteins). Crystal structures have revealed contact surfaces between G protein subunits, but not the surfaces or molecular mechanism through which Galphabetagamma responds to activation by transmembrane receptors. Such a surface was identified from the results of testing 100 mutant alpha subunits of the retinal G protein transducin for their ability to interact with rhodopsin. Sites at which alanine substitutions impaired this interaction mapped to two distinct Galpha surfaces: a betagamma-binding surface and a putative receptor-interacting surface. On the basis of these results a mechanism for receptor-catalyzed exchange of guanosine diphosphate for guanosine triphosphate is proposed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Onrust, R -- Herzmark, P -- Chi, P -- Garcia, P D -- Lichtarge, O -- Kingsley, C -- Bourne, H R -- CA-54427/CA/NCI NIH HHS/ -- GM-27800/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jan 17;275(5298):381-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143-0450, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8994033" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Aluminum Compounds/pharmacology ; Animals ; Binding Sites ; COS Cells ; Fluorides/pharmacology ; Guanosine 5'-O-(3-Thiotriphosphate)/metabolism ; Guanosine Diphosphate/metabolism ; Models, Molecular ; Mutation ; Phenotype ; *Protein Conformation ; Retinaldehyde/pharmacology ; Rhodopsin/*metabolism/pharmacology ; Rod Cell Outer Segment/metabolism ; Transducin/*chemistry/metabolism
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Response to Comment on "U-Th dating of carbonate crusts reveals Neandertal origin of Iberian cave art" (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-10-12
    Beschreibung: Slimak et al . challenge the reliability of our oldest (〉65,000 years) U-Th dates on carbonates associated with cave paintings in Spain. They cite a supposed lack of parietal art for the 25,000 years following this date, along with potential methodological issues relating to open-system behavior and corrections to detrital or source water 230 Th. We show that their criticisms are unfounded.
    Schlagwort(e): Anthropology
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    Cavity quantum electrodynamics with Anderson-localized modes (2010)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2010-03-13
    Beschreibung: A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sapienza, Luca -- Thyrrestrup, Henri -- Stobbe, Soren -- Garcia, Pedro David -- Smolka, Stephan -- Lodahl, Peter -- New York, N.Y. -- Science. 2010 Mar 12;327(5971):1352-5. doi: 10.1126/science.1185080.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Orsteds Plads 343, DK-2800 Kgs. Lyngby, Denmark. lucs@fotonik.dtu.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20223981" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    U-Th dating of carbonate crusts reveals Neandertal origin of Iberian cave art (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-02-23
    Beschreibung: The extent and nature of symbolic behavior among Neandertals are obscure. Although evidence for Neandertal body ornamentation has been proposed, all cave painting has been attributed to modern humans. Here we present dating results for three sites in Spain that show that cave art emerged in Iberia substantially earlier than previously thought. Uranium-thorium (U-Th) dates on carbonate crusts overlying paintings provide minimum ages for a red linear motif in La Pasiega (Cantabria), a hand stencil in Maltravieso (Extremadura), and red-painted speleothems in Ardales (Andalucía). Collectively, these results show that cave art in Iberia is older than 64.8 thousand years (ka). This cave art is the earliest dated so far and predates, by at least 20 ka, the arrival of modern humans in Europe, which implies Neandertal authorship.
    Schlagwort(e): Anthropology
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Brazil naturalizes non-native species (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-07-13
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 9
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    Leaking privacy and shadow profiles in online social networks (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2017-08-05
    Beschreibung: Social interaction and data integration in the digital society can affect the control that individuals have on their privacy. Social networking sites can access data from other services, including user contact lists where nonusers are listed too. Although most research on online privacy has focused on inference of personal information of users, this data integration poses the question of whether it is possible to predict personal information of nonusers. This article tests the shadow profile hypothesis, which postulates that the data given by the users of an online service predict personal information of nonusers. Using data from a disappeared social networking site, we perform a historical audit to evaluate whether personal data of nonusers could have been predicted with the personal data and contact lists shared by the users of the site. We analyze personal information of sexual orientation and relationship status, which follow regular mixing patterns in the social network. Going back in time over the growth of the network, we measure predictor performance as a function of network size and tendency of users to disclose their contact lists. This article presents robust evidence supporting the shadow profile hypothesis and reveals a multiplicative effect of network size and disclosure tendencies that accelerates the performance of predictors. These results call for new privacy paradigms that take into account the fact that individual privacy decisions do not happen in isolation and are mediated by the decisions of others.
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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