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  • Artikel  (13)
  • American Association for the Advancement of Science (AAAS)  (11)
  • Springer Nature  (2)
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  • Artikel  (13)
Erscheinungszeitraum
  • 1
    Publikationsdatum: 2016-05-12
    Beschreibung: Lightwave-driven quasiparticle collisions on a subcycle timescale Nature 533, 7602 (2016). doi:10.1038/nature17958 Authors: F. Langer, M. Hohenleutner, C. P. Schmid, C. Poellmann, P. Nagler, T. Korn, C. Schüller, M. S. Sherwin, U. Huttner, J. T. Steiner, S. W. Koch, M. Kira & R. Huber Ever since Ernest Rutherford scattered α-particles from gold foils, collision experiments have revealed insights into atoms, nuclei and elementary particles. In solids, many-body correlations lead to characteristic resonances—called quasiparticles—such as excitons, dropletons, polarons and Cooper pairs. The structure and dynamics of quasiparticles are important because they define macroscopic phenomena such as Mott insulating states, spontaneous spin- and charge-order, and high-temperature superconductivity. However, the extremely short lifetimes of these entities make practical implementations of a suitable collider challenging. Here we exploit lightwave-driven charge transport, the foundation of attosecond science, to explore ultrafast quasiparticle collisions directly in the time domain: a femtosecond optical pulse creates excitonic electron–hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying dynamics of the wave packets, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands of the optical excitation. A full quantum theory explains our observations microscopically. This approach enables collision experiments with various complex quasiparticles and suggests a promising new way of generating sub-femtosecond pulses.
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Springer Nature
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2000-11-10
    Beschreibung: Parasites do not always harm their hosts because the immune system keeps an infection at bay. Ironically, the cost of using immune defenses could itself reduce host fitness. This indirect cost of parasitism is often not visible because of compensatory resource intake. Here, workers of the bumblebee, Bombus terrestris, were challenged with lipopolysaccharides and micro-latex beads to induce their immune system under starvation (i.e., not allowing compensatory intake). Compared with controls, survival of induced workers was significantly reduced (by 50 to 70%).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moret, Y -- Schmid-Hempel, P -- New York, N.Y. -- Science. 2000 Nov 10;290(5494):1166-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Eidgenossische Technische Hochschule (ETH) Zurich, Experimental Ecology, ETH-Zentrum, NW, CH-8092 Zurich, Switzerland. moret@eco.umnw.ethz.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11073456" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Bees/*immunology/physiology ; Food ; Hemolymph/immunology ; Immunity, Innate ; Latex ; Lipopolysaccharides/immunology ; Microspheres
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1989-01-13
    Beschreibung: The c-myc protooncogene in mouse embryos was shown by RNA in situ hybridization to be preferentially expressed in tissues of endodermal and mesodermal origin. Most organs developing from the ectoderm, such as skin, brain, and spinal cord, displayed low levels of c-myc RNA. The thymus represented the only hematopoietic organ with high c-myc expression. In organs and structures strongly hybridizing to c-myc probes, for example the fetal part of the placenta, gut, liver, kidney, pancreas, submandibular glands, enamel organs of the molars, and skeletal cartilage, the level of expression depended on the stage of development. Expression was observed to be correlated with proliferation, particularly during expansion and folding of partially differentiated epithelial cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmid, P -- Schulz, W A -- Hameister, H -- New York, N.Y. -- Science. 1989 Jan 13;243(4888):226-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Abteilung Klinische Genetik, Universitat Ulm, Federal Republic of Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2911736" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Embryo, Mammalian/*physiology ; Embryonic and Fetal Development ; Mice ; Nucleic Acid Hybridization ; Organ Specificity ; *Proto-Oncogenes ; RNA Probes ; *Transcription, Genetic
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2011-09-10
    Beschreibung: The fossil record of the hominin pelvis reflects important evolutionary changes in locomotion and parturition. The partial pelves of two individuals of Australopithecus sediba were reconstructed from previously reported finds and new material. These remains share some features with australopiths, such as large biacetabular diameter, small sacral and coxal joints, and long pubic rami. The specimens also share derived features with Homo, including more vertically oriented and sigmoid-shaped iliac blades, greater robusticity of the iliac body, sinusoidal anterior iliac borders, shortened ischia, and more superiorly oriented pubic rami. These derived features appear in a species with a small adult brain size, suggesting that the birthing of larger-brained babies was not driving the evolution of the pelvis at this time.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kibii, Job M -- Churchill, Steven E -- Schmid, Peter -- Carlson, Kristian J -- Reed, Nichelle D -- de Ruiter, Darryl J -- Berger, Lee R -- New York, N.Y. -- Science. 2011 Sep 9;333(6048):1407-11. doi: 10.1126/science.1202521. Epub 2011 Sep 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Human Evolution, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21903805" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Evolution ; Biomechanical Phenomena ; Brain/anatomy & histology ; Female ; *Fossils ; Hominidae/*anatomy & histology/physiology ; Humans ; Ilium/anatomy & histology ; Ischium/anatomy & histology ; Locomotion ; Male ; Parturition ; Pelvic Bones/*anatomy & histology ; Pelvis/*anatomy & histology ; Pubic Bone/anatomy & histology ; Sacrum/anatomy & histology ; South Africa
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 5
    Publikationsdatum: 2011-09-10
    Beschreibung: Hand bones from a single individual with a clear taxonomic affiliation are scarce in the hominin fossil record, which has hampered understanding the evolution of manipulative abilities in hominins. Here we describe and analyze a nearly complete wrist and hand of an adult female [Malapa Hominin 2 (MH2)] Australopithecus sediba from Malapa, South Africa (1.977 million years ago). The hand presents a suite of Australopithecus-like features, such as a strong flexor apparatus associated with arboreal locomotion, and Homo-like features, such as a long thumb and short fingers associated with precision gripping and possibly stone tool production. Comparisons to other fossil hominins suggest that there were at least two distinct hand morphotypes around the Plio-Pleistocene transition. The MH2 fossils suggest that Au. sediba may represent a basal condition associated with early stone tool use and production.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kivell, Tracy L -- Kibii, Job M -- Churchill, Steven E -- Schmid, Peter -- Berger, Lee R -- New York, N.Y. -- Science. 2011 Sep 9;333(6048):1411-7. doi: 10.1126/science.1202625. Epub 2011 Sep 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, Leipzig 04103, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21903806" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Biological Evolution ; Biomechanical Phenomena ; Carpal Bones/anatomy & histology ; Female ; Finger Phalanges/anatomy & histology ; *Fossils ; Hand/*anatomy & histology/physiology ; Hand Bones/*anatomy & histology ; Hominidae/*anatomy & histology/classification/physiology ; Humans ; Locomotion ; Metacarpal Bones/anatomy & histology ; Motor Activity ; South Africa ; Thumb/anatomy & histology ; Tool Use Behavior
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 6
    Publikationsdatum: 2003-10-04
    Beschreibung: The dissociation of methane on a nickel catalyst is a key step in steam reforming of natural gas for hydrogen production. Despite substantial effort in both experiment and theory, there is still no atomic-scale description of this important gas-surface reaction. We report quantum state-resolved studies, using pulsed laser and molecular beam techniques, of vibrationally excited methane reacting on the nickel (100) surface. For doubly deuterated methane (CD2H2), we observed that the reaction probability with two quanta of excitation in one C-H bond was greater (by as much as a factor of 5) than with one quantum in each of two C-H bonds. These results clearly exclude the possibility of statistical models correctly describing the mechanism of this process and attest to the importance of full-dimensional calculations of the reaction dynamics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beck, Rainer D -- Maroni, Plinio -- Papageorgopoulos, Dimitrios C -- Dang, Tung T -- Schmid, Mathieu P -- Rizzo, Thomas R -- New York, N.Y. -- Science. 2003 Oct 3;302(5642):98-100.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire Chimie Physique Moleculaire, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland. rainer.beck@epfl.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14526078" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 7
    Publikationsdatum: 2010-04-10
    Beschreibung: Despite a rich African Plio-Pleistocene hominin fossil record, the ancestry of Homo and its relation to earlier australopithecines remain unresolved. Here we report on two partial skeletons with an age of 1.95 to 1.78 million years. The fossils were encased in cave deposits at the Malapa site in South Africa. The skeletons were found close together and are directly associated with craniodental remains. Together they represent a new species of Australopithecus that is probably descended from Australopithecus africanus. Combined craniodental and postcranial evidence demonstrates that this new species shares more derived features with early Homo than any other australopith species and thus might help reveal the ancestor of that genus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Berger, Lee R -- de Ruiter, Darryl J -- Churchill, Steven E -- Schmid, Peter -- Carlson, Kristian J -- Dirks, Paul H G M -- Kibii, Job M -- New York, N.Y. -- Science. 2010 Apr 9;328(5975):195-204. doi: 10.1126/science.1184944.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Human Evolution, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa. profleeberger@yahoo.com〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20378811" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Evolution ; Body Size ; Bone and Bones/anatomy & histology ; Dentition ; Female ; *Fossils ; Hominidae/anatomy & histology/*classification ; Male ; Mandible/anatomy & histology ; Skeleton ; Skull/anatomy & histology ; South Africa
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 8
    Publikationsdatum: 2013-04-13
    Beschreibung: The evolution of the human upper limb involved a change in function from its use for both locomotion and prehension (as in apes) to a predominantly prehensile and manipulative role. Well-preserved forelimb remains of 1.98-million-year-old Australopithecus sediba from Malapa, South Africa, contribute to our understanding of this evolutionary transition. Whereas other aspects of their postcranial anatomy evince mosaic combinations of primitive (australopith-like) and derived (Homo-like) features, the upper limbs (excluding the hand and wrist) of the Malapa hominins are predominantly primitive and suggest the retention of substantial climbing and suspensory ability. The use of the forelimb primarily for prehension and manipulation appears to arise later, likely with the emergence of Homo erectus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Churchill, Steven E -- Holliday, Trenton W -- Carlson, Kristian J -- Jashashvili, Tea -- Macias, Marisa E -- Mathews, Sandra -- Sparling, Tawnee L -- Schmid, Peter -- de Ruiter, Darryl J -- Berger, Lee R -- New York, N.Y. -- Science. 2013 Apr 12;340(6129):1233477. doi: 10.1126/science.1233477.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA. churchy@duke.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23580536" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Arm Bones/anatomy & histology ; Biological Evolution ; Biomechanical Phenomena ; Bones of Upper Extremity/*anatomy & histology/physiology ; Clavicle/anatomy & histology ; Female ; *Fossils ; Hominidae/*anatomy & histology/*physiology ; Humans ; Locomotion ; Male ; Principal Component Analysis ; Scapula/anatomy & histology ; South Africa ; Upper Extremity/*anatomy & histology/*physiology
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 9
    Publikationsdatum: 2013-04-13
    Beschreibung: The shape of the thorax of early hominins has been a point of contention for more than 30 years. Owing to the generally fragmentary nature of fossil hominin ribs, few specimens have been recovered that have rib remains complete enough to allow accurate reassembly of thoracic shape, thus leaving open the question of when the cylindrical-shaped chest of humans and their immediate ancestors evolved. The ribs of Australopithecus sediba exhibit a mediolaterally narrow, ape-like upper thoracic shape, which is unlike the broad upper thorax of Homo that has been related to the locomotor pattern of endurance walking and running. The lower thorax, however, appears less laterally flared than that of apes and more closely approximates the morphology found in humans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmid, Peter -- Churchill, Steven E -- Nalla, Shahed -- Weissen, Eveline -- Carlson, Kristian J -- de Ruiter, Darryl J -- Berger, Lee R -- New York, N.Y. -- Science. 2013 Apr 12;340(6129):1234598. doi: 10.1126/science.1234598.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Anthropological Institute and Museum, University of Zurich, Zurich, Switzerland. smidi@aim.uzh.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23580537" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Evolution ; Female ; *Fossils ; Hominidae/*anatomy & histology/*physiology ; Humans ; Locomotion ; Male ; Respiration ; Ribs/*anatomy & histology ; South Africa ; Thorax/*anatomy & histology
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 10
    Publikationsdatum: 2013-04-13
    Beschreibung: Two partial vertebral columns of Australopithecus sediba grant insight into aspects of early hominin spinal mobility, lumbar curvature, vertebral formula, and transitional vertebra position. Au. sediba likely possessed five non-rib-bearing lumbar vertebrae and five sacral elements, the same configuration that occurs modally in modern humans. This finding contrasts with other interpretations of early hominin regional vertebral numbers. Importantly, the transitional vertebra is distinct from and above the last rib-bearing vertebra in Au. sediba, resulting in a functionally longer lower back. This configuration, along with a strongly wedged last lumbar vertebra and other indicators of lordotic posture, would have contributed to a highly flexible spine that is derived compared with earlier members of the genus Australopithecus and similar to that of the Nariokotome Homo erectus skeleton.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Williams, Scott A -- Ostrofsky, Kelly R -- Frater, Nakita -- Churchill, Steven E -- Schmid, Peter -- Berger, Lee R -- New York, N.Y. -- Science. 2013 Apr 12;340(6129):1232996. doi: 10.1126/science.1232996.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for the Study of Human Origins, Department of Anthropology, New York University, New York, NY 10003, USA. sawilliams@nyu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23580532" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Evolution ; Biomechanical Phenomena ; Cervical Vertebrae/anatomy & histology ; *Fossils ; Hominidae/*anatomy & histology/physiology ; Humans ; Locomotion ; Lumbar Vertebrae/anatomy & histology ; Posture ; Sacrum/anatomy & histology ; South Africa ; Spine/*anatomy & histology/physiology ; Thoracic Vertebrae/anatomy & histology
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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