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  • Artikel  (84)
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  • American Association for the Advancement of Science (AAAS)  (84)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-01-05
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pennisi, E -- New York, N.Y. -- Science. 1998 Dec 4;282(5395):1796.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9874626" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Crosses, Genetic ; Drosophila/*genetics ; Female ; *Genes, Insect ; HSP90 Heat-Shock Proteins/genetics/*physiology ; Insect Proteins/genetics/physiology ; Male ; *Mutation ; Temperature
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-08-28
    Beschreibung: Class II transactivator (CIITA) is a global transcriptional coactivator of human leukocyte antigen-D (HLA-D) genes. CIITA contains motifs similar to guanosine triphosphate (GTP)-binding proteins. This report shows that CIITA binds GTP, and mutations in these motifs decrease its GTP-binding and transactivation activity. Substitution of these motifs with analogous sequences from Ras restores CIITA function. CIITA exhibits little GTPase activity, yet mutations in CIITA that confer GTPase activity reduce transcriptional activity. GTP binding by CIITA correlates with nuclear import. Thus, unlike other GTP-binding proteins, CIITA is involved in transcriptional activation that uses GTP binding to facilitate its own nuclear import.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harton, J A -- Cressman, D E -- Chin, K C -- Der, C J -- Ting, J P -- AI29564/AI/NIAID NIH HHS/ -- AI41751/AI/NIAID NIH HHS/ -- AI45580/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1999 Aug 27;285(5432):1402-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10464099" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adenosine Triphosphate/metabolism ; Animals ; Binding Sites ; COS Cells ; Cell Line ; Cell Nucleus/*metabolism ; GTP-Binding Proteins/chemistry/genetics/*metabolism ; *Genes, MHC Class II ; Guanosine Triphosphate/*metabolism ; HLA-DR Antigens/genetics ; Humans ; Mutation ; *Nuclear Proteins ; Promoter Regions, Genetic ; Temperature ; Trans-Activators/chemistry/genetics/*metabolism ; Transcription Factors/metabolism ; *Transcriptional Activation
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-10-03
    Beschreibung: NASA's Galileo mission to Jupiter and improved Earth-based observing capabilities have allowed major advances in our understanding of Jupiter's moons Io, Europa, Ganymede, and Callisto over the past few years. Particularly exciting findings include the evidence for internal liquid water oceans in Callisto and Europa, detection of a strong intrinsic magnetic field within Ganymede, discovery of high-temperature silicate volcanism on Io, discovery of tenuous oxygen atmospheres at Europa and Ganymede and a tenuous carbon dioxide atmosphere at Callisto, and detection of condensed oxygen on Ganymede. Modeling of landforms seen at resolutions up to 100 times as high as those of Voyager supports the suggestion that tidal heating has played an important role for Io and Europa.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Showman, A P -- Malhotra, R -- New York, N.Y. -- Science. 1999 Oct 1;286(5437):77-84.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Mechanical Engineering, University of Louisville, 215 Sackett Hall, Louisville, KY 40292, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10506564" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Carbon Dioxide ; Extraterrestrial Environment ; Geological Phenomena ; Geology ; Ice ; *Jupiter ; Magnetics ; *Oxygen ; Surface Properties ; Temperature ; *Water
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 4
    Publikationsdatum: 1999-11-13
    Beschreibung: Using ultrafast, time-resolved, 1.54 angstrom x-ray diffraction, thermal and ultrafast nonthermal melting of germanium, involving passage through nonequilibrium extreme states of matter, was observed. Such ultrafast, optical-pump, x-ray diffraction probe measurements provide a way to study many other transient processes in physics, chemistry, and biology, including direct observation of the atomic motion by which many solid-state processes and chemical and biochemical reactions take place.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Siders, C W -- Cavalleri, A -- Sokolowski-Tinten, K -- Toth, C -- Guo, T -- Kammler, M -- Horn von Hoegen, M -- Wilson, K R -- von der Linde, D -- Barty, C P -- New York, N.Y. -- Science. 1999 Nov 12;286(5443):1340-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, Institute for Nonlinear Science, University of California, San Diego, La Jolla, CA 92093-0339, USA. csiders@ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10558985" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Biochemistry/methods ; Crystallization ; Germanium/*chemistry ; Lasers ; Temperature ; *X-Ray Diffraction
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 5
    Publikationsdatum: 1999-12-22
    Beschreibung: The crystal structure of an efficient Diels-Alder antibody catalyst at 1.9 angstrom resolution reveals almost perfect shape complementarity with its transition state analog. Comparison with highly related progesterone and Diels-Alderase antibodies that arose from the same primordial germ line template shows the relatively subtle mutational steps that were able to evolve both structural complementarity and catalytic efficiency.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Xu, J -- Deng, Q -- Chen, J -- Houk, K N -- Bartek, J -- Hilvert, D -- Wilson, I A -- CA27489/CA/NCI NIH HHS/ -- GM38273/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Dec 17;286(5448):2345-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10600746" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antibodies, Catalytic/*chemistry/genetics/*metabolism ; Binding Sites, Antibody ; Catalysis ; Chemistry, Physical ; Crystallography, X-Ray ; *Evolution, Molecular ; Haptens/chemistry/metabolism ; Hydrogen Bonding ; Immunoglobulin Fab Fragments/chemistry/metabolism ; Ligands ; Models, Molecular ; Mutation ; Physicochemical Phenomena ; Progesterone/immunology ; Protein Conformation ; Solubility ; Temperature ; Templates, Genetic
    Print ISSN: 0036-8075
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 6
    Publikationsdatum: 1999-11-24
    Beschreibung: A general approach is presented for creating polymer gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule. Multiple-point interaction is experimentally proven by power laws found between the affinity and the concentration of the adsorbing monomers within the gels.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Oya, T -- Enoki, T -- Grosberg, A Y -- Masamune, S -- Sakiyama, T -- Takeoka, Y -- Tanaka, K -- Wang, G -- Yilmaz, Y -- Feld, M S -- Dasari, R -- Tanaka, T -- New York, N.Y. -- Science. 1999 Nov 19;286(5444):1543-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Center for Materials Science and Engineering, Department of Chemistry, George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. toyo@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10567256" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adsorption ; Ammonium Chloride/*chemistry ; Arylsulfonates/*chemistry ; Chlorides/chemistry ; Gels/*chemistry ; Methacrylates/*chemistry ; Polymers/*chemistry ; Spectrometry, Fluorescence ; Spectrophotometry, Ultraviolet ; Temperature
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 7
    Publikationsdatum: 1999-07-20
    Beschreibung: All known Rift Valley fever virus outbreaks in East Africa from 1950 to May 1998, and probably earlier, followed periods of abnormally high rainfall. Analysis of this record and Pacific and Indian Ocean sea surface temperature anomalies, coupled with satellite normalized difference vegetation index data, shows that prediction of Rift Valley fever outbreaks may be made up to 5 months in advance of outbreaks in East Africa. Concurrent near-real-time monitoring with satellite normalized difference vegetation data may identify actual affected areas.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Linthicum, K J -- Anyamba, A -- Tucker, C J -- Kelley, P W -- Myers, M F -- Peters, C J -- New York, N.Y. -- Science. 1999 Jul 16;285(5426):397-400.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Defense, Global Emerging Infections System, Division of Preventive Medicine, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10411500" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Climate ; *Disease Outbreaks ; *Forecasting ; Humans ; Kenya/epidemiology ; Oceans and Seas ; Pacific Ocean ; Rain ; Rift Valley Fever/*epidemiology/prevention & control/veterinary ; Temperature ; *Weather
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-26
    Beschreibung: In the nervous system, glial cells greatly outnumber neurons but the full extent of their role in determining neural activity remains unknown. Here the axotactin (axo) gene of Drosophila was shown to encode a member of the neurexin protein superfamily secreted by glia and subsequently localized to axonal tracts. Null mutations of axo caused temperature-sensitive paralysis and a corresponding blockade of axonal conduction. Thus, the AXO protein appears to be a component of a glial-neuronal signaling mechanism that helps to determine the membrane electrical properties of target axons.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yuan, L L -- Ganetzky, B -- GM43100/GM/NIGMS NIH HHS/ -- NS15390/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1999 Feb 26;283(5406):1343-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Neuroscience Training Program and Laboratory of Genetics, 445 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706 USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10037607" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Action Potentials ; Animals ; Axons/*physiology ; DNA, Complementary ; Drosophila/embryology/genetics/*physiology ; Embryo, Nonmammalian/physiology ; Gene Expression Regulation, Developmental ; Genes, Insect ; Insect Proteins/genetics/*physiology ; Ion Channels/physiology ; Mutation ; Neuroglia/*physiology ; Neuromuscular Junction/physiology ; *Signal Transduction ; Synaptic Transmission ; Temperature
    Print ISSN: 0036-8075
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 9
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-10-03
    Beschreibung: Tectonics, volcanism, and climate on Venus may be strongly coupled. Large excursions in surface temperature predicted to follow a global or near-global volcanic event diffuse into the interior and introduce thermal stresses of a magnitude sufficient to influence widespread tectonic deformation. This sequence of events accounts for the timing and many of the characteristics of deformation in the ridged plains of Venus, the most widely preserved volcanic terrain on the planet.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Solomon, S C -- Bullock, M A -- Grinspoon, D H -- New York, N.Y. -- Science. 1999 Oct 1;286(5437):87-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10506565" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Climate ; *Extraterrestrial Environment ; Geological Phenomena ; Geology ; Sulfur Dioxide ; Temperature ; *Venus ; Volcanic Eruptions ; Water
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-12-30
    Beschreibung: Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon's spectrum suggests the presence of ammonia ices. Ammonia ice-water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite's past.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brown, M E -- Calvin, W M -- New York, N.Y. -- Science. 2000 Jan 7;287(5450):107-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10615040" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Ammonia ; Crystallization ; Extraterrestrial Environment ; Ice ; *Pluto ; Spectrophotometry, Infrared ; Spectroscopy, Near-Infrared ; Spectrum Analysis ; Temperature ; *Water
    Print ISSN: 0036-8075
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 11
    Publikationsdatum: 1999-02-12
    Beschreibung: Single particles of the mediator of transcriptional regulation (Mediator) and of RNA polymerase II holoenzyme were revealed by electron microscopy and image processing. Mediator alone appeared compact, but at high pH or in the presence of RNA polymerase II it displayed an extended conformation. Holoenzyme contained Mediator in a fully extended state, partially enveloping the globular polymerase, with points of apparent contact in the vicinity of the polymerase carboxyl-terminal domain and the DNA-binding channel. A similarity in appearance and conformational behavior of yeast and murine complexes indicates a conservation of Mediator structure among eukaryotes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Asturias, F J -- Jiang, Y W -- Myers, L C -- Gustafsson, C M -- Kornberg, R D -- AI21144/AI/NIAID NIH HHS/ -- GM36659/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Feb 12;283(5404):985-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Structural Biology, Fairchild Building, Stanford University School of Medicine, Stanford, CA 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9974391" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; DNA-Directed RNA Polymerases/*chemistry/metabolism ; Fungal Proteins/*chemistry/metabolism ; Holoenzymes/chemistry/metabolism ; Hydrogen-Ion Concentration ; Mice ; Microscopy, Electron ; *Protein Conformation ; Protein Folding ; Temperature ; Trans-Activators/*chemistry/metabolism ; Transcription Factors/*chemistry/metabolism
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 12
    Publikationsdatum: 1999-08-28
    Beschreibung: Crystals of halite and sylvite within the Monahans (1998) H5 chondrite contain aqueous fluid inclusions. The fluids are dominantly sodium chloride-potassium chloride brines, but they also contain divalent cations such as iron, magnesium, or calcium. Two possible origins for the brines are indigenous fluids flowing within the asteroid and exogenous fluids delivered into the asteroid surface from a salt-containing icy object.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zolensky, M E -- Bodnar, R J -- Gibson, E K Jr -- Nyquist, L E -- Reese, Y -- Shih, C Y -- Wiesmann, H -- New York, N.Y. -- Science. 1999 Aug 27;285(5432):1377-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Mail Code SN2, NASA Johnson Space Center, Houston, TX 77058, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10464091" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Crystallization ; Mass Spectrometry ; *Meteoroids ; *Minor Planets ; Potassium Chloride ; *Sodium Chloride ; Spectrum Analysis, Raman ; Temperature ; Texas ; *Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 13
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-10-03
    Beschreibung: Ribozymes use a number of the same catalytic strategies as protein enzymes. However, general base catalysis by a ribozyme has not been demonstrated. In the hepatitis delta virus antigenomic ribozyme, imidazole buffer rescued activity of a mutant with a cytosine-76 (C76) to uracil substitution. In addition, a C76 to adenine substitution reduced the apparent pKa (where Ka is the acid constant) of the self-cleavage reaction by an amount consistent with differences in the pKa values of these two side chains. These results suggest that, in the wild-type ribozyme, C76 acts as a general base. This finding has implications for potential catalytic functions of conserved cytosines and adenines in other ribozymes and in ribonuclear proteins with enzymatic activity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perrotta, A T -- Shih, I -- Been, M D -- GM47322/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Oct 1;286(5437):123-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Box 3711, Duke University Medical Center, Durham, NC 27710 USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10506560" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Binding Sites ; Catalysis ; Cytosine/*chemistry/metabolism/pharmacology ; Hepatitis Delta Virus/chemistry/*enzymology ; Hydrogen-Ion Concentration ; Imidazoles/chemistry/*metabolism/pharmacology ; Magnesium Chloride/pharmacology ; Manganese/pharmacology ; Mutagenesis ; Point Mutation ; Protons ; Pyrazoles/pharmacology ; RNA, Catalytic/*chemistry/genetics/*metabolism ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 14
    Publikationsdatum: 1999-01-05
    Beschreibung: The phase diagrams of water and ammonia were determined by constant pressure ab initio molecular dynamic simulations at pressures (30 to 300 gigapascal) and temperatures (300 to 7000 kelvin) of relevance for the middle ice layers of the giant planets Neptune and Uranus. Along the planetary isentrope water and ammonia behave as fully dissociated ionic, electronically insulating fluid phases, which turn metallic at temperatures exceeding 7000 kelvin for water and 5500 kelvin for ammonia. At lower temperatures, the phase diagrams of water and ammonia exhibit a superionic solid phase between the solid and the ionic liquid. These simulations improve our understanding of the properties of the middle ice layers of Neptune and Uranus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cavazzoni, C -- Chiarotti, G L -- Scandolo, S -- Tosatti, E -- Bernasconi, M -- Parrinello, M -- New York, N.Y. -- Science. 1999 Jan 1;283(5398):44-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Nazionale per la Fisica della Materia (INFM) and International School for Advanced Studies (SISSA), Via Beirut 4, I-34014 Trieste, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9872734" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Ammonia/*chemistry ; Computer Simulation ; Electric Conductivity ; Extraterrestrial Environment ; Ice ; Ions ; Metals ; *Neptune ; Temperature ; *Uranus ; Water/*chemistry
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 15
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-04-17
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Golombek, M P -- New York, N.Y. -- Science. 1999 Mar 5;283(5407):1470-1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109, USA. mgolombek@jpl.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10206878" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Climate ; *Extraterrestrial Environment ; *Mars ; Temperature ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 16
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-10-03
    Beschreibung: An understanding of the structure and composition of the giant planets is rapidly evolving because of (i) high-pressure experiments with the ability to study metallic hydrogen and define the properties of its equation of state and (ii) spectroscopic and in situ measurements made by telescopes and satellites that allow an accurate determination of the chemical composition of the deep atmospheres of the giant planets. However, the total amount of heavy elements that Jupiter, Saturn, Uranus, and Neptune contain remains poorly constrained. The discovery of extrasolar giant planets with masses ranging from that of Saturn to a few times the mass of Jupiter opens up new possibilities for understanding planet composition and formation. Evolutionary models predict that gaseous extrasolar giant planets should have a variety of atmospheric temperatures and chemical compositions, but the radii are estimated to be close to that of Jupiter (between 0.9 and 1.7 Jupiter radii), provided that they contain mostly hydrogen and helium.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Guillot, T -- New York, N.Y. -- Science. 1999 Oct 1;286(5437):72-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Observatoire de la Cote d'Azur, Departement Cassini, CNRS UMR 6529, Boite Postale 4229, 06304 Nice Cedex 04, France. guillot@obs-nice.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10506563" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Astronomical Phenomena ; *Astronomy ; Atmosphere ; Evolution, Planetary ; Extraterrestrial Environment ; Helium ; *Hydrogen ; Metals, Heavy ; *Planets ; Pressure ; Solar System ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 17
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-01-30
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vogel, G -- New York, N.Y. -- Science. 1999 Jan 8;283(5399):155,157.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9925470" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Base Composition ; Computer Simulation ; *Evolution, Molecular ; Hot Temperature ; Models, Chemical ; *Origin of Life ; Phylogeny ; RNA, Ribosomal/*chemistry ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 18
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-07-20
    Beschreibung: The molecular basis of adaptation is a major focus of evolutionary biology, yet the dynamic process of adaptation has been explored only piecemeal. Experimental evolution of two bacteriophage lines under strong selection led to over a dozen nucleotide changes genomewide in each replicate. At least 96 percent of the amino acid substitutions appeared to be adaptive, and half the changes in one line also occurred in the other. However, the order of these changes differed between replicates, and parallel substitutions did not reflect the changes with the largest beneficial effects or indicate a common trajectory of adaptation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wichman, H A -- Badgett, M R -- Scott, L A -- Boulianne, C M -- Bull, J J -- GM57755/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Jul 16;285(5426):422-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA. hwichman@uidaho.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10411508" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Adaptation, Physiological ; Amino Acid Substitution ; Bacteriophage phi X 174/*genetics/*physiology ; *Evolution, Molecular ; *Genome, Viral ; Genotype ; Mutation ; Salmonella typhimurium/*virology ; Selection, Genetic ; Sequence Deletion ; Temperature ; Viral Plaque Assay ; Viral Proteins/chemistry/genetics ; Virus Replication
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 19
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-05-08
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Belgrader, P -- Benett, W -- Hadley, D -- Richards, J -- Stratton, P -- Mariella, R Jr -- Milanovich, F -- New York, N.Y. -- Science. 1999 Apr 16;284(5413):449-50.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lawrence Livermore National Laboratory, Biological and Biotechnology Research Program, Livermore, CA 94551, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10232992" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Bacteria/genetics/*isolation & purification ; *Bacteriological Techniques/instrumentation ; DNA, Bacterial/*analysis ; Erwinia/genetics/isolation & purification ; Fluorescent Dyes ; Polymerase Chain Reaction/instrumentation/*methods ; Software ; *Spectrometry, Fluorescence ; Temperature
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  • 20
    Publikationsdatum: 1999-01-29
    Beschreibung: All four members of the family of pentopyranosyl-(2'--〉4') oligonucleotide systems that contain beta-ribo-, beta-xylo-, alpha-lyxo-, or alpha-arabinopyranosyl units as repeating sugar building blocks are found to be much stronger Watson-Crick base-pairing systems than RNA. The alpha-arabinopyranosyl system is the strongest of all and in fact belongs to the strongest oligonucleotide base-pairing systems known. Whatever the chemical determinants by which nature selected RNA as a genetic system, maximization of base-pairing strengths within the domain of pentose-derived oligonucleotide systems was not the critical selection criterion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beier, M -- Reck, F -- Wagner, T -- Krishnamurthy, R -- Eschenmoser, A -- New York, N.Y. -- Science. 1999 Jan 29;283(5402):699-703.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Skaggs Institute for Chemical Biology at The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9924032" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Arabinose/chemistry ; *Base Pairing ; Circular Dichroism ; Evolution, Molecular ; Nucleic Acid Conformation ; Nucleic Acid Denaturation ; Oligonucleotides/*chemistry ; Oligoribonucleotides/*chemistry ; Pentoses/*chemistry ; RNA/*chemistry ; Ribose/chemistry ; Temperature ; Thermodynamics ; Xylose/chemistry
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 21
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-13
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jakosky, B M -- New York, N.Y. -- Science. 1999 Jan 29;283(5402):648-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder 80309, USA. jakosky@argyre.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9988657" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Climate ; *Exobiology ; Extraterrestrial Environment ; Ferric Compounds ; Ice ; Magnetics ; *Mars ; Minerals ; Silicates ; Temperature ; *Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-10-09
    Beschreibung: Superoxide reductase from the hyperthermophilic anaerobe Pyrococcus furiosus uses electrons from reduced nicotinamide adenine dinucleotide phosphate, by way of rubredoxin and an oxidoreductase, to reduce superoxide to hydrogen peroxide, which is then reduced to water by peroxidases. Unlike superoxide dismutase, the enzyme that protects aerobes from the toxic effects of oxygen, SOR does not catalyze the production of oxygen from superoxide and therefore confers a selective advantage on anaerobes. Superoxide reductase and associated proteins are catalytically active 80 degrees C below the optimum growth temperature (100 degrees C) of P. furiosus, conditions under which the organism is likely to be exposed to oxygen.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jenney, F E Jr -- Verhagen, M F -- Cui, X -- Adams, M W -- New York, N.Y. -- Science. 1999 Oct 8;286(5438):306-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biology, Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-7229, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10514376" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acetylation ; Amino Acid Sequence ; Anaerobiosis ; Bacteria, Anaerobic/enzymology/genetics ; Catalysis ; Cytochrome c Group/metabolism ; Hydrogen Peroxide/metabolism ; Molecular Sequence Data ; NADP/metabolism ; Oxidation-Reduction ; Oxidoreductases/chemistry/genetics/isolation & purification/*metabolism ; Pyrococcus/*enzymology/genetics ; Rubredoxins/metabolism ; Superoxide Dismutase/metabolism ; Superoxides/*metabolism ; Temperature ; Water/metabolism
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 23
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-08-28
    Beschreibung: Matrix olivines in the Allende carbonaceous chondrite are believed to have formed by condensation processes in the primitive solar nebula. However, transmission electron microscope observations of numerous matrix olivines show that they contain abundant, previously unrecognized, nanometer-sized inclusions of pentlandite and poorly graphitized carbon. Neither of these phases would have been stable at the high-temperature conditions required to condense iron-rich olivine in the solar nebula. The presence of these inclusions is consistent with formation of the olivines by parent body processes that involved overgrowth of fine-grained organic materials and sulfides in the precursor matrix materials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brearley, A J -- New York, N.Y. -- Science. 1999 Aug 27;285(5432):1380-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA. brearley@unm.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10464092" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Alloys/analysis/*chemistry ; Graphite/analysis/*chemistry ; Iron Compounds/analysis/*chemistry ; Magnesium Compounds/analysis/*chemistry ; *Meteoroids ; Microscopy, Electron ; Oxygen Isotopes/analysis ; Silicates/analysis/*chemistry ; Temperature ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 24
    Publikationsdatum: 1999-03-12
    Beschreibung: A constitutive equation based on stress-strain models of bulk solids was adapted to relate the surface pressure, compression rate, and temperature of an insoluble monolayer of monodendrons during collapse at the air-water interface. A power law relation between compression rate and surface pressure and an Arrhenius temperature dependence of the steady-state creep rate were observed in data from compression rate and creep experiments in the collapse region. These relations were combined into a single constitutive equation to calculate the temperature dependence of the collapse pressure with a maximum error of 5 percent for temperatures ranging from 10 degrees to 25 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kampf, J P -- Frank, C W -- Malmstrom, E E -- Hawker, C J -- New York, N.Y. -- Science. 1999 Mar 12;283(5408):1730-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Stanford University, Stanford, CA 94305-5025, USA. IBM Almaden Research Center, San Jose, CA 95120-6099, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10073937" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Air ; Anisotropy ; Chemistry, Physical ; Ethers/*chemistry ; Ethylene Glycols/*chemistry ; Mathematics ; Metals/*chemistry ; Physicochemical Phenomena ; Polymers/*chemistry ; Pressure ; Solubility ; Stress, Mechanical ; Surface Properties ; Temperature ; Water/chemistry
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 25
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-01-08
    Beschreibung: The G+C nucleotide content of ribosomal RNA (rRNA) sequences is strongly correlated with the optimal growth temperature of prokaryotes. This property allows inference of the environmental temperature of the common ancestor to all life forms from knowledge of the G+C content of its rRNA sequences. A model of sequence evolution, assuming varying G+C content among lineages and unequal substitution rates among sites, was devised to estimate ancestral base compositions. This method was applied to rRNA sequences of various species representing the major lineages of life. The inferred G+C content of the common ancestor to extant life forms appears incompatible with survival at high temperature. This finding challenges a widely accepted hypothesis about the origin of life.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Galtier, N -- Tourasse, N -- Gouy, M -- New York, N.Y. -- Science. 1999 Jan 8;283(5399):220-1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Biometrie, Genetique et Biologie des Populations, Universite C. Bernard Lyon 1, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9880254" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Base Composition ; Base Sequence ; Computer Simulation ; Confidence Intervals ; Cytosine/*analysis ; *Evolution, Molecular ; Guanine/*analysis ; Hot Temperature ; Likelihood Functions ; Markov Chains ; Models, Chemical ; *Origin of Life ; Phylogeny ; RNA, Archaeal/chemistry ; RNA, Bacterial/chemistry ; RNA, Ribosomal/*chemistry ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 26
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-08-14
    Beschreibung: Brownian ratchets use a time-varying asymmetric potential that can be applied to separate diffusing particles or molecules. A new type of Brownian ratchet, a geometrical Brownian ratchet, has been realized. Charged, fluorescently labeled phospholipids in a two-dimensional fluid bilayer were driven in one direction by an electric field through a two-dimensional periodic array of asymmetric barriers to lateral diffusion fabricated from titanium oxide on silica. Diffusion spreads the phospholipid molecules in the orthogonal direction, and the asymmetric barriers rectify the Brownian motion, causing a directional transport of molecules. The geometrical ratchet can be used as a continuous molecular sieve to separate mixtures of membrane-associated molecules that differ in electrophoretic mobility and diffusion coefficient.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉van Oudenaarden, A -- Boxer, S G -- New York, N.Y. -- Science. 1999 Aug 13;285(5430):1046-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10446046" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): 4-Chloro-7-nitrobenzofurazan/analogs & derivatives/chemistry/isolation & ; purification ; Chemistry, Physical ; Diffusion ; *Electrophoresis ; Fluorescence ; Fluorescent Dyes ; *Lipid Bilayers ; Membrane Fluidity ; Membrane Proteins/chemistry/*isolation & purification ; Phosphatidylethanolamines/chemistry/isolation & purification ; Phosphatidylserines/chemistry/isolation & purification ; Phospholipids/chemistry/*isolation & purification ; Physicochemical Phenomena ; Temperature ; Xanthenes
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  • 27
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-05
    Beschreibung: An off-limb scan of Callisto was conducted by the Galileo near-infrared mapping spectrometer to search for a carbon dioxide atmosphere. Airglow in the carbon dioxide nu3 band was observed up to 100 kilometers above the surface and indicates the presence of a tenuous carbon dioxide atmosphere with surface pressure of 7.5 x 10(-12) bar and a temperature of about 150 kelvin, close to the surface temperature. A lifetime on the order of 4 years is suggested, based on photoionization and magnetospheric sweeping. Either the atmosphere is transient and was formed recently or some process is currently supplying carbon dioxide to the atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Carlson, R W -- New York, N.Y. -- Science. 1999 Feb 5;283(5403):820-1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. rcarlson@lively.jpl.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9933159" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Atmospheric Pressure ; *Carbon Dioxide ; *Extraterrestrial Environment ; *Jupiter ; Temperature ; Ultraviolet Rays ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-09-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clayton, R N -- New York, N.Y. -- Science. 1999 Aug 27;285(5432):1364-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10490412" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Iron Compounds/analysis ; Magnesium Compounds/analysis ; *Meteoroids ; Silicates/analysis ; Sodium Chloride ; Temperature ; *Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 29
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-27
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arrhenius, G -- Bada, J L -- Joyce, G F -- Lazcano, A -- Miller, S -- Orgel, L E -- New York, N.Y. -- Science. 1999 Feb 5;283(5403):792.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10049121" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Adaptation, Physiological ; *Biological Evolution ; *Origin of Life ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 30
    Publikationsdatum: 1999-08-14
    Beschreibung: Intracellular membrane fusion is crucial for the biogenesis and maintenance of cellular compartments, for vesicular traffic between them, and for exo- and endocytosis. Parts of the molecular machinery underlying this process have been identified, but most of these components operate in mutual recognition of the membranes. Here it is shown that protein phosphatase 1 (PP1) is essential for bilayer mixing, the last step of membrane fusion. PP1 was also identified in a complex that contained calmodulin, the second known factor implicated in the regulation of bilayer mixing. The PP1-calmodulin complex was required at multiple sites of intracellular trafficking; hence, PP1 may be a general factor controlling membrane bilayer mixing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Peters, C -- Andrews, P D -- Stark, M J -- Cesaro-Tadic, S -- Glatz, A -- Podtelejnikov, A -- Mann, M -- Mayer, A -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1999 Aug 13;285(5430):1084-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Friedrich-Miescher-Laboratorium, Spemannstrasse 37-39, 72076 Tubingen, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10446058" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Biological Transport ; Calcium/metabolism ; Calmodulin/analysis/metabolism ; Carboxypeptidases/metabolism ; Cathepsin A ; Cell Membrane/metabolism ; Endocytosis ; Endoplasmic Reticulum/metabolism ; Enzyme Inhibitors/pharmacology ; Fluorescent Dyes ; Golgi Apparatus/metabolism ; Intracellular Membranes/*metabolism ; *Membrane Fusion ; Microcystins ; Mutation ; Peptides, Cyclic/pharmacology ; Phosphoprotein Phosphatases/antagonists & inhibitors/genetics/*metabolism ; Protein Phosphatase 1 ; Pyridinium Compounds ; Quaternary Ammonium Compounds ; Saccharomyces cerevisiae/genetics/*metabolism ; Temperature ; Vacuoles/metabolism
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 31
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-05
    Beschreibung: Oligomerization of a peptide was attempted in a flow reactor that simulated a submarine hydrothermal system. When fluid containing glycine repeatedly circulated through the hot and cold regions in the reactor, oligopeptides were made from glycine. When divalent ions (such as copper ions) were added under acidic conditions, oligoglycine was elongated up to hexaglycine. This observation suggests that prebiotic monomers could have oligomerized in the vicinity of submarine hydrothermal vents on primitive Earth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Imai, E -- Honda, H -- Hatori, K -- Brack, A -- Matsuno, K -- New York, N.Y. -- Science. 1999 Feb 5;283(5403):831-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of BioEngineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9933163" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chromatography, High Pressure Liquid ; Copper/chemistry ; Diketopiperazines ; Dimerization ; *Evolution, Chemical ; Glycine/*chemistry ; Glycylglycine/chemical synthesis/chemistry ; *Hot Temperature ; Hydrogen-Ion Concentration ; Hydrolysis ; Mass Spectrometry ; Oligopeptides/*chemical synthesis/chemistry ; Piperazines/chemical synthesis ; *Pressure ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 32
    Publikationsdatum: 1999-12-11
    Beschreibung: Data from ice 3590 meters below Vostok Station indicate that the ice was accreted from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 10(3) to 3.6 x 10(4) cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 16S ribosomal DNA genes revealed low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 10(6) years of isolation from the atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Priscu, J C -- Adams, E E -- Lyons, W B -- Voytek, M A -- Mogk, D W -- Brown, R L -- McKay, C P -- Takacs, C D -- Welch, K A -- Wolf, C F -- Kirshtein, J D -- Avci, R -- New York, N.Y. -- Science. 1999 Dec 10;286(5447):2141-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biological Sciences, Montana State University, Bozeman, MT 59717, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10591642" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antarctic Regions ; Bacteria/classification/genetics/*isolation & purification ; Bacterial Physiological Phenomena ; DNA, Bacterial/genetics/isolation & purification ; DNA, Ribosomal/genetics/isolation & purification ; Fresh Water/chemistry/*microbiology ; Genes, rRNA ; *Ice ; Microscopy, Electron, Scanning ; Microscopy, Fluorescence ; Minerals/analysis ; Pressure ; Proteobacteria/classification/genetics/isolation & purification/physiology ; RNA, Ribosomal, 16S/genetics ; Temperature ; Water Microbiology
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  • 33
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-04-16
    Beschreibung: The crystal structures of myoglobin in the deoxy- and carbon monoxide-ligated states at a resolution of 1.15 angstroms show that carbon monoxide binding at ambient temperatures requires concerted motions of the heme, the iron, and helices E and F for relief of steric inhibition. These steps constitute the main mechanism by which heme proteins lower the affinity of the heme group for the toxic ligand carbon monoxide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kachalova, G S -- Popov, A N -- Bartunik, H D -- New York, N.Y. -- Science. 1999 Apr 16;284(5413):473-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Arbeitsgruppen fur Strukturelle Molekularbiologie, Arbeitsgruppe Proteindynamik, Notkestrabetae 85, 22603 Hamburg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10205052" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Binding Sites ; Carbon Monoxide/chemistry/*metabolism ; Crystallography, X-Ray ; Heme/chemistry/metabolism ; Histidine/chemistry/metabolism ; Hydrogen Bonding ; Iron/chemistry/metabolism ; Ligands ; Metmyoglobin/chemistry ; Models, Molecular ; Myoglobin/*analogs & derivatives/*chemistry/metabolism ; Nitrogen/chemistry/metabolism ; Protein Conformation ; Protein Structure, Secondary ; Temperature ; Valine/chemistry/metabolism
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  • 34
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-06-26
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gaidos, E J -- Nealson, K H -- Kirschvink, J L -- New York, N.Y. -- Science. 1999 Jun 4;284(5420):1631-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Geology and Planetary Sciences Division, California Institute of Technology, Pasadena 91125, USA. gaidos@gps.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10383341" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Ecosystem ; *Exobiology ; Extraterrestrial Environment ; Hydrogen ; *Ice ; Iron/metabolism ; *Jupiter ; Methane/metabolism ; Oceans and Seas ; Oxidation-Reduction ; Oxygen ; Sulfur/metabolism ; Temperature ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 35
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-03-12
    Beschreibung: Efficient collection and detection of fluorescence coupled with careful minimization of background from impurities and Raman scattering now enable routine optical microscopy and study of single molecules in complex condensed matter environments. This ultimate method for unraveling ensemble averages leads to the observation of new effects and to direct measurements of stochastic fluctuations. Experiments at cryogenic temperatures open new directions in molecular spectroscopy, quantum optics, and solid-state dynamics. Room-temperature investigations apply several techniques (polarization microscopy, single-molecule imaging, emission time dependence, energy transfer, lifetime studies, and the like) to a growing array of biophysical problems where new insight may be gained from direct observations of hidden static and dynamic inhomogeneity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moerner, W E -- Orrit, M -- New York, N.Y. -- Science. 1999 Mar 12;283(5408):1670-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA. w.e.moerner@stanford.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10073924" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry, Physical/*methods ; DNA/*chemistry ; Fluorescence ; Heterocyclic Compounds/*chemistry ; Light ; Microscopy/methods ; Organic Chemicals/*chemistry ; Proteins/*chemistry ; Spectrometry, Fluorescence ; Temperature
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  • 36
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1999-02-12
    Beschreibung: The formation and growth of crystal nuclei of zeolite A from clear solutions at room temperature were studied with low-dose, high-resolution transmission electron microscopy in field emission mode and with in situ dynamic light scattering. Single zeolite A crystals nucleated in amorphous gel particles of 40 to 80 nanometers within 3 days at room temperature. The resulting nanoscale single crystals (10 to 30 nanometers) were embedded in the amorphous gel particles. The gel particles were consumed during further crystal growth at room temperature, forming a colloidal suspension of zeolite A nanocrystals of 40 to 80 nanometers. On heating this suspension at 80 degrees C, solution-mediated transport resulted in additional substantial crystal growth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mintova, S -- Olson, N H -- Valtchev, V -- Bein, T -- GM 33050/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Feb 12;283(5404):958-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9974382" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Colloids ; Crystallization ; Gels ; Light ; Microscopy, Electron ; Models, Chemical ; Scattering, Radiation ; Temperature ; Zeolites/*chemistry
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  • 37
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-01-31
    Beschreibung: Saturn's giant moon Titan has a thick (1.5 bar) nitrogen atmosphere, which has a temperature structure that is controlled by the absorption of solar and thermal radiation by methane, hydrogen, and organic aerosols into which methane is irreversibly converted by photolysis. Previous studies of Titan's climate evolution have been done with the assumption that the methane abundance was maintained against photolytic depletion throughout Titan's history, either by continuous supply from the interior or by buffering by a surface or near surface reservoir. Radiative-convective and radiative-saturated equilibrium models of Titan's atmosphere show that methane depletion may have allowed Titan's atmosphere to cool so that nitrogen, its main constituent, condenses onto the surface, collapsing Titan into a Triton-like frozen state with a thin atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lorenz, R D -- McKay, C P -- Lunine, J I -- New York, N.Y. -- Science. 1997 Jan 31;275(5300):642-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson 85721, USA.rlorenz@pl.arizona.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9005844" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Evolution, Planetary ; *Extraterrestrial Environment ; *Methane ; *Nitrogen ; Photolysis ; *Saturn ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 38
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-04-11
    Beschreibung: In experiments modeling the reactions of the reductive acetyl-coenzyme A pathway at hydrothermal temperatures, it was found that an aqueous slurry of coprecipitated NiS and FeS converted CO and CH3SH into the activated thioester CH3-CO-SCH3, which hydrolyzed to acetic acid. In the presence of aniline, acetanilide was formed. When NiS-FeS was modified with catalytic amounts of selenium, acetic acid and CH3SH were formed from CO and H2S alone. The reaction can be considered as the primordial initiation reaction for a chemoautotrophic origin of life.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huber, C -- Wachtershauser, G -- New York, N.Y. -- Science. 1997 Apr 11;276(5310):245-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Organic Chemistry and Biochemistry, Technische Universitat Munchen, Lichtenbergstrasse 4, D-85747 Garching, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9092471" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acetic Acid/*chemistry ; Carbon Monoxide/*chemistry ; Catalysis ; Cobalt/chemistry ; *Evolution, Chemical ; Ferrous Compounds/*chemistry ; Hydrogen Sulfide/chemistry ; Hydrogen-Ion Concentration ; Hydrolysis ; Nickel/*chemistry ; *Origin of Life ; Oxidation-Reduction ; Sulfhydryl Compounds/chemistry ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 39
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-04-11
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crabtree, R H -- New York, N.Y. -- Science. 1997 Apr 11;276(5310):222.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Yale University Chemistry Department, New Haven, CT 06520-8107, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9132945" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acetate-CoA Ligase/metabolism ; Acetates/*chemistry ; Acetyl Coenzyme A/chemistry ; Carbon Monoxide/chemistry ; Catalysis ; *Evolution, Chemical ; Ferrous Compounds/chemistry ; Nickel/chemistry ; *Origin of Life ; Temperature
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  • 40
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-06-20
    Beschreibung: A leucine-rich nuclear export signal (NES) allows rapid export of proteins from cell nuclei. Microinjection studies revealed a role for the guanosine triphosphatase (GTPase) Ran in NES-mediated export. Nuclear injection of a Ran mutant (Thr24 --〉 Asn) blocked protein export but not import, whereas depletion of the Ran nucleotide exchange factor RCC1 blocked protein import but not export. However, injection of Ran GTPase-activating protein (RanGAP) into RCC1-depleted cell nuclei inhibited export. Coinjection with Ran mutants insensitive to RanGAP prevented this inhibition. Therefore, NES-mediated protein export appears to require a Ran-GTP complex but does not require Ran-dependent GTP hydrolysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Richards, S A -- Carey, K L -- Macara, I G -- EST3207122/ES/NIEHS NIH HHS/ -- GM 50526/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jun 20;276(5320):1842-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, University of Vermont, Burlington, VT 05405, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9188526" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Transport ; Carrier Proteins/metabolism ; *Cell Cycle Proteins ; Cell Line ; Cell Nucleus/*metabolism ; Cricetinae ; Cytoplasm ; DNA-Binding Proteins/metabolism ; GTP Phosphohydrolases/*metabolism ; GTP-Binding Proteins/metabolism ; *GTPase-Activating Proteins ; Glutathione Transferase/metabolism ; Green Fluorescent Proteins ; *Guanine Nucleotide Exchange Factors ; Guanosine Triphosphate/*metabolism ; Luminescent Proteins/metabolism ; Mutation ; Nuclear Envelope/metabolism ; Nuclear Localization Signals ; Nuclear Proteins/genetics/*metabolism ; Receptors, Glucocorticoid/metabolism ; Recombinant Fusion Proteins/metabolism ; Temperature ; ran GTP-Binding Protein
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  • 41
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-02
    Beschreibung: Circadian rhythmicity is universally associated with the ability to perceive light, and the oscillators ("clocks") giving rise to these rhythms, which are feedback loops based on transcription and translation, are reset by light. Although such loops must contain elements of positive and negative regulation, the clock genes analyzed to date-frq in Neurospora and per and tim in Drosophila-are associated only with negative feedback and their biochemical functions are largely inferred. The white collar-1 and white collar-2 genes, both global regulators of photoresponses in Neurospora, encode DNA binding proteins that contain PAS domains and are believed to act as transcriptional activators. Data shown here suggest that wc-1 is a clock-associated gene and wc-2 is a clock component; both play essential roles in the assembly or operation of the Neurospora circadian oscillator. Thus DNA binding and transcriptional activation can now be associated with a clock gene that may provide a positive element in the feedback loop. In addition, similarities between the PAS-domain regions of molecules involved in light perception and circadian rhythmicity in several organisms suggest an evolutionary link between ancient photoreceptor proteins and more modern proteins required for circadian oscillation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crosthwaite, S K -- Dunlap, J C -- Loros, J J -- GM 34985/GM/NIGMS NIH HHS/ -- MH01186/MH/NIMH NIH HHS/ -- MH44651/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 1997 May 2;276(5313):763-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9115195" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amino Acid Sequence ; Biological Clocks/physiology ; Biological Evolution ; Circadian Rhythm/*physiology ; DNA, Fungal/metabolism ; DNA-Binding Proteins/chemistry/genetics/*physiology ; Feedback ; Fungal Proteins/genetics ; Gene Expression Regulation, Fungal ; Genes, Fungal ; Light ; Molecular Sequence Data ; Neurospora crassa/genetics/*physiology ; Phytochrome/metabolism ; Signal Transduction ; Temperature ; Transcription Factors/chemistry/genetics/*physiology ; *Transcriptional Activation
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  • 42
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-03-14
    Beschreibung: Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kirschvink, J L -- Maine, A T -- Vali, H -- New York, N.Y. -- Science. 1997 Mar 14;275(5306):1629-33.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, 170-25, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9054354" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbonates/*chemistry ; Magnetics ; *Mars ; *Meteoroids ; Minerals/*chemistry ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 43
    Publikationsdatum: 1997-08-22
    Beschreibung: A highly selective, colorimetric polynucleotide detection method based on mercaptoalkyloligonucleotide-modified gold nanoparticle probes is reported. Introduction of a single-stranded target oligonucleotide (30 bases) into a solution containing the appropriate probes resulted in the formation of a polymeric network of nanoparticles with a concomitant red-to-pinkish/purple color change. Hybridization was facilitated by freezing and thawing of the solutions, and the denaturation of these hybrid materials showed transition temperatures over a narrow range that allowed differentiation of a variety of imperfect targets. Transfer of the hybridization mixture to a reverse-phase silica plate resulted in a blue color upon drying that could be detected visually. The unoptimized system can detect about 10 femtomoles of an oligonucleotide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Elghanian, R -- Storhoff, J J -- Mucic, R C -- Letsinger, R L -- Mirkin, C A -- GM 10265/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1078-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262471" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Biosensing Techniques ; Colorimetry ; *Gold ; Microchemistry ; *Nucleic Acid Hybridization ; *Oligonucleotide Probes ; Polydeoxyribonucleotides/*analysis ; Spectrophotometry ; Temperature
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  • 44
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-02
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Morell, V -- New York, N.Y. -- Science. 1997 May 2;276(5313):699-702.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9157549" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Archaea/*classification/genetics/physiology ; Bacteria/*classification/genetics ; Base Sequence ; Biological Evolution ; History, 20th Century ; Origin of Life ; *Phylogeny ; RNA, Bacterial/genetics ; RNA, Ribosomal/genetics ; Sequence Analysis, RNA ; Temperature ; United States
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  • 45
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-12-31
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kasting, J F -- New York, N.Y. -- Science. 1997 Nov 14;278(5341):1245.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geoscience, Pennsylvania State University, State College 16802, USA. kasting@essc.psu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9411751" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Carbon Dioxide ; Climate ; Exobiology ; *Extraterrestrial Environment ; Greenhouse Effect ; Ice ; Infrared Rays ; *Mars ; Scattering, Radiation ; Temperature ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 46
    Publikationsdatum: 1997-08-15
    Beschreibung: The epithelium that lines the gut is impermeable to macromolecules and microorganisms, except in Peyer's patches (PPs), where the lymphoid follicle-associated epithelium (FAE) contains M cells that transport antigens and microorganisms. A cultured system that reproduces the main characteristics of FAE and M cells was established by cultivation of PP lymphocytes with the differentiated human intestinal cell line Caco-2. Lymphocytes settled into the epithelial monolayer, inducing reorganization of the brush border and a temperature-dependent transport of particles and Vibrio cholerae. This model system could prove useful for intestinal physiology, vaccine research, and drug delivery studies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kerneis, S -- Bogdanova, A -- Kraehenbuhl, J P -- Pringault, E -- New York, N.Y. -- Science. 1997 Aug 15;277(5328):949-52.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Swiss Institute for Experimental Cancer Research, and Institute of Biochemistry, University of Lausanne, CH-1066 Epalinges-Lausanne, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9252325" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; B-Lymphocytes/immunology ; *Bacterial Translocation ; Caco-2 Cells ; Carrier Proteins/analysis ; Cell Polarity ; Coculture Techniques ; Fluorescein-5-isothiocyanate ; Humans ; *Immunity, Mucosal ; Intestinal Mucosa/*cytology/*immunology/microbiology ; Lymphocytes/*immunology ; Mice ; Mice, Inbred BALB C ; Microfilament Proteins/analysis ; Microspheres ; Microvilli/chemistry/ultrastructure ; Peyer's Patches/cytology/*immunology ; Sucrase-Isomaltase Complex/analysis ; T-Lymphocytes/immunology ; Temperature ; Vibrio cholerae/*metabolism
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 47
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-10-23
    Beschreibung: The formation of vibrationally excited heme upon photodissociation of carbonmonoxy myoglobin and its subsequent vibrational energy relaxation was monitored by picosecond anti-Stokes resonance Raman spectroscopy. The anti-Stokes intensity of the nu4 band showed immediate generation of vibrationally excited hemes and biphasic decay of the excited populations. The best fit to double exponentials gave time constants of 1.9 +/- 0.6 and 16 +/- 9 picoseconds for vibrational population decay and 3.0 +/- 1.0 and 25 +/- 14 picoseconds for temperature relaxation of the photolyzed heme when a Boltzmann distribution was assumed. The decay of the nu4 anti-Stokes intensity was accompanied by narrowing and frequency upshift of the Stokes counterpart. This direct monitoring of the cooling dynamics of the heme cofactor within the globin matrix allows the characterization of the vibrational energy flow through the protein moiety and to the water bath.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mizutani, Y -- Kitagawa, T -- New York, N.Y. -- Science. 1997 Oct 17;278(5337):443-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Molecular Science, Okazaki National Research Institutes, Myodaiji, Okazaki 444, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9334299" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbon Monoxide/chemistry ; Heme/*chemistry ; Myoglobin/*chemistry ; Photolysis ; Photons ; Spectrum Analysis, Raman ; Temperature ; Thermodynamics
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  • 48
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-09-05
    Beschreibung: Arrest of the cell cycle at the G2 checkpoint, induced by DNA damage, requires inhibitory phosphorylation of the kinase Cdc2 in both fission yeast and human cells. The kinase Wee1 and the phosphatase Cdc25, which regulate Cdc2 phosphorylation, were evaluated as targets of Chk1, a kinase essential for the checkpoint. Fission yeast cdc2-3w Deltacdc25 cells, which express activated Cdc2 and lack Cdc25, were responsive to Wee1 but insensitive to Chk1 and irradiation. Expression of large amounts of Chk1 produced the same phenotype as did loss of the cdc25 gene in cdc2-3w cells. Cdc25 associated with Chk1 in vivo and was phosphorylated when copurified in Chk1 complexes. These findings identify Cdc25, but not Wee1, as a target of the DNA damage checkpoint.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Furnari, B -- Rhind, N -- Russell, P -- New York, N.Y. -- Science. 1997 Sep 5;277(5331):1495-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9278510" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adenosine Triphosphatases/metabolism ; CDC2 Protein Kinase/*metabolism ; Cell Cycle Proteins/*metabolism ; Cell Division ; *DNA Damage ; DNA Helicases/metabolism ; Fungal Proteins/*metabolism ; G2 Phase ; Gamma Rays ; Genes, Fungal ; *Mitosis ; Models, Biological ; Mutation ; *Nuclear Proteins ; Phosphorylation ; Phosphotyrosine/metabolism ; Protein Kinases/genetics/*metabolism ; Protein-Tyrosine Kinases/genetics/metabolism ; Recombinant Fusion Proteins/metabolism ; Saccharomyces cerevisiae Proteins ; Schizosaccharomyces/cytology/genetics/*metabolism/radiation effects ; Schizosaccharomyces pombe Proteins ; Signal Transduction ; Temperature ; *ras-GRF1
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 49
    Publikationsdatum: 1997-09-05
    Beschreibung: An image of comet Hale-Bopp (C/1995 O1) in soft x-rays reveals a central emission offset from the nucleus, as well as an extended emission feature that does not correlate with the dust jets seen at optical wavelengths. Neon was found to be depleted in the cometary ice by more than a factor of 25 relative to solar abundance, which suggests that ices in Hale-Bopp formed at (or later experienced) temperatures higher than 25 kelvin. A helium line emission at a wavelength of 584 angstroms was detected and may be attributable to charge transfer of solar wind alpha particles in the cometary coma. Ionized oxygen and another helium line contribute to an emission observed at 538 angstroms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krasnopolsky, V A -- Mumma, M J -- Abbott, M -- Flynn, B C -- Meech, K J -- Yeomans, D K -- Feldman, P D -- Cosmovici, C B -- New York, N.Y. -- Science. 1997 Sep 5;277(5331):1488-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Catholic University of America, Washington, DC 20064, USA. ys2VK@lepvax.gsfc.nasa.gov 20771, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9278508" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Cosmic Dust ; Helium/*analysis ; Ice ; *Meteoroids ; Neon/*analysis ; Oxygen/*analysis ; Temperature ; X-Rays
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 50
    Publikationsdatum: 1997-07-18
    Beschreibung: The infrared spectrum of hot water observed in a sunspot has been assigned. The high temperature of the sunspot (3200 K) gave rise to a highly congested pure rotational spectrum in the 10-micrometer region that involved energy levels at least halfway to dissociation. Traditional spectroscopy, based on perturbation theory, is inadequate for this problem. Instead, accurate variational solutions of the vibration-rotation Schrodinger equation were used to make assignments, revealing unexpected features, including rotational difference bands and fewer degeneracies than anticipated. These results indicate that a shift away from perturbation theory to first principles calculations is necessary in order to assign spectra of hot polyatomic molecules such as water.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Polyansky, O L -- Zobov, N F -- Viti, S -- Tennyson, J -- Bernath, P F -- Wallace, L -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):346-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9219686" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry, Physical ; Physicochemical Phenomena ; *Solar Activity ; *Solar System ; Spectrophotometry, Infrared ; Temperature ; Water/*analysis/chemistry
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  • 51
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-03-28
    Beschreibung: Thermal infrared (IR) imaging and spectroscopy of comet Hale-Bopp (C/1995 O1) during June, August, and September 1996 traced the development of the dust coma several months before perihelion. Images revealed nightly variations in the brightness of the inner coma from 1 to 12 June that were correlated with the appearance of a northward-pointing jet. The central IR flux increased by a factor of 8 between 1 June and 30 September, and the September data showed IR jets that corresponded to similar structures that were visible in reflected sunlight at shorter wavelengths. At all epochs, 8- to 13-micrometer spectra of the central coma revealed a strong silicate emission feature, including an 11.2-micrometer feature indicative of crystalline olivine, even when the comet was at a heliocentric distance of 4.1 astronomical units.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hayward, T L -- Hanner, M S -- New York, N.Y. -- Science. 1997 Mar 28;275(5308):1907-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA. hayward@astrosun.tn.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9072961" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Cosmic Dust ; Iron Compounds/analysis ; Magnesium Compounds/analysis ; *Meteoroids ; Silicates/analysis ; Spectrum Analysis ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 52
    Publikationsdatum: 1997-03-14
    Beschreibung: The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (〉650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (〈 approximately 300 degrees C).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Valley, J W -- Eiler, J M -- Graham, C M -- Gibson, E K -- Romanek, C S -- Stolper, E M -- New York, N.Y. -- Science. 1997 Mar 14;275(5306):1633-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9054355" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbon Isotopes ; Carbonates/*chemistry ; Chemical Precipitation ; *Mars ; *Meteoroids ; Minerals/chemistry ; Oxygen Isotopes ; Silicon Dioxide/chemistry ; Temperature
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  • 53
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-06-20
    Beschreibung: To test proposals for the origin of oxygen absorption bands in the visible reflectance spectrum of Ganymede, the reflectance of condensed films of pure oxygen (O2) and O2-water mixtures and the evolution of O2 from the films as a function of temperature were determined. Absorption band shapes and positions for oxygen at 26 kelvin were similar to those reported for Ganymede, whereas those for the mixtures were slightly shifted. The band intensity dropped by more than two orders of magnitude when the ice mixture was warmed to 100 kelvin, although about 20 percent of the O2 remained trapped in the ice, which suggested that at these temperatures O2 molecules dissolve in the ice rather than aggregate in clusters or bubbles. The experiments suggest that the absorption bands in Ganymede's spectrum were not produced in the relatively warm surface of the satellite but in a much colder source. Solid O2 may exist in a cold subsurface layer or in an atmospheric haze.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vidal, R A -- Bahr, D -- Baragiola, R A -- Peters, M -- New York, N.Y. -- Science. 1997 Jun 20;276(5320):1839-42.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory for Atomic and Surface Physics, University of Virginia, Thornton Hall, Charlottesville, VA 22901, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9188525" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Extraterrestrial Environment ; *Jupiter ; Oxygen/*analysis ; Spectrum Analysis ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 54
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-10-23
    Beschreibung: A stellar-occultation light curve for Triton shows asymmetry that can be understood if Triton's middle atmosphere is distorted from spherical symmetry. Although a globally oblate model can explain the data, the inferred atmospheric flattening is so large that it could be caused only by an unrealistic internal mass distribution or highly supersonic zonal winds. Cyclostrophic winds confined to a jet near Triton's northern or southern limbs (or both) could also be responsible for the details of the light curve, but such winds are required to be slightly supersonic. Hazes and clouds in the atmosphere are unlikely to have caused the asymmetry in the light curve.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Elliot, J L -- Stansberry, J A -- Olkin, C B -- Agner, M A -- Davies, M E -- New York, N.Y. -- Science. 1997 Oct 17;278(5337):436-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric, and Planetary Sciences and Department of Physics, Building 54-422, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA. jle@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9334297" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Extraterrestrial Environment ; Gravitation ; *Neptune ; Optics and Photonics ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 55
    Publikationsdatum: 1997-12-31
    Beschreibung: The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol = 1 martian day = 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander (VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schofield, J T -- Barnes, J R -- Crisp, D -- Haberle, R M -- Larsen, S -- Magalhaes, J A -- Murphy, J R -- Seiff, A -- Wilson, G -- New York, N.Y. -- Science. 1997 Dec 5;278(5344):1752-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. T. Schofield and D. Crisp, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9388169" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Carbon Dioxide ; *Extraterrestrial Environment ; *Mars ; Pressure ; Temperature ; Wind
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 56
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-04-04
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kerr, R A -- New York, N.Y. -- Science. 1997 Apr 4;276(5309):30-1.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9122703" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Bacteria ; *Carbonates/analysis/chemistry ; *Exobiology ; Extraterrestrial Environment ; Ferrosoferric Oxide ; Fossils ; *Iron/analysis/chemistry ; *Mars ; *Meteoroids ; *Oxides/analysis/chemistry ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 57
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-07-04
    Beschreibung: The pathogenic yeast Candida albicans regulates its cellular morphology in response to environmental conditions. Ellipsoidal, single cells (blastospores) predominate in rich media, whereas filaments composed of elongated cells that are attached end-to-end form in response to starvation, serum, and other conditions. The TUP1 gene, which encodes a general transcriptional repressor in Saccharomyces cerevisiae, was isolated from C. albicans and disrupted. The resulting tup1 mutant strain of C. albicans grew exclusively as filaments under all conditions tested. TUP1 was epistatic to the transcriptional activator CPH1, previously found to promote filamentous growth. The results suggest a model where TUP1 represses genes responsible for initiating filamentous growth and this repression is lifted under inducing environmental conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Braun, B R -- Johnson, A D -- GM37049/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jul 4;277(5322):105-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143-0414, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9204892" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amino Acid Sequence ; Candida albicans/*cytology/*genetics/growth & development/metabolism ; Cloning, Molecular ; Culture Media ; DNA-Binding Proteins/metabolism ; Epistasis, Genetic ; Fungal Proteins/chemistry/*genetics/*metabolism ; Gene Deletion ; Genes, Fungal ; Glycerol/metabolism ; Models, Genetic ; Molecular Sequence Data ; Mutation ; *Nuclear Proteins ; Phenotype ; Repressor Proteins/genetics/*metabolism ; *Saccharomyces cerevisiae Proteins ; Sequence Alignment ; Temperature ; Transcription Factors/metabolism ; Transcription, Genetic
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  • 58
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-16
    Beschreibung: Transmission electron microscope observations of the Allende carbonaceous chondrite provided evidence of widespread hydrous phases replacing enstatite in chondrules. Calcic amphibole and talc occur in thin (less than 0.3 micrometer) crosscutting veins and as alteration products of primary chondrule glass in contraction cracks within the enstatite. In addition, talc and disordered biopyriboles were found replacing enstatite grains along cracks and fractures. Although rare hydrous phases have been reported in calcium- and aluminum-rich inclusions in the Allende meteorite, these observations suggest that aqueous fluids played a much more significant role in the mineralogical and geochemical evolution of Allende than has previously been thought.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brearley, A J -- New York, N.Y. -- Science. 1997 May 16;276(5315):1103-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9148802" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Aluminum/analysis ; Asbestos, Amphibole/analysis ; Calcium/analysis ; Iron Compounds/analysis ; Magnesium Compounds/analysis ; *Meteoroids ; Microscopy, Electron ; Pressure ; Silicates/analysis ; Talc/analysis ; Temperature ; *Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 59
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-07-18
    Beschreibung: Sulfurization of meteoritic metal in H2S-H2 gas produced three different sulfides: monosulfide solid solution [(Fe,Ni)1-xS], pentlandite [(Fe,Ni)9-xS8], and a phosphorus-rich sulfide. The composition of the remnant metal was unchanged. These results are contrary to theoretical predictions that sulfide formation in the solar nebula produced troilite (FeS) and enriched the remaining metal in nickel. The experimental sulfides are chemically and morphologically similar to sulfide grains in the matrix of the Alais (class CI) carbonaceous chondrite, suggesting that these meteoritic sulfides may be condensates from the solar nebula.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lauretta, D S -- Lodders, K -- Fegley, B Jr -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):358-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Planetary Chemistry Laboratory, Department of Earth and Planetary Sciences, Campus Box 1169, Washington University, One Brookings Drive, St. Louis, MO 63130-4899, USA. lauretta@wunder.wustl.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9219690" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Ferrous Compounds/chemistry ; Hydrogen/chemistry ; Iron/chemistry ; *Meteoroids ; Nickel/chemistry ; *Solar System ; Sulfides/*chemistry ; Temperature
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  • 60
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-03-07
    Beschreibung: An x-ray spectroscopic study of scleractinian coral skeletons indicated that, although some strontium substitutes for calcium in the aragonite structure, at concentrations of about 7500 parts per million, as much as 40 percent of the strontium resides in strontianite (SrCO3). A doublet peak in the Fourier transform of the extended x-ray absorption fine structure of the coral corresponded to six metal and 13 oxygen neighbors surrounding strontium at about 4.05 angstroms in strontium-substituted aragonite and at about 4.21 angstroms in strontianite. Thus, the mechanism of the temperature-sensitive partitioning of strontium between seawater and coral skeleton used for paleothermometry is unexpectedly complex.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Greegor, R B -- Pingitore, N E Jr -- Lytle, F W -- New York, N.Y. -- Science. 1997 Mar 7;275(5305):1452-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Boeing Company, Seattle, WA 98124, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9072808" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Calcium/analysis ; Calcium Carbonate/*analysis ; Carbonates/*analysis ; Cnidaria/*chemistry ; Fourier Analysis ; Spectrum Analysis ; Strontium/*analysis ; Temperature
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  • 61
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-16
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stevenson, R D -- Woods, W A Jr -- New York, N.Y. -- Science. 1997 May 16;276(5315):1015-6; author reply 1016-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9173533" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Bees/*physiology ; Body Temperature Regulation/*physiology ; Energy Metabolism ; Flight, Animal/*physiology ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 62
    Publikationsdatum: 1997-09-12
    Beschreibung: Protein folding in the endoplasmic reticulum (ER) often involves the formation of disulfide bonds. The oxidizing conditions required within this organelle were shown to be maintained through the release of small thiols, mainly cysteine and glutathione. Thiol secretion was stimulated when proteins rich in disulfide bonds were translocated into the ER, and secretion was prevented by the inhibition of protein synthesis. Endogenously generated cysteine and glutathione counteracted thiol-mediated retention in the ER and altered the extracellular redox. The secretion of thiols might link disulfide bond formation in the ER to intra- and intercellular redox signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Carelli, S -- Ceriotti, A -- Cabibbo, A -- Fassina, G -- Ruvo, M -- Sitia, R -- New York, N.Y. -- Science. 1997 Sep 12;277(5332):1681-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉DIBIT, Istituto Scientifico San Raffaele, Milano, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9287224" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Benzopyrans/metabolism ; Brefeldin A ; Cycloheximide/pharmacology ; Cyclopentanes/pharmacology ; Cysteine/*secretion ; Cystine/secretion ; Disulfides/*metabolism ; Endoplasmic Reticulum/*metabolism ; Exocytosis ; Glutathione/analogs & derivatives/*secretion ; Glutathione Disulfide ; Golgi Apparatus/metabolism ; Hemagglutinin Glycoproteins, Influenza Virus/biosynthesis ; Immunoglobulin M/biosynthesis ; Immunoglobulin lambda-Chains/metabolism ; Oocytes ; Oxidation-Reduction ; Protein Synthesis Inhibitors/pharmacology ; Proteins/*metabolism ; Temperature ; Tumor Cells, Cultured ; Xenopus laevis
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 63
    Publikationsdatum: 1997-05-02
    Beschreibung: High resolution x-ray diffraction data from crystals of the Rhodobacter sphaeroides photosynthetic reaction center (RC) have been collected at cryogenic temperature in the dark and under illumination, and the structures were refined at 2.2 and 2.6 angstrom resolution, respectively. In the charge-separated D+QAQB- state (where D is the primary electron donor (a bacteriochlorophyll dimer), and QA and QB are the primary and secondary quinone acceptors, respectively), QB- is located approximately 5 angstroms from the QB position in the charge-neutral (DQAQB) state, and has undergone a 180 degrees propeller twist around the isoprene chain. A model based on the difference between the two structures is proposed to explain the observed kinetics of electron transfer from QA-QB to QAQB- and the relative binding affinities of the different ubiquinone species in the QB pocket. In addition, several water channels (putative proton pathways) leading from the QB pocket to the surface of the RC were delineated, one of which leads directly to the membrane surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stowell, M H -- McPhillips, T M -- Rees, D C -- Soltis, S M -- Abresch, E -- Feher, G -- GM13191/GM/NIGMS NIH HHS/ -- GM45162/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 May 2;276(5313):812-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Chemistry and Chemical Engineering, 147-75CH, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9115209" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Binding Sites ; Cell Membrane/chemistry ; Crystallization ; Crystallography, X-Ray ; Darkness ; Electron Transport ; Freezing ; Hydrogen Bonding ; *Light ; Light-Harvesting Protein Complexes ; Models, Molecular ; Photosynthetic Reaction Center Complex Proteins/*chemistry/metabolism ; *Protein Conformation ; *Protons ; Rhodobacter sphaeroides/*chemistry ; Temperature ; Ubiquinone/chemistry/metabolism
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  • 64
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-04-11
    Beschreibung: Although differences among species in enzyme maximal activity or concentration are often interpreted as adaptive and important for regulating metabolism, these differences may simply reflect phylogenetic divergence. Phylogenetic analysis of the expression of the glycolytic enzymes among 15 taxa of a North American fish genus (Fundulus) indicated that most variation in enzyme concentration is due to evolutionary distance and may be nonadaptive. However, three enzymes' maximal activities covary with environmental temperature and have adaptive value. Additionally, two pairs of enzymes covary, indicating coevolution. Thus, metabolic flux may be modulated by many different enzymes rather than by a single rate-limiting enzyme.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pierce, V A -- Crawford, D L -- New York, N.Y. -- Science. 1997 Apr 11;276(5310):256-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57 Street, Chicago, IL 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9092475" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adaptation, Physiological ; Animals ; Biological Evolution ; Glyceraldehyde-3-Phosphate Dehydrogenases/*metabolism ; *Glycolysis ; Killifishes/*metabolism ; L-Lactate Dehydrogenase/*metabolism ; *Phylogeny ; Pyruvate Kinase/*metabolism ; Species Specificity ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 65
    facet.materialart.
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-10-27
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Potera, C -- New York, N.Y. -- Science. 1997 Oct 10;278(5336):225-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9340769" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Eukaryota/*growth & development/isolation & purification ; Fish Diseases/diagnosis/*parasitology ; Fisheries ; Montana ; Oligochaeta/parasitology ; Oncorhynchus mykiss/*parasitology ; Polymerase Chain Reaction ; Protozoan Infections/diagnosis/parasitology ; *Protozoan Infections, Animal ; RNA, Protozoan/genetics ; RNA, Ribosomal/genetics ; Spores/physiology ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 66
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-16
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heinrich, B -- Esch, H -- New York, N.Y. -- Science. 1997 May 16;276(5315):1015; author reply 1016-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9173532" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Bees/*physiology ; Body Temperature Regulation/*physiology ; Energy Metabolism ; Flight, Animal/*physiology ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 67
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-09-12
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tiedemann, H -- New York, N.Y. -- Science. 1997 Sep 12;277(5332):1687-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9287226" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Earth (Planet) ; *Evolution, Chemical ; Hydrogen Cyanide/chemistry ; *Meteoroids ; *Origin of Life ; Polyphosphates/*chemistry ; Ribonucleotides/chemistry ; Temperature ; Thermodynamics
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 68
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-08-22
    Beschreibung: The minerals (Mg,Fe)SiO3-ilmenite and -perovskite were identified in the shock-induced veins in the Tenham chondritic meteorite. Both phases are inferred to have transformed from pyroxene at high pressures and temperatures by shock metamorphism. Columnar-shaped ilmenite grains, one of two types of morphologies, have a topotaxial relationship with neighboring pyroxene grains, indicating shear transformation. Granular-shaped perovskite grains showed a diffraction pattern consistent with orthorhombic perovskite, but these grains were not stable under the electron beam irradiation and became amorphous. The higher iron concentration in both phases compared with those experimentally reported may suggest their metastable transition from enstatite because of shock compression.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tomioka, N -- Fujino, K -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1084-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, Sapporo 060, Japan. tomioka@epms.hokuda i.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262473" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Calcium Compounds/*analysis/chemistry ; Iron/*analysis/chemistry ; Iron Compounds/*analysis/chemistry ; Magnesium Compounds/*analysis/chemistry ; *Meteoroids ; Microscopy, Electron ; Oxides/*analysis/chemistry ; Pressure ; Silicates/*analysis/chemistry ; Temperature ; Titanium/*analysis/chemistry
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 69
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-09-26
    Beschreibung: Numerical simulations of homogeneous crystal nucleation with a model for globular proteins with short-range attractive interactions showed that the presence of a metastable fluid-fluid critical point drastically changes the pathway for the formation of a crystal nucleus. Close to this critical point, the free-energy barrier for crystal nucleation is strongly reduced and hence, the crystal nucleation rate increases by many orders of magnitude. Because the location of the metastable critical point can be controlled by changing the composition of the solvent, the present work suggests a systematic approach to promote protein crystallization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉ten Wolde, P R -- Frenkel, D -- New York, N.Y. -- Science. 1997 Sep 26;277(5334):1975-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9302288" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Colloids ; Computer Simulation ; Crystallization ; Monte Carlo Method ; Proteins/*chemistry ; Solvents ; Temperature ; Thermodynamics
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 70
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-11-14
    Beschreibung: Vascular structures for heat conservation in the tongue of the gray whale (Eschrichtius robustus) are reported here. Numerous individual countercurrent heat exchangers are found throughout the massive tongue. These converge at the base of the tongue to form a bilateral pair of retia. Temperature measurements from the oral cavity of a live gray whale indicate that more heat may be lost through the blubber layer over the body than through the tongue, despite the fact that the tongue is far more vascularized and has much less insulation. These heat exchangers substantially reduce heat loss when these whales feed in cold waters.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heyning, J E -- Mead, J G -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1138-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Section of Vertebrates, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA. heyning@bcf.usc.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353198" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adipose Tissue/physiology ; Animals ; Body Temperature ; Body Temperature Regulation/*physiology ; Regional Blood Flow ; Temperature ; Tongue/*blood supply/*physiology ; Whales/anatomy & histology/*physiology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 71
    Publikationsdatum: 1997-03-28
    Beschreibung: The activity of comet Hale-Bopp (C/1995 O1) was monitored monthly by optical imaging and long-slit spectroscopy of its dust and gas distribution over heliocentric distances of 4.6 to 2.9 astronomical units. The observed band intensities of the NH2 radical and the H2O+ ion cannot be explained by existing models of fluorescence excitation, warranting a reexamination of the corresponding production rates, at least at large heliocentric distances. Comparing the production rate of the CN radical to its proposed parent, HCN, shows no evidence for the need of a major additional source for CN in Hale-Bopp at large heliocentric distances. The dust and CN production rates are consistent with a significant amount of sublimation occurring from icy dust grains surrounding Hale-Bopp.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rauer, H -- Arpigny, C -- Boehnhardt, H -- Colas, F -- Crovisier, J -- Jorda, L -- Kuppers, M -- Manfroid, J -- Rembor, K -- Thomas, N -- New York, N.Y. -- Science. 1997 Mar 28;275(5308):1909-12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Observatoire de Paris-Meudon, 5, Place Jules Janssen, F-92190 Meudon, France. rauer@mesiob.obspm.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9072962" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Ammonia/analysis ; Carbon Monoxide/analysis ; Cosmic Dust ; Gases ; Ice ; *Meteoroids ; Nitriles/analysis ; Spectrum Analysis ; Temperature ; Water
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 72
    Publikationsdatum: 1997-09-26
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rauer, H -- Arpigny, C -- Boehnhardt, H -- Colas, F -- Crovisier, J -- Jorda, L -- Kuppers, M -- Manfroid, J -- Rembor, K -- Thomas, N -- New York, N.Y. -- Science. 1997 Sep 5;277(5331):1526-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9304217" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Meteoroids ; Quaternary Ammonium Compounds/*analysis ; Temperature ; Water/*analysis
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 73
    Publikationsdatum: 1997-02-28
    Beschreibung: Constant-pressure, first-principles molecular dynamic simulations were used to investigate the behavior of methane at high pressure and temperature. Contrary to the current interpretation of shock-wave experiments, the simulations suggest that, below 100 gigapascals, methane dissociates into a mixture of hydrocarbons, and it separates into hydrogen and carbon only above 300 gigapascals. The simulation conditions (100 to 300 gigapascals; 4000 to 5000 kelvin) were chosen to follow the isentrope in the middle ice layers of Neptune and Uranus. Implications on the physics of these planets are discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ancilotto, F -- Chiarotti, G L -- Scandolo, S -- Tosatti, E -- New York, N.Y. -- Science. 1997 Feb 28;275(5304):1288-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Dipartimento di Fisica "G. Galilei," Universita di Padova, Via Marzolo 8, I-35131 Padova, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9036849" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Butanes/chemistry ; Computer Simulation ; Ethane/chemistry ; Extraterrestrial Environment ; Hydrocarbons/*chemistry ; Hydrogen/chemistry ; Methane/*chemistry ; *Neptune ; Pressure ; Temperature ; Thermodynamics ; *Uranus
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 74
    Publikationsdatum: 1997-08-22
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cooper, A -- Poinar, H N -- Paabo, S -- Radovcic, J -- Debenath, A -- Caparros, M -- Barroso-Ruiz, C -- Bertranpetit, J -- Nielsen-Marsh, C -- Hedges, R E -- Sykes, B -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1021-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9289843" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; DNA Primers ; DNA, Mitochondrial/*genetics ; Europe ; Haplotypes ; Hominidae/*genetics ; Humans ; Polymerase Chain Reaction ; Sequence Analysis, DNA ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 75
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-08-22
    Beschreibung: Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cooper, G W -- Thiemens, M H -- Jackson, T L -- Chang, S -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1072-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SETI Institute and NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262469" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Alkanesulfonic Acids/*chemistry ; Carbon/chemistry ; *Carbon Compounds, Inorganic ; Deuterium/*analysis ; Hydrogen/*analysis ; Mesylates/chemistry ; *Meteoroids ; Sulfides/chemistry ; *Sulfur Isotopes ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 76
    facet.materialart.
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-10-27
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGrath, M A -- New York, N.Y. -- Science. 1997 Oct 10;278(5336):237-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Telescope Science Institute, Baltimore, MD 21218, USA. mcgrath@stci.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9340770" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Extraterrestrial Environment ; *Jupiter ; Temperature
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 77
    Publikationsdatum: 1997-11-14
    Beschreibung: Cleland and Kreevoy recently advanced the idea that a special type of hydrogen bond (H-bond), termed a low-barrier hydrogen bond (LBHB), may account for the "missing" transition state stabilization underlying the catalytic power of many enzymes, and Frey et al. have proposed that the H-bond between aspartic acid 102 and histidine 57 in the catalytic triad of serine proteases is an example of a catalytically important LBHB. Experimental facts are here considered regarding the aspartic acid-histidine and cis-urocanic H-bonds that are inconsistent with fundamental tenets of the LBHB hypothesis. The inconsistencies between theory and experiment in these paradigm systems cast doubt on the existence of LBHBs, as currently defined, within enzyme active sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ash, E L -- Sudmeier, J L -- De Fabo, E C -- Bachovchin, W W -- GM27927/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1128-32.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Tufts University School of Medicine, Boston, MA 02111, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353195" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Aspartic Acid/chemistry ; Binding Sites ; Boronic Acids/metabolism ; Catalysis ; Histidine/chemistry ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Magnetic Resonance Spectroscopy ; Oligopeptides/metabolism ; Protons ; Serine Endopeptidases/*chemistry/metabolism ; Serine Proteinase Inhibitors/metabolism ; Subtilisins/chemistry ; Temperature ; Urocanic Acid/chemistry
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 78
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-05-02
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kerr, R A -- New York, N.Y. -- Science. 1997 May 2;276(5313):703-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9157550" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Bacteria/*isolation & purification ; Bacterial Physiological Phenomena ; *Environmental Microbiology ; *Geologic Sediments ; Temperature ; Water Microbiology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 79
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-09-20
    Beschreibung: In solution, biopolymers commonly fold into well-defined three-dimensional structures, but only recently has analogous behavior been explored in synthetic chain molecules. An aromatic hydrocarbon backbone is described that spontaneously acquires a stable helical conformation having a large cavity. The chain does not form intramolecular hydrogen bonds, and solvophobic interactions drive the folding transition, which is sensitive to chain length, solvent quality, and temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nelson, J C -- Saven, J G -- Moore, J S -- Wolynes, P G -- PHS 1 S10 RR10444-01/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1997 Sep 19;277(5333):1793-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, IL 61801, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9295264" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acetonitriles ; Acetylene/*analogs & derivatives/chemistry ; Chemistry, Physical ; Chloroform ; Hydrogen Bonding ; Magnetic Resonance Spectroscopy ; Models, Molecular ; *Molecular Conformation ; Physicochemical Phenomena ; Polymers/*chemistry ; Solubility ; Solvents ; Spectrophotometry, Ultraviolet ; Temperature ; Thermodynamics
    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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  • 80
    Publikationsdatum: 1997-12-31
    Beschreibung: Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 +/- 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Folkner, W M -- Yoder, C F -- Yuan, D N -- Standish, E M -- Preston, R A -- New York, N.Y. -- Science. 1997 Dec 5;278(5344):1749-52.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. william.folkner@jp.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9388168" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; Carbon Dioxide ; *Extraterrestrial Environment ; Ferrous Compounds ; Ice ; Iron ; *Mars ; Pressure ; Temperature
    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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  • 81
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-11-21
    Beschreibung: Geomorphic evidence that Mars was warm enough to support flowing water about 3.8 billion years ago presents a continuing enigma that cannot be explained by conventional greenhouse warming mechanisms. Model calculations show that the surface of early Mars could have been warmed through a scattering variant of the greenhouse effect, resulting from the ability of the carbon dioxide ice clouds to reflect the outgoing thermal radiation back to the surface. This process could also explain how Earth avoided an early irreversible glaciation and could extend the size of the habitable zone on extrasolar planets around stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Forget, F -- Pierrehumbert, R T -- New York, N.Y. -- Science. 1997 Nov 14;278(5341):1273-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Meteorologie Dynamique du CNRS, Universite Pierre et Marie Curie, Boite Postale 99, 4 place Jussieu, 75252 Paris Cedex 05, France. forget@lmd.jussieu.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9360920" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Carbon Dioxide ; *Extraterrestrial Environment ; Greenhouse Effect ; Ice ; *Infrared Rays ; *Mars ; Scattering, Radiation ; Temperature ; Water
    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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  • 82
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-07-18
    Beschreibung: The Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system. In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O2, then the principal ion is O2+ and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kliore, A J -- Hinson, D P -- Flasar, F M -- Nagy, A F -- Cravens, T E -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):355-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9219689" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere ; *Extraterrestrial Environment ; *Hydrogen ; *Jupiter ; Magnetics ; *Oxygen ; Temperature ; *Water
    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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  • 83
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1997-07-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Oka, T -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):328-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Chicago, IL 60637, USA. t-oka@uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9518362" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry, Physical ; Physicochemical Phenomena ; *Solar Activity ; *Solar System ; Spectrophotometry, Infrared ; Temperature ; Water/*analysis/chemistry
    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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  • 84
    Publikationsdatum: 1997-03-28
    Beschreibung: Spectra obtained from ground-based radio telescopes show the progressive release of CO, CH3OH, HCN, H2O (from OH), H2S, CS, H2CO, CH3CN, and HNC as comet Hale-Bopp (C/1995 01) approached the sun from 6.9 to 1.4 astronomical units (AU). The more volatile species were relatively more abundant in the coma far from the sun, but there was no direct correlation between overabundance and volatility. Evidence for H2O sublimation from icy grains was seen beyond 3.5 AU from the sun. The change from a CO-driven coma to an H2O-driven coma occurred at about 3 AU. The gas outflow velocity and temperature increased as Hale-Bopp approached the sun.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Biver, N -- Bockelee-Morvan, D -- Colom, P -- Crovisier, J -- Davies, J K -- Dent, W R -- Despois, D -- Gerard, E -- Lellouch, E -- Rauer, H -- Moreno, R -- Paubert, G -- New York, N.Y. -- Science. 1997 Mar 28;275(5308):1915-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Observatoire de Paris-Meudon, F-92195 Meudon, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9072964" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbon/analysis ; Carbon Monoxide/analysis ; Cosmic Dust ; Gases ; Hydrogen/analysis ; Ice ; *Meteoroids ; Methanol/analysis ; Nitrogen/analysis ; Spectrum Analysis ; Temperature ; Water
    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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