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  • 1
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2010-09-03
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lok, Corie -- England -- Nature. 2010 Sep 2;467(7311):18-21. doi: 10.1038/467018a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20811430" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; Financing, Government/legislation & jurisprudence ; Nanostructures/chemistry ; *Nanotechnology/economics ; *Research Support as Topic
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 2
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2010-10-15
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Agre, Peter -- England -- Nature. 2010 Oct 14;467(7317):S11. doi: 10.1038/467S11a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20944611" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Aquaporins/metabolism ; Chemistry ; Happiness ; Interdisciplinary Communication ; Mentors ; Neurosciences/trends ; *Nobel Prize ; Peer Review, Research ; Politics ; Public Policy ; Research/standards/trends ; *Research Personnel/psychology/standards
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 3
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2010-10-15
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crutzen, Paul J -- England -- Nature. 2010 Oct 14;467(7317):S10. doi: 10.1038/467S10a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20944610" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Atmosphere/chemistry ; Chemistry ; Human Activities ; Interdisciplinary Communication ; Mentors ; *Nobel Prize ; Ozone/analysis ; Politics ; Public Opinion ; Public Policy ; *Research Personnel
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 4
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1990-08-03
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waldrop, M M -- New York, N.Y. -- Science. 1990 Aug 3;249(4968):472-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2382127" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Information Systems ; Jurisprudence ; Societies, Scientific ; United States
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1991-10-25
    Beschreibung: The presence of clathrate hydrates in cometary ice has been suggested to account for anomalous gas release at large radial distances from the sun as well as the retention of volatiles in comets to elevated temperatures. However, how clathrate hydrates can form in low-pressure environments, such as in cold interstellar molecular clouds, in the outer reaches of the early solar nebula, or in cometary ices, has been poorly understood. Experiments performed with the use of a modified electron microscope demonstrate that during the warming of vapor-deposited amorphous ices in vacuo, clathrate hydrates can form by rearrangements in the solid state. Phase separations and microporous textures that are the result of these rearrangements may account for a variety of anomalous cometary phenomena.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Blake, D -- Allamandola, L -- Sandford, S -- Hudgins, D -- Freund, F -- New York, N.Y. -- Science. 1991 Oct 25;254:548-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Planetary Biology Branch, Ames Research Center, Moffett Field, CA 94035, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11538372" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; Crystallography ; Earth (Planet) ; Hydrocarbons/chemistry ; Ice/*analysis ; *Meteoroids ; Microscopy, Electron ; *Solar System
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 6
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1990-09-14
    Beschreibung: Direct osmotic stress measurements have been made of forces between helices of xanthan, an industrially important charged polysaccharide. Exponentially decaying hydration forces, much like those already measured between lipid bilayer membranes or DNA double helices, dominate the interactions at close separation. Interactions between uncharged schizophyllans also show the same kind of hydration force seen between xanthans. In addition to the practical possibilities for modifying solution and suspension properties through recognition and control of molecular forces, there is now finally the opportunity for theorists to relate macroscopic properties of a polymer solution to the microscopic properties that underlie them.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rau, D C -- Parsegian, V A -- New York, N.Y. -- Science. 1990 Sep 14;249(4974):1278-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institues of Health, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2144663" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbohydrate Sequence ; Chemical Phenomena ; Chemistry ; Gels ; *Glycosaminoglycans ; Macromolecular Substances ; Molecular Sequence Data ; Osmosis ; *Polysaccharides, Bacterial ; *Sizofiran ; Solutions ; Viscosity
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1990-02-02
    Beschreibung: Protein unfolding and the dissolution of hydrophobic compounds (including solids, liquids, and gases) in water are characterized by a linear relation between entropy change and heat capacity change. The same slope is found for various classes of compounds, whereas the intercept depends on the particular class. The feature common to these processes is exposure of hydrophobic groups to water. These observations make possible the assignment of the heat capacity change to hydrophobic solvation and lead to the description of protein stability in terms of a hydrophobic and a nonhydrophobic contribution. A general representation of protein stability is given by the heat capacity change and the temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, K P -- Privalov, P L -- Gill, S J -- New York, N.Y. -- Science. 1990 Feb 2;247(4942):559-61.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2300815" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Protein Denaturation ; *Proteins ; Thermodynamics
    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: 1990-03-02
    Beschreibung: Ultrasound has become an important synthetic tool in liquid-solid chemical reactions, but the origins of the observed enhancements remained unknown. The effects of high-intensity ultrasound on solid-liquid slurries were examined. Turbulent flow and shock waves produced by acoustic cavitation were found to drive metal particles together at sufficiently high velocities to induce melting upon collision. A series of transition-metal powders were used to probe the maximum temperatures and speeds reached during such interparticle collisions. Metal particles that were irradiated in hydrocarbon liquids with ultrasound underwent collisions at roughly half the speed of sound and generated localized effective temperatures between 2600 degrees C and 3400 degrees C at the point of impact for particles with an average diameter of approximately 10 microns.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doktycz, S J -- Suslick, K S -- New York, N.Y. -- Science. 1990 Mar 2;247(4946):1067-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Chemical Sciences, University of Illinois, Urbana 61801.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2309118" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Metals ; Microscopy, Electron, Scanning ; Microspheres ; *Ultrasonics
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    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: 1990-01-12
    Beschreibung: Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lazar, J G -- Ross, J -- New York, N.Y. -- Science. 1990 Jan 12;247(4939):189-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2294601" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adenosine Triphosphate/metabolism ; Chemical Phenomena ; Chemistry ; Glucosephosphate Dehydrogenase/*metabolism ; Horseradish Peroxidase/*metabolism ; Kinetics ; NAD/*metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Peroxidases/*metabolism ; Thermodynamics
    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: 1990-08-17
    Beschreibung: The interaction of a protein antigen, horse cytochrome c (cyt c), with a monoclonal antibody has been studied by hydrogen-deuterium (H-D) exchange labeling and two-dimensional nuclear magnetic resonance (2D NMR) methods. The H-exchange rate of residues in three discontiguous regions of the cyt c polypeptide backbone was slowed by factors up to 340-fold in the antibody-antigen complex compared with free cyt c. The protected residues, 36 to 38, 59, 60, 64 to 67, 100, and 101, and their hydrogen-bond acceptors, are brought together in the three-dimensional structure to form a contiguous, largely exposed protein surface with an area of about 750 square angstroms. The interaction site determined in this way is consistent with prior epitope mapping studies and includes several residues that were not previously identified. The hydrogen exchange labeling approach can be used to map binding sites on small proteins in antibody-antigen complexes and may be applicable to protein-protein and protein-ligand interactions in general.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432411/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3432411/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paterson, Y -- Englander, S W -- Roder, H -- GM 31847/GM/NIGMS NIH HHS/ -- GM 35926/GM/NIGMS NIH HHS/ -- R01 GM031847/GM/NIGMS NIH HHS/ -- S07-RR-05415-28/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1990 Aug 17;249(4970):755-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, University of Pennsylvania, Philadelphia 19104.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1697101" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antibodies, Monoclonal/immunology/metabolism ; Antigen-Antibody Complex ; *Binding Sites, Antibody ; Chemical Phenomena ; Chemistry ; Cytochrome c Group/*immunology ; Deuterium ; Epitopes/immunology ; Hydrogen/*metabolism ; Hydrogen Bonding ; Kinetics ; *Magnetic Resonance Spectroscopy ; Molecular Structure ; Protein Conformation
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1991-07-12
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Baskin, Y -- New York, N.Y. -- Science. 1991 Jul 12;253(5016):140-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1853198" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Academies and Institutes ; Biology ; California ; Chemical Phenomena ; Chemistry ; Research Support as Topic
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 12
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1990-02-23
    Beschreibung: Reactive or unstable molecules are key intermediates in many important reactions, but can be difficult to prepare for experimental studies. Species with missing (:CH-OH) or extra (H3) substituents can often be formed conveniently in the gas phase by neutralizing a beam of a more stable ionic counterpart (CH = O+H, H3+). Reionization of the neutral after approximately 10(-6) seconds tests its stability, whereas its unimolecular chemistry can be probed by preparing it with different amounts of internal energy. The resulting neutral products are reionized and mass analyzed. Isomers are then characterized by ion dissociation and a third mass-analysis step. Many unusual molecules have been characterized with this technique, which can also be used to probe complex unimolecular chemistry, such as that of cyclobutadiene and ethylene oxide.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McLafferty, F W -- GM-16609/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 Feb 23;247(4945):925-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cornell University, Baker Laboratory, Ithaca, NY 14853-1301.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2305261" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Butadienes ; Chemical Phenomena ; Chemistry ; Ethylene Oxide ; Free Radicals ; Hydrocarbons ; *Ions ; *Mass Spectrometry ; Methane/analogs & derivatives ; Molecular Structure ; Thermodynamics
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 13
    Publikationsdatum: 1990-05-18
    Beschreibung: The immunosuppressive agents cyclosporin A and FK506 inhibit the transcription of early T cell activation genes. The binding proteins for cyclosporin A and FK506, cyclophilin and FKBP, respectively, are peptidyl-prolyl-cis-trans isomerases, or rotamases. One proposed mechanism for rotamase catalysis by cyclophilin involves a tetrahedral adduct of an amide carbonyl and an enzyme-bound nucleophile. The potent FKBP rotamase inhibitor FK506 has a highly electrophilic carbonyl that is adjacent to an acyl-pipicolinyl (homoprolyl) amide bond. Such a functional group would be expected to form a stabilized, enzyme-bound tetrahedral adduct. Spectroscopic and chemical evidence reveals that the drug interacts noncovalently with its receptor, suggesting that the alpha-keto amid of FK506 serves as a surrogate for the twisted amide of a bound peptide substrate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rosen, M K -- Standaert, R F -- Galat, A -- Nakatsuka, M -- Schreiber, S L -- GM-38627/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 May 18;248(4957):863-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Harvard University, Cambridge, MA 02138.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1693013" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amino Acid Isomerases/*antagonists & inhibitors ; Anti-Bacterial Agents/metabolism/*pharmacology ; Binding Sites ; Carrier Proteins/antagonists & inhibitors/metabolism ; Chemical Phenomena ; Chemistry ; Cloning, Molecular ; Cyclosporins/metabolism/pharmacology ; Escherichia coli/genetics ; Gene Expression ; *Immunosuppressive Agents ; Lymphocyte Activation ; Magnetic Resonance Spectroscopy ; Molecular Structure ; Peptidylprolyl Isomerase ; Recombinant Proteins ; T-Lymphocytes/immunology ; Tacrolimus
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 14
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1991-05-03
    Beschreibung: Immunochemistry has historically focused on the nature of antigenicity and antibody-antigen recognition. However, in the last 5 years, the field of immunochemistry has taken a new direction. With the aid of mechanistic and synthetic chemistry, the vast network of molecules and cells of the immune system has been tapped to produce antibodies with a new function--catalytic antibodies. Because antibodies can be generated that selectively bind almost any molecule of interest, this new technology offers the potential to tailor-make highly selective catalysts for applications in biology, chemistry, and medicine. In addition, catalytic antibodies provide fundamental insight into important aspects of biological catalysis, including the importance of transition-state stabilization, proximity effects, general acid and base catalysts, electrophilic and nucleophilic catalysis, and strain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lerner, R A -- Benkovic, S J -- Schultz, P G -- New York, N.Y. -- Science. 1991 May 3;252(5006):659-67.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Scripps Research Institute, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2024118" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Antibodies/chemistry/immunology/metabolism ; Antibodies, Monoclonal/immunology/metabolism ; Antibody Specificity ; Antigens/chemistry/immunology/metabolism ; Binding Sites, Antibody ; *Catalysis ; Chemical Phenomena ; Chemistry ; Haptens ; Hydrogen-Ion Concentration ; Hydrolysis ; Metals ; Molecular Conformation ; Recombinant Proteins ; Thermodynamics ; Zinc
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    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 15
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2011-10-14
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lehn, Jean-Marie -- England -- Nature. 2011 Oct 12;478(7368):S8-9. doi: 10.1038/478S8a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21993827" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; Exobiology ; Hippocratic Oath ; Knowledge ; Motivation ; *Nobel Prize ; *Research Personnel/ethics/psychology/standards
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 16
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2011-04-23
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Van Noorden, Richard -- England -- Nature. 2011 Apr 21;472(7343):270-1. doi: 10.1038/472270a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21512544" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Accidents ; Chemistry ; *Laboratories ; Occupational Health/*statistics & numerical data ; Research Personnel ; Students ; Universities
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    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 17
    Publikationsdatum: 2013-04-05
    Beschreibung: The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Tianqi -- Patz, Aaron -- Mouchliadis, Leonidas -- Yan, Jiaqiang -- Lograsso, Thomas A -- Perakis, Ilias E -- Wang, Jigang -- England -- Nature. 2013 Apr 4;496(7443):69-73. doi: 10.1038/nature11934.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23552945" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Biology ; Chemistry ; Circular Dichroism ; Electronics ; Iron/chemistry ; *Magnetic Phenomena ; Magnetics ; Optics and Photonics ; Photosynthesis ; *Quantum Theory ; Temperature ; Time Factors
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    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 18
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2013-12-20
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGee, Harold -- England -- Nature. 2013 Dec 19;504(7480):372-4. doi: 10.1038/504372a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24352277" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Aspergillus/metabolism ; Beer/microbiology ; Cheese/microbiology ; Chemistry ; *Fermentation ; *Food Technology ; Microbiology ; Saccharomyces cerevisiae/metabolism
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  • 19
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2013-10-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shechtman, Dan -- England -- Nature. 2013 Oct 17;502(7471):S54-5. doi: 10.1038/502S54a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24132333" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; Developing Countries ; Education/statistics & numerical data ; Entrepreneurship/*economics ; Leadership ; Nobel Prize ; Research ; Technology/*economics
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  • 20
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2014-12-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2014 Dec 18;516(7531):S72. doi: 10.1038/516S72a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25517243" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; China ; Cities ; Periodicals as Topic/statistics & numerical data ; Research/standards/*statistics & numerical data/trends ; Universities/statistics & numerical data
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  • 21
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2010-10-15
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kroto, Harold W -- England -- Nature. 2010 Oct 14;467(7317):S13. doi: 10.1038/467S13a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20944613" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; Conservation of Energy Resources/methods ; Freedom ; Interdisciplinary Communication ; *Nobel Prize ; Nuclear Fission ; Peer Review, Research ; Private Sector/economics ; Public Opinion ; Research/economics/education ; *Research Personnel/economics/education ; Research Support as Topic/economics/methods
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    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 22
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2014-12-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2014 Dec 18;516(7531):S69. doi: 10.1038/516S69a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25517242" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; China ; Cities ; Periodicals as Topic/statistics & numerical data ; Physics ; Research/standards/*statistics & numerical data/trends ; Universities/statistics & numerical data
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    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 23
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1994-04-01
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Flam, F -- New York, N.Y. -- Science. 1994 Apr 1;264(5155):32-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8140417" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): AIDS Vaccines/*chemical synthesis/immunology ; Animals ; Antibodies, Viral/biosynthesis ; Cellobiose ; Chemistry ; HIV Antibodies/biosynthesis ; Herpesvirus 4, Human/*immunology ; Societies, Scientific ; *Vaccines, Synthetic/immunology ; Viral Proteins ; Viral Vaccines/*chemical synthesis/immunology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 24
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1992-02-28
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crease, R P -- New York, N.Y. -- Science. 1992 Feb 28;255(5048):1065-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1546307" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Canada ; Chemical Phenomena ; Chemistry ; Humans ; Sociology ; *Women, Working
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 25
    Publikationsdatum: 2011-07-30
    Beschreibung: The ocean is an important global source of nitrous oxide (N(2)O), a greenhouse gas that contributes to stratospheric ozone destruction. Bacterial nitrification and denitrification are thought to be the primary sources of marine N(2)O, but the isotopic signatures of N(2)O produced by these processes are not consistent with the marine contribution to the global N(2)O budget. Based on enrichment cultures, we report that archaeal ammonia oxidation also produces N(2)O. Natural-abundance stable isotope measurements indicate that the produced N(2)O had bulk delta(15)N and delta(18)O values higher than observed for ammonia-oxidizing bacteria but similar to the delta(15)N and delta(18)O values attributed to the oceanic N(2)O source to the atmosphere. Our results suggest that ammonia-oxidizing archaea may be largely responsible for the oceanic N(2)O source.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Santoro, Alyson E -- Buchwald, Carolyn -- McIlvin, Matthew R -- Casciotti, Karen L -- New York, N.Y. -- Science. 2011 Sep 2;333(6047):1282-5. doi: 10.1126/science.1208239. Epub 2011 Jul 28.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. asantoro@umces.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21798895" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Ammonia/*metabolism ; Archaea/enzymology/*metabolism ; Bacteria/metabolism ; Culture Media ; Denitrification ; Linear Models ; Molecular Sequence Data ; Nitrification ; Nitrogen Isotopes ; Nitrous Oxide/*metabolism ; Oxidation-Reduction ; Oxygen Isotopes ; Pacific Ocean ; Seawater/*microbiology
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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: 2014-01-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brenner, Sydney -- New York, N.Y. -- Science. 2014 Jan 17;343(6168):262. doi: 10.1126/science.1249912.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore, 138673.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24436413" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; England ; History, 20th Century ; History, 21st Century ; Molecular Biology/*history ; *Nobel Prize ; Sequence Analysis, DNA/*history/methods
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 27
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-08-14
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klotz, I M -- Haney, D N -- King, L C -- New York, N.Y. -- Science. 1981 Aug 14;213(4509):724-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7256275" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Anemia, Sickle Cell/*drug therapy ; Aspirin/analogs & derivatives/therapeutic use ; Chemical Phenomena ; Chemistry ; *Hemoglobin, Sickle ; Humans ; Protein Binding/drug effects ; Protein Conformation ; Salicylates/*therapeutic use ; Solubility ; Structure-Activity Relationship
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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: 1982-09-10
    Beschreibung: Alkyl-Substituted gamma-butyrolactones were synthesized and tested for their convulsant and anticonvulsant actions in mice and guinea pigs. The alpha-substituted compounds, alpha, alpha-dimethyl-, and alpha-ethyl-alpha-methyl-gamma-butyrolactone were anticonvulsant compounds with a spectrum of activity similar to that of ethosuximide. In contrast, beta-substituted compounds were convulsant agents similar to picrotoxinin. The alpha-substituted-gama-butyrolactones represent a new class of anticonvulsant drug with experimental and clinical potential.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klunk, W E -- McKeon, A -- Covey, D F -- Ferrendelli, J A -- GM-07200/GM/NIGMS NIH HHS/ -- GM-24483/GM/NIGMS NIH HHS/ -- NS-14834/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1982 Sep 10;217(4564):1040-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6810462" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *4-Butyrolactone/analogs & derivatives/*therapeutic use/toxicity ; Animals ; *Anticonvulsants ; Chemical Phenomena ; Chemistry ; Convulsants ; Drug Evaluation, Preclinical ; Electroencephalography ; Epilepsy, Absence/drug therapy ; Ethosuximide/pharmacology ; *Furans/*therapeutic use ; Guinea Pigs ; Mice ; Structure-Activity Relationship ; Trimethadione/pharmacology
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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: 1983-05-06
    Beschreibung: Crystalline cholesterol undergoes a phase transition a few degrees below human body temperature. The high-temperature form has an unusually complex structure with 16 independent molecules. In the transition two molecules change side chain conformation, four reorient about their long axes, and ten remain unchanged. The transition mechanism implies relatively nonspecific intermolecular interactions, qualitatively consistent with the behavior of cholesterol in biomembranes. The transition preserves a remarkably closely obeyed pseudosymmetry present in the structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hsu, L Y -- Nordman, C E -- GM15259/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 May 6;220(4597):604-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836303" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Body Temperature ; Chemical Phenomena ; Chemistry ; *Cholesterol ; Crystallization ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Conformation
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 30
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-07-20
    Beschreibung: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
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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: 1983-05-06
    Beschreibung: Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Samuelsson, B -- New York, N.Y. -- Science. 1983 May 6;220(4597):568-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6301011" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Arachidonic Acids/metabolism/pharmacology/physiology ; Bronchi/drug effects ; Cats ; Chemical Phenomena ; Chemistry ; Cricetinae ; Guinea Pigs ; Haplorhini ; Humans ; Hypersensitivity, Immediate/*physiopathology ; Inflammation/*physiopathology ; Leukocytes/drug effects/metabolism ; Leukotriene B4/pharmacology/*physiology ; Mice ; Microcirculation/drug effects ; Rabbits ; Rats ; SRS-A/*physiology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 32
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-01-20
    Beschreibung: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 33
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-10-19
    Beschreibung: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 34
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-08-31
    Beschreibung: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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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: 1984-03-09
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 36
    Publikationsdatum: 1984-10-19
    Beschreibung: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 37
    Publikationsdatum: 1984-08-31
    Beschreibung: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
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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: 1984-05-11
    Beschreibung: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 39
    Publikationsdatum: 1983-12-16
    Beschreibung: Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shimomura, K -- Mullinix, M G -- Kakunaga, T -- Fujiki, H -- Sugimura, T -- New York, N.Y. -- Science. 1983 Dec 16;222(4629):1242-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6316505" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Caenorhabditis elegans Proteins ; Carcinogens/*pharmacology ; Carrier Proteins ; Cell Line ; Cell Transformation, Neoplastic/*drug effects ; Chemical Phenomena ; Chemistry ; DNA/biosynthesis ; Epidermal Growth Factor/metabolism ; Lactones/analysis/*pharmacology ; *Lyngbya Toxins ; Mice ; Phorbol 12,13-Dibutyrate ; Phorbol Esters/metabolism ; *Protein Kinase C ; Receptor, Epidermal Growth Factor ; Receptors, Cell Surface/metabolism ; *Receptors, Drug ; Structure-Activity Relationship
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 40
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    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-03-16
    Beschreibung: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 41
    Publikationsdatum: 1984-11-16
    Beschreibung: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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  • 42
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-06-15
    Beschreibung: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 43
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-11-02
    Beschreibung: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 44
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1983-09-09
    Beschreibung: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Takeda, Y -- Ohlendorf, D H -- Anderson, W F -- Matthews, B W -- GM20066/GM/NIGMS NIH HHS/ -- GM28138/GM/NIGMS NIH HHS/ -- GM30894/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 Sep 9;221(4615):1020-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6308768" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; *DNA Helicases ; DNA-Binding Proteins ; Escherichia coli/genetics ; Gene Expression Regulation ; Models, Chemical ; Protein Conformation
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 45
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-06-08
    Beschreibung: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 46
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1980-01-04
    Beschreibung: In concentrates of water produced in a laboratory simulation of a drinking water treatment process, direct-acting, nonvolatile mutagens were readily detected by means of the Ames Salmonella test. The mutagens were shown to be produced by the chlorination process. Treatment of the water with chloramine resulted in less mutagenic activity than treatment with free chlorine. Dechlorination of drinking water with sulfite sharply reduced the mutagenic activity. Treatment with sulfur dioxide is proposed as an effective, inexpensive method of reducing the direct-acting mutagenic activity of drinking water and of aqueous industrial effluents.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cheh, A M -- Skochdopole, J -- Koski, P -- Cole, L -- New York, N.Y. -- Science. 1980 Jan 4;207(4426):90-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6985746" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; Chloramines ; Chlorine ; Mutagens/*analysis ; Salmonella typhimurium/genetics ; Sulfites ; Water Pollutants/*analysis ; Water Pollutants, Chemical/*analysis ; Water Supply/*analysis
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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: 1981-10-16
    Beschreibung: The DNA/RNA Synthesizer provides a complete and automated procedure for the synthesis of DNA sequences. Each base unit is added in a 30-minute cycle, permitting a tetradecamer to be constructed in 6 1/2 hours. The complete procedure is described, including a practical procedure for isolation and purification of the desired DNA sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Alvarado-Urbina, G -- Sathe, G M -- Liu, W C -- Gillen, M F -- Duck, P D -- Bender, R -- Ogilvie, K K -- New York, N.Y. -- Science. 1981 Oct 16;214(4518):270-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6169150" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Automation ; Chemical Phenomena ; Chemistry ; DNA/*chemical synthesis ; *Genes, Synthetic ; RNA/*chemical synthesis ; Solubility
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 48
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-05-15
    Beschreibung: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Austin, P R -- Brine, C J -- Castle, J E -- Zikakis, J P -- New York, N.Y. -- Science. 1981 May 15;212(4496):749-53.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7221561" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animal Feed ; Animals ; Cheese ; Chemical Phenomena ; Chemistry ; Chickens ; *Chitin ; Crystallography ; Lactose/metabolism ; Proteins/analysis ; Sutures ; *Technology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 49
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-12-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gilbert, W -- New York, N.Y. -- Science. 1981 Dec 18;214(4527):1305-12.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7313687" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Base Sequence ; Chemical Phenomena ; Chemistry ; DNA/*genetics ; Eukaryotic Cells/physiology ; *Genes ; Hydrazines ; Lac Operon ; Methylation ; Prokaryotic Cells/physiology ; Sulfuric Acid Esters
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 50
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1982-07-09
    Beschreibung: A new process has been developed which is called "Boradeption" to signify boronic acid--dependent phase transfer of water-insoluble agents. Highly fluorescent boronic acid dervatives, FluoroBoras, are solubilized with a physiologically compatible carrier buffer containing a receptor group for boronate adduct formation. The system can be used to stain living cells. In another variation of the Boradeption concept, an insoluble reporter molecule containing a boronate receptor is solubilized with a carrier buffer containing a boronic acid functional group. The boronate-receptor complexes, which are in dynamic equilibrium, can be designed as vital stains and reagents for a variety of biological and medical applications.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gallop, P M -- Paz, M A -- Henson, E -- AG-00376-07/AG/NIA NIH HHS/ -- HL-20764-04A1/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 9;217(4555):166-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6178158" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Biological Transport ; *Boron Compounds/therapeutic use ; *Boronic Acids/therapeutic use ; *Cell Membrane Permeability ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Chromogenic Compounds/metabolism ; Cricetinae ; Fibroblasts ; Fluorescent Dyes/metabolism ; Humans ; Rats ; Staining and Labeling
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 51
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-12-11
    Beschreibung: The scrapie agent causes a degenerative nervous system disease in sheep and goats. Studies with extensively purified preparations demonstrated that the agent contains a protein that is required for infectivity. Chemical modification of the scrapie agent by diethyl pyrocarbonate reduced the titer 1000-fold. Exposure of the inactivated agent to hydroxylamine, a strong nucleophile, resulted in complete restoration of infectivity. Presumably, nucleophilic residues within a scrapie agent protein undergo carbethoxylation on reaction with diethyl pyrocarbonate, and subsequent addition of hydroxylamine displaces these carbethoxy groups.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McKinley, M P -- Masiarz, F R -- Prusiner, S B -- NS14069/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 11;214(4526):1259-61.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6795721" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Biological Assay ; Brain/microbiology ; Chemical Phenomena ; Chemistry ; Cricetinae ; Diethyl Pyrocarbonate/pharmacology ; Histidine/pharmacology ; *Prions ; Ribonucleases/pharmacology ; Serum Albumin, Bovine/pharmacology ; Viral Proteins/*isolation & purification/pharmacology
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    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 52
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-01-30
    Beschreibung: The incubation of lens proteins with reducing sugars leads to the formation of fluorescent yellow pigments and cross-like similar to those reported in aging and cataractous human lenses. Called nonenzymatic browning or the Maillard reaction, this aging process also occurs in stored foods. Reducing sugars condense with the free amino group of proteins, then rearrange and dehydrate to form unsaturated pigments and cross-linked products. Although most proteins in living systems turn over with sufficient rapidity to avoid nonenzymatic browning, some, such as lens crystallins and skin collagen, are exceptionally long-lived and may be vulnerable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Monnier, V M -- Cerami, A -- AM 19655/AM/NIADDK NIH HHS/ -- New York, N.Y. -- Science. 1981 Jan 30;211(4481):491-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6779377" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Aging ; Animals ; Cattle ; Chemical Phenomena ; Chemistry ; *Crystallins ; Diabetes Mellitus/physiopathology ; Glucose ; Glucosephosphates ; In Vitro Techniques ; Lysine ; *Proteins ; Spectrophotometry, Ultraviolet
    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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  • 53
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1981-03-13
    Beschreibung: Great advances have been made in fundamental scientific research in recent years. The new knowledge gathered, in addition to deepening our understanding of the physical universe, contributes a range of abilities and opportunities to society that would not otherwise be available. Much research that may be called applied because it addresses needs of society is quite fundamental in character, and support of such research at the National Science Foundation is to be handled in tandem by the research directorates. Other areas that require a refocusing of support are engineering science and education, at all levels, in science and engineering. Increasing our strength in these areas is essential to achieve our national economic, social, and political goals. Steps are being taken by the National Science Foundation to make its structure better able to deal with engineering and applied research and to provide greater mutual reinforcement between applied and basic research.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slaughter, J B -- New York, N.Y. -- Science. 1981 Mar 13;211(4487):1131-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7466384" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Cell Biology ; Chemical Phenomena ; Chemistry ; *Forecasting ; Geological Phenomena ; Geology ; *Government Agencies ; Molecular Biology ; Neurochemistry ; Physical Phenomena ; Physics ; Research Support as Topic ; United States
    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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  • 54
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1982-12-10
    Beschreibung: The discovery that cis-diamminedichloroplatinum(II) (cis-DDP) has clinically useful antitumor properties and can form platinum blues spawned an extensive investigation of its chemistry in water. Several new molecules have been synthesized, some rather old ones have been characterized for the first time, and clues have begun to emerge about the chemical interaction of cis-DDP with its likely biological target, DNA.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lippard, S J -- New York, N.Y. -- Science. 1982 Dec 10;218(4577):1075-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6890712" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemical Phenomena ; Chemistry ; *Cisplatin ; *Dna ; Hydrolysis ; Pigments, Biological
    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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  • 55
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1982-12-03
    Beschreibung: The visual response is initiated by light reception and transduction into chemical and electrical energy in the outer-segment membranes of rod and cone cells. Recent research on the molecular events controlled by light has clarified the roles of some of the rod outer-segment biomolecules. These developments and the current unresolved questions are described.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Brien, D F -- New York, N.Y. -- Science. 1982 Dec 3;218(4576):961-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6291153" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Blood Proteins/metabolism ; Calcium/metabolism ; Chemical Phenomena ; Chemistry ; Enzyme Activation ; Enzymes/metabolism ; GTP-Binding Proteins ; Light ; Membranes/metabolism ; Models, Biological ; Phosphoric Diester Hydrolases/biosynthesis ; Photoreceptor Cells/*metabolism ; Receptors, Cell Surface/metabolism ; Rhodopsin/metabolism ; Rod Cell Outer Segment/*metabolism ; Vision, Ocular/*physiology
    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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  • 56
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1983-06-10
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krenitsky, T A -- Beauchamp, L -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6857236" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acyclovir/metabolism ; *Antiviral Agents/metabolism ; Chemical Phenomena ; Chemistry ; Humans ; Vidarabine/metabolism
    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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  • 57
    Publikationsdatum: 1983-05-06
    Beschreibung: Resonance Raman spectra of photolyzed carbonmonoxyhemoglobin obtained with 10-nanosecond pulses are compared with the spectra of photolyzed carbonmonoxyhemoglobin stabilized at 80 K. In comparing the deoxy with the photodissociated species, the changes in the Raman spectra are the same for these two experimental regimes. These results show that at ambient and cryogenic temperatures the heme pocket in liganded hemoglobin is significantly different from that of deoxyhemoglobin. It is concluded that measurements of the properties of intermediate species from photodissociated hemoglobin stabilized at low temperatures can be used to probe the short-lived metastable forms of hemoglobin present after photodissociation under biologically relevant solution conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ondrias, M R -- Friedman, J M -- Rousseau, D L -- New York, N.Y. -- Science. 1983 May 6;220(4597):615-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836305" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carboxyhemoglobin ; Chemical Phenomena ; Chemistry ; Freezing ; *Hemoglobins ; Humans ; Ligands ; Spectrum Analysis, Raman ; 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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  • 58
    Publikationsdatum: 1983-04-15
    Beschreibung: Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rice, K C -- Jacobson, A E -- Burke, T R Jr -- Bajwa, B S -- Streaty, R A -- Klee, W A -- New York, N.Y. -- Science. 1983 Apr 15;220(4594):314-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6132444" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Alkylation ; Animals ; Benzimidazoles/analogs & derivatives/metabolism ; Brain/physiology ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Enkephalin, Methionine/analogs & derivatives/metabolism ; Fentanyl/analogs & derivatives/metabolism ; *Isothiocyanates ; Ligands ; Rats ; Receptors, Opioid/*metabolism/physiology ; Thebaine/analogs & derivatives/pharmacology
    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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  • 59
    Publikationsdatum: 1980-10-01
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bumb, R R -- Crummett, W B -- Cutie, S S -- Gledhill, J R -- Hummel, R H -- Kagel, R O -- Lamparski, L L -- Luoma, E V -- Miller, D L -- Nestrick, T J -- Shadoff, L A -- Stehl, R H -- Woods, J S -- New York, N.Y. -- Science. 1980 Oct;210(4468):385-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6159682" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Air Pollutants/analysis ; Chemical Phenomena ; Chemistry ; Chromatography, High Pressure Liquid ; *Dioxins/analysis ; *Fires ; Power Plants ; Smoke/analysis ; Soil Pollutants/analysis ; Tetrachlorodibenzodioxin/analysis ; Vehicle Emissions/analysis ; Water Pollutants, Chemical/analysis
    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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  • 60
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1984-05-25
    Beschreibung: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
    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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  • 61
    Publikationsdatum: 2021-05-19
    Beschreibung: Daily topical application of the aqueous ethanolic extract of the marine sea grass, Thalassia testudinum, on mice skin exposed to UVB radiation resulted in a dose dependent recovery of the skin macroscopic alterations over a 6-day period. Maximal effect (90%) occurred at a dose of 240 μg/cm2, with no additional effects at higher doses. Bioassay-guided fractionation of the plant extract resulted in the isolation of thalassiolin B (1). Topical application of 1 (240 μg/cm2) markedly reduces skin UVB-induced damage. In addition, thalassiolin B scavenged 2,2-diphenyl-2-picrylhydrazyl radical with an EC50=100 μg/ml. These results suggest that thalassiolin B is responsible for the skin regenerating effects of the crude extract of T. testudinum
    Beschreibung: Published
    Beschreibung: Flavonoids, Thalassiolin B, DPPH scavenged, antioxidant activity, Skin regenerating activity, Thalassia testudinum
    Schlagwort(e): Chemistry ; Pharmacology ; Chemistry ; Pharmacology
    Repository-Name: AquaDocs
    Materialart: Journal Contribution
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  • 62
    Publikationsdatum: 2021-05-19
    Beschreibung: Bioguided fractionation of Agelas cerebrum crude extract resulted in isolation of four bromopyrrole and four bromopyrrole aminoimidazole alkaloids, identified as 5-bromopyrrole-2-carboxylic acid (1), 4-bromopyrrole-2-carboxylic acid (2), 3,4-bromopyrrole-2-carboxylic acid (3), 4,5-bromopyrrole-2-carboxylic acid (4), oroidin (5), bromoageliferin (6), dibromoageliferin (7) and dibromosceptrin (8) on the basis of spectroscopic data analyses (UV, IR, HRMS, 1D and 2D NMR) and comparison with literature data. This is the first report of compounds 2 and 3 in a marine sponge belonging to the Agelas genus and the first evidence of the presence of 1 from a natural source.
    Beschreibung: Published
    Beschreibung: Agelas cerebrum, bromopyrrole alkaloids, antitumoral, antiprotozoal activity
    Schlagwort(e): Chemistry ; Alkaloids ; Sponges ; Alkaloids ; Sponges ; Chemistry
    Repository-Name: AquaDocs
    Materialart: Journal Contribution
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    Publikationsdatum: 2021-05-19
    Beschreibung: La velocidad de descomposición de tres fenólicos, el p-hidroxibenzoico, el protocatecúico y el gálico, los cuales se diferencian en el número de grupos OH, fue investigada en el suelo. Con el aumento de grupos OH aumenta también la velocidad de descomposición microbial. El ácido gálico se descompone más rápido que el protocatecúico y este a su vez más rápido que el phidroxibenzoico.
    Beschreibung: The rate of decomposition of the three phenolics, p-hydroxybenzoic acid, protocatechuic acid and gallic acid, whose difference is the amount of OH-groups, was investigated in the soil. With the increase in OH-groups increases the rate of microbial decomposition. Gallic acid decomposes faster than protocatecuic acid and this again faster than p-hydroxybenzoic acid.
    Beschreibung: Published
    Schlagwort(e): Chemical decomposition ; OH Groups ; Microbes ; Phenols ; Chemistry ; Phenols ; Chemistry
    Repository-Name: AquaDocs
    Materialart: Journal Contribution
    Format: pp.141-143
    Standort Signatur Erwartet Verfügbarkeit
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  • 64
    facet.materialart.
    Unbekannt
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-05-25
    Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013
    Beschreibung: The stable isotopes, δ15N and δ18O, of nitrite and nitrate can be powerful tools used to interpret nitrogen cycling in the ocean. In order to interpret isotope profiles, the isotope systematics of each process involved must be known. This thesis describes numerous experiments using both cultures of nitrifying organisms as well as natural seawater samples to determine the oxygen isotope systematics of nitrification. These experiments show that the accumulation of nitrite has a large effect on the resulting δ18ONO3. Also, the δ18ONO2 was developed as a unique tracer because it undergoes abiotic equilibration with water δ18O at a predictable rate based on pH, temperature and salinity. This rate, its dependencies, and how the δ18ONO2 values can be used as not only biological source indicators but also indicators of age are described. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets multi-isotope nitrate and nitrite profiles in the Costa Rica Upwelling Dome using a simple 1D model. Overall, this thesis describes new nitrogen and oxygen isotopic tracers and uses them to elucidate the complicated nitrogen biogeochemistry in oxygen deficient zones.
    Beschreibung: The work described in this thesis was funded by the National Science Foundation grants OCE 05-26277 and OCE 09-610998 to KLC, the MIT Presidential Fellowship, the WHOI Coastal Ocean Institute, the WHOI Academic Programs Office, and the MIT Houghton fund.
    Schlagwort(e): Nitrification ; Nitrogen fixation ; Melville (Ship) Cruise MV1008 ; Melville (Ship) Cruise MV1104 ; Roger Revelle (Ship) Cruise
    Repository-Name: Woods Hole Open Access Server
    Materialart: Thesis
    Format: application/pdf
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  • 65
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Ecological Society of America, 2006. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 16 (2006): 2153–2167, doi:10.1890/1051-0761(2006)016[2153:NONADN]2.0.CO;2.
    Beschreibung: The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarém, Pará, and Nova Vida Farm, Rondônia. The 15N enrichment factors for nitrification and denitrification differ with soil texture and site: −111‰ ± 12‰ and −31‰ ± 11‰ for a clay-rich Oxisol (TNF), −102‰ ± 5‰ and −45‰ ± 5‰ for a sandier Ultisol (TNF), and −10.4‰ ± 3.5‰ (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (δ15Nα − δ15Nβ, where α indicates the central nitrogen atom and β the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2‰ ± 8.4‰ and 31.6‰ ± 8.1‰, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different 15N site preference fingerprints. Our data set strongly suggests that N2O isotopomers can be used in concert with traditional N2O stable isotope measurements as constraints to differentiate microbial N2O processes in soil and will contribute to interpretations of the isotopic site preference N2O values found in the free troposphere.
    Beschreibung: This work was funded by the National Science Foundation (SET, award #ATM-9905784; SCT, award #EAR- 0312004). We also received support from a National Science Foundation Major Research Instrumentation award (SCT, #ATM-9871077) and an instrumentation award to the University of California–Irvine from the W. M. Keck Foundation.
    Schlagwort(e): Amazon forest soils ; Denitrification ; Isotopic enrichment factors ; Isotopomers ; Nitrification ; Nitrous oxide ; Site preference
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 66
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Ecological Society of America, 2005. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Monographs 75 (2005): 139–157, doi:10.1890/04-0988.
    Beschreibung: Isotope pool dilution studies are increasingly reported in the soils and ecology literature as a means of measuring gross rates of nitrogen (N) mineralization, nitrification, and inorganic N assimilation in soils. We assembled data on soil characteristics and gross rates from 100 studies conducted in forest, shrubland, grassland, and agricultural systems to answer the following questions: What factors appear to be the major drivers for production and consumption of inorganic N as measured by isotope dilution studies? Do rates or the relationships between drivers and rates differ among ecosystem types? Across a wide range of ecosystems, gross N mineralization is positively correlated with microbial biomass and soil C and N concentrations, while soil C:N ratio exerts a negative effect on N mineralization only after adjusting for differences in soil C. Nitrification is a log-linear function of N mineralization, increasing rapidly at low mineralization rates but changing only slightly at high mineralization rates. In contrast, NH4+ assimilation by soil microbes increases nearly linearly over the full range of mineralization rates. As a result, nitrification is proportionately more important as a fate for NH4+ at low mineralization rates than at high mineralization rates. Gross nitrification rates show no relationship to soil pH, with some of the fastest nitrification rates occurring below pH 5 in soils with high N mineralization rates. Differences in soil organic matter (SOM) composition and concentration among ecosystem types influence the production and fate of mineralized N. Soil organic matter from grasslands appears to be inherently more productive of ammonium than SOM from wooded sites, and SOM from deciduous forests is more so than SOM in coniferous forests, but differences appear to result primarily from differing C:N ratios of organic matter. Because of the central importance of SOM characteristics and concentrations in regulating rates, soil organic matter depletion in agricultural systems appears to be an important determinant of gross process rates and the proportion of NH4+ that is nitrified. Addition of 15N appears to stimulate NH4+ consumption more than NO3− consumption processes; however, the magnitude of the stimulation may provide useful information regarding the factors limiting microbial N transformations.
    Beschreibung: This research was supported by a grant from The Andrew W. Mellon Foundation to The Ecosystems Center of the Marine Biological Laboratory, Woods Hole, Massachusetts, and by a grant from the National Science Foundation to Utah State University, Logan, Utah.
    Schlagwort(e): Ammonium ; N assimilation ; N immobilization ; N-15 isotope dilution ; N mineralization ; Nitrate ; Nitrification ; Soil carbon ; Soil nitrogen ; Soil organic matter ; Soil pH
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 67
    facet.materialart.
    Unbekannt
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-05-25
    Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2011
    Beschreibung: Atmospheric nitrous oxide N2O concentrations have been rising steadily for the past century as a result of human activities. In particular, human perturbation of the nitrogen cycle has increased the N2O production rates of the two major sources of this greenhouse gas, soil and the ocean. Nitrification, and particularly ammonia oxidation, is one of the major processes that produces N2O in the ocean. In this thesis, a series of stable isotopic methods have been used to characterize the biogeochemical controls on N2O production by marine nitrification as well as the natural abundance stable isotopic signatures of N2O produced by marine nitrifiers. This thesis shows that in addition to chemical controls on N2O production rates such as oxygen (O2) and nitrite (NO-2) concentrations, there are also biological controls such as nitrifier cell abundances and coastal phytoplankton blooms that may influence N2O production by ammonia oxidizers as well. Ammonia oxidizers can produce N2O through two separate biochemical mechanisms that have unique isotopic signatures. Using culture- based measurements of these signatures, we conclude that one of these pathways, nitrifier- denitrification, may be a significant source of N2O produced in the South Atlantic Ocean and possibly the global ocean.
    Beschreibung: Funding for this work was provided by NSF/OCE 05-26277, the Andrew W. Mellon Founda- tion Awards for Innovative Research, the Cecil H. and Ida M. Green Technology Innovation Awards, and the W. M. Keck Foundation.
    Schlagwort(e): Nitrification ; Biogeochemistry ; Knorr (Ship : 1970-) Cruise KN192-05
    Repository-Name: Woods Hole Open Access Server
    Materialart: Thesis
    Format: application/pdf
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  • 68
    facet.materialart.
    Unbekannt
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-05-25
    Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1998
    Beschreibung: Planktonic protozoan grazers have the potential to significantly affect the chemistry of particle-associated trace metals. This is due both to the importance of protists as consumers of bacterial-sized particles, and to the unique low-pH, enzyme-rich microenvironment of the grazer food vacuole. This thesis examines the role of protozoan grazers in the marine geochemistry of strongly hydrolyzed, particle-reactive trace metals, in particular Th and Fe. A series of tracer experiments was carried out in model systems in order to determine the effect of grazer-mediated transformations on the chemical speciation and partitioning of radioisotopes C9Fe, 234Th, 51Cr) associated with prey cells. Results indicate that protozoan grazers are equally able to mobilize intracellular and extracellular trace metals. In some cases, protozoan regeneration of trace metals appears to lead to the formation of metal-organic complexes. Protozoan grazing may generate colloidal material that can scavenge trace metals and, via aggregation, lead to an increase in the metal/organic carbon ratio of aggregated particles. Model system experiments were also conducted in order to determine the effect of grazers on mineral phases, specifically colloidal iron oxide (ferrihydrite). Several independent techniques were employed, including size fractionation ors9Fe-labeled colloids, competitive ligand exchange, and iron-limited diatoms as "probes" for bioavailable Fe. Experimental evidence strongly suggests that protozoan grazing can affect the surface chemistry and increase the dissolution rate of iron oxide phases through phagotrophic ingestion. In further work on protozoan-mediated dissolution of colloidal Fe oxides, a novel tracer technique was developed based on the synthesis of colloidal ferrihydrite impregnated with 133Ba as an inert tracer. This technique was shown to be a sensitive, quantitative indicator for the extent of ferrihydrite dissolution/alteration by a variety of mechanisms, including photochemical reduction and ligand-mediated dissolution. In field experiments using this technique, grazing by naturally occuring protistan assemblages was shown to significantly enhance the dissolution rate of colloidal ferrihydrite over that in non-grazing controls. Laboratory and field results indicate that, when integrated temporally over the entire euphotic zone, protozoan grazing may equal or exceed photoreduction as a pathway for the dissolution of iron oxides.
    Beschreibung: This work was financially supported by a Department of Defense ONR-NDSEG Graduate Fellowship, Office ofNaval Research AASERT Award (N00014-94-1-0711), and the National Science Foundation EGB Program (OCE-9523910).
    Schlagwort(e): Protozoa ; Water chemistry ; Trace elements in water ; Marine zooplankton ; Chemistry
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  • 69
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Inter-Research, 2005. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 299 (2005): 123-135, doi:10.3354/meps299123.
    Beschreibung: Measurements of N losses by denitrification from saltmarsh sediments have proved difficult because of the importance of plant metabolism and tidal cycles to sediment N cycling. In vitro approaches often do not measure the dominant coupled nitrification–denitrification pathway and/or alter in situ plant growth and redox conditions. We developed an in situ 15NH4+ tracer approach to measure coupled nitrification–denitrification fluxes in an undisturbed New England Spartina alterniflora saltmarsh. The tracer was line-injected into sediments underlying natural S. alterniflora stands and in similar areas receiving long-term N amendment (up to 11.2 mol organic N m–2 yr–1 for 16 to 23 yr), and 15N retention and loss routes were followed for 1 to 5 d. Denitrification losses in unfertilized grass stands ranged from 0.4 to 11.9 mmol N m–2 d–1 (0.77 ± 0.18 mol N m–2 yr–1). Denitrification in unfertilized sediments remained low until late summer, but underwent a ca. 4-fold increase in August and September, although sediment temperatures and respiration rates were high throughout the summer. Plant N uptake may limit the availability of N to support denitrification during the early summer, and denitrification may be released from competition with plant uptake in late summer, when plant growth slows. Denitrification rates in fertilized areas ranged from 22 to 77 mmol N m–2 d–1 (10.5 ± 4.9 mol N m–2 yr–1), and denitrification was likely controlled by the availability of fertilizer N rather than by competition with plants, since N was added in excess of plant demand. Our results emphasize the importance of in situ measurements of denitrification in understanding the dynamics of saltmarsh N cycling.
    Beschreibung: This project was supported by funding from the Coastal Systems Program of the School for Marine Science and Technology, University of Massachusetts, and by the Education Department and the Reinhart Coastal Research Center of the Woods Hole Oceanographic Institution.
    Schlagwort(e): Saltmarsh ; Denitrification ; Nitrification ; N-15 ; Spartina alterniflora
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  • 70
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Progress In Oceanography 91 (2011): 545–560, doi:10.1016/j.pocean.2011.09.001.
    Beschreibung: In the seasonally stratified Gulf of Aqaba Red Sea, both NO2- release by phytoplankton and NH4+ oxidation by nitrifying microbes contributed to the formation of a primary nitrite maximum (PNM) over different seasons and depths in the water column. In the winter and during the days immediately following spring stratification, NO2- formation was strongly correlated (R2=0.99) with decreasing irradiance and chlorophyll, suggesting that incomplete NO3- reduction by light limited phytoplankton was a major source of NO2-. However, as stratification progressed, NO2- continued to be generated below the euphotic depth by microbial NH4+ oxidation, likely due to differential photoinhibition of NH4+ and NO2- oxidizing populations. Natural abundance stable nitrogen isotope analyses revealed a decoupling of the δ15N and δ18O in the combined NO3- and NO2- pool, suggesting that assimilation and nitrification were co-occurring in surface waters. As stratification progressed, the δ15N of particulate N below the euphotic depth increased from -5‰ to up to +20‰. N uptake rates were also influenced by light; based on 15N tracer experiments, assimilation of NO3-, NO2-, and urea was more rapid in the light (434±24, 94±17, and 1194±48 nmol N L-1 day-1 respectively) than in the dark (58±14, 29±14, and 476±31 nmol N L-1 day-1 respectively). Dark NH4+ assimilation was 314±31 nmol N L-1 day-1, while light NH4+ assimilation was much faster, resulting in complete consumption of the 15N spike in less than 7 hour from spike addition. The overall rate of coupled urea mineralization and NH¬4+ oxidation (14.1±7.6 nmol N L-1 day-1) was similar to that of NH¬4+ oxidation alone (16.4±8.1 nmol N L-1 day-1), suggesting that for labile dissolved organic N compounds like urea, mineralization was not a rate limiting step for nitrification. Our results suggest that assimilation and nitrification compete for NH4+ and that N transformation rates throughout the water column are influenced by light over diel and seasonal cycles, allowing phytoplankton and nitrifying microbes to contribute jointly to PNM formation. We identify important factors that influence the N cycle throughout the year, including light intensity, substrate availability, and microbial community structure. These processes could be relevant to other regions worldwide where seasonal variability in mixing depth and stratification influence the contributions of phytoplankton and non-photosynthetic microbes to the N cycle.
    Beschreibung: This research was supported under the North Atlantic Treaty Organization (NATO) Science for Peace Grant SfP 982161 to AP and AFP, a grant from the Koret Foundation to AP, a National Science Foundation Biological Oceanography grant to AP, the Israel Science Foundation grant 135/05 to AFP, and research grant 8330-06 from the Geological Society of America to KRMM.
    Schlagwort(e): Nitrogen cycle ; Primary nitrite maximum ; Nitrification ; Light ; Mixing and stratification ; Spring bloom
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  • 71
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Inter-Research, 2013. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 492 (2013): 1-8, doi:10.3354/meps10526.
    Beschreibung: Increasing atmospheric CO2 concentrations are causing decreased pH over vast expanses of the ocean. This decreasing pH may alter biogeochemical cycling of carbon and nitrogen via the microbial process of nitrification, a key process that couples these cycles in the ocean, but which is often sensitive to acidic conditions. Recent reports have indicated a decrease in oceanic nitrification rates under experimentally lowered pH. How the composition and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) assemblages respond to decreasing oceanic pH is unknown. We sampled microbes from 2 different acidification experiments and used a combination of qPCR and functional gene microarrays for the ammonia monooxygenase gene (amoA) to assess how acidification alters the structure of ammonia oxidizer assemblages. We show that despite widely different experimental conditions, acidification consistently altered the community composition of AOB by increasing the relative abundance of taxa related to the Nitrosomonas ureae clade. In one experiment, this increase was sufficient to cause an increase in the overall abundance of AOB. There were no systematic shifts in the community structure or abundance of AOA in either experiment. These different responses to acidification underscore the important role of microbial community structure in the resiliency of marine ecosystems.
    Beschreibung: NSF funding to B.B.W. supported the barrel experiments. Funding for the coral experiments came from NSF (GRF to M.H.; OCE-1041106), the Woods Hole Oceanographic Institution’s Ocean Life Institute, and the International Society for Reef Studies.
    Schlagwort(e): Ocean acidification ; Ammonia-oxidizing archaea ; Ammonia-oxidizing bacteria ; Nitrification
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  • 72
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © Inter-Research, 2009. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Aquatic Microbial Ecology 55 (2009): 189-201, doi:10.3354/ame01294.
    Beschreibung: Pelagic archaeal phylogenetic diversity and the potential for crenarchaeotal nitrification of Group 1.1a were determined in the rivers Rhine and Têt by 16S rRNA sequencing, catalyzed reported deposition-fluorescence in situ hybridization (CARD–FISH) and quantification of 16S rRNA and functional genes. Euryarchaeota were, for the first time, detected in temperate river water even though a net predominance of crenarchaeotal phylotypes was found. Differences in phylogenic distribution were observed between rivers and seasons. Our data suggest that a few archaeal phylotypes (Euryarchaeota Groups RC-V and LDS, Crenarchaeota Group 1.1a) are widely distributed in pelagic riverine environments whilst others (Euryarchaeota Cluster Sagma-1) may only occur seasonally in river water. Crenarchaeota Group 1.1a has recently been identified as a major nitrifier in the marine environment and phylotypes of this group were also present in both rivers, where they represented 0.3% of the total pelagic microbial community. Interestingly, a generally higher abundance of Crenarchaeota Group 1.1a was found in the Rhine than in the Têt, and crenarchaeotal ammonia monooxygenase gene (amoA) was also detected in the Rhine, with higher amoA copy numbers measured in February than in September. This suggests that some of the Crenarchaeota present in river waters have the ability to oxidize ammonia and that riverine crenarchaeotal nitrification of Group 1.1a may vary seasonally.
    Beschreibung: The present study is part of the Land–Ocean Interactions in the Coastal Zone (LOICZ) project supported by the Research Council for Earth and Life Science (ALW), with financial aid from the Netherlands Organisation for Scientific Research (NWO) (grant no. 014.27.003 to J.S.S.D.).
    Schlagwort(e): Archaea ; River ; Diversity ; Nitrification
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  • 73
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 105 (2011): 53-74, doi:10.1007/s10533-010-9540-4.
    Beschreibung: Human activities that modify land cover can alter the structure and biogeochemistry of small streams but these effects are poorly known over large regions of the humid tropics where rates of forest clearing are high. We examined how conversion of Amazon lowland tropical forest to cattle pasture influenced the physical and chemical structure, organic matter stocks and N cycling of small streams. We combined a regional ground survey of small streams with an intensive study of nutrient cycling using 15N additions in three representative streams: a second-order forest stream, a second-order pasture stream and a third-order pasture stream that were within several km of each other and on similar soils and landscape positions. Replacement of forest with pasture decreased stream habitat complexity by changing streams from run and pool channels with forest leaf detritus (50% cover) to grass-filled (63% cover) channel with runs of slow-moving water. In the survey, pasture streams consistently had lower concentrations of dissolved oxygen and nitrate (NO3-) compared with similar-sized forest streams. Stable isotope additions revealed that second-order pasture stream had a shorter NH4+ uptake length, higher uptake rates into organic matter components and a shorter 15NH4+ residence time than the second-order forest stream or the third-order pasture stream. Nitrification was significant in the forest stream (19% of the added 15NH4+) but not in the second-order pasture (0%) or third-order (6%) pasture stream. The forest stream retained 7% of added 15N in organic matter compartments and exported 53% (15NH4+ =34%; 15NO3- = 19%). In contrast, the second-order pasture stream retained 75% of added 15N, predominantly in grasses (69%) and exported only 4% as 15NH4+. The fate of tracer 15N in the third-order pasture stream more closely resembled that in the forest stream, with 5% of added N retained and 26% exported (15NH4+ = 9%; 15NO3- = 6%). These findings indicate that the widespread infilling by grass in small streams in areas deforested for pasture greatly increases the retention of inorganic N in the first- and second-order streams, which make up roughly three-fourths of total stream channel length in Amazon basin watersheds. The importance of this phenomenon and its effect on N transport to larger rivers across the larger areas of the Amazon Basin will depend on better evaluation of both the extent and the scale at which stream infilling by grass occurs, but our analysis suggests the phenomenon is widespread.
    Beschreibung: This work was supported by grants from the NASA Large-Scale Biosphere and Atmosphere Experiment (NCC5-686), the National Science Foundation (DEB-0315656) and the Fundação de Ámparo à Pesquisa do Estado de São Paulo.
    Schlagwort(e): N-15 ; Ammonium uptake length ; Brazil ; Nitrification ; Nitrogen cycling ; Pasture ; Stable isotopes ; Stream ecosystem ; Tropical forest
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 18 (1994), S. 137-142 
    ISSN: 1432-0789
    Schlagwort(e): Microbial biomass ; Bamboo savanna ; N mineralization ; Nutrient pools ; Temporal variations ; Nitrification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effect of harvesting bamboo savanna on the dynamics of soil nutrient pools, N mineralization, and microbial biomass was examined. In the unharvested bamboo site NO inf3 sup- -N in soil ranged from 0.37 to 3.11 mg kg-1 soil and in the harvested site from 0.43 to 3.67 mg kg-1. NaHCO3-extractable inorganic P ranged from 0.55 to 3.58 mg kg-1 in the unharvested site and from 1.01 to 4.22 mg kg-1 in the harvested site. Over two annual cycles, the N mineralization range in the unharvested and harvested sites was 0–19.28 and 0–24.0 mg kg-1 soil month-1, respectively. The microbial C, N, and P ranges were 278–587, 28–64, and 12–26 mg kg-1 soil, respectively, with the harvested site exhibiting higher values. Bamboo harvesting depleted soil organic C by 13% and total N by 20%. Harvesting increased N mineralization, resulting in 10 kg ha-1 additional mineral N in the first 1st year and 5 kg ha-1 in the 2nd year following the harvest. Microbial biomass C, N and P increased respectively by 10, 18, and 5% as a result of bamboo harvesting.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 283-287 
    ISSN: 1432-0789
    Schlagwort(e): Nitrogen transformations ; Flooded soil ; Nitrogen loss ; Nitrification ; Dentitrification ; Urea ; NH3 volatilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Laboratory batch incubation experiments were conducted to determine in fate of urea-15N applied to floodwater of four rice soils with established oxidized and reduced soil layers. Diffusion-dependent urea hydrolysis was rapid in all soils, with rates ranging from 0.0107 to 0.0159 h-1 and a mean rate of 0.0131 h-1. Rapid loss of 53%–65% applied urea-15N occurred during the first 8 days after application, primarily by NH3 volatilization. At the end of 70 days, an additional 20%–30% of applied urea-15N was lost, primarily through nitrification-denitrification processes. The soil types showed significant differences in total applied urea-15 recovery. Conversion of urea-15N to N2-15N provided direct evidence of urea hydrolysis followed by nitrification-denitrification in flooded soils.
    Materialart: Digitale Medien
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 10 (1972), S. 82-90 
    ISSN: 1432-0827
    Schlagwort(e): Calcium ; Phosphate ; Precipitation ; Kinetics ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé La cinétique de la formation et de la transformation des précipités de phosphate de calcium, obtenus en mélangeant de volumes égaux de solutions à 6×10−3 M de calcium total et/ou phosphate total est étudiée à 25°C. Les solutions de phosphate sont préajustées à un pH de 7.4. Les changements de pH et de turbidité des solutions sont suivis simultanément en fonction du temps. Les précipités sont isolés à des intervalles de temps variables et caractérisés par diverses méthodes physico-chimiques. Initialement un précipité avec un rapport molaire Ca/P de 1.5, amorphe aux rayons X et en diffraction électronique, est formé. Le spectre IR indique la présence de PO 4 3− et de HPO 4 2− . Après une période métastable, on observe la précipitation d'un matériel cristallin dans ou sur la phase amorphe. Vingt quatre heures après préparation de l'échantillon les précipités présentent surtout les caractères du phosphate octocalcique.
    Kurzfassung: Zusammenfassung Die Kinetik der Bildung und Transformation von Calciumphosphat-Niederschlägen wurde bei 25°C untersucht. Es wurden dazu gleiche Volumen von Lösungen gemischt, bei einer Konzentration von 6×10−3M totales Calcium und/oder totales Phosphat. Die Phosphatlösungen wurden zuerst auf pH 7,4 eingestellt. Veränderungen des pH und Trübung der Lösungen wurden gleichzeitig als eine Funktion der Zeit aufgezeichnet. Niederschläge wurden in verschiedenen Zeitintervallen isoliert und mit verschiedenen physiko-chemischen Methoden charakterisiert. Am Anfang wurde ein Niederschlag mit einem molaren Ca/P-Verhältnis von 1,5, im Röntgenbild und in der Elektronendiffraktion amorph, gebildet. Infrarotspektren deuteten die Anwesenheit von PO 4 3− - und HPO 4 2− -Ionen an. Nach einer metastabilen Periode erfolgte ein Niederschlag aus kristallinem Material innerhalb oder auf der amorphen Substanz. 24 Std nach der Herstellung der Proben zeigten die Niederschläge in der Hauptsache die Charakteristiken von Octocalciumphosphat.
    Notizen: Abstract The kinetics of the formation and transformation of calcium phosphate precipitates obtained by mixing equal volumes of solutions, 6×10−3 M in total calcium and/or total phosphate was investigated at 25°. The phosphate solutions were preadjusted to pH 7.4. Changes of the pH and turbidity of the solutions were followed simultaneously as a function of time. Precipitates were isolated at various time intervals and characterized by different physicochemical methods. Initially a precipitate with a molar Ca/P ratio of 1.5, amorphous to X-ray and electron diffraction was formed. IR spectra indicated the presence of PO 4 3− and HPO 4 2− ions. After a period of metastability, precipitation of a crystalline material within or upon the amorphous matter occurred. Twenty four hours after sample preparation the precipitates showed mainly the characteristics of octacalcium phosphate.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 16 (1974), S. 145-152 
    ISSN: 1432-0827
    Schlagwort(e): EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Schlagwort(e): Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 29 (1991), S. 191-196 
    ISSN: 1573-0867
    Schlagwort(e): Nitrification ; nitrification inhibitor ; 15N-labelled N-fertilizer ; non extractable N
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The influence of the nitrification inhibitor dicyandiamide (DCD) on the turnover of15N-labelled ammonium sulfate (AS) was investigated in two soils under aerobic and waterlogged conditions. Nitrification of ammonium sulfate was markedly inhibited by addition of DCD in both soils. Up to 45% of the supplied N was transformed into a non-extractable N form, which only slowly released nitrogen over 147 or 264 days. This immobilization was higher in the presence of DCD than without DCD. In all aerobic experiments, the recovery was 100% ± max. 2.4%, indicating that no gaseous losses of N occurred. If aerobic preincubation of 28 or 42 days was followed by water-logging with H2O or a solution of glucose, considerable N losses occurred only in presence of the carbohydrate. DCD retarded nitrification and thus reduced losses by denitrification from 61 to 15%. DCD application resulted in an increased immobilization of labelled N into the non-exchangeable soil N fraction. This amounted to more than 50% of the applied N, compared to 39% without DCD.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Schlagwort(e): Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 14 (1974), S. 3-14 
    ISSN: 1432-0827
    Schlagwort(e): Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Kurzfassung: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notizen: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 7 (1971), S. 150-162 
    ISSN: 1432-0827
    Schlagwort(e): Uranium ; Bone ; Distribution ; Fission ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Une concentration moyenne de 2.4×10−8 g U/g de cendre a été obtenue à partir de l'os humain normal. La microdistribution de l'uranium dans l'os indique que cet élément est surtout limité à surface de l'endoste et, en particulier, aux surfaces de l'os lamellaire et aux parois des canaux de Havers, ouverts dans l'os corticol. Cette répartition suggère que l'uranium se présente sous une forme chimique impropre à son incorporation dans l'apatite osseux: il ne semble donc pas exister une distribution diffuse significative de l'uranium dans l'os.
    Kurzfassung: Zusammenfassung Eine mittlere Konzentration von 2,4×10−8 g Uran/g Asche wurde in normalen menschlichen Knochen gefunden. Die Feinverteilung von Uran im Knochen zeigt, daß dieses Element hauptsächlich an der endostalen Oberfläche vorkommt, insbesondere an der Oberfläche des trabeculären Knochens und an den Wänden der offenen Haversschen Kanäle im kortikalen Knochen. Diese Verteilung läßt vermuten, daß Uran in einer chemischen Form vorliegt, welche sich für den Einbau in das Knochenapatit nicht eignet. Daraus folgt, daß keine signifikante diffuse Verteilung des Urans innerhalb des Knochens vorliegt.
    Notizen: Abstract A mean concentration of 2.4×10−8 g U/g ash has been obtained for normal human bone The microdistribution of uranium in bone indicates that this element is mainly restricted to endosteal surfaces; in particular the surfaces of trabecular bone and the walls of open Haversian canals in cortical bone. This distribution suggests that uranium is present in a chemical form that is not acceptable for incorporation into bone apatite and consequently there does not appear to be a significant diffuse distribution of uranium throughout bone.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 8 (1971), S. 54-72 
    ISSN: 1432-0827
    Schlagwort(e): Morphology ; Glycosaminoglycans ; Cartilage ; Chemistry ; Audioradiography ; Healing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Une perte de substance ostéo-cartilagineuse, de taille limitée et identique, est réalisée chez le lapin adulte et la cicatrisation est étudiée histologiquement et par autoradiographie après marquagein vitro au35S-sulfate. Une analyse microchimique est pratiquée pour le contenu et la composition en glycosaminoglycanes. 1. Entre la première semaine et la 4ème et 8ème semaine, un tissu conjonctif non-métachromatique se différencie en un cartilage métachromatique et la quantité de sulfate de chondroitine augmente de façon significative aux dépens des glycoprotéines. 2. Jusqu'à la 4ème semaine, la perte de substance est surtout comblée par de l'os néoformé: après cette période, la région est comblée au delà de la limite de la surface articulaire. 3. Le cartilage hyalin, ressemblant morphologiquement, autoradiographiquement et chimiquement au cartilage articulaire, en ce qui concerne la distribution en glycosaminoglycanes, constitute la surface articulaire de la perte de substance comblée dans un tiers des cas après 8 semaines. Le cartilage hyalin s'observe surtout dans les régions où de l'os néoformé a comblé la cavité médullaire. 4. Dans les deux tiers des cas, après 8 semaines, les surfaces articulaires des zones comblées comportent, non seulement du cartilage, mais aussi du tissu fibreux se formant essentiellement sur les parties latérales et dans les régions, où la cavité médullaire, fliant face, à la surface articulaire, n'a pas été comblée par du tissue osseux. La fraction glycoprotéique augmente par rapport à la fraction chondroitine sulfate. 5. Dans la majorité des cas, après 20 semaines, le cartilage néoformé subit des phénomènes dégénératifs, qui se traduisent par une diminution en chondroitine sulfate.
    Kurzfassung: Zusammenfassung Bei ausgewachsenen Kaninchen wurde ein begrenzter, standardisierter, osteochondraler Defekt hervorgerufen, und das regenerierte Gewebe wurde histologisch und autoradiographisch durch Markierung in vitro mit35S-Sulfat und durch mikrochemische Bestimmung des Gehaltes und der Zusammensetzung der Glykosaminglykane untersucht. Die wichtigsten Befunde waren: 1. Zwischen 1 und 4–8 Wochen veränderte sich nichtmetachromatisches Bindegewebe zu metachromatisch gefärbtem Knorpel, und der Anteil an Chondroitin-Sulfat nahm auf Kosten der Glykoproteine signifikant zu. 2. Bis zu 4 Wochen war der Hauptteil des defekten Gebietes mit neugebildetem Knochen gefüllt; nach dieser Zeit lag dieser Bezirk oberhalb der Verknöcherungsgrenze in Richtung der Gelenkoberfläche. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 4. Nach 8 Wochen bestanden Teile der Gelenkoberfläche des Defektes in zwei Dritteln der Fälle nicht nur aus Knorpel, sondern auch aus fibrösem Gewebe, welches vor allem in den seitlichen Teilen des Defektes und an Stellen vorlag, wo die Markhöhle gegenüber der Gelenkoberfläche nicht mit Knochengewebe verschlossen worden war. Die Glykoproteinfraktion nahm im Vergleich zur Chondroitin-Sulfatfraktion zu. 5. Nach 20 Wochen zeigten sich in den meisten Fällen bei neugebildetem Knorpel degenerative Veränderungen, welche durch eine gewisse Abnahme des Chondroitin-Sulfats wiedergegeben wurden.
    Notizen: Abstract A limited, standardized osteochondral defect was created in adult rabbits and the regenerated tissue was examined histologically and autoradiographically after labellingin vitro with35S-sulphate, and microchemically for its content and composition of glycosaminoglycans. The principal findings were: 1. Between 1 week and 4 to 8 weeks, non-metachromatic connective tissue differentiated to metachromatically stained cartilage, and the proportion of the chondroitin sulphate increased significantly at the expense of the glycoproteins. 2. Up to 4 weeks, the major part of the defect area was filled with newly formed bone; after this time, the area lay above the level of the “tidemark”, towards the articular surface. 3. Hyaline cartilage with morphological, autoradiographic and chemical resemblance to the articular cartilage in terms of the distribution of glycosaminoglycans constituted the articular surface of the defect area in one-third of the cases at observation times after 8 weeks. Hyaline cartilage was observed mainly in areas where newly formed bone had closed the medullary cavity. 4. In two-thirds of the cases, after 8 weeks, parts of the articular surface of the defect consisted not only of cartilage but also of fibrous tissue, occurring mainly in the lateral parts of the defect and in areas where the medullary cavity facing the articular surface had not been sealed by bone tissue. The glycoprotein fraction increased relative to the chondroitin sulphate fraction. 5. In most cases after 20 weeks, newly-formed cartilage underwent degenerative changes, which were reflected in some reduction of the chondroitin sulphate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 8 (1971), S. 228-236 
    ISSN: 1432-0827
    Schlagwort(e): Skin ; Calcinosis ; Keratin ; Chemistry ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Des études histologiques antérieures ont montré que le follicle pileux est particulièrement susceptible de se calcifier, lorsque la peau de rats hypercalcémiques est lésée. Des analyses chimiques et par diffraction aux rayons X du follicule ont confirmé ce résultat. — En se basant sur l'augmentation du calcium et du phosphore, les calcifications débutent dans le tissue folliculaire 6–12 h après une blessure d'intensité moyenne de la peau de rats, ayant reçu du dihydrotachysterol (DHT), et 24–48 h après une blessure similaire chez des rats non injectés. Les diagrammes de diffraction aux rayons X sont diffus. Trois heures après la blessure, on note une augmentation du calcium du tissu folliculaire qui ne semble pas en rapport avec le DHT qui traduit probablement une liaison de calcium plutôt qu'un dépot minéral.
    Kurzfassung: Zusammenfassung Frühere histologische Untersuchungen haben gezeigt, daß der Haarfollikel besonders anfällig für Verkalkungen ist, wenn die Haut von hypercalcämischen Ratten verletzt wird. Dieses Resultat wurde nun durch direkte chemische Bestimmungen und Röntgendiffraktions-analysen von Follikelgewebe bestätigt. Aufgrund der erhöhten Calcium- und Phosphatwerte kann gesagt werden, daß nach einer leichten Quetschung der Haut von Ratten, die mit Dihydrotachysterol (DHT) behandelt wurden, im Haarfollikelgewebe nach 6–12 Std Mineral-ablagerungen stattfanden, wogegen Kontrollratten mit der gleichen leichten Hautverletzung diese Ablagerungen erst nach 24–48 Std zeigten. Röntgendiffraktionsanalysen ergaben ein diffuses Apatit-Muster. Innerhalb 3 Std nach der Verletzung wurde ein Anstieg des Calcium-gehaltes im Follikelgewebe beobachtet, der nicht im Zusammenhang mit der DHT-Behandlung stand, also nicht eine Mineralablagerung, sondern eher eine Bindung von Calcium widerspiegelte.
    Notizen: Abstract Previous histological investigations have shown that the hair follicle is particularly susceptible to mineralization when the skin of hypercalcaemic rats is injured. Direct chemical and X-ray diffraction analyses of follicle tissue have now confirmed this finding. As judged by increases in both calcium and phosphorus, mineral deposits began to form in hair follicle tissue 6–12 h after a mild crush injury to the skin of rats dosed with dihydrotachysterol (DHT), and 24–48 h after a similar injury to the skin of non-dosed rats. X-ray diffraction gave a diffuse apatite pattern. Within 3 h of injury there was a rise in the calcium content of follicle tissue which was not related to DHT-dosing and which was probably a reflection of calcium binding rather than mineral deposition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 8 (1971), S. 304-319 
    ISSN: 1432-0827
    Schlagwort(e): Chemistry ; Calcium ; Phosphate ; Solubility ; Computer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Un programme d'ordinateur a été mis au point pour calculer les activités ioniques du calcium et l'orthophosphate dans un grand nombre de solutions. Dans le cas de solutions synthétiques, les calculs sont vérifiés en comparant les valeurs de pH, obtenues par ordinateur, avec celles observées expérimentalement. Des essais de ce type, avec des solutions possèdant des concentrations de calcium et d'orthophosphate trouvées dans les liquides biologiques et à des valeurs de pH variant de 3.00 à 10.00, indiquent que le programme est adapté pour des applications biologiques. Le programme n'est pas effectif pour des solutions, dans les lesquelles l'ion bromure est la source principale de la force ionique, sans doute, par manque d'équation étendue de Debye-Hückel dans ces circonstances. Aucune formation de complexe de phosphate de sodium n'a été notée à des concentrations biologiques normales.
    Kurzfassung: Zusammenfassung Es wurde ein Computer-Programm ausgearbeitet, um die Ionenaktivitäten von Calcium und Orthophosphat in einer breiten Varietät von Lösungen zu berechnen. Die Berechnungen wurden bei synthetischen Lösungen durch Vergleiche zwischen den auf diese Weise errechneten pH-Werten und den experimentell gefundenen kontrolliert. Diese Art Kontrollen mit Calcium-und Orthophosphatkonzentrationen, wie sie in biologischen Flüssigkeiten gefunden werden, und mit pH-Werten zwischen 3,0 und 10,0 wies darauf hin, daß das Programm für biologische Anwendungen geeignet war. Das Programm konnte nicht benützt werden für solche Lösungen, bei welchen hauptsächlich das Bromidion zur Einstellung der Ionenstärke verwendet wurde, vermutlich weil die erweiterte Debye-Hückel-Gleichung unter diesen Umständen nicht anwendbar ist. Die Bildung eines Natriumphosphat-Komplexes unter normalen biologischen Konzentrationen konnte nicht nachgewiesen werden.
    Notizen: Abstract A computer program has been designed to calculate the ionic activities of calcium and orthophosphate in a wide variety of solutions. In the case of synthetic solutions the calculations were checked by comparing the computed pH values with those observed experimentally. Tests of this type with solutions having the concentrations of calcium and orthophosphate found in biological fluids and with pH values ranging from pH 3.0–10.0 indicated that the program was suitable for biological applications. The program was not effective for solutions in which the bromide ion was a principal source of ionic strength probably because of the failure of the extended Debye-Hückel equation under those circumstances. No evidence for the formation of any sodium phosphate complex at normal biological concentrations could be found.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 10 (1972), S. 171-197 
    ISSN: 1432-0827
    Schlagwort(e): Amorphous ; Crystalline ; Calcium phosphate ; Chemistry ; Composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Des échantillons non lavés de phosphate de calcium amorphe (ACP) contiennent une fraction labile, non remplaçable, riche en phosphate acide avec un rapport Ca/P faible: cette fraction est perdue de façon irréversible au cours du lavage. De l'ACP frais, précipité entre pH 6.6–10.6, varie dans un rapport molaire Ca/P de 1.18 à 1.50 et dans un rapport HPO 4 2− /P total de 33.0% à 10.1%. A pH 7.40, de l'ACP frais a un rapport molaire Ca/P de 1.36±0.02 et contient 22.8 (±2.2)% HPO 4 2− . Les résultats obtenus avec du précipité non lavé ne peuvent s'expliquer par du Ca2+ emprisonné et de l'HPO 4 2− ou du Na+, Cl− et CO 3 2− exogènes. Les phosphates de calcium amorphes constituent une classe de sels ayant des caractères chimiques variables et des propriétés physiques identiques, comparables au verre. Le CaHPO4·xH2O non cristallin peut être un ACP, surtout au cours des phases précoces de formation. A des pH physiologiques, l'ACP se transforme en petits cristaux applatis contenant de fortes quantités de phosphate acide facilement remplaçable. Le fait de laver la couche de surface produit un changement chimique dans les nouveaux cristaux: des cristaux non lavés donnent des diagrammes de diffraction d'apatite peu cristallins, ainsi que des spectres infra-rouges peu nets, intermédiaires entre des apatites et du phosphate octocalcique. Des explications structurales sont proposées et les compositions minérales amorphe/cristalline de l'os et du cartilage sont recalculées.
    Kurzfassung: Zusammenfassung Ungewaschene Proben von amorphem Calciumphosphat (ACP) enthalten eine unersetzliche labile Fraktion, welche reich an saurem Phosphat ist und ein niederes Ca/P-Verhältnis hat und welche während des Waschprozesses unwiderruflich verloren geht. Natives ACP, welches im pH-Bereich 6,6–10,6 ausgefällt wurde, variierte im molaren Ca/P-Verhältnis zwischen 1,18 und 1,50 und in HPO 4 2− /totales P zwischen 33,0 und 10,1%. Bei pH 7,40 hatte natives ACP ein molares Ca/P-Verhältnis von 1,36±0,02 und enthielt 22,8 (±2,2)% HPO 4 2− . Die Werte beim ungewaschenen Niederschlag rühren weder von aus dem Überstand aufgenommenem Ca2+ und HPO2−, noch von außen kommendem Na+, Cl− und CO 3 2− her. Die amorphen Calciumphosphate werden als eine Klasse von Salzen erkannt, welche veränderliche chemische, aber identische glasartige physicochemische Eigenschaften haben. Nicht kristallines CaHPO4·xH2O kann auch ein ACP sein, besonders in den frühen Bildungsstadien. Bei physiologischem pH verwandelt sich ACP in kleine plattenförmige Kristalle, welche große Mengen von leicht ersetzbarem saurem Phosphat enthalten. Das Waschen dieser Oberflächenschicht erzeugte chemische Veränderungen in den resultierenden Kristallen; ungewaschene Kristalle zeigten ein Diffraktionsmuster, das nur schwach demjenigen des kristallinen Aspatites glich, aber ein schlecht aufgelöstes Infrarotspektrum, welches zwischen Apatit und Octocalciumphosphat war. Es werden strukturelle Erklärungen für alle diese Phenomena diskutiert, und revidierte amorph/kristalline Mineralzusammensetzungen von Knochen und Knorpel wurden neu berechnet.
    Notizen: Abstract Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca/P molar ratio from 1.18 to 1.50 and in HPO 4 2− /total P from 33.0% to 10.1%. At pH 7.40, native ACP had a Ca/P molar ratio of 1.36±0.02 and contained 22.8 (±2.2)% HPO 4 2− . Unwashed precipitate data could not be attributed to either trapped supernatant Ca2+ and HPO 4 2− or extraneous Na+, Cl−, and CO 3 2− . The amorphous calcium phosphates are recognized as a class of salts having variable chemical but identical glass-like, physicochemical properties. Non-crystalline CaHPO4·xH2O may also be an ACP, especially during early formative stages. At physiological pH, ACP transforms to small platy crystals containing large amounts of readily-replaceable acid phosphate. Washing this surface layer produced chemical alterations in the resultant crystals; unwashed crystals had poorly-crystalline apatitic diffraction patterns but exhibited poorly-resolved infrared spectra intermediate between apatite and octacalcium phosphate. Structural explanations for all these phenomena are discussed, and revised bone and cartilage amorphous/crystalline mineral compositions have been re-calculated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 8 (1971), S. 197-210 
    ISSN: 1432-0827
    Schlagwort(e): Fluorescence ; Calcium ; Collagen ; Chemistry ; Bone ; Dentine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Des composants fluorescents de l'os et la dentine sont séparés des hydrolysats alcalins de leur marice sur des colonnes Sephadex C25 CM d'échange cationique. Les concentrations en fluorescence et le spectre d'excitation (λ max 330 nm) et d'émission (λ max 395 nm) sont les mêmes que ceux observés au niveau des matrices intactes et gélatinisées. Les paramètres de fluorescence ne sont pas altérés par hydrolyse. La filtration sur gel à l'aide de colonnes Sephadex G 10 perment de différencier le matériel isolé en deux composants, ayant la même fluorescence et la même absorption UV. La fluorescence est indépendante de pH de 3.5–9.5. Des études de dialyse et de filtration sur gel de matrices gélatinisées indiquent une association étroite du matériel fluorescent avec les chaines polypeptidiques de collagène.
    Kurzfassung: Zusammenfassung Fluorescierende Bestandteile aus Knochen und Dentin wurden in Sephadex C25 CM Kationen-Austauschersäulen von alkalischen Hydrolysaten ihrer Matrices getrennt. Die Fluorescenzintensitäten sowie die Erregungs- (λ max 330 nm) und Emissions- (λ max 395 nm) Spektren waren dieselben wie bei intakten und gelatinisierten Matrices. Die Fluorescenzparameter wurden durch die Hydrolyse nicht verändert. Eine Gelfiltration über Sephadex-G10-Säulen trennte das isolierte Material in 2 Komponenten auf, welche gleiche Fluorescenz- und UV-Absorptionseigenschaften zeigten. Im pH-Bereich zwischen 3,5 und 9,5 war die Fluorescenz unabhängig vom pH. Dialysierversuche sowie Gelfiltrationsexperimente mitden gelatinisierten Matrices zeigten eine starkgefügte Bindung des fluorescierenden Materials mit den Polypeptidketten des Kollagens.
    Notizen: Abstract Fluorescent components in bone and dentine were separated from alkaline hydrolysates of their matrices on Sephadex C25 CM cationic exchange columns. The fluorescence levels, and the excitation (λ max 330 nm) and emission (λ max 395 nm) spectra, were the same as those observed in the intact and gelatinised matrices. The fluorescence parameters were unaltered by the hydrolysis procedure. Gel filtration on Sephadex G. 10 columns further resolved the isolated material into two components with the same fluorescence and UV absorption properties. The fluorescence was independent of pH over the range 3.5–9.5. Dialysis and gel filtration studies on the gelatinised matrices indicated a firmly-bonded association of the fluorescent material with the collagen polypeptide chains.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Schlagwort(e): Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Kurzfassung: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notizen: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 13 (1973), S. 259-270 
    ISSN: 1432-0827
    Schlagwort(e): Fluorapatite ; Exchange ; Chemistry ; Crystallography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Un échantillon minéral provenant de Burgess, Canada s'est révélé être un speciment exceptionnellement pur de fluoroapatite après analyse chimique et cristallographique. La composition globale de cet échantillon est la suivante: $$(Ca^2 )9.98(Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )0.02(PO_4^{3 - } )5.98(HCO_3^ - ,CO_3^{2 - } )0.02(F^ - )2$$ . L'axe cristallographique C est de 6.865 A et l'axe a de 9.374 A. Des expériences d'échanges réalisés à l'aide de45Ca,32P et18F indiquent la présence de gros cristallites de surface spécifique de l'ordre de 1 m2/g. Il apparait que l'interprétation physique des processus d'échange ne nécessite pas l'existence de compartiments séparés, avec chacun son propre facteur cinétique, les échanges semblent être simplement liés à un changement exponentiel dans l'énergie libre de la réaction. Pour la réaction suivante: $$(Ca)_5 (PO_4 )_3 OH solide + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F solide + (OH^ - )$$ , la constante thermodynamique de 101.26 a été calculée, suggérant que le fluorapatite se forme toujours aux dépens de l'hydroxyapatite dans des conditions physiologiques. Cette transformation se continue en abaissant le pH.
    Kurzfassung: Zusammenfassung Eine Mineralprobe aus Burgess, Kanada, erwies sich nach chemischer und kristallographischer Analyse als außergewöhnlich reines Fluorapatit. Die Gesamtzusammensetzung entspricht: $$(Ca^{2 + } )_{9,98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0,02} (PO_4^{3 - } )_{5,98} (HCO_3^ - ,CO_3^{2 - } )_{0,02} (F^ - )_2 $$ . Die kristallographische c-Achse wurde bestimmt und ergab 6,865 Å, und die a-Achse ergab 9,374 Å. Austauschwerte, welche durch Anwendung von45Ca,32P und18F erhalten wurden, deuteten auf große Kristalliten mit einer spezifischen Oberfläche von ca. 1 m2/g. Die Befunde deuten darauf hin, daß für die physikalische Erklärung des Austauschvorganges keine separaten Kompartimente mit eigenen kinetischen Faktoren nötig sind, sondern daß der Austausch mit dem exponentiellen Wechsel in der freien Energie der Reaktion in einfacher Beziehung steht. Für die Reaktion $$(Ca)_5 (PO_4 )_3 OH_{in fester Form} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{in fester Form} + (OH^ - )$$ wurde als thermodynamische Konstante 101,26 errechnet, was darauf deutet, daß unter physiologischen Bedingungen immer Fluorapatit auf Kosten von Hydroxyapatit entsteht. Diese Umwandlung wird erhöht, wenn das pH erniedrigt wird.
    Notizen: Abstract A mineral specimen from Burgess, Canada, proved upon chemical and crystallographic analyses to be an exceptionally pure sample of fluorapatite. The over-all composition corresponds to $$(Ca^{2 + } )_{9.98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0.02} (PO_4^{3 - } )_{5.98} (HCO_3^ - ,CO_3^{2 - } )_{0.02} (F^ - )_2 $$ . The crystallographic c-axis was determined to be 6.865 Å, and the a-axis 9.374 A. Exchange data obtained by employing45Ca,32P, and18F indicate the presence of large crystallites with a specific surface of the order of 1 m2/g. It is indicated that the physical interpretation of the exchange process does not require the existence of separate departments, each with its own kinetic factor, but that the exchange may be simply related to the exponential change in the free energy of the reaction. For the reaction $$(Ca)_5 (PO_4 )_3 OH_{solid} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{solid} + (OH^ - )$$ the thermodynamic constant has been calculated to be 101.26, implying that fluorapatite always will form at the expense of hydroxyapatite under physiologic conditions. This transformation will be furthered by lowering the pH.
    Materialart: Digitale Medien
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  • 90
    ISSN: 1432-0827
    Schlagwort(e): Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 88 (1991), S. 189-196 
    ISSN: 1432-1939
    Schlagwort(e): N mineralization ; Nitrification ; Microbial biomass ; Denitrification ; Spatial variability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Nitrogen mineralization, nitrification, denitrification, and microbial biomass were evaluated in four representative ecosystems in east-central Minnesota. The study ecosystems included: old field, swamp forest, savanna, and upland pin oak forest. Due to a high regional water table and permeable soils, the upland and wetland ecosystems were separated by relatively short distances (2 to 5 m). Two randomly selected sites within each ecosystem were sampled for an entire growing season. Soil samples were collected at 5-week intervals to determine rates of N cycling processes and changes in microbial biomass. Mean daily N mineralization rates during five-week in situ soil incubations were significantly different among sampling dates and ecosystems. The highest annual rates were measured in the upland pin oak ecosystem (8.6 g N m−2 yr−1), and the lowest rates in the swamp forest (1.5 g N m−2 yr−1); nitrification followed an identical pattern. Denitrification was relatively high in the swamp forest during early spring (8040 μg N2O−N m−2 d−1) and late autumn (2525 μg N2O−N m−2 d−1); nitrification occurred at rates sufficient to sustain these losses. In the well-drained uplands, rates of denitrification were generally lower and equivalent to rates of atmospheric N inputs. Microbial C and N were consistently higher in the swamp forest than in the other ecosystems; both were positively correlated with average daily rates of N mineralization. In the subtle landscape of east-central Minnesota, rates of N cycling can differ by an order of magnitude across relatively short distances.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 82 (1990), S. 507-512 
    ISSN: 1432-1939
    Schlagwort(e): Forest soils ; Nitrification ; Nitrogen loading ; Cation leaching ; Norway spruce
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During July 1988 rooted and non-rooted experimental chambers were established in a Norway spruce (Picea abies. Karst) stand in south Devon U.K. Replicates were supplemented with ammonium and nitrate. The leachates were analysed to monitor the release of mineral-N species and cations over the 17-week experimental period. Ammonium treatments leached 300% more calcium and magnesium than controls. The onset of nitrification resulted in a decrease in sodium losses from ammonium treatments reflecting a decrease in the exchanging capacity of the soil solution. These results are discussed in relation to mineral ion leaching in soils subjected to increesed N-loading, and the ability of soils to buffer these perturbations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 10 (1990), S. 35-44 
    ISSN: 1432-0789
    Schlagwort(e): Pinus edulis ; Juniperus osteosperma ; Carbon ; Nitrogen ; Nitrification ; Microbial N ; N immobilization ; Fire ecology ; Nitrifying bacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Forest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NH inf4 sup+ , decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NH inf4 sup+ closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NO inf3 sup- . Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 10 (1990), S. 145-151 
    ISSN: 1432-0789
    Schlagwort(e): Nitrification ; Soil acidification ; Carbonate dissolution ; Available P ; Phosphate precipitation ; Intensive agriculture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary It is often proposed that soil acidification by microorganisms dissolves unavailable soil phosphates, especially crystalline Ca phosphates. Unavailable phosphates, it is suggested, could thus become available to crops. Microorganisms that oxidize one ammonium ion to one nitrate ion excrete two protons into the soil solution. In the present study, this universal biological process of soil acidification was used to measure, in neutral and calcareous soils, the effect of acidification on available soil phosphate and on the rate of phosphate fixation when water-soluble phosphate fertilizers are added to soils. During nitrification the Ca2+ and Mg2+ ion concentrations in soil solutions increase but the phosphate ion concentration remains constant. The excreted protons preferentially dissolve soil Ca and Mg carbonates. Soil Ca phosphates are not dissolved; they remain unavailable. When P fertilizers were applied, the rate of fixation of phosphate ions was not slowed down by acidification associated with nitrification. This biological acidification may have a long term effect, over many years, on the slow accumulation of available phosphate in soils under native grasslands, but it cannot have a significant effect on the availability of soil P under intensive agricultural practices.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 10 (1990), S. 139-144 
    ISSN: 1432-0789
    Schlagwort(e): Denitrification ; Nitrification ; Chemodenitrification ; Ammonium ; Nitrite ; Nitrate ; Nitric oxide ; Nitrous oxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary NO and N2O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8) after the pH was adjusted to values ranging from pH 4.0 to 7.8. The total release of NO and N2O during 20 h of incubation was determined together with the net changes in the concentrations of NH 4 + , NO 2 − and NO 3 − in the soil. The release of NO and N2O increased after fertilization with NH 4 + and/or NO 3 − ; it strongly decreased with increasing pH in the acidic forest soil; and it increased when the pH of the alkaline agricultural soil was decreased to pH 6.5. However, there was no simple correlation between NO and N2O release or between these compounds and activities such as the NO 2 − accumulation, NO 3 − reduction, or NH 4 + oxidation. We suggest that soil pH exerts complex controls, e.g., on microbial populations or enzyme activities involved in nitrification and denitrification.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 11 (1991), S. 105-110 
    ISSN: 1432-0789
    Schlagwort(e): Compost ; Sawdust ; Bark ; Cellulolysis ; Ammonification ; Nitrification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The decomposition of coniferous sawdust and bark with added N and P was studied in relation to its capacity to serve as a substrate for plant growth. With sawdust as a substrate, there was more microbial biomass, greater CO2 evolution, more ammonification and more actinomycetes but less nitrification and less fungi compared with bark. All groups and activities were greater in sawdust and bark compared with soil used as the substrate. Inoculation with cellulolytic strains of Bacillus sp. Cephalosporium sp. and Streptomyces sp. sometimes increased these activities but only marginally. The derived sawdust and bark composts increased the yields of tomato compared with soil to which the same nutrients had been added.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 1432-0789
    Schlagwort(e): Carbon ; Denitrification ; Immobilisation ; Mineralisation ; Nitrification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary A potato crop (Solanum tuberosum L. cv. Maris piper) was grown in a soil to which N was added, as NH4NO3, with or without added C, as sucrose or straw. Shortly after amendment the soil, in all treatments, contained only relatively low levels of mineral N. However, these levels increased later. The increase, which was greatest in the absence of added C and least with added sucrose, occurred before the emergence of the plant canopy. The addition of C to the soil had no effect on plant yield, measured either as dry matter or total N content. The potential nitrification rate was high early in the season, and decreased significantly as the plants developed. The potential denitrification rate showed two significant peaks in activity, possibly related to plant development, the first to the development of new roots and the second to root senescence. It seems probable that the amount of C released by the potato plants was only about one-quarter of that required for the maximum microbial activity.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 11 (1991), S. 231-233 
    ISSN: 1432-0789
    Schlagwort(e): Nitrification ; Hydrocarbons ; Methane ; Ethane ; Ethylene ; Acetylene ; Nitrosomonas europaea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Recent work has shown that gaseous hydrocarbons such as methane, ethane, and ethylene are competitive inhibitors of the monooxygenase enzyme responsible for oxidation of ammonia by chemoautotrophic nitrifying microorganisms such as Nitrosomonas europaea. Because methane, ethane, and ethylene are produced by microbial activity in soil, we studied the possibility that they may inhibit oxidation of ammonia by the nitrifying soil microorganisms. We found that all three of these gaseous hydrocarbons inhibited nitrification in soil and that their ability to inhibit nitrification decreased in the order: ethylene 〉 ethane 〉 methane. Ethylene was much more effective than ethane or methane for inhibiting nitrification of ammonium in soil, but it was much less effective than acetylene, and it seems unlikely that the amounts of ethylene produced in soils will be sufficient to cause significant inhibition of nitrification by soil microorganisms.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 12 (1991), S. 1-4 
    ISSN: 1432-0789
    Schlagwort(e): Microbial activity ; Gas chromatographic analysis ; Soil atmosphere ; N2O release ; CO2 evolution ; O2 uptake ; Denitrification ; Nitrification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary We have developed a simple method for the determination of gaseous compounds that reflect microbial activity in soil, as affected by factors such as the presence of an organic amendment (peat) or a variation in soil moisture. The method is based on a gas chromatographic analysis of the headspace of vials containing the soil under examination. A single gas chromatograph can detect up to 10 different gases. As expected, after peat was added to the soil, CO2 evolution and O2 uptake increased significantly. Positive relationships were found between the evolution of N2O, and soil moisture and the amount of peat added to the soil. Both the these variables influenced the CO2:O2 ratio. The results given by this method show high reproducibility.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 12 (1991), S. 19-27 
    ISSN: 1432-0789
    Schlagwort(e): Manure ; Nitrification ; Denitrification ; Silica gel ; Phospholipids ; Microbial biomass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Following the application of liquid manure to soil, the development of the two processes, nitrification and denitrification, was studied in a two-phase model system. A saturated mixture of manure and soil, stabilized with silica gel, was overlain by an aerobic soil phase. Profiles of the redox potential pH, inorganic N, dissolved organic C, nitrification and denitrification potentials, and phospholipid concentrations for an estimate of microbial biomass were measured during a 20-day period. NH 4 + diffusing into the aerobic soil was oxidized within 10 mm of the interface, but with only a small accumulation of NO 2 - and NO 3 - . It was estimated that N equivalent to approximately 70% of the NH 4 + originally present in the manure was lost through coupled nitrification-denitrification. The potentials for nitrification and denitrification increased 40-and 20-fold, respectively, around the interface. Maximum values were recorded after 14 days. Within 0–5 mm of the anaerobic zone, apparent generation times for NH 4 + -oxidizing bacteria of 1.1–1.8 days were estimated between day 1 and day 7. The phospholipid concentration profiles suggested that the biomass within 2 mm on either side of the interface was stimulated throughout the 20-day period.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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