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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Quaternary Science Reviews 121 (2015): 89-97, doi:10.1016/j.quascirev.2015.05.020.
    Description: Warming over Mongolia and adjacent Central Asia has been unusually rapid over the past few decades, particularly in the summer, with surface temperature anomalies higher than for much of the globe. With few temperature station records available in this remote region prior to the 1950s, paleoclimatic data must be used to understand annual-to-centennial scale climate variability, to local response to large-scale forcing mechanisms, and the significance of major features of the past millennium such as the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) both of which can vary globally. Here we use an extensive collection of living and subfossil wood samples from temperature-sensitive trees to produce a millennial-length, validated reconstruction of summer temperatures for Mongolia and Central Asia from 931 to 2005 CE. This tree-ring reconstruction shows general agreement with the MCA (warming) and LIA (cooling) trends, a significant volcanic signature, and warming in the 20th and 21st Century. Recent warming (2000-2005) exceeds that from any other time and is concurrent with, and likely exacerbated, the impact of extreme drought (1999-2002) that resulted in massive livestock loss across Mongolia.
    Description: This research was supported by the National Science Foundation under grants AGS-PRF #1137729, ATM0117442, and AGS0402474.
    Keywords: Mongolia ; Temperature ; Tree-ring ; Dendrochronology ; Reconstruction ; Global warming
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 82 (1970), S. 453-468 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Neuere theoretische und experimentelle Untersuchungen über die pyramidale Inversion werden dargelegt in dem Versuch, ein zusammenhängendes Bild dieser Umwandlung zu zeichnen. Quantenmechanische Studien an pyramidalen Molekülen zeigen, daß das Auftreten einer Inversionsbarriere möglicherweise davon abhängt, wie weit die Bindungswinkel während der Inversion unverändert bleiben. Die Einflüsse der Elektronegativität der Substituenten am Inversionszentrum, einsamer Elektronenpaare und der Einbeziehung von d-Orbitalfunktionen in den Basissatz werden beschrieben. Brauchbarkeit und Grenzen von Molekülorbital-Berechnungen, der Schwingungs- und Mikrowellen-Spektroskopie, direkter kinetischer Messungen und der dynamischen NMR-Spektroskopie (dNMR) zur Ermittlung der einer pyramidalen Inversion entgegenstehenden Energiebarriere werden diskutiert im Zusammenhang mit einem Überblick über die wichtigsten experimentellen Ergebnisse solcher Arbeiten. Besondere Aufmerksamkeit gilt den Zweideutigkeiten, die bei der Interpretation der durch dNMR-Spektroskopie ermittelten Energiebarrieren auftreten. Die Faktoren, von denen die Größe einer Inversionsbarriere abhängt, werden in vier großen Kategorien besprochen: sterische Effekte, Konjugation [einschließlich der (p-d)π-Konjugation] und Hyperkonjugation, Winkelspannungen und Substitution durch Heteroatome. In der letzten Kategorie findet sich eine kritische Diskussion der Einflüsse von Elektronegativität und der Abstoßung zwischen einsamen Elektronenpaaren, der Beziehung zwischen Rotation und Inversion sowie der Rolle der d-Orbitale.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 195-200 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2451-2458 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen bonding in the α-helix and β-sheet has been studied by ab initio molecular orbital calculations carried out on complexes of formamide. Hydrogen-bond geometries were taken from x-ray crystallography of polypeptides. Positive cooperativity is found in all cases. The limiting value for infinite chains is obtained by use of a double-reciprocal plot and indicates an increase in the effective bond strength of 25% over that of a single isolated bond. Parallel calculations based on a classical electrostatic model yield qualitatively similar trends but underestimate the cooperativity by half. Charge redistribution accompanying cooperativity is characterized by a new type of charge-density difference plot, the cooperativity map. The magnitude and distance over which cooperativity acts suggest several significant biological consequences. Thus the average of α-helices and the number of β-sheet strands found in protein may be influenced by cooperativity. Cooperativity in the interpeptide hydrogen bond may also be partly responsible for the rapid formation of secondary structure in renaturing proteins and help stabilize secondary structure relative to the random-coil conformation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 2157-2157 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0044-8249
    Keywords: Asymmetrische Synthesen ; Nitroxide Radikale ; Stereoselektivität ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 9 (1970), S. 400-414 
    ISSN: 0570-0833
    Keywords: Pyramidal inversion ; Inversion barriers ; Stereochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyramidal inversion is discussed from the point of view of recent theoretical and experimental investigations in an attempt to provide a unified description of this process. Quantum mechanical studies of pyramidal molecules indicate that the origin of the inversion barrier may be dependent on the degree of angular constraint. Effects due to the electronegativity of substituents on the inversion center, to the presence of adjacent lone pairs, and to inclusion of d-type functions in the basis set are discussed. The utility and limitations of molecular orbital calculations, vibrational spectroscopy, microwave spectroscopy, direct kinetic measurements, and dynamic nuclear magnetic resonance (DNMR) spectroscopy as means for determining barriers to pyramidal inversion are discussed in context with a review of the highlights of experimental observations on the subject. Ambiguities that arise in the interpretation of barriers determined by DNMR are explored in detail. Factors that affect the magnitude of inversion barriers are discussed separately in four broad categories: steric effects; effects of conjugation (including (p-d)π conjugation) and hyperconjugation; effects of angular constraint; and effects of heteroatomic substitution. In the last category, critical reference is made to the question of electronegativity vs. lone pair-lone pair repulsions, the problem of rotation vs. inversion, and the role of d orbitals.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0570-0833
    Keywords: asymmetric synthesis ; nitroxides ; radical reactions ; stereoselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 2003-2003 
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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