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  • Meteorology and Climatology  (1)
  • cytochalasin B  (1)
  • ring-opening polymerization  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Ring-Opening Polymerization of Siloxanes Using Phosphazene Base Catalysts (1999)
    Springer
    Journal of inorganic and organometallic polymers and materials 9 (1999), S. 17-34 
    Details
    ISSN: 1572-8870
    Keywords: Phosphazene base ; anionic ; ring-opening polymerization ; equilibration ; catalysis ; silicone ; organosiloxane ; polydimethylsiloxane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Phosphazene bases such as {(NMe2)3P=N–)3P=NBut} have been reported in the literature to be strongly basic materials with basicities up to 1×1018 times stronger than that of diazabicycloundecene (DBU) a strong hindered amine base used in organic reactions. A study of these phosphazene bases as catalysts revealed that they can be activated by small amounts of water, which all silicone feed stocks contain, to form an active ionic base catalyst [(NMe2)3P=N–)3P–NHBut]+[OH]−. This paper discusses the use of these types of base catalysts, and their analogues, as ring-opening polymerization catalysts for cyclosiloxanes. Phosphazene base catalysts can be used at low concentrations to make high molecular weight polydimethylsiloxanes with short reaction times over a wide temperature range. Molecular weight can easily be controlled in the presence of suitably functionalized endblockers. Water and carbon dioxide have been shown to have a significant impact on the polymerization rates. Polymers prepared show excellent thermal stability by thermogravimetric analysis (TGA), following neutralization of the catalyst, with decomposition onset temperatures 〉500°C in some cases. As a result of the extremely low levels of catalyst used, the polymers often do not require filtration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021429320083
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Microfilament reorganization in normal and cytochalasin B treated adherent thrombocytes (1981)
    New York, NY : Wiley-Blackwell
    Journal of Supramolecular Structure and Cellular Biochemistry 16 (1981), S. 209-220 
    Details
    ISSN: 0275-3723
    Keywords: adhesion ; microfilaments ; thrombocytes ; whole mount ; cytochalasin B ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Thrombocyte adhesion following activation by a Formvar surface involves a morphologic transition resulting in a fully spread cell. Correlative SEM and whole mount TEM were used to study the cytoskeletal alterations that accompany changes in surface morphology during adhesion. Following initial adhesion, thrombocytes extend slender pseudopods containing longitudinally oriented bundles of filaments that are 13-22 nm in diameter. Concomitant with pseudopod extension, a cytoplasmic hyalomere, consisting of a dense filamentous network, extends between the pseudopods and ultimately results in a fully spread cell. Treatment of thromboyctes with cytochalasin B (10-5 M) caused clumping of the hyalomere filament network and retraction of the hyalomere. Examination of partially retracted cells revealed that pseudopod filament bundles were continuous with the contracting filamentous network. It is concluded that pseudopod filament bundles and cytoplasmic hyalomere filaments are interconvertible and that their organizational relationship changes in accordance with gross morphologic changes.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jsscb.1981.380160302
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  • 3
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    Ground Water and Climate Change (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As the world's largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water. Here we critically review recent research assessing the impacts of climate on ground water through natural and human-induced processes as well as through groundwater-driven feedbacks on the climate system. Furthermore, we examine the possible opportunities and challenges of using and sustaining groundwater resources in climate adaptation strategies, and highlight the lack of groundwater observations, which, at present, limits our understanding of the dynamic relationship between ground water and climate.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN9297 , Nature Climate Change; 3; 322-329
    Format: application/pdf
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