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  • American Institute of Physics (AIP)  (1)
  • Tokyo, Japan  (1)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 3894-3902 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of ethyldifluorophosphine, CH3CH2PF2, has been investigated in the region from 18.0 to 39.5 GHz. The spectra of two conformers have been identified. The ground state and seven vibrationally excited states have been assigned for the more stable gauche conformer (phosphorus lone pair with respect to CH3 group), whereas the ground state and one excited state have been assigned for the trans form. Rotational and most quartic centrifugal distortion constants have been determined with A=6784.501(3), B=2930.156(2), C=2352.576(2) MHz for gauche and A=5444.910(3), B=3290.133(3), C=2871.915(3) MHz for trans, both in the ground state. Electric dipole moments were obtained from ground state Stark effect measurements: || μa||=1.990(4), || μb||=0.855(4), || μc||=0.091(7), || μt||=2.168(2) D for gauche and || μa||=1.780(10), || μb||=0, || μc||=1.077(10), || μt||=2.081(10) D for trans. Using a new computer program, a diagnostic least-squares fit of the structural parameters suggests significant structural differences between the conformers, notably the C–C–P angle which changes from 110.7° in the gauche form to 114.9° in the trans form. From a temperature study of the microwave spectrum, it was found that the gauche conformer is at least 80 cm−1 (229 cal/mol) more stable than the trans conformer. These results are compared to similar quantities in some corresponding molecules.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2021-05-19
    Description: Coral reefs in the Kiunga Marine National Reserve (KMNR) (40o 07’ E, 2o 00’ S) are located in a transition ecotone between the warmer East African coral reef bioregion to the south, and colder waters of the Somali Current to the north. The reefs have been monitored annually from 1998 to the present, documenting a range of ecosystem changes from large and small scale threats. Reefs in the area suffered ˜60% loss of coral cover due to mass bleaching in the 1998 El Niño event, and 25-40% loss of coral species at individual site levels. Recovery of coral community structure has been variable, with some reefs showing strong recovery, while others have declined further. A harmful algal bloom and coral disease in early 2002 further impacted these reefs, causing mass mortalities of fish and coral, and failure of coral recruitment in that year. Fishing impacts to the reserve are high, with a strong south-north decline in fish density due to easier access to the migrant and large fishing communities to the south of the reserve. Responsibility for management of the KMNR falls under multiple institutions, including the Kenya Wildlife Service, Fisheries and Forestry Departments, and the local council. Overlapping mandates, unclear relationships, limited information and understanding, and lack of resources have hampered effective management. The monitoring programme reported here is one aspect of new collaborative appro aches to coral reef and fisheries management, and has focused on improving the information and understanding of the biological and resource systems of the area. The ecosystem trends induced by larger scale threats and the south-north fish resource gradient caused by local use patterns will be analyzed in an attempt to develop sustainable management practices for the reserve.
    Description: Published
    Keywords: Fisheries management ; Overfishing ; Coral reefs ; Ecosystems ; Mass mortality
    Repository Name: AquaDocs
    Type: Book Section , Refereed
    Format: pp.1381-1390
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