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E. Matzat 《Mineralogy and Petrology》1972,18(4):312-316
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Eckhart Matzat 《Mineralogy and Petrology》1967,12(1):108-117
Zusammenfassung Die Kristallstruktur eines vonJ. A. Mandarino undS. J. Williams (1961) beschriebenen, bisher unbenannten Tellurminerals mit der Raumgruppe P 63/m und den Gitterkonstanten a0=9,41Å, c0=7,64Å wurde mit dreidimensionalen Patterson-, Fourier-und (F0–Fc)-Synthesen und einer Least-squares-Verfeinerung bestimmt und verfeinert. Unter Zugrundelegung einer halbquantitativen Mikrosondenanalyse wurde durch die Strukturbestimmung gezeigt, daß es sich um ein zeolithartiges Telluritmineral mit einem negativ geladenen Gerüst {Zn2[TeO3]3} handelt, das parallel [00.1] verlaufende, große offene Kanäle zeigt, die mit Kationen und H2O statistisch besetzt sind. Die Elementarzelle enthält zwei Formeleinheiten {(Zn,Fe)2[TeO3]3}Nax H2–x·yH2O. Je zwei über Flächen verknüpfte Sauerstoffkoordinationsoktaeder um (Zn,Fe) werden über Ecken mit TeO3-Pyramiden verknüpft und reihenförmig parallel [00.1] angeordnet. Diese Reihen werden untereinander über die dritte Ecke der TeO3-Pyramiden zu einem bienenwabenartigen Gerüst verbunden, dessen Kanäle einen Durchmesser von 8,28 Å besitzen.
Mit 3 Textabbildung
Von der mathematisch-Naturwissenschaftlichen Fakultät der Georg-August-Universität zu Göttingen im Februar 1967 angenommene Dissertationsschrift. 相似文献
Summary The crystal structure of an unnamed hexagonal tellurium mineral, described formerly byJ. A. Mandarino andS. J. Williams (1961) with space group P 63/m and lattice constants a0-9,41 Å, c0=7,64 Å has been determined and refined by 3-dimensional Patterson-, Fourier-, and (F0–Fe)-syntheses, and by leastsquares-refinement. Based on a semiquantitative electron microprobe analysis, the structure determination has shown that the described mineral is a zeolite-like tellurite with a negative charged framework {Zn2[TeO3]3} with large open channels running parallel [00.1], which are statistically occupied by cations and H2O. The unit cell contains two formula units {(Zn,Fe)2[TeO3]3} Nax H2–x·yH2O. Two oxygen octahedrons coordinating (Zn,Fe) share faces and are linked by TeO3-pyramids sharing corners, to form an array parallel [00.1]. These arrays are linked by the third corner of TeO3-pyramids and form a hexagonal honeycomb-like framework, the channels having a diameter of 8,28 Å.
Mit 3 Textabbildung
Von der mathematisch-Naturwissenschaftlichen Fakultät der Georg-August-Universität zu Göttingen im Februar 1967 angenommene Dissertationsschrift. 相似文献
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Oil-pollution monitoring at sea through beach bird surveying would undoubtedly benefit from a further standardisation of methods, enhancing the efficiency of data collection. In order to come up with useful recommendations, we evaluated various approaches of beached bird collection at the Belgian coast during seven winters (1993-1999). Data received in a passive way by one major rehabilitation centre were compared to the results of targeted beach surveys carried out at different scales by trained ornithologists: 'weekly' surveys - with a mean interval of 9 days - restricted to a fixed 16.7 km beach stretch, 'monthly' surveys over the entire coastline (62.1 km) and an annual 'international' survey in Belgium over the same distance at the end of February. Data collected through Belgian rehabilitation centres concern injured, living birds collected in a non-systematical way. Oil rates derived from these centres appear to be strongly biased to oiled auks and inshore bird species, and are hence of little use in assessing the extent of oil pollution at sea. The major asset of rehabilitation centres in terms of data collection seems to be their continuous warning function for events of mass mortality. Weekly surveys on a representative and large enough section rendered reliable data on oil rates, estimates of total number of bird victims, representation of various taxonomic groups and species-richness and were most sensitive in detecting events quickly (wrecks, oil-slicks, severe winter mortality, etc.). Monthly surveys gave comparable results, although they overlooked some important beaching events and demonstrated slightly higher oil rates, probably due to the higher chance to miss short-lasting wrecks of auks. Since the monthly surveys in Belgium were carried out by a network of volunteers and were spread over a larger beach section, they should be considered as best performing. Single 'international beached bird surveys' in February gave reliable data on total victim number (once the mean ratio between numbers in various months is known) and oil rate (provided a sufficiently large sample can be collected), but failed in tracking events. It is a particularly attractive approach because of its long tradition, resulting in invaluable long-term databases, and the uniformity in which these surveys are organised on a large scale. The minimal distance for a monthly survey amounts to 25-30 km (40-50% of Belgian coastline) up to 40 km (65%) in order to attain sound figures for oil rate and species-richness, respectively. These distances are primarily determined by the number of bird corpses that may be collected and are hence a function of beaching intensity and corpse detection rate. 相似文献
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