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1983 (3)

Digitale Medien

Chalcides and pnictides of group VIII transition metals: Far-infrared spectroscopic studies on compounds MX 2, MXY, and MY 2 with pyrite, marcasite, and arsenopyrite structure (1983)

Lutz, H. D. ; Schneider, G. ; Kliche, G.

Springer

Physics and chemistry of minerals 9 (1983), S. 109-114

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ISSN: 1432-2021

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Notizen: Abstract The far-infrared (FIR) spectra of pyrites, marcasites and loellingites, and arsenopyrites of the type MX 2, MY 2, and MXY with M=Fe, Co, Ru, Rh, Os, Ir X=S, Se, Te, and Y=P, As, and Sb have been studied, including group theoretical treatment of the phonon modes. The internal Y - Y and X - Y stretching modes, infrared (IR) allowed only in the case of the arsenopyrites, have been found to be in the range 440–490, 470–510, 450–490, 430–450 and 400–420 cm−1 for MP 2, MPS, MPSe, MAsS, and MSbS type compounds, respectively. From the obtained spectra intensity weighted mean phonon frequencies, i.e. central frequencies as defined by Plendl (1961), and mass weighted ones have been calculated and interpreted in terms of the strength of the MX and MY bonds, especially comparing 3d, 4d, and 5d transition metal compounds. Method of preparation and X-ray data of the chalcides and pnictides studied are also given.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00308366

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Digitale Medien

Morphometric and chronobiological studies on the dynamics of the nuclear envelope and the nucleolus during mitosis of the colorless phytoflagellatePolytoma papillatum (1983)

Gaffal, K. P. ; Wolf, K. W. ; Schneider, G. J.

Springer

Protoplasma 118 (1983), S. 19-35

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ISSN: 1615-6102

Schlagwort(e): Morphometry ; Mitosis ; Nuclear envelope ; Nucleolus ; Polytoma

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Quantitative electron microscopy of serial sections was used to study the cyclical changes in the nucleus ofPolytoma papillatum during its vegetative life cycle with special reference to mitosis. Particular attention was paid to the fluctuations in the nuclear volume, the nuclear envelope, and the nucleolus. Whereas a volumetric balance exists between the cell (100%) and the nucleus (ca. 8%) from early interphase to late anaphase, the nucleus-to-cell volume ratio is gradually reduced up to ca. 2% during telophase. This disproportion is gradually equalized during cytokinesis. The decrease in nuclear size is brought about by: (a) Constrictive abscission of hernia-like protrusions of the nucleus (“blebbing process”); (b) Ade novo production of membraneous septa across peripheral regions of the nucleus (“internal septation”). Just before or immediately after completion of this internal compartmentalization of the nucleus, the original envelope opens, releasing a portion of nucleoplasm into the cytoplasm (“membrane sluice process”); (c) Gaps in the nuclear envelope were occasionally found during telophase and may also permit nucleoplasm to leak out. Disorganization of the nucleolos, which is preceded by blending of its two major components (pars fibrosa, pars granulosa) starts at prophase via fragmentation. Subsequent dispersion continues until the nucleolus is more or less homogeneously distributed across the metaphase nucleus. During anaphase a good deal of the preexisting material recondenses around the separating chromosomes, but a considerable amount remains dispersed in the nucleoplasm and is extruded into the cytoplasm during nuclear volume reduction. Reorganization of the nucleolus occurs during telophase and early cytokinesis via further coalescence of the recondensed material and simultaneous reconstruction of the spatial separation of pars fibrosa and pars granulosa. Morphofunctional aspects of nucleo- and nucleologenesis are also discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01284743

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Digitale Medien

Determination of the capacity ratios of some fatty acid phenyl esters in supercritical carbon dioxide by supercritical fluid chromatography (SFC) (1983)

Wilsch, A. ; Schneider, G. M.

Springer

Fresenius' Zeitschrift für analytische Chemie 316 (1983), S. 265-267

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ISSN: 1618-2650

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Summary Capacity ratios k have been determined for phenyl myristate, phenyl palmitate and phenyl stearate from SFC experiments at 35 to 56° C and 85 to 190 bar, using supercritical CO2 as the mobile phase and Perisorb A and Perisorb RP8 as stationary phases. For the esters examined a rise in pressure from 90 to 190 bar produces a drop of k of at least one order of magnitude giving evidence of the rapidly increasing solvent power of supercritical CO2 with increasing density. At a constant CO2 density, k decreases with increasing temperature. The separation of the three esters was found to be the better the lower the pressure was.

Notizen: Zusammenfassung Es wurden die Kapazitätsverhältnisse k von Phenylmyristat, Phenylpalmitat und Phenylstearat aus fluid-chromatographischen Untersuchungen mit überkritischem CO2 als mobiler Phase und den stationären Phasen Perisorb A und Perisorb RP8 bestimmt. Die Messungen wurden bei Temperaturen von 35 bis 56° C und bei Drücken von 85 bis 190 bar durchgeführt. Die Kapazitätsverhältnisse der Probesubstanzen werden durch eine Druckerhöhung von 90 auf 190 bar um mindestens eine Größenordnung verringert; das zeigt, daß die Löslichkeit der untersuchten Ester in überkritischem CO2 stark mit steigender Dichte des CO2 zunimmt. Bei konstanter Dichte bewirkt eine Temperaturerhöhung eine Verkleinerung des Kapazitätsverhältnisses. Mit beiden stationären Phasen ist die Trennung der drei Ester bei niedrigeren Drücken besser als bei höheren Drücken.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00488199

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