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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 51 (1979), S. 145-162 
    ISSN: 1432-2234
    Keywords: Transition metal compounds ; Adsorbate systems ; Extended CNDO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An extended CNDO formalism for the treatment of large transition metal cluster systems is presented. After a detailed discussion of parametrization it is applied to a family of compounds, namely to Co(CO) 4 − , Co2(CO)8, Co4(CO)12, Mn2(CO)10. The results can be interpreted in the light of simple electron counting rules and additionally allow detailed insight in bonding capabilities of large metal cluster systems. Bridged and unbridged clusters are compared and the results are extrapolated to surface systems. In the case of Co4(CO)12 two possible stereoisomers of symmetryC 3v andT d are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 57 (1980), S. 181-207 
    ISSN: 1432-2234
    Keywords: Transition metal compounds ; Multiple metal-metal bonds ; Extended CNDO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A recently developed extension of the CNDO-method is used to study the electronic structure of a number of binuclear transition metal carbonyls and carboxylates with fourfold or quasi-fourfold symmetry. The results are compared to those available from nonempirical calculations. Special attention is paid to the nature of the metal-metal bond. Connections with qualitative MO-considerations allow a fairly general discussion of metal-metal bonding in binuclear transition metal complexes with basic fourfold symmetry. A few, up to now unknown, but possibly existing, complexes are considered.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European archives of psychiatry and clinical neuroscience 222 (1976), S. 177-190 
    ISSN: 1433-8491
    Keywords: Doppler Sonography ; Identification of Neck Arteries ; Carotid Arteries ; Vertebral Artery ; Screening of Stenoses ; Doppler ; Sonographie ; Unterscheidung der Halsarterien ; Karotiden ; Vertebralarterien ; Verschluß und Stenose ; Unterscheidung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 300 Gesunden und Patienten ohne stenosierende Gefäßerkrankung wird gezeigt, daß durch die direktionelle Doppler-Sonographie mit geringem Zeitaufwand die Differenzierung und damit die direkte selektive Beschallung aller extrakraniellen Hirnarterien möglich ist. Im Normalfall sind die Aa. carotis communis, interna, externa und die A. vertebralis bereits durch ihre Pulskurvencharakteristika unterscheidbar. Diese Unterschiede werden auch durch die akustische Pulswiedergabe deutlich. Im pathologischen Fall wird die zuverlässige Differenzierung der Arterien insbesondere im Bereich der Karotisbifurkation, durch Kompression von Ästen der A. carotis externa notwendig. Entsprechend den haemodynamischen Gesetzen ändert sich die Strömungsgeschwindigkeit durch eine solche Änderung des peripheren Widerstandes. Die Auswirkungen dieser Widerstandsänderungen auf die Dopplerpulskurven werden zuerst am Modell der A. radialis, dann für die Halsarterien gezeigt. Grundlage der Unterscheidung der Halsarterien ist die Änderung der Pulskurven einzelner Externaäste durch selektive Kompression. Die Unterscheidung arterieller und venöser Gefäße wird besprochen. Die Unterscheidung der Halsgefäße ermöglicht die Differentialdiagnose zwischen Verschlüssen und hochgradigen Stenosen und die Lokalisation dieser Prozesse.
    Notes: Summary The Doppler examination of the neck arteries of 300 subjects showed, that the common, internal and external carotid arteries and the vertebral artery can reliably be distinguished on the basis of their different pulse-curve characteristics. In addition, the compression of branches of the external carotid artery can identify these vessels in particular in pathologic cases. The details of the normal flow profiles and their changes by the compression tests are described. Compression of the vessels leads to a rise in flow resistance. The effect of such a rise in resistance is demonstrated using the A. radialis as a model. The identification of the neck arteries provides the basis for diagnostic examination and localization of their stenoses and occlusions.
    Type of Medium: Electronic Resource
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