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  • 1
    ISSN: 1572-8927
    Keywords: Quadrupole relaxation ; 23Na+,87Rb+, and14N NMR ; ion-solvent interaction ; asymmetry effects ; preferential solvation ; acetonitrile-water mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nuclear magnetic relaxation rates of23Na+,87Rb+, and14N in acetonitrile-water mixtures have been measured over the complete mixture range. The interaction of the quadrupole moment of ionic nuclei with electric field gradients is an excellent short ranged probe for the direct neighborhood of ions in solution. Thus the23Na+ and87Rb+ relaxation contains information about dynamics composition and symmetry of the inner solvation sphere in the mixed solvent. It was found that the relaxation rate of both ionic nuclei has an unexpected marked maximum in the acetonitrile (AN) rich region. The14N and2H relaxation rates of the solvent molecules revealed that the maximum could not be explained by dynamic effects. Further experimental results showed that it is caused by local symmetry changes. By measuring 1/T1 of the cationic nuclei in AN-H2O and AN-D2O it was possible for the first time to separate quantitatively asymmetry effects from selective solvation effects. It turned out that both cations are strongly preferentially hydrated. Comparison of the results of two approaches for the evaluation of the D2O-H2O isotope effect led to interesting hints concerning the location of the electric point dipole in acetonitrile molecules having contact with cations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 356 (1982), S. 141-149 
    ISSN: 1435-2451
    Keywords: Acute pancreatitis ; Computed tomography ; Ultrasound ; Operative treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die „stadiengerechte Therapie” der akuten Pankreatitis, die jedem Schweregrad der Erkrankung angemessen ist, besteht neben der konservativen Basistherapie und Intensivmedizin im richtigen Einsatz operativer Maßnahmen. Voraussetzung dafür ist die frühe Diagnose und Beurteilung des Schweregrades der akuten Pankreatitis. Neben klinischen und klinisch-chemischen Befunden und dem Verlauf unter konservativer Therapie ermöglichen die Sonographie und die Computer-Tomographie eine bessere Beurteilung der jeweiligen Verlaufsform. Die für die Klinik der Erkrankung so wichtigen morphologischen Veränderungen der Bauchspeicheldrüse und ihrer Umgebung werden durch diese neuartigen Untersuchungsmethoden transparenter. Wäh rend bei der leichten Pankreatitis die Sonographie als erstes morphologisches Untersuchungsverfahren eingesetzt wird, besteht bei den schweren Verlaufsformen eine klassische Indikation zur Computer-Tomographie. Durch Einsatz von Sonographie und Computer-Tomographie läßt sich die Indikation zur frühzeitigen oder verzögerten Operation der hämorrhagisch-nekrotisierenden Pankreatitis, die bisher nach klinischen Kriterien erfolgte, in den meisten Fällen exakter stellen.
    Notes: Summary Adequate stage-depending therapy of acute pancreatitis includes basic conservative treatment, intensive care measurements, and operative interventions depending on the grade of severity. Prerequisites are early diagnosis and accurate clinical assessment of the stage of severity. Beside clinical and laboratory findings, as well as the development of acute pancreatitis under conservative treatment, sonography and computed tomography allow a better prediction of the underlying morphological changes, thus leading to an exact staging of the patient's individual situation. Sonography is regarded a screening procedure of high accuracy in mild forms of acute pancreatitis. Computed tomography is the method of choice in all severe forms of this disease. The indication for immediate or delayed operative treatment of hemorrhagic necrotising pancreatitis, heretofore depending on clinical findings solely, is supported by these new-invasive diagnostic modalities.
    Type of Medium: Electronic Resource
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