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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2598-2604 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy surface points computed from variants of density functional theory (DFT) are used to calculate directly the anharmonic vibrational frequencies of H2O, Cl−H2O, and (H2O)2. The method is an adaptation to DFT of a recent algorithm for direct calculations of anharmonic vibrational frequencies using ab initio electronic structure codes. The DFT calculations are performed using the BLYP and the B3LYP functionals and the results are compared with experiment, and also with those calculated directly from a potential energy surface obtained using ab initio Möller-Plesset second–order perturbation theory (MP2). The direct calculation of the vibrational states from the potential energy points is performed using the correlation-corrected vibrational self-consistent field (CC-VSCF) method. This method includes anharmonicity and correlations between different vibrational modes. The accuracy of this method is examined and it is shown that for the experimentally measured transitions the errors in the CC-VSCF calculations are much less than the errors due to the potential energy surface. By comparison with the experimentally measured frequencies the CC-VSCF method thus provides a test for the quality of the potential energy surfaces. The results obtained with the B3LYP functional, in contrast to those of the BLYP functional, are of comparable quality to those obtained with MP2. The B3LYP anharmonic frequencies are in good agreement with experiment, showing this DFT method describes well the anharmonic part of the potential energy surface. The BLYP results systematically underestimate both the harmonic and anharmonic frequencies and indicate that using this functional for the description of hydrogen-bonded systems may cause significant errors. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8763-8768 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method for the treatment of correlation effects between modes in vibrational self-consistent-field (VSCF) calculations is introduced. It is based upon using a partially separable form for the wave function. As a result, some of the modes are treated as mutually fully correlated, while the rest are separable. The modes which are explicitly coupled together in the calculation are chosen on physical grounds. Trial calculations are performed upon H2O, H3O+, and CH3NH2 and indicate that the method performs well. The agreement with experiment for the explicitly coupled modes is improved when compared to both the vibrational self-consistent-field method and its correlation-corrected extension. When interfaced with an electronic structure code this method opens the way for the accurate first-principles prediction of vibrational frequencies of strongly coupled modes. If only a few modes are mutually strongly coupled, the method has a very favorable scaling with system size, as does VSCF itself. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-0563
    Keywords: Schlüsselwörter Periduralanalgesie • Urologie • Postoperative Schmerztherapie • Nebenwirkungen • Komplikationen ; Key words Epidural analgesia • Urology • Post-operative analgesia • Side effects • Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The benefits of epidural analgesia are well known, but it is not well understood which types of urologic surgery benefit most from epidural analgesia. In this study, the effects and side effects of prolonged epidural analgesia are prospectively examined and analysed on 172 adult patients in three different operation groups. An epidural infusion of local anaesthetic combined with an opioid and adrenaline was given for a period of ¶5–7 days. There was no difference between the groups with respect to the effectiveness of the analgesia and patients' perception of the treatment. Mobilization differed, as expected, between the groups, however even after the most major surgery (e. g. cystectomy with bladder substitution), mobilization was impressively unproblematic. Retarded return of regular intestinal function after the transperitoneal operation and partly after lumbotomy compared with the extraperitoneal operation depended on which operation was performed and the amount of analgesia given. The side effects such as sedation, nausea and pruritis were conditional partly on the opiate and partly on the intervention. Up to 11 % showed slight muscular weakness of the lower limbs as a specific side effect of the local anaesthetic. Complications: One patient died of cerebral hypoxy due to an initially undetected subdural catheter placement complicated by severe pre-existent carotid stenosis. In four patients, the epidural analgesia had to be stopped because of catheter migration. There was no clinical evidence of hematoma, abscess or permanent neurological damage. Epidural analgesia works well in terms of analgesia, mobilization and patient satisfaction, bearing in mind the potential side effects and complications. It can be recommended for lumbotomy and long transperitoneal operations however not for extraperitoneal interventions in the lower abdomen such as radical prostatectomy.
    Notes: Zusammenfassung Während die günstigen Effekte der kontinuierlichen Periduralanalgesie (PDA) hinlänglich bekannt sind, stellt sich die Frage, bei welchen operativen Eingriffen die Indikation zu diesem Verfahren zu stellen ist und mit welchen Nebenwirkungen und Komplikationen zu rechnen ist. Hierfür untersuchten wir die Unterschiede der PDA in Wirkung und Nebenwirkungen prospektiv an 172 erwachsenen Patienten in Abhängigkeit vom durchgeführten operativen Eingriff. Verwendung fand eine Kombinationslösung, welche für die Dauer von 5–7 Tagen kontinuierlich appliziert wurde. Keine Unterschiede fanden sich in bezug auf die ausgezeichnete Analgesie und Patientenzufriedenheit. Die Mobilisation war je nach vorangegangenem Eingriff erwartungsgemäß unterschiedlich, auch nach maximalem operativen Trauma jedoch beeindruckend problemlos. Ein verzögertes Einsetzen einer geregelten Darmfunktion nach transperitonealem Eingriff und z. T. auch nach Lumbotomie gegenüber extraperitonealem Unterbaucheingriff ist eingriffsbedingt und z. T. dosisabhängig. Nebenwirkungen wie Sedierung, Nausea und Juckreiz waren geringgradig sehr häufig zu finden, eine strenge Dosiskorrelation war jedoch nicht zu erkennen. Z. T. dürften die Nebenwirkungen eingriffsbedingt sein. Bis zu 11 % der Patienten berichteten anfänglich über eine leichte Muskelschwäche der Beine. Komplikationen: 1 Patient verstarb nach initial unbemerkter intraduraler Katheterlage durch eine cerebrale Hypoxie auf dem Boden einer vorbestehenden gravierenden cerebralen Minderperfusion. Abbruch der PDA bei 4 Patienten wegen falscher Katheterlage. Hämatome, Abszesse oder bleibende neurologische Schäden wurden nicht beobachtet. Die PDA ist in bezug auf Analgesie, Mobilisation und Patientenzufriedenheit ein bewährtes Verfahren, sofern die möglichen Nebenwirkungen und Komplikationen sorgfältig im Auge behalten werden. Das Verfahren kann für große Lumbotomien und ausgedehnte transabdominelle Eingriffe empfohlen werden, nicht jedoch für extraperitoneale Unterbaucheingriffe, wie die radikale Prostatektomie.
    Type of Medium: Electronic Resource
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