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  • 1
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (36 Seiten, 1.81 MB) , Diagramme
    Edition: Als Manuskript gedruckt
    Series Statement: Wissenschaftliche Berichte / Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 6961
    DDC: 520
    Language: English
    Note: Literaturverzeichnis: Seite 29-30 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Zusammenfassungen: Deutsch, Englisch
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4805-4816 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoisomerization of diphenylbutadiene was studied by picosecond absorption spectroscopy over wide pressure and temperature ranges in liquid and supercritical alkanes, CO2, SF6, and He. The reaction shows typical features of a thermal unimolecular reaction on the S1 potential energy surface. The rate can be expressed by a combination of standard unimolecular rate theory and Kramers–Smoluchowski theory. However, multidimensional behavior manifests itself in the transition to the gas phase low pressure range as well as to the high density Kramers–Smoluchowski range: in the former case, the low pressure limit of a unimolecular reaction of the polyatomic molecule is approached; in the latter case, the effective imaginary barrier frequency shows a marked apparent temperature dependence. The experiments also suggest contributions of reactant–solvent cluster interactions, which modify the barrier height even in nonpolar solvents.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2393-2404 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The pressure and temperature dependence of the photoisomerization rate coefficient of trans-stilbene in the S1 state have been measured in the solvents C2H6, C3H8, C4H10, Xe, Co2, SF6, and CHF3. At constant temperature, the pressure dependences up to 6 kbar can be well represented by the Kramers–Smoluchowski model. The comparison of results in different solvents clearly indicates the importance of reactant–solvent cluster formation modifying the height and imaginary frequency of the barrier. The change of the temperature dependence with pressure points towards a multidimensional barrier of nonseparable character. Multidimensional barrier effects manifest themselves most clearly via the temperature dependence of the rate coefficient in the Kramers–Smoluchowski limit.
    Type of Medium: Electronic Resource
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  • 4
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    Wiesbaden : Periodicals Archive Online (PAO)
    Geographische Zeitschrift. 58:3 (1970:Okt.) 214 
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 299 (1990), S. 60-65 
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 292 (1990), S. 595-618 
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1435-1285
    Keywords: Key words Syncope – elderly – electrophysiology ; Schlüsselwörter Synkope – geriatrische Patienten – Elektrophysiologie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die invasive elektrophysiologische Untersuchung hat bei der Abklärung von Synkopen unklarer Genese einen hohen Stellenwert. Im höheren Lebensalter steht dem Wunsch nach einer richtungsweisenden Diagnostik eine gewisse Zurückhaltung gegenüber invasiven, potentiell komplikationsreichen Untersuchungen entgegen. Durch einen altersspezifischen Vergleich von diagnostischem Zugewinn, Komplikationsraten und elektrophysiologischen Parametern sollte in der vorliegenden Arbeit geklärt werden, ob die invasive elektrophysiologische Untersuchung auch bei älteren Patienten empfohlen werden kann und ob altersabhängige Schwankungen von Leitungs- und Refraktärmessungen berücksichtigt werden müssen. Invasive elektrophysiologische Untersuchungen wurden bei 96 Patienten im Alter zwischen 70 und 80 Jahren sowie bei 21 über Achtzigjährigen durchgeführt. Als Vergleichsgruppe dienten 65 Patienten mit einem Lebensalter unter 40 Jahren. Mit zunehmendem Lebensalter stieg die Wahrscheinlichkeit eines richtungsweisenden Befundes in der elektrophysiologischen Untersuchung von etwa 20% bei jüngeren auf 54% bei den ältesten untersuchten Patienten. Komplikationen waren mehrheitlich von untergeordneter klinischer Bedeutung, die Komplikationsraten unterschieden sich nicht signifikant zwischen den Altersgruppen. Auch zeigten die erhobenen Refraktär- und Leitungsparameter keine eindeutige Altersabhängigkeit. Gerade beim älteren Menschen erweist sich das Verhältnis zwischen diagnostischem Zugewinn und Komplikationsrate der invasiven elektrophysiologischen Untersuchung zur Synkopenabklärung als besonders günstig. Geltende Normalwerte für Refraktär- und Leitungsparameter scheinen altersunabhängig Gültigkeit zu besitzen.
    Notes: Summary Invasive electrophysiologic study (EPS) is an important tool in the assessment of patients with unexplained syncope. Especially in the elderly, the need for a complete diagnostic work-up is counterbalanced by the fear of complications associated with invasive procedures. Thus, the present study specifically addressed the question whether the risk/benefit ratio of EPS in geriatric patients with unexplained syncope justifies this invasive procedure. An invasive EPS was performed in 96 patients between 70 and 80 years and 21 patients older than 80 years. The control group consisted of 65 patients younger than 40 years. With increasing age, the diagnostic yield of EPS also increased (positive EPS finding in 20% of the control group and in 54% of the oldest patients). The majority of complications were of minor clinical significance and no significant differences were found between the three groups. Finally, no age-related difference in measured standard electrophysiological parameters was evident. Due to the high diagnostic value and the low complication rate, EPS can be recommended in elderly patients with unexplained syncope. An age-specific standardization of electrophysiologic parameters, measured during EPS, does not seem to be required.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Herzschrittmachertherapie & Elektrophysiologie 10 (1999), S. S029 
    ISSN: 1435-1544
    Keywords: Key words Atrial fibrillation – catheder ablation – wavelength – reentry ; Schlüsselwörter Vorhofflimmern – Katherablation – Wellenlänge – kreisende Erregungen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Hintergrund: Obwohl die Pathophysiologie von Vorhofflimmern durch eine Reihe grundlegender, fast schon historischer Arbeiten weitgehend aufgeklärt schien, zwingen neue Erkenntnisse zu einer Modifikation gängiger Konzepte. Studienziel: Durch die vorliegende Übersicht soll die aktuelle Datenlage in das System etablierter Hypothesen und Konzepte integriert werden. Methoden: Analysiert wurde die verfügbare Literatur seit Anfang des Jahrhunderts bis hin zu aktuellen, auch eigenen Befunden. Ergebnisse: Basierend auf den Befunden von Garrey sowie von Moe und Abildskov galt Vorhofflimmern bislang als der Prototyp einer durch multiple, zufällig sich etablierende Kreiserregungen bedingte Rhythmusstörung, deren Stabilität von der Anzahl simultan aktivierter Erregungskreise abhängt. Lokale Refraktär- und Leitungseigenschaften sollen die Größe individueller Erregungskreise festlegen, wobei sich diese Hypothese zwar schlüssig für die Refraktärzeit, aber bislang kaum für die Leitungsgeschwindigkeit belegen läßt. Die Zufälligkeit im Aktivierungsmuster multipler kreisender Erregungen wird durch die dominierende Rolle des linken Vorhofs für die Aufrechterhaltung von Vorhofflimmern in Frage gestellt, ebenso durch eine erst jüngst beschriebene, räumliche und zeitliche Periodizität der elektrischen Aktivierung. Schließlich belegen die Erfahrungen mit ablativen Verfahren, daß auch fokales oder zumindest fokal induziertes Vorhofflimmern klinisch eine Rolle spielt. Schlußfolgerungen: Aufgrund neuerer Erkenntnisse müssen die Vorstellungen zur Pathophysiologie von Vorhofflimmern zwar nicht gänzlich revidiert, aber doch erheblich modifiziert werden.
    Notes: Background: Although several classical studies seemed to provide clear ideas on the pathophysiology of atrial fibrillation, current concepts have to be modified on the basis of more recent findings. Aims of the study: The present review is an attempt to integrate current knowledge into the system of established hypotheses and concepts. Methods: The review is based on the available literature from the beginning of this century to the present. Results: Based on the findings of Garrey and of Moe and Abildskov, atrial fibrillation has been considered as the prototype of an arrhythmia being caused by multiple, random reentrant circuits, the number of which would determine the stability of the reentrant process. Local refractory and conduction properties would determine the size of individual circuits, a hypothesis quite convincing with respect to refractoriness, but so far hard to prove with respect to conduction. Atrial fibrillation as a random phenomenon is questioned not only by the dominat role of the left atrium for the maintenance of the arrhythmia, but also by most recent data demonstrating a spatio-temporal periodicity in activation patterns. Finally, ablation studies have provided convincing evidence that there is a subset of patients with focal or at least focally induced atrial fibrillation. Conclusions: More recent insights into the pathophysiology of atrial fibrillation do not imply a complete reappraisal of current ideas and concepts, but definitely a thorough revision.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2013-11-27
    Description: Aims To provide a nationwide survey (and reference for the future) on cardiac electrophysiologists, types and numbers of invasive electrophysiological procedures, and training opportunities in 2010. Methods and results German cardiology centres performing invasive electrophysiology were identified from quality reports and contacted to fill a questionnaire. A majority of 122 centres (65%) responded. Electrophysiology (ablation procedures and device therapy) was mainly part of a cardiology department (82%), and only in 9% independent (own budget). In only 58% of the centres, (at least) two physicians were present during catheter ablations. Although in 2010, women represented 59.4% of physicians 〈35 years old, only 26% of physicians in electrophysiology training were female. In total, 33 420 catheter ablations were performed with a median number of 180 per centre. Atrial fibrillation (AF) was the most common arrhythmia invasively treated (35%). At least 50 AF ablations were performed in 53% of the centres. Of the centres performing AF ablations, consecutive left atrial arrhythmias were treated by catheter ablation only in 75%, and only 44% had in-house surgical backup. Only one-fourth of the 122 centres fulfilled all requirements for training centre accreditation according to the European Heart Rhythm Association and the German Cardiac Society. Conclusion The results indicate a high number of electrophysiology centres and procedures in Germany. Atrial fibrillation was the most common arrhythmia invasively treated. An increasing demand for catheter ablation is likely, but training opportunities are limited. Women are clearly underrepresented. A co-operation of higher and lower volume electrophysiology centres may be necessary for training purposes.
    Print ISSN: 1099-5129
    Electronic ISSN: 1532-2092
    Topics: Medicine
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