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  • 1
    ISSN: 1572-8757
    Keywords: coalbed methane ; coal (porous structure, micropores) ; adsorption (of xenon, carbon dioxide, methane) ; Xe-129 NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An experimental and theoretical study of adsorption and diffusion of carbon dioxide and methane in coals of widely varying rank was carried out. Low pressures adsorption isotherms of CO2 were obtained and analyzed using Dubinin's theory of volume filling of micropores. High-pressure adsorption isotherms of CH4 were obtained and analyzed using tracer pulse chromatography in conjunction with an appropriate adsorption/diffusion model. A preliminary129Xe NMR analysis of chemical shifts experienced by xenon atoms in particles of different sizes is also reported. The heretofore undocumented and/or underestimated effects of activated diffusion of CO2 at 273–298 K complicate the elucidation of the true microporous structure of coals, especially its dependence on coal rank. Activated diffusion of both CO2 and methane at room temperature does not allow reliable estimates of coalbed gas content to be made. A model of an interconnected network of pores which includes randomly distributed, numerous and ultramicroporous constrictions (at any size scale) is consistent with all these experimental and theoretical findings.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Tachyarrhythmie ; Kardioverter Defibrillator ; Psychogene Triggerung ; Emotional-kognitive Faktoren ; Key words Tachyarrhythmia ; Implantable cardioverter defibrillator ; Emotional stress ; Psychic arousal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Tachyarrhytmias often occur during increased emotional arousal or mental excitation. The implantable cardioverter defibrillator (ICD) allows the exact documentation of arrhythmic episodes and their time of onset. Therefore, the type of arrhythmia can be differentiated as well as the circumstances surrounding the event. These features allow the assessment of possible psychic arrhythmogenic factors in the natural environment. We analyzed the ICD-protocols of three male patients (in ages between 60 and 68), whose devices had successfully terminated a ventricular tachycardia and compared the onset of the episodes with the patients' detailed descriptions of the corresponding life situations. The analysis of the circumstances at the time of arrhythmia-onset revealed a relationship between the occurrence of life-threatening arrhythmias in natural environment and emotional stress. The stressors could be defined as situations of increased vulnerability leading to sympathetic excitation. The induction of tachyarrhythmia was promoted in case 1 by acute psychic distress (public speaking), by the increasing panic-attack-like vicious circle of the cognitive anticipation of an unfavorable outcome (case 2), and an adverse anger reaction superimposed on persistent feelings of help- and hopelessness (case 3). These findings are in line with several experimental and epidemiological studies providing evidence for a relationship between psychic arousal and the induction of tachyarrhythmias. The knowledge of emotional and mental factors that function as a trigger for arrhythmias may lead to new therapeutic approaches in the prevention of sudden cardiac death.
    Notes: Zusammenfassung Tachyarrhythmien treten häufig während erhöhter psychischer Erregung auf. Bei Patienten, bei denen ein Kardioverter Defibrillator (ICD) implantiert wurde, lassen sich arrhythmische Episoden und deren Onset-Zeitpunkt exakt aufzeichnen und erlauben so einerseits die Differenzierung der aufgetretenen Rhythmusstörung und andererseits eine detailliertere Analyse der situativen Umstände und möglicher an der Auslösung beteiligter psychischer Komponenten. In der vorliegenden einzelfallbezogenen Studie wurden bei 3 männlichen Patienten im Alter zwischen 60 und 68 Jahren, bei denen der ICD erfolgreich eine ventrikuläre Tachykardie terminiert hatte, die ICD-Protokolle und die damit korrespondierenden Patientenaussagen analysiert. Die Analyse der akuten Onset-Bedingungen konnte ausgeprägte Zusammenhänge zwischen lebensbedrohlichen Herzrhythmusstörungen in natürlicher Umgebung und emotionalen Stressoren aufdecken. Als Stressoren wurden unterschieden eine vulnerable Situation, die eine psychogene Triggerung maligner Arrhythmien bewirkte (Fall 1); eine Panikepisoden-ähnliche Erwartungsspannung (Fall 2) sowie eine aversive Ärgerreaktion, die auf dem Boden eines andauernden Zustandes von Hilf- und Ausweglosigkeit (Fall 3) einen besonders potenten sympathiko-exzitatorischen Stimulus darstellt. Dieses Ergebnis deckt sich mit einer Reihe von laborexperimentellen und epidemiologischen Studien, die einen Zusammenhang zwischen psychischer Erregung und der Entstehung von Tachyarrhythmien belegen. Die Berücksichtigung emotional-kognitiver Faktoren bei der Arrhythmogenese könnte ein Beitrag bei der Therapie zur Prävention des plötzlichen Herztodes werden.
    Type of Medium: Electronic Resource
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