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  • 1
    Publication Date: 2011-08-24
    Description: Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this bone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PYD) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short (14-day) and long (119-day) bed-rest studies. During space flight, the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden.
    Keywords: Life Sciences (General)
    Type: The Journal of clinical endocrinology and metabolism (ISSN 0021-972X); Volume 83; 10; 3584-91
    Format: text
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  • 2
    Publication Date: 2011-08-24
    Description: Magnetic resonance imaging (MRI), histomorphometry and electron microscopy of muscle demonstrate that long-term exposure to actual or simulated weightlessness (including head down bed rest) leads to decreased volume of antigravity muscles in mammals. In muscles interbundle space is occupied by the connective tissue. Rat studies show that hindlimb unloading induces muscle fiber atrophy along with increase in muscle non-fiber connective tissue compartment. Beside that, usually 20% of the muscle fiber volume is comprised by non-contractile (non-myofibrillar) compartment. The aim of the present study was to compare changes in muscle volume, and in muscle fiber size with alterations in myofibrillar apparatus, and in connective tissue compartment in human m. soleus under conditions of 120 day long head down bed rest (HDBR).
    Keywords: Aerospace Medicine
    Type: Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology (ISSN 1077-9248); Volume 8; 1; P71-2
    Format: text
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 46 (1985), S. 1025-1029 
    ISSN: 0022-3697
    Keywords: EXAFS ; layer system ; partial disorder ; vacancies
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Solid State Communications 51 (1984), S. 259-262 
    ISSN: 0038-1098
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 13 (1975), S. 370-381 
    ISSN: 1741-0444
    Keywords: E.C.G. ; Arrhythmia ; Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Un nouveau programme d'ordinateur a été mis au point pour extraire les paramètres pertinents de l'électrocardiogramme d'adulte, afin d'interpréter l'arythmie automatique dans le cadre de l'analyse routinière. Aucun programme d'interprétation ne serait acceptable par les cardiologues sans une interprétation de rythme conjuguée à l'interprétation de morphologie, même si, dans une situation de routine, l'interprétation du rythme n'est pas aussi rigoureuse que dans les milieux ambiants du contrôle. Le programme de mesure fonctionne simultanément sur les lignesX, Y etZ du système Frank modifié. Les caractéristiques considérées de l'e.c.g. sont le train d'ondesQRS, les caractéristiques morphologiquesQRS et le train d'ondesP. Bien que le programme fasse toujours l'objet d'une évaluation, plusieurs résultats importants ont été obtenus à partir de l'analyse d'une quantité donnée d'e.c.g. Le mode utilisant la détectionQRS donne une erreur totale de 0,79% par l'addition du nombre de complexesQRS omis et des fausses détections. Le système est apte à réaliser une détection parfaite sur 95% des e.c.g. analysés. La performance sur le classementQRS est de 1,15% des formes d'ondes mal classées, avec un autre taux de 0.67% qui demeure indéfini par suite de la limitation de la capacité de mesure de l'algorithme utilisé; 89·7% des tracés sont complètement exempts d'erreur. L'identification du train d'ondeP est réalisée avec un succès notable. Dans le mode ‘Battement à Battement’, 92·5% des ondesP pour le programme sont présentes dans les tracés pendant la production de 2·2% de phénomènes étrangers.
    Abstract: Zusammenfassung Zum Auszug der entsprechenden Parameter aus den e.k.g.s von Erwachsenen wurde ein neues Rechnerprogramm entwickelt, um automatische Arrhythmien bei der routinemäßigen Untersuchung interpretieren zu können. Ohne Rhythmusinterpretation, die mit der morphologischen Interpretation gekoppelt ist, sollten die Kardiologen keine Interpretations-programme annehmen, selbst wenn die Rhythmusinterpretation bei Routineuntersuchungen nicht so streng ist wie bei der Überwachung. Das Meßprogramm läßt sich gleichzeitig auf denX-,Y- andZ-Abeleitungen des modifizierten Frank-Systems einsetzen. Die berücksichtigten e.k.g.-merkmale sind die WellenserieQRS, die morphologischen WerteQRS und dieP-Wellenserie. Obgleich das Programm noch nicht voll bewertet ist, erhielt man mehrere wichtige Ergebnisse, die auf der Analyse einer bestimmten Anzahl von e.k.g.s beruhen. Bei derQRS-Suche ergibt sich ein Fehler von insgesamt 0·79%, wenn man die Anzahl der ausgelassenenQRS-Komplexe und der falschen Entdeckungen zusammenzählt. Das System kann bei über 95% der analysierten e.k.g.s eine perfekte Entdeckung herbeiführen. Die Leistung bei derQRS-Klassifikation beträgt 1·15% der falsch klassifizierten Wellenformen, mit zusätzlichen 0·67%, die'durch die beschränkte Meßfähigkeit des verwendeten Algorithmus nicht definiert werden. 89·7% der Messungen sind völlig fehlerfrei. Die Identifizierung derP-Wellenserie erreicht man mit weitgehendem Erfolg. Auf der Grundlage von Pulsschlag zu Pulsschlag findet das Programm 92·5% derP-Wellen, während Außeneinwirkungen in Höhe von 2·2% entstehen.
    Notes: Abstract A new computer program has been developed to extract pertinent parameters from the adult e.c.g., for the purpose of automatic arrhythmia interpretation in the context of routine analysis. No interpretation program would be acceptable by cardiologists without a rhythm interpretation coupled to the morphology interpretation even if in routine situations rhythm interpretation is not as stringent as in monitoring environments. The measurements program operates simultaneously on the X, Y and Z leads of the modified Frank system. The e.c.g. features considered are the QRS wavetrain, the QRS morphological characteristics and the P wavetrain. Although the program is still under evaluation, a number of important results have been obtained based on the analysis of a given population of e.c.g.s. The performance on QRS detection gives a total error of 0·79% when adding the number of omitted QRS complexes and false det ections, and the system is able to realise perfect detection on over 95% of the e.c.g.s analysed. The performance on QRS classification is 1·85% of misclassified waveforms, with a further 0·67% which remains undefined due to the limitation in measurement capability of the algorithm used; 89·7% of the tracings are completely error free. The identification of the P wavetrain is achieved with a good degree of success. On a beat-to-beat basis, the program finds 92·5% of the P waves present in the tracings while generating 2·2% extraneous events. However, only 53% of the tracings are error free.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 31 (1993), S. 545-556 
    ISSN: 1741-0444
    Keywords: Cardiac ; Electrical ; Mathematical ; Network ; Retrograde ; and anterograde conduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A model is proposed to explain mechanisms of propagation in the atrioventricular (AV) node of the heart. The model is based on a simplified twodimensional anatomic description of the central node region and on a bidomain tissue model for the propagation. The central region is described as a three-tissue compartment model: The proximal tissue composed of ANL cells, the central tissue composed of N cells and the distal tissue composed of NH cells. The central N region is outlined as an unexcitable gap by forcing these cells to behave as depressed cells for which the fast ionic currents are inactivated. This model has allowed the authors to test the electrotonic gap hypothesis, which explains the time-delay properties of the AV node. Typical conduction curves have been obtained, as well as common patterns of Wenckebach blocks. Premature stimulus and resulting mapping of cell responses in the N region of the model show typical membrane potential dissociation in two components. The model has also been submitted to several programmed stimulation protocols in documented anterograde and retrograde conduction. The results show that the model is valid and covers several well known dynamic properties of the AV node.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 11 (1973), S. 326-335 
    ISSN: 1741-0444
    Keywords: Dilation ; arteries ; viscoelasticity ; plethysmograph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Un instrument a été conçu et fabriqué pour le mesuragein vivo des changements instantanés (de phase) au diamètre des artères. L'enregistrement continu de cette dimension des vaisseaux sanguins, quand il est relevé en même temps que la tension artérielle, peut être utilisé pour évaluer les propriétés visco-élastiques de la paroi artérielle.
    Abstract: Zusammenfassung Entwurf und Konstruktion eines Instrumentes für die in-vivo Messung augenblicklicher (phasischer) Arteriendurchmesseränderungen werden beschrieben. Die fortlaufende Aufzeichnung dieser Blutgefässabmessung kann, wenn sie gleichzeitig mit dem Blutdruck registriertwird, zur Abschätzung der viskoelastischen Eigenschaften der Arterienwand benutzt werden.
    Notes: Abstract An instrument has been designed and constructed for thein-vivo measurement of instantaneous (phasic) diameter changes of arteries. The continuous record of this blood-vessel dimension, when recorded simultaneously with blood pressure, may be used to estimate the viscoelastic properties of the arterial wall.
    Type of Medium: Electronic Resource
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  • 8
  • 9
    Publication Date: 2018-01-01
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 10
    Publication Date: 2017-10-13
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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