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  • 1
    Digitale Medien
    Digitale Medien
    On the structure and stability of nanoscale materials: a two-dimensional model (1995)
    Springer
    The European physical journal 97 (1995), S. 503-510 
    Details
    ISSN: 1434-6036
    Schlagwort(e): 61.55.F
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have investigated numerically using the Metropolis Monte Carlo algorithm two-dimensional systems of about 3000 classical particles interacting via a Lennard-Jones potential and being subjected to periodic boundary conditions. In this model we consider metastable structures of small crystalline grains which are randomly oriented relative to each other and which are interconnected by a network of boundaries. The atomic structure within the grains being composed of about 500 atoms each is a nearly ideal triangular lattice. The network of boundaries however has a highly defective structure which is determined by the boundary conditions enforced by the crystalline grains. It is the objective of our work to develop a conceptually simple model for nanocrystalline materials, which can be used for a qualitative description of their complex properties. The main ingredient of the model is its property to relax into a metastable state consisting of intrinsically well ordered crystalline grains connected by a highly defective intergranular component. For that state we compute the static structure factor and the pair correlation function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01322431
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  • 2
    Digitale Medien
    Digitale Medien
    Das Verhalten einiger biochemischer Parameter bei der physischen Beanspruchung durch einen der physischen beanspruchung durch einen Langstreckenmarsch (1978)
    Springer
    International archives of occupational and environmental health 41 (1978), S. 103-115 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Physical Strain and Stress ; Long-distance March ; Catecholamines ; Glucocorticoids ; Cyclic Nucleotides ; Physische Belastung und Beanspruchung ; Langstreckenmarsch ; Catecholamine ; Glucocorticoide ; cylische Nukleotide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Beanspruchung in Arbeit und Beruf und ihre Auswirkungen auf biochemische Größen stehen seit Jahren zur Diskussion. In vorliegender Studie sollte das Verhalten verschiedener biochemischer Parameter bei physischer Belastung geprüft werden. Wir untersuchten Blut- und Urinproben von 31 Offiziers-anwärten der Bundeswehr vor und unmittelbar im Anschluß an einen Langstrecken marsch von 25 km. Analysiert wurden das Laktat im Vollblut, Noradrenalin, Cortisol und die cyclischen Nukleotide c-AMP und c-GMP im Plasma sowie Adrenalin, Noradrenalin, Vanillinmandelsäure und die 17-Hydroxycorticosteroide im Urin. Signifikante Erhöhungen ergaben sich für die Konzentrationen der Catecholamine und der cyclischen Nukleotide nach der physischen Belastung. Keine signifikanten Abweichungen waren für die Substanzen des Glucocorticoid-Stoffwechsels festzustellen. Die einzelnen Parameter werden hinsichtlich ihrer Relevanz für die Objektivierung physischer Beanspruchung diskutiert.
    Notizen: Summary The study presented was performed to evaluate the behaviour of some stress-related biochemical parameters induced by physical stress. We investigated urine and blood samples of 32 graduating officers of the German Bundeswehr before and after a long-distance march over 25 km. The concentrations of lactate in blood, noradrenaline, cortisol and the cyclic nucleotides c-AMP and c-GMP in plasma and adrenaline, noradrenaline, vanillic mandelic acid and 17-hydroxycorticosteroids in urine were determined. Significant elevations were detectable for the concentrations of catecholamines and cyclic nucleotides after the physical work-load. No significant differences were observed for the substances of the glucocorticoid metabolism. The single parameters are discussed in respect to their significance for the objectification of physical strain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00381795
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  • 3
    Digitale Medien
    Digitale Medien
    Cardiotoxicity of chlorodibromomethane and trichloromethane in rats and isolated rat cardiac myocytes (1997)
    Springer
    Archives of toxicology 71 (1997), S. 766-777 
    Details
    ISSN: 1432-0738
    Schlagwort(e): Key words Chlorodibromomethane ; Trichloromethane ; Cardiotoxicity ; [Ca2+] i transients ; Catecholamine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The cardiovascular effects were investigated after acute and subacute treatment with chlorodibromomethane (CDBM; 0.4 to 3.2 mmol/kg p.o.), trichloromethane (TCM; 0.31 and 1.25 mmol/kg p.o.) and mixtures of CDBM and TCM (acute, 0.8 mmol CDBM/kg + 1.25 mmol TCM/kg p.o.; subacute, 0.4 mmol CDBM/kg+0.31 mmol TCM/kg p.o.) in conscious and urethane anaesthetized male Wistar rats (n=610 per treatment). Furthermore it was observed whether cardiovascular responses were modified in CDBM or TCM treated rats after administration of exogenous catecholamines (epinephrine, 1 μg/kg; norepinephrine, 2 μg/kg) and underpinned with in vitro alterations of Ca2+ dynamics in cardiac myocytes. The present findings demonstrated that single and subacute oral administration of CDBM or TCM and mixtures of CDBM and TCM resulted in arrhythmogenic and negative chronotropic and dromotropic effects in conscious and urethane anaesthetized rats. The atrioventricular conduction time and the intraventricular extension time were extended. A slight shortening of the repolarization velocity was observed. The myocardial contractility was depressed and the heart was sensitized to the arrhythmogenic effects of epinephrine. After catecholamine injection the adrenergic cardiovascular responses in urethane anesthetized rats were modified: increased hypertensive epinephrine and norepinephrine action as well as augmentation of negative chronotropic and negative dromotropic cardiac effects of catecholamines were observed. The positive inotropic adrenergic response was diminished. The present in vivo findings, myocardial depression after acute CDBM treatment, as determined by different indices of contractility, correlate well with the observed inhibitory actions of CDBM on Ca2+ dynamics in isolated cardiac myocytes. All cardiovascular alterations found after CDBM or TCM treatment were not intensified after treatment with mixtures of CDBM and TCM. The effects observed were distinctly stronger after TCM (1.25 and 0.31 mmol/kg) treatment compared to CDBM (0.8 and 0.4 mmol/kg) treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002040050459
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