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  • Polymer and Materials Science  (10)
  • Cell & Developmental Biology  (3)
  • Electrical impedance  (3)
  • Finite elements  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 851-863 
    ISSN: 0887-624X
    Keywords: polymerization ; kinetics ; free radical ; transfer ; photolysis ; propagation ; rate coefficients ; termination ; EPR ; copolymerization ; initiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problems of determining reliable, well-characterized values of kinetic parameters in free-radical polymerizations are discussed. The origins of the fact that experimental determinations of rate coefficients of ostensibly identical systems often result in quite different values being reported can be ascribed to subtle mechanistic assumptions made in data interpretation, which are considered in detail. A series of recommendations to assist in overcoming these problems, and to highlight their origins, are presented, with emphasis placed on new techniques including those employing laser photolysis and EPR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2439-2454 
    ISSN: 0887-624X
    Keywords: radiation ; nitrile rubber ; NMR ; ESR ; radicals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of radiation-induced structural changes in nitrile rubber with different acrylonitrile contents were investigated by ESR, NMR, and FTIR. To investigate new structures solid-state NMR methods had to be used due to crosslinking of the irradiated rubbers, and higher probe temperatures were used to obtain better resolution. The radicals generated on the acrylonitrile groups were found to abstract hydrogen from the adjacent butadiene units resulting in the formation of allylic radicals. These allylic radicals reacted to form intermolecular crosslinks and cyclisation. Cyclisation of the butadiene units were found to occur in the initial stages of the irradiation. Radiation yields of radicals increased with acrylonitrile content from 1.42, 1.58, to 2.42 for 18, 30, and 45% acrylonitrile rubbers. The radiation yields for intermolecular crosslinking were higher in rubbers with higher acrylonitrile contents, giving G values of 17.8, 21.3, and 24.5 for 18, 30, and 45% acrylonitrile rubbers, respectively. However, the crosslink clustering was found to be less in the rubbers with a higher acrylonitrile content. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Commercial thermoplastic polyurethanes have been melt blended on a standard laboratory extruder with low levels of commercial poly(dimethyl siloxane) fluid. The resultant polyurethanes show improvements in wear resistance of up to 25% (c.f. virgin polyurethane) for an optimal PDMS concentration of 1.5-2.0%, beyond which the properties diminish rapidly. Unexpectedly, the mechanical properties of the blends (as measured by an Instron tensile testing machine) have been even more significantly enhanced, by up to 40% for tensile strength and 50% for elongation to break. Surface studies of the blends are also reported for x-ray photoelectron spectroscopy (XPS), contact angles and coefficient of friction (CoF). © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 1155-1171 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanism of radiation vulcanization of natural rubber with 2-ethyl hexyl acrylate (2EHA) monomer was investigated using electron spin resonance spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The primary radicals formed in the arcylate molecule were found to abstract the allylic hydrogens of the polyisoprene. Crossliking may occur through the allylic radicals and/or main chain radicals formed on the polyacrylate. Acrylate was found to concentrate in the rigid regions of the crosslinked rubber indicating heterogeneity and a nonuniform distribution of the acrylate in the latex particles. The addition of the acrylate and the irradiation seems to effect the Brownian motion of the latex particles. Both the viscosity and the NMR peak widths are effected by the irradiation. Addition of 5% 2EHA increases the crosslinking by a factor of 3.6. The thermal stability of the rubber first increases with the dose in the presence of acrylate, but drops at higher doses due to peroxide formation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 13 (1975), S. 307-308 
    ISSN: 1741-0444
    Keywords: Residual urine volume ; Electrical impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 13 (1975), S. 182-186 
    ISSN: 1741-0444
    Keywords: Blood resistivity ; Electrical impedance ; Cardiac output
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Pour pouvoir appliquer la méthode de l'impédance électrique pour la mesure du débit sanguin chez des patients à l'hémodialyse où l'on peut rencontrer use vaste gamme d'hématocrites, il est nécessaire d'avoir des connaissances sur la relation entre la résistivité et l'hématocrite du sang. Une relation linéaire optimale a été déterminée pour le sang humain à 37°C et 100 kHz sur la gamme d'hématocrites de 14 à 45%.
    Abstract: Zusammenfassung Um die elektrische Impedanzmethode zur Messung der Herzleistung bei Patienten anwenden zu können, die durch Blutidialyse behandelt werden, wo ein breiterer Bereich von Blutzentrifugenwerten angetroffen werden kann, ist die Kenntnis des Verhältnisses zwischen dem spezifischen Widerstand des Blutes und dem Blutzentrifugenwert enforderlich. Es wurde ein Verhältnis nach der linearen Methode der kleisten Quadrate für das menschliche Blut bei 37°C und 100 kHz über einen Blutzentrifugenwertbereich von 14 bis 45% bestimmt.
    Notes: Abstract In order to be able to employ the electrical-impedance method for the measurement of cardiac output in patients on haemodialysis where a wide range of haematocrits may be encountered, a knowledge of the relationship between the resistivity and haematocrit of blood is required. A linear least-squares relationship has been determined for human blood at 37°C and 100 kHz over the haematocrit range from 14 to 45%
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 13 (1975), S. 187-191 
    ISSN: 1741-0444
    Keywords: Cardiac output ; Electrical impedance ; Radiocardiogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Vingt paires simultanées de valeurs de débit sanguin en provenance de patients ne présentant pas d'anormalités valvulaires ont été obtenues par la méthode radio-isotopique et la méthode d'impédance életrique deKubicek et al (1966). Si on a admis pour la résistité sanguine de chaque patient une valeur-type de 150Ω, la valeur d'impédance moyenne de débit sanguin était supérieure de 14·5% par rappórt à la valeur radio-isotopique moyenne. Dans la présente étude, les hématocrites des patients s'échelonnaient de 20 à 48%. En faisant passer la valeur de résistivité appropriée pour chaque patient dans l'équation de volume d'apoplexie de Kubicek à partir des données de Geddes et de Sadler (1973), on obtient une valeur d'impédance moyenne inférieure de 10·3% par rapport à la valeur isotopique moyenne. L'utilisation de nos données de résistivité mesurées ont amené la valeur d'impédance moyenne de débit sanguin à 21·5% au-dessous de la valeur isotopique moyenne. Le coefficient de corrélation entre les techniques à impédance et les techniques à isotopes était de 0·61 pour la valeur-type de résistivité de 150Ωcm. Ce coefficient a été amené à 0.87 par l'utilisation des données de résistivité de Geddes et Sadler (1973), contre 0·88 avec nos données.
    Abstract: Zusammenfassung Zwanzig simultane Herzleistungspaarwerte von Patienten ohne Herzklappen-Anomalitäten wurden durch das Radioisotopenverfahren und das elektrische Impedanzverfahren von Kubicek und anderen (1966) erhalten. Wenn ein Standardwert von 150Ωcm für den spezifischen Widerstand des Blutes eines jeden Patienten angenommen wurde, betrug der Durchschnittswert für die Impedanz-herzleistung 14·5%, was im Vergleich zum durchschnittlichen Radioisotopenwert hoch ist. In dieser Untersuchung lagen die Blutzentrifugenwerte der Patienten zwischen 20 and 48%. Wenn man den entsprechenden spezifischen Widerstandswert für jeden Patienten in die Hubvolumengleichung von Kubicek aus den Daten nach Geddes und Sadler (1973) eisetzt, ist der mittlere Impedanzwert von 10·3% im Vergleich zum mittleren Isotopenwert niedrig. Bei Anwendung unserer gemessenen Widerstandsdaten lag der mittlere Herzleistungs-impedanzwert um 21·5% unter dem mittleren Isotopenwert. Der Korrelationskoeffizient zwischen Impedanz-und Isotopen-technik betrug 0·61 für den Standard-Widerstandswert von 150Ωcm. Bei Verwendung der Widerstandsdaten nach Geddes und Sadler (1973) betrug der Korrelationskoeffizient 0·87 mit unseren Daten 0·88.
    Notes: Abstract Twenty simultaneous pairs of cardiac output values from patients who did not have valvular abnormalities were obtained by the radioisotope method and the electrical-impedance method of Kubicek et al. (1966). If a standard value of 150Ω-cm was assumed for the resistivity of each patient's blood, the mean value for the impedance cardiac output was 14·5% high compared with the mean radioisotope value. In this study the patient's haematocrits ranged from 20 to 48%. Inserting the appropriate value of the resistivity for each patient into the stroke volume equation of Kubicek from the data of Geddes and Sadler (1973) made the mean impedance value 10·3% low compared with the mean isotope value. The use of our measured resistivity data made the mean impedance cardiac output value 21·5% lower than the mean isotope value. The correlation coefficient between the impedance and isotope techniques was 0·61 for the standard value of resistivity of 150Ω-cm. Using the resistivity data of Geddes and Sadler (1973) the correlation became 0·87, and with our data it was 0·88.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 128 (1986), S. 322-328 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We investigated the influence of transforming growth factor-β (TGF-β) on DNA synthesis in human fetal fibroblasts, as measured by the incorporation of [3H] thymidine and cell replication. In serum-free medium, without additional peptide growth factors, TGF-β had no action on thymidine incorporation. However, in the presence of 0.1% v/v fetal calf serum, TGF-β exhibited a bi-functional action on the cells. A dose-dependent stimulation of [3H] thymidine incorporation, and an increase in cell number, occurred with fibroblasts established from fetuses under 50 g body weight, with a maximum stimulation seen at 1.25 ng/ml. For fibroblasts from fetuses of 100 g or greater body weight, TGF-β caused a dose-related decrease in thymidine uptake with a maximal inhibition at 2.5 ng/ml, and a small decrease in cell number. When DNA synthesis was stimulated by the addition of somatomedin-C/insulin-like growth factor I, epidermal growth factor, or platelet-derived growth factor, their actions were potentiated by the presence of TGF-β on cells derived from fetuses under 50 g body weight, but inhibited on cells obtained from the larger fetuses wieghing more than 100 g. Similar results were found for changes in cell number in response to TGF-β when stimulated by SM-C/IGF I. The ability of TGF-β to modulate [3H] thymidine incorporation did not involve a change in the time required for growth-restricted cells to enter the S phase of the replication cycle. These data suggest that TGF-β may exert either a growth-promoting or growth-inhibiting action on human fetal connective tissues in the presence of other peptide growth factors, which is dependent on fetal age and development.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We investigated the actions of human placental lactogen (HPL) and human growth hormone (HGH) on [3H]thymidine incorporation and the release of immunoassyable somatomedin-C (SM-C) by isolated myoblasts, dermal fibroblasts, and costal cartilage explants taken from human fetuses, at 11-21 weeks of gestation. The incorporation of [3H] thymidine by myoblasts and fibroblasts was significantly increased after incubation for 20 hr or 44 hr, and cell number after incubation for 7 days, in the presence of 50-250 ng/ml HPL. Incubation with HPL did not increase [3H]thymidine incorporation into cartilage explants, whereas incubation with HGH failed to enhance the uptake of this isotope by any of the tissues. Following extraction with acid-ethanol, culture medium conditioned by exposure to myoblasts or fibroblasts for 44 hr, and to cartilage explants for 7 days, contained radioimmunoassayable SMC. Myoblast-conditioned medium contained significantly more SM-C [1,609 ± 953 mU/mg cell protein (mean ± SD) n = 10] than did that conditioned by fibroblasts (637 ± 323; n = 5; P 〈 0.02). In 1 week of culture, cartilage explants released 4.1 ± 1.1 mU/mg wet weight (n = 7). The release of immunoassayable SM-C from cultured cells was significantly increased in the presence of 250 ng/ml HPL in five of eight experiments with myoblasts and two of four experiments with fibroblasts. Neither fibroblasts or myoblasts showed increased SM-C release following exposure to HGH.The results suggest that HPL, but not HGH, is growth-promoting for some human fetal tissues in vitro and that this action is mediated, at least in part, by an increased release of somatomedins.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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