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  • American Physical Society  (66)
  • Springer  (58)
  • American Association for the Advancement of Science (AAAS)  (6)
  • 2000-2004  (86)
  • 1975-1979  (44)
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Keywords
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Year
  • 11
    Electronic Resource
    Electronic Resource
    Isolation and some properties of a mammalian ribosomal DNA (1976)
    Springer
    Chromosoma 58 (1976), S. 41-50 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The DNA coding for 28 S and 18 S ribosomal RNA, including the spacer regions, has been isolated from calf (Bos taurus) thymus gland. The method used included shearing of the total DNA to a highly homogeneous size population, selective heat denaturation and S 1 nuclease treatment to remove single stranded DNA. Repeated centrifugation on density gradients yields a 140-fold purified rDNA fraction with a GC content of 61.2%. Eco RI nuclease cleaves this DNA into two fragments of 16.4 and 4.9×106 daltons. Hybridization of these fragments with 28 S and 18 S rRNA shows that the 28 S coding sequence is located mostly on the 4.9×106 dalton fragment, while both the 16.4 and 4.9×106 dalton fragments contain the 18 S sequence. The data indicate that the ribosomal RNA gene has a repeat unit of 21.3×106 daltons which includes a nontranscribed spacer of about 12.5×106 daltons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293439
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  • 12
    Electronic Resource
    Electronic Resource
    The porosity dependence of flexural modulus and strength for capsule-free hot isostatically pressed porous alumina (2000)
    Springer
    Journal of materials science 35 (2000), S. 1205-1211 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Structural properties such as flexural moduli and strength have been measured for a range of porous alumina specimens of different initial powder sizes and final porosities, sintered using the capsule-free hot isostatic pressing method. This processing method produces a porous body in which the closed porosity is negligible. The relationship of these structural properties to total porosity has been investigated. The results indicate that both a power and an exponential function could adequately describe the porosity dependence of flexural strength. The strength values obtained were test method dependent, and were significantly lower for specimens with sintering aids. A power law model based on a critical porosity, as proposed by Phani, gave the best fit for the modulus measurement data. No dependence of mechanical properties on particle size was observed. The strength measurement results did not appear to support suggestions that better strength could be obtained by the capsule-free hot isostatic pressing method than conventional sintering, as reported elsewhere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004792605528
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  • 13
    Electronic Resource
    Electronic Resource
    Characterization of replication-defective transforming RNA tumor viruses by in vitro translation (1979)
    Springer
    Molecular biology reports 5 (1979), S. 115-120 
    Details
    ISSN: 1573-4978
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777497
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  • 14
    Electronic Resource
    Electronic Resource
    A mathematical model of proximal tubule absorption (1979)
    Springer
    The journal of membrane biology 47 (1979), S. 377-399 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A previous model of the mechanisms of flow through epithelia was modified and extended to include hydrostatic and osmotic pressures in the cells and in the peritubular capillaries. The differential equations for flow and concentration in each region of the proximal tubule were derived. The equations were solved numerically by a finite difference method. The principal conclusions are: (i) Cell NaCl concentration remains essentially isotonic over the pressure variations considered; (ii) channel NaCl concentration varies only a few mosmol from isotonicity, and the hydrostatic and osmotic pressure differences across the cell wall are of the same order of magnitude; (iii) both reabsorbate osmolality and pressure-induced flow are relatively insensitive to the geometry of the system; (iv) a strong equilibrating mechanism exists in the sensitivity of the reabsorbate osmolality to luminal osmolality; this mechanism is far more significant than any other parameter change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869745
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  • 15
    Electronic Resource
    Electronic Resource
    Intracellular calcium during fatigue of cane toad skeletal muscle in the absence of glucose (2000)
    Springer
    Journal of muscle research and cell motility 21 (2000), S. 481-489 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mechanisms of fatigue were studied in single muscle fibres of the cane toad (Bufo marinus) in which force, intracellular calcium ([Ca2+]i), [Mg2+]i, glycogen and the rapidly releasable Ca2+ from the sarcoplasmic reticulum (SR) were measured. Fatigue was produced by repeated tetani continued until force had fallen to 50%. Two patterns of fatigue in the absence of glucose were studied. In the first fatigue run force fell to 50% in 8–10 min. Fatigue runs were then repeated until force fell to 50% in 〈3 min in the final fatigue run. Addition of extracellular glucose after the final fatigue run prolonged a subsequent fatigue run. In the first fatigue run peak tetanic [Ca2+]i initially increased and then declined and at the time when force had fallen to 50% tetanic [Ca2+]i was 54 ± 5% of initial value. In the final fatigue run force and peak tetanic [Ca2+]i declined more rapidly but to the same level as in first fatigue runs. At the end of the first fatigue run, the rapidly releasable SR Ca2+ store fell to 46 ± 6% of the pre-fatigue value. At the end of the final fatigue run the rapidly releasable SR Ca2+ store was 109 ± 16% of the pre-fatigue value. In unstimulated fibres the nonwashable glycogen content was 176 ± 30 mmol glycosyl units/l fibre. After one fatigue run the glycogen content was 117 ± 17 mmol glycosyl units/l fibre; at the end of the final fatigue run the glycogen content was reduced to 85 ± 9 mmol glycosyl units/l fibre. [Mg2+]i did not change significantly at the end of fatigue in either the first or the final fatigue run suggesting that globally-averaged ATP does not decline substantially in either pattern of fatigue. These results suggest that different mechanisms are involved in the decline of tetanic [Ca2+]i in first compared to final fatigue runs. The SR Ca2+ store is reduced in first fatigue runs; this is not the case for the final fatigue run which is associated with a decline in glycogen and possibly related to either a non-metabolic effect of glycogen or a spatially-localised metabolic decline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005650425513
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  • 16
    Electronic Resource
    Electronic Resource
    Glycogen stability and glycogen phosphorylase activities in isolated skeletal muscles from rat and toad (2000)
    Springer
    Journal of muscle research and cell motility 21 (2000), S. 655-662 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract There is increasing evidence that endogenous glycogen depletion may affect excitation–contraction (E–C) coupling events in vertebrate skeletal muscle. One approach employed in physiological investigations of E–C coupling involves the use of mechanically skinned, single fibre preparations obtained from tissues stored under paraffin oil, at room temperature (RT: 20–24°C) and 4°C for several hours. In the present study, we examined the effect of these storage conditions on the glycogen content in three muscles frequently used in research on E–C coupling: rat extensor digitorum longus (EDL) and soleus (SOL) and toad iliofibularis (IF). Glycogen content was determined fluorometrically in homogenates prepared from whole muscles, stored under paraffin oil for up to 6 h at RT or 4°C. Control muscles and muscles stored for 0.5 and 6 h were also analysed for total phosphorylase (Phostotal) and phosphorylase a (Phos a) activities. No significant change was observed in the glycogen content of EDL and SOL muscles stored at RT for 0.5 h. In rat muscles stored at RT for longer than 0.5 h, the glycogen content decreased to 67.6% (EDL) and 78.7% (SOL) of controls after 3 h and 25.3% (EDL) and 37.4% (SOL) after 6 h. Rat muscles stored at 4°C retained 79.0% (EDL) and 92.5% (SOL) of glycogen after 3 h and 75.2% (EDL) and 61.1% (SOL) after 6 h. The glycogen content of IF muscles stored at RT or 4°C for 6 h was not significantly different from controls. Phostotal was unchanged in all muscles over the 6 h period, at both temperatures. Phos a was also unchanged in the toad IF muscles, but in rat muscles it decreased rapidly, particularly in EDL (4.1-fold after 0.5 h at RT). Taken together these results indicate that storage under paraffin oil for up to 6 h at RT or 4°C is accompanied by minimal glycogen loss in toad IF muscles and by a time- and temperature-dependent glycogen loss in EDL and SOL muscles of the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005628500892
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  • 17
    Electronic Resource
    Electronic Resource
    The spike-strain test for polymeric liquids and its relevance for irreversible destruction of network connectivity by deformation (1979)
    Springer
    Rheologica acta 18 (1979), S. 463-468 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Die Grundannahmen derLodgeschen Theorie der gummiartigen Flüssigkeit werden zusammengefaßt. Zwei weitere Annahmen sind notwendig, wenn man das Scher- und Dehnverhalten von Polymerschmelzen und konzentrierten Polymerlösungen bei finiten Deformationen beschreiben will: (1) die Annahme der Zerstörung des temporären Netzwerkes polymerer Flüssigkeiten mit zunehmender Deformation und (2) die Annahme, daß diese Zerstörung ein irreversibler Vorgang ist. Hier wird ein neuer Versuch, der sogenannte „Spike-Strain-Test“, vorgeschlagen. Damit ist es möglich, die Annahme einer irreversiblen Zerstörung des temporären Netzwerkes polymerer Flüssigkeiten mit zunehmender Deformation zu überprüfen. Die Bedeutung dieses Experimentes für eine größere Klasse von rheologischen Zustandsgleichungen wird diskutiert.
    Notes: Summary The basic assumptions ofLodge's rubberlike-liquid constitutive equation for polymer melts and concentrated solutions are summarized. By two additional assumptions — (i) the network disentanglement assumption and (ii) the irreversibility assumption — a modified rubberlike-liquid constitutive equation is obtained, which has been shown to be a valid description of material behaviour in shear and elongational flow. In this paper a novel test — the spikestrain test — is proposed. On the basis of this experiment the assumption of irreversible destruction of network connectivity by deformation can be examined. The significance of the spike-strain test for a larger class of constitutive equations is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01736952
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  • 18
    Electronic Resource
    Electronic Resource
    A dynamical model for gravitation (1976)
    Springer
    Foundations of physics 6 (1976), S. 143-155 
    Details
    ISSN: 1572-9516
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A gravitational model is proposed that relates the terrestrially measured value of the gravitational constantG directly to the density and angular velocity of the galaxy. The model indicates a constant scalar value forG within most regions of our galaxy, but predicts thatG will be different in other galaxies and zero in intergalactic space. The model offers explanations for galactic cluster stability, discrepancies in terrestrial measurements ofG, and atomic particle stability. The model also provides a causal relationship between strong, electromagnetic, weak, and gravitational interactions. The two postulates required for the proposed model reduce to two assumptions made in GRT in regions whereG is constant; these postulates are consistent with the existence of a 2.7 K blackbody background radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708956
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  • 19
    Electronic Resource
    Electronic Resource
    Clarification of an apparent asymmetry in electromagnetic theory (1978)
    Springer
    Foundations of physics 8 (1978), S. 921-926 
    Details
    ISSN: 1572-9516
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The status of the advanced potential solution in electromagnetic theory is analyzed and assessed. It is shown that the advanced potential solution does not violate a causality argument and that its existence in electromagnetic theory is on an exactly equal footing with the retarded potential solution. The general potential solution is thus completely symmetric. It is further shown that there is no “one-sidedness” in nature; oscillating electrons and orbiting electrons are just as good at absorbing energy as they are at radiating it. These conclusions are sufficient to invalidate a number of theoretical models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00715063
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  • 20
    Electronic Resource
    Electronic Resource
    The gauge in general relativity. II (1978)
    Springer
    General relativity and gravitation 9 (1978), S. 21-38 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The present paper and a companion work are intended as one possible realization of a non-customary gauge theory of general relativity-as set forth in only broad outline in an earlier work. In this first paper, it is found that both radar echo delay and the perihelion shift differ slightly from their customary expressions. Unfortunately, it is also found that the usual statement of the principle of equivalence does not hold in the present formulation. Finally, in the second paper, a single cosmological model is investigated that appears to be promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00772548
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