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  • Articles  (6)
  • Rheology
  • Springer  (6)
  • American Geophysical Union
  • American Geophysical Union (AGU)
  • American Physical Society
  • Annual Reviews
  • Nature Publishing Group
  • 1990-1994  (4)
  • 1980-1984  (2)
  • 1970-1974
  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Rheological modelling of physiological variables during temperature variations at rest (1990)
    Springer
    International journal of biometeorology 34 (1990), S. 76-86 
    Details
    ISSN: 1432-1254
    Keywords: Rheology ; Human ; Heart rate ; Oxygen consumption ; Body temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract The evolution with time of cardio-respiratory variables, blood pressure and body temperature has been studied on six males, resting in semi-nude conditions during short (30 min) cold stress exposure (0°C) and during passive recovery (60 min) at 20°C. Passive cold exposure does not induce a change inHR but increasesVO 2,VCO 2 Ve and core temperatureT re, whereas peripheral temperature is significantly lowered. The kinetic evolution of the studied variables was investigated using a Kelvin-Voigt rheological model. The results suggest that the human body, and by extension the measured physiological variables of its functioning, does not react as a perfect viscoelastic system. Cold exposure induces a more rapid adaptation for heart rate, blood pressure and skin temperatures than that observed during the rewarming period (20°C), whereas respiratory adjustments show an opposite evolution. During the cooling period of the experiment the adaptative mechanisms, taking effect to preserve core homeothermy and to obtain a higher oxygen supply, increase the energy loss of the body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01093451
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  • 2
    Electronic Resource
    Electronic Resource
    The viscoelasticity of entangled actin networks: the influence of defects and modulation by talin and vinculin (1993)
    Springer
    European biophysics journal 22 (1993), S. 309-321 
    Details
    ISSN: 1432-1017
    Keywords: Rheology ; Semiflexible biopolymers ; Cytoskeletal viscoelasticity ; Actin-talin-vinculin interaction ; Binding defects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Rheological measurements of the frequency-dependent complex elastic module G*(ω) of entangled F-actin solutions in the frequency range 10−5 − 1 Hz were carried out in three dynamic regimes: 1.) A terminal relaxation from gel-like to liquid-like behaviour measured at frequencies ω 〈 τd −1 2.) a rubber-type plateau and 3.) a regime determined by chain conformational transitions at frequencies ω 〉 τi −1. A major point of interest was to clarify whether rheological, high precision measurements can yield quantitative information about the influence of talin and vinculin on the structure, chain dynamics, elasticity and viscoelasticity of actin filaments with time. We show that in the regime reflecting internal chain dynamics (10−2 to 1 s time domain), F-actin behaves as a random coil of the Rouse type. This contrasts with dynamic light scattering and correlation spectroscopic studies of actin filament flickering, which indicate that filaments behave as semiflexible rods. The internal chain dynamics, which are determined by thermically excited bending undulations, exhibit a persistence length of 0.3−1 μm Evidence is provided that this discrepancy is due to a cross-over of semiflexible rod behaviour at excitation wavelengths (Λ) below approximately 1 gm to random-coil behaviour at Λ 1 µ (expected at a frequency ω ∼ 1 Hz). The random coil behaviour is largely determined by defects in actin filaments leading to sharp bends of the chain which act as semiflexible hinges. Talin produces drastic effects on the time course of viscoelasticity during actin polymerization. It promotes the rapid formation of short filament fragments (∼ 1 gmm, within time scales of min) which anneal slowly into long filaments (within several hours), most probably by fusion. The viscoelasticity depends on the coexistence of short and very long filaments indicated by the elongation of the rubber plateau. The most dramatic effect is a reduction of the ratio of the terminal ('Ed) to the Rouse relaxation time of τi by more than one order of magnitude (τd/τi = 100 compared to ratio τd/i = 2000 for pure actin). From this it is concluded that talin causes a remarkable decrease in the effective segment length of the macromolecule and, thus induces an increase in chain stiffness. Vinculin on the other hand shows no such effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213554
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  • 3
    Electronic Resource
    Electronic Resource
    Time-dependent density anomalies in a stratified, viscoelastic mantle: Implications for the geoid, Earth's rotation and sea-level fluctuations (1993)
    Springer
    Surveys in geophysics 14 (1993), S. 537-553 
    Details
    ISSN: 1573-0956
    Keywords: Rheology ; viscosity and density jumps ; geoid ; rotation ; sea levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The effects on the ℓ = 2 geoid component and Earth's rotation due to internal mass anomalies are analyzed for a stratified viscoelastic mantle described by a Maxwell rheology. Our approach is appropriate for a simplified modeling of subduction. Sea-level fluctuations induced by long-term rotational instabilities are also considered. The displacement of the Earth's axis of rotation, called true polar wander (TPW) and the induced eustatic sea-level fluctuations, are extremely sensitive to viscosity and density stratification at the 670 km seismic discontinuity. Phase-change models for the transition zone generally allow for huge amount of TPW, except for large viscosity increases; the dominant contribution in Liouville equations comes from a secular term that reflects the viscous behaviour of the mantle. In chemically stratified models, TPW is drastically reduced due to dynamic compensation of the mass anomalies at the upper-lower mantle interface. When the source is embedded in the upper mantle close to the chemical density jump, transient rotational modes are the leading terms in the linear Liouville equations. Long-term rotation instabilities are valuable contributors to the third order cycles in the eustatic sea-level curves. Rates of sea-level fluctuations of the order of 0.05–0.1 mm/yr are induced by displacements of the Earth's axis of rotation compatible with paleomagnetic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690576
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  • 4
    Electronic Resource
    Electronic Resource
    Investigations on a detergent system with rodlike micelles (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 1042-1056 
    Details
    ISSN: 1435-1536
    Keywords: Rodlike Micelles ; Micellar Interaction ; Rheology ; Light Scattering ; Electric Birefrugence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Conductivity, kinetic, static and dynamic light scattering, electric birefringence and rheological measurements were carried out on aqueous solutions of Tetradecylpyridinium-n-Heptanesulfonate (C14PyC7SO3) up to high concentrations. In dilute solutions between the critical micelle concentration (cmc) and another characteristic concentration (c t) spherical micelles were detected whose radii were independent of detergent concentration and equal to the length of a detergent molecule; the aggregation numbern of these micelles of about 100 monomers per micelle was also in agreement with the existence of normal spherical micelles of aC 14-detergent. Above the concentrationc t, the spherical micelles were found to grow to rodlike aggregates whose short axis was still independent of concentration and equal to the length of a monomer, while the lengthsL of the rods increased with increasing detergent concentration. When the lengthsL of the rods became comparable with the mean distancea between them, the starting interaction between the rods slowed down their growth. In this concentration range of overlapping rods, the data could be evaluated with a recently developed theory by Doi and Edwards for stiff rods. The rods reached finally a maximum length of about 500 å and decreased again in size upon further increase of concentration when the overlap ratioL/a reached a value of about 1,5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451652
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  • 5
    Electronic Resource
    Electronic Resource
    Generalized reptation model (1981)
    Springer
    Colloid & polymer science 259 (1981), S. 908-910 
    Details
    ISSN: 1435-1536
    Keywords: Rheology ; concentrated polymer solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Ein verallgemeinertes Reptationsmodell wird vorgestellt. Entlang einer Polymerkette berücksichtigt es die gehinderte Difussion von Defekten, die Länge speichern. Dieser Effekt wird beschrieben mittels einer Wartezeitverteilung für die Defektplatzwechselvorgänge. In der Folge findet man für wichtige rheologische Größen Molekulargewichtsabhängigkeiten in Form von Potenzgesetzen mit gebrochenen Exponenten an Stelle der ganzzahligen Exponenten des konventionellen Reptationsmodells.
    Notes: Summary The reptation model is generalized on the basis of a theory which accounts for hindered defect diffusion along the chain. A basic ingredient of the theory is a waiting time distribution for the hops of elementary defects which store length. Important rheological quantities are found to generally depend on fractional powers of the molecular mass rather than on integer powers as in the conventional reptation picture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01524812
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  • 6
    Electronic Resource
    Electronic Resource
    Rheology of suspensions of rodlike particles (1991)
    Springer
    Journal of statistical physics 62 (1991), S. 1073-1094 
    Details
    ISSN: 1572-9613
    Keywords: Rheology ; rods ; viscosity ; aspect ratio ; suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Suspensions of rigid rodlike particles in Newtonian suspending fluids are considered. We discuss the dependence of the relative viscosityμ r upon the volume fraction of particlesϕ, their aspect ratioa r, and the particle orientation distribution when the particles are sufficiently large that hydrodynamic forces are dominant. Theoretical results are reviewed for a variety of long slender particles. Experimental results obtained using classical rheometrical techniques are discussed. It is shown that whena r⩽25, data from several laboratories agree and they indicate thatμ r depends more strongly uponϕ thana r. Previous experimental results using falling ball rheometry are discussed as well as some more recent findings. These are shown to provide insights heretofore unavailable into the macroscopic rheology of suspensions of randomly oriented and oriented rods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01128178
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