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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 23 (1989), S. 527-577 
    ISSN: 0066-4197
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 87 (1999), S. 269-275 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mechanisms for the deposition of heat in the lower coronal plasma are discussed, emphasizing recent attempts to reconcile the fluid and kinetic perspectives. Structures at the MHD scales are believed to act as reservoirs for fluctuation energy, which in turn drive a nonlinear cascade process. Kinetic processes act at smaller spatial scales and more rapid time scales. Cascade-driven processes are contrasted with direct cyclotron absorption, and this distinction is echoed in the contrast between frequency and wavenumber spectra of the fluctuations. Observational constraints are also discussed, along with estimates of the relative efficiency of cascade and cyclotron processes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 645-650 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Irradiation sterilization is in wide use among tissue banks, for both hard and soft tissue grafts. Irradiation of tendon can impair its mechanical properties. Following implantation of a tendon graft, re-vascularization and resorption processes reduce its mechanical performance. Tendon with severely impaired properties may not be suitable for use as a load-bearing graft, e.g. as anterior cruciate ligament replacement. An important factor determining the extent of the reduction of the mechanical performance is the condition of the tendon during irradiation, especially the presence of water. There has not yet been a study of the effects of both irradiation dose and hydration on tendon mechanical properties. This study measured the changes in tensile mechanical properties, including strength and stiffness, following γ irradiation doses of 15 kGy (1.5 MRad) and 25 kGy (2.5 MRad), in the frozen state and following freeze-drying. The strength of the freeze-dried irradiated tendons was lower compared to fresh tendons, whereas the strength of the frozen irradiated tendons was very similar to that of the fresh. The tangent modulus of both of the freeze-dried irradiated groups were lower than the fresh tendons, as was the 15 kGy frozen group. The modulus of the 25 kGy frozen irradiated group was similar to the fresh. The general pattern of the results indicate that the two freeze-dried tendon groups were more affected than the frozen irradiated, and of the frozen irradiated groups the 25 kGy group was least affected. The results fit well with suggested mechanisms for the action of irradiation upon collagen; that intramolecular crosslinking and scission of the tropocollagen α chains occur when water is present, and α chain scission alone occurs when water is absent. lrradiation of tendons for use as grafts may produce minimal deleterious changes if the irradiation is performed while the tendon is frozen with water present.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 10 (1974), S. 337-352 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Une série d'essais de photo-élasticité à trois dimensions a été conduite sur des plaques comportant des fissures traversantes, sollicitées en flexion avec une composante de traction suffisante pour éviter que les fissures ne se referment du côté comprimé de la plaque. Les géométries des plaques fissurées ont été choisies de sorte à couvrir la gamme de la transition “mince” à “épais”. Des tranches ont été découpées parallèlement aux surfaces de la plaque, après que l'on eût figé les contraintes dans le matériau. Ces tranches ont été analysées par photo-élasticité, et des fonctions correspondant aux distributions des facteurs d'intensité des contraintes ont été évaluées expérimentalement. Les résultats ont été comparés avec la théorie de G. C. Sih. L'accord est excellent pour les tôles fissurées correspondant aux géométries “minces”. Ils divergent progressivement au fur et à mesure que l'on passe à des géométries “épaisses”. Pour tous les cas étudiés, l'emploi d'une distribution linéaire de la fonction représentant le facteur d'intensité des contraintes au travers de l'épaisseur de la plaque apparaît satisfaisant.
    Abstract: Zusammenfassung Eine Reihe von dreidimensionalen photoelastischen Versuchen wurden auf Platten, die durchgehende Risse enthalten, unter Biegebelastung und genügendem Zug um das Schließen auf der Druckseite der Platte zu verhindern, ausgeführt. Die Dimensionen der gerissenen Platten wurden so gewählt daß sie das Übergangsgebiet “dünn auf dick” enthalten. Man machte Streifen paralell zu den Plattenoberflächen im spannungsgefrohrenen Material um die Teile um die Rißspitze zu entfernen. Die Streifen wurden photoelastisch untersucht und man stellte experimentelle Funktionen auf, die der Verteilung der Spannungsintensitätsfaktoren über die Plattendicke entsprechen. Die Ergebnisse wurden mit der Theorie von G. C. Sih verglichen. Die Übereinstimmung war ausgezeichnet für “dünne” Platten mit Rissen. Für “dickere” Platten mit Rissen gehen die Ergebnisse progressiv auseinander. Für alle untersuchten Fälle erwies sich die Anwendung einer linearen Verteilung der Spannungsintensitätsfaktorenfunktion über die dicke der Platte als zufriedenstellend.
    Notes: Abstract A series of three-dimensional photoelastic experiments were conducted on plates containing through cracks which were loaded in bending with sufficient extension to prevent closure on the compressive side of the plate. Cracked plate geometries were selected so as to span the transitional “thin to thick” range. Slices were made parallel to the plate surfaces in the stress frozen material so as to remove the region around the crack tips. These slices were analyzed photoelastically and functions were evaluated experimentally corresponding to stress intensity factor distributions through the plate thickness. Results were compared with the theory of G. C. Sih. Agreement was excellent with theory for “thin” cracked plate geometries. For “thicker” cracked plate geometries results diverged progressively. For all cases studied, the use of a linear distribution of the stress intensity factor function through the plate thickness appeared to be satisfactory.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 6 (1985), S. 669-708 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Contraction in vertebrate smooth and striated muscles results from the interaction of the actin filaments with crossbridges arising from the myosin filaments. The functions of the actin based thin filaments are (1) interaction with myosin to produce force; (2) regulation of force generation in response to Ca2+ concentration; and (3) transmission of the force to the ends of the cell. The major protein components of smooth muscle thin filaments are actin, tropomyosin and caldesmon, present in molar ratios of 28:4:1 respectively. Other smooth muscle proteins which may be associated with the thin filaments in the cell are filamin, vinculin, α-actinin, myosin light chain kinase and calmodulin. We have reviewed the structural and functional properties of these proteins and where possible we have suggested what their function and mechanism of action may be. We propose that actin and tropomyosin are involved in the force producing interaction with myosin, and that this interaction is controlled by a Ca2+-dependent mechanism involving caldesmon, tropomyosin and calmodulin. Vinculin, α-actinin and filamin appear to be involved in the attachment of the thin filaments to the cell membrane and their spatial organization within the cell. We conclude that the filaments of smooth muscles share many common properties with those from skeletal muscle, but that they are also quite distinct in terms of both their caldesmon based regulatory mechanism and their mode of organization into a contractile apparatus.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Origins of life and evolution of the biospheres 3 (1972), S. 260-264 
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Xenon trioxide was compared for toxicity in the few common oxidants using three bioassays. On a molar basis XeO3 and HOCl were similar, but XeO3 was less active than expected when comparisons were based on normality.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 14 (1986), S. 15-20 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Dispersion effects in bacteriorhodopsin both in suspension and incorporated into liposomes have been studied by measuring the changes in the dielectric properties induced by electric and magnetic fields at low and medium frequencies. The samples exhibit very high values of relative permittivity and dielectric loss. Dispersions have been measured up to 200 kHz and are believed to be due to the reorientation of the bacteriorhodopsin chromophore within the membrane fragments. A study of relaxation times vs temperature shows a transition at 28°C, the same temperature as found using other techniques.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 36 (1996), S. 290-295 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study, edge cracked sheet specimens made from polybutadiene rubber embedded with hard particles were used in crack propagation tests. Crack propagation tests were conducted under two crosshead speeds (2.54 mm/min and 12.7 mm/min) at three temperatures (−53.9°C, 22.2°C and 73.9°C). The experimental data were analyzed and the crack growth resistance curves and the crack growth rate versus the Mode I stress intensity factor were plotted. Based on these experimental results, the effects of temperature and loading rate on the crack growth behavior were investigated and the results are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 12 (1972), S. 67-74 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A controlled-strain apparatus capable of performing the tests essential to establishing the yield locus of polycarbonate was designed and built. Material characterization tests were performed in the form of uniaxial strain rate, creep, isotropy, isoclinic and reloading tests. The yield locus for polycarbonate was determined and an analytical expression in the form of a hypotrochoid was developed. Yield locus results indicate that, although polycarbonate is not a Mises material, the yield locus may be approximated by a circle over a substantial range of Lode’s variable. Tests were run on large plates with holes. Good correlation with two-dimensional theory was obtained in the elastic zone and in the plastic zone where plastic strains were small.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 39 (1999), S. 356-362 
    ISSN: 1741-2765
    Keywords: Engineering strain ; nonlinear ; Poisson's ratio ; strain dependent ; true strain ; auxetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The Poisson's ratio of a material is strictly defined only for small strain linear elastic behavior. In practice, engineering strains are often used to calculate Poisson's ratio in place of the mathematically correct true strains with only very small differences resulting in the case of many engineering amterials. The engineering strain definition is often used even in the inelastic region, for example, in metals during plastic yielding. However, for highly nonlinear elastic materials, such as many biomaterials, smart materials and microstructured materials, this convenient extension may be misleading, and it becomes advantageous to define a strainvarying Poisson's function. This is analogous to the use of a tangent modulus for stiffness. An important recent application of such a Poisson's function is that of auxetic materials that demonstrate a negative Poisson's ratio and are often highly strain dependent. In this paper, the importance of the use of a Poisson's function in appropriate circumstances is demonstrated. Interpretation methods for coping with error-sensitive data or small strains are also described.
    Type of Medium: Electronic Resource
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