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  • 1
    Publication Date: 1990-12-07
    Description: Time-resolved lattice spacing changes were measured (10-millisecond time resolution) by x-ray diffraction of synchrotron radiation in single intact muscle fibers of the frog Rana temporaria undergoing electrically stimulated tension development during application of stretches and releases. Ramp releases, which decreased fiber length at constant speed, caused a lattice expansion. After the ramp, increasing tension during recovery was accompanied by lattice compression. Ramp stretches caused a compression of the lattice. While the fiber was held at a constant length after the stretch, tension decreased and lattice spacing increased. These observations demonstrate the existence of a previously undetected radial component of the force generated by a cycling crossbridge. At sarcomere lengths of 2.05 to 2.2 micrometers, the radial force compresses the myofilament lattice. Hence, the myofilament lattice does not maintain a constant volume during changes in force.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cecchi, G -- Bagni, M A -- Griffiths, P J -- Ashley, C C -- Maeda, Y -- New York, N.Y. -- Science. 1990 Dec 7;250(4986):1409-11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Dipartmento di Scienze Fisiologiche, Universita degli studi di Firenze, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2255911" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; *Muscle Contraction ; Muscles/*physiology/ultrastructure ; Particle Accelerators ; Rana temporaria ; Sarcomeres/physiology/ultrastructure ; Stress, Mechanical ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1982-07-02
    Description: Instantaneous stiffness of frog skeletal muscle, an indication of the proportion of attached crossbridges, was determined drug the tetanus rise and after a step length change imposed during the tetanus plateau. During the onset of contraction as well as after a step, the ratio of stiffness to force differed from that determined during the tetanus plateau. The data after a step are predicted by the Huxley-Simmons model of muscular contraction, but the results during the rise suggest that a long-lived state may exist between crossbridge attachment and force generation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cecchi, G -- Griffiths, P J -- Taylor, S -- NS 14268/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 2;217(4554):70-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6979780" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Mathematics ; *Muscle Contraction ; Muscles/physiology/ultrastructure ; Rana temporaria
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 5 (1985), S. 473-482 
    ISSN: 0392-6737
    Keywords: Electronic conduction in metals and alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Leghe di ferro-nichel, con contenuto in Ni variabile dal 29% al 32%, sono state irradiate con un fascio di neutroni avente flusso integrale di 3·1018 n cm−2 a 80°C e sono state successivamente sottoposte a trasformazione martensitica mediante raffreddamento. Le misure di resistività, di magnetoresistenza e di effetto Hall compiute sui campioni irradiati consentono di fare l'ipotesi della presenza nella fase supersatura γ di microstrutture ordinate, ricche di Fe o di Ni, oltre ad una fase α addizionale. Dal comportamento dell'effetto Hall anomalo nei campioni irradiati si è valutato il contenuto di Ni presente nelle regioni ordinate.
    Notes: Summary Iron-nickel alloys in the range from 29 to 32 wt.% Ni have been irradiated with an integral flux of 3·1018 n cm−2 and then subjected to martensitic transformation. the resistivity, magnetoresistivity and Hall-effect measurements performed on the irradiated samples allow us to support the formation of iron-rich or nichel-rich ordered microstructures and additional α-phase from the supersaturated γ-matrix. The nickel content of the above-ordered region, is evaluated from the behaviour of the anomalous Hall effect in the irradiated specimens with different composition.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 3 (1984), S. 436-446 
    ISSN: 0392-6737
    Keywords: Electronic conduction in metals and alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si sono effettuate misure di resistività, di effetto Hall e di magnetoresistività in alcuni campioni di Fe−Ni, con contenuto di nichel variabile dal 29 al 32% in peso e sottoposti a transformazione martensitica. I risultati sono stati interpretati, da una parte, tenendo conto delle modalità con cui si attua la trasformazione martensitica, diverse nelle leghe al 29 ed al 30% di Ni rispetto a quelle nelle leghe al 31 e al 32% di Ni e, dall’altra, estendendo alle suddette leghe la teoria di Smith e di Berger per l’effetto Hall nelle leghe ferromagnetiche diluite. Confrontando i dati Hall con quelli magnetoresistivi presentati alla maniera di Kohler è stato anche possibile individuare con buona approssimazione il meccanismo di scattering dei portatori di carica prevalente nelle leghe studiate, diverso nelle leghe al 29 ed al 30% di Ni (skew scattering) da quello nelle leghe al 31 e al 32% di Ni (side jump scattering).
    Abstract: Резюме Проведены измерения сопротивления, эффекта Холла и мчгнитосопротивления в образцах сплава Fe−Ni с содержанием никеля от 29 до 32 весовых процентов и подвергнутых мартенситному преобразованию. Предлагается интерпретация полученных результатов, рассматривая оба механизма мартенситного преобразования, которые различаются для сплавов с содержанием никекя 29 и 30% (по весу) и для сплавов с содержанием никеля 31 и 32% (по весу), и используя теории Смитта и Бергера для эффекта Холла в разбавленных ферромагнитных сплавах, которые применяются для описанных выше сплавов. Анализ данных по эффекту Холла, с помощью кривых Кохлера, позволяет понятв механизмы рассеяния носителей заряда, которые превалируют в различных сплавах.
    Notes: Summary Resistivity, Hall effect and magnetoresistivity measurements in Fe−Ni alloy specimens with Ni content ranging from 29 to 32 wt.% and subjected to martensitic transformation have been performed. The results have been interpreted by considering both the mechanisms of the martensitic transformation, different in 29 and 30 wt.% Ni alloys from that in 31 and 32 wt.% Ni ones, and the theories of Smith and Berger on the Hall effect in dilute ferromagnetic alloys, which have been applied to the above-described alloys. The Hall data, analysed by means of Kohler polts, have allowed us to identify the charge carrier scattering mechanisms prevailing in the different alloys,i.e. the skew scattering in 29 and 30 wt.% Ni alloys and the side jump scattering in 31 and 32 wt.% Ni ones.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 3 (1993), S. 51-62 
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model of a hard oscillator with analytic solution is presented. Its behavior under periodic kicking, for which a closed form stroboscopic map can be obtained, is studied. It is shown that the general structure of such an oscillator includes four distinct regions; the outer two regions correspond to very small or very large amplitude of the external force and match the corresponding regions in soft oscillators (invertible degree one and degree zero circle maps, respectively). There are two new regions for intermediate amplitude of the forcing. Region 3 corresponds to moderate high forcing, and is intrinsic to hard oscillators; it is characterized by discontinuous circle maps with a flat segment. Region 2 (low moderate forcing) has a certain resemblance to a similar region in soft oscillators (noninvertible degree one circle maps); however, the limit set of the dynamics in this region is not a circle, but a branched manifold, obtained as the tangent union of a circle and an interval; the topological structure of this object is generated by the finite size of the repelling set, and is therefore also intrinsic to hard oscillators.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Photochemistry 38 (1987), S. 345-355 
    ISSN: 0047-2670
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0649
    Keywords: PACS: 86.70.L; 93.85
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 fluxes of the order of 1000, 100, and 10 tonnes/day were measured for Mt. Etna, Stromboli, and Vulcano, respectively.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 4 (1983), S. 395-404 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The force-velocity (P–V) relation for single fibres isolated from the semitendinosus muscle of the frog was determined at preset times during the rise of tension and the plateau of isometric tetani. The controlled-velocity release method was used. Experiments were performed at a sarcomere length of about 2.25 µm. Addition of dantrolene-sodium (DaNa) to Ringer's solution resulted in a large reduction of the peak twitch tension and of the speed of rise of twitch and tetanic tensions. The plateau tetanic tension was either unaffected or only slightly reduced by DaNa. In all fibres the speed of rise of isometric tension after a quick release imposed at the tetanus plateau was not affected by DaNa. DaNa did not significantly affect the observed value ofV 0 and the calculated values of Hill's constantsV 0,P 0 * , a/P 0 * andb for andP–V relation determined at the tetanus plateau. In accordance with previous work, during the tetanus rise theP–V relation gradually attained its final characteristics, but there was a significant delay of the development of the isometric tension with respect to the development of theP–V relation. Treatment of the fibre with DaNa increased both the development time of theP–V relation and the level of isometric tension at which during the tetanus rise theP–V relation attained its final characteristics. It is concluded that DaNa, which inhibits the release of Ca2+ from the sarcoplasmic reticulum, also depresses the rate of development of activation.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 11 (1990), S. 371-377 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Stiffness measurements in activated skeletal muscle fibres are often used as one means of estimating the number of attached crossbridges on the assumption that myofilament compliances do not contribute significantly to the fibre compliance. This assumption was tested by studying the effects of sarcomere length on fibre stiffness in the plateau region of the length-tension diagram (from 1.96 to 2.16μm sarcomere length in the tibialis anterior muscle of the frog). Lengthening of the sarcomere across this region in fact, produces only an increase in the proportion of actin filament free from cross-bridges without altering the amount of effective overlap; no change in fibre stiffness is therefore expected if actin filaments are perfectly rigid. The results show that while tetanic tension remained constant within 1.5%, as the sarcomere length was increased from 1.96 to 2.16μm fibre stiffness decreased by about 4%, indicating that a significant proportion of sarcomere compliance is localized in the actin filaments. A simple model based on the sliding filament theory was used in order to calculate the relative contribution of actin filaments to fibre compliance. In the model it was assumed that fibre compliance resulted from the combination of crossbridge compliance (distributed over the overlap zone) in series with thin filament and tendon compliances. The calculations show that the experimental data could be adequately predicted only assuming that about 19% of sarcomere compliance is due to actin filament compliance.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 19 (1998), S. 33-42 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Force responses to fast ramp stretches at various velocities were recorded from single muscle fibres isolated from either lumbricalis digiti IV or tibialis anterior muscle of the frog (Rana esculenta) at sarcomere length between 2.15 and 3.25 μm at 15° C. Stretches were applied at rest, at tetanus plateau and during the tetanus rise. Stretches with the same velocity but different accelerations were imposed to the fibre to evaluate the effect of fibre inertia on the force responses. Length changes were measured at sarcomere level with either a laser diffractometer or a striation follower apparatus. The force response to a fast ramp stretch could be divided into two phases. The initial fast one (phase 1) lasts for the acceleration period during which the stretching velocity rises up to the steady state. The second slower phase (phase 2) lasts for the remainder of the stretch and corresponds to the well-known elastic response of the fibre. Most of this paper is concerned with phase 1. The amplitude of the initial fast phase was proportional to the stretching velocity as expected from a viscous response. This viscosity was associated with a very short (about 10 μs) relaxation time. The amplitude of the fast phase increased progressively with tension during the tetanus rise and scaled down with sarcomere length approximately in the same way as tetanic tension and fibre stiffness. These data suggest that activated fibres have a significant internal viscosity which may arise from crossbridge interaction
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