We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between 0.09A and 1.93A GeV. For the ...heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.
Nature of PEVK-Titin Elasticity in Skeletal Muscle Linke, Wolfgang A.; Ivemeyer, Marc; Mundel, Peter ...
Proceedings of the National Academy of Sciences - PNAS,
07/1998, Volume:
95, Issue:
14
Journal Article
Peer reviewed
Open access
A unique sequence within the giant titin molecule, the PEVK domain, has been suggested to greatly contribute to passive force development of relaxed skeletal muscle during stretch. To explore the ...nature of PEVK elasticity, we used titin-specific antibodies to stain both ends of the PEVK region in rat psoas myofibrils and determined the region's force-extension relation by combining immunofluorescence and immunoelectron microscopy with isolated myofibril mechanics. We then tried to fit the results with recent models of polymer elasticity. The PEVK segment elongated substantially at sarcomere lengths above 2.4 μ m and reached its estimated contour length at ≈ 3.5 μ m. In immunofluorescently labeled sarcomeres stretched and released repeatedly above 3 μ m, reversible PEVK lengthening could be readily visualized. At extensions near the contour length, the average force per titin molecule was calculated to be ≈ 45 pN. Attempts to fit the force-extension curve of the PEVK segment with a standard wormlike chain model of entropic elasticity were successful only for low to moderate extensions. In contrast, the experimental data also could be correctly fitted at high extensions with a modified wormlike chain model that incorporates enthalpic elasticity. Enthalpic contributions are likely to arise from electrostatic stiffening, as evidenced by the ionic-strength dependency of titin-based myofibril stiffness; at high stretch, hydrophobic effects also might become relevant. Thus, at physiological muscle lengths, the PEVK region does not function as a pure entropic spring. Rather, PEVK elasticity may have both entropic and enthalpic origins characterizable by a polymer persistence length and a stretch modulus.
Detailed studies of the azimuthal dependence of the mean fragment and flow energies in the Au+Au and Xe+CsI systems are reported as a function of incident energy and centrality. Comparisons between ...data and model calculations show that the flow energy values along different azimuthal directions could be viewed as snapshots of the fireball expansion with different exposure times. For the same number of participating nucleons more transversally elongated participant shapes from the heavier system produce less collective transverse energy. Good agreement with Boltzmann-Uehling-Uhlenbeck calculations is obtained for a soft nuclear equation of state.
Experimental data on K
+ meson and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru+Ru at 1.69
A GeV and Ni+Ni at 1.93
A GeV are presented. The K
+ sideward flow is ...found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the data favour the existence of an in-medium repulsive K
+-nucleon potential.
Using the large acceptance apparatus FOPI, we study central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca + 40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni + 58Ni (0.15, ...0.25, 0.4), 96Ru + 96Ru (0.4, 1.0, 1.5), 96Zr + 96Zr (0.4, 1.0, 1.5), 129Xe + CsI (0.15, 0.25, 0.4), 197Au + 197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include cluster multiplicities, longitudinal and transverse rapidity distributions and stopping, and radial flow. The data are compared to earlier data where possible and to transport model simulations.
The poly-immunoglobulin domain region of titin, located within the elastic section of this giant muscle protein, determines the extensibility of relaxed myofibrils mainly at shorter physiological ...lengths. To elucidate this region's contribution to titin elasticity, we measured the elastic properties of the N-terminal I-band Ig region by using immunofluorescence/immunoelectron microscopy and myofibril mechanics and tried to simulate the results with a model of entropic polymer elasticity. Rat psoas myofibrils were stained with titin-specific antibodies flanking the Ig region at the N terminus and C terminus, respectively, to record the extension behaviour of that titin segment. The segment's end-to-end length increased mainly at small stretch, reaching approximately 90% of the native contour length of the Ig region at a sarcomere length of 2.8 microm. At this extension, the average force per single titin molecule, deduced from the steady-state passive length-tension relation of myofibrils, was approximately 5 or 2.5 pN, depending on whether we assumed a number of 3 or 6 titins per half thick filament. When the force-extension curve constructed for the Ig region was simulated by the wormlike chain model, best fits were obtained for a persistence length, a measure of the chain's bending rigidity, of 21 or 42 nm (for 3 or 6 titins/half thick filament), which correctly reproduced the curve for sarcomere lengths up to 3.4 microm. Systematic deviations between data and fits above that length indicated that forces of >30 pN per titin strand may induce unfolding of Ig modules. We conclude that stretches of at least 5-6 Ig domains, perhaps coinciding with known super repeat patterns of these titin modules in the I-band, may represent the unitary lengths of the wormlike chain. The poly-Ig regions might thus act as compliant entropic springs that determine the minute levels of passive tension at low extensions of a muscle fiber.
Using the large acceptance apparatus FOPI, we study central and semi-central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), ...58Ni+58Ni (0.15, 0.25, 0.4), 96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 129Xe+CsI (0.15, 0.25, 0.4), 197Au+197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include directed and elliptic flow. The data are compared to earlier data where possible and to transport model simulations. A stiff nuclear equation of state is found to be incompatible with the data. Evidence for extra-repulsion of neutrons in compressed asymmetric matter is found.
The ALICE detector is a dedicated heavy-ion detector currently built at the Large Hadron Collider (LHC) at CERN. The detector control system (DCS) covers the task of controlling, configuring and ...monitoring the detector. One sub-system is the control system for the Front-end electronics of the time projection chamber (TPC). It controls in total 216 readout systems with 4356 Front-End Cards serving roughly 560 000 channels. The system consists of a large number of distributed nodes in a layer-structured hierarchy. The low-level node controlling the Front-end electronics is an embedded computer system, the DCS board, which provides the opportunity to run a light-weight Linux system on the card. The board interfaces to the Front-end electronics via a dedicated hardware interface and connects to the higher DCS-layers via the DIM communication framework over Ethernet. Since the experiment will be running in a radiation environment, fault tolerance, error correction and system stability in general are major concerns. Already the low level devices carry out intelligent error handling and act automatically upon several conditions. This paper presents the architecture of the system, the application of the DCS board and experiences from integration tests.
We present measurements of the excitation function of elliptic flow at midrapidity in Au+Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the ...interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of elliptic flow is presented for the first time in this energy range, revealing a rapid change with incident energy below 0.4 AGeV, followed by an almost perfect scaling at the higher energies. The equation of state of compressed nuclear matter is addressed through comparisons to microscopic transport model calculations.
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