2,215 research outputs found

    Weight-Training Injuries: A Systematic Review of the Etiology, Risk Factors, and Interventions

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    A hysteresis model with dipole interaction: one more devil-staircase

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    Magnetic properties of 2D systems of magnetic nanoobjects (2D regular lattices of the magnetic nanoparticles or magnetic nanostripes) are considered. The analytical calculation of the hysteresis curve of the system with interaction between nanoobjects is provided. It is shown that during the magnetization reversal system passes through a number of metastable states. The kinetic problem of the magnetization reversal was solved for three models. The following results have been obtained. 1) For 1D system (T=0) with the long-range interaction with the energy proportional to r−pr^{-p}, the staircase-like shape of the magnetization curve has self-similar character. The nature of the steps is determined by interplay of the interparticle interaction and coercivity of the single nanoparticle. 2) The influence of the thermal fluctuations on the kinetic process was examined in the framework of the nearest-neighbor interaction model. The thermal fluctuations lead to the additional splitting of the steps on the magnetization curve. 3) The magnetization curve for system with interaction and coercivity dispersion was calculated in mean field approximation. The simple method to experimentally distinguish the influence of interaction and coercivity dispersion on the magnetization curve is suggested.Comment: 22 pages, 8 figure

    Space charge in drift chambers operated with the Xe,CO2(15%) mixture

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    Using prototype modules of the ALICE Transition Radiation Detector we investigate space charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe,CO2(15%) mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detailed simulations of detector signals, which reproduce the measurements and lend strong support to our interpretation of the measurements in terms of space charge effects.Comment: 18 pages, 10 figures, accepted for publication in Nucl.Instrum.Meth. A. Data files available at http://www-alice.gsi.de/tr

    Small molecules and targeted therapies in distant metastatic disease

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    Chemotherapy, biological agents or combinations of both have had little impact on survival of patients with metastatic melanoma. Advances in understanding the genetic changes associated with the development of melanoma resulted in availability of promising new agents that inhibit specific proteins up-regulated in signal cell pathways or inhibit anti-apoptotic proteins. Sorafenib, a multikinase inhibitor of the RAF/RAS/MEK pathway, elesclomol (STA-4783) and oblimersen (G3139), an antisense oligonucleotide targeting anti-apoptotic BCl-2, are in phase III clinical studies in combination with chemotherapy. Agents targeting mutant B-Raf (RAF265 and PLX4032), MEK (PD0325901, AZD6244), heat-shock protein 90 (tanespimycin), mTOR (everolimus, deforolimus, temsirolimus) and VEGFR (axitinib) showed some promise in earlier stages of clinical development. Receptor tyrosine-kinase inhibitors (imatinib, dasatinib, sunitinib) may have a role in treatment of patients with melanoma harbouring c-Kit mutations. Although often studied as single agents with disappointing results, new targeted drugs should be more thoroughly evaluated in combination therapies. The future of rational use of new targeted agents also depends on successful application of analytical techniques enabling molecular profiling of patients and leading to selection of likely therapy responder

    Comparative study of an Eden model for the irreversible growth of spins and the equilibrium Ising model

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    The Magnetic Eden Model (MEM) with ferromagnetic interactions between nearest-neighbor spins is studied in (d+1)−(d+1)-dimensional rectangular geometries for d=1,2d = 1,2. In the MEM, magnetic clusters are grown by adding spins at the boundaries of the clusters. The orientation of the added spins depends on both the energetic interaction with already deposited spins and the temperature, through a Boltzmann factor. A numerical Monte Carlo investigation of the MEM has been performed and the results of the simulations have been analyzed using finite-size scaling arguments. As in the case of the Ising model, the MEM in d=1d = 1 is non-critical (only exhibits an ordered phase at T=0T= 0). In d=2d = 2 the MEM exhibits an order-disorder transition of second-order at a finite temperature. Such transition has been characterized in detail and the relevant critical exponents have been determined. These exponents are in agreement (within error bars) with those of the Ising model in 2 dimensions. Further similarities between both models have been found by evaluating the probability distribution of the order parameter, the magnetization and the susceptibility. Results obtained by means of extensive computer simulations allow us to put forward a conjecture which establishes a nontrivial correspondence between the MEM for the irreversible growth of spins and the equilibrium Ising model. This conjecture is certainly a theoretical challenge and its confirmation will contribute to the development of a framework for the study of irreversible growth processes.Comment: 21 pages, 11 figure

    Growth modes of Fe(110) revisited: a contribution of self-assembly to magnetic materials

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    We have revisited the epitaxial growth modes of Fe on W(110) and Mo(110), and propose an overview or our contribution to the field. We show that the Stranski-Krastanov growth mode, recognized for a long time in these systems, is in fact characterized by a bimodal distribution of islands for growth temperature in the range 250-700°C. We observe firstly compact islands whose shape is determined by Wulff-Kaischev's theorem, secondly thin and flat islands that display a preferred height, ie independant from nominal thickness and deposition procedure (1.4nm for Mo, and 5.5nm for W on the average). We used this effect to fabricate self-organized arrays of nanometers-thick stripes by step decoration. Self-assembled nano-ties are also obtained for nucleation of the flat islands on Mo at fairly high temperature, ie 800°C. Finally, using interfacial layers and solid solutions we separate two effects on the preferred height, first that of the interfacial energy, second that of the continuously-varying lattice parameter of the growth surface.Comment: 49 pages. Invited topical review for J. Phys.: Condens. Matte

    Order-disorder criticality, wetting, and morphological phase transitions in the irreversible growth of far-from-equilibrium magnetic films

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    An exhaustive numerical investigation of the growth of magnetic films in confined (d+1)(d+1)-dimensional stripped geometries (d=1,2d=1,2) is carried out by means of extensive Monte Carlo simulations. Thin films in contact with a thermal bath are grown by adding spins with two possible orientations and considering ferromagnetic (nearest-neighbor) interactions. At low temperatures, it is observed that the films exhibit ``spontaneous magnetization reversals'' during the growth process. Furthermore, it is found that for d=1d=1 the system is non-critical, while a continuous order-disorder phase transition at finite temperature takes place in the d=2d=2 case. Using standard finite-size scaling procedures, the critical temperature and some relevant critical exponents are determined. Finally, the growth of magnetic films in (2+1)(2+1) dimensions with competing short-range magnetic fields acting along the confinement walls is studied. Due to the antisymmetric condition considered, an interface between domains with spins having opposite orientation develops along the growing direction. Such an interface undergoes a localization-delocalization transition that is the precursor of a wetting transition in the thermodynamic limit. Furthermore, the growing interface also undergoes morphological transitions in the growth mode. A comparison between the well-studied equilibrium Ising model and the studied irreversible magnetic growth model is performed throughout. Although valuable analogies are encountered, it is found that the nonequilibrium nature of the latter introduces new and rich physical features of interest.Comment: 23 pages, 10 figure

    Cranked Relativistic Hartree-Bogoliubov Theory: Superdeformed Bands in the A∼190A\sim 190 Region

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    Cranked Relativistic Hartree-Bogoliubov (CRHB) theory is presented as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type and approximate particle number projection is performed by Lipkin-Nogami method. This theory is applied to the description of yrast superdeformed rotational bands observed in even-even nuclei of the A∼190A\sim 190 mass region. Using the well established parameter sets NL1 for the Lagrangian and D1S for the pairing force one obtains a very successful description of data such as kinematic (J(1)J^{(1)}) and dynamic (J(2)J^{(2)}) moments of inertia without any adjustment of new parameters. Within the present experimental accuracy the calculated transition quadrupole moments QtQ_t agree reasonably well with the observed data.Comment: 6 pages including 4 PostScript figures, uses RevTex, revised version, Phys.Rev. C, Rapid Communications, in pres
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