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
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 , 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
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
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
The Magnetic Eden Model (MEM) with ferromagnetic interactions between
nearest-neighbor spins is studied in dimensional rectangular geometries
for . 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 is non-critical (only exhibits an ordered phase at ). In
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
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
An exhaustive numerical investigation of the growth of magnetic films in
confined -dimensional stripped geometries () 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 the system
is non-critical, while a continuous order-disorder phase transition at finite
temperature takes place in the case. Using standard finite-size scaling
procedures, the critical temperature and some relevant critical exponents are
determined. Finally, the growth of magnetic films in 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
Surface and Interface Properties in Thin-Film Solar Cells: Using Soft X-rays and Electrons to Unravel the Electronic and Chemical Structure
Cranked Relativistic Hartree-Bogoliubov Theory: Superdeformed Bands in the Region
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 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 () and dynamic ()
moments of inertia without any adjustment of new parameters. Within the present
experimental accuracy the calculated transition quadrupole moments 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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