662 research outputs found
The Site-Diluted Ising Model in Four Dimension
In the literature, there are five distinct, fragmented sets of analytic
predictions for the scaling behaviour at the phase transition in the
random-site Ising model in four dimensions. Here, the scaling relations for
logarithmic corrections are used to complete the scaling pictures for each set.
A numerical approach is then used to confirm the leading scaling picture coming
from these predictions and to discriminate between them at the level of
logarithmic corrections.Comment: 15 pages, 5 ps figures. Accepted for publication in Phys. Rev.
Mesozooplankton community structure during summer months in the bay of Cádiz.
Mesozooplankton organisms (>250 μm) were
sampled at two stations (inner and outer Bay) in
the Bay of Cádiz between May and July 2008.
Samples were analysed by means of a semi-automated
technique in order to give a preliminary view of
the mesoozooplankton community structure in the
Bay, based on taxonomic diversity and biomass
distribution among size classes. The abundance of
organisms increased from May to July in accordance
with the increase in temperature and Chlorophyll a
(Chla) concentrations. Abundances were higher in
the outer Bay station, where Chla concentrations
are greater and the water column is more stable. The
community changed from being meroplankton- to
holoplankton-based due to an increase of Calanoida
and especially Cladocera individuals (mainly Penilia
avirostris), which are known to peak acutely in the
summer. The analysis of Normalised Biomass-Size
spectra revealed fairly steep slopes (average -1.3)
and relatively high departures from steady state (r2
= 0.8 – 0.94), expectable in a coastal system such
as the Bay of Cádiz were disturbance factors are
introduced from benthic and tidal processes, together
with anthropogenic pressure
Scaling behavior of the Heisenberg model in three dimensions
We report on extensive numerical simulations of the three-dimensional
Heisenberg model and its analysis through finite-size scaling of Lee-Yang
zeros. Besides the critical regime, we also investigate scaling in the
ferromagnetic phase. We show that, in this case of broken symmetry, the
corrections to scaling contain information on the Goldstone modes. We present a
comprehensive Lee-Yang analysis, including the density of zeros and confirm
recent numerical estimates for critical exponents.Comment: 19 pages, 9 figure
Physiological responses in a simulated canarian wrestling contest
La Lucha Canaria (LC) ha sido recientemente reconocida como deporte por el Consejo Superior de Deportes, aunque su origen se pierde en el tiempo. Sin embargo, no hay ningún trabajo en la bibliografía científica que describa qué ocurre fisiológicamente durante la competición en esta modalidad de lucha, y éste es el objetivo del presente trabajo. Con una muestra de 12 luchadores de alto nivel (puntales) simulamos el sistema de competición actual en Lucha Canaria. Se estudió la frecuencia cardiaca, la tensión arterial y la concentración de lactato en sangre en diferentes momentos de la simulación. Los patrones observados de respuesta de FC, TA y lactato, caracterizan a la competición en LC como un ejercicio intermitente, con picos de intensidad que superan el umbral láctico y determinan incrementos importantes de FC y TA sistólica. Este estudio es el primero en que se valora la respuesta fisiológica del luchador canario en competición.The aim of this article is to describe what happens from a physiological point of view in a Canarian Wrestling (CW) contest. The Spanish National Sports Council recognized Canarian Wrestling as a sport on June 1st, 2009, although its origin is not very well documented. No scientific article exists in the scientific literature to describe what happens physiologically during a CW contest. Twelve high level wrestlers were recruited to simulate a CW match. The study involved data about heart rate (HR), blood pressure (BP) and blood lactate levels (L) at different moments of the combat. The conclusions of the data observed concerning HR, BP and L classify Canarian Wrestling as an intermittent exercise, with intensity peaks that exceed the lactic threshold and high levels of HR and systolic BP. This is the first paper in which the physiological responses in a Canarian Wrestling competition are reported
Thermal stability of copper nitride thin films: The role of nitrogen migration
The atomic composition, structural, morphological, and optical properties of N-rich copper nitride thin films have been investigated prior to and after annealing them in vacuum at temperatures up to 300 °C. Films were characterized by means of ion-beam analysis (IBMA), X-ray diffraction (XRD), atomic force microscopy (AFM), and spectroscopic ellipsometry techniques (SE). The data reveal that even when the total (integrated over the whole thickness) atomic composition of the films remains constant, nitrogen starts to migrate from the bulk to the film surface, without out-diffusing, at temperatures as low as 100 °C. This migration leads to two chemical phases with different atomic concentration of nitrogen, lattice parameters, and crystallographic orientation but with the same crystal structure. XRD experimental and Rietveld refined data seem to confirm that nitrogen excess accommodates in interstitial locations within the anti-ReO3 crystal lattice forming a solid solution. The influence of nitrogen migration on the optical (electronic) properties of the films will be discusse
Stopping power dependence of nitrogen sputtering yields in copper nitride films under swift-ion irradiation: Exciton model approach
Nitrogen sputtering yields as high as 104 atoms/ion, are obtained by irradiating N-rich-Cu3N films (N concentration: 33 ± 2 at.%) with Cu ions at energies in the range 10?42 MeV. The kinetics of N sputtering as a function of ion fluence is determined at several energies (stopping powers) for films deposited on both, glass and silicon substrates. The kinetic curves show that the amount of nitrogen release strongly increases with rising irradiation fluence up to reaching a saturation level at a low remaining nitrogen fraction (5?10%), in which no further nitrogen reduction is observed. The sputtering rate for nitrogen depletion is found to be independent of the substrate and to linearly increase with electronic stopping power (Se). A stopping power (Sth) threshold of ?3.5 keV/nm for nitrogen depletion has been estimated from extrapolation of the data. Experimental kinetic data have been analyzed within a bulk molecular recombination model. The microscopic mechanisms of the nitrogen depletion process are discussed in terms of a non-radiative exciton decay model. In particular, the estimated threshold is related to a minimum exciton density which is required to achieve efficient sputtering rates
Compositional, structural and morphological modifications of N-rich Cu3N films induced by irradiation with Cu at 42 MeV
N-rich Cu3N films were irradiated with Cu at 42 MeV in the fluences range from 4 × 1011 to 1 × 1014 cm−2. The radiation-induced changes in the chemical composition, structural phases, surface morphology and optical properties have been characterized as a function of ion fluence, substrate temperature and angle of incidence of the incoming ion by means of ion-beam analysis (IBA), x-ray diffraction, atomic force microscopy, profilometry and Fourier transform infrared spectroscopy techniques. IBA methods reveal a very efficient sputtering of N whose yield (5 × 103 atom/ion) is almost independent of substrate temperature (RT-300 °C) but slightly depends on the incidence angle of the incoming ion. The Cu content remains essentially constant within the investigated fluence range. All data suggest an electronic mechanism to be responsible for the N depletion. The release of nitrogen and the formation of Cu2O and metallic Cu are discussed on the basis of existing models
On the possibility to supercool molecular hydrogen down to superfluid transition
Recent calculations by Vorobev and Malyshenko (JETP Letters, 71, 39, 2000)
show that molecular hydrogen may stay liquid and superfluid in strong electric
fields of the order of . I demonstrate that strong local
electric fields of similar magnitude exist beneath a two-dimensional layer of
electrons localized in the image potential above the surface of solid hydrogen.
Even stronger local fields exist around charged particles (ions or electrons)
if surface or bulk of a solid hydrogen crystal is statically charged.
Measurements of the frequency shift of the photoresonance transition
in the spectrum of two-dimensional layer of electrons above positively or
negatively charged solid hydrogen surface performed in the temperature range 7
- 13.8 K support the prediction of electric field induced surface melting. The
range of surface charge density necessary to stabilize the liquid phase of
molecular hydrogen at the temperature of superfluid transition is estimated.Comment: 5 pages, 2 figure
Fermions and Disorder in Ising and Related Models in Two Dimensions
The aspects of phase transitions in the two-dimensional Ising models modified
by quenched and annealed site disorder are discussed in the framework of
fermionic approach based on the reformulation of the problem in terms of
integrals with anticommuting Grassmann variables.Comment: 11 pages, 1 table, no figures. The discussion is merely based on a
talk given at the International Bogoliubov Conference on Problems of
Theoretical and Mathematical Physics, MIRAS--JINR, Moscow--Dubna, Russia,
August 21--27, 200
Plasma-wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials
Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong
bursts of fast charged particles which will deposit tens of kJ m and
implant more than 10 particles m in a few microseconds at a
repetition rate of some Hz. Large chamber dimensions and resistant
plasma-facing materials must be combined to guarantee the chamber performance
as long as possible under the expected threats: heating, fatigue, cracking,
formation of defects, retention of light species, swelling and erosion. Current
and novel radiation resistant materials for the first wall need to be validated
under realistic conditions. However, at present there is a lack of facilities
which can reproduce such ion environments.
This contribution proposes the use of ultra-intense lasers and high-intense
pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By
target normal sheath acceleration, ultra-intense lasers can generate very short
and energetic ion pulses with a spectral distribution similar to that of the
inertial fusion ion bursts, suitable to validate fusion materials and to
investigate the barely known propagation of those bursts through background
plasmas/gases present in the reactor chamber. HIPIB technologies, initially
developed for inertial fusion driver systems, provide huge intensity pulses
which meet the irradiation conditions expected in the first wall of LIF
chambers and thus can be used for the validation of materials too
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