331 research outputs found
Antiferromagnetic O(N) models in four dimensions
We study the antiferromagnetic O(N) model in the F_4 lattice. Monte Carlo
simulations are applied for investigating the behavior of the transition for
N=2,3. The numerical results show a first order nature but with a large
correlation length. The limit is also considered with analytical
methods.Comment: 14 pages, 3 postscript figure
The influence of rifle carriage on the kinetics of human gait
The influence that rifle carriage has on human gait has received little attention in the published literature. Rifle carriage has two main effects, to add load to the anterior of the body and to restrict natural arm swing patterns. Kinetic data were collected from 15 male participants, with 10 trials in each of four experimental conditions. The conditions were: walking without a load (used as a control condition); carrying a lightweight rifle
simulator, which restricted arm movements but applied no additional load; wearing a 4.4 kg diving belt, which allowed arms to move freely; carrying a weighted (4.4 kg)
replica SA80 rifle. Walking speed was fixed at 1.5 m/s (+5%) and data were sampled at 400 Hz. Results showed that rifle carriage significantly alters the ground reaction forces produced during walking, the most important effects being an increase in the impact peak and mediolateral forces. This study suggests that these effects are due to the increased range of motion of the body’s centre of mass caused by the impeding of natural arm swing patterns. The subsequent effect on the potential development of injuries in rifle carriers is unknown
Variational Mean Field approach to the Double Exchange Model
It has been recently shown that the double exchange Hamiltonian, with weak
antiferromagnetic interactions, has a richer variety of first and second order
transitions than previously anticipated, and that such transitions are
consistent with the magnetic properties of manganites. Here we present a
thorough discussion of the variational Mean Field approach that leads to the
these results. We also show that the effect of the Berry phase turns out to be
crucial to produce first order Paramagnetic-Ferromagnetic transitions near half
filling with transition temperatures compatible with the experimental
situation. The computation relies on two crucial facts: the use of a Mean Field
ansatz that retains the complexity of a system of electrons with off-diagonal
disorder, not fully taken into account by the Mean Field techniques, and the
small but significant antiferromagnetic superexchange interaction between the
localized spins.Comment: 13 pages, 11 postscript figures, revte
An infinite family of superintegrable systems from higher order ladder operators and supersymmetry
We will discuss how we can obtain new quantum superintegrable Hamiltonians
allowing the separation of variables in Cartesian coordinates with higher order
integrals of motion from ladder operators. We will discuss also how higher
order supersymmetric quantum mechanics can be used to obtain systems with
higher order ladder operators and their polynomial Heisenberg algebra. We will
present a new family of superintegrable systems involving the fifth Painleve
transcendent which possess fourth order ladder operators constructed from
second order supersymmetric quantum mechanics. We present the polynomial
algebra of this family of superintegrable systems.Comment: 8 pages, presented at ICGTMP 28, accepted for j.conf.serie
Los montes submarinos en los márgenes continentales de Iberia
Seamounts are first-order morphological elements on continental margins and in oceanic domains, which
have been extensively researched over recent decades in all branches of oceanography. These features
favour the development of several geological processes, and their study gives us a better understanding of
their geological and morphological domains. The seamounts around Iberia are numerous and provide excellent
examples of the geodiversity of these morphological elements. Here we present a compilation of 15
seamounts around the Iberian Peninsula. These seamounts have different origins related to the geodynamic
evolution (volcanism, extensional or compressive tectonics, and diapirism) of the domains where they are
located. The current configuration of their relief has been influenced by Neogene-Quaternary tectonics. Their
positioning controls the current morpho-sedimentary processes in the basins and on the margins, and highlights
the fact that downslope processes on seamount flanks (mass flows, turbidite flows, and landslides) and
processes parallel to seamounts (contouritic currents) correspond to the major geological features they are
associated with them. Biogenic structures commonly develop on the tops of seamounts where occasionally
isolated shelves form that have carbonate-dominated sedimentation.Los montes submarinos son rasgos morfológicos singulares, cuyo estudio tiene gran relevancia desde el
punto de vista de las distintas ramas de la oceanografía. Su presencia favorece el desarrollo de diferentes
procesos geológicos y proporciona un mejor conocimiento de los dominios geológicos y morfológicos en los
que se encuentran. En el entorno de Iberia, los montes submarinos tienen una amplia representación y tipología.
En este trabajo, se presenta una recopilación geológica de 15 montes submarinos (ocho en el Mar
Mediterráneo y siete en el Océano Atlántico) de los márgenes continentales de Iberia y en el dominio
Oceánico Atlántico, utilizándose levantamientos batimétricos y geofísicos. El origen de estos montes es muy
diferente y está relacionado con la evolución geodinámica del dominio geológico en el que aparecen (volcanismo,
tectónica extensional o compresional y diapirismo). La configuración actual del relieve ha sido controlada
por la actividad tectónica en el Neógeno-Cuaternario. Su presencia controla el desarrollo de los procesos
morfosedimentarios recientes de márgenes y cuencas. Los principales procesos sedimentarios
asociados a estos montes se relacionan con procesos longitudinales (flujos en masa, flujos turbidíticos, deslizamientos)
y transversales a dichos montes (corrientes de contorno). Además es frecuente en ellos el desarrollo
de cuerpos biogénicos sobre sus cimas e incluso de plataformas con sedimentación carbonatada. Los montes submarinos de Iberia muestran una gran geodiversidad y constituyen un elemento morfológico de
primer orden para comprender los procesos geológicos que tienen lugar en sus márgenes continentales y
dominios oceánicos adyacentes.Versión del editor0,000
Mars Sulfate Formation Sourced in Sulfide-Enriched Subsurface Fluids: The Rio Tinto Model
The extensive evidence for sulfate deposits on Mars provided by analyses of MER and Mars Express data shows that the sulfur played an essential role in the geochemical cycles of the planet, including reservoirs in the atmosphere, hydro-sphere and geosphere. Overall the data are consistent with a fluvial/lacustrine-evaporative origin of at least some of the sulfate deposits, with mineral precipitation through oversaturation of salty acidic fluids enriched in sulfates. This scenario requires reservoirs of sulfur and associated cations, as well as an acidic and oxidizing hydrochemistry which could be provided by surface and subsurface catching of meteoric waters resulting in the presence of sulfur-bearing gases and steam photochemistry. In this work we suggest a new scenario for the extensive generation of sulfates in Mars based on the observation of seasonal changes in the redox and pH of subsurface waters enriched in sulfur that supply the acidic Mars process analog of Rio Tinto. This model considers the long-term subsurface storage of sulfur during most of Noachian and its release from the late Noachian to Hesperian time through weathering by meteoric fluids that would acidify and oxidize the sulfur bearing compounds stored in the subsurface
Equilibrium random-field Ising critical scattering in the antiferromagnet Fe(0.93)Zn(0.07)F2
It has long been believed that equilibrium random-field Ising model (RFIM)
critical scattering studies are not feasible in dilute antiferromagnets close
to and below Tc(H) because of severe non-equilibrium effects. The high magnetic
concentration Ising antiferromagnet Fe(0.93)Zn(0.07)F2, however, does provide
equilibrium behavior. We have employed scaling techniques to extract the
universal equilibrium scattering line shape, critical exponents nu = 0.87 +-
0.07 and eta = 0.20 +- 0.05, and amplitude ratios of this RFIM system.Comment: 4 pages, 1 figure, minor revision
Egg Consumption and Risk of Type 2 Diabetes in Men and Women
OBJECTIVE—Whereas limited and inconsistent findings have been reported on the relation between dietary cholesterol or egg consumption and fasting glucose, no previous study has examined the association between egg consumption and type 2 diabetes. This project sought to examine the relation between egg intake and the risk of type 2 diabetes in two large prospective cohorts
Towards a classificatión of dendrogeomorphological evidences and their utility in flood hazard analysis
Se analizan los diferentes parámetros dendrogeomorfológicos válidos para la estimación de riesgo
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