917 research outputs found
Transhumant GPS tracked sheep flocks from lowlands to highlands in Spain: grazing resources use and difficulties of walking/herding
The need for preserving walking/herding transhumance drove roads on the Iberian Peninsula hasbeen widely recognized, as they provide a wide range of ecosystem services. In spite of the decline of walkingtranshumance in Spain, some drove roads are being reactivated due mainly to the high price of lorrytransport and feeds for livestock. The objectives of this work were: (i) develop a method to track the transhumantflocks in order to know the route followed and detail the type of pastures that the sheep use during thetrip; (ii) know the main difficulties of the activity, either technical, economic or social. Collars with GPS wereinstalled around the neck of some animals of five transhumant flocks. The data provided by GPS were analyzedby a GIS and overlapped with pastures/vegetation maps. For each flock, interviews with the farmersprovided data in terms of difficulties for the activity to be continued. The method provided highly accurate dataof the routes. The main types of vegetation used by sheep and main difficulties perceived by the farmers tocontinue the activity are summarized
Magnetism in Dense Quark Matter
We review the mechanisms via which an external magnetic field can affect the
ground state of cold and dense quark matter. In the absence of a magnetic
field, at asymptotically high densities, cold quark matter is in the
Color-Flavor-Locked (CFL) phase of color superconductivity characterized by
three scales: the superconducting gap, the gluon Meissner mass, and the
baryonic chemical potential. When an applied magnetic field becomes comparable
with each of these scales, new phases and/or condensates may emerge. They
include the magnetic CFL (MCFL) phase that becomes relevant for fields of the
order of the gap scale; the paramagnetic CFL, important when the field is of
the order of the Meissner mass, and a spin-one condensate associated to the
magnetic moment of the Cooper pairs, significant at fields of the order of the
chemical potential. We discuss the equation of state (EoS) of MCFL matter for a
large range of field values and consider possible applications of the magnetic
effects on dense quark matter to the astrophysics of compact stars.Comment: To appear in Lect. Notes Phys. "Strongly interacting matter in
magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Ye
Emission Spectrum of Fundamental Strings: An Algebraic Approach
We formulate a linear difference equation which yields averaged
semi-inclusive decay rates for arbitrary, not necessarily large, values of the
masses. We show that the rates for decays M \to m+\M' of typical heavy open
strings are independent of the masses and , and compute the ``mass
deffect''. For closed strings we find decay rates proportional to , where is the reduced mass of the decy products. Our
method yields exact interaction rates valid for all mass ranges and may provide
a fully microscopic basis, not limited to the long string approximation, for
the interactions in the Boltzmann equation approach to hot string gases.Comment: 35 pages, 3 figure
Neutrino Propagation in a Strongly Magnetized Medium
We derive general expressions at the one-loop level for the coefficients of
the covariant structure of the neutrino self-energy in the presence of a
constant magnetic field. The neutrino energy spectrum and index of refraction
are obtained for neutral and charged media in the strong-field limit () using the lowest Landau level
approximation. The results found within the lowest Landau level approximation
are numerically validated, summing in all Landau levels, for strong and weakly-strong fields. The neutrino energy in
leading order of the Fermi coupling constant is expressed as the sum of three
terms: a kinetic-energy term, a term of interaction between the magnetic field
and an induced neutrino magnetic moment, and a rest-energy term. The leading
radiative correction to the kinetic-energy term depends linearly on the
magnetic field strength and is independent of the chemical potential. The other
two terms are only present in a charged medium. For strong and weakly-strong
fields, it is found that the field-dependent correction to the neutrino energy
in a neutral medium is much larger than the thermal one. Possible applications
to cosmology and astrophysics are considered.Comment: 23 pages, 4 figures. Corrected misprints in reference
Study of hysteretic thermoelectric behavior in photovoltaic materials using the finite element method, extended thermodynamics and inverse problems
The main objective of the present work is to develop and prove a theoretical explanation based on the
Extended Non-Equilibrium Thermodynamics (ENETs) for the hysteretical thermoelectric behavior
observed in certain thin-film photovoltaic materials. The ENET introduces dissipative fluxes in the
entropy balance that could explain this behavior. To verify this explanation from a numerical point of
view, results are generated using a Finite Element (FE) formulation based on the ENET and already developed
in previous publications by the authors. In addition, an identification Inverse Problem (IP) is formulated;
a cost function is defined as the quadratic difference between experimental and numerical results
and the IP is solved minimizing the cost function using genetic algorithms. The conclusion is that the
loop-like distributions are due to energy dissipation introduced by dissipative fluxes that are closely
related with relaxation times. Also, the FE-IP combination permits to find an approximated characterization
of properties for several materials from single experimental curves. Finally, several numerical simulations
are proposed for laboratory experiments to further validate the theoretical interpretation and to
confirm the relation between relaxation times and hysteresis.This research was partially supported by the Grants CSD2008-00037 Canfranc Underground Physics, Excelencia Junta Andalucia P08-TEP-03641 and Polytechnic University of Valencia under programs PAID 02-11-1828 and 05-10-2674.Palma, R.; Pérez-Aparicio, JL.; Bravo, R. (2013). Study of hysteretic thermoelectric behavior in photovoltaic materials using the finite element method, extended thermodynamics and inverse problems. Energy Conversion and Management. 65(92):557-563. https://doi.org/10.1016/j.enconman.2012.07.009S557563659
Micromegas detector developments for MIMAC
The aim of the MIMAC project is to detect non-baryonic Dark Matter with a
directional TPC. The recent Micromegas efforts towards building a large size
detector will be described, in particular the characterization measurements of
a prototype detector of 10 10 cm with a 2 dimensional readout
plane. Track reconstruction with alpha particles will be shown.Comment: 8 pages, 7 figures Proceedings of the 3rd International conference on
Directional Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10
June 2011; corrections on author affiliation
Microscopic Theory of Josephson Mesoscopic Constrictions
We present a microscopic theory for the d.c. Josephson effect in model
mesoscopic constrictions. Our method is based on a non-equilibrium Green
function formalism which allows for a self-consistent determination of the
order parameter profile along the constriction. The various regimes defined by
the different length scales (Fermi wavelength , coherence length
and constriction length ) can be analyzed, including the case
where all these lengths are comparable. For the case phase oscillations with spatial period can be
observed. In the case of solutions with a phase-slip center inside
the constriction can be found, in agreement with previous phenomenological
theories.Comment: 4 pages (RevTex 3.0), 3 postscript figures available upon request,
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