2,536 research outputs found
Impact of radiative corrections on sterile neutrino scenarios
In sterile neutrino scenarios, radiative corrections induce mass splittings
proportional to the top Yukawa coupling, in contrast to the three active
neutrino case where the induced splittings are proportional to the tau Yukawa
coupling. In view of this, we have analyzed the stability of the four-neutrino
schemes favored by oscillation experiments, consisting in two pairs of nearly
degenerate neutrinos separated by the LSND gap. Requiring compatibility with
the measurements of the abundances of primordial elements produced in Big Bang
Nucleosynthesis, we find that when the heaviest pair corresponds to the solar
neutrinos (mainly an admixture of nu_e - nu_s) the natural mass splitting is
3-5 orders of magnitude larger than the observed one, discrediting the scenario
from a theoretical point of view. On the contrary, the scheme where the
heaviest pair corresponds to the atmospheric neutrinos (mainly an admixture of
nu_mu - nu_tau) is safe from radiative corrections due to the small sterile
component of these mass eigenstates.Comment: 14 pages, LaTeX, 2 figures. Discussion enlarged, references added and
typos correcte
An experimental study of oil-water flows in horizontal pipes
© BHR Group 2015 Multiphase 17.This paper reports an effort to investigate the effect of flow velocities and inlet configurations on horizontal oil-water flows in a 32 mm ID acrylic pipe using water and an aliphatic oil (Exxsol D140) as test fluids. The flows of interest were analysed using pressure drop measurements and high-speed photography in an effort to obtain a flow pattern map, pressure gradient profiles and measures of the in situ phase fractions. The experiments reveal a particular effect of the inlet configuration on the observed flow patterns. A horizontal plate, installed at the inlet, generates a transition to stratified flow when the plate height closely matched the in situ water height at low water cuts
PAMELA's cosmic positron from decaying LSP in SO(10) SUSY GUT
We propose two viable scenarios explaining the recent observations on cosmic
positron excess. In both scenarios, the present relic density in the Universe
is assumed to be still supported by thermally produced WIMP or LSP (\chi). One
of the scenarios is based on two dark matter (DM) components (\chi,X) scenario,
and the other is on SO(10) SUSY GUT. In the two DM components scenario,
extremely small amount of non-thermally produced meta-stable DM component
[O(10^{-10}) < n_X /n_\chi] explains the cosmic positron excess. In the SO(10)
model, extremely small R-parity violation for LSP decay to e^\pm is naturally
achieved with a non-zero VEV of the superpartner of one right-handed neutrino
(\tilde{\nu}^c) and a global symmetry.Comment: 6 pages, Talks presented in PASCOS, SUSY, and COSMO/CosPA in 201
Theoretical Constraints on the Vacuum Oscillation Solution to the Solar Neutrino Problem
The vacuum oscillation (VO) solution to the solar anomaly requires an
extremely small neutrino mass splitting, Delta m^2_{sol}\leq 10^{-10} eV^2. We
study under which circumstances this small splitting (whatever its origin) is
or is not spoiled by radiative corrections. The results depend dramatically on
the type of neutrino spectrum. If m_1^2 \sim m_2^2 \geq m_3^2, radiative
corrections always induce too large mass splittings. Moreover, if m_1 and m_2
have equal signs, the solar mixing angle is driven by the renormalization group
evolution to very small values, incompatible with the VO scenario (however, the
results could be consistent with the small-angle MSW scenario). If m_1 and m_2
have opposite signs, the results are analogous, except for some small (though
interesting) windows in which the VO solution may be natural with moderate
fine-tuning. Finally, for a hierarchical spectrum of neutrinos, m_1^2 << m_2^2
<< m_3^2, radiative corrections are not dangerous, and therefore this scenario
is the only plausible one for the VO solution.Comment: 13 pages, LaTeX, 3 ps figures (psfig.sty
PolÃtica comercial de los años ochenta en El Salvador
Cuando se trata de hablar sobre la estrategia comercial de un paÃs, esta no puede ser aislada del resto de la estructura económica nacional ni del entorno. En el presente trabajo, se lleva a cabo un análisis sobre la evolución de la polÃtica comercial de El Salvador en los años ochenta, partiendo de una breve descripción del contexto histórico, económico y polÃtico. En segundo lugar se desarrolla un análisis, principalmente descriptivo, de las medidas macroeconómicas utilizadas a lo largo de la década y, finalmente, se establecen las conclusiones, siendo la principal de ellas, la ausencia de una polÃtica comercial congruente en El Salvador durante la década
Looking for a charge asymmetry in cosmic rays
We combine the data from PAMELA and FERMI-LAT cosmic ray experiments by
introducing a simple sum rule. This allows to investigate whether the lepton
excess observed by these experiments is charge symmetric or not. We also show
how the data can be used to predict the positron fraction at energies yet to be
explored by the AMS-02 experiment.Comment: Contribution to the proceedings of DISCRETE 2010, 5 pages, 2 figure
Cell death induced by the application of alternating magnetic fields to nanoparticle-loaded dendritic cells
In this work, the capability of primary, monocyte-derived dendritic cells
(DCs) to uptake iron oxide magnetic nanoparticles (MNPs) is assessed and a
strategy to induce selective cell death in these MNP-loaded DCs using external
alternating magnetic fields (AMFs) is reported. No significant decrease in the
cell viability of MNP-loaded DCs, compared to the control samples, was observed
after five days of culture. The amount of MNPs incorporated into the cytoplasm
was measured by magnetometry, which confirmed that 1 to 5 pg of the particles
were uploaded per cell. The intracellular distribution of these MNPs, assessed
by transmission electron microscopy, was found to be primarily inside the
endosomic structures. These cells were then subjected to an AMF for 30 min, and
the viability of the blank DCs (i.e., without MNPs), which were used as control
samples, remained essentially unaffected. However, a remarkable decrease of
viability from approximately 90% to 2-5% of DCs previously loaded with MNPs was
observed after the same 30 min exposure to an AMF. The same results were
obtained using MNPs having either positive (NH2+) or negative (COOH-) surface
functional groups. In spite of the massive cell death induced by application of
AMF to MNP-loaded DCs, the amount of incorporated magnetic particles did not
raise the temperature of the cell culture. Clear morphological changes at the
cell structure after magnetic field application were observed using scanning
electron microscopy. Therefore, local damage produced by the MNPs could be the
main mechanism for the selective cell death of MNP-loaded DCs under an AMF.
Based on the ability of these cells to evade the reticuloendothelial system,
these complexes combined with an AMF should be considered as a potentially
powerful tool for tumour therapy.Comment: In Press. 33 pages, 11 figure
Gamma Ray Constraints on Flavor Violating Asymmetric Dark Matter
We show how cosmic gamma rays can be used to constrain models of asymmetric
Dark Matter decaying into lepton pairs by violating flavor. First of all we
require the models to explain the anomalies in the charged cosmic rays measured
by PAMELA, FERMI and HESS; performing combined fits we determine the allowed
values of the Dark Matter mass and lifetime. For these models, we then
determine the constraints coming from the measurement of the isotropic
gamma-ray background by FERMI for a complete set of lepton flavor violating
primary modes and over a range of DM masses from 100 GeV to 10 TeV. We find
that the FERMI constraints rule out the flavor violating asymmetric Dark Matter
interpretation of the charged cosmic ray anomalies.Comment: 11 pages, 3 figures. v2: constraints derivation slightly modified,
conclusions unchanged; some clarifications and some references added; matches
version published on JCA
Control optimo de par para maquinas SynRM aplicadas a vehiculo electrico
Las maquinas de reluctancia sincrona asistidas por imanes estan atrayendo un considerable interes como alternativa a las maquinas sıncronas de imanes permanentes para su uso en sistemas de propulsion de vehıculos electricos. El control optimo de estas maquinas (incluyendo operacion en debilitamiento de campo) puede resultar complejo, ya que estas son, por lo general, muy sensibles al fenomeno de la saturacion magnetica. En este articulo se trata su control, desde los reguladores hasta el precalculo de referencias de corriente optimas para todo el rango de operacion de la maquina. Finalmente, se muestran resultados experimentales obtenidos en una maquina de 51 kW.El trabajo descrito en este articulo ha sido generado y patrocinado
por el Departamento de Educacion, Politica Linguistica
y Cultura del Gobierno Vasco en base a las ayudas para
apoyar las actividades de grupos de investigacion del sistema
universitario vasco IT978-16 y ha sido financiado por el
Ministerio de Economia y Competitividad a traves del proyecto
de investigacion DPI2014-53685-C2-2-R y los fondos
FEDER, por el Gobierno Vasco a traves del proyecto de
investigacion KT4TRANS del programa ELKARTEK (KK-
2015/00047 y KK-2016/00061) y por los proyectos DPI2013-
41224-P (Ministerio de Economia y Competitividad) y 2014
SGR 267 (AGAUR)
- …