394 research outputs found
Anomalous optical absorption in a random system with scale-free disorder
We report on an anomalous behavior of the absorption spectrum in a
one-dimensional lattice with long-range-correlated diagonal disorder with a
power-like spectrum in the form S(k) ~ 1/k^A. These type of correlations give
rise to a phase of extended states at the band center, provided A is larger
than a critical value A_c. We show that for A < A_c the absorption spectrum is
single-peaked, while an additional peak arises when A > A_c, signalling the
occurrence of the Anderson transition. The peak is located slightly below the
low-energy mobility edge, providing a unique spectroscopic tool to monitor the
latter. We present qualitative arguments explaining this anomaly.Comment: 4 pages, 4 postscript figures, uses revtex
Dynamic equivalence between atomic and colloidal liquids
We show that the kinetic-theoretical self-diffusion coefficient of an atomic
fluid plays the same role as the short-time self-diffusion coefficient D_S in a
colloidal liquid, in the sense that the dynamic properties of the former, at
times much longer than the mean free time, and properly scaled with D_S, will
indistinguishable from those of a colloidal liquid with the same interaction
potential. One important consequence of such dynamic equivalence is that the
ratio D_L/ D_S of the long-time to the short-time self-diffusion coefficients
must then be the same for both, an atomic and a colloidal system characterized
by the same inter-particle interactions. This naturally extends to atomic
fluids a well-known dynamic criterion for freezing of colloidal liquids[Phys.
Rev. Lett. 70, 1557 (1993)]. We corroborate these predictions by comparing
molecular and Brownian dynamics simulations on (soft- and hard-sphere) model
systems, representative of what we may refer to as the "hard-sphere" dynamic
universality class
Evaluación de calidad de agua en un sistema ribereño utilizado para riego agrícola de subsistencia
En la evaluación del impacto de la contaminación en el ambiente, existen diversas herramientas y técnicas que se aplican para conocer la calidad ambiental de los recursos naturales. El objetivo de este trabajo fue evaluar la calidad del agua en un sistema ribereño en San Luis Potosí, México asociado al impacto del uso agrícola, urbano e industrial. Fueron establecidos cinco puntos de muestreo asociado a diversos usos y descargas residuales en donde se evaluaron 28 muestras durante cuatro días de muestro. Estas fueron distribuidas a los 20, 40, 60, 80, 100 y 120 minutos del trayecto determinando con un medidor multiparámetro los sólidos
disueltos totales (SDT), temperatura (T), conductividad eléctrica (CE), pH y oxígeno disuelto (OD). El resultado más destacado de las 28 muestras diarias y del total de 112 que los promedios oxígeno disuelto indican condición hipoxia que indica la desaparición de organismos y especies sensibles, concluyendo que el área ribereña requiere un constante monitoreo y diversificación de parámetros para evaluar su condición para actividades agrícolas.In the assessment of the impact of pollution on the environment, there are various tools and techniques that are applied to know the environmental quality of natural resources. The objective of this work was to evaluate water quality in a river system in San Luis Potosí, Mexico associated with the impact of agricultural, urban and industrial use. Five sampling points associated to various uses and residual discharges were established where 28 samples were evaluated during four days of sampling. The total dissolved solids (SDT), temperature (T), electrical conductivity (CE), pH and dissolved oxygen (OD) were distributed at 20, 40, 60, 80, 100 and 120 minutes of the path. The most outstanding result of the 28 daily samples and the total of 112 that dissolved oxygen averages indicate hypoxia condition indicating the disappearance of sensitive organisms and species, concluding that the riparian area requires constant monitoring and diversification of parameters to evaluate agricultural activities.Fil: Alcalá Jáuregui, J. A.
Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Acosta Doporto Geiler, A.
Instituto Tecnológico Superior de los Ríos de Balancan (México)Fil: Rodríguez Ortiz, J.C.
Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Hernández Montoya, A.
Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Martínez Carretero, Eduardo.
Consejo Nacional de Investigaciones Científicas y TécnicasFil: Filippini, Maria Flavia.
Universidad Nacional de Cuyo. Facultad de Ciencias AgrariasFil: Díaz Flores, P. E.
Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Lara Mireles, J. L.
Universidad Autónoma de San Luis Potosí. Facultad de Agronomí
The Higgs Mass as the Discriminator of Electroweak Models
In the Minimal Supersymmetric Model (MSSM) and the Next to Minimal
Supersymmetric Model [(M+1)SSM], an upper bound on the lightest higgs mass can
be calculated. On the other hand, vacuum stability implies a lower limit on the
mass of the higgs boson in the Standard Model (SM). We find that a gap exists
for GeV between the SM and both the MSSM and the
(M+1)SSM bounds. Thus, if the new top quark mass measurement by CDF remains
valid, a first measurement of the higgs mass will serve to exclude either the
SM or the MSSM/(M+1)SSM higgs sectors. In addition, we discuss Supersymmetric
Grand Unified Theories, other extentions of the SM, the discovery potential of
the lightest higgs, and the assumptions on which our conclusions are based.Comment: 9 pages, 2 figures, VAND-TH-94-1
Effective Lagrangian description of the lepton flavor violating decays Z-->li lj
A comprehensive analysis of the lepton flavor violating (LFV) decays Z-->li
lj is presented within the effective Lagrangian approach. Both the decoupling
and nondecoupling scenarios are explored. The experimental constraints from li
--> lj lk \bar{lk} and li -->lj gamma as well as some relationships arising
from the gauge invariance of the effective Lagrangian are used to put
constraints on Z-->li lj. It is found that while current experimental data
impose very strong constraints on Z-->mu e, the channel Z --> tau mu (e)still
may be at the reach of the planned TESLA collider.Comment: References added, final version to appear in Physical Review
Yukawa Unified Supersymmetric SO(10) Model: Cosmology, Rare Decays and Collider Searches
It has recently been pointed out that viable sparticle mass spectra can be
generated in Yukawa unified SO(10) supersymmetric grand unified models
consistent with radiative breaking of electroweak symmetry. Model solutions are
obtained only if , and positive -term
contributions to scalar masses from SO(10) gauge symmetry breaking are used. In
this paper, we attempt to systematize the parameter space regions where
solutions are obtained. We go on to calculate the relic density of neutralinos
as a function of parameter space. No regions of the parameter space explored
were actually cosmologically excluded, and very reasonable relic densities were
found in much of parameter space. Direct neutralino detection rates could
exceed 1 event/kg/day for a Ge detector, for low values of GUT scale
gaugino mass . We also calculate the branching fraction for decays, and find that it is beyond the 95% CL experimental limits in
much, but not all, of the parameter space regions explored. However, recent
claims have been made that NLO effects can reverse the signs of certain
amplitudes in the calculation, leading to agreement between
theory and experiment in Yukawa unified SUSY models. For the Fermilab Tevatron
collider, significant regions of parameter space can be explored via
and searches. There also exist some limited regions of
parameter space where a trilepton signal can be seen at TeV33. Finally, there
exist significant regions of parameter space where direct detection of bottom
squark pair production can be made, especially for large negative values of the
GUT parameter .Comment: Added comparison to Blazek/Raby results and added Comments on de Boer
et al. b->s gamma result
A modern network approach to revisiting the positive and negative affective schedule (PANAS) construct validity
Introduction: The factor structure of the Positive and Negative Affective Schedule (PANAS) is still a topic of debate. There are several reasons why using Exploratory Graph Analysis (EGA) for scale validation is advantageous and can help understand and resolve conflicting results in the factor analytic literature. Objective: The main objective of the present study was to advance the knowledge regarding the factor structure underlying the PANAS scores by utilizing the different functionalities of the EGA method. EGA was used to (1) estimate the dimensionality of the PANAS scores, (2) establish the stability of the dimensionality estimate and of the item assignments into the dimensions, and (3) assess the impact of potential redundancies across item pairs on the dimensionality and structure of the PANAS scores. Method: This assessment was carried out across two studies that included two large samples of participants. Results and Conclusion: In sum, the results are consistent with a two-factor oblique structure.Fil: Flores Kanter, Pablo Ezequiel. Universidad Empresarial Siglo XXI; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garrido, Luis Eduardo. Pontificia Universidad Católica Madre y Maestra; República DominicanaFil: Moretti, Luciana Sofía. Universidad Empresarial Siglo XXI; Argentina. Pontificia Universidad Católica Madre y Maestra; República Dominicana. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Medrano, Leonardo. Universidad Empresarial Siglo XXI; Argentina. Pontificia Universidad Católica Madre y Maestra; República Dominicana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation
We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey,
which has been designed to provide a first step in this direction.We summarize
the survey goals and design, including sample selection and observational
strategy.We also showcase the data taken during the first observing runs
(June/July 2010) and outline the reduction pipeline, quality control schemes
and general characteristics of the reduced data. This survey is obtaining
spatially resolved spectroscopic information of a diameter selected sample of
galaxies in the Local Universe (0.005< z <0.03). CALIFA has been
designed to allow the building of two-dimensional maps of the following
quantities: (a) stellar populations: ages and metallicities; (b) ionized gas:
distribution, excitation mechanism and chemical abundances; and (c) kinematic
properties: both from stellar and ionized gas components. CALIFA uses the PPAK
Integral Field Unit (IFU), with a hexagonal field-of-view of
\sim1.3\sq\arcmin', with a 100% covering factor by adopting a three-pointing
dithering scheme. The optical wavelength range is covered from 3700 to 7000
{\AA}, using two overlapping setups (V500 and V1200), with different
resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey,
intended for the community. The reduced data will be released, once the quality
has been guaranteed. The analyzed data fulfill the expectations of the original
observing proposal, on the basis of a set of quality checks and exploratory
analysis.
We conclude from this first look at the data that CALIFA will be an important
resource for archaeological studies of galaxies in the Local Universe.Comment: 32 pages, 29 figures, Accepted for publishing in Astronomy and
Astrophysic
Land Restoration for Achieving the Sustainable Development Goals - An International Resource Panel Think Piece
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