1,382 research outputs found
Monitoring Natural Pasture Status in Uruguay Using Satellite Images and a Soil Water Balance Model
Prompt photon yield and coefficient from gluon fusion induced by magnetic field in heavy-ion collision
We compute the production of prompt photons and the harmonic
coefficient in relativistic heavy-ion collisions induced by gluon fusion in the
presence of an intense magnetic field, during the early stages of the reaction.
The calculations take into account several parameters which are relevant to the
description of the experimental transverse momentum distribution, and elliptic
flow for RHIC and LHC energies. The main imput is the strength of the magnetic
field which varies in magnitude from 1 to 3 times the pion mass squared, and
allows the gluon fusion that otherwise is forbidden in the absence of the
field. The high gluon occupation number and the value of the saturation scale
also play an important role in our calculation, as well as a flow velocity and
geometrical factors. Our results support the idea that the origin of at least
some of the photon excess observed in heavy-ion experiments may arise from
magnetic field induced processes, and gives a good description of the
experimental data.Comment: 6 pages, 2 figures, conference paper from ISMD 201
Gluon polarization tensor and dispersion relation in a weakly magnetized medium
We study the polarization and dispersion properties of gluons moving within a
weakly magnetized background at one-loop order. To this end, we show two
alternative derivations of the charged fermion propagator in the weak field
expansion and use this expression to compute the lowest order magnetic field
correction to the gluon polarization tensor. We explicitly show that, in spite
of its cumbersome appearance, the gluon polarization tensor is transverse as
required by gauge invariance. We also show that none of the three polarization
modes develops a magnetic mass and that gluons propagate along the light cone,
non withstanding that Lorentz invariance is lost due to the presence of the
magnetic field. By comparing with the expression for the gluon polarization
tensor valid to all orders in the magnetic field, the existence of a second
solution, corresponding to a finite gluon mass, is shown to be spurious and an
artifact of the lowest order approximation in the field strength. We also study
the strength of the polarization modes for real gluons. We conclude that,
provided the spurious solutions are discarded, the lowest order approximation
to the gluon polarization and dispersion properties is good as long as the
field strength is small compared to the loop fermion mass.Comment: 14 pages, 6 figures. Ref.[35] was adde
Lifting urban mobility for the poor: Cable-cars, travel satisfaction and subjective well-being
Studies on travel and life satisfaction in vulnerable Global South contexts are scarce. This paper contributes by addressing how travel satisfaction, neighborhood satisfaction, and social capital relate to life satisfaction among a low-income community in Bogotá (Colombia) as a case study. Building on the available literature, we propose six hypotheses to understand such relationships before and after a cable car implementation, considering control and treatment groups. We defined seven latent variables and three objective indicators. We tested the hypotheses using a multiple-cause multiple-indicator modeling approach, which allowed us to identify how the comprehensive cable car intervention impacts perceptions and life satisfaction. Results showed that the principal factors associated with life satisfaction were neighborhood satisfaction as well as leisure activity participation, while travel time and transport affordability had negative effects. Positive changes in satisfaction regarding the travel experience can trigger significant improvements in life satisfaction in low-income communities in Latin America
Comparative proteomics of cerebrospinal fluid in neuropathologically- confirmed Alzheimer's disease and non-demented elderly subjects
Objectives: Diagnostic tests able to reveal Alzheimer's disease (AD) in living patients before cognitive ability is destroyed are urgently needed. Such tests must distinguish AD from other dementia causes, as well as differentiate subtle changes associated with normal aging from true pathology emergence. A single biomarker offering such diagnostic and prognostic capacities has eluded identification. Therefore, a valuable test for AD is likely to be based on a specific pattern of change in a set of proteins, rather than a single protein. Methods: We examined pooled cerebrospinal fluid (CSF) samples obtained from neuropathologically-confirmed AD (n=43) and non-demented control subjects (n=43) using 2-dimensional gel electrophoresis (2DE) proteomic methodology to detect differentially expressed proteins. Proteins exhibiting expression level differences between the pools were recovered and identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. Results: Five differentially-expressed proteins with potential roles in amyloid-β metabolism and vascular and brain physiology [apolipoprotein A-1 (Apo A-1), cathepsin D (CatD), hemopexin (HPX), transthyretin (TTR), and two pigment epithelium-derived factor (PEDF) isoforms] were identified. Apo A-1, CatD and TTR were significantly reduced in the AD pool sample, while HPX and the PEDF isoforms were increased in AD CSF. Discussion: These results suggest that multi-factor proteomic pattern analysis of the CSF may provide a means to diagnose and assess AD. © 2006 W. S. Maney & Son Ltd.Fil: Castaño, Eduardo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Sun Health Research Institute; Estados UnidosFil: Roher, Alex E.. Sun Health Research Institute; Estados UnidosFil: Esh, Chera L.. Sun Health Research Institute; Estados UnidosFil: Kokjohn, Tyler A.. Sun Health Research Institute; Estados UnidosFil: Beach, Thomas. Sun Health Research Institute; Estados Unido
Proposal of a production and management index (PMI) for tilapia farms
Tilapia is one of the most important species in aquaculture; however, there is no available index to show the performance of a production unit. It is desirable to assess the productivity using indexes, such as the production and management index for shrimps and the European production efficacy factor for broilers. These indexes are based on data production: growth, survival, and feed conversion of a full production cycle. Taking into account these parameters, we propose a production and management index (PMI) for tilapia that is applicable for a specific period of the production cycle. For the construction and validation of the PMI we have used production data from 8, 614 monthly records of 2 tilapia farms in Huila Department (Colombia), and because of the complexity of tilapia management, different anomalous situations have been detected and then defined as exceptions. As a result, 419 records were considered extreme values because 1 or more exceptions were met. The value of the PMI varies from 0 (the worst situation) to 3.55, which reflects high variability. We have constructed a PMI for tilapia as the product of 3 elements to obtain a positive value index. Instead of classic parameters, we had to calculate an adapted version of them: the relative average daily growth, the survival (as a complementary value of the estimated monthly mortality), and a feed conversion ratio index. To assess the utility of the PMI, some comparisons were performed using records from black and red tilapia. We observed significant differences depending on tilapia strain (PMIblack = 1.0248 vs. PMIred = 1.1661; P < 0.001), age (better values for small fish), and season (PMIrainy = 1.0847 vs. PMIdry = 1.1011; P = 0.026). According to these results, we can conclude that the PMI could be a useful tool for tilapia farmers, despite the complexity of the calculation
Zinc nitride thin films: Basic properties and applications
A. Redondo-Cubero, M. Gómez-Castaño, C. García Núñez, M. Domínguez, L. Vázquez, J. L. Pau , "Zinc nitride thin films: basic properties and applications", Oxide-based Materials and Devices VIII, Proc. SPIE 10105, 101051B (24 February 2017); doi: 10.1117/12.2253044. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibitedProceedings of VIII Oxide-based Materials and Devices Conference (San Francisco, California, United States)Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.This research is supported by the MINECO (CTQ2014-53334-C2-2-R) and Comunidad de Madrid (NANOAVANSENS ref. S2013/MIT-3029). ARC acknowledges Ramón y Cajal program (under contract number RYC-2015-18047
Inverting the Supersymmetric Standard Model Spectrum: from Physical to Lagrangian Ino Parameters
We examine the possibility of recovering the supersymmetric (and soft
supersymmetry breaking) Lagrangian parameters as direct {\em analytical}
expressions of appropriate physical masses, for the unconstrained (but CP and
R-parity conserving) minimal supersymmetric standard model. We concentrate
mainly on the algebraically non-trivial "inversion" for the ino parameters, and
obtain, for given values of , simple analytical expressions for the
, and parameters in terms of three arbitrary input physical
masses, namely either two chargino and one neutralino masses, or alternatively
one chargino and two neutralino masses. We illustrate and discuss in detail the
possible occurrence of ambiguities in this reconstruction. The dependence of
the resulting ino Lagrangian parameters upon physical masses is illustrated,
and some simple generic behaviour uncovered in this way. We finally briefly
sketch generalizing such an inversion to the full set of MSSM Lagrangian
parameters.Comment: Latex, 28 pages, 6 figures, 1 table, some typos corrected, one
paragraph extended in section 4.2. Version to appear in Phys. Rev.
Anisotropic photon emission from gluon fusion and splitting in a strong magnetic background I: The two-gluon one-photon vertex
Having in mind the pre-equilibrium stage in peripheral heavy-ion collisions
as a possible scenario for the production of electromagnetic radiation, we
compute the two-gluon one-photon vertex in the presence of an intense magnetic
field at one-loop order. The quarks in the loop are taken such that two of them
occupy the lowest Landau level, with the third one occupying the first exited
Landau level. When the field strength is the largest of the energy (squared)
scales, the tensor basis describing this vertex corresponds to two of the three
vector particles polarized in the longitudinal direction whereas the third one
is polarized in the transverse direction. However, when the photon energy is of
order or larger than the field strength, the explicit one-loop computation
contains extra tensor structures that spoil the properties of the basis,
compared to the case when the field strength is the largest of the energy
scales, which signals that the calculation is incomplete. Nevertheless, by
projecting the result onto the would-be basis, we show that the squared
amplitude for processes involving two gluons and one photon exhibits the
expected properties such as a preferred in-plane photon emission and a slightly
decreasing strength for an increasing magnetic field strength. We comment on
possible venues to improve the one-loop calculation that include accounting for
progressive occupation of the three quarks of the lowest and first excited
Landau levels such that, still working in the large field limit, a more
complete description can be achieved when the photon energy increases.Comment: 12 pages, 4 figures. Part
R-mediation of Dynamical Supersymmetry Breaking
We propose a simple scenario of the dynamical supersymmetry breaking in four
dimensional supergravity theories. The supersymmetry breaking sector is assumed
to be completely separated as a sequestered sector from the visible sector,
except for the communication by the gravity and U(1)_R gauge interactions, and
the supersymmetry breaking is mediated by the superconformal anomaly and U(1)_R
gauge interaction. Supersymmetry is dynamically broken by the interplay between
the non-perturbative effect of the gauge interaction and Fayet-Iliopoulos
D-term of U(1)_R which necessarily exists in supergravity theories with gauged
U(1)_R symmetry. We construct an explicit model which gives phenomenologically
acceptable mass spectrum of superpartners with vanishing (or very small)
cosmological constant.Comment: 12 pages, to be published in Phys. Rev.
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