886 research outputs found
Effective photon mass and exact translating quantum relativistic structures
Using a variation of the celebrated Volkov solution, the Klein-Gordon
equation for a charged particle is reduced to a set of ordinary differential
equations, exactly solvable in specific cases. The new quantum relativistic
structures can reveal a localization in the radial direction perpendicular to
the wave packet propagation, thanks to a non-vanishing scalar potential. The
external electromagnetic field, the particle current density and the charge
density are determined. The stability analysis of the solutions is performed by
means of numerical simulations. The results are useful for the description of a
charged quantum test particle in the relativistic regime, provided spin effects
are not decisive
On the multiplicity of ALMA Compact Array counterparts of far-infrared bright quasars
We present ALMA Atacama Compact Array (ACA) 870 micron continuum maps of 28
infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4,
the largest such sample ever observed with ALMA. The ACA detections are centred
on the SDSS coordinates to within 1 arcsec for about 80 per cent of the sample.
Larger offsets indicate that the far-infrared (FIR) emission detected by
Herschel might come from a companion source. The majority of the objects (about
70 per cent) have unique ACA counterparts within the SPIRE beam down to 3-4
arcsec resolution. Only 30 per cent of the sample shows clear evidence for
multiple sources with secondary counterparts contributing to the total 870
micron flux within the SPIRE beam to at least 25 per cent. We discuss the
limitations of the data based on simulated pairs of point-like sources at the
resolution of the ACA and present an extensive comparison of our findings with
recent works on the multiplicities of sub-millimetre galaxies. We conclude
that, despite the coarse resolution of the ACA, our data support the idea that,
for a large fraction of FIR-bright quasars, the sub-mm emission comes from
single sources. Our results suggest that, on average, optically bright quasars
with strong FIR emission are not triggered by early-stage mergers but are,
instead, together with their associated star formation rates, the outcome of
either late-stage mergers or secular processes.Comment: 16 pages, 10 figure
Hearing Impairment and Quality of Life in Adults with Asymmetric Hearing Loss: Benefits of Bimodal Stimulation
Objectives: Bimodal stimulation for asymmetric hearing loss is an emerging treatment with proven audiometric outcomes. Our objectives are to assess the changes of the hearing impairment and the quality of life of patients treated with this type of stimulation, when compared to a unilateral Cochlear Implant (CI) stimulated condition.
Materials and methods: 31 patients with asymmetric hearing loss (Group 1) were recruited for the study. They were divided into three groups, based on their hearing loss in the ear treated with the hearing aid: Group 1A (Pure Tone Audiometry (PTA) between 41 and 70 decibels (dB)); Group 1B, (PTA between 71 and 80 dB) and Group 1C (PTA between 81 and 90 dB). 30 patients had profound, bilateral hearing loss. Then, users of a unilateral cochlear implant were recruited for the control group. Their hearing impairment and quality of life were analyzed with questionnaires Abbreviated Profile of Hearing Aid Benefit (APHAB), Speech, Spatial and Qualities of Hearing Scale (SSQ) and the Health Utilities Index (HUI). They were followed up for at least 2 years.
Results: The group with the asymmetric hearing loss obtains a statistically significant clinical improvement in the APHAB under category "with hearing aid" compared to "without hearing aid". The group with the asymmetric hearing loss benefits more across basically all variables compared with the control group in the SSQ. Group 1A obtains the best outcome of the sample in the HUI.
Conclusion: Bimodal stimulation and better hearing in the ear treated with the hearing aid reduce hearing impairment and improve the quality of life
Sequía experimental en plántulas en un claro y en el sotobosque de un bosque de niebla, Veracruz, México
Background and Aims: Droughts induced by climate change are expected to affect tropical cloud forests. As functional traits are useful indicators of plant species performance, this study aimed to determine the effect of light environment and drought on leaf area (LA), specific leaf area (SLA), chlorophyll content, leaf thickness and toughness, survival and relative growth rate (RGR) of seedlings in forest understory and gap.
Methods: In a cloud forest from Veracruz, Mexico, rainout shelters to simulate drought in the forest understory and gap were used. Leaf area, SLA, chlorophyll content, leaf thickness and toughness, survival, and RGR in Eugenia capuli (shade-tolerant understory tree), Liquidambar styraciflua (intermediate shade-tolerant canopy tree), and Trema micranthum (pioneer tree that colonizes gaps) in understory-control and -drought, and gap-control and -drought were measured.
Key results: Leaf area increased with drought in E. capuli in gaps and decreased in L. styraciflua in both light environments. Chlorophyll content was similar between water treatments for E. capuli and L. styraciflua in the understory. Leaf thickness and toughness differed with drought for E. capuli and L. styraciflua in the gap. Leaf traits of T. micranthum tended to change in understory and not in gap. Overall, the highest survival occurred in gap. Eugenia capuli displayed the highest and similar survival across treatments. Liquidambar styraciflua displayed higher survival in gap-drought, and T. micranthum in gap conditions. Eugenia capuli had the highest RGR in understory, whereas T. micranthum has the highest RGR in gap.
Conclusions: Plant functional traits of E. capuli and L. styraciflua seedlings responded to moderate drought more in gap than in understory. The results suggest that functional traits of intermediate and shade-tolerant species may shift less under a moderate drought than those of a pioneer tree, as long as the forest light environment is maintained.Antecedentes y Objetivos: Se espera que las sequías inducidas por el cambio climático afecten al bosque de niebla. Como los rasgos funcionales son indicadores útiles del desempeño de especies vegetales, el objetivo de este trabajo fue determinar el efecto del ambiente lumínico y la sequía sobre área foliar (AF), área foliar específica (AFE), contenido de clorofila, grosor, dureza foliar, supervivencia y tasas de crecimiento relativo (TCR) de plántulas en sotobosque y claro.
Métodos: En un bosque de niebla en Veracruz, México, se usaron exclusiones de lluvia para simular sequía en sotobosque y claro. Se midieron AF, AFE, contenido de clorofila, grosor, dureza, supervivencia y TCR en Eugenia capuli (especie de sotobosque tolerante a la sombra), Liquidambar styraciflua (especie del dosel de tolerancia intermedia) y Trema micranthum (árbol pionero colonizador de claros) en sotobosque-control y -sequía, y claro-control y -sequía.
Resultados clave: El AF aumentó con sequía en E. capuli en claro y decreció para L. styraciflua en ambos ambientes lumínicos. El contenido de clorofila fue similar entre tratamientos de agua para E. capuli y L. styraciflua en sotobosque. El grosor y dureza foliares difirieron con sequía para E. capuli y L. styraciflua en claro. Los rasgos foliares de T. micranthum cambiaron solo en sotobosque. Eugenia capuli presentó la mayor y similar supervivencia entre tratamientos. Liquidambar styraciflua mostró una mayor supervivencia en claro-sequía, y T. micranthum en claro. Eugenia capuli tuvo la mayor TCR en sotobosque, mientras que T. micranthum en claro.
Conclusiones: Los rasgos funcionales de plántulas de E. capuli y L. styraciflua respondieron a sequía moderada más en claro que en sotobosque. Los resultados sugieren que los rasgos funcionales de las especies intermedia y tolerante a la sombra tienden a cambiar menos bajo una sequía moderada, que los del árbol pionero si se mantiene el ambiente lumínico forestal
33- #1102 PROTOTIPO DE SOPORTE A DECISIONES LOGÍSTICAS DE RUTEO EN ATENCIÓN MÉDICA DOMICILIARIA: APLICACIÓN EN EL VALLE DE ABURRÁ, COLOMBIA
VEl incremento de la población y de la expectativa de vida en Colombia ha generado un aumento en las necesidades de prestación de servicios de salud, así como del desarrollo de nuevas herramientas para responder a dichos incrementos. La atención médica domiciliaria (HHC por sus siglas en inglés Home Health Care) es un servicio en el que personal asistencial capacitado viaja a los hogares de los pacientes, y aplica procedimientos médicos cumpliendo con una prescripción establecida. Esto implica tomar decisiones relativas a la asignación y secuenciación del personal teniendo en cuenta las características del servicio, y asegurando que los pacientes sean atendidos en las condiciones definidas. Dichas decisiones han sido estudiadas haciendo uso de métodos para el problema de ruteo de vehículos. En HHC, el problema consiste en asignar un conjunto de personal asistencial con características y habilidades determinadas, a un conjunto de pacientes. Algunas de las condiciones que deben considerarse son el tipo de personal, el tipo de paciente, la distancia de recorrido, entre otras, con el objetivo de diseñar la mejor ruta para tener un buen servicio y cumplir con dichas condiciones. El problema de ruteo de vehículos en HHC ha sido uno de los más estudiados, y la literatura evidencia el uso de diferentes métodos de formulación y solución. Con el objetivo de dar soporte a la toma de decisiones logísticas de ruteo en HHC en el contexto colombiano, en este trabajo se presenta un prototipo computacional que, basado en métodos aproximados, permite mejorar las métricas de desempeño del sistema, y agiliza el proceso de la decisión. El prototipo es aplicado con datos del servicio en el Valle de Aburrá, Colombia, y los resultados muestran las oportunidades de mejora en las métricas de desempeño, así como en los tiempos del proceso de toma de decisiones
Produccion de semillas en yacon (Smallanthus sonchifolius (Poepp. & Endl.)) mediante tecnicas de polinizacion controladas.
Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario
We present an entirely analytic model for a preheated, polytropic
intergalactic medium in hydrostatic equilibrium within a NFW dark halo
potential in which the evolution of the halo structure between major merger
events proceeds inside-out by accretion. This model is used to explain, within
a standard CDM cosmogony, the observed X-ray properties of nearby
relaxed, non-cooling flow groups and clusters of galaxies. We find that our
preferred solution to the equilibrium equations produces scaling relations in
excellent agreement with observations, while simultaneously accounting for the
typical structural characteristics of the distribution of the diffuse baryons.
In the class of preheating models, ours stands out because it offers a unified
description of the intrahalo medium for galaxy systems with total masses above
\sm 2\times 10^{13}\msun, does not produce baryonic configurations with large
isentropic cores, and reproduces faithfully the observed behavior of the gas
entropy at large radii. All this is achieved with a moderate level of energy
injection of about half a keV, which can be easily accommodated within the
limits of the total energy released by the most commonly invoked feedback
mechanisms, as well as with a polytropic index of 1.2, consistent with both
many observational determinations and predictions from high-resolution
gas-dynamical simulations of non-cooling flow clusters. More interestingly, our
scheme offers a physical motivation for the adoption of this specific value of
the polytropic index, as it is the one that best ensures the conservation after
halo virialization of the balance between the total specific energies of the
gas and dark matter components for the full range of masses investigated.Comment: 18 pages, 11 figures, accepted for publication in the Astrophysical
Journa
GOLLUM: a next-generation simulation tool for electron, thermal and spin transport
We have developed an efficient simulation tool 'GOLLUM' for the computation
of electrical, spin and thermal transport characteristics of complex
nanostructures. The new multi-scale, multi-terminal tool addresses a number of
new challenges and functionalities that have emerged in nanoscale-scale
transport over the past few years. To illustrate the flexibility and
functionality of GOLLUM, we present a range of demonstrator calculations
encompassing charge, spin and thermal transport, corrections to density
functional theory such as LDA+U and spectral adjustments, transport in the
presence of non-collinear magnetism, the quantum-Hall effect, Kondo and Coulomb
blockade effects, finite-voltage transport, multi-terminal transport, quantum
pumps, superconducting nanostructures, environmental effects and pulling curves
and conductance histograms for mechanically-controlled-break-junction
experiments.Comment: 66 journal pages, 57 figure
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