Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment

In this paper, we review theoretical and experimental research on rare region effects at quantum phase transitions in disordered itinerant electron systems. After summarizing a few basic concepts about phase transitions in the presence of quenched randomness, we introduce the idea of rare regions and discuss their importance. We then analyze in detail the different phenomena that can arise at magnetic quantum phase transitions in disordered metals, including quantum Griffiths singularities, smeared phase transitions, and cluster-glass formation. For each scenario, we discuss the resulting phase diagram and summarize the behavior of various observables. We then review several recent experiments that provide examples of these rare region phenomena. We conclude by discussing limitations of current approaches and open questions.Comment: 31 pages, 7 eps figures included, v2: discussion of the dissipative Ising chain fixed, references added, v3: final version as publishe

Engaging stakeholders across a socio-environmentally diverse network of water research sites in North and South America

Maintaining and restoring freshwater ecosystem services in the face of local and global change requires adaptive research that effectively engages stakeholders. However, there is a lack of understanding and consensus in the research community regarding where, when, and which stakeholders should be engaged and what kind of researcher should do the engaging (e.g., physical, ecological, or social scientists). This paper explores stakeholder engagement across a developing network of aquatic research sites in North and South America with wide ranging cultural norms, social values, resource management paradigms, and eco-physical conditions. With seven sites in six countries, we found different degrees of engagement were explained by differences in the interests of the stakeholders given the history and perceived urgency of water resource problems as well as differences in the capacities of the site teams to effectively engage given their expertise and resources. We categorized engagement activities and applied Hurlbert and Gupta's split ladder of participation to better understand site differences and distill lessons learned for planning comparative socio-hydrological research and systematic evaluations of the effectiveness of stakeholder engagement approaches. We recommend research networks practice deliberate engagement of stakeholders that adaptively accounts for variations and changes in local socio-hydrologic conditions. This, in turn, requires further efforts to foster the development of well-integrated research teams that attract and retain researchers from multiple social science disciplines and enable training on effective engagement strategies for diverse conditions

A global reference database of crowdsourced cropland data collected using the Geo-Wiki platform

A global reference data set on cropland was collected through a crowdsourcing campaign using the Geo-Wiki crowdsourcing tool. The campaign lasted three weeks, with over 80 participants from around the world reviewing almost 36,000 sample units, focussing on cropland identification. For quality assessment purposes, two additional data sets are provided. The first is a control set of 1,793 sample locations validated by students trained in satellite image interpretation. This data set was used to assess the quality of the crowd as the campaign progressed. The second data set contains 60 expert validations for additional evaluation of the quality of the contributions. All data sets are split into two parts: the first part shows all areas classified as cropland and the second part shows cropland average per location and user. After further processing, the data presented here might be suitable to validate and compare medium and high resolution cropland maps generated using remote sensing. These could also be used to train classification algorithms for developing new maps of land cover and cropland extent

7th Drug hypersensitivity meeting: part two

No abstract availabl

Saturn Atmospheric Structure and Dynamics

2 Saturn inhabits a dynamical regime of rapidly rotating, internally heated atmospheres similar to Jupiter. Zonal winds have remained fairly steady since the time of Voyager except in the equatorial zone and slightly stronger winds occur at deeper levels. Eddies supply energy to the jets at a rate somewhat less than on Jupiter and mix potential vorticity near westward jets. Convective clouds exist preferentially in cyclonic shear regions as on Jupiter but also near jets, including major outbreaks near 35°S associated with Saturn electrostatic discharges, and in sporadic giant equatorial storms perhaps generated from frequent events at depth. The implied meridional circulation at and below the visible cloud tops consists of upwelling (downwelling) at cyclonic (anti-cyclonic) shear latitudes. Thermal winds decay upward above the clouds, implying a reversal of the circulation there. Warm-core vortices with associated cyclonic circulations exist at both poles, including surrounding thick high clouds at the south pole. Disequilibrium gas concentrations in the tropical upper troposphere imply rising motion there. The radiative-convective boundary and tropopause occur at higher pressure in the southern (summer) hemisphere due to greater penetration of solar heating there. A temperature “knee ” of warm air below the tropopause, perhaps due to haze heating, is stronger in the summer hemisphere as well. Saturn’s south polar stratosphere is warmer than predicted by radiative models and enhanced in ethane, suggesting subsidence-driven adiabatic warming there. Recent modeling advances suggest that shallow weather laye

Nonlinear optical response in a zincblende GaN cylindrical quantum dot with donor impurity center

We calculate the nonlinear optical absorption coefficient of a cylindrical zincblende GaN-based quantum dot. For this purpose, we consider Coulomb interactions between electrons and an impurity ionized donor atom. The electron-donor-impurity spectrum and the associated quantum states are calculated using the effective mass approximation with a parabolic potential energy model describing both the radial and axial electron confinement. We also include the effects of the hydrostatic pressure and external electrostatic fields. The energy spectrum is obtained through an expansion of the eigenstates as a linear combination of Gaussian-type functions which reduces the computational effort since all the matrix elements are obtained analytically. Therefore, the numerical problem is reduced to the direct diagonalization of the Hamiltonian. The obtained energies are used in the evaluation of the dielectric susceptibility and the nonlinear optical absorption coefficient within a modified two-level approach in a rotating wave approximation. This quantity is investigated as a function of the quantum dot dimensions, the impurity position, the external electric field intensity and the hydrostatic pressure. The results of this research could be important in the design and fabrication of zincblende GaN-quantum-dot-based electro-optical devices

Variables relacionadas con los factores protectores en estudiantes de una universidad pública colombiana, 2016

Introducción: Los factores protectores se definen como aquellos que fomentan los comportamientos favorables y positivos y desestimulan e inhiben los comportamientos de riesgo, limitando los efectos de los riesgos a los cuales se exponen los individuos. El fomento de factores protectores facilita el desarrollo de comportamientos y hábitos saludables así como la prevención de factores de riesgo. Objetivo: Analizar las variables relacionadas con los factores protectores en estudiantes de una universidad pública colombiana. Material y método: Estudio descriptivo, correlacional. La población de estudio fueron los estudiantes de todas las facultades de una universidad pública matriculados en el 2016, con una muestra de 1.253 estudiantes. La información se recolectó mediante una encuesta electrónica estructurada previo consentimiento informado. Resultados: Edad promedio 21,7 años +/– 3,3 años, rango 18-44 años. Al analizar los factores protectores se encontraron diferencias estadísticamente significativas p<0,05 entre el nivel socieconómico, la afiliación al sistema de salud y el programa que cursa con factores como: “compartir el tiempo libre con la familia”, “asistir al médico al menos una vez al año”, “realiza exámenes de colesterol, triglicéridos y glicemia una vez al año”, “como conductor o pasajero usa cinturón de seguridad”, “atiende las señales de seguridad”, “consumo dulces, helados y pasteles más de dos veces en la semana”, “la alimentación incluye vegetales, frutas, panes, cereales, productos lácteos, granos enteros y fuentes adecuadas de proteína”, “consume de carne más de cuatro veces a la semana”, “evita las dietas y los métodos que le prometen una rápida y fácil pérdida de peso”, “hace siesta”, ”respeta los horarios de sueño”. Conclusiones: Se espera que los factores protectores permitan orientar las acciones que se desarrollan con los estudiantes Universitarios, lo anterior motivado por las diferencias encontradas, y a la luz del paradigma de salud dirigido hacia calidad de vida y bienestar

Creencias sobre hábitos y estilos de vida en universitarios de una universidad pública colombiana, 2016

Introducción: Los estilos de vida configuran patrones de comportamiento y condicionan oportunidades de vida según el contexto. Su análisis, permite orientar las prácticas personales y profesionales. Las creencias son experiencias de vida, identificarlas permite redireccionar los procesos de formación hacia prácticas saludables. Objetivo: Analizar las creencias sobre hábitos y estilos de vida, y su diferencia por género. Material y método: Estudio descriptivo, correlacional. Población: estudiantes de todas las facultades de una universidad pública matriculados en 2016, muestra: 1.253 estudiantes. Información recolectada por encuesta electrónica, previo con-sentimiento informado. Análisis univariado y bivariado. Resultados: 724 mujeres, 509 hombres. Se encontraron diferencias estadísticamente significativas (p<0,05) por género en: “La recreación es para los que no tienen mucho trabajo”, “Sólo cuando se está enfermo se debe ir al médico”, “Los factores ambientales influyen sobre la salud”, “Tener buena salud es asunto de la suerte o del destino”, “Es difícil cambiar comportamientos no saludables”, “Por más cuidado que se tenga, de algo se va a morir uno”, “Lo más importante es la figura”, “Comer cerdo es dañino”, “Entre más grasosita la comida, mejor”, “Las comidas rápidas permiten aprovechar mejor el tiempo”, “Consumir uno o dos cigarrillos al día no es dañino”, “Al consumir licor mayor sociabilidad”, “Un traguito de vez en cuando no hace daño”, “Tomar es menos dañino que consumir drogas”, “Una borrachera de vez en cuando no le hace mal”, “Se disfruta más una rumba si se consume licor o drogas”, “El café permite estar despierto”, “Tomar una copita de vino para que funcione bien el organismo”, “Dormir bien alarga la vida”, “Si no duerme al menos 8 horas al día, no funciona bien”. Conclusiones: En los participantes existen diferencias en creencias sobre hábitos y estilos de vida favorables y nocivos. Esto permite reformular programas y políticas en Universidades Promotoras de Salud