Magnetic-field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters

We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semiconductors become ideal hyperbolic near-field emitters. More importantly, by changing the magnetic field, the system can be continuously tuned from a situation where the surface waves dominate the heat transfer to a situation where hyperbolic modes completely govern the near-field thermal radiation. We show that this high tunability can be achieved with accessible magnetic fields and very common materials like n-doped InSb or Si. Our study paves the way for an active control of NFRHT and it opens the possibility to study unique hyperbolic thermal emitters without the need to resort to complicated metamaterials.Comment: 21 pages, 10 figure

Monte Carlo simulation of a liquid scintillation counter using geant4 code

This paper presents a first approach to the use of the GEANT4 Monte Carlo (MC) technique in liquid scintil-lation counting (LSC) applied to measurements in radiological laboratories. The GEANT4 software was developed by RD44,a worldwide collaboration of national institutes, laboratories, and large high-energy physics experiments. GEANT4 is a pub-lic software package composed of tools that can be used to accurately simulate the passage of particles through matter. TheGEANT4 catalog of processes at optical wavelengths includes refraction and reflection at medium boundaries, bulk absorp-tion, and Rayleigh scattering. Processes that produce optical photons include the Cherenkov effect, transition radiation, andscintillation.The simulated setup includes a vial containing the scintillation cocktail in between 2 opposite photomultipliers tubes (PMTs)working in sum-coincidence mode. The decay of several beta emitters (such as 14C and 3H) can be simulated, as well as alphaor EC emitters. Additionally, significant information could be obtained, such as the energy deposited by decay into the scin-tillation cocktail or the light output generated into the scintillation cocktail. GEANT4 is a useful tool for efficiency calibra-tion, stopping power calculations, or wall effect studies for different scintillation cocktails and geometries.Junta de Andalucia Excellence Project RNM-0256

Interaction of Eu-isotopes with saponite as a component of the engineered barrier

Bentonite is accepted as the best clay material in the engineered barrier of deep geological repositories (DGRs) for radioactive waste disposal. In recent years, the interactions between a wide range of rare-earth (REE) cations and smectites have been studied. A combined study of stable europium and radioactive isotopes is reported here. Saponite was subjected to hydrothermal reactions with stable and radioactive (152Eu) europium ions under subcritical conditions. The structural changes of saponite were evaluated by XRD and SEM. The effect of temperature and reaction time on the changes was quantified by measuring 152Eu through gamma spectrometry. The reaction between europium and saponite was a first-order reaction. The presence of Eu in the precipitate in an amount much higher than the cation exchange capacity of saponite confirmed participation of chemical reactions or surface adsorption in the europium immobilization, even at temperatures as low as 150°C. The reaction rate constant indicated that an 8- to 9-month period was needed for the completion, without significant changes, of the europium/saponite chemical reaction under the subcritical conditions of 200°C and 350°C.Medio Ambiente y Medio Rural y Marino 300/PC08/3-01.1Dirección General de Investigación Científica y Técnica CTQ2010-1487

Propuesta para estructurar una oferta de valor al mercado colombiano de productos farmacéuticos derivados del cannabis con enfoque hacia el desarrollo sostenible del campo.

Este estudio busca reunir información valiosa para evaluar la viabilidad hacia el desarrollo de proyectos agrícolas con cannabis medicinal bajo un foco de progreso sostenible e inclusivo para el campo colombiano. Para la elaboración del trabajo se investigó el marco regulatorio nacional junto con los factores que convierten a nuestro país uno de los más indicados para ser pionero de esta industria.Resumen ; Introducción ; Estado del arte ; Marco teórico ; Marco conceptual ; Metodología ; Desarrollo objetivos ; Conclusiones ; Recomendaciones.Administrador de EmpresasThis study seeks to gather valuable information to evaluate the viability towards the development of agricultural projects with medicinal cannabis under a focus of sustainable and inclusive progress for the Colombian countryside. For the preparation of the work, the national regulatory framework was investigated along with the factors that make our country one of the most suitable for being a pioneer in this industry.Pregrad

Túnel musical

Con la intención de fomentar el desarrollo del aprendizaje en los niños al momento en el que se divierten, nació la idea de crear un túnel musical. Dicho túnel consta de un conjunto de cuatro bloques que toman la forma de un trapecio creado con dimensiones adecuadas para la talla de un rango de edad específico, teniendo siempre como objetivo principal impulsar a los niños desde los tres hasta los seis años a relacionar de una manera divertida los colores y sonidos. El proyecto se llevó a cabo aplicando los conocimientos en electrónica, programación y áreas psicosociales adquiridos a lo largo de los 3 últimos años de colegio; unificando a la especialidad de mecatrónica y ciencias experimentales. Tuvo su inicio en el diciembre del 2018 y concluyó en mayo del 2019

Kinetics of nopyl acetate synthesis by homogeneously catalyzed esterification of acetic acid with nopol

The esterification of nopol with acetic acid to produce nopyl acetate using sulfuric acid as homogeneous catalyst was studied. The reactions were carried out in a batch reactor, at different temperatures (50, 60, 70 and 80 °C), catalyst concentrations (0.0184, 0.0275, 0.0367 and 0.0480 molL−1 and molar ratio of acetic acid to nopol (1: 1, 1:2, 1:3 and 1: 4); the chemical equilibrium composition was measured at those reaction conditions. It was found that the equilibrium composition is a weak function of temperature, equilibrium conversion was 63, 68, 71 and 75% at 50, 60, 70 and 80°C, respectively. The reaction was described with a simple power-law model with a second-order kinetic model for both the forward and the backward reaction, using concentration and activities which were predicted by the Universal Functional group Contribution (UNIFAC) method for considering non-ideal behavior of the liquid phase. The forward reaction rate and the equilibrium constants increased with temperature; the relation of the pre-exponential factor with the catalyst amount was evaluated. The activation energy and pre-exponential factor estimated for the forward reaction using the kinetic model based on concentration, were respectively, 28.08 kJmol−1 and 11126 Lmol−1h −1 with a concentration of catalyst of 0.0275 M. Using the kinetic model based on activities, the forward reaction rate constant was 28.56 kJmol−1 and the kfo,act was 33860 Lmol−1h −1 . The enthalpy (34.90 kJmol−1 ) and the entropy (0.12 kJmol−1K−1 ) of reaction were determined using van’t Hoff equation

Manchas mongólicas, una anomalía congénita común del recién nacido. Revisión de tema.

Dermal melanocytosis (DM), or Mongolian spot (MS), is the most common pigmented lesion in newborns, with a high prevalence in the Asian and black populations. These lesions apear when the melanocytes stop in their migration from the neural crest to the epidermis, giving rise to hyperpigmented lesions in the skin of the newborn that usually disappear during the first years of life, however, approximately 3% of these persist until adulthood. Most are located in the sacro-gluteal region, although they can also occupy extra sacral sites such as the head, face or flexor surface of the extremities. MM have commonly been considered a benign lesion, however, recent data suggests that they could appear in association with other pathological conditions, such as coexistence with inborn errors of metabolism, especially lysosmal storage diseases, but there is still not enough evidence  to correlate these conditions directly.La melanocitosis dérmica (MD) o mancha mongólica (MM), es la lesión pigmentada más común en los recién nacidos, con una mayor prevalencia en la poblacion asiática y de raza negra. Estas lesiones surgen cuando los melanocitos se detienen en su migración de la cresta neural a la epidermis, dando origen a lesiones hiperpigmentadas en la piel del recién nacido que usualmente desaparecen durante los primeros años de vida,  sin embargo, aproximadamente un 3% de estas persiste hasta la edad adulta. La mayoria se localizan en la región sacro-glútea, aunque pueden ocupar también sitios extra sacros como cabeza,  cara o superficie flexora de las extremidades. Comúnmente las MM se han considerado una lesión benigna, pero datos recientes sugieren que pueden presentarse en asociación con otras condiciones patológicas, como por ejemplo la coexistencia con errores innatos del metabolismo, en especial de enfermedades de depósito lisosmal. No obstante, aún no existe evidencia suficiente para correlacionar estas condiciones de manera directa