Listar Física por título
Mostrando ítems 70-89 de 111
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Negative Thermal Expansion in Open Perovskites near the Precipice of Structural Stability
(2018)Negative thermal expansion (NTE) describes the anomalous propensity of materials to shrink when heated. Since its discovery, the NTE effect has been found in a wide variety of materials with an array of magnetic, electronic ... -
Negative thermal expansion near two structural quantum phase transitions Connor
(2017-12-18)Recent experimental work has revealed that the unusually strong, isotropic structural negative thermal expansion in cubic perovskite ionic insulator ScF3 occurs in excited states above a ground state tuned very near a ... -
Observed Changes (1970-1999) in Extreme Hydroclimatic Events in Central America
(2018-04-20)Previous studies have shown that most of Central America has been experiencing warming trends during the last 30-50 years, while precipitation annual totals have not changed much. Warming alone can exacerbate the effects ... -
OpenDose: Open access resources for nuclear medicine dosimetry
(2020)Radiopharmaceutical dosimetry depends on the localization in space and time of radioactive sources and requires the estimation of the amount of energy emitted by the sources deposited within targets. In particular, when ... -
Optical component
(2010-02-15)El invento trata de un componente óptico, que comprende un primer reflector esférico y un segundo reflector esférico, el cual está colocado para reflejar un rayo de luz varias veces entre el primer reflector y el segundo ... -
Ozonesonde Quality Assurance: The JOSIE–SHADOZ (2017) Experience
(2019)The ozonesonde is a small balloon-borne instrument that is attached to a standard radiosonde to measure profiles of ozone from the surface to 35 km with ∼100-m vertical resolution. Ozonesonde data constitute a mainstay of ... -
Phototransport Properties of a-SiC:H Alloys
(1995)We report a study of the mobility-lifetime products of the two charge carriers in a-SiC:H alloys. The measurements were carried out as a function of the carbon concentration and the temperature. An analysis, relying on the ... -
Pressure dependence of ferroelectric quantum critical fluctuation
(2019-12-13)Phase transitions to a long-range-ordered state driven by a softened phonon mode are ubiquitous across condensed matter physics, but the evolution of such a mode as the system is tuned to or from the transition has never ... -
Probing the origin of 4FGL J0822.8–4207: cosmic ray illumination from the SNR Puppis A and the Herbig-Haro object HH219
(2021)4FGL J0822.8–4207 is a point source found in the 4FGL-DR2 catalogue by the gamma-ray observatory Fermi-LAT and has no known association. We carry out X-ray observations of 4FGL J0822.8–4207 to help understand its nature. ... -
Propuesta de estrategias metodológicas para el contenido curricular “Oscilaciones y ondas mecánicas” que propicie el aprendizaje significativo en el estudiantado que asiste al curso Laboratorio de Física General II de la Universidad de Costa Rica, Sede de Occidente durante el II semestre del 2020
(2020)El presente trabajo tiene por objetivo general el proponer estrategias metodológicas para el contenido curricular “Oscilaciones y ondas mecánicas” que propicien un aprendizaje significativo en el estudiantado que asiste ... -
Pruebas técnicas de aceptación de la PET/CT del modelo Biograph Vision 450 de Siemens
(2023-11-09)Esta tesis académica, para optar por el título de maestría académica en física médica, versa sobre las pruebas técnicas de aceptación del sistema tomográfico PET/CT BV 450, el cual pertenece al proyecto ciclotrón-PET/CT ... -
QA Programme of the TLD laboratory of the University of Costa Rica: IEC 61066 testing
(2008)The Thermoluminescence Personal Dosimetry Laboratory of the University of Costa Rica provides dose measurements for around 90% of occupational radiation workers in the country. The assessment of doses to workers routinely ... -
Quantum ferroelectric instabilities in superconducting SrTiO3
(2018)We examine the effects of strain and cation substitution on the superconducting phase of polar semiconductors near a ferroelectric quantum phase transition with a model that combines a strong coupling theory of ... -
Quantum Theory of Triboelectricity
(2020-10-30)We propose a microphysical theory of the triboelectric effect by which mechanical rubbing separates charges across the interface between two materials. Surface electrons are treated as an open system coupled to two baths, ... -
Random Electric Field Instabilities of Relaxor Ferroelectrics
(2017-06-13)Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the ... -
Relation between Luminescence and Electronic Surface Characteristics in p-type Porous Silicon
(1997)Measurements of photoluminescence, electronic surface states and effective surface area, at various stages of the anodization process, are presented. The results show a behavior different from that observed on n-type porous Si. -
Renormalización mejorada y multipolos armónicos
(2023)En este trabajo se proporciona una prueba de la estructura multipolar de los propagadores cinemáticos no regularizados de intensidades de campo de espín superior. Siguiendo el patrón identificado por primera vez en el ... -
Revealing a new region of gamma-ray emission in the vicinity of HESS J1825–137
(2019-02-17)HESS J1825–137 is a bright very high-energy gamma-ray source that has been firmly established as a pulsar wind nebula (PWN), and one of the most extended gamma-ray objects within this category. The progenitor supernova ... -
Search for gamma-ray emission from star-forming galaxies with Fermi LAT
(2016-08)Recent studies have found a positive correlation between the star-formation rate of galaxies and their gamma-ray luminosity. Galaxies with a high star-formation rate are expected to produce a large amount of high-energy ...