• Lamellar fluctuations melt ferroelectricity 

      Guzmán Verri, Gian Giacomo; Liang, Charles H.; Littlewood, Peter B. (2023)
      We consider a standard Ginzburg-Landau model of a ferroelectric whose electrical polarization is coupled to gradients of elastic strain [1–4]. At the harmonic level, such flexoelectric interaction is known to hybridize ...
    • Landau theory and giant room-temperature barocaloric effect 

      Corrales Salazar, A.; Brierley, Richard T.; Littlewood, Peter B.; Guzmán Verri, Gian Giacomo (2017-10-17)
      The structural phase transitions of MF3 (M = Al, Cr, V, Fe, Ti, Sc) metal trifluorides are studied within a simple Landau theory consisting of tilts of rigid MF6 octahedra associated with soft antiferrodistortive optic ...
    • Large isotropic negative thermal expansion above a structural quantum phase transition 

      Handunkanda, Sahan U.; Curry, Erin B.; Voronov, Vladimir; Said, Ayman H.; Guzmán Verri, Gian Giacomo; Brierley, Richard T.; Littlewood, Peter B.; Hancock, Jason N. (2015-10-01)
      Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing ...
    • Leaking elastic capacitor as model for active matter 

      Alicki, Robert; Gelbwaser Klimovsky, David; Jenkins Villalobos, Alejandro (2021-05-24)
      We introduce the “leaking elastic capacitor” (LEC) model, a nonconservative dynamical system that combines simple electrical and mechanical degrees of freedom. We show that an LEC connected to an external voltage source ...
    • Modelado del espacio-tiempo en el interior de una estrella de neutrones en rotación con un cuadrupolo agregado de forma perturbativa 

      Morales Montenegro, Julio César (2021-11-07)
      The potentials and multipolar parameters for a neutron star internal space-time model are calculated in a perturbative series using the angular velocity as perturbation parameter. Twelve equations of state are considered, ...
    • Modelling SPECT auto-contouring acquisitions for 177Lu & 131I molecular radiotherapy using new developments in Geant4/GATE 

      Kayal, Gunjan; Chauvin, Maxime; Mora Ramírez, Erick; Clayton, Naomi; Vergara Gil, Alex; Tran Gia, Johannes; Lassmann, Michael; Calvert, Nicholas; Tipping, Jill; Struelens, Lara; Bardiès, Manuel (2022)
      Purpose Monte Carlo modelling of SPECT imaging in Molecular Radiotherapy can improve activity quantification. Until now, SPECT modelling with GATE only considered circular orbit (CO) acquisitions. This cannot reproduce ...
    • Monte Carlo dosimetry of a realistic multicellular model of follicular lymphoma in a context of radioimmunotherapy 

      Bordes, Julien; Incerti, Sébastien; Mora Ramírez, Erick; Tranel, Jonathan; Rossi, Cédric; Bezombes, Christine; Bordenave, Julie; Bardiès, Manuel; Brown, Richard; Bordage, Marie Claude (2020)
      Purpose Small-scale dosimetry studies generally consider an artificial environment where the tumors are spherical and the radionuclides are homogeneously biodistributed. However, tumor shapes are irregular and radiopharmaceutical ...
    • Negative Thermal Expansion in Open Perovskites near the Precipice of Structural Stability 

      Occhialini, Connor A.; Guzmán Verri, Gian Giacomo; Handunkanda, Sahan U.; Hancock, Jason N. (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 

      Guzmán Verri, Gian Giacomo; Hancock, Jason N. (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 

      Hidalgo León, Hugo G.; Alfaro Martínez, Eric J. (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 

      Chauvin, Maxime; Borys, Damian; Botta, Francesca; Bzowski, Pawel; Dabin, Jérémie; Denis Bacelar, Ana M.; Desbrée, Aurélie; Falzone, Nadia; Lee, Boon Quan; Mariani, Andrea; Malaroda, Alessandra; Mathieu, Gilles; McKay, Erin; Mora Ramírez, Erick; Robinson, Andrew P.; Sarrut, David; Struelens, Lara; Vergara Gil, Alex; Bardiès, Manuel (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 

      Padilla Víquez, Gerardo José (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 

      Thompson, Anne M.; Smit, Herman G. J.; Witte, Jacquelyn C.; Stauffer, Ryan M.; Johnson, Bryan J.; Morris, Gary; von der Gathen, Peter; Van Malderen, Roeland; Davies, Jonathan; Piters, Ankie; Allaart, Marc; Posny, Françoise; Kivi, Rigel; Cullis, Patrick; Hoang Anh, Nguyen Thi; Corrales, Ernesto; Machinini, Tshidi; da Silva, Francisco R.; Paiman, George; Thiong’o, Kennedy; Zainal, Zamuna; Brothers, George B.; Wolff, Katherine R.; Nakano, Tatsumi; Stübi, Rene; Romanens, Gonzague; Coetzee, Gert J. R.; Díaz Díaz, Jorge Andrés; Mitro, Sukarni; Mohamad, Maznorizan; Ogino, Shin-Ya (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 

      Balberg, I.; Nery, Guillermo; Ramírez Porras, Arturo; Resto, O.; Weisz, S. Z.; Lubianiker, Y. (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 

      Coak, Matthew J.; Haines, Charles Robert Sebastian; Liu, Cheng; Guzmán Verri, Gian Giacomo; Saxena, Siddharth S. (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 

      Araya Arguedas, Miguel; Gutiérrez, Luis; Kerby, Stephen (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 

      Campos Fernández, María Gabriela (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 

      Ramírez Morera, Óscar Paul (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 

      Mora Rodríguez, Patricia; Porra Chaverri, Mariela (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 

      Arce Gamboa, José Rafael; Guzmán Verri, Gian Giacomo (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 ...