Pressure and temperature dependence of the band-gap in CdTe

2003

In this paper we report on isothermal compression measurements (up to 5 GPa and 500 K) of the optical absorption edge of 1 μm epitaxial layers of CdTe growth by metalorganic chemical vapor deposition (MOCVD) on GaS substrates. The isothermal blue shift under pressure of the direct energy gap (Γ v 15 → Γ c 1 ) in the zinc-blende phase is about 7.1 × 10 -2 eV GPa -1 and is found to be independent of temperature within the experimental errors. The isobaric red shift in the stability range of the zinc-blende phase is about -3.76 × 10 -4 eV K -1 . Regarding the phase transitions, no discontinuity in the energy gap has been found in the narrow pressure range where the cinnabar phase can be presen…

Variation of the optical absorption edge in AgGaS2 single crystals at high pressure

2003

In this paper the optical absorption edge of AgGaS 2 is measured as a function of pressure up to 26 GPa in order to verify the effect of the three phases transitions occurring in that pressure domain. The direct energy gap increases linearly with pressure at the rate of about 4.0 x 10 -2 eV GPa -1 up to 10.2 GPa. The absence of any discontinuity in the energy gap in the pressure range of 4.2-10.2 GPa confirms that the volume change, in the chalcopirite to monoclinic second-order transition, if it exists, is very small. When the pressure is raised above 10.2 GPa, the energy gap drops suddenly by about 1.1 eV and the spectral form of the absorption coefficient is typical of semiconductors wit…

NON-PERTURBATIVE VACUUM WAVE-FUNCTIONAL AND CLOSED STRING EQUATIONS OF MOTION

1989

The anomalous conformal dependence of the vacuum wave-functional is studied in the non-perturbative regime of the closed bosonic string theory. It is shown that the vanishing of the vacuum expectation value of the stress-energy tensor trace leads to the implementation of a suitable variational condition on the wave-functional, provided that the dilaton condensate be taken as a conformal compensator for the graviton condensate of the embedding space.

Optical absorption and Raman spectroscopy of CuWO4

2010

Th e electronic absorption and Raman spectra of CuWO4 are studied as a function of pressure in the 0 - 20 GPa range. The below-gap absorption bands at 1.15, 1.38 and 1.56 eV correspond to Cu 2+ d-transitions split by the Jahn-Teller distortion of CuO6 (Req = 1.98 A; Rax = 2.39 A; Qθ = 0.47 A). Pressure induces a strong reduction of the JT distortion up to 10 GPa. Above this pressure we observe, by optical absorption and Raman spectroscopy, a first-order phase transition at 11 GPa with phase coexistence in the 10-12 GPa range, as it is confirmed by Raman spectroscopy. The absorption spectra suggest that two different Cu 2+ sites are formed in the high pressure phase, each having rather diffe…

ON THE STABILITY OF SUPERSYMMETRY IN CURVED SPACE-TIME

1990

We discuss the stability of the classical supergravity background in a simple supersymmetric model at the quantum level, showing that two different pictures emerge depending on whether the emphasis is placed on the conformal invariance or on the supersymmetry invariance of the theory.

Work-related burnout syndrome in physicians in Spain

2020

Abstract This article brings together the views of a working group to deliberate on burnout among physicians in Spain. The document is the result of the answers that different members of the group have prepared to different questions on the subject with conclusions derived from the discussion among all the participants. Burnout is an entity with a high incidence in physicians, with serious work, personal and economic repercussions, whose recognition as a disease is changing in recent years. Particularly affected are some specialties, such as Primary Care, Oncology, Intensive Care Medicine, and Palliative Care. The common factor being an increased qualitative or quantitative demand on the pr…

Síndrome de quemarse por el trabajo (burnout) en los médicos de España

2020

Resumen Este articulo reune las opiniones de un grupo de trabajo para deliberar sobre el sindrome de burnout entre los medicos en Espana. El documento es el resultado de las respuestas que los miembros del grupo han preparado a diferentes preguntas sobre el tema con conclusiones derivadas de la discusion entre todos los participantes. El burnout es una entidad con una alta incidencia en los medicos, con graves repercusiones laborales, personales y economicas, cuyo reconocimiento como enfermedad esta cambiando en los ultimos anos. Se ven especialmente afectadas especialidades como Atencion Primaria, Oncologia, Medicina Intensiva y Cuidados Paliativos. El factor comun es un aumento de la dema…

Electronic structure and optical properties of CdTe rock-salt high pressure phase

2003

This paper reports on optical absorption and reflectance measurements in thin CdTe samples up to 15 GPa. All studied samples become virtually opaque at the pressure transition between the zinc-blende and rock-salt phases (3.9 GPa). As pressure increases up to 10 GPa, a relative transparency region is observed between 1.2 eV and 2.4 eV, whose high energy edge shifts to higher photon energies. Above 10 GPa the transparency region gradually shrinks and disappears at about 11 GPa. The low energy side of the absorption spectrum is attributed to free carrier absorption, as electronic structure calculations show that rock-salt CdTe is a semimetal or a low gap semiconductor. Band filling effects lo…

Quantum dots of Cd0.5Mn0.5Te semimagnetic semiconductor formed by the cold isostatic pressure method

2005

Abstract Cd0.5Mn0.5Te is a semimagnetic semiconductor, which crystallizes in the zinc-blende structure (ZB) and exhibits a magnetic spin glass like transition at 21 K. Under pressure it shows a first-order phase transition around 2.6 GPa to the NaCl like structure. In this work, the pressure cycled method using a Paris–Edinburgh cell up to 8 GPa has been applied to Cd0.5Mn0.5Te samples in order to obtain recovered nanocrystals. The nanoparticles have been characterized by EDX and electron microscopy. The X-ray and electron diffraction results confirmed the existence of nanocrystals in the ZB phase with an average size of 7 nm. Magnetization measurements made in the range of 2–300 K at low f…

MOCVD growth of CdTe on glass: analysis of in situ post-growth annealing

2004

Abstract In this paper, we analyse the growth by MOCVD of CdTe on glass substrates using in situ post-growth annealing. First, in order to perform a systematic study, polycrystalline layers of CdTe were deposited by MOCVD on glass substrates. The structure and morphology of the layers was investigated as a function of different growth parameters, temperature, VI/II precursor molar ratio and substrate position on the susceptor. An activation energy of Ek=20.7 kcal/mol was obtained from the experimental data. In order to better understand the process and the effects of different growth parameters, a numerical model that simulated the gas flow in the reactor, was developed. Secondly we analyse…

II–VI and II1−xMnxVI semiconductor nanocrystals formed by the pressure cycle method

2005

II–VI and II1−x Mn x VI nanocrystals were prepared by the pressure cycle method using the Paris–Edinburgh cell. The recovered samples are nanocrystals in the cubic phase zinc-blend (ZB) structure and were characterized using transmission electron microscopy, electron diffraction, X-ray diffraction and Raman scattering. Transmission electron micrographs show that these nanocrystals are nearly spherical with diameters ranging from 20 to 50 nm depending on the sample under investigation. The Raman scattering measurements confirm the existence of II–VI nanocrystals in the cubic phase (ZB). The magnetic properties of Cd0.5Mn0.5Te nanoparticles were found to vary with the particle size and were d…

High-pressure Raman spectroscopy and lattice-dynamics calculations on scintillating MgWO4: Comparison with isomorphic compounds

2011

Research was financed by the Spanish Ministerio de Educacion y Ciencia (MEC) under Grants No. MAT2010-21270-C04-01/02/04, and No. CSD-2007-00045. J. R.-F. thanks the MEC for support through the FPI program, as well as the SPP1236 central facility in Frankfurt for its use. F. J. M. acknowledges support from Vicerrectorado de Investigacion y Desarrollo de la Universitat Politecnica de Valencia (UPV) (Grant No. UPV2010-0096). A. M. and P. R.-H. acknowledge the supercomputer time provided by the Red Espanola de Supercomputacion. A. F. appreciates support from the German Research Foundation (Grant No. FR2491/2-1).

Polarization calibration techniques for the new-generation VLBI

2020

The calibration and analysis of polarization observations in Very Long Baseline Interferometry (VLBI) requires the use of specific algorithms that suffer from several limitations, closely related to assumptions in the data properties that may not hold in observations taken with new-generation VLBI equipment. Nowadays, the instantaneous bandwidth achievable with VLBI backends can be as high as several GHz, covering several radio bands simultaneously. In addition, the sensitivity of VLBI observations with state-of-the-art equipment may reach dynamic ranges of tens of thousands, both in total intensity and in polarization. In this paper, we discuss the impact of the limitations of common VLBI …

Ardides dobles de amor : comedia en tres actos, y en verso, original,

Filets Text a 1 col A la contraport.: Esta comedia es propiedad de la Sociedad Espartana

Síndrome de quemarse por el trabajo (burnout) en los médicos de España.

2020

El Síndrome de Quemarse por el Trabajo (SQT) o "Burnout" es un problema de salud que puede afectar a profesionales de todo tipo, pero muy especialmente a aquellos cuya actividad guarda relación con el cuidado de seres humanos. Los profesionales de la salud están particularmente expuestos a este cuadro y los médicos son el prototipo de trabajador expuesto al mismo. Se trata de un problema de salud tremendamente destructivo que afecta a la vida laboral y personal, que lesiona la calidad del trabajo prestado y que deteriora los planos cognitivo y emocional del individuo, su vida familiar y hasta su salud física.

Comparison of European ICU patients in 2012 (ICON) versus 2002 (SOAP)

2018

Purpose: To evaluate differences in the characteristics and outcomes of intensive care unit (ICU) patients over time. Methods: We reviewed all epidemiological data, including comorbidities, types and severity of organ failure, interventions, lengths of stay and outcome, for patients from the Sepsis Occurrence in Acutely ill Patients (SOAP) study, an observational study conducted in European intensive care units in 2002, and the Intensive Care Over Nations (ICON) audit, a survey of intensive care unit patients conducted in 2012. Results: We compared the 3147 patients from the SOAP study with the 4852 patients from the ICON audit admitted to intensive care units in the same countries as those…