Browsing Física by Title
Now showing items 27-46 of 50
-
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 ... -
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 ... -
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 ... -
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. -
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 ... -
Stochastic approach to the smart quantum confinement model in porous silicon
(Surface Science 515 (2002) L509-L513, 2002)A model that encompasses two approaches to explain the photoluminescence in p-type porous silicon is proposed. The model considers a stochastic distribution of nanocrystallite sizes within the porous matrix and explain the ... -
Structure factor of a relaxor ferroelectric
(2015-04-14)We study a minimal model for a relaxor ferroelectric including dipolar interactions, and short-range harmonic and anharmonic forces for the critical modes as in the theory of pure ferroelectrics together with quenched ... -
Study of oxide bands in p-type porous silicon layers
(2019)The interest in developing fast and reliable chemical and biochemical sensors in an inexpensive way is something that has attracted a lot of efforts in the last decades. One of the potential material candidates is ... -
The 2:3:6 quasi-periodic oscillation structure in GRS 1915+105 and cubic subharmonics in the context of relativistic discoseismology
(Monthly Notices of the Royal Astronomical Society 440:3011-3015, 2014-06-01)We propose a simple toy model to explain the 2:3:6 quasi-periodic oscillation (QPO) structure in GRS 1915+105 and, more generally, the 2:3 QPO structure in XTE J1550−564, GRO J1655−40 and H1743−322. The model exploits the ... -
The early rainy season in Central America: the role of thetropical North Atlantic SSTs
(2016)We explored the relationship between the precipitation anomalies during May to June as the first peak of the rainy season in the Pacific slope of Central America, and sea surface temperature (SST) fluctuations in the ... -
The gigaelectronvolt counterpart of ver j2019+407 in the northern shell of the supernova remnant g78.2+2.1 (γ cygni)
(2016-07)Analysis of gamma-ray emission from the supernova remnant G78.2+2.1 (γ Cygni) with 7.2 years of cumulative data from the Fermi Large Area Telescope shows a distinct hard, bright, and extended component to the north of the ... -
The Hubble Constant and the Deceleration Parameter in Anisotropic Cosmological Spaces of Petrov type D
(2016-11)In this paper the Hubble parameter and the deceleration parameter are analyzed for a group of anisotropic homogeneous solutions of the Petrov type-D. It is obtained that for the said set of solutions can be constructed a ... -
The mechanical career of Councillor Orffyreus, confidence man
(2013-05)In the early 18th century, J. E. E. Bessler, known as Orffyreus, constructed several wheels that he claimed could keep turning forever, powered only by gravity. He never revealed the details of his invention, but he ... -
Tropical precipitation anomalies and d‐excess evolution during El Niño 2014‐16
(2016)The last 2014-16 El Niño event was among the three strongest episodes on record. El Niño considerably changes annual and seasonal precipitation across the tropics. Here, we present a unique stable isotope data set of daily ...