1,924 research outputs found
Two-step phase changes in cubic relaxor ferroelectrics
The field-driven conversion between the zero-field-cooled frozen relaxor
state and a ferroelectric state of several cubic relaxors is found to occur in
at least two distinct steps, after a period of creep, as a function of time.
The relaxation of this state back to a relaxor state under warming in zero
field also occurs via two or more sharp steps, in contrast to a one-step
relaxation of the ferroelectric state formed by field-cooling. An intermediate
state can be trapped by interrupting the polarization. Giant pyroelectric noise
appears in some of the non-equilibrium regimes. It is suggested that two
coupled types of order, one ferroelectric and the other glassy, may be required
to account for these data.Comment: 27 pages with 8 figures to appear in Phys. Rev.
A self-consistent renormalized Jellium approach for calculating structural and thermodynamic properties of charge stabilized colloidal suspensions
An approach is proposed which allows to self-consistently calculate the
structural and thermodynamic properties of highly charged aqueous colloidal
suspensions. The method is based on the renormalized Jellium model with the
background charge distribution related to the colloid-colloid correlation
function. The theory is used to calculate the correlation functions and the
effective colloidal charges for suspension containing additional monovalent
electrolyte. The predictions of the theory are in excellent agreement with the
Monte Carlo simulations
Aging in the Relaxor Ferroelectric PMN/PT
The relaxor ferroelectric
(PbMnNbO)(PbTiO), ,
(PMN/PT(90/10)) is found to exhibit several regimes of complicated aging
behavior. Just below the susceptibility peak there is a regime exhibiting
rejuvenation but little memory. At lower temperature, there is a regime with
mainly cumulative aging, expected for simple domain-growth. At still lower
temperature, there is a regime with both rejuvenation and memory, reminiscent
of spin glasses. PMN/PT (88/12) is also found to exhibit some of these aging
regimes. This qualitative aging behavior is reminiscent of that seen in
reentrant ferromagnets, which exhibit a crossover from a domain-growth
ferromagnetic regime into a reentrant spin glass regime at lower temperatures.
These striking parallels suggest a picture of competition in PMN/PT (90/10)
between ferroelectric correlations formed in the domain-growth regime with
glassy correlations formed in the spin glass regime. PMN/PT (90/10) is also
found to exhibit frequency-aging time scaling of the time-dependent part of the
out-of-phase susceptibility for temperatures 260 K and below. The stability of
aging effects to thermal cycles and field perturbations is also reported.Comment: 8 pages RevTeX4, 11 figures; submitted to Phys. Rev.
Alpha-Synuclein and Parkinson’s Disease Motor and Non-Motor Symptoms: what is new?
Although it was discovered about 25 years ago, alpha-synuclein (αS) misfolding and accumulation in neuronal tissues is still recognized as one of the most crucial aspects in Parkinson's disease (PD) pathology [...]
Software process improvement behavior of small and medium organizations in Argentina
Este artÃculo reporta el trabajo de investigación realizado en base a datos extraÃdos de la Encuesta Anual realizada por la CESSI durante el año 2007 entre organizaciones dedicadas al desarrollo de Software en Argentina. Si bien la temática de mejora de procesos de software há sido investigada previamente muy pocos datos existen sobe el comportamiento de organizaciones en Argentina. El análisis realizado contribuye a la comprensión del perfil de las organizaciones en cuanto a las tendencias de Mejora de Procesos de Software, las motivaciones que las movilizan y los facilitadores de estas iniciativas. Las conclusiones pueden ser utilizadas para entender que facilitadores mejoran la adopción de iniciativas de mejora por parte de organizaciones PyME de forma que incrementen su competitividad en los mercados domésticos y off-shoreThis paper reports on a research work performed on data extracted from the 2007 Annual CESSI survey among Argentina software development organizations. Although SPI has been researched before little data exists about the behavior of organizations in Argentina. The analysis provides insights on the profile of the companies regarding Software Process Improvement (SPI) trends, their motivations and drivers. The conclusions can be used to understand what drivers facilitate SPI adoption by SME organizations in order to increase their competitiveness in domestic and off-shore markets.Workshop de IngenierÃa de Software y Bases de Datos (WISBD)Red de Universidades con Carreras en Informática (RedUNCI
A Culture of Righteousness and Martyrdom
The mainstream American critique of the centrality of Islam in Arab culture often implies that religion is not important at home. Yet evangelical Christianity has been occupying an increasingly more prominent place in contemporary popular American culture. Just as Mel Gibson’s, The Passion of the Christ, has towered over competitors at the box office, so too have millenarian Christian texts—fictional and otherwise— been appearing in, and dominating, American best-seller lists. The popularity of these texts suggests that many American audiences are viewing contemporary events in the Middle East through an extremist evangelical lens
Equation of state of charged colloidal suspensions and its dependence on the thermodynamic route
The thermodynamic properties of highly charged colloidal suspensions in
contact with a salt reservoir are investigated in the framework of the
Renormalized Jellium Model (RJM). It is found that the equation of state is
very sensitive to the particular thermodynamic route used to obtain it.
Specifically, the osmotic pressure calculated within the RJM using the contact
value theorem can be very different from the pressure calculated using the
Kirkwood-Buff fluctuation relations. On the other hand, Monte Carlo (MC)
simulations show that both the effective pair potentials and the correlation
functions are accurately predicted by the RJM. It is suggested that the lack of
self-consistency in the thermodynamics of the RJM is a result of neglected
electrostatic correlations between the counterions and coions
Nontrivial dependence of dielectric stiffness and SHG on dc bias in relaxors and dipole glasses
Dielectric permittivity and Second Harmonic Generation (SHG) studies in the
field-cooled mode show a linear dependence of dielectric stiffness (inverse
dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in
KTaO:Li at small Li concentrations. We explain this unusual result in the
framework of a theory of transverse, hydrodynamic-type, instability of local
polarization.Comment: 5 figure
Marco para evaluar garantÃa en desarrollos de software
Este artÃculo expone un marco simplificado para estudiar los costos de garantÃa en el desarrollo de software. Se proponen métodos para obtener los parámetros requeridos por los modelos de confiabilidad citados en la bibliografÃa desde métricas de proceso comúnmente encontradas en la lÃnea de base de organizaciones desarrolladoras. El marco propuesto es validado mediante técnicas de simulación por el método de Montecarlo para explorar la magnitud de los resultados y la sensibilidad a los parámetros utilizados. Se extraen conclusiones preliminares y se identifican lÃneas de trabajo futuras.Sociedad Argentina de Informática e Investigación Operativa (SADIO
Uso de opciones reales para evaluar la contribución de metodologÃas KANBAN en desarrollo de software
Este artÃculo aborda el estudio preliminar de los factores que aportan valor al utilizar una metodologÃa ágil Kanban aplicada al desarrollo de software, en particular en el desarrollo de software asociado a sistemas embebidos. La adopción de esta metodologÃa se hace mayormente en base a expectativas subjetivas e historias de éxito, pero el abordaje formal de la caracterización de los factores que contribuyen al valor de la organización otras que la gestión de la capacidad del proceso y su ciclo de trabajo es aún escaso. Se modelan estos factores, se estiman los principales parámetros del modelo y se valida el resultado por medio de simulación. Finalmente se obtienen conclusiones y avizoran lÃneas de trabajo futuro.Sociedad Argentina de Informática e Investigación Operativa (SADIO
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