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 (PbMn$_{1/3}$Nb$_{2/3}$O$_3$)$_{1-x}$(PbTiO$_3$)$_{x}$, $x=0.1$, (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 artículo reporta el trabajo de investigación realizado en base a datos extraídos 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 Ingeniería 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$_{3}$: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 garantía en desarrollos de software

Este artículo expone un marco simplificado para estudiar los costos de garantía en el desarrollo de software. Se proponen métodos para obtener los parámetros requeridos por los modelos de confiabilidad citados en la bibliografía desde métricas de proceso comúnmente encontradas en la línea 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 líneas de trabajo futuras.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Uso de opciones reales para evaluar la contribución de metodologías KANBAN en desarrollo de software

Este artículo aborda el estudio preliminar de los factores que aportan valor al utilizar una metodología ágil Kanban aplicada al desarrollo de software, en particular en el desarrollo de software asociado a sistemas embebidos. La adopción de esta metodología 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 líneas de trabajo futuro.Sociedad Argentina de Informática e Investigación Operativa (SADIO