Composite polymer membranes for laserinduced fluorescence thermometry

We demonstrate a modified version of laser-induced fluorescence thermometry (LIFT) for mapping temperature gradients in the vicinity of small photothermal devices. Our approach is based on temperature sensitive fluorescent membranes fabricated with rhodamine B and polydimethylsiloxane (PDMS). Relevant membrane features for LIFT, such as temperature sensitivity, thermal quenching and photobleaching are presented for a range of 25 °C to 90 °C, and their performance is evaluated upon obtaining the temperature gradients produced in the proximity of optical fiber micro-heaters. Our results show that temperature measurements in regions as small as 750 μm x 650 μm, with a temperature resolution of 1 °C, can be readily obtained

Revolving rivers in sandpiles: from continuous to intermittent flows

In a previous paper [Phys. Rev. Lett. 91, 014501 (2003)], the mechanism of "revolving rivers" for sandpile formation is reported: as a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a river of sand on one side owing from the apex of the pile to the edge of the base. For small piles the river is steady, or continuous. For larger piles, it becomes intermittent. In this paper we establish experimentally the "dynamical phase diagram" of the continuous and intermittent regimes, and give further details of the piles topography, improving the previous kinematic model to describe it and shedding further light on the mechanisms of river formation. Based on experiments in Hele-Shaw cells, we also propose that a simple dimensionality reduction argument can explain the transition between the continuous and intermittent dynamics.Comment: 8 pages, 11 figures, submitted to Phys Rev

Phase diagram of silicon from atomistic simulations

In this letter we present a calculation of the temperature-pressure phase diagram of Si in a range of pressures covering from -5 to 20 GPa and temperatures up to the melting point. The phase boundaries and triple points between the diamond, liquid, $\beta$-Sn and ${Si}_{34}$ clathrate phases are reported. We have employed efficient simulation techniques to calculate free energies and to numerically integrate the Clausius-Clapeyron equation, combined with a tight binding model capable of an accuracy comparable to that of first-principles methods. The resulting phase diagram agrees well with the available experimental data.Comment: 5 pages, 1 figure, accepted in PR

A useful form of the recurrence relation between relativistic atomic matrix elements of radial powers

Recently obtained recurrence formulae for relativistic hydrogenic radial matrix elements are cast in a simpler and perhaps more useful form. This is achieved with the help of a new relation between the $r^a$ and the $\beta r^b$ terms ($\beta$ is a $4\times 4$ Dirac matrix and $a, b$ are constants) in the atomic matrix elements.Comment: 7 pages, no figure

Ψ=We±Φ\rm \Psi= W e^{\pm \Phi} quantum cosmological solutions for Class A Bianchi Models

We find solutions for quantum Class A Bianchi models of the form $\rm \Psi=W e^{\pm \Phi}$ generalizing the results obtained by Moncrief and Ryan in standard quantum cosmology. For the II and IX Bianchi models there are other solutions $\rm \tilde\Phi_2$, $\rm \tilde\Phi_9$ to the Hamilton-Jacobi equation for which $\rm \Psi$ is necessarely zero, in contrast with solutions found in supersymmetric quantum cosmology.Comment: 15 pages, Late

New non-unitary representations in a Dirac hydrogen atom

New non-unitary representations of the SU(2) algebra are introduced for the case of the Dirac equation with a Coulomb potential; an extra phase, needed to close the algebra, is also introduced. The new representations does not require integer or half integer labels. The set of operators defined are used to span the complete space of bound state eigenstates of the problem thus solving it in an essentially algebraic way

Cálculo del ranking acumulado para la encuesta de expectativas de inflación y tasa de cambio nominal, a través de una prueba no paramétrica

En este documento se presenta una metodología para el cálculo del Ranking acumulado de las entidades financieras que participan en la encuesta mensual de expectativas de inflación y tasa de cambio nominal (TRM), realizada por el Banco de la República. La metodología se basa en la prueba estadística no paramétrica propuesta por Jonckheere (1954), que consiste en un sistema de hipótesis de igualdad de distribuciones de probabilidad acumulada con alternativa de ordenamiento estricto para k muestras (k = 2). La metodología busca determinar el orden óptimo con el cual se rechaza la hipótesis nula, esto último se hace por medio de permutaciones. Ésta metodología es implementada en el programa R.Encuesta de expectativas económicas, Prueba de hipótesis no paramétrica, Prueba de Jonckheere. Classification JEL:C12, C14, D00, D21.

Recurrence relation for relativistic atomic matrix elements

Recurrence formulae for arbitrary hydrogenic radial matrix elements are obtained in the Dirac form of relativistic quantum mechanics. Our approach is inspired on the relativistic extension of the second hypervirial method that has been succesfully employed to deduce an analogous relationship in non relativistic quantum mechanics. We obtain first the relativistic extension of the second hypervirial and then the relativistic recurrence relation. Furthermore, we use such relation to deduce relativistic versions of the Pasternack-Sternheimer rule and of the virial theorem.Comment: 10 pages, no figure

Capital social, metas del milenio y desarrollo local : el caso de la Iniciativa de Carapeguá en Desarrollo, Paraguay

¿Puede lo global y lo local generar una sinergia catalizadora del desarrollo comunitario en forma sostenible? ¿Puede la aplicación de la "caja de herramientas" de la gerencia social fortalecer el capital social, que a su vez impulsará el desarrollo local? ¿Puede la capacitación en gerencia social ser un elemento articulador y catalizador del desarrollo local? El objetivo a corto plazo del programa fue el de fortalecer el capital social local para catalizar una estrategia de desarrollo local sostenible, que mejore las condiciones de vida de la población en forma consistente con los objetivos de desarrollo del milenio. Para evaluar el impacto del programa sobre el capital social, se presentan y analizan las acciones y procesos del programa que pudieron haber impactado sobre los distintos elementos que constituyen el acervo de capital social de una comunidad