Anisotropic dynamics of a vicinal surface under the meandering step instability

We investigate the nonlinear evolution of the Bales-Zangwill instability, responsible for the meandering of atomic steps on a growing vicinal surface. We develop an asymptotic method to derive, in the continuous limit, an evolution equation for the two-dimensional step flow. The dynamics of the crystal surface is greatly influenced by the anisotropy inherent to its geometry, and is characterized by the coarsening of undulations along the step direction and by the elastic relaxation in the mean slope direction. We demonstrate, using similarity arguments, that the coalescence of meanders and the step flow follow simple scaling laws, and deduce the exponents of the characteristic length scales and height amplitude. The relevance of these results to experiments is discussed.Comment: 10 pages, 7 figures; submitted to Phys. Rev.

Investigations on nucleophilic layers made with a novel plasma jet technique

In this work a novel plasma jet technique is used for the deposition of nucleophilic films based on (3-aminopropyl)trimethoxysilane at atmospheric pressure. Film deposition was varied with regard to duty cycles and working distance. Spectral ellipsometry and chemical derivatization with 4-(trifluoromethyl)benzaldehyde using ATR- FTIR spectroscopy measurements were used to characterize the films. It was found that the layer thickness and the film composition are mainly influenced by the duty cycle

Aerogels for energy and environmental applications

Aerogels are emerging as one of the most intriguing and promising groups of microporous materials, characterized by impressive properties such as low density, high surface area, high porosity and tunable surface chemistry. Fostering unique thermal and acoustic insulation features, for several decades they mainly received attention from the aerospace and building sectors. More recently, new great opportunities arose due to significant advances in the drying technologies that currently, represent the enabling step for aerogel synthesis and fabrication. This process-ability dramatically increased the interest toward aerogels from new disciplines. This explains why in the last decade the Environmental Science and Energy fields significantly contributed to the expansion of the aerogel technology, suggesting novel uses and applications and contributing to extend the group of materials that can be synthetized by aerogel processing. New, unforeseen properties emerged for aerogel materials, such as adsorption of contaminants and fluids purification, catalysis of different reactions, electrical conductivity. The present short-review aims at providing a critical overview of the key advances in the development of aerogels for energy and environmental applications, especially emphasizing the common strategies and properties that are turning aerogels into one of the new key emerging technologies of these areas of science

Atom-projected and angular momentum resolved density of states in the ONETEP code

Local and angular momentum projected densities of states (DOS) are invaluable sources of information that can be obtained from density functional theory calculations. In this work, we describe a theoretical framework within ONETEP's linear-scaling DFT formalism that allows the calculation of local (atom-projected) and angular momentum projected density of states l-p-DOS. We describe four different bases that can be used for projecting the DOS with angular momentum resolution and perform a set of tests to compare them. We validate the results obtained with ONETEP's l-p-DOS against the plane-wave DFT code CASTEP. Comparable results between ONETEP's and CASTEP's charge spilling parameters are observed when we use pseudo-atomic orbitals as the projection basis sets. In general, the charge spilling parameters show remarkably low values for projections using non-contracted spherical waves as the angular momentum resolved basis. We also calculate the d-band and d-band centres for Pt atoms in (1 1 1) facets of cuboctahedral Pt nanoparticles of increasing size, which is an example of l-p-DOS application commonly used as an electronic descriptor in heterogeneous catalysis. Interestingly, the different projection bases lead to similar conclusions, showing the reliability of the implemented method for such studies. The implementation of these methods in a linear-scaling framework such as ONETEP provides another tool for analysing the electronic structure of complex nanostructured materials

Ecuaciones cinéticas para un plasma E-E relativista en un campo magnético fuerte

Se parte de un hamiltoniano que incluye la interacción de un plasma de electrones y positrones en un campo magnético fuerte con el campo electromagnético autoconsistente, despreciando las colisiones entre partículas. Dado que la interacción es débil (∼ e²/hc), este hamiltoniano establece una jerarquía de tiempos de relajación que permite describir al sistema mediante las matrices densidad a una partícula para cada especie. A primer orden en el desarrollo de potencias de la interacción, se deduce la ecuación de Vlasov cuántica, y se establece su límite clásico. A segundo orden se deducen las ecuaciones de la teoría cuasi-lineal de la turbulencia débil.Asociación Argentina de Astronomí

Evaluation of skin temperature change as stress indicator in rabbit through infrared thermography

AbstractStress-induced reactions in animals include behavioural and physiological modifications aiming at coping towards the stressor, such as manipulations. Thermography, that is the detection of ..

Impacto del cambio climático sobre la distribución de Prosopis Hassleri y P.alba en la región chaqueña

El algarrobo, principalmente Prosopis alba y P. hassleri son las especies nativas de mayor uso para madera de aserrío en nuestro país, registrándose en los últimos años un aumento constante en la tasa de consumo. Dado que la totalidad de la madera de algarrobo consumida proviene de bosques nativos, la explotación del recurso es insostenible no sólo desde el punto de vista ambiental sino también económico. A esta situación crítica se le agregan además problemáticas que están afectando a los bosques a escala global como es la expansión de la frontera agrícola sobre áreas de bosque nativo, forestación con especies exóticas de crecimiento rápido, y la interacción de estos factores con el cambio climático actual. En este trabajo indagamos sobre el posible impacto del cambio climático sobre la distribución de P. hassleri (Algarrobo paraguayo) y de tres morfotipos de P. alba (santiagueño, chaqueño y chaqueño sur) en el norte de Argentina, para proveer información útil en la planificación de estrategias de conservación y manejo de los recursos genéticos nativos. Para ello, se utilizaron modelos predictivos de nicho que permitieron estimar la distribución potencial de ambas especies bajo un escenario actual y de cambio climático futuro. De esta manera se pudieron establecer áreas de alto y bajo impacto, y nuevas áreas adecuadas para la persistencia de las respectivas especies. Se utilizaron datos georreferenciados de 30-77 individuos de poblaciones naturales de cada una de las especies y morfotipos, y los 19 parámetros bioclimáticos disponibles en la base de datos mundial WorldClim. Los análisis de modelado de nicho actual y futuro se realizaron mediante el algoritmo de máxima entropía implementado en el programa Maxent; posteriormente los modelados resultantes fueron procesados en el programa DIVA-GIS. Los resultados indican que todas las especies/morfotipos tienden a desplazar su área de distribución hacia el sur, excepto el morfotipo P. alba chaqueño sur que se expandiría hacia el norte. Prosopis hassleri sería la especie que perdería la mayor proporción de superficie de su distribución actual. Sin embargo, en un escenario futuro surgirían áreas favorables para su persistencia cuya superficie duplicaría la distribución actual. Contrariamente, el morfotipo santiagueño de P. alba conservaría casi la totalidad de su área de distribución actual, y es la que menos ampliaría su rango de distribución en un escenario futuro. A partir de los resultados obtenidos se sugieren estrategias de manejo y conservación para estas especies, a través de la identificación y protección de refugios climáticos y del establecimiento de corredores biológicos que favorezcan la dispersión natural de las especies hacia nuevas áreas adecuadas. (Nuestro agradecimiento al Proyecto Específico INTA PNFOR044341 y al Banco Nacional de Germoplasma de Prosopis, FCA-UNC, por facilitar la información básica para este trabajo).Fil: Venier, Maria Paula. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cosacov Martinez, Andrea. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: López Lauenstein, D.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Vega, C.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; ArgentinaFil: Verga, A.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; Argentin

Workflow for the Validation of Geomechanical Simulations through Seabed Monitoring for Offshore Underground Activities

Underground fluid storage is gaining increasing attention as a means to balance energy production and consumption, ensure energy supply security, and contribute to greenhouse gas reduction in the atmosphere by CO2 geological sequestration. However, underground fluid storage generates pressure changes, which in turn induce stress variations and rock deformations. Numerical geomechanical models are typically used to predict the response of a given storage to fluid injection and withdrawal, but validation is required for such a model to be considered reliable. This paper focuses on the technology and methodology that we developed to monitor seabed movements and verify the predictions of the impact caused by offshore underground fluid storage. To this end, we put together a measurement system, integrated into an Autonomous Underwater Vehicle, to periodically monitor the seabed bathymetry. Measurements repeated during and after storage activities can be compared with the outcome of numerical simulations and indirectly confirm the existence of safety conditions. To simulate the storage system response to fluid storage, we applied the Virtual Element Method. To illustrate and discuss our methodology, we present a possible application to a depleted gas reservoir in the Adriatic Sea, Italy, where several underground geological formations could be potentially converted into storage in the futur

Thyroid Hormone T3 Counteracts STZ Induced Diabetes in Mouse

This study intended to demonstrate that the thyroid hormone T3 counteracts the onset of a Streptozotocin (STZ) induced diabetes in wild type mice. To test our hypothesis diabetes has been induced in Balb/c male mice by multiple low dose Streptozotocin injection; and a group of mice was contemporaneously injected with T3. After 48 h mice were tested for glucose tolerance test, insulin serum levels and then sacrified. Whole pancreata were utilized for morphological and biochemical analyses, while protein extracts and RNA were utilized for expression analyses of specific molecules. The results showed that islets from T3 treated mice were comparable to age- and sex-matched control, untreated mice in number, shape, dimension, consistency, ultrastructure, insulin and glucagon levels, Tunel positivity and caspases activation, while all the cited parameters and molecules were altered by STZ alone. The T3-induced pro survival effect was associated with a strong increase in phosphorylated Akt. Moreover, T3 administration prevented the STZ-dependent alterations in glucose blood level, both during fasting and after glucose challenge, as well as in insulin serum level. In conclusion we demonstrated that T3 could act as a protective factor against STZ induced diabetes