Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

3 páginas, 3 figuras.-- Progress in Applied Surface, Interface and Thin Film Science - SURFINT SREN II.-- PACS codes: 68.37.Lp; 81.05.Ea; 81.15.HiThe compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.This work was supported by the Spanish MCI (TEC2008-06756-C03-02/TEC), CONSOLIDER CSD2009-00013, and the Junta de Andalucia (PAI research groups TEP-120 and TIC-145, project P08-TEP-03516).Peer reviewe

Soluble iron dust export in the high altitude Saharan Air Layer

Every summer huge amounts of desert dust particles are exported from the hyperarid subtropical Sahara to the North Atlantic the so-called Saharan Air Layer (SAL), a dry, warm and dust-laden corridor that expands from the North African coast (1-5 km.a.s.I.) to the Americas above the marine boundary layer. Because of the potential impact of the dust deposited on the ocean on marine biogeochemistry and climate, we studied the Fe solubility (in seawater) of atmospheric aerosols samples directly collected in the SAL off the North African coast, i.e, the fresh aerosols recently exported from the Sahara in the SAL. The aerosol sampling was performed at 2400 m.a.s.l. in Izana observatory in Tenerife island. In the total aerosols, we found low Fe concentrations and high fractional Fe solubility (FFS-2%) in the North Atlantic free troposphere airflows and high Fe concentrations and low FFS (-0.7%) within the SAL; the resulting FFS versus total dust (or total Fe) plot shows a hyperbolic trend attributed to the conservative mixing of 'fine combustion aerosols' and 'lithogenic mineral dust'. We then focused on the soluble Fe in the SAL Our results indicate that 70% of soluble Fe is associated with the dissolution of submicron dust particles, probably involving Fe-bearing clays. We found a FFS of submicron dust (-6%) higher than that typically observed in submicron particles of soil dust samples (<1%).This study is part of the project AEROATLAN e 2015-66229 -, funded by the Ministry of Economy and Competitiveness of Spain. M.I. García holds a research grant e TESIS20120054 e co-funded by the Canarian Agency for Research, Innovation and Information Society and the European Social Fund

The inversion, formulae for some bessel and hypergeometric transforms

By an appeal to the Laplace transform and their inverses we have obtained five inversión formulae for some Bessel function transforms. The inversion formula for hyperqeometric transforms have been given whose kernel are the confluent hypergeometric function  1F1(γ - a;  γ; μx) and Gauss hypergeometric function  2F1( a, β, γ;  - 1/ μ x). The results given earlier by Gómez López [8] follow as special cases of our results given in section. 3

The latest (version 4.3) Mars Climate Database

Introduction: The Mars Climate Database (MCD) is a database of meteorological fields derived from General Circulation Model (GCM) numerical simulations of the Martian atmosphere and validated using available observational data. The MCD includes complementary post-processing schemes such as high spatial resolution interpolation of environmental data and means of reconstructing the variability thereof. The GCM is developed at Laboratoire de Météorologie Dynamique du CNRS (Paris, France) [1,2] in collaboration with the Open University (UK), the Oxford University (UK) and the Instituto de Astrofisica de Andalucia (Spain) with support from the European Space Agency (ESA) and the Centre National d'Etudes Spatiales (CNES)

The new Mars climate database

Not available

Hilbert space of wormholes

Wormhole boundary conditions for the Wheeler--DeWitt equation can be derived from the path integral formulation. It is proposed that the wormhole wave function must be square integrable in the maximal analytic extension of minisuperspace. Quantum wormholes can be invested with a Hilbert space structure, the inner product being naturally induced by the minisuperspace metric, in which the Wheeler--DeWitt operator is essentially self--adjoint. This provides us with a kind of probabilistic interpretation. In particular, giant wormholes will give extremely small contributions to any wormhole state. We also study the whole spectrum of the Wheeler--DeWitt operator and its role in the calculation of Green's functions and effective low energy interactions.Comment: 23 pages, 2 figures available upon request, REVTE

Comportamiento mecánico de restos de pirámides y templos americanos y los edificios históricos construidos sobre ellos

Una característica bastante habitual de monumentos y edificios históricos suele ser el estar construidos sobre otros edificios que bien fueron demolidos para levantar los actuales o bien fueron olvidados. Las nuevas construcciones suelen estar edificadas en parte sobre rellenos artificiales relativamente blandos y sobre zonas rígidas, restos de los muros anteriores. Esta disposición llega a provocar una serie de patologías características. Un caso singular de este tipo de levantamientos es la construcción de iglesias y palacios en Hispanoamérica sobre los restos de las antiguas pirámides. Además de los casos en México D.F., existen bastantes poblaciones en Guatemala y en el resto de México con pirámides parcialmente destruidas que están siendo o fueron utilizadas como base para cimentaciones de “nuevos” edificios históricos. Existen también otros casos en los que, al no disponer de cubrición en su parte superior, permiten el paso del agua de lluvia. En este artículo se muestra como el comportamiento de estas pirámides y construcciones antiguas incluidas en el terreno es más parecido al de estructuras de contención (muros) que al de plataformas horizontales debido a que el agua de lluvia aumenta los empujes sobre las capas exteriores y estos edificios, como sucede con pirámides de Guatemala y México, sufren una degradación importante. Además, se demuestra el efecto de rigidización lateral del terreno y reducción de asientos en las construcciones cimentadas sobre suelos que contienen estos restos, los cuales suponen una mejora importante de la capacidad portante.Universidad de Las Palmas de Gran CanariaColegio Oficial de Ingenieros Industriales de CanariasAgencia Canaria de Investigación, Innovación y Sociedad de la Informació

Circular strings, wormholes and minimum size

The quantization of circular strings in an anti-de Sitter background spacetime is performed, obtaining a discrete spectrum for the string mass. A comparison with a four-dimensional homogeneous and isotropic spacetime coupled to a conformal scalar field shows that the string radius and the scale factor have the same classical solutions and that the quantum theories of these two models are formally equivalent. However, the physically relevant observables of these two systems have different spectra, although they are related to each other by a specific one-to-one transformation. We finally obtain a discrete spectrum for the spacetime size of both systems, which presents a nonvanishing lower bound.Comment: 11 pages, LaTeX2e, minor change

Tunneling and transmission resonances of a Dirac particle by a double barrier

We calculate the tunneling process of a Dirac particle across two square barriers separated a distance $d$, as well as the scattering by a double cusp barrier where the centers of the cusps are separated a distance larger than their screening lengths. Using the scattering matrix formalism, we obtain the transmission and reflection amplitudes for the scattering processes of both configurations. We show that, the presence of transmission resonances modifies the Lorentizian shape of the energy resonances and induces the appearance of additional maxima in the transmission coefficient in the range of energies where transmission resonances occur. We calculate the Wigner time-delay and show how their maxima depend on the position of the transmission resonance.Comment: To appear in Physica Script

Pleiotropic contribution of rbfox1 to psychiatric and neurodevelopmental phenotypes in two zebrafish models

RBFOX1 is a highly pleiotropic gene that contributes to several psychiatric and neurodevelopmental disorders. Both rare and common variants in RBFOX1 have been associated with several psychiatric conditions, but the mechanisms underlying the pleiotropic effects of RBFOX1 are not yet understood. Here we found that, in zebrafish, rbfox1 is expressed in spinal cord, mid- and hindbrain during developmental stages. In adults, expression is restricted to specific areas of the brain, including telencephalic and diencephalic regions with an important role in receiving and processing sensory information and in directing behaviour. To investigate the contribution of rbfox1 to behaviour, we used rbfox1sa15940, a zebrafish mutant line with TL background. We found that rbfox1sa15940 mutants present hyperactivity, thigmotaxis, decreased freezing behaviour and altered social behaviour. We repeated these behavioural tests in a second rbfox1 mutant line with a different genetic background (TU), rbfox1del19, and found that rbfox1 deficiency affects behaviour similarly in this line, although there were some differences. rbfox1del19 mutants present similar thigmotaxis, but stronger alterations in social behaviour and lower levels of hyperactivity than rbfox1sa15940 fish. Taken together, these results suggest that mutations in rbfox1 lead to multiple behavioural changes in zebrafish that might be modulated by environmental, epigenetic and genetic background effects, and that resemble phenotypic alterations present in Rbfox1-deficient mice and in patients with different psychiatric conditions. Our study, thus, highlights the evolutionary conservation of rbfox1 function in behaviour and paves the way to further investigate the mechanisms underlying rbfox1 pleiotropy on the onset of neurodevelopmental and psychiatric disorders