2,107 research outputs found

    Top dimensional group of the basic intersection cohomology for singular riemannian foliations

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    It is known that, for a regular riemannian foliation on a compact manifold, the properties of its basic cohomology (non-vanishing of the top-dimensional group and Poincar\'e Duality) and the tautness of the foliation are closely related. If we consider singular riemannian foliations, there is little or no relation between these properties. We present an example of a singular isometric flow for which the top dimensional basic cohomology group is non-trivial, but its basic cohomology does not satisfy the Poincar\'e Duality property. We recover this property in the basic intersection cohomology. It is not by chance that the top dimensional basic intersection cohomology groups of the example are isomorphic to either 0 or R\mathbb{R}. We prove in this Note that this holds for any singular riemannian foliation of a compact connected manifold. As a Corollary, we get that the tautness of the regular stratum of the singular riemannian foliation can be detected by the basic intersection cohomology.Comment: 11 pages. Accepted for publication in the Bulletin of the Polish Academy of Science

    Dielectric confinement of excitons in type-I and type-II semiconductor nanorods

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    We theoretically study the effect of the dielectric environment on the exciton ground state of CdSe and CdTe/CdSe/CdTe nanorods. We show that insulating environments enhance the exciton recombination rate and blueshift the emission peak by tens of meV. These effects are particularly pronounced for type-II nanorods. In these structures, the dielectric confinement may even modify the spatial distribution of electron and hole charges. A critical electric field is required to separate electrons from holes, whose value increases with the insulating strength of the surroundings.Comment: Journal of Physics: Condensed Matter (in press

    Emission spectrum of quasi-resonant laterally coupled quantum dots

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    We calculate the emission spectrum of neutral and charged excitons in a pair of laterally coupled InGaAs quantum dots with nearly degenerate energy levels. As the interdot distance decreases, a number of changes take place in the emission spectrum which can be used as indications of molecular coupling. These signatures ensue from the stronger tunnel-coupling of trions as compared to that of neutral excitons.Comment: 7 pages, 7 figure

    Response of potential cucurbit rootstocks against Meloidogyne spp

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    the Cucurbita hybrids, usually used as cucurbit rootstocks, are susceptible to Meloidogyne. Its cultivation increases the nematode population densities at similar levels than ungrafted cucumber or melon crops, and higher 'Ievels than watermelon.Postprint (published version

    Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields

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    Vertically coupled double quantum rings submitted to a perpendicular magnetic field BB are addressed within the local spin-density functional theory. We describe the structure of quantum ring molecules containing up to 40 electrons considering different inter-ring distances and intensities of the applied magnetic field. When the rings are quantum mechanically strongly coupled, only bonding states are occupied and the addition spectrum of the artificial molecules resembles that of a single quantum ring, with some small differences appearing as an effect of the magnetic field. Despite the latter has the tendency to flatten the spectra, in the strong coupling limit some clear peaks are still found even when B≠0B\neq 0 that can be interpretated from the single-particle energy levels analogously as at zero applied field, namely in terms of closed-shell and Hund's-rule configurations. Increasing the inter-ring distance, the occupation of the first antibonding orbitals washes out such structures and the addition spectra become flatter and irregular. In the weak coupling regime, numerous isospin oscillations are found as a function of BB.Comment: 27 pages, 11 figures. To be published in Phys. Rev.

    Using heat maps to identify areas prone to violence against women in the public sphere

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    The lack of accessible crime data, especially geolocations, in developing countries often acts as a barrier to identifying environmental or situational factors in high crime areas that might contribute to the facilitation of those crimes. This paper presents a methodology for conducting fieldwork for creating heat maps to identify areas prone to violence against women (VAW) in Corregidora, Mexico. Heat maps were produced based on household survey data. The results were used to select specific high concentration locations to conduct structured observations and inductive visual analysis at street level in order to identify if and what situational factors might influence the perpetration of VAW in those locations. Four broad features were identified in the urban built environment during the site visits linked to the facilitation of opportunities for the commission of VAW: (1) lacking infrastructure, (2) presence of physical obstacles, (3) poor visibility and (4) restricted pedestrian mobility. The paper demonstrates the utility of this method for aiding situational crime prevention strategies in areas where official spatial crime data is unavailable or lacking. This study presents a relatively low cost (although labour intensive) and independent method of aiding crime prevention strategies, which will hopefully be of practical value for organisations in areas with poor crime recording practices and limited access to expensive mapping technologies

    Volumetric Study of the Binary Mixtures Containing a Branched Hexane and an Isomeric Chlorobutane

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    This paper reports densities at atmospheric pressure and at three temperatures T = (283.15, 298.15, and 313.15) K of eight binary mixtures involving a branched hexane (3-methylpentane or 2,2-dimethylbutane) and each one of the isomeric chlorobutanes (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane). Excess volumes were calculated from experimental densities and correlated with the Redlich-Kister equation. Moreover, the excess volumes were analysed using the Prigogine-Flory-Patterson theory
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