488,345 research outputs found

    The Chávez Administration at 10 Years: The Economy and Social Indicators

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    This paper looks at some of the most important economic and social indicators during the 10 years of the Chávez administration in Venezuela, as well as the current economic expansion. It also looks at the current situation and challenges.Venezuela, Chavez

    Restructuring Venezuela\u27s Debt Using Pari Passu

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    Given the depth of Venezuela\u27s economic crisis, many fear that the government and the state-owned oil company Petroleos de Venezuela, S.A. ( PDVSA ) are on the brink of insolvency. In this paper, we introduce a restructuring plan that would allow Venezuela to restructure its external debt in an orderly manner. We propose that Venezuela restructure both PDVSA debt and its own external debt via Exchange Offers. To maximize the number of participating bondholders and receive sufficient debt relief, we suggest that Venezuela primarily utilize the pari passu clauses included in the vast majority of PDVSA and Venezuelan bonds, which are modified versions of a typical pari passu clause and can be read to allow the subordination of the bonds in accordance with Venezuelan law. To minimize the number of holdout creditors, Venezuela can introduce a law that subordinates non-exchanged debt to exchanged debt, making timely or full payment of holdout debt unlikely. This tactic would minimize the need to rely solely on alternative restructuring techniques, such as exit consents and Collective Action Clauses (CACs). We argue that while these techniques might alone prove insufficient to successfully restructure Venezuela\u27s debt, they could supplement the restructuring options we propose here. Because the parties contracted for debt subordination in the bond contracts, we predict that using a debt subordination technique would be more viable in Venezuela\u27s case than it has been in past sovereign debt restructurings. Ironically, the pari passu clause that doomed Argentina might be what saves Venezuela

    Imprisonment and internment: Comparing penal facilities North and South

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    Recent references to the ‘warehouse prison’ in the United States and the prisión-depósito in Latin America seem to indicate that penal confinement in the western hemisphere has converged on a similar model. However, this article suggests otherwise. It contrasts penal facilities in North America and Latin America in terms of six interrelated aspects: regimentation; surveillance; isolation; supervision; accountability; and formalization. Quantitatively, control in North American penal facilities is assiduous (unceasing, persistent and intrusive), while in Latin America it is perfunctory (sporadic, indifferent and cursory). Qualitatively, North American penal facilities produce imprisonment (which enacts penal intervention through confinement), while in Latin America they produce internment (which enacts penal intervention through release). Closely entwined with this qualitative difference are distinct practices of judicial involvement in sentencing and penal supervision. Those practices, and the cultural and political factors that underpin them, represent an interesting starting point for the explanation of the contrasting nature of imprisonment and internment

    Building portfolios of stocks in the S\~ao Paulo Stock Exchange using Random Matrix Theory

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    By using Random Matrix Theory, we build covariance matrices between stocks of the BM&F-Bovespa (Bolsa de Valores, Mercadorias e Futuros de S\~ao Paulo) which are cleaned of some of the noise due to the complex interactions between the many stocks and the finiteness of available data. We also use a regression model in order to remove the market effect due to the common movement of all stocks. These two procedures are then used to build stock portfolios based on Markowitz's theory, trying to obtain better predictions of future risk based on past data. This is done for years of both low and high volatility of the Brazilian stock market, from 2004 to 2010. The results show that the use of regression to subtract the market effect on returns greatly increases the accuracy of the prediction of risk, and that, although the cleaning of the correlation matrix often leads to portfolios that better predict risks, in periods of high volatility of the market this procedure may fail to do so.Comment: 23 page

    Energetics and stability of vacancies in carbon nanotubes

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    In this work we present ab initio calculations of the formation energies and stability of different types of multi-vacancies in carbon nanotubes. We demonstrate that, as in the case of graphene, the reconstruction of the defects has drastic effects on the energetics of the tubes. In particular, the formation of pentagons eliminates the dangling bonds thus lowering the formation energy. This competition leads to vacancies having an even number of carbon atoms removed to be more stable. Finally the appearance of magic numbers indicating more stable defects can be represented by a model for the formation energies that is based on the number of dangling bonds of the unreconstructed system, the pentagons and the relaxation of the final form of the defect formed after the relaxation

    Theoretical polarization dependence of the two-phonon double-resonant Raman spectra of graphene

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    The experimental Raman spectra of graphene exhibit a few intense two-phonon bands, which are enhanced through double-resonant scattering processes. Though there are many theoretical papers on this topic, none of them predicts the spectra within a single model. Here, we present results for the two-phonon Raman spectra of graphene calculated by means of the quantum perturbation theory. The electron and phonon dispersions, electronic lifetime, electron-photon and electron-phonon matrix elements, are all obtained within a density-functional-theory-based non-orthogonal tight-binding model. We study systematically the overtone and combination two-phonon Raman bands, and, in particular, the energy and polarization dependence of their Raman shift and intensity. We find that the ratio of the integrated intensities for parallel and cross polarized light for all two-phonon bands is between 0.33 and 0.42. Our results are in good agreement with the available experimental data

    Line Shape of the Raman 2D Peak of Graphene in Van Der Waals Heterostructures

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    The Raman 2D line of graphene is widely used for device characterization and during device fabrication as it contains valuable information on e.g. the direction and magnitude of mechanical strain and doping. Here we present systematic asymmetries in the 2D line shape of exfoliated graphene and graphene grown by chemical vapor deposition. Both graphene crystals are fully encapsulated in van der Waals heterostructures, where hexagonal boron nitride and tungsten diselenide are used as substrate materials. In both material stacks, we find very low doping values and extremely homogeneous strain distributions in the graphene crystal, which is a hall mark of the outstanding electronic quality of these samples. By fitting double Lorentzian functions to the spectra to account for the contributions of inner and outer processes to the 2D peak, we find that the splitting of the sub-peaks, 6.6±0.56.6 \pm 0.5 cm−1^{-1}(hBN-Gr-WSe2) and 8.9±1.08.9 \pm 1.0 cm−1^{-1} (hBN-Gr-hBN), is significantly lower than the values reported in previous studies on suspended graphene

    Stable unidimensional arrays of coherent strained islands

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    We investigate the equilibrium properties of arrays of coherent strained islands in heteroepitaxial thin films of bidimensional materials. The model we use takes into account only three essential ingredients : surface energies, elastic energies of the film and of the substrate and interaction energies between islands via the substrate. Using numerical simulations for a simple Lennard-Jones solid, we can assess the validity of the analytical expressions used to describe each of these contributions. A simple analytical expression is obtained for the total energy of the system. Minimizing this energy, we show that arrays of coherent islands can exist as stable configurations. Even in this simple approach, the quantitative results turn out to be very sensitive to some details of the surface energy.Comment: 24 pages, 7 figures. to be published in Surface Scienc
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