4,143 research outputs found

    Correlation and regression analysis between residual gradation and uncorrected visual acuity one year after refractive surgery with LASIK, FS-LASIK, PRK, PRK Xtra techniques and the implantation of ICL® posterior chamber phakic lens in myopic correction

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    Purpose To analyze the influence of the final spherical equivalent (SE) in LogMAR uncorrected distance visual acuity (UDVA) one year after refractive surgery. We analysed refractive results, their predictability and efficacy, and the safety results of the different methods as secondary outcomes. Setting Refractive Surgery Unit of the Institut Català de Retina (ICR) in Barcelona, Spain. Design Retrospective, analytical observational study. Methods Retrospective and observational study of 654 eyes of 327 patients who underwent refractive surgery to treat their myopia or myopic astigmatism using LASIK, FS-LASIK, PRK, PRK Xtra or ICL-type lens implantation surgery were included. Results The correlation between the SE in absolute value was statistically significant in all techniques utilized, reaching higher values in the FS-LASIK and LASIK techniques, 0.774 and0.706 respectively, and lesser values in PRK (0.480) and PRK Xtra (0.482). A significant adjustment via a univariate linear regression model could be implemented in all techniques, albeit the R2 coefficient of determination values were higher than those for the FS-LASIK (0.599) and LASIK (0.494) techniques. Conclusions There is a positive correlation between post-surgical SE value and post-operative LogMAR UDVA. These regression models can be adjusted to predict the final UDVA according to the final SE. The techniques that are most influenced by the final SE in terms of their visual results are FS-LASIK and LASIK

    Bohr-Sommerfeld quantization and meson spectroscopy

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    We use the Bohr-Sommerfeld quantization approach in the context of constituent quark models. This method provides, for the Cornell potential, analytical formulae for the energy spectra which closely approximate numerical exact calculations performed with the Schrodinger or the spinless Salpeter equations. The Bohr-Sommerfeld quantization procedure can also be used to calculate other observables such as r.m.s. radius or wave function at the origin. Asymptotic dependence of these observables on quantum numbers are also obtained in the case of potentials which behave asymptotically as a power-law. We discuss the constraints imposed by these formulae on the dynamics of the quark-antiquark interaction.Comment: 13 page

    Final implementation of SEACON: new scope and new open system platform.

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    SEACON is a hybrid (heuristic & algorithmic) expert system for contingency analysis and preventive or corrective control of the transmission network, that has been recently redesigned to implement new end user requirements and to increase its performance. This paper describes the main results and the operational experience from the development and implementation of a new system based on the initial idea. Software reuse strategies became capital in this project. The new design includes advanced functionalities demanded by the practical use of the former system. Because of the high performance of the new system (up to fifteen times faster than the original) and its friendly user interface, SEACON has become a very valuable tool among dispatchers. SEACON is in operation in the Red Electrica’s National Control Centre and in Iberdrola’s Central and Regional Control Centres, dealing with transmission and subtransmission networks (ranging between 4OOkV and 66kV), attached to the on-line state estimators and screening over 2000 possible contingencies. Results are presented using natural language, and a client-server scheme provided for corporate access. KeywOrdr - Expert system, security assessment, contingency analysis, power systems, real-time system

    Analysis of the genome content of Lactococcus garvieae by genomic interspecies microarray hybridization

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    BACKGROUND: Lactococcus garvieae is a bacterial pathogen that affects different animal species in addition to humans. Despite the widespread distribution and emerging clinical significance of L. garvieae in both veterinary and human medicine, there is almost a complete lack of knowledge about the genetic content of this microorganism. In the present study, the genomic content of L. garvieae CECT 4531 was analysed using bioinformatics tools and microarray-based comparative genomic hybridization (CGH) experiments. Lactococcus lactis subsp. lactis IL1403 and Streptococcus pneumoniae TIGR4 were used as reference microorganisms. RESULTS: The combination and integration of in silico analyses and in vitro CGH experiments, performed in comparison with the reference microorganisms, allowed establishment of an inter-species hybridization framework with a detection threshold based on a sequence similarity of >or= 70%. With this threshold value, 267 genes were identified as having an analogue in L. garvieae, most of which (n = 258) have been documented for the first time in this pathogen. Most of the genes are related to ribosomal, sugar metabolism or energy conversion systems. Some of the identified genes, such as als and mycA, could be involved in the pathogenesis of L. garvieae infections. CONCLUSIONS: In this study, we identified 267 genes that were potentially present in L. garvieae CECT 4531. Some of the identified genes could be involved in the pathogenesis of L. garvieae infections. These results provide the first insight into the genome content of L. garvieae.This work was supported partially by projects AGL2005-04775 and AGL2009-12447 of the Ministerio Español de Ciencia e Innovación. M. Aguado-Urda was a recipient of a grant from Centro de Vigilancia Sanitaria Veterinaria (VISAVET), and a PhD grant from the Universidad Complutense de Madrid. The work of Dr. López-Campos and Dr. Martín-Sanchez was partially funded by the COMBIOMED Network and ONTOMINEBASE reseach project (Ministerio Español de Ciencia e Innovación). The authors thank M.P. Gaya for providing the Lactococcus lactis subsp lactis IL1403 strain.S

    Fibre Inflation: Observable Gravity Waves from IIB String Compactifications

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    We introduce a simple string model of inflation, in which the inflaton field can take trans-Planckian values while driving a period of slow-roll inflation. This leads naturally to a realisation of large field inflation, inasmuch as the inflationary epoch is well described by the single-field scalar potential V=V0(34eφ^/3)V = V_0 (3-4 e^{-\hat\varphi/\sqrt{3}}). Remarkably, for a broad class of vacua all adjustable parameters enter only through the overall coefficient V0V_0, and in particular do not enter into the slow-roll parameters. Consequently these are determined purely by the number of \e-foldings, NeN_e, and so are not independent: ε32η2\varepsilon \simeq \frac32 \eta^2. This implies similar relations among observables like the primordial scalar-to-tensor amplitude, rr, and the scalar spectral tilt, nsn_s: r6(ns1)2r \simeq 6(n_s - 1)^2. NeN_e is itself more model-dependent since it depends partly on the post-inflationary reheat history. In a simple reheating scenario a reheating temperature of Trh109T_{rh}\simeq 10^{9} GeV gives Ne58N_e\simeq 58, corresponding to ns0.970n_s\simeq 0.970 and r0.005r\simeq 0.005, within reach of future observations. The model is an example of a class that arises naturally in the context of type IIB string compactifications with large-volume moduli stabilisation, and takes advantage of the generic existence there of Kahler moduli whose dominant appearance in the scalar potential arises from string loop corrections to the Kahler potential. The inflaton field is a combination of Kahler moduli of a K3-fibered Calabi-Yau manifold. We believe there are likely to be a great number of models in this class -- `high-fibre models' -- in which the inflaton starts off far enough up the fibre to produce observably large primordial gravity waves.Comment: Extended calculations beyond the leading approximations, including numerical integrations of multi-field evolution; Display an example with r=0.01r = 0.01; Simplify the discussion of large fields; Corrected minor errors and typos; Added references; 41 pages LaTeX, 25 figure

    When do colliding bubbles produce an expanding universe?

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    It is intriguing to consider the possibility that the Big Bang of the standard (3+1) dimensional cosmology originated from the collision of two branes within a higher dimensional spacetime, leading to the production of a large amount of entropy. In this paper we study, subject to certain well-defined assumptions, under what conditions such a collision leads to an expanding universe. We assume the absence of novel physics, so that ordinary (4+1) -dimensional Einstein gravity remains a valid approximation. It is necessary that the fifth dimension not become degenerate at the moment of collision. First the case of a symmetric collision of infinitely thin branes having a hyperbolic or flat spatial geometry is considered. We find that a symmetric collision results in a collapsing universe on the final brane unless the pre-existing expansion rate in the bulk just prior to the collision is sufficiently large in comparison to the momentum transfer in the fifth dimension. Such prior expansion may either result from negative spatial curvature or from a positive five-dimensional cosmological constant. The relevance of these findings to the Colliding Bubble Braneworld Universe scenario is discussed. Finally, results from a numerical study of colliding thick-wall branes is presented, which confirm the results of the thin-wall approximation.Comment: 24 pages, 13 figures. Minor changes and references include

    Shift Symmetry and Inflation in Supergravity

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    We consider models of inflation in supergravity with a shift symmetry. We focus on models with one moduli and one inflaton field. The presence of this symmetry guarantees the existence of a flat direction for the inflaton field. Mildly breaking the shift symmetry using a superpotential which depends not only on the moduli but also on the inflaton field allows one to lift the inflaton flat direction. Along the inflaton direction, the eta-problem is alleviated. Combining the KKLT mechanism for moduli stabilization and a shift symmetry breaking superpotential of the chaotic inflation type, we find models reminiscent of ``mutated hybrid inflation'' where the inflationary trajectory is curved in the moduli--inflaton plane. We analyze the phenomenology of these models and stress their differences with both chaotic and hybrid inflation.Comment: 29 pages, 13 figure

    Neutrino Interactions at Ultrahigh Energies

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    We report new calculations of the cross sections for deeply inelastic neutrino-nucleon scattering at neutrino energies between 10^{9}\ev and 10^{21}\ev. We compare with results in the literature and assess the reliability of our predictions. For completeness, we briefly review the cross sections for neutrino interactions with atomic electrons, emphasizing the role of the WW-boson resonance in νˉee\bar{\nu}_{e}e interactions for neutrino energies in the neighborhood of 6.3\pev. Adopting model predictions for extraterrestrial neutrino fluxes from active galactic nuclei, gamma-ray bursters, and the collapse of topological defects, we estimate event rates in large-volume water \v{C}erenkov detectors and large-area ground arrays.Comment: 32 pages, 11 figures, uses RevTeX and boxedep
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