21,353 research outputs found

    Evaluation of the cutaneous microbiome in psoriasis

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    Psoriasis, a highly prevalent disease of humans of unknown cause, is a chronic inflammatory disorder primarily involving skin, with distinctive clinical characteristics. With the newly developed tools that facilitate microbiome research, it now is possible to assess whether the cutaneous microbiome plays a role in the pathogenesis of this disorder. Preliminary data from our studies suggest that the cutaneous microbiome in psoriasis is complex and possibly different from normal. To deal with this complexity, we propose to examine the cutaneous microbiome in relation to psoriasis with explorations at several taxonomic and informatic levels. Our overall objective is to examine how changes in the normal cutaneous microbiome contributes to the pathogenesis of psoriasis. Since causality is complex and often difficult to prove, our overall hypothesis is that there are alterations in the cutaneous microbiome in areas of skin affected by psoriasis in comparison with the range observed in clinically unaffected areas, or in healthy persons. We also hypothesize that the characteristics of the microbiome may affect clinical responses to the immunomodulatory agents used to treat psoriasis. An alternative hypothesis is that effective treatment of psoriasis with systemic immunomodulatory agents will not substantially affect the disordered microbial ecosystem. Such observations would provide evidence for the roles of the microbiota in this disorder. Since an important consideration in microbiome research is the optimal level (e.g. phylum, genus, species, strain, gene) at which to examine a scientific question, and we are not yet certain what are the optimal levels for psoriasis, this also will be examined. Our studies of psoriasis should allow development of both approaches and tools that will have general utility for microbiome research. To test our hypothesis, we propose the following specific aims: 1. To understand the cutaneous microbiome species composition overlaying psoriatic lesions; 2. To investigate differences in metagenome content for psoriatic lesions compared to normal skin; 3. To identify differences in the transcriptional profiles of the microbiome and the host between normal skin and psoriatic lesions using high-throughput sequencing; and 4. To estimate the effects of systemic immunomodulatory therapy for psoriasis on microbiome composition. In total, these studies should help us understand the role of the microbiome in psoriasis pathogenesis

    Multi-scale path planning for a planetary exploration vehicle with multiple locomotion modes

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    Planetary exploration vehicles (rovers) can encounter with a great variety of situations. Most of them are related to the terrain, which can cause the end of the mission if these vehicles are not able to traverse it. It was the case of Spirit rover, which got stuck in loose sand, making it impossible to continue advancing. A solution to this is to make rovers capable of modifying their locomotion to traverse terrains with particular terramechanic parameters.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂ­a Tech

    What Happened to Risk Management During the 2008-09 Financial Crisis?

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    When dealing with market risk under the Basel II Accord, variation pays in the form of lower capital requirements and higher profits. Typically, GARCH type models are chosen to forecast Value-at-Risk (VaR) using a single risk model. In this paper we illustrate two useful variations to the standard mechanism for choosing forecasts, namely: (i) combining different forecast models for each period, such as a daily model that forecasts the supremum or infinum value for the VaR; (ii) alternatively, select a single model to forecast VaR, and then modify the daily forecast, depending on the recent history of violations under the Basel II Accord. We illustrate these points using the Standard and Poorñ€ℱs 500 Composite Index. In many cases we find significant decreases in the capital requirements, while incurring a number of violations that stays within the Basel II Accord limits.risk management;violations;conservative risk strategy;aggressive risk strategy;value-at-risk forecast

    A decision rule to minimize daily capital charges in forecasting value-at-risk

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    Under the Basel II Accord, banks and other Authorized Deposit-taking Institutions (ADIs) have to communicate their daily risk estimates to the monetary authorities at the beginning of the trading day, using a variety of Value-at-Risk (VaR) models to measure risk. Sometimes the risk estimates communicated using these models are too high, thereby leading to large capital requirements and high capital costs. At other times, the risk estimates are too low, leading to excessive violations, so that realised losses are above the estimated risk. In this paper we propose a learning strategy that complements existing methods for calculating VaR and lowers daily capital requirements, while restricting the number of endogenous violations within the Basel II Accord penalty limits. We suggest a decision rule that responds to violations in a discrete and instantaneous manner, while adapting more slowly in periods of no violations. We apply the proposed strategy to Standard & Poorñ€ℱs 500 Index and show there can be substantial savings in daily capital charges, while restricting the number of violations to within the Basel II penalty limits.value-at-risk;daily capital charges;optimizing strategy;risk forecasts;endogenous violations;frequency of violations

    GFC-Robust Risk Management Strategies under the Basel Accord

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    A risk management strategy is proposed as being robust to the Global Financial Crisis (GFC) by selecting a Value-at-Risk (VaR) forecast that combines the forecasts of different VaR models. The robust forecast is based on the median of the point VaR forecasts of a set of conditional volatility models. This risk management strategy is GFC-robust in the sense that maintaining the same risk management strategies before, during and after a financial crisis would lead to comparatively low daily capital charges and violation penalties. The new method is illustrated by using the S&P500 index before, during and after the 2008-09 global financial crisis. We investigate the performance of a variety of single and combined VaR forecasts in terms of daily capital requirements and violation penalties under the Basel II Accord, as well as other criteria. The median VaR risk management strategy is GFC-robust as it provides stable results across different periods relative to other VaR forecasting models. The new strategy based on combined forecasts of single models is straightforward to incorporate into existing computer software packages that are used by banks and other financial institutions.Value-at-Risk (VaR);daily capital charges;optimizing strategy;robust forecasts;violation penalties;global financial crisis;Basel II Accord;aggressive risk management strategy;conservative risk management strategy

    Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association

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    We present the discovery of a companion near the deuterium burning mass limit located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec (projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very young Upper Scorpius association. Optical and near-infrared photometry and spectroscopy confirm the cool nature of both objects, with spectral types of M7 and M9.5, respectively, and that they are bona fide members of the association, showing low gravity and features of youth. Their masses, estimated from the comparison of their bolometric luminosities and theoretical models for the age range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The existence of this object around a brown dwarf at this wide orbit suggests that the companion is unlikely to have formed in a disk based on current planet formation models. Because this system is rather weakly bound, they did not probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table

    Binary frequency of planet-host stars at wide separations: A new brown dwarf companion to a planet-host star

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    The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. We cross-matched approximately 6200 square degree area of the Southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (~9000 au) from HIP70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4+/-3.8% and 2.7+/-2.7% (1 sigma confidence level), respectively, for projected physical separations larger than ~60-160 au assuming the range of distances of planet-host stars (24-75 pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e > 0.2) for periods less than 40 days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40 days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions.Comment: Accepted for publication in A&A, 13 pages, 5 figures, 3 tables, optical spectra will be available at CDS Strasbour

    The Seeds of Cosmic structure as a door to New Physics

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    There is something missing in our understanding of the origin of the seeds of Cosmic Structuture. The fact that the fluctuation spectrum can be extracted from the inflationary scenario through an analysis that involves quantum field theory in curved space-time, and that it coincides with the observational data has lead to a certain complacency in the community, which prevents the critical analysis of the obscure spots in the derivation. The point is that the inhomogeneity and anisotropy of our universe seem to emerge from an exactly homogeneous and isotropic initial state through processes that do not break those symmetries. This article gives a brief recount of the problems faced by the arguments based on established physics, which comprise the point of view held by a large majority of researchers in the field. The conclusion is that we need some new physics to be able to fully address the problem. The article then exposes one avenue that has been used to address the central issue and elaborates on the degree to which, the new approach makes different predictions from the standard analyses. The approach is inspired on Penrose's proposals that Quantum Gravity might lead to a real, dynamical collapse of the wave function, a process that we argue has the properties needed to extract us from the theoretical impasse described above.Comment: Prepared for the proceedings of the conference NEBXII " Recent Developments in Gravity", Napfio Grece June 2006. LateX, 15 page

    A signature of quantum gravity at the source of the seeds of cosmic structure?

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    This article reviews a recent work by a couple of colleagues and myself about the shortcomings of the standard explanations of the quantum origin of cosmic structure in the inflationary scenario, and a proposal to address them. The point it that in the usual accounts the inhomogeneity and anisotropy of our universe seem to emerge from an exactly homogeneous and isotropic initial state through processes that do not break those symmetries. We argued that some novel aspect of physics must be called upon to able to address the problem in a fully satisfactory way. The proposed approach is inspired on Penrose's ideas regarding an quantum gravity induced, real and dynamical collapse of the wave function.Comment: LateX, (jpconference macros), Prepared for the proceedings the Third International Workshop DICE 2006, " Quantum Mechanics between decoherence and Determinism
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