2,544 research outputs found

    Efficient Mechanisms for Access to Storage with Imperfect Competition in Gas Markets

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    Scarce storage capacity and distortions in access to gas storage are considered causes of market foreclosure in liberalized gas markets. We consider rules currently adopted in Europe for storage rationing and propose efficient rationing mechanism based on the value of storage, when other flexibility inputs are available. Firstly we analyse productive efficiency issues neglecting vertical restraints and strategic behaviour in the final market. Then we assume imperfect compettion in the downstream market for gas supplies, given the avaialbility of storage capacity upstream. We consider effciency issues in a two stage model comparing regulated storage tariffs – coupled with a centralizedrationing mechanism – with storage auctions. Finally we consider as an optimal mechanism the allocation of storage arising from welfare maximization by a social planner. We find that it is usually optimal to maximize the amount of storage capacity allocated to new entrants in the gas markets. Storage auctions deviates from the optimal mechanism, but still improve efficiency, with respect to current mechanisms, to the extent that they allocate storage according to its value. Furthermore storage allocation appear to be an extremeley powerful mechanism to improve competition and efficiency in gas markets.Liberalization, Auctions, Essential Facilities

    Bayesian outlier detection in Capital Asset Pricing Model

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    We propose a novel Bayesian optimisation procedure for outlier detection in the Capital Asset Pricing Model. We use a parametric product partition model to robustly estimate the systematic risk of an asset. We assume that the returns follow independent normal distributions and we impose a partition structure on the parameters of interest. The partition structure imposed on the parameters induces a corresponding clustering of the returns. We identify via an optimisation procedure the partition that best separates standard observations from the atypical ones. The methodology is illustrated with reference to a real data set, for which we also provide a microeconomic interpretation of the detected outliers

    Rigidity and compactness with constant mean curvature in warped product manifolds

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    We prove the rigidity of rectifiable boundaries with constant distributional mean curvature in the Brendle class of warped product manifolds (which includes important models in General Relativity, like the deSitter--Schwarzschild and Reissner--Nordstrom manifolds). As a corollary we characterize limits of rectifiable boundaries whose mean curvatures converge, as distributions, to a constant. The latter result is new, and requires the full strength of distributional CMC-rigidity, even when one considers smooth boundaries whose mean curvature oscillations vanish in arbitrarily strong CkC^k-norms.Comment: 42 pages; added references [LX19,SX22] and, correspondingly, subsection 1.5 has been slightly expande

    Endocrinologic Control of Men's Sexual Desire and Arousal/Erection

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    Several hormones and neurotransmitters orchestrate men's sexual response, including the appetitive (sexual desire) and consummative (arousal and penile erection) phases. AIM: To provide an overview and recommendations regarding endocrinologic control of sexual desire and arousal and erection and their disturbances. METHODS: Medical literature was reviewed by the subcommittee of the International Consultation of Sexual Medicine, followed by extensive internal discussion, and then public presentation and discussion with other experts. The role of pituitary (prolactin, oxytocin, growth hormone, and α-melanocyte-stimulating hormone), thyroid, and testicular hormones was scrutinized and discussed. MAIN OUTCOME MEASURES: Recommendations were based on grading of evidence-based medical literature, followed by interactive discussion. RESULTS: Testosterone has a primary role in controlling and synchronizing male sexual desire and arousal, acting at multiple levels. Accordingly, meta-analysis indicates that testosterone therapy for hypogonadal individuals can improve low desire and erectile dysfunction. Hyperprolactinemia is associated with low desire that can be successfully corrected by appropriate treatments. Oxytocin and α-melanocyte-stimulating hormone are important in eliciting sexual arousal; however, use of these peptides, or their analogs, for stimulating sexual arousal is still under investigation. Evaluation and treatment of other endocrine disorders are suggested only in selected cases. CONCLUSION: Endocrine abnormalities are common in patients with sexual dysfunction. Their identification and treatment is strongly encouraged in disturbances of sexual desire and arousal

    Le licenciement des salariés protégés : processus et enjeux

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    Documents d'Etudes Dares n° 108, février 2006, 122 p. Rapport mis en ligne sur le site du Ministère du travail http://www.travail.gouv.fr/etudes-recherche-statistiques/etudes-recherche/publications-dares/les-documents-etudes/2006-108-licenciement-salaires-proteges-processus-enjeux-3018.htmlLe licenciement (ou le transfert) d'un salarié protégé ne peut pas avoir lieu sans l'autorisation préalable de l'inspecteur du travail. Cette étude, issue d'une enquête qualitative, analyse, dans une perspective sociologique et juridique, les processus et les enjeux des licenciements de salariés dits « protégés »

    Small Sample Properties of Copula-GARCH Modelling: A Monte Carlo Study

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    Copula-GARCH models have been recently proposed in the financial literature as a statistical tool to build flexible multivariate distributions. Our extensive simulation studies investigate the small sample properties of these models and examine how misspecification in the marginals may affect the estimation of the dependence function represented by the copula. We show that the use of normal marginals when the true Data Generating Process is leptokurtic or asymmetric, produces negatively biased estimates of the normal copula correlations. A striking result is that these biases reach their highest value when correlations are strongly negative, and viceversa. This result remains unchanged with both positively skewed and negatively skewed data, while no biases are found if the variables are uncorrelated. Besides, the effect of marginals asymmetry on correlations is smaller than that of leptokurtosis. We finally analyse the performance of these models in terms of numerical convergence and positive definiteness of the estimated copula correlation matrix.Copulas, Copula-GARCH models, Maximum Likelihood, Simulation, Small Sample Properties.
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