5,692 research outputs found

    Can VMD improve the estimate of the muon g-2 ?

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    We show that a VMD based theoretical input allows for a significantly improved accuracy for the hadronic vacuum polarization of the photon which contributes to the theoretical estimate of the muon g-2. We also show that the only experimental piece of information in the τ\tau decay which cannot be accounted for is the accepted value for {\rm Br}(\tau \ra \pi \pi \nu_\tau), while the spectum lineshape is in agreement with expectations from e+e−e^+ e^- annihilations.Comment: 6 pages, 1 figure Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, Chin

    Social distancing strategies against disease spreading

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    The recurrent infectious diseases and their increasing impact on the society has promoted the study of strategies to slow down the epidemic spreading. In this review we outline the applications of percolation theory to describe strategies against epidemic spreading on complex networks. We give a general outlook of the relation between link percolation and the susceptible-infected-recovered model, and introduce the node void percolation process to describe the dilution of the network composed by healthy individual, i.ei.e, the network that sustain the functionality of a society. Then, we survey two strategies: the quenched disorder strategy where an heterogeneous distribution of contact intensities is induced in society, and the intermittent social distancing strategy where health individuals are persuaded to avoid contact with their neighbors for intermittent periods of time. Using percolation tools, we show that both strategies may halt the epidemic spreading. Finally, we discuss the role of the transmissibility, i.ei.e, the effective probability to transmit a disease, on the performance of the strategies to slow down the epidemic spreading.Comment: to be published in "Perspectives and Challenges in Statistical Physics and Complex Systems for the Next Decade", Word Scientific Pres

    On the zero set of G-equivariant maps

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    Let GG be a finite group acting on vector spaces VV and WW and consider a smooth GG-equivariant mapping f:V→Wf:V\to W. This paper addresses the question of the zero set near a zero xx of ff with isotropy subgroup GG. It is known from results of Bierstone and Field on GG-transversality theory that the zero set in a neighborhood of xx is a stratified set. The purpose of this paper is to partially determine the structure of the stratified set near xx using only information from the representations VV and WW. We define an index s(Σ)s(\Sigma) for isotropy subgroups Σ\Sigma of GG which is the difference of the dimension of the fixed point subspace of Σ\Sigma in VV and WW. Our main result states that if VV contains a subspace GG-isomorphic to WW, then for every maximal isotropy subgroup Σ\Sigma satisfying s(Σ)>s(G)s(\Sigma)>s(G), the zero set of ff near xx contains a smooth manifold of zeros with isotropy subgroup Σ\Sigma of dimension s(Σ)s(\Sigma). We also present a systematic method to study the zero sets for group representations VV and WW which do not satisfy the conditions of our main theorem. The paper contains many examples and raises several questions concerning the computation of zero sets of equivariant maps. These results have application to the bifurcation theory of GG-reversible equivariant vector fields

    The mtDNA 15497 G/A polymorphism in cytochrome b in severe obese subjects from Southern Italy.

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    Background and aim: A large number of mitochondrial DNA (mtDNA) mutations have been implicated in degenerative diseases and aging. The aim of this study was to evaluate whether the 15497 G/A mtDNA polymorphism (G251S) in the cytochrome b subunit of respiratory complex III, which has been associated with obesity-related variables and lipid metabolism in a Japanese population, is associated with severe obesity also in adult Caucasians from southern Italy. Methods and results: Unrelated severely obese patients (n Z 317; BMI > 40 kg/m2) and controls (n Z 217; BMI < 25 kg/m2) from Southern Italy were genotyped by allelic discrimination TaqMan assay for the 15497 G/A mtDNA polymorphism. In obese patients fasting serum total cholesterol, triglycerides, HDL-cholesterol and glucose were measured enzymatically and sitting blood pressure and heart rate were also collected. Mean levels of total cholesterol, triglycerides and glucose were below the upper reference limit for healthy subjects. Female obese subjects showed lower levels of blood pressure and heart rate and higher levels of HDL cholesterol than male obese patients (P < 0.001). All the control subjects and 315/317 severely obese patients were homozygous for the G allele (wild type), whereas only 2/317, were females homozygous for the A allele. Conclusions: The mtDNA 15497 G/A polymorphism in cytochrome b was present in 0.6% obese subjects, two females whose lipid parameters and BMI were similar to those of the overall group. Therefore, this mutation may appear to contribute in rare instances to severe obesity but does not explain the majority of cases in our population. A more extensive genetic haplogroup characterization is required to identify associations to obesity in Caucasians

    Slow epidemic extinction in populations with heterogeneous infection rates

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    We explore how heterogeneity in the intensity of interactions between people affects epidemic spreading. For that, we study the susceptible-infected-susceptible model on a complex network, where a link connecting individuals ii and jj is endowed with an infection rate ÎČij=λwij\beta_{ij} = \lambda w_{ij} proportional to the intensity of their contact wijw_{ij}, with a distribution P(wij)P(w_{ij}) taken from face-to-face experiments analyzed in Cattuto et  al.et\;al. (PLoS ONE 5, e11596, 2010). We find an extremely slow decay of the fraction of infected individuals, for a wide range of the control parameter λ\lambda. Using a distribution of width aa we identify two large regions in the a−λa-\lambda space with anomalous behaviors, which are reminiscent of rare region effects (Griffiths phases) found in models with quenched disorder. We show that the slow approach to extinction is caused by isolated small groups of highly interacting individuals, which keep epidemic alive for very long times. A mean-field approximation and a percolation approach capture with very good accuracy the absorbing-active transition line for weak (small aa) and strong (large aa) disorder, respectively

    Effect of degree correlations above the first shell on the percolation transition

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    The use of degree-degree correlations to model realistic networks which are characterized by their Pearson's coefficient, has become widespread. However the effect on how different correlation algorithms produce different results on processes on top of them, has not yet been discussed. In this letter, using different correlation algorithms to generate assortative networks, we show that for very assortative networks the behavior of the main observables in percolation processes depends on the algorithm used to build the network. The different alghoritms used here introduce different inner structures that are missed in Pearson's coefficient. We explain the different behaviors through a generalization of Pearson's coefficient that allows to study the correlations at chemical distances l from a root node. We apply our findings to real networks.Comment: In press EP

    Poor Outcome in a Mitochondrial Neurogastrointestinal Encephalomyopathy Patient with a Novel TYMP Mutation: The Need for Early Diagnosis.

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    Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a devastating autosomal recessive disorder due to mutations in TYMP, which cause loss of function of thymidine phosphorylase (TP), nucleoside accumulation in plasma and tissues and mitochondrial dysfunction. The clinical picture includes progressive gastrointestinal dysmotility, cachexia, ptosis and ophthalmoparesis, peripheral neuropathy and diffuse leukoencephalopathy, which usually lead to death in early adulthood. Therapeutic options are currently available in clinical practice (allogeneic hematopoietic stem cell transplantation and carrier erythrocyte entrapped TP therapy) and newer, promising therapies are expected in the near future. However, successful treatment is strictly related to early diagnosis. We report on an incomplete MNGIE phenotype in a young man harboring the novel heterozygote c.199 C>T (Q67X) mutation in exon 2, and the previously reported c.866 A>C (E289A) mutation in exon 7 in TYMP. The correct diagnosis was achieved many years after the onset of symptoms and unfortunately, the patient died soon after diagnosis because of multiorgan failure due to severe malnutrition and cachexia before any therapeutic option could be tried. To date, early diagnosis is essential to ensure that patients have the opportunity to be treated. MNGIE should be suspected in all patients who present with both gastrointestinal and nervous system involvement, even if the classical complete phenotype is lacking

    The good, the bad and the blend: The strategic role of the “middle leadership” in work-family/life dynamics during remote working

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    The ongoing epidemiological crisis has suddenly steered us towards a new futuristic work scenario in which most service sector employees work remotely, which could be a permanent reality for most service sector employees. This paper focuses on the strategic role that leadership could play in the radical change process that is taking place in work environments. Particular attention was paid to the role of ‘middle managers’ who perform an important function as a link between the strategic vision of top management and the workforce. In addition, special attention was paid to gender differences in work-life dynamics, which are particularly relevant in countries with traditional cultural identities. As this is a conceptual contribution, the most recent studies on this specific role of middle managers have been taken into account and embedded in the current scenario. Therefore, the main contribution in terms of originality was that the current review aimed to leverage such a legacy of knowledge and create a system of evidence-based practical implications for effectively supporting change in organizational culture through the identification of the most appropriate middle management leadership models for remote working that could prevent and/or limit any psychosocial risks (e.g., workaholism and technostress) and longer-term outcomes such as sustainable work-life interface