427 research outputs found

    Convergence to stable laws for multidimensional stochastic recursions: the case of regular matrices

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    Given a sequence (Mn,Qn)n≄1(M_{n},Q_{n})_{n\ge 1} of i.i.d.\ random variables with generic copy (M,Q)∈GL(d,R)×Rd(M,Q) \in GL(d, \R) \times \R^d, we consider the random difference equation (RDE) Rn=MnRn−1+Qn, R_{n}=M_{n}R_{n-1}+Q_{n}, n≄1n\ge 1, and assume the existence of Îș>0\kappa >0 such that \lim_{n \to \infty}(\E{\norm{M_1 ... M_n}^\kappa})^{\frac{1}{n}} = 1 . We prove, under suitable assumptions, that the sequence Sn=R1+...+RnS_n = R_1 + ... + R_n, appropriately normalized, converges in law to a multidimensional stable distribution with index Îș\kappa. As a by-product, we show that the unique stationary solution RR of the RDE is regularly varying with index Îș\kappa, and give a precise description of its tail measure. This extends the prior work http://arxiv.org/abs/1009.1728v3 .Comment: 15 page

    Validation and reconstruction of flow meter data in the Barcelona water distribution network

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    12 pĂĄginas, 16 figuras, 1 tabla.-- El PDF es la versiĂłn pre-print.-- et al.This paper presents a signal analysis methodology to validate (detect) and reconstruct the missing and false data of a large set of flow meters in the telecontrol system of a water distribution network. The proposed methodology is based on two time-scale forecasting models: a daily model based on a ARIMA time series, while the 10-min model is based on distributing the daily flow using a 10-min demand pattern. The demand patterns have been determined using two methods: correlation analysis and an unsupervised fuzzy logic classification, named LAMDA algorithm. Finally, the proposed methodology has been applied to the Barcelona water distribution network, providing very good results.This work is part of a applied research project granted by ADASA and AGBAR companies. The authors also wish to thank the support received by the Research Commission of the Generalitat of Catalunya (Group SAC Ref. 2009 SGR 1491) and by CICYT (Ref. HYFA DPI2008-01996 and WATMAN DPI2009-13744) of Spanish Ministry of Education.Peer reviewe

    Financial Transaction Tax: Small is Beautiful

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    The case for taxing financial transactions merely to raise more revenues from the financial sector is not particularly strong. Better alternatives to tax the financial sector are likely to be available. However, a tax on financial transactions could be justified in order to limit socially undesirable transactions when more direct means of doing so are unavailable for political or practical reasons. Some financial transactions are indeed likely to do more harm than good, especially when they contribute to the systemic risk of the financial system. However, such a financial transaction tax should be very small, much smaller than the negative externalities in question, because it is a blunt instrument that also drives out socially useful transactions. There is a case for taxing over-the-counter derivative transactions at a somewhat higher rate than exchange-based derivative transactions. More targeted remedies to drive out socially undesirable transactions should be sought in parallel, which would allow, after their implementation, to reduce or even phase out financialtransaction taxes

    Validation and reconstruction of flow meter data in the Barcelona water distribution network

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    This paper presents a signal analysis methodology to validate (detect) and reconstruct the missing and false data of a large set of flow meters in the telecontrol system of a water distribution network. The proposed methodology is based on two time-scale forecasting models: a daily model based on a ARIMA time series, while the 10-min model is based on distributing the daily flow using a 10-min demand pattern. The demand patterns have been determined using two methods: correlation analysis and an unsupervised fuzzy logic classification, named LAMDA algorithm. Finally, the proposed methodology has been applied to the Barcelona water distribution network, providing very good results.Peer ReviewedPostprint (author’s final draft

    Mutations in alpha-B-crystallin cause autosomal dominant axonal Charcot–Marie–Tooth disease with congenital cataracts

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    Background and purpose: Mutations in the alpha-B-crystallin (CRYAB) gene have initially been associated with myofibrillar myopathy, dilated cardiomyopathy and cataracts. For the first time, peripheral neuropathy is reported here as a novel phenotype associated with CRYAB. // Methods: Whole-exome sequencing was performed in two unrelated families with genetically unsolved axonal Charcot–Marie–Tooth disease (CMT2), assessing clinical, neurophysiological and radiological features. // Results: The pathogenic CRYAB variant c.358A>G;p.Arg120Gly was segregated in all affected patients from two unrelated families. The disease presented as late onset CMT2 (onset over 40 years) with distal sensory and motor impairment and congenital cataracts. Muscle involvement was probably associated in cases showing mild axial and diaphragmatic weakness. In all cases, nerve conduction studies demonstrated the presence of an axonal sensorimotor neuropathy along with chronic neurogenic changes on needle examination. // Discussion: In cases with late onset autosomal dominant CMT2 and congenital cataracts, it is recommended that CRYAB is considered for genetic testing. The identification of CRYAB mutations causing CMT2 further supports a continuous spectrum of expressivity, from myopathic to neuropathic and mixed forms, of a growing number of genes involved in protein degradation and chaperone-assisted autophagy

    The materiality of the intangible: Literary metaphor in multimodal texts

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    Based on a larger practice-based research project in digital writing, this article examines how the materiality of digital media contributes to a layered metaphor that delivers meaning, reflects on the cognitive processes (the writer’s and the reader’s) of navigation and generates a dynamic narrative structure through multimodality, unnatural narration and user interaction. Many writers and artists engage with their chosen medium through an instinctive understanding of the materials at hand, gained through experience; the explicit study of a medium’s materiality is not always required for artistic success, however, that may be judged. This article offers insights into the creative process of creating digital, multimodal fiction, based on a practice-based research project designed to explore the effects of digital media on author and text, and argues that digital media have a significant effect on the outcome of the artefact itself. Awareness of these effects, their variations according to hardware and software, and the affordances of these various materials offer the digital writer greater insight and capability to craft his/her texts for the desired metaphorical meaning

    Absence of Dystrophin Related Protein-2 disrupts Cajal bands in a patient with Charcot-Marie-Tooth disease

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    Using exome sequencing in an individual with Charcot-Marie-Tooth disease (CMT) we have identified a mutation in the X-linked dystrophin-related protein 2 (DRP2) gene. A 60-year-old gentleman presented to our clinic and underwent clinical, electrophysiological and skin biopsy studies. The patient had clinical features of a length dependent sensorimotor neuropathy with an age of onset of 50 years. Neurophysiology revealed prolonged latencies with intermediate conduction velocities but no conduction block or temporal dispersion. A panel of 23 disease causing genes was sequenced and ultimately was uninformative. Whole exome sequencing revealed a stop mutation in DRP2, c.805C>T (Q269*). DRP2 interacts with periaxin and dystroglycan to form the periaxin-DRP2-dystroglycan complex which plays a role in the maintenance of the well-characterized Cajal bands of myelinating Schwann cells. Skin biopsies from our patient revealed a lack of DRP2 in myelinated dermal nerves by immunofluorescence. Furthermore electron microscopy failed to identify Cajal bands in the patient's dermal myelinated axons in keeping with ultrastructural pathology seen in the Drp2 knockout mouse. Both the electrophysiologic and dermal nerve twig pathology support the interpretation that this patient's DRP2 mutation causes characteristic morphological abnormalities recapitulating the Drp2 knockout model and potentially represents a novel genetic cause of CMT

    Patient-reported symptom burden of Charcot-Marie-Tooth Disease Type 1A: findings from an observational digital lifestyle study

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    Objectives: This study aims to explore the impact of Charcot-Marie-Tooth disease type 1A (CMT1A) and its treatment on patients in European (France, Germany, Italy, Spain, and the United Kingdom) and US real-world practice. Methods: Adults with CMT1A (n = 937) were recruited to an ongoing observational study exploring the impact of CMT. Data were collected via CMT&Me, an app through which participants completed patient-reported outcome measures. Results: Symptoms ranked with highest importance were weakness in the extremities, difficulty in walking, and fatigue. Almost half of participants experienced a worsening of symptom severity since diagnosis. Anxiety and depression were each reported by over one-third of participants. Use of rehabilitative interventions, medications, and orthotics/walking aids was high. Conclusions: Patient-reported burden of CMT1A is high, influenced by difficulties in using limbs, fatigue, pain, and impaired quality of life. Burden severity appears to differ across the population, possibly driven by differences in rehabilitative and prescription-based interventions, and country-specific health care variability
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