5,537 research outputs found

    On the MHD load and the MHD metage

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    In analogy with the load and the metage in hydrodynamics, we define magnetohydrodynamic load and magnetohydrodynamic metage in the case of magnetofluids. They can be used to write the magnetic field in MHD in Clebsch's form. We show how these two concepts can be utilised to derive the magnetic analogue of the Ertel's theorem and also, how in the presence of non-trivial topology of the magnetic field in the magnetofluid one may associate the linking number of the magnetic field lines with the invariant MHD loads. The paper illustrates that the symmetry translation of the MHD metage in the corresponding label space generates the conservation of cross helicity.Comment: Some issues in the paper are yet to be addressed. Constructive critisicms are most welcom

    The post-Higgs MSSM scenario: Habemus MSSM?

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    We analyze the Minimal Supersymmetric extension of the Standard Model that we have after the discovery of the Higgs boson at the LHC, the hMSSM (habemus MSSM?), i.e. a model in which the lighter hh boson has a mass of approximately 125 GeV which, together with the non-observation of superparticles at the LHC, indicates that the SUSY-breaking scale MSM_S is rather high, MS>1M_S > 1 TeV. We first demonstrate that the value Mh≈125M_h \approx 125 GeV fixes the dominant radiative corrections that enter the MSSM Higgs boson masses, leading to a Higgs sector that can be described, to a good approximation, by only two free parameters. In a second step, we consider the direct supersymmetric radiative corrections and show that, to a good approximation, the phenomenology of the lighter Higgs state can be described by its mass and three couplings: those to massive gauge bosons and to top and bottom quarks. We perform a fit of these couplings using the latest LHC data on the production and decay rates of the light hh boson and combine it with the limits from the negative search of the heavier H,AH,A and H±H^\pm states, taking into account the current uncertainties.Comment: 1+12 pages, pdflatex, 7 figure

    SafeOCS Industry Safety Data: The Value Proposition for the Oil & Gas Industry

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    PresentationThis paper summarizes efforts by the U.S. Department of Transportation, Bureau of Transportation Statistics (BTS) to develop and manage an industry-wide safety data framework under an agreement with the U.S. Department of the Interior’s Bureau of Safety and Environmental Enforcement (BSEE). The Industry Safety Data (ISD) program provides a trusted, proactive means for the oil and gas industry to voluntarily and securely report safety information to identify early warnings of safety problems by uncovering hidden at-risk conditions not previously exposed from analysis of reportable accidents and incidents. Besides agency-reportable incidents, this program captures near miss and other significant safety event information that is maintained by individual companies as part of their internal safety programs. Phase I of this program was completed in June 2019, and plans are progressing to expand industry participation. Companies have long realized the benefits of collecting and analyzing data around safety and environmental incidents to identify risk, then develop systems and processes to prevent recurrence. These activities have been supported and supplemented by industry associations that collect and share event information and develop recommended practices to aid in performance improvement. In high-reliability industries, such as aviation and nuclear, it is common practice to report and share events among companies and regulators to identify hidden trends and create or update existing recommended practices or regulations. The challenge for the oil and gas industry operating within the U.S. Gulf of Mexico Outer Continental Shelf (OCS) was that, while industry associations and the regulator were collecting data on significant incidents, lesser safety events or observed unsafe conditions/behaviors are not required to be reported and therefore may go unnoticed as a trend until a major event occurs. This represented an opportunity for industry, BSEE, and BTS to collaborate on a means of gathering incident data that would allow for analysis and identification of trends or events of significance enabling appropriate interventions to prevent major incidents. The value proposition of this effort is development of a comprehensive safety data repository that facilitates the continual improvement in safety and environmental performance from the implementation of learnings shared from trends or lesser incidents and events occurring within industry

    Dynamic Provenance for SPARQL Update

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    While the Semantic Web currently can exhibit provenance information by using the W3C PROV standards, there is a "missing link" in connecting PROV to storing and querying for dynamic changes to RDF graphs using SPARQL. Solving this problem would be required for such clear use-cases as the creation of version control systems for RDF. While some provenance models and annotation techniques for storing and querying provenance data originally developed with databases or workflows in mind transfer readily to RDF and SPARQL, these techniques do not readily adapt to describing changes in dynamic RDF datasets over time. In this paper we explore how to adapt the dynamic copy-paste provenance model of Buneman et al. [2] to RDF datasets that change over time in response to SPARQL updates, how to represent the resulting provenance records themselves as RDF in a manner compatible with W3C PROV, and how the provenance information can be defined by reinterpreting SPARQL updates. The primary contribution of this paper is a semantic framework that enables the semantics of SPARQL Update to be used as the basis for a 'cut-and-paste' provenance model in a principled manner.Comment: Pre-publication version of ISWC 2014 pape

    On knotted streamtubes in incompressible hydrodynamical flow and a restricted conserved quantity

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    For certain families of fluid flow, a new conserved quantity -- stream-helicity -- has been established.Using examples of linked and knotted streamtubes, it has been shown that stream-helicity does, in certain cases, entertain itself with a very precise topological meaning viz, measure of the degree of knottedness or linkage of streamtubes.As a consequence, stream-helicity emerges as a robust topological invariant.Comment: This extended version is the basically a more clarified version of the previous submission physics/0611166v

    Treatment of patients with multiple myeloma progressing on frontline-therapy with lenalidomide

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    Over the last years, there has been great progress in the treatment of multiple myeloma with many new agents and combinations having been approved and being now routinely incorporated into treatment strategies. As a result, patients are experiencing benefits in terms of survival and better tolerance. However, the multitude of treatment options also presents a challenge to select the best options tailored to the specific patient situation. Lenalidomide is increasingly being used as part of frontline therapy in newly diagnosed multiple myeloma. This agent is typically administered until disease progression. It is currently unclear, how to best manage patients, who relapse while receiving lenalidomide as part of their frontline treatment. We conducted a review to summarize the available evidence in this setting. Our summary shows that there are very few data from current trials testing new combinations based on carfilzomib, pomalidomide, or daratumumab that address this specific patient population. Our review is aimed to summarize the available evidence to assist treatment decision making and to raise awareness of this lack of data to encourage further analyses and the incorporation of sequencing questions in future trial designs

    Structure and reactivity of small arteries in aging

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    Objective: Increased pulse pressure has been observed in aging subjects, but the impact on the structure and reactivity of small arteries has been scarcely evaluated. Methods: This study presents the modifications of vascular structure and function observed in female rats of 5, 18 and 32 months of age, and their relation to the prevailing hemodynamic status. Geometry and reactivity of perfused and pressurized basilar and mesenteric small arteries were analyzed in vitro using a video dimension analyzer. Results: Mean arterial pressure was similar in the three age groups, and only pulse pressure was increased in the oldest group. Media thickness and cross sectional area increased in basilar and mesenteric arteries of the oldest rats and these structural abnormalities were positively related to pulse pressure but not to mean, systolic or diastolic arterial pressure. Only minor changes of vascular reactivity were noted with age: there was a decreased contraction to angiotensin II in mesenteric arteries and an enhanced contraction to endothelin-1 in the basilar arteries. Conclusion: In conclusion, aging is associated with increased pulse pressure and hypertrophy of basilar and mesenteric resistance arteries, suggesting that this hemodynamic variable may influence cerebral and peripheral vascular structure in agin

    Optimal estimation for Large-Eddy Simulation of turbulence and application to the analysis of subgrid models

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    The tools of optimal estimation are applied to the study of subgrid models for Large-Eddy Simulation of turbulence. The concept of optimal estimator is introduced and its properties are analyzed in the context of applications to a priori tests of subgrid models. Attention is focused on the Cook and Riley model in the case of a scalar field in isotropic turbulence. Using DNS data, the relevance of the beta assumption is estimated by computing (i) generalized optimal estimators and (ii) the error brought by this assumption alone. Optimal estimators are computed for the subgrid variance using various sets of variables and various techniques (histograms and neural networks). It is shown that optimal estimators allow a thorough exploration of models. Neural networks are proved to be relevant and very efficient in this framework, and further usages are suggested

    An interactive medical image segmentation system based on the optimal management of regions of interest using topological medical knowledge

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    This paper presents an original interactive system for efficient medical image segmentation in computer aided diagnosis. The main originality concerns the method used to manage, according to an a priori topological-based structural model, regions of interest (ROIs) within which computations can be constrained. The goal is then to avoid the processing of irrelevant image points, therefore improving and accelerating segmentations. In the case of a hierarchical modeling procedure, our ROI management method enables, for delineating a given medical structure, to optimally determine image points of interest by taking previously segmented structures into account. We propose a mathematical formulation of the method as well as a possible implementation within an interactive system. We also detail an experience report focussing on the segmentation of several abdominal structures from a CT image. It illustrates the behavior and the potential of our method

    Magnetic hydrodynamics with asymmetric stress tensor

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    In this paper we study equations of magnetic hydrodynamics with a stress tensor. We interpret this system as the generalized Euler equation associated with an abelian extension of the Lie algebra of vector fields with a non-trivial 2-cocycle. We use the Lie algebra approach to prove the energy conservation law and the conservation of cross-helicity
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