3,542 research outputs found

    Recent CMS Results on Forward and Small-x QCD Physics

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    Recent CMS results on Forward and Small-x QCD Physics are presented. Those include the measurement of the Underlying Event activity and the study of jet production at large rapidity separation.Comment: 4 pages, 2 figures, proceedings of Physics at LHC 2012, 4-9 June 2012, UBC, Vancouver, B

    Forward Physics Capabilities of CMS with the CASTOR and ZDC detectors

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    The two calorimeters CASTOR and ZDCs enhance the hermeticity of the CMS detector at the LHC by extending the rapidity coverage in the forward region. After having described these detectors, their forward physics capabilities are presented. These latters include the study of parton shower, multiple parton interactions, diffraction and ultra high energy cosmic rays models. The processes to be measured to constrain these topics are multi-jet events with a forward jet, central-forward activity correlation, rapidity gaps and forward neutron production.Comment: 5 pages - 6 figures - DIS 2009 proceeding

    Log-Sobolev inequality for the φ24\varphi^4_2 and φ34\varphi^4_3 measures

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    The continuum φ24\varphi^4_2 and φ34\varphi^4_3 measures are shown to satisfy a log-Sobolev inequality uniformly in the lattice regularisation under the optimal assumption that their susceptibility is bounded. In particular, this applies to all coupling constants in any finite volume, and uniformly in the volume in the entire high temperature phases of the φ24\varphi^4_2 and φ34\varphi^4_3 models. The proof uses a general criterion for the log-Sobolev inequality in terms of the Polchinski (renormalisation group) equation, a recently proved remarkable correlation inequality for Ising models with general external fields, the Perron--Frobenius theorem, and bounds on the susceptibilities of the φ24\varphi^4_2 and φ34\varphi^4_3 measures obtained using skeleton inequalities.Comment: Minor revisions, accepte

    Opposing Mechanisms Support the Voluntary Forgetting of Unwanted Memories

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    SummaryReminders of the past can trigger the recollection of events that one would rather forget. Here, using fMRI, we demonstrate two distinct neural mechanisms that foster the intentional forgetting of such unwanted memories. Both mechanisms impair long-term retention by limiting momentary awareness of the memories, yet they operate in opposite ways. One mechanism, direct suppression, disengages episodic retrieval through the systemic inhibition of hippocampal processing that originates from right dorsolateral prefrontal cortex (PFC). The opposite mechanism, thought substitution, instead engages retrieval processes to occupy the limited focus of awareness with a substitute memory. It is mediated by interactions between left caudal and midventrolateral PFC that support the selective retrieval of substitutes in the context of prepotent, unwanted memories. These findings suggest that we are not at the mercy of passive forgetting; rather, our memories can be shaped by two opposite mechanisms of mnemonic control

    Ductile to brittle transition of an A508 steel characterized by Charpy impact test, part I., experimental results

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    International audienceThis study is devoted to the ductile–brittle transition behavior of a French A508 Cl3 (16MND5) steel. Due to its importance for the safety assessment of PWR vessels, a full characterization of this steel with Charpy V-notch test in this range of temperature was undertaken. The aim of this study is to provide a wide experimental database and microstructural observations to supply, calibrate and validate models used in a local approach methodology. Mechanical and fracture properties of the steel have been investigated over a wide range of temperatures and strain-rates. Effects of impact velocity on ductile–brittle transition curve, on ductile tearing and on notch temperature rise are presented and discussed. A detailed study of ductile crack initiation and growth in Charpy specimens is also carried out. From fractographic investigations of the microvoids nucleation around carbide second phase particles, a plastic strain threshold for nucleation is determined for this material. A508 Cl3 steels undergo a transition in fracture toughness properties with temperature, due to a change in fracture mode from microvoids coalescence to cleavage fracture. A systematic investigation on the nature and the position of cleavage triggering sites and on any change in the ductile to brittle transition (DBT) range has been carried out. This leads to the conclusion that manganese sulfide inclusions do not play an increasing role with increasing test temperature as recently mentioned in other studies on A508 Cl3 steel with a higher sulfur content. In a companion paper [Tanguy et al., Engng. Fract. Mech., in press], the numerical simulation of the Charpy test in the ductile–brittle transition range using fully coupled local approach to fracture is presented

    Ductile to brittle transition of an A508 steel characterized by Charpy impact test, part II., Modeling of the Charpy transition curve

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    International audienceA finite element simulation of the Charpy test is developed in order to model the ductile to brittle transition curve of a pressure vessel steel. The material (an A508 steel) and the experimental results are presented in a companion paper (Part I [Engng. Fract. Mech.]). The proposed simulation includes a detailed description of the material viscoplastic behavior over a wide temperature range. Ductile behavior is modeled using modified Rousselier model. The Beremin model is used to describe brittle fracture. The Charpy test is simulated using a full 3D mesh and accounting for adiabatic heating and contact between the specimen, the striker and the anvil. The developed model is well suited to represent ductile tearing. Using brittle failure parameters identified below −150 °C, it is possible to represent the transition curve up to −80 °C assuming that the Beremin stress parameter σu is independent of temperature. Above this temperature, a temperature dependent Beremin stress parameter, σu, must be used to correctly simulate the transition curve. Quasi-static and dynamic tests can then be consistently modeled
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