Coherent Vector Meson Photoproduction with Nuclear Breakup in Relativistic Heavy Ion Collisions

Relativistic heavy ions are copious sources of virtual photons. The large photon flux gives rise to a substantial photonuclear interaction probability at impact parameters where no hadronic interactions can occur. Multiple photonuclear interactions in a single collision are possible. In this letter, we use mutual Coulomb excitation of both nuclei as a tag for moderate impact parameter collisions. We calculate the cross section for coherent vector meson production accompanied by mutual excitation, and show that the median impact parameter is much smaller than for untagged production. The vector meson rapidity and transverse momentum distribution are very different from untagged exclusive vector meson production.Comment: 14 pages, including 4 figure

Performance indicators for roadway bridges

Publicado em "Maintenance, monitoring, safety, risk and resilience of bridges and bridge networks". ISBN 978-1-138-02851-7The performance indicators should, by its definition, allow capturing the life-cycle degradation processes affecting maintenance plans or the remaining lifetime. The qualitative or quantitative performance indicators are obtained through visual inspections, non-destructive tests or monitoring systems. After their quantification and the comparison with the respective performance goals and thresholds, a Quality Control plan should be accomplished. The COST TU1406 Action aims to uniform the European performance indicators, systemize the knowledge on the Quality Control plans for bridges, establish quality specifications and finally to develop the guideline and recommendations for the assessment of performance indicators. This contribution focuses on the current work of the first Working Group, WG1, where the first step is a collection of the key performance indicators at a European level. First those key performance indicators which capture mechanical and technical properties and its degradation behavior are assessed, while the further consideration reflect on the natural aging, quality of the material, service life design methods, and sustainable, environmental, economic and social based indicators.COST (European Cooperation in Science and Technology)Project “LeCIE – Life-cycle assessment for railway construction – strategies and methods

Interference in Exclusive Vector Meson Production in Heavy Ion Collisions

Photons emitted from the electromagnetic fields of relativistic heavy ions can fluctuate into quark anti-quark pairs and scatter from a target nucleus, emerging as vector mesons. These coherent interactions are identifiable by final states consisting of the two nuclei and a vector meson with a small transverse momentum. The emitters and targets can switch roles, and the two possibilities are indistinguishable, so interference may occur. Vector mesons are negative parity so the amplitudes have opposite signs. When the meson transverse wavelength is larger than the impact parameter, the interference is large and destructive. The short-lived vector mesons decay before amplitudes from the two sources can overlap, and so cannot interfere directly. However, the decay products are emitted in an entangled state, and the interference depends on observing the complete final state. The non-local wave function is an example of the Einstein-Podolsky-Rosen paradox.Comment: 13 pages with 3 figures; submitted to Physical Review Letter

Communication of a Modern Trading Company in the Function of the Drafting of the Final Decision on Shopping

The aim of this paper is communication of modern trading business based on two-way communication between traders and customers. It is very important for buyers to have the opportunity to express themselves freely about the products or services that a particular trading company provides, and the buyers give suggestions on what should be improved. The objective of a modern trading company is to understand each client individually and use it to facilitate the decision making of customers to prefer to work with a particular company rather than with competition. Nothing provides loyalty better than excellent service. Merchandising as a form of communication seeks to influence all of its elements and knowledge to draw attention of the person-consumer in order to adopt and memorize the content communicated to him. The company, the supermarket, the hypermarket is able to define the strategies and policies of the merchandising elements, which will help build the image of the sales, as well as the way of presenting the products, resulting in the main hypothesis of work: Timely communication with consumers influences to a large extent final consumption decision

Language Acquisition Intervention: A Prototype in Supplemental Children\u27s Education Through Media

The purpose of this project is to design a game which will help narrow the divide in child development between households and improve vocabulary skills. It has been found that there is a positive correlation between parent’s speaking with their children and the child’s educational development, particularly in language (Fernald, Marchman, & Weisleder, 2013). This is thought to be a result of the child being exposed to more words more often, which aids in their language development and continues to assist in their educational development over time. Further studies have also indicated that early life interventions’, such as educational tv shows’ and games such as Sesame Street, can benefit a child’s cognitive development, even in household’s with lacking parental involvement (Kearney & Levine, 2019), or in children living with a specific learning disability. This game will be made with similar goals in mind, using preexisting research on successful interventions to formulate a game that will assist children in their long-term language development by expanding their vocabulary. The game will also contain a program that can anonymously track the progress of participants longitudinally, which will monitor the helpfulness of the program as an educational tool over time. That same program can be used to update the program over time as well, providing more helpful word lists and a larger pool of words across a wider age range

Coulomb corrections to e+e−e^+ e^- production in ultra-relativistic nuclear collisions

The purpose of this paper is to explain the discrepancies existing in the literature relative to $e^+e^-$ pair production in peripheral heavy ion collisions at ultra-relativistic energies. A controversial issue is the possible cancellation of Coulomb corrections to the Born term in the pair production cross-section. Such a cancellation has been observed in a recent approach based on finding retarded solutions of the Dirac equation, but does not seem to hold in a perturbative approach. We show in this paper that the two approaches are in fact calculating different observables: the perturbative approach gives the exclusive cross-section of single pair production, while the other method gives the inclusive cross-section. We have also performed a thorough study of the electron propagator in the non-static background field of the two nuclei, the conclusion of which is that the retarded propagator is in the ultra-relativistic limit a much simpler object than the Feynman propagator, and can be calculated exactly.Comment: 31 pages LaTeX document, 10 postscript figures (expanded 3rd section, version to be published in Nucl. Phys. A

Particle emission following Coulomb excitation in ultrarelativistic heavy-ion collisions

We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments and pions, produced electromagnetically, are also calculated. These results provide important information for designing large-rapidity detectors and zero-degree calorimeters at RHIC and LHC. The electromagnetic dissociation of nuclei imposes some constrains on the investigation of exotic particle production in gamma-gamma fusion reactions.Comment: 26 LaTeX pages including 8 figures, uses epsf.st

Inclusive meson production in peripheral collisions of ultrarelativistic heavy ions

There exist several proposals to use Weizs\"{a}cker-Williams photons generated by ultrarelativistic heavy ions to produce exotic particles in $\gamma\gamma$ fusion reactions. To estimate the background conditions for such reactions we analyze various mechanisms of meson production in very peripheral collisions of ultrarelativistic heavy ions at RHIC and LHC energies. Besides $\gamma\gamma$ fusion they include also electromagnetic $\gamma A$ interactions and strong nucleon-nucleon interactions in grazing $AA$ collisions. All these processes are characterised by low multiplicities of produced particles. $\gamma A$ and $AA$ events are simulated by corresponding Monte Carlo codes, RELDIS and FRITIOF. In each of these processes a certain fraction of pions is produced close to the mid-rapidity region that gives a background for the $\gamma\gamma$ events. The possibility of selecting mesons produced in $\gamma\gamma$ fusion events via different $p_t$ cut procedures is demonstrated.Comment: 27 pages with 4 eps-figures included, uses axodraw.sty Tab.2 and 3 correcte

Lymphocyte subsets and the role of Th1/Th2 balance in stressed chronic pain patients

Background: The complex regional pain syndrome (CRPS) and fibromyalgia (FM) are chronic pain syndromes occurring in highly stressed individuals. Despite the known connection between the nervous system and immune cells, information on distribution of lymphocyte subsets under stress and pain conditions is limited. Methods: We performed a comparative study in 15 patients with CRPS type I, 22 patients with FM and 37 age- and sex-matched healthy controls and investigated the influence of pain and stress on lymphocyte number, subpopulations and the Th1/Th2 cytokine ratio in T lymphocytes. Results: Lymphocyte numbers did not differ between groups. Quantitative analyses of lymphocyte subpopulations showed a significant reduction of cytotoxic CD8+ lymphocytes in both CRPS (p < 0.01) and FM (p < 0.05) patients as compared with healthy controls. Additionally, CRPS patients were characterized by a lower percentage of IL-2-producing T cell subpopulations reflecting a diminished Th1 response in contrast to no changes in the Th2 cytokine profile. Conclusions: Future studies are warranted to answer whether such immunological changes play a pathogenetic role in CRPS and FM or merely reflect the consequences of a pain-induced neurohumoral stress response, and whether they contribute to immunosuppression in stressed chronic pain patients. Copyright (c) 2008 S. Karger AG, Basel

Developmental axon pruning mediated by BDNF-p75NTR–dependent axon degeneration

The mechanisms that regulate the pruning of mammalian axons are just now being elucidated. Here, we describe a mechanism by which, during developmental sympathetic axon competition, winning axons secrete brain-derived neurotrophic factor (BDNF) in an activity-dependent fashion, which binds to the p75 neurotrophin receptor (p75NTR) on losing axons to cause their degeneration and, ultimately, axon pruning. Specifically, we found that pruning of rat and mouse sympathetic axons that project to the eye requires both activity-dependent BDNF and p75NTR. p75NTR and BDNF are also essential for activity-dependent axon pruning in culture, where they mediate pruning by directly causing axon degeneration. p75NTR, which is enriched in losing axons, causes axonal degeneration by suppressing TrkA-mediated signaling that is essential for axonal maintenance. These data provide a mechanism that explains how active axons can eliminate less-active, competing axons during developmental pruning by directly promoting p75NTR-mediated axonal degeneration