Chiral dynamics in the presence of bound states: kaon-nucleon interactions revisited

We study the S-wave kaon-nucleon interactions for strangeness S=-1 in a novel relativistic chiral unitary approach based on coupled channels. Dispersion relations are used to perform the necessary resummation of the lowest order relativistic chiral Lagrangian. A good description of the data in the K^- p, \pi \Sigma and \pi \Lambda channels is obtained. We show how this method can be systematically extended to higher orders, emphasizing its applicability to any scenario of strong self-interactions where the perturbative series diverges even at low energies. Discussions about the differences to existing approaches employing pseudo-potentials in a regulated Lippmann-Schwinger equation are included. Finally, we describe the resonance content of our meson-baryon amplitudes and discuss its nature.Comment: 12 pp, LaTeX2e, FZJ-IKP(TH)-2000-2

A Comment on the Topological Phase for Anti-Particles in a Lorentz-violating environment

Recently, a scheme to analyse topological phases in Quantum Mechanics by means of the non-relativistic limit of fermions non-minimally coupled to a Lorentz-breaking background has been proposed. In this letter, we show that the fixed background, responsible for the Lorentz-symmetry violation, may induce opposite Aharonov-Casher phases for a particle and its corresponding antiparticle. We then argue that such a difference may be used to investigate the asymmetry for particle/anti-particle as well as to propose bounds on the associated Lorentz-symmetry violating parameters.Comment: 4 pages - A published versio

New interpretation of arterial stiffening due to cigarette smoking using a structurally motivated constitutive model

Cigarette smoking is the leading self-inflicted risk factor for cardiovascular diseases; it causes arterial stiffening with serious sequelea including atherosclerosis and abdominal aortic aneurysms. This work presents a new interpretation of arterial stiffening caused by smoking based on data published for rat pulmonary arteries. A structurally motivated “four fiber family” constitutive relation was used to fit the available biaxial data and associated best-fit values of material parameters were estimated using multivariate nonlinear regression. Results suggested that arterial stiffening caused by smoking was reflected by consistent increase in an elastin-associated parameter and moreover by marked increase in the collagen-associated parameters. That is, we suggest that arterial stiffening due to cigarette smoking appears to be isotropic, which may allow simpler phenomenological models to capture these effects using a single stiffening parameter similar to the approach in isotropic continuum damage mechanics. There is a pressing need, however, for more detailed histological information coupled with more complete biaxial mechanical data for a broader range of systemic arteries

N=1 Supersymetric Quantum Mechanics in a Scenario with Lorentz-Symmetry Violation

We show in this paper that the dynamics of a non-relativistic particle with spin, coupled to an external electromagnetic field and to a background that breaks Lorentz symmetry, is naturally endowed with an N=1-supersymmetry. This result is achieved in a superspace approach where the particle coordinates and the spin degrees of freedom are components of the same supermultiplet.Comment: 6 pages, no figure

Immersed boundary-finite element model of fluid-structure interaction in the aortic root

It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe fluid-structure interaction models of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employ a version of Peskin's immersed boundary (IB) method with a finite element (FE) description of the structural elasticity. We develop both an idealized model of the root with three-fold symmetry of the aortic sinuses and valve leaflets, and a more realistic model that accounts for the differences in the sizes of the left, right, and noncoronary sinuses and corresponding valve cusps. As in earlier work, we use fiber-based models of the valve leaflets, but this study extends earlier IB models of the aortic root by employing incompressible hyperelastic models of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backwards displacement method that determines the unloaded configurations of the root models. Our models yield realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations demonstrate that IB models of the aortic valve are able to produce essentially grid-converged dynamics at practical grid spacings for the high-Reynolds number flows of the aortic root

Threshold analyses and Lorentz violation

In the context of threshold investigations of Lorentz violation, we discuss the fundamental principle of coordinate invariance, the role of an effective dynamical framework, and the conditions of positivity and causality. Our analysis excludes a variety of previously considered Lorentz-breaking parameters and opens an avenue for viable dispersion-relation investigations of Lorentz violation.Comment: 9 page

Customer emotions in service failure and recovery encounters

Emotions play a significant role in the workplace, and considerable attention has been given to the study of employee emotions. Customers also play a central function in organizations, but much less is known about customer emotions. This chapter reviews the growing literature on customer emotions in employee–customer interfaces with a focus on service failure and recovery encounters, where emotions are heightened. It highlights emerging themes and key findings, addresses the measurement, modeling, and management of customer emotions, and identifies future research streams. Attention is given to emotional contagion, relationships between affective and cognitive processes, customer anger, customer rage, and individual differences

A review of diagnostic and functional imaging in headache

The neuroimaging of headache patients has revolutionised our understanding of the pathophysiology of primary headaches and provided unique insights into these syndromes. Modern imaging studies point, together with the clinical picture, towards a central triggering cause. The early functional imaging work using positron emission tomography shed light on the genesis of some syndromes, and has recently been refined, implying that the observed activation in migraine (brainstem) and in several trigeminal-autonomic headaches (hypothalamic grey) is involved in the pain process in either a permissive or triggering manner rather than simply as a response to first-division nociception per se. Using the advanced method of voxel-based morphometry, it has been suggested that there is a correlation between the brain area activated specifically in acute cluster headache — the posterior hypothalamic grey matter — and an increase in grey matter in the same region. No structural changes have been found for migraine and medication overuse headache, whereas patients with chronic tension-type headache demonstrated a significant grey matter decrease in regions known to be involved in pain processing. Modern neuroimaging thus clearly suggests that most primary headache syndromes are predominantly driven from the brain, activating the trigeminovascular reflex and needing therapeutics that act on both sides: centrally and peripherally

Physics with the KLOE-2 experiment at the upgraded DAϕ\phiNE

Investigation at a $\phi$--factory can shed light on several debated issues in particle physics. We discuss: i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled kaon states, iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta$^\prime$ mesons, iv) the contribution to understand the nature of light scalar mesons, and v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the $e^+ e^-$ physics in the continuum with the measurements of (multi)hadronic cross sections and the study of gamma gamma processes.Comment: 60 pages, 41 figures; added affiliation for one of the authors; added reference to section