Dilepton Production in e−pe^- p and e+e−e^+ e^- Colliders

In an $e^- p$ collider, a striking signature for a dilepton gauge boson is \ep \ ; this cross-section is calculated by using the helicity amplitude technique. At HERA, with center-of-mass energy $\sqrt s = 314 GeV$, a dilepton mass above $150 GeV$ is inaccessible but at LEPII-LHC, with a center-of-mass energy $\sqrt s = 1790 GeV$, masses up to 650 GeV can be discovered. In an $e^+ e^-$ collider, the signature is \ee \ . The cross-sections of this process are also calculated for the center-of-mass energies $\sqrt s = 200, 500$ and $1000 GeV$.Comment: 16 pages, 3 figures (not included), IFP-428-UN

The Scalar Sector of 3-3-1 Models

We study the mass spectrum and the eigenstates of the scalar sectors in 3-3-1 models. We show that, in one of the models, the physical scalar masses lead to theoretical constraints to the vacuum expectation values. The models allow very light Higgs bosons. One of the neutral scalars can be identified with the standard model one.Comment: 14 pages, Revtex 3.0, four figures available upon reques

ZZ--Z′Z' mixing and oblique corrections in an SU(3)×U(1){\rm SU(3) \times U(1)} model

A global fit for experiments is included in this revised version.Comment: IFP-460-UNC, TRI-PP-93-11, 20 pages, 2 figures are appende

Magnetic Resonance Imaging in Cervical Facet Dislocation: A Third World Perspective

Study Design:Retrospective case series. Purpose: The objective of our study was to determine the change in management brought about by magnetic resonance imaging (MRI) of the cervical spine in alert and awake Patients with facet dislocation and spinal cord injury presenting within 4 hours after injury. Overview Of Literature: Spinal cord injury is a common clinical entity. The role of MRI is well established in evaluating spinal trauma. However, the time at which MRI should be used is still controversial. Methods: Retrospective data from 2002-2010 was evaluated. All of the alert and awake Patients with spinal cord injury, based on clinical examination with facet dislocation diagnosed on lateral cervical spine X-rays, were included. A questionnaire was also conducted, the data of which consisted of demographic details including age and sex, the mechanism of injury, clinical examination, X-ray findings, MRI findings, whether or not surgery was performed and the time elapsed since injury. Data was analyzed using SPSS ver. 17.0. Continuous variables such as age were expressed in terms of mean standard deviation. Categorical variables such as change in management, X-ray/MRI findings and neurological motor level were assessed in terms of percentage. Results: Fifty Patients participated in our study. All these Patients had spinal cord injury with defined motor levels. The mean age was 35.5 8.95 years (range, 20 to 52 years). Fifty percent showed a motor level at C6 level. None of the Patients required any change in management based on the MRI. Conclusions: MRI of the spine in awake Patients within 4 hours after injury does not change the management of Patients. However, we can hypothesize that such Patients can proceed to traction without waiting for the MRI

Aerothermodynamic Analysis of a Reentry Brazilian Satellite

This work deals with a computational investigation on the small ballistic reentry Brazilian vehicle SARA (acronyms for SAt\'elite de Reentrada Atmosf\'erica). Hypersonic flows over the vehicle SARA at zero-degree angle of attack in a chemical equilibrium and thermal non-equilibrium are modeled by the Direct Simulation Monte Carlo (DSMC) method, which has become the main technique for studying complex multidimensional rarefied flows, and that properly accounts for the non-equilibrium aspects of the flows. The emphasis of this paper is to examine the behavior of the primary properties during the high altitude portion of SARA reentry. In this way, velocity, density, pressure and temperature field are investigated for altitudes of 100, 95, 90, 85 and 80 km. In addition, comparisons based on geometry are made between axisymmetric and planar two-dimensional configurations. Some significant differences between these configurations were noted on the flowfield structure in the reentry trajectory. The analysis showed that the flow disturbances have different influence on velocity, density, pressure and temperature along the stagnation streamline ahead of the capsule nose. It was found that the stagnation region is a thermally stressed zone. It was also found that the stagnation region is a zone of strong compression, high wall pressure. Wall pressure distributions are compared with those of available experimental data and good agreement is found along the spherical nose for the altitude range investigated.Comment: The paper will be published in Vol. 42 of the Brazilian Journal of Physic

Modelling the nucleon wave function from soft and hard processes

Current light-cone wave functions for the nucleon are unsatisfactory since they are in conflict with the data of the nucleon's Dirac form factor at large momentum transfer. Therefore, we attempt a determination of a new wave function respecting theoretical ideas on its parameterization and satisfying the following constraints: It should provide a soft Feynman contribution to the proton's form factor in agreement with data; it should be consistent with current parameterizations of the valence quark distribution functions and lastly it should provide an acceptable value for the \jp \to N \bar N decay width. The latter process is calculated within the modified perturbative approach to hard exclusive reactions. A simultaneous fit to the three sets of data leads to a wave function whose $x$-dependent part, the distribution amplitude, shows the same type of asymmetry as those distribution amplitudes constrained by QCD sum rules. The asymmetry is however much more moderate as in those amplitudes. Our distribution amplitude resembles the asymptotic one in shape but the position of the maximum is somewhat shifted.Comment: 32 pages RevTex + PS-file with 5 figures in uu-encoded, compressed fil

Trilinear gauge boson couplings and bilepton production in the SU(3)_C X SU(3)_L X U(1)_N models

The trilinear gauge boson couplings in the SU(3)_C X SU(3)_L X U(1)_N (3 - 3 - 1) models are presented. We find that new $Z_2$ does not interact with the usual (in the standard model) gauge bosons $Z, W^\pm$. Based on these results, production of new heavy gauge bosons at high energy colliders such as e^+ e^- is calculated. We show that the cross sections obtained in the 3 - 3 - 1 model with right-handed neutrinos can be one order bigger than the same in the minimal 3 - 3 - 1 model.Comment: 20 pages, 4 figure, late

3-3-1 exotic quark search at CERN LEPII-LHC

The 3-3-1 electroweak model is the simplest chiral extension of the standard model which predicts single and double charged bileptons and exotic quarks carrying -4/3 and 5/3 units of the positron charge. In this paper we study the possibilities of the production and decay of one of these exotic quarks at CERN LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing angles we obtained between 20 and 750 events per year. Angular distributions are also presented.Comment: 5 pages, RevTex 3.1, 9 eps figures, to appear in Phys. Rev.

Emergence of Multidrug-resistant Salmonella Paratyphi B dT+, Canada

We document an increase in the number of multidrug-resistant Salmonella enterica serovar Paratyphi B dT+ identified in Canada. Most of these strains harbor Salmonella genomic island 1 (SGI1). Further studies are needed to determine factors contributing to the observed emergence of this multidrug-resistant strain