Four-Lepton Resonance at the Large Hadron Collider

A spin-1 weakly interacting vector boson, Z', is predicted by many new physics theories. Searches at colliders for such a Z' resonance typically focus on lepton-antilepton or top-antitop events. Here we present a novel channel with a Z' resonance that decays to 4 leptons, but not to 2 leptons, and discuss its possible discovery at the Large Hadron Collider. This baryonic gauge boson is well motivated in a supersymmetry framework.Comment: Version to appear in PR

Lightest Neutralino in Extensions of the MSSM

We study neutralino sectors in extensions of the MSSM that dynamically generate the mu-term. The extra neutralino states are superpartners of the Higgs singlets and/or additional gauge bosons. The extended models may have distinct lightest neutralino properties which can have important influences on their phenomenology. We consider constraints on the lightest neutralino from LEP, Tevatron, and (g-2)_mu measurements and the relic density of the dark matter. The lightest neutralino can be extremely light and/or dominated by its singlino component which does not couple directly to SM particles except Higgs doublets.Comment: 17 pages, revtex4, 5 figure

Epidemic and pandemic influenza in tropical Singapore : impact and effectiveness of response strategies

Influenza is a disease of global significance, including in tropical regions where it spreads throughout the year. Understanding the spread and impact of influenza in the tropics is therefore important for preparedness planning. While there are numerous pharmaceutical and public health measures that attempt to reduce the spread and impact of influenza, few conclusive epidemiological studies are available to document their effectiveness. Scientific evidence is especially lacking for pandemic preparedness and response measures due to the rarity of pandemics. Singapore, a globally-connected, tropical Asian city-state, provides an excellent platform to determine the spread and impact of influenza in the tropics, and the effectiveness of public health measures in reducing the impact. This thesis aims to detail the impact of epidemic and pandemic influenza in Singapore, and to assess the effectiveness of various assessment and response measures in Singapore during the 2009 H1N1 influenza pandemic. Results: Influenza epidemics and pandemics were the likely cause of most excess mortality periods in Singapore from 1950 to 2000. Good surveillance is therefore important to detect epidemics for appropriate response. During the 2009 H1N1 influenza epidemic in Singapore, different methods for estimating influenza infection rates provided comparable findings if accurate input parameters were used. There are advantages and disadvantages to each method, and multiple methods should be used where possible for cross validation. One such method, a seroepidemiology cohort study, showed a 13% seroconversion rate in adults in the community and lower rates among hospital workers, suggesting that most of the population remained susceptible and required further protection. A surveillance program in the Singapore military during the peri-pandemic period showed the different clinical presentation of influenza compared to non-influenza cases, and introduced a clinical diagnostic model to help predict influenza among febrile respiratory illness cases for management. The possible effectiveness of combination strategies in reducing the impact of influenza was shown via a systematic review of mathematical modeling studies. It provides new evidence for the effectiveness of different strategies to reduce the spread of influenza in the military setting. One study showed that influenza vaccination may confer cross protection to other H1N1 strains, and previous exposure to pre-1957 H1N1 strains may confer some protection against the 2009 H1N1 strain. Another study showed the effectiveness of post-exposure ring prophylaxis with oseltamivir, together with prompt outbreak detection and isolation, as a containment strategy to reduce influenza spread. In the same setting, cessation of post-exposure prophylaxis did not result in subsequent disproportionate increase in infection rates, and asymptomatic infections occurred which may confer additional protection against future infection. While prophylaxis failures occurred, none were due to mutations that conferred resistance. Another study documented that public health measures such as enhanced surveillance with isolation, segregation and social distancing, and wearing personal protective equipment limited transmission of influenza

Compressive creep of high alumina refractories

The deformation of refractory materials consisting of 90% sintered or fused alumina plus 10% silica was measured at temperatures from 1450 to 1515⁰C and a compressive stress of 100 psi. Creep rates and activation energies were determined from the steady state portion of deformation vs. time data and correlated with the mineralogical composition. Supplemental measurements included x-ray diffraction, electron probe microanalysis, apparent porosity and tensile strength. conditions having an important effect upon the mineralolgical composition were: (1) duration of heat treatment, (2) amount of sodium oxide impurity, and (3) reactivity of the alumina grain. Prolonged heat treatment and sodium oxide impurity enhanced mullite formation, thus lowering creep rates. The activation energies ranged from 75 kcal/mole for samples containing sintered alumina doped with 0.5% sodium oxide, to 140-150 kcal/mole for regular sintered or fused alumina. The magnitude of the activation energy was approximately proportional to the mullite content --Abstract, page [i]

Ionic Conductivity Of Rubidium Chloride

This investigation describes a theoretical and experimental examination of the defect properties of rubidium chloride. A theoretical study of the defect properties of RbBr and RbI is also presented.;Defect energy calculations were carried out on RbCl, RbBr and RbI using the HADES code and electron-gas potentials that were fitted to the crystal properties. Damping of the long-range dispersion energy was introduced during fitting of the potential and in the calculation of perfect lattice and defect properties.;In addition, defect energy calculations were done on Rb{dollar}\sb2{dollar}S using potentials developed for the RbCl:S{dollar}\sp{lcub}2-{rcub}{dollar} system. These calculations represent the first theoretical study of the defect energies of Rb{dollar}\sb2{dollar}S.;Ionic conductivity measurements were made on pure, strontium-doped and sulphide-doped rubidium chloride using a new automated system. The data were analysed by means of a nonlinear least squares fitting routine. The analysis of the data suggested that both Schottky and anion Frenkel defects play a role in matter transport in RbCl. Cation interstitials were also found to be present in a small concentration. Vacancy pairs were found to contribute to diffusion, as had been indicated previously in diffusion studies of RbCl{dollar}\sp{lcub}1,2{rcub}{dollar}.;The calculated defect energies and the experimental enthalpies were in good agreement, suggesting the reliability of both the data analysis and the calculation methods used

Z' Mediated Flavor Changing Neutral Currents in B Meson Decays

We study the effects of an extra U(1)' gauge boson with flavor changing couplings with fermion mass eigenstates on certain B meson decays that are sensitive to such new physics contributions. In particular, we examine to what extent the current data on B_d -> \phi K, B_d -> \eta' K and B_s -> \mu^+ \mu^- decays may be explained in such models, concentrating on the example in which the flavor changing couplings are left-chiral. We find that within reasonable ranges of parameters, the Z' contribution can readily account for the anomaly in S_{\phi K_S} but is not sufficient to explain large branching ratio of B_d -> \eta' K with the same parameter value. S_{\phi K_S} and S_{\eta' K_S} are seen to be the dominant observables that constrain the extra weak phase in the model.Comment: 12 pages, 6 figures. Additional references added. Small modifications and corrections to Eq.(33) and (34) adde