Reionization by active sources and its effects on the cosmic microwave background

We investigate the possible effects of reionization by active sources on the cosmic microwave background. We concentrate on the sources themselves as the origin of reionization, rather than early object formation, introducing an extra period of heating motivated by the active character of the perturbations. Using reasonable parameters, this leads to four possibilities depending on the time and duration of the energy input: delayed last scattering, double last scattering, shifted last scattering and total reionization. We show that these possibilities are only very weakly constrained by the limits on spectral distortions from the COBE FIRAS measurements. We illustrate the effects of these reionization possibilities on the angular power spectrum of temperature anisotropies and polarization for simple passive isocurvature models and simple coherent sources, observing the difference between passive and active models. Finally, we comment on the implications of this work for more realistic active sources, such as causal white noise and topological defect models. We show for these models that non-standard ionization histories can shift the peak in the CMB power to larger angular scales.Comment: 21 pages LaTeX with 11 eps figures; replaced with final version accepted for publication in Phys. Rev.

A measurement of the tau mass and the first CPT test with tau leptons

We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Measurements of RbR_{b}, AFBbA_{FB}^{b} and AFBcA_{FB}^{c} in e+e−e^{+}e^{-} Collisions at 130-189 GeV

The cross-section ratio Rb=sigma(e+e- to b-antib)/sigma(e+e- to q-antiq) andthe bottom and charm forward-backward asymmetries AFB^b and AFB^c are measuredusing event samples collected by the OPAL detector at centre-of-mass energiesbetween 130 and 189 GeV. Events with bottom quark production are selected witha secondary vertex tag, and a hemisphere charge algorithm is used to extractAFB^b. In addition, the bottom and charm asymmetries are measured using leptonsfrom semileptonic decays of heavy hadrons and pions from D*+ to D0pi+ decays.The results are in agreement with the Standard Model predictions.The cross-section ratio Rb=sigma(e+e- to b-antib)/sigma(e+e- to q-antiq) and the bottom and charm forward-backward asymmetries AFB^b and AFB^c are measured using event samples collected by the OPAL detector at centre-of-mass energies between 130 and 189 GeV. Events with bottom quark production are selected with a secondary vertex tag, and a hemisphere charge algorithm is used to extract AFB^b. In addition, the bottom and charm asymmetries are measured using leptons from semileptonic decays of heavy hadrons and pions from D*+ to D0pi+ decays. The results are in agreement with the Standard Model predictions

Dynamic mechanical thermal analysis of aqueous sugar solutions containing fructose, glucose, sucrose, maltose and lactose

The glass transition of glucose, fructose, lactose, maltose and sucrose solutions at maximum cryo-concentration was studied by Dynamic Mechanical Thermal Analysis (DMTA), using the disc bending technique. The glass transition temperatures were determined from the peaks in the loss modulus E′′, which corresponds theoretically to the resonance point (Maxwell model) for several input frequencies. The frequency dependence was well described by both an Arrhenius-type model and by the WLF (Williams, Landel and Ferry) equation, yielding glass transition temperatures for an average molecular vibration time of 100 s, which were similar to published midpoint temperatures determined by DSC scans. Some sugar mixtures were studied, yielding results that were well described by the Gordon–Taylor equation, using literature data. The frequency dependence of the viscoelastic ratio was also well approximated by an Arrhenius-type equation, with activation energies similar to those of the glass transition temperature and corresponded well to published values of the endset of glass transition

Enhanced solubility Ag-Cu nanoparticles and their thermal transport properties

Ag-Cu alloy nanoparticles were prepared by the inert gas condensation (IGC) process. X-ray diffraction (XRD) patterns show that particles were phase separated as pure Cu and Ag with some Cu incorporated in the Ag matrix. The particle size obtained either from Scherer's formula or electron microscopy images shows no systematic change of the size of either pure Cu or Ag-Cu particles in the evaporation temperature range between 800 degrees C and 1400 degrees C. By using lattice constant values and Vegard's law, the composition of Cu in Ag particles was calculated to be 6.6 vol pct. Analyses of the alloy nanoparticles suspended in hydrocarbon rotary pump oil were also carried out in order to determine the changes in thermal conductivity and viscosity of nanofluids. Thermal transport measurements have shown that there is a limit to the nanoparticle loading for the enhancement of the thermal conductivity. This maximum value was determined to be 0.006 vol pct Ag-Cu nanoparticles, which led to the enhancement of the thermal conductivity of the pump oil by 33 pct. Beyond this maximum loading, thermal conductivity decreased and reached back to the pure oil thermal conductivity value