Pion Leptonic Decays and Supersymmetry

We compute supersymmetric contributions to pion leptonic (\pi_{l2}) decays in the Minimal Supersymmetric Standard Model (MSSM). When R-parity is conserved, the largest contributions to the ratio R_{e/\mu} = \Gamma[ \pi^+ \to e^+ \nu_e(\gamma)]/\Gamma[ \pi^+ \to \mu^+ \nu_\mu(\gamma)] arise from one-loop (V-A)x(V-A) corrections. These contributions can be potentially as large as the sensitivities of upcoming experiments; if measured, they would imply significant bounds on the chargino and slepton sectors complementary to current collider limits. We also analyze R-parity violating interactions, which may produce a detectable deviation in R_{e/\mu} while remaining consistent with all other precision observables.Comment: 12 pages, 11 figures; included additional electroweak constraints in analysis, simplified abstract, ref. adde

Lepton-mediated electroweak baryogenesis

We investigate the impact of the tau and bottom Yukawa couplings on the transport dynamics for electroweak baryogenesis in supersymmetric extensions of the Standard Model. Although it has generally been assumed in the literature that all Yukawa interactions except those involving the top quark are negligible, we find that the tau and bottom Yukawa interaction rates are too fast to be neglected. We identify an illustrative "lepton-mediated electroweak baryogenesis" scenario in which the baryon asymmetry is induced mainly through the presence of a left-handed leptonic charge. We derive analytic formulae for the computation of the baryon asymmetry that, in light of these effects, are qualitatively different from those in the established literature. In this scenario, for fixed CP-violating phases, the baryon asymmetry has opposite sign compared to that calculated using established formulae.Comment: 26 pages, 5 figure

Isolation and optimization of the production of Staphylococcus epidermidis bacteriophage from environmental samples

Staphylococcus epidermidis is now among the most important nosocomial pathogenic agents owing its virulence to the adhesion and biofilm-forming abilities on medical surfaces, such as catheters. Biofilm control by antibiotics is often innefective and new strategies of biofilm control are being sought. One promising strategy is the use of bacteria-specific virus, known as bacteriophages, to control infections by pathogenic bacteria. Bacteriophages, also know as phages, have been suggested to be one of the most abundant biological agents on the planet. Phages are currently suggested as possible alternatives to antibiotics for the treatment of bacterial diseases in humans to minimize the pathogen loads in medical devices . The goal of this study was to isolate new phages with potential bactericidal activity against S. epidermidis clinical isolates. Bacteriophages were isolated from an effluent from Waste Water Treatment Plants or from Hospital efluents, using a set of 40 bacterial strains as background. Five phages were isolated but when determining the phage titer the achieved concentration was around 10E5 pfu/ml and this titer was reduced 1 fold in two week‘s time. In order to increase the concentration of bacteriophages, since the obtained concentration was not sufficient to use in biofilm assays, severall optimization steps were performed, using previous described isolation protocols, namelly: using different concentrations of CaCl2, using different concentrations of top agar, using different buffers, and using different phage filtration systems. For the optimization protocols we selected the bacteriophage with the higher titters and found that an optimized protocol was achieved by using Tris Buffer, Top Agar at 0.4%, and purification with CsCl2 gradient (q = 1.3, 1.5, and 1.7) with ultracentrifugation at 100,000g for 1 h at 4⁰C. This phage titter was determined to be around 10E8-10E9 pfu/ml. The optimized produced phage was then characterized by determining the lytic spectrum. The phage was able to lyse 13 strains, and of these strains 10 had the biofilms genes present. Finally, the 10 selected strains were tested for biofilm formation, using the microtiter assay, and it was confirmed that they formed biofilms in TSB supplemented with 1% glucose. For future work; we need to determine if we have lytic or temperate phages with DNA sequence analyses and to test the Phage against to the Biofilm formation of relevant bacterial strains

Flavored Quantum Boltzmann Equations

We derive from first principles, using non-equilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading non-trivial order in ratios of relevant time scales, we study in detail a toy model for weak scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a non-trivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.Comment: 41 pages, 7 figures. v2: references added, minor corrections and clarification

Spectral up- and downshifting of Akhmediev breathers under wind forcing

We experimentally and numerically investigate the effect of wind forcing on the spectral dynamics of Akhmediev breathers, a wave-type known to model the modulation instability. We develop the wind model to the same order in steepness as the higher order modifcation of the nonlinear Schroedinger equation, also referred to as the Dysthe equation. This results in an asymmetric wind term in the higher order, in addition to the leading order wind forcing term. The derived model is in good agreement with laboratory experiments within the range of the facility's length. We show that the leading order forcing term amplifies all frequencies equally and therefore induces only a broadening of the spectrum while the asymmetric higher order term in the model enhances higher frequencies more than lower ones. Thus, the latter term induces a permanent upshift of the spectral mean. On the other hand, in contrast to the direct effect of wind forcing, wind can indirectly lead to frequency downshifts, due to dissipative effects such as wave breaking, or through amplification of the intrinsic spectral asymmetry of the Dysthe equation. Furthermore, the definitions of the up- and downshift in terms of peak- and mean frequencies, that are critical to relate our work to previous results, are highlighted and discussed.Comment: 30 pages, 11 figure

Yukawa Interactions and Supersymmetric Electroweak Baryogenesis

We analyze the quantum transport equations for supersymmetric electroweak baryogenesis including previously neglected bottom and tau Yukawa interactions and show that they imply the presence of a previously unrecognized dependence of the cosmic baryon asymmetry on the spectrum of third generation quark and lepton superpartners. For fixed values of the CP-violating phases in the supersymmetric theory, the baryon asymmetry can vary in both magnitude and sign as a result of the squark and slepton mass dependence. For light, right-handed top and bottom quark superpartners, the baryon number creation can be driven primarily by interactions involving third generation leptons and their superpartners.Comment: 4 pages, 1 figur

Nonlinear electron transport in normally pinched-off quantum wire

Nonlinear electron transport in normally pinched-off quantum wires was studied. The wires were fabricated from AlGaAs/GaAs heterostructures with high-mobility two-dimensional electron gas by electron beam lithography and following wet etching. At certain critical source-drain voltage the samples exhibited a step rise of the conductance. The differential conductance of the open wires was noticeably lower than e^2/h as far as only part of the source-drain voltage dropped between source contact and saddle-point of the potential relief along the wire. The latter limited the electron flow injected to the wire. At high enough source-drain voltages the decrease of the differential conductance due to the real space transfer of electrons from the wire in GaAs to the doped AlGaAs layer was found. In this regime the sign of differential magnetoconductance was changed with reversing the direction of the current in the wire or the magnetic field, whet the magnetic field lies in the heterostructure plane and is directed perpendicular to the current. The dependence of the differential conductance on the magnetic field and its direction indicated that the real space transfer events were mainly mediated by the interface scattering.Comment: LaTeX 2e (epl.cls) 6 pages, 3 figure

Multiple superconducting ring ratchets for ultrasensitive detection of non-equilibrium noises

Magnetic quantum periodicity in the dc voltage is observed when asymmetric rings are switched between superconducting and normal state by a noise or ac current. This quantum effect is used for detection of a non-equilibrium noise with the help of a system of 667 asymmetric aluminum rings of $1 \ \mu m$ in diameter connected in series. Any noise down to the equilibrium one can be detected with the help of such system with enough great number of asymmetric rings.Comment: 6 pages, 6 figure

Poly(ADP-Ribose) Polymerase 1 (PARP-1) Regulates Ribosomal Biogenesis in Drosophila Nucleoli

Poly(ADP-ribose) polymerase 1 (PARP1), a nuclear protein, utilizes NAD to synthesize poly(AD-Pribose) (pADPr), resulting in both automodification and the modification of acceptor proteins. Substantial amounts of PARP1 and pADPr (up to 50%) are localized to the nucleolus, a subnuclear organelle known as a region for ribosome biogenesis and maturation. At present, the functional significance of PARP1 protein inside the nucleolus remains unclear. Using PARP1 mutants, we investigated the function of PARP1, pADPr, and PARP1-interacting proteins in the maintenance of nucleolus structure and functions. Our analysis shows that disruption of PARP1 enzymatic activity caused nucleolar disintegration and aberrant localization of nucleolar-specific proteins. Additionally, PARP1 mutants have increased accumulation of rRNA intermediates and a decrease in ribosome levels. Together, our data suggests that PARP1 enzymatic activity is required for targeting nucleolar proteins to the proximity of precursor rRNA; hence, PARP1 controls precursor rRNA processing, post-transcriptional modification, and pre-ribosome assembly. Based on these findings, we propose a model that explains how PARP1 activity impacts nucleolar functions and, consequently, ribosomal biogenesis