268 research outputs found
A linear plasmid truncation induces unidirectional flagellar phase change in H:z66 positive Salmonella Typhi
The process by which bacteria regulate flagellar expression is known as phase variation and in Salmonella enterica this process permits the expression of one of two flagellin genes, fliC or fljB, at any one time. Salmonella Typhi (S. Typhi) is normally not capable of phase variation of flagellar antigen expression as isolates only harbour the fliC gene (H:d) and lacks an equivalent fljB locus. However, some S. Typhi isolates, exclusively from Indonesia, harbour an fljB equivalent encoded on linear plasmid, pBSSB1 that drives the expression of a novel flagellin named H:z66. H:z66+S. Typhi isolates were stimulated to change flagellar phase and genetically analysed for the mechanism of variation. The phase change was demonstrated to be unidirectional, reverting to expression from the resident chromosomal fliC gene. DNA sequencing demonstrated that pBSSB1 linear DNA was still detectable but that these derivatives had undergone deletion and were lacking fljAz66 (encoding a flagellar repressor) and fljBz66. The deletion end-point was found to involve one of the plasmid termini and a palindromic repeat sequence within fljBz66, distinct to that found at the terminus of pBSSB1. These data demonstrate that, like some Streptomyces linear elements, at least one of the terminal inverted repeats of pBSSB1 is non-essential, but that a palindromic repeat sequence may be necessary for replication
Charged lepton electric dipole moments with the localized leptons and the new Higgs doublet in the two Higgs doublet model
We study the lepton electric dipole moments in the split fermion scenario, in
the two Higgs doublet model, where the new Higgs scalars are localized around
the origin in the extra dimension, with the help of the localizer field. We
observe that the numerical value of the electron (muon, tau) electric dipole
moment is at the order of the magnitude of 10^{-31} (10^{-24}, 10^{-22}) (e-cm)
and this quantity is sensitive the new Higgs localization in the extra
dimension.Comment: 20 pages, 7 figure
Bilinear R-parity Violation and Small Neutrino Masses: a Self-consistent Framework
We study extensions of supersymmetric models without R-parity which include
an anomalous U(1)_H horizontal symmetry. Bilinear R-parity violating terms
induce a neutrino mass at tree level of approximately eV
where is the U(1)_H breaking parameter and is an
integer number that depends on the horizontal charges of the leptons. For
a unique self-consistent model arises in which i) all the
superpotential trilinear R-parity violating couplings are forbidden by
holomorphy; ii) the tree level neutrino mass falls in the range suggested by
the atmospheric neutrino problem; iii) radiative contributions to neutrino
masses are strongly suppressed resulting in a squared solar mass difference of
few 10^{-8} eV^2 which only allows for the LOW (or quasi-vacuum) solution to
the solar neutrino problem; iv) the neutrino mixing angles are not suppressed
by powers of and can naturally be large.Comment: Latex, 15 pages including 1 figure, some typos correcte
Alternative approach to in the uMSSM
The gluino contributions to the Wilson coefficients for are calculated within the unconstrained MSSM. New stringent bounds on
the and mass insertion parameters are
obtained in the limit in which the SM and SUSY contributions to
approximately cancel. Such a cancellation can plausibly appear within several
classes of SUSY breaking models in which the trilinear couplings exhibit a
factorized structure proportional to the Yukawa matrices. Assuming this
cancellation takes place, we perform an analysis of the decay. We
show that in a supersymmetric world such an alternative is reasonable and it is
possible to saturate the branching ratio and produce a CP
asymmetry of up to 20%, from only the gluino contribution to
coefficients. Using photon polarization a LR asymmetry can be defined that in
principle allows for the and contributions to the decay to be disentangled. In this scenario no constraints on the ``sign
of '' can be derived.Comment: LaTeX2e, 23 pages, 7 ps figure, needs package epsfi
Bifurcations of a driven granular system under gravity
Molecular dynamics study on the granular bifurcation in a simple model is
presented. The model consists of hard disks, which undergo inelastic
collisions; the system is under the uniform external gravity and is driven by
the heat bath. The competition between the two effects, namely, the
gravitational force and the heat bath, is carefully studied. We found that the
system shows three phases, namely, the condensed phase, locally fluidized
phase, and granular turbulent phase, upon increasing the external control
parameter. We conclude that the transition from the condensed phase to the
locally fluidized phase is distinguished by the existence of fluidized holes,
and the transition from the locally fluidized phase to the granular turbulent
phase is understood by the destabilization transition of the fluidized holes
due to mutual interference.Comment: 35 pages, 17 figures, to be published in PR
The Potential for Neutrino Physics at Muon Colliders and Dedicated High Current Muon Storage Rings
Conceptual design studies are underway for muon colliders and other
high-current muon storage rings that have the potential to become the first
true ``neutrino factories''. Muon decays in long straight sections of the
storage rings would produce precisely characterized beams of electron and muon
type neutrinos of unprecedented intensity. This article reviews the prospects
for these facilities to greatly extend our capabilities for neutrino
experiments, largely emphasizing the physics of neutrino interactions.Comment: 107 pages, 16 figures, to be published in Physics Report
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Parallel computing in information retrieval - An updated review
The progress of parallel computing in Information Retrieval (IR) is reviewed. In particular we stress the importance of the motivation in using parallel computing for Text Retrieval. We analyse parallel IR systems using a classification due to Rasmussen [1] and describe some parallel IR systems. We give a description of the retrieval models used in parallel Information Processing.. We describe areas of research which we believe are needed
Lepton polarization correlations in
In this work we will study the polarizations of both leptons () in the
decay channel . In the case of the dileptonic inclusive
decay , where apart from the polarization asymmetries
of single lepton , one can also observe the polarization asymmetries of
both leptons simultaneously. If this sort of measurement is possible then we
can have, apart from decay rate, FB asymmetry and the six single lepton
polarization asymmetries (three each for and ), nine more
double polarization asymmetries. This will give us a very useful tool in more
strict testing of SM and the physics beyond. We discuss the double polarization
asymmetries of leptons in the decay mode within
the SM and the Minimal Supersymmetric extensions of it.Comment: 21 pages, 21 figures; version to match paper to appear in PR
Atmospheric Neutrino Oscillations and New Physics
We study the robustness of the determination of the neutrino masses and
mixing from the analysis of atmospheric and K2K data under the presence of
different forms of phenomenologically allowed new physics in the nu_mu--nu_tau
sector. We focus on vector and tensor-like new physics interactions which allow
us to treat, in a model independent way, effects due to the violation of the
equivalence principle, violations of the Lorentz invariance both CPT conserving
and CPT violating, non-universal couplings to a torsion field and non-standard
neutrino interactions with matter. We perform a global analysis of the full
atmospheric data from SKI together with long baseline K2K data in the presence
of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together
with sub-dominant effects due to these forms of new physics. We show that
within the present degree of experimental precision, the extracted values of
masses and mixing are robust under those effects and we derive the upper bounds
on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include
Comparative evaluation of a new lactation curve model for pasture-based Holstein-Friesian dairy cows
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