2,699 research outputs found
Soft Yukawa couplings in supersymmetric theories
The possibility of radiatively generated fermion masses arising from chiral
flavor violation in soft supersymmetry-breaking terms is explored. Vacuum
stability constraints are considered in various classes of models, and allow in
principle all of the first- and second-generation quarks and leptons and the
-quark to obtain masses radiatively. Radiatively induced Higgs-fermion
couplings have non-trivial momentum-dependent form factors, which at low
momentum are enhanced with respect to the case of tree-level Yukawa couplings.
These form factors may be probed by various sum rules and relations among Higgs
boson decay widths and branching ratios to fermion final states. An apparent,
large, hard violation of supersymmetry also results for Higgsino couplings.
Mixing between left- and right-handed scalar superpartners is enhanced. A
radiative muon mass is shown to lead to a relatively large and potentially
measurable contribution to the muon anomalous magnetic moment. If the
light-quark masses arise radiatively, the neutron electric dipole moment is
suppressed by a natural phase alignment between the masses and dipole moment,
and is below the current experimental bound. The possibility of neutrino masses
arising from softly broken lepton number, and concomitant enhanced
sneutrino-antisneutrino oscillations, is briefly discussed.Comment: 66 pages. LaTex + RevTex. 16 figures (included). Published version
(minor changes and typos corrected
Additional symmetries of constrained CKP and BKP hierarchies
The additional symmetries of the constrained CKP (cCKP) and BKP (cBKP)
hierarchies are given by their actions on the Lax operators, and their actions
on the eigenfunction and adjoint eigenfunction are
presented explicitly. Furthermore, we show that acting on the space of the wave
operator, forms new centerless and
-subalgebra of centerless respectively. In
order to define above symmetry flows of the cCKP and cBKP
hierarchies, two vital operators are introduced to revise the additional
symmetry flows of the CKP and BKP hierarchies.Comment: 14 pages, accepted by SCIENCE CHINA Mathematics(2010
The scalar gluonium correlator: large-beta_0 and beyond
The investigation of the scalar gluonium correlator is interesting because it
carries the quantum numbers of the vacuum and the relevant hadronic current is
related to the anomalous trace of the QCD energy-momentum tensor in the chiral
limit. After reviewing the purely perturbative corrections known up to
next-next-to-leading order, the behaviour of the correlator is studied to all
orders by means of the large-beta_0 approximation. Similar to the QCD Adler
function, the large-order behaviour is governed by the leading ultraviolet
renormalon pole. The structure of infrared renormalon poles, being related to
the operator product expansion are also discussed, as well as a low-energy
theorem for the correlator that provides a relation to the renormalisation
group invariant gluon condensate, and the vacuum matrix element of the trace of
the QCD energy-momentum tensor.Comment: 14 pages, references added, discussion of IR renormalon pole at u=3
extended, similar version to appear in JHE
Testing Anomalous Color-Electric Dipole Moment of the c-Quark from psi'->J/psi+pi(+)+pi(-) at Beijing Spectrometer
If the c-quark has an anomalous color-electric dipole moment (CEDM), it may
serve as a new source of CP violation. The strength of such a CP violation
depends on the size of the CEDM, d'_c. We propose two effective ways of testing
it from the large sample of psi'->J/psi+pi(+)+pi(-) at the Beijing
Spectrometer, and the obtained result, |d'_c|<3X10^{-14} e cm (95% C.L.), gives
the first experimentally determined upper bound on the CEDM of the c quark.Comment: 26 pages RevTex4 file with 4 eps files for the figures. Some
discussions and new references adde
Non-linear sigma models with anti-de Sitter target spaces
We present evidence that there is a non-trivial fixed point for the AdS_{D+1}
non-linear sigma model in two dimensions, without any matter fields or
additional couplings beyond the standard quadratic action subject to a
quadratic constraint. A zero of the beta function, both in the bosonic and
supersymmetric cases, appears to arise from competition between one-loop and
higher loop effects. A string vacuum based on such a fixed point would have
string scale curvature. The evidence presented is based on fixed-order
calculations carried to four loops (corresponding to O(\alpha'^3) in the
spacetime effective action) and on large D calculations carried to O(D^{-2})
(but to all orders in \alpha'). We discuss ways in which the evidence might be
misleading, and we discuss some features of the putative fixed point, including
the central charge and an operator of negative dimension. We speculate that an
approximately AdS_5 version of this construction may provide a holographic dual
for pure Yang-Mills theory, and that quotients of an AdS_3 version might stand
in for Calabi-Yau manifolds in compactifications to four dimensions.Comment: 44 pages, 4 figures. v2: references adde
A Recombinant Rift Valley Fever Virus Glycoprotein Subunit Vaccine Confers Full Protection against Rift Valley Fever Challenge in Sheep
Citation: Faburay, B., Wilson, W. C., Gaudreault, N. N., Davis, A. S., Shivanna, V., Bawa, B., . . . Richt, J. A. (2016). A Recombinant Rift Valley Fever Virus Glycoprotein Subunit Vaccine Confers Full Protection against Rift Valley Fever Challenge in Sheep. Scientific Reports, 6, 12. doi:10.1038/srep27719Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen causing disease outbreaks in Africa and the Arabian Peninsula. The virus has great potential for transboundary spread due to the presence of competent vectors in non-endemic areas. There is currently no fully licensed vaccine suitable for use in livestock or humans outside endemic areas. Here we report the evaluation of the efficacy of a recombinant subunit vaccine based on the RVFV Gn and Gc glycoproteins. In a previous study, the vaccine elicited strong virus neutralizing antibody responses in sheep and was DIVA (differentiating naturally infected from vaccinated animals) compatible. In the current efficacy study, a group of sheep (n=5) was vaccinated subcutaneously with the glycoprotein-based subunit vaccine candidate and then subjected to heterologous challenge with the virulent Kenya-128B-15 RVFV strain. The vaccine elicited high virus neutralizing antibody titers and conferred complete protection in all vaccinated sheep, as evidenced by prevention of viremia, fever and absence of RVFV-associated histopathological lesions. We conclude that the subunit vaccine platform represents a promising strategy for the prevention and control of RVFV infections in susceptible hosts
Contrast of LiFeAs with isostructural, isoelectronic, and non-superconducting MgFeGe
Stoichiometric LiFeAs at ambient pressure is an 18 K superconductor while
isoelectronic MgFeGe is not, despite their extremely similar electronic
structures. To investigate possible sources of this distinctively different
superconducting behavior, we quantify the differences using first principles
density functional theory, establishing first that the Fe total 3d occupations
are identical in the two compounds. Individual 3d orbital occupations also
differ very little (). The differences in Fermi surfaces (FSs) do
not seem significant; however a redistribution of bands just above the Fermi
level does represent a possibly significant distinction. Because the bands and
FSs of LiFeAs are less in agreement with experiment than for other
iron-pnictides, we study the effects of additional exchange-correlations
effects beyond GGA (the generalized gradient approximation) by applying the
modified Becke-Johnson potential (mBJ) exchange potential, which gives much
improved bandgaps in insulators compared to GGA and might be useful for
semimetals such as the Fe-based superconductors. Overall, we conclude that the
mBJ corrections do not improve the description of LiFeAs as compared to
experiment
Experimental infection of calves by two genetically-distinct strains of rift valley fever virus
Citation: Wilson, W. C., Davis, A. S., Gaudreault, N. N., Faburay, B., Trujillo, J. D., Shivanna, V., . . . Richt, J. A. (2016). Experimental infection of calves by two genetically-distinct strains of rift valley fever virus. Viruses, 8(5). doi:10.3390/v8050145Additional Authors: McVey, D. S.Recent outbreaks of Rift Valley fever in ruminant livestock, characterized by mass abortion and high mortality rates in neonates, have raised international interest in improving vaccine control strategies. Previously, we developed a reliable challenge model for sheep that improves the evaluation of existing and novel vaccines in sheep. This sheep model demonstrated differences in the pathogenesis of Rift Valley fever virus (RVFV) infection between two genetically-distinct wild-type strains of the virus, Saudi Arabia 2001 (SA01) and Kenya 2006 (Ken06). Here, we evaluated the pathogenicity of these two RVFV strains in mixed breed beef calves. There was a transient increase in rectal temperatures with both virus strains, but this clinical sign was less consistent than previously reported with sheep. Three of the five Ken06-infected animals had an early-onset viremia, one day post-infection (dpi), with viremia lasting at least three days. The same number of SA01-infected animals developed viremia at 2 dpi, but it only persisted through 3 dpi in one animal. The average virus titer for the SA01-infected calves was 1.6 logs less than for the Ken06-infected calves. Calves, inoculated with either strain, seroconverted by 5 dpi and showed time-dependent increases in their virus-neutralizing antibody titers. Consistent with the results obtained in the previous sheep study, elevated liver enzyme levels, more severe liver pathology and higher virus titers occurred with the Ken06 strain as compared to the SA01 strain. These results demonstrate the establishment of a virulent challenge model for vaccine evaluation in calves. © 2016 by the authors; licensee MDPI, Basel, Switzerland
The Fungal Cell Wall : Structure, Biosynthesis, and Function
N.G. is funded by the Wellcome Trust via a senior investigator award and a strategic award and by the MRC Centre for Medical Mycology. C.M. acknowledges the support of the Wellcome Trust and the MRC. N.G. and C.M. are part of the MRC Centre for Medical Mycology. J.P.L. acknowledges support from ANR, Aviesan, and FRM.Peer reviewedPublisher PD
Tridimensional model structure and patterns of molecular evolution of Pepino mosaic virus TGBp3 protein
<p>Abstract</p> <p>Background</p> <p><it>Pepino mosaic virus </it>(PepMV) is considered one of the most dangerous pathogens infecting tomatoes worldwide. The virus is highly diverse and four distinct genotypes, as well as inter-strain recombinants, have already been described. The isolates display a wide range on symptoms on infected plant species, ranging from mild mosaic to severe necrosis. However, little is known about the mechanisms and pattern of PepMV molecular evolution and about the role of individual proteins in host-pathogen interactions.</p> <p>Methods</p> <p>The nucleotide sequences of the triple gene block 3 (TGB3) from PepMV isolates varying in symptomatology and geographic origin have been analyzed. The modes and patterns of molecular evolution of the TGBp3 protein were investigated by evaluating the selective constraints to which particular amino acid residues have been subjected during the course of diversification. The tridimensional structure of TGBp3 protein has been modeled <it>de novo </it>using the Rosetta algorithm. The correlation between symptoms development and location of specific amino acids residues was analyzed.</p> <p>Results</p> <p>The results have shown that TGBp3 has been evolving mainly under the action of purifying selection operating on several amino acid sites, thus highlighting its functional role during PepMV infection. Interestingly, amino acid 67, which has been previously shown to be a necrosis determinant, was found to be under positive selection.</p> <p>Conclusions</p> <p>Identification of diverse selection events in TGB3p3 will help unraveling its biological functions and is essential to an understanding of the evolutionary constraints exerted on the <it>Potexvirus </it>genome. The estimated tridimensional structure of TGBp3 will serve as a platform for further sequence, structural and function analysis and will stimulate new experimental advances.</p
- …