510 research outputs found
A simple mean field model for social interactions: dynamics, fluctuations, criticality
We study the dynamics of a spin-flip model with a mean field interaction. The
system is non reversible, spacially inhomogeneous, and it is designed to model
social interactions. We obtain the limiting behavior of the empirical averages
in the limit of infinitely many interacting individuals, and show that phase
transition occurs. Then, after having obtained the dynamics of normal
fluctuations around this limit, we analize long time fluctuations for critical
values of the parameters. We show that random inhomogeneities produce critical
fluctuations at a shorter time scale compared to the homogeneous system.Comment: 37 pages, 2 figure
Manganese-Enhanced Magnetic Resonance Imaging in Takotsubo Syndrome
Acknowledgments The authors thank the Edinburgh Imaging Facility. Sources of Funding This work and T. Singh, S. Joshi, and Drs Dweck and Newby are supported by the British Heart Foundation (grants FS/17/19/32641, CS/17/1/32445, RG/16/10/32375, RE/18/5/34216, FS/ICRF/20/26002, and FS/SCRF/21/32010). T. Singh is supported by the Medical Research Council (grant MR/T029153/1). Dr Newby is the recipient of a Wellcome Trust Senior Investigator Award (WT103782AIA). Dr McCann is supported by an NIHR Research Professorship (08-2017-ST2-007). The Edinburgh Clinical Research Facilities and Edinburgh Imaging Facility are supported by the National Health Service Research Scotland through the National Health Service Lothian Health Board.Peer reviewe
Constraints on Baryon-Nonconserving Yukawa Couplings in a Supersymmetric Theory
The 1-loop evolution of couplings in the minimal supersymmetric standard
model, extended to include baryon nonconserving operators through
explicit -parity violation, is considered keeping only
superpotential terms involving the maximum possible number of third generation
superfields. If all retained Yukawa couplings are required to remain in
the perturbative domain upto the scale of gauge group unification,
upper bounds ensue on the magnitudes of the coupling strengths at
the supersymmetry breaking scale, independent of the model of unification. They
turn out to be similar to the corresponding fixed point values reached from a
wide range of (including all greater than unity) at the unification
scale. The coupled evolution of the top and Yukawa couplings results
in a reduction of the fixed point value of the former.Comment: PRL-TH-94/8 and TIFR/TH/94-7, 15 pages, LaTe
Therapeutic targeting of vascular malformation in a zebrafish model of hereditary haemorrhagic telangiectasia
Hereditary haemorrhagic telangiectasia (HHT) causes arteriovenous malformations (AVMs) in multiple organs to cause bleeding, neurological and other complications. HHT is caused by mutations in the BMP co-receptor endoglin. We characterised a range of vascular phenotypes in embryonic and adult endoglin mutant zebrafish and the effect of inhibiting different pathways downstream of Vegf signalling. Adult endoglin mutant zebrafish developed skin AVMs, retinal vascular abnormalities and cardiac enlargement. Embryonic endoglin mutants developed an enlarged basilar artery (similar to the previously described enlarged aorta and cardinal vein) and larger numbers of endothelial membrane cysts (kugeln) on cerebral vessels. Vegf inhibition prevented these embryonic phenotypes, leading us to investigate specific Vegf signalling pathways. Inhibiting mTOR or MEK pathways prevented abnormal trunk and cerebral vasculature phenotypes, whereas inhibiting Nos or Mapk pathways had no effect. Combined subtherapeutic mTOR and MEK inhibition prevented vascular abnormalities, confirming synergy between these pathways in HHT. These results indicate that the HHT-like phenotype in zebrafish endoglin mutants can be mitigated through modulation of Vegf signalling. Combined low-dose MEK and mTOR pathway inhibition could represent a novel therapeutic strategy in HHT
Tuberculosis serosurveillance and management practices of captive African elephants (Loxodonta africana) in the Kavango-Zambezi Transfrontier Conservation Area
Transfrontier conservation areas represent an international effort to encourage conservation and sustainable development. Their success faces a number of challenges, including disease management in wildlife, livestock and humans. Tuberculosis (TB) affects humans and a multitude of nonâhuman animal species and is of particular concern in subâSaharan Africa. The KavangoâZambezi Transfrontier Conservation Area encompasses five countries, including Zimbabwe, and is home to the largest contiguous population of freeâranging elephants in Africa. Elephants are known to be susceptible to TB; thus, understanding TB status, exposure and transmission risks to and from elephants in this area is of interest for both conservation and human health. To assess risk factors for TB seroprevalence, a questionnaire was used to collect data regarding elephant management at four ecotourism facilities offering elephantâback tourist rides in the Victoria Falls area of Zimbabwe. Thirtyâfive working African elephants were screened for Mycobacterium tuberculosis complex antibodies using the ElephantTB StatâPak and the DPP VetTB Assay for elephants. Six of 35 elephants (17.1%) were seropositive. The risk factor most important for seropositive status was time in captivity. This is the first study to assess TB seroprevalence and risk factors in working African elephants in their home range. Our findings will provide a foundation to develop guidelines to protect the health of captive and freeâranging elephants in the southern African context, as well as elephant handlers through simple interventions. Minimizing exposure through shared feed with other wildlife, routine TB testing of elephant handlers and regular serological screening of elephants are recommended as preventive measures.Financial support for elephant sample collection was provided by the Institute of Tropical Medicine, Antwerp, Belgium and the framework agreement (FA3) with the Belgian Development Cooperation, the National Research Foundation South African Research Chair Initiative (NRF SARChI), and the International Wildlife Health Institute. Laura Rosen was supported by a Morris Animal Foundation Veterinary Fellowship for Advanced Study (grant ID: D15ZOâ906).http://wileyonlinelibrary.com/journal/tbed2019-04-01hj2018Veterinary Tropical Disease
Genetic characterization of a brangus-ibage cattle population: biochemical polymorphisms and reproductive efficiency
Neutrino masses in R-parity violating supersymmetric models
We study neutrino masses and mixing in R-parity violating supersymmetric
models with generic soft supersymmetry breaking terms. Neutrinos acquire masses
from various sources: Tree level neutrino--neutralino mixing and loop effects
proportional to bilinear and/or trilinear R-parity violating parameters. Each
of these contributions is controlled by different parameters and have different
suppression or enhancement factors which we identified. Within an Abelian
horizontal symmetry framework these factors are related and specific
predictions can be made. We found that the main contributions to the neutrino
masses are from the tree level and the bilinear loops and that the observed
neutrino data can be accommodated once mild fine-tuning is allowed.Comment: 18 pages; minor typos corrected. To be published in Physical Review
Isolating a light Higgs boson from the di-photon background at the LHC
We compute the QCD corrections to the gluon fusion subprocess gg to gamma
gamma, which forms an important component of the background to the search for a
light Higgs boson at the LHC. We study the dependence of the improved pp to
gamma gamma X background calculation on the factorization and renormalization
scales, on various choices for photon isolation cuts, and on the rapidities of
the photons. We also investigate ways to enhance the statistical significance
of the Higgs signal in the di-photon channel.Comment: Additional reference included, 17 pages, 16 figure files, revte
Lepton Flavour Violating Leptonic/Semileptonic Decays of Charged Leptons in the Minimal Supersymmetric Standard Model
We consider the leptonic and semileptonic (SL) lepton flavour violating (LFV)
decays of the charged leptons in the minimal supersymmetric standard model
(MSSM). The formalism for evaluation of branching fractions for the SL LFV
charged-lepton decays with one or two pseudoscalar mesons, or one vector meson
in the final state, is given. Previous amplitudes for the SL LFV charged-lepton
decays in MSSM are improved, for instance the -penguin amplitude is
corrected to assure the gauge invariance. The decays are studied not only in
the model-independent formulation of the theory in the frame of MSSM, but also
within the frame of the minimal supersymmetric SO(10) model within which the
parameters of the MSSM are determined. The latter model gives predictions for
the neutrino-Dirac Yukawa coupling matrix, once free parameters in the model
are appropriately fixed to accommodate the recent neutrino oscillation data.
Using this unambiguous neutrino-Dirac Yukawa couplings, we calculate the LFV
leptonic and SL decay processes assuming the minimal supergravity scenario. A
very detailed numerical analysis is done to constrain the MSSM parameters.
Numerical results for SL LFV processes are given, for instance for tau -> e
(mu) pi0, tau -> e (mu) eta, tau -> e (mu) eta', tau -> e (mu) rho0, tau -> e
(mu) phi, tau -> e (mu) omega, etc.Comment: 36 pages, 3 tables, 5 .eps figure
- âŠ