880 research outputs found
Probing EWSB Naturalness in Unified SUSY Models with Dark Matter
We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the
context of two unified Supersymmetry scenarios: the Constrained Minimal
Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM),
in light of current and upcoming direct detection dark matter experiments. We
consider both those models that satisfy a one-sided bound on the relic density
of neutralinos, , and also the subset that satisfy
the two-sided bound in which the relic density is within the 2 sigma best fit
of WMAP7 + BAO + H0 data. We find that current direct detection searches for
dark matter probe the least fine-tuned regions of parameter-space, or
equivalently those of lowest Higgs mass parameter , and will tend to probe
progressively more and more fine-tuned models, though the trend is more
pronounced in the CMSSM than in the NUHM. Additionally, we examine several
subsets of model points, categorized by common mass hierarchies; M_{\chi_0}
\sim M_{\chi^\pm}, M_{\chi_0} \sim M_{\stau}, M_{\chi_0} \sim M_{\stop_1}, the
light and heavy Higgs poles, and any additional models classified as "other";
the relevance of these mass hierarchies is their connection to the preferred
neutralino annihilation channel that determines the relic abundance. For each
of these subsets of models we investigated the degree of fine-tuning and
discoverability in current and next generation direct detection experiments.Comment: 26 pages, 10 figures. v2: references added. v3: matches published
versio
Raf kinase activation of adenylyl cyclases: isoform-selective regulation
ABSTRACT Adenylyl cyclases (AC), a family of enzymes that catalyze the synthesis of cyclic AMP, are critical regulators of cellular functions. The activity of adenylyl cyclase is stimulated by a range of hormone receptors, primarily via interactions with G-proteins; however, recently we identified an alternate mechanism by which growth factors sensitize adenylyl cyclase activation. We suggested that this mechanism might involve a Raf kinasemediated serine phosphorylation of adenylyl cyclase. However, the direct involvement of a specific form of Raf kinase is yet to be demonstrated. Furthermore, whether this mechanism is generalized to other isoforms of adenylyl cyclase is unknown. In human embryonic kidney 293 cells, we now demonstrate that in reconstitution studies, c-Raf kinase can mediate phosphorylation of AC VI. Furthermore, AC VI coimmunoprecipitates with c-Raf. Raf kinase-dependent regulation of adenylyl cyclase VI is dependent on the integrity of Ser750 in the fourth intracellular loop of the enzyme and Ser603/Ser608 in the C1b region of the molecule. To examine how generalized this effect is, we studied representative isoforms of the major subfamilies of adenylyl cyclase viz., AC I, AC II, and AC V. Raf kinase-dependent sensitization/ phosphorylation of adenylyl cyclases is common to AC VI, AC V, and AC II isoforms but not AC I. In aggregate, these studies indicate that Raf kinase associates with adenylyl cyclases. Furthermore, Raf kinase regulation of adenylyl cyclase is isoform-selective. These functional interactions (as well as the physical association) between adenylyl cyclases and Raf kinases suggest an important but previously unrecognized interaction between these two key regulatory enzymes
Semiclassical Effects and the Onset of Inflation
We present a class of exact solutions to the constraint equations of General
Relativity coupled to a Klein - Gordon field, these solutions being isotropic
but not homogeneous. We analyze the subsequent evolution of the consistent
Cauchy data represented by those solutions, showing that only certain special
initial conditions eventually lead to successfull Inflationary cosmologies. We
argue, however, that these initial conditions are precisely the likely outcomes
of quantum events occurred before the inflationary era.Comment: 22 pages, file written in RevTe
Improved Experimental Limits on the Production of Magnetic Monopoles
We present new limits on low mass accelerator-produced point-like Dirac
magnetic monopoles trapped and bound in matter surrounding the D\O collision
region of the Tevatron at Fermilab (experiment E-882). In the context of a
Drell-Yan mechanism, we obtain cross section limits for the production of
monopoles with magnetic charge values of 1, 2, 3, and 6 times the minimum Dirac
charge of the order of picobarns, some hundred times smaller than found in
similar previous Fermilab searches. Mass limits inferred from these cross
section limits are presented.Comment: 5 pages, 4 eps figures, REVTe
Increased Blood Pressure and Hyperdynamic Cardiovascular Responses in Carriers of a Common Hyperfunctional Variant of Adenylyl Cyclase 6
ABSTRACT Adenylyl cyclase (ADCY) is a critical regulator of metabolic and cardiovascular function. We have identified a genetic variant (A674S) in ADCY isoform 6 (ADCY6). Subsequent studies demonstrated that the expression of this ADCY6 variant paralleled an increase in adenylyl cyclase-mediated functions. However, the impact of this hyperfunctional variant on cardiovascular function is unknown. Therefore, we evaluated the hemodynamic profile of carriers of ADCY6 A674S. The association of ADCY6 A674S with anthropometric and hemodynamic parameters was assessed in 364 healthy white subjects. The allele encoding this variant was present in 6.9% of the subjects, and those individuals had increased blood pressure. To determine the hemodynamic basis for increased blood pressure in carriers of ADCY6 A674S, we assessed forearm blood flow (FBF) and cardiac output at rest, during handgrip exercise (to test vasodilator responsiveness), and with lower body negative pressure [to test forearm vasoconstrictor and heart rate (HR) responsiveness] in a subsample of 21 subjects. At rest, cardiac output and blood pressure were higher in carriers of ADCY6 A674S. This was paralleled by an increase in plasma renin activity, but not in plasma norepinephrine. During handgrip exercise, FBF and vasodilator responses were greater in carriers of ADCY6 A674S. Responses to reactive hyperemia were not different between genotypes. With lower body negative pressure, the HR response to this orthostatic stress was markedly higher in carriers of ADCY6 A674S. These data indicate that the relatively common hyperfunctional ADCY6 A674S variant underlies a hyperdynamic cardiovascular response and increased blood pressure
Hypertension in Canada: Past, Present, and Future
Canada has an extremely successful hypertension detection and treatment program. The aim of this review was to highlight the historic and current infrastructure and initiatives that have led to this success, and the outlook moving forward into the future. We discuss the evolution of hypertension awareness and control in Canada; contributions made by organizations such as the Canadian Hypertension Society, Blood Pressure Canada, and the Canadian Hypertension Education Program; the amalgamation of these organizations into Hypertension Canada; and the impact that Hypertension Canada has had on hypertension care in Canada. The important contribution that public policy and advocacy can have on prevention and control of blood pressure in Canada is described. We also highlight the importance of population-based strategies, health care access and organization, and accurate blood pressure measurement (including ambulatory, home, and automated office modalities) in optimizing hypertension prevention and management. We end by discussing how Hypertension Canada will move forward in the near and longer term to address the unmet residual risk attributable to hypertension and associated cardiovascular risk factors. Hypertension Canada will continue to strive to enhance hypertension prevention and control rates, thereby improving the quality of life and cardiovascular outcomes of Canadians, while at the same time creating a hypertension care model that can be emulated across the world
Tuning supersymmetric models at the LHC: A comparative analysis at two-loop level
We provide a comparative study of the fine tuning amount (Delta) at the
two-loop leading log level in supersymmetric models commonly used in SUSY
searches at the LHC. These are the constrained MSSM (CMSSM), non-universal
Higgs masses models (NUHM1, NUHM2), non-universal gaugino masses model (NUGM)
and GUT related gaugino masses models (NUGMd). Two definitions of the fine
tuning are used, the first (Delta_{max}) measures maximal fine-tuning wrt
individual parameters while the second (Delta_q) adds their contribution in
"quadrature". As a direct result of two theoretical constraints (the EW minimum
conditions), fine tuning (Delta_q) emerges as a suppressing factor (effective
prior) of the averaged likelihood (under the priors), under the integral of the
global probability of measuring the data (Bayesian evidence p(D)). For each
model, there is little difference between Delta_q, Delta_{max} in the region
allowed by the data, with similar behaviour as functions of the Higgs, gluino,
stop mass or SUSY scale (m_{susy}=(m_{\tilde t_1} m_{\tilde t_2})^{1/2}) or
dark matter and g-2 constraints. The analysis has the advantage that by
replacing any of these mass scales or constraints by their latest bounds one
easily infers for each model the value of Delta_q, Delta_{max} or vice versa.
For all models, minimal fine tuning is achieved for M_{higgs} near 115 GeV with
a Delta_q\approx Delta_{max}\approx 10 to 100 depending on the model, and in
the CMSSM this is actually a global minimum. Due to a strong (
exponential) dependence of Delta on M_{higgs}, for a Higgs mass near 125 GeV,
the above values of Delta_q\approx Delta_{max} increase to between 500 and
1000. Possible corrections to these values are briefly discussed.Comment: 23 pages, 46 figures; references added; some clarifications (section
2
New Constraints (and Motivations) for Abelian Gauge Bosons in the MeV-TeV Mass Range
We survey the phenomenological constraints on abelian gauge bosons having
masses in the MeV to multi-GeV mass range (using precision electroweak
measurements, neutrino-electron and neutrino-nucleon scattering, electron and
muon anomalous magnetic moments, upsilon decay, beam dump experiments, atomic
parity violation, low-energy neutron scattering and primordial
nucleosynthesis). We compute their implications for the three parameters that
in general describe the low-energy properties of such bosons: their mass and
their two possible types of dimensionless couplings (direct couplings to
ordinary fermions and kinetic mixing with Standard Model hypercharge). We argue
that gauge bosons with very small couplings to ordinary fermions in this mass
range are natural in string compactifications and are likely to be generic in
theories for which the gravity scale is systematically smaller than the Planck
mass - such as in extra-dimensional models - because of the necessity to
suppress proton decay. Furthermore, because its couplings are weak, in the
low-energy theory relevant to experiments at and below TeV scales the charge
gauged by the new boson can appear to be broken, both by classical effects and
by anomalies. In particular, if the new gauge charge appears to be anomalous,
anomaly cancellation does not also require the introduction of new light
fermions in the low-energy theory. Furthermore, the charge can appear to be
conserved in the low-energy theory, despite the corresponding gauge boson
having a mass. Our results reduce to those of other authors in the special
cases where there is no kinetic mixing or there is no direct coupling to
ordinary fermions, such as for recently proposed dark-matter scenarios.Comment: 49 pages + appendix, 21 figures. This is the final version which
appears in JHE
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