1,920 research outputs found
Dark Matter in Universal Extra Dimension Models: vrs
We show that in a class of universal extra dimension models (UED), which
solves both the neutrino mass and proton decay problem, an admixture of KK
photon and KK right handed neutrinos can provide the required amount of cold
dark matter (CDM). This model has two parameters and ( is
the radius of the extra space dimensions and the extra neutral gauge boson
of the model). Using the value of the relic CDM density, combined with the
results from the cryogenic searches for CDM, we obtain upper limits on
of about 400-650 GeV and TeV, both being accessible to LHC. In
some regions of the parameter space, the dark matter-nucleon scattering cross
section can be as high as of cm, which can be probed by the next
round of dark matter search experiments.Comment: 13 pages, 2 figures; minor changes; to appear in Phys. Rev.
Unification requirements of electric vehicle charging infrastructure
By increasingelectric vehicles in numbers and getting the public attention, availability, safety and accessibility of its charging infrastructure are key factorsto users’ satisfaction. Charging infrastructure in electric vehicle industry can have a role as an interface for exchanging information among other components as well. Currently, lack of universality in electric vehicle industry has caused anisolation in networks of electric vehicles. This isolationwill cause difficulty in having an aggregated set of information about electric vehicles and their consumption pattern. The paper reviews current charging infrastructure and the possibility of providing universality based on candidate protocols and technologies. © 2016 Institute of Advanced Engineering and Science
Reconciling the CAST and PVLAS Results
The PVLAS experiment has recently claimed evidence for an axion-like particle
in the milli-electron-Volt mass range with a coupling to two photons that
appears to be in contradiction with the negative results of the CAST experiment
searching for solar axions. The simple axion interpretation of these two
experimental results is therefore untenable and it has posed a challenge for
theory. We propose a possible way to reconcile these two results by postulating
the existence of an ultralight pseudo-scalar particle interacting with two
photons and a scalar boson and the existence of a low scale phase transition in
the theory.Comment: 4 pages, 2 figures; references update
Year in review 2011: Critical Care – neurocritical care
Contributions from the neurosciences to Critical Care in 2011 covered an array of topics. We learned about potential biomarkers for, and the effect of cerebral oxygen metabolism on, delirium, in addition to treatment of the latter. A group of investigators studied surface cooling in healthy awake volunteers, and incidence of infection associated with therapeutic hypothermia. The effects of statin and erythropoietin on stroke were revisited, and the role of adhesion molecule in the inflammatory reaction accompanying intracerebral hemorrhage was scrutinized. Biomarkers in subarachnoid hemorrhage and their relationship to vasospasm and outcome, and effect of daylight on outcome in this patient population, as well as a new meta-analysis of statin therapy were among the research in subarachnoid hemorrhage. Moreover, 2011 witnessed the publication of a multidisciplinary consensus conference's recommendations on the critical care management of subarachnoid hemorrhage. Results of studies regarding the diagnosis and vascular complications of meningitis were reported. Traumatic brain injury received its share of articles addressing therapy with hypertonic saline and surgical decompression, the development of coagulopathy, and biomarkers to help with prognostication. Finally, research on the treatment of Guillain-Barre syndrome in children, prediction of long-term need of ventilatory support, and pathophysiology of critical illness polyneuropathy and myopathy were reported
An approach to permutation symmetry for the electroweak theory
The form of the leptonic mixing matrix emerging from experiment has, in the
last few years, generated a lot of interest in the so-called tribimaximal type.
This form may be naturally associated with the possibility of a discrete
permutation symmetry () among the three generations. However, trying to
implement this attractive symmetry has resulted in some problems and it seems
to have fallen out of favor. We suggest an approach in which the holds to
first approximation, somewhat in the manner of the old SU(3) flavor symmetry of
the three flavor quark model. It is shown that in the case of the neutrino
sector, a presently large experimentally allowed region can be fairly well
described in this first approximation.
We briefly discuss the nature of the perturbations which are the analogs of
the Gell-Mann Okubo perturbations but confine our attention for the most part
to the invariant model. We postulate that the invariant mass
spectrum consists of non zero masses for the and zero masses for
the other charged fermions but approximately degenerate masses for the three
neutrinos. The mixing matrices are assumed to be trivial for the charged
fermions but of tribimaximal type for the neutrinos in the first approximation.
It is shown that this can be implemented by allowing complex entries for the
mass matrix and spontaneous breakdown of the invariance of the
Lagrangian.Comment: 24 pages, 1 figure, minor corrections and acknowledgment added. To
appear in IJM
The Sensitivity of First Generation Epoch of Reionization Observatories and Their Potential for Differentiating Theoretical Power Spectra
Statistical observations of the epoch of reionization (EOR) power spectrum
provide a rich data set for understanding the transition from the cosmic "dark
ages" to the ionized universe we see today. EOR observations have become an
active area of experimental cosmology, and three first generation
observatories--MWA, PAST, and LOFAR--are currently under development. In this
paper we provide the first quantitative calculation of the three dimensional
power spectrum sensitivity, incorporating the design parameters of a planned
array. This calculation is then used to explore the constraints these first
generation observations can place on the EOR power spectrum. The results
demonstrate the potential of upcoming power spectrum observations to constrain
theories of structure formation and reionization.Comment: 7 pages with 5 figures. Submitted to Ap
Clinical review: Prevention and therapy of vasospasm in subarachnoid hemorrhage
Vasospasm is one of the leading causes of morbidity and mortality following aneurysmal subarachnoid hemorrhage (SAH). Radiographic vasospasm usually develops between 5 and 15 days after the initial hemorrhage, and is associated with clinically apparent delayed ischemic neurological deficits (DID) in one-third of patients. The pathophysiology of this reversible vasculopathy is not fully understood but appears to involve structural changes and biochemical alterations at the levels of the vascular endothelium and smooth muscle cells. Blood in the subarachnoid space is believed to trigger these changes. In addition, cerebral perfusion may be concurrently impaired by hypovolemia and impaired cerebral autoregulatory function. The combined effects of these processes can lead to reduction in cerebral blood flow so severe as to cause ischemia leading to infarction. Diagnosis is made by some combination of clinical, cerebral angiographic, and transcranial doppler ultrasonographic factors. Nimodipine, a calcium channel antagonist, is so far the only available therapy with proven benefit for reducing the impact of DID. Aggressive therapy combining hemodynamic augmentation, transluminal balloon angioplasty, and intra-arterial infusion of vasodilator drugs is, to varying degrees, usually implemented. A panoply of drugs, with different mechanisms of action, has been studied in SAH related vasospasm. Currently, the most promising are magnesium sulfate, 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors, nitric oxide donors and endothelin-1 antagonists. This paper reviews established and emerging therapies for vasospasm
- …