2,027 research outputs found
Aspects of Neutrino Mass Matrices
After an Introduction briefly describing the rise and fall of the three-zero
texture of the Zee model, we discuss still-allowed two-zero textures for the
Majorana three-neutrino mass matrix. Finally, a model with two right-handed
neutrinos and two Dirac texture zeros is described (FGY model) which can relate
CP violation in leptogenesis to CP violation in long-baseline neutrino
oscillations.Comment: 9 pages latex. Talk at Coral Gables 2003. Added reference
Structure of Equilenin at 100â K: an estrone-related steroid
The structure of the estrone-related steroid, Equilenin, C18H18O2 (systematic name 3-hy-droxy-13-methyl-11,12,13,14,15,16-hexa-hydro-cyclo-penta-[a]phen-anthren-17-one), has been determined at 100â
K. The crystals are ortho-rhom-bic, P212121, and the absolute structure of the mol-ecule in the crystal has been determined by resonant scattering [Flack parameter = -0.05â
(4)]. The C atoms of the A and B rings are almost coplanar, with an r.m.s. deviation from planarity of 0.0104â
Ă
. The C ring has a sofa conformation, while the D ring has an envelope conformation with the methine C atom as the flap. The keto O atom and the methyl group are translated 0.78 and 0.79â
Ă
, respectively, from the equivalent positions on 17ÎČ-estrone. In the crystal, mol-ecules are linked by O-HâŻO hydrogen bonds, forming chains parallel to the c-axis direction
Smart double panel with decentralised active dampers for control of sound transmission
This report presents the results of a theoretical study of active sound transmission control through a double panel. The double panel material and geometrical properties have been chosen so as to emulate section of an aircraft fuselage, or bodywork of a vehicle. It consists of two plates: an aluminium plate simply supported along all the edges and a honeycomb plate with all the edges free. The two plates, having the same length and width, are connected using elastic mounts, so that a double panel with a thin rectangular cavity between the plates is formed. Since the two plates are linked by the mounting system, and since the air is confined in the cavity between them, they form a structurally and acoustically coupled system. The sound transmission properties of the system are studied in such a way that the aluminium plate (âsource panelâ) is excited using a plane acoustic wave, while the honeycomb plate (âradiating panelâ) radiates sound into free field.The aim of the active control is to reduce the sound transmitted in a broad frequency band, but with a particular focus on the reduction of the sound transmission at lower frequencies of the band. Decentralised velocity feedback control systems (applying active damping) are implemented, with purpose of reducing sound transmission at resonance frequencies. Control sensors and actuators are embedded into the double plate system as a regular array, so that a smart double panel is created. The theoretical study includes analysis of the passive sound transmission in terms of a parametric study, implementation of the active control using skyhook velocity sensors and skyhook force actuators, and the performance/stability analysis in case when reactive actuators and skyhook velocity sensors are used. In the latter case the actuating force is obtained using actuators located in the air cavity which can react off the two plate
Constraints on Deflation from the Equation of State of Dark Energy
In cyclic cosmology based on phantom dark energy the requirement that our
universe satisfy a CBE-condition ({\it Comes Back Empty}) imposes a lower bound
on the number of causal patches which separate just prior to
turnaround. This bound depends on the dark energy equation of state with . More accurate measurement of will
constrain . The critical density in the model has a lower
bound or
when the smallest bound state has size m, or m,
respectively.Comment: 23 pages, 3 figures, typos fixe
In Adult Patients With PC-BPPV, Is the Semont Maneuver Effective in Reducing Symptoms of Vertigo?
OBJECTIVE: The objective of this selective EBM review is to determine whether or not in adult patients with PC-BPPV, is the Semont Maneuver effective in reducing symptoms of vertigo?
STUDY DESIGN: Review of three published, randomized controlled trials (two double-blind and one single blinded), all English language.
DATA SOURCES: The three randomized controlled trials that were used for this review were found using PubMed and Medline. Articles were selected based on relevance and that the outcomes were patient oriented.
OUTCOME(S) MEASURED: Dix-Hallpike Test performed before and after the Semont Maneuver to asses nystagmus and questionnaires/self reported symptom status after the Semont Maneuver to asses resolution of vertigo.
RESULTS: Mandala et al. and Chen et al. compared the Semont Maneuver to a Sham treatment. Salvinelli et al. compared the Semont Maneuver to a no treatment group. All three studies demonstrated statistically significant improvement in patientâs vertigo after receiving the Semont Maneuver compared to other treatment strategies. Salvinelli et al. demonstrated that cure rates with the Semont Maneuver (94.2%) were significantly higher and more effective than the no treatment group (35.4%). Mandala et al. determined that at the 1 hr and 24 hr follow up, 79.3% and 86.8% of subjects undergoing the Semont Maneuver recovered from vertigo, respectively. Chen et al. concluded that on the fourth day, 84.62% of patients being treated with the Semont Maneuver showed complete resolution of vertigo symptoms compared to 14.29% of patients receiving Sham treatment.
CONCLUSIONS: The results of these three randomized controlled trials suggest that the Semont Maneuver is a safe, easily performed, and effective treatment modality for patients with PCBPPV
3-3-1 exotic quark search at CERN LEPII-LHC
The 3-3-1 electroweak model is the simplest chiral extension of the standard
model which predicts single and double charged bileptons and exotic quarks
carrying -4/3 and 5/3 units of the positron charge. In this paper we study the
possibilities of the production and decay of one of these exotic quarks at CERN
LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing
angles we obtained between 20 and 750 events per year. Angular distributions
are also presented.Comment: 5 pages, RevTex 3.1, 9 eps figures, to appear in Phys. Rev.
White holes and eternal black holes
We investigate isolated white holes surrounded by vacuum, which correspond to
the time reversal of eternal black holes that do not evaporate. We show that
isolated white holes produce quasi- thermal Hawking radiation. The time
reversal of this radiation, incident on a black hole precursor, constitutes a
special preparation that will cause the black hole to become eternal.Comment: 5 pages, 2 figures, revtex; revised version to appear in Classical
and Quantum Gravit
Primordial Black Holes, Hawking Radiation and the Early Universe
The 511 keV gamma emission from the galactic core may originate from a high
concentration () of primordial black holes (PBHs) in the core
each of whose Hawking radiation includes positrons per second.
The PBHs we consider are taken as near the lightest with longevity greater than
the age of the universe (mass kg; Schwarzschild radius
fm). These PBHs contribute only a small fraction of cold dark matter,
. This speculative hypothesis, if confirmed implies
the simultaneous discovery of Hawking radiation and an early universe phase
transition.Comment: 4 Page
Search for Heavy Leptons at Hadron Colliders
Four models are considered which contain heavy leptons beyond the three
families of the standard model. Two are fourth-generation extensions of the
standard model in which the right-handed heavy leptons are either isosinglets
or in an isodoublet; the other two are motivated by the aspon model of CP
violation. In all these models, the heavy neutrino can either be heavier than,
or comparable in mass to, the charged lepton leading to the possibility that
the charged lepton is very long-lived. Production cross section and signatures
for the heavy leptons are computed for the SSC and LHC.Comment: 17 pages(8 figures are not included),TRI-PP-92-9
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