194 research outputs found
Extending the Ehresmann-Schein-Nambooripad Theorem
We extend the `join-premorphisms' part of the Ehresmann-Schein-Nambooripad
Theorem to the case of two-sided restriction semigroups and inductive
categories, following on from a result of Lawson (1991) for the `morphisms'
part. However, it is so-called `meet-premorphisms' which have proved useful in
recent years in the study of partial actions. We therefore obtain an
Ehresmann-Schein-Nambooripad-type theorem for meet-premorphisms in the case of
two-sided restriction semigroups and inductive categories. As a corollary, we
obtain such a theorem in the inverse case.Comment: 23 pages; final section on Szendrei expansions removed; further
reordering of materia
Quantum Mirrors and Crossing Symmetry as Heart of Ghost Imaging
In this paper it is proved that the key to understanding the ghost imaging
mystery are the crossing symmetric photon reactions in the nonlinear media.
Hence, the laws of the plane quantum mirror (QM) and that of spherical quantum
mirror, observed in the ghost imaging experiments, are obtained as natural
consequences of the energy-momentum conservation laws. So, it is shown that the
ghost imaging laws depend only on the energy-momentum conservation and not on
the photons entanglement. The extension of these results to the ghost imaging
with other kind of light is discussed. Some fundamental experiments for a
decisive tests of the [SPDC-DFG]-quantum mirror are suggested.Comment: 11 pages, 9 figure
Scales of the Extra Dimensions and their Gravitational Wave Backgrounds
Circumstances are described in which symmetry breaking during the formation
of our three-dimensional brane within a higher-dimensional space in the early
universe excites mesoscopic classical radion or brane-displacement degrees of
freedom and produces a detectable stochastic background of gravitational
radiation. The spectrum of the background is related to the unification energy
scale and the the sizes and numbers of large extra dimensions. It is shown that
properties of the background observable by gravitational-wave observatories at
frequencies Hz to Hz contain information about
unification on energy scales from 1 to TeV, gravity propagating
through extra-dimension sizes from 1 mm to mm, and the dynamical
history and stabilization of from one to seven extra dimensions.Comment: 6 pages, Latex, 1 figure, submitted to Phys. Re
Comparison of text-messaging to voice telephone interviews for active surveillance of adverse events following immunisation
Objectives: In 2013, the Follow-up and Active Surveillance of Trivalent Influenza Vaccine in Mums (FASTMum) program began using short message service (SMS) to collect adverse event information in pregnant women who recently received trivalent influenza vaccine (TIV). This study was designed to compare data collected via SMS and telephone for the purposes of monitoring vaccine safety.
Methods: A number of 344 women who received TIV were randomly assigned to a telephone interview group. They were telephoned seven days post-vaccination and administered a standard survey soliciting any adverse events following immunisation (AEFI) they experienced. They were matched by brand of vaccine, age group, and residence to 344 women who were sent a SMS seven days post-vaccination. The SMS solicited similar information. AEFI reported by SMS and telephone interview were compared by calculating risk ratios.
Results: Response rate was higher to SMS compared to telephone interview (90.1% vs. 63.9%). Women who were surveyed by SMS were significantly less likely to report an AEFI compared to women who were surveyed by telephone (RR: 0.41; 95% CI: 0.29–0.59). The greatest discrepancies between SMS and telephone interview were for self-reported injection site reactions (3.1% vs. 16.8%) and unsolicited (or “other”) events (11.4% vs. 4.1%). Data collected by SMS was significantly timelier.
Conclusions: Data collection by SMS results in significantly improved response rates and timeliness of vaccine safety data. Systems which incorporate SMS could be used to more rapidly detect safety signals and promote more rapid public health response to vaccine quality issues
Cost effectiveness of thrombolytic therapy with tissue plasminogen activator as compared with streptokinase for acute myocardial infarction
BACKGROUND. Patients with acute myocardial infarction who were treated with accelerated tissue plasminogen activator (t-PA) (given over a period of 1 1/2 hours rather than the conventional 3 hours, and with two thirds of the dose given in the first 30 minutes) had a 30-day mortality that was 15 percent lower than that of pati
The Hyperfine Spin Splittings In Heavy Quarkonia
The hyperfine spin splittings in heavy quarkonia are studied using the
recently developed renormalization group improved spin-spin potential which is
independent of the scale parameter . The calculated energy difference
between the and the fits the experimental data well, while
the predicted energy difference between the center of the gravity
of states and the state of charmonium has the correct
sign but is somewhat larger than the experimental data. This is not surprising
since there are several other contributions to , which we discuss,
that are of comparable size ( MeV) that should be included, before
precise agreement with the data can be expected. The mass differences of the
, , , and
are also predicted.Comment: 17 page
Production of singlet P-wave and states
No spin-singlet quarkonium state has yet been observed. In this
paper we discuss the production of the singlet P-wave and
states and . We consider two possibilities. In the first the
states are produced via the electromagnetic cascades \ups(3S) \to
\eta_b(2S) + \gamma \to h_b + \gamma \gamma \to \eta_b +\gamma\gamma\gamma
and . A more promising process consists of single pion
transition to the state followed by the radiative transition to the
state: \ups(3S)\to h_b + \pi^0 \to \eta_b + \pi^0 +\gamma and . For a million \ups(3S) or
's produced we expect these processes to produce several hundred events.Comment: 13 pages, LaTeX, 1 figure, to be published Phys. Rev. D. Some
equation numbers and one table number correcte
Strong evidences of hadron acceleration in Tycho's Supernova Remnant
Very recent gamma-ray observations of G120.1+1.4 (Tycho's) supernova remnant
(SNR) by Fermi-LAT and VERITAS provided new fundamental pieces of information
for understanding particle acceleration and non-thermal emission in SNRs. We
want to outline a coherent description of Tycho's properties in terms of SNR
evolution, shock hydrodynamics and multi-wavelength emission by accounting for
particle acceleration at the forward shock via first order Fermi mechanism. We
adopt here a quick and reliable semi-analytical approach to non-linear
diffusive shock acceleration which includes magnetic field amplification due to
resonant streaming instability and the dynamical backreaction on the shock of
both cosmic rays (CRs) and self-generated magnetic turbulence. We find that
Tycho's forward shock is accelerating protons up to at least 500 TeV,
channelling into CRs about the 10 per cent of its kinetic energy. Moreover, the
CR-induced streaming instability is consistent with all the observational
evidences indicating a very efficient magnetic field amplification (up to ~300
micro Gauss). In such a strong magnetic field the velocity of the Alfv\'en
waves scattering CRs in the upstream is expected to be enhanced and to make
accelerated particles feel an effective compression factor lower than 4, in
turn leading to an energy spectrum steeper than the standard prediction
{\propto} E^-2. This latter effect is crucial to explain the GeV-to-TeV
gamma-ray spectrum as due to the decay of neutral pions produced in nuclear
collisions between accelerated nuclei and the background gas. The
self-consistency of such an hadronic scenario, along with the fact that the
concurrent leptonic mechanism cannot reproduce both the shape and the
normalization of the detected the gamma-ray emission, represents the first
clear and direct radiative evidence that hadron acceleration occurs efficiently
in young Galactic SNRs.Comment: Minor changes. Accepted for publication in Astronomy & Astrophysic
Particle acceleration mechanisms
We review the possible mechanisms for production of non-thermal electrons
which are responsible for non-thermal radiation in clusters of galaxies. Our
primary focus is on non-thermal Bremsstrahlung and inverse Compton scattering,
that produce hard X-ray emission. We briefly review acceleration mechanisms and
point out that in most astrophysical situations, and in particular for the
intracluster medium, shocks, turbulence and plasma waves play a crucial role.
We consider two scenarios for production of non-thermal radiation. The first is
hard X-ray emission due to non-thermal Bremsstrahlung by nonrelativistic
particles. Non-thermal tails are produced by accelerating electrons from the
background plasma with an initial Maxwellian distribution. However, these tails
are accompanied by significant heating and they are present for a short time of
<10^6 yr, which is also the time that the tail will be thermalised. Such
non-thermal tails, even if possible, can only explain the hard X-ray but not
the radio emission which needs GeV or higher energy electrons. For these and
for production of hard X-rays by the inverse Compton model, we need the second
scenario where there is injection and subsequent acceleration of relativistic
electrons. It is shown that a steady state situation, for example arising from
secondary electrons produced from cosmic ray proton scattering by background
protons, will most likely lead to flatter than required electron spectra or it
requires a short escape time of the electrons from the cluster. An episodic
injection of relativistic electrons, presumably from galaxies or AGN, and/or
episodic generation of turbulence and shocks by mergers can result in an
electron spectrum consistent with observations but for only a short period of
less than one billion years.Comment: 22 pages, 5 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 11; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
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