1,658 research outputs found
Streaming H.264 scalable video over data distribution service in a wireless environment
The Data Distribution Service (DDS) middleware is enjoying a rapid adoption in high-performance, mission-critical networks. At the same time, the H.264 Scalable Video Coding (SVC) has been recently standardized and it is deemed to be an effective solution for video streaming over a channel with time-varying bandwidth, like the wireless one. In these conditions, it is critical to adapt the video bit-rate to the actual wireless capacity, and bit-rate adaptation is extremely simple for a H.264 SVC video. In this paper we devise, evaluate and demonstrate a technique for streaming H.264 SVC video over a DDS middleware. The contribution is threefold: i) we design a structure of the DDS data-unit able to carry H.264 SVC video-units; ii) we devise a receiver-driven rate-control mechanism based on our DDS data-unit and exploiting specific DDS functionality; iii) we implement and show the effectiveness of our mechanism in an 802.11 wireless scenario, comparing our proposal with other solution
The MSW effect in a fluctuating matter density
We consider the effect on matter-enhanced neutrino flavor transformation of a
randomly fluctuating, delta-correlated matter density. The fluctuations will
produce a distribution of neutrino survival probabilities. We find the mean and
variance of the distribution for the case of solar neutrinos, and discuss the
possibility of placing a limit on solar density fluctuations using neutrino
data.Comment: 20 LaTeX pages plus 24 Postscript figures; submitted to Phys. Rev. D;
also available at http://nucth.physics.wisc.edu/preprints/mad-nt-96-01.tar.g
Shock Breakout in Core-Collapse Supernovae and its Neutrino Signature
(Abridged) We present results from dynamical models of core-collapse
supernovae in one spatial dimension, employing a newly-developed Boltzmann
neutrino radiation transport algorithm, coupled to Lagrangean hydrodynamics and
a consistent high-density nuclear equation of state. We focus on shock breakout
and its neutrino signature and follow the dynamical evolution of the cores of
11 M_sun, 15 M_sun, and 20 M_sun progenitors through collapse and the first 250
milliseconds after bounce. We examine the effects on the emergent neutrino
spectra, light curves, and mix of species of artificial opacity changes, the
number of energy groups, the weak magnetism/recoil corrections, nucleon-nucleon
bremsstrahlung, neutrino-electron scattering, and the compressibility of
nuclear matter. Furthermore, we present the first high-resolution look at the
angular distribution of the neutrino radiation field both in the
semi-transparent regime and at large radii and explore the accuracy with which
our tangent-ray method tracks the free propagation of a pulse of radiation in a
near vacuum. Finally, we fold the emergent neutrino spectra with the
efficiencies and detection processes for a selection of modern underground
neutrino observatories and argue that the prompt electron-neutrino breakout
burst from the next galactic supernova is in principle observable and usefully
diagnostic of fundamental collapse/supernova behavior. Though we are not in
this study focusing on the supernova mechanism per se, our simulations support
the theoretical conclusion (already reached by others) that spherical (1D)
supernovae do not explode when good physics and transport methods are employed.Comment: 16 emulateapj pages, plus 24 postscript figures, accepted to The
Astrophysical Journal; text revised; neutrino oscillation section expanded;
Fig. 22 correcte
Analysis of Italian isolates of Pantoea stewartii subsp. stewartii and development of a real-time PCR-based diagnostic method
Pantoea stewartii subsp. stewartii (Pss) causes Stewart's vascular wilt of maize, and it is responsible for serious crop losses. Pss is indigenous to North America and spreads with maize seeds. The presence of Pss has been notified in Italy since 2015. The risk assessment of the entry of Pss in the EU from the United States through seed trade is in the order of magnitude of hundred introductions per year. Several molecular or serological tests were developed for the detection of Pss and used as official analysis for the certification of commercial seeds. However, some of these tests lack adequate specificity, not allowing to correctly discriminate Pss from P. stewartii subsp. indologenes (Psi). Psi is occasionally present in maize seeds and is avirulent for maize. In this study, several Italian isolates of Pss recovered in 2015 and 2018 have been characterized by molecular, biochemical, and pathogenicity tests; moreover, their genomes have been assembled through MinION and Illumina-sequencing procedures. Genomic analysis reveals multiple introgression events. Exploiting these results, a new primer combination has been defined and verified by real-time PCR, allowing the development of a specific molecular test able to detect the presence of Pss down to the concentration of 103  CFU/ml in spiked samples of maize seed extracts. Due to the high analytical sensitivity and specificity achieved with this test, the detection of Pss has been improved disentangling the inconclusive results in Pss maize seed diagnosis, overcoming its misidentification in place of Psi. Altogether, this test addresses the critical issue associated with maize seeds imported from regions where Stewart's disease is endemic
Finite dimensional systems with random external fields and Neutrino propagation in fluctuating media
We develop the general formalism for the study of neutrino propagation in
presence of stochastic media. This formalism allows the systematic derivation
of evolution equations for averaged quantities as survival probabilities and
higher order distribution moments. The formalism applies equally to any finite
dimensional Schroedinger equation in presence of a stochastic external force.
New integro-differential equations valid for finite correlated processes are
obtained for the first time. For the particular case of exponentially
correlated processes a second order ordinary equation is obtained. As a
consequence, the Redfield equation valid for Gaussian delta-correlated noise is
rederived in a simple way. The formalism, together with the quantum correlation
theorem is applied to the computation of higher moments and correlation
functions of practical interest in forthcoming high precision neutrino
experiments. It is shown that equal and not equal time correlators follow
similar differential equations.Comment: 12 pags., Latex. 1 fig., ps. epsfig macro. minor typo errors
correcte
Resonant origin for density fluctuations deep within the Sun: helioseismology and magneto-gravity waves
We analyze helioseismic waves near the solar equator in the presence of
magnetic fields deep within the solar radiative zone. We find that reasonable
magnetic fields can significantly alter the shapes of the wave profiles for
helioseismic g-modes. They can do so because the existence of density gradients
allows g-modes to resonantly excite Alfven waves, causing mode energy to be
funnelled along magnetic field lines, away from the solar equatorial plane. The
resulting wave forms show comparatively sharp spikes in the density profile at
radii where these resonances take place. We estimate how big these waves might
be in the Sun, and perform a first search for observable consequences. We find
the density excursions at the resonances to be too narrow to be ruled out by
present-day analyses of p-wave helioseismic spectra, even if their amplitudes
were to be larger than a few percent. (In contrast it has been shown in
(Burgess et al. 2002) that such density excursions could affect solar neutrino
fluxes in an important way.) Because solar p-waves are not strongly influenced
by radiative-zone magnetic fields, standard analyses of helioseismic data
should not be significantly altered. The influence of the magnetic field on the
g-mode frequency spectrum could be used to probe sufficiently large
radiative-zone magnetic fields should solar g-modes ever be definitively
observed. Our results would have stronger implications if overstable solar
g-modes should prove to have very large amplitudes, as has sometimes been
argued.Comment: 18 pages, 6 figures; misprints correcte
Relativistic diffusion of elementary particles with spin
We obtain a generalization of the relativistic diffusion of Schay and Dudley
for particles with spin. The diffusion equation is a classical version of an
equation for the Wigner function of an elementary particle. The elementary
particle is described by a unitary irreducible representation of the Poincare
group realized in the Hilbert space of wave functions in the momentum space.
The arbitrariness of the Wigner rotation appears as a gauge freedom of the
diffusion equation. The spin is described as a connection of a fiber bundle
over the momentum hyperbolic space (the mass-shell). Motion in an
electromagnetic field, transport equations and equilibrium states are
discussed.Comment: 21 pages,minor changes,the version published in Journ.Phys.
Neutrino propagation in a random magnetic field
The active-sterile neutrino conversion probability is calculated for neutrino
propagating in a medium in the presence of random magnetic field fluctuations.
Necessary condition for the probability to be positive definite is obtained.
Using this necessary condition we put constraint on the neutrino magnetic
moment from active-sterile electron neutrino conversion in the early universe
hot plasma and in supernova.Comment: 11 page
Supernova Neutrino-Nucleus Astrophysics
In this brief review we explore the role of neutrino-nucleus interactions in
core-collapse supernovae and discuss open questions. In addition implications
of neutrino mass and mixings in such environments are summarized.Comment: Revtex 4 figure
Progress towards sustainable control of xylella fastidiosa subsp. Pauca in olive groves of salento (apulia, italy)
Xylella fastidiosa subsp. pauca is the causal agent of “olive quick decline syndrome” in Salento (Apulia, Italy). On April 2015, we started interdisciplinary studies to provide a sustainable control strategy for this pathogen that threatens the multi-millennial olive agroecosystem of Salento. Confocal laser scanning microscopy and fluorescence quantification showed that a zinc-copper-citric acid biocomplex—Dentamet® —reached the olive xylem tissue either after the spraying of the canopy or injection into the trunk, demonstrating its effective systemicity. The biocomplex showed in vitro bactericidal activity towards all X. fastidiosa subspecies. A mid-term evaluation of the control strategy performed in some olive groves of Salento indicated that this biocomplex significantly reduced both the symptoms and X. f. subsp. pauca cell concentration within the leaves of the local cultivars Ogliarola salentina and Cellina di Nardò. The treated trees started again to yield. A1 H-NMR metabolomic approach revealed, upon the treatments, a consistent increase in malic acid and γ-aminobutyrate for Ogliarola salentina and Cellina di Nardò trees, respectively. A novel endotherapy technique allowed injection of Dentamet® at low pressure directly into the vascular system of the tree and is currently under study for the promotion of resprouting in severely attacked trees. There are currently more than 700 ha of olive groves in Salento where this strategy is being applied to control X. f. subsp. pauca. These results collectively demonstrate an efficient, simple, low-cost, and environmentally sustainable strategy to control this pathogen in Salento
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