3,263 research outputs found
Interpolation of Non-abelian Lattice Gauge Fields
We propose a method for interpolating non-abelian lattice gauge fields to the
continuum, or to a finer lattice, which satisfies the properties of (i)
transverse continuity, (ii) (lattice) rotation and translation covariance,
(iii) gauge covariance, (iv) locality. These are the properties required for
use in our earlier proposal for non-perturbative formulation and simulation of
chiral gauge theories.Comment: A few typos corrected, a reference and a clarifying comment added. To
appear in Nuclear Physics B. 16 pages, LateX, 1 figure. This interpolation
scheme is intended for use in our formulation of lattice chiral gauge theory,
Nucl. Phys. B455 (1990) 287, hep-ph/950633
The SseC translocon component in Salmonella enterica serovar Typhimurium is chaperoned by SscA
Background: Salmonella enterica is a causative agent of foodborne gastroenteritis and the systemic disease known as typhoid fever. This bacterium uses two type three secretion systems (T3SSs) to translocate protein effectors into host cells to manipulate cellular function. Salmonella pathogenicity island (SPI)-2 encodes a T3SS required for intracellular survival of the pathogen. Genes in SPI-2 include apparatus components, secreted effectors and chaperones that bind to secreted cargo to coordinate their release from the bacterial cell. Although the effector repertoire secreted by the SPI-2 T3SS is large, only three virulence-associated chaperones have been characterized. Results: Here we report that SscA is the chaperone for the SseC translocon component. We show that SscA and SseC interact in bacterial cells and that deletion of sscA results in a loss of SseC secretion, which compromises intracellular replication and leads to a loss of competitive fitness in mice. Conclusions: This work completes the characterization of the chaperone complement within SPI-2 and identifies SscA as the chaperone for the SseC translocon
Tycho Brahe's supernova: light from centuries past
The light curve of SN 1572 is described in the terms used nowadays to
characterize SNeIa. By assembling the records of the observations done in
1572--74 and evaluating their uncertainties, it is possible to recover the
light curve and the color evolution of this supernova. It is found that, within
the SNe Ia family, the event should have been a SNIa with a normal rate of
decline, its stretch factor being {\it s} 0.9. Visual light curve near
maximum, late--time decline and the color evolution sustain this conclusion.
After correcting for extinction, the luminosity of this supernova is found to
be M --19.58 --5 log (D/3.5 kpc) 0.42.Comment: 28 pages, 3 figures, 3 tables. submitted to ApJ (Main Journal
The origin of the cosmic gamma-ray background in the MeV range
There has been much debate about the origin of the diffuse --ray
background in the MeV range. At lower energies, AGNs and Seyfert galaxies can
explain the background, but not above 0.3 MeV. Beyond 10 MeV
blazars appear to account for the flux observed. That leaves an unexplained gap
for which different candidates have been proposed, including annihilations of
WIMPS. One candidate are Type Ia supernovae (SNe Ia). Early studies concluded
that they were able to account for the --ray background in the gap,
while later work attributed a significantly lower contribution to them.
All those estimates were based on SN Ia explosion models which did not
reflect the full 3D hydrodynamics of SNe Ia explosions. In addition, new
measurements obtained since 2010 have provided new, direct estimates of high-z
SNe Ia rates beyond 2. We take into account these new advances to see
the predicted contribution to the gamma--ray background.
We use here a wide variety of explosion models and a plethora of new
measurements of SNe Ia rates. SNe Ia still fall short of the observed
background. Only for a fit, which would imply 150\% systematic error in
detecting SNe Ia events, do the theoretical predictions approach the observed
fluxes. This fit is, however, at odds at the highest redshifts with recent SN
Ia rates estimates. Other astrophysical sources such as FSRQs do match the
observed flux levels in the MeV regime, while SNe Ia make up to 30--50\% of the
observed flux.Comment: 40 pages, 13 Figures, accepted to be published in Ap
An algebraic approach to the prefix model analysis of binary trie structures and set intersection algorithms
AbstractThe trie, or digital tree, is a standard data structure for representing sets of strings over a given finite alphabet. Since Knuth's original work (1973), these data structures have been extensively studied and analyzed. In this paper, we present an algebraic approach to the analysis of average storage and average time required by the retrieval algorithms of trie structures under the prefix model. This approach extends the work of Flajolet et al. for other models which, unlike the prefix model, assume that no key in a sample set is the prefix of another. As the main application, we analyze the average running time of two algorithms for computing set intersections
The role of promotion tools used in the Spanish campaign to promote new lamb meat cuts
Aim of study: The first purpose of the present study was to investigate the level of recall of the adverting campaign promoting the new lamb meat cuts. The second objective was to investigate which promotion tools are more important to consumers and retailers.Area of study: This study took place in the city of Zaragoza, where lamb meat promotional activities have been conducted at three different levels: generic promotion of the sector, Regulatory Council of Ternasco de AragĂłn promotion campaign and producer brand promotion.Material and methods: Data was collected through personal questionnaires (401 consumers and 55 retailers).Main results: Results suggest that the promotion campaign has not contributed as much as expected to spread the knowledge of the new lamb cuts among consumers. Both consumers and retailers attached more importance to in-store marketing promotional tools. Three consumers segments were identified based on promotion tools preferences. Comparing between consumers and butchersâ opinion the only significant difference was found in using internet and social network as a promotional tool.Research highlights: A general trend has been observed since the majority of consumers and retailers consider that the most important promotions tools are those conducted inside the point of sale. On the view of these results, it could be better for future campaigns to increase promotional effort inside the point of sale, where consumers make their final purchase choice
Measurement of the Bs0-Bs0 oscillation frequency ÎŽms in Bs0âDs-(3)Ï decays
The Bs0-Bs0 oscillation frequency ÎŽms is measured with 36 pb-1 of data collected in pp collisions at s=7TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 Bs0âDs-Ï+ and Bs0âDs-Ï+Ï-Ï + signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6Ï is observed. The measured oscillation frequency is ÎŽm s=17.63±0.11(stat)±0.02(syst)ps -1
A New Lattice Action for Studying Topological Charge
We propose a new lattice action for non-abelian gauge theories, which will
reduce short-range lattice artifacts in the computation of the topological
susceptibility. The standard Wilson action is replaced by the Wilson action of
a gauge covariant interpolation of the original fields to a finer lattice. If
the latter is fine enough, the action of all configurations with non-zero
topological charge will satisfy the continuum bound. As a simpler example we
consider the -model in two dimensions, where a numerical
analysis of discretized continuum instantons indicates that a finer lattice
with half the lattice spacing of the original is enough to satisfy the
continuum bound.Comment: 12 pages, LateX, 1 figur
Movimientos verticales diarios de larvas de peces en estadĂo pre-flexiĂłn asociados a las praderas de Posidonia oceanica
Habitat complexity is a strong determinant of fish assemblage structure. Enhanced food resources and protection from predators are generally considered the main benefits of vegetated areas. We investigated the diel and vertical movements of preflexion fish larvae within and above the leaf canopy of Posidonia oceanica to determine if it acts as an important habitat for larval stage fish. Samples were taken with moored plankton nets during the night and day at two depths (13 and 15 m) over five consecutive days in July 2000 in the Marine Protected Area off Tabarca Island (Spain, SW Mediterranean Sea). In total, 353 fish larvae were captured. The most abundant taxa were Sardinella aurita, Sparidae, Engraulis encrasicolus and Gobiidae. Sparidae were more abundant within the leaf canopy during the day but increased in waters 2 m above the canopy at night. In contrast, Sardinella aurita were present throughout the entire water column during both the day and night. We conclude that the P. oceanica leaf canopy is important as a transitional shelter for the early stage larvae of some demersal fish species.El tipo de hĂĄbitat determina la estructura del poblamiento larvario de peces. Los principales beneficios que proporciona un hĂĄbitat con vegetaciĂłn son el incremento de las fuentes de alimento y una mayor protecciĂłn frente a los predadores. Este estudio se ha centrado en praderas de Posidonia oceanica para evaluar su papel como zonas de refugio, funciĂłn que ha sido poco estudiada. Este trabajo se ha llevado a cabo en la Reserva Marina de Tabarca (España, SW Mar MediterrĂĄneo). Las muestras se recolectaron con redes de plancton fijas en periodos diurnos y nocturnos, y a dos profundidades (13 y 15 m), durante 5 dĂas consecutivos en el mes de Julio de 2000. Se capturaron 353 larvas y 256 fueron identificadas. Los taxones mĂĄs abundantes fueron S. aurita, Sparidae, Engraulis encrasicolus y Gobiidae. Sparidae dominĂł al nivel de las hojas de la pradera durante el dĂa, incrementando su presencia en la columna de agua durante la noche; mientras que la S. aurita se encontrĂł a lo largo de toda la columna de agua en los dos periodos estudiados. Nuestro estudio confirma el papel de las praderas de P. oceanica como zona de refugio transitoria para los primeros estadios de larvas de de peces, aunque limitado a algunas especies demersales.
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