1,337 research outputs found
The replicative fitness of primary human immunodeficiency virus type 1 (HIV-1) group M, HIV-1 group O, and HIV-2 isolates
Filtenna Integration Achieving Ideal Chebyshev Return Losses
This paper demonstrates that it is possible to find an ideal filter response (Chebyshew, Butterworth,..) considering the antenna as the last resonator of a filter under certain circumstances related with the antenna performance and the bandwidth of the filtenna device. If these circumstances are not accomplished, we can achieve excellent performance as well, by means of an iterative process the goal of which is defined by either a filter mask or a classical filter function itself. The methodology is based on the conventional coupling matrix technique for filter design and has been validated by fabricating a microstrip prototype using hairpin resonators and a rectangular patch antenna
The Ellipse Law: Kirchhoff Meets Dislocations
In this paper we consider a nonlocal energy I \u3b1 whose kernel is obtained by adding to the Coulomb potential an anisotropic term weighted by a parameter \u3b1 08 R. The case \u3b1 = 0 corresponds to purely logarithmic interactions, minimised by the circle law; \u3b1 = 1 corresponds to the energy of interacting dislocations, minimised by the semi-circle law. We show that for \u3b1 08 (0 , 1) the minimiser is the normalised characteristic function of the domain enclosed by the ellipse of semi-axes 1-\u3b1 and 1+\u3b1. This result is one of the very few examples where the minimiser of a nonlocal anisotropic energy is explicitly computed. For the proof we borrow techniques from fluid dynamics, in particular those related to Kirchhoff\u2019s celebrated result that domains enclosed by ellipses are rotating vortex patches, called Kirchhoff ellipses
Top Quark Mass Calibration for Monte Carlo Event Generators -- An Update
We generalize and update our former top quark mass calibration framework for
Monte Carlo (MC) event generators based on the hadron-level
2-jettiness distribution in the resonance region for boosted
production, that was used to relate the PYTHIA 8.205 top mass parameter
to the MSR mass and the pole mass . The current most precise direct top mass measurements specifically
determine . The updated framework includes the addition of the
shape variables sum of jet masses and modified jet mass , and
the treatment of two more gap subtraction schemes to remove the renormalon related to large-angle soft radiation. These
generalizations entail implementing a more versatile shape-function fit
procedure and accounting for a certain type of power corrections to
achieve gap-scheme and observable independent results. The theoretical
description employs boosted heavy-quark effective theory (bHQET) at
next-to-next-to-logarithmic order (NLL), matched to soft-collinear
effective theory (SCET) at NLL and full QCD at next-to-leading order (NLO),
and includes the dominant top width effects. Furthermore, the software
framework has been modernized to use standard file and event record formats. We
update the top mass calibration results by applying the new framework to PYTHIA
8.205, HERWIG 7.2 and SHERPA 2.2.11. Even though the hadron-level resonance
positions produced by the three generators differ significantly for the same
top mass parameter value, the calibration shows that these
differences arise from the hadronization modeling. Indeed, we find that
agrees with m_t^{\rm MSR}(1\,\mbox{GeV}) within MeV for
the three generators and differs from the pole mass by to MeV.Comment: 70 pages, 15 figure
Searching for RR Lyrae stars in the Canis Major Overdensity
The Canis Major overdensity (CMa) was initially proposed to be the remnant of
a tidally disrupting dSph galaxy. Since its nature is still subject of debate,
the goal of the present work was to conduct a large-scale RR Lyrae survey in
CMa, in order to see if there is an overdensity of these stars. The survey
spans a total area of ~34 sq. deg. with observations in V and R filters, made
with the 1.0m Jurgen Stock Schmidt telescope at the National Astronomical
Observatory of Venezuela. Current results in a subregion, including
spectroscopic observations, show that the small number of RR Lyrae stars found
can be accounted for by the halo and thick disk components of our Galaxy.Comment: 2 pages, 1 figure, to appear in the proceedings of IAU Symposium
No241 "Stellar Populations as Building Blocks of Galaxies
Datos imprecisos y mapas de distribución: el ejemplo de Phylan semicostatus Mulsant y Rey, 1854 (Coleoptera, Tenebrionidae) en la Serra de Tramuntana (Mallorca, Mediterráneo occidental)
Distribution maps are key tools for environmental management and biogeographic analyses. However, success in predicting spatial distribution is limited when using noisy presence/absence data sets. Both false absences and presences can be related with local departures from equilibrium (for example, temporary extinctions or unsuccessful colonisations). Moreover, false absences can arise from limited sampling effort. Here we explore an analytical strategy to get additional information on the presence/absence pattern of one target species from the presence/absence of all other species in the community. The logic is simple: the target species should display higher probability of presence at a site if a sample from this site is faunistically very close to the samples from other sites where the species occurs. Therefore, we first model presence/absence of the target species as a function of between-sample faunistic similarity. Second, the observed data for the target species are readjusted as a function of the expected probability of presence: current presences at sites with extreme low probability of presence are interpreted as unstable presences, and are recoded as absences. Seemingly, absences at sites with high probability of presence are interpreted as false absences, and are recoded as presences. In the experimental case presented herein, the recoding procedure is based on the presence/absence of 174 species, covering a broad taxonomic scope (snails, beetles, spiders and isopods). 1 km2 distribution maps of presence/absence of the endemic beetle Phylan semicostatus were modelled from these recoded data. Mapping is done using GARP based on four environmental explanatory variables. These maps seem to be more stable and less prone to fail in predicting presence than those derived directly from the observed data.Los mapas de distribución son herramientas clave para la gestión medioambiental y los análisis biogeográficos. Pero el éxito en las predicciones de distribución espacial es limitado cuando se dispone de datos imprecisos de la presencia/ausencia. Tanto falsas ausencias como falsas presencias pueden estar relacionadas con desviaciones locales del equilibrio (por ejemplo, extinciones temporales o colonizaciones no exitosas). Además, las falsas ausencias pueden surgir de un esfuerzo de muestreo limitado. Aquí se explora una estrategia analítica para obtener información adicional sobre el patron de presencia/ausencia de una especie diana a partir de la presencia/ausencia de otras especies en la comunidad. La logica es simple: la especie diana debería tener una mayor probabilidad de presencia en un punto si una muestra de este punto es faunísticamente muy similar a las muestras de otros puntos donde la especie ha sido detectada. Por tanto, primeros se modela la presencia/ausencia de la especie diana en función de la similaridad faunística entre puntos. En segundo lugar, los datos observados para la especie diana son reajustados en función de la probabilidad esperada de presencia: las presencias observadas en puntos con probabilidad de presencia muy baja son interpretadas como presencias inestables, y recodificadas como ausencias. De manera similar, las ausencias en puntos con probabilidad de presencia muy elevada son interpretadas como falsas ausencias, y recodificadas como presencias. En el caso experimental estudiado, el procedimiento de recodificación esta basado en los datos de presencia/ausencia de 174 especies, abarcando un abanico taxonómico muy amplio (caracoles terrestres, coleópteros, arañas e isópodos). El mapa de distribución de celdas de 1 km2 del coleóptero endémico Phylan semicostatus es modelado a partir de estos datos. El mapa de distribución es elaborado a partir de cuatro variables medioambientales, usando una estrategia analítica basada en algoritmos genéticos (GARP). Los mapas obtenidos con los datos recodificados parecen ser mas estables y menos susceptibles de fallar en sus predicciones que los mapas elaborados directamente con los datos originales
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