Fiebre amarilla y el cambio global: ¿existe una variante adicional además de la selvática y urbana?

La Fiebre amarilla es una infección viral endémica que afecta a los seres humanos y a primates no humanos en las regiones tropicales de los países de Sudamérica y gran parte del África subsahariana. Es causada por el virus de la fiebre amarilla (Yellow fever virus, YFV), un virus del género Flavivirus, de la familia Flaviviridae y es transmitida por artrópodos. El YFV es una causa importantede fiebre hemorrágica en todo el mundo, y se considera que ocurren aproximadamente 200.000 casos al año, el 90% de ellos en el Africa subsahariano. A partir de los '80 un dramático incremento de casos se observa tanto en el Africa como en América del Sur, reportándose aproximadamente 300 casos anuales en este continente. Sin embargo, se considera que las cifras reales son 10 a 50 veces mayores a los reportes oficiales. Además, personas que habitan en el mundo desarrollado y que viajan a áreas endémicas sin vacunación previa anti-fiebre amarilla pueden adquirir la infección.Universidad Nacional de La Plat

Fiebre amarilla y el cambio global: ¿existe una variante adicional además de la selvática y urbana?

La Fiebre amarilla es una infección viral endémica que afecta a los seres humanos y a primates no humanos en las regiones tropicales de los países de Sudamérica y gran parte del África subsahariana. Es causada por el virus de la fiebre amarilla (Yellow fever virus, YFV), un virus del género Flavivirus, de la familia Flaviviridae y es transmitida por artrópodos. El YFV es una causa importantede fiebre hemorrágica en todo el mundo, y se considera que ocurren aproximadamente 200.000 casos al año, el 90% de ellos en el Africa subsahariano. A partir de los '80 un dramático incremento de casos se observa tanto en el Africa como en América del Sur, reportándose aproximadamente 300 casos anuales en este continente. Sin embargo, se considera que las cifras reales son 10 a 50 veces mayores a los reportes oficiales. Además, personas que habitan en el mundo desarrollado y que viajan a áreas endémicas sin vacunación previa anti-fiebre amarilla pueden adquirir la infección.Universidad Nacional de La Plat

Note per la storia dell’estetica musicale

This article explores possible ways of conceiving the history of musical aes- thetics. The debate related to the notions of consonance and dissonance is used as an example to emphasise the necessity of taking into account and compare different sources and theoretical paradigms (from mathematics to physics, from music theory to acoustics, from perception theory to the history of ideas). The article also underlines the opportunity to base the historical reconstruction not only on solid contextual knowledge, but also on a reflection informed by a philosophical approach. The latter is necessary to face the the- oretical problems identified in the sources

Time-dependent density-functional theory approach to nonlinear particle-solid interactions in comparison with scattering theory

An explicit expression for the quadratic density-response function of a many-electron system is obtained in the framework of the time-dependent density-functional theory, in terms of the linear and quadratic density-response functions of noninteracting Kohn-Sham electrons and functional derivatives of the time-dependent exchange-correlation potential. This is used to evaluate the quadratic stopping power of a homogeneous electron gas for slow ions, which is demonstrated to be equivalent to that obtained up to second order in the ion charge in the framework of a fully nonlinear scattering approach. Numerical calculations are reported, thereby exploring the range of validity of quadratic-response theory.Comment: 14 pages, 3 figures. To appear in Journal of Physics: Condensed Matte

First-light LBT nulling interferometric observations: warm exozodiacal dust resolved within a few AU of eta Corvi

We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81 - 12.41 um) emission around the nearby main-sequence star eta Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% +/- 0.35% over a field-of-view of 140 mas in radius (~2.6\,AU at the distance of eta Corvi) and shows no significant variation over 35{\deg} of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by Spitzer/IRS (~23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the Solar zodiacal cloud, unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (~3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust at the distance where the insolation is the same as Earth's (2.3 AU).Comment: 9 pages, 6 figures, accepted for publication in Ap

The HOSTS Survey for Exozodiacal Dust: Preliminary results and future prospects

[abridged] The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed an N band nulling interferometric survey to determine the typical amount of such exozodiacal dust around a sample of nearby main sequence stars. The majority of our data have been analyzed and we present here an update of our ongoing work. We find seven new N band excesses in addition to the high confidence confirmation of three that were previously known. We find the first detections around Sun-like stars and around stars without previously known circumstellar dust. Our overall detection rate is 23%. The inferred occurrence rate is comparable for early type and Sun-like stars, but decreases from 71% [+11%/-20%] for stars with previously detected mid- to far-infrared excess to 11% [+9%/-4%] for stars without such excess, confirming earlier results at high confidence. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal luminosity function of the dust, we find upper limits on the median dust level around all stars without previously known mid to far infrared excess of 11.5 zodis at 95% confidence level. The corresponding upper limit for Sun-like stars is 16 zodis. An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a corresponding limit of 7.5 zodis. We provide important new insights into the occurrence rate and typical levels of habitable zone dust around main sequence stars. Exploiting the full range of capabilities of the LBTI provides a critical opportunity for the detailed characterization of a sample of exozodiacal dust disks to understand the origin, distribution, and properties of the dust.Comment: To appear in SPIE Astronomical Telescopes + Instrumentation 2018 proceedings. Some typos fixed, one reference adde

Testing the Distraction Hypothesis:do extrafloral nectaries reduce ant-pollinator conflict?

1. Ant guards protect plants from herbivores, but can also hinder pollination by damaging reproductive structures and/or repelling pollinators. Natural selection should favour the evolution of plant traits that deter ants from visiting flowers during anthesis, without waiving their defensive services. The Distraction Hypothesis posits that rewarding ants with extrafloral nectar could reduce their visitation of flowers, reducing ant-pollinator conflict while retaining protection of other structures. 2. We characterised the proportion of flowers occupied by ants and the number of ants per flower in a Mexican ant-plant, Turnera velutina. We clogged extrafloral nectaries on field plants and observed the effects on patrolling ants, pollinators and ants inside flowers, and quantified the effects on plant fitness. Based on the Distraction Hypothesis we predicted that preventing extrafloral nectar secretion should result in fewer ants active at extrafloral nectaries, more ants inside flowers and a higher proportion of flowers occupied by ants, leading to ant-pollinator conflict, with reduced pollinator visitation and reduced plant fitness. 3. Overall ant activity inside flowers was low. Preventing extrafloral nectar secretion through clogging reduced the number of ants patrolling extrafloral nectaries, significantly increased the proportion of flowers occupied by ants from 6.1% to 9.7%, and reduced plant reproductive output through a 12% increase in the probability of fruit abortion. No change in the numbers of ants or pollinators inside flowers was observed. This is the first support for the Distraction Hypothesis obtained under field conditions, showing ecological and plant fitness benefits of the distracting function of extrafloral nectar during anthesis. 4. Synthesis: Our study provides the first field experimental support for the Distraction Hypothesis, suggesting that extrafloral nectaries located close to flowers may bribe ants away from reproductive structures during the crucial pollination period, reducing the probability of ant-occupation of flowers, reducing ant-pollinator conflict, and increasing plant reproductive success

Vacuum decay in quantum field theory

We study the contribution to vacuum decay in field theory due to the interaction between the long and short-wavelength modes of the field. The field model considered consists of a scalar field of mass $M$ with a cubic term in the potential. The dynamics of the long-wavelength modes becomes diffusive in this interaction. The diffusive behaviour is described by the reduced Wigner function that characterizes the state of the long-wavelength modes. This function is obtained from the whole Wigner function by integration of the degrees of freedom of the short-wavelength modes. The dynamical equation for the reduced Wigner function becomes a kind of Fokker-Planck equation which is solved with suitable boundary conditions enforcing an initial metastable vacuum state trapped in the potential well. As a result a finite activation rate is found, even at zero temperature, for the formation of true vacuum bubbles of size $M^{-1}$. This effect makes a substantial contribution to the total decay rate.Comment: 27 pages, RevTeX, 1 figure (uses epsf.sty