Isotropically polarized speckle patterns

The polarization of the light scattered by an optically dense, random solution of dielectric nanoparticles shows peculiar properties when the scatterers exhibit strong electric and magnetic polarizabilities. While the distribution of the scattering intensity in these systems shows the typical irregular speckle patterns, the helicity of the incident light can be fully conserved when the electric and magnetic polarizabilities of the scatterers are equal. We show that the multiple scattering of helical beams by a random dispersion of "dual" dipolar nano-spheres leads to a speckle pattern exhibiting a perfect isotropic constant polarization, a situation that could be useful in coherent control of light as well as in lasing in random media.Comment: 5 pages, 3 figure

Prediction and prevention of the next pandemic zoonosis.

Most pandemics--eg, HIV/AIDS, severe acute respiratory syndrome, pandemic influenza--originate in animals, are caused by viruses, and are driven to emerge by ecological, behavioural, or socioeconomic changes. Despite their substantial effects on global public health and growing understanding of the process by which they emerge, no pandemic has been predicted before infecting human beings. We review what is known about the pathogens that emerge, the hosts that they originate in, and the factors that drive their emergence. We discuss challenges to their control and new efforts to predict pandemics, target surveillance to the most crucial interfaces, and identify prevention strategies. New mathematical modelling, diagnostic, communications, and informatics technologies can identify and report hitherto unknown microbes in other species, and thus new risk assessment approaches are needed to identify microbes most likely to cause human disease. We lay out a series of research and surveillance opportunities and goals that could help to overcome these challenges and move the global pandemic strategy from response to pre-emption

On Rationality

Rationality is an enduring topic of interest across the disciplines and has become even more so, given the current crises that are unfolding in our society. The four books reviewed here, which are written by academics working in economics, political science, political theory and philosophy, provide an interdisciplinary engagement with the idea of rationality and the way it has shaped the institutional frameworks and global political economy of our time. Rational choice theory has certainly proved to be a useful analytic tool in certain contexts, and instrumental reason has been a key tenet of human progress in several periods of history, including the industrial revolution and the modernity that emerged in the nineteenth century. Given the complexity of our current challenges, however, is it time to ask whether this paradigm might be better complemented by more holistic and heterodox approaches? Hindmoor A and Taylor TY (2015) Rational Choice (Political Analysis), 2nd edn. London; New York: Palgrave Macmillan. Massumi (2015) The Power at the End of the Economy. Durham: Duke University Press. Brown (2015) Undoing the Demos: Neoliberalism’s Stealth Revolution. New York: Zone Books. Ludovisi SG (ed.) (2015) Critical Theory and the Challenge of Praxis: Beyond Reification. Farnham; Burlington, VT: Ashgate

Prospects of Detecting Non-thermal Protons in Solar Flares via Lyman Line Spectroscopy: Revisiting the Orrall-Zirker Effect

Solar flares are efficient particle accelerators, with a substantial fraction of the energy released manifesting as non-thermal particles. While the role that non-thermal electrons play in transporting flare energy is well studied, the properties and importance of non-thermal protons is rather less well understood. This is in large part due to the paucity of diagnostics, particularly at the lower-energy (deka-keV) range of non-thermal proton distributions in flares. One means to identify the presence of deka-keV protons is by an effect originally described by \cite{1976ApJ...208..618O}. In the Orrall-Zirker effect, non-thermal protons interact with ambient neutral hydrogen, and via charge exchange produce a population of energetic neutral atoms (ENAs) in the chromosphere. These ENAs subsequently produce an extremely redshifted photon in the red wings of hydrogen spectral lines. We revisit predictions of the strength of this effect using modern interaction cross-sections, and numerical models capable of self-consistently simulating the flaring non-equilibrium ionization stratification, and the non-thermal proton distribution (and, crucially, their feedback on each other). We synthesize both the thermal and non-thermal emission from \lya\ and \lyb, the most promising lines that may exhibit a detectable signal. These new predictions are are weaker and more transient than prior estimates, but the effects should be detectable in fortuitous circumstances. We degrade the \lyb\ emission to the resolution of the Spectral Imaging of the Coronal Environment (SPICE) instrument on board Solar Orbiter, demonstrating that though likely difficult, it should be possible to detect the presence of non-thermal protons in flares observed by SPICE.Comment: Accepted for publication in The Astrophysical Journa

Abundancia relativa de la londra (Pteronura brasiliensis) en los ríos Blanco y San Martin (cuenca del río Iténez, Beni-Bolivia)

Pteronura brasiliensis es uno de los mamíferos acuáticos más amenazados del mundo. En Bolivia, alrededor de los años 80 se lo creía extinto y recientemente sus poblaciones se encuentran en un proceso lento de recuperación. En este trabajo, se estimaron las abundancias relativas y se calcularon las tasas de crecimiento de las poblaciones de londras de los ríos Blanco y San Martín entre los años 2004 y 2007. El río Blanco es un río sin muchos cuerpos de agua asociados y sus aguas son turbias, mientras que el río San Martín se caracteriza por una alta heterogeneidad de hábitats acuáticos y por sus aguas claras. Las abundancias relativas en los ríos San Martín y Blanco incrementaron en esos 3 años de 0.20 a 0.31 ind./km y de 0.00 a 0.06 ind./km, respectivamente. En ese mismo periodo, el número de individuos observados en el río San Martín aumentó de 34 a 55, agrupados en respectivamente 6 y 13 grupos familiares. La tasa de crecimiento en el río San Martín en este período fue de 6.33 londras/año. Esta población podría estar cercana a alcanzar su capacidad de carga y esto podría ser uno de los motivos para la paulatina recolonización del río Blanco por la especie.Pteronura brasiliensis é um dos mamíferos aquáticos mais ameaçados do mundo. Na Bolivia, por volta dos anos de 1980, acreditava-se em sua extingo, mas recentemente suas populações se encontram em um processo lento de recuperação. Neste trabalho, foram estimadas as abundáncias relativas e foram calculadas as taxas de crescimento das populações de ariranhas dos ríos Blanco e San Martín entre os anos 2004 e 2007. O rio Blanco é um rio sem muitos corpos de água associados e suas águas sao turvas, enquanto que o rio San Martín se caracteriza por urna alta heterogeneidade de habitats aquáticos e pour suas águas claras. As abundáncias relativas nos rios San Martín e Blanco aumentaram, durante esses tres anos, de 0,20 a 0,31 indivíduos/km e de 0,00 a 0,06 indivíduos/km, respectivamente. Nesse mesmo período, o número de individuos observados no rio San Martín aumentou de 34 a 55, agrupados em, respectivamente, 6 e 13 grupos familiares. A taxa de crescimento no rio San Martín neste período foi de 6,33 lontras/ano. Esta população poderia estar cerca de alcançar sua capacidade de suporte e isto poderia ser um dos motivos para a paulatina recolonização do rio Blanco pela espécie.Pteronura brasiliensis is one of the most threatened aquatic mammals in the world. In Bolivia the species was believed extinct in the 1980’s and recently populations have begun to show signs of recovery. In this study we estímate the relative abundances and the population growth rates of the giant otter populations in the San Martin and Blanco rivers between 2004 and 2007. The Rio Blanco is a river without important backwaters and with turbid water, whereas the Rio San Martin is characterized by its high habitat heterogeneity, wide floodplain and clear waters. The relative abundance of giant otters in the San Martin and Blanco rivers increased in those 3 years from 0.20 to 0.31 ind./km and from 0.00 to 0.06 ind./km, respectively. The number of individuais in the Rio San Martin increased from 34 to 55, distributed among 6 and 13 family groups respectively. The growth rate in the San Martin river was 6.33 individuals per year. We suppose that the giant otter populations in this river are close to carrying capacity, which may explain recolonization of the nearby Rio Blanco

Analysis of five-year trends in self-reported language preference and issues of item non-response among Hispanic persons in a large cross-sectional health survey: implications for the measurement of an ethnic minority population

<p>Abstract</p> <p>Background</p> <p>Significant differences in health outcomes have been documented among Hispanic persons, the fastest-growing demographic segment of the United States. The objective of this study was to examine trends in population growth and the collection of health data among Hispanic persons, including issues of language preference and survey completion using a national health survey to highlight issues of measurement of an increasingly important demographic segment of the United States.</p> <p>Design</p> <p>Data from the 2003-2007 United States Census and the Behavioral Risk Factor Surveillance System were used to compare trends in population growth and survey sample size as well as differences in survey response based on language preference among a Hispanic population. Percentages of item non-response on selected survey questions were compared for Hispanic respondents choosing to complete the survey in Spanish and those choosing to complete the survey in English. The mean number of attempts to complete the survey was also compared based on language preference among Hispanic respondents.</p> <p>Results</p> <p>The sample size of Hispanic persons in the Behavioral Risk Factor Surveillance System saw little growth compared to the actual growth of the Hispanic population in the United States. Significant differences in survey item non-response for nine of 15 survey questions were seen based on language preference. Hispanic respondents choosing to complete the survey in Spanish had a significantly fewer number of call attempts for survey completion compared to their Hispanic counterparts choosing to communicate in English.</p> <p>Conclusions</p> <p>Including additional measures of acculturation and increasing the sample size of Hispanic persons in a national health survey such as the Behavioral Risk Factor Surveillance System may result in more precise findings that could be used to better target prevention and health care needs for an ethnic minority population.</p