Approximate closed-form formulas for the zeros of the Bessel Polynomials

We find approximate expressions x(k,n) and y(k,n) for the real and imaginary parts of the kth zero z_k=x_k+i y_k of the Bessel polynomial y_n(x). To obtain these closed-form formulas we use the fact that the points of well-defined curves in the complex plane are limit points of the zeros of the normalized Bessel polynomials. Thus, these zeros are first computed numerically through an implementation of the electrostatic interpretation formulas and then, a fit to the real and imaginary parts as functions of k and n is obtained. It is shown that the resulting complex number x(k,n)+i y(k,n) is O(1/n^2)-convergent to z_k for fixed kComment: 9 pages, 2 figure

Fitting Effective Diffusion Models to Data Associated with a "Glassy Potential": Estimation, Classical Inference Procedures and Some Heuristics

A variety of researchers have successfully obtained the parameters of low dimensional diffusion models using the data that comes out of atomistic simulations. This naturally raises a variety of questions about efficient estimation, goodness-of-fit tests, and confidence interval estimation. The first part of this article uses maximum likelihood estimation to obtain the parameters of a diffusion model from a scalar time series. I address numerical issues associated with attempting to realize asymptotic statistics results with moderate sample sizes in the presence of exact and approximated transition densities. Approximate transition densities are used because the analytic solution of a transition density associated with a parametric diffusion model is often unknown.I am primarily interested in how well the deterministic transition density expansions of Ait-Sahalia capture the curvature of the transition density in (idealized) situations that occur when one carries out simulations in the presence of a "glassy" interaction potential. Accurate approximation of the curvature of the transition density is desirable because it can be used to quantify the goodness-of-fit of the model and to calculate asymptotic confidence intervals of the estimated parameters. The second part of this paper contributes a heuristic estimation technique for approximating a nonlinear diffusion model. A "global" nonlinear model is obtained by taking a batch of time series and applying simple local models to portions of the data. I demonstrate the technique on a diffusion model with a known transition density and on data generated by the Stochastic Simulation Algorithm.Comment: 30 pages 10 figures Submitted to SIAM MMS (typos removed and slightly shortened

Evaluating The Effect Of Water Supplementation On Ring-Necked Pheasant And Mesocarnivore Occupancy In Western Kansas

A “guzzler” is any structure that stores and supplements water for wildlife populations. They are often used to target economically influential game species where water is thought to be potentially limiting. Upland game, like the ring-necked pheasant (Phasianus colchicus) in the semi-arid landscape of western Kansas, represent such populations as guzzlers have become common practice in wildlife management applications across the region, especially on lands enrolled in the Conservation Reserve Program (CRP). However, little is known about the spatial response, if any, of wildlife populations to guzzlers or the potential increased risk they pose for predation. From June to August of 2011 and 2012 my project used occupancy modeling techniques to identify if guzzlers potentially influenced occupancy by Phasianus colchicus and their potential predators (i.e., mesocarnivores) on CRP lands in western Kansas. Phasianus colchicus detection was most explained by month of survey (highest in June; P \u3c 0.001), with occupancy being most influenced by distance from edge and percent forb cover at cameras, and land cover type at sites (camera data aggregated). For mesocarnivores, guzzler was the top performing habitat feature for explaining detection at cameras, but only raccoon (Procyon lotor) had guzzler best explain detection across sites as well. This suggested that increased predation near guzzlers, especially from an efficient nest predator like P. lotor, might be possible. While controlling for differences in detection, however, guzzlers did not perform well for explaining any target species occupancy. However, future studies are needed to truly evaluate this potential, as well as to assess the capacity for guzzlers to augment local population abundance, even if only during times of drought

SPITZER observations of the λ Orionis cluster. II. Disks around solar-type and low-mass stars

We present IRAC/MIPS Spitzer Space Telescope observations of the solar-type and the low-mass stellar population of the young (~5Myr) λ Orionis cluster. Combining optical and Two Micron All Sky Survey photometry, we identify 436 stars as probable members of the cluster. Given the distance (450 pc) and the age of the cluster, our sample ranges in mass from 2 M_⊙ to objects below the substellar limit. With the addition of the Spitzer mid-infrared data, we have identified 49 stars bearing disks in the stellar cluster. Using spectral energy distribution slopes, we place objects in several classes: non-excess stars (diskless), stars with optically thick disks, stars with “evolved disks” (with smaller excesses than optically thick disk systems), and “transitional disk” candidates (in which the inner disk is partially or fully cleared). The disk fraction depends on the stellar mass, ranging from ~6% for K-type stars (R_C − J 4). We confirm the dependence of disk fraction on stellar mass in this age range found in other studies. Regarding clustering levels, the overall fraction of disks in the λ Orionis cluster is similar to those reported in other stellar groups with ages normally quoted as ~5Myr

Searching for star-forming dwarf galaxies in the Antlia cluster

The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any H{\alpha} emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data.Comment: Accepted for publication in A&A (early 2014

Matrilineal Heritage in Southern Iberia Reveals Deep Genetic Links between Continents

Within the Mediterranean Basin, the Iberian Peninsula has been a focus of attraction for several cultures and civilizations from its prehistory and history, making it a target territory for studying human migration patterns and peopling processes using a wide and heterogeneous spectrum of genomic markers. While its Cantabrian fringe represents the most regularly analysed area in terms of its mitochondrial diversity, the absence of monographic surveys on the maternal genetic composition of southern Iberians (i.e., Andalusians) is striking. In this work, we present a comprehensive view of various aspects of the human maternal heritage of the autochthonous Andalusian population regarding specific mitochondrial haplogroups considered key candidates to determine the genetic relationship between Europe and Africa. Data reveal that southern Iberian populations do not have genetically homogeneous mitochondrial DNA profiles, and their observed genetic affinity with north-western African populations represents strong signals of old, sustained and bidirectional human movements between the northern and southern shores of the western Mediterranean. Thorough analyses of African mtDNA haplogroups have shown that the most relevant African contribution within Iberian Peninsula could be explained as a consequence of prehistoric events. The subsequent historic episodes helped to strengthen the ties between both shores. In southern Iberia, mitochondrial and other genetic markers show that the Strait of Gibraltar together with its surrounding maritime areas should be considered a bridge between continents. More broadly, the Mediterranean Sea has acted as a transport surface, that is, as a permeable barrier to human migrations from prehistoric and historic times. In conclusion, this research contributes to our knowledge of processes that have shaped the recent human genetic history in the Mediterranean and, more specifically, of the population dynamics that the inhabitants of southern Iberia have experienced with respect to other neighbouring North African populations

Evaluación del Proceso Consultivo Ciudadano en Villa el Salvador, Lima, Peru

El presente informe contiene un estudio de caso sobre “Evaluación del Proceso Consultivo Ciudadano en Villa el Salvador, Lima, Perú” realizado para el Instituto de Estudios de Vivienda y Desarrollo Urbano - IHS (Institute for Housing and Urban Development Studies) y el Programa SINPA (Support for the Implementation of National Plans of Action - Habitat II), que realiza estudios en varios países de América Latina sobre procesos de gestión urbana con el objetivo de apoyar a los gobiernos locales al mejoramiento de su gestión urbana. Una misión fue ejecutada por Rein Skinner supervisor del IHS y el trabajo fue realizado por Julio Calderón Cockburn, Consultor, como investigador local, y por la Arq. Liliana Marulanda como investigadora del IHS. Como lineamientos guía para el desarrollo de la investigación, el equipo local ha seguido los lineamientos del documento “Diseño de Investigación para los Procesos Consultivos" proporcionado por el IHS. El informe final se orienta en términos de contenidos, estructura y presentación por el documento “Review of the Lusaka City Consultation Process”, aunque se han efectuado algunas modificaciones atendiendo a la peculiaridad del caso de Villa El Salvador (VES). Las preguntas de investigación han sido las siguientes: ¿Cuáles son los resultados e impactos del proceso consultivo sobre la gobernanza urbana, la reducción de la pobreza y el medio ambiente urbano?; ¿ Qué lecciones pueden ser aprendidas de esas experiencias? Y ¿Cómo puede efectuarse un seguimiento de las acciones a ser recomendadas