A square-well model for the structural and thermodynamic properties of simple colloidal systems

A model for the radial distribution function $g(r)$ of a square-well fluid of variable width previously proposed [S. B. Yuste and A. Santos, J. Chem. Phys. {\bf 101}, 2355 (1994)] is revisited and simplified. The model provides an explicit expression for the Laplace transform of $rg(r)$, the coefficients being given as explicit functions of the density, the temperature, and the interaction range. In the limits corresponding to hard spheres and sticky hard spheres the model reduces to the analytical solutions of the Percus-Yevick equation for those potentials. The results can be useful to describe in a fully analytical way the structural and thermodynamic behavior of colloidal suspensions modeled as hard-core particles with a short-range attraction. Comparison with computer simulation data shows a general good agreement, even for relatively wide wells.Comment: 23 pages, 10 figures; Figs. 4 and 5 changed, Fig. 6 new; to be published in J. Chem. Phy

Influence of Secondary Offerings on the Liquidity and Trading Activity of Stocks Outstanding

This paper examines the influence of secondary offerings (SOs) on the liquidity and trading activity of stocks outstanding. The results reveal that liquidity and trading activity increase after the execution of SOs. We observe that the offering discount is explained by the size of the offering and its retail composition. We have also shown that changes in liquidity and trading activity are explained by the retail composition of the offering, such that the choice of ownership structure is decisive in the level of liquidity afforded by SOs. The offering discount is one of the chosen methods of attracting small-scale investors and promoting share liquidity following these operations.secondary offerings (SOs), liquidity, trading activity, microstructure, capital structure

Heat capacity of square-well fluids of variable width

We have obtained by Monte Carlo NVT simulations the constant-volume excess heat capacity of square-well fluids for several temperatures, densities and potential widths. Heat capacity is a thermodynamic property much more sensitive to the accuracy of a theory than other thermodynamic quantities, such as the compressibility factor. This is illustrated by comparing the reported simulation data for the heat capacity with the theoretical predictions given by the Barker-Henderson perturbation theory as well as with those given by a non-perturbative theoretical model based on Baxter's solution of the Percus-Yevick integral equation for sticky hard spheres. Both theories give accurate predictions for the equation of state. By contrast, it is found that the Barker-Henderson theory strongly underestimates the excess heat capacity for low to moderate temperatures, whereas a much better agreement between theory and simulation is achieved with the non-perturbative theoretical model, particularly for small well widths, although the accuracy of the latter worsens for high densities and low temperatures, as the well width increases.Comment: 11 pages, 4 figures; figures now include additional perturbation data; to be published in Mol. Phy

Observaciones sobre el género Carex en la provincia de León (NW España)

Para completar el catálogo caricológico de la provincia de León (NW España) se incorporan cinco táxones del género Carex (C. diandra, C. muricata subsp. muricata, C. guestphalica, C. umbrosa subsp. umbrosa y C. depressa subsp. depressa) y se eliminan seis (C. paniculata subsp. paniculata, C. vulpina, C. stenophylla, C. hispida, C. puntacta y C. flava) anteriormente citados. También se realizan observaciones sobre ocho especies más, indicando segundas o terceras citas, y concretando su área de distribución. En todos los casos se indica, además del hábitat y el comportamiento fitosociológico, el estado de conservación y, cuando es necesario, se aportan caracteres diagnósticos morfológicos y anatómicos para su correcta identificación. Finalmente, se realiza una valoración de la presencia de los Carex en la provincia.In order to complete and correct the sedges checklist of León province in NW Spain, five new taxa are reported (Carex diandra, C. muricata subsp. muricata, C. guestphalica, C. umbrosa subsp. umbrosa and C. depressa subsp. depressa). Six taxa previously reported are removed from the León checklist (C. paniculata subsp. paniculata, C. vulpina, C. stenophylla, C. hispida, C. puntacta y C. flava). Some comments helping to know the distribution of other very scarce eight species in this area are made. For all of the nineteen taxa, we make some considerations about the habitat, point out the phytosociological behavior, the conservation state, and when necessary, we give some diagnostic characters. Finally, an assessment of the presence of all the sedges living in León province is made

G1430 Using the Sugar Roll Technique to Detect Varroa Mites in Honey Bee Colonies

Description of a rapid and efficient technique for detecting and assessing varroa mite infestations using powdered sugar to dislodge mites from bees. The varroa mite was first discovered in the United States in 1987. Globally, it is the most important pest of honey bees and it has caused extensive losses in feral and managed colonies. Once introduced, varroa mites have never been eradicated from any country or region, and beekeepers must adopt an integrated pest management strategy to protect their colonies. Early detection and assessment of infestation levels are important components of a varroa management plan. Since varroa mites feed by piercing the intersegmental membranes on the underside of the bee\u27s abdomen, they are not easily observed on bees until colonies are severely injured. Beekeepers need to use a detection technique to check their colonies for mites. In addition to detecting mites, beekeepers need to accurately assess the infestation level to determine when control measures are warranted. Topics covered include: 1) comparing inert dusts for detecting and assessing varroa mite infestations; 2) using powdered sugar to detect and assess varroa mite infestations; 3) why dust-like materials dislodge varroa mites from bees; and 4)interpreting the results of sugar roll testing

La reacción frente a una crisis generalizada: Un enfoque teórico al consumo de recursos en las empresas familiares

Research to date has shown that companies can accumulate resources over those strictly needed in order to overcome the uncertainty associated to a crisis. But the usage, redeployment, or consumption of this excess of resources when facing an adverse environment is yet underexplored. As suggested by the literature, the condition of family business can exert an important effect in such behaviour. This paper proposes a theoretical framework, focused on family business, about how firms manage the different slack resources when facing a general crisis. We make a call on family business scholars to leverage our propositions and the existing literature on slack resources to develop a guidance for family owners when facing an economic downturn.Las investigaciones realizadas hasta la fecha han demostrado que las empresas pueden acumular recursos por encima de los estrictamente necesarios para superar la incertidumbre asociada a una crisis. Pero la utilización, redistribución o consumo de este exceso de recursos cuando se enfrentan a un entorno adverso está todavía poco explorada. Como sugiere la literatura, la condición de empresa familiar puede ejercer un efecto importante en dicho comportamiento. Este trabajo propone un marco teórico, centrado en la empresa familiar, sobre cómo las empresas gestionan los diferentes recursos slack cuando se enfrentan a una crisis. En este sentido, se plantea la necesidad de que los investigadores en el campo de la empresa familiar aprovechen nuestras propuestas, y la literatura existente sobre los recursos slack, para desarrollar una guía que facilite la toma de decisiones en las empresas familiares cuando se enfrentan a una recesión económica

Cartografía detallada y catalogación de Draba Hispanica subsp. Lebrunii P. Monts

Draba hispanica subsp. lebrunii P. Monts. es un endemismo ibérico exclusivo de la Sierra de la Peña (Parque Regional Fuentes Carrionas y Fuente CobreMontaña Palentina). Por presentar una reducida distribución, se catalogó Vulnerable para España, pero tras la revisión para la Lista Roja 2008, resultó En Peligro. En Castilla y León, donde viven sus efectivos, está protegida (anexo II, Decreto de Flora Protegida 63/2007). Para el desarrollo de AFA4, fue seleccionado en el subproyecto piloto “Cartografía detallada de las poblaciones de fl ora vascular amenazada”. Se realizó un seguimiento minucioso en toda el área de distribución, y se censaron todas las poblaciones conocidas. La prospección de los hábitats semejantes resultó en la localización de cuatro nuevas poblaciones: Alto de los Llanos, Pico Rabanal, Peña Blanca, y dos en el Cueto de la Horca. Los efectivos totales, se calcularon mediante censos directos realizados en todas las poblaciones, lo que sirvió de referencia para realizar una estimación global. Con base en todos los datos obtenidos, se reevaluó la categoría de amenaza, y se corroboró la categoría En Peligro afi nando los criterios con los datos de campo. Por último, teniendo en cuenta la georreferenciación precisa que se realizó en todas las poblaciones, se elaboró su cartografía detallada, según la metodología específi ca propuesta en esta fase de AFA. Se calculó el área de ocupación y la extensión de presencia. Se evaluaron algunos factores determinantes en la presencia de este taxon y se realizó una modelización del área potencial de ocupación. Se descartaron todas las localidades de características semejantes situadas fuera de la Sierra de Peña, tras ser visitadas con el fi n de afi nar la extensión de presencia.Draba hispanica Boiss. subsp. lebrunii P. Monts. is an Iberian endemism exclusive from the Sierra de la Peña (Natural Park Fuentes Carrionas y Fuente CobreMontaña Palentina). Because of its reduced distribution, it was cataloged Vulnerable from Spain but, after the revision for the Red List 2008, resulted Endangered. In Castilla y León region, where it lives is protected (annex II of the Act of Protected Flora 63/2007). It was selected under AFA4, for the project scheme “Detailed cartography of threatened vascular fl ora populations”. A meticulous survey was made all over its distribution area, and we took a census in every known population. Furthermore, we prospected similar habitats resulting in the location of four new populations: Alto de los Llanos, Pico Rabanal, Peña Blanca, and two more in Cueto de la Horca. The total amount of specimens was calculated by means of direct census in every population, which served as a reference to make a global estimation. The threaten category was revised in the bases of all the collected data. It was confi rmed as Endangered, and the criteria were completed. Finally, with all sampled data we made a detailed mapping of every population following the methodology proposed in this stage of AFA. The occupation area and extension of presence were calculated. Some determining factors were evaluated for modeling the potential occupation area. All locations with similar features outside Sierra de Peña were dismissed, after our visit in order to complete its extension of presence.Proyecto AFA-4. Ministerio de Medio Ambiente y Medio Rural y Marin