Seasonal changes in the population dynamics of Aurelia aurita in Thau lagoon

Seasonal dynamics of the scyphomedusae, Aurelia aurita, was investigated twice a month from January 2010 to June 2011 and related to environmental conditions in Thau lagoon, southwestern Mediterranean Sea. Strobilation, indicated by the presence of 1 mm ephyrae, occurred from November to the middle of April. Maximum abundances up to 330 ind.100 m-3 were reached in May 2011, few weeks after the last ephyrae release. The population declines afterwards steadily until disappearing from the water column. Concurrent with increased water temperature and mesozooplankton predation during May, growth rates increased from 0.04 mm.day-1 to a peak of 4.5 mm.day-1, with a maximum bell diameter of 11.3 cm reached on the 7th May. During the study period, there was no advection of A. aurita between Thau lagoon and the coastal waters

Making students sensitive to entrepreneurship

The aim of this paper is to present a {proposal to make students sensitive to entrepreneurship} aiming at familiarizing students to the setting up of new firms and stimulating such a course of action. This {{awareness campaign}} would take place during the student's curriculum and rest on a simulation exercise. This campaign is based on the results of a survey conducted at the Technical University of Cartagena (Spain). This study has identified some students’ aspirations to salaried employment and entrepreneurship. This survey also recognized some specific features that the campaign must integrate, in particular the need to make entrepreneurship compatible with the preparation for salaried employment. The results of this study are completed comparing them with the opinion from entrepreneurs of the same region. This comparison highlights some barriers to entrepreneurship among the students population, making it possible to complete the content of the proposed simulation exercise. This paper also highlights the absence of barriers of a psychological nature usually put forward by the literature, such as a low level of the {need for achievement or the propensity for risk-taking}.career, company, entrepreneurship, making sensitive, student

One spatial filter limits speed of detecting low and middle frequency gratings

AbstractReaction times for detecting sinusoidal gratings depend jointly on grating contrast and spatial frequency. We examine whether the effect of spatial frequency results from low-pass filtering in a single channel or reflects processing of different frequencies by two or more different processing streams. Observers performed a speeded two-alternative spatial forced-choice detection. Errors and reaction times were measured. Contrasts varied from 0.05 to 0.67, and spatial frequencies from 0.72 to 6.51 cpd. No effect of uncertainty about spatial frequency was found, arguing against multiple channels. The data are well fit by a single channel model driven by a low pass filter

Fast, high-order numerical evaluation of volume potentials via polynomial density interpolation

This article presents a high-order accurate numerical method for the evaluation of singular volume integral operators, with attention focused on operators associated with the Poisson and Helmholtz equations in two dimensions. Following the ideas of the density interpolation method for boundary integral operators, the proposed methodology leverages Green's third identity and a local polynomial interpolant of the density function to recast the volume potential as a sum of single- and double-layer potentials and a volume integral with a regularized (bounded or smoother) integrand. The layer potentials can be accurately and efficiently evaluated everywhere in the plane by means of existing methods (e.g. the density interpolation method), while the regularized volume integral can be accurately evaluated by applying elementary quadrature rules. Compared to straightforwardly computing corrections for every singular and nearly-singular volume target, the method significantly reduces the amount of required specialized quadrature by pushing all singular and near-singular corrections to near-singular layer-potential evaluations at target points in a small neighborhood of the domain boundary. Error estimates for the regularization and quadrature approximations are provided. The method is compatible with well-established fast algorithms, being both efficient not only in the online phase but also to set-up. Numerical examples demonstrate the high-order accuracy and efficiency of the proposed methodology; applications to inhomogeneous scattering are presented.</p