Predation risk reduces a female preference for heterospecific males in the green swordtail

The presence of a predator can result in the alteration, loss or reversal of a mating preference. Under predation risk, females often change their initial preference for conspicuous males, favouring less flashy males to reduce the risk of being detected by predators. Previous studies on predator-induced plasticity in mate preferences have given females a choice between more and less conspicuous conspecific males. However, in species that naturally hybridize, it is also possible that females might choose an inconspicuous heterospecific male over a conspicuous conspecific male under predation risk. Our study addresses this question using the green swordtail (Xiphophorus helleri) and the southern platyfish (Xiphophorus maculatus), which are sympatric in the wild. We hypothesized that X. helleri females would prefer the sworded conspecific males in the absence of a predator but favour the less conspicuous, swordless, heterospecific males in the presence of a predator. Contrary to our expectation, females associated more with the heterospecific male than the conspecific male in the control (no predator) treatment, and they were non-choosy in the predator treatment. This might reflect that females were attracted to the novel male phenotype when there was no risk of predation but became more neophobic after predator exposure. Regardless of the underlying mechanism, our results suggest that predation pressure may affect female preferences for conspecific versus heterospecific males. We also found striking within-population, between-individual variation in behavioural plasticity: females differed in the strength and direction of their preferences, as well as in the extent to which they altered their preferences in response to changes in perceived predation risk. Such variation in female preferences for heterospecific males could potentially lead to temporal and spatial variation in hybridization rates in the wild

Effect of cylindrical geometry on the wet thermal oxidation of AlAs

We have investigated the wet thermal oxidation of AlAs in cylindrical geometry, a typical configuration for vertical-cavity surface-emitting lasers. Through both experiment and theoretical calculations, we demonstrate a significantly different time dependence for circular mesas from what has been reported in the literature both in studies of stripes and in a study of circular mesas. We attribute this different time dependence to the effect of geometry on the oxidation

Strain in wet thermally oxidized square and circular mesas

In this paper, we report the observation, through optical microscopy, of drumhead-like patterns in square and circular mesas which have been wet thermally oxidized to completion. Micro-Raman spectroscopy measurements are used to show that these patterns roughly correspond to variations in strain induced in surrounding semiconductor layers by the oxidation process. In addition, the patterns have a specific orientation with respect to the crystallographic axes of the semiconductor. A crystallographic dependence of the oxidation process itself is demonstrated and used to explain the orientation of the drumhead patterns

Estimating Disease Prevalence in Two-Phase Studies

Disease prevalence is ideally estimated using a “gold standard” to ascertain true disease status on all subjects in a population of interest. In practice, however, the gold standard may be too costly or invasive to be applied to all subjects, in which case a two-phase design is often employed. Phase 1 data consisting of inexpensive and non-invasive screening tests on all study subjects are used to determine the subjects that receive the gold standard in the second phase. Naïve estimates of prevalence in two-phase studies can be biased (verification bias). Imputation and re-weighting estimators are often used to avoid this bias. We contrast the forms and attributes of the various prevalence estimators. Distribution theory and simulation studies are used to investigate their bias and efficiency. We conclude that the semiparametric efficient approach is the preferred method for prevalence estimation in two-phase studies. It is more robust and comparable in its efficiency to imputation and other re-weighting estimators. It is also easy to implement. We use this approach to examine the prevalence of depression in adolescents with data from the Great Smoky Mountain Study

Community Organisations, Misiones and Integration of Barrios of Caracas: The Case of the CAMEBA Upgrading Project

The paper is an attempt to analyse the likely effects of compensatory social programmes such as Misiones Bolivarianas on community organisations in barrios and their participation in the planning and implementation of barrio upgrading projects, based on the case of the CAMEBA project in Caracas, Venezuela. The low level of community (target group) participation in Project CAMEBA has been compounded by a profoundly paternalistic approach of the national government that promised immediate relief and benefits in the form of compensatory programmes thus reinforcing habitual dependency amongst the poor people. These immediate-benefit programmes seem to have had an inhibiting effect on the community organisation and participation in the upgrading project, which had long term objectives and had aspired to create sustainable self-reliant communities in the project’s intervention areas. Such conclusion is reinforced by the results of the survey, which clearly shows that the awareness of the community regarding compensatory programmes is by and large greater than that of the upgrading project, even though project CAMEBA implementation started about four years before the apperance of the Misiones Bolivarianas. This situation has somehow hindered the process of community organisation which in any case involves training of communities to be legitimate and autonomous by getting rid of their chronic dependency syndrome. IHS Workin

Why the students of fifth year of the morning shift at Salomón de la Selva high school in Managua have a low level of proficiency in speaking and pronunciation skills in English as a foreign language

Nowadays English language has been one of the most relevant educational factors in Nicaragua and the population is being demanded to acquire it as a second language to exchange our cultural, social, political and economical aspects with foreign countries. During many years students in high schools have been taking English as a part of the curriculum set by the minister of education and therefore used by the teachers in public schools. In this research, we intend to find out the reasons that cause a low level of proficiency in speaking and pronunciation skills that students have in the second language acquisition and mostly, we have observed that the students of fifth year at Salomón de la Selva high school have a lot of difficulties in speaking and pronunciation skills through the teaching and learning process in the classroom. The problem has aroused our interest to look for specific information to help us find a solution. We focus our attention on the possible factors that lead to the problem of our concern: the materials used in the classroom and the kind of techniques the teacher carries out in class in order to fulfill his objectives. Our work lets you know about the previous knowledge and the linguistic problems the students have in English. And also how this can negatively affect them during their learning process in their last level of secondary schoo

Assessing the Accuracy of a New Diagnostic Test When a Gold Standard Does Not Exist

Often the accuracy of a new diagnostic test must be assessed when a perfect gold standard does not exist. Use of an imperfect test biases the accuracy estimates of the new test. This paper reviews existing approaches to this problem including discrepant resolution and latent class analysis. Deficiencies with these approaches are identified. A new approach is proposed that combines the results of several imperfect reference tests to define a better reference standard. We call this the composite reference standard (CRS). Using the CRS, accuracy can be assessed using multistage sampling designs. Maximum likelihood estimates of accuracy and expressions for the variance of sensitivity and specificity are provided. Data from clinical literature on the detection of Chlamydia trachomatis are used to illustrate and compare the different approaches. Advantages of the CRS relative to other approaches include that the CRS reference is explicitly defined, does not depend on the results of the new test under investigation, and is easy to interpret

Event-triggered attitude control for flying robots using an event approach based on the control

International audienceThis paper presents the development of a quaternion-based nonlinear event-triggered control for the attitude stabilization of Flying robots. Firstly, it is proved the existence of a Control Lyapunov Function. Unlike some previously proposed schemes, the aim of this paper is to propose a new and simpler event function. The control law ensures the asymptotic stability of the closed-loop system to the desired attitude. The approach is validated in real-time using a quadrotor mini-helicopter. The experiments show that the event driven controller reduces the control update without deteriorating the closed-loop system performance

Morphology evolution of thermally annealed polycrystalline thin films

Investigation of the morphology evolution of annealed polycrystalline Au(111) films by atomic force microscopy and x-ray diffraction leads to a continuous model that correlates such an evolution to local interactions between grains triggering different mechanisms of stress accommodation (grain zipping and shear strain) and relaxation (gap filling and grain rotation). The model takes into consideration findings concerning the in-plane reorientation of the grains during the coalescence to provide a comprehensive picture of the grain-size dependence of the interactions (underlying the origin of the growth stress in polycrystalline systems); and in particular it sheds light on the postcoalescence compressive stress as a consequence of the kinetic limitations for the reorientation of larger surface structuresThis paper was supported by the projects F1-54173 (bilateral program CSIC-Conacyt) 200960I182 (CSIC), and CCG10-UAM/MAT-5537 (DGUI-Comunidad de Madrid and Universidad Aut´onoma deMadrid). A.G.G. acknowledges the financial support of the MICINN Spanish Ministry under the project ESP2006-14282-C02-0

Autonomous Rover Traverse and Precise Arm Placement on Remotely Designated Targets

This software controls a rover platform to traverse rocky terrain autonomously, plan paths, and avoid obstacles using its stereo hazard and navigation cameras. It does so while continuously tracking a target of interest selected from 10 20 m away. The rover drives and tracks the target until it reaches the vicinity of the target. The rover then positions itself to approach the target, deploys its robotic arm, and places the end effector instrument on the designated target to within 2-3-cm accuracy of the originally selected target. This software features continuous navigation in a fairly rocky field in an outdoor environment and the ability to enable the rover to avoid large rocks and traverse over smaller ones. Using point-and-click mouse commands, a scientist designates targets in the initial imagery acquired from the rover s mast cameras. The navigation software uses stereo imaging, traversability analysis, path planning, trajectory generation, and trajectory execution. It also includes visual target tracking of a designated target selected from 10 m away while continuously navigating the rocky terrain. Improvements in this design include steering while driving, which uses continuous curvature paths. There are also several improvements to the traversability analyzer, including improved data fusion of traversability maps that result from pose estimation uncertainties, dealing with boundary effects to enable tighter maneuvers, and handling a wider range of obstacles. This work advances what has been previously developed and integrated on the Mars Exploration Rovers by using algorithms that are capable of traversing more rock-dense terrains, enabling tight, thread-the-needle maneuvers. These algorithms were integrated on the newly refurbished Athena Mars research rover, and were fielded in the JPL Mars Yard. Forty-three runs were conducted with targets at distances ranging from 5 to 15 m, and a success rate of 93% was achieved for placement of the instrument within 2-3 cm of the target