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

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

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

Alien Registration- Rae, Alonzo A. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/22965/thumbnail.jp

Alien Registration- Rae, Alonzo A. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/22965/thumbnail.jp

Alien Registration- Rae, Alonzo A. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/22965/thumbnail.jp

The Obligations of Citizenship

The Atlanta school system is committed to three goals for students: (1) preparation for lifelong learning; (2) preparation for gainful employment; and (3) education for citizenship

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

All-Optical Reinforcement Learning in Solitonic X-Junctions

L'etologia ha dimostrato che gruppi di animali o colonie possono eseguire calcoli complessi distribuendo semplici processi decisionali ai membri del gruppo. Ad esempio, le colonie di formiche possono ottimizzare le traiettorie verso il cibo eseguendo sia un rinforzo (o una cancellazione) delle tracce di feromone sia spostarsi da una traiettoria ad un'altra con feromone più forte. Questa procedura delle formiche possono essere implementati in un hardware fotonico per riprodurre l'elaborazione del segnale stigmergico. Presentiamo qui innovative giunzioni a X completamente integrate realizzate utilizzando guide d'onda solitoniche in grado di fornire entrambi i processi decisionali delle formiche. Le giunzioni a X proposte possono passare da comportamenti simmetrici (50/50) ad asimmetrici (80/20) utilizzando feedback ottici, cancellando i canali di uscita inutilizzati o rinforzando quelli usati.Ethology has shown that animal groups or colonies can perform complex calculation distributing simple decision-making processes to the group members. For example ant colonies can optimize the trajectories towards the food by performing both a reinforcement (or a cancellation) of the pheromone traces and a switch from one path to another with stronger pheromone. Such ant's processes can be implemented in a photonic hardware to reproduce stigmergic signal processing. We present innovative, completely integrated X-junctions realized using solitonic waveguides which can provide both ant's decision-making processes. The proposed X-junctions can switch from symmetric (50/50) to asymmetric behaviors (80/20) using optical feedbacks, vanishing unused output channels or reinforcing the used ones

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