Web decoration of Micrathena sexpinosa (Araneae: Araneidae): a frame-web-choice experiment with stingless bees

The function of silk web decorations in orb weaving spiders has been debated for decades. The most accepted hypothesized functions are that web decorations I) provide camouflage against predators, 2) are an advertisement for vertebrates to avoid web damage, or 3) increase the attraction of prey to the web. Most studies have focused on only a few genera, Argiope being the most common. In this study, I evaluated the prey attraction hypothesis of silk decorations for a species of a poorly studied genus in this topic, Micrathena sexpinosa Hahn 1822. I used a web-choice experiment in which I presented empty or web-bearing frames at the end of a tunnel to stingless bees (Tetragonisca angustula). This frame-choice experiment consisted of the following comparisons: decorated web vs. empty frame, decorated web vs. undecorated web, and undecorated web vs. empty frame. Webs with decoration intercepted significantly more bees than empty frames and undecorated webs. Therefore, the decorations of Micrathena sexpinosa might play a role in increasing foraging success.

Mating order-dependent female mate choice in the polygynandrous common lizard Lacerta vivipara.

Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising due to intra-sexual selection (e.g. male-male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness, or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous mating history affects female choice. We show that body size and body condition of the male with which a female mated for the first time were bigger and better, respectively, than the average body size and body condition of the rejected males. There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate choice is dependent on the previous mating history and it shows that the female's choice criteria are non-static, i.e. non-directional. Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions, but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice might be more frequent than previously thought.

Comparison of two strategies to prevent varicella outbreaks in housing facilities for asylum seekers.

BACKGROUND: The proportion of adults with positive varicella serology is lower in populations from tropical countries. Therefore immigrants to countries with a temperate climate are at risk of acquiring varicella infection during adulthood. METHODS: We tested two different strategies to prevent varicella outbreaks in housing facilities for asylum seekers arriving in the Canton of Vaud, Switzerland. The first strategy consisted of a rapid response with isolation of the affected individuals and vaccination of the susceptible contacts. The second strategy consisted of a general vaccination upon arrival of all asylum seekers aged 15-39 years with no history of chickenpox. RESULTS: From May 2008 to January 2009 we applied the rapid response strategy. Eight hundred and fifty-eight asylum seekers arrived in the Canton and an attack rate of 2.8% (seven cases among 248 exposed asylum seekers) was observed. The mean cost was US$ 31.35 per asylum seeker. The general vaccination strategy was applied from February 2009 to May 2010, a period during which 966 asylum seekers were registered. This second strategy completely prevented any outbreak at a mean cost of US$ 83.85 per asylum seeker. CONCLUSIONS: Of the two analyzed interventions to prevent varicella outbreaks in housing facilities for asylum seekers, the general vaccination strategy was more effective, more sustainable, and ethically preferable, although more costly.

Out-of-sample forecast tests robust to the choice of window size

This paper proposes new methodologies for evaluating out-of-sample forecastingperformance that are robust to the choice of the estimation window size. The methodologies involve evaluating the predictive ability of forecasting models over a wide rangeof window sizes. We show that the tests proposed in the literature may lack the powerto detect predictive ability and might be subject to data snooping across differentwindow sizes if used repeatedly. An empirical application shows the usefulness of themethodologies for evaluating exchange rate models' forecasting ability.

Immigration and housing: rethinking the role of fiscal policies to manage diversity

We study the two key social issues of immigration and housing in lightof each other and analyse which housing policies work best to distributediversity (racial, economic, cultural) equally across our cities and towns. Inparticular, we compare the impact of direct government expenditure andtax incentives on the housing conditions of immigrants in four Europeancountries: France, Germany, Spain and the United Kingdom. The analysisshows that the different policies which have been adopted in these countrieshave not succeeded in preventing immigrants from being concentratedin certain neighbourhoods. The reason is that housing benefits andtax incentives are normally “spatially blind”. In our opinion, governmentsshould consider immigration indirectly in their housing policies and, forinstance, distribute social housing more evenly across different areas topromote sustainable levels of diversity.

On the tractability of the piecewise-linear approximation for general discrete-choice network revenue management

The choice network revenue management (RM) model incorporates customer purchase behavioras customers purchasing products with certain probabilities that are a function of the offeredassortment of products, and is the appropriate model for airline and hotel network revenuemanagement, dynamic sales of bundles, and dynamic assortment optimization. The underlyingstochastic dynamic program is intractable and even its certainty-equivalence approximation, inthe form of a linear program called Choice Deterministic Linear Program (CDLP) is difficultto solve in most cases. The separation problem for CDLP is NP-complete for MNL with justtwo segments when their consideration sets overlap; the affine approximation of the dynamicprogram is NP-complete for even a single-segment MNL. This is in contrast to the independentclass(perfect-segmentation) case where even the piecewise-linear approximation has been shownto be tractable. In this paper we investigate the piecewise-linear approximation for network RMunder a general discrete-choice model of demand. We show that the gap between the CDLP andthe piecewise-linear bounds is within a factor of at most 2. We then show that the piecewiselinearapproximation is polynomially-time solvable for a fixed consideration set size, bringing itinto the realm of tractability for small consideration sets; small consideration sets are a reasonablemodeling tradeoff in many practical applications. Our solution relies on showing that forany discrete-choice model the separation problem for the linear program of the piecewise-linearapproximation can be solved exactly by a Lagrangian relaxation. We give modeling extensionsand show by numerical experiments the improvements from using piecewise-linear approximationfunctions.

1980 Census of population & housing: Iowa by place. Report 1A, Population characteristics, 1982

As with the 1970 Census, the U.S. Department of labor's Employment and Training Administration (ETA) has compiled a series of special reports for the use of program managers and other social scientists concerned with human resources. These reports. which were designed cooperatively by federal, state and local government research staff, include much unpublished data from the 1980 Census Summary Tape Files. The reports in this series cover not only all of the major government and census designated geographic areas in the United States, but also the unique administrative areas that concern program managers.