Penis-rejection in a mangrove littorinid snail: why do females reject males?

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Forward curves, scarcity and price volatility in oil and natural gas markets

The role of inventory in explaining the shape of the forward curve and spot price volatility in commodity markets is central in the theory of storage developed by Kaldor [Kaldor, N. (1939) "Speculation and Economic Stability", The Review of Economic Studies 7, 1–27] and Working [Working, H. (1949) “The theory of the price of storage”, American Economic Review, 39, 1254–1262] and has since been documented in a vast body of financial literature, including the reference paper by Fama and French [Fama, E.F. and K.R. French (1987) “Commodity futures prices: some evidence on forecast power, premiums and the theory of storage”, Journal of Business 60, 55–73] on metals. The goal of this paper is twofold: i) validate in the case of oil and natural gas the use of the slope of the forward curve as a proxy for inventory (the slope being defined in a way that filters out seasonality); ii) analyze directly for these two major commodities the relationship between inventory and price volatility. In agreement with the theory of storage, we find that: i) the negative correlation between price volatility and inventory is globally significant for crude oil; ii) this negative correlation prevails only during those periods of scarcity when the inventory is below the historical average and increases importantly during the winter periods for natural gas. Our results are illustrated by the analysis of a 15 year-database of US oil and natural gas prices and inventory

The effect of learning styles on course performance: A quantile regression analysis: Working paper series--08-02

In this study, we investigated the relationship between student performance and learning styles for students enrolled in a basic business statistics course. This course used a learner-centered approach that incorporated multiple teaching styles. To assess our success in designing a course that facilitates learning for all learning styles, we evaluated the impact of students' learning style on their performance in the course. To accomplish this analysis, we utilized quantile regression, a statistical technique from the economics literature developed by Koenker and Bassett (1978) that is an alternative to the classical ordinary least squares (OLS) regression. Quantile regression allowed investigation of a more complete picture of student performance over the entire population as opposed to the mean effect from OLS regression. Learning style was not significant in determining a student's overall course score for the entire cohort of students. For small cohorts of students, learning styles were significant for exam average. That is, some students experienced either a disadvantage or advantage due to their learning style for the exam course component. However, for the overall course performance, a student with a particular learning style was neither advantaged nor disadvantaged

Fighting for mates: the importance of individual size in mating contests in rocky shore littorinids

Studies of mating contests have reported how traits (e.g. body size) related to resource holding potential (RHP) and strategies to assess RHP and resource value influence contest outcome in many taxa but are rare in the Gastropoda. The influence of male size (as an index of RHP) and female size (as a measure of resource value) on contest outcome were investigated in two littorinid snails, Echinolittorina malaccana and E. radiata, in Hong Kong during May－June 2013. In these snails, contests between males take the form of a 'challenger' attempting to take over the copulation position occupied by a 'defender'. Both challengers and defenders were, generally, smaller than the females in both species. In both species, the larger the challenger relative to the defender, the more likely he would replace the defender in the copulation position. The challengers were, however, more successful in E. radiata, as they generally challenged defenders that were smaller than themselves, suggesting an ability to detect rival size before entering into a contest in this species. When sizes of the contestants were similar, defenders were more likely to win contests in E. malaccana but not in E. radiata. Evidence for pure self-assessment of RHP and the ability to assess resource value in challengers was found in E. malaccana. Different fighting strategies appear to have evolved in these congeneric marine snail species and decisions based on male and female sizes play an important role in determining male reproductive success

Development of Non-Petroleum-Based Binders for Use in Flexible Pavements – Phase II

Bio-binders can be utilized as asphalt modifiers, extenders, and replacements for conventional asphalt in bituminous binders. From the rheology results of Phase I of this project, it was found that the bio-binders tested had good performance, similar to conventional asphalt, except at low temperatures. Phase II of this project addresses this shortcoming and evaluates the Superpave performance of laboratory mixes produced with the enhanced bio-binders. The main objective of this research was to develop a bio-binder capable of replacing conventional asphalt in flexible pavements by incorporating ground tire rubber (GTR) into bio-oil derived from fast pyrolysis of agriculture and forestry residues. The chemical compatibility of the new bio-binder with GTR was assessed, and the low-temperature performance of the bio-binders was enhanced by the use of GTR. The newly developed binder, which consisted of 80 percent conventional binder and 20 percent rubber-modified bio-oil (85 percent bio-oil with 15 percent GTR), was used to produce mixes at two different air void contents, 4 and 7 percent. The laboratory performance test results showed that the performance of the newly developed bio-binder mixes is as good as or better than conventional asphalt mixes for fatigue cracking, rutting resistance, moisture sensitivity, and low-temperature cracking. These results need to be validated in field projects in order to demonstrate adequate performance for this innovative and sustainable technology for flexible pavements

Applying a SPA model to examine the impact of climate change on GPP of open woodlands and the potential for woody thickening

Woody thickening is a global phenomenon that influences landscape C density, regional ecohydrology and biogeochemical cycling. The aim of the work described here is to test the hypothesis that increased atmospheric CO2 concentration, with or without photosynthetic acclimation, can increase gross primary production (GPP) and that this can explain woody thickening. We examine mechanisms underlying the response of GPP and highlight the importance of changes in soil water content by applying a detailed soil-plant-atmosphere model. Through this model, we show that CO2 enrichment with decreased or increased D and photosynthetic acclimation results in decreased canopy water use because of reduced gs. The decline in water use coupled with increased photosynthesis resulted in increased GPP, water-use efficiency and soil moisture content. This study shows that this is a valid mechanism for GPP increase because of CO2 enrichment coupled with either a decrease or an increase in D, in water-limited environments. We also show that a large increase in leaf area index could be sustained in the future as a result of the increased soil moisture content arising from CO2 enrichment and this increase was larger if D decreases rather than increases in the future. Large-scale predictions arising from this simple conceptual model are discussed and found to be supported in the literature. We conclude that woody thickening in Australia and probably globally can be explained by the changes in landscape GPP and soil moisture balance arising principally from the increased atmospheric CO2 concentration. © 2010 John Wiley & Sons, Ltd

Culture moderates the relationship between interdependence and face recognition

Recent theory suggests that face recognition accuracy is affected by people’s motivations, with people being particularly motivated to remember ingroup versus outgroup faces. In the current research we suggest that those higher in interdependence should have a greater motivation to remember ingroup faces, but this should depend on how ingroups are defined. To examine this possibility, we used a joint individual difference and cultural approach to test (a) whether individual differences in interdependence would predict face recognition accuracy, and (b) whether this effect would be moderated by culture. In Study 1 European Canadians higher in interdependence demonstrated greater recognition for same-race (White), but not cross-race (East Asian) faces. In Study 2 we found that culture moderated this effect. Interdependence again predicted greater recognition for same-race (White), but not cross-race (East Asian) faces among European Canadians; however, interdependence predicted worse recognition for both same-race (East Asian) and cross-race (White) faces among first-generation East Asians. The results provide insight into the role of motivation in face perception as well as cultural differences in the conception of ingroups

Temporal genetic variation in populations of the limpet Cellana grata from Hong Kong shores

Variations in the relative contributions of gene flow and spatial and temporal variation in recruitment are considered the major determinants of population genetic structure in marine organisms. Such variation can be assessed through repeated measures of the genetic structure of a species over time. To test the relative importance of these two phenomena, temporal variation in genetic composition was measured in the limpet Cellana grata, among four annual cohorts over 10 years at four rocky shores in Hong Kong. A total of 408 limpets, comprising individuals from 1998, 1999, 2006 and 2007 cohorts were screened for genetic variation using five microsatellite loci. Minor but significant genetic differentiation was detected among samples from the 1998/1999 collection (FST = 0.0023), but there was no significant differentiation among the 2006/2007 collection (FST = 0.0008). Partitioning of genetic variation among shores was also significant in 1998/1999 but not in the 2006/2007 collection, although there was no correlation between genetic and geographic distances. There was no significant difference between collections made in 1998/1999 and 2006/2007. This lack of clear structure implies a high level of gene flow, but differentiation with time may be the result of stochastic recruitment variation among shores. Estimates of effective population size were not high (599, 95% C. L. 352-11397), suggesting the potential susceptibility of the populations to genetic drift, although a significant bottleneck effect was not detected. These findings indicate that genetic structuring between populations of C. grata in space and time may result from spatio-temporal variation in recruitment, but the potential development of biologically significant differentiation is suppressed by a lack of consistency in recruitment variability and high connectivity among shores. © Springer-Verlag 2009.postprin

Sampling scale can cause bias in positive assortative mating estimates: The first evidence in two intertidal snails

Assortative mating in the wild is commonly estimated by correlating between traits in mating pairs (e.g. size of males and females). Unfortunately such an approach may suffer from considerable sampling bias when the distribution of different expressions of a trait in the wild is non-random; for example, when segregation of different size classes of individuals occur in different microhabitats or areas. Consequently, any observed trait correlation in the wild can be an artifact of pooling heterogeneous samples of mating pairs from different microhabitats or areas rather than true non-random matings. This bias in estimating trait correlations due to sampling scale is termed the scale-of-choice effect (SCE). Here we use two intertidal littorinid species from Hong Kong to show how the SCE can bias size-assortative mating estimates from mating pairs captured in the wild, empirically demonstrating the influence of this effect on measures of positive assortative mating. This finding cautions that studies that have overlooked SCE may have misinterpreted the magnitude and the cause of assortative mating, and we provide a new analytical approach to protect against this potential bias in future studies

Adaptive Physiology at a local scale, and implications for species distribution models under climate change scenarios.

In heterogeneous environments, individuals experience different combinations of physical and biological pressures over small spatial scales. For many marine organisms with limited adult mobility, but planktonic dispersal, localised adaptation may occur over an organism's life cycle through acclimation. Understanding the plasticity of physiology through acclimation is vital in predicting species' vulnerability to climate change. In this study we assessed local conditions on four sections (<500 m apart) of a tropical rocky shore to determine whether differences in local conditions affect the physiology of the limpet, Cellana grata. Shore sections differed in aspect, exposure and topography, and in biological characteristics such as levels of competition (grazer density) and facilitation (barnacle cover). Using a bootstrapped principal component analysis, we demonstrated that sections of shore differed significantly in terms of the relative contributions of the multiple variables measured. As a measure of physiological acclimation, detachment temperatures of limpets from each site were measured in the laboratory and higher detachment temperatures were found in limpets from shore sections with greater physical stress and lower biological stress. These results demonstrate that physiological limits can acclimate to local conditions over short temporal scales and uniform physiology should not be assumed in species distribution or climate change models