Search results for "Copula"
showing 10 items of 59 documents
Associations between sexual activity and weight status: Findings from the English Longitudinal Study of Ageing.
2019
Objective To investigate the association between weight status and sexual activity in middle-aged and older adults. Methods Cross-sectional analysis on Wave 6 (2012/13) of the English Longitudinal Study of Ageing. Data were from 2,200 men and 2,737 women aged ≥50 years (mean 68.2 years). The explanatory variable was weight status, defined as normal-weight (BMI: ≤24.9), overweight (BMI: 25.0–29.9) or obese (BMI: ≥30) based on objective measurements of height and weight. Outcome variables were any self-reported sexual activity in the last year (yes/no) and, if yes, frequency of sexual intercourse in the last month. Covariates included a range of sociodemographic, lifestyle, and health-related…
Life begins when the sea lion is ashore: microhabitat use by a louse living on a diving mammal host
2012
AbstractAmong Anoplura, the family Echinophthiriidae includes species that infest pinnipeds and otters. Previous evidence obtained from pinnipeds infested by echinophthiriids, specifically from seals, indicates that flippers are the preferred infestation sites, while lice from fur seals select areas in the pelage. We studied habitat selection of Antarctophthirus microchir on South American sea lion pups (Otaria flavescens Shaw, 1800) from Patagonia, Argentina, during the austral summer of 2009. We found a clear pattern of habitat selection: eggs are laid on the dorsal surface; nymphs 1 hatch there and then migrate to the belly, where they develop into adults and copulate; and then ovigerous…
The effects of age at menarche and first sexual intercourse on reproductive and behavioural outcomes:A Mendelian randomization study
2020
SummaryThere is substantial variation in the timing of significant reproductive life events such as menarche and first sexual intercourse. Life history theory explains this variation as an adaptive response to the developmental environment. In environments characterized by harsh conditions, adopting a fast life history strategy may increase fitness. In line with this, there is evidence demonstrating that greater childhood adversity is associated with earlier age at menarche. Here we applied Mendelian randomization (MR) methods to investigate whether there is a causal effect of variation in age at menarche and age at first sexual intercourse on outcomes related to reproduction, education and…
Chemosensory assessment of sperm competition levels and the evolution of internal spermatophore guarding
2006
Males of many species adjust their reproductive behaviour according to the perceived risk of sperm competition. Although this phenomenon is widespread in insects and other animals, the mechanisms that allow mates to assess sperm competition levels remain largely unexplored. In this study, we analysed the mating behaviour of pairs ofTenebrio molitorbeetles under three odour treatments representing increasing levels of sperm competition risk (SCR) and sperm competition intensity (SCI). Copula duration and male and female post-copulatory behaviour varied significantly with odour treatment. Both copula duration and post-copulatory associations (PCAs) increased significantly in odour treatments …
The Dynamics of Quote Prices in an Artificial Financial Market with Learning Effects
2007
In this paper we study the evolution of bid and ask prices in an electronic financial market populated by portfolio traders who optimally choose their allocation strategy on the basis of their views about market conditions. Recently, a growing literature has investigated the consequences of learning about the returns process1. There has been an increasing interest in analyzing what are the implications of relaxing the assumption that agents hold correct expectations. In particular, it has been asked the fundamental question of understanding if typical asset-pricing anomalies (like returns predictability, and excess volatility) can be generated by a learning process about the underlying econ…
Nouvelles données sur les Asellidae épigés d’Extrême-Orient (Crustacea, Isopoda, Asellota)
1995
Numerous samples of oculate Asellus from eastern Siberia and the Japanese Islands, one from southern China, and one from Alaska, have been studied. The epigean fresh waters of this large Asiatic region generally harbour populations identified as Asellus (Asellus) hilgendorfii Bovallius, 1886, or some of its geographical forms previously considered as species, subspecies, or not yet named. The “hilgendorfii” complex seems to possess the dimension of a superspecies. A new pigmented-oculate species, Asellus (Asellus) levanidovorum is sympatric with A. (A.) hilgendorfii in the lake Bolon region (lower part of the Amur River basin) and is present also in the Sakhalin and Kunashir Islands. Its co…
Uncertainty evaluation of design rainfall for urban flood risk analysis
2011
A reliable and long dataset describing urban flood locations, volumes and depths would be an ideal prerequisite for assessing flood frequency distributions. However, data are often piecemeal and long-term hydraulic modelling is often adopted to estimate floods from historical rainfall series. Long-term modelling approaches are time- and resource-consuming, and synthetically designed rainfalls are often used to estimate flood frequencies. The present paper aimsto assess the uncertainty of such an approach and for suggesting improvements in thedefinition of synthetic rainfall data for flooding frequency analysis. According to this aim, a multivariate statistical analysis based on a copulameth…
Probabilistic Flood Hazard Mapping Using Bivariate Analysis Based on Copulas
2017
This study presents a methodology to extract probabilistic flood hazard maps in an area subject to flood risk, taking into account uncertainties in the definition of design hydrographs. Particularly, the authors present a new method to produce probabilistic inundation and flood hazard maps in which the hydrological input (i.e., synthetic flood design event) to a 2D hydraulic model has been obtained by using a bivariate statistical analysis (copulas) to generate flood peak discharges and volumes. This study also aims to quantify the contribution of boundary conditions’ uncertainty in order to evaluate the effect of this uncertainty source on probabilistic flood hazard mapping. Different comb…
Extra-pair paternity and male characteristics in the pied flycatcher
1995
The pied flycatcher (Ficedula hypoleuca) is sexually dichromatic with extreme variation in male plumage coloration. The benefit for males of having black plumage is controversial, and few studies have found evidence for a sexual selection benefit of being black rather than brown. However, blacker males may be better able to achieve extra-pair fertilizations (EPFs), which may be an important component of sexual selection. We studied the role of EPFs in sexual selection in the pied flycatcher by establishing a set-up where two males with different back coloration (blacker vs browner) bred simultaneously near each other. DNA fingerprinting analysis revealed that 11% of offspring resulted from …
The ability of soil-borne fungi to degrade organophosphonate carbon-to-phosphorus bonds
1997
The ability of a wide variety of soil-borne fungal strains to degrade four structurally different compounds containing P-C bonds, namely the naturally occurring amino acid ciliatine, the popular herbicide glyphosate, phosphonoacetic acid and 2-amino-3-phosphonopropionic acid, was studied in order to show that soil fungi may play an important role in the biodegradation of organophosphonates. Most of the strains appeared to utilize ciliatine as the sole source of phosphorus for growth. Only a limited number of strains were able to grow on the other phosphonates used in this work. The strains of Trichoderma harzianum, Scopulariopsis sp. and Aspergillus niger chosen for more detailed study show…