Search results for "age effect"

2016

Ecological communities are structured by competitive, predatory, mutualistic and parasitic interactions combined with chance events. Separating deterministic from stochastic processes is possible, but finding statistical evidence for specific biological interactions is challenging. We attempt to solve this problem for ant communities nesting in epiphytic bird’s nest ferns (Asplenium nidus) in Borneo’s lowland rainforest. By recording the frequencies with which each and every single ant species occurred together, we were able to test statistically for patterns associated with interspecific competition. We found evidence for competition, but the resulting co-occurrence pattern was the opposit…

Interspecific competition/facilitation among insect parasitoids.

2015

Competition for limited resources is a widespread ecological interaction in animals. In the case of insect parasitoids, species can compete for host resources both at the adult stage as well as at the larval stage. Interspecific competition can play a role in sizing and shaping community structures. In addition of being relevant for basic ecological studies, understanding how interspecific competition between parasitoids affects pest suppression is important for biological control. In this opinion paper we review recent advances in the field of interspecific competition among parasitoids in a biological control perspective. We first discuss adult competition, highlighting which factors are …

Wheelchair half-marathon and marathon performance: The ‘Oita International Wheelchair Marathon’ 1983-2011

2013

Knechtle, B. & Lepers, R. (2013). Wheelchair half-marathon and marathon performance ‐ the ‘Oita International Wheelchair Marathon’ 1983-2011. J. Hum. Sport Exerc., 8(4), pp.974-985. We compared participation and performance trends of individuals with disabilities competing in the half- and full-marathon in the ‘Oita International Wheelchair Marathon’ from 1981 to 2011. The performance times decreased during the 1980’s until the middle 1990’s and stabilized thereafter for both half-marathoners and marathoners. The mean top five overall finishers times were 0:52±0:07 h:min for half-marathoners and 1:36 ±0:11 h:min for marathoners, respectively. The mean age of the finishers increased signific…

Sex and age-related differences in performance in a 24-hour ultra-cycling draft-legal event - a cross-sectional data analysis

2014

International audience; BackgroundThe purpose of this study was to examine the sex and age-related differences in performance in a draft-legal ultra-cycling event.MethodsAge-related changes in performance across years were investigated in the 24-hour draft-legal cycling event held in Schötz, Switzerland, between 2000 and 2011 using multi-level regression analyses including age, repeated participation and environmental temperatures as co-variables.ResultsFor all finishers, the age of peak cycling performance decreased significantly (β = −0.273, p = 0.036) from 38 ± 10 to 35 ± 6 years in females but remained unchanged (β = −0.035, p = 0.906) at 41.0 ± 10.3 years in males. For the annual faste…

Extra-virgin olive oils storage: Effect on constituents of biological significance

2021

Abstract The high oxidative stability of virgin olive oil with respect to other vegetable oils is mainly due to its fatty acid composition, in particular, to the high monounsaturated-to-polyunsaturated ratio, and to the presence of minor compounds that play a major role in preventing oxidation. In spite of its high stability, virgin olive oil is susceptible to oxidative processes, such as enzymatic oxidation, photooxidation, and autoxidation, which mainly occur during processing and storage. Generally, extra-virgin olive oil has a relatively long shelf life of 16–18 months of storage at room temperature. The study of shelf life is generally based on determining of quality parameters (acidit…

Effects of achievement goals on perceptions of competence in conditions of unfavourable social comparisons: The mastery goal advantage effect

2017

Background Previous prospective studies have documented that mastery-approach goals are adaptive because they facilitate less negative psychological responses to unfavourable social comparisons than performance-approach goals. Aims This study aimed to confirm this so-called ‘mastery goal advantage’ effect experimentally. Methods A 2 × 3 design was adopted where achievement goals (mastery vs. performance) and normative information (favourable vs. no-normative information vs. unfavourable) were manipulated as between participant factors. Sample Participants were 201 undergraduates, 57 males and 144 females, ranging in age from 17 to 55 years (Mage = 22.53, SD = 6.51). Results Regression analy…

Retour en formation et parcours d'études atypiques : déterminants et valorisation sur le marché du travail

2019

Life long learning appears as a major concern for our societies. After leaving the educational system, learning can imply returning to school or continuing education. Academic careers in France seem less and less linear. Young peopleare encouraged to make the most of college breaks in order to diversify their experiences. During their career, they are to be trained to « be free to choose their professional future », as mentions a new law. This thesis, then, aims atidentifying the reasons why people go back to training and at stuying how such returns are seen by the labor market.This work includes a preliminary chapter and three other chapters, each with specific data. Based on a literature …

Intramolecular caging in polybutadiene due to rotational barriers

2003

We present molecular dynamics simulations of a chemically realistic model of 1,4-polybutadiene and a freely rotating chain model derived from the first model by neglecting all dihedral potentials. We show that the presence of energy barriers hindering dihedral rotation leads to an intermediate plateau regime in the tagged particle mean-squared displacement reminiscent of the cage effect underlying the mode-coupling description of the liquid-glass transition. This intramolecular caging, however, occurs already at temperatures well above the glass transition regime. Because of its different physical origin, it also does not comply with the theoretical predictions of the mode-coupling theory. …

Molecular-dynamics simulation of a glassy polymer melt: Incoherent scattering function

1999

We report results of molecular-dynamics simulations for a glassy polymer melt consisting of short, linear bead-spring chains. It was shown in previous work that this onset of the glassy slowing down is compatible with the predictions of the mode coupling theory. The physical process of `caging' of a monomer by its spatial neighbors leads to a distinct two step behavior in the particle mean square displacements. In this work we analyze the effects of this caging process on the Rouse description of the melt's dynamics. We show that the Rouse theory is applicable for length and time scales above the typical scales for the caging process. Futhermore, the monomer displacement is compared with si…

Dynamics of a supercooled polymer melt above the mode-coupling critical temperature: cage versus polymer-specific effects

2000

This paper reports results of molecular dynamics simulations for a glassy polymer melt consisting of short, non-entangled chains. The temperature region studied covers the supercooled state of the melt above the mode-coupling critical temperature. The analysis focuses on the interplay of simple-liquid and polymer-specific effects. One can clearly distinguish two regimes: a regime of small and one of large monomer displacements. The first regime corresponds to motion of a monomer in its local environment. It is dominated by the cage effect and well described by the idealized mode-coupling theory. The second regime is governed by the late-β/early-α process. In this regime the connectivity of …