Search results for "intermediate"
showing 10 items of 440 documents
SCHOOL PSYCHOLOGISTS’ ETHICAL STRAIN AND RUMINATION: INDIVIDUAL PROFILES AND THEIR ASSOCIATIONS WITH WEEKLY WELL-BEING
2016
We investigated school psychologists’ experiences of ethical strain (the frequency of ethical dilemmas at work and the stress caused by these dilemmas) and dilemma-related rumination outside working hours. Individual latent profiles were estimated at the study baseline based on these three dimensions. The psychologists’ weekly well-being (vigor, exhaustion, and sleep quality) was compared against their profile during the following three working weeks. The sample included 133 school psychologists, among whom four groups were identified: Low ruminators (39%), an Intermediate group (39%), High ruminators (20%), and Atypical outliers (2%). High ruminators fared least well in terms of weekly wel…
Sulfur Dioxide Oxidation Catalyzed by Photosensitized Ytterbium Diphthalocyanine
2008
Oxidation of SO2 into SO3 was found effectively catalyzed by photosensitized ytterbium diphthalocyanine, YbPc2 (Pc = phthalocyanine ligand, C32H16N8) when performed in air-saturated dimethylformamide (DMF) solution at 20 °C. The process follows according to a multi-step complex mechanism involving chemical induction as its driving force. Excitation energy of the sandwich molecular system in YbPc2 is used to promote the reaction by creating a reactive intermediate form of the ytterbium complex hosting up to eight SO2 molecules. The conversion of SO2 proved complete.
Increased susceptibility to predation and altered anti-predator behaviour in an acanthocephalan-infected amphipod.
2007
7 pages; International audience; According to the 'parasitic manipulation hypothesis', phenotypic changes induced by parasites in their intermediate hosts are effective means of increasing trophic transmission to final hosts. One obvious prediction, although seldom tested, is that increased vulnerability of infected prey to an appropriate predator should be achieved by the parasite altering the anti-predator behaviour of its intermediate host. In this study, we tested this prediction using the fish acanthocephalan Pomphorhynchus tereticollis and the freshwater amphipod Gammarus pulex. Firstly, we estimated the relative vulnerability of infected and uninfected gammarids to predation by the b…
Modification of hosts' behavior by a parasite: field evidence for adaptive manipulation.
2007
9 pages; International audience; Parasites relying on trophic transmission to complete their life cycles often induce modifications of their host's behavior in ways that may increase their susceptibility to predation by final hosts. These modifications have often been interpreted as parasite adaptations, but very few studies have demonstrated that host manipulation has fitness benefits for the parasite. The aim of the present study was to address the adaptive significance of parasite manipulation by coupling observations of behavioral manipulation to estimates of trophic transmission to the definitive host in the natural environment. We show that the acanthocephalan parasite Pomphorhynchus …
Manipulative parasites may not alter intermediate host distribution but still enhance their transmission: field evidence for increased vulnerability …
2013
SUMMARYBehavioural alterations induced by parasites in their intermediate hosts can spatially structure host populations, possibly resulting in enhanced trophic transmission to definitive hosts. However, such alterations may also increase intermediate host vulnerability to non-host predators. Parasite-induced behavioural alterations may thus vary between parasite species and depend on each parasite definitive host species. We studied the influence of infection with 2 acanthocephalan parasites (Echinorhynchus truttae and Polymorphus minutus) on the distribution of the amphipod Gammarus pulex in the field. Predator presence or absence and predator species, whether suitable definitive host or …
Carotenoid-based colour of acanthocephalan cystacanths plays no role in host manipulation.
2009
Manipulation by parasites is a catchy concept that has been applied to a large range of phenotypic alterations brought about by parasites in their hosts. It has, for instance, been suggested that the carotenoid-based colour of acanthocephalan cystacanths is adaptive through increasing the conspicuousness of infected intermediate hosts and, hence, their vulnerability to appropriate final hosts such as fish predators. We revisited the evidence in favour of adaptive coloration of acanthocephalan parasites in relation to increased trophic transmission using the crustacean amphipodGammarus pulexand two species of acanthocephalans,Pomphorhynchus laevisandPolymorphus minutus. Both species show car…
Parasite-induced alteration of plastic response to predation threat: increased refuge use but lower food intake in Gammarus pulex infected with the a…
2014
6 pages; International audience; Larvae of many trophically-transmitted parasites alter the behaviour of their intermediate host in ways that increase their probability of transmission to the next host in their life cycle. Before reaching a stage that is infective to the next host, parasite larvae may develop through several larval stages in the intermediate host that are not infective to the definitive host. Early predation at these stages results in parasite death, and it has recently been shown that non-infective larvae of some helminths decrease such risk by enhancing the anti-predator defences of the host, including decreased activity and increased sheltering. However, these behavioura…
Larval size in acanthocephalan parasites : Influence of intraspecific competition and effects on intermediate host behavioural changes
2012
Abstract Background Parasites often face a trade-off between exploitation of host resources and transmission probabilities to the next host. In helminths, larval growth, a major component of adult parasite fitness, is linked to exploitation of intermediate host resources and is influenced by the presence of co-infecting conspecifics. In manipulative parasites, larval growth strategy could also interact with their ability to alter intermediate host phenotype and influence parasite transmission. Methods We used experimental infections of Gammarus pulex by Pomphorhynchus laevis (Acanthocephala), to investigate larval size effects on host behavioural manipulation among different parasite sibshi…
Quantum dynamics of the oxygen isotopic exchange : lifetimes of metastable states of the ozone intermediate complex
2021
This thesis aims to describe the ozone dynamics during the isotopic exchange reactions of oxygen of type xO + yO zO (xO yO zO)* xO yO + zO, where x, y and z are the atomic masses of the stable oxygen isotopes (16, 17, 18). Firstly, we analyze several methods of accurate description of the atom interactions and numerical schemes to obtain the observables for the collision. Then, in a full-quantum hyperspherical formalism, we study the actual dynamics of the reactive process O + O2 -> O3* -> O2 + O. The metastable ozone created can then either decompose into oxygen by the inverse reaction, or relax into stable ozone by exchanging energy with the environment, typically N2 or O2 molecules. Thes…
The occurrence of Echinorhynchus salmonis Müller, 1784 in benthic amphipods in the Baltic Sea
2015
Abstract: The acanthocephalan Echinorhynchus salmonis Müller, 1784 is a common parasite of salmonid fish, but it has rarely been reported from an intermediate host. Samples of benthic amphipods, Monoporeia affinis (Lindström), were taken from multiple, deep sites (usually below 70 m) in the Gulf of Bothnia over the course of more than a decade and examined for acanthocephalans. Overall, only 0.44% of 23 296 amphipods were infected, all with just a single worm. This prevalence is consistent with several previous reports of acanthocephalans in deep-water, benthic amphipods, but it appears low compared to that often reported for acanthocephalan species infecting littoral amphipods. Parasite oc…