Dans le cas des générations de transistors sub-14nm, l’intégration de contacts métalliques classiques soumis aux limitations de la lithographie optique ne permet pas d’atteindre les performances d’alignement requises par les règles de dessin (pitch de grille 64nm en FDSOI 10nm) et les rendements industriels. Dans le cadre de ce travail de thèse, une nouvelle architecture de contacts auto-alignés (Self-Aligned Contacts ou SAC) est adressée pour les technologies FDSOI CMOS. Tout d’abord, nous avons proposé et validé l’intégration d’un module SAC dans une route CMOS FDSOI 14nm. Nous avons aussi démontré morphologiquement la faisabilité de contacts SAC pour des pitchs plus agressifs (noeud technologique 10nm). Par le biais de simulations numériques (TCAD et SPICE) l’impact de l’intégration des contacts auto-alignés sur les performances du transistor et du circuit, en termes de capacités parasites notamment, a ensuite été évalué dans le cas de la technologie 10nm FDSOI. Finalement, différentes techniques de transfert de contraintes mécaniques dans le canal du transistor ont été analysées en vue d’améliorer les performances de PFET en 10nm FDSOI. La génération des contraintes mécaniques via les contacts sur source-drain a également été investiguée. / For sub-14nm transistor generations, the integration of classical metallic contacts subjected to optical lithography limitations prevents the fulfillment of alignment performance required by design rules (64nm gate pitch for the 10nm node) and industrial yields. In the frame of this PhD. work, an original transistor architecture featuring self-aligned contacts (SAC) is studied for CMOS FDSOI technologies. First, a SAC module has been integrated and validated on a CMOS 14nm FDSOI process flow. The feasibility of SAC integration at a more aggressive gate pitch (10nm node) has also been demonstrated morphologically. The impact of such integration on the transistor and circuit performance, in terms of parasitic capacitances especially, has been evaluated through numerical simulations (TCAD, SPICE) in the case of the 10nm FDSOI technology. Finally, several techniques inducing mechanical stress within the transistor channel have been analyzed in order to improve the device performance. Among those, the use of contacts on source-drain to induce such stress has been particularly investigated.

Diarrhoea (“scouring”) in sheep increases the risk of faecal soiling of the breech (“dag”) that in turn causes significant production losses for sheep producers and increases susceptibility of sheep to breech blowfly strike. The common causes of scouring in sheep of post-weaning age in Western Australia have not been well described. In a written questionnaire sent to sheep producers in the south west of Western Australia, about half of the respondents reported lamb, hogget and ewe flocks with moderate or severe dag. Flocks with moderate or severe dag were reported more commonly in the winter and spring months in all age groups. Young sheep and mated ewes were most susceptible to moderate or severe dag. The utilisation of professional worm control advice and parasite management tools did not reduce the risk of moderate/severe dag. A study conducted at an abattoir showed that large strongyle worm egg counts (WEC) were frequently identified in lamb lines but were much less common in adult lines. The relationship between WEC and scouring was not clear, suggesting that factors other than large strongyle infections were important, particularly in adult sheep. The low WEC and seasonal scouring pattern observed in adult sheep was consistent with the larval hypersensitivity scouring syndrome and/or factors related to green pasture as potential common causes of scouring in adult sheep. This observation was consistent with detailed investigations of flocks with “low WEC scouring” that found larval hypersensitivity scouring syndrome or factors associated with green pasture were the most likely causes of scouring in eight of the nine flocks examined. Large immature worm burdens were common and the scouring sheep had more fourth stage larvae than normal sheep. Treatment with a fully effective drench and an ivermectin controlled-release rumen capsule did not result in a reduction of faecal moisture content between three and seven weeks after treatment. The effects of dietary soluble non-starch polysaccharides were studied using carboxymethylcellulose (CMC) as a model. The CMC model was used to demonstrate that significant interactions between diet and strongyle larvae determined both faecal consistency and strongyle establishment. Sheep fed CMC had softer, looser and wetter faeces, but the factors that determined faecal consistency were complex. Establishment of T. colubriformis was significantly greater in sheep fed CMC suggesting that the environment within the gut may affect establishment of T. colubriformis in the small intestine. The findings suggested that dietary factors may interact with strongyle larvae to determine both worm establishment and severity of scouring. The results of the studies described in this thesis suggested that factors related to immature strongyle larvae, diet and the immune response interact to determine the severity of the scouring observed in sheep of post-weaning age in the south west of Western Australia.

Fewer than 200 fish species are found in freshwater habitats in Australia, of which 144 are confined exclusively to freshwater. At least 22 species of exotic freshwater fish have been introduced into Australia, and 19 of these have established self-sustaining populations. However, the parasite fauna of both native and exotic freshwater fishes in Australia is poorly known. This is particularly the case in the south-west of Western Australia, where there have been no previous comprehensive studies of the parasites of 14 native species and nine or more exotic species of fish found in freshwater habitats. This study represents a survey of the parasites of freshwater fishes in the South West Coast Drainage Division and reports 44 putative species of parasites in 1429 individual fishes of 18 different species (12 native and six exotic) from 29 locations. Parasites were found in 327 (22.88%) fishes, and of the infected fishes, 200 (61.16%) were infected with only one species of parasite and 127 (38.84%) were infected with two or more species of parasites. For helminth and arthropod parasites, which were more comprehensively surveyed than protozoan and myxozoans, I found 37 species compared to 77 species found in a recent study of fishes from the East Coast Drainage Division. The present study demonstrated that parasitic infection was significantly more common in native fish species (mean prevalence of infection with any species of parasite = 0.36 ± 0.09) than in exotic fish species (0.01 ± 0.12). Parasites were found in all native fish species, but in only two exotic fish species that were examined. Parasite regional and component community diversity were estimated by species richness (the number of species, S) and by an index of taxonomic diversity (HT). Both parasite species richness and parasite taxonomic diversity were significantly greater in native fish species (mean S = 10.5 ± 2.3; mean HT = 1.19 ± 0.14) than in exotic fish species (mean S = 1.6 ± 3.3; mean HT = 0.27 ± 0.20). These relationships were consistent over all geographic locations that were sampled. The reduced parasite load of exotic species compared to native species has been previous reported across a wide range of taxa. It is thought to arise partly because founding populations of hosts have a low probability of harbouring the species’ total parasite fauna, and partly because parasites that infect introduced exotic species may not be able to maintain their life cycle in the new environment. It has been suggested that a reduced parasite load increases the competitive ability of exotic species compared to native species (the parasite release hypothesis) and this may partly explain the abundance and apparent competitive success of exotic over native species of freshwater fish in the South West Coast Drainage Division. For native species of fish, there were major differences among species in both prevalence of parasitic infection and parasite community diversity, but this variation was not related to fish size, whether the fish were primarily freshwater or primarily estuarine, or whether they were primarily demersal or pelagic. In this study, I report two new parasites in south western Australian waters. Both are copepod parasites; Lernaea cyprinacea and a new species of Dermoergasilus. The Dermoergasilus appears to be native to the south-west of Western Australia and has been described as Dermoergasilus westernensis. It differs from previously described species in the genus principally by the armature of the legs. This new species was found on the gills of freshwater cobbler, Tandanus bostocki and western minnow, Galaxias occidentalis in two different river systems. Lernaea cyprinacea is an introduced parasitic copepod found on the skin and gills of freshwater fishes in many areas of the world. The parasite has not previously been reported in Western Australia. We found infestations of L. cyprinacea on four native fish species (G. occidentalis; Edelia vittata; Bostockia porosa; T. bostocki) and three introduced fish species (Carassius auratus; Gambusia holbrooki; Phalloceros caudimaculatus) at two localities in the Canning River, in the south-west of Western Australia. The parasite has the potential to have serious pathogenic effects on native fish species, although it appears to be currently localised to a small section of the Canning River. Over all localities from which fishes were sampled in the present study, the proportion of native freshwater fishes with parasitic infections and the component community diversity of the parasite fauna of native fishes were both negatively related to habitat disturbance, in particular to a suite of factors (river regulation, loss of riparian vegetation, eutrophication and presence of exotic fish species) that indicate increased human usage of the river and surrounding environment. The reduced parasite load and diversity in native fishes from south-west rivers with greater human usage was due principally to the loss of a number of species of trematode, cestode and nematode endoparasites which use fishes as intermediate hosts. Other studies have also found that endoparasites with complex life cycles are most likely to be adversely affected by environmental changes, presumably because any environmental changes which impact on either free-living parasite stages or on any of the hosts in the complex train of parasite transmission will reduce parasite population size and may cause local extinction of the parasite species. The most heavily infected species of native freshwater fish in the South West Coast Drainage Division was T. bostocki with 96% of all individuals containing at least one species of parasite. As with most freshwater fishes of south-west Australia, T. bostocki is limited in its distribution to waterways with relatively low salinity. The degree of parasitism and histopathology of internal and external organs in T. bostocki from the Blackwood River was examined over a period of rapid, seasonal changes in water salinity. As salinity increased, the infracommunity richness and prevalence of ectoparasites on the skin of fishes decreased, while the infracommunity richness and prevalence of endoparasites increased. This was associated with a decrease in histopathological lesion scores in the skin and an increase in histopathological lesion scores in internal organs, particularly the intestine. I hypothesise that the seasonal spike in salinity had two contrasting effects on parasitic infections of T. bostocki. Firstly, it increased the mortality rate of parasites directly exposed to water, leading to a decrease in ectoparasitic infection and associated pathology. Secondly, it suppressed immune function in fish, leading to a decreased mortality rate of parasites not directly exposed to water and a more severe pathological response to endoparasitism.

Most, if not all, animals will at some stage in their lives encounter parasites. Some of the most widespread and abundant parasites belong to the Class Trematoda. Trematodes often have a substantial negative impact on individual intermediate host ecology. In this thesis, I investigate ecological and evolutionary consequences of the interaction between the microphallid trematode, Maritrema novaezealandensis, and its intermediate snail and crustacean hosts. Parasites often show a heterogeneous spatial distribution pattern in natural animal host populations. In this study, factors determining the spatial distribution of larval trematodes in Zeacumantus subcarinatus were investigated at two spatial scales (within and among bays). The distribution of shorebird definitive hosts explained a significant amount of the variation in the distribution of trematodes among bays. However, within a bay, other factors override the effect of bird distribution. The influence of larval trematodes on reproduction, survival and population density of Z. subcarinatus was investigated using laboratory and field studies. In the laboratory, it was found that larval trematodes induce castration and mortality of Z. subcarinatus. The field study revealed that the local prevalence of trematodes had a significant negative effect on population density of Z. subcarinatus. Through castration, trematodes act as strong selective agents on snail host life history. The effect of trematodes on life history characteristics (reproductive effort, juvenile growth, size at maturity and susceptibility to trematode infections) were investigated among natural populations of Z subcarinatus. Reproductive effort was not higher for uninfected females from populations where the risk of becoming infected was high. However, offspring from those populations were significantly larger, and laboratory-reared juveniles grew significantly faster than conspecifics from other populations. In addition, size at maturity was negatively correlated with trematode prevalence across snail populations. Z. subcarinatus thus adapts to a high local risk of trematode infection by reaching maturity early, thereby increasing the chance of reproducing. The influence of M. novaezealandensis on the survial of the amphipod host, Paracalliope novizealandiae was examined using experimental infections and field observations. The experimental infections demonstrated that parasite-induced mortality was intensity-dependent. The number of M. novaezealandensis per amphipod was too low to significantly induce host mortality in the field. However, the transmission strategy of this parasite allows it to affect host populations during weather conditions ideal for trematode transmission. Trematode strategies in the second intermediate host are important to the understanding of host-parasite co-evolution and the evolution of parasite life cycles. In this study, potential density-dependent effects at the metacercarial stage on size and fecundity of in vitro adult M. novaezealandensis was examined in both experimentally infected P. novizealandiae and naturally infected Macrophthalmus hirtipes. For this purpose, a method to excyst and cultivate M. novaezealandensis metacercariae to an egg producing stage, was developed. Naturally infected M. hirtipes also harboured larval stages of three other helminths. Crowding effects in the two crustacean hosts were expressed as a decreased volume and smaller egg production of in vitro adult M. novaezealandensis. In addition, interspecific interactions among parasite species were observed in crab hosts. The work in this thesis provides evidence that M. novaezealandensis significantly and negatively affect intermediate host ecology. The heterogeneous distribution of trematodes causes differential effects among host populations with subsequent effects on the life history of snail hosts. In addition, this study demonstrates that parasites interact within their second intermediate host with possible implications for the way parasites exploit their hosts.

Some ill. mounted. Bibliography: leaves [473]-504.

No description available.

Graduation date: 1995

This project was initiated to fill knowledge gaps on the occurrence of pathogens in different streams of wastewater, e.g. greywater and domestic wastewater. The aims were also to measure the removal of pathogens in different treatment processes, conventional and innovative, and correlate the removal to that of common microbial process indicators, such as faecal coliforms, enterococci, Cl. perfringens spores and bacteriophages. One study also assessed the correlation between the removal of microorganisms and some commonly measured physico-chemical process indicators. The results can be applied in microbial risk assessments (MRAs) of urban wastewater systems. Indicators and parasitic (oo)cysts were enumerated with standard methods and viruses with rtPCR. High levels of Giardia cysts and enteroviruses were found in untreated wastewater (103.2 and 104.2 L-1 respectively) indicating high incidences in the society. Noroviruses were also often found in high numbers (103.3 L-1) during winter, but less frequent and in lower numbers (102.3 L-1) during the rest of the year. This temporal variation correlated to the clinical laboratory reporting of noroviruses. A temporal variation was also shown for Giardia with significantly lower cyst counts in untreated wastewater during spring. Cryptosporidium oocysts were not as numerous in untreated wastewater (5 L-1) reflecting a lower incidence in the society than for the other pathogens during the time of the study. Since temporal variation had a larger impact than spatial, site-specific measurements may not be necessary to perform screening level MRAs of wastewater discharge and reuse. Good data can be found in the literature and corrected for by recovery of the detection method, flow and incidence in the society. Removal of microorganisms in wastewater treatments varied from 0 to >5.8 log due to process combination and organism in question. Treatment in integrated hydroponics removed microorganism more efficiently than did secondary conventional treatment, though having longer hydraulic retention time. Tertiary treatment and treatment in a membrane bioreactor (MBR) showed better removal potential than treatment in upflow anaerobic sludge blankets (UASB) in a pilot plant. Human virus genomes were less removed and Giardia cysts more removed than all of the studied indicators. Enumeration with PCR, however, may underestimate infectious virion removal. Spores of sulphite-reducing anaerobes and somatic coliphages were significantly less removed than E. coli and enterococci in all the studied processes. Bacterial indicator and spore removals correlated to enterovirus genome removal (p<0.05), but the predictive values were low (R<0.4). Removals between microbial indicators and NH4-N, Kjeldal-N, COD and TOC correlated stronger (10-18<p<0.02; 0.43<R<0.90). To manage the risk with reuse and discharge of wastewater, treatment performance targets have been calculated as a step in a hazard analysis and critical control point (HACCP) approach. These targets varied from 0 to 10.4 log removal due to water (grey or wastewater), organism (rotavirus, Campylobacter or parasitic (oo)cysts) and exposure (drinking water, surface water, aerosols, irrigation of crops or public parks). Faecal contamination in greywater was measured by coprostanol and was shown to be 980 times lower than in wastewater, corresponding to 2.9 log removal in treatment. Somatic coliphages were suggested to function as an index of virus removal in wastewater treatment processes as well as to be included in the monitoring of bathing water. The guideline level was suggested to be 300 PFU 100 mL-1 based on MRA of enteroviruses. This level in a water sample would equal a probability of infection of 0.3% (95th percentile 4%). The risk is overestimated if animal sources dominate the faecal pollution. Development in methods to track sources of faecal pollution showed that if somatic coliphages are enumerated together with phages infecting Bacteroides strain GA17, discriminating human from animal faecal pollution is possible based on the ratio between the phages / QC 20101013

Reproduction de : Thèse doctorat : Ecologie parasitaire : Reims : 2007. / Titre provenant de l'écran titre. Bibliogr. p. 245-272.

Reproduction de : Thèse de doctorat : Qualité et sécurité des aliments : Toulouse, INPT : 2006. / Titre provenant de l'écran-titre. Bibliogr. 348 réf.