Cette recherche a été réalisée grâce à l'aide financière du Programme Innov'action agroalimentaire de l'entente Cultivons l'Avenir 2 conclue entre le Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec (MAPAQ) et Agriculture et Agri-Food Canada. / La drosophile à ailes tachetées s’avère être un ravageur exotique particulièrement dommageable pour les cultures de petits fruits puisqu’elle s’attaque aux fruits en murissement. Depuis son invasion des continents américain et européen en 2008, ses populations sont contrôlées majoritairement avec des insecticides chimiques. L’objectif de cette étude était d’explorer le potentiel de la technique des insectes stériles (TIS) comme approche de lutte à la drosophile à ailes tachetées, d’abord en irradiant des pupes à différentes doses pour identifier la dose optimale pour la stérilisation des mâles et, par la suite, en évaluant les capacités reproductives de ces mâles irradiés. En premier lieu, il a été observé que l’irradiation n’avait pas d’effet significatif sur l’émergence, la malformation et la longévité des adultes à chacune des doses testées. Suite à l’accouplement de mâles irradiés avec des femelles saines, deux équations ont été obtenues permettant d’établir une relation entre la dose d’irradiation et un taux d’éclosion des œufs et leur survie jusqu’au stade adulte. Ces résultats ont permis de choisir la dose de 120 Gy comme dose d’irradiation pour la drosophile à ailes tachetées dans un contexte de TIS. Les capacités reproductives des mâles irradiés à cette dose ont ensuite été comparées à celles des mâles non-irradiés. Les mâles irradiés se sont révélés significativement aussi efficaces que les mâles non-irradiés pour accoupler et transmettre du sperme aux femelles en absence de compétition. En conditions de compétition, le succès d’accouplement par le mâle irradié a été de 37,5% et de 62,5% par le mâle non-irradié, mais sans différence significative. Puis, une expérience sur le ré-accouplement des femelles a conclu que celui-ci était peu fréquent et n’était pas influencé significativement par l’irradiation des mâles. / Spotted wing drosophila is an exotic pest especially damaging to berry crops because of its ability to lay eggs inside ripening fruits. Since its invasion of North America and Europe in 2008, its populations are controlled mainly with chemical insecticides. The objective of this study was to explore the potential of the sterile insect technique (SIT) as a control method for the spotted wing drosophila, first by irradiating pupae at different doses to identify the optimum dose for male sterilization, and secondly by evaluating the reproductive capacities of these irradiated males. First, it was observed that irradiation had no significant effect on emergence, malformation and longevity of adults at any of the doses tested. Following mating of irradiated males with healthy females, two equations were obtained to establish a relation between the irradiation dose and the egg hatch rate, and the survival rate to the adult stage. These results made it possible to choose the dose of 120 Gy as the irradiation dose for the spotted wing drosophila in an SIT context. The reproductive capacities of males irradiated at this dose were later compared with those of non-irradiated males. Irradiated males were shown to be significantly as effective as non-irradiated males to mate and transfer sperm to females in absence of competition. In competitive conditions however, the success of irradiated males was of 37.5% and of 62.5% for the non-irradiated males, but without significant difference. Then, an experiment on the re-mating of the females concluded that it was infrequent and was not significantly influenced by the irradiation of the males.

Abstract The life histories of ectoparasites are shaped by both host and off-host environment. A suitable host is primarily needed during reproduction, whereas juvenile stages outside the host are directly exposed to environmental variability. Viviparity, i.e. the development of an embryo inside the body of the mother resulting in large offspring size, increases offspring survival. The production of large offspring has its consequences in terms of high variation in offspring age and in the environment that each young individual will face. I used a viviparous ectoparasite, the deer ked (Lipoptena cervi), to investigate the consequences of long reproductive lifespan and varying offspring environment on offspring life-histories and seasonal adaptations. Offspring life-histories varied seasonally. I showed that the resources provided by the deer ked females determine offspring performance throughout its off-host period. Offspring size increased towards the spring and the end of the reproductive period, and simultaneously offspring survival and cold tolerance increased. Seasonal variation in offspring size did not reflect the resources that would guarantee offspring survival during the longest diapause or the highest cold tolerance during the harshest winter period. Diapause intensity varies with birth time according to the expected length of the winter ahead. However, the deer ked pupae, regardless of their age, overwinter at an opportunistic diapause, which may be terminated rapidly only by an exposure to high temperature. Contrary to general observations, photoperiod has no role in regulating the seasonal shifts of the deer ked. Neither is high cold tolerance associated only with diapause, but it remains high through four seasons, also in the active developmental and adult stages. I also evaluated the effects of life-history variation on the invasion potential of the deer ked. I conducted a large-scale transplant experiment to test the survival and pupal development at and beyond the current range. I found that the lower spring and summer temperatures and the shorter growth season in the north cause a deterioration in pupal performance and shorten the flight period. However, the colder climate may not totally prevent further spread. A more important factor that will affect deer ked invasion is host availability, and especially in Finland, the density of the moose population. Seasonal variation in offspring life histories in viviparous ectoparasites differs from the variation patterns reported in most invertebrates. This may be due to the extremely large offspring size and to the fact that maternally derived resources determine offspring performance through the entire off-host period. Variation in offspring performance is thus determined by maternal resources and seasonal variation in the condition of the moose. / Tiivistelmä Useimpien ulkoloisten elinkierto on riippuvainen isännästä ja isännän ulkopuolella kasvavien jälkeläisten kohtaamista ympäristöoloista. Viviparia eli jälkeläisen kehitys naaraan sisällä ja siitä usein seuraava suuri jälkeläiskoko parantavat jälkeläisten selviytymistä. Suurten jälkeläisten tuottaminen pitkällä aikavälillä johtaa siihen, että eri-ikäiset jälkeläiset kohtaavat vuodenajasta riippuen hyvin erilaiset olosuhteet. Väitöstyössäni tarkastelin Suomessa nopeasti yleistyneen hirvieläinten ulkoloisen, hirvikärpäsen (Lipoptena cervi), avulla, mitä seurauksia viviparialla, pitkällä lisääntymiskaudella ja ympäristön vuodenaikaisvaihtelulla on jälkeläisten elinkierto-ominaisuuksiin. Väitöskirjatyössäni havaitsin, että hirvikärpäsjälkeläisten elinkiertopiirteet vaihtelevat jälkeläisen syntymäajan mukaan. Osoitin myös, että hirvikärpäsnaaraan jälkeläisilleen tarjoamat ravintovarat määrittelevät jälkeläisten isännästä riippumattoman elinkierron aikaisen menestyksen. Jälkeläisten keskimääräinen koko kasvoi lisääntymiskauden edetessä talvesta kohti kevättä, jolloin myös selviytyminen ja kylmänsietokyky paranivat. Jälkeläiskoon vuodenaikaisvaihtelu ei näin ollen vastaa jälkeläisten tarvitsemia resursseja suhteessa talvehtimisen pituuteen eikä korreloi koville talvipakkasille altistumisen todennäköisyyden kanssa. Lepotilan keston määrittelevä diapaussin syvyys vaihteli syntymävuodenaikaa vastaavasti. Diapaussin havaitsin kuitenkin olevan ensisijaisesti opportunistinen, jolloin pelkästään korkea lämpötila voi nopeasti päättää lepotilan kaikenikäisillä yksilöillä. Vastoin yleisiä käsityksiä valorytmi ei vaikuta diapaussin säätelyyn. Vastoin ennakko-odotuksia kylmänsietokyky säilyy korkeana vuoden ympäri ja kaikissa tutkituissa elinkierron vaiheissa. Sovelsin tutkimieni elinkiertopiirteiden vaikutusta myös lajin invaasiokykyyn, ja tutkin istutuskokeen avulla koteloiden selviytymistä ja kehitystä nykyisellä esiintymisalueella ja sen pohjoispuolella. Alhaisemmat kevät- ja kesälämpötilat sekä lyhyempi kasvukausi vähentävät aikuiseksi selviytymistä ja lyhentävät lentoaikaa syksyllä. Ilmastotekijöiden suhteen hirvikärpänen voisi esiintyä nykyistä pohjoisempana. Tärkein tekijä hirvikärpäsen leviämistä tarkasteltaessa on kuitenkin sopivien isäntäeläimien saatavuus ja Suomen oloissa erityisesti hirven eli hirvikärpäsen pääisännän kannan tiheys. Tutkimukseni perusteella ulkoloisten vivipariasta seuraava jälkeläisten elinkiertopiirteiden ajallinen vaihtelu eroaa muiden selkärangattomien vastaavasta vaihtelusta. Yhtenä syynä eroihin lienee se, että hirvikärpäsnaaras tuottaa erityisen suuria jälkeläisiä ja että jälkeläiset puolestaan ovat täysin riippuvaisia emon antamista resursseista. Emon lisääntymisresurssit ja hirven kunnon vuodenaikaisvaihtelu vaikuttavat mahdollisesti siihen, minkälaisia jälkeläisiä hirvikärpänen milloinkin kykenee tuottamaan.

Doctor of Philosophy / Department of Entomology / Ming-Shun Chen / Gerald E. Wilde / Analysis of transcriptomes from salivary glands and midgut of the Hessian fly [Mayetiola destructor (Say)] identified a diverse set of cDNAs that were categorized into five groups, group I – V, based on their phylogenetic relationship. All five of these groups may encode putative protease inhibitors based on structural similarity with known proteins. The sequences of these putative proteins among different groups are highly diversified. However, sequence identity and structural analysis of the proteins revealed that all of them contained high cysteine residues that were completely conserved at their respective positions among these otherwise diversified proteins. Analysis of bacterial artificial chromosome (BAC) DNA for two groups, group I (11A6) and group II (14A4), indicated that group I might be a single copy gene or genes with low copy number whereas group II exists as multiple copies clustered within the Hessian fly genome. To test the inhibitory activity and specificity of these putative proteins, recombinant proteins were generated. Enzymatic analysis of the recombinant proteins against commercial and insect gut proteases demonstrated that recombinant proteins indeed are strong inhibitors of proteases with different specificities. Northern analysis of the representative members of five groups revealed that the group I-IV genes were expressed exclusively in the larval stage with variations among groups at different larval stages. The group V (11C4) genes were expressed in the late larval and pupal stage. Tissue specific gene expression analysis revealed that group I-IV genes were predominantly expressed in malpighian tubules whereas the group V genes were abundantly expressed in the salivary glands. Localization experiments with the antibody for representative members from group II (14A4) demonstrated that the protein was predominantly localized in the malpighian tubules and in low amounts in the midgut, suggesting that malpighian tubules are the primary tissue of 14A4 inhibitor synthesis. The overall results indicated that the Hessian fly contains a complex network of genes that code for protease inhibitors which regulate protease activities through different developmental stages of the insect.

Doctor of Philosophy / Department of Agronomy / Gina Brown-Guedira / Allan K. Fritz / Aegilops tauschii, the D-genome donor of modern wheat, has served as an important source of genetic variation in wheat breeding. The objective of this research was to characterize and utilize multiple Ae. tauschii-derived pest resistance genes contained in the germplasm KS96WGRC40. Two Ae. tauschii-derived genes, H23 and Cmc4, provide resistance to the Hessian fly (HF) and wheat curl mite (WCM), respectively. A linkage analysis of a testcross population estimated 32.67% recombination between H23 and Cmc4 on chromosome 6DS in wheat indicating that the two genes are not tightly linked as previous mapping reports show. Haplotype data of recombinant lines and physical mapping of linked microsatellite markers located Cmc4 distal to H23. Haplotype data indicated that both KS89WGRC04 and KS96WGRC40 have the distal portion of 6DS derived from Ae. tauschii. Microsatellite primer pairs BARC183 and GDM036 were more useful than the previously published linked markers in identifying lines carrying Cmc4 and H23, respectively. Through phenotypic selection and advancement within the testcross population, three TC1F2:4 lines were identified as homozygous resistant for H23 and Cmc4 and have the complete terminal segment of 6DS from Ae. tauschii. Two lines are more desirable than the original germplasm releases and can serve as a source of resistance to both HF and WCM in an elite background. A linkage analysis of a segregating recombinant inbred line population identified an Ae. tauschii-derived gene of major effect conferring resistance to Septoria leaf blotch (STB) and another Ae. tauschii-derived gene of major effect conferring resistance to soil-borne wheat mosaic virus (SBWMV) in the germplasm KS96WGRC40. The STB resistance gene in KS96WGRC40 is located in the distal 40% of the short arm of chromosome 7D flanked by microsatellite markers Xgwm044 and Xbarc126. Two previously reported STB genes, Stb4 and Stb5, have been mapped to 7DS in the same region as the STB resistance gene in KS96WGRC40. The uniqueness of the STB resistance genes on 7DS is questionable. The SBWMV resistance gene in KS96WGRC40 is located on chromosome 5DL linked to microsatellite marker Xcfd010. The SBWMV resistance gene within KS96WGRC40 was derived from TA2397 via KS95WGRC33.

>Magister Scientiae - MSc / Millions of tonnes of fly ash are generated worldwide every year to satisfy the large demand for energy. Management of this fly ash has been a concern and various approaches for its beneficial use have been investigated. Over the last two decades, there has been intensive research internationally that has focused on the use of different sources of fly ash for zeolite synthesis.However, most of the studies have concentrated on class C fly ash and very few have reported the use of South African class F fly ash as feedstock for zeolite synthesis.Class F fly ash from South Africa has been confirmed to be a good substrate for zeolite synthesis due to its compositional dominance of aluminosilicate and silicate phases. However, because differences in quartz-mullite/glass proportions of fly ash from different sources produces impure phases or different zeolite mineral phases under the same activation conditions, the present study focused on optimization of synthesis conditions to obtain pure phase zeolite Na-P1 from class F South African coal fly ash. Synthesis variables evaluated in this study were; hydrothermal treatment time (12 - 48 hours), temperature (100 – 160 oC) and addition of varying molar quantities of water during the hydrothermal treatment step (H2O:SiO2 molar ratio ranged between 0 - 0.49).Once the most suitable conditions for the synthesis of pure phase zeolite Na-P1 from fly ash were identified, a statistical approach was adopted to refine the experiments, that was designed to evaluate the interactive effects of some of the most important synthesis variables. In this case, the four synthesis variables; NaOH concentration (NaOH: SiO2 molar ratio ranged between 0.35– 0.71), ageing temperature (35 oC – 55 oC), hydrothermal treatment time (36 - 60 hours) and temperature (130 oC – 150 oC) were studied. The response was determined by evaluating the improvement in the cation exchange capacity of the product zeolite.The starting materials (fly ashes from Arnot, Hendrina and Duvha power stations) and the synthesized zeolite product were characterized chemically, mineralogically and morphologically by X-Ray fluorescence spectrometry, X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. Other characterization technique used in the study were Fourier transform infrared spectroscopy to provide structural information and also monitor evolution of crystallinity during synthesis, as well as cation exchange capacity to determine the amount of exchangeable positively charged ions. Nitrogen adsorption was used to determine the surface area and porosity, and inductively coupled mass spectrometry for multi-elemental analysis of the post-synthesis supernatants.The results from the X-ray diffraction spectroscopy showed that the most pure zeolite Na-P1 phase was achieved when the molar regime was 1 SiO2 : 0.36 Al2O3 : 0.59 NaOH : 0.49 H2O and at synthesis conditions such that ageing was done at 47 oC for 48 hours while the hydrothermal treatment time and temperature was held at 48 hours and 140 oC, respectively. Results from statistically designed experiments show that there was a distinct variation of phase purity with synthesis conditions. From the analysis of linear and non linear interactions, it was found that the main effects were ageing temperature and hydrothermal treatment time and temperature, which also showed some interactions. This experimental approach enabled a clearer understanding of the relationship between the synthesis conditions and the purity of the zeolite Na-P1 obtained.The quality of zeolites is a major determinant in the efficiency of toxic element removal from waste water. Preliminary experiments conducted using optimised zeolite Na-P1 obtained in this study with a cation exchange capacity of 4.11 meq/g showed a high percentage removal of Pb,Cd, Ni, Mn, V, As, B, Fe, Se, Mo Sr, Ba and Zn from process brine obtained from Emalahleni water reclamation plant.In summary, a pure phase of zeolite Na-P1 was obtained from South African class F fly ash feedstock at relatively mild temperature. The systematic approach, incorporating statistical design of experiments, developed in this study resulted in a better understanding regarding the relationships of synthesis parameters in the formation of zeolites from fly ash. The zeolite Na-P1 synthesized with a high cation exchange capacity was effective for removal of toxic elements from brine.

Doctor Educationis / The research focused on the synthesis, characterisation and activity of zeolite supported metal catalysts for the Friedel-Crafts alkylation of benzene with t-butyl chloride. Alkyl benzenes are traditionally produced via systems that employ the use of Lewis acids or strong mineral acids. There have been widespread concerns over these approaches based on their environmental impacts and separation difficulties. Recent approaches have endeavoured the much to use more environmentally eco-friendly systems and zeolites have proved to be versatile support materials. The use of zeolites has also shown to greatly improve product selectivity as well as easing separation constraints. However the adoption of zeolites on large scale Friedel-Crafts alkylation has been hampered by the high cost of zeolite production from commercial sources. On the other hand fly ash has been found to be a viable starting material for zeolite synthesis. Apart from that South Africa is faced with fly disposal challenges and there is continual accumulation of fly ash at the coal fired power stations, which provide about 77 % of the power produced in the country. In this light the use of fly ash will help to reduce the disposal constraints as well as providing a cheap starting material for zeolite synthesis. In this study the hierarchical Zeolite X has been successfully synthesised from fly ash via a hydrothermal treatment. The zeolite was then loaded with Fe/Mn via two approaches namely liquid phase ion exchange and incipient wetness impregnation. For comparison purposes seasoned commercial support materials namely HBEA and MCM- 41 were also loaded with the same metals and characterised with various techniques namely; HRSEM, EDS, HRTEM, XRD, SAED, ICP-OES and N2 adsorption analysis, It was found from the characterisation undertaken that the integrity of the respective supports was generally retained upon metal loading. Both the ICP-OES and the EDS proved that the desired metals were successfully introduced onto the zeolitic support materials. The calculated percentage metal loading for the catalysts prepared via incipient wetness impregnation was closely related to the actual values obtained from the ICP-OES analysis for both the monometallic and the bimetallic catalysts (Fe/Mn). It was observed that the amount of metal that can be introduced on a zeolite via liquid phase ion exchange is largely dependent on the cation exchange capacity of the zeolite Supported metal catalysts for FC alkylation Page v and of the catalysts prepared using 0.25 M Fe solution it was found that Zeolite X had the highest Fe wt% loading of 11.4 %, with the lowest loading of 2.2 % obtained with the MCM-41 supported catalyst. The XRD patterns for the both HBEA and the MCM-41 supported metal catalysts resembled the patterns of the respective prestine support materials except in the case of catalysts with anFe wt % of more than 10, which exhibited peaks due to the Fe2O3 crystallites. In the case of the hierarchical Zeolite X, the metal loaded support had a significant reduction in the XRD peak intensities. The prepared catalysts were tested for the alkylation of benzene with t-butyl chloride. The benzene was also used as the solvent. The alkylation reaction was carried out in a round bottomed flask under reflux conditions and stirring at a temperature of 45 oC over a period of 5 h. A total of 18 catalysts was tested and the highest percentage conversion of 100 % was obtained with the 10%FeH after a reaction time of 2 h. The general trend obtained with the majority of the catalysts was characterised with a rapid initial increase and then steady state was achieved. Generally after a reaction time of 3 h almost all the catalysts had reached steady state in terms of the percentage conversion obtained. The outcomes reflect that the inclusion of Mn does not enhance the conversion but rather decreases it. It was also found that the Mn was not active in the alkylation of benzene as shown by the inactivity of the 10%MnM, where 10% by weight Mn was loaded on MCM-41. However the other monometallic catalysts containing Mn supported on Zeolite X and HBEA were found to be active. The activity is attributed to the presence of Brønsted acid sites in these zeolites which are not present in MCM-41. The selectivity studies reflect that the inclusion of Mn does slightly improve the selectivity towards the formation of the monoalkylated product (t-butyl benzene). The highest selectivity of 91.1 % was obtained with the 10%FeMnM after a reaction time of 4 h. MCM-41 supported catalysts had a relatively higher selectivity compared to the other supports. Considering the Fe monometallic catalysts tested it generally can be said that the yield were in the order HBEA > MCM-41 > Zeolite X. It however should be noted that the percentage yield is calculated from the conversion and selectivity percentages, this implies that the factors affecting these parameters will consequently affect the percentage yield obtained. Supported metal catalysts for FC alkylation Page vi The alkylation reaction was found to be characterised by the formation of two intermediate products which could not be identified. These products were formed during the transient start up stages of the reaction and would disappear from the reaction mixture with longer reaction times, and after 3 h in almost all the reactions studied the intermediates were not detected in the reaction mixture. The main products found were the monoalkylated product (desired product) and the para isomer (1,4-t-di-butyl benzene). There were no other dialkylated isomers or trialkylated products detected. The formation of the para isomer was usually after a reaction time of 2 h in most reactions. The research managed to show that the hierarchical Zeolites X can be synthesised from fly ash and ion exchange and incipient wetness impregnation are appropriate approaches that can be used to introduce Fe/Mn onto the support materials studied. The catalysts prepared were active to varying degrees in the Friedel-Crafts alkylation of benzene with t-butylchloride, with the exception of the 10%MnM which was found to be inactive.

No description available.

Evolution of concrete is continuously taking place to meet the ever-growing demands of the construction industry. Self compacting concrete (SCC) has emerged as a result of this demand to overcome the scarcity of labour. SCC is widely replacing normal vibrated concrete (NVC) these days owing to its advantages such as homogeneity of the mix, filling ability even in heavily congested reinforcement, smooth finish, reduction in construction time etc. The ingredients used for SCC is the same as that of the NVC. But the proportioning of ingredients to achieve self compactability alters the microstructure of SCC which in turn affects the mechanical and fracture properties. Moreover, the mineral admixtures such as fly ash and silica fume when used for improving the workability of SCC help in the development of the microstructural skeleton. In this study, three SCC mixes SCC1- made with only cement, SCC2 - with fly ash in addition to cement and SCC3 - with fly ash and silica fume in addition to cement for achieving normal, medium and high strength SCC respectively are cast. The microstructural changes in SCC with and without mineral admixtures over a period of time are studied using different techniques such as scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The modification of mechanical properties at microstructural level brings difference in the behavior at macro level. Hence in this study, the mechanical properties at microstructural are obtained by using microindentation test and are scaled up to the macro level to predict the influence of micromechanical properties on macro response. The fracture properties of SCC is considered to be the interest of this study and is carried out with the help of advanced techniques such as acoustic emission (AE) and digital image correlation (DIC). From the various studies carried out, it is inferred that the mixes with mineral admixtures behave in a more brittle manner when compared to mix having no mineral admixture. It is also observed that class ‘F’ fly ash hydrates at a slow pace and the strength gain is observed after 28 days and even beyond 90 days. Hence, it is concluded that it is appropriate to consider the strength at 90 days instead of 28 days for a SCC mix with class ‘F’ fly ash. Silica fume on the other hand is observed to result in a more rapid gain in strength and this can partially offset the delay in strength gain due to fly ash.

The aim of the present investigation is to improve the geotechnical properties of dispersive soil by reducing their dispersivity after elucidating the important mechanisms controlling the dispersivity of the soils. Dispersive soils have unique properties, which under certain conditions deflocculate and are rapidly eroded and carried away by water flow. These soils are found extensively in the United States, Australia, Greece, India, Latin America, South Africa and Thailand. The mechanism of dispersivity of soils is a subject matter of great interest for geotechnical engineers. In the earlier days clays were considered to be non erosive and highly resistant to water erosion. However, recently it was found that highly erosive clay soils do exist in nature. Apart from clayey soil, dispersivity is also observed in silty soils. The tendency of the clays to disperse or deflocculate depends upon the mineralogy and soil chemistry and also on the dissolved salts in the pore water and the eroding water. Such natural dispersive soils are problematic for geotechnical engineers. They are clayey soils which are highly susceptible to erosion in nature and contain a high percentage of exchangeable sodium ions, (Na+). It is considered that the soil dispersivity is mainly due to the presence of exchangeable sodium present in the structure. When dispersive clay soil is immersed in water, the clay fraction behaves like single-grained particles; that is, the clay particles have a minimum of electrochemical attraction and fail to closely adhere to, or bond with, other soil particles. This implies that the attractive forces are less than the repulsive forces thus leading to deflocculation (in saturated condition).This weakens the aggregates in the soil causing structural collapse. Such erosion may start in a drying crack, settlement crack, hydraulic fracture crack, or other channel of high permeability in a soil mass. Total failure of slopes in natural deposits is initiated by dispersion of clay particles along cracks, fissures and root holes, accelerated by seepage water. For dispersive clay soils to erode, a concentrated leakage channel such as a crack (even a very small crack) must exist through an earth embankment. Erosion of the walls of the channel then occurs along the entire length at the same time. Many slope and earth dam failures have occurred due to the presence of dispersive soils. Unlike erosion in cohesionless soils, erosion in dispersive clay is not a result of seepage through the pores of clay mass. However, the role of type of clay and its Cation exchange capacity in the dispersion of soil is not well understood. Data on the presence, properties, and tests for identification of dispersive clays is scarce. Hence, an attempt is made, in this thesis, to develop reliable methods to identify these soils and understand the extent of their dispersivity as well as to develop methods to control their dispersivity. The present study deals with the characterization of a local dispersive soil collected from southern part of Karnataka State. This study has focused on comprehensive tests to assess the dispersivity of the soils by different methods and to methods to improve geotechnical properties by reducing the dispersivity of the soil. An attempt is made to reduce the dispersivity of soil by using calcium based stabilizers such as lime, cement and fly ash. The mechanism of improvement in reducing the dispersivity of the soil with calcium based stabilizers has been studied. One of the important mechanism by which the dispersivity of the soil is reduced is by inducing cementation of soil particles. The differences in effectiveness of different additives are due to their differences in abilities to produce cementitious compounds. Although all the additives increased the strength of the soil and reduced the dispersivity of the soil, cement was found to significantly reduce the dispersivity of the soil, compared to the other two additives lime and fly ash. Cement is more effective as sufficient cementitious compounds are produced on hydration without depending on their formation. A detailed review of literature on all aspects connected with the present study is given in Chapter 2. A comprehensive description of dispersive soils present worldwide has been brought out in this section. Based on this survey, the scope of the present investigation has been elaborated at the end of the chapter. To understand the reasons for dispersivity of the soil and to estimate its degree of dispersivity, it is essential to assess standard methods to characterize the soil. Chapter 3 presents a summary of material properties and testing programs. The results of geotechnical characterization of the soil, the index properties of the soilspecific gravity, sieve analysis, Atterberg’s limits are discussed in Chapter 4. The physico chemical characteristics play an important role in determining the amount of dispersivity of the soil. Dispersive soils have two main characteristics which define its dispersivity chemically. These are Sodium Adsorption Ratio (S.A.R) and Exchangeable Sodium Percentage (E.S.P). The two characteristics are determined from the Cation exchange capacity of the soil. Exchangeable Sodium Percentage is defined as the concentration of sodium ions present in the soil with respect to the Cat ion exchange capacity of the soil. And Sodium Adsorption Ratio is used to quantify the free salts present in the pore water. Since Atterberg’s limits and grain size analysis do not help in identifying dispersive soils or in quantifying its dispersivity, two other tests- Emerson Crumb test and double hydrometer test were carried out on the soil. Emerson crumb test is a simple way for identification of dispersive soils. In this test, a crumb of soil measuring about 1mm diameter is immersed in a beaker containing distilled water and the subsequent reaction is observed for 5 minutes. It is solely based on direct qualitative observations. Depending on the degree of turbidity of the cloud formed in the beaker, the soil is classified in one of the four levels of dispersion in accordance with ASTM-D6572. Since this test is mainly a qualitative test and does not help in quantifying the dispersivity, it cannot be depended upon completely in identifying a dispersive soil. Another test double hydrometer test, which helps in quantifying the dispersivity of the soil, was also conducted on the soil. This test involves in conducting the particle size distribution using the standard hydrometer test in which the soil specimen was dispersed in distilled water with a chemical dispersant. A parallel hydrometer test was conducted on another soil specimen, but without a chemical dispersant. The dispersing agent used for the experiment was sodium hexametaphosphate. The percent dispersion is the ratio of the dry mass of particles smaller than 0.005 mm diameter of the test without dispersing agent to the test with dispersing agent expressed as a percentage. The double hydrometer test was carried out according to Double Hydrometer Test (ASTM D4221). Apart from the conventional tests, attempts are made to consider shrinkage limit test and unconfined compression test to determine the dispersivity of the soil. For this purpose, the shrinkage limit of the soil was determined with and without dispersing agent. The initial shrinkage limit of the untreated soil reduced on treating it with dispersing agent, thus indicating that the soil had further dispersed on addition of dispersing agent. In order to carry out the unconfined compression strength, the maximum dry density and optimum moisture content was determined through the compaction test. The soil was then treated with dispersing agent and compacted at the optimum moisture content. The soil exhibited high degree of dispersion through the strength test. Hence it is necessary to stabilize the soil with additives. Detailed experimental program has been drawn to find methods to improve the geotechnical properties and to reduce the dispersivity of the soil. Chapter 5 presents the investigations carried out on the dispersive soil with lime. The importance of lime stabilization and the mechanism of lime stabilization have been discussed initially. Commercially obtained hydrated lime was used in the present study. The soil was treated with three different percentages of lime 3, 5 and 8. The curing period was varied from one day to twenty eight days. The effect of addition of lime on various properties of the soil such as pH, Atterberg’s limits, compaction test and unconfined compression test is elaborated in chapter 5. The pH of the soil was maximum on addition of 3% lime. On further addition, the pH decreased and remained constant. The liquid limit of the soil increased on adding 3% lime and decreased with further lime content. The compaction test conducted on the soil showed an increase in maximum dry density of the soil and reduction in optimum moisture content with 3% lime content. On further increase in the lime content, the soil showed a decrease in the maximum dry density and increase in optimum moisture content. The unconfined compressive strength of the soil also increased on increasing lime content upto 5%. The variation in strength of the soil with respect to curing period was also compared. Optimum lime content arrived at based on the above conducted tests was 3%. The effect of lime in reducing the dispersivity of the soil through shrinkage limit test and unconfined compression test is also presented in this chapter. Details of the efforts made on the soil with fly ash are presented in Chapter 6.The fly ash used for stabilization of Suddha soil was of Class F type. This type of fly ash contains low reactive silica and lime. The effect of varying fly ash content on the properties of Suddha soil by varying the percentage of fly ash from 3 to 10 percentages is discussed in this chapter. The tests conducted on fly ash treated Suddha soil were pH test, compaction test, Atterberg’s limits and unconfined compression test with varying curing period. The fly ash treated Suddha soil was cured from one day to twenty eight days for the unconfined compressive strength analysis. The pH of the soil system increased with increasing percentage of fly ash. The increase in liquid limit was marginal on addition of fly ash. The maximum dry density of fly ash treated Suddha soil decreased continuously and the optimum moisture content of the treated soil increased with increasing fly ash content. The unconfined compressive strength of Suddha soil increased with increase in fly ash content upto 8% and then decreased for fly ash content of 10%. For all the percentages of fly ash added, the strength of the soil increased with increase in the curing period. The effect of fly ash in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. It was seen that on increasing the fly ash content, the soil treated with dispersing agent showed an increase in the shrinkage limit. Also, the same trend was observed for the unconfined compression strength to determine dispersivity. Optimum fly ash was determined as 8% with the help of all the tests conducted on the soil. Since the improvement in the properties of the soil with lime and fly ash was not very high, Cement was also considered as another additive used for stabilization of Suddha soil. It is known that soil with lesser amount of clay content will respond well with cement. The effect of cement addition on various properties of Suddha soil has been brought out in Chapter 7. It was found that addition of cement had positive effects on all the properties of Suddha soil. The pH of the soil increased for all the percentages of cement addition. The liquid limit of the soil increased on increasing the cement content. The shrinkage limit also showed a similar trend. The optimum moisture content of the soil decreased on increasing the cement content for Suddha soil and the maximum dry density increased for cement treated Suddha soil. The soil showed the maximum dry density at 8% cement content. The unconfined compression strength conducted on cement treated Suddha soil increased significantly for higher cement contents and also with curing period. Suddha soil when treated with 8% cement content exhibited maximum strength in comparison to other percentages. Also, the effect of cement in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. The shrinkage limit of the soil increased for all percentages of cement content, even in the presence of dispersing agent. Through the unconfined compression strength for dispersivity, it could be seen that 8% cement treated Suddha soil had the least dispersion. Optimum cement content was derived as 8% with the help of the tests conducted on the soil. A comparison of effect of all the additives on the strength of the soil as well as effect of the additives in reducing the dispersivity of the soil is discussed in Chapter 8. The effect of additives on the shrinkage limit of the soil with and without dispersing agent has been compared. The variation in shrinkage limit of the soil when treated with the additives was due to the different mechanisms involved in reducing the dispersivity by each additive. The effect on the unconfined compression strength of the soil treated with the additives with and without dispersing agent is also brought out in this chapter. It was noted that the dispersion exhibited through shrinkage limit test was lesser as compared to the percentage dispersivity exhibited through unconfined compression test. Hence it could be said that dispersion of the soil is due to loss of cohesion than volume change behavior. Also, the unconfined compression strength of the soils with respect to curing period is compared. The percentage dispersivity calculated through these tests is summarized and compared. With the help of this it could be said that to control the dispersivity of the soil, it is necessary to enhance the strength of the soil. The general summary and major conclusions drawn from the thesis are presented in Chapter 9.

La communauté Rurale de Mont-Rolland (région de Thiès, Sénégal) est un foyer endémique de leishmaniose canine décrit depuis 1970. Des études épidémiologiques récentes ont montré que l'agent étiologique est Leishmania (Leishmania) infantum et que le cycle de transmission est bien établi sur l'ensemble de la commune, avec plus de 30% des chiens et plus de 20% des hommes séropositifs. Néanmoins, malgré les différentes études épidémiologiques, le vecteur reste toujours inconnu. Jusqu'à présent, aucune espèce de Phlebotomus, connue pour être vecteur de L. infantum (sous genre Larroussius et secondairement Adlerius), n'a été identifiée au Sénégal. Dans ce contexte, l'objectif principal de cette thèse était d'identifier les vecteurs potentiels de la maladie et de caractériser le cycle de transmission de la leishmaniose canine par des études écologiques, parasitologiques et moléculaires des populations de phlébotomes. Ainsi, 7442 spécimens de phlébotomes ont été récoltés par piégeage adhésif, piégeage lumineux et par pulvérisations intradomiciliaires d'insecticides pyréthrinoïdes. Neuf espèces de phlébotomes ont été identifiées : deux appartiennent au genre Phlebotomus, P. duboscqi (vecteur de la leishmaniose cutanée au Sénégal) et P. rodhaini, les autres espèces appartiennent au genre Sergentomyia, S. adleri, S. clydei, S. antennata, S. buxtoni, S. dubia, S. schwetzi, et S. magna. La distribution spatiale des phlébotomes est hétérogène selon le village, selon l'écosystème et l'environnement de capture. Les études parasitologiques et les études moléculaires (PCR diagnostique de Leishmania) ont révélé trois espèces de Sergentomyia infectées par L. infantum, S. dubia (dissection et PCR), S. schwetzi (dissection et PCR) et S. magna (PCR). Il faut noter que plus de 2% des individus femelles à jeun testées étaient PCR positives, soulignant la survie des parasites chez ces espèces après la digestion. Toutes les autres espèces étaient négatives aussi bien en dissection qu'en PCR. Les analyses statistiques ont montré : que la distribution de S. dubia est significativement associée à la séroprévalence chez les chiens, que les individus de S. schwetzi positifs en PCR sont significativement associés à la séroprévalence chez le chien, qu'il y a un effet significatif du nombre de phlébotomes positifs en PCR (les 3 espèces confondues) sur la séroprévalence chez l'homme. Toutes ces données démontrent pour la première fois que 3 espèces du genre Sergentomyia, S. dubia, S. schwetzi et probablement S. magna, sont les vecteurs de la leishmaniose canine dans le foyer de Mont-Rolland. Ces résultats remettent en question le dogme qui stipule que seul le genre Phlebotomus serait capable de transmettre le parasite Leishmania dans l'Ancien-Monde. L'étude du comportement et de la distribution de ces trois espèces et de leurs spécimens infectés nous ont permis de proposer un modèle de transmission dans ce foyer. / AbstractThe rural community of Mont-Rolland (Thiès, Sénégal) is an endemic focus of canine leishmaniasis described since 1970. Recent epidemiological studies showed that the causative agent is Leishmania infantum with well established transmission cycle throughout the area. However, despite the several epidemiological studies, the vector species is still unknown. So far, no species of Phlebotomus belongs to Larroussius and Adlerius subgenera, known as vector of L. infantum, was identified in Senegal. In this context, the main objective of this thesis was to identify potential vectors of the disease and to characterize the cycle of canine leishmaniasis transmission by ecological, parasitological and molecular studies on sandfly populations. Thus, 7442 specimens were collected by sticky traps, light traps and indoor spraying with pyrethroid insecticide from different environments (intradomiciliary, peridomiciliary, culture area, isolated area) and different villages and ecosystems (sandy soils, lateritic gravel soils and sandy clay soils). Nine species of sand flies were identified; two belong to the Phlebotomus genus, P. duboscqi (vector of cutaneous leishmaniasis in Senegal) and P. rodhaini, the other species belong to the Sergentomyia genus, S. adleri, S. clydei, S. antennata, S. buxtoni, S. dubia, S. schwetzi, and S. magna. Two species of the Phlebotomus genus were significantly underrepresented (292 specimens) compared to species of the Sergentomyia genus (7150 specimens). The spatial distribution of sand flies is heterogeneous depending on the village, the ecosystem and environment, suggesting that several species are capable of transmitting the parasite. Parasitological and molecular studies (diagnostic PCR of Leishmania) revealed that three species of Sergentomyia were infected with L. infantum, S. dubia (dissection and PCR), S. schwetzi (dissection and PCR) and S. magna (PCR). It is worth noting that more than 2% of un-fed females of these species were PCR-positive, emphasizing the survival of parasites after digestion. All other species were found to be negative in both PCR and dissection. In addition, statistical analysis showed that 1) the distribution of S. dubia is significantly associated with seroprevalence in dogs, 2) PCR-positive individuals of S. schwetzi are significantly associated with seroprevalence in dogs, 3) there is a significant effect of PCR-positive sand flies (all species considered) on seroprevalence in humans. All these data demonstrated for the first time that three species of Sergentomyia, S. dubia, S. schwetzi and probably S. magna, are the vectors of the canine leishmaniasis in the Mont-Rolland commune. The results presented in this study challenge the dogma which states that only the Phlebotomus genus would be capable of transmitting Leishmania parasites in the Old World. The behaviour and distribution of these three species and their infected specimens allowed us to propose a model of transmission in the focus.