Thèse de doctorat : Physique. Sciences des matériaux : Paris 12 : 2005. / Titre provenant de l'écran-titre. Bibliogr. en fin de chapitres.

Reproduction de : Thèse de doctorat : Génie des procédés et de l'environnement : Toulouse, INPT : 2008. / Titre provenant de l'écran-titre. Bibliogr. 89 réf.

Nigeria is the most densely populated country in Africa and one of the most advanced economically in terms of both industry and soil and landscape utilization. This country is projected to have one of the largest urban growth rates by 2050. Thus, the demands of the rapidly increasing human population and its material consumption represent a severe threat to biodiversity. Nigeria has the highest deforestation rate of natural forest in the world, its original vegetation has largely been replaced by farming activities, urban development and other products of human activities. The principal causes of the decline and loss of biodiversity in Nigeria include human exploitation of natural resources, fragmentation of habitats and populations, conversion of wild areas to agriculture and other intensive human use and alterations in the structure and function of ecosystems. Amphibians are the vertebrate group with the highest number of species threatened with extinction and habitat loss and fragmentation are considered to be among the leading causes of their declines and extinctions. It has been recognized that one of the most severe problems in conservation biology is the scarcity of baseline data. Such lack prevents evaluation of the effect of the expanding anthropogenic impact and determination of potential population declines. The mountains of eastern Nigeria, within Taraba State, are regionally important in terms of biodiversity and endemism, however, its herpetofaunal diversity has received little attention. Moreover, no studies have investigated how habitat loss and fragmentation may affect dispersal and gene flow among small and isolated amphibian populations, and in the absence of such studies attempts at amphibian conservation are compromised. The aims of this project were threefold. Firstly, a comprehensive inventory of the amphibians and reptiles of Ngel Nyaki and Kurmin Danko Reserve on the Mambilla Plateau was compiled. The outcome, an annotated list of 21 amphibians and 11 reptiles, represent the most thorough inventory to date of the herpetofauna on the Mambilla Plateau. Based on this inventory four key anuran species were selected to conduct a population genetics study. Secondly, molecular tools specifically AFLP markers were developed and used to analyze the genetic population structures of the four frog species Cardioglossa schioetzi, Leptodactylodon bicolor, Astylosternus sp. 1 and Astylosternus sp. 2. differing in geographic distribution and life history traits within the study area. Thirdly, these species were assessed to understand dispersal and connectivity among fragmented and continuous populations on the Ngel Nyaki and Kurmin Danko Reserve. Genetic differentiation among the forest and the riparian fragment populations was observed for three of the target species, however, no significant genetic differentiation was detected among the populations located in continuous forest for any of the four frog species. In addition, geographic and genetic distances were not correlated significantly for any of the four target species, suggesting no isolation by distance at this fine geographic scale. Results from both the inventory and the genetic population structure study revealed that the riparian forest fragments are of utmost importance for the persistence and migration of Cardioglossa schioetzi, and potentially for many other amphibian species. The new scientific findings are now part of the valuable baseline data on the diversity and genetic population structure of amphibian species in Ngel Nyaki and Kurmin Danko Forest Reserve. These results will better inform conservation managers who need to make decisions around management of montane habitat for amphibian species.

The assessment of fragmentation is an important aspect of the design and planning of any excavation. The distribution of fragment sizes in situ helps assess the requirement of explosive energy to excavate the rock material. In addition, the information can also be used to evaluate the ground water flow, leaching characteristics and the requirement of additional rock handling equipment in construction projects. In the block cave mining method, the assessment of in situ and secondary fragmentation is an integral part of the design of the excavations at the extraction level and the selection of material handling systems for transporting the ore to the processing stations. Secondary blasting requirements can also be estimated based on the fragment size distributions developed for the block cave. Methods of estimating fragment size distributions in block cave mines have been based on joint set parameters estimated from structural mapping in available excavations or outcrops. While this is acceptable in the absence of any other means of assessing the fragmentation, the results can often be misleading since the structural mapping is often carried out in limited areas and the results applied uniformly to the entire deposit. This new study proposes to use the core piece lengths information gathered from the boreholes to develop in situ and primary fragmentation estimates for block cave operations. Under this proposed study, drill core piece lengths from an exploration program in Indonesia will be used along with structural mapping data to develop estimates for in situ and primary fragment size distributions. Methods for estimating secondary fragmentation from primary fragmentation will be evaluated and the estimates of secondary fragmentation from the different methods will be compared with the actual fragmentation characteristics observed at the drawpoints. The primary assumption in the development of primary fragment size distributions from drill core data is that each drill hole piece represents one in situ rock block. The relationships between the joint spacings and lengths of the different joint sets, evaluated from the joint set characteristics gathered from available excavations, outcrops or oriented core drilling programs, can be utilized for estimating the shape of the rock blocks.

The gas-phase chemistry of butanal, propanal, and acetaldehyde has been investigated using electron bombardment matrix isolation techniques. Each aldehyde was diluted in excess argon gas and subjected to electron bombardment with 300eV electrons. The products of subsequent reaction processes were matrix isolated and analyzed by FTIR absorption spectroscopy. Ionized butanal produced a variety of decomposition products including propane, propene, propyne, ethene, ethyne, CCCO, ketene, formaldehyde, CO, CH2=CHCH2•, CH2CHO•, HCO• and methane. Products resulting from ionized propanal included the ethyl radical, ethane, ethene, ethyne, CO, CH2CHO•, HCO• and methane. In both cases the products are believed to be formed from C—C cleavages of the parent ion followed by hydrogen atom scavenging and/or hydrogen atom abstraction from proximally located species. Dehydrogenation products of propane and ethane are proposed to result from product secondary ionization, a process dependent on high electron currents. Surprisingly, in the case of butanal, the McLafferty Rearrangement, a dominant process in electron ionization mass spectrometry, was not observed to occur. Electron bombardment of acetaldehyde:Ar mixtures produced many decomposition products including methane, CO, HCO•, CH3CO•, CH2CHO•, CH3• and ketene. The isomerization product, vinyl alcohol, was also observed. As way of investigating the mechanisms of the above products, experiments were performed in which the acetaldehyde:Ar mole ratio was varied. Variations in the acetaldehyde:Ar mole ratio produced dramatic variations in the products formed, demonstrating a transition from unimolecular chemistry at low acetaldehyde mole ratios, to processes consistent with bimolecular processes at intermediate mole ratios. Variations in the total flow rate of gas resulted in nonsystematic changes in product yields but provided further evidence for unimolecular methane formation via the elimination of neutral CO. Finally, an investigation into the mechanism of vinyl alcohol using the acetaldehyde isotopomer, CD3CHO, in conjunction with computational methods provided further evidence that enol formation occurs as a result of a direct 1,3-H-transfer and not consecutive 1,2-H-transfers. / Thesis (Master, Chemistry) -- Queen's University, 2009-06-26 10:51:32.331

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Introduction The National Superconducting Cyclotron Laboratory (NSCL) is a national nuclear physics facility in which heavy ion beams are fragmented to produce exotic nuclei. In this process of fragmentation many nuclei are created, however, only one isotope is selected for experimentation. The remaining isotopes that are created go unused. The future upgrade of the NSCL to the Facility for Rare Isotope Beams (FRIB) will increase the incident energy of these heavy ion beams and amplify the current by three orders of magnitude. An aqueous beam dump will be created to collect the unused isotopes created in the process of fragmentation. Several of these isotopes are of interest for many applications including nuclear security, medical imaging, and therapy and are not currently available or are only available in very limited supply. Harvesting these isotopes from the aqueous beam dump could provide a consistent supply of these im-portant isotopes as an ancillary service to the existing experimental program. Material and Methods A liquid water target system was designed and tested to serve as a mock beam dump for exper-iments at the NSCL1. A 25 pnA 130 MeV/u 76Ge beam was fragmented using a 493 mg/cm2 thick beryllium production target. After fragmentation the beam was separated using the A1900 frag-ment separator2 set up for maximum 67Cu pro-duction using a 240 mg/cm2 aluminum wedge and a 2% momentum acceptance. The secondary beam was collected for four hours in the liquid water target system before being transferred to a collection vessel. Four additional four hour collections were made before finally shipping the five collections to Washington University and Hope College for chemical separation. Four of the five samples were separated using a two part separation scheme. First they were passed through and 3M Empore iminodiacetic acid functionalized chelation disk in a 1.25M ammonium acetate solution at pH 5. The flow through was collected and analyzed using an HPGe detector. Then 10mL of 6M HCl acid was passed through the chelation disk to remove the 2+ transition metals. The 10mL of 6M HCl acid was collected after passing through the disk and added to an anion-exchange column with 2.5 g AG1-X8 resin. The eluate was collected and then an additional 10mL of 6M HCl was passed through the column to remove the nickel. The 67Cu was then collected by passing 10mL of 0.5M HCl and the eluate was collected in 1mL fractions each analyzed by HPGe for 67Cu concentration and purity. The two highest 67Cu fractions were heated to dryness and reconstituted in 50 μL 0.1M ammonium acetate pH 5.5. 2 μL of 7.9 mg/mL NOTA-Bz-Trastuzumab was added to 45 μL of 67Cu and 3 μL 0.1M ammonium acetate pH 5.5. This solution was placed in a shaking incubator at 37 °C for twenty minutes and then analyzed by radio-instant thin layer chromatography in order to determine the per-cent of 67Cu bound to the antibody. Results and Conclusion 67Cu was collected into the liquid water target system with an average efficiency of 85 ± 5 %. The secondary beam was 73 % pure with the impurities, half-lives greater than 1 minute, listed in TABLE 1. Separation of 67Cu from the impurities resulted in an average recovery of 88 ± 3 % for a total recovery of 67Cu from the beam and separation of 75 ± 4 %. No detectable radioactive impurities were found in the final samples when analyzed using an HPGe detector. TABLE 2 shows the amount of 67Cu collected from the beam and the amount recovered decay corrected to end of bombardment. Labeling NOTA-Bz-Trastuzumab with 67Cu resulted in > 95 % radiochemical yield. Collection of the 73 % pure 67Cu beam in water and the resulting separation proved successful. These results demonstrate that radioisotopes can be collected from fragmented heavy ion beams and isolated in usable quantities and purity for many radiochemical applications. Further experimentation with an unpurified beam to better simulate conditions in the beam dump at the Facility for Rare Isotope Beams will be performed in the near future.

The Cameroon Highlands that run along the Cameroon-Nigeria border are an important source of biodiversity. Not only are they rich in species and high in endemics, but biota from West Africa have not been studied as extensively relative to other parts of the Afrotropics, or the tropics in general. Threatening these rare and diverse habitats is anthropogenic pressure, which fragments forests and changes local animal communities. This thesis wished to address the impact of humans on seed dispersal and recruitment processes on selected tree species in forests on the Mambilla Plateau - a montane region in Nigeria's north-east. Research was conducted at Ngel Nyaki Forest Reserve, a conservation area established by the Nigerian Montane Forest Project. The reserve comprises a moderately-large forest patch (Ngel Nyaki Forest) and many small riparian fragments embedded in a grassland matrix. Cattle grazing and burning of this grassland are major threats to the survival of forest in this area.Hunting of local wildlife for bushmeat is also of concern, considering many of the region’s large-mammalian fauna are now locally extirpated (e.g. elephants) or at low abundances (many primate species). Loss of large-bodied frugivorous species has the potential to negatively impact the recruitment of large-seeded tree species that solely rely on them as seed dispersers. In this study, the ability for scatterhoarding rodents to act as surrogate dispersers for large-seeded species is tested. While much research has been carried out on secondary rodent dispersal in the Neotropics, work in the Afrotropics is still in its infancy. Because the outcome of plant-rodent interactions (i.e. predated or dispersed) may vary with season, habitat, or traits of the seed species in question, a number of experiments were established to quantify how local rodents at Ngel Nyaki may or may not be acting as effective dispersers. Additionally, the benefits of rodent dispersal were examined by creating an experiment that simulated secondary dispersal on seedling recruitment. The results of this study demonstrated that rodents can act as effective dispersers in Afromontane forests, but this is influenced by habitat, seasonal abundance of resources, and palatability of seed species. Furthermore, it was demonstrated that burial of seeds by rodents can increase the establishment probability of a seed by protecting it from removal by other rodents. However, while rodents play a strong driver of seed survival, it was also demonstrated that seedling mortality factors (such as herbivory) can also be heavy filters to seedling success. It is hoped that the results of this study will help to inform better management decisions and understand how the composition of the forest might change in the future.

Habitat fragmentation is one of the most important factors affecting species extinction and biodiversity loss, Species habitat response expects to differ with habitat feature at different spatial scales and this study was to identify how bat diversity and individual bat species respond to different habitat amounts. The local bat species richness was observed in 156 different locations in Östergötland and the proportion of different habitats were calculated for circular areas with diameters ranging from 400 m. to 12 km. from each location. Although we found that the individual bat species responded differently to the amount of each habitat at different spatial scales, the bat species richness showed a decreasing response with increasing spatial scale. The strongest response of bat species richness to habitat characteristics was at a scale of 939 m.

An intermittently connected network (ICN) is defined as a mobile network that uses cooperation between nodes to facilitate communication. This cooperation consists of nodes carrying messages from other nodes to help deliver them to their destinations. An ICN does not require an infrastructure and routing information is not retained by the nodes. While this may be a useful environment for message dissemination, it creates routing challenges. In particular, providing satisfactory delivery performance while keeping the overhead low is difficult with no network infrastructure or routing information. This dissertation explores solutions that lead to a high delivery probability while maintaining a low overhead ratio. The efficiency of message fragmentation in ICNs is first examined. Next, the performance of the routing is investigated when erasure coding and network coding are employed in ICNs. Finally, the use of social networking in ICNs to achieve high routing performance is considered. The aim of this work is to improve the better delivery probability while maintaining a low overhead ratio. Message fragmentation is shown to improve the CDF of the message delivery probability compared to existing methods. The use of erasure coding in an ICN further improve this CDF. Finally, the use of network coding was examined. The advantage of network coding over message replication is quantified in terms of the message delivery probability. Results are presented which show that network coding can improve the delivery probability compared to using just message replication. / Graduate / 0544 / 0984 / ahmedbdr@engr.uvic.ca