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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Grodsamhällen längs vattendrag på Borneo : En identifiering av habitatkaraktärer viktiga för diversitet och abundans av grodor i tropisk regnskog / Frog communities along streams in Borneo : An identification of habitat characteristics important for the diversity and abundance of frogs in tropical rain forest

Sandberg, Lisa January 2012 (has links)
The stretch from the riparian zone of a major river, through the mouth and upstream in tributaries forms a range of differing habitats. The aim of this study was to investigate the effect of these different habitats on the riparian frog community in primary rain forest in Borneo; i.e. examine whether any gradients could be demonstrated in terms of species composition, diversity and density of frogs, as well as which environmental characteristics that seem to be of most importance in forming habitats of high conservational value. A major river, Segama, and three of its tributaries were investigated. The surveys were carried out at night by searching for frogs visually and acoustically along the streams, from the shore of the Segama river and 400 metres upstream in the tributaries. In all transects 10 habitat variables were also measured. The results from the study show a significantly lower diversity and abundance of frogs along the shores of Segama and close to the mouths of the tributaries compared to further upstream, and a significant difference in species assemblage. Most species exhibited a negative correlation with the downstream transects or were not found there at all. The habitat characteristics waterfalls and boulders were found to be of most importance for the diversity and abundance of frogs, making these characteristics key components of habitats with high conservational value. Major rivers could also potentially form dispersal corridors for invasive species, which findings of the introduced species Fejervarya limnocharis along the shores of Segama shows.
142

Local adaptation of larval life history in the moor frog Rana arvalis across a landscape mosaic

Lustenhouwer, Monique January 2012 (has links)
Growth rate is an important life history trait, which impacts fitness indirectly through its effect on the age and size at maturity, as well as directly through costs associated with accelerated growth such as increased predation risk. Genetic variation and plasticity in growth are widespread in nature, and local adaptation of growth rate may evolve due to divergent selection in different environments, for example related to predation risk, temperature or time constraints. I studied local adaptation of larval life history in the moor frog Rana arvalis, in a local network of ponds close to Uppsala. Local adaptation of growth rate and survival was studied in a reciprocal transplant experiment between ponds with different habitat characteristics. Meanwhile, differences among the populations in intrinsic growth, activity and response to predation were studied in a common garden experiment in the laboratory, where tadpoles were raised in the presence or absence of a predator and tested in direct predation trials. In the field, differences in growth among populations were found, independent of which pond the tadpoles were raised in, indicating that the ponds were similar growth environments. Survival differences among the populations depended on the pond, but local populations did not do better than foreign ones. In the laboratory, similar patterns in growth rate were found. All populations were highly plastic in their response to predation, having lower growth and activity in the predator-induced treatment and decreased mortality in the predation trials. Tadpole size was an important factor in escaping predation. One population clearly grew faster than the others in the field and in the lab, which could be explained in terms of its habitat of origin but was most likely related to the relatively late hatching of this population. Future studies are necessary concerning the possible costs of this accelerated growth and the importance of breeding phenology. Apart from the one differential population, I did not find evidence of local adaptation in the field or in the laboratory. The influence of habitat characteristics on tadpole life history was difficult to study, due to the limited number of ponds and many environmental differences among them. However, this thesis was a valuable pilot study concerning the design of experiments to study factors promoting and constraining local adaptation in landscape mosaics. An understanding of local adaptation at the scale at which gene flow occurs is important for the conservation of populations in fragmented landscapes as well as for the study of ecological speciation.
143

The Effects of Recreational Trail Design and Management Decisions on Northern Leopard Frog (Rana pipiens) Populations in an Urban Park

McAllister, Catherine January 2006 (has links)
In addition to their original purpose as recreational areas, urban parks provide important habitats for species living in urban settings. Reconciling recreational and environmental goals is problematic, especially for park planners. RIM Park, in Waterloo, Ontario, is an example of this attempted reconciliation, where planners and managers attempted to conserve herpetofauna in a provincially significant wetland. However, this area includes a paved nature trail used by hikers, in-line skaters and cyclists and is adjacent to a golf course (which lies within the boundaries of the park). Herpetofauna breeding ponds were constructed and a series of culverts and clearspans included in order to provide reptiles and amphibians with safe passage under the trails. My objective was to determine whether these measures have been effective, whether the park sustains a viable population of Northern Leopard Frogs, and what factors influence frog populations in the park. Two spring field seasons involving mark and recapture techniques were attempted to estimate population sizes of Northern Leopard Frogs at RIM Park, as well as control sites. In both seasons, a control site was a cedar swamp 14 km to the west of the park within an Environmentally Sensitive Policy Area in Waterloo city limits affected by housing development and shared trails. Also within Waterloo city limits, a storm water management pond 8 km to the west was added in field season two. In 2005 (field season 1), because there was a serious drought almost no Northern Leopard Frogs were captured at the two sites examined ? RIM Park and the cedar swamp. In 2006, the more "normal" weather conditions revealed that RIM Park had significantly fewer Northern Leopard Frogs than either of the control sites. Given the lack of data in year 1, I compared the 2006 results to seven years of monitoring reports on RIM Park from consultants. The 2006 data were consistent with previous reports of small Northern Leopard Frog populations at RIM Park. Mark and recapture sessions revealed relatively low numbers, with a catch average of 4. 33 (SD = 1. 15). Calculations revealed an estimated population of 23 (SE = 13. 42). The highest number of observed Northern Leopard Frogs ever recorded at the same location in consulting reports is 5. It is likely that the ponds at RIM Park do not support breeding in Northern Leopard Frogs as the only adults caught were late in the season, during the last week of May, and adults likely were transients from the nearby wetlands and uplands. It is possible, given the historical monitoring data, that the Northern Leopard Frogs were long absent from RIM Park because of intensive farming activities that had replaced the wetlands, and that construction of the golf course and trails further precluded colonization. The lack of adult frogs in the breeding ponds and the lack of dead or injured frogs on the trails or golf course support the hypothesis that the trails are not presently causing frog mortality. It is possible that the frogs are avoiding recolonizing the trail and golf course area. It is also likely that the breeding ponds need to be deepened and only then will it be apparent whether the frogs will colonize the ponds, lay eggs, and use the clearspans and culverts. Recommendations include a shift in priorities to put the emphasis on restoration, a discussion of restoration options (including a possible restoration plan), possible improvements in amphibian monitoring techniques (such as reducing the reliance on audio methods), and general suggestions for urban park planning and management.
144

Next Generation Ultrashort-Pulse Retrieval Algorithm for Frequency-Resolved Optical Gating: The Inclusion of Random (Noise) and Nonrandom (Spatio-Temporal Pulse Distortions) Error

Wang, Ziyang 14 April 2005 (has links)
A new pulse-retrieval software for Frequency-Resolved Optical Gating (FROG) technique has been developed. The new software extends the capacity of the original FROG algorithm in two major categories. First is a new method to determine the uncertainty of the retrieved pulse field in FROG technique. I proposed a simple, robust, and general technique?tstrap method?ch places error bars on the intensity and phase of the retrieved pulse field. The bootstrap method was also extended to automatically detect ambiguities in the FROG pulse retrieval. The second improvement deals with the spatiotemporal effect of the input laser beam on the measured GRENOUILLE trace. I developed a new algorithm to retrieve the pulse information, which includes both pulse temporal field and the spatiotemporal parameters, from the spatiotemporal distorted GRENOUILLE trace. It is now possible to have a more complete view of an ultrashort pulse. I also proposed a simple method to remove the spatial profile influence of the input laser beam on the GRENOUILLE trace. The new method extends the capacity of GRENOUILLE technique to measure the beams with irregular spatial profiles.
145

Detection Of Species Boundaries In The Rana Ridibunda Complex Of Southwestern Turkey Using Mitochondrial Nd3 Marker

Akin, Cigdem 01 January 2007 (has links) (PDF)
Water frogs are one of the most interesting vertebrate groups, showing great diversity and complexity in their reproductive modes, ecology and evolutionary relationships, and with many cryptic species due to high morphological similarity. For many decades, a single species, Rana ridibunda, has been suggested to exist in Turkey. However, the application of new morphometric, molecular and bioacoustic techniques has recently revealed the occurrence of several distinct water frog taxa in Turkey. In this study, 340 bp long mtDNA ND3 region in 195 specimens was sequenced and subjected to phylogenetic analyses to detect geographical structure and species boundaries. Neighbor joining tree, minimum spanning network, SAMOVA and AMOVA were used to understand relationship within and among clades. Population demography was studied through mismatch distribution and neutrality tests. Results indicated that populations in southwestern Turkey show high diversity and strong geographic structuring. In Turkey there are four major maternal lineages, each probably representing a species: Thrace lineage represents Rana ridibunda Pallas 1771 in European Turkey / Ceyhan lineage indicates an unnamed taxon in Cilicia plain / South-central lineage occurs at the Lake District, Antalya, Konya and Karaman provinces and represents Rana caralitana Arikan, 1988 / Anatoliaca lineage (occuring in Asiatic Turkey except for central southern Turkey, Rhodes &amp / Karpathos, northeastern Syria, and probably also Iraq and Transcaucasia) is designated either as Rana cerigensis Beerli, Hotz, Tunner, Heppich, and Uzzell 1994 or as a new subspecies of R. caralitana, based on the degree of reproductive isolation present between the last two lineages.
146

The morphology and function of the peritoneum in lower vertebrates with special reference to teleosts

Lewis, Philip Nigel January 2001 (has links)
No description available.
147

Bridge Management System with Integrated Life Cycle Cost Optimization

Elbehairy, Hatem January 2007 (has links)
In recent years, infrastructure renewal has been a focus of attention in North America and around the world. Municipal and federal authorities are increasingly recognizing the need for life cycle cost analysis of infrastructure projects in order to facilitate proper prioritization and budgeting of maintenance operations. Several reports have highlighted the need to increase budgets with the goal of overcoming the backlog in maintaining infrastructure facilities. This situation is apparent in the case of bridge networks, which are considered vital links in the road network infrastructure. Because of harsh environments and increasing traffic volumes, bridges are deteriorating rapidly, rendering the task of managing this important asset a complex endeavour. While several bridge management systems (BMS) have been developed at the commercial and research level, they still have serious drawbacks, particularly in integrating bridge-level and network-level decisions, and handling extremely large optimization problems. To overcome these problems, this study presents an innovative bridge management framework that considers network-level and bridge-level decisions. The initial formulation of the proposed framework was limited to bridge deck management. The model has unique aspects: a deterioration model that uses optimized Markov chain matrices, a life cycle cost analysis that considers different repair strategies along the planning horizon, and a system that considers constraints, such as budget limits and desirable improvement in network condition. To optimize repair decisions for large networks that mathematical programming optimization are incapable of handling, four state-of-the art evolutionary algorithms are used: Genetic algorithms, shuffled frog leaping, particle swarm, and ant colony. These algorithms have been used to experiment on different problem sizes and formulations in order to determine the best optimization setup for further developments. Based on the experiments using the framework for the bridge deck, an expanded framework is presented that considers multiple bridge elements (ME-BMS) in a much larger formulation that can include thousands of bridges. Experiments were carried out in order to examine the framework???s performance on different numbers of bridges so that system parameters could be set to minimize the degradation in the system performance with the increase in numbers of bridges. The practicality of the ME-BMS was enhanced by the incorporation of two additional models: a user cost model that estimates the benefits gained in terms of the user cost after the repair decisions are implemented, and a work zone user cost model that minimizes user cost in work zones by deciding the optimal work zone strategy (nighttime shifts, weekend shifts, and continuous closure), also, decides on the best traffic control plan that suits the bridge configuration. To verify the ability of the developed ME-BMS to optimize repair decisions on both the network and project levels, a case study obtained from a transportation municipality was employed. Comparisons between the decisions provided by the ME-BMS and the municipality policy for making decisions indicated that the ME-BMS has great potential for optimizing repair decisions for bridge networks and for structuring the planning of the maintenance of transportation systems, thus leading to cost savings and more efficient sustainability of the transportation infrastructure.
148

Quantitative Simulation of Synaptic Vesicle Release at the Neuromuscular Junction

Ma, Jun 01 May 2014 (has links)
Nerve signals in the form of action potentials are relayed between neurons through specialized connections called synapses via neurotransmitter released from synaptic vesicles. The release process is Ca2+ dependent, and relies on fusion of neurotransmitter filled synaptic vesicle with the presynaptic membrane. During high frequency stimulation, the amount of vesicle release increases at some synapses (e.g., frog neuromuscular junction (NMJ)), a process known as short-term plasticity. Due to the micron scale size of the presynaptic active zone where vesicle fusion takes place, experimentally study is often difficult. Thus, computational modeling can provide important insight into the mechanism of synaptic vesicle release at active zones. In the first part of my thesis, I used the frog NMJ as a model synapse for computer simulation studies aimed as testing various mechanistic hypotheses proposed to underlie short-term plasticity. Building off a recently reported excess-bindingsite model of synaptic vesicle release at the frog NMJ (Dittrich et al., 2013), I have investigated several mechanisms of short-term facilitation at the frog NMJ. My studies placed constraints on previously proposed mechanistic models, and concluded that the presence of a second calcium sensor protein on synaptic vesicles distinct from synaptotagmin, can explain known properties of facilitation observed at the frog NMJ. In addition, I was able to identify a second facilitation mechanism, which relied on the persistent binding of calcium bound synaptotagmin molecules to lipids of the presynaptic membrane. In the second part of my thesis, I investigated the structure function relationship at active zones, with the hypothesis that active zones are organized from the same basic synaptic building block consisting of a docked vesicle and a small number of closely associated voltage-gated-calcium-channels (VGCCs). To test this hypothesis, I constructed a vesicle release model of the mouse NMJ by reassembling frog NMJ model building blocks based on electron-microscopy imaging data. These two models successfully predicted the functional divergence between frog and mouse NMJ in terms of average vesicle release and short-term plasticity. In the meanwhile, I found that frog NMJ loses facilitation when VGCCs were systematically removed from active zone. By tracking Ca2+ ions from each individual VGCCs, I further show how the difference in short-term plasticity between frog and mouse NMJ may rise from their distinct release building block assemblies. In summary, I have developed a stochastic computer model of synaptic transmission, which not only shed light on the underlying mechanisms of short-term plasticity, but was also proved powerful in understanding structural and functional relationships at synaptic active zones.
149

Novel diagnostic technologies for optical communication systems

Watts, Regan Trevor January 2008 (has links)
The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.
150

Novel diagnostic technologies for optical communication systems

Watts, Regan Trevor January 2008 (has links)
The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

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