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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.
161

Artificial Grammar Recognition Using Spiking Neural Networks

Cavaco, Philip January 2009 (has links)
This thesis explores the feasibility of Artificial Grammar (AG) recognition using spiking neural networks. A biologically inspired minicolumn model is designed as the base computational unit. Two network topographies are defined with different ideologies. Both networks consists of minicolumn models, referred to as nodes, connected with excitatory and inhibitory connections. The first network contains nodes for every bigram and trigram producible by the grammar’s finite state machine (FSM). The second network has only nodes required to identify unique internal states of the FSM. The networks produce predictable activity for tested input strings. Future work to improve the performance of the networks is discussed. The modeling framework developed can be used by neurophysiological research to implement network layouts and compare simulated performance characteristics to actual subject performance.
162

K’asba’e T’oh: sustaining the intergenerational transmission of Tāłtān

Morris, Kāshā Julie Anne 01 September 2017 (has links)
The Tahltan language is endangered and at a critical juncture because there are now fewer than 30 fluent speakers. The Tahltan Nation is working to change this by creating many different opportunities for language learning, focusing on programming, documentation, and professional development and training. One way that our language is being revitalized is through immersion programs for young children. Using ‘Tahltan Voiceability’ as the overarching methodology, this study reports on the language nest model as an immersion method of Indigenous language revitalization in Tahltan communities in northern British Columbia. Parents, language mentors, and administrators shared their perspectives and experiences regarding the way in which K’asba’e T’oh (the Dease Lake Language Nest) began in Tātl’ah (Dease Lake), how things are progressing, and what motivated and continues to motivate people to be involved. Through an analysis of these conversations, I share esdahūhedech (their tellings) and report on emerging themes. With this immersion setting in place, there is hope that this program will create speakers, inspire others to learn our language, and be part of increasing the proficiency of language learners, thereby moving our language out of the endangered status. This study is part of a growing body of research in Canada studying language nests to promote the intergenerational transmission of Indigenous languages. / Graduate
163

Responses of grassland birds to patch-burn grazing in the Flint Hills of Kansas

Erickson, Amy Nicole January 1900 (has links)
Master of Science / Department of Biology / Brett K. Sandercock / Grassland birds are declining throughout their native range. The Flint Hills of eastern Kansas and Oklahoma contain large tracts of tallgrass prairie, but intensification of agricultural practices may be contributing to ongoing population declines. Common rangeland management practices include annual burning coupled with heavy grazing by cattle. This system, known as intensive early stocking and burning, promotes homogeneous utilization of forage by cattle but may not provide habitat for some grassland bird species. Patch-burn grazing is an alternative management system that aims to restore heterogeneity on rangelands by recreating the fire-grazing interaction that would have historically occurred throughout the Great Plains. From 2011-2013, we examined responses of grassland birds to traditional rangeland management and patch-burn grazing by conducting vegetation surveys, line transect surveys, and nest monitoring on privately-owned pastures in Chase County and Greenwood County, Kansas. Vegetative heterogeneity was higher on patch-burned pastures, with unburned patches having higher visual obstruction and less bare ground. Densities of grassland birds differed by species and among habitat strata. Unburned patches on patch-burned pastures were associated with increased densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna) and Grasshopper Sparrows (Ammodramus savannarum). Henslow’s Sparrows (A. henslowii) were only detected on patch-burned pastures. Nest survival of grassland songbirds was similar among management systems but varied by year. Probability of nest parasitism by Brown-headed Cowbirds (Molothrus ater) varied among years and between treatments for Dickcissels and Grasshopper Sparrows, with overall lower rates on burned areas and during drought years. For Dickcissels and Grasshopper Sparrows, there was a significant reduction in host clutch size between parasitized versus unparasitized nests. Overall, nest survival of grassland songbirds in managed rangelands was low. Patch-burn grazing improved rangeland conditions and provided habitat for more species of birds, but did not increase nest survival. Drought conditions in 2012 and 2013 may have influenced the results of this study, as many landowners were unable to burn as planned. Further study is needed to determine underlying factors driving variation in nest success and parasitism rates for grassland birds, particularly on private lands which make up the vast majority of remnant tallgrass prairies.
164

Factors affecting the demography of a lek-mating bird: the greater prairie-chicken

Nooker, Jacqueline Kay January 1900 (has links)
Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter ‘T’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5% of males obtaining 87.2% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because < 10% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.
165

The Effects of Suburbanization on Nest Ectoparasites and Nest Defense Behavior in the Wood Thrush

Dalton, Evan N 07 November 2014 (has links)
The Wood Thrush (Hylocichla mustelina) is declining throughout its range, yet is capable of persisting in both contiguous forests and small forest patches surrounded by human suburban development. Thus, it is an ideal species for gaining insight into the effects of suburbanization on migrant songbirds. I investigated two aspects of Wood Thrush nesting ecology: nest ectoparasites and nest defense behavior in order to determine if suburbanization influences either aspect. Nests from suburban forests had fewer haematophagous mites, though the abundance of haematophagous blowfly larvae did not differ between suburban and contiguous forests. There was no relationship between the abundance of mites and nest site characteristics, though blowfly abundance may be related to nesting substrate species. Parasites had little effect on nestling condition. In regard to nest defense, suburban Wood Thrushes had shorter flight initiation distances and mounted more active defenses during initial nest visits than birds nesting in contiguous forests, suggesting a previously-established sensitization response to human disturbances in suburban birds. I found no consistent shifts in aggression over subsequent nest visits in either habitat type, suggesting that throughout the breeding season, Wood Thrushes neither habituate nor sensitize further to repeated human disturbances. My results suggest that Wood Thrushes nesting in suburban forest patches are subject to fewer nest ectoparasites and defend their nests more aggressively than conspecifics nesting in contiguous forests. These results draw attention to the fact that although Wood Thrushes persist in both rural and suburban habitats, their nesting ecology may be different between these habitat types.
166

Movements and Space-Use of Female Greater Sage-Grouse (Centrocercus urophasianus) During Nesting and Breeding Seasons

Retherford, Drew W 25 November 2020 (has links)
Greater sage-grouse (Centrocercus urophasianus) are a species of conservation concern throughout their range including the state of Idaho. Little is known about the size of areas used by female sage-grouse during the breeding and nesting seasons, fidelity of females to those areas, or fidelity of female sage-grouse to specific leks or nest sites. The recent miniaturization of global positioning system (GPS) transmitting devices allows for a more thorough analysis of this behavior. We placed GPS transmitters on 234 female sage-grouse in Idaho, USA, from 2015 to 2019. We monitored 145 nest attempts, 15 of which occurred in consecutive years, from 130 female sage-grouse (Centrocercus urophasianus) with GPS transmitters to document movements and space-use during nesting. We quantified the length and direction of off-nest excursion distances for all 145 nest attempts. Also, for the 15 consecutive nest attempts, we compared the excursion distances for each bird, each year. The mean distance for an off-nest excursion across all study areas was 93.7 m (n = 145, SD = 57.9, range = 15.5 to 275.8 m). Rayleigh’s test of uniformity indicated that eight of 145 nest attempts had off-nest excursions that were not in a consistent direction. Mean excursion distances in the consecutive year were longer than those of the initial year (T = -3.1, n = 15, p-value = 0.013), and females with smaller excursion distances in the initial year also had smaller excursion distances in the consecutive year. We also quantified size of breeding areas for 50 female sage-grouse and identified factors that influenced breeding-area size. For 18 of those females, we quantified size and fidelity to breeding areas and leks between successive years. We generated 95% brownian bridge estimates of breeding-area size for each bird and counted the number of leks those females visited. To quantify breeding-area fidelity for the 18 females, we overlaid 95% brownian bridge estimates for females with consecutive breeding attempts, calculated percent overlap, and documented number of leks visited each year. Median size of breeding areas for all females was 21 km2 (interquartile range = 7.8 to 59.3 km2). Each bird visited a mean of 2 leks (SD = 1.2, range = 1 to 6 leks). Between years, breeding areas overlapped for all 18 females, and size of breeding areas did not differ between the first and second year (W-value = 61, p-value = 0.49). For those 18 females, only 7 visited the same lek in consecutive years, and none visited more than one common lek in consecutive years. Our results indicate that females use large areas while breeding and nesting and exhibit strong fidelity to those areas. Our results provide novel information on the breeding and nesting ecology of this species that will help agencies that manage sage-grouse and their habitat.
167

A Study of the Relationship Between Plains Sharp-Tailed Grouse Nest Site Selection and Survival and Ecological Site Descriptions in the Northern Plains

Klostermeier, Derek Wade January 2019 (has links)
Nest site selection and nesting success of plains sharp-tailed grouse were examined on the Grand River National Grassland in South Dakota during the nesting season from 2009-2012. We used conditional logistic regression to assess vegetation production, ecological site description, and landscape position on nest site selection. Two competing models regarding nest site selection: top model consisted of non-native forbs and native cool-season grasses, second best model included all grass and forb. Nine ESDs were used for nesting; loamy and clayey ecological sites most frequently used and produced the highest standing crop. Most frequent observed nest site State were Annual/Pioneer Perennial and Introduced and Invaded Grass. Top model for nest daily survival rates included litter, second-best model included ESD; second-best model showed negative effect for nests initiated in thin claypan, limy backslope, and sandy ecological sites. Based on daily survival estimate and 23-day incubation period, nests were 59% successful.
168

Influences maternelles prénatales chez les oiseaux nidifuges : facteurs de variation et effets sur le développement comportemental des jeunes / Prenatal maternal influences in precocial birds : factors of variation and effects on offspring behavioural development

Le Bot, Océane 19 December 2014 (has links)
Ce travail de thèse explore les influences maternelles non génétiques chez un oiseau nidifuge, la caille japonaise Coturnix c. japonica. Un premier axe s'intéresse à l'influence d'un facteur intrinsèque sur le comportement de la femelle pondeuse, les caractéristiques de ses œufs et le développement de ses descendants. Nos travaux montrent que les caractéristiques intrinsèques du comportement de ponte modulent l'émotivité des femelles. Les œufs pondus par des femelles présentant un profil de ponte stable (i.e. ovipositions à la même heure chaque jour) diffèrent des œufs pondus par des femelles présentant un profil de ponte décalé (i.e. ovipositions un peu plus tard chaque jour). Les descendants de ces femelles montrent une plus grande émotivité face à la nouveauté et à la séparation sociale. De plus, il existe des variations des caractéristiques des œufs spécifiques à chaque profil de ponte. Le second axe s'intéresse à une influence environnementale. Au sein de l'environnement biotique, le partenaire sexuel est un congénère particulier pour la femelle. Lorsque les deux partenaires ont la possibilité de développer un lien (par un appariement permanent), leurs descendants sont moins émotifs et plus sociaux comparés à des jeunes dont les parents ont été appariés de façon ponctuelle et n'ont pas développé de lien. Enfin, le dernier axe explore pour la première fois chez l'oiseau nidifuge l'interaction entre des influences maternelles prénatales et postnatales. Ainsi, des jeunes stressés prénatalement ont une émotivité moindre face à la nouveauté et à la séparation sociale si ils sont maternés après l'éclosion, comparés à des jeunes non maternés. L'ensemble de ce travail améliore nos connaissances des facteurs de variations des influences maternelles, leurs mécanismes et leurs conséquences, permettant de mieux comprendre la variabilité phénotypique des individus et l'évolution des populations. / This thesis explored non-genetic maternal influences in a precocial bird, the Japanese quail Coturnix c. japonica. A first approach investigated the influence of an intrinsic factor on the behaviour of a laying female, its eggs' characteristics and its offspring's development. Our results demonstrate that intrinsic characteristics of egg laying behaviour influence females' emotivity. Eggs laid by females that present a stable laying profile (i.e. ovoposition at the same time each day) differed from eggs laid by females that present a delayed laying profile (i.e. oviposition later each day). Offspring of females delayed laying profile showed higher emotivity in novel situations and social isolation. Moreover, eggs presented specific characteristics within each of both egg laying profiles. A second approach focused on the biotic environment. For a female, the mating partner is a particular congener. When mates could develop a pair bond (by continuous pairing), their offspring were more emotive and less social compared to chicks whose parents were not continuously paired and thus did not develop a pair bond. In a final approach and for the first time in a precocial bird, interactions between prenatal and postnatal maternal influences were explored. Chicks that were prenatally stressed showed lower emotivity in novel situations and social isolation when they are mothered after hatching compared to non-mothered, prenatally stressed chicks. Overall, our work improves the knowledge about maternal influence factors of variation, their mechanisms and consequences, allowing a better understanding of individuals' phenotypic variability and populations' evolution.
169

Teoretická studie vlivu defektů silanolového hnízda na hydrolýzu zeolitu chabazitu / Theoretical Study of Influence of Silanol Nest Defects on Hydrolysis of Zeolite Chabazite

Vacek, Jaroslav January 2020 (has links)
This thesis is focused on theoretical study of influence of the silanol nest defects on the hydrolysis of zeolite Chabazite under harsh steaming conditions. The motivation of the thesis was a recent experiment proving that the silanol nest defect enhances the hydrolysis of a zeolite. The harsh steaming conditions have been chosen as some important technological processes involving zeolites require high temperatures and have water vapour present. The study was performed by using density functional theory calculations. To investigate the influence of the defect two models were used a reference pristine model and a defected model containing the silanol nest defect. The two models were pure siliceous Chabazite periodical models with supercell containing 36 and 35 Si tetrahedra respectively. A multi-step hydrolysis leading to detachment of a Si(OH)4 cluster from the zeolite, known as total desilication, was calculated for the two models. Multiple possible paths of the hydrolysis were discovered, compared and discussed on both models. Both the most favourable hydrolysis paths of the two model as well as their arithmetic means were compared. The experimentally set expectations that a silanol nest defect enhances the hydrolysis of the zeolite have been met.
170

Nest Success of Dabbling Ducks in a Human-Mod ified Prairie : Effects of Predation and Habitat Variables at Different Spatial Scales

Jimenez, Jaime E. 01 May 1999 (has links)
Nest success of dabbling ducks in the Prairie Pothole region of North America has been declining for the past 40 years in parallel with declines in duck populations. Low nest success seems to result from the combination of an extremely fragmented breeding ground in a human-dominated landscape with an abundant and expanding ii community of generalist nest predators. Studies that examined variables associated with nest vulnerability to predation have produced contradictory results, likely because of simplistic approaches, lack of spatio-temporal replication, use of artificial nests , and the effect of confounding variables. I attempted to clarify the equivocal findings of previous studies by using multiple regression to simultaneously examine the effect of several variables purportedly related to nest predation risk. I collected data on >1,800 dabbling duck nests and associated variables for 16 habitat patches (14 managed for duck production) during two nesting seasons in North Dakota. At the habitat patch level, early and late in each breeding season, I studied the relationship of nest success and upland area, nest density, predator abundance and richness, abundance of alternative prey for predators, and visual and physical obstruction provided by the vegetation . At the spatial scale of the nest and its neighborhood, I examined the likelihood of nest predation in association to nest initiation date, year, distance from nest to a wetland and to an edge, vegetation type at the nest, visual obstruction and heterogeneity of the vegetation around the nest, duck nest species , predator abundance, and presence/absence of 5 carnivorous predators at the nest habitat patch. Nest success was generally low and highly variable in time, and among and within habitat patches. I found no relationship between nest success and any of the variables measured at the patch scale. At the nest level, only initiation date, distance to water, visual obstruction, predator abundance, and duck species had an effect. High variability in the data and the lack of patterns in the relationship of nest predation and the predictor variables precluded me from building a predictive model that explains nest success. Nest success could not be predicted, predation was incidental and risk was high, and there were no safe nest sites for hens to choose in a landscape swamped by nest predators . Nests were located randomly; therefore, there were no clues predators could use to enhance their success in finding nests.

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