<p>Recombination occurs during meiosis to produce new allelic combinations in natural populations, and thus strongly affects evolutionary processes. The model system Drosophila has been crucial for understanding the mechanics underlying recombination and assessing the association between recombination rate and several evolutionary parameters. Drosophila was the first system in which genetic maps were developed using recombination frequencies between genes. Further, Drosophila has been used to determine genetic and environmental conditions that cause variation in recombination rate. Finally, Drosophila has been instrumental in elucidating associations between local recombination rate and nucleotide diversity, divergence and codon bias, as well as helping determine the causes of these associations.</p><p>Here I present a fine-scale map of recombination rates across two major chromosomes in Drosophila persimilis using 181 SNP markers spanning two of five major chromosome arms. Using this map, I report significant fine-scale heterogeneity of local recombination rates. However, I also observed "recombinational neighborhoods", where adjacent intervals had similar recombination rates after excluding regions near the centromere and telomere. I further found significant positive associations of fine-scale recombination rate with repetitive element abundance and a 13-bp sequence motif known to associate with human recombination rates. I noted strong crossover interference extending 5-7 Mb from the initial crossover event. Further, I observed that fine-scale recombination rates in D. persimilis are strongly correlated with those obtained from a comparable study of its sister species, D. pseudoobscura. I documented a significant relationship between recombination rates and intron nucleotide sequence diversity within species, but no relationship between recombination rate and intron divergence between species. These results are consistent with selection models (hitchhiking and background selection) rather than mutagenic recombination models for explaining the relationship of recombination with nucleotide diversity within species. Finally, I found significant correlations between recombination rate and GC content, supporting both GC-biased gene conversion (BGC) models and selection-driven codon bias models. </p><p>Next, I looked at the role of chromosomal inversions in species maintenance by examining the impact of inversions distinguishing species to disrupt recombination rates within inverted regions, at inversion boundaries and throughout the remainder of the genome. By screening nearly 10,000 offspring from females heterozygous for 3 major inversions, I observed recombination rates within an inverted region in hybrids between Drosophila pseudoobscura and D. persimilis to be ~10-4 (similar to rates of exchange for inversion heterozygotes within species). However, despite the apparent potential for exchange, I do not find empirical evidence of ongoing gene exchange within the largest of 3 major inversions in DNA sequence analyses of strains isolated from natural populations. Finally, I observe a strong 'interchromosomal effect' with up to 9-fold higher (>800% different) recombination rates along collinear segments of chromosome 2 in hybrids, revealing a significantly negative association between interchromosomal effect and recombination rate in homokaryotypes, and I show that interspecies nucleotide divergence is lower in regions with larger changes in recombination rates in hybrids, potentially resulting from greater interspecies exchange. This last result suggests an effect of chromosomal inversions on interspecies gene exchange not considered previously.</p><p>Finally, I experimentally tested for a novel male-mediated effect on female recombination rates by crossing males that differed by either induced treatment variation or standing genetic variation to genetically identical females. After assaying recombination frequency in the offspring of these genetic crosses, I fitted these data to a statistical model where I showed no effect of male temperature treatment or male genetic background on offspring recombination rate. However, I did observe a difference of recombination rates of offspring laid 5-8 days post-mating between males treated with Juvenile Hormone relative to control males. Environmental variation in male ability to affect recombination rate in their mates suggests the potential for sexual conflict on optimal proportion of recombinant offspring, perhaps leading to changes in population-level recombination rates with varying levels of sexual selection.</p><p>Overall, my map of fine-scale recombination rates allowed me to confirm findings of broader-scale studies and identify multiple novel features that merit further investigation. Furthermore, I have identified several similarities and differences between inversions segregating within vs. between species in their effects on recombination and divergence, and I have identified possible effects of inversions on interspecies gene exchange that had not been considered previously. Finally, I have provided some evidence that males may impact female recombination rates, although future work should attempt to explore the range of male differences that impact this trait and the mechanism through which males impact the outcome of female meiosis.</p> / Dissertation

In daily life, there are a lot of inconveniences for the vision disabled people, even thought there are few equipments for them to use. However, there has no equipment to guide the vision disabled people on the pedestrian crossing, it will cause them being a dangerous situation while through the pedestrian crossing. To design an intelligent vehicle to help vision disabled people through the pedestrian crossing safely is an important topic. This thesis presents an autonomous transportation robot in intersections to provide older and vision disabled people to through the pedestrian crossing safely. This robot is based on a commercial wheelchair which equipped with cameras, inertial measurement unit, encoder, GPS module, hearts rate sensor, etc. In this study, by using the camera settled in the top of the robot to capture the picture, it could detect the region of pedestrian crossing and find the obstacles and pedestrian on the pedestrian crossing with image processing techniques. Then using the fuzzy controller to do the obstacle avoidance or people following. This robot can make the automatic parking after through the pedestrian crossing and transmit the position of the robot and the user¡¦s heart rate to the remote monitor system.

Abstract This thesis sets out to explore Shirley Geok-lin Lim's poetry collection Monsoon History in terms of three aspects: language, migrancy, and ethnicity. It also attempts to examine Shirley Lim's diasporic identity by embracing the border thinking. The notion of border-crossing, either physically or psychologically, passes through each chapter to represent the poet's identity and to re-create a space for herself to articulate. It is a study of Lim's exile experiences and how she establishes the poetics of diaspora for Asian American literature. In the introduction, the concept of diaspora and the theoretical framework will be explicated. The first chapter probes into the relationship between Shirley Lim and her choice of language in writing. I adopt Gilles Deleuze and F&#x00E9;lix Guattari's analysis of language and definition of ¡§minor literature¡¨ to discuss the deterritorialization of Lim's writing. The second chapter traces Lim's migrant status, in which I resort to Edward Said's ¡§Reflections on Exile¡¨ and his different categorizations of exile. The third chapter, appealing to several theorists or critics, such as Benedict Anderson, Ernest Gellner, and Ling-chi Wang, deals with Lim's problem of ethnic identity displayed in her poetry. The last chapter concludes with an overall argumentation that the destination and dissolution of Lim's identity is an Asian American because of reterritorialization of language, migrancy, and ethnicity.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 142-144).

This research investigates the safety performance of two types of pedestrian crossing control systems by examining driver compliance at these crosswalks in Winnipeg. The research analyzes driver compliance as a function of type of treatment, weather conditions, pedestrian approach location, and site characteristics. In addition, the research analyzes driver compliance before-and-after the implementation of 30 km/h speed limits in school zones. The findings from this research suggest that: (1) treatment and certain site characteristics (i.e., number of lanes) have a significant impact on driver compliance at crosswalks; and (2) weather conditions, pedestrian approach locations, and reduced speed school zones likely impact driver compliance at crosswalks but the findings were not always statistically significant. The research recognizes numerous factors that influence driver compliance and in turn pedestrian safety at crosswalks and highlights the importance of considering these factors in the provision, selection, and maintenance of pedestrian crossing control systems. / October 2015

The present study utilizes survey data (n = 415) collected in the Migrant Border Crossing Study from repatriated Mexican migrants to examine three important questions regarding unauthorized migration attempts through southern Arizona. First, what factors explicate migrants' modes of crossing? Second, do coyote fees vary among people who rely on smuggling services to cross the border? If so, what accounts for this variation? Third, what factors shape encounters with bajadores while traversing the desert? The present analyses expand on previous studies examining the unauthorized crossing in multiple ways. For instance, I empirically test the role of a "culture of migration" in explaining modes of crossing, coyote fees, and bajador encounters. I also differentiate between two main types of coyotes: "border business" and "interior." I then examine whether crossing with a coyote mediates the risk of encountering bajadores during the journey. Overall, there are important differences in crossing modes and coyote fees. Women are more likely to travel with both coyote types, while the opposite is true for more experienced migrants. Older migrants and people who cross during summer months are less likely to travel with an "interior" coyote. The strongest predictor of higher smuggling fees is the region of a person's U.S. destination. Higher coyote fees are also associated with immigrants' higher educational attainment, being married, being the sole economic provider for one's household, and higher household income. More experienced migrants, and those crossing in larger groups or during the summer also pay higher fees, however fees do not vary by gender, age, or social capital. These findings are somewhat consistent with the extant literature on human capital and risk tolerance/aversion, but run counter to the vast migration literature emphasizing the importance of social capital in the migration process. Finally, the risk of encountering bajadores is not higher for males, young adults, the less educated, and the more impoverished, which contradicts extant findings in the victimology literature. With the exception of crossing corridor and time spent in the desert, no other factors increase the risk of encountering bandits more than traveling with a coyote. Implications and possible future research are discussed.

Let Md be the moduli space of algebraic maps (morphisms) of degree d from P^1 to a fixed Grassmannian. The main purpose of this thesis is to provide an explicit construction of a compactification of Md satisfying the following property: the compactification is a smooth projective variety and the boundary is a simple normal crossing divisor. The main tool of the construction is blowing-up. We start with a smooth compactification given by Quot scheme, which we denote by Qd. The boundary Qd\Md is singular and of high codimension. Next, we give a filtration of the boundary Qd\Md by closed subschemes: Zd,0 subset Zd,1 subset ... Zd,d-1=Qd\Md. Then we blow up the Quot scheme Qd along these subschemes succesively, and prove that the final outcome is a compactification satisfying the desired properties. The proof is based on the key observation that each Zd,r has a smooth projective variety which maps birationally onto it. This smooth projective variety, denoted by Qd,r, is a relative Quot scheme over the Quot-scheme compactification Qr for Mr. The map from Qd,r to Zd,r is an isomorphism when restricted to the preimage of Zd,r\ Zd,r-1. With the help of the Qd,r's, one can show that the final outcome of the successive blowing-up is a smooth compactification whose boundary is a simple normal crossing divisor.

The analysis of grade crossing safety has long focused on vehicle-train crashes using statistical models based on crash data. The potential crashes generated by vehicle-vehicle rear-end conflicts have often been ignored. The interaction of different traffic attributes on safety performance of a grade crossing is also not well-understood. The primary objective of this thesis is to model the causal relationship of vehicle-vehicle interactions by developing the operation logic of gate-equipped grade crossing using a commercially available microscopic simulation package that models human driver behaviors. The simulation-generated vehicle trajectory data allows detail safety performance analysis on vehicle-vehicle interaction over time as they approach the track. A dual-gate equipped crossing at Kitchener, Ontario is selected as the study area. Initially, logic modifications are made to the simulation package (VISSIM) in order to accurately model the grade crossing segment. A two-step calibration is used in this thesis. Firstly, model input parameters for a signalized intersection from literature are used to model typical car-following behavior along this type of roadway. Secondly, parameters used to model drivers’ decision and reaction when approaching crossing is fine tuned through data collection and calibration. After incorporating all the modifications to the simulation package, validation is undertaken by comparing model-generated speed profiles to on-site observed speed profile. The established model is tested for its safety performance sensitivity through varying three traffic attributes in the simulation: (i) percentage of bus, (ii) total traffic volume, (iii) percentage of cars in the center lane of a 2-lane approach. Four safety performance measures were selected. The overall results indicate that the established model is functional and reliable in modeling grade crossing vehicles interactions at gated crossings. In the absence of a train, vehicles’ reduction in speed in the vicinity of a crossing results in traffic flow turbulence that increases the opportunity for high risk rear-end vehicle interactions. The sensitivity test revealed that the spillback behavior of vehicles due to the stopping behaviors of buses increases risk in the upstream section. Also, overloading of vehicles into the network indeed improves safety as the effect of differential speed diminishes. Among the four selected safety performance measures, DRAC seems to reflect problems with rear-end vehicle interactions in the vicinity of a crossing as a function of the traffic attributes considered in this research.

We evaluated the influence of a landscape dominated by agriculture and an extensive road network on fine-scale movements of black bears (Ursus americanus) in south-central Florida. The objectives of this study were to (1) define landscape functionality including corridor use by the directionality and speed of bear movements, (2) to develop a model reflecting selected habitat characteristics during movements, (3) to identify habitat characteristics selected by bears at road-crossing locations, and (3) to develop and evaluate a predictive model for road-crossing locations based on habitat characteristics. We assessed models using GPS data from 20 adult black bears (9 F, 11 M), including 382 unique road-crossing events by 16 individuals. Directionality of bear movements were influenced by the density of cover and proximity to human infrastructure, and movement speed was influenced by density of cover and proximity to paved roads. We used the Brownian bridge movement model to assess road-crossing behavior. Landscape-level factors like density of cover and density of roads appeared more influential than roadside factors, vegetative or otherwise. Model validation procedures suggested strong predictive ability for the selected road-crossing model. These findings will allow managers to prioritize and implement sound strategies to promote connectivity and reduce road collisions.

This thesis consists of two novel contributions to the computation of first passage time distribution for Brownian motion. First, we extend the known formula for boundary crossing probabilities for Brownian motion to the discontinuous piecewise linear boundary. Second, we derive explicit formula for the first passage time density of Brownian motion crossing piecewise linear boundary. Further, we demonstrate how to approximate the boundary crossing probabilities and density for general nonlinear boundaries. Moreover, we use Monte Carlo simulation method and develop algorithms for the numerical computation. This method allows one to assess the accuracy of the numerical approximation. Our approach can be further extended to compute two-sided boundary crossing probabilities.