Thesis advisor: Michael A. McDannald / Thesis advisor: John P. Christianson / The ability to accurately evaluate and respond to threats is vital to survival. Disruptions in neural circuits of fear give rise to maladaptive threat responding, and have clinical implications in fear and anxiety disorders. To better inform therapeutic interventions, it is imperative that roles for regions classically associated with fear continue to be refined, and that novel nodes are incorporated into what is most certainly a larger fear circuit. In the canonical view, threat estimates are generated at the level of the amygdala and sent to the ventrolateral periaqueductal gray (vlPAG), which organizes an appropriate behavioral response, most notably freezing. Despite a multitude of studies successfully linking the vlPAG and Pavlovian fear behavior, evidence of a direct neural correlate for fear expression in the vlPAG is lacking. By contrast, a role for the caudal substantia nigra (cSN) in fear, stands apart from its canonical associations with movement and reward processes. Although there is new interest in examining a role for the nigra in fear modulation, this is essentially an uncharted area of discovery. The goals of this dissertation are three-fold. First, to propose a role for vlPAG activity in threat estimation, a function previously restricted to the upstream amygdala. Second, to scrutinize vlPAG neural activity using a novel multi-cue Pavlovian procedure and identify the long-anticipated, direct neural correlate for fear expression. Third, to present causal evidence supporting the cSN as a potential node in a circuit that most certainly extends beyond regions canonically associated with fear. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

The use of multi-robot teams in the Robot Operating System (ROS) has encountered difficulty in advancement because of a lack of effective ways for the robots to communicate. Several attempts towards solving this problem have been made, but these approaches have had trouble with either low fault tolerance or high network load. The Gray Transceiver is an interface and communication protocol for inter-robot communication using ROS. The Gray Transceiver leverages multicasting for reduced network load and increased fault tolerance. Results from simulations, high throughput testing, and live multi-robot evaluations are included. The live mult-robot and simulation evaluations show that it functions properly operating across multiple robots while tolerating faults. The high throughput test shows how the Gray Transceiver operates under high load across a several types of conditions.

During 1987 through 1992, 85 wolves (Canis lupus) were captured, radio-collared, and relocated from aircraft 1,123 times in northwest Alaska. Wolf packs usually did not follow migratory caribou (Rangifer tarandus) but maintained year-round resident territories that averaged 3,652 km². During years when caribou were absent and moose densities were low, ≤ 25% of the wolf packs moved 64 to 272 km to the caribou wintering grounds. Wolves used different slopes, aspects, and habitats in summer versus winter. Twenty-five percent of the radio-collared wolves dispersed. Annual finite rates of increase ranged from 0.64 to 1.43. Annual wolf survival rates averaged 0.59. There were differences in survival rates among years. Sixty-one percent of the wolves died. Hunting was the main cause of death (69%) followed by rabies (21%). Rabies was a significant natural limiting factor. This wolf population could sustain mortality rates of about 53% annually. Caribou and moose composed 51 and 42%, respectively, of the observed wolf prey. Adjusted for prey size, each pack killed 1 adult moose equivalent per 6.7 days. Wolf pack sizes and adjusted kill rates and kgs of available prey per wolf per day were correlated from several areas across North America. When caribou were present they were the principal prey. However, when caribou densities were <100/1,000 km² wolves preyed upon moose. Wolves preyed upon relatively healthy caribou and moose that were in marginal condition. Wolves were killing about 6-7% of the caribou herd and from 11 to 14% of the moose population annually. Existing wolf predation may have serious impacts on resident, low-density moose populations. During spring 1990 I tested the line-intercept method of sampling tracks for estimating wolf densities for a known wolf population (i.e., 48 wolves). The population estimate based upon line-intercept sampling was 50.7 (80% CI = 33.4 to 67.9) suggesting that the survey method provided relatively accurate population estimates. I placed 23 satellite transmitters on wolves aged 10-months to 8 years with no apparent adverse effects on them. Accuracy of 1,855 relocations at 9 sites averaged 336 and 728 m for best and worst quality relocations, respectively. Satellite telemetry has potential for providing improved data sets for evaluation of wolf territory sizes and movements.

A radiação térmica é o principal mecanismo de transferência de calor em fenômenos que envolvem meios participantes em temperaturas elevadas, tais como em processos de combustão. A dependência fortemente irregular do coeficiente de absorção em relação ao número de onda torna desafiador o estudo de situações em que a radiação é apenas parte de um problema mais complexo. A exatidão do cálculo da radiação fica condicionada à solução da equação da transferência radiativa (RTE) por meio da integração linha-por-linha (LBL), sendo, muitas vezes, impraticável, em virtude do esforço computacional requerido para contabilizar as centenas de milhares ou milhões de linhas espectrais do coeficiente de absorção. Alternativamente, modelos espectrais, como a soma-ponderada-de-gases-cinza (WSGG), têm sido empregados de maneira eficaz na obtenção de resultados em substituição à integração LBL. Nessa dissertação, o modelo WSGG é aplicado na solução da transferência de calor radiativa em um sistema unidimensional, formado por duas placas planas paralelas infinitas e preenchido por uma mistura homogênea de dióxido de carbono e vapor de água, considerando-se perfis distintos de temperatura. Diferentemente da maioria dos estudos da literatura que empregam a mesma geometria, mas com paredes negras, o presente trabalho supõe superfícies cinzas e não cinzas. O objetivo central é, portanto, avaliar o erro em se assumir fronteiras negras quando estas não apresentam esse comportamento. Os resultados para o modelo WSGG aplicado a superfícies não cinzas, cinzas e negras são comparados com a solução linha-por-linha para paredes não cinzas. As análises dos desvios entre as soluções pelo modelo da soma-ponderada-de-gases-cinza e pela integração LBL mostram que a suposição de paredes negras, para casos em que as superfícies deveriam ser consideradas não cinzas, pode levar a erros de até 50% nos resultados para o fluxo de calor e para o termo fonte radiativo. / Thermal radiation is the main heat transfer mechanism in phenomena that involves high temperatures, such as in combustion processes. The strongly irregular dependence of the absorption coefficient on the wavenumber makes challenger the study of situations in which the radiation is only part of a more complex problem. The accuracy of the calculation of the radiation is conditioned to the solution of the radiative transfer equation (RTE) by line-by-line (LBL) integration, being frequently impracticable, due to the computational effort required to account for the hundreds of thousands or millions spectral lines of the absorption coefficient. Alternatively, spectral models, such as the weighted-sum-of-gray-gases (WSGG) model, have been used with success to obtain results in comparison to LBL integration. In this study, the WSGG model is applied to solve the radiative heat transfer in a one-dimensional system, formed by two infinite flat parallel plates and filled by a homogeneous mixture of carbon dioxide and water vapor, for different temperature profiles. Unlike most studies of the literature that employ the same geometry, but with black walls, the present work supposes gray and non-gray surfaces. The central objective is, therefore, to evaluate the error in assuming black boundaries when they do not present this behavior. The results for the WSGG model applied to non-gray, gray and black surfaces are compared with the line-by-line solution for non-gray walls. Analyzes of the deviations between the solutions by the weighted-sum-of-gray-gases model and the LBL integration show that the assumption of black walls, for cases where the surfaces should be considered as non-gray, may lead to errors of up to 50% in results for the heat flux and the radiative source term.

A radiação térmica é o principal mecanismo de transferência de calor em fenômenos que envolvem meios participantes em temperaturas elevadas, tais como em processos de combustão. A dependência fortemente irregular do coeficiente de absorção em relação ao número de onda torna desafiador o estudo de situações em que a radiação é apenas parte de um problema mais complexo. A exatidão do cálculo da radiação fica condicionada à solução da equação da transferência radiativa (RTE) por meio da integração linha-por-linha (LBL), sendo, muitas vezes, impraticável, em virtude do esforço computacional requerido para contabilizar as centenas de milhares ou milhões de linhas espectrais do coeficiente de absorção. Alternativamente, modelos espectrais, como a soma-ponderada-de-gases-cinza (WSGG), têm sido empregados de maneira eficaz na obtenção de resultados em substituição à integração LBL. Nessa dissertação, o modelo WSGG é aplicado na solução da transferência de calor radiativa em um sistema unidimensional, formado por duas placas planas paralelas infinitas e preenchido por uma mistura homogênea de dióxido de carbono e vapor de água, considerando-se perfis distintos de temperatura. Diferentemente da maioria dos estudos da literatura que empregam a mesma geometria, mas com paredes negras, o presente trabalho supõe superfícies cinzas e não cinzas. O objetivo central é, portanto, avaliar o erro em se assumir fronteiras negras quando estas não apresentam esse comportamento. Os resultados para o modelo WSGG aplicado a superfícies não cinzas, cinzas e negras são comparados com a solução linha-por-linha para paredes não cinzas. As análises dos desvios entre as soluções pelo modelo da soma-ponderada-de-gases-cinza e pela integração LBL mostram que a suposição de paredes negras, para casos em que as superfícies deveriam ser consideradas não cinzas, pode levar a erros de até 50% nos resultados para o fluxo de calor e para o termo fonte radiativo. / Thermal radiation is the main heat transfer mechanism in phenomena that involves high temperatures, such as in combustion processes. The strongly irregular dependence of the absorption coefficient on the wavenumber makes challenger the study of situations in which the radiation is only part of a more complex problem. The accuracy of the calculation of the radiation is conditioned to the solution of the radiative transfer equation (RTE) by line-by-line (LBL) integration, being frequently impracticable, due to the computational effort required to account for the hundreds of thousands or millions spectral lines of the absorption coefficient. Alternatively, spectral models, such as the weighted-sum-of-gray-gases (WSGG) model, have been used with success to obtain results in comparison to LBL integration. In this study, the WSGG model is applied to solve the radiative heat transfer in a one-dimensional system, formed by two infinite flat parallel plates and filled by a homogeneous mixture of carbon dioxide and water vapor, for different temperature profiles. Unlike most studies of the literature that employ the same geometry, but with black walls, the present work supposes gray and non-gray surfaces. The central objective is, therefore, to evaluate the error in assuming black boundaries when they do not present this behavior. The results for the WSGG model applied to non-gray, gray and black surfaces are compared with the line-by-line solution for non-gray walls. Analyzes of the deviations between the solutions by the weighted-sum-of-gray-gases model and the LBL integration show that the assumption of black walls, for cases where the surfaces should be considered as non-gray, may lead to errors of up to 50% in results for the heat flux and the radiative source term.

A radiação térmica é o principal mecanismo de transferência de calor em fenômenos que envolvem meios participantes em temperaturas elevadas, tais como em processos de combustão. A dependência fortemente irregular do coeficiente de absorção em relação ao número de onda torna desafiador o estudo de situações em que a radiação é apenas parte de um problema mais complexo. A exatidão do cálculo da radiação fica condicionada à solução da equação da transferência radiativa (RTE) por meio da integração linha-por-linha (LBL), sendo, muitas vezes, impraticável, em virtude do esforço computacional requerido para contabilizar as centenas de milhares ou milhões de linhas espectrais do coeficiente de absorção. Alternativamente, modelos espectrais, como a soma-ponderada-de-gases-cinza (WSGG), têm sido empregados de maneira eficaz na obtenção de resultados em substituição à integração LBL. Nessa dissertação, o modelo WSGG é aplicado na solução da transferência de calor radiativa em um sistema unidimensional, formado por duas placas planas paralelas infinitas e preenchido por uma mistura homogênea de dióxido de carbono e vapor de água, considerando-se perfis distintos de temperatura. Diferentemente da maioria dos estudos da literatura que empregam a mesma geometria, mas com paredes negras, o presente trabalho supõe superfícies cinzas e não cinzas. O objetivo central é, portanto, avaliar o erro em se assumir fronteiras negras quando estas não apresentam esse comportamento. Os resultados para o modelo WSGG aplicado a superfícies não cinzas, cinzas e negras são comparados com a solução linha-por-linha para paredes não cinzas. As análises dos desvios entre as soluções pelo modelo da soma-ponderada-de-gases-cinza e pela integração LBL mostram que a suposição de paredes negras, para casos em que as superfícies deveriam ser consideradas não cinzas, pode levar a erros de até 50% nos resultados para o fluxo de calor e para o termo fonte radiativo. / Thermal radiation is the main heat transfer mechanism in phenomena that involves high temperatures, such as in combustion processes. The strongly irregular dependence of the absorption coefficient on the wavenumber makes challenger the study of situations in which the radiation is only part of a more complex problem. The accuracy of the calculation of the radiation is conditioned to the solution of the radiative transfer equation (RTE) by line-by-line (LBL) integration, being frequently impracticable, due to the computational effort required to account for the hundreds of thousands or millions spectral lines of the absorption coefficient. Alternatively, spectral models, such as the weighted-sum-of-gray-gases (WSGG) model, have been used with success to obtain results in comparison to LBL integration. In this study, the WSGG model is applied to solve the radiative heat transfer in a one-dimensional system, formed by two infinite flat parallel plates and filled by a homogeneous mixture of carbon dioxide and water vapor, for different temperature profiles. Unlike most studies of the literature that employ the same geometry, but with black walls, the present work supposes gray and non-gray surfaces. The central objective is, therefore, to evaluate the error in assuming black boundaries when they do not present this behavior. The results for the WSGG model applied to non-gray, gray and black surfaces are compared with the line-by-line solution for non-gray walls. Analyzes of the deviations between the solutions by the weighted-sum-of-gray-gases model and the LBL integration show that the assumption of black walls, for cases where the surfaces should be considered as non-gray, may lead to errors of up to 50% in results for the heat flux and the radiative source term.

Animal foraging behavior is shaped by patterns and processes that operate on several temporal and spatial scales. In chapter 1, I briefly review the meaning and importance of temporal and spatial scales. In chapter 2, I examine the foraging behavior of the Long Jawed spider (Tetragnatha elongata). In North Carolina, the spider exhibits the counter intuitive behavior of relocating its web daily in rich habitats, but rebuilding its web on the same site for many days in a row in poor habitats. I test a risk-sensitive foraging model of this behavior, but its predictions were not met. I develop an alternative hypothesis to explain the behavior of Long Jawed spiders: that the higher density of spiders in rich habitats results in more frequent interactions between spiders, and that these interactions provoke spiders to relocate more often in rich habitats. I report the results of density-reduction experiments, which corroborate my hypothesis. In chapter 3, I examine the foraging and storing strategy of the Eastern Gray Squirrel (Sciurus carolinensis). The squirrels ate most of the white oak (WO) acorns, and buried most of the red oak (RO) acorns, confirming my prediction. I also present the results of an experiment designed to reveal whether squirrels used tannin and/or fat content of acorns to distinguish between acorns of different species. The results of this experiment were inconclusive. In another experiment, I buried a large number of acorns, and assessed samples of acorns retrieved at intervals through the fall/winter season. I found that tannin levels in RO acorns did not decline during their interment, rendering an alternative hypothesis untenable. Further, I confirmed an earlier assumption: stored WO acorns do suffer more insect damage than RO acorns. I hypothesize that the storing and foraging strategy of squirrels may affect the distribution of oaks, and review evidence from the literature that supports this hypothesis. Finally, I argue that Clark's Nutcracker (Columbiana nucifraga) may employ the same strategy as it forages for pine seeds, and again review evidence from the literature to support this hypothesis. (Abstract shortened by UMI.)

No description available.

Virtually all nineteenth and twentieth century accounts of Thomas Gray's 'Elegy Written in a Country Churchyard' find in the Curfew bell of the opening lines primarily a figure of death evoked by the growing darkness, the fading sounds, the emptying landscape and ultimate solitude of the speaker, and most of all the funerary associations of tolling bells and the 'passing bell' tradition. And yet, culturally, despite some symbolic overlap, the Curfew bell and the passing bell are quite distinct, each with its own characteristic history, practices, traditions, and connotations, distinctions recognized widely in eighteenth century literary and antiquarian circles. In this thesis, I explore the literary historical question of why so many readers, popular and scholarly, of the 'Elegy' have avoided the overt political implications of these Curfew traditions in favor of the more allusive funerary associations. I develop an argument grounded in both literary tradition and cultural history for taking Gray's famous Curfew seriously as a literal Curfew bell, rather than as merely a symbolic passing bell or funeral bell. The result is a view of the 'Elegy' as engaging with class on a more fundamental level than usually assumed, both anticipating and informing the language of political economic discourse in the latter half of the eighteenth century, suggesting that whether we take the poem most fundamentally as a moral meditation on the ultimate universality of death or as a more socio-political reflection on the disparities of class depends greatly on how we hear this tolling bell.

No description available.