No description available.

Auditory neurons selectively respond to frequency and amplitude of sound. In the auditory midbrain, duration-tuned neurons (DTNs) are subsets of neurons that selectively respond to the duration of sound. DTNs may help further understand the neural mechanism underlying temporal processing in the central nervous system. Temporal processing has been shown to play important roles in speech, discriminating species-specific signals, and echolocation. The goal of this thesis is to explore the role of DTNs through single-unit electrophysiological recordings in the auditory midbrain of the big brown bat (Eptesicus fuscus). Monotic and dichotic paired-tone stimulation was used to evoke excitatory and inhibitory responses from DTNs. Two stimuli consisted of best duration (BD) excitatory and non-excitatory (NE) tones. In the monotic condition, both tones were presented to the contralateral ear, and when they were close in time, the NE tone always suppressed spikes evoked by the BD tone. In the dichotic condition, the BD tone was presented to the contralateral ear. The NE tone was presented to the ipsilateral ear and suppressed BD tone evoked spiking in ~50% of cells. Properties of the ipsilaterally-evoked inhibition were investigated by varying the frequency of the NE tone from the best excitatory frequency (BEF), throughout a cell’s excitatory bandwidth (eBW). We measured the inhibitory frequency response area, best inhibitory frequency (BIF), and inhibitory bandwidth (iBW) of each cell. We found inhibition became weaker as the frequency of the NE tone moved further from the middle of the eBW. We found that a DTN’s BEF and BIF closely matched, but the eBW was broader than the iBW and overlapped the iBW measured from the same cell. This suggests temporal selectivity of midbrain DTNs are created by monaural inputs, with binaural inputs playing a lesser role in shaping duration selectivity. / Thesis / Master of Science (MSc)

Background: Brown adipose tissue (BAT) preferentially oxidizes stored triglycerides (TAGs) to generate heat during acute exposure to cold. However, the time course of its activation is not well described as we are currently limited to BAT measurements before and after an acute stimulus. Magnetic resonance imaging (MRI) is a preferred modality to uncover such evidence, as it estimates TAG content via fat fraction (FF), and permits repeat scans in the same subject. As such, serial FF measurements in a defined BAT region of interest during a uniform whole-body temperature challenge is warranted. Objectives: The first objective of this study was to assess the pattern of change in supraclavicular (SCV) BAT and posterior neck subcutaneous adipose tissue (SAT; a region with an unestablished role in non-shivering thermogenesis) FF during a mild cold exposure in adult males. The second objective was to evaluate if indices of body composition were related to the pattern of cold-induced change in SCV BAT FF. The final objective was to assess the influence of warming immediately following cooling on these changes. Methods: Twelve males between the ages of 19 and 28 were recruited to this cross-sectional study. Users of tobacco, nicotine, and/or alcohol, those with contraindications for magnetic resonance imaging (MRI), and diseases, surgeries, and/or medications associated with thermogenesis were excluded. There were two study visits in total. During the initial visit, anthropometric measurements were carried out in triplicate (i.e. height and weight to determine body mass index (BMI), and body composition measurements (i.e. % body total fat and lean mass (kg)) were obtained using Dual Emission X-Ray Absorptiometry. Within 30 days of this initial visit, subjects attended a time course MRI session. At this visit, participants underwent standardized cold (3-hours at 18°C) and subsequent warm (30 minutes at 32°C) exposures using a water-perfused suit while lying in a 3 Tesla MRI scanner, and the temperature of the water entering and leaving the suit was recorded throughout. FF in the SCV region and posterior neck SAT was measured at defined intervals during both temperature challenges. Separate time course plots of the mean reduction in FF from baseline were constructed for the cooling and warming phases. For the first objective, the rate and magnitude of FF changes in SCV BAT and posterior neck SAT over defined time intervals were determined through calculations of slope and area under the curve (AUC), respectively. Identification of the earliest point of change from baseline, and the point at which changes were no longer different from those measured after 3 hours of cooling, were accomplished through paired comparisons using a random-slope linear mixed model with measures at 0 minutes and 180 minutes used as the reference values, respectively. A random-intercept multilevel regression model was used to define the cold-induced change in FF over time. For the second objective, a Spearman rank-order correlation assessed the association between indices of body composition (i.e. BMI and % total body fat) and indices of BAT activity (i.e. AUC and FF reduction) at time points of interest as identified by objective 1. Results: The mean±SD of BMI, LMI, and % total body fat were 24.7±2.8kg/m2, 17.6±1.6kg/m2 and 25.0±7.4%, respectively. Seven of the twelve subjects completed three hours of cold exposure (58.3%), and a further five endured at least one hour. A significant cold-induced reduction in SCV BAT FF was detected at 10 minutes following the onset of cold exposure (mean difference = -1.6%; p=0.005), and changes in FF beyond 30 minutes of cooling were similar to those measured after three hours (p<0.05). Meanwhile, the posterior neck SAT did not experience significant cold-induced changes in FF. A novel attempt at identifying a quadratic model to predict one’s BAT-specific response to a cold challenge was carried out, and the intercept, time, time2, and intraclass correlation coefficient (i.e. parameters which described the relationship between FF and time) were highly significant (p<0.001). Although every participant had a measurable decline in FF, those with a higher BMI and % body fat had a smaller magnitude of change throughout the time course. In particular, a strong negative correlation between BMI and AUC FF decline existed as soon as 10 minutes following the onset of cold (rho=-0.786), indicating that those with a lower BMI had a larger magnitude of change in SCV BAT FF at this point. Finally, warming did not visually influence the trajectory of SCV BAT FF. Limitations: Only seven of the twelve participants completed the full 180 minutes of cold exposure, which further limited the already low statistical power of this study. Moreover, complementary measures of BAT activity, such as energy expenditure, and objective measurements of shivering, such as electromyography, could not be evaluated. Conclusions: These findings suggest that significant cold-induced changes in BAT FF occur much sooner than three hours. Thus, a shorter duration of cold exposure may be considered in future studies using MRI to detect BAT activity, as this could increase the feasibility of gathering larger and younger sample populations. / Thesis / Master of Science (MSc)

Many neurons in the auditory midbrain are tuned to binaural cues. Two prominent binaural cues are the interaural intensity difference (IID) and the interaural time difference (ITD). The ITD cue can further be classified as either an ongoing ITD, which compares the phase difference in the waveform of low frequency stimuli present at either ear, or an onset ITD, which compares the onset time of arrival of two stimuli at either ear. Little research has been done on the sensitivity of single neurons to onset ITDs in the auditory system, particularly in bats. The current study examines the response properties of neurons in the inferior colliculus (IC) of the big brown bat, Eptesicus fuscus, to onset ITDs in response to high frequency pure tones. Measures of neurons’ dynamic response—the segment of the ITD function exhibiting the highest rate of change in activity—revealed an average change of 36% of its maximum response within the estimated behaviorally relevant range of ITDs. Time-intensity trading describes the ability of the brain to compensate the binaural time cue (ITD) cue for the binaural intensity cue (IID) and can be measured as the horizontal shift of an ITD function at various IIDs. Across all IC neurons, an average time-intensity trading ratio of 30 μs/dB was calculated to measure the sensitivity of IC neurons’ ITD response to changing IIDs. Minimum and maximum ITD responses were found to be clustered within a narrow range of ITDs. The average peak ITD response occurred at 268 μs and is consistent with findings in other mammals. All results in ITD tuning, time-intensity trading, and response maximum were invariant to stimulus frequency, confirming that IC neurons responded to onset ITDs and not ongoing ITDs. These results suggest the potential for high frequency onset cues to assist in the azimuthal localization of sound in echolocating bats. / Thesis / Master of Science (MSc)

Nina Varah MSc Thesis / BACKGROUND: Brown adipose tissue (BAT) has emerged as an attractive target to address the dramatic rise in obesity and non-alcoholic fatty liver disease (NAFLD) in adults and children due to its ability to clear lipids through thermogenesis when activated with cold stimulation. Cross-sectional studies have identified an inverse relationship between BAT and NAFLD in adults, although no linking mechanism or relevance in children is known. Metabolomics provides a non-invasive platform to investigate BAT physiology and its relationship with hepatic fat in an effort to identify potential targets for further investigation. PROJECT OBJECTIVES: 1) To explore the associations between the plasma metabolome and BAT in adults and children. 2) To explore the associations between the plasma metabolome and hepatic fat in adults and children. 3) To identify metabolites associated with both BAT and hepatic fat as potential linking mechanisms for further study. METHODOLOGY: We recruited 63 male and female adults aged 18 to 57 years and 25 healthy male children aged 8 to 10 years into this cross-sectional study. Study participants underwent blood work, body composition measurement (dual energy X-ray absorptiometry; DXA) and magnetic resonance imaging (MRI) - proton density fat fraction (PDFF) measurements of whole liver hepatic fat, pre- and post-cold supraclavicular fat. BAT activity was calculated as the percent change between post and pre-cold BAT PDFF with the cold stimulus consisting of a water-perfused suit maintained at 18°C for 3-hours (adult) or 1-hour (pediatric). Targeted liquid-chromatography/mass spectrometry metabolomics of 102 metabolites was conducted on fasted plasma and multivariate linear regression with multiple testing correction was used to examine metabolite predictors of BAT measures and hepatic fat. RESULTS: In the adult cohort (n=63, median age 25.9 years, median body mass index (BMI) 25.4 kg/m2), five metabolites were associated with baseline BAT lipid content, where an elevated lipid content may indicate a whiter adipose tissue-like phenotype. Aconitate and creatine commonly predict increased baseline BAT lipid content (β=0.420, P=0.001 and β=0.408, P=0.001, respectively), and reduced BAT activity (β=-0.462, P=0.002 and (β=-0.402, P=0.002, respectively). Alanine and two acyl-carnitines also predicted reduced BAT activity. Glutamic acid was similarly related to higher baseline BAT (β=0.480, P<0.001) and hepatic lipid content independent of age and sex (β=0.392, P=0.002). Three other metabolites were directly related to hepatic fat, and serine inversely. In children (n=25, median age 9.89 years, mean BMI Z-score 1.25), cysteine and cystine were trending towards a significant relationship with higher baseline BAT lipid content, and were both related to elevated hepatic fat independent of adiposity (cysteine: quadratic β=-0.714, p<0.001 and cystine: quadratic β=0.592, p<0.001). Two hydroxy-proline isomers and L-carnitine were associated with reduced BAT activity. CONCLUSION: In adults, several metabolites were associated with reduced BAT activity and with a higher baseline BAT lipid content in the non-stimulated state – aconitate and creatine were related to both. Acylcarnitines or their metabolites related to BAT in both children and adults, which may suggest areas for subsequent investigation of BAT metabolism. Glutamic acid in adults and cysteine and cystine in children were weakly related to elevated baseline BAT and hepatic fat content. Further, amino acids such as glutamic acid and cysteine may be markers of increased ectopic fat accumulation – and are also associated with a whiter ambient BAT phenotype. Cumulatively, these findings highlight targets for further investigation into BAT physiology and the link to the liver. / Thesis / Master of Science (MSc)

This essay investigates why the Myth of the Holy Grail continue to occur within popular culture. Myths, tales and legends from ancient times have inspired authors throughout the centuries. The readers are not only served with a spectacular adventure, but the myths also contain messages with a moral and ethical guidance for us as beholders. This particular myth can be found within different media in our time and the essay will attempt to give some answers as to why the myth reappears in new forms over and over again. An analysis is performed by using the methodology of aesthetic reception within reception theory. The material chosen for the analysis is the work of art; The Da Vinci Code by author Dan Brown, where two different media forms will be represented, the novel and the film. The findings in the analysis revealed that the key to understanding the reasons for the occurrence of this medieval myth is the element of a quest that is present within the myth. This ingredient, where you embark on an adventure, will create feelings of excitement for the beholder. A second aspect found is that we as humans have an interest in our history. Therefore, myths and legends from our historical past will be naturally alluring for beholders and especially if they are linked to philosophical questions and ideas that can be applied to our modern society. The success that has followed The Da Vinci Code has its explanation in the fact that Brown has managed to make the myth of the Holy Grail more contemporary, the myth has then been rejuvenated. A suggestion for further research is to perform a study on beholders in focus group interviews in order to validate the findings in the analysis.

This research serves two main purposes: to create an analyzed edition of Ray Brown's bass lines from the Oscar Peterson Trio's 1964 recording We Get Requests, and to better understand Brown's lines through the lens of Ray Brown's Bass Method. This comparative analysis identifies significant events in the recorded music that closely relate to or resemble exercises from the book. By analyzing the music from the lens of Ray Brown's Bass Method, performers, students, and educators will gain a stronger understanding of the application of select technical devices provided by Brown in his book. The most prominent techniques discussed include scales and intervals, major triads, minor triads, and chords, exercises in tenths, rhythm patterns with drops, and diminished patterns. These evidence-based conclusions have significant applications in jazz bass pedagogy by revealing potential relationships between technical ideals and practical use. Although these conclusions may seem of concern only to jazz bassists, it should in fact concern anyone who cares about the connection between pedagogy and performance.

For the first time in many decades, a hemp pilot program was initiated in Virginia in 2016. Outdoor surveys were conducted in the 2017 and 2018 field seasons to record insect presence and feeding injury to plants. Multiple insect pests were present, including corn earworm (Helicoverpa zea [Boddie]) (Lepidoptera: Noctuidae), brown marmorated stink bug (Halyomorpha halys [Stål]) (Hemiptera: Pentatomidae), and cannabis aphid (Phorodon cannabis) (Hemiptera: Aphididae). In 2019, indoor production surveys revealed that cannabis aphid, twospotted spider mite (Tetranychus urticae Koch) (Acari: Tetranychidae), and hemp russet mite (Aculops cannabicola [Farkas]) (Acari: Eriophyidae) would likely cause production issues. Very little is known about the impact of insect defoliation in hemp so studies were conducted in 2018-2020 to determine impacts on yield and cannabinoid content of grain and cannabinoid variety hemp due to leaf surface area loss. In Virginia over two growing seasons, manual removal of leaf tissue in grain and CBD cultivars did not significantly impact observable effects on physical yield (seed or bud weight) or cannabinoid content (CBD or THC) at time of harvest. Corn earworm is the major pest of hemp produced outdoors and studies occurred to evaluate monitoring and management strategies. Pheromone traps may be valuable in determining when corn earworm moths are present in the vicinity of hemp fields but are not useful in predicting larval presence in buds or final crop damage. Larval presence and final crop damage are related. Brown marmorated stink bug does not appear to be a concern in hemp, at least at this time. / Doctor of Philosophy / For the first time in many decades, a hemp pilot program was initiated in Virginia in 2016. Outdoor surveys were conducted in the 2017 and 2018 field seasons to record insect presence and feeding injury to plants. Multiple insect pests were present, including corn earworm, brown marmorated stink bug, and cannabis aphid. In 2019, indoor production surveys revealed that cannabis aphid, twospotted spider mite, and hemp russet mite would likely cause production issues. Very little is known about the impact of leaf area loss due to insect feeding in hemp so studies were conducted in 2018-2020 to determine impacts on yield and cannabinoid content of grain and cannabinoid variety hemp due to leaf surface area loss. In Virginia over two growing seasons, manual removal of leaf tissue in grain and CBD cultivars did not significantly impact observable effects on physical yield (seed or bud weight) or cannabinoid content (CBD or THC) at time of harvest. Corn earworm is the major pest of hemp produced outdoors and studies occurred to evaluate monitoring and management strategies. Pheromone traps may be valuable in determining when corn earworm moths are present in the vicinity of hemp fields but are not useful in predicting larval presence in buds or final crop damage. Larval presence and final crop damage are related. Brown marmorated stink bug does not appear to be a concern in hemp, at least at this time.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), brown marmorated stink bug, is an invasive, polyphagous pest that has disrupted integrated pest management programs in Mid-Atlantic tree fruit orchards since 2010. The amount of damage to fruit caused by H. halys feeding is highly variable, even within adjacent orchard blocks, and the influence of orchards and wild host plants nearby on H. halys relative abundance is unknown. Pheromone-based trapping studies conducted along woodland-to-orchard transects, along woodland borders at sites with and without adjacent orchards, and within the mid-canopy of several common wild host trees in woodland borders were used to investigate biotic factors underlying the variability of H. halys populations among sites within a geographically proximate area. Additionally, the retention duration of H. halys on wild and cultivated tree hosts was used as a proxy for host acceptability throughout the season. All trapping studies yielded significantly greater H. halys captures during the late season, and in the transect study, pyramid traps deployed at orchard and woodland edges during this period yielded the highest captures. The presence of orchards or open fields adjacent to woodlands had no significant impact on H. halys captures in sticky traps deployed along wooded edges, but captures varied significantly among orchard and open field sites. Among 11 common wild host plant genera surveyed at these sites, five genera, Elaeagnus, Fraxinus, Lonicera, Ailanthus, and Sassafras, were significantly related to H. halys relative densities. Conversely, studies measuring captures in small pyramid traps within the canopy of wild tree hosts revealed no significant differences among hosts at any point in the season, suggesting that this approach might not be appropriate for assessing host plant suitability. Finally, harmonic radar trials assessing host plant retention as a proxy for host suitability revealed that adults released on peach and pheromone-baited apple trees had significantly greater retention durations than those released on non-host, grass, and that adult retention duration increased from the early to late season. In combination, results indicate that the risk posed by H. halys to cultivated orchard crops varied across locations and seasonally, and may be related to the species composition of wild host trees in adjoining woodlands. / Doctor of Philosophy / Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive insect that has inflicted feeding damage on fruit grown in Mid-Atlantic orchards since 2010. The agricultural landscape in the Mid-Atlantic region complicates BMSB management, as many orchards are bordered by woodlots containing a variety of BMSB host plants. The amount of BMSB feeding injury at harvest can vary greatly among nearby orchards, and even within individual orchards, but it is unknown why these differences exist. Several BMSB trapping studies using pheromone-baited traps revealed that BMSB populations were greatest in the late-season, confirming previous work. Furthermore, captures in traps positioned in lines intersecting orchards and adjacent woodlots revealed late-season BMSB presence was greatest at the orchard and woodland edges. Captures in traps next to woodlots adjacent to orchards and open field sites indicated that the presence of orchards had no impact on captures, but that captures varied significantly among orchard sites and open field sites. A survey of the woody plants in the woodlots adjacent to these sites revealed that five host plant genera were strongly related to BMSB abundance. A study examining BMSB captures in small pyramid traps deployed in the canopy of several common wild tree hosts did not yield differences in captures among hosts at any point in the season, and thus was not a suitable method for assessing seasonal differences in BMSB host use. Finally, harmonic radar technology was used to assess how long BMSB remained on several wild and cultivated host plants at different points in the growing season, as a proxy for host suitability. Peach and pheromone-baited apple showed significantly greater adult retention durations than non-host, grass, and adults remained on host plants longer in the early than late season. Ultimately, these results should aid in the monitoring and management of BMSB by providing a broader understanding of factors underlying the presence and abundance of BMSB on a localized geographic scale.

Tall fescue (Festuca arundinacea Schreb.) has great utility as a low maintenance turfgrass in the northern and transition zone regions of the United States. However, it is difficult to successfully maintain tall fescue of high quality over consecutive summers because of its susceptibility to the fungal pathogen Rhizoctonia solani, which causes the disease brown patch. Not only is brown patch aesthetically unpleasing in a stand of tall fescue but it can also thin out the turf and allow for the encroachment of undesirable weedy species. Cultivar selection, cultural practices, mixing turf species and timing of pesticide applications all can impact the epidemiology of brown patch in tall fescue. Research was conducted in tall fescue to quantify chitinase activity in different cultivars, elucidate the impact of mowing height and nitrogen fertility on brown patch and bermudagrass (Cynodon dactylon L.) encroachment, to evaluate seeding mixtures of tall fescue with hybrid bluegrass (Poa pratensis x Poa arachnifera) on diseases and weeds as well as measuring the impact of the herbicide bispyribac-sodium on brown patch. Chitinase activity was greater in the tall fescue cultivar that was less susceptible to brown patch. In the mowing-fertility studies, cutting tall fescue at 10 cm generally reduced brown patch and bermudagrass encroachment compared to 6 cm. Mixing hybrid bluegrass with tall fescue reduced disease and weed species infestations compared to tall fescue alone. Applying bispyribac-sodium earlier in April resulted in less brown patch and better weed control compared to application in May. Based on this research brown patch severity and subsequent weed species infestations can be reduced by selecting a tall fescue cultivar with a high basal level of chitinase, mowing it at 10 cm and mixing it with a hybrid bluegrass cultivar. / Ph. D.