8413 research outputs found
Sort by
Describing the Terminal Wealth of a Predetermined Schedule of Investments and Withdrawals
No full textThe terminal wealth of a predetermined schedule of investments and withdrawals is described in various settings. A lower bound is given for the terminal wealth of a schedule of investments in a single asset having a geometric Lévy alpha-stable wealth process. By means of a transformation, the lower bound is used to construct an upper bound on the probability to complete a schedule of withdrawals following an initial investment. For multiple investable assets, the probability to complete a schedule of investments and withdrawals is optimized over time-adapted portfolio weight functions. Lastly, the return of a daily leveraged ETF is bounded using simple characteristics of the underlying index's daily log-returns. Results are applied to portfolios involving the S&P Composite Index and an inflation-protected bond
Explore the Dosimetric Relationship Between Intake of Chemical Contaminants and Their Occurrence in Blood and Urine
No full textThe dosimetric relationship between the human intake of a chemical contaminant (an “external dose”) and its concentrations in bodily fluids such as blood and urine (related to an “internal dose”), often characterized by a dose-to-concentration ratio, has critical applications in exposure science, toxicology, and risk assessment, especially in the “new approach methods” era. However, there is a lack of a mechanistic, systematic understanding of how such a dosimetric relationship depends on fundamental chemical properties, such as partition coefficients and biotransformation half-lives. Here, we investigate this issue using a well-evaluated toxicokinetic model, which links external and internal doses by quantifying the absorption and elimination of chemicals. Results are visualized in a series of chemical partitioning space plots, whereby a chemical’s dose-to-concentration ratio can be approximately predicted based on its partitioning between air, water, and octanol phases. Our results indicate that when taken in equal doses, chemicals with low volatility and moderate to high hydrophobicity exhibit the highest concentrations in blood, and chemicals undergoing significant biotransformation tend to exhibit lower concentrations in comparison to their counterparts undergoing negligible biotransformation but possessing similar partitioning properties. Chemicals with high hydrophilicity have the highest concentrations in urine. Such revealed property dependence is similar for both adults and children, and for individuals with normal body weights and with obesity. Overall, insights gained from this study are important in predicting blood and urinary concentrations from exposure information and in determining the exposure rate that produces the blood or urinary concentrations observed in biomonitoring studies
Neural Correlates of Object-Based Attention in Retinotopic Visual Cortex in a 100% Valid Cueing Task
No full textA central debated question in the study of Object-Based Attention (OBA) is whether attention spreads automatically to the entire object (Chen & Cave, 2006) or whether the pattern of results is driven by other non-obligatory factors, such as prioritization of target locations (Shomstein & Yantis, 2002). However, virtually all behavioral measures attributed to OBA are based on examining performance on invalid-cue trials, the inclusion of which confounds the assessment of the automaticity hypothesis. A critical test of the hypothesis attention spreads over objects that lacks this confound would be to determine whether or not effects of OBA can be observed in a 100% valid cueing paradigm. In this paper we investigate the obligatory nature of OBA by leveraging the spatial specificity of functional magnetic resonance imaging (fMRI) and the retinotopic organization of the early visual cortex. We aimed to identify potential neural correlates of OBA in the complete absence of invalid trials. Participants perform a version of the classic two-rectangle OBA paradigm while simultaneously measuring changes in BOLD signals arising from retinotopically organized cortical areas V1, V2 and V3. In the first half of the experiment, we used the classic two-rectangle OBA paradigm except that the cue was 100% valid. In the second half, we reduced cue validity to more closely match standard OBA paradigms (runs containing invalid trials). We analyzed BOLD signals arising from our regions of interest in V1, V2, and V3 according to their topographic correspondences with the ends of the rectangles in the visual field and compared these. We then compared responses in each ROI according to where the cue had occurred (Cued, Uncued-Same-Object, Uncued-Other-Object location). We replicated this procedure in Experiment 2, but changed the layout of the two rectangles from a vertical to a horizontal configuration. Critical result: we observed statistically significant effects of OBA in V3 (Experiment 1) and V1-2 (Experiment 2) in both the 100% valid runs and in runs containing invalid trials. Moreover, the effects of OBA were no smaller in the 100% runs compared to runs containing invalid trials. Conclusion: we see BOLD modulation at the uncued locations consistent with neural correlates of OBA
Schools as Societal Change Agencies
Get PDFThere is a call to action to close disparities and address inequalities throughout various institutions across the United States. There is a growing amount of research on the topic of education in relation to how schools can better serve as critical societal change agencies. This qualitative study serves to answer questions on the experiences and perceptions of school leaders, school district leaders, and community agency leaders on the roles and responsibilities of school systems and personnel to serve as societal change agents. This comparative case study is reported through the ethnographic perspectives in individualized interviews around one centralized public school district. The nine participants were selected through purposive and snowball sampling due to their work in the school district or partnership with schools. In Vivo and Process Coding with elements of Values and Emotion Coding were utilized to determine themes and responses. First, findings for agency leaders included the inherent good behind the responsibilities of school leaders, hope for change with advancing partnerships, and identified issues preventing change. Findings for school and school district leaders covered the demands of their roles, the value of partnerships, and identified unintended consequences. Secondly, participants shared responses on how they sustain practice and reduce disparities. Finally, the study reports on how participants collaborate to drive change through enhancing and leveraging partnerships, emphasizing the roles of school and school district leaders, and advocating for policy change. The study's final discussion discusses implications and suggestions for ongoing or future research
The Brain Renin-Angiotensin System in the Regulation of Blood Pressure
No full textHypertension, or high blood pressure, affects over one-third of the adult US population and over a billion people globally. Hypertension is the main risk factor for cardiovascular diseases and stroke, demonstrating the importance of blood pressure regulation. The local brain renin-angiotensin system (RAS) has emerged as a key player in the development and pathogenesis of hypertension. However, the mechanisms and localization of this complex cascade of peptides, enzymes, and receptors are not well understood and under debate whether all components are expressed within the brain, especially endogenous prorenin. This dissertation focuses on the role of the brain RAS in the development of salt-sensitive hypertension (SSH) in the subfornical organ (SFO) and the paraventricular nucleus (PVN) of the hypothalamus, key brain nuclei in blood pressure and body fluid homeostasis. We show in this dissertation that renin-a, the endogenously secreted prorenin, is elevated within the SFO after DOCA-Salt treatment (a model for SSH). Ablation of renin-a within SFO neurons is able to attenuate blood pressure and improve autonomic function after the DOCA-Salt challenge. We also clearly show that renin is present within the brain, specifically in glutamatergic and GABAergic neurons. We then utilize advanced single nuclei multiomic sequencing to characterize the RAS within the PVN. We observe the presence of the RAS components within the PVN, primarily in glutamatergic and GABAergic neurons. Interestingly, we show that after DOCA-Salt treatment the neurons undergo a cell-type population shift, with the inhibitory GABAergic neurons switching to the excitatory glutamatergic cell type. We also see this trend in the PRR-expressing neurons, with PRR-neurons shifting to the glutamatergic subtype. Collectively our data support the importance for the brain RAS and glutamatergic neurons in the development and/or maintenance of SSH
The Use of a Virtual Reality Platform for Standardization of the Vestibular Ocular-Motor Screen
Get PDFPublic awareness of sport-related concussion (SRC) has risen in recent history. This is evident through a couple of factors. One is the increased self-reporting of SRC. It has been estimated that 2.5 million American High School students reported having at least one SRC within the previous year. Of that same group, 1 million reported having more than one SRC.1 The second factor is the development of various sports injury surveillance systems that have been implemented to track this data over the past decade. The Vestibular Ocular Motor Screen (VOMS) is a standard clinical tool for the assessment, diagnosis, and management of SRC. The VOMS consists of seven subtests that challenge the subject's oculomotor and vestibular function. The subtests are designed to elicit symptomology consistent with SRC. The current clinical protocol involves hand-held use of targets and administrator interpretation of the distances the targets are held in front of the subject. Variability among raters with this process may alter the symptom reporting from the subject and near-point convergence (NPC) measurements. This creates the potential for misdiagnosis, management, and treatment of SRC. The objective of this study is to explore a means of standardization of the VOMS among clinicians such that subjective symptomology recording is reliable in the diagnosis and management of SRC. This study consists of three experiments. Experiment one is an examination of the current clinical protocol compared to a novel prototype (PRO) and a virtual reality (VR) stimulus to determine if the latter two platforms are suitable means of standardization of the VOMS with a healthy population. The results indicate the PRO and VR elicit less symptoms but the VR had higher NPC measurements. Experiment two compares the Total Symptom Provocation Change Score (TSPCS) and Near Point Convergence (NPC) between the PRO and the VR stimuli at baseline and post-injury. Post-injury comparison data indicate no significant difference with TSPCS and NPC measurements and VR may be used with post-injury assessments. Experiment three is a direct comparison of the current clinical manual method of VOMS administration to the VR method that includes baseline and post-injury data. This experiment also examined self-reported motion sickness. The results indicate that VR can be used to administer the VOMS despite any history of motion sickness. The goal of this study is to provide proof of concept that leads to the development of a standardized, mobile VOMS VR stimuli that can record symptoms, eye movement, measure near-point convergence (NPC), and is completely automated such that the field healthcare professional can use this platform for a quick digital relay of this information to a physician for diagnosis and management of SRC
Investigation of the Integrity of Tailings Dam Surfaces Using Aerial Imaging and Computer Vision
Get PDFThis thesis explores the critical analysis of seepage and rill erosion. This study tackles the difficulties in tracking and evaluating the condition of tailings dam surfaces by utilizing cutting-edge methods in computer vision and aerial imagery. The study uses multispectral imaging, a robust technique for detecting subtle changes in surface conditions that offer important insights into possible weak points in dam structures, to measure seepage. The thesis investigates the use of U-Net for semantic segmentation and Convolutional Neural Networks for picture classification in the setting of rill erosion. By enhancing the precision and effectiveness of rill erosion detection, this dual-methodology approach aims to enable the identification and delineation of erosion structures on dam surfaces. A thorough examination is made easier by the combination of CNN and U-Net, which helps to provide a more complex knowledge of the location and magnitude of rill erosion. The field of environmental monitoring and dam safety will benefit greatly from the research findings. In the end, the use of multispectral imaging and sophisticated computer vision algorithms helps identify and mitigate possible problems related to seepage and rill erosion by promoting a more thorough and proactive approach to the evaluation of tailings dam surfaces
Steps to Reduce Use of Cutback Asphalt in Pavement Maintenance and Preservation
Get PDFThis Technical Brief provides information to facilitate better understanding of the current usage levels of cutback asphalt in pavement construction, maintenance, and preservation as well as State DOT specifications that may allow use of cutback asphalt. Areas where use of cutback asphalt can be reduced and alternatives to cutback asphalt are identified.U.S. Department of Transportatio
Comparing the effects of nanosecond electric pulses to those evoked by conventional electrical stimulation
No full textElectrical stimulation is a medical technique used in a wide variety of applications, from chronic pain management to smart prosthetics to neuromodulation. Conventionally, electrical stimulation is delivered in low voltage, millisecond-range pulses and comes in the form of implants that require invasive surgery, such as with pacemakers. Our research seeks to change this. Unlike conventional electric pulses (CEPs), nanosecond electric pulses (NEPs) offer a mechanism to target and stimulate tissues within the body without the need for invasive procedures. With that in mind, this project seeks to compare the effectiveness of CEPs to that of NEPs in evoking responses in bovine chromaffin cells. Using a combination of techniques such as cell dissociation and fluorescence microscopy, we are able to test each stimulation method on single cells and record the cells’ chemical responses in real time. The biomedical sector is one of constant technological innovation, and we see our research on electrical stimulation as one more step in the advancement of modern medicine
Epidemiological Assessment of Harmful Environmentally Linked Factors and Their Relationships With Environmental Justice
No full textIntroduction: This dissertation evaluates the exposure to and disparities in measured environmental pollutants distributed across the United States (U.S.) through air, water, and dusts and soils within the framework of Environmental Justice (EJ). EJ is the equitable distribution of environmental hazards with respect to socioeconomic factors like income, race, and country of origin. Environmental pollution has been linked to various negative public health outcomes, including both acute injury and chronic disease. Health outcome burdens linked to environmental pollution have been demonstrated to have strong socioeconomic ties, and those who experience the bulk of the pollution, tend to be from a minority racial group and low-income status. While the scope and interest in EJ has grown in the past two decades, studies on environmental pollution and its relationship with the socioeconomics across the country tend to be localized to single cities, zip code tabulated areas, zip code tabulations within single census tracts, or single regions. Results of these studies tend to find minority and low-income areas experience high environmental pollution burden, but these studies do not often assess multiple media or present a comprehensive picture of the magnitude of injustice across the U.S. Because of the existing literature is still growing, and typical EJ studies are computationally intense and suffer data availability issues, it is difficult to ascertain how widespread environmental injustice is in the U.S., and whether conditions are improving, worsening, or remaining static. Here, I include a series of studies to analyze the environmental conditions across the U.S. with respect to the air, the water, the soil, and dust in the households, with respect to the socioeconomic makeup of the U.S. Methods: The overall methodological frameworks for the included studies are similar yet the details vary. Chapter two evaluates the disparity in exposure to estimated lifetime cancer risks with respect to race along the rural-urban continuum. I use five years of census tract level estimated cancer risks from the National Air Toxics Assessment and AirToxScreen datasets produced by the United States Environmental Protection Agency (EPA) alongside paired socioeconomic factors from the United States Census Bureau (USCB) using multivariable linear and spatial regression modeling techniques to demonstrate disparity in exposure to air toxics by demographic makeup along the rural-urban continuum within census tracts for the entire U.S over nearly a decade. Chapter three evaluates the disparity with respect to racial makeup across U.S. counties in measured sediment metal pollution using the Water Quality Portal (WQP). I use stratified generalized linear modeling to demonstrate the existence of disparity in exposure to harmful metals in sediment. In the fourth chapter I use air quality data including the Air Quality Index (AQI), air Toxic Release Inventories (TRI), and annual monitored hazardous air pollutants (HAP) and multivariable linear regression to control for important confounders and explore variation in pollution distribution by exposure first, then risk with the help of different assessment approaches. And finally, I present preliminary results of an ongoing cohort study among children aged six months to six years analyzing exposure to harmful environmental compounds in soil and dust, as well as the children's prevalent exposures to these compounds by urine and excrement measurements in chapter five. Results: Results of multivariable linear regressions demonstrated widespread EJ issues with increasing proportions of Black, Asian, and Hispanic individuals, but not for increasing proportions of mixed-race individuals with respect to estimated cancer risk from air toxics exposures. Some meaningful inequality in deposited lead to sediment was found in increasingly Black and Hispanic areas, but the magnitude and degree of certainty is variable by state, and increasing proportions of mixed-race individuals was observed to be increasingly protective. In ambient air quality, emitted air pollutants from industry, and their estimated health effects, some disparity for Black, Asian, and Hispanic individuals were found, however data limitations are likely masking the full disparity. While on average air pollution is decreasing through time, there is a strong relationship along the urban-rural continuum and spikes in industry related pollution were observed. In children, there is high variation in measured metal concentration with available sample by the child's race, however no meaningful environmental injustice was found in preliminary sampling. Discussion: Environmental injustice for increasing proportions of Black, Hispanic, and Asian communities across the U.S. was consistently found, however the magnitude of the results are mixed. Income and increasing proportions of mixed-race/Other individuals relative to White individuals were consistently found to be protective against estimated cancer risks and distribution of environmental pollution. The rural-urban continuum plays an important role in the magnitude of exposure and the disparity in demographic makeup with respect to the exposure. While it was observed that overall environmental conditions are improving across the U.S. in the last decade, disparity in exposure and the magnitude for some of the pollution distribution in some areas remains high. Coverage error likely plays an important role in evaluating the magnitude and significance of EJ in the U.S., yielding possible underestimates in the association between environmental pollution and socioeconomic status. In some cases, increasing proportions of minority populations produce negative associations with environmental pollution, which indicates disparity against resident White populations, which are often in poor or remote areas. Future research should prioritize analyzing areas where there are large gaps in data coverage like mountainous populations and the southern states, and policy-makers should pay keen attention to areas where high concentrations of air pollution, water pollution, and estimated risks are prevalent. Where extreme inequity exists, like parts of California or the deep south, policy-makers should prioritize these areas in all regulatory and remediation capacity first