Multilevel variance components and brain volume mediation of life stress on post-traumatic stress disorder symptoms in children via regularization

Alterations of volume in brain regions of interest (ROIs) are associated with post-traumatic stress disorder (PTSD). Most of the extant neuroimaging research in PTSD has studied adults. The present study extends this research by using data from children (N=11,869, M age =9.92) from the ABCD study, a multisite longitudinal long-term study of brain development and childhood health in the U.S. Traumatic events (TEs) and PTSD symptoms were measured through the K- SADS for DSM-5. Values of brain ROIs were assessed using structural MRI measures. The unidirectional model was able to detect the small differences from site variance in sMRI mediators (subc: VS\u3c.009, SE\u3c.004; cort: VS\u3c.009, SE\u3c.004). Additive genetic factors explained 23.49% of the variance in TEs, 41.73% in subcortical and 19.94% in cortical mediators, and residual 21.01% in PTSD symptoms. Environmental factors explained most of the variance in TEs (C=.61, E=.16) and PTSD symptoms (resC=.19, resE=.21), as well as unique environmental factors in the cortical mediators (cort=.66). TEs highly influenced PTSD symptoms (.92). However, the indirect effect of TEs on PTSD symptoms through the mediation of volume in brain ROIs was small to non-influential at this age (subc=-.0003-.001, cort=-.001- .002). Several estimates of mediation effects were notably higher than most. Regularization via elastic net is implemented to train the mediation model to reduce bias and noise from overfitting, and to select the ROIs with mediation effects that explain the data with increased sparsity.https://scholarscompass.vcu.edu/gradposters/1102/thumbnail.jp

The challenge of integrating non-continuous processes-milk powder plant case study

The integration of non-continuous processes such as a milk powder plant present a challenge for existing process integration techniques. Current techniques are generally based on steady and continuous operation which for some industries is not the case. Milk production varies considerably during the year as dairy cows in New Zealand are grazed on pasture, which affects the scheduling and operation of plants on site. The frequency and duration of cleaning cycles and non-productive operating states can have a major affect on energy demand and the availability of heat sources and heat sinks. In this paper the potential for indirect heat transfer between the several plants using a heat recovery loop and stratified tank at a typical New Zealand dairy factory is investigated. The maximum amount of heat recovery is calculated for a range of recirculation loop temperatures. The maximum amount of heat recovery can be increased considerably if the temperature of the hot fluid in the recirculation loop is varied depending on which condition the site is operating under

Integrating heat recovery from milk powder spray dryer exhausts in the dairy industry

Heat recovery from milk powder spray dryer exhausts has proven challenging due to both economic and thermodynamic constraints. Integrating the dryer with the rest of the process (e.g. evaporation stages) can increase the viability of exhaust recovery. Several potential integration schemes for a milk powder plant have been investigated. Indirect heat transfer via a coupled loop between the spray dryer exhaust and various heat sinks were modeled and the practical heat recovery potential determined. Hot utility use was reduced by as much as 21% if suitable heat sinks are selected. Due to high particle loading and operating temperatures in the particle sticky regime, powder deposition in the exhaust heat exchanger is perhaps the greatest obstacle for implementing heat recovery schemes on spray dryers. Adequate cleaning systems are needed to ensure continuous dyer operation

Assessing tradeoffs of urban water demand reduction strategies

2019 Fall.Includes bibliographical references.In many cities across the World, traditional sources of potable water supply can become susceptible to shortage due to increased water demands from rapid urbanization and more frequent and extreme drought conditions. Understanding impacts of city-scale conservation and water reuse is important for water managers to implement cost effective water saving strategies and develop resilient municipal water systems. Innovative water reuse systems are becoming more cost effective, technologically viable and socially accepted. However, there is still a need for comparative assessment of alternative sources; graywater, stormwater and wastewater use along with indoor and outdoor conservation, implemented at the municipal scale. This study applies the Integrated Urban Water Model (IUWM) to three U.S. cities; Denver, CO; Miami, FL; and Tucson, AZ. We assess the tradeoffs between cost and water savings for a range of solutions composed of up to three strategies; to understand interactions between strategies and their performance under the influence of local precipitation, population density and land cover. A global sensitivity analysis method was used to fit and test model parameters to historical water use in each city. Alternative source and conservation strategies available in IUWM were simulated to quantify annual water savings. Alternative source strategies simulate collection of graywater, stormwater and wastewater to supplement demands for toilet flushing, landscape irrigation and potable supply. A non-dominated sorting function was applied that minimizes annual demand and total annualized cost to identify optimal strategies. Results show discrete strategy performance in demand reduction between cities influenced by local climate conditions, land cover and population density. Strategies that include use of stormwater can achieve highest demand reduction in Miami, where precipitation and impervious area is large resulting in larger generation of stormwater compared to other study cities. Indoor conservation was frequently part of optimal solutions in Tucson, where indoor water use is higher per capita compared to other study cities. The top performing strategies overall in terms of water savings and total cost were found to be efficient irrigation systems and stormwater for irrigation. While use of stormwater achieves large demand reduction relative to other strategies, it only occurred in non-dominated solutions that were characterized by higher cost. This strategy can be very effective for demand reduction, but is also costly. On the contrary, efficient irrigation systems are frequently part of low-cost solutions across all three study cities. Overall, this study introduces a framework for assessing cost and efficacy of water conservation and reuse strategies across regions. Results identify optimal strategies that can meet a range of demand reduction targets and stay within financial constraints

Substance Use and Depression Symptomatology: Measurement Invariance of the Beck Depression Inventory (BDI-II) among Non-Users and Frequent-Users of Alcohol, Nicotine and Cannabis

Depression is a highly heterogeneous condition, and identifying how symptoms present in various groups may greatly increase our understanding of its etiology. Importantly, Major Depressive Disorder is strongly linked with Substance Use Disorders, which may ameliorate or exacerbate specific depression symptoms. It is therefore quite plausible that depression may present with different symptom profiles depending on an individual’s substance use status. Given these observations, it is important to examine the underlying construct of depression in groups of substance users compared to non-users. In this study we use a non-clinical sample to examine the measurement structure of the Beck Depression Inventory (BDI-II) in non-users and frequent-users of various substances. Specifically, measurement invariance was examined across those who do vs. do not use alcohol, nicotine, and cannabis. Results indicate strict factorial invariance across non-users and frequent-users of alcohol and cannabis, and metric invariance across non-users and frequent-users of nicotine. This implies that the factor structure of the BDI-II is similar across all substance use groups

Development and application of a clothed thermoregulatory model

Mathematical models of human thermoregulation can be used to assess the habitability of thermal environments prior to human exposure. Work continues to improve the performance of these models to reduce concerns surrounding the accuracy of their predictions. The aims of this thesis were to develop an existing thermoregulatory model (LUT25-node model). The developments made to the LUT25-node model, now enable it to predict the thermal responses of heat acclimated subjects of differing size, while its clothing model was improved to consider the addition and distribution of clothing properties. Validations of these modifications, confirmed that predictions from the model were improved. The thesis also looks at practical applications of the LUT25-node model. This included a modification to the model enabling backward modelling; predicting how the thermal stress should be altered to achieve a desired limit of thermal strain. Several hypothetical scenarios illustrated the practical applications of this modification. In addition, the LUT25-node model was used to explain the initial drop in deep body temperature at the onset of exercise. This investigation concluded that the temperature drop is due to the return of cool blood to the body core from initially cool working muscles. Finally, the poor predictions of the LUT25-node model for cold exposures was investigated. Previous investigators suspected that this was due to the limited number of thermal layers in the body segments of the model. However, predictions from a multi-layered LUT25-node model, developed with the finite volume software package PHOENICS, suggest that increasing the number of thermal layers reduces the accuracy of the model's predictions for cold exposures. In conclusion, this thesis has contributed to the continued development of a human thermoregulatory model and illustrated its practical benefits. It is recommended that future work centres on addressing additional limitations of the LUT25-node model identified in this study

Area targeting and storage temperature selection for heat recovery loops

Inter-plant heat integration across a large site can be achieved using a Heat Recovery Loop (HRL). In this paper the relationship between HRL storage temperatures, heating and cooling utility savings (heat recovery) and total HRL exchanger area is investigated. A methodology for designing a HRL based on a ΔTmin approach is compared to three global optimisation approaches where heat exchangers are constrained to have either the same Number of Heat Transfer Units (NTU), Log-Mean Temperature Difference (LMTD) or no constraints (actual global optimum). Analysis is performed using time averaged flow rate and temperature data. Attention is given to understanding the actual temperature driving force of the HRL heat exchangers compared to the apparent driving force as indicated by the composite curves. The cold storage temperature is also varied to minimise the total heat exchanger area. Results for the same heat recovery level show that the ΔTmin approach is effective at minimising total area to within 5 % of the unconstrained global optimisation approach. The study also demonstrates the efficiency of the ΔT min approach to HRL design compared to the other methods which require considerable computational resources

An investigation of milk powder deposition on parallel fins

One method to reduce the energy consumption of industrial milk spray dryers is to recover waste heat from the exhaust dryer air. A significant challenge associated with this opportunity is the air contains a small amount of powder that may deposit on the face and surfaces of a recuperator. This paper introduces a novel lab based test that simulates powder deposition on a bank of parallel plate fins at exhaust dryer air conditions. The fin bank acts like the face of a typical finned tube row in a recuperator. The aim of this study is to look at how deposition on the front of fins is affected by the air conditions. Results show similar characteristics to other milk powder deposition studies that exhibit a dramatic increase in deposition once critical stickiness levels are reached. As powder deposits on the face of the fins, the pressure drop across the bank increases until eventually an asymptote occurs, at which point the rates of deposition and removal are similar. For very sticky conditions, deposition on the face of the fins can cause a rise in the pressure drop by as much as 65%. The pressure drop has also been successfully related to the percentage of open frontal area of the fins with and without deposition. Deposition inside and at the rear of the fin bank was found to be minimal

Integration of solar heating into heat recovery loops using constant and variable temperature storage

Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable

Design and operation methods for better performing heat recovery loops

Inter-plant integration via a heat recovery loop (HRL) is an economic method for increasing total site process energy efficiency of semi-continuous processes. Results show that both the constant storage temperature approach and variable storage temperature approach have merit. Depending on the mix of source and sink streams attached, it may be advantageous to change the operation of an existing HRL from a constant temperature storage to a variable temperature storage. To realise the full benefits of this change in operation, a redistribution of the existing heat exchanger area may be needed