16484 research outputs found
Sort by
Incorporating the Host-Pathogen Kinetics of Time-Dose-Response into Epidemic Outbreak Models
Get PDFMathematical models charting disease outbreaks have been a central tenant of epidemiology since its inception. Pathogens responsible for these outbreaks replicate in the host, leading to adverse reactions over time. It may be concluded, therefore, that the incubation period is a function of pathogen reproduction, which is time-dependent. Yet no outbreak model has considered the effects of in-vivo kinetics to date. It is postulated that outbreak models which consider host-pathogen kinetics can provide better fits to outbreak data than models that do not consider this system. This dissertation demonstrates the relationship between the incubation function of a host-pathogen system and outbreak models. To examine this relationship, this work is divided into two categories: (1) derivations and model development, which includes (a) deriving time-dose-response (TDR) models, (b) deriving primary (common-source) and secondary (person-to-person spread) outbreak models that incorporate the TDR equations, and (c) developing a Matlab code which models a convolution of the exposure and incubation distributions; and (2) data modelling, which includes (a) mining the literature to find appropriate TDR and outbreak datasets for each respective pathogen, (b) generating dose-response model fits for each respective pathogen, (c) generating TDR model fits for each pathogen, and (d) generating fits for the TDR and non-time-dependent outbreak models. This methodology was partially verified using data from a Cryptosporidium parvum outbreak that occurred in Milwaukee. The pathogens modelled using this method are (1) Legionella spp.; (2) Giardia lamblia; (3) Salmonella spp.; (4) Shigella spp.; (5) Escherichia coli O157:H7; and (6) Campylobacter jejuni. The results of this work suggest good support for the TDR incorporation into the outbreak model. In several cases, the TDR outbreak had the lowest deviance values among time-dependent and non-time-dependent models, which was the metric that was used to determine the best-fit model. However, since the TDR contained extra parameters, it did not necessarily have the lowest Akaike information criterion (AIC) and Bayesian information criterion (BIC) values. Parameter estimates were generally consistent across different species. This work seeks to characterize the relationship between the time-dose-response functions, which reflect the in-vivo kinetics of the host-pathogen system, and the models that predict the number of ill persons per day of an outbreak, based on available data from epidemiological studies.Ph.D., Environmental Engineering -- Drexel University, 201
Responsivity to an Analogue Psychological Acceptance Task and Neurophysiological Measures as Predictors of Treatment Response for Public Speaking Anxiety
No full textBackground: Individuals seeking treatment for mental health conditions often explore multiple therapeutic modalities before finding one that is beneficial. Early identification of individuals likely to respond to a particular psychotherapy modality may substantially decrease this burden. Objective: The current study tested novel variables as potential predictors of response to psychotherapy for public speaking anxiety (PSA). Specifically, the current study (1) evaluated whether responsivity to a laboratory-based analogue intervention for acceptance and commitment therapy (ACT) predicted subsequent treatment response to an actual ACT-based intervention, and (2) evaluated whether frontal brain activity (frontal asymmetry; bilateral activity) at baseline or (3) in anticipation of public speaking predicted subsequent treatment response. Participants: A total of 48 individuals with PSA completed all study components. Methods: Participants completed a public speaking task prior to and following receipt of a brief ACT-based analogue intervention. In association with each public speaking task, neurophysiological measurements, including frontal brain activity measured by electroencephalography (EEG) and heart rate (HR), were collected. Analogue intervention responsivity was considered based on residualized change in self-reported anxiety and openness to anxiety, neurophysiological measurement (EEG; HR), behavioral ratings of speech performance, and an analogue responsivity composite factor. Participants subsequently received a 2.5 hour ACT treatment over two days. A final public speaking task was completed and psychological, physiological (HR), and behavioral ratings were collected as primary measures of treatment outcome, along with a composite treatment outcome factor. Results: The analogue responsivity composite factor predicted ACT treatment outcome on several measures, with greater analogue intervention symptom improvement associated with greater subsequent ACT treatment symptom improvement on most measures. Individual analogue responsivity variables generally did not predict ACT treatment responsivity. Greater right-frontal asymmetry at baseline and in anticipation of a public speaking task trended towards an association with greater symptom improvement over treatment across several outcome measures. Greater bilateral frontal activity – a measure associated with self-reported mindfulness at baseline – significantly predicted greater symptom improvement over treatment across several outcome measures; higher mindfulness at baseline also predicted greater symptom improvement across several outcome measures. Implications: Findings suggest that an individual’s response to an analogue intervention, or a small ‘dose’ of psychotherapy, may inform their response to a longer course of psychotherapy, particularly in ACT for PSA. Individuals with greater bilateral frontal activity and (to a lesser degree) individuals with greater right-frontal asymmetry may experience greater symptom reduction in an ACT-based treatment for PSA. Future studies should evaluate whether any of these variables (analogue responsivity; frontal brain activity) differentially predict response to two or more different psychotherapies in a quest towards personalized medicine. Future research should also evaluate whether interventions designed to increase baseline mindfulness (e.g., meditation training) prior to a course of ACT for PSA, or a similar intervention, improves treatment efficacy.Ph.D., Psychology -- Drexel University, 201
Stacking Faults in the Transition Metal Carbides and Nitrides: Stability and Mechanical Properties
No full textUltra-high-temperature ceramics (UHTCs) are a class of refractory materials that have melting temperatures above 3000 K. As a major subclass of UHTCs, the transition metal carbides and nitrides (TMC/Ns) are ideal for high temperature applications especially in aerospace field. Despite the fact that the crystal structures and types of bonding are very similar within these materials, their mechanical properties such as hardness and plasticity are different at room temperature. In addition, TMC/Ns suffer from low fracture toughness at room temperature, which may cause unexpected failures during operations and handling, therefore limiting their applications. Recent experimental work has found that the precipitation of certain stacking fault phases (SFPs) may increase the fracture toughness of these materials. However, the stability of these phases and the mechanisms behind the enhanced fracture toughness are still debated. To better understand the interplay between the chemistry, bonding, microstructure, and mechanical properties in TMC/Ns, this thesis focuses on two major topics: (1) the thermodynamic and structural stability of stacking faults and SFPs; (2) the key factors, including the chemistry and bonding, that control the mechanical properties of these materials, such as the slip and fracture toughness. In this thesis, numerical methods including ab-initio simulations are widely used to fill the gap between experimental observations and intrinsic properties of the material. This study serves as a bridge to connect theory to empirical observations, which would provide insights into engineering tougher and stronger TMC/Ns for high temperature applications.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Experimental Testbed for Load Control on an AC/DC Microgrid
Get PDFMicrogrids are becoming increasingly popular in the world of power systems to mitigate the effects of high impact events that can lead to blackouts. They are also integral to including distributed renewable energy generation in the grid. A major challenge in effective implementation of DC microgrids, in particular, is the lack of adequate testing platforms. This thesis primarily aims to build a testbed of an AC/DC microgrid in a laboratory environment using programmable sources and loads. A central measurement and control platform is developed to monitor and actuate all the loads from a single unit. While this enhances data measurement, it also enables simultaneous operation of the loads. The use of such state-of-the-art technology gives a better understanding of integration of microgrids into existing power systems.
Having a microgrid testbed allows for the study of the control of hybrid AC/DC microgrids under various operating conditions. This thesis uses this capability to test a load shedding problem on a 3 bus and 4 bus AC/DC microgrid. An algorithmic solution to the problem is proposed and implemented in hardware. The results are compared to more traditional control strategies. The microgrid testbed developed in this thesis can prove integral to future research work on AC/DC microgrid controllers. The central control platform can also be used for future research into the effect of communication networks on the performance of the microgrid and power system as a whole.M.S., Electrical Engineering -- Drexel University, 201
Functional Near Infrared Spectroscopy in the Investigation of Hemodynamic Changes during General Anesthesia
Get PDFAnesthesiologists, physiologists and medical device professionals have long been working to design advanced depth of anesthesia monitoring systems in addition to routine physiological measures such as blood pressure (BP), heart rate (HR), respiration rate (RR), peripheral oxygen saturation (SpO2) and end tidal CO2 (EtCO2). Various devices have been designed to monitor depth of anesthesia. However, none of the systems have gained widespread use mainly because the warning signal associated with the depth of anesthesia is often evidenced after the anesthesiologist has already noted the change in anesthetic state. Further, there still remains an unmet clinical need for a practical, inexpensive tool for the reliable and objective assessment of the effects of general anesthetics during surgery. Advanced functional imaging modalities such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans deliver superior spatial information, which comes at a high equipment and maintenance cost. Therefore, they are not readily accessible for routine clinical use in general anesthesia. On the other hand, functional near infrared spectroscopy (fNIRS) is non-invasive, safe, portable, and affordable and has a better temporal resolution with a short set up time which makes it more suitable for operating room settings. In this thesis we explore the feasibility of using the fNIRS measures to detect the transition from maintenance to emergence during general anesthesia. The goals of this thesis are to i) examine the effect of volatile anesthetics, specifically sevoflurane, on hemodynamic parameters measured by the fNIRS, the heart rate, end-tidal carbon dioxide concentration and peripheral oxygen saturation, ii) investigate features extracted from these signals that contain information related to anesthetic states, and iii) propose a method for the automatic classification of maintenance and emergence during general anesthesia with sevoflurane using machine learning algorithms. The results reveal the ability of fNIRS biomarkers to automatically differentiate between maintenance and emergence states in real time during general anesthesia. The maintenance state was identified as a period of relative signal stability, while the emergence state was characterized by signal variability. This suggests that the hemodynamic changes observed during emergence reflect the competing effects of increased vasoconstriction and increased cerebral metabolic rate that occur during sevoflurane washout. We examined linear and non-linear classification methods and concluded that a non-linear method can increase the performance of an fNIRS based classifier. Furthermore, this investigation determined that fNIRS based classifiers are able to outperform the EEG based Bispectral Index (BIS) and minimum alveolar concentration (MAC) when examined individually. When combined, fNIRS and MAC demonstrated the better performance. In summary, this thesis provides evidence that biomarkers derived from the fNIRS measures can reveal differences between anesthetic depths and can be used for real time and automatic detection of maintenance and emergence states during the delivery of general anesthesia with sevoflurane.Ph.D., Biomedical Engineering -- Drexel University, 201
Predicting Weight-Related Outcomes in Healthy Adolescents: Clinical Applications of fMRI and Machine Learning
Get PDFObesity and obesity-related diseases have increased dramatically worldwide in recent years; however, previous studies have shown that weight loss interventions are largely ineffective in the long term. As a result, focus has shifted to determining objective predictors of weight gain, including neural correlates of such weight behaviors. Previous imaging studies have investigated the brain using univariate methods that do not enable detection of the multivariate complex patterns that may separate those prone to weight gain from those who are not. The present study used a supervised machine learning method (SVM; support vector machine) to classify adolescents (N = 135) into those who would gain weight or become weight variable over a 3-year period. Whole brain SVM analyses were performed for a) structural MRI, b) fMRI during milkshake tasting, c) fMRI during an inhibitory control go/no-go task, d) fMRI during a food image task and e) a combination of modalities. Structural scans did not significantly predict weight gain or weight variability. For functional scans in the milkshake and food image paradigms, SVMs significantly predicted weight gain using a linear mixed-effects method. Predictive accuracy increased when these two paradigms were concatenated in a single model. SVMs did not reach significance for classification of weight variability in any of the paradigms. These results support that weight gain proneness can be characterized by different neural activation to food stimuli and that these differences precede weight gain. The findings suggest that SVM may be useful for identifying neural markers of weight gain proneness.Ph.D., Psychology -- Drexel University, 201
Effect of a Preoperative Briefing Tool and Education on Negative Operative Events
Get PDFBackground: Evidence supports the use of preoperative communication as a strategy to anticipate perioperative needs and mitigate surgical error. The purpose of this QI project was to improve perioperative safety through enhanced interprofessional communication using an educational intervention and to pilot a structured communication tool, the World Health Organization's Surgical Safety Checklist (WHO SSC) to facilitate a preoperative briefing. Methods: The project used a pre-test post-test survey, i.e. the Agency for Healthcare Research and Quality’s (AHRQ) Hospital Survey on Patient Safety (HSOPS), to assess the educational intervention with a convenience sample of perioperative team members. The WHO SSC, the Association of Operating Room Nurses (AORN) Practices for Transfer of Care, and the TeamSTEPPS (TM) communication content informed the educational intervention. The Midas Incident Reporting System measured adverse events. The AHRQ - HSOPS measured reported Patient Safety Grade. Evaluation: Fifty-two in-patient employees (63% response rate) completed the AHRQ-HSOPS and 49 completed the post educational survey. There were no significant differences on the AHRQ-HSOPS’s four domains of Teamwork, Communication Openness, Overall Perception of Safety, or Handoffs and Transitions. For one of the outcome measures of the AHRQ - HSOPS, Patient Safety Grade, the median ratings by the post education group were significantly higher (p = .001) than the pre-education group. There were no reportable sentinel events. A slight increase in reported near miss events were reported following the educational program. Clinical Implications and Summary: The use of tools such as the WHO SSC could expand the current communication preoperatively among caregivers and reduce surgical error.D.N.P., Nursing Practice -- Drexel University, 201
PFF1320C an Essential but Presumptive Plasmodium Myosin Light Chain
No full textLittle is known regarding the nature and function of the myosin motors of Plasmodium. Analysis of the genome reveals that there are six myosin heavy chains but only two, PfMyoA and PfMyoB, have been characterized with the role of PfMyoA, along with its cognate light chain partner MTIP, being directly involved in the process of parasite invasion. PFF1320c is annotated in the Plasmodium genome as a putative myosin light chain but to date there is no biochemical evidence to support this designation. Interestingly, this molecule is only found in the primate malaria parasites and is not found in the rodent parasites. Preliminary studies of PFF1320c have shown that the protein is essential due to our inability to delete the gene. Expression of a tagged version of the gene at an ectopic site permitted the successful knockout of PFF1320c. Studies are currently underway to identify the myosin heavy chain (MHC) partner and other potential binding partners using PFF1320c fused to promiscuous biotin ligase (BirA*) to label proteins in close proximity to the presumptive light chain, where the 1320-BirA* fusion is also subject to translational regulation by use of a small molecule aptamer. We are also working to phenotypically elucidate the role of this presumptive actin-myosin motor within the parasite using the glmS ribozyme or the aptamer system as an alternate knockdown strategy. Further characterization of this presumptive myosin light chain and identification of the MHC partner will provide an insight into the role of this unique myosin motor in the growth and development of the parasite.Ph.D., Microbiology and Immunology -- Drexel University, 201
Consuming Yoga: Promotional Culture and the Media Representation of Yoga
Get PDFThe practice of yoga has gone through a resurgence and geographical shift in the past hundred years. In the Western world, and to some extent in India, yoga has been decontextualized from its spiritual, religious, and even cultural history. Yoga is often paired with unrelated traditions to create a collage of spirituality based on the needs of the individual. This syncretic borrowing has become the norm for many practitioners who may or may not realize they are participating in this decontextualization and accept teachings about yoga that are historically inaccurate. Modern yoga has taken on certain traits and values which can be thought of as the image or style of yoga. Many of these traits have no historical or religious basis but are seen with frequency in mass media and social media. This dissertation looks at the current cultural meaning of yoga in the United States. It demonstrates how yoga has been used in mass and social media and what messages are conveyed when people conspicuously consume yoga as a practice or by carrying products related to yoga. It explores whether the shift in yoga has harmed the practice or the people who practice yoga.Ph.D., Communication, Culture, and Media -- Drexel University, 201
Religiosity, Depression, and Infertility-Related Stress in Muslim Women Struggling with Infertility and Living in the West
Get PDFInfertility is a deeply distressing experience that affects millions of women each year, with many also suffering from depression. Depression may increase the risk of experiencing infertility, and decrease the success rate of infertility treatment. Studies suggest that religiosity/spirituality (R/S) may be protective against depression; however, in the Western world these connections remain largely unexplored outside of Christian populations. This study sought to extend our understanding of the relationship between R/S, depression, and infertility-related stress among Muslim women struggling with infertility and living in a Western context. An ethnically diverse sample of 496 Muslim women residing in Australia, Canada, the United Kingdom, and the United States with self-reported fertility problems was recruited using online platforms. Participants completed an online cross-sectional self-report survey consisting of a sociodemographics questionnaire, the Center of Epidemiologic Studies Depression Scale - Revised (CESD-R), the Fertility Problem Inventory (FPI), the Brief RCOPE, and the Religious Commitment Inventory - 10 (RCI-10). As hypothesized, there was a significant and positive relationship between depression and infertility-related distress. While negative religious coping (NRC) was significantly related to depression and infertility-related stress, positive religious coping (PRC) and religious commitment were not. Findings may guide the development of interventions that improve mental health and increase chances of successful pregnancy among Muslim women with fertility problems. Implications for clinical applications and future research are discussed.M.S., Psychology -- Drexel University, 201