The Optical Variability of Active Galactic Nuclei

Active Galactic Nuclei (AGN) exhibit strong, rapid optical luminosity fluctuations that are often described as stochastic (exhibiting intrinsic randomness). The physical mechanisms that produce stochastic fluctuations may be studied by characterizing the correlation structure of such data in both the time domain and the frequency domain. We find evidence that AGN do not exhibit a universal optical PSD; the PSD shape (or light curve correlation structure) may be a function of fundamental AGN properties. In this work, we develop an application of continuous-time autoregressive moving average models (CARMA) to AGN optical light curves, and we discuss their relationships to more traditional techniques such as the structure function (SF) and the power spectral density (PSD). We present a study of AGN variability using the Damped Harmonic Oscillator (DHO) or CARMA(2,1) model. We estimate DHO timescales and optical variability amplitudes for 7492 objects with both SDSS (Stripe 82) r-band and CRTS V-band light curves. We employ clustering methods (t-distributed stochastic neighbor embedding) in this work to test the non-universality of AGN variability (deviations from the damped random walk; DRW or CARMA(1,0)). This approach groups together light curves with similar correlation structure as described by DHO timescales. We identify three classes of AGN variability. We find a "long memory" variability class characterized by milder variability amplitudes ($\sim12\%$) and steeper SFs than DRWs. We also detect a variability class characterized by an excess of short timescale variability ($<100$ days). The onset of the excess takes the form of a secondary break in the SF/PSD at short timescales. The break timescale (CRTS light curves) is anti-correlated with bolometric luminosity ($\text{log }\tau_{perturb} = (-0.26\pm 0.03) \text{ log } L_{Bol}$ +13.2). Finally, we identify failed DHO model-fits with characteristic timescales that are greater than the timescale detection limit of a single 8-10 year survey. We estimate that for $40\%$ of AGN we cannot meaningfully estimate timescales without combining decades-long surveys. We find a strong discrepancy between SDSS and CRTS light curves for the same AGNs at timescales relevant to the secondary SF break. The discrepancy calls into question the impact of sparse cadence (SDSS) and large photometric uncertainties (CRTS) on similar methods such as the SF and PSD that are used to characterize the correlation structure of stochastic data. We also explore a Kepler/K2 dataset of well-sampled ($\sim30$ minute cadence) light curves for $\sim 4000$ spectroscopic AGN and AGN candidates. We detect instrumental systematics in K2 data that require careful error mitigation. Our investigations provide characterizations of the noise dependence on CCD channel, pixel row/column, and magnitude. We provide recommendations for continued development of processing software to rehabilitate K2 data for the study of AGN PSD shapes at short timescale as a function of physical properties (luminosity, black hole mass and Eddington ratio). The results of this investigation suggest that the optical variability of AGN specifically, at short timescales ($<100$ days), may contain the richest insights for AGN science.Ph.D., Physics -- Drexel University, 201

Enhancing Engagement: Dance/Movement Therapy with a Mother and Child with ASD

This case conceptualization explores how dance/movement therapy can foster social interactions in an African American family with a child who is diagnosed with Autism Spectrum Disorder. Autism Spectrum Disorder is a pervasive developmental disorder that can cause persistent impairments in social communication and social interactions across multiple contexts with restricted, repetitive patterns of behavior. Deficits in social communication and social interaction are often the early indicators of ASD. It makes it difficult for those who are diagnosed with ASD to relate to others and typically becomes the main focus in intervention planning. The Creative Arts Therapies can encompass many developmental goals for children with ASD. Dance/movement therapy, a modality within the field of the creative arts therapies addresses this deficit through relational intervention attending to non-verbal, as well as verbal behaviors, creating play scenarios and supporting shared focus of attention. This case conceptualization takes an in-depth look into six dance/movement therapy sessions with mother and son dyad to further explore the impact that DMT has on social interactions.M.A., Dance/Movement Therapy and Counseling -- Drexel University, 201

Piezoelectric Plate Sensor for Isolation-free and Amplification-free Detection through an Innovative Combustion-Free Aqueous Materials Synthesis Route

Piezoelectric plate sensor (PEPS) is a unique sensor platform developed in Shih and Shih laboratory capable of direct, in situ genetic detection with polymerase chain reaction (PCR) sensitivity and specificity but without the need of gene isolation or amplification. The heart of the PEPS technology is a highly piezoelectric lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3)0.65-(PbTiO3)0.35 (PMN-PT) freestanding film. The difficulty and complexity of the synthesis processes for the lead magnesium niobate (PMN) power rendered PEPSs not reproducible. The goal of this thesis is to investigate the aqueous synthesis processes of PMN powder to achieve reproducible PEPSs for isolation-free and amplification-free genetic and immune- detections. The most challenging part of the initial PMN powder synthesis was a combustion step as a result of using ethylene glycol as the medium. The combustion step made the PMN powder finer, essential for making the freestanding film from which PEPSs were made. However, combustion also made the process uncontrollable and difficult to obtain reproducible PEPSs. In this study, we have successfully circumvented the combustion process and achieved similarly fine PMN powder through (1) stringent control of the aqueous synthesis process, (2) mechanical particle size reduction, and (3) creative two-step heating process to crystallize the PMN powder at the same crystallization temperature. The repeatability of these steps and reproducibility of the PEPSs sensors are characterized by X-ray diffraction, particle size measurements, Scanning electron microscopy (SEM) examination sintering of the freestanding film, and the temperature stability and detection performances of the PEPSs. Results showed that the newly fabricated PEPSs made by the new aqueous synthesis routes detected anti-Tn antigen IgM in serum at a concentration 25,000 times lower than the comparing ELISA and detected DNA at 60 copies/ml as comparable to the PEPSs made from the combustion method. We further carried out hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA detection in simulated sera in 30 min without isolation and amplification to illustrate the reliable performance of these newly fabricated PEPSs.Ph.D., Biomedical Engineering -- Drexel University, 201

Generation, Computational Biofluid Mechanics, and Visualization of Complex Blood Flow Dynamics

The advent of new non-invasive imaging modalities (i.e. 4D MRI, 3D Echocardiography) in recent years have facilitated the study and growing recognition that some of the blood flow in the cardiovascular system is naturally spiral and three-dimensional. The helical organization of the myocardial fibers, the heart's torsional contraction dynamics, aortic valve structure, the out-of-plane geometry of the aorta and tortuosity of vessels all contribute to the generation of spiral patterns of blood flow. In nature, many forms of fluid transport (e.g. whirlpool, cyclones) demonstrate high efficiency, flow entrainment, and stability due to their spirality. Flow in the cardiovascular system may also benefit from similar self-stabilizing impulsion dynamics. Although spiral blood flow structures have been observed in the aorta and other large arteries, many questions remain unanswered regarding its influence on normative cardiovascular physiology and pathophysiology. The research work herein aims to study spiral flow dynamics and to understand its specific characteristics, especially those in athero-susceptible regions. Computational fluid dynamics (CFD) was used to study the modulation of spiral flow and its impact in idealized vascular phantoms (Aim 1) and realistic vascular geometries, namely the aortic arch with an anastomosed cannula, representative of the outflow graft of a mechanical circulatory support device (Aim 2). Aim 1 served as a test platform for studying spiral flow characteristics. Aim 2 provided an example of the translational applicability of spiral flow. Benchtop flow circuits were used to validate key aspects of the in-silico simulations. This research work brought together computational fluid dynamics with 3D vascular printing and benchtop mock circulatory flow loop visualization and analysis methodologies. The ability of spiral flow to clear and reduce the size of recirculation zones in a set of idealized vascular phantoms was demonstrated in Aim 1. The phantoms tested were angled conduits with 45°, 90°, and 135° turns and idealized asymmetric and axisymmetric stenosis models. A spiral flow inducer was utilized to enable in-silico to in-vitro comparisons, while standalone phantoms were used to test the impact of spiral flow modulation. In the vascular phantoms coupled to spiral flow inducer models, the recirculation zones at the corners of the angled conduits and the flow separation post-coarctation in stenosis models demonstrated a marked decrease in size of regions of low velocities ( 80 dyn/cm2) for the highest helical content compared to straight flow. The highest WSS at the fluid impact site in the inner curvature of the aorta belonged to the test case with the highest helical content, reaching 150 dyn/cm2. Cannula angle variation dictated the impact site of the outflow jet. In all cases, counter-clockwise spiral flow decreased regions of low velocity (up to 1.2-fold reduction) and resultant areas of low WSS (up to 1.1-fold decrease). The cannula angled down case provided the best decrease in low WSS areas, however, it had the largest area of high WSS. With clockwise and counter-clockwise spiral flow, the areas of high WSS in the cannula angled down case decreased by 10.5% and 29.8% respectively. Spiral flow has been shown to improve washout of hard-to-reach recirculation zones, reducing regions of low velocity and decreasing areas of low WSS. In particular, the clinical translation may prove to be impactful in blood recirculating devices, helping improve near-wall transport and flow dynamics, diminishing jetting and fluid collisions, mitigating device-related adverse events, and encouraging athero-protective conditions. The findings of this research are expected to inform the next generation engineering designs of vascular/endovascular prosthesis, stents, cardiac valves, and mechanical circulatory support devices.Ph.D., Biomedical Engineering -- Drexel University, 201

Early Extubation Wean Protocol Development in Cardiac Surgery with Expert Content Validation

Background: Cardiothoracic surgery patients remain intubated while transferred to the intensive care unit where ventilator weaning is initiated post-operatively. Prolonged intubation times can lead to patient complications and increased costs for the healthcare system. Wean protocols can be implemented to decrease ventilator times and meet quality measures set by The Society of Thoracic Surgeons while improving patient outcomes. Purpose: To: (a) evaluate current guidelines, standards, and trends in care for ventilator weaning and early extubation protocols in cardiothoracic surgery; (b) develop an evidence-based extubation protocol for cardiothoracic surgery patients; and (c) obtain expert content validation of the extubation protocol. Goal: Development of a content validated, evidence-based, early extubation protocol. Methods: Development of evidenced-based early ventilator wean protocol with expert content validation utilizing a two-step content validation technique. This single-center project was conducted in a community medical center with an internal and external multidisciplinary panel of ten experts. Selection of the expert panel was based on area of expertise, publications, and positions held. The protocol was distributed to the panel as an electronic survey with a four-point Likert Scale assigned to content relevance and clarity. The collected data was analyzed for level of expert consensus using both item and scale content validity indexes with percentage of agreement ≥78% determining achieved consensus. Findings: All twenty-six items obtained item content validity. The instrument reached excellent scale-content validity index, scoring 1 when calculating average and universal agreement. Three items were revised based on comments from the expert panel. Keywords: cardiothoracic surgery, extubation, ventilator hours, length of stay, ICU hours, cardiac surgical procedures, heart surgery, airway extubation, mechanical ventilators, wean protocol, quality, outcomes, content validation, protocol development, evidence-based practiceD.N.P., Nursing Practice -- Drexel University, 201

Knowledge Retention in Older Adults with Heart Failure and Impact on Readmission

People are living longer due to the development of improved care modalities and older adults comprise the most rapidly growing percentage of the population (National Council on Aging, 2016). Congestive Heart Failure (CHF), a complication of Coronary Artery Disease (CAD), is a frequently diagnosed disease syndrome in this age group and is associated with increased hospital admissions because of its complexity (Ding, Yehle, Edward & Griggs, 2014). Decreased length of stay, additional comorbidities and perceptual/functional deficits also place elderly individuals at risk for acute care readmissions within 30 days or less (Whittaker, Sonia & Erich, 2015). The frequency of early readmissions is problematic from both a quality of care and cost perspective (Centers for Medicare and Medicaid Services, 2014). If patients are considered clinically stable at discharge it is important to investigate what issues contribute to these rates and are they addressed comprehensively. Transfer from the hospital setting to the home environment is a vulnerable transition period and can result in potential setbacks (Albert, Trochelman, Li & Lin, 2009; Moser, Doering & Chung, 2005). The Discharge Planning Process, a broad spectrum of education and identification of needed services, can be implemented at various times during a hospital stay based on the facility’s protocol (Hunter, Nelson & Birmingham, 2013). Patients and families need accurate information and time to absorb the material in order to manage possible setbacks using learned self-care skills (Paul, 2008; Rockwell & Riegel, 2001). The quality of educational content is critical to building confidence in self-care management (Rockwell & Riegel, 2001).D.N.P., Nursing Practice -- Drexel University, 201

In vitro neuroprotective properties of positive allosteric modulators and expression enhancers of EAAT2

Glutamate excitotoxicity has been shown to be associated with several acute and chronic disorders of the CNS, including stroke, epilepsy, traumatic brain injury (TBI), and Alzheimer's disease. Excitatory amino acid transporter 2 (EAAT2) is responsible for rapid removal of most extracellular glutamate, thus maintaining glutamate homeostasis and preventing excitotoxicity. Therefore, compounds that enhance its expression or function could serve as valuable neuroprotective agents. Previous studies identified an allosteric site on EAAT2, allowing for virtual screening approaches to identify novel compounds that were characterized as positive allosteric modulators (PAMs) of this transporter. Medicinal chemistry efforts generated several analogs with better drug-like properties. Previous studies in the lab further characterized the potency and selectivity of these compounds in glutamate uptake assays in transfected COS-7 cells and glial cultures. In this study, we investigated the potential neuroprotective properties of one of these compounds, NA-014, a selective EAAT2 PAM. We also investigated the potential neuroprotective properties of a natural compound, Parawixin10, that has previously been characterized as a PAM of EAAT1 and EAAT2, and clavulanic acid, a -lactam that has been identified as an enhancer of the expression of EAAT2. For these studies, mixed neuron-glia cultures were subjected to four different types of excitotoxic insults: exogenous glutamate application, exogenous application of H2O2 (an in vitro model of oxidative stress), oxygen-glucose deprivation (OGD, an in vitro stroke model), and low magnesium buffer (an in vitro model of epilepsy). Neuronal survival and dendritic arborization were assessed 24 hours following the insults using immunocytochemistry against MAP-2 and GFAP (neuronal and glial markers, respectively). Our results indicate that NA-014 is neuroprotective in the glutamate, OGD, and low magnesium in vitro models and has a therapeutic time window of approximately 8 hours. However, the compound lacks effectiveness in the oxidative stress model, and we suggest that this insult damages the glial transporters. Our results also show that Parawixin10 and clavulanic acid are both neuroprotective in the glutamate and OGD in vitro models. Ongoing and future studies aim to determine the extracellular glutamate concentration following insults and treatments with NA-014. Preliminary in vivo studies in models of TBI and neuropathic pain demonstrate that this compound has neuroprotective and nociceptive properties. Future studies will address whether this compound can be developed for stroke therapy and will further investigate the potential additivity of combining treatments of allosteric modulator and expression enhancer. Finally, future studies will optimize the drug-like properties of NA-014 and Parawixin10 through medicinal chemistry. In summary, these studies indicate that EAAT2 PAMs and expression enhancers display neuroprotective properties in several in vitro models of excitotoxicity, and they may be developed for clinical use in treating disorders involving excitotoxicity, like stroke, epilepsy, and traumatic brain injury (TBI).M.S., Pharmacology and Physiology -- Drexel University, 201

Dance/Movement Therapy, Creative Arts Therapy, and How Dance and Performing Arts Managers Can Assist Program Participants and Employees in Times of Need

The purpose of this study was to analyze dance/movement therapy’s role within the creative arts therapy landscape and the process of determining when dance/movement therapy would be recommended over other creative arts therapy modalities. The thesis provides information to help dance and performing arts managers to assist a program participant, or employee, potentially navigate the emotional, psychological, and potentially physical side of a situation they are facing. The final chapter includes resources and references for arts managers, offers of encouragement to use the resources, and a discussion on why being brave and vulnerable is more important than playing it safe.M.S., Arts Administration -- Drexel University, 201

Machine Learning Techniques for Forensic Camera Model Identification and Anti-forensic Attacks

The goal of camera model identification is to determine the manufacturer and model of an image's source camera. Camera model identification is an important task in multimedia forensics because it helps verify the origin of an image and uncover possible image forgeries. Forensic camera model identification is generally performed by searching an image for model-specific traces left by a camera's internal image processing components. Many techniques, including recent data-driven deep learning algorithms, have been developed to perform camera model identification. In the meantime, forensic researchers have discovered that existing camera model identification algorithms can be maliciously attacked by altering images without leaving visually distinguishable artifacts. These anti-forensic attacks arouse concerns about the robustness of camera model identification techniques and urge the need for effective defense strategies. In this thesis, we propose new algorithms to perform forensic camera model identification, and new anti-forensic attacks. We first introduce a highly accurate and robust camera model identification framework developed by fully exploiting demosaicing traces left by cameras' internal demosaicing process. In light of the complexity of demosaicing traces, we build an ensemble of statistical models to capture diverse demosaicing information in the form of content-dependent color value correlations. Diversity among these statistical models is critical for each model to capture a unique set of color correlations introduced by the demosaicing process. We obtain a diverse set of linear and non-linear demosaicing residuals and extract both intra-channel and inter-channel color correlations following a variety of geometric structures. The ensemble of collect diverse color correlations forms a comprehensive representation of the sophisticated demosaicing process inside a camera. This proposed framework not only achieves high camera model identification accuracy, but more importantly, it is robust to image post-processing operations and anti-forensic camera model attacks. Given recent popularity of deep learning algorithms, forensic researchers have started to build deep neural networks, especially convolutional neural networks, to perform camera model identification. In this thesis, we investigate the robustness of deep learning based camera model identification algorithms by developing anti-forensic camera model attacks to expose vulnerability of these algorithms. We propose a generative adversarial attack to perform targeted camera model falsification. Given full access to the camera model identification networks, this attack has been proven to be able to falsify camera models of images from arbitrary sources. Under black-box scenarios where no information about the camera model identification networks is available, we train a substitute network which mimics the camera model identification networks and provides gradient information to craft adversarial images.Ph.D., Electrical Engineering -- Drexel University, 201

The Role of Chtf18 in Sister Chromatid Cohesion and Post-Replicative Genome Maintenance

Mitosis is a critical process that all living cells undergo to produce two identical daughter cells. To ensure that each daughter cell contains the same requisite genetic material, cohesion must be established and maintained between sister chromatids. Chromosome Transmission Fidelity factor 18 (CTF18), a protein subunit of the Replication Factor C-like complex (CTF18-RLC), has functions in DNA replication and also helps to establish cohesion between sister chromatids in yeast. Previously, we demonstrated a function for CHTF18 (the mouse ortholog) in meiotic recombination that is consistent with a role in chromosome cohesion during mammalian meiosis. We used Chtf18−/− and wild type murine embryonic fibroblasts (MEFs) to investigate a possible function for CHTF18 in sister chromatid cohesion and post-replicative genome maintenance. Cultured Chtf18−/− MEFs ceased proliferating after the 6th population doubling compared to wild type MEFs, which continued to proliferate until the 11th doubling. Immunofluorescence staining with 53BP1 antibody, a marker of DNA double strand breaks (DSBs) showed that DSBs are increased in Chtf18−/− MEFs. These findings suggest that defects in cellular proliferation of Chtf18−/− MEFs are due to DNA damage. Analysis of chromosome spreads reveals that Chtf18−/− MEFs may have a propensity for increased sister chromatid separation and breakage. Together, our data indicate a role for CHTF18 in sister chromatid cohesion and post-replicative genome maintenance.M.S., Biochemistry -- Drexel University, 201