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Radon injection for light response calibration of the nEXO detector
No full textNeutrinoless double beta decay (0vbb) is a second-order process that occurs in isotopes for which single beta decay is energetically forbidden. Observation of 0vbb would demonstrate that the neutrino is a Majorana particle and would violate total lepton number conservation. The nEXO experiment will search for 0vbb of 136-Xe using 5 tonnes of enriched liquid xenon in a low-background single-phase time projection chamber. nEXO is expected to reach a 10 year sensitivity to the 0vbb halflife of 136-Xe of approximately 10^28 years. This dissertation presents a novel technique for calibrating the response of the nEXO detector to scintillation signals using an injection of radon into the xenon recirculation loop. The baseline calibration plan for nEXO is a series of external gamma-ray sources which suffer from xenon's self-shielding properties. Dissolved calibration sources, on the other hand, are capable of characterizing the center of nEXO's large drift chamber, especially when complemented by liquid xenon fluid simulations. Better characterization of the detector response to light improves the energy resolution of the detector and therefore its sensitivity to the halflife of 0vbb. I present results from an end-of run calibration campaign on nEXO's predecessor experiment, EXO-200, using two candidate isotopes: 220-Rn and 222-Rn. I report observed alpha populations, efficiency corrections, and validation of EXO-200 fluid simulations using these data. This work also presents a new framework that combines fluid simulations with nEXO Monte Carlo to produce position-dependent functions of the detector response to light. Finally, I propose possible calibration schemes for radon injection for the nEXO detector.Ph.D., Physics -- Drexel University, 201
High-Content Screening Analysis of Dopamine-Mediated Changes in Human Macrophages in the context of HIV infection
No full textHigh-content screening (HCS) is a relatively new methodology by which we are able to address biological questions using immunocytochemistry and large-scale, data-driven analyses. This technique has become more accessible due to the, advances in computer science and technology. Utilizing this advanced technique provides a more robust and diverse analysis of large scale data sets. In this project, we are using high-content screening to examine two mechanisms by which the neurotransmitter dopamine could influence HIV neuropathogenesis. Although HIV is one of the most devastating viruses in the world, its effects on the central nervous system (CNS), are poorly understood. HIV enters the CNS within 8 days after initial infection, where the virus targets primarily myeloid cells such as perivascular macrophages and microglia. The infection of these populations leads to neuroinflammation and HIV-associated neurocognitive disorders (HAND). Drug abuse is a major comorbidity in HIV infection, and all drugs of abuse increase dopamine, so the impact of dopamine on HIV neuropathogenesis is very important. Using the high content imaging technique, we found that dopamine does not alter the localization of CCR5 within lipid raft and non-lipid raft regions. However, we demonstrated that CCR5(3A9) but not CCR5(2D7) is preferentially localized to lipid raft domains, which could lead to a new target for HIV treatment by targeting CCR5(3A9) in the lipid raft. We also used high content screening to show that dopamine treatment increases the number of macrophages within a population that have elevated nuclear NF-[kappa]B. This suggests dopamine increases the number of macrophages which could produce a more robust inflammatory response. This could be beneficial to the future therapeutic strategies for treating inflammation. Together, these studies provide new insight into the mechanisms by which dopamine influences HIV infection and demonstrate the utility and power of high content screening.M.S., Pharmacology and Physiology -- Drexel University, 201
Analyzing the Entrepreneurial Intentions of Orchestra Musicians
No full textClassical musicians commonly share a goal of earning a full-time position in an orchestra. In the music industry, this is one of the most financially stable positions. Earning a full-time position in an orchestra, however, is extremely difficult due to the decreasing number of openings in top orchestras, the increasing competition for a single spot, and the time and financial demands for a musician to hone their craft to the level of a professional orchestra musician. Musicians frequently have to pick up additional work to provide the necessary financial income, such as school or private teaching jobs, studio jobs, or side jobs outside of the music field. In my research study, I analyzed orchestra musicians who created their own entrepreneurial venture to begin assessing the viability of entrepreneurism as a form of income for musicians. By analyzing the characteristics, traits, and personalities of entrepreneurial orchestra musicians, the music field can better understand an alternative that is available for musicians to earn a living; entrepreneurism.M.S., Arts Administration -- Drexel University, 201
New Protective Stent for Intravenous Fontan Blood Pump
No full textThousands of infants are born every year with cardiac defects leaving them with only one functioning ventricle. As a result of these defects, these infants undergo strenuous palliative procedures to create what is known as a Fontan physiology and still are left facing numerous complications including congestive heart failure, thrombosis, arrhythmias and more. Treatment and management costs for these Fontan patients exceeds $1 billion every year, and the available donor supply is too small to be considered a feasible solution. The available blood pumps and ventricular assist devices, while they have been implemented successfully in some cases, were not specifically designed for these single ventricle patients and thus have several shortcomings. The size of these pumps in addition to rigid design leads to irregular flow dynamics, insufficient performance and blood damage. It is suggested that only 1-5 mmHg would be sufficient to alleviate the many complications associated with single ventricle physiology, making a purposely designed blood pump a viable solution as a bridge therapy to heart transplantation. Using computational means and experimental testing, this study investigated the use of a minimally invasive axial flow blood pump with a cage and impeller to support the Fontan physiology until a donor heart becomes available. Prior research focused on cage filament direction and impeller angle separately, making the focus of this thesis determining an optimal combination of cage and impeller design. Design geometries were rapid prototyped to be experimentally tested and Solidworks models were used in ANSYS CFX to run computational simulations. Geometries varied in the number of filaments, cross-sectional shape of the filament and the impeller blade angle of twist. Pressure generation, capacity range, estimated shear stresses and blood damage levels were examined. Both the simulations and experiments demonstrated that the new cage designs were within the desired pressure rise and hemodynamic ranges, but qualitatively some designs were able to outperform others. A resulting combination of the 5-filament cage design with the 350°impeller angle was determined as optimal, thus furthering the support in the development of an axial flow blood pump for a failing Fontan physiology.M.S., Biomedical Engineering -- Drexel University, 201
Dynamic Fracture and Fragmentation Investigations of Brittle Polymers and Composites
No full textDynamic fracture and fragmentation of brittle solids can result from the application of a single or repetitive impulsive load. As such, investigating the interactions between the geometric discontinuities of cracks with the surrounding material medium is imperative to further understand the effects of nonlinearities, material inhomogeneities, and length scale dependencies in failure. This thesis examines two types of brittle materials: nominally isotropic amorphous polymers and cermets, and (effectively) transversely isotropic cortical bone; as well as presents an improved experimental technique and a new piece of equipment used in failure investigations. Quasi-static and dynamic compressive behavior of ox bone and a commercial bone surrogate material has been examined, and the corresponding fragmentation characteristics quantified. A power law fit predicts both materials resulting fragmentation, however fragment sizes had clear links to the underlying osteon structure and direction of loading in the ox bone that was not present in the surrogate. To explore the efficacy of utilizing digital image correlation (DIC), a full-field kinematic mapping technique, in classical dynamic fracture investigations, the model material of PMMA has been investigated in mode-I (opening) crack initiation and formation. Higher order terms in the elastodynamic solution are added to account for inertial effects and built upon previous work exploring the relevant region of maintaining K-dominance. Based on the PMMA findings, the effect of inhomogeneous toughening on mode-I dynamic fracture conditions of a common composite matrix material, DGEBA, with various hardeners has been explored, and an improved speckling technique for DIC utilizing dot-on-demand colloidal inkjet printing is presented. Lastly, in order to explore the relevance of repetitive sub-critical impulsive loading on material fracture behavior, a unique impact fatigue device has been constructed and a case study investigating the effect of impact cycles and cobalt binder volume percent on the mode-I dynamic fracture behavior of tungsten carbide is presented.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Engaging with surveillance in public and semi-public spaces
No full textThis project investigates design strategies for the user to engage with surveillance in both private and public spaces. Surveillance technology has become much more prevalent in today's society with the advent of machine learning and ubiquitous computing. It exists in many forms: from the security cameras staring from every corner in the public realm, to the face detection algorithms, metadata, and smartphones that are track their users' every move. The freedoms of anonymity through obscurity, especially in urban environments, are vanishing. Artists, designers and social scientists are becoming more and more aware of this potentially problematic development, and the prescribed strategies may be categorized into two main groups: behavioral and technological. Behavioral strategies are best described as different ways to passively resist data collection: turning off location services on a smartphone, not checking in with social media, refusing to give out personal data online, or using less privacy-invasive technologies such as duckduckgo instead of Google. The technological interventions are best characterized as more active interventions that exploit technology's reliance on other methods to collect data: discovering flaws in the surveillance technology so that camera chips become overexposed, or wearing unusual makeup to confuse facial recognition software. Both strategies, behavioral and technological, may be used to regain control over individual privacy in an ever increasingly connected world; the goal of this research is to generate speculative solutions that use both strategies to formulate a plan to maximize privacy in today's digital world.M.S., Design Research -- Drexel University, 201
Chemical Pre-intercalation Synthesis Approach for Novel Layered Cathode Materials for Li-ion and Beyond Li-ion Batteries
No full textBeyond-lithium ion (BLI) alkali ion-based batteries are rising in interest among researchers because of their utilization of more abundant, cost-effective charge carriers, including Na+ and K+ ions, compared to traditionally used Li+ ions. However, because such systems utilize electrochemically cycling ions with larger ionic radii, achieving fast diffusion and high insertion rates of the BLI carriers into traditional, close-packed electrode materials is challenging. As such, these new systems require the development of novel electrode materials with high capacity, rapid charge transfer, and stable behavior over extended cycling. Materials with open, layered crystal structures have proven themselves among the most reliable electrode materials for Na-ion and K-ion based batteries, enabling high performance in these emerging systems. Tuning and control of interlayer spacing and chemical composition in open layered structures, can be accomplished via simple wet chemical modification approaches. Such tailoring has the capability to increase ion insertion and movement as well as electrochemical stability, which may lead to improvements in electrochemical performance of these electrode structures. Layered vanadium pentoxide (V2O5) phases are promising candidates for BLI batteries in part because vanadium can be present in its highest oxidation state, 5+, and can undergo multiple reduction steps down to a 3+ state, allowing for the transfer of up to two electrons per vanadium ion. In particular, bilayered delta-V2O5·nH2O is an ideal phase for Li-ion and BLI systems due to its large open-layered structure offering facile movement of larger charge-carrying ions. The bilayered structure is built from double layers of VOx polyhedra which are separated by a large interlayer spacing of 11.5 (ANGSTROM SIGN) which is stabilized only by intercalated water molecules. When this delta-V2O5·nH2O phase is synthesized via scalable sol-gel and hydrothermal treatment capacity typically decays over extended cycling, due to lattice breathing and the gradual breakdown of the lamellar stacking of the V-O layers. This dissertation focuses on a novel chemical pre-intercalation synthesis approach as a means to improve electrochemical performance of bilayered vanadium oxide electrodes in Na- and K-ion systems. Via this approach, ion-containing delta-MxV2O5, where M represents alkali (Li+, Na+, K+), alkali-earth (Mg2+ and Ca2+) ions, phases can be synthesized. This synthesis technique allows for the tunability of the interlayer spacing from 9.65 to 13.4 (ANGSTROM SIGN) depending on the nature of the inserted ion. Further, synthesis of the electrode materials via chemical pre-intercalation approach can lead to increased capacities and electrochemical stability in Li-ion, Na-ion, and K-ion cells. Electrochemical performance of delta-MxV2O5 (M = Li, Na, K, Mg, Ca) in Li-ion cells will also be presented as a reference. Further, it will be demonstrated that this synthesis approach can lead to improved electrochemical performance of delta-V2O5 electrodes in intercalation-based batteries through three modes: (1) pre-intercalation of charge-carrying into the bilayered delta-V2O5 phase can lead to tailored ion transport and increase overall specific capacities, (2) optimization of interlayer water content, improvement of structural order, and increase of intralayer bonding via low-temperature vacuum annealing to improve electrochemical stability, and (3) pre-intercalation of electrochemically inactive organic and inorganic ions in order to stabilize the bilayered structure and improve capacity retention in both Li+ ion and BLI ion cycling. While this pre-intercalation synthesis route may lead to the partial reduction of the oxidation state of vanadium present in the structure, high discharge capacities over 200 mAh·g-1 are observed in all three ion-based systems in the voltage range of 2.0 - 4.3 V and a higher discharge capacity of 365 mAh·g-1 observed for the delta-NaxV2O5 electrodes in the Na-ion system in an expanded voltage range of 1.0 - 4.3 V. A detailed study of the mechanism of charge storage and the effect of charge-carrying ion size on experimentally achieved specific capacities and electrochemical stability in Li-ion, Na-ion and K-ion batteries will also be discussed. Additionally, organic cation-intercalated delta-OrgxV2O5 (DTA, DMO, CTA) phases can be synthesized via this approach, with interlayer spacings from 12.5 to 30.5 (ANGSTROM SIGN) depending on the cation and precursor concentration. The electrochemical performance of delta-OrgxV2O5 phases in Li-ion and Na-ion will be determined.Ph.D., Materials Science and Engineering -- Drexel University, 201
Survey of Etching Techniques to Produce Cr2C MXene from Cr2AlC
No full textTwo-dimensional chromium carbide MXene (Cr2CTX) is predicted to possess a high hydrogen capacity and antiferromagentism which may be employed in hydrogen storage and spintronic applications. As of the time of the work detailed in this thesis, there have not yet been any reported success synthesis of Cr2CTX. Herein is a systematic survey of different possible etching conditions to produce Cr2CTX from Cr2AlC. Three distinct etching techniques previously used to synthesize MXenes were studied. Wet etchings were conducted using either hydrofluoric acid along with sulfuric and hydrochloric acid or hydrochloric acid with fluoride salts. HF/HCl and KF/HCl were the most promising etchants, producing XRD peaks consistent with MXenes. Importantly, samples produced using the wet etchants often contained both unreacted MAX and degradation products, such as CrO3, demonstrating that chromium and aluminum are being etched at comparable rates, preventing the formation of the desired MXene. Additionally, a molten salt technique using zinc chloride was also studied by varying the time and ratio of reagents. This technique also hold promise with several samples possessing XRD peaks consistent with Cr2CTX. Additionally, the lack of chromium chlorides and presence of zinc chromite indicate that MXene degradation is due to oxygen in the system rather than the molten salt treatment itself.M.S., Materials Science and Engineering -- Drexel University, 201
Moral Disengagement in Minority Adolescents: A Literature Review
No full textMoral disengagement is defined as a cognitive distortion that leads to negative conduct being rationalized as reasonable and justified behavior, and it is a harmful behavior that can have a particularly negative impact on adolescents. Research on moral disengagement in minority adolescents remains limited, which encourages the examination of the extant literature to determine important areas for future empirical research. This study presents a literature review on moral disengagement in ethnic majority and ethnic minority adolescents. The literature review includes research that has been conducted over the past thirty years and was identified via online databases including: Jstorr, Ebscohost, Psychinfo, and ProQuest. This literature review will focus on precursors to moral disengagement, psychosocial outcomes of morally disengaged ethnic minority youth, as well as treatment recommendations for morally disengaged ethnic minority youth. Much of the review points to significant gaps in the existing research on ethnic minority youths, negative sequelae of moral disengagement (e.g. antisocial behavior, aggression, and depression) and discussions on future directions research and treatment options. This literature review serves as a meaningful preliminary step to guide future studies, which help increase knowledge on moral disengagement in ethnic minority adolescent and support the development of culturally-sensitive strategies for effective intervention in this population.M.S., Psychology -- Drexel University, 201
The Role of The Target Audience and Their Preference for Programming in Increasing Subscribers to China's Online Video Website iQiyi
No full textWith the advent of China's first streaming video website in 2004, video websites have become the main channels for viewers to watch TV shows, movies and short videos. But behind the industry boom, profitability problems have been a concern for streaming video websites. This thesis examines audience attitudes toward programming on streaming video websites, to find a way to increase iQiyi's number of subscribers. Based on the features of the target audiences for iQiyi, from other literature and the results of a survey, the author provided reasonable suggestions for programming improvement.M.S., Television Management -- Drexel University, 201