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The Infusion of Mobile Learning: Understanding Pedagogical Implications for Today's African American Female High School Students
No full textToday's generation espouses mobile phones more than any other generation in cell-phone history. Madden, Lenhart, Duggan, Cortesi, and Gasser (2013) found that "about three in four (74%) teens aged 12-17, are 'mobile Internet users' who say they access the Internet on cell-phones, tablets, and other mobile devices at least occasionally" (p. 4). Despite this prevalence, schools continue to hold fast to a policy of no personal devices at school (Bauerlein, 2009; Bitner & Bitner, 2002; Thomas, O'Bannon, & Britt, 2014). Therefore, the problem this study will address is the lack of understanding of the pedagogical implications of mobile learning. The purpose of this phenomenological qualitative study is to examine the perceptions of African American female high school students regarding the use of mobile devices as experienced through a Bring Your Own Device Program. The overarching question guiding this research is: What are the perceptions of African American female high school students towards the implementation of a Bring Your Own Device (BYOD) program in a private single-sex high school? Building on Prenksy's (2001) model for the importance of a technological environment to better serve digital natives, the goal of this study is to encourage BYOD institutional environments to better serve today's mobile natives.Ed.D., Educational Leadership and Management -- Drexel University, 201
Plasma Transfer Processes in Medical and Agricultural Applications
No full textAtmospheric pressure plasmas are being investigated for medical and agricultural applications. Examples include cancer treatment, inactivation of microbial organisms, stimulation of the immune system, treatment of chronic wounds to promote wound healing, and treatment of water to enhance plant growth. Plasma is considered a surface treatment; thus, it is a transport limited process when considering treatment through tissue or large volumes of liquid for the disinfection of produce. In this study, we examine physical, chemical and biochemical methods to enhance the transport of plasma effects for these applications. We consider plasma treatment of micron-sized droplets to enhance the diffusion of plasma-generated species into liquid when compared with bulk water treatment. Additionally, we investigate the stabilization of nitric oxide for the inactivation of microbes suspended in liquids with high chemical oxygen demand. Furthermore, we demonstrate how intercellular signaling enhances the depth of penetration of plasma effects. These results will provide insight on how to enhance transport of plasma-generated species and plasma-induced effects in biological systems.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Pulsed Transcranial Ultrasound Stimulation and Its Applications in Treatment of Focal Cerebral Ischemia and Depression
Get PDFThe aims of this thesis were to investigate the therapeutic effects of pulsed transcranial ultrasound stimulation (pTUS) on focal cerebral ischemia and depression, respectively, in rodent models. Neurological and psychiatric disorders, such as Parkinson's disease, epilepsy, Alzheimer's disease, stroke (vascular disorder that results in neurological defects), depression, and etc., present an increasing challenge and a substantial social and economic burden for an aging and stressed population. However, conventional treatments, especially pharmacologic interventions, have significant limitations, such as nonspecific effects, insufficient tailoring to the individual, adverse effects such as drowsiness, weight gain and nausea, or inadequate uptake into the brain due to the blood-brain-barrier (BBB). In contrast, neuromodulation techniques have gained more attention, which are able to enhance or inhibit the neural activities in specific cortex, such as motor, somatosensory or other areas related to cognition. Neuromodulation thus could potentially restore the disrupted neural network due to neurological disorders. Capitalizing on its noninvasiveness, high precision (in the scale of mm) and penetration depth (several centimeters), low-intensity (typically <1 W/cm2 spatial-peak-pulse-average intensity-ISPTA) low-frequency (typically <1MHz), pulsed transcranial ultrasound stimulation (pTUS) has been emerging as a promising therapeutic tool for neurological and psychiatric disorders. This thesis provided the first in-vivo demonstrations that pTUS might serve as neuroprotective preconditioning of ischemic brain injury and treatment of depression. Additionally, it also proposed a novel optical imaging-based technique to characterize the neuromodulatory effect of pTUS, which facilitates the parameter optimization of therapeutic pTUS in practice. Both suppressive and excitatory pTUS are applied in this thesis. The corresponding pTUS parameters were: (a) suppressive pTUS (or pTUSS): ISPPA = 8W/cm2, frequency (f) = 0.5 MHz, pulse repetition frequency (PRF) = 100 Hz, and duty cycle (DC) =5%, and (b) excitatory pTUS (or pTUSE): ISPPA = 8W/cm2, f = 0.5MHz, PRF = 1.5 kHz, and DC = 60%, respectively. Before the therapeutic experiments, the neuromodulatory effects of both pTUSS and pTUSE were examined using laser speckle imaging(LSCI) and multispectral reflectance imaging (MSRI) in aspect of the neurovascular responses. Specifically, this thesis consists of: (1) Study on the neurovascular response to pTUS. Compared with other methods, such as pTUS-triggered motor response and visual evoked potentials (VEP), optical imaging allows to measure the neurovascular change at high spatiotemporal resolution (in the scale of μm and ms), including cortical suppression without evoked output. LSCI and MSRI were used to monitor the primary somatosensory response (Chapter 2) to hind limb electrical stimulation before, immediately, and 1 h after 5-min application of pTUSS and pTUSE, respectively. Several indicators, including Response Index, Peak Response, Latency and Response Duration, were derived from optical images to characterize the neuromodulatory effects of pTUS on primary somatosensory cortex. Our results showed that pTUSS could suppress the primary somatosensory cortex across all rats whereas pTUSE only presented excitatory effects in 5 out of 11 rats. The neuromodulatory effects of pTUS were correlated with the baseline cortical excitability. The results showed that: (i) pTUSs could serve in investigating cognitive function by silencing the neurons in the target region; (ii) pTUSE exposure should be treated with caution due to individual differences in neuromodulatory effects, which were associated with the initial brain state of rats; and (iii) optical imaging was useful in evaluating the pTUS neuromodulatory effects. (2) Neuroprotection of preconditioning pTUS. By applying suppressive pTUS, it was investigated whether the severity of stroke could be minimized or alleviated by prior exposure to ultrasound stimulation (Chapter 3). Preconditioning was supposed to increase the tolerance of brain to subsequent ischemic insult. It can potentially be used to prevent the perioperative stroke in patients undergoing cardiovascular surgeries with a series of complications. Considering the noninvasiveness and safety of ultrasound, pTUS may provide a novel preconditioning method. To test the effectiveness of preconditioning pTUS, rats were randomly assigned to control (n=12) and preconditioning pTUS (pTUS-PC) groups (n=14). The pTUS-PC animals received ultrasound stimulation before the induction of photothrombotic stroke, whereas control animals were handled identically except the ultrasound stimulation. The cerebral blood flow was monitored using LSCI in both groups during stroke induction, as well as 24 hours and 48 hours after stroke, respectively. Also, infarct volumes and edema were measured at 48 hours after euthanatizing the rats. Results showed that pTUS-PC rats had smaller ischemic volume during stroke induction, as well as 24 hours and 48 hours after the stroke than the controls. Moreover, the pTUS-PC group showed lower volume of brain edema than the control group. (3) Antidepressant-like effect by pTUS. The potential antidepressant-like effects of pTUS were further investigated in a rat model of depression with excitatory pTUS. Stimulating the left prefrontal cortex (PFC) by TMS has been clinically used for depression treatment, it was thus hypothesize that pTUSE on PFC would act similarly with TMS and result in antidepressant-like effect. To test this hypothesis, pTUS was applied for 2 weeks daily to the left PFC of depressed rats induced by 48-hour restraint. The long-term (3 weeks) efficacy of the depression model as well as the antidepressant-like effects of pTUS were investigated with a group of behavioral tests. In addition, the hippocampal BDNF was measured by western blot to study the mechanisms underlying antidepressant-like effects of pTUS. The safety of long-term (2 weeks) pTUS was assessed by histologic analysis. Results showed that 48-hour-restraint stress could stably lead to at least 3-week reduction of exploratory behavior and protracted anhedonia, whereas pTUSE treatment could successfully reverse the depression-like phenotypes and promote the BDNF expression in the left hippocampus. In addition, H& E staining of brain tissues confirmed the safety of the long-term pTUS treatment. In conclusion, the results in this work suggested that pTUS could serve as preconditioning of perioperative stroke and therapeutics for depression. Additionally, the results also demonstrated that optical neurovascular imaging could measure the neuromodulatory effect of pTUS. This study documented more evidence that pTUS is a promising tool for basic neuroscience and therapeutic applications. KEY WORDS: Neurological and psychiatric disorders, brain stimulation, pulsed ultrasound stimulation, neurovascular imaging, preconditioning, stroke, depression.Ph.D., Biomedical Engineering -- Drexel University, 201
Effects of surgical misalignment of total ankle arthroplasty with anatomical surface morphology on ankle mechanics through a three-dimensional image based dynamic model of the ankle
No full textMisalignment was identified as a cause for failure of total ankle replacement (TAR) [1,2]. The presumed mechanism leading to this failure is altered mechanical properties leading to elevated and concentrated contact pressure [1] and increased in micro-motion [2]. In this study we use image-based, three-dimensional (3D) musculoskeletal models to identify the changes in ankle mechanics due to TAR misalignment. Previously developed and validated 3D musculoskeletal models of the ankle complex were used to identify the effect of TAR misalignment on joint mechanics. A generic TAR with cylindrical articular surfaces replaced the natural surfaces of the ankles. The tibial and talar components were first inserted in an optimal fashion with the surfaces parallel to each other. A misalignment was then produced by translating (2 mm Elevation/Depression, 3 mm Anterior/Posterior) and rotating (10º Dorsi/Plantar Flexion, 10º Inversion/Eversion, 10º Internal/External Rotation) the tibial component. Simulations, conducted in ADAMSTM consisted of loading the model in all three planes while recording the applied loads, the displacements produced and the forces in the ligaments. From these results the following parameters were derived: surface-to-surface distance maps at the ankle, Range of Motion (ROM), stiffness, ligament forces, ligament strains, and kinematic couplings. Misalignment of the tibial component of TAR produces changes in the stiffness of the ankle joint complex, changes in the surface to surface interaction at the ankle joint and affects the forces and strains developed in the surrounding ligaments. Knowledge of the effect of misalignment of TAR is clinically relevant since it indicates the sensitivity of the mechanical behavior of the joint to component misalignment [3]. As such, this technique can be used as a predictive tool to indicate the most sensitive direction in which misalignment is critical.M.S., Mechanical Engineering and Mechanics -- Drexel University, 201
Effect of an Educational Program for Nurse Informaticists to Reduce Medication Errors through use of the Import Feature of the EHR
No full textObjective: To evaluate the effect of an educational intervention on the use of the medication reconciliation module import feature in the electronic health record (EHR) to reduce the incidence of medication errors. Design: Pre and post-interventional survey to measure the nurse informaticists knowledge about the EHR import feature. Setting: Surveys conducted online from 26 January 2018 through 9 March 2018. Participants: Eighty (80) nurse informaticists identified from the ANIA and LinkedIn websites volunteered to participate in this pilot project. This group selected because of their role as a nurse informaticist. Methods: Surveys were completed before and after the educational intervention to measure knowledge about the use of the EHR import feature and its impact on medication errors. Results: Analysis of the surveys identified that the recommended settings for the import feature before the intervention using a paired t-test which demonstrated a statistically significant result (t= 6.452, p>.000). Most significant finding identified (post-education survey) of 3-6 months setting (M=5.81) recommended compared to (M=8.92) pre-education survey. Conclusion: The level of knowledge indicated a lack of understanding before the education, related to establishing settings for past medication information to pull into the EHR through the import feature.D.N.P., Nursing Practice -- Drexel University, 201
Investigating acetaldehyde-induced DNA protein crosslinks in esophageal cells
No full textChronic alcohol consumption is a world-wide health problem, leading to a variety of adverse health issues. The primary metabolite of alcohol, acetaldehyde, is a major carcinogen that can cause DNA damage and is thought to increase the risk of esophageal cancer (EC). EC is one of the serious cancers ranking as the eighth most common cancer in the world. Its five-year survival rate is less than 20%. EC is mainly classified into two types: esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EA). Studies showed that chronic alcohol consumption increases the risk of ESCC in individuals with the ALDH2*2 (E487K) allele. The ALDH2*2 subunit impairs the tetramer enzymatic activity. Thus, the catalytic activity of the enzyme containing ALDH2*2 subunit is less than wild-type (ALDH2*1/*1), resulting in acetaldehyde accumulation in digestive organs, such as upper aerodigestive tract (UADT), stomach, and gut. 1 The liver is also commonly affected by ethanol since ethanol metabolism mainly occurs in this organ.2 Acetaldehyde accumulation causes DNA adduct formation, such as DNA-protein crosslinks (DPCs). DPCs impede DNA transactions which induces DNA double-stranded breaks (DSBs). A specific repair mechanism is required to cope with DPCs because canonical DNA repair pathways, such as homologous recombination (HR), nucleotide excision repair (NER), and translesion synthesis (TLS), cannot efficiently remove the DPCs. Recent studies reported that a protease called Spartan recognizes cross-linked proteins and contributes to survival of DPCs-harboring cells. In this report, we used the human esophageal cancer cell line TE11 as a model to investigate the effects of acetaldehyde on genomic integrity. To sensitize TE11 cells to acetaldehyde, we treated cells with the ALDH2 inhibitor disulfiram before acetaldehyde exposure. This treatment reduced TE11 cell viability and allowed us to investigate how acetaldehyde induces genomic instability. To investigate the role of Spartan protease in the repair of acetaldehyde-induced DPCs, we depleted Spartan in TE11 cells using RNAi technology. Spartan-depleted TE11 cells showed hypersensitivity to acetaldehyde and an increased level of DNA damage represented by 53BP1 DNA repair foci. The rapid approach to DNA adduct recovery (RADAR) assay revealed that Spartan-depleted TE11 cells displayed elevated levels of DPCs after acetaldehyde exposure when compared to control cells. These results suggest that Spartan protease is involved in the repair of acetaldehyde-induced DPCs.M.S., Molecular and Cell Biology and Genetics -- Drexel University, 201
Assessment of Work Environment Health in a Suburban Nursing Facility
No full textBackground: Developing and maintaining healthy work environments in healthcare organizations is vital to quality outcomes and optimized reimbursement. While the American Association of Critical Care Nurses’ Standards for Establishing and Sustaining Healthy Work Environments are well established in the acute care setting, little is known about their impact in the post-acute environment. Methods: A modified version of the Healthy Work Environment Assessment Tool (HWEAT) was distributed electronically to nurses, unlicensed assistive personnel, and nurse leaders over a 30-day period. Descriptive statistics were used to analyze demographics and survey responses by item and in the aggregate. Results: The response rate was low, rendering any inferential analysis moot. Participants somewhat-to-strongly agreed in greater than 80% of the responses that the site upholds the Standards in skilled communication, effective decision making, and authentic leadership. Conversely, participants somewhat-to-strongly disagreed in 20% or greater of the responses that the site could improve Standards performance in true collaboration, appropriate staffing, and meaningful recognition. Discussion: Recommendations are made for further exploration of specific aspects of the Standards as well as to repeat the survey. Major limitations of the study include the modification of the HWEAT and a low response rate. Conclusion: Further exploration is necessary to provide trustworthy data for site-specific quality improvement. Further research would better describe how healthy work environment standards may benefit post-acute settings overall.D.N.P., Nursing Practice -- Drexel University, 201
Effect of alkyl chain length on properties of epoxy-amidoamine systems: A molecular simulation study
No full textPolyamine crosslinkers functionalized with pendant fatty acids are commercially used in epoxy coatings in part to enhance water barrier properties for corrosion prevention. However, a systematic understanding of the links between monomer molecular structure and material properties of such systems remains elusive, which limits our ability to design newer and more environmentally friendly coating systems. In this dissertation, the effect of n-alkyl chain length in fatty-acid-functionalized polyamines on the properties of crosslinked epoxy-amidoamine systems is studied using molecular dynamics (MD) simulations. Simulations are compared with experiments whenever available. Both experiments and simulations show that density decreases and volume expansion coefficients increase with increasing pendant chain length. Furthermore, it is shown that the trends in density and coefficient of volume thermal expansion with chain length obtained from simulations are consistent with an ideal mixing approximation. Interestingly, however, the glass-transition temperature Tg is found to be insensitive to chain length. Molecular simulations reveal that increasing the alkyl chain length from four to ten carbons does not introduce new flexibility mechanisms to the dense thermosets which explains the Tg insensitivity. The mechanical properties of epoxy-amidoamine systems were also analyzed. The glassy-state Young's modulus was estimated using non-equilibrium molecular dynamics simulations and compared with experiments. Both simulations and experiments showed that Young's modulus decreases with increase in n. Stress partitioning based on molecular interaction types showed that both Lennard-Jones and covalent bond interactions were responsible for this sensitivity, with Coulombic interactions playing no significant role. The dependence of Young's modulus on n was strain-rate dependent in the simulations, with moderate to high strain rates showing no sensitivity. A strong correlation was observed between Young's modulus from non-equilibrium MD and volume fraction of methylenes estimated from equilibrium MD. Poissons ratios of all systems predicted from the simulations were insensitive to n, indicating a lack of anisotropy. The yield stress and strain hardening modulus were predicted for two systems with and without the alkyl chain (n=10). It was found that the thermoset with alkyl chain had lower yield stress and strain hardening modulus compared to the one without. Stress partitioning revealed that LJ (Lennard-Jones) and covalent interactions contribute significantly to the yield stress and the strain hardening modulus with electrostatic interactions having no significant effect. It was found that the lower yield stress is due to the dilution effect. The decrease in strain hardening modulus is due to both dilution effect and LJ (Lennard-Jones) interactions of methylenes in the network. This dissertation demonstrates some new and generic ways to assess the role of inter and intra-molecular interactions of molecular constituents on the properties of the crosslinked networks using molecular dynamics which are otherwise difficult or impossible to obtain from experiments and therefore may provide sounder rationale for molecular-based design of epoxy-based coatings.Ph.D., Chemical Engineering -- Drexel University, 201
Three Essays in Hedge Fund Activism
No full textIn the first essay, I apply behavioral finance theories to hypothesize one reason why hedge funds choose to engage in activism. Specifically, I predict that if hedge funds see the purchase price of their passive positions as a reference point, then, when they are suffering absolute losses, they are more likely to switch and become activists. I find results consistent with my prediction, even after controlling for the underperformance of the target firms. This study presents new evidence about what causes hedge fund activism. The behavioral finance literature has documented that retail investors, professional traders, and mutual funds are reluctant to realize their losses. I contribute to this literature by showing that a further effect of the loss is to cause activism. The second essay (with Naveen D. Daniel) examines the short-term incentives that activists are facing. The average announcement return to hedge fund activism is around 5%. Thus, activists that want to inflate their reported returns have incentives to initiate activism in target firms before the end of the reporting period. Our contribution is to document that activists engage in such opportunistic activism. Consistent with this, we find that activists are more likely to start their campaigns just before the end of the quarter. This heightened activity cannot be explained by increased news flow at the end of the quarter. In contrast to the typical positive market reaction to activist initiation, reaction to opportunistic activism is virtually zero. This is suggestive of activists initiating campaigns without completing their research on firms, which were potentially targeted for activism in the following quarter. The final essay (with Naveen D. Daniel) investigates how activists are able to be successful despite typically owning a stake of 6-7% in the target firms. We hypothesize that activists have incentives to (implicitly) coordinate with other institutional shareholders and to use this collective firepower to force target firms to change. Our contribution is to document that such coordination is pervasive and is mutually beneficial. In nearly two-thirds of the campaigns, there is coordination between the activist and institutional investors. Coordination is more likely in large firms where the activists would not have sufficient capital to build a large stake. Activist hedge funds that coordinate with other institutional shareholders are more successful in their activism as reflected in higher abnormal returns over the duration of the campaign. We attribute causation by instrumenting for coordination with the geographic proximity between the activist and the institutional investors.Ph.D., Finance -- Drexel University, 201
Study of Substrate-induced Effect on CVD-grown MoS2 Thin Films
No full textTwo-dimensional (2D) materials have become a hot topic in materials research since the successful isolation of stable graphene through mechanical exfoliation. Graphene has many attractive properties however it has zero bandgap, which limits its application as a transistor material in logical circuits. The transition metal dichalcogenides (TMDCs) family has emerged as a promising alternative due to their excellent semiconductor properties. Among various TMDC materials, MoS2 has received the most intensive research due to an indirect bandgap to direct bandgap transition when its thickness is reduced from bulk to a monolayer. Chemical vapor deposition (CVD) has become a popular technique to synthesize TMDC and MoS2 atomically thin films in large-scale, excellent quality and low cost. However, little work has been done to study the properties of CVD-grown MoS2 on functional perovskite substrates such as SrTiO3 (STO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT). In this work, MoS2 atomically thin films were synthesized via CVD on various substrates including SiO2, Al2O3 (0001), STO (001) and LSAT (001). The obtained MoS2 islands were characterized by optical microscopy and atomic force microscopy (AFM) to show their morphology and confirm their thickness. Subsequently, Raman and photoluminescence (PL) spectroscopy were employed to characterize the substrate-induced effect on as-grown MoS2 thin films. From Raman spectroscopy, it was confirmed that the synthesized MoS2 crystals were 1-4 atomic layers and no prominent substrate-induced strain was found, which may be due to the weak van der Waals interaction between substrate and MoS2. PL spectra revealed significant substrate-induced charge doping effect on MoS2 which changes the relative population of trions and neutral excitons and as a result modifies the PL spectra. The charge doping was quantified by estimating the electron density in MoS2 on different substrates based on a three-level model and mass-action model between trions, neutral excitons and free electrons. It is anticipated that this thesis study can help to provide a feasible route to tailor the electronic properties of TMDC-based heterostructures as needed to enable novel device design in the future via substrate engineering.M.S., Materials Science and Engineering -- Drexel University, 201