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Pauson-Khand Cycloaddition via Boron and Silicon Tethered 1,7-Enynes
No full textThis thesis highlights the studies of silicon and boron tether synthesis of bicyclic cyclopentenones via the Pauson-Khand Reaction. The first chapter summarizes the discovery, key advancements, and mechanism of the Pauson-Khand reaction. The Pauson-Khand reaction has been utilized in total synthesis of natural products. The second chapter illustrates the Pauson-Khand reaction utilizing silicon as a tethering agent. Silicon employed as a tethering agent can lead the Pauson- Khand bicyclic cyclopentenone to a variety of synthetic applications, primarily focusing on natural product syntheses. The key developments described involves the use of catalytic cobalt to promote the Pauson-Khand reaction. The final chapter utilizes a boron tethering agent in the Pauson-Khand reaction, which has yet to be reported in literature. Boron has been utilized as a tethering agent in different reactions and shows its versatility in applications towards natural product syntheses.M.S., Chemistry -- Drexel University, 201
Social Problem-Solving and Posttraumatic Growth among United States Military Veterans
No full textThe present study hypothesized that social problem-solving (SPS), or the process by which a person understands, devises, and implements strategies to resolve problems they encounter in life, is a factor that contributes to the experience of PTG in United States Military Veterans. This research study was developed to examine the relative contributions of components in the SPS model to levels of PTG in Veterans, and explore additional relationships that may provide insight to the nature of SPS and PTG in relation to stressful or traumatic events. Participants were 154 individuals who indicated that they were Veterans of the United States Military and completed a demographics questionnaire and three standardized self-report instruments. Recruitment was conducted through a mixed-methods approach, consisting of individuals recruited in-person through a local Veterans organization in Philadelphia, PA, and online through the use of snowball sampling and Amazon’s Mechanical Turk. The three study instruments completed by participants were the Social Problem-Solving Inventory – Revised: Short Form (SPSI-R:SF) to measure social problem-solving orientations and styles, the Posttraumatic Checklist for the DSM-V (PCL-5) to measure posttraumatic stress symptoms, and the Posttraumatic Growth Inventory – Revised (PTGI) to measure perceived growth after a stressful or traumatic event. The main research questions of this study consisted of hierarchical multiple linear regression models that investigated the relative contributions of SPS model components to PTG and symptoms of PTSD. Reported tobacco use was found to be a significant predictor of PTG in the sample, while combat experience, deployment experience, and alcohol use were significant predictors. These variables were included as covariates in the main regression analyses to control for their impact on the outcomes of interest. The effective SPS factors of positive problem orientation (PPO) and rational/planful problem-solving style (RPS) were significant predictors of PTG, while the ineffective SPS factor of negative problem orientation (NPO) was a significant predictor of PTSD symptoms. The secondary aim of this study was to explore the form of the relationship between PTG and PTSD, and explore the contributions of trauma-related characteristics to variability in PTG. PTG was found to have a curvilinear association with PTSD symptoms, and was unrelated to both the perceived stressfulness and perceived impact of the event at the time it occurred. The findings of this study establish an important association between SPS and PTG, which reveals that increases in effective SPS factors corresponds to increases in PTG. Further, this study replicates previous research findings that NPO to be an important predictor of PTSD symptoms, and PTG to be highest in individuals with moderate levels of PTSD symptoms. Our results suggest that SPS plays a role in both symptoms of PTSD and levels of PTG, indicating that Problem-Solving Therapy (PST), an evidence-based psychosocial intervention that aims to facilitate adaptive problem-solving attitudes and strategies to reduce the negative impact of stressors, can be effective in reducing symptoms of PTSD and facilitating PTG in the wake of trauma. Future studies should replicate these initial findings and explore factors underlying the connection between SPS and PTG. Future PST interventions and programs aimed toward those who have experienced psychological trauma should include measures of perceived growth, and examine the longitudinal associations between SPS and PTG.M.S., Psychology -- Drexel University, 201
Identifying Online Streaming User Value in the Netflix Recommendation System
Get PDFNetflix is one of the most successful providers of Over-The-Top content, delivered via the internet. By using a massive amount of data generated by its streaming users, a personalized recommendation system is one of Netflix’s value propositions. However, due to a lack of publically available data and studies, it is difficult to determine whether its recommendation system has brought true value to streaming users, and how important this feature is to its users. The purpose of this study is to evaluate the recommendation system from the streaming users’ point of view. By collecting survey results from 119 participants, this study will attempt to reveal the relationship between streaming users and the personalized recommendation system, and to show whether or not streaming users are satisfied with this feature.M.S., TV Management -- Drexel University, 201
Eye glance as a measure of visual attention in driving: Comparing acquired brain injury (ABI) and healthy control (HC) groups
Get PDFResearchers have observed poor driving performance among those who have sustained an ABI, compared to their pre-morbid selves and healthy controls. Because of the role that attention plays in driving, attentional impairment typically observed after an ABI may contribute to this driving deficit. Eye glance is a well-established measure of visual attention. The current study sought to evaluate participants’ glances while driving, comparing those with ABI to a healthy control group on two conditions: baseline and performing a secondary task. During all driving conditions, the ABI had more overlong glances than the HC group. Both ABI and HC groups had more glances away during the task condition than during baseline. There were also significant interactions of group x driving condition. Results showed that group and task affected the frequency of long glances away from the road, but secondary task performance had greater effects on glances of the ABI group than on the HC group. A secondary aim of this study was to compare performance on traditional neuropsychological tests to eye glances, a more ecologically valid measure of attention. The lack of many significant correlational findings are likely due to the complexity of the construct of attention, and the contributions of other cognitive abilities to tests and during driving. This study showed that ABI have poorer glance behavior than HCs during driving, but additional research is necessary to determine the implications of these findings.M.S., Psychology -- Drexel University, 201
Sexual Health Knowledge, Attitudes, and Beliefs Among Nurse Practitioners and Certified Nurse Midwives Who Work with Adolescents in Non-acute Care Settings
Get PDFAdolescents frequently experience perceived and actual barriers to sexual and reproductive healthcare related to confidentiality, access, and their relationship with healthcare providers. Advanced Practice Registered Nurses (APRNs) are well positioned to work with adolescents in a variety of non-acute care settings to provide preventative sexual healthcare services. No studies have recorded Nurse Practitioners’ (NPs) and Certified Nurse Midwives’/Certified Midwives’ (CNMs/CMs) adolescent sexual health knowledge, attitudes, and beliefs. The purpose of this study was to determine whether there were any differences between Women’s Health Nurse Practitioners (WHNPs) and CNMs/CMs whose educational programs have a concentration in sexuality, and APRNs from other specialties (ANPs, FNPs, PNPs, and PMHNPs) regarding knowledge, attitudes, and beliefs toward adolescents’ sexual health. The study used a cross-sectional, descriptive comparative design. A convenience sample was recruited through the National Association of Nurse Practitioners in Women’s Health (NPWH) and the Nurse Practitioner Association- New York State (NPA) e-newsletters and surveyed online with The Sex Knowledge Attitude Test (SKAT), the Sexuality Attitudes and Beliefs Survey (SABS), and the National Violence Against Women Survey (NVAWS) to assess sexual health knowledge, sexuality attitudes, beliefs about addressing adolescent’s sexual health, and personal experience of sexual violence. One open ended question elicited responses of qualitative data. Demographic data of participants (n = 204) were analysed and 171 participants finished the online survey. Multiple logistic regression analysis shows that the WHNP/CNM/CM group have significantly more positive beliefs about addressing adolescents’ sexual health than the Other NPs group, [beta] = -3.36, p = .003. Chi-square of attitude scores by region of the U.S. show that positive attitudes toward adolescent sexuality vary significantly with the South showing the least positive attitude scores (p < .01). Religion (not being Christian), [beta] = 1.69, p = .04, and religiosity (frequency of attending religious services), [beta] = -6.05, p < .0001, were significant predictors of adolescent sexuality attitudes. In addition, results of logistic regression of sexual health knowledge, and adolescent sexuality attitudes between the WHNP/CNM/CM group and the Other NPs group trends towards significance. The open ended question was analyzed using content analysis. Categories and constructs derived from respondents (n = 29, 17%) further support the quantitative findings, such as adolescents’ lack of access to comprehensive sexual health education and sexual health care services led by APRNs, discomfort in addressing adolescent’s sexual health, and the need for further adolescent sexual health education. Further research needs to be done with a larger sample size and more advanced knowledge questions for APRNs. Competency-based curriculum in the area of adolescent sexual health that promotes professional values and compassionate care in educational programs for APRNs is essential to improve adolescent’s access to sexual healthcare services and outcomes.Dr.N.P., Nursing Practice -- Drexel University, 201
The Role of Air Entrainment in Drop Impact Dynamics on Lubricated Surfaces
No full textDrop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray coating technologies. The recent discovery of the role of the air entrainment between the droplet and impacting surface has produced numerous works uncovering the unique physics that correlates the micro-scale and nano-scale spatio-temporal dynamics to the macro-scale impact outcomes such as droplets bouncing on thin air films no thicker than a few microns. In this work, the macroscopic droplet morphologies under impacting conditions are juxtaposed with the microscopic behavior of the air film underneath the droplet where an interplay of various forces - inertial, viscous, capillary and intermolecular forces - coexist and dictate the final outcomes of the impacting drop. Lubricant infused surfaces (LIS) have recently been studied due to their potential benefit in various applications such as pressure-stable, self-healing, ice- and liquid-repellent materials. Combining the techniques of total internal reflection microscopy and reflection interference microscopy, we examine the dynamics of an underlying air film upon drop impact on lubricated substrates where the thin liquid film is immiscible to the drop. In contrast to drop impact on solid surfaces where even the smallest asperities cause random breakup of the entraining air film, we report two air film failure mechanisms on lubricated surfaces. In particular, using ≈ 5 µm thick liquid films of high viscosity, which should make the substrate nearly atomically smooth, we show that air film rupture shifts from asperity-driven to a controlled event. At low Weber numbers (We < 2) the droplet bounces. At intermediate We ( ), the air film fails at the center as the top surface of the drop crashes downward owing to impact-induced capillary waves; the resulting liquid-liquid contact time is found to be independent of We. In contrast, at high We ( ), the air film failure occurs much earlier in time at the first inflection point of the air film shape away from the drop center, where the liquid-liquid van der Waals interactions become important. The predictable failure modes of the air film upon drop impact sheds light on droplet deposition in applications such as lubricant-infused self-cleaning surfaces. While the pre-contact air entrainment effects have been well studied, the post-air entrainment effects and the subsequent wetting instability at the contact line is not well understood - particularly for Weber (We) numbers well below the splash threshold. We uncover the post-air entrainment dynamics of impacting droplets on lubricated surfaces by changing both the droplet impact velocities (0.9 - 1.4 m/s) and viscosities (10 - 100 mPa s) under ambient conditions to elucidate the growth of instabilities at the wetting front on atomically smooth, viscous silicone oil films of varying viscosities at constant thickness of . For We number greater than 10 at which the disjoining pressure overcomes the capillary pressure, the air film fails at the lowest air film thickness and the liquid-liquid contact line grows radially outward. What is the criterion for the interface to be unstable? We suspect that it is the air rim that moves with the wetting front that is unstable due to the air pushing against the liquid. Overall, this work focused on developing a novel dual TIRM-RIM technique enabling the facile in situ measurements of the underlying air film under various drop impact scenarios. Future work will focus on the droplet jetting dynamics on LIS.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
Using Digital Media Technologies to Improve Museum Archival Monitoring Systems
No full textArchival collections composed of vulnerable materials require careful monitoring of temperature and humidity. Archivists currently use a variety of data loggers to monitor relative temperature and humidity. Normal data logging systems including the HOBO and eClimateNotebook use expensive digital data loggers whose data is typically converted from an excel spreadsheet to a basic line graph. This project sought to convene with the archival department at the Academy of Natural Sciences in Philadelphia, PA to see how improving the collection and visualization of environmental data for museum archives. With assistance from a group of experts from the Academy of Natural Sciences, this project developed a low-cost data logging system using Arduino microcontrollers to collect the data, and a custom-built web based interface to visualize the data. We believe that this created an improved data logging system that allowed live data to be accessed via web interface while also generating new visualization methods that highlighted problem areas within the archival collection facilities.M.S., Digital Media -- Drexel University, 201
Porelike Morphologies in Amyloidogenic Proteins
Get PDFIntrinsically disordered proteins (IDPs) have been linked to a variety of human diseases. The roles that IDPs play in physiological functions and disease pathology are frequently an enigma. Their disordered nature and structural complexity presents significant experimental and computational challenges, and makes IDPs difficult to study and characterize effectively. Soluble, low molecular weight (LMW) oligomers of the IDPs amyloid beta-protein (Abeta) and alpha-synuclein (alphaS) have been hypothesized to be the primary neurotoxic agents in Alzheimer's Disease (AD) and Parkinson's Disease (PD) respectively, however their structure remains elusive. In this thesis, we take a varied computational approach in studies of Abeta and alphaS oligomers in order to probe and elucidate their structure. A oligomers have been observed to impair cognition in live rats and to negatively affect memory by hindering long-term potentiation in the hippocampus. Of the two predominant A alloforms, Abeta40 and Abeta42, the latter is more strongly associated with AD. Here, we structurally characterize Abeta40 and Abeta42 monomers through pentamers via a multi-scale computational approach, wherein conformations derived by discrete molecular dynamics combined with an implicit--solvent intermediate--resolution protein model and amino acid-specific interactions (DMD4B-HYDRA) were converted into all-atom conformations and subjected to explicit-solvent MD. Unlike the initial DMD4B-HYDRA conformations, fully atomistic Abeta40 and Abeta42 trimers, tetramers, and pentamers form water-permeable pores, whereby the tendency for pore formation sharply increases with oligomer order and is the highest for Abeta42 pentamers. Our findings reveal an extraordinary ability of Abeta oligomers to form pores in pure water prior to their insertion into a membrane. PD is characterized in part by the cerebral accumulation of alpha-synuclein, a 140 amino acids--long protein produced naturally in the body, into abnormal intracellular protein deposits in the brain. Soluble alphaS oligomers in particular have been shown to be toxic to neuronal cell cultures in vitro. We here characterize the structure of alphaS oligomers computationally using the DMD4B-HYDRA approach. We vary the implicit-solvent parameter corresponding to the strength of electrostatic interactions (E_CH) to fine tune the solvent conditions in order to obtain an alphaS oligomer distribution consistent with experimental data. The population of alphaS oligomers is characterized by a monotonically decreasing propensity of monomers through septamers followed by an increase in octamers. We observe that alphaS forms water-permeable pores in all assembly states, with a propensity for pore formation that increases with oligomer order. Previous studies have reported that both Abeta and alphaS oligomers form ion channels when embedded into a cellular membrane, which causes an abnormal ion flux and eventually leads to cell death. These observations form a leading theory for the mechanism behind the cytotoxicity associated with AD and PD, known as the ion channel hypothesis. The observations of porelike morphologies in our studies of LMW oligomers of Abeta and alphaS, which form in the absence of a membrane and increase in propensity with oligomer order, provides important insights and further support to the ion channel hypothesis of AD and PD.Ph.D., Physics -- Drexel University, 201
Predicting Angular Displacement of Medical Devices in a MRI Scanner Bore Using COMSOL Multiphysics
Get PDFMedical devices undergo a series of evaluations in order to determine their performance and level of safety in a magnetic resonance (MR) environment. The standard of focus for this work is ASTM F2052-15 which measures the induced displacement of a device due to the spatial gradient fields present in the MRI scanner bore. This test entails suspending the device from a string near the entrance of the MRI bore and measuring the angle of deflection. Evaluating the performance of medical devices in the MR environment is a costly endeavor, both in time and resources. This work aims to develop a predictive model to help eliminate some of the burden associated with this testing. The current method of testing magnetically induced displacement force is by measuring the deflection angle between the device and the test fixture. The displacement force is then computed using this deflection angle. It is expected that this deflection angle can be recreated within the simulation and the forces acting on the device be accurately displayed, and the associated displacement force estimated numerically. This model provides the freedom of manipulating a device and evaluating its performance almost instantaneously. Extensions of this model have the potential to further the detailed numerical evaluation of medical devices in the MR environment. This information could lead to reevaluation of the current ASTM standards surrounding medical devices in the MR environment.M.S., Biomedical Engineering -- Drexel University, 201
Learnability through Adaptive Discovery Tools in Voice User Interfaces
Get PDFThe invisible nature of VUIs has been attributed to challenging discoverability of VUIs. When discoverability is challenging, learnability can be compromised. Some researchers have designed visual tools for VUIs to help users learn as they go. How- ever, few have used adaptation to ensure that learnability with the help of these tools extends beyond initial use. We create DiscoverCal, a calendar application designed using an adaptive discovery tool to improve learnability in VUIs. DiscoverCal is created using Api.ai enabled wall mounted display at home. We identify characteristics of discovery tools created by researchers and extend their work by designing a system that adapts based on contextual relevance and user performance, in order to extend learnability beyond initial use. We nd that an adaptive approach is slightly more favorable for learnability. However, further iterations to our design of adaptivity are necessary.M.S., Digital Media -- Drexel University, 201