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Investigations into Synthesis and Reactions of Black and Red Phosphorus Nanomaterials
Get PDFResearch discoveries in carbon nanostructures have encouraged scientists to look for the next generation of versatile nanomaterials with novel electronic and optical properties to generate new scientific knowledge and discover materials with unanticipated or enhanced functionality. One element that has become of great interest in the last few years is phosphorus. Although studies investigating phosphorus nanostructures and properties are still in their infancy, unique properties of various phosphorus nanostructures are expected. First, in a literature review, this work will summarize some optical and optoelectronic applications of both black and red phosphorus. The role of phosphorus as a photocatalyst is also discussed. Next, this work will explore liquid exfoliation techniques applied to 2D black phosphorus with several exotic and common laboratory solvents, both with and without the use of potentially damaging ultrasonication. Lastly, investigations into reactions of black phosphorus and boron trifluoride under ambient conditions will be undergone to study the formation of boron phosphate.M.S., Chemistry -- Drexel University, 201
Towards Rational Design of Functional Fluoride and Oxyfluoride Materials from First Principles
No full textComplex transition metal compounds (TMCs) research has produced functional materials with a range of properties, including ferroelectricity, colossal magnetoresistance, nonlinear optical activity and high-temperature superconductivity. Conventional routes to tune properties in transition metal oxides, for example, have relied primarily on cation chemical substitution and interfacial effects in thin film heterostructures. In heteroanionic TMCs, exhibiting two chemically distinct anions coordinating the same or different cations, engineering of the anion sub-lattice for property control is a promising alternative approach. The presence of multiple anions provides additional design variables, such as anion order, that are absent in homoanionic counterparts. The more complex structural and chemical phase space of heteroanionic materials provides a unique opportunity to realize enhanced or unanticipated electronic, optical, and magnetic responses. Although there is growing interest in heteroanionic materials, and synthetic and characterization advances are occurring for these materials, the crystal-chemistry principles for realizing structural and property control are only slowing emerging. This dissertation employs anion engineering to investigate phenomena in transition metal fluorides and oxyfluorides compounds using first principles density functional theory calculations. Oxyfluorides are particularly intriguing owing their tendency to stabilize highly ordered anion sublattices as well as the potential to combine the advantageous properties of transition metal oxides and fluorides. This work 1) addresses the challenges of studying fluorides and oxyfluorides using first principles calculations; 2) evaluates the feasibility of using external stimuli, such as epitaxial strain and hydrostatic pressure, to control properties of fluorides and oxyfluorides; and 3) formulates a computational workflow based on multiple levels of theory and computation to elucidate structure-property relationships and anion-order descriptors. The insights gained in this work advance the understanding of oxide-fluoride anion engineered materials and we anticipate that it will motivate novel experimental efforts and materials by design in the future.Ph.D., Materials Science and Engineering -- Drexel University, 201
Perceptions of School Principals on Participation in Professional Learning Communities as Job-Embedded Learning
Get PDFPrincipal Professional Learning Communities (PPLCs) have emerged as a vehicle for professional development of principals, but there is little research on how principals experience PPLCs or how districts can support principal learning in a PPLC. This hermeneutical phenomenological study focused on perceptions of principals on participation in Professional Learning Communities as a form of job-embedded professional development for school principals. The target population for the study was elementary and middle school principals and assistant principals in a suburban district participating in an existing professional development initiative conducted by the researcher in a central office role as facilitator. The questions guiding this interpretive research were (1) How do principals describe their experience in a district-wide administrative PLC, called the Admin Council (AC PLC)?; (2) How do principals describe their experience in a Principal Professional Learning Community (PPLC), led by a central office administrator?; (3) What have principals experienced in these PLCs that is beneficial to them? Multiple interviews, observation data and meeting transcripts were analyzed to identify themes and develop a description of the lived experience of principals in a professional learning community nested within a district administrative PLC facilitated by central office. The primary results of the study are that 1) Participants described participation in PPLCs as valuable in providing connection, collegial support, collaboration, shared vision and dedicated time to focus on instructional leadership; 2) Principals experience new learning and collaborative work in PPLCs in relation to its direct relevance as something they can apply to lead change in their building contexts; 3) Principals experience a complex interior journey as part of PLC participation; and 4) Principals described having greater understanding of PLCS through participation in PLCs. Recommendations for districts include analyzing and developing structures to support common opportunities for PPLC members to enact instructional leadership. A district's alignment of leadership calendars and opportunities can support the development of joint enterprise for principals in a PPLC. Preplanned instructional leadership opportunities can ensure principals have opportunities for experiential learning as they apply new learning in their buildings. This research can support understanding of how principals experience central-office facilitated professional learning communities as job-embedded professional development.Ed.D., Educational Leadership and Management -- Drexel University, 201
Survivors of Sex Trafficking in Healthcare Settings and their Recommendations Regarding Identification Screening Protocols and Practices
No full textToday, millions of children, women, and men are suffering gross human rights violations in every corner of the world, including the United States (US) and manifested through Human Trafficking (HT). This type of victimization is a public health concern and a human rights issue. US-born victims are typically commercially sexual exploited through sex trafficking. Once victimized, they become an extremely hidden population. Yet, they interact with healthcare providers (HCP) when seeking medical care at some point during their period of victimization. Although few protocols and trainings to identify HT victims in healthcare settings exist, only a limited number of hospitals and healthcare facilities implement them. Therefore, sex trafficking victims go unidentified. There is scant research investigating patient-healthcare provider interactions from the survivor of sex trafficking (SST) perspective. Therefore, this study sought to: 1) identify the type of healthcare settings sex trafficking survivors frequented during their victimization period and reasons for their visit; 2) explore SST's perceptions about their interactions with HCPs; and 3) document survivors' recommendations on how to best screen, identify, and assist victims of sex trafficking within healthcare settings. This study utilized an exploratory, concurrent mixed-methods research approach with a triangulation design model. Recruitment took place in San Diego, CA and Philadelphia, PA. A 48-item questionnaire and semi-structured interview guide were utilized to collect data. Data analyses were based on descriptive and inductive processes. Participants were US-born and self-identified as SST (N=21). Almost one-half of them were white (47.6%), followed by Blacks (23.8%). On average, SST were victimized for 4.9 years. Most commonly sought healthcare settings were Emergency Departments (ED) and community care clinics, specifically Planned Parenthood (PP). SST's non-disclosure of their victimization to medical professionals was high, 61.9%. Participants' recommendations to the healthcare community encompassed three types: 1) Knowledge and Skills; 2) Attitudes and Behaviors; and 3) Safe Plans and Resources. This study confirmed previous findings that sex trafficking victims seek care at different types of healthcare settings and reasons for seeking medical care. Most importantly, it presented noteworthy insights regarding barriers limiting SSTs from disclosing their victimization to HCPs, and thus contributes key facts with which to identify and intervene on behalf of sex trafficking victims within healthcare settings.Dr.P.H., Community Health and Prevention -- Drexel University, 201
On the Surface of Things: The Organization and Ideological Functionality of Buildings, Bodies, and Cash as Visual Surfaces
No full textThis dissertation examines the functionality of the general concept of 'the surface' as it physically exists within space. This study engages in a theoretical approach to the surface from the point of view of it being a specifically visually organized liminal space where ideological dissemination can be made to flow from and, thus, where the foundations of hegemonic control can be established. This study argues that although there are a variety of surfaces that one can encounter, that they all share these common traits of visual organization, hegemonic structuring, and the potential for ideological dissemination. In order to explore this concept and successfully make this argument, I have chosen three case studies focusing on three different aspects of the organization and utilization of surfaces from various vantage points, all of which involve these surfaces in moments of contention between hegemonic and counter-hegemonic forces. The first case study will concern itself with the visual organization of monetary design as a surface. This case study will look at the phenomenon of writing anti-regime messages on paper currency and re-circulating them as a protest tactic during the 2009 Iranian Green Revolution. The second case study will analyze the body as a surface. It will look at the feminist, anti-patriarchal protest movement known as Femen as an example of body-centric protest and its relation to the concept of the visual surface. The third and final case study will look at the built environment of the cityscape as a cohesive surface. It will focus on the series of public anti-austerity protests in London from 2010 to 2011, starting with the student protests of 2010, then looking at the riots surrounding the death of Mark Duggan in London in mid-2011, and lastly looking at the Occupy London protests in late 2011 and early 2012. This dissertation provides a review of the relevant literature, an overview of the methodological approach that will be taken for analyses, an examination of the historical context of each case study, before engaging in an analysis of the case studies themselves.Ph.D., Communication, Culture, and Media -- Drexel University, 201
Mitochondria Malate-Aspartate and Lactate Shuttle Mechanisms Cooperate in Coupling of Glycolysis and Oxidative Phosphorylation in Colon Cancer
No full textThe requirement for metabolic efficiency forces cancer cells to generate sufficient energy equivalents to support their high proliferative activity. One cycle of glycolysis supplies cells with two molecules of ATP only, while oxidative phosphorylation provides around 36 molecules of ATP. Therefore, many cancer types, including colon cancer, reprogram their metabolism to accelerate mitochondria processes to fulfill the elevated energy demands. However, the long known signature of cancer is elevated glycolysis according to the classical work of Otto Warburg, while little is known about the processes underlying this effect. Yet, there is a growing number of studies showing that mitochondria remain highly active across cancers even under glycolytic conditions. In attempt to understand this discrepancy this work is aimed in exploring the mechanisms that could couple glycolysis and oxidative phosphorylation to enable aerobic oxidation of glucose by mitochondria. The oxidation of glycolytic lactate in mitochondria with involvement of lactate dehydrogenase (LDH) has been shown in heart, skeletal muscles and neurons, i.e. highly energetic tissues. It would be reasonable to speculate that cancer cells adapt similar mechanisms to support their elevated energetic status. We studied the activities of mitochondria malate-aspartate shuttle (MAS), consisting of glutamate-aspartate (Aralar/Citrin) and malate-alpha-ketoglutarate transporters, and lactate dehydrogenase which is supposedly localized in mitochondria inter-membrane space. We demonstrated that cooperation of these shuttles is required in generating of respiratory substrate NADH in mitochondria matrix which otherwise is membrane impermeable. It is proposed that MAS supplies NAD+ to mitochondria LDH to convert glycolytic lactate to pyruvate which then enters matrix and gets involved in NADH generation for oxidative phosphorylation.M.S., Biomedical Engineering -- Drexel University, 201
Excitation, Model and Analysis Uncertainties in Seismic Assessment of Bridges
No full textIn seismic assessments, structural engineers must visualize the structure and its environment. As a matter of fact, the visualized system is obviously not the actual one, and, hence, the numerical simulation of structural systems possess some inherent uncertainties associated with the simplification/abstraction. The uncertainty sources affecting the seismic assessment of structures are often characterized as either aleatoric or epistemic in nature. Aleatoric uncertainty refers to randomness, i.e. stems from the unpredictable nature of events, and epistemic uncertainty refers to the lack of knowledge, i.e. stems from incomplete data, ignorance, or modeling assumptions. The main objective of this dissertation is to examine the current strategy in seismic design/assessment of bridges by considering the effect of various sources of uncertainty. This research effort investigates the impact of three main sources of uncertainty in seismic assessments, i.e. excitation scenario, system modeling strategy, and analysis methodology, on the reliability of the computational prediction of the seismic behavior of bridges. Analytical considerations and numerical results of the present study highlight the difficulties with the conventional procedures proposed by codes in the seismic design/assessment of bridges, and provide practice-oriented recommendations for: (1) increasing the reliability of the numerical results, and (2) decreasing the dispersion of the structural response.Ph.D., Civil engineering -- Drexel University, 201
Evaluation of the Potential Use of Spherical Porous Reactive Aggregate (SPoRA) for Internal Curing of Cementitious System
No full textCuring has been considered as an essential process for cementitious materials. Proper curing enables the cement to hydrate developing its potential strength and improving its durability. Inadequate curing can lead to the plastic shrinkage cracking and stress due to drying or temperature changes. Using external water or placing a curing compound on the surface of the concrete to reduce water loss due to evaporation are traditional ways of curing concrete. These methods may not cure the entire concrete and may require longer curing time. Methods have been proposed to help increase curing efficiency such as providing internal curing in concrete. Internal curing is often referred to as curing concrete from the inside by using pre-wetted porous lightweight aggregate (LWA) to provide additional curing water throughout the concrete mixture. This thesis focuses on a novel lightweight aggregate, Spherical Porous Reactive Aggregate (SPoRA), which is produced from waste coal combustion bottom ash and its potential use for internal curing in cementitious system. The production of SPoRA is first introduced in this study, which is converting bottom ash to porous lightweight aggregate using sintering process. Physical properties of SPoRA such as specific gravity and vacuum absorption were determined and analyzed. The LWA used for internal curing should supply a sufficient volume of water to counteract the effect of self-desiccation. Therefore, the water absorption property test was conducted to determine if SPoRA could absorb sufficient water. Once mixing the SPoRA with cement, the desorption property of releasing water for internal curing is also significant as SPoRA should be able to release water over time to properly cure concrete internally. The loss of water from SPoRA can be described through a desorption isotherm that was determined using sorption analyzer in this study. Finally, the physical properties, absorption and desorption behavior of SPoRA are compared to two traditional types of lightweight aggregate (i.e., Expanded Shale, Clay, and Slate) and one foamed glass (produced from waste glass) available in the market.M.S., Civil engineering -- Drexel University, 201
Exploring the Relationship between Soluble Fiber Intake and Bone Mineral Density in Endurance Athletes
Get PDFBackground: Dietary recommendations to athletes are tailored to enhance performance and accelerate recovery. Recommendations focused on these parameters are rarely made in consideration of gut or bone health. Fermentable fibers may play a role in attenuating exercise-induced inflammation and in enhancing calcium absorption; thus, augmenting bone mineral density (BMD) in endurance athletes. Objective: The purpose of this study was to determine whether a relationship could be identified between: 1) soluble fiber and anterior-posterior (AP) lumbar spine BMD among a population of endurance athletes, and 2) total fiber intake and AP lumbar spine BMD among a population of endurance athletes. The study also aimed to assess whether calcium intake, sex, and physical activity levels would influence the relationship between soluble fiber intake and AP lumbar spine BMD. Design: This cross-sectional study included 95 athletes who self-defined their primary form of physical activity as an endurance sport. Dual-energy x-ray absorptiometry scans were employed to measure AP lumbar spine BMD and body composition. A self-administered 2005 Block Food Frequency Questionnaire was provided to assess average daily consumption of macronutrients and micronutrients. Reported energy intake was used to compute an individualized Adequate Intake (AI) for total fiber for each participant, based on the Food and Nutrition Board's AI recommendation that men and women consume 14 grams of fiber per 1,000 kilocalories of energy. Physical activity habits were measured by Actical(TM) accelerometers, which were worn by a subset of 55 participants for seven days. The accelerometers measured average number of minutes spent in sedentary behavior and light, moderate, and vigorous physical activity states. To determine whether physical activity influenced the relationship between soluble fiber intake and AP lumbar spine BMD, the median time spent in combined moderate and vigorous physical activity was used to divide the population into lower and upper quartile groups, and analyses were conducted in each group and compared. To determine whether sex, meeting fiber AI recommendations, or meeting calcium Recommended Dietary Allowances (RDAs), analyses were conducted in each group and compared. Results: Data were analyzed for 95 athletes (n = 47 male athletes, 48 female athletes; 38.15 ± 10.07 years of age). Twenty-one of the 95 participants met nutrient needs for total fiber (22%), 46 participants met nutrient needs for calcium (48%), and 11 participants met nutrient needs for vitamin D (12%). Fat-free mass, body mass index, and dietary vitamin D intake were significantly correlated with AP spine lumbar BMD (p = 0.008, p = 0.007, p = 0.015, respectively). No significant correlations were found between soluble fiber and AP lumbar spine BMD, or between total fiber intake and AP lumbar spine BMD in the overall sample or among any of the subgroups (p > 0.05). No significant between-group differences in regression slopes were found between men and women, between participants who met or did not meet fiber AI guidelines, between participants who met or did not meet calcium RDAs, or between participants in the lower versus the upper quartiles of combined time spent in moderate and vigorous physical activity. Conclusions A majority of participants in this cohort did not meet AI recommendation guidelines for fiber consumption. Nutrient recommendations to athletes may consider encouraging increased fiber consumption to help resolve this gap. The data presented here seem to indicate that fiber intake and bone mineral density are not related. A longitudinal study is required to assess if fiber intake plays a role in bone health in athletes.M.S., Human Nutrition -- Drexel University, 201
Comparing Perceptions of Conflict Mediation Strategies between School Administrators and Non-Administrators
Get PDFPrior research has explored the impact of conflict mediation practices in schools, regarding students’ perceptions, but existing research has not examined how principals and other school staff members perceive these practices. Given the significant shift away from zero tolerance and towards more restorative practices such as conflict mediation, the current study seeks to examine if school administrators and non-administrators differ in their perceptions of the value of conflict mediation, perceptions of existing conflict mediation skills, and perceptions of the effects of current practices on school climate, as perceptions can influence how information is applied. As these two groups have their own distinct interactions with students, it is hypothesized that they will have differing opinions regarding the instruction and implementation of these conflict mediation techniques. Data were collected from 150 school staff members (108 administrators, 42 non-administrators) from the School District of Philadelphia prior to a professional development training; participants completed a survey assessing perceptions of conflict mediation. School staff were categorized post hoc as administrators or non-administrators based on their self-identification within the survey. A chi-square analysis and three separate multivariate analysis of variance were conducted. Analyses revealed that the two groups did not differ in their experience with conflict mediation, perceptions of the value of conflict mediation, perceptions of their existing mediation skills, or perceptions of the effects of the current practices on school climate. Therefore, school administrators and non-administrators can continue to receive the same training, as long as they maintain similar perceptions regarding these strategies. These findings have implications for current practices, both in terms of designing future mediation trainings, as well as applying these skills within schools.M.S., Psychology -- Drexel University, 201