http://idea.library.drexel.edu/handle/1860/10 Search the Channel search http://idea.library.drexel.edu/simple-search http://idea.library.drexel.edu/handle/1860/4128 Title: Study of Ultrasound-Induced Leakage from DOPC/DPPC/Cholesterol Model Membranes <br/> <br/>Authors: Waweru, Maureen Wanjiku <br/> <br/>Abstract: Ultrasound-mediated controlled drug release is beneficial because it is a non invasive process that is effective in the treatment of diseases, and which minimizes toxic side effects that are common with other systemic treatments. As a model for the application of ultrasound in drug delivery, this paper outlines a quantitative study of the controlled release of calcein from small unilamellar vesicles (SUVs) (~100nm) after exposure to low frequency ultrasound (LFUS). The SUVs comprise of varying compositions of 1, 2-dioleoyl-phosphocholine (DOPC), 1, 2-dipaltimoyl-phosphocholine (DPPC), and cholesterol. Together, these compounds provide a model lipid membrane system that can be used to study how lipid composition and membrane phase behavior affect ultrasound-induced release of molecules encapsulated within the core of lipid vesicles. In this study, small unilamellar vesicles encapsulating fluorescent dye, calcein, were prepared by Rapid Solvent Exchange (RSE) technique. These lipid vesicles were exposed to ultrasound at a frequency of 24 kHz using a probe sonicator, at 30 sec time intervals followed by 3 min resting time. The leakage of calcein from the vesicles was then quantified by steady state fluorescence spectroscopy. Calcein release profiles obtained indicated that varying the molar amounts of cholesterol had different effects on the lipid membranes ability to resist leakage by ultrasound. Further studies were performed to investigate the effect that polyethylene glycol (PEG) has on ultrasound-mediated leakage of calcein from liposomes in the solid-ordered phase. Previous studies have shown that PEGylated liposomes are considered to be more susceptible to ultrasound. In this work, calcein leakage from liposomes that contained different molar quantities of DPPC and 1, 2 Distearoyl-Sn-Glycero-3-Phosphoethanolamin-N-methoxy(poly(ethylene glycol))2000 (DSPE-PEG2000) was analyzed and the results showed an increase in ultrasound-mediated leakage of calcein at 1% and 5% molar quantities of the polymer. <br/> <br/>Description: Thesis (M.S., Biomedical engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4127 Title: PATHOS: A MATLAB‐based Weak Stability Boundary Orbital Trajectory Simulator for Use in Interplanetary Mission Design <br/> <br/>Authors: Tran, Eric <br/> <br/>Abstract: Trajectory design is traditionally performed under very strict constraints or simplifications. This is because full‐force models have thus far eluded analytical solution. One common simplification is the two‐body assumption, where the only bodies considered are the spacecraft and a central mass. This simplification yields fairly accurate results for a small number of specific cases (binary stars, low‐Earth orbit). However, once the orbital regime enters the interplanetary range, where multiple gravitational bodies are relevant, simple two‐body calculations prove inadequate. In response, the patched‐conic approach was used, where multiple two‐body trajectories would be “patched” together to form an approximate path for the spacecraft. This approach, however, still employed the two‐body simplification and so the hidden constraints of the two‐body problem are carried over. Consequently, while this method produces useful trajectories, it does not yield the most efficient ones. While the n‐body problem had not been explicitly solved, numerical methods with modern computational software programs can be used to identify extremely efficient trajectories by taking into account a greater number of bodies. It was recently discovered that gravitational pathways linking the Solar System’s Lagrange points can provide extremely cheap interplanetary travel. While only a handful of missions have flown these so‐called “Weak Stability Boundary” (WSB) trajectories in the past, they have the potential to gain widespread use for their extremely low fuel costs. This document will discuss the construction of these WSB trajectories through the use of a Dead‐Reckoning numerical simulation tool, called PATHOS, which accounts for at least 3‐body gravitational effects. The simulation will be used to generate a group of sample trajectories as validation, as well as compared against similar software tools. <br/> <br/>Description: Thesis (M.S., Mechanical engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4126 Title: Implementation of a non-parametric rainfall simulation method to size rainwater harvesting systems for stormwater management and irrigation of urban agricultural facilities <br/> <br/>Authors: Sunder, Ajay <br/> <br/>Abstract: Combined Sewer Overflows (CSOs) are one of the biggest problems associated with stormwater runoff in Philadelphia. Rainwater harvesting (RWH) for the purpose of storage and non-potable reuse is one of several highly advocated solutions for reduction of stormwater runoff especially in urban areas. Various RWH systems have been designed based on simple supply vs. demand water balance concepts and somewhat more complex parametric rainfall simulation methods. This project involves the use of a non-parametric rainfall simulation method incorporated in the Storage and Reliability Estimation Tool (SARET) developed by Basinger, Montalto, & Lall (2010) to size a RWH system collecting stormwater runoff from residential roofs at an urban agricultural facility situated at 53rd and Wyalusing Avenue, Philadelphia. Two methods were used to obtain the irrigation requirements for the urban agricultural facility, one uses the Blaney-Criddle method (Blaney & Criddle, 1950) while the second uses water consumption bills obtained at the site. SARET then uses historical daily precipitation data for Philadelphia to develop storage vs. catchment area reliability curves based on which the desired volume of the storage facility as well as the catchment area are chosen. During the design phase, a bioretention facility was preferred as a treatment facility to improve the water quality of runoff collected from the roofs before application to the crops. Analyzing various options, StormChamber® developed by Hydrologic Solutions was chosen as a underground water storage facility. The specifications and construction plans for the bioretention facility, storage facility and other aspects of the system were then laid out to enable the final construction. Once the construction was complete, a preliminary assessment was performed by estimating the depth vs. volume relationship of the storage facility and conducting a statistical test on the observed data, based on which it was concluded tentatively that the system was working as designed. A more in depth analysis, based on a longer observation period is, however, required for a more conclusive assessment. Finally, a GIS analysis was performed using planimetrics data in ArcGIS 10.1 that looks at other residential sites within Philadelphia where a similar system can be replicated consisting of both the RWH system as well as the agricultural facility. <br/> <br/>Description: Thesis (M.S., Civil engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4125 Title: In-situ Grain Scale Strain Measurements using Digital Image Correlation <br/> <br/>Authors: Saralaya, Raghavendra Nataraj <br/> <br/>Abstract: Materials used in engineering structures fatigue and ultimately fail due to the various applied loads they are subject to, a process which compromises structural performance and potentially poses threats to society. Commonly employed theoretical models capable of describing and predicting deformation and failure are typically validated by relevant experimental results obtained from laboratory testing. However, such models are also often based on simplifying assumptions including for example homogeneous composition and isotropic behavior, since available experimental information relates primarily to bulk behavior. Metals are crystalline in nature and their failure depends on several parameters that span a wide range of time and length scales. Therefore, significant efforts have been made over the past decades to investigate the mechanical behavior of polycrystalline metals by formulating important microstructure-properties relations. In this context, this thesis presents a framework to obtain reliable, non-destructive, non-contact, full field measurements of deformation and strain at the grain-scale of polycrystalline materials to assist the understanding of materials phenomena and contribute in the development of realistic mechanics models. To this aim, the method of Digital Image Correlation is used, adapted and expanded. Digital Image Correlation relies on images of the surface of tested specimens, components or structures and the identification of surface contrast patterns which are tracked as a function of deformation and are subsequently used to define displacements and strains. To quantify stains at the grain-scale, three different approaches based on Digital Image Correlation are described. The first involves the use of a commercial system adapted to make grain-scale measurements at the meso-scale (~4mm). A magnesium AZ31alloy was observed for this purpose and full field strain maps are reported. The second employs the same commercial system augmented with a long distance optical microscope to in-situ quantify strains at the tip of a propagating crack in a Compact Tension specimen of an Al2024 aluminum alloy subjected to Mode I loading and using a field of view of ~870 x 730 μm. Finally, the third approach uses an image series acquired from loading a stainless steel sample inside a scanning electron microscope equipped with a micro-tensile stage. Such information was post processed ex-situ and strains were obtained. The advantages and limitations of the proposed approaches are critically evaluated and future work is described to further enhance the reliability and repeatability of grain scale strain measurements using Digital Image Correlation. <br/> <br/>Description: Thesis (M.S., Mechanical engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4124 Title: Variable Fractional Digital Delay Filter on Reconfigurable Hardware <br/> <br/>Authors: Sangaiah, Karthik Ramu <br/> <br/>Abstract: This thesis describes a design for a variable fractional delay (VFD) finite impulse reponse (FIR) filter implemented on reconfigurable hardware. Fractionally delayed signals are required for several audio-based applications, including echo cancellation and musical signal analysis. Traditionally, VFD FIR filters have been implemented using a fixed structure in software based upon the order of the filter. This fixed structure restricts the range of valid fractional delay values permitted by the filter. This proposed design implements an order-scalable FIR filter, permitting fractionally delayed signals of widely varying integer sizes. Furthermore, the proposed design of this thesis builds upon the traditional Lagrange interpolator FIR filter using either a software-based coefficient computational unit or hardware-based coefficient computational unit in reconfigurable hardware for updating the FIR coefficients in real-time. Traditional Lagrange interpolator FIR filters have only permitted fixed fractional delay. However, by leveraging todays (2012) low-cost high performance reconfigurable hardware, an FIR-based fractional delay filter was created to permit varying fractional delay. A software/hardware hybrid VFD filter was prototyped using the Xilinx System Generator toolkit. The resulting real-time VFD FIR filter was tested using System Generator, as well as Xilinx ISE and ModelSim. <br/> <br/>Description: Thesis (M.S., Electrical engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4123 Title: Investigation into Compositional and Mechanical Property Differences of the Microstructure in Two Strains of Mouse Femoral Bone <br/> <br/>Authors: Patel, Melanie A <br/> <br/>Abstract: Hierarchical linkages of bone structure and mechanical properties at lower length scales to macroscopic properties remain poorly understood [1, 2]. Critically assessing the bone architecture at different length scales using a combination of advanced materials characterization techniques is necessary to study connections between bone structure and properties. The gap in understanding these linkages from higher length scales to microscopic features is clearly needed for assessing bone health. Oftentimes fracture risk is assessed using Dual-Energy X-ray Absorptiometry (DXA) to measure bone mineral density (BMD) [3]. Bone strength is not accurately described solely by BMD as evidenced by the fact that BMD only accounts for 60-70% of variation in bone strength [3]. More attention must be paid to understanding bone quality, looking at tissue and matrix level composition as well as geometry, assessing tissue quantity and distribution [4]. This research is preliminary work aimed at establishing methodologies for reliably assessing bone composition and mechanical structure at the microscale. Two strains of inbred mice were chosen as the bone model because they offer an identical genome within a strain and are well-established in bone disease research [5]. The bulk of this research focuses on using Raman spectroscopy to assess compositional differences between two strains of inbred mouse femoral bone. These strains were selected because of their known macroscopic property differences. Looking at the postero-lateral cortex, areas of newly formed bone and matured bone are sampled using line maps. This captures the entire formation process of bone from deposition to resorption. Particular attention was paid to impurities of the crystal lattice, carbonate and monohydrogen phosphate. Typically, B-type carbonate substitution is studied since it makes up the bulk of impurities in the phosphate lattice [2]. This research investigated monohydrogen phosphate impurities as well, looking at the maturation process of the mineral across the bone cortex. Mineral to matrix ratios were also assessed to determine peak level of mineralization in each strains. 2-D maps of mineral to matrix composition gave more insight into the bone formation process between strains. Lastly, nanoindentation tests were performed to elucidate the modulus of the material from the postero-lateral cortex, again sampling bone from the depositional edge to the resorption edge. This gives a good picture of the difference in modulus between newly laid down bone versus fully mineralized bone. The AJ strain should show an increased mineral to matrix ratio and modulus since it has a higher ash content versus the B6 strain. The mineral maturation process in both strains is not well known so it will be interesting to see which strain has higher level of impurities in the crystal lattice. <br/> <br/>Description: Thesis (M.S., Materials engineering)--Drexel University, 2006. http://idea.library.drexel.edu/handle/1860/4122 Title: Multitasking Ability in Multiple Sclerosis: Can it Inform Complex Behavior? <br/> <br/>Authors: Morse, Chelsea <br/> <br/>Abstract: Cognitive dysfunction is one of most disabling features of MS, occurring in about 43-65% of MS individuals, and has been shown to be associated with difficulty maintaining employment in MS. A review of the literature demonstrates that previous domain-specific approaches to examining the effects of cognitive impairment on employment have not adequately explained high unemployment rates in MS. Performance on a more complex task that integrates multiple cognitive domains may be a useful predictor of vocational functioning among individuals with MS. Evidence for a more complex and integrated cognitive task comes from studies assessing patient self-report, which demonstrate that individuals with MS have difficulties with job functions including planning, problem solving, and organizing. Together these abilities support a function termed multitasking. Multitasking ability has not been fully examined in MS, and this study will initiate the first examination of the relationship between multitasking and vocational functioning. The study consisted of two specific aims; 1) to examine multitasking ability in MS, and 2) to examine the relationship between multitasking ability and vocational functioning. It was hypothesized that a percentage of individuals would be impaired on the multitasking measure. It was hypothesized that an inverse relationship would exist between multitasking ability and self-reported level of difficulty multitasking at work. Finally, it was hypothesized that individuals who were unemployed at the time of the study would demonstrate significantly more multitasking impairment and report higher level of difficulty with multitasking related tasks and abilities at work than individuals who were employed. Demographic and disease characteristics were coded, and the measures analyzed in the present study included: 1) neuropsychological measures of executive functioning (PASAT; Trail Making Test; COWAT; Oral Symbol Digit Modalities Test; Zoo Map Test); 2) measure of multitasking ability (Modified Six Elements Test, SET); 3) measures of physical functioning (Nine-Hole Peg Test; Timed Walk Test); 4) measure of difficulty experienced with multitasking at work (Structured Interview of Multitasking at Work); and 5) measures of psychosocial functioning (Beck Depression Inventory-II; Chicago Multiscale Depression Inventory; Fatigue Severity Scale; MS Quality of Life-54). Vocational groups were analyzed by two methods: 1) unemployed (UE) and employed (E) individuals; and 2) individuals who had reduced their work hours since being diagnosed with MS (CB), and those who had not reduced their work hours (S). In a sample of 30 participants with confirmed MS, multitasking ability was characterized by three performance measures shown to be independent of each other and sensitive to multitasking impairment. No significant relationship was found between performance on the SET and self-reported level of difficulty multitasking at work. Both UE and CB participants demonstrated more multitasking impairment than respective E and S participants (p=.05). Significant group differences in level of difficulty beginning new projects at work and rate of performance at work were found between UE and E participants. Significant group differences in fatigue and rate of performance at work were found between CB and S participants. Together, level of fatigue interference and multitasking ability predicted vocational group placement with 76.7-77.8% accuracy. The current study initiated the first theoretically based characterization of multitasking ability in MS. Multitasking was identified as a significant and independent predictor of vocational functioning, whereas performance on neuropsychological measures were not. Results can be utilized in vocational rehabilitation efforts to both modify the structure of an individual’s work environment and in making recommendations for vocational placement. Future research could continue to explore the clinical utility of measuring multitasking ability as related to employment, using more ecologically valid measures of multitasking ability and extending studies to examine the contribution of multitasking to other activities of everyday functioning. <br/> <br/>Description: Thesis (M.S., Clinical psychology)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4121 Title: Development of a Unique Surface Magneto-Optical Kerr Effect Magnetometer to Correlate Magnetism and Structure in Fe-Fe3O4 Thin Film Bilayers <br/> <br/>Authors: McDonald, Ian Joseph <br/> <br/>Abstract: As the automotive industry moves steadily toward electric vehicles, there is an increasing need for more efficient electric motors. Currently, the state of the art in electric motor design is limited by silicon-steel laminations that restrict 3-dimensional flux-carrying capability. Oxide-coated ferrous powder metals offer the electrical resistivity and magnetic flux density needed for advanced electric motor design, but coating compatibility and performance are still the subject of much research. Here we have designed a unique magnetometer capable of characterizing this system in thin film form as well as future material systems. Additionally, we examine the microstructure and magnetic properties of Fe - Fe3O4, a promising system for this application. This study explores the structural compatibility between the core and coating material, as well as the magnetic hysteresis of the resulting composite, using a combination of electron microscopy and surface magneto-optical Kerr effect (SMOKE) magnetometry. We have designed a customized magnetometer with the ability to perform hysteresis measurements in a longitudinal geometry under magnetic fields up to 8 kOe with the option of adding modular improvements for in situ electric field application. This instrument allows for both static and dynamic measurements of thin film samples with high surface sensitivity. Structure-property relationships can be determined through this magnetic characterization and associated microstructural information provided by electron microscopy. The characterization of this system in thin film form will inform the eventual production of coated ferrous powders with improved electromagnetic properties. <br/> <br/>Description: Thesis (M.S., Materials engineering)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4120 Title: Romantic Rendering: Romanticism in Visual Stylization And Story Conception in 3D Animation <br/> <br/>Authors: Littlejohn, Simon Mason <br/> <br/>Abstract: Romanticism emerged in the mid-18th century as a way to transport the audience to a setting that couldn’t be experienced in normal life. Its themes dealt with epic depictions of nature, and emphasized emotion over reason. While there was no one specific artistic style, the movement began to distance itself from idealistic representation and antiquity, and moved toward more Baroque sensibilities that emphasized form and color. The study of Romanticism and how its effects can be applied in storytelling and visualization present both opportunity and challenge. Translating the look, feel, and overarching effects of Romanticism into a digital time based narrative poses unique and challenging possibilities in storytelling and artistic direction as it pertains to 3D animation, and can aid in the creative process and visualization. <br/> <br/>Description: Thesis (M.S., Digital Media)--Drexel University, 2012. http://idea.library.drexel.edu/handle/1860/4119 Title: Feasibility of Inkjet Printing as a Viable Solar Cell Fabrication Method <br/> <br/>Authors: Lee, Brandon Scott <br/> <br/>Abstract: In this study, the flexible polymer substrate polyethylene naphthalate (PEN) was modified under two different plasma chemistries, namely helium-oxygen (He-O2) and helium-water vapor (He-H2O) plasmas at atmospheric pressure and room temperature. Surface changes related to wettability, chemical functionalization, surface energy, and morphology after plasma treatment were investigated using water contact angle (WCA) goniometry, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Each plasma resulted in a more hydrophilic PEN surface, with WCA decreasing by 68% and 85% for He-O2 and He-H2O plasma treated PEN, respectively, after only 1.0 second of exposure. An aging study of plasma treated PEN shows an increase in WCA that is still 30° lower than that of the as-received PEN after one month. XPS and AFM results show that improved wettability of the plasma modified PEN is due to the oxidation of the surface and not due to the increased surface roughness. To promote a roll-to-roll process of tmospheric plasma treatment and inkjet deposition, printing was performed using the conductive polymer poly(3,4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS) on the as-received and plasma treated PEN surfaces where the shape and morphology of the lines were studied. Each plasma treated PEN surface exhibited well-defined, uniform inkjet-printed lines due to the improved wettability and increased surface energy. After scanning electron microscopy (SEM) analysis of the PEDOT:PSS dispersion of a single drop on each substrate, the He-H2O plasma treated surface led to less agglomeration of PEDOT:PSS and a more homogeneous drop deposit. This study also focused on the feasibility of inkjet printing organic solar cells consisting of an active layer of poly(3-hexylthiophene):phenyl-c61-butyric acid methyl ester (P3HT:PCBM) on zinc oxide (ZnO) coated indium tin oxide (ITO) glass slides. The inkjet printing frequency, drop spacing, and effect of multiple layers were investigated by analyzing optical images of the inkjet printed P3HT:PCBM active layers. From these images the optimal parameters were determined and consisted of 1.5 kHz inkjet printing frequency, 65 μm drop spacing, and two layers printed in a crossed pattern. After determining the optimal parameters, solar cell testing was conducted on the inkjet printed organic solar cells. The solar cell testing consisted of using a solar simulator in order to measure the absorption spectrum for the inkjet printed P3HT:PCBM films and the I-V curves for the inkjet printed organic solar cells. From the I-V curves generated it can be seen that the two layers crossed organic solar cell provided the best results. <br/> <br/>Description: Thesis (M.S., Mechanical engineering)--Drexel University, 2012.