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/1860/3147 Title: High glucose and glycated substrates alter endothelial cell shape change response to shear stress <br/> <br/>Authors: Kemeny, Steven Frank <br/> <br/>Abstract: Endothelial cells line the walls of all blood vessels, where they maintain homeostasis through control of vascular tone, permeability, inflammation, and growth and regression of blood vessels. Endothelial cells are mechanosensitive to fluid shear stress, and hyperglycemia, a hallmark of diabetes, affects endothelial cell function. Clinical evidence suggests interaction between mechanics and high glucose, since diabetic patients have accelerated atherosclerosis at locations of disturbed blood flow. The central hypothesis of this thesis is that high glucose conditions alter endothelial cell adhesion strength and response to fluid shear stress. Two systems were developed to study endothelial cells under shear stress: microfluidic channels and parallel plate system. These systems were successfully designed to apply constant laminar stress onto endothelial cells. However due to inconsistencies and challenges with access to cells inside microchannels, the parallel plate system was used for experimentation. Endothelial cell adhesion strength was tested and cells cultured in high glucose were found to have a response dependent with attachment time. The initial adhesion strength after 6 hours of attachment was higher than low glucose but after 48 hours high glucose adhesion strength was less than low glucose. Separately it was found that substrate glycation had no effect on endothelial cell adhesion strength after 48 hours of attachment. Endothelial cell elongation and alignment was reduced in high glucose and prevented when the cells were grown on glycated collagen substrates. The native collagen and low glucose condition showed the most actin fiber alignment. High glucose reduced alignment only slightly, whereas glycated collagen prevented alignment. This research furthers our understanding of the combine effects of hyperglycemia and shear stress on endothelial cells. Futures studies into the mechanisms of endothelial cell shape change will help elucidate the causes. By understanding the affected pathways, atherosclerosis treatments for people with diabetes can be directly tailored, which would increase efficacy and reduce side effects. http://idea.library.drexel.edu/handle/1860/3138 Title: Traffic rerouting optimization in network recovery: a performance study <br/> <br/>Authors: Bao, Fei <br/> <br/>Abstract: In recent decades, the Internet has evolved from a special purpose computer network to a central platform of our daily communications. As it takes an increasingly important role in our everyday life, network reliability becomes even more critical. This is also one of the reasons why the Internet has been widely ubiquitous, due to its recovery ability. Internet protocol (IP) routing, such as Open Shortest Path First (OSPF) protocol, updates the forwarding tables to reflect alternative routes when the network topology changes. Due to the time consumed by the rerouting process after a failure, most recovery mechanisms are proposed to be proactive instead of reactive [1], [2], [3], [4], [5]. That is because in proactive approaches backup paths are preconfigured while reactive schemes such as that of OSPF usually are too slow to satisfy the recovery time requirements. After failures, all the traffic is moved to the backup path. After the traffic is transferred to the backup path, the fault on the primary path is r paired. Following the repair of the primary path, the trafficmay or may not be switched back to the primary path. There are two important points that need to be considered when deciding on rerouting traffic: i) the primary path may be flapping (fails again), ii) traffic rerouting cost may be too high. In this thesis, we investigate the performance of a mathematical model for traffic rerouting after repairs. Our contribution is to verify the the optimal traffic rerouting threshold-type control algorithm with simulations and an experiment. The simulations were performed in OPNET and the experiments were built on Sun VM VirtualBox technology. http://idea.library.drexel.edu/handle/1860/3137 Title: Market structure in banking and the bank lending channel: evidence from the bank-level data in Asian and Latin American countries <br/> <br/>Authors: Li, Yuan <br/> <br/>Abstract: The market structure of the global banking sector has changed dramatically in recent years. Since the mid-1990s, Asian and Latin American countries have experienced deregulation, foreign bank penetration, and an accelerated process of consolidation and competition in the banking sector. This thesis examines how the recent changes in concentration and competition in Asian and Latin American banking sectors have affected the monetary policy transmission mechanism, while specifically focusing on the bank lending channel. The first essay examines the relationship between increased consolidation in banking and the bank lending channel of monetary policy in 20 Asian and Latin American countries, using unique bank-level panel data for the period from 1996 to 2006. The estimation results provide consistent evidence that as concentration in banking increases, the bank lending channel weakens, causing monetary policy to be less effective. This is found to be true even after accounting for the effects brought by changes in loan demand and financial constraints faced by individual banks of varying size, liquidity and capitalization. To my knowledge, this study is the first to use bank-level balance sheets and income statement data to study this issue at a global scale. Doing so enables this study to contribute to the literature in two different ways. First, the effects of the supply-side bank lending channel from those of the demand-side interest rate channel can be identified more accurately. Second, any systematic differences in the impact of consolidation in banking on the monetary policy transmission mechanism across banks of different types and levels of financial strength can be tested properly. This essay also discusses potential explanations for the findings that increased consolidation reduces the sensitivity of bank lending to changes in monetary policy shocks. The second essay examines the evolution of banking competition and how banking competition affects the transmission of monetary policy through the bank lending channel. I use annual bank-level panel data for commercial banks of 10 Asian and 10 Latin American countries from 1996 to 2006. A two-step estimation procedure is applied. In the first step, the degree of banking competition in each country and year is measured using the methodology proposed by Panzar and Rosse (1987). The result shows that the banking sector in these emerging economies has experienced a significant increase in competition. In the second step, the empirical results on the loan equation provide consistent evidence that increase in banking sector competition has weakened the transmission of monetary policy through the bank lending channel in the Asian and Latin American countries. It is found that overall, banking competition is higher in Latin America than in Asia and the bank lending channel is weaker in Latin America than in Asia. The third essay investigates the relationship between banking concentration and competition. According to the traditional structure-conduct-performance paradigm, greater concentration results in less competition in the banking industry. On the contrary, the efficiency structure hypothesis indicates that higher concentration may cause banks to become more efficient and competitive. Additional factors such as foreign bank penetration, information technology, and asymmetric information may also affect banking competition. Furthermore, the measurement issue could also contribute to the contradictory relationship between the two. In the literature, banking concentration is measured as the market share held by the largest banks using the Herfindahl index, the concentration ratio CR3 (the largest 3 banks share of assets) and CR5 (the largest 5 banks share of assets), while banking competition is often measured as a bank’s ability to affect the price in the market for bank loans using the Panzar and Rosse approach. This paper studies this issue empirically using aggregate panel data on the banking industry and macroeconomic environments from a total of 14 Asian and Latin American countries during the period from 1996 to 2006. The empirical results provide evidence that banking concentration reduces banking competition in the Asian and Latin American countries for our sample period. http://idea.library.drexel.edu/handle/1860/3136 Title: A model-based fault detection and diagnostic methodology for secondary HVAC systems <br/> <br/>Authors: Li, Shun <br/> <br/>Abstract: In the U.S., buildings consume 39 % of primary energy, of which, 13.5% is attributed to HVAC systems. Faults, arising from sensors, equipment, and control systems in building HVAC systems, are major contribution to the energy wastage and equipment failures in buildings. Among all HVAC systems, the focus of this study is on air handling units (AHU) which greatly affect building energy consumption and indoor environment quality. The first stage of this study is to develop and validate an AHU and building zone simulation model to produce fault free and faulty data for a large variety of faults with a range of fault severities that can be used to assess the performance of AHU automated fault detection and diagnosis (AFDD) methods. Experiments for three different seasons are designed and implemented in a full scale test facility to collect AHU operation data with known faults. The second stage of this study is to develop a new data-driven AFDD methodology using Principal Components Analysis (PCA) method. Two methods, namely, Wavelet-PCA and Pattern Matching-PCA are developed in this study. The feasibility of using these two methods for AHU AFDD is examined using both experimental and simulation data. Keyword: Air handling units (AHU), automated fault detection and diagnosis (AFDD), model validation, Principal Components Analysis (PCA) http://idea.library.drexel.edu/handle/1860/3135 Title: An analysis of cyclic tidal deposits: statistical time series properties, extraction of earth-moon parameters, and observed intertidal sedimentation <br/> <br/>Authors: Coughenour, Christopher Lynn <br/> <br/>Abstract: Tidal rhythmites/bundles are facies that can encode process-related depositional information and luni-solar periodicities. These deposits have been widely recognized in the stratigraphic record. Detailed empirical studies of deposition in the modern regime, and more precise analyses of the frequency content of tidalite signals, can facilitate more detailed sedimentological interpretations and extraction of paleotidal parameters. In this study, rhythmic sedimentation at two unique fluvio-estuarine transitions in a macrotidal estuary is discussed. Further work on general rhythmite signals addresses time series properties and describes a method to extract primary tidal constituents. A formulation is then provided to calculate past day length and Earth-Moon distance from sub-yearly data. Turnagain Arm, Alaska possesses a number of glacial meltwater streams that drain transversely into the fjord/estuary, forming unique fluvio-estuarine depositional systems. Two such systems, one located within a small embayment in a broad alluvial valley and the other where a stream debouches into mudflats directly from mountain slopes, were studied and compared. The embayed site exhibited slower deposition rates, finer-grained sediments with pronounced mud drapes, and slower evolution than the open-flat transition. Position in the tidal frame was a sensitive parameter determining deposition, with lower regions more subject to fluvial erosion (seasonal-scale), and higher regions only exhibiting spring-cycle deposition. Deposition is well-approximated by a linear flow model. Grain size statistics were gathered and revealed laminae thicknesses correlated to median grain diameter. Time series properties of sub-yearly tidalite records were investigated and numerical experiments were performed utilizing maximum entropy and periodogram spectral analysis methods. Analyzing precision as a function of record length and missing deposits reveals approximately 90-95% precision can be obtained for records of 6-7 neap-spring cycles missing few deposits. Amplitude modulation properties of tidalite signals facilitate extraction of M2 and S2 frequencies and, thus, relative lengths of the lunar and solar days. Employing these analytical methods and fundamental physical relations, the past sidereal period and day length can be calculated in consistent temporal units, along with Earth-Moon distance. A calculation using Carboniferous tidalites reveals an average lunar recession rate of 0.740 + 0.069 cm/year and day length of 23.572 + 0.379 hours. http://idea.library.drexel.edu/handle/1860/3134 Title: Combining holographic patterning and block copolymer self-assembly to fabricate hierarchical volume gratings <br/> <br/>Authors: Birnkrant, Michael J. <br/> <br/>Abstract: The top-down nanomanufacturing technique is approaching its theoretic limits and processes such as e-beam lithography are extremely costly. In contrast, the bottomup method such as self-assembly can easily reach nanometer (even sub-nanometer) feature sizes. One drawback of self assembly, however, is the di culty to achieve large scale, defect-free structures. Combining the top-down and bottom-up methods in one system can lead to novel hierarchical nanostructures with tailored properties and this approach is generally referred to as \top-down helps bottom-up." While most of the existing systems deal with (quasi) two-dimensional patterning, partly due to the demands from semicomductor industry, in this dissertation, we demonstrate that three-dimensional, dynamic tunable, optical volume gratings can be manufactured via combining holographic patterning (HP) and block copolymer (BCP) self-assembly into one system. A number of semicrystalline homopolymers and BCP have been successfully patterned into one-dimensional and two-dimensional optical structures. In the onedimensional homopolymer case, a Bragg re ector structure with continuous alternating layers of patterned polymer and the crosslinked resin were formed. The result of combining HP and BCP was a hierarchical structure fabricated from a homogenous solution in one step. HP formed 200 nm periodic lamellar structures, con ning a BCP to 100 nm domains. Subsequently, the BCP self-assembles into a lamellar structure with a period of 21 nm. This system provides an interesting basis for studying the thermo-optic behavior of the hierarchical volume grating formed by combining top-down manufacturing and bottom-up self-assembly. Upon heating and cooling a unique thermal switching occurred that can be attributed to the melting/phase separation that the BCP undergoes within the con ned region of the volume grating. There are at least ve advantages of this novel nanomanufacturing approach. First, two di erent nanomanufacturing techniques are seamlessly combined together and the resulting hierarchical structures span from a few nm to the 200 nm scale. Second, by combining these two techniques, the shortcomings of each method can be overcome. Third, this hierarchical structure can be fabricated in a few seconds. Fourth, the HP method enables the fabrication of a multiple layered structure, which is critical for three-dimensional nanodevice applications. Fifth, a variety of twodimensional and three-dimensional nanostructures can be readily achieved by changing the HP laser set-up and BCP structures. http://idea.library.drexel.edu/handle/1860/3133 Title: Systematic data-driven modeling of cellular systems for experimental design and hypothesis evaluation <br/> <br/>Authors: Zhao, He <br/> <br/>Abstract: Despite the rapid growth in biological information, drug development is still limited by our ability to understand complex cell systems that are involved in diseases. The need to model complex cell processes at many different scales requires (a) quantitative measurements from experimental techniques in cell biology and (b) mathematical modeling approaches to organize and structure information, test and validate hypotheses for the new phenomena. The goal of my thesis work was to maximally obtain and interpret information on the dynamic behavior of cellular systems using an optimal combination of computer simulations and experimental observations. I focused on two realistic biological problems to develop and demonstrate methods to generate high quality hypotheses through mathematical modeling to define the optimal next step for experimental and clinical trial design: (1) I developed a hybrid stochastic model to simulate microtubule dynamics and anti-cancer drug effects on microtubules. Model parameters were taken directly from experimental observations, and model validation was conducted against published experimental data. Our work revealed limitations in previous experimental methods to measure microtubule kinetics. (2) I developed a quantitative biological system modeling scheme to interpret flow cytometric data, and I validated this method experimentally. To do so, I designed a novel combination of protocols, assay technologies, and data analysis techniques to obtain plausible flow cytometric data. Multiple mathematical methods and reversed engineering methods, such as parameter estimation, sensitivity analysis, nonlinear regression, Akaike Information Criterion (AIC) were integrated to use a data-driven modeling to distinguish between different biological hypotheses. Our modeling and validation methodology can be generalized to apply to other biological problems with limited data. http://idea.library.drexel.edu/handle/1860/3132 Title: Actuation and control of microfabricated structures using flagellated bacteria <br/> <br/>Authors: Steager, Edward Brian <br/> <br/>Abstract: In this work methods of actuation and control of microfabricated structures are investigated using bacteria as configurable, scalable actuators. Bacteria offer many benefits as microfluidic actuators. They draw chemical energy directly from their environment, they can be operated in a wide range of temperature and pH, and literally billions of bacteria may be cultured within hours. Additionally, the well-documented responses of individual motile bacterial cells may be expected to scale up to arrays of cells. On this population scale, the cellular responses can be employed en masse creating controlled forces that actuate inorganic microfabricated elements. For these investigations the bacterium Serratia marcescens has been chosen. S. marcescens has properties that are particularly appropriate for engineering applications. When cultured on soft agar, the bacteria demonstrate a form of surface motility known as swarming. These investigations start with an experimental analysis of the swarming cell motility using a non-labeled cell tracking technique. The results of these studies reveal that the most energetic bacteria populate the progressing edge of the swarm. A technique of biocompatible microfabrication and chemical release of bacteria-driven microstructures is also presented. This method is used to pattern structure surfaces with the rigorous swarming cells by direct blotting. The self-coordinated motion of the cells is investigated for use as arrays of actuators. Control mechanisms are investigated to adjust rotational and translational motion using optical and electrical stimuli, respectively. The fundamentals of the electrokinetics are also investigated and integrated into a system demonstrating controlled manipulation of target objects and phenotypic chemical sensing. http://idea.library.drexel.edu/handle/1860/3131 Title: Computational and experimental study of spontaneous thermal polymerization of alkyl acrylates <br/> <br/>Authors: Srinivasan, Sriraj <br/> <br/>Abstract: This project is aimed at answering two unanswered fundamental and industriallyimportant questions: What are the species that initiate the spontaneous thermal polymerization of alkyl acrylates? What are the initiation mechanisms? Density functional calculations (B3LYP/6-31G*) level of theory was used to investigate mechanism of spontaneous initiation in thermal polymerization of methyl, ethyl and n-butyl acrylate. Flory and Mayo mechanisms of self initiation were investigated. Potential energy surface maps for [4+2] and [2+2] cycloaddition reactions were constructed. It was found that diradical mechanism of self-initiation occurs in spontaneous thermal polymerization of alkyl acrylates, with the diradical species in a triplet spin state Hydrogen transfer from the triplet diradical intermediate was found to be the lower energy pathway in comparison to hydrogen abstraction from triplet diradical intermediate and is proposed to generate monoradicals for initiating polymerization. DFT calculations was used to identify the occurrence of diradical mechanism of selfinitiation in spontaneous polymerization of MMA and that the diradical exists in a triplet state. This provided theoretical evidence to existing postulate and experimental observations. Experiments of spontaneous thermal homo-polymerization of methyl, ethyl and n-butyl acrylates in the absence of any known added initiators were conducted at 120 and 140 oC in xylene, dimethyl sulfoxide (DMSO) and cyclohexanone and in the presence of nitrogen and air in a 1 liter reaction calorimeter (RC1 Mettler Toledo). Highest initial monomer conversion was found to occur in cyclohex anone and lowest in DMSO. Highest average molecular weight polymers were found to form in DMSO. Higher initial monomer conversion and lower average molecular weight polymers was found in air than nitrogen. Mass-spectrometric studies were used to identify that the two dominant mechanisms of chain initiation and transfer in spontaneous thermal polymerization of methyl and n-butyl acrylate are monomer self-initiation and ¯-scission respectively. The initiation rate constants estimated from macroscopic process modeling and experimental monomer conversion, numberaverage and weight-average molecular weight measurements was in good agreement with rate constant for triplet diradical formation predicted via quantum chemical studies. http://idea.library.drexel.edu/handle/1860/3130 Title: Mesoporous materials for dental and biotechnological applications, curcumin polymers and enzymatic saccharification of biomass <br/> <br/>Authors: Mukherjee, Indraneil <br/> <br/>Abstract: The nonsurfactant templated sol–gel route has been demonstrated to be a cost effective, green and biofriendly pathway to obtain mesoporous materials with an interconnected network of wormhole–like pores. It involves the formation of a metal–oxide network around an inert organic molecule (e.g., sugar molecules) which functions as a template and can be later removed by simple extraction with water or other solvents. This research describes the preparation of mesoporous zirconia and organo–functionalized silica by the acid–catalyzed nonsurfactant templated sol–gel route and also describes the use of sublimation as a method for the template removal. Mesoporous silica nanospheres with tunable particle size were also prepared by modifying the base–catalyzed Stober process with the addition of various sugar molecules as templates. The materials were characterized using TGA, nitrogen adsorption–desorption, SEM, TEM, XRD and FTIR. The application of nonsurfactant templated mesoporous materials in the area of enzyme encapsulation and stabilization is explored in this research. A novel ‘double encapsulation’ approach that enables a sol–gel encapsulated protease to retain 60 % of its original activity after 4 weeks in harsh environments, such as high pH buffer and laundry detergent, is demonstrated. The need for aesthetic, as well as durable, dental restorations has led to extensive research in the area of dental composites. This study examines the use of nonsurfactant templated mesoporous materials as fillers in dental composites. Mesoporous materials of irregular morphology prepared by acid–catalyzed sol–gel routes as well as mesoporous silica spheres prepared via base–catalyzed sol–gel reactions were both employed as fillers in experimental dental composites. This research led to the development of novel ‘dental monomer templated mesoporous materials’, which were also evaluated as fillers in dental composites. Various approaches, such as dense packing, addition of nanosilica and spherical fillers, etc., were employed to fabricate nanocomposites with improved mechanical properties. The composites were evaluated using flexural and compression testing. Curcumin, the ground rhizome of Curcuma longa, a common South Asian herb has attracted much attention due to its chemopreventive and anti–inflammatory properties. This research describes the synthesis of a series of poly [(arylenedioxy)(diorganylsilylene)]s via polycondensation between curcumin and various diorganodichlorosilanes. These novel polymers incorporate the β–diketone unit of curcumin as well as the Si–O bond in the backbone. The polymer structure was characterized by means of 1HNMR, FTIR and elemental analysis, while GPC results showed high molecular weights. Preliminary cell culture results suggested lack of cytotoxicity, which is important for potential applications, such as implants and tissue engineering scaffold materials. The unique and interesting thermal behavior of these polymers was studied by DSC. The technology of enzymatically degrading biomass into simple sugars, such as glucose, is a critical step towards viable production of bio–based ethanol from non–food related sources. This research demonstrates the use of a biosensor–based diabetic blood glucose monitor as a rapid glucose detector and compares it to time consuming UV assays that are currently employed in research laboratories. Pretreatment of wood shavings with ferric chloride, followed by treatment in cold NaOH/urea solution was found to significantly enhance glucose production upon enzymatic hydrolysis. Finally, accounts of exploratory experiments in the areas of thermally crosslinkable high temperature elastomers and inorganic–organic hybrid materials are provided in the appendix sections of this thesis.