University of Maryland, Baltimore County
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Dynamic Document Clustering Using Singular Value Decomposition
No full textDocument Clustering is a widely researched area in data mining. It is a technique of grouping similar documents based on a measure of similarity. Document Clustering forms an important aspect in Information Retrieval for improving precision and recall in search applications, navigation and presentation of search results. But due to the tremendous amount of features, textual data suffers from the Curse of Dimensionality. Moreover, adding new features increases the noise in the data. To address these issues, in this thesis we investigate the use of Singular Value Decomposition (SVD) and propose a sophisticated Document Clustering algorithm combining folding-in method and k-means algorithm, to efficiently store and dynamically incorporate new textual data into the existing cluster formations. We test our approach by introducing new documents in increments of 1%, 5%, 10%, 15%, and 20%. These new documents are added in two variations. One document set comprises of completely new documents and the other is formed by modifying the existing documents. Our method promises significant improvements in computation costs, storage costs and cluster quality compared to recomputing-SVD method. We also present a novel approach for retrieving documents of interest to the users. The user can choose documents using different window sizes either time windows or subset of documents. Our experimental evaluations show that the proposed method of document retrieval outperforms recomputing-SVD method significantly in computation time with promise of flexibility and good cluster quality
Changes in Retirement Decisions: Determinants of Plans and Timing
No full textPurpose: This study examined dynamic factors in a worker's background, resources, jobs or health which influence their expectations about future decisions to work or retire at ages 62 or 65, as well as how these influences and expected timing change as the individual approaches retirement. Design and Methods : Employing a conceptual framework based on Andersen's (1995) model of health care utilization, the first research question used Generalized Estimating Equations (GEE) to determine which predictors were associated with workers' expected retirement timing. The second question examined changes in expectations over time in response to changes in predictors, using a two-level approach modeled on Singer and Willett (2003). Utilizing the Core sample of the Health and Retirement Study (HRS); data on 5,989 individuals (48.3% female) were examined longitudinally across seven waves, 1992 and 2006. Results: For research question one, female gender was associated with a lower expectations to continue working at both early (62), and normal (65) retirement ages. Non-married status had a similar effect for 62 but not for age 65. Differences emerged among sub-groups with non-married females reporting greater plans to continue working at both retirement ages; non-married blacks however were less likely to report plans to continue working at age 65 only. Non-whites with poorer subjective health or health that limited work were less likely to expect to work at age 62, but there was no impact on plans for age 65. Changes were also important. Leaving married status was linked with changes in plans to work at 65 but not 62. Gaining employer sponsored benefits (pension and health coverage) increased likelihood of continued work at both ages. Implications: Findings confirmed that known predictors of retirement decisions are also associated with workers' expectations well before retirement age is reached. Andersen's model was useful for understanding the dynamic process leading up to retirement. Results also support the importance of employer sponsored benefits, such as pension and health insurance, on changes in plans as individuals approach retirement. Policy makers interested in prolonging work lives should look to modifiable factors (pensions and health insurance), which may impact retirement timing
Extensible Dynamic Form (XDF) for Supplier Discovery
No full textDiscovery of suppliers (supplier discovery) is essential for building a flexible network of suppliers in a supply chain. The first step for supplier discovery is to collect manufacturing capabilities of suppliers and requirements of customers. In traditional e-marketplaces, online form interfaces are typically used to collect the requirements and capabilities. However, those forms are mostly lack of flexibility to capture a variety of requirements and capabilities in a structured way. In this thesis, we propose new innovative form architecture called eXtensible Dynamic Form (XDF) to facilitate data collection process of supplier discovery. This architecture provides several key innovations including: 1) architecture for users (suppliers or customers) to create new structure of form for their own contents; 2) an intelligent search engine facilitating users to reuse the existing form components 3) hierarchical representation of the requirements and capabilities as XML instances. Experimental results demonstrate that the proposed architecture is valuable for facilitating the supplier discovery proces
Miniaturized probes for cell microenvironment: development, characterization, and application of fluorescent oxygen-sensing microparticles
No full textOxygen concentration is a key parameter in tissue culture and tissue engineering. As such, oxygen diffusion through biomaterials plays an important role in maintaining healthy tissues. As such, oxygen is one of the most important cues within the cell microenvironment, playing a role in the regulation of cellular responses that concern such cellular phenomena as cell migration, proliferation, and apoptosis. Oxygen supply has become a limiting factor during the growth of highly metabolic tissues and large tissue masses, mainly as a result of insufficient vascularization and the low aqueous solubility of oxygen. In addition, limited oxygen supply has been linked to the propagation of bacterial infections due to bacterial detachment from biofilms within the body. Therefore, gaining an understanding of the cellular response to changes in soluble cues, such as oxygen concentration, through their microenvironment may potentially lead to optimized oxygen delivery within biomaterials, improved methods to control cell behavior in engineered tissues, and improved therapies to treat bacterial infections. However, mapping oxygen concentration and characterizing oxygen transport in three-dimensional culture systems has proven difficult due to the lack of adequate tools. To address this need, we have developed oxygen-sensing microparticles that can be suspended through the volume of a transparent biomaterial and measure oxygen concentration and characterize oxygen transport in a non-invasive manner. These microparticles sense oxygen by fluorescence quenching of the oxygen-sensitive fluorophore tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride, or Ru(Ph2phen3)Cl2, while immobilized onto silica carriers. These microparticles are geared towards applications in both mammalian and bacterial cell culture where oxygen concentration and transport can be directly correlated to cell function. We provide a detailed description of the synthesis processes of these microparticles, their characterization, and calibration. Subsequently, we show that they are suited for their intended applications by demonstrating that they can be suspended through the volume of a biomaterial and are compatible with both mammalian and bacterial culture. Finally, we propose methodologies for the intended applications of the microparticles regarding the correlation cell function to oxygen transport during 3D mammalian cell culture and bacterial biofilm culture. This correlation will mark the first time oxygen concentration is linked to cellular functions that it directly impacts during three-dimensional culture
Lesson Study: A Professional Development Approach for University English Language, Mathematics, and Science Teachers
No full textThe purpose of this study was to establish and analyze the impact of a collaborative professional development program across the disciplines among the faculty of the Foundation Program at the Petroleum Institute in Abu Dhabi, United Arab Emirates through the use of a lesson study model. Though widely used among teachers in the same discipline, lesson study has also been identified as a means of bridging the professional expertise of teachers across disciplines. This study is the first to report on the use of lesson study to integrate language and content instruction in a university preparation program. In this study, science, mathematics, and English teachers collaboratively developed and taught integrated lessons, observed these lessons being taught, discussed their impact upon students, and revised and re-taught the lessons with a new group of students. In the process, the teachers also reflected upon their own teaching practices and those of their colleagues in other disciplines by working together in a supportive and enriching cross-disciplinary environment. As a result, they were also able to provide instruction that helped make clear to students the relationships among the courses in which they were enrolled. Although time-consuming, the lesson study process was viewed as a valuable form of professional development. It promoted collaboration, increased curricular cohesion, and provided opportunities for teachers to reflect on their own practice and learn from each other. Recommendations for further study of lesson study and for extending the application of this model of professional development are also provided
QUANTIFYING THE EFFECT OF HYDRODYNAMIC SHEAR ON POLYMORPHONUCLEAR LEUKOCYTE ADHESION TO STAPHYLOCOCCUS AUREUS BIOFILMS
No full textStaphylococcus aureus (S. aureus) is a gram positive pathogen known to cause multiple infectious diseases for both animal and humans, and is responsible for community-associated and nosocomial infections. S. aureus possess the ability to form biofilms, which have a profound ability to adapt and thrive in undesirable conditions as well as resist antibiotic treatment. Recent studies suggest that polymorphonuclear leukocytes are able to attack S. aureus biofilms, thus implying the innate immune system indeed has mechanisms to respond to S. aureus biofilms. We determined if shear affected both the structure of the biofilm as well as the number on PMNs adhering to the S. aureus biofilm, and quantify where these cells adhere with respect to the biofilm. We conclude that shear does not have a significant effect on the number of cells adhering, but affects the depth of penetration in a maturing S. aureus biofilm
Face Recognition using Gabor Jets for Images of Mass Disaster Victims
No full textMass disasters such as earthquakes, tsunamis, floods, landslides, blizzards and other natural calamities affect a large number of people in a short time duration. After such emergencies occur, people affected need medical aid and are admitted into hospitals. In such conditions, it becomes difficult to locate one's family members and friends. Hospitals and medical centers take triage pictures of people getting admitted for their records. The content of these images could be very disturbing for some people to see. Such pictures cannot be posted on notification walls or internet websites for people to identify their missing family members or friends. This thesis addresses this problem by developing methods for searching triage image databases using query images provided by friends or family of missing people. The dataset for this thesis consist of mug shot images of people affected by calamity. These are also called the triage images. The test dataset consist of clean or regular mug shot images of people. In order to automate the process of locating missing people, our thesis has a goal of developing a face recognition system based on Gabor Jets to match a clean image to the existing triage images. Here, a clean image means a mug shot image of a person where all features such as eyebrows, eyes, nose, lips, skin, ears, etc. are seen. The system aims at pulling up the exact match from the triage dataset into the top 'N' matches filtered out based on a similarity measure. Face recognition has been studied for clean images, where all features are visible. We have developed a system to work on the domain of triage images by experimenting with existing Gabor Jets-based similarity measures and modifying the algorithm to best fit our needs
Modeling of the balloon-stent-vessel expansion mechanics
No full textThis thesis sought to develop a model to emulate coronary balloon-stent angioplasty. A model predictive of the radial expansion experienced by a balloon-stent-vessel system under internal pressure was developed. Seven parametric stent configurations modeled after the Boston Scientific TAXUStm Express2tm stent were generated in Pro/Engineer 4.0 which varied in strut cross section. These stents were expanded using finite element package ABAQUS/CAE 6.7 under non-linear, large deformation conditions. An elasto-plastic, Ramberg-Osgood material model for 316L stainless steel with two different work hardening exponents was used. Radial expansion vs. internal pressure data was collected in each simulation. The blood vessel expansion behavior was analytically developed using a hyperelastic model borrowed from existing literature. An area fraction model was used to assess the load transfer from the balloon external surface to the stent inner surface. The balloon, stent, and vessel models were combined and favorably compared to the manufacturing data that accompanied the TAXUS stent. It was found that stent strut cross section and material work hardening greatly affected the radial expansion-pressure curves. Balloon effects were found to be prominent and increased in severity as the stent unfolded. Vessel behavior was found to be relatively compliant compared to the stent, but with the inclusion of atherosclerotic plaque the simple rule of mixtures showed that the effective shear modulus of the vessel stiffened significantly. These results verify the feasibility of generating an accurate predictive model of balloon-stent-vessel expansion and serve as the foundation for future modeling
Combining Biological Knowledge with Sampling Know-How: Kinetic Space Modeling & Control Over Growth in Chlamydomonas reinhardtii
No full textMetabolic models aid in the rational genetic engineering and cultivation of valuable microorganisms, and genome-scale dynamic models of metabolism are highly desirable because they can describe time-based perturbations and complex enzymatic and gene interactions. However, kinetic modeling is considered challenging because of informational and computational limitations associated with parameterizing and solving large systems of nonlinear differential equations. We describe a methodology called `kinetic space' modeling, which utilizes the ample amount of available biological knowledge, while recognizing that biological constants required to parameterize dynamic systems are inherently uncertain, especially for less-characterized organisms. In this approach, Monte Carlo sampling is employed to generate ensembles of thousands of kinetic models allowable within known thermodynamic and experimental bounds. These ensembles are screened to identify models that replicate in vivoChlamydomonas reinhardtii<<</interest for production of biofuels and other value-added chemicals. The model comprised 4 organeller compartments and 369 metabolic reactions, and incorporated inhibition kinetics for highly regulated pathways (e.g. Calvin cycle). After generating and screening an ensemble of 1000 models, a model was identified that reproduced known nutrient exchange trends and observed shifts in growth precursors, energy stores, and intracellular metabolite contents under nitrogen deprivation. A control study was then executed to identify enzymes that exerted great control over growth-related fluxes and CO2 uptake, which revealed diffuse control over growth and suggested several gene targets for improved biomass accumulation
Novel Ring-Expanded Heterocycles and Nucleosides as Anticancer Agents
No full textThe research project was initiated after the discovery of potent, broad spectrum in vitro anticancer activity of parent ring-expanded nucleoside previously synthesized in this laboratory by my predecessors. The parent compound exhibited tumor growth inhibition in vitro in more than 50 human tumor cell lines at micro or submicromolar concentration levels (GI₅₀=10⁻⁵-10⁻⁶ ℳ and 10⁻⁵-10⁻⁷ ℳ respectively) with no apparent host toxicity. Later in our lab, the heterocyclic aglycon containing a long C₁₈ alkyl chain at N⁶ was also found to exhibit potent in vitro anti-cancer activity against prostate, breast, ovarian and lung cancers. In light of the promising biological results described above, this dissertation represents a continuation of the efforts in order to fully explore the anticancer potential of the compounds containing the 5:7-fused 4,6,8-triaminoimidazo [4,5-e] [1,3] diazepine ring system. The first part of my project concerns synthesis of a series of analogues with various substituents at the 1-position e.g., benzyl, para-methoxy benzyl, para-fluoro group, etc.) and/or 2-position e.g., halogen, methoxy, hydroxyl, amino, thiol group, etc.) and/or N⁶ -position ((e.g., alkyl, aryl, and aralkyl group, etc.) of the parent heterocyclic ring. The second part of my project is to synthesize a series of nucleoside analogues with ribosyl or (2-hydroxyethoxy)methyl substituent at 1-position (acyclic &ldquofat&rdquo nucleosides), along with alkyl, aryl, or arakyl substituents at the 6-amino position. The third part of my project is to explore anticancer activities as well as structure-activity relationships (SAR) of the above compounds against the speculated target enzyme DDX3, known to be involved in a number of cancers, including but not limited to breast, prostate and lung cancers. The anticancer screening against a variety of tumor cell lines was performed at the Greenbaum Cancer Center of the University of Maryland School of Medicine. A series of ring-expanded heterocyclic bases with modifications at N-1, and/or N⁶ as well as a series of ring-expanded nucleosides with modifications at N⁶ have been synthesized and tested against six different cancer cell lines. The biological results indicate that even without the &beta-ribose attached at N-1, the heterocyclic bases with various aglycons at N-1 exhibit promising anticancer activity.