Physical Sciences and Mathematics Commons^™

Temporal Synchronization Of Ca1 Pyramidal Cells By High-Frequency, Depressing Inhibition, In The Presence Of Intracellular Noise, Stephen A. Kunec

Dissertations

The Sharp Wave-associated Ripple is a high-frequency, extracellular recording observed in the rat hippocampus during periods of immobility. During the ripple, pyramidal cells synchronize over a short period of time despite the fact that these cells have sparse recurrent connections. Additionally, the timing of synchronized pyramidal cell spiking may be critical for encoding information that is passed on to post-hippocampal targets. Both the synchronization and precision of pyramidal cells is believed to be coordinated by inhibition provided by a vast array of interneurons. This dissertation proposes a minimal model consisting of a single interneuron which synapses onto a network of …

Experimental And Theoretical Study Of An Integrated Silicon Mach-Zehnder Interferometer For Chemical Sensing Applications, Yew Fong Hor

Dissertations

This thesis involves the design, fabrication and characterization of an integrated optical waveguide sensor. Prior to fabrication, design parameters of the waveguide need to be determined and optimized. The waveguide parameters such as waveguide dimension and the refractive index of the core and cladding are obtained from the single-mode cutoff frequency calculated using either analytical or numerical methods. In this thesis, details of analytical calculations to determine the cutoff frequency in terms of the waveguide parameters will be presented. The method discussed here is Marcatili's approximation. The purpose is to solve the scalar wave equation derived from Maxwell's equations because …

Instability Of Electrified Viscous Films, Knograt Savettaseranee

Dissertations

We examine the stability of a thin two-dimensional liquid film with a regular electric field applied in a direction parallel to an initially flat bounding fluid interface. We study the distinct physical effects of surface tension, van der Waals and electrically induced forces for a viscous incompressible fluid. The film is assumed to be sufficiently thin, and the surface tension and electrically induced forces are large enough that gravity can be ignored to the leading order. Our target is to analyse the nonlinear stability of the flow. We attain this by deriving and numerically solving a set of nonlinear evolution …

Development And Characterization Of Methodology And Technology For The Alignment Of Fmri Time Series, Carlo Ciulla

Dissertations

This dissertation has developed, implemented and tested a novel computer based system (AUTOALIGN) that incorporates an algorithm for the alignment of functional Magnetic Resonance Image (fMRI) time series. The algorithm assumes the human brain to be a rigid body and computes a head coordinate system on the basis of three reference points that lie on the directions correspondent to two of the eigenvectors of inertia of the volume, at the intersections with the head boundary. The eigenvectors are found weighting the inertia components with the voxel's intensity values assumed as mass. The three reference points are found in the same …

Two-Dimensional Reflectivity Polarization Elastometry Imaging Techniques (Piet) Of Soft Tissue, Hee Chuan Lim

Dissertations

A non-invasive polarized light reflection measurement method to measure the stretch of soft tissue, such as skin, is described. The technique utilizes changes in the reflectivity of polarized light intensity as a monitor of skin stretch. Measurements on in-vitro pigskin and invivo human skin show that the reflectivity of polarized light intensity increases linearly with stretch over a range. The changes in diffusive reflectivity properties of skin result from the alterations that take place in the roughness across the thickness of the skin layers due to stretch. Conceptually, as the roughness of a layer decreases with stretch, a smoother reflecting …

An Analysis Of Field Data For Evidence Of Anaerobic Degradation Of Pah And Btex Plumes At Manufactured Gas Plant Sites, Georgene Mortimer

Dissertations

Field data (including geology, hydrogeology, soil chemistry, groundwater chemistry, and aquifer characteristics) were analyzed at eight MGP sites located in the New Jersey Coastal Plain. These data were used to calculate biodegradation rate constants, which were then compared with laboratory microcosm data and published values. Isopleths were drawn from the field data to indicate the dominant biodegradation mechanisms at each of the sites, and stoichiometric calculations were used to determine the total capacity of the electron acceptors present to degrade the plume contaminants. In examining these data, the protocol described by the Air Force Center for Environmental Excellence (AFCEE) was …

Collaborative Problem Solving And Program Development Model, Joanna Defranco-Tommarello

Dissertations

A model to enhance collaborative problem solving and program development is presented. The collaborative model is a detailed cognitive model that takes into consideration the cognitive and social activities that occur during collaborative problem solving and program development. The cognitive activities required for collaborative problem solving and program development are identified and integrated into a six-stage model. An extensive literature review in the associated fields is presented to show the need for the model described in this dissertation. In addition, a comprehensive study of tools to support collaboration during problem solving and program development was also performed as well as …

Chemical, Isotopic, And Hydrogeologic Investigations Of An Agriculturally Impacted Area, Nottawa Creek Watershed, Calhoun County, Michigan, Gerald A. Unterreiner

Dissertations

A 4 km2 agricultural area within the somewhat poorly drained Nottawa Creek Watershed, south central Michigan, was investigated to help understand transport and transformation processes of nutrients and herbicides to surface water. Geology o f the study area is comprised of a thin glacial drift cover overlying shale bedrock. A one layer, two-dimensional numerical triangular finite element groundwater flow model was developed to evaluate regional groundwater flow. Selected horizontal hydraulic conductivities ranged from 3 x 10‘3 m/day to 107 m/day. Field-scale infiltration modeling with the computer program GLEAMS, substantiated with water level measurements, suggest significant recharge events occur during summer, …

A New Theory Of Premixed Flames In Near-Stoichiometric Mixtures, Eliana S. Antoniou

Dissertations

In this dissertation, a new model of premixed flames in near-stoichiometric mixtures is derived. Unlike most previous theories, which are valid only for very lean or very rich, i.e. off-stoichiometric conditions, our model remains valid over the entire spectrum of mixture compositions, from lean to rich, including the near-stoichiometric regime. Since fuel-mixture composition is known to have a significant effect on flame behavior, such a model is expected to contribute new insights into classical problems in premixed combustion.

In the first part of this dissertation, we describe the derivation of a model for premixed flames in two-reactant mixtures in a …

Simultaneous Removal Of Ortho-Dichlorobenzene And Ethanol Vapors In A Biotrickling Filter : Experimental Results And Process Modeling, Suchismita Bhattacharya

Dissertations

This study investigated the possibility of simultaneous removal of vapors of dissimilar volatile organic compounds from air streams in a biotrickling filter (BTF). Using a rricrobial consortium known to utilize ortho-dichlorobenzene (o-DCB) as sole carbon and energy source, a culture was developed on o-DCB/ethanol mixtures and a BTF unit was developed and operated with air streams carrying o-DCB and ethanol vapors. Simultaneous removal of the two compounds was observed in experiments that span a period of over three years.

Experiments were performed at air residence times ranging from 4 to 6.5 min, liquid flow rates from 3.6 to 9 Lh …

Development Of Analytical Systems And Monitoring Of Vocs Emissions During Polymer Processing, Qin Xiang

Dissertations

A method using direct flame ionization detector (FID) measurement was developed to study total volatile organic compounds (VOCs) emissions during thermal degradation of polymers. This was used to estimate organic emissions from both virgin polymer resins and commingled plastics. The effects of process parameters, i. e., temperature, heating rate and residence time, were also studied. Significant VOCs emissions were observed at normal processing temperatures, particularly from recycled polymers. Each polymer showed a distinct evolution pattern during its thermal degradation. Kinetics of VOCs emissions were also studied using a non-isothermal technique. The kinetic parameters were in agreement with data from the …

Modeling Hydrogen Diffusion For Solar Cell Passivation And Process Optimization, Yi Zhang

Dissertations

A diffusion model for hydrogen (H) in crystalline silicon was established which takes into account the charged state conversion, junction field, mobile traps, and complex formation and dissociation at dopant and trap sites. Carrier exchange among the various charged species is a "fast" process compared to the diffusion process. A numerical method was developed to solve the densities of various charged species from the Poisson's equation that involves shallow-level dopants and one "negative U" impurity, e.g., H. Time domain implicit method was adopted in finite difference scheme to solve the fully coupled equations.

Limiting versions of the model were applied …

Variables Related To The Successful Completion Of The First Course In Business Calculus At Three Jamaican Universities, Martin Nkhrama Richards

Dissertations

Problem. Many students at all levels of the education system in Jamaica perform poorly at mathematics. In particular, the results of both the Caribbean Examinations Council and Business Calculus 1 at the university level have reflected a declining trend in mathematics performance in recent years. Consequently, this study sought to investigate the variables related to the successful completion of the first course in business calculus at Jamaican universities. To this end, the study looked at perceptions of students and their professors regarding students' cognitive, affective, and professor effectiveness variables impacting success.

Method. The sample for this study consisted of 389 …

The Structure And Stability Of Expanding And Converging Near-Stoichiometric Flames, Raymond Addabbo

Dissertations

The stability of expanding and converging premixed flames is investigated theoretically. These configurations are inherently unsteady and represent simple examples of positively (expanding) and negatively (converging) stretched flames. A new model is employed in this study that incorporates both hydrodynamic and diffusional-thermal effects. The model expands earlier works by incorporating variable transport properties, variations in the mixture strength and a more realistic dependence on viscosity.

The expanding flame is shown to remain stable at small radii provided the thermal diffusivity exceeds the mass diffusivity of the deficient reactant. However, once the flame achieves a critical size, a cellular instability appears, …

Asymptotic Methods In Applied Waveguide Problems, Helen Martynov

Dissertations

Some of the most challenging problems in acoustics and electromagnetics involve the study of scattered fields in waveguides caused by targets of elaborate shape. The complexity of the resulting scattered field depends on the geometry of the scatterer, and exact solutions exist only for the simple geometries.

The asymptotic methods developed in this dissertation give the approximate solutions for the scattered fields in two practically important geometries: an object placed inside a stratified waveguide, and a waveguide with multiple abrupt width transitions. The solutions for these geometries are obtained by approximating the field near the target or junction by the …

Structural, Transport And Magnetic Studies Of Perovskite Bi1-X Cax Mn O3, Hyungje Woo

Dissertations

This dissertation presents an investigation of the fundamental physics of the perovskite system Bi_1-xCa_xMn0₃. This material belongs to a group of simple perovskites called the manganites which are of technological importance for magnetic device applications as read-head sensors.

The Bi_1-xCa_xMnO₃ system is known to exhibit charge ordering (and high sensitivity to magnetic fields) for a much broader range of x than the well-characterized La_1-xCa_xMnO₃ system. However, the properties of Bi_1-xCa_xMnO₃ over the entire doping range are not well understood. …

Detection Of Vapor Phase Mercury Species By Laser Fluorescence Methods, Xiaomei Tong

Dissertations

Elemental and compound mercury are often both volatile and air stable. Several mercury species emissions have been identified in off-gases from industrial processes. The high toxicity of mercury species and the presence of mercury species in municipal waste and coal have prompted a demand for a cost-effective, accurate, and rugged technique for real-time, continuous detection of mercury species vapors. Real-time, continuous emission measurements are important for process control, monitoring, and remediation. At present, there is no commercial continuous emission monitoring (CEM) technique or instrumentation to reliably monitor volatile mercury species emissions from industrial stacks. Conventional measurement methods, such as cold …

Electrostatic Micro Actuators For Mirror And Other Applications, Xingtao Wu

Dissertations

Micro-electro-mechanical systems (MEMS) based electrostatic micro actuators are becoming important building blocks for innovations in optical signal processing and computing systems due to their inherently small size, high density, high speed and low power consumption. Generally, the principle of operation in these systems can be described as: an electrostatic attractive force causes a mechanical rotation, translation or deformation of a mirror plate, controlling the power, phase or direction of a light beam while it propagates through some medium or through free space. The fast paced, competitive research and development efforts widely being undertaken, both in academia and industry, are demanding …

Vortex-Defect Interactions In High-Temperature Superconductors, Valentina Tobos

Dissertations

The topics covered in this thesis are related to two objectives: one refers to the search for methods of improving die critical current density of high-temperature superconductors, a subject which remains of continuing interest for its importance in technological applications. The other direction is aimed at clarifying the phase diagram of high-Tc materials.

The interaction between the structural defects and the vortex system plays a significant role in the capability of these materials to carry large electrical transport currents. Through proton irradiation induced defects we follow the evolution of the critical current density, and its enhancement with increasing point-like defects …

Empirical Spectral Analysis Of Random Number Generators, David Zeitler

Dissertations

Computer simulation procedures have become a staple of research and development in many fields, including statistics. The generation of pseudo random number sequences is the core of computer simulation procedures. Validity of research results often depend on the underlying validity of the generator being used.

In this work we develop the machinery for a class of tests of spatial uniformity based on a multi-dimensional Fourier transform of the empirical probability density function. The test can be adapted to specific requirements and has the added advantage that it has computational complexity that is relatively independent of the number of data points …

Quantification Of Benzo[A]Pyrene-Guanine Adducts In In Vitro And In Vivo Tissue Samples By Lc Tandem Mass Spectrometry, Po-Chang Chiang

Dissertations

No abstract provided.

Cost Domination In Graphs, David John Erwin

Dissertations

Let G be a connected graph having order at least 2. A function f : V (G) —> {0 , 1 , . . . , diam G} for which f ( v ) < e(v) for every vertex v of G is a cost function on G. A vertex v with f ( v ) > 0 is an f-dominating vertex, and the set Vj~ = {v 6 V(G) : f(v) > 0} of f-dominating vertices is the f-dominating set. An /-dominating vertex v is said to f-dominate every vertex u with d(n, v) < f(u ), while …

E-Docspros : Exploring Texpros Into E-Business Era, Zhenfu Cheng

Dissertations

Document processing is a critical element of office automation. TEXPROS (TEXt PROcessing System) is a knowledge-based system designed to manage personal documents. However, as the Internet and e-Business changed the way offices operate, there is a need to re-envision document processing, storage, retrieval, and sharing. In the current environment, people must be able to access documents remotely and to share those documents with others. e-DOCPROS (e-DOCument PROcessing System) is a new document processing system that takes advantage of many of TEXPROS's structures but adapts the system to this new environment. The new system is built to serve e-businesses, takes advantage …

Ultrathin Silicon Wafer Bonding Physics And Applications, Michael H. Beggans

Dissertations

Ultrathin silicon wafer bonding is an emerging process that simplifies device fabrication, reduces manufacturing costs, increases yield, and allows the realization of novel devices. Ultrathin silicon wafers are between 3 and 200 microns thick with all the same properties of the thicker silicon wafers (greater than 300 microns) normally used by the semiconductor electronics industry. Wafer bonding is one technique by which multiple layers are formed.

In this thesis, the history and practice of wafer bonding is described and applied to the manufacture of microelectomechanical systems (MEMS) devices with layer thickness on the scale of microns. Handling and processing problems …

Waqs : A Web-Based Approximate Query System, George Jyh-Shian Chang

Dissertations

The Web is often viewed as a gigantic database holding vast stores of information and provides ubiquitous accessibility to end-users. Since its inception, the Internet has experienced explosive growth both in the number of users and the amount of content available on it. However, searching for information on the Web has become increasingly difficult. Although query languages have long been part of database management systems, the standard query language being the Structural Query Language is not suitable for the Web content retrieval.

In this dissertation, a new technique for document retrieval on the Web is presented. This technique is designed …

Broadband Whole Package Fdtd Simulation, Shenjun Li

Dissertations

Whole package analysis is becoming more and more important with the rapid expansion of high frequency electronics. The motivation of this thesis is to find and implement a new method for broadband whole package simulation. 3-dimension (3-D) whole package Finite Difference Time Domain (FDTD) simulation result was first reported in detail in this thesis.

The FDTD method is a widely used full-wave time-domain simulation method used in the design and analysis for electromagnetic (EM) systems, such as antennas, wave propagating, and microwave circuits. Absorbing boundary condition (ABC), such as the perfect matched layer (PML) method, makes it possible to accurately …

Augmenting Applications With Hyper Media, Functionality And Meta-Information, Roberto Galnares

Dissertations

The Dynamic Hypermedia Engine (DHE) enhances analytical applications by adding relationships, semantics and other metadata to the application's output and user interface. DHE also provides additional hypermedia navigational, structural and annotation functionality. These features allow application developers and users to add guided tours, personal links and sharable annotations, among other features, into applications. DHE runs as a middleware between the application user interface and its business logic and processes, in a n-tier architecture, supporting the extra functionalities without altering the original systems by means of application wrappers.

DHE automatically generates links at run-time for each of those elements having relationships …

Volume Change Behavior Of Clay Soils And The Effect On Discrete Fractures, Heather Ann Hall

Dissertations

This study examines the behavior of subsurface fractures in fine-grained soil such as clays in response to changing environmental conditions. Fractures serve as conduits for moisture transfer, which can lead to substantial shrinking and swelling of the surrounding fracture boundary soils. These volume changes, in turn, affect fracture geometry and moisture transmission rates. A new predictive model, termed the 'Fracture Volume Change Model' (FVC Model), has been developed to relate moisture transfer, soil volume change and associated changes in fracture aperture. The model assumes a discrete horizontal fracture in a laterally-infinite, saturated, expansive clay with rigid, outer no-flow boundaries and …

A Dynamical Model Of The Distributed Interaction Of Intracellular Signals, Adrienne C.N. James

Dissertations

A major goal of modern cell biology is to understand the regulation of cell behavior in the reductive terms of all the molecular interactions. This aim is made explicit by the assertion that understanding a cell's response to stimuli requires a full inventory of details. Currently, no satisfactory explanation exists to explain why cells exhibit only a relatively small number of different behavioral modes.

In this thesis, a discrete dynamical model is developed to study interactions between certain types of signaling proteins. The model is generic and "connectionist" in nature and incorporates important concepts from the biology. The emphasis is …

Knowledge-Based Document Retrieval With Application To Texpros, Fang Sheng

Dissertations

Document retrieval in an information system is most often accomplished through keyword search. The common technique behind keyword search is indexing. The major drawback of such a search technique is its lack of effectiveness and accuracy. It is very common in a typical keyword search over the Internet to identify hundreds or even thousands of records as the potentially desired records. However, often few of them are relevant to users' interests.

This dissertation presents knowledge-based document retrieval architecture with application to TEXPROS. The architecture is based on a dual document model that consists of a document type hierarchy and, a …