Search

The aim of the current study is to develop an efficient model which can predict low-energy compatible microstructures in ferroelectric bulks and film devices and their dynamic behaviour. The results are expected to assist in the interpretation of microstructure observations and provide a knowledge of the possible domain arrangements that can be used to design future materials with optimum performance. Several recent models of ferroelectric crystals assume low energy domain configurations. They are mainly based on the idea of fine phase mixtures and average compatibility, and can require intensive computation resulting in complex domain configurations which rarely occur in nature. In this research, criteria for the exact compatibility of domain structure in the form of a periodic multi-rank laminate are developed. Exactly compatible structure is expected to be energetically favourable and does not require the concept of a fine mixture to eliminate incompatibilities. The resulting method is a rapid and systematic procedure for finding exactly compatible microstructures. This is then used to explore minimum rank compatible microstructure in various crystal systems and devices. The results reveal routes in polarization and strain spaces along which microstructure can continuously evolve, including poling paths for ferro- electric single crystals. Also, the method is capable to generate all possible exactly compatible laminate configurations for given boundary conditions. It is found that simple configurations are often energetically favourable in conditions where previous approaches would predict more complex domain patterns. Laminate domain patterns in ferroelectrics are classified and corre- lated with observations of domains in single crystals, showing good agreement. The evolution of microstructures under applied mechanical and electrical loads is studied. A variational method, which minimises the overall energy of the crystal is developed. A new concept of transitional “pivot states” is introduced which allows the model to capture the feature that the microstructure in ferroelectric crystal switches between possible domain patterns that are energetically favourable, rather than assuming one particular domain pattern throughout. This model is applied to study the hysteresis responses of barium titanate (BaTiO3) single crystals subjected to a variety of loads. The results have good agreement with experimental data in the literature. The relationship between domain patterns and ferroelectric hysteresis responses is discussed.

Over the past decade real time kinematic (RTK) GPS has evolved into an important practical tool for a wide range of positioning applications. For short baselines the current accuracy is limited only by multipathing problems but as the distance increases so other errors begin to decorrelate. In particular errors due to the ionosphere play an increasingly important role and typically RTK cannot be used beyond about 10km. Many practical applications require RTK to operate over longer distances and this thesis is concerned with the ionospheric modelling necessary for this to be possible. At present global and regional ionosphere maps (broadcast on web) based on global ionosphere models (GIM) and regional ionosphere models (RIM) are available for worldwide DGPS (WWDGPS) and wide area DGPS (WDGPS). Because of the limited accuracy of these models, a local ionosphere model (LIM) has been developed to see whether it would be possible to enhance the performance of RTK GPS. Several LIMs based on different mapping functions, and using data from one station only, have been constructed. These have been used to predict the double difference ionospheric corrections for a pair of stations and compared with the "true" corrections based on the data actually collected at the two stations (and knowing the exact coordinates of the two stations). In this way the accuracy of the different LIMs has been compared. These (LEM-based) corrections have also been used to correct raw GPS phase data before use in RTK software in order to see whether or not integer ambiguity determination can be improved - especially over distances greater than those currently used in practical RTK GPS. It has been found that significant improvements can result from the use of these corrections over distances of up to 20km when using clean GPS data in relatively benign multipathing.

By what means do mothers' developmental histories potentially influence their sense of maternal self-efficacy? This qualitative dissertation examines the perspectives and experiences of sixteen Japanese mothers concerning relationships with her children, her husband and her parents. Analyses in this study are based on interview transcripts and field notes. This study proposed that mothers who recalled having warm and positive relationships with one or both parents were more likely to feel confident in their parenting choices and thus experience higher maternal self-efficacy. On the other hand, mothers who recalled having a rejecting or negative relationship with one or both parents were proposed to be more likely to feel ineffective and thus threatened in their parenting approaches resulting in lower maternal self-efficacy. It is further proposed that the negative effects of having experienced rejecting parental relationships can be buffered or offset in mothers who perceive supportive, positive relationships with their husbands. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]

Mass spectrometry (MS) is one of the main techniques for high throughput discovery- and targeted-based proteomics experiments. The most popular method for MS data acquisition has been data dependent acquisition (DDA) strategy which primarily selects high abundance peptides for MS/MS sequencing. DDA incorporates stochastic data acquisitions to avoid repetitive sequencing of same peptide, resulting in relatively irreproducible results for low abundance peptides between experiments. Data independent acquisition (DIA), in which peptide fragment signals are systematically acquired, is emerging as a promising alternative to address the DDA's stochasticity. DIA results in more complex signals, posing computational challenges for complex sample and high-throughput analysis. As a result, targeted extraction which requires pre-existing spectral libraries has been the most commonly used approach for automated DIA data analysis. However, building spectral libraries requires additional amount of analysis time and sample materials which are the major barriers for most research groups. In my dissertation, I develop a computational tool called DIA-Umpire, which includes computational and signal processing algorithms to enable untargeted DIA identification and quantification analysis without any prior spectral library. In the first study, a signal feature detection algorithm is developed to extract and assemble peptide precursor and fragment signals into pseudo MS/MS spectra which can be analyzed by the existing DDA untargeted analysis tools. This novel step enables direct and untargeted (spectral library-free) DIA identification analysis and we show the performance using complex samples including human cell lysate and glycoproteomics datasets. In the second study, a hybrid approach is developed to further improve the DIA quantification sensitivity and reproducibility. The performance of DIA-Umpire quantification approach is demonstrated using an affinity-purification mass spectrometry experiment for protein-protein interaction analysis. Lastly, in the third study, I improve the DIA-Umpire pipeline for data obtained from the Orbitrap family of mass spectrometers. Using public datasets, I show that the improved version of DIA-Umpire is capable of highly sensitive, untargeted analysis of DIA data for the data generated using Orbitrap family of mass spectrometers. The dissertation work addresses the barriers of DIA analysis and should facilitate the adoption of DIA strategy for a broad range of discovery proteomics applications.

p { } For each k ≥ 1, we study the eigenvalue distributions of permutation representations of the symmetric group ?n on k-tuples and k-subsets as well as the S(n-k,1,...,1) irreduciblerepresentation of ?n (we will call these k-representations). First, we consider the fluctuations of eigenvalue statistics. Endow ?n with the uniform measure and let α and θ be linearly independent irrational numbers over ℚ. Then we show that as n → ∞, the scaled count of the number of eigenangles in a fixed interval (α, θ) of a k-representation evaluated at a random element σ ∈ ?n converges weakly to a compactly supported distribution. In particular, we compute the limiting moments and moreover provide a formula for the limiting density in the case k = 2. Next, we study the scaled eigenvalue point process of the k-representations. Here, we endow ?n with the Ewens measure of parameter θ for which the uniform distribution corresponds to the special case θ = 1. The eigenvalue point processes exhibit drastically different behavior depending on whether one “zooms in” at rational angles or irrational angles. We obtain the limiting eigenvalue point process at rational angles as well as angles of irrationality measure 2 for all k-representations. A power series representation for the limiting gap probability is also given. Finally, we study the distribution of entries of a random permutation matrix under a “randomized basis.” This means that we conjugate the random permutation matrix by a random orthogonal matrix drawn from Haar measure. Then it is shown that under certain conditions, the linear combination of entries of a random permutation matrix under a “randomized basis” converges to a sum of independent variables sY + Z where Y is Poisson distributed, Z is normally distributed, and s is a constant.

The Global System for Mobile (GSM) cellular standard, having been in existence for over two decades, is the most widely deployed wireless technology in the world. While third generation networks and beyond, such as Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE), are undergoing extraordinary growth and driving a large share of current cellular development, technologies and deployments based on GSM are still dominant on a global scale and, like more recent standards, continue to evolve very rapidly. The software-defined radio (SDR) base station is one technology that is driving rapid change in cellular infrastructure. While commercial vendors have now embraced SDR, there is another movement that has recently gained prominence. That movement is the convergence of open source software and hardware with cellular implementation. OpenBTS, a deployable implementation of the GSM radio air interface, and the Universal Software Radio Peripheral (USRP), a RF hardware platform, are two primary examples of such open source software and hardware products. OpenBTS and the USRP underlie three GSM features that are implemented and presented in this thesis. This thesis describes the extension of the OpenBTS software-defined radio transceiver in the three critical areas of user capacity, transmit signal integrity, and the embedded small form factor. First, an optimized wideband multicarrier implementation is presented that substantially increases the capacity beyond that of a single carrier system. Second, the GSM modulator is examined in depth and extended to provide performance that exceeds standards compliance by a significant margin. Third, operation of the GSM transceiver on an E100 embedded platform with ARM and fixed point DSP processors will be explored, optimized, and tested.

One of the goals of tissue engineering is to create technologies that will improve or replace biological function of diseased or damaged cells and tissues. The purpose of my thesis work is to determine how the mechanical properties of the murine microenvironment, specifically matrix stiffness, can affect the function and behavior of cells and tissues. Previous research has shown that stiffness is a powerful mechanical property; it is associated with breast and liver cancer, and can also be used to control stem cell differentiation. In order to create an optimal microenvironment for the generation of new cells and tissues, it is essential that we further investigate how matrix stiffness controls cells and tissue behavior. The motivation for this thesis work is twofold; the first is to find an improved system and cell source for the generation of hematopoietic progenitors and stem cells, and the second is to characterize better technologies for tissue-engineered vascular grafts.The first chapter of this thesis work investigates how to create an in vitro microenvironment that can be used to study matrix stiffness. I then examine how to use the system to create mESC-derived Flk-1+ hemangioblasts, which are precursor cells for the hematopoietic, cardiac and vascular lineages. Both natural and synthetic hydrogel systems are examined using three different techniques for measuring substrate elastic modulus: a comparator, a rheometer and an atomic force microscope (AFM). The data shows that polyacrylamide and AFM are the most appropriate systems for this work. Cell spreading studies demonstrate the morphological differences of cells on various stiffnesses. Short-term studies show that mESC differentiation is dependent on both matrix stiffness and the extracellular matrix protein that is used to attach the cells to the surface, but is not affected by the addition of certain growth factors (i.e. TGF-β, PDGF-BB) in culture media. In addition, the data shows that the effect of matrix stiffness on cell fate may be determined within 3 days of seeding on a particular surface, suggesting that mESCs can "remember" the effects of their mechanical microenvironment for a short period of time.The second part of this work looks at how matrix stiffness affects the differentiation of mESC-derived Flk-1+ hemangioblasts into the hematopoietic, vascular and cardiac lineages. The results demonstrate that matrix stiffness has a bimodal effect on the derivation of Flk-1+ hemangioblasts from mESCs, with a medium stiffness (~43kPa) generating the highest quantity. Data from long-term studies shows that cells grown on softer surfaces (~0.4kPa) generate more hematopoietic progenitor cells, whereas cells on stiffer surfaces (~43kPa to 1GPa) derive more vascular-like cells. The study also suggests that softer surfaces may also be more appropriate for cardiac cell generation, though this may be because softer surfaces encourage cells to grow more in a three-dimensional conformation, which is known to contribute to cardiac cell development.The last part of the work focuses on the effects of matrix stiffness on a more macro scale, by examining the stiffness of embryonic and adult tissues. For the embryonic tissues, the goal is to measure and correlate the matrix stiffness of the blood-deriving organs to those used in the in vitro studies in order to create a better system for studying the generation of hematopoietic stem cells and progenitors. For the adult tissue studies, tissue-engineering vascular grafts supported with either collagen I hydrogels supplemented with or without TGF- β, or Matrigel hydrogels are implanted into rats for 3 months so as to better simulate the mechanical properties of healthy vascular tissue. The results show that TGF- β increases the stiffness of the tissue surrounding the vascular graft, resulting in elastic moduli similar to that of native healthy tissue. The Matrigel hydrogels only moderately increase the stiffness of the surrounding tissue and may be too weak to be a viable option for tissue-engineered vascular grafts.This work demonstrates the importance of matrix stiffness when designing systems to control cell fate and for tissue regenerative purposes. On a cellular level, although chemical factors can regulate stem cell differentiation to a certain extent, the surrounding physical environment can also influence stem cell differentiation, specifically into the hemangioblast-related fate. On a tissue level, researchers may be able to better mimic vascular tissue by manipulating the stiffness and composition of tissue-engineered grafts, thus helping the patency of these grafts. Future considerations for this work would include the addition of in vivo analyses for the mESC differentiation studies, as well as using other types of hydrogel systems, such as those made from biocompatible materials. Research should also be conducted using induced pluripotent stem cells to eliminate ethical concerns and the possibility of rejection by the host. For the tissue mechanics studies, there is still a need for an accurate, comprehensive system for measuring embryonic tissue in vivo. These mechanotransduction experiments are important for the foundation of creating better microenvironments for tissue engineering applications.

This thesis studies qualitative data to examine the lived experiences of Kentucky Transitional Assistance Program (K-TAP) recipients in Appalachian Kentucky. This research suggests that PRWORA legislation utilize the importance of place-based analyses to implement and evaluate poverty policy. For women who are attempting to meet PRWORA’s goals, the local services available to the women and the barriers they face to employment highlight the role place has in this national policy discussion. Of the women interviewed, recipients who resided in economically distressed areas had fewer opportunities to participate in employment activities than women in at-risk or transitional areas. While many strived to transition from PRWORA aide to economic independence through education and employment, others sought to exit through disability insurance. Nevertheless, the women interviewed had adopted PRWORA’s goals of economic independence.

Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+ -transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. We used a transgenic approach to modulate calcium stores in the lumen of the endoplasmic reticulum in plants. We were able to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin (CRT) to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. I fused the CRT C-domain to the C-terminal portion of the green fluorescent protein (GFP) and obtained transgenic plants that expressed high levels of the GFP-CRT C-domain fusion protein in the ER. I showed that this fusion protein was able to bind Ca2+ in vitro. These plants had increased Ca2+ stores in the ER and the ER calcium stores were used by the plant in times of calcium stress. The transformed seedlings also showed delayed loss of chlorophyll after transfer to high salt medium. The data suggest that expression of this calcium binding protein not only has the ability to increase bioavailable calcium stores but that the ER Ca2+ stores are important for plants to relieve the effect of salt stress. In the process of developing the transgenic plants, I also developed an array of other tools for subcellular localization, and targeting of the C-domain to various subcellular organelles. With two other colleagues, we also developed a GFP imaging system using the onion epidermal cells for visualizing subcellular localization of GFP and GFP fusion proteins.

Cathodoluminescence and kinetics of gallium nitride doped with thulium.

This research investigated formal information modelling techniques and the object-oriented knowledge representation on the domain of building cost control during early design stages. The findings contribute to an understanding of the advantages and disadvantages of applying formal modelling techniques to the analysis of architectural problems and the representation of domain knowledge in an object-oriented environment. In this study, information modelling techniques were reviewed, formal information analysis was performed, a conceptual model based on the cost control problem domain was created, a computational model based on the object-oriented approach was developed, a mechanism to support information broadcasting for representing interrelationships was implemented, and an object-oriented cost analysis system for early design (OBCIS) was demonstrated. The conceptual model, based on the elemental proposition analysis of NIAM, supports a formal approach for analyzing the problem domain; the analysis results are represented by high-level graphical notations, based on the AEC Building System Model, to visually display the information framework of the domain. The conceptual model provides an intermediate step between the system designer's view of the domain and the internal representation of the implementation platform. The object-oriented representation provides extensive data modelling abilities to help system designers intuitively represent the semantics of the problem domain. The object-oriented representation also supports more structured and integrated modules than conventional programming approaches. Although there are many advantages to applying this technique to represent the semantics of cost control knowledge, there are several issues which need to be considered: no single satisfactory classification method can be directly applied; object-oriented systems are difficult to learn; and designing reusable classes is difficult. The dependency graph and information broadcasting implemented in this research is an attempt to represent the interrelationships between domain objects. The mechanism allows users to explicitly define the interrelationships, based on semantic requirements, among domain objects. In the conventional approach, these relationships are directly interpreted by system designers and intertwined into the programming code. There are several issues which need to be studied further: indirect dependency relationship, conflict resolution, and request-update looping based on least-commitment approach.

Owing to the continued increase in kilowatt capacity of new power stations being built today, proper sizing and selection of mechanical equipment has a vital effect on dollar savings, both for operation and maintenance costs as well as the initial cost of unit installation. In today's steam-electric plants, the power consumption of the motor-driven boiler feed pumps has been rising along with the increase of operating pressures and capacities. Power savings thus becomes a more significant factor than ever in selection of boiler feed pumping arrangement. Therefore, use of a more economical and justifiable boiler feed pumping arrangement with constant speed drive or variable speed drive through hydraulic couplings would vastly improve power plant economy and operation. This study compares the costs and operating characteristics of two constant-speed boiler feed pumps operating in parallel, against those of one constant-speed pump operating in parallel with one variable speed pump which is driven through hydraulic coupling (all pumps are of half-size capacity, motor-driven). This cost comparison shows that the former pumping arrangement is more economical than the latter at the unit base load.

The effect of thyroid hormones on purine biosynthesis was studied in vitro. With 100,000 x g supernatant fraction of rat liver homogenate, the results suggested that thyroid hormones stimulated total purine synthesis from labeled glycine-1-¹⁴C. Further studies indicated that these hormones stimulated AMP synthesis but inhibited GMP synthesis. The stimulatory effect on AMP synthesis was found to be due to the stimulation of adenylosuccinate synthetase. Adenylosuccinate synthetase was isolated and purified from rat liver. The maximum stimulatory effect of these hormones occurred with 2.5 x 10⁻⁵ M thyroxine (T₄) and 2.5 x 10⁻⁹ M triiodo-L-thyronine (T₃). A slight increase or decrease in concentration of these hormones caused a drastic decrease in their stimulatory effect. Some analogues of T₄ were also studied and results of such experiments agreed qualitatively with their effects in vivo. Those which are physiologically active are capable of stimulating this enzyme and those which are physiologically inactive had little or no effect on this enzyme. Based on these results, a hypothesis, that thyroid hormones regulate the levels of AMP and GMP synthesis, was proposed. The significance of this preferential stimulatory effect on AMP synthesis was discussed.

It has been recognized that many convection heat transfer problems involve internal heat generation. Nuclear fuel elements, chemically reactive liquids and transparent shell solar energy collectors are a few examples. Theoretically, this type of problem has not been studied extensively. Lumsdaine solved the internal heat generation problem with constant temperature boundary conditions in spherical coordinates. The purpose of this thesis is to follow Lumsdaine's analysis to study those problems where internal heat generation is a function of radius. The governing partial differential equation in spherical coordinates is of the second order, non-homogeneous and has variable coefficients. The non-homogeneity arises from the internal heat generation function in the energy equation. The boundary conditions are also non-homogeneous. In order to solve this problem, steady state, an incompressible inviscid fluid, a constant fluid entrance temperature, and constant ambient temperatures are assumed. In solving the problem, the method of superposition is first used to form a non-homogeneous ordinary differential equation and a homogeneous partial differential equation. By doing this, the boundary conditions are also simplified. These two equations are then solved separately. The ordinary differential equation can be integrated directly. The partial differential equation is solved by using separation of variables. The solution is given as an infinite series of Euler functions. The temperature field is finally obtained by superimposing the two solutions. The expression for the average exit temperature is derived from the temperature field. The average exit temperature is non-dimensionalized in terms of Graetz number, Nusselt number, radius ratio and other dimensionless groups. Computer programs are developed to obtain numerical results. In the first part of the thesis, the inner shell is assumed to be at a constant temperature. The problem is first solved in general without specifying the internal heat generation function; therefore the solution holds for any type of internal heat generation. In the sample problem the internal heat generation function is assumed to consist _of a constant term and an exponential term to account for the decay from the outer shell. In the second part of the thesis, the solution emphasizes its -application to the solar heat exchanger. By assuming the outer shell transparent, the absorption of solar energy by the water can be interpreted as internal heat generation. The inner shell is assumed to be a black body which absorbs all the energy not absorbed by the water; this energy is then conducted back to the fluid. The efficiency of this type of solar heat exchanger should be higher than in exchangers with an opaque outer shell since the latter have higher temperatures at the outer shell and thus lose more heat to the surroundings.

In this thesis we investigate whether a rank-one rotating mass matrix extended to solve the strong CP problem can, through the mass leakage mechanism, account for fermion masses, mixing angles and a $theta_{CP}$ term of order unity. In the first part we find restrictions placed on the rotation of the rank-one mass matrix by experimental data. We demonstrate that a smooth rotation of the mass matrix can reproduce the experimentally determined fermion masses and mixing angles and give $theta_{CP}$ = 1.45 radians. We then fit the speed of rotation at high ($> 1$ GeV) scales. Using this rotation we make predictions for Higgs branching ratios for a range of Higgs masses, finding a suppression of $Gamma(H ightarrow car{c})$ compared to the standard model and significant flavour violating branching ratios. In the second part we study the framed standard model (FSM). We calculate the strong framon one-loop contribution to the rotation of its rank-one mass matrix and account for the non-trivial metric on its internal symmetry space. We find that the FSM can reproduce the hierarchy seen in the fermion masses and the CKM matrix, fit $theta_{CP}sim0.3$ radians and find $|U_{mu3}|sim0.8$. Similar results are found if QCD running is included, except that $|U_{mu3}|>0.95$. We compare the FSM rotation to the rotation found in first part and find they are in good agreement above $mu=m_c$. We go on to show that the predictions for Higgs decay are comparable to those found in the general study. In the final part we calculate the framon mass spectrum of the FSM in the hermitian gauge and find that, as expected, it agrees with the calculation performed in the triangular gauge. We find that none of the framons are massless.

We interpret the generalised gauge symmetry introduced in string theory and M-Theory as a special case of Grothendieck's stability equivalence relation in the definition of the 0th K-group and we calculate the Euler number of the elliptic de Rham complex twisted by a flat connection. Then using Polyakov's classical equivalence of flat bundles with non-linear sigma models we define a new topological invariant for foliations using techniques from noncommutative geometry, in particular the Connes' pairing between K-Theory and cyclic cohomology. This new invariant classifies foliations up to Morita equivalence.