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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Characterization of the mas protein as an angiotensin ii receptor

Raynor, James E., Jr. 01 July 1994 (has links)
The mas proto-oncogene encodes a seven transmembrane protein (MAS) which is suggested to function as a receptor for angiotensin. It (MAS) was initially identified in NIH-3T3 cells that were transformed with DNA isolated from a human epidermoid carcinoma. These cells formed foci in culture and tumors when injected into nude mice. On the other hand, untransformed cells did not. Further analysis of these cells showed that transformed cells bind increased levels of angiotensin when compared to untransformed cells. These studies also demonstrated that the Mas protein was structurally similar to the angiotensin receptor transmembrane proteins, AT1 and AT2 . This investigation was undertaken to examine the ability of the Mas protein to function as an receptor for angiotensin and promote cell proliferation. To this end, quantitation of mas genes by Polymerase Chain Reaction (PCR) and serial dilutions, and Southern blot analysis support an increased in mas genes in transformed cells. Northern blot analysis demonstrated an increased expression of the mas gene in transformed cells. No changes in the level of the AT2 angiotensin receptor gene expression was observed in the transformed and untransformed cell lines. Expression of the AT1 angiotensin receptor gene was not observed in these cell lines. Anti-peptide antibodies were generated against the 1st and 2nd extracellular regions of the Mas protein. Flow cytometric analysis using these antibodies indicated an increased presence of the Mas protein on the surf ace of transformed cells recognized by anti-peptide antibodies. Western blot analysis showed two cross-reacting proteins of approximately ll0kd and 66kd in transformed cells; whereas, only a 66kd protein was found in untransformed cells. Transformed cells exposed to mas antisense oligos greatly reduced the synthesis of Mas, decreased cell proliferation and the binding of angiotensin. Binding studies using [3H]-DUP- 753 (a non-peptidyl ligand which recognizes Ang subtype AT1 receptors) showed little binding to transformed cells. Similar studies using PD-123319 (a non-peptidyl ligand that recognizes AT2 subtype receptors) indicated that approximately 60% of [125I]-Ang II was displaced using PD-123319. Further binding analysis of transformed cells suggests that [Sarl]-Ang II (an Ang II antagonist) could not completely displace [ 125I]-Ang II. Taken together, these data suggest that Mas protein is an Ang receptor which functions in the regulation of cell proliferation. Mas appears to be a member of a subtype different from AT1 or AT2.
102

RADIO FREQUENCY PATH CHARACTERIZATION FOR WIDE BAND QUADRATURE AMPLITUDE MODULATION

Bracht, Roger 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Remote, high speed, high explosive wave front monitoring requires very high bandwidth telemetry to allow transmission of diagnostic data before the explosion destroys the sensor system itself. The main motivation for this study is that no known existing implementation of this sort has been applied to realistic weapons environments. These facts have prompted the research and gathering of data that can be used to extrapolate towards finding the best modulation method for this application. In addition to research of similar existing analysis and testing operations, data was recently captured from a Joint Test Assembly (JTA) Air Launched Cruise Missile (ALCM) flight.
103

THE EFFECTS OF CARRIER FREQUENCY AND ANTENNA DIAMETER ON FREQUENCY SELECTIVE MULTIPATH FADING

Paje, Vladimir I. 10 1900 (has links)
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / This paper uses ARTM channel sounding data collected at Edwards Air Force Base to investigate the dependency between the characteristics of frequency selective multipath fading and carrier frequency and ground based received antenna diameter. Channel model parameters are obtained from data sets measured at different frequencies and various ground based antenna diameters. The analysis shows that the multipath characteristics do not statistically change between the L-band and S-band carrier frequencies, but do change with antenna diameter. Furthermore, Flight 18 data shows that antenna diversity may be a useful technique to reduce data loss from multipath fading.
104

Statistical characterization for timing sign-off : from silicon to design and back to silicon

Sundareswaran, Savithri 23 October 2009 (has links)
With aggressive technology scaling, within-die random variations are becoming the most dominant source of process variations. Gate-level statistical static timing is becoming a widely accepted approach as an alternative to static timing analysis. However, statistical timing approaches lack good models for handling timing variations due to within-die random variations. Before performing statistical timing analysis on a design or System On Chip (SoC), the cells in the library are pre-characterized for delay as well as constraints due to these random variations. This is referred to as statistical characterization of the cells. The major contribution of this dissertation is the development of novel techniques for statistical characterization and optimization of cells. The methods couple the knowledge of circuits along with the significant factor analysis methods to compute the sensitivities, to perform statistical timing and to perform sensitivity-aware cell optimizations. The first contribution of this dissertation is a statistical delay characterization method developed for computing delay sensitivities of standard cells considering both global and mismatch process variations. In addition to the cells being characterized for delay, the sequential cells are characterized for timing constraints like setup and hold time constraints. The second contribution of this dissertation addresses the problem of constraint sensitivity characterization in sequential cells. Block-based statistical timing approaches lack accurate consideration of the impact of slew variations on both delay and arrival time variations. Specifically, the delay variations due to within-die random variables (mismatch variables) result in a slew-based correlation during timing propagation. Handling within-die random variations more accurately during statistical timing propagation is the topic of the third contribution of this dissertation. Clock networks are more prone to these within-die random variations and can result in significant clock-skew variations. In the fourth contribution, a timing margining methodology is presented that accurately accounts for the clock skew variations in a timing sign-off flow. Typically, the standard cells are designed very early in the design cycle and long before the process reaches production maturity. Any subtle improvements to reduce variability in standard cells can improve parametric yield significantly. Statistical characterization of cells for timing provides a key baseline for understanding the circuit behavior due to different sources of variation. The sensitivity information can also help increase yield by reducing the variability during the circuit design itself. The final contribution in the dissertation addresses this by defining key cell and device criticality metrics. A sensitivity-aware standard cell layout optimization is demonstrated using the proposed criticality metrics. / text
105

Characterizing Polymers for Cardiovascular Devices

Warren, Phillip Daniel January 2012 (has links)
Abdominal aortic aneurysm (AAA) occurs in developed nations. The current treatment, endovascular aneurysm repair (EVAR), while successful, has shortcomings. A solution to the concerns with EVAR is a polymeric endo-aortic paving (PEAP). Our goal is to further develop this treatment for AAA. We hypothesize that PEAP will overcome the current limitations associated with current AAA repair, while maintaining the desirable qualities of these materials are biocompatibility, thermoformability, and material compliance with aortic tissue. The purpose of this work was to evaluate potential PEAP material candidates, which include acrylate-based shape memory polymers (SMPs), polycaprolactone (PCL) and polyurethane (PU) blends, and finally a PCL-based bioresorbable copolymer poly (ester-urethane-urea) (PEUU). Materials were assessed by characterization of their chemical, thermomechanical and degradation properties. It was determined that acrylate- SMPs were too stiff to be candidates for use in PEAP. The control of the PEUU copolymer composition yielded a material that had increased degradability while maintaining valuable characteristics of the PCL/PU blend prior to, during, and following degradation. The difference between the PU hydrophobicity dictated MTM sensitivity to water immersion and degradation characteristics. Conventional statistics were used to develop three models for predicting key properties of PEUU. Important variables, such as PCL M(n), temperature, and crystallinity were found to impact both copolymer microstructure and mechanical properties.
106

The synthesis and characterization of thermotropic liquid crystalline copolyesters

Onwumere, Fidelis C. 01 July 1985 (has links)
The synthesis of polyesters and copolyesters containing the bicycl o[2. 2.2]octane ring and 1,4-cycl ohexanedi acetic acid and 1,4-cyclohexanedimethanol spacers are discussed. The following homopolyesters were synthesized: poly[oxy(2-methyll, 4-phenylene)oxycarbonyl-l,4-bicyclo[2.2.2]octylenecarbonyl] I; and poly[oxy(2-chloro-l,4-phenylene)oxycarbonyl-l,4-bicyclo[2.2.2]octy-1 enecarbonyl] II. The following copolyesters were synthesized: poly[oxy (2-chl oro- 1,4-phenyl ene )oxycarbonyl-l ,4-bi cycl o[2. 2. 2]octyl enecarbonyl-co-oxy- (2-chloro-1,4-phenylene)oxysebacoyl] III; poly[oxy(2-methyl-l,4- phenylene)oxycarbonyl-l,4-bicyclo[2.2.2]octylene-co-oxy(2-methyl-l,4- phenyl ene)oxysebacoyl] IV; poly[oxy(2-methyl-l,4-phenylene)oxyterephthaloyl- co-oxy(2-methyl-l,4-phenylene)oxy-l,4-cyclohexanediacetoyl] V; poly[oxy(2-methyl-1,4-phenylene)oxyterephthaloyl-co-oxymethylene-1,4 cyclohexylenemethyleneoxyterephthaloyl] VI; and poly[oxy(2-chloro-1,4 phenylene)oxyterephthaloyl-co-oxymethylene-1,4 cyclohexylenemethyleneoxyterephthaloyl]VII. The resulting homopolyesters and copolyesters were characterized by proton NMR, DSC, TGA, IR, solution viscosity, and polarizing optical microscopy.
107

Investigation on Model Based Observers for SpaceStructure Load Characterization

Exposito Garcia, Adrian January 2016 (has links)
The experimental determination of dynamic characteristics of elastic structures, in particularof space flight related structures typically is performed by experimental modal analysis(EMA) or output-only modal analysis (OMA). This document is focused on the OMA methodsand state-space modelling, the motivation for this approach is the possibility to monitorthe real loading of a structure in order to provide a loading history which may be used foran assessment of safe remaining life once the dynamic characteristics has been determined. Previous work has demonstrated that Extened Kalman Filter is not sufficient in thecase when the forces are unkown and the only resource available are the responses of thestructure. In this research a new method called Unscented Kalman Filter is investigated andimplemented, proving its capability to obtain a better approximation of the elastic structurebehaviour and a correction of the modal parameters.
108

Surface, Aggregation, and Phase Characterization of Microbially-Produced & Chemically-Synthesized Monorhamnolipids

Eismin, Ryan J., Eismin, Ryan J. January 2017 (has links)
The purpose of this research has been to explore the native monorhamnolipid (mRL) mixture produced by Pseudomonas aeruginosa ATCC 9027, as well as newly- synthesized monorhamnolipid diastereomers (R,R)-Rha-C10-C10, (R,S)-Rha-C10-C10, (S,S)-Rha-C10-C10 and (S,R)-Rha-C10-C10, to understand their aggregation and phase behavior in aqueous solution. This work is in response to the consideration that biosurfactants offer a "greener" alternative to conventional surfactants. Relationships between chemical structure of the diastereomers and surface activity were studied using surface tension measurements. It was found that the critical aggregation concentration (CAC) values are lower for deprotonated (R,S)-Rha-C10-C10 and higher for protonated (R,S)-Rha-C10-C10 compared to the other diastereomers or the native mRL mixture. Furthermore, the 1:1:1:1 diastereomeric mixture has the overall lowest cross-sectional area for deprotonated rhamnolipids. Dynamic light scattering (DLS) was used to study the hydrodynamic radii (Rh) of the mRL aggregates and the four diastereomers in aqueous solution. In all five surfactants studied, each observed at pH 8.0 and 4.0, three aggregate populations were observed. For all deprotonated rhamnolipids the micelle, at a hydrodynamic radius of ~2 nm, was found to be in the highest abundance where the two lower abundant other population take on a lamellar aggregate structure. Data to support this were collected using fluorescence probing techniques. For the surfactants in the protonated state, pH 4.0, it was found that all form primarily lamellar structures, also confirmed using fluorescence probing. The average aggregation numbers (Nagg) of the micelles for the deprotonated native mRL mixture and the four diastereomers were studied using steady-state and time-resolved fluorescence quenching measurements. Somewhat unexpectedly, the Nagg values were observed to be a strong function of the rhamnolipid concentration for all systems. At low concentrations, pre-micellar aggregates with aggregation numbers too small for micelles were observed. A critical concentration is identified at which a critical aggregation number is defined; this is proposed to be the smallest fully-formed micelle in solution with values of ~25-30 molecules/micelle for the native mRL mixture and all four diastereomers. Thus, the aggregation properties of the native mRL mixture and the four diastereomers are generally similar at this critical concentration. However, the increase in aggregation number above this critical point varies for all the surfactants, where the (R,R)-Rha-C10-C10 diastereomer has the greatest increase in monomers with concentration and the (S,S) and (R,S) diastereomers have the lowest. The increased observed aggregation number is consistent with the computational work showing increased growth with concentration for the deprotonated rhamnolipid micelles. Furthermore, these computations have confirmed the ability of protonated rhamnolipids to form lamellar structures in solution. Fluorescence probing work was also used to study rhamnolipid phase behavior as a function of varying solution conditions, such as ionic strength, solution pH, surfactant concentration, and temperature. Steady-state fluorescence methods are utilized to probe the surfactant microenvironment using the polarity-sensitive dyes prodan and laurdan. By dissolving the dye within the rhamnolipid aggregates and observing their solvatochromic behavior, all surfactants studied are known to form more micellar aggregates at high pH and low surfactant concentration, whereas elongation of the micelle is observed at low pH and moderate to high surfactant concentration.
109

Characterization of the Schoolteacher in Nineteenth Century American Fiction

Duncan, Mozelle 08 1900 (has links)
This study is limited largely to teachers in the public or common schools, although a few academy and female seminary teachers and at least one governess are included. It is not a definitive study, but a sufficient number of writings have been examined to make a fair sampling of the range of the nineteenth century American fiction.
110

Characterization of Ecg Signal Using Programmable System on Chip

Ravuru, Anusha 12 1900 (has links)
Electrocardiography (ECG) monitor is a medical device for recording the electrical activities of the heart using electrodes placed on the body. There are many ECG monitors in the market but it is essential to find the accuracy with which they generate results. Accuracy depends on the processing of the ECG signal which contains several noises and the algorithms used for detecting peaks. Based on these peaks the abnormality in the functioning of the heart can be estimated. Hence this thesis characterizes the ECG signal which helps to detect the abnormalities and determine the accuracy of the system.

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