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Zhong, JiaExploring the Three-Dimensional Regional Myocardial Function in Transgenic Mouse Models of Cardiac Diseases using Novel MR Tissue Tracking Techniques
Doctor of Philosophy, Case Western Reserve University, 2009, Biomedical Engineering

The advent of the genomic age is revolutionizing the experimental cardiovascular research irreversibly. Dissecting molecular switches that control the changes of cardiac physiology with transgenic mouse models has proven to offer important insights into the control of cardiac function. The integration of novel MR tissue tracking techqniques with these genetically manipulated mice may allow comprehensive characterization of contractile dysfunction non-invasively at the earliest diseased stages, thus facilitate our understanding of the pathogenesis of human cardiac diseases.

In the current thesis, we aimed at developing fast and accurate MR tissue tracking techniques and applying them for the assessment of ventricular function in transgenic mouse models of cardiac diseases. First, spatial modulation of magnetization (SPAMM) tagging was implemented in the mouse heart; and a 3D SPAMM tagging analysis method was developed based on harmonic phase (HARP) and homogeneous strain analysis. Using this 3D tagging analysis method, longitudinal strain and circumferential-longitudinal shear was quantified in addition to the 2D ventricular wall strain. Second, to improve the limited tagging resolution of existing SPAMM techniques, a HARP-based high-resolution tagging analysis method was proposed in mouse. The utility of such method was demostrated by quantifying the transmural heterogeneity of the left ventricle. Third, a 2D multi-phase displacement encoding with stimulated echoes (DENSE) imaging and analysis method was developed which allows direct and automatic Lagrangian strain quantification with high spatial and temporal resolution. Additionally, the utility of this multi-phase DENSE method was demonstrated in mouse both at baseline and with high workload. Functional enhancement was identified upon dobutamine stimulation both at the global and the regional levels. Fourth, for the evaluation of longitudinal wall motion within the short axis (SA) plane, 2D multi-phase DENSE imaging method was extended to the third dimension. Last, the application of MR tagging and DENSE methods was investigated in diabetic mouse hearts with cardiac-specific GLUT1-overexpression. Normalized cardiac function was found in diabetic mice with enhanced glucose metabolism through GLUT1-overexpression. Our results demonstrated the capability of MR tagging and DENSE in delineating left ventricular function in the mouse heart.

Committee:

XIN YU (Committee Chair); DAVID WILSON (Committee Member); MARK GRISWOLD (Committee Member); CHRIS FLASK (Committee Member); BRIAN HOIT (Committee Member)

Subjects:

Biomedical Research; Engineering

Keywords:

transgenic mouse models ; cardiac diseases; spatial modulation of magnetization (SPAMM) tagging ; harmonic phase (HARP);displacement encoding with stimulated echoes (DENSE); strain; regional myocardial function

Joshi, Rimesh M.Analog and Digital Array Processor Realization of a 2D IIR Beam Filter for Wireless Applications
Master of Science in Engineering, University of Akron, 2012, Electrical Engineering
A broadband digital beamforming algorithm is proposed for directional filtering of temporally-broadband bandpass space-time (ST) plane-waves (PWs) at radio frequencies (RFs). The enhancement of desired waves, as well as rejection of undesired interfering PWs, is simulated. A massively-parallel synchronous and asynchronous array architecture is proposed for the real-time implementation of 2nd-order two-dimensional (2D) infinite impulse response (IIR) spatially-bandpass (SBP) beam filters having potential applications in broadband beamforming of temporally down-converted RF signals. The higher speed of operation and potentially reduced power consumption of the asynchronous architecture in comparison to the conventional synchronous hardware have emerging applications in radio-astronomy, radar, navigation, space science, cognitive radio and wireless communications. Further, the bit error rate (BER) performance improvement along with the reduced computational complexity of these digital filters over digital phased array feed (PAF) beamformer is provided. A nominal BER versus signal-to-interference ratio (SIR) gain of 2-3 dB at approximately half the number of parallel multipliers compared to digital PAF, is observed. A novel discrete-space continuous-time (DSCT) analog circuit implementation of the 2D IIR SBP beam filter using ideal operational amplifiers is also proposed.

Committee:

Arjuna Madanayake, Dr. (Advisor); Hamid Bahrami, Dr. (Committee Member); S. I. Hariharan, Dr. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Array processors; bit error rate (BER); digital phased array feed (PAF); field-programmable gate array (FPGA); multi-dimensional digital filters; spatial modulation; systolic; wavefront; wireless

Alizadeh, ArdalanCognitive Communications for Emerging Wireless Systems
Doctor of Philosophy, University of Akron, 2016, Electrical Engineering
The current explosion of information and demand for high speed data communication call for novel solutions to utilize the radio resources more efficiently. The cognitive communication paradigm aims to mitigate this spectrum crunch by exploiting unused resources that are allocated to the primary communications systems. The aim of this research is to employ the concept of cognition in wireless devices and combine it with three recently introduced wireless communication techniques namely, K-user multi-input multi-output (MIMO) interference networks, spatial modulation scheme and molecular communications. Firstly, the feasibility of cognitive radio (CR) is studied in the presence of a K-user MIMO interference channel as the primary network. Assuming that the primary interference network has unused spatial degrees of freedom, the sufficient condition on the number of antennas is investigated at the secondary transmitter under which the secondary system can communicate and then the secondary precoding and decoding matrices are derived to have zero interference leakage into the primary network. A fast sensing method based on the eigenvalue analysis of the received signal covariance matrix is proposed to determine the availability of spatial holes. Also, a fine sensing method is provided based on the generalized likelihood ratio test to decide the absence of individual primary streams. The second part of this research is relevant to the application of spatial modulation (SM) in overlay CR networks, in which the primary and secondary networks work concurrently over the same spectrum band. The CR transmitter assists the primary network as a relay to amplify-and-forward (AF) the transmitted symbols of the primary. The secondary transmitter retransmits the primary symbols in amplitude-phase modulation domain, while its own information is transmitted by the index of transmitting antenna. The performance of the optimal detectors in terms of the average symbol error rate (ASER) and the asymptotic behavior of the ASER at both the primary and secondary at high signal-to-noise ratios (SNRs) are then provided. In the last part, a novel nanonetwork with cognitive capabilities is proposed, which is able to intelligently sense a primary molecular channel and use the channel opportunistically for its own transmission. In the proposed method, the secondary nanonetwork measures the concentration of molecules as a criterion to decide the presence or absence of the primary communication using a molecular energy detection scheme. When the molecular channel is available, the secondary transmitter sends its information using the same carrier molecules. Depending on the availability of timing information at the sensing nanodevice, two synchronous and asynchronous sensing mechanisms are provided based on the likelihood ratio test as the optimal detection method.

Committee:

Hamid Reza Bahrami, PhD (Advisor); Nathan Ida, PhD (Committee Member); Nghi Tran, PhD (Committee Member); Ping Yi, PhD (Committee Member); Malena Ines Espanol, PhD (Committee Member)

Subjects:

Electrical Engineering; Nanoscience

Keywords:

Cognitive radio networks; K-user MIMO interference channel; spatial sensing; spatial hole; spatial modulation; amplify-and-forward overlay CR networks; molecular communications; nano-networks, molecular channel sensing