Master of Science, Miami University, 2024, Biology

Coordination between central pattern generators (CPG) is important in proper functioning of related rhythmic behaviors such as vocalization, breathing and locomotion. Despite their importance, the cellular mechanisms of inter-network coordination and how it impacts muscles remain largely unidentified. Using the small, well-characterized networks in the stomatogastric nervous system of the crab, Cancer borealis, I identify the role of a dual-network neuron in coordinating the feeding-related pyloric (“fast”: 1 Hz: filtering food) and gastric mill (“slow”: 0.1 Hz: chewing) CPG networks, during a unique modulatory state elicited by the neuropeptide Gly1-SIFamide. The dual-network neuron, LPG, rhythmically increases and decreases the frequency of the pyloric rhythm in time with different phases of the slower gastric mill rhythm. Using these findings, I show that this complex coordination pattern is distinctly translated into electrical responses of two behaviorally different muscles, innervated by LPG. Where the LPG innervated pyloric muscle follows LPG's dual-network activity, while the gastric mill muscle prioritizes gastric mill over pyloric activity. This study provides insight into a unique coordination mechanism that is funneled through a dual-network neuron, and how the muscles innervated by this neuron respond to and participate in the overall coordination of related but distinct behaviors.

Committee: Dawn Blitz Dr (Advisor); Joseph Ransdell Dr (Committee Member); Kathleen Killian Dr (Committee Member) Subjects: Neurobiology; Neurosciences; Physiology

Master of Science, The Ohio State University, 2020, Electrical and Computer Engineering

Capacitance measurements are commonly conducted for many types of semiconductor devices. Because they can detect separated charges, they are able to characterize doping concentration, built-in voltage, speed, and more for p/n junctions. This information provides feedback to the crystal growers and help them grow higher quality materials. However, these measurements do have limitations. The complex circuit model used to calculate capacitance from a measured impedance requires assumptions and simplifications. This thesis reviews analyses and best practices for capacitance measurements and presents two innovations that expand their applications. These new approaches use double-mesa p-i-n devices and the dependence of capacitance upon area to characterize important semiconductor properties. This work is especially relevant to infrared detectors based on narrow gap antimonide semiconductors such as Type-II superlattices. One analysis determines the doping polarity (p-type or n-type) of the intrinsic layer in p-i-n devices, and the other provides a more thorough analysis of the components in the circuit model, reducing the number of error-inducing simplifications. These analyses were applied to GaSb and/or 10 monolayer by 10 monolayer InAs/AlSb superlattice p-i-n and n-i-p devices.

Committee: Sanjay Krishna Dr. (Advisor); Siddharth Rajan Dr. (Committee Member); Daniel Jardine Dr. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2004, Electrical Engineering

The epitaxial integration of III-V semiconductors with Si is of interest for photovoltaics since Si substrates offer a lighter, stronger, and cost effective platform for device production. By using compositionally step-graded SiGe layers to 100% Ge, the 4% lattice-mismatch between Si and GaAs and In 0.49 Ga 0.51 P is accommodated; this method has produced record low threading dislocation densities (TDD) of 1x10 6 cm -2 in fully relaxed the Ge/SiGe/Si (SiGe) substrates. In this dissertation, this method of III-V/Si integration is used for the development of GaAs and In 0.49 Ga 0.51 P single junction (SJ) solar cells and In 0.49 Ga 0.51 P /GaAs dual junction (DJ) solar cells, integrated on a Si platform. As such, we report that the minority carrier electron lifetime in p-type GaAs grown on Si is lower than that of holes in n-type GaAs at a given TDD and is a consequence of the higher mobility of electrons. This lower lifetime produced higher reverse saturation currents and lower open-circuit voltages for n+/p compared to p+/n configuration GaAs cells grown on SiGe with the same TDD. The higher performance of the p+/n GaAs/Si cell, by virtue of its higher open-circuit voltage, has demonstrated a record terrestrial efficiency of 18.1% and has been produced in areas up to 4 cm 2 with no degradation in cell performance. In 0.49 Ga 0.51 P SJ cells were integrated on Si substrates and an increase in depletion region recombination component of the reverse saturation current with TDD was also measured. A p+/n polarity preference for In 0.49 Ga 0.51 P on Si was demonstrated, although, the lower mobility of both carriers in In 0.49 Ga 0.51 P compared to GaAs, suggests a greater TDD tolerance. Based on these SJ results, the first realization of an In 0.49 Ga 0.51 P/GaAs DJ cell on Si with an output voltage greater than 2 V was demonstrated. A comparison with an identical DJ cell on GaAs found that the DJ cell on Si retained 91% of open-circuit voltage and 99% of short-circuit cu (open full item for complete abstract)

Committee: Steven Ringel (Advisor) Subjects: Physics, Condensed Matter