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Mechanisms Of Feedback In The Visual System, Adam Eggebrecht
Mechanisms Of Feedback In The Visual System, Adam Eggebrecht
All Theses and Dissertations (ETDs)
Feedback is an ubiquitous feature of neural systems though there is little consensus on the roles of mechanisms involved with feedback. We set up an in vivo preparation to study and characterize an accessible and isolated feedback loop within the visual system of the leopard frog, Rana pipiens. We recorded extracellularly within the nucleus isthmi, a nucleus providing direct topographic feedback to the optic tectum, a nucleus that receives the vast majority of retinal output. The optic tectum and nucleus isthmi of the amphibian are homologous structures to the superior colliculus and parabigeminal nucleus in mammals, respectively. We formulated a …
Advances In Computational Solvation Thermodynamics, Matthew Wyczalkowski
Advances In Computational Solvation Thermodynamics, Matthew Wyczalkowski
All Theses and Dissertations (ETDs)
The aim of this thesis is to develop improved methods for calculating the free energy, entropy and enthalpy of solvation from molecular simulations. Solvation thermodynamics of model compounds provides quantitative measurements used to analyze the stability of protein conformations in aqueous milieus. Solvation free energies govern the favorability of the solvation process, while entropy and enthalpy decompositions give insight into the molecular mechanisms by which the process occurs. Computationally, a coupling parameter λ modulates solute-solvent interactions to simulate an insertion process, and multiple lengthy simulations at a fixed λ value are typically required for free energy calculations to converge; entropy …
Multi-Element Isotopic Analyses Of Presolar Graphite Grains From The Orgueil Meteorite, Manavi Jadhav
Multi-Element Isotopic Analyses Of Presolar Graphite Grains From The Orgueil Meteorite, Manavi Jadhav
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This dissertation presents the results and implications of the isotopic analyses of presolar graphite grains from the primitive carbonaceous chondrite, Orgueil. Graphite grains from low- and high-density fractions were analyzed for C, N, O, Si, Al-Mg, K, Ca, and Ti isotopes. These analyses indicate that isotopic properties are density dependent. Most low-density grains come from supernovae as indicated by large 18O, 15N, 28Si excesses, high inferred 26Al/27Al and 41Ca/40Ca ratios, and the initial presence of the short-lived radionuclide 44Ti in some grains. Some high-density grains also show supernovae signatures, but a majority seems to originate from low-metallicity asymptotic giant branch …
Solar Wind Helium, Neon, And Argon In Genesis Aluminum Collectors, Jennifer Mabry
Solar Wind Helium, Neon, And Argon In Genesis Aluminum Collectors, Jennifer Mabry
All Theses and Dissertations (ETDs)
The Genesis mission collected samples of solar wind: SW) for 853 days and returned them to Earth for analysis. There are several processes that have the potential to significantly alter the composition between the time when SW ions are accelerated away from the sun, to the time the laboratory measurements are made. This work attempts to constrain these sources of fractionation and present the best estimate of the isotopic composition of SW helium, neon, and argon implanted into two different aluminum SW collectors on board the Genesis Mission. We have conducted a diffusion experiment on a similar time scale as …
Backscatter And Attenuation Characterization Of Ventricular Myocardium, Allyson Gibson
Backscatter And Attenuation Characterization Of Ventricular Myocardium, Allyson Gibson
All Theses and Dissertations (ETDs)
This Dissertation presents quantitative ultrasonic measurements of the myocardium in fetal hearts and adult human hearts with the goal of studying the physics of sound waves incident upon anisotropic and inhomogeneous materials. Ultrasound has been used as a clinical tool to assess heart structure and function for several decades. The clinical usefulness of this noninvasive approach has grown with our understanding of the physical mechanisms underlying the interaction of ultrasonic waves with the myocardium. In this Dissertation, integrated backscatter and attenuation analyses were performed on midgestational fetal hearts to assess potential differences in the left and right ventricular myocardium. The …
Phase Formation, Liquid Structure, And Physical Properties Of Amorphous- And Quasicrystal-Forming Alloys, Victor Wessels
Phase Formation, Liquid Structure, And Physical Properties Of Amorphous- And Quasicrystal-Forming Alloys, Victor Wessels
All Theses and Dissertations (ETDs)
Since the discovery of quasicrystals in 1985 and the development of commercially viable bulk metallic glasses: BMGs) in the mid 1990's a great deal of attention has been given to the characterization of new alloys with desirable properties, such as larger amorphous casting thickness, higher mechanical strength, or hydrogen storage capacity. Here, the results of a number of investigations into the structures and properties of some noncrystalline solid alloys will be presented and analyzed. Beamline electrostatic levitation: BESL), a method for determining supercooled liquid structure and phase formation insitu, was used. Using BESL, the development of structural and chemical inhomogeneity …
Properties Of Neutron Star Critical Collapses, Mew-Bing Wan
Properties Of Neutron Star Critical Collapses, Mew-Bing Wan
All Theses and Dissertations (ETDs)
Critical phenomena in gravitational collapse opened a new mathematical vista into the theory of general relativity and may ultimately entail fundamental physical implication in the astrophysical realm, especially in gravitational collapse scenarios. However, at present, the dynamics of critical phenomena in realistic astrophysical gravitational collapse scenarios are still largely unknown. My thesis seeks to understand the properties of the neutron star critical solution, understand the properties of the threshold in the solution space of the Einstein field equations between the black hole and a neutron star phases, and clarify the implication these results on realistic astrophysical scenarios. We develop a …