Physical Sciences and Mathematics Commons^™

Neutron Diffraction Study Of Heavy Water Intercalation In Superconducting Deuterated Sodium Cobaltate Na0.35Coo21.4d2O, Cinzia Metallo

Masters Theses

When Na-deficient Na_xCoO₂ is intercalated with water¹ or heavy water², it becomes a superconductor. The maximum critical temperature of 4.5 K is found for the composition Na_xCoO₂yD₂O (x= 0.3 and y=1.4). In spite of its low transition temperature, several similarities with high temperature superconducting cuprates have raised interest in this compound. Nevertheless, up to now, a clear understanding of the role of water has not been achieved.

Since superconductivity appears only when water is inserted in the parent compound, the goal of this research work was to understand …

Four-Dimensional Mvct Imaging And Spatial Translation Of Helical Tomotherapy Dose Distributions Using Sinogram Modification, Samuel Scott Outten

Masters Theses

Helical tomotherapy systems have the unique attribute of using sinograms as a machine input and a machine output. These sinograms have well understood properties that may allow for operational changes that simplify and/or improve radiation treatment.

In the first part of this work, the detector array output sinogram of an MVCT imaging study is used to produce images of an object at different locations along a pattern of motion and the multi-leaf collimator (MLC) control sinogram is used to translate dose distributions in space. A temporal re-binning algorithm was written that divided the MVCT sinogram projections into positional bins that …

Photochemical Route To The Production Of Fullerene Allotropes, Olga Ovchinnikova

Masters Theses

A photochemical route to the formation of two C₆₀ molecules which are bridged by one and up to eighteen carbon atoms to form bucky-dumbbell shaped molecules, i.e., C₆₀ > C < C₆₀ to C₆₀ > C = C = C = C = C = C = C = C = C = C < C₆₀, etc. is described. Irradiation of C60 in solutions of chloroform and iodine (magenta color) with pulsed laser light from the frequency tripled (355 nm) Nd:YAG laser produced a dark crimson color. Matrix assisted laser desorption ionization (MALDI) negative ion mass spectroscopy was used to …

Ultraviolet Image Analysis Of Spacecraft Exhaust Plumes, Karen L. Norton

Masters Theses

Data obtained during the April 26, 2000 MirEx experiment is used to infer the chemical mechanisms responsible for ultraviolet radiation observed to emanate from Russian spacecraft exhaust plumes in low Earth orbit. The principle objective of this experiment was to use the Mir Space Station instruments to study the plume collisional processes occurring in the rarified atmosphere of the far-field; at distances greater than one kilometer away from the spacecraft. This was accomplished by observing the automated Progress cargo ship as the auxiliary engines were being retrofired in a ram-burn configuration at 330 kilometers in altitude above Earth. The primary …

Surface Studies Of Selective Hydrogen Desorption From Silicon, Jason Kenneth Smith

Masters Theses

This thesis examines quantum confined quasi-one-dimensional structures on silicon surfaces. An in situ prepared and hydrogenated Si(100)-(2x1) is investigated, on which a quasi-dimensional nanostructure is fabricated via scanning tunneling microscopy. Also, the feasibility of STM-based nanolithography on an ex situ hydrogenated Si(111)-(1x1) surface is explored. Using methods such as those discussed herein it is possible to create quasi one-dimensional semiconducting metallic nanowires as well as contact pads, useful for four point probe measurements at the nanoscale. Using a STM, dimer wide strips of hydrogen are removed from the passivated layer to reveal bare silicon surface bonds forming a nanowire approximately …