Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7098. Adviser: Narayana R. Aluru. Includes bibliographical references (leaves 130-140) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2010. / Adviser: Yujie J. Ding.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3313. Advisers: Taekjip Ha; Paul Selvin. Includes bibliographical references (leaves 70-75) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6879. Adviser: Enrico Gratton. Includes bibliographical references (leaves 90-93) Available on microfilm from Pro Quest Information and Learning.

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Only very few molar polarizabilities are known with high accuracy; and when so, they are in general only known at a given wavelength. There is therefore a need to assess the molar polarizability with high accuracy of various gases, at different wavelengths. The molar polarizability of a gas is a measure of the susceptibility of a molecule to have its charge distribution affected by light. It is also the entity that relates the index of refraction to the (molar) density of a gas in Lorentz-Lorenz equation. Hence, for high precision measurements of the density of a gas, it is important to know the molar polarizability of the gas to high accuracy. In this work a GAMOR system has been used to determine the wavelength-dependent molar polarizability of Ar at 1550 nm.  However, a high accuracy assessment of the molar polarizability of a gas requires that the gas density is known with high accuracy. Since this is not trivial to assess, the molar polarizability of argon has been assessed in terms of that of nitrogen, which is assumed to be known with high accuracy. Hence, to minimise measurement errors, the measurement cavity was alternately filled with nitrogen and argon and the ratio between the signals provided by the GAMOR system represents the ratio of the molar polarizabilities of the two gases. It was found that the molar polarizability of argon was  0.94393(5) times that of nitrogen. Since the latter one has been assessed to 4.34828(3) x 10^-6  m^/mol, the molar polarizability of argon could be assessed to 4.10446(5) x 10^-6 m^3/mol.

This Thesis describes the progress made in the area of solid sample introduction in Inductively Coupled Plasma Emission Spectrometry (ICP-ES). As an alternative to solution nebulisation two methods of introducing samples to the ICP are investigated. The first of these uses the direct insertion probe technique first described by Horlick and Salin (63). The assembly utilised an electrically operated graphite rod system. This could be used equally well with small volumes of solution sample (5ul) or small masses of solid sample (Ca.5mg). The variables of cup dimensions and material were investigated along with volume and masses of sample used. Results of calibration of both solution residues and solid samples are presented along with details of Limit of Detection and sample Relative Standard Deviation (RSD). The comparative data were found to be in good agreement and it was established that solutions derived calibration data could be used for the analysis of Ni-base samples. Other solid matrices, elemental and alloyed were investigated. These materials divided into two groups, (1) low volatility matrix, from which trace elements were released and only minimal emission from matrix elements was detected and there were no spectral interference effects, (2) volatile matrix in which the matrix vaporized in the same temperature range as the trace elements, giving rise to substantial matrix emission and spectral interferences. It was concluded that DI-ICP-ES is at its most useful when dealing with easily volatilized trace elements in a relatively involatile matrix. The second approach to sample introduction involved the use of an electrothermal vaporization cell. This provided precise control of temperature and offered considerably higher final temperatures than the direct insertion probe system. An Electrothermal Vaporization (ETV) device was designed and built in the laboratory and interfaced to the ICP such that vapour produced in the cell was carried into the plasma discharge by the 'injector' gas stream. ETV was used for liquid and solid samples and results for these samples are presented.

In the last decades the scientific development has made it possible to produce pulses with durations below the femtosecond time scale (1 fs = 1015 s), reaching to attoseconds (1 as = 1018 s). This is the time scale of electronic motion inside atoms and molecules. One way to produce isolated attosecond pulses is through high harmonic generation in gases with intense few-cycle laser pulses. This process depends strongly on the electric field shape relative to the pulse envelope, which is characterized by the so called carrier-envelope phase (CEP).The goal of this master’s thesis is to measure and investigate the possibility to improve the CEP stability of sub-two-cycle laser pulses from the laser, Light Wave Synthesizer 20 (LWS-20). The first step of the master’s thesis was to modify a Labview program used to evaluate the CEP change to be able to reevaluate the already acquired raw data. The measurements are done with an f-to-2f interferometer, whichis a spectral interference device, which measures the CEP difference between two pulses. The CEP change of the laser system was measured at three positions: after the multi-pass amplifier of the laser front end (MP), after a hollow-core fiber (HCF), which is used for spectral broadening, and at the end of the laser system. The stability is determined as the RMS error (standard deviation) of the phase change overall shots in one sample (lower RMS is better stability). The measurements show an average stability of 160±20 mrad RMS after the MP, 280±31 mrad RMS after the HCF and 560±53 mrad RMS at the end of the system. The stability at the end of the system could be improved to 475±40 mrad RMS after a scan of the pump energy for one of the amplifier stages. The HCF appears to provide a lower limit in stability and influences it only if it is very good after the MP. The alignment of the HCF does also seem to influence the CEP stability and the best stability appears to coincide with maximum output energy. An acousto-optic modulator (Dazzler) has been used to manipulate the CEP change at the end of the system and can thereby compensate for long-term drifts, but the source of the CEP stability degradation at the end of the system should be further investigated.

The work reported in this thesis describes the first part of a continuing programme of research and development of Nuclear Magnetic Resonance Imaging ('Zeugmatography') at the University of Surrey. In recent years techniques have been developed for the localised detection of the magnetic resonance of spin I = 1/2 nuclei in vivo. Research has shown that the technique has considerable clinical potential, combining the attributes of sensitivity to soft tissue and some pathological lesions with the absence of 'dose'. Zeugmatography also has the ability to define and locate one or more tomographic images with the flexibility which comes from the absence of moving parts within the scanner. This thesis describes the design and construction of a prototype NMR scanner and presents a critical appraisal of the first images obtained. In addition a new and powerful method for the simultaneous acquisition of multiple tomographic planes is described and demonstrated. Furthermore, analyses of the problems, of signal acquisition and reconstruction are given.

Computer programs for simulating the kaonic-atom cascade process require the rates for strong-interaction absorption as well as for radiative and Auger transitions. Due to difficulties in computing the absorption rates, it has been standard practice to only approximately allow for them. In this section of the thesis, the effects of this procedure on the cascade results are investigated. As the approximate methods used heretofore are based on perturbation theory, this approximation is investigated first. A method of computing the widths to second-order in this framework is devised, but perturbation theory is still found to be inadequate. The black-sphere model is more successful, and by using extrapolation to obtain those widths which this model does not directly give, the absorption rates for all states appearing in the cascade calculation are fed in. On the way, the experimentally-observed relationship between the strong-interaction shift and the width in kaonic atoms is theoretically justified. The X-ray intensities from the cascade calculation are found to be negligibly improved by the comprehensive treatment of absorption. It is found that comparing absolute experimental and theoretical intensities is less successful than comparing relative intensities. The conclusion is drawn that previously used methods of dealing with strong-interaction absorption are sufficiently accurate.