This report contains a general introduction, the experimental section, general conclusions, and two appendices: using projection operators to construct the basis functions and the magnetic transition of bulk pyrrhotite samples in the low-temperature range. Four chapters have been removed for separate processing. They are: From pyrrhotite to troilite: An application of the Landau theory of phase transitions; Phase transition in near stoichiometric iron sulfide; A ordering, incommensuration and phase transitions in pyrrhotite. Part 1: A TEM study of Fe{sub 7}S{sub 8}; and Part 2: A high-temperature X-ray powder diffraction and thermomagnetic study.

This dissertation describes the measurement of the top quark mass m{sub t} using events recorded during a 125 pb{sup -1} exposure of the D0 detector to {radical}s=1.8 TeV {anti p}p collisions. Six events consistent with the hypothesis t{anti t} {yields} bW{sup +}, {anti b}W{sup -} {yields} b{anti l}{nu}, {anti b}l{anti {nu}} form the dilepton sample. The kinematics of such events may be reconstructed for any assumed mt, and the likelihood of each such solution evaluated. A measurement of m{sub t} based on these relative solution likelihoods gives m{sub t} = 169.9 {+-} 14.8 (stat.) {+-} 3. 8 (syst.) GeV/c{sup 2}. A 2C kinematic fit is performed on a sample of 77 events consistent with t{anti t} {yields} bW{sup +}, {anti b}W{sup -} {yields} b{anti l}{nu}, {anti b}q{anti q} , and this, in combination with an estimate on the likelihood that each event is top, yields m{sub t} = 173.3 {+-} 5.6 (stat.) {+-} 6.2 (syst.) GeV/c{sup 2} . A combination of these two measurements gives m{sub t} = 173.1 {+-} 5.2 (stat.) {+-} 5.7 (syst.) GeV/c{sup 2}.

This thesis reports on the measurement of the W and Z boson inclusive production cross sections ({sigma}{sub W} and {sigma}{sub Z}) times electronic branching ratios (Br(W {yields} e{nu}) and Br(Z {yields} ee)) in p{anti p} collisions at {radical}s = 1.8 TeV. The analysis is based on 12.8 pb{sup -1} of data taken in the 1992-1993 run by the D0 detector at the Fermilab Tevatron collider; the cross sections were measured to be: {sigma}{sub W} {center_dot} Br(W {yields} e{nu}) = 2. 36 {+-} 0.02 {+-} 0.07 {+-} 0.13 nb and {sigma}{sub Z} {center_dot} Br(Z {yields} ee) = 0.218 {+-} 0.008 {+-} 0.008 {+-} 0.012 nb. The first error is statistical, the second error represents the non- luminosity systematic error, and the third error shows the uncertainty in the luminosity determination. Future prospects for similar measurements based on larger samples of data are discussed.

Microdosimetry was used to investigate three issues at the neutron therapy facility (NTF) at Fermilab. Firstly, the conversion factor from absorbed dose in A-150 tissue equivalent plastic to absorbed dose in ICRU tissue was determined. For this, the effective neutron kerma factor ratios, i.e. oxygen tissue equivalent plastic and carbon to A-150 tissue equivalent plastic, were measured in the neutron beam. An A-150 tissue equivalent plastic to ICRU tissue absorbed dose conversion factor of 0.92 {+-} 0.04 determined. Secondly, variations in the radiobiological effectiveness (RBE) in the beam were mapped by determining variations in two related quantities, e{sup *} and R, with field size and depth in tissue. Maximal variation in e{sup *} and R of 9% and 15% respectively were determined. Lastly, the feasibility of utilizing the boron neutron capture reaction on boron-10 to selectively enhance the tumor dose in the NTF beam was investigated. In the unmodified beam, a negligible enhancement for a 50 ppm boron loading was measured. To boost the boron dose enhancement to 3% it was necessary to change the primary proton energy from 66 MeV and to filter the beam by 90 mm of tungsten.

Since the gains associated with solar thermal energy technologies are comparatively small in relation to the required capital investment, it is vital to maximize conversion efficiency. While providing the necessary function of freeze protection, the heat exchanger commonly included in solar domestic water heating systems represents a system inefficiency. This thesis explores two alternate methods of providing freeze protection without resorting to a heat exchanger. Commonly, collectors are made of rigid copper tubes separated by copper or aluminum fins. Cracking damage can occur when water is allowed to freeze and expand inside the non compliant tubes. The possibility of making collectors out of an elastic material was investigated and shown to be effective. Since unlike copper, elastomers typically have low thermal conductivities, the standard collector performance prediction equations do not apply. Modified thermal performance prediction equations were developed which can be used for both low and high thermal conductivity materials to provide accurate predictions within a limited range of plate geometries. An elastomeric collector plate was then designed and shown to have comparable performance to a copper plate collector whose aperture area is approximately 33% smaller. Another options for providing freeze protection to an SDHW system is to turn it …