An AC method of measuring the conductivity of dielectric liquids.

The problem undertaken in this thesis is the presentation of a method of measuring the conductivity of dielectric liquids in which the liquid is used as the parallel tank circuit of a modified Wien-bridge oscillator. The main advantage of this method is that the frequency of the voltage applied to the liquid can be varied by simply varying the oscillator frequency. This allows the selection of a frequency which is best suited to the liquid in regard to polarization and relaxation time. An oscillator was designed, built and used in the laboratory to measure the conductivity of the dielectric liquids -- distilled water, glycerin, and chloroform. The results of these measurements, which are presented in tabular form, agree well with published values for these liquids --Abstract, page ii

Rotation periods of exoplanet host stars

The stellar rotation periods of ten exoplanet host stars have been determined using newly analysed Ca II H & K flux records from Mount Wilson Observatory and Stromgren b, y photometric measurements from Tennessee State University's automatic photometric telescopes (APTs) at Fairborn Observatory. Five of the rotation periods have not previously been reported, with that of HD 130322 very strongly detected at Prot = 26.1 \pm 3.5 d. The rotation periods of five other stars have been updated using new data. We use the rotation periods to derive the line-of-sight inclinations of the stellar rotation axes, which may be used to probe theories of planet formation and evolution when combined with the planetary orbital inclination found from other methods. Finally, we estimate the masses of fourteen exoplanets under the assumption that the stellar rotation axis is aligned with the orbital axis. We calculate the mass of HD 92788 b (28 MJ) to be within the low-mass brown dwarf regime and suggest that this object warrants further investigation to confirm its true nature.Comment: Accepted for publication in MNRAS. 15 pages, 11 figure

The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785

We report the discovery of planets orbiting two bright, nearby early K dwarf stars, HD 97658 and Gl 785. These planets were detected by Keplerian modelling of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth with minimum mass Msini = 8.2 +/- 1.2 M_Earth, orbital period P = 9.494 +/- 0.005 d, and an orbit that is consistent with circular. Gl 785 b is a Neptune-mass planet with Msini = 21.6 +/- 2.0 M_Earth, P = 74.39 +/- 0.12 d, and orbital eccentricity 0.30 +/- 0.09. Photometric observations with the T12 0.8 m automatic photometric telescope at Fairborn Observatory show that HD 97658 is photometrically constant at the radial velocity period to 0.09 mmag, supporting the existence of the planet.Comment: Submitted to ApJ, 7 pages, 6 figures, 5 table

Identification of the relative distribution of rare-earth ions in phosphate glasses

The relative distribution of rare-earth ions R3+ (Dy3+ or Ho3+) in the phosphate glass RAl0.30P3.05O9.62 was measured by employing the method of isomorphic substitution in neutron diffraction. It is found that 7.9(7) R-R nearest neighbors reside at 5.62(6) Angstrom in a network made from interlinked PO4 tetrahedra. Provided that the role of Al is explicitly considered, a self-consistent account of the local matrix atom correlations can be developed in which there are 1.68(9) bridging and 2.32(9) terminal oxygen atoms per phosphorus

Two Jovian-Mass Planets in Earthlike Orbits

We report the discovery of two new planets: a 1.94 M_Jup planet in a 1.8-year orbit of HD 5319, and a 2.51 M_Jup planet in a 1.1-year orbit of HD 75898. The measured eccentricities are 0.12 for HD 5319 b and 0.10 for HD 75898 b, and Markov Chain Monte Carlo simulations based on derived orbital parameters indicate that the radial velocities of both stars are consistent with circular planet orbits. With low eccentricity and 1 < a < 2 AU, our new planets have orbits similar to terrestrial planets in the solar system. The radial velocity residuals of both stars have significant trends, likely arising from substellar or low-mass stellar companions.Comment: 32 pages, including 11 figures and 5 tables. Accepted by Ap

Low Mass Companions for Five Solar-Type Stars from the Magellan Planet Search Program

We report low mass companions orbiting five Solar-type stars that have emerged from the Magellan precision Doppler velocity survey, with minimum (Msini) masses ranging from 1.2 to 25 Mjup. These nearby target stars range from mildly metal-poor to metal-rich, and appear to have low chromospheric activity. The companions to the brightest two of these stars have previously been reported from the CORALIE survey. Four of these companions (HD 48265-b, HD 143361-b, HD 28185-b, HD 111232-b) are low-mass Jupiter-like planets in eccentric intermediate and long-period orbits. On the other hand, the companion to HD 43848 appears to be a long period brown dwarf in a very eccentric orbit.Comment: Accepted for publication on ApJ, 26 pages, 10 figures, 7 table

Structure of lanthanum and cerium phosphate glasses by the method of isomorphic substitution in neutron diffraction

Neutron diffraction was used to measure the total structure factors for several rare-earth ion R3+ (La3+ or Ce3+) phosphate glasses with composition close to RAl0.35P3.24O10.12. By assuming isomorphic structures, difference function methods were employed to separate, essentially, those correlations involving R3+ from the remainder. A self-consistent model of the glass structure was thereby developed in which the Al correlations were taken into explicit account. The glass network was found to be made from interlinked PO4 tetrahedra having 2.2(1) terminal oxygen atoms, OT, at 1.51(1) Angstrom, and 1.8(1) bridging oxygen atoms, OB, at 1.60(1) Angstrom. Rare-earth cations bonded to an average of 7.5(2) OT nearest neighbors in a broad and asymmetric distribution. The Al3+ ion acted as a network modifier and formed OT-A1-OT linkages that helped strengthen the glass. The connectivity of the R-centered coordination polyhedra was quantified in terms of a parameter f(s) and used to develop a model for the dependence on composition of the A1-OT coordination number in R-A1-P-O glasses. By using recent 17 A1 nuclear-magnetic-resonance data, it was shown that this connectivity decreases monotonically with increasing Al content. The chemical durability of the glasses appeared to be at a maximum when the connectivity of the R-centered coordination polyhedra was at a minimum. The relation of f(s) to the glass transition temperature, Tg, was discussed

Germination of Silene regia Seeds from Four Sites in Lawrence County, Illinois, Following Scarification or Stratification

Silene regia Sims is an endangered prairie forb in Illinois where small isolated colonies are scattered. In La·wrence County, two sites (Allison Prairie and Chauncey Marsh) have fewer plants (6-23) than two other sites (Cmmty Road and Cemetery) with 26-45 plants. Information on seed germination in these isolated colonies is needed. Our goal was to evaluate seed germination of S. regia from colonies in Lawrence County, illinois. S. regia fruits were collected from these four sites on August 9 and 19, 1999. Seeds were scarified by cutting the seed coat, or they were stratified at 2 C for 12 or 15 weeks. Seeds from Chaun.cey Marsh weighed less than those from other sites. With the exception of seeds from Chauncey Marsh, scariiication increased gemrination within each site. When significant germination differences occurred due to site, they were apparent on stratified seed, where frequently Allison Prairie was highest and Chauncey Marsh was lowest. Germination clifferences between stratified and control seeds were inconsistent, although stratified seeds had up to 67% higher gemrination than control seeds when significant differences occurred. These increases in seed germination were most evident in seeds collected on August 9th and stratified for 12 weeks. Seed that was neither scarified nor stratified gemrinated after storage, indicating that scarification and stratification are not absolute gemrination requirements with after-ripened seeds. Seed germination at different sites did not correspond directly with population sizes, and multiple mechanisms were present for breaking seed donnancy in S. regia

Germination of Silene regia Seeds from Four Sites in Lawrence County, Illinois, Following Scarification or Stratification

Silene regia Sims is an endangered prairie forb in Illinois where small isolated colonies are scattered. In La·wrence County, two sites (Allison Prairie and Chauncey Marsh) have fewer plants (6-23) than two other sites (Cmmty Road and Cemetery) with 26-45 plants. Information on seed germination in these isolated colonies is needed. Our goal was to evaluate seed germination of S. regia from colonies in Lawrence County, illinois. S. regia fruits were collected from these four sites on August 9 and 19, 1999. Seeds were scarified by cutting the seed coat, or they were stratified at 2 C for 12 or 15 weeks. Seeds from Chaun.cey Marsh weighed less than those from other sites. With the exception of seeds from Chauncey Marsh, scariiication increased gemrination within each site. When significant germination differences occurred due to site, they were apparent on stratified seed, where frequently Allison Prairie was highest and Chauncey Marsh was lowest. Germination clifferences between stratified and control seeds were inconsistent, although stratified seeds had up to 67% higher gemrination than control seeds when significant differences occurred. These increases in seed germination were most evident in seeds collected on August 9th and stratified for 12 weeks. Seed that was neither scarified nor stratified gemrinated after storage, indicating that scarification and stratification are not absolute gemrination requirements with after-ripened seeds. Seed germination at different sites did not correspond directly with population sizes, and multiple mechanisms were present for breaking seed donnancy in S. regia