We analyze HST and FUSE ultraviolet spectroscopic data for 11 sight lines passing through the infalling high-velocity cloud (HVC) Complex C. These sight lines pass through regions with H I column densities in the range N H I = 1018.1 -1020.1 cm-2. From [OI/HI] abundances, we find that Complex C metallicities range from 0.09 to 0.29 Z⊙, with a column density weighted mean of 0.13 Z ⊙. Nitrogen (N I) is underabundant by factors of (0.01 -0.07)(N/H)⊙, significantly less than oxygen relative to solar abundances. This pattern suggests nucleosynthetic enrichment by Type II SNe, consistent with an origin in the Galactic fountain or infalling gas produced in winds from Local Group galaxies. The range of metallicity and its possible (2 σ) dependence on NH I could indicate some mixing of primordial material with enriched gas from the Milky Way, but the mixing mechanism is unclear. We also investigate the significant highly ionized component of Complex C, detected in C IV, Si IV, and O VI, but not in N V. High-ion column density ratios show little variance and are consistent with shock ionization or ionization at interfaces between Complex C and a hotter surrounding medium. Evidence for the former mechanism is seen in the Mrk 876 line profiles, where the offset in line centroids between low and high ions suggests a decelerating bow shock.

We use spectroscopic data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) to study the wide range of ionization states of the "highly ionized high-velocity clouds" (HVCs). Studied extensively in O VI absorption, these clouds are usually assumed to be infalling gas in the Galactic halo at distances less than 50 kpc. An alternative model attributes the O VI (and O VII X-ray absorption) to cosmological structures of low-density, shock-heated intergalactic gas, distributed over 1-3 Mpc surrounding the Milky Way. The latter interpretation is unlikely, owing to the enormous required mass of gas (4 × 1012 M⊙). Our detection, in 9 of 12 sight lines, of low-ionization stages (C II/III/IV; Si II/III/IV) at similar high velocities as O vi requires gas densities far above that (nH ≈ 5 × 10-6 cm-3) associated with the warm-hot intergalactic medium (WHIM). These HVCs are probably cooling, multiphase gas in the Galactic halo, bow shocks, and interfaces between clouds falling through a hot, rotating gaseous halo. The velocity segregation of these HVCs in Galactic coordinates is consistent with a pattern in which infalling clouds reflect the sense of Galactic rotation, with peculiar velocities superposed.

To gain insight into four highly ionized high-velocity clouds (HVCs) discovered by Sembach et al., we have analyzed data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in O VI and column densities of multiple ionization stages of silicon (Si II, III, and IV) and carbon (C II, III, and IV). We interpret this ionization pattern as a multiphase medium that contains both collisionally ionized and photoionized gas. Toward PKS 2155-304, for HVCs at -140 and -270 km s-1, respectively, we measure logN(O VI) = 13.80 ± 0.03 and logN(O VI) = 13.56 ± 0.06; from Lyman series absorption, we find logN(H I) = 16.37 -0.14+0.22 and 15.23-0.22+0.38. The presence of high-velocity O VI spread over a broad (100 km s-1) profile, together with large amounts of low-ionization species, is difficult to reconcile with the low densities, ne ≈ 5 × 10-6 cm-3, in the collisional/photoionization models of Nicastro et al., although the HVCs show a similar relation in N(Si IV)/N(C IV) versus N(C II)/N(C IV) to that of high-z intergalactic clouds. Our results suggest that the high-velocity O VI in these absorbers does not necessarily trace the warm-hot intergalactic medium but instead may trace HVCs with low total hydrogen column density. We propose that the broad high-velocity O VI absorption arises from shock ionization, at bow shock interfaces produced from infalling clumps of gas with velocity shear. The similar ratios of high ions for HVC Complex C and these highly ionized HVCs suggest a common production mechanism in the Galactic halo.

Indiana University-Purdue University Indianapolis (IUPUI) / Animals depend on inheriting non-genetic information early in life to grow and develop naturally. This inherited, non-genetic information was previously thought to be limited to DNA modifications and DNA binding proteins. But recent studies have expanded our understanding of inheritance to include RNA and RNA binding proteins. We currently lack methods to identify and enrich for RNA binding proteins that might be involved in providing non-genetic information from mother to daughter cells. Others have developed a method using modified enzyme tags to pulse-label proteins with small molecule fluorescent ligands and follow these proteins as they are inherited by cells. Here I characterized and tested the application of a fluorescent small molecule targeting antibody to enrich for these labeled proteins. I first tested the ability of this antibody to bind to fluorescent ligand-labeled enzymes. I determined that the antibody can efficiently bind to at least one of the labeled enzymes. Second, I determined crystallization conditions for the ligand binding antibody fragment. This thesis sets the stage for structure determination and to test whether this antibody can work in vivo to enrich for RNA binding proteins involved in the delivery of non-genetic information to cells.

No description available.

In this thesis, we study low energy capture reactions and neutron-deuteron elastic scattering using halo effective field theory (EFT). At low energy, EFT provides a general framework to analyze physical systems regarding as an expansion of short-distance over large distance scales. We provide a model-independent calculation for neutron capture on carbon-14, radiative capture of 3He-4He, radiative capture of 3H-4He, and neutrondeuteron (n-d) doublet channel elastic scattering using halo EFT. These reactions play a significant role in the carbon-nitrogen-oxygen (CNO) cycle, solar neutrino flux measurement, lithium production, and big bang nucleosynthesis (BBN) in the early universe. The cross section is calculated for radiative neutron capture in carbon-14 using halo EFT. This reaction is slowest in the CNO cycle, and it acts as a bottleneck in the production of heavier nuclei A greater than 14. The capture contribution is different from Brett-Wigner resonance because of interference between resonant and non-resonant contribution. Also, we calculated, electromagnetic form factors for one-neutron halo nuclei such as carbon-15, beryllium-11, and carbon-19 using EFT. The electromagnetic form factors depend on the nucleon separation energy, effective range, and the two-body current. The EFT expressions are presented to leading order (LO) for 15C and next-to-leading order (NLO) for 11Be and 19C. We also calculated astronomical Sactor for 3He-4He and 3H-4He radiative capture reactions. The low energy Sactor for these reactions are important to understand the Li problem and neutrino physics. At the LO, the capture amplitude contains the initial state swave strong and Coulomb interactions summed to all orders. The NLO contribution comes from non-perturbative Coulomb interaction. Our calculated astrophysical Sactor for 3He- 4He is slightly above the average compared to the other measurement and prediction but consistent within current error bars. The Sactor for 3H-4He is also compatible with the experimental extrapolation. Finally, we studied doublet channel n-d scattering using halo EFT. A two dimer halo EFT is developed to describe the virtual state and three-body bound state in n-d scattering. We show the connection between virtual state and three-body bound state using S-matrix analysis and phase shift analysis which is supported by the Efimov plots.

The use of rating scales in the evaluation of secondary teacher performance has been called into question and widely criticized. Of particular concern has been the use of student ratings of teacher performance. A review of instruments and practices used in the rating process reveals serious design flaws that account for the criticisms leveled against the use of rating scales. This study sought to address the limitations evident in previous rating efforts by utilizing a combination of design methodologies and measurement models including elements of Classical Test Theory (CTT), factor analysis, and Item Response Theory (IRT). The IRT model employed was the one-parameter logistic model also known as the Rasch model. Twelve scales were developed consisting of a total of ninety-two items. These scales were developed to facilitate student ratings of secondary level teachers of religion in the Church Educational System (CES) of the Church of Jesus Christ of Latter-day Saints (LDS). In addition to exploring rating scale design methodology and scale performance, this study also examined a potential threat to the validity of decisions based on ratings referred to as halo effect. Using a variety of approaches to operationally define and estimate halo error, the extent to which male and female students exhibit differing degrees of halo in their ratings of teachers was examined. The results of the study revealed that of the twelve teacher traits hypothesized in the design of the rating scales, only three met defensible criteria based on CTT and Rasch model standards: the Student-Teacher Rapport Scale (STRS), the Scripture Mastery Expectation Scale (SMES), and the Spiritual Learning Environment Scale (SLES). Secondary students were unable to meaningfully discriminate between all twelve traits. Traditional approaches to halo effect estimation suggest that males exhibited halo to a greater degree than females, whereas Rasch model approaches to halo effect estimation were less consistent. Considered together, however, the evidence suggests differential halo error by gender, with males exhibiting halo to a greater degree than females. The implications of these findings for teacher evaluation, instructional design, and future research efforts are also addressed.

New ion trap mass spectrometry (ITMS) instrumentation, the toroidal IT and halo IT, were developed to meet the significant growth in on-site analysis applications. The miniature toroidal IT mass analyzer was operated with radio frequency (RF) trapping voltages of 3 kVp-p or less. Despite its reduced dimensions, it has roughly the same ion trapping capacity as conventional 3D quadrupole ITs. Unit-mass resolved spectra for n-butylbenzene, xenon, and naphthalene were obtained. The desired linear mass scale was obtained using conventional mass-selective instability scan combined with resonance ejection. The halo IT was also based on toroidal trapping geometry and microfabrication technology, consisting of two parallel ceramic plates, the facing surfaces of which were imprinted with sets of concentric ring electrodes. Unlike conventional ITs, in which hyperbolic metal electrodes establish equipotential boundary conditions, electric fields in the halo IT were established by applying different RF potentials to each ring. The potential on each ring could be independently optimized to provide the best trapping field. The halo IT featured an open structure, allowing easy access for in situ ionization. The toroidal geometry provided a large trapping volume. The photolithographic fabrication method avoided difficulty in meeting the required machining tolerances. Preliminary mass spectra showed resolution (m/δ m) of 60–75 when the trap was operated at 1.9 MHz and 500 Vp-p. Ion ejection through a hole in the center of the trap, and through slits machined in the ceramic plates were evaluated. The latter ejection method was done to mimic the design of the toroidal IT. The preferred electric fields containing higher order components were optimized by adjusting the potentials applied to the electrode rings of the halo IT without changing the original trapping plates and structure of the IT. The performance of the halo IT with 1% to 7% octopole field (A4/A2) components was determined. A best resolution of 280 (m/δ m) was obtained with 5% octopole field. SIMION simulations were used to demonstrate the toroidal trapping of ions and their mass analysis in both toroidal and halo ITs.

Superior properties of Silicon Carbide (SiC), such as wide bandgap, high breakdown field and high thermal conductivity, have made it the frontrunner to replace Silicon for applications requiring high breakdown strength, mechanical and radiation hardness. Commercial SiC devices are already available, although their expected performance has not yet been realized due to a few problems related to device fabrication technologies, such as selective doping. This work explores non-traditional techniques for SiC doping (and selective doping in particular) based on previously unknown types of defect reactions in SiC and novel epitaxial growth techniques, which offer advantages over currently available technologies. Recent developments in SiC epitaxial growth techniques at MSU have enabled the growth of high quality SiC epitaxial layers at record low temperatures of 1,300°C. Lower growth temperatures have enabled highly doped epilayers for device applications. Prototypes of SiC PiN diodes fabricated, demonstrated low values of the series resistance associated with anodes grown by the low temperature epitaxial growth technique. At room temperature, 100 ìm-diameter diodes with a forward voltage of 3.75 V and 3.23V at 1,000 A/cm2 before and after annealing were achieved. The reverse breakdown voltage was more than 680 V on average, even without surface passivation or edge termination. Reduced growth temperatures also enabled the possibility of selective epitaxial growth (SEG) of SiC with traditional masks used in the SEG in Si technology. Previously, SEG of SiC was impossible without high temperature masks. Good quality, defect free, selectively grown 4H-SiC epilayers were obtained using SiO2 mask. Nitrogen doped selectively grown epilayers were also obtained, which were almost completely ohmic, indicating doping exceeding 1x1019 cm-3. Moreover, conductivity modulation via defect reactions in SiC has been reported as a part of this work for the first time. The approach is based on a new phenomenon in SiC, named Recombination Induced Passivation (RIP), which was observed when hydrogenated SiC epilayers were subjected to above bandgap optical excitation. Additional acceptor passivation, and thereby modification of the conductivity of the epilayer, was observed. Results of investigations of the RIP process are presented, and conductivity modulation techniques based on the RIP process are proposed.

No description available.