We constructed a 3.0 meter diameter f/1.5 Liquid Mirror Telescope (LMT) between 1990 and 1994 at the NASA Johnson Space Center, Houston, Texas. We have subsequently operated it since 1995 at the NASA Orbital Debris Observatory (NODO), Cloudcroft, NM. Employing an inexpensive rotating container of mercury as its primary parabolic mirror, the NASA LMT is a cost-effective alternative to telescopes utilizing glass mirrors. We detail criteria for mirror construction including environmental considerations via Hg vapor emission analysis. We describe performance optimization to the NODO site seeing limit of 0.8 arcseconds FWHM via analysis of perturbations to image quality from mirror angular velocity stability, dynamic balance, rotational axis tilt, and prime focus lateral and tilt displacements. We detail the behavior of the two prominent mirror surface wave phenomena---spiral and concentric forms. We demonstrate that the former probably results from vorticity in the air boundary layer above the mirror and show diffraction effects from the latter. We describe mirror stabilization in terms of boundary layer theory. The prime focus NASA-LMT utilizes corrective optics yielding a field of 46 arcminute diameter. Utilizing Micro-Channel-Plate (MCP) intensified video cameras we have obtained 750 hours of zenith staring orbital object event data with a limiting object diameter of approximately 1 cm at 1000 km altitude and 0.1 albedo. We have extended to 17.75 the lower magnitude limit of optical detections among the telescopes employed for orbital object surveys, further demonstrated the incompleteness of the SATCAT, and corroborated results of RADAR employed in orbital object detection. Utilizing CCDs we have conducted a 135 night broadband and multi-narrowband survey of 20 square degrees of sky at high galactic latitude down to a limiting magnitude of ∼22.0. The survey data will yield information on object morphology, spectral classifications, and large-scale structure to a redshift (z) of 0.5 with an accuracy of Deltaz ≤ 0.02. Broadband images from this survey are presented, demonstrating that the NASA-LMT optical performance is comparable to conventional telescopes of equivalent size located at a similar site.

When measured with sufficient spectral range, resolution, and signal-to-noise ratio, nearly every mineral has a unique infrared spectral signature. However, determining which minerals are present on Mars using infrared spectroscopy has proven to be very difficult. The goal of this work is to examine complicating factors inherent to spacecraft-based infrared spectral measurements of Mars, and to determine methods to extract mineralogical information from spectra that cover the wavelength range 0.77 to 50 mum. On Earth, infrared spectra of an unknown mineral or gas can be measured under controlled conditions. However, a spacecraft spectrometer measures Mars through both atmospheric gases and aerosols, and at varying viewing geometries. Spectra of the surface of Mars have very subtle variations, so examining them requires well-calibrated spectra of excellent quality, and extended spectral range. These combined effects greatly complicate interpretations. The work presented here details a straightforward method to remove effects of varying viewing geometry on near-infrared spectra of Mars, using 1989 Phobos 2 ISM spectra. Next, it details the recovery and calibration of the 1969 Mariner Mars IRS data set, and presents IRS spectral evidence for goethite on Mars. Finally, a method is developed to utilize night spectra to examine the aerosol mineralogy, followed by a discussion of the importance of accounting for the aerosol re-emission when utilizing day measurements to examine surface mineralogy. This work utilizes spectra from all five infrared spectrometers flown to Mars. It addresses a range of issues, but the unifying theme is how to extract mineralogic information from the spectra. The results show that the most important spectral criteria for determining mineralogy from spacecraft infrared spectra are an extended spectral range, high spectral resolution, and high signal-to-noise ratio. Here, an extended spectral range is defined as coverage of at least two of the three infrared spectral regions: reflected (∼0.8--3 mum), overtone (∼3--7 mum), and fundamental (∼7--50 mum). Spectra with low spectral resolution, low spectral range, or low signal-to-noise ratio allow different spectral type units to be mapped, but such data sets do not provide enough information to determine uniquely the mineral phases present.

Surface observations, lake evaporation data and upper-air soundings were collected in a special data-collection effort during the months of August and September of 2004 and 2005 on an island in the middle of Great Bear Lake, Northwest Territories. For this period of the year, the late summer, when increasing variability in surface pressure starts occurring, the effect of different synoptic-scale regimes on the lake-atmosphere interface is investigated to understand the regional specificities, with comparisons to nearby stations and a high spatial and temporal resolution reanalysis model (North American Regional Reanalysis). The planetary boundary layer over the lake systematically shows typical surface and mixed layer structures but with varying depths depending on the mean lower tropospheric temperature. Inversions in the surface layer, linked with warm regimes, support deep mixed layers. Within the surface layer, during warm regimes, a superadiabatic lapse rate can support (or not) a higher-stability sublayer on top of it, in which case the mixed layer happens to be much deeper. The first mechanism for lake evaporation includes the occasional passage of synoptic-scale storm systems with both warm and cold frontal features creating strong, short-lived latent heat interactions between the lake and the atmosphere, but relatively low total amounts of evaporation. The main mechanism for extensive evaporation is a cold anticyclone allowing for significant daytime insolation. A lake-breeze circulation can then develop and provide strong-enough mesoscale winds for diurnal upward latent heat exchanges, with wind channelling into Keith Arm of the lake for strong lake-breeze onshore winds.

<p> Polymer brushes consist of multiple monomers connected together with one of the polymer chain's ends attached to a surface. Polymer brushes have shown great promise for a wide variety of applications including drug delivery dendrimer systems and as tunable brushes that can change their shape and physical properties in response to changes in their environment. Regularly branched polymer brushes which are structured as a function of their chemical indices are investigated here using the self-consistent mean field theory for electrically neutral polymers. The brushes were described using weighting functions, <i> f(n)</i>, were <i>n</i> was the fewest number of monomers from a specified location to a free end. Brushes with weighting functions of the form <i>f(n)=n^b, f(n)=e^bn</i>, as well as <i>f(n)=d^an</i> when <i>d</i> 2 and &alpha; > 2 were found to match the parabolic free chain end profile expected, while it was determined that polymer brushes described using <i>f(n)=n^b</i> must be very small in order to remain in equilibrium. However, brushes described by <i>f(n)</i>=2<i>G^(N-n)_N</i> and <i>f(n)</i>2<i>ⁿ</i> were found to be unstable for real, positive values of the potential of the system.</p>

<p> I use N-body simulations of the Milky Way and its satellite population of dwarf galaxies to probe the small-scale power spectrum and the properties of the unknown dark matter particle. The number of dark matter satellites decreases with decreasing mass of the dark matter particle. Assuming that the number of dark matter satellites exceeds or equals the number of observed satellites of the Milky Way, I derive a lower limit on the dark matter particle mass of <i>m_WDM</i> > 2.1 keV for a thermal dark matter particle, with 95% confidence. The recent discovery of many new dark matter dominated satellites of the Milky Way in the Sloan Digital Sky Survey allows me to set a limit comparable to constraints from the complementary methods of Lyman-&alpha; forest modeling and X-ray observations of the unresolved cosmic X-ray background and of halos from dwarf galaxy to cluster scales. </p><p> I also investigate the claim that the largest subhalos in high resolution dissipationless cold dark matter (CDM) simulations of the Milky Way are dynamically inconsistent with observations of its most luminous satellites. I quantify the effects of the adopted cosmological parameters on the satellite densities and show the tension between observations and simulations adopting parameters consistent with WMAP9 is greatly diminished. I explore warm dark matter (WDM) cosmologies for 1-4 keV thermal relics. In 1 keV cosmologies subhalos have circular velocities at kpc scales 60% lower than their CDM counterparts, but are reduced by only 10% in 4 keV cosmologies. Recent reports of a detected X-ray line in emission from galaxy clusters has been argued as evidence of sterile neutrinos with properties similar to a 2 keV thermal relic. If confirmed, my simulations show they would naturally reconcile the densities of the brightest satellites and be consistent with the abundance of ultra-faint dwarfs. </p><p> I conclude by using N-body simulations of a large set of dark matter halos in different CDM and WDM cosmologies to demonstrate that the spherically averaged density profile of dark matter halos has a shape that depends on the power spectrum of initial conditions. Virialization isotropizes the velocity dispersion in the inner regions of the halo but does not erase the memory of the initial conditions in phase space. I confirm that the slope of the inner density profile in CDM cosmologies depends on the halo mass with more massive halos exhibiting steeper profiles. My simulations support analytic models of halo structure that include angular momentum and argue against a universal form for the density profile.</p>

<p> In this work, we determine heating rates in reconnection formed flare loops with analysis of observations and models. We utilize the spatially resolved ultraviolet (UV) light curves and the thick-target hard X-ray (HXR) emission to construct heating rates of a few thousand flare loops anchored at the UV footpoints. These loops are formed and heated by magnetic reconnection taking place successively. These heating rates are then used as an energy input in the zero-dimensional Enthalpy-Based Thermal Evolution of Loops (EBTEL) model to calculate the evolution of plasmas in these loops and compute synthetic spectra and light curves in Soft X-ray (SXR) and extreme ultraviolet (EUV), which compare favorably with those observed by the <i> Geostationary Operational Environmental Satellite (GOES),</i> <i> Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)</i>, and <i> Solar Dynamics Observatory (SDO).</i> With a steady-state assumption, we also compute the transition-region differential emission measure (DEM) at the base of each flare loop during its decay phase, and compare the predicted UV and EUV emissions at the footpoints with AIA observations. This study presents a method to constrain heating of reconnection-formed flare loops using all available observations, and provides insight into the physics of energy release and plasma heating during the flare. Furthermore, using <i> RHESSI</i> HXR observations, we could also infer the fraction of non-thermal beam heating in the total heating rate of flare loops. For an M8.0 flare on 2005 May 13, the lower limit of the total energy used to heat the flare loops is estimated to be 1.22&times;10³¹ ergs, out of which, less than 20% is carried by beam-driven upflows during the impulsive phase. The method is also applied to analyzing an eruptive M3.7 flare on 2011 March 7 and a compact C3.9 flare on 2012 June 17. Both flares are observed in EUV wavelengths by the Atmospheric Imaging Assembly (AIA) and Extreme Ultraviolet Variability Experiment (EVE) onboard the <i>SDO,</i> which allow us to investigate the flare evolution from the heating to cooling phase. The results show that the model-computed synthetic EUV emissions agree very well with those observed in AIA bands or EVE lines, indicating that the method successfully captures heating events and appropriately describes mean properties of flare plasma shortly after the heating phase.</p>

<p> Large multiwavelength surveys are now driving the frontiers of astronomical research. I describe results from my work using data from two large astronomical surveys: the Cosmic Evolution Survey (COSMOS), which has obtained deep photometric and spectroscopic data on two square degrees of the sky using many of the most powerful telescopes in the world, and the WFC3 Infrared Spectroscopic Parallels (WISP) Survey, which uses the highly sensitive slitless spectroscopic capability of the Hubble Space Telescope Wide Field Camera 3 to detect star-forming galaxies over most of the universe's history. First I describe my work on the evolution of the high-redshift quasar luminosity function, an important observational quantity constraining the growth of the supermassive black holes in the early universe. I show that the number density of faint quasars declines rapidly above <i>z</i> &sim; 3. This result is discussed in the context of cosmic reionization and the coevolution of galaxies and their central black holes.</p><p> Next I present results of a multi-year campaign of near-infrared spectroscopy with FIRE, a world-class near-infrared spectrometer on the Magellan Baade 6.5 meter telescope in Chile, targeting emission-line galaxies at <i> z</i> &sim; 2 discovered with the Hubble Space Telescope. Our results showed that the typical emission-line galaxy at this redshift has low-metallicity, low dust obscuration, high ionization parameter, and little evidence for significant active galactic nucleus (AGN) contribution to the emission lines. We also find evidence that high redshift star-forming galaxies have enhanced nitrogen abundances. This result has interesting implications for the nature of the star formation in such galaxies &ndash; in particular, it could mean that a large fraction of such galaxies harbor substantial populations of Wolf-Rayet stars, which are massive, evolved stars ejecting large amounts of enriched matter into the interstellar medium.</p><p> Finally, I will discuss the discovery of three distant, ultracool brown dwarfs in the WISP survey. These objects, larger than massive planets but smaller than dwarf stars, are very difficult to detect, but their numbers and distribution in our galaxy have profound implications for our understanding of the formation of low-mass stars and planets. The brown dwarfs were found in the WFC3 grism spectroscopy, where they were identified through their strong atmospheric absorption features of water and methane. A systematic search for such objects in all WISP fields yielded three in total, allowing statistical inferences to be made regarding their distribution and number density in the Milky Way.</p>

Using a dataset of weekly ice cover in the Gulf of St. Lawrence, the intraseasonal and interannual variabilities of the mean ice cover fraction were investigated over the Gulf and six of its subregions for the 1963-90 period. Climatological seasonal cycles were calculated by averaging the weekly ice cover fraction means over the sampling period. The interannual variability was investigated using seasonal and monthly means. The major findings are the positive trend of the seasonal means and the prominence of variability at the interdecadal scale (12-15 yr). / Relationships with runoff, monthly surface air temperature, monthly air circulation, autumnal water salinity and temperature profiles, and particular climatic events are investigated to determine the major causes of the variability. / From the original 83-cell grid data, the monthly-averaged icefields of the Gulf were calculated and their maps generated for the months of January, February, March, April and May for every sample year.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7386. Adviser: Stuart L. Shapiro. Includes bibliographical references (leaves 140-147) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of California, San Francisco, 2006. / Source: Dissertation Abstracts International, Volume: 67-02, Section: B, page: 0749. Adviser: John W. Sedat.