<p>The primary focus of the research presented here is the characterization of diffusion using Fluorescence Correlation Spectroscopy (FCS). To understand the nature of the anomalous diffusion observed in living systems, we characterized diffusion in complex in vitro systems including the diffusion of proteins. random-coil polymers. or dyes in crowded random-coil polymer solutions and the diffusion of polymer beads in agarose gels. Anomalous diffusion is defined where the mean-square-displacement follows a power law in time,</p> / Doctor of Philosophy (PhD)

<p>The discovery of high temperature superconductors prompted the reconsideration of numerous aspects of superconductivity. Among the most fundamental and controversial is the origin of dissipation in a current carrying superconductor. This is also very important from an applied perspective since the onset of dissipation, often described by the critical current density Jc, determines the current carrying capacity of a material. In this thesis, low energy, light ion irradiation has been implemented as a means of controlled sample modification. This type of irradiation has the advantage that it does not alter the stoichiometry of the sample but only results in disorder through the creation of point defects. This thesis explores the influence of ion damage on the normal and superconducting properties of YBa₂Cu₃O₇₋δ thin films. Of particular interest is the contrast between the strong sensitivity of Jc and the more modest sensitivity of the critical temperature, Tc, to ion damage. The evolution of the temperature dependent resistivity was measured systematically as a function of ion damage. The decrease in Tc with ion damage was compared to the predictions of several relevant models. A simple model based on Matthiessen's rule was used to describe the scattering rate and carrier density at low damage levels. At higher damage levels the system undergoes a superconductor-insulator transition which was found to be consistent with the Ioffe-Regel criterion. However, the resistivity in the insulating state is not described by any conventional models for strongly disordered materials. Measurements of the non-linear electric field-current density characteristics were performed for several levels of ion damage over a range of temperatures and compared with several models for dissipation. The data were found to be well described at all temperatures and damage levels by a model involving the quantum nucleation of vortex loops. The variation of the superconducting carrier density, ns, with ion damage was extracted and compared with independent measurements of the same quantity by infrared transmission in identically irradiated YBa₂Cu₃O₇₋δ thin films. This represents the first time a direct connection has been established between Jc and ns in high temperature superconductors.</p> / Doctor of Philosophy (PhD)

<p> The observation of gravitational waves from compact stars (neutron and quark stars) is a promising method of determining their internal composition. This research presents the details and results for calculations of some of the principal modes of compact star oscillations, by which they radiate gravitational waves. These are: the <i>f</i>-modes, <i>p</i>-modes, and <i>g</i>-modes. We find that for the same stellar mass, the <i> f</i>-modes for quark stars are higher in frequency than for neutron stars. The <i>p</i>-mode frequency of quark stars decrease with stellar mass, displaying an opposite trend to that of neutron stars. Two-component models were also considered. A core-ocean model was examined for a neutron star, using a polytropic equation of state (EOS), and a core-crust model for a quark star, using a bag model EOS. We find that <i>g</i>-mode oscillations in neutron star oceans depend on the dominant chemical species of the ocean as well as the mass of the underlying core. The addition of a solid crust onto a quark star increases the frequencies, attributable to shear stresses between the core and crust. These results pave the way to model and contrast the gravitational wave signals emitted by oscillating compact stars.</p>

<p> The Sun is the best observed object in astrophysics, but despite this distinction the nature of its well-ordered generation of magnetic field in 11-year activity cycles remains a mystery. In this work, we place the solar cycle in a broader context by examining the long-term variability of solar analog stars within 5% of the solar effective temperature, but varied in rotation rate and metallicity. Emission in the Fraunhofer H &amp; K line cores from singly-ionized calcium in the lower chromosphere is due to magnetic heating, and is a proven proxy for magnetic flux on the Sun. We use Ca H &amp; K observations from the Mount Wilson Observatory HK project, the Lowell Observatory Solar Stellar Spectrograph, and other sources to construct composite activity time series of over 100 years in length for the Sun and up to 50 years for 26 nearby solar analogs. Archival Ca H &amp; K observations of reflected sunlight from the Moon using the Mount Wilson instrument allow us to properly calibrate the solar time series to the S-index scale used in stellar studies. We find the mean solar <i>S</i>-index to be 5&ndash;9% lower than previously estimated, and the amplitude of activity to be small compared to active stars in our sample. A detailed look at the young solar analog HD 30495, which rotates 2.3 times faster than the Sun, reveals a large amplitude ~12-year activity cycle and an intermittent short-period variation of 1.7 years, comparable to the solar variability time scales despite its faster rotation. Finally, time series analyses of the solar analog ensemble and a quantitative analysis of results from the literature indicate that truly Sun-like cyclic variability is rare, and that the amplitude of activity over both long and short timescales is linearly proportional to the mean activity. We conclude that the physical conditions conducive to a quasi-periodic magnetic activity cycle like the Sun&rsquo;s are rare in stars of approximately the solar mass, and that the proper conditions may be restricted to a relatively narrow range of rotation rates.</p>

<p> The formation history of galaxy clusters is a powerful probe of cosmology. In particular, one may place strong constraints on the dark energy equation of state by examining the evolution across redshift of the number density of galaxy clusters as a function of mass. In this thesis, I describe my contributions to cluster cosmology, in particular to the development of the richness optical observable mass proxy. </p><p> I introduce <i>redMaPPer</i>, an optical cluster finder which represents an important upstream input for my thesis work. I next introduce the <b>M</b>ass <b>A</b>nalysis <b>T</b>ool for <b>Cha </b>ndra (<i><b>MATCha</b></i>), a pipeline which uses a parallelized algorithm to analyze archival Chandra data. <i>MATCha</i> simultaneously calculates X-ray temperatures and luminosities and performs centering measurements for hundreds of potential galaxy clusters using archival X-ray exposures. I run <i>MATCha</i> on the <i>redMaPPer</i> SDSS DR8 cluster catalog and use <i>MATCha</i>'s output X-ray temperatures and luminosities to analyze the galaxy cluster temperature-richness, luminosity-richness, luminosity-temperature, and temperature-luminosity scaling relations. I investigate the distribution of offsets between the X-ray center and <i>redMaPPer</i> center within 0.1 &lt; <i>z</i> &lt; 0.35 and explore some of the causes of <i>redMaPPer</i> miscentering. I collaborate with members of the Dark Energy Survey in order to repeat this analysis on Dark Energy Survey Year 1 data. I outline the various ways in which <i>MATCha </i> constitutes an important upstream work for a variety of astrophysical applications. These include the calibrations of two separate mass proxies, the study of the AGN fraction of galaxy clusters, and cosmology from cluster number densities and stacked weak lensing masses. Finally, I outline future upgrades and applications for <i>MATCha</i> throughout the lifespan of the Dark Energy Survey and the Large Synoptic Survey Telescope.</p><p>

No description available.

No description available.

Ring galaxies are specific types of interacting galaxies in which a smaller galaxy has passed through the center of the disk of another larger galaxy. The intrusion of the smaller galaxy causes the structure of the larger galaxy to compress as the smaller galaxy falls through, and to recoil back after the smaller galaxy passes through, hence the ring-like shape. In our research, we studied the star-forming regions of a sample of ring galaxies and compared to those of other interacting galaxies and normal galaxies. Using UV, optical, and IR archived images in twelve wavelengths from three telescopes, we analyzed samples of star-forming regions in ring and normal spiral galaxies using photometry. To measure the star formation rates of the star forming regions, we used computer software that picked out the regions and measured their luminosities in all twelve wavelengths, before comparing the luminosities in these wavelengths to determine the rate of star formation. We have determined that ring galaxies have proportionally more clumps with higher star formation rates than spirals, and a similar trend was suggested when comparing ring galaxies to other interacting galaxies (though more data is required for that comparison). These findings can help us understand galaxy evolution, including the evolution of our own galaxy.

This research encompasses two quite distinct searches for exotic matter. The first half concerns exotic matter on the scale of elementary particles. In this chapter, I consider the production of gluinos, the supersymmetric partner of the gluon, in models where the gluino is very light. Cross sections are calculated for electroproduction and hadroproduction of gluinos and the results indicate that existing accelerators are capable of probing the region of gluino masses between 1.0 and 2.0GeV with lifetimes between 10{dollar}\sp{lcub}-10{rcub}{dollar} and 10{dollar}\sp{lcub}-6{rcub}{dollar} seconds. Such experiments could find a light gluino if it exists, or to close this unexplored mass-lifetime window. The second half concerns the search for exotic forms of matter on the macroscopic scale, namely the search for stable strange quark matter. If stable strange matter exists, then all neutron stars may in fact be strange stars. I examine a recent proposal that strange star oscillations may result in a detectable millimeter-wave radio signal. The effects of rotation on this signal are calculated with the motivation of providing a more distinctive signature for the detection of strange matter stars.

No description available.