Library: Physics

Debris disks are optically thin circumstellar disks around mainsequence stars, comprised of micron-sized grains. The dust is generated from destructive collisions of planetesimals, induced from gravitational perturbations by large planets. Debris disks can as signposts for planetary systems, through which, a universal picture can be obtained that encompasses the evolution and architecture of the Solar System’s own dust disk and planetary system. The dust in these disks can be detected by their thermal infrared flux, measured as an excess above the photospheric emission. Dust at different circu...

This book centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-...

We study the spatially resolved properties of star-forming galaxies at redshift z ~ 2 - 3 on scales ~ 1 kpc using a combination of morphological and kinematic analyses in an effort to characterize the major mechanisms of galaxy formation in the young universe. Using a sample of 216 galaxies which have been spectroscopically confirmed to lie between redshifts z = 1.8 - 3.4 in the GOODS-N field we demonstrate that rest-UV morphology (as seen by the Hubble Space Telescope) is statistically uncorrelated with physical properties such as star formation rate and is therefore unable to support the hy...

This study is a theoretical investigation of the electronic and optical properties of intrinsic semiconductors using the orthogonal empirical tight binding model. An analysis of the bulk properties of semiconductors with the zincblende, diamond and rocksalt structures has been carried out. We have extended the work of others to higher order in the interaction integrals and derived new parameter sets for certain semiconductors which better fit the experimental data over the Brillouin zone. The Hamiltonian of the heterostructures is built up layer by layer from the parameters of the bulk c...

The phenomena of superconductivity has enormous industrial potential, but the penetration of superconductor-based products has, thus far, been slow. An indisputable fact is that there are prizes, and profits, for the teams that solve the critical problems in understanding and processing these complex materials. The continuous processing of superconducting tapes and wires is a necessary stage that will open up the industrial market to the designers of a diverse range of time and energy saving devices, particularly in ultra-fast computing and lossless power transmission. The aim of the resear...

The electrostatic interaction between two charged spheres in the presence of a screening electrolyte is calculated at the level of the linearized Debye-Hückel theory. The calculation is performed analytically as a multipole expansion by applying two-center spherical harmonic expansions and symbolic manipulation methods. I focus on charge-charge and charge-induced dipole interactions, calculated for two spheres of possibly unequal size. The former interaction is given to good approximation by the familiar Debye-Hückel form ~ q1q2exp[-k(R-2a)]/[(epsilon*r(1+ka)^2]. The new results are ...

Processive enzymes are a special class of enzymes which presumably remain attached to their polymeric substrates between multiple rounds of catalysis. Due to this property, the substrate slides along the enzyme and reduces the time for the random diffusional enzyme-substrate encounters thereby increasing the efficiency of these enzymes manifold. Although structural information from many processive enzymes is available, the atomistic details of particularly the substrate sliding process, which is an inherently dynamic process, remain largely unknown. We take first steps to understand the slidin...