Dissecting the Oligomeric Behavior of Caveolin-1 using the Analytical Ultracentrifuge

https://nsuworks.nova.edu/nsudigital_harrison/3450/thumbnail.jp

The synthesis of sterically demanding ligands and examples of their copper complexes

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.Vita.Includes bibliographical references.Conditions for promoting the Pd-catalyzed arylation of (N-pyrrolyl)zinc derivatives have been established using aryl bromides, chlorides, and iodides as substrates. In most cases, 0.5 mol% Pd(OAc)₂ can achieve the desired transformation in roughly 24 hours, with the more sterically demanding substrates requiring altered conditions. Typical isolated yields are in excess of 70%. Moreover, methyl- and aryl-substituted pyrrolyl anions have been shown to display similar chemistry using 5.0 mol% Pd(OAc)₂. Though they require longer reaction times, the isolated yields rival those of the unsubstituted analogs. Two new copper(I) N-heterocyclic carbene complexes containing the 2,4,6,2",4",6"-hexaisopropyl-1,1':3',1"-terphenyl moiety have been synthesized and isolated. The LCuCl complex (92% isolated yield) was made via a one-pot synthesis from the corresponding imidazolinium tetrafluoroborate salt, NaH, and CuCl (L = [1,3-bis-(2,4,6,2",4",6"-hexaisopropyl- [1,1':3',1"]terphenyl-5'-yl)-4,5-dihydroimidazol-2-ylidene]). The LCuOAc complex (71% isolated yield) was made the same way using CuOAc in place of CuCl.by Ryan D. Rieth.S.M

The Loschmidt Echo as a robust decoherence quantifier for many-body systems

We employ the Loschmidt Echo, i.e. the signal recovered after the reversal of an evolution, to identify and quantify the processes contributing to decoherence. This procedure, which has been extensively used in single particle physics, is here employed in a spin ladder. The isolated chains have 1/2 spins with XY interaction and their excitations would sustain a one-body like propagation. One of them constitutes the controlled system S whose reversible dynamics is degraded by the weak coupling with the uncontrolled second chain, i.e. the environment E. The perturbative SE coupling is swept through arbitrary combinations of XY and Ising like interactions, that contain the standard Heisenberg and dipolar ones. Different time regimes are identified for the Loschmidt Echo dynamics in this perturbative configuration. In particular, the exponential decay scales as a Fermi golden rule, where the contributions of the different SE terms are individually evaluated and analyzed. Comparisons with previous analytical and numerical evaluations of decoherence based on the attenuation of specific interferences, show that the Loschmidt Echo is an advantageous decoherence quantifier at any time, regardless of the S internal dynamics.Comment: 12 pages, 6 figure

New insights into microstructure of neutron-irradiated tungsten

The development of appropriate materials for fusion reactors that can sustain high neutron fluence at elevated temperatures remains a great challenge. Tungsten is one of the promising candidate materials for plasma-facing components of future fusion reactors, due to several favorable properties as for example a high melting point, a high sputtering resistivity, and a low coefficient of thermal expansion. The microstructural details of a tungsten sample with a 1.25 dpa (displacements per atom) damage dose after neutron irradiation at 800 °C were examined by transmission electron microscopy. Three types of radiation-induced defects were observed, analyzed and characterized: (1) voids with sizes ranging from 10 to 65 nm, (2) dislocation loops with a size of up to 10 nm and (3) W–Re–Os containing σ- and χ-type precipitates. The distribution of voids as well as the nature of the occurring dislocation loops were studied in detail. In addition, nano-chemical analyses revealed that the σ- and χ-type precipitates, which are sometimes attached to voids, are surrounded by a solid solution cloud enriched with Re. For the first time the crystallographic orientation relationship of the σ- and χ-phases to the W-matrix was specified. Furthermore, electron energy-loss spectroscopy could not unambiguously verify the presence of He within individual voids

Circular orbits and spin in black-hole initial data

The construction of initial data for black-hole binaries usually involves the choice of free parameters that define the spins of the black holes and essentially the eccentricity of the orbit. Such parameters must be chosen carefully to yield initial data with the desired physical properties. In this paper, we examine these choices in detail for the quasiequilibrium method coupled to apparent-horizon/quasiequilibrium boundary conditions. First, we compare two independent criteria for choosing the orbital frequency, the "Komar-mass condition" and the "effective-potential method," and find excellent agreement. Second, we implement quasi-local measures of the spin of the individual holes, calibrate these with corotating binaries, and revisit the construction of non-spinning black hole binaries. Higher-order effects, beyond those considered in earlier work, turn out to be important. Without those, supposedly non-spinning black holes have appreciable quasi-local spin; furthermore, the Komar-mass condition and effective potential method agree only when these higher-order effects are taken into account. We compute a new sequence of quasi-circular orbits for non-spinning black-hole binaries, and determine the innermost stable circular orbit of this sequence.Comment: 24 pages, 17 figures, accepted for publication in Physical Review D, revtex4; Fixed error in computing proper separation and updated figures and tables accordingly, added reference to Sec. IV.A, fixed minor error in Sec. IV.B, added new data to Tables IV and V, fixed 1 reference, fixed error in Eq. (A7b), included minor changes from PRD editin

Gravitational radiation reaction in compact binary systems: Contribution of the quadrupole-monopole interaction

The radiation reaction in compact spinning binaries on eccentric orbits due to the quadrupole-monopole interaction is studied. This contribution is of second post-Newtonian order. As result of the precession of spins the magnitude $L$ of the orbital angular momentum is not conserved. Therefore a proper characterization of the perturbed radial motion is provided by the energy $E$ and angular average $\bar{L}$. As powerful computing tools, the generalized true and eccentric anomaly parametrizations are introduced. Then the secular losses in energy and magnitude of orbital angular momentum together with the secular evolution of the relative orientations of the orbital angular momentum and spins are found for eccentric orbits by use of the residue theorem. The circular orbit limit of the energy loss agrees with Poisson's earlier result.Comment: accepted for publication in Phys. Rev.