Experimental and analytical study of thermal acoustic oscillations

The thermal acoustic oscillations (TAO) data base was expanded by running a large number of tubes over a wide range of parameters known to affect the TAO phenomenon. These parameters include tube length, wall thickness, diameter, material, insertion length and length-to-diameter ratio. Emphasis was placed on getting good boiloff data. A large quantity of data was obtained, reduced, correlated and analyzed and is presented. Also presented are comparisons with previous types of correlations. These comparisons show that the boiloff data did not correlate with intensity. The data did correlate in the form used by Rott, that is boiloff versus TAO pressure squared times frequency to the one-half power. However, this latter correlation required a different set of correlation constants, slope and intercept, for each tube tested

S15RS SGR No. 6 (Disability Access)

A RESOLUTION To Urge and Request the Louisiana State University (LSU) Disability Services to reevaluate campus accessiblity for permanently and temporarily disabled students

An Investigation, Using Standard Experimental Techniques, to Determine FLCs at Elevated Temperature for Aluminium Alloys

An experimental procedure has been developed for the determination of FLCs at elevated temperatures. The GOM ARGUS system was employed for measuring surface strain based on pre-applied grids (pattern), and limit strains were determined according to the ISO 12004-2:2008 standard. Forming limit curves (FLCs) have been determined for AA5754 under warm forming conditions in an isothermal environment. The tests were carried out at various temperatures up to 300oC and forming speeds ranging from 5 – 300 mm s-1 . Results reveal the significant effect of both temperature and forming speed on FLCs of AA5754. Formability increases with increasing temperature above 200oC. Formability also increases with decreasing speed. The presented FLC results show that the best formability exists at low forming speed and the high temperature end of the warm forming range

Phosphoramidite Gold(I)-Catalyzed Diastereo- and Enantioselective Synthesis of 3,4-Substituted Pyrrolidines

In this article the utility of phosphoramidite ligands in enantioselective AuI catalysis was explored in the development of highly diastereo- and enantioselective AuI-catalyzed cycloadditions of allenenes. A Au^I-catalyzed synthesis of 3,4-disubstituted pyrrolidines and γ-lactams is described. This reaction proceeds through the enantioselective AuI-catalyzed cyclization of allenenes to form a carbocationic intermediate that is trapped by an exogenous nucleophile, resulting in the highly diastereoselective construction of three contiguous stereogenic centers. A computational study (DFT) was also performed to gain some insight into the underlying mechanisms of these cycloadditions. The utility of this new methodology was demonstrated through the formal synthesis of (−)-isocynometrine

First-order melting of a weak spin-orbit Mott insulator into a correlated metal

The electronic phase diagram of the weak spin-orbit Mott insulator (Sr(1-x)Lax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x~0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Neel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. As the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state.Comment: 5 pages, 4 figure

Mechanistic Study of Gold(I)-Catalyzed Intermolecular Hydroamination of Allenes

The intermolecular hydroamination of allenes occurs readily with hydrazide nucleophiles, in the presence of 3-12% Ph_3PAuNTf_2. Mechanistic studies have been conducted to establish the resting state of the gold catalyst, the kinetic order of the reaction, the effect of ligand electronics on the overall rate, and the reversibility of the last steps in the catalytic cycle. We have found the overall reaction to be first order in gold and allene and zero order in nucleophile. Our studies suggest that the rate-limiting transition state for the reaction does not involve the nucleophile and that the active catalyst is monomeric in gold(I). Computational studies support an “outersphere” mechanism and predict that a two-step, no intermediate mechanism may be operative. In accord with this mechanistic proposal, the reaction can be accelerated with the use of more electron-deficient phosphine ligands on the gold(I) catalyst

Extinction Map of Baade's Window

Recently Wo\'zniak \& Stanek (1996) proposed a new method to investigate interstellar extinction, based on two band photometry, which uses red clump stars as a means to construct the reddening curve. I apply this method to the color-magnitude diagrams obtained by the Optical Gravitational Lensing Experiment (OGLE) to construct an extinction map of $(40')^2$ region of Baade's Window, with resolution of $\sim30\;arcsec$. Such a map should be useful for studies of this frequently observed region of the Galactic bulge. The map and software useful for its applications are available via {\tt anonymous ftp}. The total extinction $A_V$ varies from $1.26\;mag$ to $2.79\;mag$ within the $(40')^2$ field of view centered on $(\alpha_{2000}, \delta_{2000}) =$ (18:03:20.9,--30:02:06), i.e. $(l,b)=(1.001,-3.885)$. The ratio $A_V/E(V-I) = 2.49\pm0.02$ is determined with this new method.Comment: revised version accepted for publication in ApJ Letters, 8 pages, uuencoded PostScript with 4 figures included; complete paper available through WWW at http://www.astro.princeton.edu/~library/prep.html; tables and auxiliary software available at ftp://www.astro.princeton.edu/stanek/Extinctio

On the distribution of estimators of diffusion constants for Brownian motion

We discuss the distribution of various estimators for extracting the diffusion constant of single Brownian trajectories obtained by fitting the squared displacement of the trajectory. The analysis of the problem can be framed in terms of quadratic functionals of Brownian motion that correspond to the Euclidean path integral for simple Harmonic oscillators with time dependent frequencies. Explicit analytical results are given for the distribution of the diffusion constant estimator in a number of cases and our results are confirmed by numerical simulations.Comment: 14 pages, 5 figure