8,192 research outputs found
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 â 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 Îł-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 (â)-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 âoutersphereâ 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 region of
Baade's Window, with resolution of . 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 varies from to
within the field of view centered on (18:03:20.9,--30:02:06), i.e. . The
ratio 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
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