The Stellar Content Near the Galactic Center

High angular resolution J, H, K, and L' images are used to investigate the stellar content within 6 arcsec of SgrA*. The data, which are complete to K ~ 16, are the deepest multicolor observations of the region published to date.Comment: 34 pages, including 12 figure

An experimental investigation of two large annular diffusers with swirling and distorted inflow

Two annular diffusers downstream of a nacelle-mounted fan were tested for aerodynamic performance, measured in terms of two static pressure recovery parameters (one near the diffuser exit plane and one about three diameters downstream in the settling duct) in the presence of several inflow conditions. The two diffusers each had an inlet diameter of 1.84 m, an area ratio of 2.3, and an equivalent cone angle of 11.5, but were distinguished by centerbodies of different lengths. The dependence of diffuser performance on various combinations of swirling, radially distorted, and/or azimuthally distorted inflow was examined. Swirling flow and distortions in the axial velocity profile in the annulus upstream of the diffuser inlet were caused by the intrinsic flow patterns downstream of a fan in a duct and by artificial intensification of the distortions. Azimuthal distortions or defects were generated by the addition of four artificial devices (screens and fences). Pressure recovery data indicated beneficial effects of both radial distortion (for a limited range of distortion levels) and inflow swirl. Small amounts of azimuthal distortion created by the artificial devices produced only small effects on diffuser performance. A large artificial distortion device was required to produce enough azimuthal flow distortion to significantly degrade the diffuser static pressure recovery

Parametric correlations versus fidelity decay: the symmetry breaking case

We derive fidelity decay and parametric energy correlations for random matrix ensembles where time--reversal invariance of the original Hamiltonian is broken by the perturbation. Like in the case of a symmetry conserving perturbation a simple relation between both quantities can be established.Comment: 8 pages, 8 figure

The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining Optimal 1-5 μ\mum Bandpasses

A new MKO-NIR infrared filter set is described, including techniques and considerations given to designing a new set of bandpasses that are useful at both mid- and high-altitude sites. These filters offer improved photometric linearity and in many cases reduced background, as well as preserve good throughput within the JHKLM atmospheric windows. MKO-NIR filters have already been deployed with a number of instruments around the world as part of a filter consortium purchase to reduce the unit cost of filters. Through this effort we hope to establish, for the first time, a single standard set of infrared fitlers at as many observatories as possible.Comment: PASP, in press; 32 pages, 11 figures, 3 Table

Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes

We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M_w > 7.5 do not reliably predict available geodetic data. In particular, we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic (teleseismic and two strong motion stations) or geodetic (InSAR and GPS) data. The differences might be related to postseismic deformation or, more likely, the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties. The earthquakes studied here follow the pattern of earthquake directivity along the coast of western South America, north of 5°S, earthquakes rupture to the north; south of about 12°S, directivity is southerly; and in between, earthquakes are bilateral. The predicted deformation at the Arequipa GPS station from the seismic-only slip model for the 7 July 2001 aftershock is not consistent with significant preseismic motion

Electromagnetically Induced Transparency (EIT) and Autler-Townes (AT) splitting in the Presence of Band-Limited White Gaussian Noise

We investigate the effect of band-limited white Gaussian noise (BLWGN) on electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, when performing atom-based continuous-wave (CW) radio-frequency (RF) electric (E) field strength measurements with Rydberg atoms in an atomic vapor. This EIT/AT-based E-field measurement approach is currently being investigated by several groups around the world as a means to develop a new SI traceable RF E-field measurement technique. For this to be a useful technique, it is important to understand the influence of BLWGN. We perform EIT/AT based E-field experiments with BLWGN centered on the RF transition frequency and for the BLWGN blue-shifted and red-shifted relative to the RF transition frequency. The EIT signal can be severely distorted for certain noise conditions (band-width, center-frequency, and noise power), hence altering the ability to accurately measure a CW RF E-field strength. We present a model to predict the changes in the EIT signal in the presence of noise. This model includes AC Stark shifts and on resonance transitions associated with the noise source. The results of this model are compared to the experimental data and we find very good agreement between the two.Comment: 14 page, 15 figures, 1 tabl

Global versus local billiard level dynamics: The limits of universality

Level dynamics measurements have been performed in a Sinai microwave billiard as a function of a single length, as well as in rectangular billiards with randomly distributed disks as a function of the position of one disk. In the first case the field distribution is changed globally, and velocity distributions and autocorrelation functions are well described by universal functions derived by Simons and Altshuler. In the second case the field distribution is changed locally. Here another type of universal correlations is observed. It can be derived under the assumption that chaotic wave functions may be described by a random superposition of plane waves

Microwave cavity perturbation studies on H-form and Cu ion-exchanged SCR catalyst materials: correlation of ammonia storage and dielectric properties

Ammonia-based selective catalytic reduction (SCR) has become the major control strategy for NOx emissions from light and heavy duty diesel engines. Before reducing NOx on the SCR active material, ammonia storage on the active sites of the catalyst is crucial. The in operando measurement of the dielectric properties of the catalyst material using microwave cavity perturbation is a promising indicator of ammonia loading. In this work, the influence of copper ion-exchange of the zeolite-based SCR material ZSM-5 on the NH3 storage and the dielectric properties is highlighted. The catalyst powder samples were monitored by microwave cavity perturbation as a function of the stored ammonia content at a frequency of approximately 1.2 GHz in a temperature range between 200 and 350 °C. Due to ion exchange, the NH3 storage behavior changes, what could be monitored in the sensitivity of the dielectric permittivity to NH3. The dependence of the complex dielectric permittivity on ammonia loading is decreased by ion exchange, hinting that mostly ammonia storage on Brønsted sites affects the dielectric permittivity. This finding adds new knowledge to the electrical conduction and polarization mechanisms occurring in these zeolite materials

Universal parametric correlations in the transmission eigenvalue spectra of disordered conductors

We study the response of the transmission eigenvalue spectrum of disordered metallic conductors to an arbitrary external perturbation. For systems without time-reversal symmetry we find an exact non-perturbative solution for the two-point correlation function, which exhibits a new kind of universal behavior characteristic of disordered conductors. Systems with orthogonal and symplectic symmetries are studied in the hydrodynamic regime.Comment: 10 pages, written in plain TeX, Preprint OUTP-93-36S (University of Oxford), to appear in Phys. Rev. B (Rapid Communication

Fidelity and level correlations in the transition from regularity to chaos

Mean fidelity amplitude and parametric energy--energy correlations are calculated exactly for a regular system, which is subject to a chaotic random perturbation. It turns out that in this particular case under the average both quantities are identical. The result is compared with the susceptibility of chaotic systems against random perturbations. Regular systems are more susceptible against random perturbations than chaotic ones.Comment: 7 pages, 1 figur