A total production index for Washington, D.C.

A heavy concentration of services characterizes the economy of the District of Columbia. Growth in the D.C. economy, although usually heavily insulated from the swings of the U.S. business cycle, varies in intensity and, sometimes, in direction. Now, a new monthly index of total production provides a timely measure of services and goods production in Washington, D.C.Industrial production index ; Federal Reserve District, 5th

The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope

We designed, built, and calibrated a new spectropolarimeter for the HiVIS spectrograph (R 12000-49000) on the AEOS telescope. We also did a polarization calibration of the telescope and instrument. We will introduce the design and use of the spectropolarimeter as well as a new data reduction package we have developed, then discuss the polarization calibration of the spectropolarimeter and the AEOS telescope. We used observations of unpolarized standard stars at many pointings to measure the telescope induced polarization and compare it with a Zemax model. The telescope induces polarization of 1-6% with a strong variation with wavelength and pointing, consistent with the altitude and azimuth variation expected. We then used scattered sunlight as a linearly polarized source to measure the telescopes spectropolarimetric response to linearly polarized light. We then made an all-sky map of the telescope's polarization response to calibrate future spectropolarimetry.Comment: PASP 118, June 200

Structure and Stability of Si(114)-(2x1)

We describe a recently discovered stable planar surface of silicon, Si(114). This high-index surface, oriented 19.5 degrees away from (001) toward (111), undergoes a 2x1 reconstruction. We propose a complete model for the reconstructed surface based on scanning tunneling microscopy images and first-principles total-energy calculations. The structure and stability of Si(114)-(2x1) arises from a balance between surface dangling bond reduction and surface stress relief, and provides a key to understanding the morphology of a family of surfaces oriented between (001) and (114).Comment: REVTeX, 4 pages + 3 figures. A preprint with high-resolution figures is available at http://cst-www.nrl.navy.mil/papers/si114.ps . To be published in Phys. Rev. Let

Sentencing Outcomes of Convicted Child Sex Offenders

This research examines the sentencing outcomes of convicted child sexual offenders from data collected over an eight year period. Multiple regression and nominal log linear regression are used to examine length of prison sentence, length of probation sentence, and whether or not the convicted offender is actually sent to prison or to probation. While many independent variables appear to be related to sentence outcome, they fall into three categories: characteristics of the offender, characteristics of the victim, and characteristics of the crime. Additionally, while many variables appear related at the bivariate level, when multivariate analysis is applied, fewer variables remain significant and these are mostly from the characteristics of the offense

Atomic Scale Memory at a Silicon Surface

The limits of pushing storage density to the atomic scale are explored with a memory that stores a bit by the presence or absence of one silicon atom. These atoms are positioned at lattice sites along self-assembled tracks with a pitch of 5 atom rows. The writing process involves removal of Si atoms with the tip of a scanning tunneling microscope. The memory can be reformatted by controlled deposition of silicon. The constraints on speed and reliability are compared with data storage in magnetic hard disks and DNA.Comment: 13 pages, 5 figures, accepted by Nanotechnolog

Localized Excitons and Breaking of Chemical Bonds at III-V (110) Surfaces

Electron-hole excitations in the surface bands of GaAs(110) are analyzed using constrained density-functional theory calculations. The results show that Frenkel-type autolocalized excitons are formed. The excitons induce a local surface unrelaxation which results in a strong exciton-exciton attraction and makes complexes of two or three electron-hole pairs more favorable than separate excitons. In such microscopic exciton "droplets" the electron density is mainly concentrated in the dangling orbital of a surface Ga atom whereas the holes are distributed over the bonds of this atom to its As neighbors thus weakening the bonding to the substrate. This finding suggests the microscopic mechanism of a laser-induced emission of neutral Ga atoms from GaAs and GaP (110) surfaces.Comment: submitted to PRL, 10 pages, 4 figures available upon request from: [email protected]

First principles theory of inelastic currents in a scanning tunneling microscope

A first principles theory of inelastic tunneling between a model probe tip and an atom adsorbed on a surface is presented, extending the elastic tunneling theory of Tersoff and Hamann. The inelastic current is proportional to the change in the local density of states at the center of the tip due to the addition of the adsorbate. We use the theory to investigate the vibrational heating of an adsorbate below an STM tip. We calculate the desorption rate of H from Si(100)-H(2$\times$1) as function of the sample bias and tunnel current, and find excellent agreement with recent experimental data.Comment: 5 pages, RevTeX, epsf file

Axisymmetric Stationary Solutions as Harmonic Maps

We present a method for generating exact solutions of Einstein equations in vacuum using harmonic maps, when the spacetime possesses two commutating Killing vectors. This method consists in writing the axisymmetric stationry Einstein equations in vacuum as a harmonic map which belongs to the group SL(2,R), and decomposing it in its harmonic "submaps". This method provides a natural classification of the solutions in classes (Weil's class, Lewis' class etc).Comment: 17 TeX pages, one table,( CINVESTAV- preprint 12/93