3,741 research outputs found
Development and applications of optical interferometric micrometrology in the angstrom and subangstrom range
The recent development of the scanning electron tunneling microscope and the atomic force microscope requires absolute standards for measurements in the angstrom and subangstrom range. Optical interferometry with lasers and multiple mode laser resonances can provide absolute measurements as the laser wavelengths are very accurately known. A key feature of such measurements is the use of piezoelectric crystals as translators of the highest accuracy for very small disturbances. However, the dimensional changes of these crystals resulting from electrical potential changes depend on many variables, among them the method of mounting, so that accurate calibrations are necessary. Starting from advances in optical metrology made by physicists trying to find gravity waves, advances which led to measurements down to 10 to the -5 A, the author designed and built a much simpler system for the angstrom range. The major limiting factors were mechanical vibrations, air currents, thermal changes and laser instabilities
Collective Bargaining Laws and Threat Effects of Unionism in the Determination of Police Compenstation
This study examines the effect of public sector unions on compensation packages. The model of the compensation determination process incorporates distinctive institutional aspects of public sector labor relations, particularly the differences in collective bargaining laws across states. The model is estimated using data on over 800 municipal police departments. Our results indicate that the effect of public sector unions depend critically on these institutional features of the public sector. First, unionism thrives only in those states with protective legislation. Second, in states where unionism has flourished,unionism exerts a strong upward pressure on both union and nonunion compensation packages. Cross section estimates for 1978 indicate that salaries of union and nonunion departments in highly unionized states are some 30% higher than are the salaries in states with low levels of unionism. However, no significant difference between union and nonunion salaries within states is observed. Before-after estimates of the "state-wide union effect" are more modest (9.9% to 18.1%). Finally, this "state-wide union effect" on union and nonunion departments appears to 'be even more pronounced on fringe benefits than it is on salaries. The net result is that in highly unionized states, a greater proportion of the larger compensation packages is paid in fringe benefits.
The stellar content of brightest cluster galaxies
We present near-infrared K-band spectroscopy of 21 elliptical or cD Brightest
Cluster Galaxies (BCGs), for which we have measured the strength of the 2.293
micron CO stellar absorption feature. We find that the strength of this feature
is remarkably uniform among these galaxies, with a smaller scatter in
equivalent width than for the normal elliptical population in the field or
clusters. The scatter for BCGs is 0.156 nm, compared with 0.240 nm for Coma
cluster ellipticals, 0.337 nm for ellipticals from a variety of other clusters,
and 0.422 nm for field ellipticals. We interpret this homogeneity as being due
to a greater age, or more uniform history, of star formation in BCGs than in
other ellipticals; only a small fraction of the scatter can be due to
metallicity variations, even in the BCGs. Notwithstanding the small scatter,
correlations are found between CO strength and various galaxy properties,
including R-band absolute magnitude, which could improve the precision of these
galaxies as distance indicators in measurements of cosmological parameters and
velocity flows.Comment: 7 pages, 8 figures, accepted for publication by MNRA
Iron mineralogy of a Hawaiian palagonitic soil with Mars-like spectral and magnetic properties
Visible and near-IR spectral data for some palagonitic soils from Mauna Kea, Hawaii, are similar to corresponding spectral data for Mars. It is important to understand the composition, distribution, and mineralogy of the ferric-bearing phases for the best spectral analogues because the correspondence in spectral properties implies that the nature of their ferric-bearing phases may be similar to those on Mars. In order to constrain interpretations of the Martian data, a variety of palagonitic soils should be studied in order to establish to what extent differences in their spectral data correspond to differences in the mineralogy of their ferric-bearing phases. Spectral (350-2100 nm), Mossbauer, magnetic, and some compositional data for one of a suite of Hawaiian palagonitic soils are presented. The soil (HWMK1) was collected below the biologically active zone from the sides of a gully cut at 9000 ft elevation on Mauna Kea. The soil was wet sieved with freon into seven size fractions less than 1 mm
Electron-positron bremsstrahlung and pair creation in very high magnetic fields
Cross-sections for Rutherford scattering, Coulomb bremsstrahlung and pair
creation, have been calculated at very high magnetic fields in order to
investigate the photo-production of protons at the polar caps of pulsars whose
spin is antiparallel with the polar magnetic flux density. The
Landau-Pomeranchuk-Migdal effect at very high magnetic fields is included in a
simple electron Green function.Comment: 10 pages; to be published in Monthly Notices of the Royal
Astronomical Societ
A Search for the Most Massive Galaxies. III. Global and Central Structure
We used the Advanced Camera for Surveys on board the Hubble Space Telescope
to obtain high resolution i-band images of the centers of 23 single galaxies,
which were selected because they have SDSS velocity dispersions larger than 350
km/s. The surface brightness profiles of the most luminous of these objects
(M_i<-24) have well-resolved `cores' on scales of 150-1000 pc, and share
similar properties to BCGs. The total luminosity of the galaxy is a better
predictor of the core size than is the velocity dispersion. The correlations of
luminosity and velocity dispersion with core size agree with those seen in
previous studies of galaxy cores. Because of high velocity dispersions, our
sample of galaxies can be expected to harbor the most massive black holes, and
thus have large cores with large amounts of mass ejection. The mass-deficits
inferred from core-Sersic fits to the surface-brightness profiles are
approximately double the black-hole masses inferred from the M_bh-sigma
relation and the same as those inferred from the M_bh-L relation. The less
luminous galaxies (M_i>-23) tend to have steeper `power-law' inner profiles,
higher-ellipticity, diskier isophotes, and bulge-to-total ratios of order 0.5
-- all of which suggest that they are `fast-rotators' and rotational motions
could have contaminated the velocity dispersion estimate. There are obvious
dust features within about 300 pc of the center in about 35% of the sample,
predominantly in power-law rather than core galaxies.Comment: 27 Pages, 22 Figures, 2 Tables, Accepted for Publication in MNRA
Bremsstrahlung in alpha-Decay Reexamined
A high-statistics measurement of bremsstrahlung emitted in the alpha decay of
210Po has been performed, which allows to follow the photon spectra up to
energies of ~ 500 keV. The measured differential emission probability is in
good agreement with our theoretical results obtained within the quasi classical
approximation as well as with the exact quantum mechanical calculation. It is
shown that due to the small effective electric dipole charge of the radiating
system a significant interference between the electric dipole and quadrupole
contributions occurs, which is altering substantially the angular correlation
between the alpha particle and the emitted photon.Comment: 10 pages, 5 figures, v2: fix of small typo
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