11,712 research outputs found
Shifts in U.S. Relative Wages: The Role of Trade, Technology, and Factor Endowments
This paper investigates three hypotheses to account for the observed shifts in U.S. relative wages of less educated workers compared to more educated workers during the period from 1967 to 1992: (1) increased import competition, (2) changes in the relative supplies of labor of different educational levels, and (3) changes in technology. Our analysis relies on a basic relationship of the standard general equilibrium trade model that relates changes in product prices to factor price changes and factor shares, together with information about changes in the composition of output and trade, within-industry factor use, and factor supplies. For the period from 1967 to 1973, we conclude that the relative increase in the supply of well-educated labor was the dominant economic force that narrowed the wage gap among workers of different educational levels. In the 1980s and early 1990s, however, the wage gap between more educated and less educated workers widened sharply, despite the continued relative increase in the supply of workers with more education. We conclude that increased import competition cannot account for the observed increase in inequality among the major education groups, although it could have been a contributory cause of the decrease in the relative wages of the least educated workers. Instead, we find support for technical progress that is saving of less educated labor and that is more rapid in some manufacturing sectors intensively using highly educated labor as the dominant force in widening the wage gaps among college-educated workers, workers with a completed high school education, and workers with 1–11 years of schooling. Finally, we use the Deardorff-Staiger model, which allows changes in the factor content of trade to reveal the effects of trade on relative factor prices. Our empirical tests reinforce the conclusion that increased import competition between 1977 and 1987 was not the dominant force in widening the wage
Diffraction-limited CCD imaging with faint reference stars
By selecting short exposure images taken using a CCD with negligible readout
noise we obtained essentially diffraction-limited 810 nm images of faint
objects using nearby reference stars brighter than I=16 at a 2.56 m telescope.
The FWHM of the isoplanatic patch for the technique is found to be 50
arcseconds, providing ~20% sky coverage around suitable reference stars.Comment: 4 page letter accepted for publication in Astronomy and Astrophysic
Economic and demographic issues related to deployment of the Satellite Power System (SPS)
Growth in energy consumption stimulated interest in exploitation of renewable sources of electric energy. One technology that was proposed is the Satellite Power System (SPS). Before committing the U.S. to such a large program, the Department of Energy and the National Aeronautics and Space Administration are jointly participating in an SPS Concept Development and Evaluation Program. This white paper on industrial and population relocation is part of the FY 78 preliminary evaluation of related socio-economic issues. Results of four preliminary assessment activities are documented
Self-Consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential
We calculate the self-consistent response of an axisymmetric galactic disk
perturbed by an elliptical halo potential of harmonic number m = 2, and obtain
the net disk ellipticity. Such a potential is commonly expected to arise due to
a galactic tidal encounter and also during the galaxy formation process. The
self-gravitational potential corresponding to the self-consistent,
non-axisymmetric density response of the disk is obtained by inversion of
Poisson equation for a thin disk. This response potential is shown to oppose
the perturbation potential, because physically the disk self-gravity resists
the imposed potential. This results in a reduction in the net ellipticity of
the perturbation halo potential in the disk plane. The reduction factor
denoting this decrease is independent of the strength of the perturbation
potential, and has a typical minimum value of 0.75 - 0.9 for a wide range of
galaxy parameters. The reduction is negligible at all radii for higher
harmonics (m > or = 3) of the halo potential. (abridged).Comment: 26 pages (LaTex- aastex style), 3 .eps figures. To appear in the
Astrophysical Journal, Vol. 542, Oct. 20, 200
Use of Agrotain to reduce the seedbed toxicity of urea
Non-Peer Reviewe
A warped disk model for M33 and the 21-cm line width in spiral galaxies
To determine the actual HI distribution and the velocity field in the
outermost disk of the spiral galaxy M33, a tilted-ring model is fitted to 21-cm
line data taken with the Arecibo Telescope. Since M33 is one of the main
calibrators for the extragalactic distance scale derived through the
Tully-Fisher relation, the outer disk warping is of interest for a correct
determination and deprojection of the galaxy's line width. Even though our best
model predicts small effects on the observed line width of M33, we show that
similar outer disk warping in galaxies oriented differently along our line of
sight could affect the widths considerably. Therefore there may be systematic
effects in the determination of the rotation velocities and dynamic masses of
spiral galaxies, whose exact value depends also on which method is used for
measuring the galaxy's total line width.Comment: 27 pages, ps files only, ApJ in pres
The Nature of the H2-Emitting Gas in the Crab Nebula
Understanding how molecules and dust might have formed within a rapidly
expanding young supernova remnant is important because of the obvious
application to vigorous supernova activity at very high redshift. In previous
papers, we found that the H2 emission is often quite strong, correlates with
optical low-ionization emission lines, and has a surprisingly high excitation
temperature. Here we study Knot 51, a representative, bright example, for which
we have available long slit optical and NIR spectra covering emission lines
from ionized, neutral, and molecular gas, as well as HST visible and SOAR
Telescope NIR narrow-band images. We present a series of CLOUDY simulations to
probe the excitation mechanisms, formation processes and dust content in
environments that can produce the observed H2 emission. We do not try for an
exact match between model and observations given Knot 51's ambiguous geometry.
Rather, we aim to explain how the bright H2 emission lines can be formed from
within the volume of Knot 51 that also produces the observed optical emission
from ionized and neutral gas. Our models that are powered only by the Crab's
synchrotron radiation are ruled out because they cannot reproduce the strong,
thermal H2 emission. The simulations that come closest to fitting the
observations have the core of Knot 51 almost entirely atomic with the H2
emission coming from just a trace molecular component, and in which there is
extra heating. In this unusual environment, H2 forms primarily by associative
detachment rather than grain catalysis. In this picture, the 55 H2-emitting
cores that we have previously catalogued in the Crab have a total mass of about
0.1 M_sun, which is about 5% of the total mass of the system of filaments. We
also explore the effect of varying the dust abundance. We discuss possible
future observations that could further elucidate the nature of these H2 knots.Comment: 51 pages, 15 figures, accepted for publication in MNRAS, revised
Figure 12 results unchange
High dynamic range imaging by pupil single-mode filtering and remapping
Because of atmospheric turbulence, obtaining high angular resolution images
with a high dynamic range is difficult even in the near infrared domain of
wavelengths. We propose a novel technique to overcome this issue. The
fundamental idea is to apply techniques developed for long baseline
interferometry to the case of a single-aperture telescope. The pupil of the
telescope is broken down into coherent sub-apertures each feeding a single-mode
fiber. A remapping of the exit pupil allows interfering all sub-apertures
non-redundantly. A diffraction-limited image with very high dynamic range is
reconstructed from the fringe pattern analysis with aperture synthesis
techniques, free of speckle noise. The performances of the technique are
demonstrated with simulations in the visible range with an 8 meter telescope.
Raw dynamic ranges of 1: can be obtained in only a few tens of seconds of
integration time for bright objects.Comment: 5 pages, 3 figures. accepted for publication in MNRA
Cookies for children (1964)
Pages six and seven are missing.Cookies are favorites with juSt about everybody especially hungty boys and girls juSt home from school or a session of play. Such a popular food needs to be good for you as well as good to ear. Many cookies are high in carbohydrates, sugar, and fat, and supply few nutrienrs other than calories. Recipes in this bulletin have been developed to make cookies tasty as well as to contain many nutrients needed for growth; for muscle, bone, and tooth development; and for general well-being.Cooky ingredients -- General Suggestions. Mixing ; Baking ; Storing ; Freezing -- Cooky recipies. Carrot-raisin ; Fruit ; Golden yellow ; Cereal ; Honey Whole Wheat ; Molasses ginger ; Soft molasses ; Molasses whole wheat ; Peanut butter molasses ; Peanut butter ; Chocolate whole wheat-oatmeal -- Lunch wafers -- Teething cooky -- Recipies using cooky mix -- Basic cooky mix. Raisin drop ; Lemon drops ; Peanut butter ; oatmeal ; Cocoa drop -- Comparision of food nutrients of different cookies ; Aproximate percentage of minimum daily requirements of certain nutrients supplied by selected cookie
Low frequency m=1 normal mode oscillations of a self-gravitating disc
A continuous system such as a galactic disc is shown to be well approximated
by an N-ring differentially rotating self-gravitating system. Lowest order
(m=1) non-axisymmetric features such as lopsidedness and warps are global in
nature and quite common in the discs of spiral galaxies. Apparently these two
features of the galactic discs have been treated like two completely disjoint
phenomena. The present analysis based on an eigenvalue approach brings out
clearly that these two features are fundamentally similar in nature and they
are shown to be very Low frequency Normal Mode (LNM) oscillations manifested in
different symmetry planes of the galactic disc. Our analysis also show that
these features are actually long-lived oscillating pattern of the N-ring
self-gravitating system.Comment: 5 figures. Accepted for publication in MNRAS Letter
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