1,440 research outputs found
Implications of a Production Entitlement Guarantee (PEG) Program for World Commodity Markets, 1992-2000
A Production Entitlement Guarantee (PEG) program would replace existing agricultural policies with a program that would allow governments to subsidize only a fixed proportion of each farmer\u27s historical production. World supply and demand conditions would determine the price farmers receive for any production in excess of the guaranteed PEG quality because all import barriers and export subsidies would be eliminated. A dynamic multicountry, multicommodity model is used to evaluate the impact of replacing current agricultural policies in the United States, the European Community, Japan, and Canada with a PEG program. For all countries and commodities, the guaranteed PEG quantity is set equal to 80 percent of each farmer\u27s average production between 1985 and 1989. Government payments are made to farmers on their PEG production as partial compensation for revenue losses. Except for programs with environmental aims, all other programs that subsidize or protect domestic agriculture would be eliminated
Can Protostellar Outflows Set Stellar Masses?
The opening angles of some protostellar outflows appear too narrow to match
the expected core-star mass efficiency SFE = 0.3-0.5 if outflow cavity volume
traces outflow mass, with a conical shape and a maximum opening angle near 90
deg. However, outflow cavities with paraboloidal shape and wider angles are
more consistent with observed estimates of the SFE. This paper presents a model
of infall and outflow evolution based on these properties. The initial state is
a truncated singular isothermal sphere which has mass 1 ,
free fall time 80 kyr, and small fractions of magnetic, rotational,
and turbulent energy. The core collapses pressure-free as its protostar and
disk launch a paraboloidal wide-angle wind. The cavity walls expand radially
and entrain envelope gas into the outflow. The model matches SFE values when
the outflow mass increases faster than the protostar mass by a factor 1 - 2,
yielding protostar masses typical of the IMF. It matches observed outflow
angles if the outflow mass increases at nearly the same rate as the cavity
volume. The predicted outflow angles are then typically 50 deg as they
increase rapidly through the stage 0 duration of 40 kyr. They increase
more slowly up to 110 deg during their stage I duration of 70 kyr.
With these outflow rates and shapes, model predictions appear consistent with
observational estimates of typical stellar masses, SFEs, stage durations, and
outflow angles, with no need for external mechanisms of core dispersal.Comment: Accepted for publication by The Astrophysical Journal; 47 pages, 10
figure
Polymeric alkali fullerides are stable in air
Infrared transmission, electron spin resonance, and X-ray diffraction
measurements show unambiguously that RbC and KC are stable in
air, in contrast to RbC which decomposes rapidly upon exposure.
The specimens studied transform into pure C and other byproducts when
heated above 100\dd C, approximately the temperature of the orthorhombic-fcc
phase transition. The stability of these compounds raises the possibility of
applying them as protective layers for the superconducting fullerides.Comment: Scheduled for publication in Appl. Phys. Lett. 66, 20 Feb. 1995,
typeset in REVTEX v3.0 in LaTeX. Postscript file including all figures is
available on WWW http://insti.physics.sunysb.edu/~mmartin/ under my list of
publications, or will be e-mailed by request
FAPRI U.S. Agricultural Sector Elasticities, Volume I: Crops
This report presents estimates of supply, demand, and price transmission elasticities for the U.S. crops sector. The estimates are derived from the U.S. crops model maintained by the Food and Agricultural Policy Research Institute (FAPRI) and are prepared in accordance with procedures stipulated by the Organization for Economic Cooperation and Development (OECD). The first section of this report provides a general overview and describes the procedures used to perform the elasticity calculations. Each succeeding section provides general information about the elasticity estimates for a particular activity. Specific attention is given to those results that may not be intuitively clear and, in particular, to the elasticities that depend on the interaction of two or more equations in the FAPRI modeling system
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Genome-wide profiling of human cap-independent translation-enhancing elements.
We report an in vitro selection strategy to identify RNA sequences that mediate cap-independent initiation of translation. This method entails mRNA display of trillions of genomic fragments, selection for initiation of translation and high-throughput deep sequencing. We identified >12,000 translation-enhancing elements (TEEs) in the human genome, generated a high-resolution map of human TEE-bearing regions (TBRs), and validated the function of a subset of sequences in vitro and in cultured cells
FAPRI U.S. Agricultural Sector Elasticities, Volume II: Livestock, Poultry, and Dairy
This report presents estimates of supply, demand, and price transmission elasticities for the U.S. livestock, poultry, and dairy sectors. The estimates are derived from models maintained by the Food and Agricultural Policy Research Institute (FAPRI) and are prepared in accordance with procedures stipulated by the Organization for Economic Cooperation and Development (OECD)
The Relationship of Age to Level of Performance and Independence Associated with Rehabilitative Interventions Provided to Older Adults Who Are Blind
The purpose of this study was to investigate the relationship between rehabilitative interventions and older adults with visual impairments. This study employed an ex post facto, quasi-experimental design which analyzed changes that occurred based on composite pretest and posttest scores representing levels of performance and independence. Participants were visually impaired adults, age 65 and above, who successfully completed a rehabilitation program intended to increase their skills for independent living. A repeated measures multivariate analysis of variance (MANOVA) was conducted to determine if there were significant improvements on pretest to posttest levels of performance and independence derived from the rehabilitative interventions, and if improvements were related to age. Statistically significant gains were noted on overall performance and independence for both the ADL and IADL domains.
Insulating and Conducting Phases of RbC60
Optical measurements were performed on thin films of RbC,
identified by X-ray diffraction as mostly material. The samples were
subjected to various heat treatments, including quenching and slow cooling from
400K. The dramatic increase in the transmission of the quenched samples, and
the relaxation towards the transmission observed in slow cooled samples
provides direct evidence for the existence of a metastable insulating phase.
Slow cooling results in a phase transition between two electrically conducting
phases.Comment: Minor revisions. Submitted to PRB, RevTeX 3.0 file, 2 postscript
figures included, ir_dop
Physical and Spectral Characteristics of the T8 and Later-Type Dwarfs
We use new and published near-IR spectra, with synthetic spectra, to derive
physical properties of three of the latest-type T dwarfs. A new R~1700 spectrum
of the T7.5 dwarf HD 3651B, with existing data, allows a detailed comparison to
the well-studied and very similar dwarf, Gl 570D. We find that HD 3651B has
both higher gravity and metallicity than Gl 570D, with Teff=820-830K, log g=
5.4-5.5, [m/H]= +0.2 and Kzz=10^4cm^2/s. Its age is 8-12 Gyr and its implied
mass is 60-70 M_Jup. We perform a similar analyis of the T8 and T7.5 dwarfs
2MASS J09393548-2448279 and 2MASS J11145133-2618235 using published data,
comparing them to the well-studied T8, 2MASS J04151954-0935066. We find that
the two dwarfs have the same Teff as the reference dwarf, and similar
gravities, but lower metallicities. The parameters are Teff=725-775K and [m/H]=
-0.3; log g=5.3-5.45 for 2MASS J09393548-2448279 and log g=5.0-5.3 for 2MASS
J11145133- 261823. The age and mass are ~10Gyr and 60M_Jup for 2MASS
J09393548-2448279, and ~5 Gyr and 40M_Jup for 2MASS J11145133-261823. A serious
limitation is the incompleteness of the line lists of CH4 and NH3 at lambda
<1.7um. Spectra of Saturn and Jupiter, and of laboratory CH4 and NH3 gas,
suggest that NH3 features in the Y- and J-bands may be useful as indicators of
the next cooler spectral type, and not features in the H- and K-bands as
previously thought. However large uncertainties remain, as the abundance of NH3
is likely to be significantly below the chemical equilibrium value, and
inclusion of laboratory NH3 opacities predicts band shapes that are discrepant
with existing data. It is possible that the T spectral class will have to be
extended to low temperatures around 400K, when water clouds condense in the
atmosphere [abridged].Comment: 34 pages including 10 figures and two tables; accepted for
publication in the Astrophysical Journa
Superconductivity in Co-doped LaFeAsO
Here we report the synthesis and basic characterization of LaFe1-xCoxAsO for
several values of x. The parent phase LaFeAsO orders antiferromagnetically (TN
~ 145 K). Replacing Fe with Co is expected to both electron dope the system and
introduce disorder in the FeAs layer. For x = 0.05 antiferromagnetic order is
destroyed and superconductivity is observed at Tconset = 11.2 K. For x = 0.11
superconductivity is observed at Tc(onset) = 14.3 K, and for x = 0.15 Tc = 6.0
K. Superconductivity is not observed for x = 0.2 and 0.5, but for x = 1, the
material appears to be ferromagnetic (Tc ~ 56 K) as judged by magnetization
measurements. We conclude that Co is an effective dopant to induce
superconductivity. Somewhat surprisingly, the system appears to tolerate
considerable disorder in the FeAs planes.Comment: 19 pages, 9 figure
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