3,099 research outputs found
Child Care and Mothers' Employment Decisions
Rising female labor force participation and recent changes to the welfare system have increased the importance of child care for all women and, particularly, the less-skilled. This paper focuses on the child care decisions of women who differ by their skill level and the role that costs play in their work decision. After reviewing government child-care programs targeted at less-skilled women, we present a descriptive analysis of current utilization and child care costs. We emphasize differences across skill groups, showing that the least-skilled women both use less costly paid care and are more likely to use unpaid care. We then survey the existing evidence regarding the responsiveness of female labor supply to child care costs, reviewing both econometric studies and demonstration projects that include child care components. To investigate variation in the response to child care cost across skill levels, we implement models similar to this past literature. We conclude that while the overall elasticity of labor force participation with respect to the market price of child care is between -0.05 and -0.35, this elasticity is larger for the least skilled women and declines with skill. Throughout the paper, we reflect upon the implications of our analysis for welfare reform.
THE ECONOMICS OF CLEANING WINTER WHEAT FOR EXPORT: AN EVALUATION OF PROPOSED FEDERAL "CLEAN GRAIN" STANDARDS
Buyer complaints about poor quality U.S. wheat have led to proposals to enforce minimum dockage standards for exports. An economic-engineering approach is used to evaluate costs and benefits of cleaning wheat in order to meet these standards for 13 possible cleaning configurations. These results are used in an optimization framework to estimate costs and benefits of cleaning all U.S. export wheat. The estimates indicate that cleaning U.S. export winter wheat to .35% dockage would cost an average of 1 cent/bu., requiring an initial capital investment of $28 million. Value of wheat lost in cleaning is a significant cost that previously has been overlooked.Agricultural and Food Policy,
Doped Mott insulators are insulators: hole localization in the cuprates
We demonstrate that a Mott insulator lightly doped with holes is still an
insulator at low temperature even without disorder. Hole localization obtains
because the chemical potential lies in a pseudogap which has a vanishing
density of states at zero temperature. The energy scale for the pseudogap is
set by the nearest-neighbour singlet-triplet splitting. As this energy scale
vanishes if transitions, virtual or otherwise, to the upper Hubbard band are
not permitted, the fundamental length scale in the pseudogap regime is the
average distance between doubly occupied sites. Consequently, the pseudogap is
tied to the non-commutativity of the two limits ( the on-site
Coulomb repulsion) and (the system size).Comment: 4 pages, 3 .eps file
The Somali Current response to the Southwest Monsoon: The relative importance of local and remote forcing
A simple model of the Somali current is formul ated which allows both local longshore forcing and remote east-west forcing. Asymptotic solutions for the pressure perturbation and velocity fields are obtained for both cases and the sensitivity of the boundary response to changes in the shape and position of the forcing is examined. The local forcing drives a flow whose north-south velocity increases linearly with time and the remote forcing , a flow in which the north-south velocity increases quadratically...
THE EFFECT OF ROUNDING ON THE PROBABILITY DISTRIBUTION OF REGRADING IN THE U.S. PEANUT INDUSTRY
This article determines the effect of rounding (pointing-off) of grade percentages to the nearest whole number on the probability distribution of regrading in the peanut industry. Results show that rounding causes graders to have to regrade an extra 4% of samples even when they follow all directions and make no mistakes. When rounding was not used, the sample weight had little effect on the probability of regrading. With rounding, the probability of regrading was reduced by beginning with a larger than 500-gram sample. Thus, rounding provides an incentive to take overweight samples in order to avoid regrading. Overweight samples can overestimate the value of peanuts. A low-cost way to improve peanut grading accuracy would be to round to tenths rather than whole numbers.grading, normal-jump distribution, peanuts, regrading, rounding, Crop Production/Industries,
On the magnetic structure of the solar transition region
We examine the hypothesis that ``cool loops'' dominate emission from solar
transition region plasma below temperatures of K. We compare
published VAULT images of H L, a lower transition region line, with
near-contemporaneous magnetograms from Kitt Peak, obtained during the second
flight (VAULT-2) on 14 June 2002. The measured surface fields and potential
extrapolations suggest that there are too few short loops, and that L
emission is associated with the base regions of longer, coronal loops. VAULT-2
data of network boundaries have an asymmetry on scales larger than
supergranules, also indicating an association with long loops. We complement
the Kitt Peak data with very sensitive vector polarimetric data from the
Spectro-Polarimeter on board Hinode, to determine the influence of very small
magnetic concentrations on our analysis. From these data two classes of
behavior are found: within the cores of strong magnetic flux concentrations ( Mx) associated with active network and plage, small-scale mixed
fields are absent and any short loops can connect just the peripheries of the
flux to cell interiors. Core fields return to the surface via longer, most
likely coronal, loops. In weaker concentrations, short loops can connect
between concentrations and produce mixed fields within network boundaries as
suggested by Dowdy and colleagues. The VAULT-2 data which we examined are
associated with strong concentrations. We conclude that the cool loop model
applies only to a small fraction of the VAULT-2 emission, but we cannot
discount a significant role for cool loops in quieter regions. We suggest a
physical picture for how network L emission may occur through the
cross-field diffusion of neutral atoms from chromospheric into coronal plasma.Comment: Accepted by ApJ, 9 May 200
Accurate theoretical fits to laser ARPES EDCs in the normal phase of cuprate superconductors
Anderson has recently proposed a theory of the strange metal state above Tc
in the high Tc superconductors. [arXiv:cond-mat/0512471] It is based on the
idea that the unusual transport properties and spectral functions are caused by
the strong Mott- Hubbard interactions and can be computed by using the formal
apparatus of Gutzwiller projection. In ref. 1 Anderson computed only the
tunneling spectrum and the power-law exponent of the infrared conductivity. He
had calculated the energy distribution curves (EDCs) in angle resolved
photoemission spectroscopy (ARPES) but was discouraged when these differed
radically from the best ARPES measurements available at the time, and did not
include them. In this letter we compare the spectral functions computed within
this model to the novel laser-ARPES data of the Dessau group.These are found to
capture the shape of the experimental EDCs with unprecedented accuracy and in
principle have only one free parameter
Prediction and benefits of minimal disease activity in patients with psoriatic arthritis and active skin disease in the ADEPT trial
Objectives: To determine the proportion of patients with psoriatic arthritis in the Adalimumab Effectiveness in Psoriatic Arthritis trial achieving minimal disease activity (MDA) and its individual components at 1 or more visits over 144 weeks, identify baseline predictors of MDA achievement, and evaluate the association of MDA status with independent quality of life (QoL)-related patient-reported outcomes (PROs).
Methods: Univariate and multivariate analyses were used to identify the baseline characteristics that predicted achievement of MDA at individual time points (weeks 12 through 144) or sustained MDA (achievement of MDA at 2 consecutive time points 12 weeks apart). The association of independent QoL-related PROs with MDA achievement was evaluated at weeks 24 and 144.
Results: In univariate analyses, higher baseline patient assessment of pain, tender joint count (TJC), enthesitis and Health Assessment Questionnaire-Disability Index (HAQ-DI) score were significantly associated with lower likelihood of achieving MDA at later time points. Multivariate analyses confirmed higher baseline HAQ-DI as a significant predictor for failure to achieve MDA at later time points. Achievement of sustained MDA was associated with lower baseline TJC and HAQ-DI score. Achievement of different MDA components appeared to be treatment dependent. MDA achievers had significantly better QoL-related PROs and greater improvements in PROs from baseline to week 24 compared with non-achievers.
Conclusions: Higher HAQ-DI score was the most consistent baseline factor that decreased the likelihood of achieving MDA and sustained MDA at later time points. Achieving MDA was associated with better independent QoL-related PROs
Indication, from Pioneer 10/11, Galileo, and Ulysses Data, of an Apparent Anomalous, Weak, Long-Range Acceleration
Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft
indicate an apparent anomalous, constant, acceleration acting on the spacecraft
with a magnitude cm/s, directed towards the Sun.
Two independent codes and physical strategies have been used to analyze the
data. A number of potential causes have been ruled out. We discuss future
kinematic tests and possible origins of the signal.Comment: Revtex, 4 pages and 1 figure. Minor changes for publicatio
Opportunities and conditions to learn (OCL): A conceptual framework
“Opportunity to learn” has evolved into an umbrella phrase for describing a large range of settings, resources, structures, and processes. The aim of this study is to develop a conceptual framework that can accommodate a wide range of opportunities to learn, not just those provided by teachers in classrooms. An inclusive framework can bring together diverse studies about opportunity to learn, increasing synergies and uncovering interconnections, and making more visible marginalized forms of learning. It can also be used as a framework for holding governments, education authorities, and policy makers accountable for providing equitable opportunities and conditions to learn. This article presents a three-dimensional conceptual framework of opportunities and conditions to learn (OCL) that captures (a) notions of what opportunities exist and where those opportunities exist and opportunities offered by whom, as well as (b) a spate of conditions that can shape those opportunities
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