828 research outputs found
Educational Expectations and Attainment
This paper examines the role of educational expectations in the educational attainment process. We utilize data from a variety of datasets to document and analyze the trends in educational expectations between the mid-1970s and the early 2000s. We focus on differences across racial/ethnic and socioeconomic groups and examine how young people update their expectations during high school and beyond. The results indicate that expectations rose for all students with the greatest increases among young women. Expectations have become somewhat less predictive of attainment over the past several decades but expectations remain strong predictors of attainment above and beyond other standard determinants of schooling. Interestingly, the data demonstrate that the majority (about 60 percent) of students update their expectations at least once between eighth grade and eight years post-high school. Updating appears to be based, in part, on the acquisition of new information about academic ability.
The Kernel Interaction Trick: Fast Bayesian Discovery of Pairwise Interactions in High Dimensions
Discovering interaction effects on a response of interest is a fundamental
problem faced in biology, medicine, economics, and many other scientific
disciplines. In theory, Bayesian methods for discovering pairwise interactions
enjoy many benefits such as coherent uncertainty quantification, the ability to
incorporate background knowledge, and desirable shrinkage properties. In
practice, however, Bayesian methods are often computationally intractable for
even moderate-dimensional problems. Our key insight is that many hierarchical
models of practical interest admit a particular Gaussian process (GP)
representation; the GP allows us to capture the posterior with a vector of O(p)
kernel hyper-parameters rather than O(p^2) interactions and main effects. With
the implicit representation, we can run Markov chain Monte Carlo (MCMC) over
model hyper-parameters in time and memory linear in p per iteration. We focus
on sparsity-inducing models and show on datasets with a variety of covariate
behaviors that our method: (1) reduces runtime by orders of magnitude over
naive applications of MCMC, (2) provides lower Type I and Type II error
relative to state-of-the-art LASSO-based approaches, and (3) offers improved
computational scaling in high dimensions relative to existing Bayesian and
LASSO-based approaches.Comment: Accepted at ICML 2019. 20 pages, 4 figures, 3 table
Dopant-modulated pair interaction in cuprate superconductors
Comparison of recent experimental STM data with single-impurity and
many-impurity Bogoliubov-de Gennes calculations strongly suggests that random
out-of-plane dopant atoms in cuprates modulate the pair interaction locally.
This type of disorder is crucial to understanding the nanoscale electronic
structure inhomogeneity observed in BSCCO-2212, and can reproduce observed
correlations between the positions of impurity atoms and various aspects of the
local density of states such as the gap magnitude and the height of the
coherence peaks. Our results imply that each dopant atom modulates the pair
interaction on a length scale of order one lattice constant.Comment: 5 pages, 4 figure
Andreev states near short-ranged pairing potential impurities
We study Andreev states near atomic scale modulations in the pairing
potential in both - and d-wave superconductors with short coherence lengths.
For a moderate reduction of the local gap, the states exist only close to the
gap edge. If one allows for local sign changes of the order parameter, however,
resonances can occur at energies close to the Fermi level. The local density of
states (LDOS) around such pairing potential defects strongly resembles the
patterns observed by tunneling measurements around Zn impurities in
BiSrCaCuO (BSCCO). We discuss how this phase impurity model
of the Zn LDOS pattern can be distinguished from other proposals
experimentally.Comment: 4 pages, 4 figure
Performance of UK wastewater treatment works with respect to trace contaminants
This is the post-print version of the final paper published in Science of Total Environment. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 Elsevier B.V.This study examined the performance of 16 wastewater treatment works to provide an overview of trace substance removal in relation to meeting the objectives of the Water Framework Directive (WFD). Collection and analysis of over 2400 samples including sewage influent, process samples at different stages in the treatment process and final effluent has provided data on the performance of current wastewater treatment processes and made it possible to evaluate the need for improved effluent quality. Results for 55 substances, including metals, industrial chemicals and pharmaceuticals are reported. Data for sanitary parameters are also provided. A wide range of removal efficiencies was observed. Removal was not clearly related to the generic process type, indicating that other operational factors tend to be important. Nonetheless, removals for many substances of current concern were high. Despite this, current proposals for stringent water quality standards mean that further improvements in effluent quality are likely to be required
A blinded determination of from low-redshift Type Ia supernovae, calibrated by Cepheid variables
Presently a tension exists between values of the Hubble constant
derived from analysis of fluctuations in the Cosmic Microwave Background
by Planck, and local measurements of the expansion using calibrators of type Ia
supernovae (SNe Ia). We perform a blinded reanalysis of Riess et al. 2011 to
measure from low-redshift SNe Ia, calibrated by Cepheid variables and
geometric distances including to NGC 4258. This paper is a demonstration of
techniques to be applied to the Riess et at. 2016 data. Our end-to-end analysis
starts from available CfA3 and LOSS photometry, providing an independent
validation of Riess et al. 2011. We obscure the value of throughout our
analysis and the first stage of the referee process, because calibration of SNe
Ia requires a series of often subtle choices, and the potential for results to
be affected by human bias is significant. Our analysis departs from that of
Riess et al. 2011 by incorporating the covariance matrix method adopted in SNLS
and JLA to quantify SN Ia systematics, and by including a simultaneous fit of
all SN Ia and Cepheid data. We find (stat)
(sys) km s Mpc with a three-galaxy (NGC 4258+LMC+MW) anchor. The
relative uncertainties are 4.3% statistical, 1.1% systematic, and 4.4% total,
larger than in Riess et al. 2011 (3.3% total) and the Efstathiou 2014
reanalysis (3.4% total). Our error budget for is dominated by statistical
errors due to the small size of the supernova sample, whilst the systematic
contribution is dominated by variation in the Cepheid fits, and for the SNe Ia,
uncertainties in the host galaxy mass dependence and Malmquist bias.Comment: 38 pages, 13 figures, 13 tables; accepted for publication in MNRA
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