4,702 research outputs found
An Evaluation of the Working Income Tax Benefit
The federal government has implemented an earned income tax credit what it has called the Working Income Tax Benefit in the 2007 Budget. Edmund Phelps has argued that the earned income tax credit in the United States should be replaced with an employment subsidy. This paper assesses the importance of Phelps' concern, and related issues, for Canada. This debate is important for two reasons: the plight of those blocked by the "welfare wall" is dire, and the entire community has an interest in lower structural unemployment in an environment that involves an aging population and an accompanying labour shortage.earned income tax credit, employment subsidy, open economy
Posterior propriety and admissibility of hyperpriors in normal hierarchical models
Hierarchical modeling is wonderful and here to stay, but hyperparameter
priors are often chosen in a casual fashion. Unfortunately, as the number of
hyperparameters grows, the effects of casual choices can multiply, leading to
considerably inferior performance. As an extreme, but not uncommon, example use
of the wrong hyperparameter priors can even lead to impropriety of the
posterior. For exchangeable hierarchical multivariate normal models, we first
determine when a standard class of hierarchical priors results in proper or
improper posteriors. We next determine which elements of this class lead to
admissible estimators of the mean under quadratic loss; such considerations
provide one useful guideline for choice among hierarchical priors. Finally,
computational issues with the resulting posterior distributions are addressed.Comment: Published at http://dx.doi.org/10.1214/009053605000000075 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
FGF23 metabolism, a new paradigm for chronic kidney disease
Introduction: Â Fibroblast growth factor-23 (FGF23) is a major regulator of phosphate metabolism often elevated in genetic hypophosphataemic disorders and in chronic kidney disease. Recent studies have identified relationships between FGF23 and various markers of iron status including ferritin. New assays measuring the intact form of FGF23 have been released. Â Objective: Â To determine the relationship between ferritin and C-terminal and intact FGF23 concentrations in blood. Â Method: Â FGF23 concentrations were measured using the 2nd generation, two-site enzyme-linked immunosorbent assay for either C-terminal or intact FGF23 (Immutopics Inc., Ca, USA). Ferritin was measured on a COBAS 6000 (Roche Diagnostics). Assay accuracy and precision were monitored using kit controls supplied by the manufacturers. Â Results: Â We observe a weak negative correlation between measurements of C-terminal and intact FGF23 (Pearsonâs rho=0.85 p<0.0001). We observed no statistically significant correlation of ferritin concentrations with either FGF23 C-terminal or intact. However high concentrations of ferritin were observed in samples showing low concentrations of C-terminal FGF23 (<140RU/mL) and intact FGF23 (<122pg/mL). Â Conclusion: Â Although not statistically significant, we observe a negative relationship between concentrations of ferritin and FGF23. High level of C-terminal FGF23 is found in patients with chronic kidney disease, especially in patients with end-stage renal disease usually regarded as a compensatory response to hyperphosphatemia or phosphate overload. We observed a cluster of patients with retention of both C-terminal and intact FGF23 associated with low levels of ferritin suggesting that metabolism and/or excretion of FGF23 in CDK patients might be an iron dependent mechanism
Slow Atomic Motion in Zr-Ti-Cu-Ni-Be Metallic Glasses Studied by NMR
Nuclear magnetic resonance is used for the first time to detect slow atomic motion in metallic glasses, specifically, Be motion in Zr-Ti-Cu-Ni-Be bulk metallic glasses. The observations are not consistent with the vacancy-assisted and interstitial diffusion mechanisms and favor the spread-out free volume fluctuation mechanism for Be diffusion. Comparison with the results of Be diffusion measured by elastic backscattering the NMR results also indicates that the energy barriers for short- and long-range Be motion are the same
A role for recurrent processing in object completion: neurophysiological, psychophysical and computational"evidence
Recognition of objects from partial information presents a significant
challenge for theories of vision because it requires spatial integration and
extrapolation from prior knowledge. We combined neurophysiological recordings
in human cortex with psychophysical measurements and computational modeling to
investigate the mechanisms involved in object completion. We recorded
intracranial field potentials from 1,699 electrodes in 18 epilepsy patients to
measure the timing and selectivity of responses along human visual cortex to
whole and partial objects. Responses along the ventral visual stream remained
selective despite showing only 9-25% of the object. However, these visually
selective signals emerged ~100 ms later for partial versus whole objects. The
processing delays were particularly pronounced in higher visual areas within
the ventral stream, suggesting the involvement of additional recurrent
processing. In separate psychophysics experiments, disrupting this recurrent
computation with a backward mask at ~75ms significantly impaired recognition of
partial, but not whole, objects. Additionally, computational modeling shows
that the performance of a purely bottom-up architecture is impaired by heavy
occlusion and that this effect can be partially rescued via the incorporation
of top-down connections. These results provide spatiotemporal constraints on
theories of object recognition that involve recurrent processing to recognize
objects from partial information
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