Growth in Disability Benefits: Explanations and Policy Implications

This collection of original papers reveals why caseloads of the nation\u27s two largest income entitlement programs for disability - Social Security Disability Income (SSDI) and Supplemental Security Income (SSI) - have soared.https://research.upjohn.org/up_press/1191/thumbnail.jp

Power-Law Statistics Of Driven Reconnection In The Magnetically Closed Corona

Numerous observations have revealed that power-law distributions are ubiquitous in energetic solar processes. Hard X-rays, soft X-rays, extreme ultraviolet radiation, and radio waves all display power-law frequency distributions. Since magnetic reconnection is the driving mechanism for many energetic solar phenomena, it is likely that reconnection events themselves display such power-law distributions. In this work, we perform numerical simulations of the solar corona driven by simple convective motions at the photospheric level. Using temperature changes, current distributions, and Poynting fluxes as proxies for heating, we demonstrate that energetic events occurring in our simulation display power-law frequency distributions, with slopes in good agreement with observations. We suggest that the braiding-associated reconnection in the corona can be understood in terms of a self-organized criticality model driven by convective rotational motions similar to those observed at the photosphere.Comment: Accepted by Ap

Tail-Recursive Distributed Representations and Simple Recurrent Networks

Representation poses important challenges to connectionism. The ability to structurally compose representaitons is critical in achieving the capability considered necessary for cognition. We are investigating distributed patterns that represent structure as part of a larger effort to develop a natural language processor. Recursive Auto-Associative Memory (RAAM) representations show unusual promise as a general vehicle for representing classical symbolic structures in a way that supports compositionality. However, RAAMs are limited to representations for fixed-valence structures and can often be difficult to train. We provide a technique for mapping any ordered collection (forest) of hierarchical structures (trees) into a set of training patterns which can be used effectivelyin training a simple recurrent network (SRN) to develop RAAM-style distributed representations. The advantages in our technique are three-fold: first, the fixed-valence restriction on structures represented by patterns trained with RAAMs is removed; second, representations resulting from training corresponds to ordered forests of labeled trees thereby extending what can be represented in this fashion; and third, training can be accomplished with an auto-associative SRN, making training a much more straightforward process and one which optimally utilizes the n-dimensional space of patterns

The equation of state in lattice QCD: with physical quark masses towards the continuum limit

The equation of state of QCD at vanishing chemical potential as a function of temperature is determined for two sets of lattice spacings. Coarser lattices with temporal extension of N_t=4 and finer lattices of N_t=6 are used. Symanzik improved gauge and stout-link improved staggered fermionic actions are applied. The results are given for physical quark masses both for the light quarks and for the strange quark. Pressure, energy density, entropy density, quark number susceptibilities and the speed of sound are presented.Comment: 14 pages, 9 figures. Version published in JHEP: discussions added in Sects. 1, 2. Fig. 1 changed and a new figure for the interaction measure added. Information on statistics added in Table 1. Raw values of the pressure added in Table 3. A few references adde

High-Performance Training of Feedforward & Simple Recurrent Networks

TRAINREC is a system for training feedforward and recurrent neural networks that incorporates several ideas. It uses the conjugate-gradient method which is demonstrably more efficient than traditional backward error propagation. We assume epoch-based training and derive a new error function having several desirable properties absent from the traditional sum-of-squared-error function. We argue for skip (shortcut) connections where appropriate and the preference for a sigmoidal yielding values over the [-1,1] interval. The input feature space is often over-analyzed, but by using singular value decomposition, input patterns can be conditioned for better learning often with a reduced number of input units. Recurrent networks, in their most general form, require special handling and cannot be simply a re-wiring of the architecture without a corresponding revision of the derivative calculations. There is a careful balance required among the network architeucture (specifically, hidden and feedback units), the amount of training applied, and the ability of the network to generalize. These issues often hinge on selecting the proper stopping criterion. Discovering methods that work in theory as well as in practice is difficult and we have spent a substantial amount of effort evaluating and testing these ideas on real problems to determine their value. This paper encapsulates a number of such ideas ranging from those motivated by a desire for efficiency of training to those motivated by correctness and accuracy of the result. While this paper is intended to be self-contained, several references are provided to other work upon which many of our claims are based

Microsatellite markers for hoop-petticoat daffodils (Narcissus sect. Bulbocodii; Amaryllidaceae)

• Premise of the study: Microsatellite markers were developed using hoop-petticoat daffodils ( Narcissus sect. Bulbocodii ; Amaryllidaceae) to aid in the taxonomic revision of the section, and further to evaluate their broad applicability for daffodil cultivar identification. • Methods and Results: Three hundred fifty-one primer pairs were developed using a commercial service. Nineteen polymorphic and repeatable markers were developed by screening 67 of these primer pairs. Of these, 11 chosen markers were used to screen 317 samples; the number of alleles per locus ranged from four to 21, and the observed heterozygosity ranged from 0.101 to 0.297. There were null genotypes in some samples for six of the markers. All the microsatellites were transferable to other Narcissus sections. • Conclusions: The results indicate that these new markers have sufficient potential variation to be used for taxonomic revision of the genus and to distinguish many commercial daffodil cultivars

Do correlations create an energy gap in electronic bilayers? Critical analysis of different approaches

This paper investigates the effect of correlations in electronic bilayers on the longitudinal collective mode structure. We employ the dielectric permeability constructed by means of the classical theory of moments. It is shown that the neglection of damping processes overestimates the role of correlations. We conclude that the correct account of damping processes leads to an absence of an energy gap.Comment: 4 page

Highlights of the SLD Physics Program at the SLAC Linear Collider

Starting in 1989, and continuing through the 1990s, high-energy physics witnessed a flowering of precision measurements in general and tests of the standard model in particular, led by e+e- collider experiments operating at the Z0 resonance. Key contributions to this work came from the SLD collaboration at the SLAC Linear Collider. By exploiting the unique capabilities of this pioneering accelerator and the SLD detector, including a polarized electron beam, exceptionally small beam dimensions, and a CCD pixel vertex detector, SLD produced a broad array of electroweak, heavy-flavor, and QCD measurements. Many of these results are one of a kind or represent the world's standard in precision. This article reviews the highlights of the SLD physics program, with an eye toward associated advances in experimental technique, and the contribution of these measurements to our dramatically improved present understanding of the standard model and its possible extensions.Comment: To appear in 2001 Annual Review of Nuclear and Particle Science; 78 pages, 31 figures; A version with higher resolution figures can be seen at http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8985.html; Second version incorporates minor changes to the tex

Single shot parameter estimation via continuous quantum measurement

We present filtering equations for single shot parameter estimation using continuous quantum measurement. By embedding parameter estimation in the standard quantum filtering formalism, we derive the optimal Bayesian filter for cases when the parameter takes on a finite range of values. Leveraging recent convergence results [van Handel, arXiv:0709.2216 (2008)], we give a condition which determines the asymptotic convergence of the estimator. For cases when the parameter is continuous valued, we develop quantum particle filters as a practical computational method for quantum parameter estimation.Comment: 9 pages, 5 image