Endogeneity in nonparametric and semiparametric regression models

This paper considers the nonparametric and semiparametric methods for estimating regression models with continuous endogenous regressors. We list a number of different generalizations of the linear structural equation model, and discuss how two common estimation approaches for linear equations — the "instrumental variables" and "control function" approaches — may be extended to nonparametric generalizations of the linear model and to their semiparametric variants. We consider the identification and estimation of the "Average Structural Function" and argue that this is a parameter of central interest in the analysis of semiparametric and non- parametric models with endogenous regressors. We consider a particular semiparametric model, the binary response model with linear index function and nonparametric error distribution, and describes in detail how estimation of the parameters of interest can be constructed using the "control function" approach. This estimator is applied to estimating the relation of labor force participation to nonlabor income, viewed as an endogenous regressor

Analysis of steady-state and pulsed operating regimes for controlled thermonuclear reactors with very large power ratings

The operating regimes of large CTR's are identified and examined for cases of steady-state and pulsed operation. Several technological benefits of these large reactors are determined: (1) low maximum magnetic field strength requirements (25 to 50 percent less than for 5000 MW(th) reactors), (2) high n tau products (10$sup 15$ to 10$sup 17$ sec/cm$sup 3$) with associated high burn- up fractions (10 to 50 percent), (3) relatively little problem with impurity build-up, and (4) long confinement times (50 to 500 seconds). The advantages of pulsed operation are also discussed: (1) smaller problem with impurities than in the steady-state case, (2) alleviation of any possible fueling difficulties, and (3) no problem with control of temperature in the pulsed reactor based on a simple control function model incorporating a finite delay time. (auth

Steady-state plasma and reactor parameters for elliptical cross section tokamaks with very large power ratings

In previous studies only circular cross section reactor plasmas were considered. The purpose of this research is to examine the effects of elliptical plasma cross sections. Several technological benefits have been determined. Maximum magnetic field strength requirements are 30 to 65 percent less than for 5000 MW (th) reactors and may be as much as 40 percent less than for circular cross section reactors of comparable size. Very large n tau values are found (10$sup 15$ to 10$sup 17$ sec/cm$sup 3$), which produce large burn-up fractions (15 to 60 percent). There is relatively little problem with impurity build-up. Long confinement times (60 to 500 seconds) are found. Finally, the elliptical cross section reactors exhibit a major toroidal radius reduction of as large as 30 percent over circular reactors operating at comparable power levels. (auth

EnzMet™: An Enzymatic Metallography Reagent for Accurately Delineating Neuronal Boundaries for Segmenting Gap Junction-Coupled Neurons in their Three-dimensional Space

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 201

Probing the primordial power spectra with inflationary priors

We investigate constraints on power spectra of the primordial curvature and tensor perturbations with priors based on single-field slow-roll inflation models. We stochastically draw the Hubble slow-roll parameters and generate the primordial power spectra using the inflationary flow equations. Using data from recent observations of CMB and several measurements of geometrical distances in the late Universe, Bayesian parameter estimation and model selection are performed for models that have separate priors on the slow-roll parameters. The same analysis is also performed adopting the standard parameterization of the primordial power spectra. We confirmed that the scale-invariant Harrison-Zel'dovich spectrum is disfavored with increased significance from previous studies. While current observations appear to be optimally modeled with some simple models of single-field slow-roll inflation, data is not enough constraining to distinguish these models.Comment: 23 pages, 3 figures, 7 tables, accepted for publication in JCA

We are what we (think we) eat: The effect of expected satiety on subsequent calorie consumption

Varying expected satiety (ES) for equi-calorie portions of different foods can affect subsequent feelings of hunger and fullness and alter consumption. To our knowledge, no study has manipulated ES for an equal portion of the same solid food, appetite has not been measured >3 h and studies have not consistently measure later consumption. It is also unclear whether changes in hunger, fullness or later consumption are related to a physiological response. The aims of this study were to use the same solid food, to measure participants' response over a 4-h inter-meal period, to measure later consumption and to assess whether any effect of ES was related to a physiological (i.e. total ghrelin) response. Using a within-subjects design, 26 healthy participants had their ES for omelettes manipulated experimentally, believing that a 3-egg omelette contained either 2 (small condition) or 4 (large condition) eggs. When ES was higher (large condition) participants ate significantly fewer calories at a lunchtime test meal (mean difference = 69 kcal [± 95% CI 4–136]) and consumed significantly fewer calories throughout the day (mean difference = 167 kcal [± 95% CI 26–309]). As expected, there was a main effect of time on hunger and fullness, but no main effect of ‘portion size’ (p > .05). There was also a significant interaction between time and portion size for hunger. There was no evidence for any significant differences being the result of changes in total ghrelin. Overall, the data suggest that ES for a solid food can be manipulated and that, when given at breakfast, having a higher ES for a meal reduces lunchtime and whole day caloric consumption

Coupled electron-photon radiation transport

Massively-parallel computers allow detailed 3D radiation transport simulations to be performed to analyze the response of complex systems to radiation. This has been recently been demonstrated with the coupled electron-photon Monte Carlo code, ITS. To enable such calculations, the combinatorial geometry capability of ITS was improved. For greater geometrical flexibility, a version of ITS is under development that can track particles in CAD geometries. Deterministic radiation transport codes that utilize an unstructured spatial mesh are also being devised. For electron transport, the authors are investigating second-order forms of the transport equations which, when discretized, yield symmetric positive definite matrices. A novel parallelization strategy, simultaneously solving for spatial and angular unknowns, has been applied to the even- and odd-parity forms of the transport equation on a 2D unstructured spatial mesh. Another second-order form, the self-adjoint angular flux transport equation, also shows promise for electron transport

Aspects of Nucleon Compton Scattering

We consider the spin-averaged nucleon forward Compton scattering amplitude in heavy baryon chiral perturbation theory including all terms to order ${\cal O} (q^4)$. The chiral prediction for the spin-averaged forward Compton scattering amplitude is in good agreement with the data for photon energies $\omega \le 110$ MeV. We also evaluate the nucleon electric and magnetic Compton polarizabilities to this order and discuss the uncertainties of the various counter terms entering the chiral expansion of these quantities.Comment: 17 pp, TeX, 7 figures available from the authors, preprint CRN-93/5

Genomic differentiation during speciation-with-gene-flow: Comparing geographic and host-related variation in divergent life history adaptation in rhagoletis pomonella

A major goal of evolutionary biology is to understand how variation within populations gets partitioned into differences between reproductively isolated species. Here, we examine the degree to which diapause life history timing, a critical adaptation promoting population divergence, explains geographic and host-related genetic variation in ancestral hawthorn and recently derived apple-infesting races of Rhagoletis pomonella. Our strategy involved combining experiments on two different aspects of diapause (initial diapause intensity and adult eclosion time) with a geographic survey of genomic variation across four sites where apple and hawthorn flies co-occur from north to south in the Midwestern USA. The results demonstrated that the majority of the genome showing significant geographic and host-related variation can be accounted for by initial diapause intensity and eclosion time. Local genomic differences between sympatric apple and hawthorn flies were subsumed within broader geographic clines; allele frequency differences within the races across the Midwest were two to three-fold greater than those between the races in sympatry. As a result, sympatric apple and hawthorn populations displayed more limited genomic clustering compared to geographic populations within the races. The findings suggest that with reduced gene flow and increased selection on diapause equivalent to that seen between geographic sites, the host races may be recognized as different genotypic entities in sympatry, and perhaps species, a hypothesis requiring future genomic analysis of related sibling species to R. pomonella to test. Our findings concerning the way selection and geography interplay could be of broad significance for many cases of earlier stages of divergence-with-gene flow, including (1) where only modest increases in geographic isolation and the strength of selection may greatly impact genetic coupling and (2) the dynamics of how spatial and temporal standing variation is extracted by selection to generate differences between new and discrete units of biodiversity