On Intercept Estimation in the Sample Selection Model

We provide a proof of the consistency and asymptotic normality of the estimator suggested by Heckman (1990) for the intercept of a semiparametrically estimated sample selection model. The estimator is based on "identification at infinity" which leads to non-standard convergence rate. Andrews and Schafgans (1998) derived asymptotic results for a smoothed version of the estimator. We examine the optimal bandwidth selection for the estimators and derive asymptotic MSE rates under a wide class of distributional assumptions. We also provide some comparisons of the estimators and practical guidelines.

Phase Diagram and Thermodynamic and Dynamic Anomalies in a Pure Repulsive Model

Using Monte Carlo simulations a lattice gas model with only repulsive interactions was checked for the presence of anomalies. We show that this system exhibits the density (temperature of maximum density - TMD) and diffusion anomalies as present in liquid water. These anomalous behavior exist in the region of the chemical potential vs temperature phase diagram where two structured phases are present. A fragile-to-strong dynamic transition is also observed in the vicinity of the TMD line

Nutrition Education in Clark County, Nevada

Over 51 million school hours are missed annually by school-aged children due to a dental problem or visit, with 117 hours missed per 100 children (NIDCR, 2002). Approximately half a million of California\u27s 7.2 million school-age children missed at least one day of school in 2007 because of dental issues such as toothaches (Pourat, & Nicholson, 2009). Independent research regarding various educational and intervention programs have been conducted in elementary schools across the country that focus on nutrition and/or physical activity, some of which have found that the programs positively impacted students’ dietary behaviors (Edwards, Mauch, & Winkelman, 2011; Muth, Chatterjee, Williams, Cross, & Flower, 2008; Tuuri et al., 2009). However, there does not appear to be literature regarding the standardization of nutrition and oral health education curricula for elementary school children. Nevertheless, there are school districts that have well structured health education curricula that cover nutrition and oral health education (California Department of Education, 2009; Central Michigan University, 2005). All of these reports are in agreement with Dietz, et al (2008) which reported that nutrition and oral hygiene education should be an integral part of keeping growing children healthy and forming good nutrition habits that will carry into adulthood

Quantum density anomaly in optically trapped ultracold gases

We show that the Bose-Hubbard Model exhibits an increase in density with temperature at fixed pressure in the regular fluid regime and in the superfluid phase. The anomaly at the Bose-Einstein condensate is the first density anomaly observed in a quantum state. We propose that the mechanism underlying both the normal phase and the superfluid phase anomalies is related to zero point entropies and ground state phase transitions. A connection with the typical experimental scales and setups is also addressed. This key finding opens a new pathway for theoretical and experimental studies of water-like anomalies in the area of ultracold quantum gases

Thermodynamic and Dynamic Anomalies for Dumbbell Molecules Interacting with a Repulsive Ramp-Like Potential

Using collision driven discrete molecular dynamics (DMD), we investigate the thermodynamics and dynamics of systems of 500 dumbbell molecules interacting by a purely repulsive ramp-like discretized potential, consisting of $n$ steps of equal size. We compare the behavior of the two systems, with $n = 18$ and $n = 144$ steps. Each system exhibits both thermodynamic and dynamic anomalies, a density maximum and the translational and rotational mobilities show anomalous behavior. Starting with very dense systems and decreasing the density, both mobilities first increase, reache a maximum, then decrease, reache a minimum, and finally increase; this behavior is similar to the behavior of SPC/E water. The regions in the pressure-temperature plane of translational and rotational mobility anomalies depend strongly on $n$. The product of the translational diffusion coefficient and the orientational correlation time increases with temperature, in contrast with the behavior of most liquids