7,623 research outputs found
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 steps of
equal size. We compare the behavior of the two systems, with and 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 . The product of the translational
diffusion coefficient and the orientational correlation time increases with
temperature, in contrast with the behavior of most liquids
Environmental Law -- Admiralty Law -- Validity of States\u27 Oil Pollution Sanctions -- Askew v. American Waterways Operators, Inc.
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