Optimal and efficient crossover designs for comparing test treatments with a control treatment

This paper deals exclusively with crossover designs for the purpose of comparing t test treatments with a control treatment when the number of periods is no larger than t+1. Among other results it specifies sufficient conditions for a crossover design to be simultaneously A-optimal and MV-optimal in a very large and appealing class of crossover designs. It is expected that these optimal designs are highly efficient in the entire class of crossover designs. Some computationally useful tools are given and used to build assorted small optimal and efficient crossover designs. The model robustness of these newly discovered crossover designs is discussed.Comment: Published at http://dx.doi.org/10.1214/009053604000000887 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Lévy stable distributions for velocity and velocity difference in systems of vortex elements

The probability density functions (PDFs) of the velocity and the velocity difference field induced by a distribution of a large number of discrete vortex elements are investigated numerically and analytically. Tails of PDFs of the velocity and velocity difference induced by a single vortex element are found. Treating velocities induced by different vortex elements as independent random variables, PDFs of the velocity and velocity difference induced by all vortex elements are found using limit distribution theorems for stable distributions. Our results generalize and extend the analysis by Takayasu [Prog. Theor. Phys. 72, 471 (1984)]. In particular, we are able to treat general distributions of vorticity, and obtain results for velocity differences and velocity derivatives of arbitrary order. The PDF for velocity differences of a system of singular vortex elements is shown to be Cauchy in the case of small separation r, both in 2 and 3 dimensions. A similar type of analysis is also applied to non-singular vortex blobs. We perform numerical simulations of the system of vortex elements in two dimensions, and find that the results compare favorably with the theory based on the independence assumption. These results are related to the experimental and numerical measurements of velocity and velocity difference statistics in the literature. In particular, the appearance of the Cauchy distribution for the velocity difference can be used to explain the experimental observations of Tong and Goldburg [Phys. Lett. A 127, 147 (1988); Phys. Rev. A 37, 2125, (1988); Phys. Fluids 31, 2841 (1988)] for turbulent flows. In addition, for intermediate values of the separation distance, near exponential tails are found

Random contamination and select response styles affecting measures of fit and reliability in factor analysis

This research examines the effects of nonattending response pattern contamination and select response style patterns on measures of model fit (CFI) and internal reliability (Cronbach's α). A simulation study examines the effects resulting from percentage of contamination, number of manifest items measured and sample size. Initial results indicate that sample size very mildly affects CFI but does not influence α. Percent contamination decreases both CFI and α in a nearly linear fashion over a limited range of contamination. Finally, whereas an increase in the number of manifest items increases resilience to random contamination for α, the opposite was observed for CFI. An increase in the number of manifest items resulted in larger decreases in CFI. Implications are briefly discussed

On the Distribution of Plasmoids In High-Lundquist-Number Magnetic Reconnection

The distribution function $f(\psi)$ of magnetic flux $\psi$ in plasmoids formed in high-Lundquist-number current sheets is studied by means of an analytic phenomenological model and direct numerical simulations. The distribution function is shown to follow a power law $f(\psi)\sim\psi^{-1}$, which differs from other recent theoretical predictions. Physical explanations are given for the discrepant predictions of other theoretical models.Comment: Accepted for publication in Phys. Rev. Let

Whale-watching and Herring Fishing: Joint or Independent Production?

The effects of "localized depletion" of a pelagic fishery (herring) on a non-extractive marine activity (tourism) are investigated. Proponents of the localized depletion theory claim that intense fishing effort can lead to areas that are unsuitable for predators like tuna, groundfish, and whales. This leads to poor outcomes for the fishing and whale-watching industries. However, there has been no consensus in the scientific community about the existence of this phenomenon. Localized depletion would be consistent with an economic theory of joint production, in which nearshore herring stocks are an input in production of both herring and whale-watching trips. A unique dataset of daily whale-watching outcomes is combined with fishing effort and oceanographic data. This dataset is used to test the hypothesis that intensive fishing effort increases the search time of whale-watching companies. Our results suggest that while fishing has a statistically significant impact on sightings, this magnitude of this effect is fairly small. Sightings seem to be determined mostly by large scale oceanographic processes. These results should be of interest to policymakers in determining future fishing regulations.whales, fishing, panel data, search, Ecosystem Based Management, Resource /Energy Economics and Policy, Q57, Q26, Q22,

Non-linear excitations in 1D correlated insulators

In this work we investigate charge transport in one-dimensional (1D) insulators via semi-classical and perturbative renormalization group (RG) methods. We consider the problem of electron-electron, electron-phonon and electron-two-level system interactions. We show that non-linear collective modes such as polarons and solitons are reponsible for transport. We find a new excitation in the Mott insulator: the polaronic soliton. We discuss the differences between band and Mott insulators in terms of their spin spectrum and obtain the charge and spin gaps in each one of these systems. We show that electron-electron interactions provide strong renormalizations of the energy scales in the problem.Comment: 29 page

Early Delirium Assessment for Hospitalized Older People in Indonesia: a Systematic Review

Background: Due to the increasing risk of getting co-morbidity and frailty, older people tend to be prone to hospitalization. Hospitalization in older people brings many adverse effects. Moreover, when these elderly get delirium, the mortality and morbidity will increase. The risk of getting deterioration and worsening condition because of delirium would also increase. In fact, delirium assessment is not a high priority in taking care older people during hospitalization because the focus of care is treating the disease.Delirium screening as an early recognition of delirium in the hospitalized elderly inIndonesia remains unreported and even do not well evaluated. Therefore, delirium as a preventable problem or causing problems remains unrecognized.Purpose: This paper aims to review the current evidence of early assessment of delirium in hospitalized older people.Methods: A systematic review was conducted from four databases yielding to 4 articles which met the inclusion and exclusion criteria.Results: There are four focuses on the result, namely delirium screening tools, patient characteristics, identified early delirium assessment, and outcomes affected by early delirium assessment. Confusion Assessment Method (CAM) was used as the delirium screening tool in the hospital. Establishing the care team involving many disciplines will give a better way to improve the integrated care and collaborative care.Conclusion: Performing CAM integrated into comprehensive geriatric assessment can be the most important thing to be undertaken when looking after the hospitalized elderly

Modeling Staple Food Consumption: Measuring the Trade Effect on Food Security for Chinese Grain Farmers

This paper derives a simulation model that examines the food security of the grain producing households in China in an open border model regime. We define a food inadequacy index (F.I.) to measure the change of the food security status under alternative scenarios of border liberalization for the households. We conclude that if opening the border of grain market is followed by a more variable grain price distribution, the food security status will deteriorate for the low-income households on average. However, if border liberalization is followed by a decrease in mean of the price distribution, even with a more variable distribution, the food security status improves.International Relations/Trade,

ηc\eta_c - glueball Mixing and Resonance X(1835)

The mixing of $\eta_c$ and the lowest mass pseudoscalar glueball is estimated within the framework of the instanton liquid model. It is demonstrated that the mixing is large and may explain the difference between the observed mass of the glueball candidate X(1835) and the theoretical prediction of QCD sum rule analysis.Comment: 5 pages, 1 figure, Late