47,747 research outputs 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
Effect of single-value response styles on latent factor model convergence and measures of fit
This research examines the effects of single-value response style contamination on measures of model fit and model convergence issues. A simulation study examines the effects resulting from percentage of contamination, number of manifest, number of reverse coded items, magnitude of standardized factor loadings, response scale granularity, and sample size. Initial results indicate that sample size, scale granularity, factor loadings and number of manifest items had little to no effect on measures of fit. Both percent contamination and number of reverse coded items had a large effect on measures of fit. Measures of fit were more readily effected by percent contamination in models with higher standardized factor loadings. Model convergence issues were most strongly related to percent contamination and factor loadings
Superalgebra Realization of the 3-algebras in N=6, 8 Chern-Simons-matter Theories
We use superalgebras to realize the 3-algebras used to construct N=6, 8
Chern-Simons-matter (CSM) theories. We demonstrate that the superalgebra
realization of the 3-algebras provides a unified framework for classifying the
gauge groups of the N \geq 5 theories based on 3-algebras. Using this
realization, we rederive the ordinary Lie algebra construction of the general
N=6 CSM theory from its 3-algebra counterpart, and reproduce all known examples
as well. In particular, we explicitly construct the Nambu 3-bracket in terms of
a double graded commutator of PSU(2|2). The N = 8 theory of Bagger, Lambert and
Gustavsson (BLG) with SO(4) gauge group is constructed by using several
different ways. A quantization scheme for the 3-brackets is proposed by
promoting the double graded commutators as quantum mechanical double graded
commutators.Comment: 29 pages, minor changes, published in JM
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
Electronic structure of multilayer graphene
We study the electronic structure of multilayer graphene using a
-orbital continuum model with nearest-neighbor intralayer and interlayer
tunneling. Using degenerate state perturbation theory, we show that the
low-energy electronic structure of arbitrarily stacked graphene multilayers
consists of chiral pseudospin doublets with a conserved chirality sum.Comment: 25 pages, 15 figures; Expanded version of PRB 77,155416 (2008),
arXiv:0711.4333; Published in the proceedings of YKIS2007; Typos correcte
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,
Radio and Far-Infrared Emission as Tracers of Star Formation and AGN in Nearby Cluster Galaxies
We have studied the radio and far-infrared (FIR) emission from 114 galaxies
in the 7 nearest clusters (<100 Mpc) with prominent X-ray emission to
investigate the impact of the cluster environment on the star formation and AGN
activity in the member galaxies. The X-ray selection criterion is adopted to
focus on the most massive and dynamically relaxed clusters. A large majority of
cluster galaxies show an excess in radio emission over that predicted from the
radio-FIR correlation, the fraction of sources with radio excess increases
toward cluster cores, and the radial gradient in the FIR/radio flux ratio is a
result of radio enhancement. Of the radio-excess sources, 70% are early-type
galaxies and the same fraction host an AGN. The galaxy density drops by a
factor of 10 from the composite cluster center out to 1.5 Mpc, yet galaxies
show no change in FIR properties over this region, and show no indication of
mass segregation. We have examined in detail the physical mechanisms that might
impact the FIR and radio emission of cluster galaxies. While collisional
heating of dust may be important for galaxies in cluster centers, it appears to
have a negligible effect on the observed FIR emission for our sample galaxies.
The correlations between radio and FIR luminosity and radius could be explained
by magnetic compression from thermal ICM pressure. We also find that simple
delayed harassment cannot fully account for the observed radio, FIR, and mid-IR
properties of cluster galaxies.Comment: 21 pages, 15 figures, Accepted by Ap
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