2,151 research outputs found
Glass state of superfluid 3He-A in aerogel
Glass states formed in the superfluid He confined in aerogel are
discussed. If the short range order corresponds to the A-phase state, the glass
state is nonsuperfluid in the long wave length limit. The superfluidity can be
restored by application of a small mass current. Transitions between the
superfluid and nonsuperfluid glass states can be triggered by small magnetic
field and by the change of the tipping angle of magnetization in NMR
experiments.Comment: 6 pages, LaTeX file, no figures, submitted to JETP Letter
Universal Behaviour of the Superfluid Fraction and Tc of He-3 in 99.5% Open Aerogel
We have investigated the superfluid transition of He-3 in a 99.5% porosity
silica aerogel. This very dilute sample shows behaviour intermediary between
bulk He-3 and He-3 confined to the denser aerogels previously studied. We
present data on both the superfluid transition temperature and the superfluid
density and compare our results with previous measurements. Finally, we show
that the suppression of the superfluid transition temperature and suppression
of the superfluid density of He-3 in aerogel follow a universal relation for a
range of aerogel samples.Comment: 4 pages, 5 figures; 1 new figure, minor change
Revisiting measurement invariance in intelligence testing in aging research: Evidence for almost complete metric invariance across age groups.
Background / Objectives: Invariance of intelligence across age is often assumed but infrequently explicitly tested. Horn and McArdle (1992) tested measurement invariance of intelligence, providing adequate model fit but might not consider all relevant aspects like subtest differences. The goal of the current paper is to explore age-related invariance of the WAIS-R using an alternative model that allows direct tests of age on WAIS-R subtests.
Methods: Cross-sectional data on 940 participants aged 16-75 from the WAIS-R normative values were used. Subtests examined were information, comprehension, similarities, vocabulary, picture completion, block design, picture arrange-ment, and object assembly. The two intelligence factors considered were fluid and crystallized intelligence. Self-reported ages were divided into young (16-22, n = 300), adult (29-39, n = 275), middle (40-60, n = 205), and older (61-75, n = 160) adult groups.
Results: Partial metric invariance holds in the WAIS-R. Although most subtests reflected fluid and crystalized intelligence similarly across different ages, invariance did not hold for block design on fluid intelligence and picture arrangement on crystallized intelligence for older adults. Additionally, there was evidence of a correlated residual between information and vocabulary for the young adults only. This partial metric invariance model yielded acceptable model fit compared to previously-proposed invariance models of Horn and McArdle (1992).
Conclusion: Almost complete metric invariance holds for a two-factor model of intelligence. Most subtests were invariant across age groups, suggesting little evidence for age-related bias in the WAIS-R. However, we did find unique relationships between two subtests and intelligence. Future studies should examine age-related differences in subtests when testing measurement invariance in intelligence
A log analysis study of 10 years of ebook consumption in academic library collections
Even though libraries have been offering eBooks for more than a decade, very little is known about eBook access and consumption in academic library collections. This paper addresses this gap with a log analysis study of eBook access at the library of the University of Waikato. This in-depth analysis covers a period spanning 10 years of eBook use at this university. We draw conclusions about the use of eBooks at this institution and compare the results with other published studies of eBook usage at tertiary institutes
Sub-picosecond injection of electrons from excited [Ru(2,2′-bipy-4,4′-dicarboxy)<sub>2</sub>(SCN)<sub>2</sub>] into TiO<sub>2</sub> using transient mid-infrared spectroscopy
We have used femtosecond pump-probe spectroscopy to time resolve the injection of electrons into nanocrystalline TiO2 film electodes under ambient conditions following photoexcitation of the adsorbed dye, [Ru(4,4’-dicarboxy-2,2’-bipyridine)2(NCS)2] (N3). Pumping at one of the metal-to-ligand charge transfer adsorption peaks and probing the absorption of electrons injected into the TiO2 conduction band at 1.52 µm and in the range of 4.1 to 7.0 µm, we have directly observed the arrival of the injected electrons. Our measurements indicate an instrument-limited ~50-fs upper limit on the electron injection time under ambient conditions in air. We have compared the infrared transient absorption for noninjecting (blank) systems consisting of N3 in ethanol and N3 adsorbed to films of nanocrystalline Al2O3 and ZrO2, and found no indication of electron injection at probe wavelengths in the mid-IR (4.1 to 7.0 µm). At 1.52 µm interferences exist in the observed transient adsorption signal for the blanks
Thin helium film on a glass substrate
We investigate by Monte Carlo simulations the structure, energetics and
superfluid properties of thin helium-four films (up to four layers) on a glass
substrate, at low temperature. The first adsorbed layer is found to be solid
and "inert", i.e., atoms are localized and do not participate to quantum
exchanges. Additional layers are liquid, with no clear layer separation above
the second one. It is found that a single helium-three impurity resides on the
outmost layer, not significantly further away from the substrate than
helium-four atoms on the same layer.Comment: Six figures, submitted for publication to the Journal of Low
Temperature Physic
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Nonlinear Legendre Spectral Finite Elements for Wind Turbine Blade Dynamics: Preprint
This paper presents a numerical implementation and examination of new wind turbine blade finite element model based on Geometrically Exact Beam Theory (GEBT) and a high-order spectral finite element method. The displacement-based GEBT is presented, which includes the coupling effects that exist in composite structures and geometric nonlinearity. Legendre spectral finite elements (LSFEs) are high-order finite elements with nodes located at the Gauss-Legendre-Lobatto points. LSFEs can be an order of magnitude more efficient that low-order finite elements for a given accuracy level. Interpolation of the three-dimensional rotation, a major technical barrier in large-deformation simulation, is discussed in the context of LSFEs. It is shown, by numerical example, that the high-order LSFEs, where weak forms are evaluated with nodal quadrature, do not suffer from a drawback that exists in low-order finite elements where the tangent-stiffness matrix is calculated at the Gauss points. Finally, the new LSFE code is implemented in the new FAST Modularization Framework for dynamic simulation of highly flexible composite-material wind turbine blades. The framework allows for fully interactive simulations of turbine blades in operating conditions. Numerical examples showing validation and LSFE performance will be provided in the final paper
Blinded interpretation of study results can feasibly and effectively diminish interpretation bias
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