Estimating Operational Validity Under Incidental Range Restriction: Some Important but Neglected Issues

Operational validities are important to personnel selection research because they estimate how well a predictor in practical use correlates with a criterion construct, if the criterion measure were purged of measurement error variance. Because range restriction on a predictor or predictor composite creates incidental range restriction on the criterion, existing methodologies offer limited information and guidance for estimating operational validities. Although these effects of range restriction and criterion unreliability could be corrected with existing equations in a sequential fashion, proper use of sequential correction equations is not always as straightforward as it appears. This research reviews the existing equations for correcting validities, outlines the appropriate method for correcting validity coefficients via sequential equations, and proposes a new equation that performs a combined correction for the effects of incidental range restriction and criterion unreliability

Estimating Operational Validity Under Incidental Range Restriction: Some Important but Neglected Issues

Operational validities are important to personnel selection research because they estimate how well a predictor in practical use correlates with a criterion construct, if the criterion measure were purged of measurement error variance. Because range restriction on a predictor or predictor composite creates incidental range restriction on the criterion, existing methodologies offer limited information and guidance for estimating operational validities. Although these effects of range restriction and criterion unreliability could be corrected with existing equations in a sequential fashion, proper use of sequential correction equations is not always as straightforward as it appears. This research reviews the existing equations for correcting validities, outlines the appropriate method for correcting validity coefficients via sequential equations, and proposes a new equation that performs a combined correction for the effects of incidental range restriction and criterion unreliability. Accessed 1,910 times on https://pareonline.net from August 06, 2017 to December 31, 2019. For downloads from January 1, 2020 forward, please click on the PlumX Metrics link to the right

Universality in the Crossover between Edge Channel and Bulk Transport in the Quantum Hall Regime

We present a new theoretical approach for the integer quantum Hall effect, which is able to describe the inter-plateau transitions as well as the transition to the Hall insulator. We find two regimes (metallic and insulator like) of the top Landau level, in which the dissipative bulk current appears in different directions. The regimes are separated by a temperature invariant point.Comment: 4 page, 2 eps figures included, submitte

Time-dependent Hamiltonian estimation for Doppler velocimetry of trapped ions

The time evolution of a closed quantum system is connected to its Hamiltonian through Schroedinger's equation. The ability to estimate the Hamiltonian is critical to our understanding of quantum systems, and allows optimization of control. Though spectroscopic methods allow time-independent Hamiltonians to be recovered, for time-dependent Hamiltonians this task is more challenging. Here, using a single trapped ion, we experimentally demonstrate a method for estimating a time-dependent Hamiltonian of a single qubit. The method involves measuring the time evolution of the qubit in a fixed basis as a function of a time-independent offset term added to the Hamiltonian. In our system the initially unknown Hamiltonian arises from transporting an ion through a static, near-resonant laser beam. Hamiltonian estimation allows us to estimate the spatial dependence of the laser beam intensity and the ion's velocity as a function of time. This work is of direct value in optimizing transport operations and transport-based gates in scalable trapped ion quantum information processing, while the estimation technique is general enough that it can be applied to other quantum systems, aiding the pursuit of high operational fidelities in quantum control.Comment: 10 pages, 8 figure

Theory and computation of directional nematic phase ordering

A computational study of morphological instabilities of a two-dimensional nematic front under directional growth was performed using a Landau-de Gennes type quadrupolar tensor order parameter model for the first-order isotropic/nematic transition of 5CB (pentyl-cyanobiphenyl). A previously derived energy balance, taking anisotropy into account, was utilized to account for latent heat and an imposed morphological gradient in the time-dependent model. Simulations were performed using an initially homeotropic isotropic/nematic interface. Thermal instabilities in both the linear and non-linear regimes were observed and compared to past experimental and theoretical observations. A sharp-interface model for the study of linear morphological instabilities, taking into account additional complexity resulting from liquid crystalline order, was derived. Results from the sharp-interface model were compared to those from full two-dimensional simulation identifying the specific limitations of simplified sharp-interface models for this liquid crystal system. In the nonlinear regime, secondary instabilities were observed to result in the formation of defects, interfacial heterogeneities, and bulk texture dynamics.Comment: first revisio

Elasticity of smectic liquid crystals with focal conic domains

We study the elastic properties of thermotropic smectic liquid crystals with focal conic domains (FCDs). After the application of the controlled preshear at different temperatures, we independently measured the shear modulus G' and the FCD size L. We find out that these quantities are related by the scaling relation G' ~ \gamma_{eff}/L where \gamma_{eff} is the effective surface tension of the FCDs. The experimentally obtained value of \gamma_{\rm eff} shows the same scaling as the effective surface tension of the layered systems \sqrt{KB} where K and B are the bending modulus and the layer compression modulus, respectively. The similarity of this scaling relation to that of the surfactant onion phase suggests an universal rheological behavior of the layered systems with defects.Comment: 14 pages, 7 figures, accepted for publication in JPC

Colloidal particles at a nematic-isotropic interface: effects of confinement

When captured by a flat nematic-isotropic interface, colloidal particles can be dragged by it. As a result spatially periodic structures may appear, with the period depending on a particle mass, size, and interface velocity~\cite{west.jl:2002}. If liquid crystal is sandwiched between two substrates, the interface takes a wedge-like shape, accommodating the interface-substrate contact angle and minimizing the director distortions on its nematic side. Correspondingly, particles move along complex trajectories: they are first captured by the interface and then `glide' towards its vertex point. Our experiments quantify this scenario, and numerical minimization of the Landau-de Gennes free energy allow for a qualitative description of the interfacial structure and the drag force.Comment: 7 pages, 9 figure

Optical Structure and Proper-Motion Age of the Oxygen-rich Supernova Remnant 1E 0102-7219 in the Small Magellanic Cloud

We present new optical emission-line images of the young SNR 1E 0102-7219 (E0102) in the SMC obtained with the HST Advanced Camera for Surveys (ACS). E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen, neon , and other metal-line emissions in its optical and X-ray spectra, and an absence of H and He. The progenitor of E0102 may have been a Wolf-Rayet star that underwent considerable mass loss prior to exploding as a Type Ib/c or IIL/b SN. The ejecta in this SNR are fast-moving (V > 1000 km/s) and emit as they are compressed and heated in the reverse shock. In 2003, we obtained optical [O III], H-alpha, and continuum images with the ACS Wide Field Camera. The [O III] image captures the full velocity range of the ejecta, and shows considerable high-velocity emission projected in the middle of the SNR that was Doppler-shifted out of the narrow F502N bandpass of a previous Wide Field and Planetary Camera 2 image from 1995. Using these two epochs separated by ~8.5 years, we measure the transverse expansion of the ejecta around the outer rim in this SNR for the first time at visible wavelengths. From proper-motion measurements of 12 ejecta filaments, we estimate a mean expansion velocity for the bright ejecta of ~2000 km/s and an inferred kinematic age for the SNR of \~2050 +/- 600 years. The age we derive from HST data is about twice that inferred by Hughes et al.(2000) from X-ray data, though our 1-sigma error bars overlap. Our proper-motion age is consistent with an independent optical kinematic age derived by Eriksen et al.(2003) using spatially resolved [O III] radial-velocity data. We derive an expansion center that lies very close to X-ray and radio hotspots, which could indicate the presence of a compact remnant (neutron star or black hole).Comment: 28 pages, 8 figures. Accepted to the Astrophysical Journal, to appear in 20 April 2006 issue. Full resolution figures are posted at: http://stevenf.asu.edu/figure

The troubadour Marcabru and his public

Vanadium(V)-containing oxides show superior intercalation properties for alkaline ions, although the performance of the material strongly depends on its surface morphology. In this work, intercalation activity of LiV$_{3}$O$_{8}$, prepared by a conventional solid state synthesis, is demonstrated for the first time in non-aqueous Li,Na-ion hybrid batteries with Na as negative electrode, and different Na/Li ratios in the electrolyte. In the pure Na-ion cell, one Na per formula unit of LiV$_{3}$O$_{8}$ can be reversibly inserted at room temperature via a two-step process, while further intercalation leads to gradual amorphisation of the material, with a specific capacity of 190 mAhg$^{−1}$ after 10 cycles in the potential window of 0.8–3.4 V. Hybrid Li,Na-ion batteries feature simultaneous intercalation of Li$^+$ and Na$^+$ cations into LiV$_{3}$O$_{8}$, resulting in the formation of a second phase. Depending on the electrolyte composition, this second phase bears structural similarities either to Li$_{0.7}$Na$_{0.7}$V$_{3}$O$_{8}$ in Na-rich electrolytes, or to LiV$_{3}$O$_{8}$ in Li-rich electrolytes. The chemical diffusion coefficients of Na+ and Li+ in crystalline LiV$_{3}$O$_{8}$ are very close, hence explaining the co-intercalation of these cations. As DFT calculations show, once formed, the Li$_{0.7}$Na$_{0.7}$V$_{3}$O$_{8}$-type structure favors intercalation of Na$^+$, whereas the LiV$_{3}$O$_{8}$-type prefers to accommodate Li$^+$ cations