John W. Wilkins

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We propose a new direct mechanism for the pressure driven ! ! martensitic transformation in pure titanium. A systematic algorithm enumerates all possible pathways whose energy barriers are evaluated. A new, homogeneous pathway emerges with a barrier at least 4 times lower than other pathways. The pathway is shown to be favorable in any nucleation model.(More)
  • Hyoungki Park, Michael R Fellinger, Thomas J Lenosky, William W Tipton, Dallas R Trinkle, Sven P Rudin +3 others
  • 2012
Density-functional theory energies, forces, and elastic constants determine the parametrization of an empirical, modified embedded-atom method potential for molybdenum. The accuracy and transferability of the potential are verified by comparison to experimental and density-functional data for point defects, phonons, thermal expansion, surface and stacking(More)
I mpurities control phase stability and phase transformations in natural and man-made materials, from shape-memory alloys 1 to steel 2 to planetary cores 3. Experiments and empirical databases are still central to tuning the impurity eff ects. What is missing is a broad theoretical underpinning. Consider, for example, the titanium martensitic(More)
A description of the martensitic transformations between the ␣, ␤, and ␻ phases of titanium that includes nucleation and growth requires an accurate classical potential. Optimization of the parameters of a modified embedded atom potential to a database of density-functional calculations yields an accurate and transferable potential as verified by comparison(More)
The assessment of relatively intact individuals poses special problems for neuropsychologists, because fine discriminations are often needed to identify subtle deficits or gradual declines in performance. Many neuropsychological tests, however, are not well-suited for making such exact discriminations. 117 HIV+ individuals were administered 26 different(More)
P3 event-related evoked potentials (ERP) were recorded from 47 human immunodeficiency virus (HIV)-positive subjects examined twice and 29 HIV-positive subjects examined three times at 6-month intervals. The P3 latency significantly increased over time for asymptomatic subjects and subjects with acquired immunodeficiency syndrome (AIDS) and AIDS-related(More)
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