Browsing by Author "Zhou, Hua"

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    Imaging genetics via sparse canonical correlation analysis
    (IEEE, 2013) Chi, Eric C.; Allen, Genevera I.; Zhou, Hua; Kohannim, Omid; Lange, Kenneth; Thompson, Paul M.
    The collection of brain images from populations of subjects who have been genotyped with genome-wide scans makes it feasible to search for genetic effects on the brain. Even so, multivariate methods are sorely needed that can search both images and the genome for relationships, making use of the correlation structure of both datasets. Here we investigate the use of sparse canonical correlation analysis (CCA) to home in on sets of genetic variants that explain variance in a set of images. We extend recent work on penalized matrix decomposition to account for the correlations in both datasets. Such methods show promise in imaging genetics as they exploit the natural covariance in the datasets. They also avoid an astronomically heavy statistical correction for searching the whole genome and the entire image for promising associations.
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    Size-Induced Ferroelectricity in Antiferroelectric Oxide Membranes
    (Wiley, 2023) Xu, Ruijuan; Crust, Kevin J.; Harbola, Varun; Arras, Rémi; Patel, Kinnary Y.; Prosandeev, Sergey; Cao, Hui; Shao, Yu-Tsun; Behera, Piush; Caretta, Lucas; Kim, Woo Jin; Khandelwal, Aarushi; Acharya, Megha; Wang, Melody M.; Liu, Yin; Barnard, Edward S.; Raja, Archana; Martin, Lane W.; Gu, X. Wendy; Zhou, Hua; Ramesh, Ramamoorthy; Muller, David A.; Bellaiche, Laurent; Hwang, Harold Y.
    Despite extensive studies on size effects in ferroelectrics, how structures and properties evolve in antiferroelectrics with reduced dimensions still remains elusive. Given the enormous potential of utilizing antiferroelectrics for high-energy-density storage applications, understanding their size effects will provide key information for optimizing device performances at small scales. Here, the fundamental intrinsic size dependence of antiferroelectricity in lead-free NaNbO3 membranes is investigated. Via a wide range of experimental and theoretical approaches, an intriguing antiferroelectric-to-ferroelectric transition upon reducing membrane thickness is probed. This size effect leads to a ferroelectric single-phase below 40 nm, as well as a mixed-phase state with ferroelectric and antiferroelectric orders coexisting above this critical thickness. Furthermore, it is shown that the antiferroelectric and ferroelectric orders are electrically switchable. First-principle calculations further reveal that the observed transition is driven by the structural distortion arising from the membrane surface. This work provides direct experimental evidence for intrinsic size-driven scaling in antiferroelectrics and demonstrates enormous potential of utilizing size effects to drive emergent properties in environmentally benign lead-free oxides with the membrane platform.