Browsing by Author "Clark, J"

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    Learning and memory in bipolar and unipolar major depression: Effects of aging
    (Neuropsychiatry, Neuropsychology and Behavioral Neurology, 2000) Burt, T; Prudic, J; Peyser, S; Clark, J; Sackeim, HA
    Objective: The goal of this study was to examine the effects of aging on neuropsychological functions in bipolar and unipolar major depression. Background: Earlier studies suggested that neurocognitive deficits in mood disorder patients correlate with duration and severity of illness and also that bipolar disorder has a more virulent course than unipolar disorder. We hypothesized that elderly patients with bipolar disorder will demonstrate greater neurocognitive dysfunction than young patients with bipolar disorder and elderly patients with unipolar disorder. Method: A battery of tests of general intelligence and learning and memory was administered to 79 inpatients with major depression referred for electroconvulsive therapy. With patients 60 years of age and older defined as elderly, there were 29 young and 24 elderly unipolar patients and 13 young and 13 elderly bipolar patients. Results: Unipolar and bipolar patients did not differ in measures of general intelligence or global cognitive status. Generally, across tests of memory, young bipolar patients exhibited the best performance and elderly bipolar patients exhibited the poorest performance. Conclusions: The results suggest that over the course of their illness, patients with bipolar disorder experience greater deterioration in memory functions than patients with unipolar disorder. Longitudinal studies are required to support the preliminary findings of this cross-sectional study.
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    Save the WHO Program for Hearing Loss Prevention
    (The Hearing Journal, 2013-09) Mamo, SK; Johnson, J; Saunders, J; Clark, J; Emmett, S; Afridi, S; Wilson, LJ
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    The origin of incipient ferroelectricity in lead telluride.
    (Nat Commun, 2016-07-22) Jiang, MP; Trigo, M; Savić, I; Fahy, S; Murray, ÉD; Bray, C; Clark, J; Henighan, T; Kozina, M; Chollet, M; Glownia, JM; Hoffmann, MC; Zhu, D; Delaire, O; May, AF; Sales, BC; Lindenberg, AM; Zalden, P; Sato, T; Merlin, R; Reis, DA
    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.