7 research outputs found

    García, Xavier (ed.) (2015). Joan Oliver-Joaquim Molas: Diàleg epistolar il·lustrat (1959-1982). Lleida: Pagès Editors, pp. 186

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    <p><i>Objectives</i>: Attention-deficit/hyperactivity disorder (ADHD) has been associated with spatial working memory as well as frontostriatal core deficits. However, it is still unclear how the link between these frontostriatal deficits and working memory function in ADHD differs in children and adults. This study examined spatial working memory in adults and children with ADHD, focussing on identifying regions demonstrating age-invariant or age-dependent abnormalities. <i>Methods</i>: We used functional magnetic resonance imaging to examine a group of 26 children and 35 adults to study load manipulated spatial working memory in patients and controls. <i>Results</i>: In comparison to healthy controls, patients demonstrated reduced positive parietal and frontostriatal load effects, i.e., less increase in brain activity from low to high load, despite similar task performance. In addition, younger patients showed negative load effects, i.e., a decrease in brain activity from low to high load, in medial prefrontal regions. Load effect differences between ADHD and controls that differed between age groups were found predominantly in prefrontal regions. Age-invariant load effect differences occurred predominantly in frontostriatal regions. <i>Conclusions</i>: The age-dependent deviations support the role of prefrontal maturation and compensation in ADHD, while the age-invariant alterations observed in frontostriatal regions provide further evidence that these regions reflect a core pathophysiology in ADHD.</p

    Oxygen Evolution at Hematite Surfaces: The Impact of Structure and Oxygen Vacancies on Lowering the Overpotential

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    Simulations of the oxygen evolution reaction (OER) are essential for understanding the limitations of water splitting. Most research has focused so far on the OER at flat metal oxide surfaces. The structure sensitivity of the OER has, however, recently been highlighted as a promising research direction. To probe the structure sensitivity, we investigate the OER at 11 hematite (Fe<sub>2</sub>O<sub>3</sub>) surfaces with density functional theory + Hubbard U (DFT+U) calculations. The results show that the O–O coupling (O–O bond formation via two adjacent terminal Os at dual site) OER mechanism at the (110) surface is competing with the mechanism of OOH formation at single site. We study the effects of surface orientation (110 vs 104), active surface sites (bridge vs terminal site), presence of surface steps and oxygen vacancy concentration on the OER and explore strategies to reduce the OER overpotential. It is found that the oxygen vacancy concentration is the most effective parameter in reducing the overpotential. In particular, an overpotential of as low as 0.47 V is obtained for the (110) surface with an oxygen vacancy concentration of 1.26 vacancies/nm<sup>2</sup>

    Representative MEGA-PRESS spectra.

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    <p>(A) Averaged MEGA-PRESS spectra (averaged across the subject group) acquired at rest (left) and during the WM task. The GABA peak at 3.0 ppm appears to increase between the resting spectrum and the first WM spectrum, and then decrease during performance of the WM task (panels 2-5). The dashed line marks the resting state peak. Glx: glutamate + glutamine concentration, GABA: gamma-aminobutyric acid, NAA: N-acetylaspartate, IU: institutional units. (B) LCModel output for a single subject: the fit is shown in red, superimposed on the edited spectrum (in black). The top panel shows the residuals between the MRS data and the spectral fit.</p

    Areas of significant perfusion change during the WM task (p<0.001, uncorrected, k = 150).

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    <p>The location of the left DLPFC voxel (white rectangle) is shown for comparison. Results are presented on an axial slice (MNI z-coordinate = 24) of a T1-weighted image from a single subject.</p

    Women show higher perfusion than men and DHEAS correlates negatively with perfusion.

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    <p>a) Sex difference in whole brain grey matter perfusion: perfusion is higher in women (<i>M</i> = 35.97 ml/min/100 ml, <i>SD</i> = 5.37) than in men (<i>M</i> = 30.47 ml/min/100 ml, <i>SD</i> = 5.91, <i>p</i> = .006). Single dots represent the subjects' individual values. The horizontal line within the boxes indicate medians, the edges of the boxes are the 25<sup>th</sup> and 75<sup>th</sup> percentiles, and the whiskers represent 1.5 times the interquartile range. b) Sex difference (women > men) in regional perfusion: women show higher regional perfusion than men (<i>p</i> = .004, FWE-corrected). c) Simple regression analysis with whole brain perfusion values as the dependent variable and DHEAS as the only predictor: a significant model was found (<i>p</i> = .007, adjusted <i>R</i><sup><i>2</i></sup> = .180) with a standardised β = -.452 for DHEAS. d) DHEAS effects in men and women: DHEAS correlates negatively with regional perfusion in both sexes (<i>p</i> = .004, FWE-corrected). Colour bar in a) and c) denotes a non-parametric <i>t</i> score, given by <i>a1</i>/[standard error(<i>a1</i>)], see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135827#sec002" target="_blank">methods</a>. Images are shown in neurological orientation. Slices are at MNI z-coordinates -45, -30, -15, 0, 15, 30, 45, 60, 75 (from top left to bottom right).</p