488 research outputs found
Longitudinal structural brain changes in bipolar disorder: A multicenter neuroimaging study of 1232 individuals by the ENIGMA Bipolar Disorder Working Group
Background Bipolar disorder (BD) is associated with cortical and subcortical structural brain abnormalities. It is unclear whether such alterations progressively change over time, and how this is related to the number of mood episodes. To address this question, we analyzed a large and diverse international sample with longitudinal magnetic resonance imaging (MRI) and clinical data to examine structural brain changes over time in BD. Methods Longitudinal structural MRI and clinical data from the ENIGMA-BD Working Group, including 307 BD patients and 925 healthy controls (HC), were collected from 14 sites worldwide. Male and female participants, aged 40 ± 17 years, underwent MRI at two time points. Cortical thickness, surface area, and subcortical volumes were estimated using FreeSurfer. Annualized change rates for each imaging phenotype were compared between BD and HC. Within patients, we related brain change rates to the number of mood episodes between time points and tested for effects of demographic and clinical variables. Results Compared with HC, BD patients showed faster enlargement of ventricular volumes and slower thinning of fusiform and parahippocampal cortex (0.18<d<0.22). More (hypo)manic episodes were associated with faster cortical thinning, primarily in the prefrontal cortex. Conclusion In the hitherto largest longitudinal MRI study on BD, we did not detect accelerated cortical thinning but noted faster ventricular enlargements in BD. Abnormal fronto-cortical thinning was however observed in association with frequent manic episodes. Our study yields insights into disease progression in BD, and highlights the importance of mania prevention in BD treatment
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Pulsed Laser-Based X-Ray Sources for Rapid-Cool DT Layer Characterization
Ignition targets for the National Ignition Facility (NIF) will contain a cryogenically cooled {approx} 75 {micro}m-thick deuterium/tritium (DT) ice layer surrounded by a {approx} 150 {micro}m-thick beryllium (Be) shell [1]. Ignition target design optimization depends sensitively on the achievable inner surface quality of the ice layer and on the pressure of the DT gas inside the ice, which is determined by the temperature of the ice. The inner ice layer surface is smoothest at temperatures just below the DT ice/liquid/gas triple point (3T), but current ignition target designs require central gas pressures of 0.3 mg/cm3, corresponding to an ice layer temperature 1.5 K below the triple point (3T-1.5). At these lower temperatures, the ice layer quality degrades due to the formation of cracks and other features
Joint analysis of psychiatric disorders increases accuracy of risk prediction for schizophrenia, bipolar disorder, and major depressive disorder
Genetic risk prediction has several potential applications in medical research and clinical practice and could be used, for example, to stratify a heterogeneous population of patients by their predicted genetic risk. However, for polygenic traits, such as psychiatric disorders, the accuracy of risk prediction is low. Here we use a multivariate linear mixed model and apply multi-trait genomic best linear unbiased prediction for genetic risk prediction. This method exploits correlations between disorders and simultaneously evaluates individual risk for each disorder. We show that the multivariate approach significantly increases the prediction accuracy for schizophrenia, bipolar disorder, and major depressive disorder in the discovery as well as in independent validation datasets. By grouping SNPs based on genome annotation and fitting multiple random effects, we show that the prediction accuracy could be further improved. The gain in prediction accuracy of the multivariate approach is equivalent to an increase in sample size of 34% for schizophrenia, 68% for bipolar disorder, and 76% for major depressive disorders using single trait models. Because our approach can be readily applied to any number of GWAS datasets of correlated traits, it is a flexible and powerful tool to maximize prediction accuracy. With current sample size, risk predictors are not useful in a clinical setting but already are a valuable research tool, for example in experimental designs comparing cases with high and low polygenic risk
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High order reflectivity of graphite (HOPG) crystals for x ray energies up to 22 keV
We used Kr K{alpha} (12.6 keV) and Ag K{alpha} (22.1 keV) x-rays, produced by petawatt class laser pulses interacting with a Kr gas jet and a silver foil, to measure the integrated crystal reflectivity of flat Highly Oriented Pyrolytic Graphite (HOPG) up to fifth order. The reflectivity in fourth order is lower by a factor of 50 when compared to first order diffraction. In second order the integrated reflectivity decreases from 1.3 mrad at 12.6 keV to 0.5 mrad at 22.1 keV. The current study indicates that HOPG crystals are suitable for measuring scattering signals from high energy x ray sources (E {ge} 20 keV). These energies are required to penetrate through the high density plasma conditions encountered in inertial confinement fusion capsule implosions on the National Ignition Facility
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Observation of amplification of a 1ps pulse by SRS of a 1 ns pulse in a plasma with conditions relevant to pulse compression
The compression of a laser pulse by amplification of an ultra short pulse beam Which seeds the stimulated Raman scatter of the first beam has been long been discussed in the context of solid and gas media. We investigate the possibility of using intersecting beams in a plasma to compress nanosecond pulses to picosecond duration by scattering from driven electron waves. Recent theoretical studies have shown the possibility of efficient compression With large amplitude, non-linear Langmuir waves driven either by SRS or non-resonantly. We describe experiments in which a plasma suitable for pulse compression is created , and amplification of an ultra short pulse beam is demonstrated
Developing a platform for Fresnel diffractive radiography with 1 μm spatial resolution at the National Ignition Facility
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Amplification of an ultra short pulse laser by stimulated Raman scattering of a 1 ns pulse in a low density plasma
Experiments are described in which a 1mJ, 1ps, 1200 nm seed laser beam is amplified by interaction with an intersecting 350 J, 1ns, 1054 nm pump beam in a low density (1 x 10{sup 19}/cm{sup 3}) plasma. The transmission of the seed beam is observed to be enhanced by > {approx} 25 x when the plasma is near the resonant density for stimulated Raman scattering (SRS), compared to measured transmissions at wavelengths just below the resonant value. The amplification is observed to increase rapidly with increases in both pump intensity and plasma density
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