The electric-field-assisted hydrogenation and corresponding resistance modulation of NdNiO3 (NNO) thin-film resistors were systematically studied as a function of temperature and dc electric bias. ...Catalytic Pt electrodes serve as triple-phase boundaries for hydrogen incorporation into a perovskite lattice. A kinetic model describing the relationship between resistance modulation and proton diffusion was proposed by considering the effect of the electric field during hydrogenation. An electric field, in addition to thermal activation, is demonstrated to effectively control the proton distribution along its gradient with an efficiency of ∼22% at 2 × 105 V/m. The combination of an electric field and gas-phase annealing is shown to enable the elegant control of the diffusional doping of complex oxides.
A number of MR-derived quantitative metrics have been suggested to assess the pathophysiology of MS, but the reports about combined analyses of these metrics are scarce. Our aim was to assess the ...spatial distribution of parameters for white matter myelin and axon integrity in patients with relapsing-remitting MS by multiparametric MR imaging.
Twenty-four patients with relapsing-remitting MS and 24 age- and sex-matched controls were prospectively scanned by quantitative synthetic and 2-shell diffusion MR imaging. Synthetic MR imaging data were used to retrieve relaxometry parameters (R1 and R2 relaxation rates and proton density) and myelin volume fraction. Diffusion tensor metrics (fractional anisotropy and mean, axial, and radial diffusivity) and neurite orientation and dispersion index metrics (intracellular volume fraction, isotropic volume fraction, and orientation dispersion index) were retrieved from diffusion MR imaging data. These data were analyzed using Tract-Based Spatial Statistics.
Patients with MS showed significantly lower fractional anisotropy and myelin volume fraction and higher isotropic volume fraction in widespread white matter areas. Areas with different isotropic volume fractions were included within areas with lower fractional anisotropy. Myelin volume fraction showed no significant difference in some areas with significantly decreased fractional anisotropy in MS, including in the genu of the corpus callosum and bilateral anterior corona radiata, whereas myelin volume fraction was significantly decreased in some areas where fractional anisotropy showed no significant difference, including the bilateral posterior limb of the internal capsule, external capsule, sagittal striatum, fornix, and uncinate fasciculus.
We found differences in spatial distribution of abnormality in fractional anisotropy, isotropic volume fraction, and myelin volume fraction distribution in MS, which might be useful for characterizing white matter in patients with MS.
Synthetic FLAIR images are of lower quality than conventional FLAIR images. Here, we aimed to improve the synthetic FLAIR image quality using deep learning with pixel-by-pixel translation through ...conditional generative adversarial network training.
Forty patients with MS were prospectively included and scanned (3T) to acquire synthetic MR imaging and conventional FLAIR images. Synthetic FLAIR images were created with the SyMRI software. Acquired data were divided into 30 training and 10 test datasets. A conditional generative adversarial network was trained to generate improved FLAIR images from raw synthetic MR imaging data using conventional FLAIR images as targets. The peak signal-to-noise ratio, normalized root mean square error, and the Dice index of MS lesion maps were calculated for synthetic and deep learning FLAIR images against conventional FLAIR images, respectively. Lesion conspicuity and the existence of artifacts were visually assessed.
The peak signal-to-noise ratio and normalized root mean square error were significantly higher and lower, respectively, in generated-versus-synthetic FLAIR images in aggregate intracranial tissues and all tissue segments (all
< .001). The Dice index of lesion maps and visual lesion conspicuity were comparable between generated and synthetic FLAIR images (
= 1 and .59, respectively). Generated FLAIR images showed fewer granular artifacts (
= .003) and swelling artifacts (in all cases) than synthetic FLAIR images.
Using deep learning, we improved the synthetic FLAIR image quality by generating FLAIR images that have contrast closer to that of conventional FLAIR images and fewer granular and swelling artifacts, while preserving the lesion contrast.
Synthetic MR imaging creates multiple contrast-weighted images based on a single time-efficient quantitative scan, which has been mostly performed for 2D acquisition. We assessed the utility of 3D ...synthetic MR imaging in patients with MS by comparing its diagnostic image quality and lesion volumetry with conventional MR imaging.
Twenty-four patients with MS prospectively underwent 3D quantitative synthetic MR imaging and conventional T1-weighted, T2-weighted, FLAIR, and double inversion recovery imaging, with acquisition times of 9 minutes 3 seconds and 18 minutes 27 seconds for the synthetic MR imaging and conventional MR imaging sequences, respectively. Synthetic phase-sensitive inversion recovery images and those corresponding to conventional MR imaging contrasts were created for synthetic MR imaging. Two neuroradiologists independently assessed the image quality on a 5-point Likert scale. The numbers of cortical lesions and lesion volumes were quantified using both synthetic and conventional image sets.
The overall diagnostic image quality of synthetic T1WI and double inversion recovery images was noninferior to that of conventional images (
= .23 and .20, respectively), whereas that of synthetic T2WI and FLAIR was inferior to that of conventional images (both
s
<
.001). There were no significant differences in the number of cortical lesions (
= .17 and .53 for each rater) or segmented lesion volumes (
= .61) between the synthetic and conventional image sets.
Three-dimensional synthetic MR imaging could serve as an alternative to conventional MR imaging in evaluating MS with a reduced scan time.
What makes a movement feel voluntary, and what might make it feel involuntary? Motor conversion disorders are characterized by movement symptoms without a neurologic cause. Conversion movements use ...normal voluntary motor pathways, but the symptoms are paradoxically experienced as involuntary, or lacking in self-agency. Self-agency is the experience that one is the cause of one's own actions. The matched comparison between the prediction of the action consequences (feed-forward signal) and actual sensory feedback is believed to give rise to self-agency and has been in part associated with the right inferior parietal cortex. Using fMRI, we assessed the correlates of self-agency during conversion tremor.
We used a within-subject fMRI block design to compare brain activity during conversion tremor and during voluntary mimicked tremor in 8 patients.
The random effects group analysis showed that conversion tremor compared with voluntary tremor had right temporoparietal junction (TPJ) hypoactivity (p < 0.05 family-wise error whole brain corrected) and lower functional connectivity between the right TPJ, sensorimotor regions (sensorimotor cortices and cerebellar vermis), and limbic regions (ventral anterior cingulate and right ventral striatum).
The right TPJ has been implicated as a general comparator of internal predictions with actual events. We propose that the right TPJ hypoactivity and lower TPJ and sensorimotor cortex interactions may reflect the lack of an appropriate sensory prediction signal. The lack of a match for the proprioceptive feedback would lead to the perception that the conversion movement is not self-generated.
Background and purpose
Whether the neuromelanin‐positive substantia nigra pars compacta area (NM‐SNc) on neuromelanin magnetic resonance imaging (NM‐MRI) and the specific binding ratio (SBR) on ...123I‐N‐v‐fluoropropyl‐2b‐carbomethoxy3b‐(4‐iodophenyl)nortropane single photon emission computed tomography (DaT‐SPECT) can be correlated with motor fluctuations (MFs) in advanced Parkinson's disease (PD) was investigated.
Methods
Thirty‐five PD patients (60 ± 13 years) and 23 healthy individuals as controls (59 ± 19 years) were enrolled. The relationships between NM‐MRI and DaT‐SPECT were prospectively examined in two subgroups divided according to the presence or absence of MFs. Multivariate analysis was performed using the Cox proportional hazard model to screen for association factors.
Results
The NM‐SNc size was correlated with the SBR (Spearman's ρ = 0.43, P < 0.05). The NM‐SNc size was significantly reduced in PD with MFs compared with the subgroup without (P < 0.001), whereas the SBR did not significantly differ between the groups. NM‐SNc size was a significant association factor for MFs (hazard ratio 0.94, P = 0.04). In receiver operating characteristic analysis of the factors for MF occurrence, the area under the receiver operating characteristic curve of the NM‐SNc size showed a significant difference of 0.89 (P < 0.05) but no significant difference was found in the SBR.
Conclusions
NM‐SNc size was significantly correlated with the SBR in PD, but several factors in advanced PD were more closely associated with NM‐SNc size than the SBR. NM‐MRI might reflect the status of advanced PD more accurately than DaT‐SPECT. Therefore, NM‐MRI appears to provide a better marker for discriminating advanced PD than DaT‐SPECT.
Strongly correlated perovskite lithium ion shuttles Sun, Yifei; Kotiuga, Michele; Lim, Dawgen ...
Proceedings of the National Academy of Sciences - PNAS,
09/2018, Letnik:
115, Številka:
39
Journal Article
Recenzirano
Odprti dostop
Solid-state ion shuttles are of broad interest in electrochemical devices, nonvolatile memory, neuromorphic computing, and biomimicry utilizing synthetic membranes. Traditional design approaches are ...primarily based on substitutional doping of dissimilar valent cations in a solid lattice, which has inherent limits on dopant concentration and thereby ionic conductivity. Here, we demonstrate perovskite nickelates as Li-ion shuttles with simultaneous suppression of electronic transport via Mott transition. Electrochemically lithiated SmNiO₃ (Li-SNO) contains a large amount of mobile Li⁺ located in interstitial sites of the perovskite approaching one dopant ion per unit cell. A significant lattice expansion associated with interstitial doping allows for fast Li⁺ conduction with reduced activation energy. We further present a generalization of this approach with results on other rare-earth perovskite nickelates as well as dopants such as Na⁺. The results highlight the potential of quantum materials and emergent physics in design of ion conductors.
The control of three-dimensional (3D) geometrical shapes is one of important approaches that contribute the development of new functionalities in material science. We produced 3D Si pyramids with ...atomically flat and reconstructed {111} facet surfaces supporting atomically resolved material growth in 3D space for the first time. The complex 4-fold clean 7×7 and 2×2-Fe low-energy electron diffraction (LEED) patterns reflecting the pyramidal geometry showed the realization of atomically reconstructed facet surfaces on the 3D patterned Si. Cross-sectional transmission electron microscopy (TEM) revealed the epitaxial heterointerfaces between Fe nanofilm and Si facet surfaces. The LEED and TEM results indicate the applicability of the Si pyramid as a supporting substrate for arbitrarily oriented 3D functional structures. The pyramidal Fe nanofilm displayed magnetic properties depending on the geometric shape, owing to the facet surfaces and the sharp facet edges. The unique anisotropic magnetization behavior of the 3D pyramid shape indicates that the epitaxial growth of an arbitrary geometry by virtue of the atomically ordered substrate surfaces in 3D space can contribute to the modification of the functionality.
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