28 research outputs found

    A sustainable reaction process for phase pure LiFeSi2O6 with goethite as an iron source

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    Lithium-iron methasilicate (LiFeSi2_{2}O6_{6}, LFS), a member of clinopyroxene family, is an attractive compound for its multiferroic properties and applicability in energy-related devices. Conventional preparative method requires heating at elevated temperatures for long periods of time, with inevitable severe grain growth. We demonstrate that α-FeO(OH) (goethite) is superior as an iron source toward phase pure LFS over conventional hematite, α-Fe2_{2}O3_{3}. The exact phase purity, i.e., no trace of iron containing reactant, is confirmed in the goethite-derived LFS by 57Fe Mössbauer spectroscopy. The grain growth of LFS during heating is suppressed to keep its crystallite size of 120 nm. Higher reactivity of goethite in comparison with hematite is mainly attributed to the dehydration of goethite, which in our case was accelerated by Li2_{2}O. Related reaction mechanisms with the possible product pre-nucleation during mechanical activation are also mentioned. The magnetic properties of goethite-derived LFS are equivalent to those prepared via a laborious solid-state route. Thus, the presented preparative method offers a more sustainable route than conventional processing, and thus enables practical application of LFS

    Elevated Pontine and Putamenal GABA Levels in Mild-Moderate Parkinson Disease Detected by 7 Tesla Proton MRS

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    Background: Parkinson disease (PD) is characterized by the degeneration of nigrostriatal dopaminergic neurons. However, postmortem evidence indicates that the pathology of lower brainstem regions, such as the pons and medulla, precedes nigral involvement. Consistently, pontomedullary damage was implicated by structural and PET imaging in early PD. Neurochemical correlates of this early pathological involvement in PD are unknown. Methodology/Principal Finding: To map biochemical alterations in the brains of individuals with mild-moderate PD we quantified neurochemical profiles of the pons, putamen and substantia nigra by 7 tesla (T) proton magnetic resonance spectroscopy. Thirteen individuals with idiopathic PD (Hoehn & Yahr stage 2) and 12 age- and gender-matched healthy volunteers participated in the study. c-Aminobutyric acid (GABA) concentrations in the pons and putamen were significantly higher in patients (N = 11, off medications) than controls (N = 11, p,0.001 for pons and p,0.05 for putamen). The GABA elevation was more pronounced in the pons (64%) than in the putamen (32%). No other neurochemical differences were observed between patients and controls. Conclusion/Significance: The GABA elevation in the putamen is consistent with prior postmortem findings in patients with PD, as well as with in vivo observations in a rodent model of PD, while the GABA finding in the pons is novel. The more significant GABA elevation in the pons relative to the putamen is consistent with earlier pathological involvement of th

    Academy of Sciences of the Czech Republic

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    Methodological consensus on clinical proton MRS of the brain: Review and recommendations

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    Proton MRS (1H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good‐quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi‐adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use
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