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Psilocin, the active metabolite of psilocybin, is a psychedelic and agonist at the serotonin 2A receptor (5-HT2AR) that has shown positive therapeutic effects for brain disorders such as depression. To elucidate the brain effects of psilocybin, we directly compared the acute effects of 5-HT2AR agonist (psilocybin) and antagonist (ketanserin) on cerebral blood flow (CBF) using pseudo-continuous arterial spin labeling magnetic resonance imaging (MRI) in a single-blind, cross-over study in 28 healthy participants. We evaluated associations between plasma psilocin level (PPL) or subjective drug intensity (SDI) and CBF. We also evaluated drug effects on internal carotid artery (ICA) diameter using time-of-flight MRI angiography. PPL and SDI were significantly negatively associated with regional and global CBF (∼11.6% at peak drug effect, p < 0.0001). CBF did not significantly change following ketanserin (2.3%, p = 0.35). Psilocybin induced a significantly greater decrease in CBF compared to ketanserin in the parietal cortex (pFWER < 0.0001). ICA diameter was significantly decreased following psilocybin (10.5%, p < 0.0001) but not ketanserin (−0.02%, p = 0.99). Our data support an asymmetric 5-HT2AR modulatory effect on CBF and provide the first in vivo human evidence that psilocybin constricts the ICA, which has important implications for understanding the neurophysiological mechanisms underlying its acute effects. - Book : ()
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Abstract
The doping of UO2 ceramics with transition metal elements such as vanadium is a topical enterprise due to the relevance to advanced technology nuclear fuels in addition to understanding fuel-cladding interactions in spent nuclear fuel. Herein, the lattice and microstructural dependence of V-doped UO2 ceramics synthesized under conditions of − 420 kJ/mol and 1700 °C with elemental additions of 0, 500, 1000 and 2000 ppm was established using high-resolution synchrotron X-ray powder diffraction and scanning electron microscopy. Microstructural analysis indicates moderate growth of the UO2 grain structure is achieved with V doping, but not as appreciable as gold-standard Cr-doped UO2. Collected diffractograms, analysed using the Rietveld method, indicate similar levels of solubility of V in comparison to Cr-doped UO2 under like conditions. The results of this investigation were discussed in relation to current structural models of lattice incorporation of transition metals in UO2.
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AbstractThis article investigates the performance of a commercial BeO optically stimulated luminescent (OSL) dosimetry system (myOSLchip, RadPro GmbH International, Remscheid, Germany) through the application of the commissioning framework for luminescent dosimeters as described in the American Association of Physicists in Medicine Task Group 191 (AAPM TG191) report. Initial clinical experiences and dosimetric results are also presented. The following properties of the system were characterized: linearity correction factors ranged from ‐0.5% to +3% for dose levels spanning 0.1 to 20 Gy. Beam quality correction factors (relative to 6 MV) ranged from ‐4.5% (2.5FFF) to +4.5% (15MV) for photon beams and +1.9% (6 MeV) to +4.3% (20 MeV) for electron beams. An average (µ) signal loss per reading of ‐2.13% ± 0.20% was measured, however greater signal loss was observed in the first reading (µ = ‐2.6% ± 0.46%). An initial decline in individual element sensitivity relative to baseline was observed from 0–15 Gy cumulative dose (µ = ‐1.98% ± 0.55%), with negligible further deterioration from 15–32 Gy (µ = ‐2.38% ± 0.85%). Post‐irradiation, there was a transient OSL signal which faded with a half‐life of 1.8 min; this signal enhancement was +5% at 5 min post‐irradiation and +1% at 15 min relative to 24 h. Dosimeter response was not dependent on average dose rate in the range of 100–2500 MU/min. With respect to clinical testing, equal or superior performance compared with aluminum oxide OSLs (nanoDots) is shown for a range of clinical techniques and modalities including TSET, TBI, en‐face electrons, and pacemaker/out‐of‐field measurements. The feasibility of myOSLchip to serve as a primary clinical in vivo dosimetry system and direct replacement for Landauer's microStar system is demonstrated.- Book : ()
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