PubMed · 14247445
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
V W PALEN. 1964. ELECTRON MICROSCOPY.. https://pubmed.ncbi.nlm.nih.gov/14247445/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
PURPOSE: In breast radiotherapy, delivery of manually-calculated electron boosts limits retrospective dose-response analyses as dose distribution is unavailable. This work evaluates the feasibility of reconstructing dose distributions from manually planned electron boosts in breast-conserving radiotherapy. METHODS: Only 72 out of 198 breast cancer patients had complete stored dose distributions from sequential electron boosts in the REQUITE study. Arbitrary data from 70/72 patients were used to develop and validate dose reconstruction method. Twenty patients were used to determine optimal parameters for Monte-Carlo-based (MC) electron dose reconstruction on RayStation (v.11B-R), considering CT-calibration curve, MC-history number, andcalculation grid resolution. Remaining 50 patients were used to quantify dose reconstruction accuracy. The similarity between reconstructed and stored dose was evaluated using 3D-gamma index and dosimetric parameters extracted from breast and tumour bed contours. Dose difference location was evaluated using dose-location histogram. RESULTS: Calculation grid resolution significantly impacted electron dose distribution (p < 0.01), where the finest grid (0.15 cm) showed highest similarity to stored doses. CT-calibration curve and MC-history number had a negligible influence on dose reconstruction. Dosimetric difference between reconstructed and stored doses was < 1 Gy for breast and tumour bed. Reconstructed dose was achieved > 90% gamma passing rate in the validation set. However, around 2.5 Gy dose differences were observed at the skin and tissue interface regions. CONCLUSIONS: Retrospective electron boost dose reconstruction is feasible with acceptable accuracy, and could increase data completeness in large cohort studies. Caution is advised when assessing dose near tissue interface and further validation is needed outside the REQUITE dataset.
Imidazolium salts with suitable substituents are readily deprotonated to stable NHC carbenes using the electron-reservoir complex [FeICp(eta6-C6Me6)], 1, in the presence of air (via a superoxide radical anion acting as a base). Less stable NHC carbenes can be conveniently obtained from imidazolium salts using the neutral base [FeIICp(eta5-C6Me5CH2)] obtained from 1 and air.
In the framework of an extraterrestrial origin of biological homochirality, universal mechanisms are of particular interest. In this sense we consider the weak parity-violating neutrino-electron interaction through weak charged currents W (+/-) between the relic flux of cosmological neutrinos and the electrons of a chiral molecule. We use the known theoretical result of the split in energy of the two helicity sates of an electron in the cosmic neutrino bath, due to weak charged currents. In the case that electrons of a chiral molecule are submitted to a helicoidal potential due to the nuclear conformation, these electrons have opposite helicities for the two enantiomers of the molecule and consequently the mentioned neutrino-electron interaction would produce a splitting in energy between the two enantiomers. An estimation of this energy for the case of a single electron yields a small value of the order of 10(-26) eV. This value results amplified by the contribution of all the molecular electrons having helicity and other possible mechanisms.