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Anisotropic optical absorption of oriented ultrathin films, (down to 50 nm thickness) of low density polyethylene (LDPE) was measured in the vacuum ultraviolet (VUV) region between 6 and 12 eV. Clear anisotropy was found in the observed spectra. The lowest-energy absorption feature at 9 eV was polarized perpendicular to the chain axis, and the second at about 11.5 eV parallel to the chain axis. The edge of the lowest perpendicular absorption was determined to be 8.05±0.1 eV. The usefulness of the anisotropic absorption data in testing two theories was verified; the anisotropy predicted by the independent system model disagrees with the data, but the energy band model gives some promising results. The photoemission threshold of the oriented LDPE was determined to be 8.5±0.1 eV. The spectral dependence of the anisotropy ratio of the photoemission quantum yield was found to coincide with that of the optical absorption in the energy range above 9.5 eV. This coincidence was explained in terms of the three-step model of photoemission.

Total body irradiation using intensity-modulated radiation therapy total body irradiation (IMRT-TBI) by helical tomotherapy in allogeneic hematopoietic stem cell transplantation (allo-HSCT) allows for precise evaluation and adjustment of radiation dosage. We conducted a single-center pilot study to evaluate the safety of IMRT-TBI for allo-HSCT recipients. Patients with hematological malignancies in remission who were scheduled for allo-HSCT with TBI-based myeloablative conditioning were eligible. The primary endpoint was the incidence of adverse events (AEs). Secondary endpoints were engraftment rate, overall survival, relapse rate, non-relapse mortality, and the incidence of acute and chronic graft-versus-host disease (aGVHD and cGVHD, respectively). Between July 2018 and November 2018, ten patients were recruited with a median observation duration of 571 days after allo-HSCT (range, 496–614). D80% for planning target volume (PTV) in all patients was 12.01 Gy. Average D80% values for lungs, kidneys and lenses (right/left) were 7.50, 9.03 and 4.41/4.03 Gy, respectively. Any early AEs (within 100 days of allo-HSCT) were reported in all patients. Eight patients experienced oral mucositis and gastrointestinal symptoms. One patient experienced Bearman criteria grade 3 regimen-related toxicity (kidney and liver). All cases achieved neutrophil engraftment. There was no grade III–IV aGVHD or late AE. One patient died of sinusoidal obstruction syndrome 67 days after allo-HSCT. The remaining nine patients were alive and disease-free at final follow-up. Thus, IMRT-TBI was well tolerated in terms of early AEs in adult patients who underwent allo-HSCT; this warrants further study with longer observation times to monitor late AEs and efficacy.

Articles you may be interested inFemtosecond time-resolved photoelectron spectroscopy with a vacuum-ultraviolet photon source based on laser high-order harmonic generation Rev. Sci. Instrum. 82, 063114 (2011); 10.1063/1.3600901 Vacuum-ultraviolet spectroscopy measurement of poly(methylphenylsilylene) photosensitivity J. Appl. Phys. 102, 033110 (2007); 10.1063/1.2761843Vacuum-ultraviolet spectroscopy of poly(methylphenylsilylene) Photoelectron spectra of hexatriacontane (n-C 36 H 74 ) films evaporated in situ under vacuum were measured at 12 photon energies between IIA eV and 21.2 eV. The escape depth of the photoelectrons was found to be much less than 10 nm. Although five valence band features on the photoelectron spectra are expected in this region from the findings by the XPS method, only one or two valence band features were observed; four features from the conduction band were found to dominate the spectra. The short escape depth and the smearing out of the valence band structure are attributed to scattering, which includes the scattering by phonons, and the appearance of the conduction band structure is attributed to accumulation of the secondary electrons to the high density of states parts associated with the conduction bands. The threshold energy of photoemission was found to be 9.1 ± 0.5 eV. The finding for the evaporated films of polyethylene, despite some degree of decomposition, gave essentially the same result. The results for the conduction bands were compared with the theoretical band calculation on an isolated polyethylene chain. The lack of reliable theoretical calculations of the conduction band of solid polyethylene is pointed out.

For small fields of size 1.6 × 1.6 cm or less, it was clarified that the volume averaging and density perturbation were the dominant effects responsible for the variation in the RPLD response. Moreover, perturbation correction is required when measuring a field size 1.0 × 1.0 cm or less. Under the IMRT conditions, the difference in the responses of the RPLD between the reference conditions and the PTV region calculated by Monte Carlo simulation did not exceed 0.8%. These results indicate that it is feasible to measure IMRT dosage using an RPLD at the PTV region.