We report the generation of dose point kernels for clinically-relevant radionuclide beta decays and monoenergetic electrons in various tissues to understand the impact of tissue type on dose point kernels. Currently available voxel-wise dosimetry approaches using dose point kernels ignore tissue composition and density heterogeneities. Therefore, the study on the impact of tissue type on dose point kernels is warranted. Simulations were performed using the GATE Monte Carlo toolkit, which encapsulates GEANT4 libraries. Dose point kernels were simulated in phantoms of water, compact bone, lung, adipose tissue, blood and red marrow for radionuclides 90Y, 188Re, 32P, 89Sr, 186Re, 153Sm and 177Lu and monoenergetic electrons (0.015–10 MeV). All simulations were performed by assuming an isotropic point source of electrons at the center of a homogeneous spherical phantom. Tissue-specific differences between kernels were investigated by normalizing kernels for effective pathlength. Transport of 20 million particles was found to provide sufficient statistical precision in all simulated kernels. The simulated dose point kernels demonstrate excellent agreement with other Monte Carlo packages. Deviation from kernels reported in the literature did not exceed a 10% global difference, which is consistent with the variability among published results. There are no significant differences between the dose point kernel in water and kernels in other tissues that have been scaled to account for density; however, tissue density predictably demonstrated itself to be a significant variable in dose point kernel distribution.
There is a long history of Computer Supported Collaborative Learning (CSCL) being applied to students on distance learning courses, and there is a significant body of literature in this area [5,6,10]. This paper reports by contrast the use of CSCL for conventional full time face to face students. It comprised part of the final phase of a research council funded study of innovative CSCW applications.
Annual modulation of $\gamma$ rays from ($\alpha$, $\gamma$) reactions in the Soudan Underground Lab has been observed using a 12-liter scintillation detector. This significant annual modulation, measured over 4 years, can mimic the signature for dark matter and can also generate potential background events for neutrinoless double-$\beta$ decay experiments. The measured annual modulation of the event rate from ($\alpha$, $\gamma$) reactions is strongly correlated with the time-varying radon concentration observed independently in the Lab. The $\alpha$ flux from radon decay is simulated starting from the measured radon concentration, and the $\gamma$-ray flux is determined using the convolution of the $\alpha$ flux and the cross sections for ($\alpha$, $\gamma$) reactions. The calculated $\gamma$-ray flux is sufficient to generate the measured event rate that exhibits an annual modulation.
Note: The version 1.1 dataset has been corrected to include only accurate kernels. Errors were found in Version 1.0 kernels with the following sizes: 1.953, 2.21, 2.4, 3.9, 4, 4.42, 4.8, and 6.8 mm Cartesian matrix dose point kernels, generated by resampling of prior radial dose point kernels. See accompanying paper for additional details: "Accurate resampling of radial dose point kernels to a Cartesian matrix for voxelwise dose calculation" Refer to the upload titled "Kernel_Format_README.xlsx" for details regarding kernel format and modification for use. Source (radial) kernel generation is described in the Medical Physics article titled "Dose point kernels for 2,174 radionuclides." - https://doi.org/10.1002/mp.13789 Source (radial) kernels can be downloaded here: https://doi.org/10.5281/zenodo.2564036
Cartesian matrix dose point kernels, generated by resampling of prior radial dose point kernels. See accompanying paper for additional details: "Accurate resampling of radial dose point kernels to a Cartesian matrix for voxelwise dose calculation" Refer to the upload titled "Kernel_Format_README.xlsx" for details regarding kernel format and modification for use. Source (radial) kernel generation is described in the Medical Physics article titled "Dose point kernels for 2,174 radionuclides." - https://doi.org/10.1002/mp.13789 Source (radial) kernels can be downloaded here: https://doi.org/10.5281/zenodo.2564036
Abstract The half-life of 67 Cu was determined through serial gamma-ray spectrometry measurements of the dominant gamma emission (E γ : 184.6 keV; branching ratio: 48.7%) produced following β - decay. Data were collected consecutively for 1000 s per measurement, with a total of 3063 measurements over the duration of 36 days. The incidence rate for the 184.6 keV gamma-ray was determined from the spectral peak area and duration of each measurement. This rate was then corrected to account for detector dead-time, radioactive decay during each acquisition and drift in the computer clock in comparison to NIST nuclear clock. Least-squares regression analysis was performed to determine the half-life of 67 Cu. The result was 61.761 ± 0.004 h, which is the highest precision measurement to date, and marks a 24-fold precision improvement over the current Nuclear Data Sheets value.
This chapter reviews the support of asynchronous teams utilizing intranet-based mini-case study publication with web-based conferencing The specific situation relates to large groups of one-year full-time MBA students. The chapter reports on this exercise from both pedagogic and groupware perspectives. Implications, and planned future developments of this approach, are reviewed.
Annual modulation of $\ensuremath{\gamma}$ rays from $(\ensuremath{\alpha},\ensuremath{\gamma})$ reactions induced by the $\ensuremath{\alpha}$ activity of radon and its daughters was reported by Tiwari, Zhang, Mei, and Cushman (TZMC). While Mohr does not contest the measurements themselves, he has commented that unrealistic $(\ensuremath{\alpha},\ensuremath{\gamma})$ cross sections were used in the analysis of the $\ensuremath{\gamma}$-ray flux, and thus the $\ensuremath{\gamma}$-ray fluxes calculated by TZMC are not reliable. We demonstrate that the $(\ensuremath{\alpha},\ensuremath{\gamma})$ cross sections obtained from talys include the energy-broadened cross sections for discrete states in the high-energy tail of the spectra, which are required in order to compare with the angle-integrated and double-differential spectra obtained from a liquid scintillator detector with an energy resolution of only $\ensuremath{\approx}15%$. A comparison with varying ``elwidth'' shows that cross sections indeed are reliable within the energy region (4 to 10 MeV) reported by TZMC, especially for the dominant contribution, which is the aluminum wall of the detector. Any differences in the $(\ensuremath{\alpha},\ensuremath{\gamma})$ cross sections for $^{16}\mathrm{O}$ at the level detailed by Mohr will have negligible effect on the final flux.
