Simulation study of dose enhancement in a cell due to nearby carbon and oxygen in particle radiotherapy

The aim of this study is to investigate the dose-deposition enhancement by alpha-particle irradiation in a cellular model using carbon and oxygen chemical compositions.A simulation study was performed to study dose enhancement due to carbon and oxygen for a human cell where Geant4 code used for the alpha-particle irradiation to the cellular phantom. The characteristic of dose enhancement in the nucleus and cytoplasm by the alpha-particle radiation was investigated based on concentrations of the carbon and oxygen compositions and was compared with those by gold and gadolinium.The results show that both the carbon and oxygen-induced dose enhancement was found to be more effective than those of gold and gadolinium. We found that the dose-enhancement effect was more dominant in the nucleus than in the cytoplasm if carbon or oxygen is uniformly distributed in a whole cell. In the condition that the added chemical composition was inserted only into the cytoplasm, the effect of the dose enhancement in nucleus becomes weak.We showed that high-stopping-power materials offer a more effective dose-enhancement efficacy and suggest that the carbon nanotubes and oxygenation are promising candidates for dose utilization as dose enhancement tools in particle therapy.Comment: 19 pages, 6 figures, 4 tables. presented to 7th KOREA-JAPAN Joint Meeting on Medical Physics (2014.09.25) accepted to Journal of the Korean Physical Society (2015.03.10

Trends in Internet Use Among Older Adults in the United States, 2011-2016

The present study examined the trends in internet use among older adults (60+ years) in the United States from 2011 to 2016 by considering not only the entire study sample as a whole but also specific subgroups by age, gender, race/ethnicity, and education. Using data from 107,500 older adults in the California Health Interview Survey between 2011 and 2016, the significance of linear trends was tested by including the survey year as a continuous variable in the logistic regression. Findings confirm the general knowledge that an increased number of the older U.S. population used the internet over the period of 2011–2016. Furthermore, closer inspection indicates that this upward trend does not apply to all, but specifically to those with advanced age, male gender, racial/ethnic minority background, and low educational attainment. Findings provide implications for identifying and prioritizing a target group for internet technology training

Enhancement of Light Absorption in Photovoltaic Devices using Textured Polydimethylsiloxane Stickers

We designed and fabricated a random-size inverted-pyramid-structured polydimethylsiloxane (RSIPS-PDMS) sticker to enhance the light absorption of solar cells and thus increase their efficiency. The fabricated sticker was laminated onto bare-glass and crystalline-silicon (c-Si) surfaces; consequently, low solar-weighted reflectance values were obtained for these surfaces (6.88% and 17.2%, respectively). In addition, we found that incident light was refracted at the PDMS-air interface of each RSIPS, which redirected the incident power and significantly increased the optical path length in the RSIPS-PDMS sticker which was 14.7% greater than that in a flat-PDMS sticker. Moreover, we investigated power reflection and propagation through the RSIPS-PDMS sticker using a finite-difference time-domain method. By attaching an RSIPS-PDMS sticker onto both an organic solar cell (OSC) based on a glass substrate and a c-Si solar cell, the power conversion efficiency of the OSC and the c-Si solar cell were increased from 8.57% to 8.94% and from 16.2% to 17.9%, respectively. Thus, the RSIPS-PDMS sticker is expected to be universally applicable to the surfaces of solar cells to enhance their light absorption