249 research outputs found
Verification of TG-61 dose for synchrotron-produced monochromatic x-ray beams using fluence-normalized MCNP5 calculations
Ion chamber dosimetry is being used to calibrate dose for cell irradiations
designed to investigate photoactivated Auger electron therapy at the Louisiana
State University CAMD synchrotron facility. This study performed a dosimetry
intercomparison for synchrotron-produced monochromatic x-ray beams at 25 and 35
keV. Ion chamber depth-dose measurements in a PMMA phantom were compared with
the product of MCNP5 Monte Carlo calculations of dose per fluence and measured
incident fluence. Monochromatic beams of 25 and 35 keV were generated on the
tomography beamline at CAMD. A cylindrical, air-equivalent ion chamber was used
to measure the ionization created in a 10x10x10-cm3 PMMA phantom for depths
from 0.6 to 7.7 cm. The American Association of Physicists in Medicine TG-61
protocol was applied to convert measured ionization into dose. Photon fluence
was determined using a NaI detector to make scattering measurements of the beam
from a thin polyethylene target at angles 30 degrees to 60 degrees.
Differential Compton and Rayleigh scattering cross sections obtained from
xraylib, an ANSI C library for x-ray-matter interactions, were applied to
derive the incident fluence. MCNP5 simulations of the irradiation geometry
provided the dose deposition per photon fluence as a function of depth in the
phantom. At 25 keV the fluence-normalized MCNP5 dose overestimated the
ion-chamber measured dose by an average of 7.2+/-3.0% to 2.1+/-3.0% for PMMA
depths from 0.6 to 7.7 cm, respectively. At 35 keV the fluence-normalized MCNP5
dose underestimated the ion-chamber measured dose by an average of 1.0+/-3.4%
to 2.5+/-3.4%, respectively. These results showed that TG-61 ion chamber
dosimetry, used to calibrate dose output for cell irradiations, agreed with
fluence-normalized MCNP5 calculations to within approximately 7% and 3% at 25
and 35 keV, respectively.Comment: 22 pages, 5 figure
Beauty During a Pandemic: The Impact of COVID-19 on the Cosmetic Industry
The cosmetic industry is a multi-billion-dollar industry that has taken a financial hit in 2020 due to COVID-19. The drop in cosmetic usage leaves the industry in question for future consumer intention and behavior. Survey responses from 1,715 female students at a southeastern U.S. public university was obtained using Qualtrics. Results indicate significant differences in cosmetic usage; however, post-COVID predicted usage indicates that cosmetic usage will revert back to pre-COVID levels for eye, lip, and skin cosmetics. For face cosmetics, usage will still be slightly below pre-COVID levels. The most important cosmetic category was skincare, which had the highest levels of usage pre-, mid-, and post-COVID. Price maintained a high priority in pre-, mid-, and post responses. Convenience was not as essential pre-COVID but became extremely important mid-COVID and is shown to continue a high level of importance for post intentions. Managerial implications of these results are discussed
Apex : A Point of Departure, Vol.2, No.03 (April 1993)
https://digitalcommons.usm.maine.edu/apex/1014/thumbnail.jp
Apex : A Point of Departure, Vol.4, No.03 (April 1995)
https://digitalcommons.usm.maine.edu/apex/1036/thumbnail.jp
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