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- Mancusi, Davide, 1980, et al.
(författare)
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Calculation of Energy-Deposition Distributions and Microdosimetric Estimation of the Biological Effect of a 9C Beam
- 2009
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Ingår i: Radiation and Environmental Biophysics. - 1432-2099 .- 0301-634X. ; 48:2, s. 135-143
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Tidskriftsartikel (refereegranskat)abstract
- Among the alternative beams being recently considered for external cancer radiotherapy, C-9 has received some attention because it is expected that its biological effectiveness could be boosted by the beta-delayed emission of two alpha particles and a proton that takes place at the ion-stopping site. Experiments have been performed to characterise this exotic beam physically and models have been developed to estimate quantitatively its biological effect. Here, the particle and heavy-ion transport code system (PHITS ) is used to calculate energy-deposition and linear energy transfer distributions for a C-9 beam in water and the results are compared with published data. Although PHITS fails to reproduce some of the features of the distributions, it suggests that the decay of C-9 contributes negligibly to the energy-deposition distributions, thus contradicting the previous interpretation of the measured data. We have also performed a microdosimetric calculation to estimate the biological effect of the decay, which was found to be negligible; previous microdosimetric Monte-Carlo calculations were found to be incorrect. An analytical argument, of geometrical nature, confirms this conclusion and gives a theoretical upper bound on the additional biological effectiveness of the decay. However, no explanation can be offered at present for the observed difference in the biological effectiveness between C-9 and C-12; the reproducibility of this surprising result will be verified in coming experiments.
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- Sihver, Lembit, 1962, et al.
(författare)
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Recent developments and benchmarking of the PHITS code
- 2007
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Ingår i: Advances in Space Research. - : Elsevier BV. - 1879-1948 .- 0273-1177. ; 40:9, s. 1320-1331
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Tidskriftsartikel (refereegranskat)abstract
- Many new options have recently been included in PHITS, e.g., to calculate LET distributions of particles in matter or energy-deposition distributions event by event and correlations between energy depositions in different regions. This makes it possible to calculate the effects of particle radiation on biological and non-biological materials, e.g., risk for single event upsets in electronic devices. As a part of an extensive ongoing benchmarking of PHITS, we have compared calculated partial projectile fragmentation cross sections with accelerator-based measurements from the reactions of 200-1000 MeV/n He-4, C-12, N-14, O-16, Ne-20, Si-28, Ar-40, and Fe-56 on polyethylene, carbon, aluminum, copper, tin and lead, with different thicknesses, using different total reaction cross section models in PHITS. We have compared simulated and measured Bragg and attenuation curves of 200 MeV/n C-12 in water, and neutron energy spectra, at different angles, from 100 to 400 MeV/n C-12 stopped in water. Bragg curves for 110, 140, 170, 190 and 225 MeV/n He-3 in water have been studied, as well as gamma-ray dose decay curves of activated Cu target bombarded by 400 and 800 MeV/n Ar-40. When using the default total reaction cross section model developed by Tripathi et al. (1996,1997 and 1999) [Tripathi, R.K., Cucinotta, F.A., Wilson, J.W. Accurate universal parameterization of absorption cross sections, Nucl. Instr. Methods B117, 347, 1996; Tripathi, R.K., Wilson, J.W., Cucinotta, F.A. Accurate universal parameterization of absorption cross sections II - neutron absorption cross sections. Nucl. Instr. Methods B129, 11, 1997; Tripathi, R.K., Cucinotta, F.A., Wilson, J.W. Accurate universal parameterization of absorption cross sections III - light systems. Nucl. Instr. Methods B155, 349, 1999.] the partial fragmentation cross sections appear to be systematically slightly underestimated by a factor which is independent on the fragment species within the same data set, and so do the simulated neutron energy spectra from selected heavy ion reactions; especially in the forward direction. The simulated attenuation and Bragg curves, however, show good agreement with measured ones. These observations stimulate further benchmarking to confirm the accuracy of the code and gives directions on possible improvements to be applied to the code in the near future. (C) 2007 Published by Elsevier Ltd on behalf of COSPAR.
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- Aalto, Susanne, 1964, et al.
(författare)
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High-resolution HNC 3-2 SMA observations of Arp 220
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 493:2, s. 481-487
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We study the properties of the nuclear molecular gas of the ultra luminous merger Arp 220 and effects of the nuclear source on gas excitation and chemistry. Specifically, our aim is to investigate the spatial location of the luminous HNC 3-2 line emission and address the underlying cause of its unusual brightness.Methods. We present high resolution observations of HNC J=3-2 with the submillimeter array (SMA).Results. We find luminous HNC 3-2 line emission in the western part of Arp 220, centred on the western nucleus, while the eastern side of the merger shows relatively faint emission. A bright (36 K at $0\hbox{$.\!\!^{\prime\prime}$ }4$ resolution), narrow (60 ${\rm km~s}^$) emission feature emerges from the western nucleus, superposed on a broader spectral component. A possible explanation is weak maser emission through line-of-sight amplification of the background continuum source. There is also a more extended HNC 3-2 emission feature north and south of the nucleus. This feature resembles the bipolar OH maser morphology around the western nucleus. Substantial HNC abundances are required to explain the bright line emission from this warm environment - even when the high gas column density towards the western nucleus is taken into account. We discuss this briefly in the context of an X-ray affected chemistry and radiative excitation.Conclusions. The luminous and possibly amplified HNC emission of the western nucleus of the Arp 220 merger reflects the unusual, and perhaps transient environment of the starburst/AGN activity there. The faint HNC line emission towards Arp 220-east reveals a real difference in physical conditions between the two merger nuclei.
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- Mishima, T, et al.
(författare)
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Chicken breast attenuates high-intensity-exercise-induced decrease in rat sarcoplasmic reticulum Ca2+ handling
- 2008
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Ingår i: International journal of sport nutrition and exercise metabolism. - : Human Kinetics. - 1526-484X .- 1543-2742. ; 18:4, s. 399-411
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Tidskriftsartikel (refereegranskat)abstract
- This study was conducted to determine whether dietary chicken-breast extract (CBEX), a rich source of histidine-containing dipeptides, could modify exerciseinduced changes in sarcoplasmic reticulum (SR) function. After 5 weeks of dietary CBEX, SR Ca2+-handling ability was examined in the vastus lateralis muscles of rats subjected to high-intensity running for 2.5 min. Dietary CBEX caused an approximately 15% and 45% increase (p < .01) in muscle carnosine and anserine concentrations, respectively. In resting muscles, depressions in SR Ca2+–ATPase activity were evoked by dietary CBEX without concomitant changes in SR Ca2+ uptake and release rates. The data confirm that high-intensity exercise depresses SR Ca2+ handling. In spite of the same run time, SR Ca2+ handling was reduced to a lesser degree in muscles of CBEX-containing-chow-fed rats than in standard-chow-fed rats (p < .05). These results suggest that dietary CBEX might attenuate deteriorations in SR Ca2+-handling ability that occur with high-intensity exercise.
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