The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation deri...The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation derived from resonance radiation theory (RRT). Theresonance radiation formulae are derived from classical Rayleigh normal mode solution, which areuseful for understanding the mechanism of sound radiation from submerged shells. As an example,numerical calculation of a thin steel cylindrical shell is done by using these two methods. It seemsthat the results of RRT solutions are in good agreement with that of Rayleigh normal modesolutions.展开更多
Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly...Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly understood, while the alternations could be sensitively detected by proton （~H） nuclear magnetic resonance spectroscopy （MRS）. In this study, we investigated the metabolic characteristics of radiation-induced brain injury through a long-term tbllow-up after radiation treatment using MRS m vivo. Methods： A total of 12 adult Sprague-Dawley rats received a single dose of 30 Gy radiation treatment to semi-brain （field size： 1.0 cm x 2.0 cm; anterior limit： binocular posterior inner canthus connection; posterior limit： external acoustic meatus connection; internal limit： sagittal suture）. Conventional magnetic resonance imaging and single-voxel H-MRS were performed at different time points （in month 0 before irradiation as well as in the 1st, 3rd, 5th, 7th, and 9th months after irradiation） to investigate the alternations in irradiation field. N-acetylaspartate/choline （NAA/ChoL NAA/creatinine （Cr）, and Cho/Cr ratios were measured in the bilateral hippocampus and quantitatively analyzed with a repeated-measures mixed-effects model and multiple comparison test. Results： Significant changes in the ratios of NAA/Cho （F = 57.37, P 〈 0.001）, NAA/Cr （F = 54.49, P 〈 0.001） and Cho/Cr （F = 9.78, P = 0.005） between the hippocampus region of the irradiated semi-brain and the contralateral semi-brain were observed. There were 〈, significant differences in NAA/Cho （F = 9.17, P 〈 0.001 ） and NAA/Cr （F = 13.04, P 〈 0.001 ） ratios over time. The tendency of NAA/Cr to change with time showed no significant difference between the irradiated and contralateral sides. Nevertheless, there were significant differences in the Cho/Cr ratio between these two sides. Conclusions： MRS can sensitively detect metabolic alternations. Significant changes of metabolites ratio in the first few months after radiation treatment reflect the metabolic disturbance in the acute and early-delayed stages of radiation-induced brain injuries.展开更多
基金This project is supported by National Natural Science Foundation of China(No.19974024).
文摘The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation derived from resonance radiation theory (RRT). Theresonance radiation formulae are derived from classical Rayleigh normal mode solution, which areuseful for understanding the mechanism of sound radiation from submerged shells. As an example,numerical calculation of a thin steel cylindrical shell is done by using these two methods. It seemsthat the results of RRT solutions are in good agreement with that of Rayleigh normal modesolutions.
文摘Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly understood, while the alternations could be sensitively detected by proton （~H） nuclear magnetic resonance spectroscopy （MRS）. In this study, we investigated the metabolic characteristics of radiation-induced brain injury through a long-term tbllow-up after radiation treatment using MRS m vivo. Methods： A total of 12 adult Sprague-Dawley rats received a single dose of 30 Gy radiation treatment to semi-brain （field size： 1.0 cm x 2.0 cm; anterior limit： binocular posterior inner canthus connection; posterior limit： external acoustic meatus connection; internal limit： sagittal suture）. Conventional magnetic resonance imaging and single-voxel H-MRS were performed at different time points （in month 0 before irradiation as well as in the 1st, 3rd, 5th, 7th, and 9th months after irradiation） to investigate the alternations in irradiation field. N-acetylaspartate/choline （NAA/ChoL NAA/creatinine （Cr）, and Cho/Cr ratios were measured in the bilateral hippocampus and quantitatively analyzed with a repeated-measures mixed-effects model and multiple comparison test. Results： Significant changes in the ratios of NAA/Cho （F = 57.37, P 〈 0.001）, NAA/Cr （F = 54.49, P 〈 0.001） and Cho/Cr （F = 9.78, P = 0.005） between the hippocampus region of the irradiated semi-brain and the contralateral semi-brain were observed. There were 〈, significant differences in NAA/Cho （F = 9.17, P 〈 0.001 ） and NAA/Cr （F = 13.04, P 〈 0.001 ） ratios over time. The tendency of NAA/Cr to change with time showed no significant difference between the irradiated and contralateral sides. Nevertheless, there were significant differences in the Cho/Cr ratio between these two sides. Conclusions： MRS can sensitively detect metabolic alternations. Significant changes of metabolites ratio in the first few months after radiation treatment reflect the metabolic disturbance in the acute and early-delayed stages of radiation-induced brain injuries.
