The Dragon-I linear induction accelerator(LIA)at China Academy of Engineering Physics generates 20 Me V flash X-rays mainly for radiography applications in fluid dynamics.Its spectral information is quite important fo...The Dragon-I linear induction accelerator(LIA)at China Academy of Engineering Physics generates 20 Me V flash X-rays mainly for radiography applications in fluid dynamics.Its spectral information is quite important for diagnostic X-ray imaging applications,but because of its short pulse and great radiation intensity,direct measurement is impossible.In this work,we propose a new method based on transmission measurements to obtain the flash X-ray spectrum.Pure iron cylinders were used as attenuation material,and alanine dosimeters were attached on their rear bottom to record the dose after different degrees of attenuation.Iterative least square method was used to unfold the spectrum,while Geant4 Monte Carlo code was used to simulate the X-ray spectrum.The unfolded spectrum and the simulated spectrum have a high degree of consistency,with the reduced chi-square value of 0.044.This shows that the method is reliable in estimating megavoltage highintensity X-ray spectrum.展开更多
一个图 G 的分数荫度定义为,著名的 Nash-Williams 定理指出:当且仅当 γf (G) ≤ k 时,图 G 最多能边分解为 k 个森林。对此 强九龙树猜想断言,对千任意非负整数 k 和 d 任何分数荫度至多为的图都能边分解为 k + 1 个森林,并且存在其...一个图 G 的分数荫度定义为,著名的 Nash-Williams 定理指出:当且仅当 γf (G) ≤ k 时,图 G 最多能边分解为 k 个森林。对此 强九龙树猜想断言,对千任意非负整数 k 和 d 任何分数荫度至多为的图都能边分解为 k + 1 个森林,并且存在其中一个森林,它的每个连通分支最多包含 d 条边。在本文中,我们将 τi(G) 定义为,当然,τ1(G) = γf (G)。对于整数 i ≥ 1,图 G 的 i-森林是图 G 的支撑森林,其至少包含了 i 个连通分支。而一个 i-树是指一个 i-森林恰好有 i 个连通分支。我们证明了,当 k = 1, d = 2 时,分数 i-荫度至多为的图 G 能边分解2个 i -森林并且其中一个 i-森林,它的每个连通分支最多包含 2 条边。展开更多
Lipstick is the most widely used cosmetic product. Although lipstick gives a lot of social, psychological and therapeutic benefits, it may harm the consumers. Because most lipsticks contained high lead level and long ...Lipstick is the most widely used cosmetic product. Although lipstick gives a lot of social, psychological and therapeutic benefits, it may harm the consumers. Because most lipsticks contained high lead level and long term use of high lead level lipstick may harm the consumers. Research findings have suggested that administration of various antioxidants can prevent or subdue various toxic effects of lead and generation of oxidative stress. <strong><em>Hylocereus polyrhizus</em></strong> (Red dragon fruit) is widely available in Myanmar and it contains powerful antioxidant amaranth colorant called betacyanin pigment. It can prevent the oxidative stress caused by low level of lead, thus suitable as natural colorant for lipstick. As a role of pharmacist, this research was intended to minimize the adverse effects of lipsticks by formulating natural lipstick with betacyanin pigment obtained from <strong><em>H. polyrhizus</em></strong> and other natural ingredients. Formulation of lipstick was carried out by heating and blending method with homogenizer at a speed of 12000 rpm. Then, pH, melting point, surface abnormalities, aging stability, perfume stability and antioxidant activity were performed as quality evaluation. Skin irritation test, microbial analysis and lead content determination were carried out as safety evaluation. Formulated lipsticks with betacyanin pigment of <em><strong>H. polyrhizus</strong></em> have acceptable quality. The IC50 of standard ascorbic acid and formulated lipstick were 4.51 μg/ml and 22.23 μg/ml respectively. In quantitative analysis for microbiological control, formulated lipstick had no visible colony and in qualitative analysis, <strong><em>Staphylococcus aureus</em></strong>, <strong><em>E. coli</em></strong> and <strong><em>Pseudomonas aeruginosa</em></strong> were not detected in 0.5 g of formulated lipsticks. Moreover, lead content of formulated lipstick was only 2.9 ppm that is within allowable limit and it had negligible skin irritancy. Therefore, lipstick with betacyanin pigment of <em><strong>H. polyrhizus</strong></em> can utilize as Cosmeceutical.展开更多
Spot size is one of the parameters to characterize the performance of a radiographic X-ray source. It determines the degree of blurring due to magnification directly. In recent years, a variety of measurement methods ...Spot size is one of the parameters to characterize the performance of a radiographic X-ray source. It determines the degree of blurring due to magnification directly. In recent years, a variety of measurement methods have been used to diagnose X-ray spot size at Laboratory of Accelerator Physics and Application (LAPA). Computer simulations and experiments showed that using a rolled-edge to measure the spot size are more accurate, and the intensity distribution of X-ray source was obtained by a device with a square aperture. Experimental and simulation results on a flash X-ray source at our laboratory are presented and discussed in this paper. In addition, a new method for time resolved diagnostics of X-ray spot size is introduced too.展开更多
基金Supported by National Natural Science Foundation of China(Nos.11375263 and 11375195)National magnetic confinement fusion energy development research(No.2013GB104003)
文摘The Dragon-I linear induction accelerator(LIA)at China Academy of Engineering Physics generates 20 Me V flash X-rays mainly for radiography applications in fluid dynamics.Its spectral information is quite important for diagnostic X-ray imaging applications,but because of its short pulse and great radiation intensity,direct measurement is impossible.In this work,we propose a new method based on transmission measurements to obtain the flash X-ray spectrum.Pure iron cylinders were used as attenuation material,and alanine dosimeters were attached on their rear bottom to record the dose after different degrees of attenuation.Iterative least square method was used to unfold the spectrum,while Geant4 Monte Carlo code was used to simulate the X-ray spectrum.The unfolded spectrum and the simulated spectrum have a high degree of consistency,with the reduced chi-square value of 0.044.This shows that the method is reliable in estimating megavoltage highintensity X-ray spectrum.
文摘一个图 G 的分数荫度定义为,著名的 Nash-Williams 定理指出:当且仅当 γf (G) ≤ k 时,图 G 最多能边分解为 k 个森林。对此 强九龙树猜想断言,对千任意非负整数 k 和 d 任何分数荫度至多为的图都能边分解为 k + 1 个森林,并且存在其中一个森林,它的每个连通分支最多包含 d 条边。在本文中,我们将 τi(G) 定义为,当然,τ1(G) = γf (G)。对于整数 i ≥ 1,图 G 的 i-森林是图 G 的支撑森林,其至少包含了 i 个连通分支。而一个 i-树是指一个 i-森林恰好有 i 个连通分支。我们证明了,当 k = 1, d = 2 时,分数 i-荫度至多为的图 G 能边分解2个 i -森林并且其中一个 i-森林,它的每个连通分支最多包含 2 条边。
文摘Lipstick is the most widely used cosmetic product. Although lipstick gives a lot of social, psychological and therapeutic benefits, it may harm the consumers. Because most lipsticks contained high lead level and long term use of high lead level lipstick may harm the consumers. Research findings have suggested that administration of various antioxidants can prevent or subdue various toxic effects of lead and generation of oxidative stress. <strong><em>Hylocereus polyrhizus</em></strong> (Red dragon fruit) is widely available in Myanmar and it contains powerful antioxidant amaranth colorant called betacyanin pigment. It can prevent the oxidative stress caused by low level of lead, thus suitable as natural colorant for lipstick. As a role of pharmacist, this research was intended to minimize the adverse effects of lipsticks by formulating natural lipstick with betacyanin pigment obtained from <strong><em>H. polyrhizus</em></strong> and other natural ingredients. Formulation of lipstick was carried out by heating and blending method with homogenizer at a speed of 12000 rpm. Then, pH, melting point, surface abnormalities, aging stability, perfume stability and antioxidant activity were performed as quality evaluation. Skin irritation test, microbial analysis and lead content determination were carried out as safety evaluation. Formulated lipsticks with betacyanin pigment of <em><strong>H. polyrhizus</strong></em> have acceptable quality. The IC50 of standard ascorbic acid and formulated lipstick were 4.51 μg/ml and 22.23 μg/ml respectively. In quantitative analysis for microbiological control, formulated lipstick had no visible colony and in qualitative analysis, <strong><em>Staphylococcus aureus</em></strong>, <strong><em>E. coli</em></strong> and <strong><em>Pseudomonas aeruginosa</em></strong> were not detected in 0.5 g of formulated lipsticks. Moreover, lead content of formulated lipstick was only 2.9 ppm that is within allowable limit and it had negligible skin irritancy. Therefore, lipstick with betacyanin pigment of <em><strong>H. polyrhizus</strong></em> can utilize as Cosmeceutical.
基金Supported by National Defense Foundation of China
文摘Spot size is one of the parameters to characterize the performance of a radiographic X-ray source. It determines the degree of blurring due to magnification directly. In recent years, a variety of measurement methods have been used to diagnose X-ray spot size at Laboratory of Accelerator Physics and Application (LAPA). Computer simulations and experiments showed that using a rolled-edge to measure the spot size are more accurate, and the intensity distribution of X-ray source was obtained by a device with a square aperture. Experimental and simulation results on a flash X-ray source at our laboratory are presented and discussed in this paper. In addition, a new method for time resolved diagnostics of X-ray spot size is introduced too.
