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Beam Characteristics at Low Dose Monitor Unit Settings for Vero4DRT

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2015年第4期4卷 284-289页

The stability of delivery of low monitor unit (MU) setting is important especially for step-and-shoot intensity-modulated radiotherapy (IMRT), because the nature of the technique is inherent to repeat beam on/off according to the number of the segments. This study evaluates the dose linearity and profile flatness/symmetry under low MU settings for Vero4DRT, a new linear-accelerator based irradiation system that currently implements step-and-shoot IMRT. To evaluate the dose linearity and flatness/symmetry, the point doses and beam profiles were measured as functions of MU and dose rates. The accuracy of dose delivery depended on the dose rate. Under all dose rates, the dose was linear within 1% above 5 MU and within 2% above 3 MU. The beam symmetry was degraded in-line compared with crossline, although both profiles were symmetric within 2% at all dose settings. The profile flatness was also within 2% above 5 MU at any dose rate and showed no significant variation among the low MU settings. To ensure stable beam delivery without increasing the treatment time of Vero4DRT, we recommend a delivery of 5 MU per segment at a dose rate of 500 MU/min.

关键词： Vero4DRT Step-and-Shoot IMRT Low Monitor Unit Beam Characteristic

Molecular dynamics simulation of the A-DNA to B-DNA transition in aqueous RbCl solution

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Science China Chemistry 2013年第4期56卷 524-532页

作者： YU YangXin FUJIMOTO shintaro Laboratory of Chemical Engineering Thermodynamics Department of Chemical Engineering Tsinghua University

Unrestrained molecular dynamics （MD） simulations have been carded out to characterize the stability of DNA conformations and the dynamics of A-DNA^B-DNA conformational transitions in aqueous RbC1 solutions. The PARM99 force field in the AMBER8 package was used to investigate the effect of RbC1 concentration on the dynamics of the A^B conformational tran- sition in the DNA duplex d（CGCGAATTCGCG）2. Canonical A- and B-form DNA were assumed for the initial conformation and the final conformation had a length per complete turn that matched the canonical B-DNA. The DNA structure was moni- tored for 3.0 ns and the distances between the C5＇ atoms were obtained from the simulations. It was found that all of the double stranded DNA strands of A-DNA converged to the structure of B-form DNA within 1.0 ns during the unrestrained MD simula- tions. In addition, increasing the RbC1 concentration in aqueous solution hindered the A^B conformational transition and the transition in aqueous RbC1 solution was faster than that in aqueous NaC1 solution for the same electrolyte strength. The effects of the types and concentrations of counterions on the dynamics of the A^B conformational transition can be understood in terms of the variation in water activity and the number of accumulated counterions in the major grooves of A-DNA. The ru- bidium ion distributions around both fixed A-DNA and B-DNA were obtained using the restrained MD simulations to help ex- plain the effect of RbC1 concentration on the dynamics of the A^B conformational transition.

关键词： DNA conformational transition molecular dynamics aqueous RbCI solution

Numerical simulation of dam break flow impact on vertical cylinder by cumulant lattice Boltzmann method

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Journal of Hydrodynamics 2021年第2期33卷 185-194页

作者： Seiya Watanabe shintaro Fujisaki Changhong Hu Research Institute for Applied Mechanics Kyushu UniversityFukuokaJapan School of Engineering Sciences Kyushu UniversityFukuokaJapan

The purpose of this study is to apply the cumulant lattice Boltzmann method(LBM)to simulate high Reynolds number free surface *** single-phase cumulant LBM is extended to solve the free surface flows by using the phase-field method as the interface capturing *** simulations are performed on an experimental problem of dam break flow impact on a vertical *** numerical aspects such as collision model,grid resolution,time step and interface mobility parameter are *** is found that the severe impact pressure oscillation in the simulation by the conventional SRT model,can be significantly suppressed by the cumulant *** agreement between the cumulant LBM numerical simulation and the experiment has been obtained on both the free surface profiles and the impact *** numerical results obtained by the present study demonstrate that the cumulant LBM can be a powerful numerical tool for simulations of violent free surface flow problems.

关键词： Lattice Boltzmann method(LBM) free surface flow wave impact pressure dam break flow cumulant model

Simulation study on dynamics of A- to B-form transition in aqueous DNA solution:Effect of alkali metal counterions

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Science China Chemistry 2013年第12期56卷 1735-1742页

作者： YU YangXin FUJIMOTO shintaro Laboratory of Chemical Engineering Thermodynamics Department of Chemical EngineeringTsinghua University

DNA and its conformational transition can be used to design nanometer-scale structures, nano-tweezers and nanomechanical devices. Experiments and molecular simulations have been used to study the concentration effect on the A-DNA→B-DNA conformational transition, but a systematical investigation on counterion effect on the dynamics of this transition has not been reported up to now. In present work, restrained and unrestrained molecular dynamics （MD） simulations have been performed to characterize the stability of DNA conformations and the dynamics of A-DNA→B-DNA transitions in aqueous solutions with different alkali metal counterions. The DNA duplex d（CGCGAATTCGCG）2, coion Cl- and counterions Li＋, Na＋, K＋, Rb＋ and Cs~ as well as water molecule were considered using the PARM99 force field in the AMBER8 package. It was found that B-form DNA is more stable than A-form DNA in aqueous electrolyte solutions with different alkali metal counterions. In- creasing KCI concentration in solution hinders the A-DNA^B-DNA transition and the transition times for different alkali metal counterions conform to neither the simple sequence related to naked ion size nor to hydrated diameter, but an apparently abnormal sequence of K＋〈 Rb＋〈 Cs＋〈 Na＋〈 Li＋. This abnormal sequence can be well understood in terms of an electrostatic model based on the effective cation diameters and the modified mean-spherical approximation （MMSA）. The present results provide valuable information for the design of DNA-based nanomaterials and nanodevices.

关键词： A-DNA B-DNA conformational transition alkali metal ion molecular dynamics

A two-stage process with temperature-shift for enhanced anthocyanin production in strawberry cell suspension cultures

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Science China Chemistry 1999年第4期42卷 345-350页

作者：张卫 shintaro Furusaki Chris Franco Department of Chemistry and Biotechnology Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113 Japan Biotechnology School of Medicine Flinders University of South Australia Bedford Park SA 5042 Australia

A two-stage process with temperature-shift has been developed to enhance the anthocyanin yield in suspension cultures of strawbeny cells. The effect of the temperature-shift interval and the shift-time point was investigated for the optimization of this strategy. In this process, strawbeny cells were grown at 30°C (the optimum temperature for cell gowth) for a certain period as the first stage, with the temperature shifted to a lower temperature for the second stage. In response to the temperature shift-down, anthocyanin synthesis was stimulated and a higher content could be achieved than that at both boundary temperatures but cell growth was suppressed. When the lower boundary temperature. was decreased, cell growth was lowered and a delayed, sustained maximum anthocyanin content was achieved. Anthocyanin synthesis was strongly influenced by the shift-time point but cell growth was not. Consequently, the maximum anthocyanin content of 2.7 mg.g-fresh cell-1 was obtained on day 9 by a temperature-shift from 309°C, after 3-d culture, to 15°C. The highest anthocyanin yield of 318 mg. L-1 on day 12 was achieved when the temperature was shifted from 30°C, after 5-d culture, to 20°C. For a global optimization of both the yield and productivity, the optimum anthocyanin yield and productivity of 272 mg.L-1 1 and 30.2 mg.L-1d1 on day 9 were achieved by a two-stage culture with a temperature-shift from 30°C after 3 d to 20°C.

关键词： strawberry cell suspension cultures anthocyanin temperature two-stage culture temperature-shift.

Small-for-size syndrome in living donor liver transplantation

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Hepatobiliary & Pancreatic Diseases International 2012年第6期11卷 570-576页

作者： shintaro Yagi Shinji Uemoto Department of Hepatobiliary Pancreas and Transplant Surgery Kyoto University Graduate School of Medicine 54 Kawara-cho Shogoin Sakyo-ku Kyoto 606-8507 Japan

When the graft volume is too small to satisfy the recipient’s metabolic demand, the recipient may thus experience small-for-size syndrome (SFSS). Because the occurrence of SFSS is determined by not only the liver graft volume but also a combination of multiple negative factors, the definitions of small-for-size graft (SFSG) and SFSS are different in each institute and at each time. In the clinical setting, surgical inflow modulation and maximizing the graft outflow are keys to overcoming SFSS. Accordingly, relatively smaller-sized grafts can be used with surgical modification and pharmacological manipulation targeting portal circulation and liver graft quality. Therefore, the focus of the SFSG issue is now shifting from how to obtain a larger graft from the living donor to how to manage the use of a smaller graft to save the recipient, considering donor safety to be a priority.

关键词： living donor liver transplantation small-for-size syndrome

Large deformation simulations of geomaterials using moving particle semi-implicit method

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第6期10卷 1122-1132页

作者： shintaro Nohara Hiroshi Suenaga Kunihiko Nakamura Central Research Institute of Electric Power Industry ChibaJapan

Numerical simulation tools are required to describe large deformations of geomaterials for evaluating the risk of geo-disasters. This study focused on moving particle semi-implicit(MPS) method, which is a Lagrangian gridless particle method, and investigated its performance and stability to simulate large deformation of geomaterials. A calculation method was developed using geomaterials modeled as Bingham fluids to improve the original MPS method and enhance its stability. Two numerical tests showed that results from the improved MPS method was in good agreement with the theoretical ***, numerical simulations were calibrated by laboratory experiments. It showed that the simulation results matched well with the experimentally observed free-surface configurations for flowing sand. In addition, the model could generally predict the time-history of the impact force. The MPS method could be a useful tool to evaluate large deformation of geomaterials.

关键词： Particle method Moving particle semi-implicit(MPS) method Large deformation analysis Geomaterials Bingham model

Subduction of the primordial crust into the deep mantle

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Geoscience Frontiers 2017年第2期8卷 347-354页

作者： Hiroki Ichikawa Steeve Gréaux shintaro Azum Geodynamics Research Center Ehime University Earth-Life Science Institute Tokyo Institute of Technology Department of Earth and Planetary Sciences Faculty of ScienceUniversity of Kyushu

The primordial crust on the Earth formed from the crystallization of the surface magma ocean during the ***,geological surveys have found no evidence of rocks dating back to more than 4 Ga on the Earth＇s surface,suggesting the Hadean crust was lost due to some *** investigated the subduction of one of the possible candidates for the primordial crust,anorthosite and KREEP crust similar to the Moon,which is also considered to have formed from the crystallization of the magma *** to the present Earth,the subduction of primordial crust by subduction erosion is expected to be an effective way of eliminating primordial crust from the *** this study,the subduction rate of the primordial crust via subduction channels is evaluated by numerical *** subduction channels are located between the subducting slab and the mantle wedge and are comprised of primordial crust materials supplied mainly by subduction *** have found that primordial anorthosite and KREEP crust of up to - 50 km thick at the Earth＇s surface was able to be conveyed to the deep mantle within 0.1-2 Gy by that mechanism.

关键词： Primordial crust Anorthosite KREEP Subduction erosion Subduction channel

Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment

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Geoscience Frontiers 2018年第4期9卷 1033-1048页

作者： Shigenori Maruyama M.Santosh shintaro Azuma Earth-Life Science Institute Tokyo Institute of Technology Institute for Study of the Earth’s Interior Okayama University Centre for Tectonics Resources and ExplorationDepartment of Earth SciencesUniversity of Adelaide School of Earth Sciences and Resources China University of Geosciences Beijing Faculty of Science Kochi University

When plate tectonics began on the Earth has been long debated and here we argue this topic based on the records of Earth-Moon geology and asteroid belt to conclude that the onset of plate tectonics was during the middle Hadean（4.37-4.20 Ga）. The trigger of the initiation of plate tectonics is the ABEL Bombardment, which delivered oceanic and atmospheric components on a completely dry reductive Earth, originally comprised of enstatite chondrite-like materials. Through the accretion of volatiles, shock metamorphism processed with vaporization of both CI chondrite and supracrustal rocks at the bombarded location, and significant recrystallization went through under wet conditions, caused considerable eclogitization in the primordial continents composed of felsic upper crust of 21 km thick anorthosite, and 50 km or even thicker KREEP lower crust. Eclogitization must have yielded a powerful slab-pull force to initiate plate tectonics in the middle Hadean. Another important factor is the size of the bombardment. By creating Pacific Ocean class crater by 1000 km across impactor, rigid plate operating stagnant lid tectonics since the early Hadean was severely destroyed, and oceanic lithosphere was generated to have bi-modal lithosphere on the Earth to enable the operation of plate *** the importance of the ABEL Bombardment event which initiated plate tectonics including the appearance of ocean and atmosphere, we propose that the Hadean Eon can be subdivided into three periods：（1） early Hadean（4.57-4.37 Ga）,（2） middle Hadean（4.37-4.20 Ga）, and（3） late Hadean（4.20-4.00 Ga）.

关键词： Initiation of plate tectonics ABEL Bombardment Eclogitization Stagnant lid tectonics Primordial continents