Elaborate calibration procedure for cell irradiation at the CAS-LIBB single-particle microbeam

Single-particle microbeam is uniquely capable of precisely delivering a preset number of charged particles to individual cells or sub-cellular targets to be determined in vitro, It is crucial to find a reference point that relates the microbeam＇s location to the microscope＇s plane, and align individual targets at this reference point for cell irradiation. To choose an appropriate reference point, an approach based on analysing the intensity distribution of fluorescence in a thin scintillator excited by traversing particles is newly developed using the CAS-LIBB single-particle microbeam, which features decisive physical signification and sufficient resolution. As its bonus, this on-line analysis provides precise and fast response to the determination of beam profile and potentially optimizes the microbeam quality by further adjusting hardware setup.

Preliminary Study of the CAS-LIBB Single-Particle Microbeam Ⅱ Endstation: Ⅰ. Proposed Multi-Dimensional Quantitative Fluorescence Microscopy

Single-particle microbeam as a powerful tool can open a research field to find answers to many enigmas in radiobiology. A single-particle microbeam facility has been constructed at the Key Laboratory of Ion Beam Bioengineering （LIBB）, Chinese Academy of Sciences （CAS）, China. However there has been less research activities in this field concerning the original process of the interaction between low-energy ions and complicated organisms. To address this challenge, an in situ multi-dimensional quantitative fluorescence microscopy system combined with the CAS-LIBB single-particle microbeam II endstation is proposed. In this article, the rationale, logistics and development of many aspects of the proposed system are discussed.

Preliminary Study of CAS-LIBB Single-Particle MicrobeamⅡEndstation:Ⅱ.Considerations for Choosing the Right CCD Camera

The proposed multi-dimensional quantitative fluorescence microscopy for the CASLIBB single-particle microbeam II endstation is a CCD-based imaging system. We systematically analyse the theoretical and the practical considerations pertinent to choosing the right CCD camera and unveiling the principles underlying multifarious parameters. Therefore, this analysis can be a valuable tool in scrutinizing each parameter and clarifying proper usage of a scientific CCD camera.

The Experiment of Obtaining Micron Beam in the Single-Particle Microbeam Facility of the Institute of Plasma Physics

The Experiments, methods and results of obtaining micron beam in the Microbeam Facility of the Institute of Plasma Physics were discussed in this paper. The H+2 beam was accelerated by the Van de GraafF electrostatic accelerator, and the collimator at the end of the beam line is a 60 μm thick stainless steel chip. And as a result, particle tracks on the solid track probes (CR39 film) etched in the solution of NaOH showed that the beam can go through the collimator with a small aperure (2000, 300, 55, 30, or 10 μm) and 3.5 μm thick vacuum film (Mylar). Besides the CR39 method, the beam was measured by an energy spectrum detector after the 10 μm diameter aperture and the 3.5 μm thick vacuum film too.

Cell Locating with the Image Analysis System of the CAS-LIBB Single-Particle Microbeam Facility

A single-particle microbeam facility has been constructed at the Key Laboratory of Ion Beam Bioengineering (LIBB), Chinese Academy of Sciences (CAS). At the CAS-LIBB microbeam facility, we have developed protocols to place exact numbers of charged particles through nuclear centroids of cells, at defined positions in the cytoplasm relative to the nucleus, and through defined fractions of cells in a population. In this paper, we address the methods for nucleus, cytoplasm and bystander (either a single or an exact number of ions is delivered to a certain percentage of cells in a population to study the bystander effects of radiation) irradiation in detail from the precision of target finding and cell locating in the image analysis system. Moreover, for cells touching slightly in an image, a watershed method is used to separate these touching objects; after that, the number of objects in an image is counted accurately and the irradiation points are located precisely.

Simulation of nanofluid natural convection based on single-particle hydrodynamics in energy-conserving dissipative particle dynamics(eDPD)

In the present study,the nanofliud natural convection is investigated by the energy-conserving dissipative particle dynamics(eDPD)method,where the nanoparticles are considered at the single-particle level.The thermal expansion coefficientβand the viscosityμof the simulated system containing nanoparticles are calculated and found to be in close alignment with the previous simulation results.The single-particle hydrodynamics in e DPD enables simulations of nanofluid natural convection with higher Rayleigh numbers and greater nanoparticle volume fractions.Additionally,this approach is utilized to simulate the nanoparticle distribution during the enhanced heat transfer process in the nanofluid natural convection.The localized aggregation of nanoparticles enhances the heat transfer performance of the nanofluid under specific Rayleigh numbers and nanoparticles volume fractions.

Size-dependent thermomechanical vibration characteristics of rotating pre-twisted functionally graded shear deformable microbeams

A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).

Searching for single-particle resonances with the Green’s function method

Single-particle resonances in the continuum are crucial for studies of exotic nuclei.In this study,the Green’s function approach is employed to search for single-particle resonances based on the relativistic-mean-field model.Taking^(120)Sn as an example,we identify singleparticle resonances and determine the energies and widths directly by probing the extrema of the Green’s functions.In contrast to the results found by exploring for the extremum of the density of states proposed in our recent study[Chin.Phys.C,44:084105(2020)],which has proven to be very successful,the same resonances as well as very close energies and widths are obtained.By comparing the Green’s functions plotted in different coordinate space sizes,we also found that the results very slightly depend on the space size.These findings demonstrate that the approach by exploring for the extremum of the Green’s function is also very reliable and effective for identifying resonant states,regardless of whether they are wide or narrow.

Description of N=7～9 Isotones with a Modified Single-Particle Potential

We study the level structures of N = 7 - 9 isotones and their mirror nuclei in the framework of the single-particle potential model. Considering the limitation of the conventional potential-model calculation, the isospindependent 12 coupling is newly introduced in the average potential. The modified model gives a unified description for the structures of all studied nuclei. Galculations self-consistently produce the s-d level inversion in N = 9 isotones and their mirror nuclei. Meanwhile, the s-p level inversion in the mirror nuclei ^11Be and ^11N is reproduced. The study confirms the neutron halo structures in ^11Be（2s1/2）, ^11Be（1p1/2）, ^12B（2s1/2）, ^14B（2s1/2）, ^13C（2sl/2）, ^15C（2s1/2） and the proton halo structure in ^17F（2s1/2）. The agreement between theory and experiment indicates that the inclusion of the i2 coupling is a feasible way to explain the abnormal structures of exotic light nuclei.

Investigation of intense sheet electron beam transport using the macroscopic cold-fluid model and the single-particle orbit theory

The focusing and the stable transport of an intense elliptic sheet electron beam in a uniform magnetic field are investigated thoroughly by using the macroscopic cold-fluid model and the single-particle orbit theory.The results indicate that the envelopes and the tilted angles of the sheet electron beam obtained by the two theories are consistent.The single-particle orbit theory is more accurate due to its treatment of the space-charge fields in a rectangular drift tube.The macroscopic cold-fluid model describes the collective transport process in order to provide detailed information about the beam dynamics,such as beam shape,density,and velocity profile.The tilt of the elliptic sheet beam in a uniform magnetic field is carefully studied and demonstrated.The results presented in this paper provide two complete theories for systemically discussing the transport of the sheet beam and are useful for understanding and guiding the practical engineering design of electron optics systems in high power vacuum electronic devices.

Design of 50 MeV proton microbeam based on cyclotron accelerator

High-energy proton microbeam facilities are powerful tools in space science,biology and cancer therapy studies.The primary limitations of the 50 MeV proton microbeam system are the poor beam quality provided by the cyclotron and the problem of intense scattering in the slit position.Here,we present an optical design for a cyclotron-based 50 MeV high-energy proton microbeam system with a micron-sized resolution.The microbeam system,which has an Oxford triplet lens configuration,has relatively small spherical aberrations and is insensitive to changes in the beam divergence angle and momentum spread.In addition,the energy filtration included in the system can reduce the beam momentum spread from 1 to 0.02%.The effects of lens parasitic aberrations and the lens fringe field on the beam spot resolution are also discussed.In addition,owing to the severe scattering of 50 MeV protons in slit materials,a slit system model based on the Geant4 toolkit enables the quantitative analysis of scattered protons and secondary particles.For the slit system settings under a 10-micron final beam spot,very few scattered protons can enter the quadrupole lens system and affect the focusing performance of the microbeam system,but the secondary radiation of neutrons and gamma rays generated at the collimation system should be considered for the 50 MeV proton microbeam.These data demonstrate that a 50 MeV proton microbeam system with a micron-sized beam spot based on a cyclotron is feasible.

中国先进研究堆瞬发γ元素成像技术研究

无损分析样品内部的元素分布,对于材料、考古、地质科学等领域的研究具有重要意义。基于瞬发γ活化分析方法,结合中子照相技术,分析了模拟样品的结构和对称性,首次利用中国先进研究堆(CARR)水平孔道聚焦的微束中子束流,开展样品瞬发γ扫描分析和材料内部元素分布研究。通过蒙特卡罗软件(MCNP)对样品元素分布实验模型进行分析,模拟结果获得了样品不同区域的铜、铁、铝元素分布,基本实现了元素空间分辨。MCNP计算结果表明在瞬发γ扫描分析中,优化准直几何参数和提高中子通量能进一步提高元素空间分辨和元素测量准确度。

基于玻璃毛细管的大气环境MeV质子微束的产生与测量

本文采用玻璃毛细管产生了大气环境中工作的2.5 MeV质子外束微束,并对束斑直径及能量分布随玻璃毛细管与束流方向之间角度(倾角)变化进行测量.测量结果表明,在玻璃毛细管轴向与束流方向一致时(倾角为0°),产生的微束中存在保持初始入射能量的直接穿透部分以及散射部分,其中直接穿透的质子占比最大,束斑直径也最大.随着玻璃毛细管倾角的增大,当其大于几何张角时,束斑直径变小,产生的微束全部为能量减小的散射部分,直接穿透质子消失.我们对质子在玻璃毛细管内传输时的内壁散射过程进行了模拟计算及离子轨迹分析,发现大角度的散射部分决定了形成的外束微束斑外围轮廓,而束斑中心区域由不与毛细管内壁产生任何作用的直接穿透离子构成,其大小由玻璃毛细管出口直径以及几何容许张角决定.采用玻璃毛细管产生的外束微束具有产生简单廉价,微束区域定位简单的特点,有望在辐射生物学、医学、材料等领域得到广泛应用.

Nano-sized stationary phase packings retained by single-particle frit for microchip liquid chromatography

Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tensionbased single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates(10~6plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.

Quantifying Contribution of Recycled Moisture to Precipitation in Temperate Glacier Region,Southeastern Tibetan Plateau,China

Recycled moisture is an important indicator of the renewal capacity of regional water resources.Due to the existence of Yulong Snow Mountain,Lijiang in Yunnan Province,southeast of the Qinghai-Tibet Plateau,China,is the closest ocean glacier area to the equator in Eurasia.Daily precipitation samples were collected from 2017 to 2018 in Lijiang to quantify the effect of sub-cloud evaporation and recycled moisture on precipitation combined with the d-excess model during monsoon and non-monsoon periods.The results indicated that the d-excess values of precipitation fluctuated between–35.6‰and 16.0‰,with an arithmetic mean of 3.5‰.The local meteoric water line(LMWL)wasδD=7.91δ^(18)O+2.50,with a slope slightly lower than the global meteoric water line(GMWL).Subcloud evaporation was higher during the non-monsoon season than during the monsoon season.It tended to peak in March and was primarily influenced by the relative humidity.The source of the water vapour affected the proportion of recycled moisture.According to the results of the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)model,the main sources of water vapour in Lijiang area during the monsoon period were the southwest and southeast monsoons.During the non-monsoon period,water vapour was transported by a southwesterly flow.The recycled moisture in Lijiang area between March and October 2017 was 10.62%.Large variations were observed between the monsoon and non-monsoon seasons,with values of 5.48%and 25.65%,respectively.These differences were primarily attributed to variations in the advection of water vapour.The recycled moisture has played a supplementary role in the precipitation of Lijiang area.

单离子束-微流控细胞高通量辐照技术

辐照通量是指单位时间里离子辐照的细胞数量,是单离子束细胞辐照系统的重要性能指标。为提高单离子定位辐照通量,将微流控技术应用于单离子束细胞辐照系统,实现了单离子-单细胞精确定位自动辐照技术。微流控芯片上建立细胞储液池、O_(2)和CO_(2)注入通道、恒温加热、p H检测、细胞检测等功能机构。细胞微流受驱动在通道中保持运动,离子经微流控芯片辐照点射入微通道,对动态细胞进行辐照。基于CASLIBB装置,建立离子定位微流细胞的计算模型,研究离子精确瞄准微流细胞的基本方法和规律,获得微流细胞速度、最大辐照通量、辐照剂量、细胞间距等多个参量之间的相互约束关系,成为系统运行的理论指导。提出“即测即打”运行模式,以加快辐照速度,提高离子定位准确性。结果表明,细胞速度和辐照通量均存在上限值,提高微流细胞数密度和离子发射密度,是提高辐照通量的可选方法。采用微流控技术后,辐照通量达到10 000细胞/h,相比之前提高10倍以上。计算数据和实验结果基本吻合。

面向微束等离子选区熔化的在线检测系统

为解决微束等离子选区熔化过程中的自动化检测问题,开发出一套面向微束等离子选区熔化的在线检测系统.该系统以每一层的成形金属为研究对象,基于深度学习目标检测原理,对金属成形表面进行缺陷检测,并根据检测结果控制设备启停,确保每一层成形质量达到要求.同时,通过双目相机与线激光相配合,利用线阵扫描方式对成形表面形貌进行三维重建,并显示在自主开发的可视化软件上,实现缺陷检测和三维重建相结合的检测方案.实验结果表明,该系统能够快速、精确地检测出成形过程中产生的缺陷,实时性强、漏检率低,并可将结果及时反馈到系统,实现成形过程的主动、有效调控.

Nonlinear static and dynamic responses of an electrically actuated viscoelastic microbeam

On the basis of the Euler-Bernoulli hypothesis, nonlinear static and dynamic responses of a viscoelastic microbeam under two kinds of electric forces [a purely direct current （DC） and a combined current composed of a DC and an alternating current] are studied. By using Taylor series expansion, a governing equation of nonlinear integro-differential type is derived, and numerical analyses are performed. When a purely DC is applied, there exist an instantaneous pull-in voltage and a durable pull-in voltage of which the physical meanings are also given, whereas under an applied combined current, the effect of the element relaxation coefficient on the dynamic pull-in phenomenon is observed where the largest Lyapunov exponent is taken as a criterion for the dynamic pull-in instability of viscoelastic microbeams.

Modeling size-dependent thermo-mechanical behaviors of shape memory polymer Bernoulli-Euler microbeam

The objective of this paper is to model the size-dependent thermo-mechanical behaviors of a shape memory polymer (SMP) microbeam.Size-dependent constitutive equations,which can capture the size effect of the SMP,are proposed based on the modified couple stress theory (MCST).The deformation energy expression of the SMP microbeam is obtained by employing the proposed size-dependent constitutive equation and Bernoulli-Euler beam theory.An SMP microbeam model,which includes the formulations of deflection,strain,curvature,stress and couple stress,is developed by using the principle of minimum potential energy and the separation of variables together.The sizedependent thermo-mechanical and shape memory behaviors of the SMP microbeam and the influence of the Poisson ratio are numerically investigated according to the developed SMP microbeam model.Results show that the size effects of the SMP microbeam are significant when the dimensionless height is small enough.However,they are too slight to be necessarily considered when the dimensionless height is large enough.The bending flexibility and stress level of the SMP microbeam rise with the increasing dimensionless height,while the couple stress level declines with the increasing dimensionless height.The larger the dimensionless height is,the more obvious the viscous property and shape memory effect of the SMP microbeam are.The Poisson ratio has obvious influence on the size-dependent behaviors of the SMP microbeam.The paper provides a theoretical basis and a quantitatively analyzing tool for the design and analysis of SMP micro-structures in the field of biological medicine,microelectronic devices and micro-electro-mechanical system (MEMS) self-assembling.

Single-event response of the SiGe HBT in TCAD simulations and laser microbeam experiment

In this paper the single-event responses of the silicon germanium heterojunction bipolar transistors(SiGe HBTs) are investigated by TCAD simulations and laser microbeam experiment. A three-dimensional(3D) simulation model is established, the single event effect(SEE) simulation is further carried out on the basis of Si Ge HBT devices, and then, together with the laser microbeam test, the charge collection behaviors are analyzed, including the single event transient(SET) induced transient terminal currents, and the sensitive area of SEE charge collection. The simulations and experimental results are discussed in detail and it is demonstrated that the nature of the current transient is controlled by the behaviors of the collector–substrate(C/S) junction and charge collection by sensitive electrodes, thereby giving out the sensitive area and electrode of SiGe HBT in SEE.