Application of local Monte Carlo method in neutronics calculation of EAST radial neutron camera

The Local Monte Carlo(LMC)method is used to solve the problems of deep penetration and long time in the neutronics calculation of the radial neutron camera(RNC)diagnostic system on the experimental advanced superconducting tokamak(EAST),and the radiation distribution of the RNC and the neutron flux at the detector positions of each channel are obtained.Compared with the results calculated by the global variance reduction method,it is shown that the LMC calculation is reliable within the reasonable error range.The calculation process of LMC is analyzed in detail,and the transport process of radiation particles is simulated in two steps.In the first step,an integrated neutronics model considering the complex window environment and a neutron source model based on EAST plasma shape are used to support the calculation.The particle information on the equivalent surface is analyzed to evaluate the rationality of settings of equivalent surface source and boundary.Based on the characteristic that only a local geometric model is needed in the second step,it is shown that the LMC is an advantageous calculation method for the nuclear shielding design of tokamak diagnostic systems.

中试制备临床级别第三代慢病毒

基因治疗是一个快速发展的领域,其中关于慢病毒介导的外源基因导入研究得最为广泛。随着研发技术的不断发展,在安全性方面慢病毒已经从第一代发展至第三代,而如何工程化获得高滴度慢病毒仍是当今技术一大瓶颈。运用Fibra-Cel片状载体作为HEK293T细胞载体基质,联合多个无菌细胞转瓶在滚瓶机上培养,对贴壁细胞进行规模放大化生产。通过对第三代慢病毒包装过程中影响慢病毒滴度的因素进行逐一筛选,使病毒滴度达到最优。研究结果成功运用Fibra-Cel片状载体作为HEK293T细胞粘附载体基质,作为一种贴壁细胞规模放大的方法,筛选出了利用滚瓶机制备第三代慢病毒的最优条件,规模化生产了3批慢病毒。在时间上,将慢病毒的生产时间从质粒转染到病毒收集的120 h缩短至54 h;在成本上,利用滚瓶机代替生物反应器实现了无需反复灭菌、全程一次性产品的安全有效低成本的运行,为慢病毒的规模化制备提供了技术上的支持,为临床应用奠定了坚实的基础。

Simultaneously enhancing capacity and security in free-space optical chaotic communication utilizing orbital angular momentum

Optical chaotic signals emitted from an external-cavity feedback or injected laser diode enable small-signal information concealment in a noise-like carrier for secure optical communications.Due to the chaotic bandwidth limitation resulting from intrinsic relaxation oscillation frequency of lasers,multiplexing of optical chaotic signal,such as wavelength division multiplexing in fiber,is a typical candidate for high-capacity secure applications.However,to our best knowledge,the utilization of the spatial dimension of optical chaos for free-space secure communication has not yet been reported.Here,we experimentally demonstrate a free-space all-optical chaotic communication system that simultaneously enhances transmission capacity and security by orbital angular momentum(OAM)multiplexing.Optical chaotic signals with two different OAM modes totally carrying 20 Gbps on-off keying signals are secretly transmitted over a 2 m free-space link,where the channel crosstalk of OAM modes is less than-20 d B,with the mode spacing no less than 3.The receiver can extract valid information only when capturing approximately 92.5% of the OAM beam and correctly demodulating the corresponding mode.Bit error rate below the 7%hard-decision forward error correction threshold of 3.8×10^(-3)can be achieved for the intended recipient.Moreover,a simulated weak turbulence is introduced to comprehensively analyze the influence on the system performance,including channel crosstalk,chaotic synchronization,and transmission performance.Our work may inspire structured light application in optical chaos and pave a new way for developing future high-capacity free-space chaotic secure communication systems.

反收购条款会诱发管理层短视行为吗——基于MD&A文本分析的经验证据

随着资本市场的发展,恶意收购事件层出不穷,这也引起了上市公司对反收购条款的重视。本文以制定反收购条款的重要主体管理层为切入点,以我国2007年至2020年A股上市公司为研究对象,探讨反收购条款对管理层短视行为的影响。研究结果表明,公司设置反收购条款会诱发管理层的短视行为,该结论在稳健性检验后仍然成立。研究还发现,反收购条款会减少公司的长期资本支出和研发投入及产出,增加代理成本,降低管理层变更业绩敏感性和管理层薪酬业绩敏感性,损害公司价值,进一步验证了反收购条款对管理层短视行为的诱发作用。本研究丰富了反收购条款对管理层决策视域影响的相关研究,对上市公司反收购行为和管理层激励方法有一定的现实指导意义。