免疫缺陷大鼠模型的研究进展

免疫缺陷动物模型是指通过筛选自发突变或者基因工程改造建立的缺失一种或多种免疫系统组分，并用于生物医学研究的动物模型。免疫缺陷小鼠模型发展较为成熟，为人源化、患者来源异种移植(patient-derived xenograft, PDX)、干细胞移植以及传染性疾病等研究提供了良好的工具。与小鼠相比，大鼠具有体型更大，代谢和生理与人更接近，更易进行手术操作、样本获取，以及长期应用于临床前毒理和药理的评估等优势。因此，近年来出现了各种免疫缺陷大鼠模型。文章通过动物模型之间的比较，着重综述了免疫缺陷大鼠模型的最新进展，并展望其在干细胞研究和抗肿瘤治疗中的应用前景。     

融媒体背景下传统民营科技型企业的互联网转型:协同进化视角

借助隐喻手段,基于融媒体发展背景,以协同进化为理论依据,剖析传统民营科技型企业的互联网转型过程,总结机理与路径,提出协同进化式转型的理论模型.以千城智联(上海)网络科技有限公司为案例企业,分析其与地方电视台的协同进化过程,研究发现:①基因改变意味着组织认知模式的变化,具体表现是互联网思维的建立以及从单式思维到链式思维的转变;②协同进化基本路径为企业基因改变→企业行为转变→合作方基因改变→合作方行为转变→企业与合作方性状变化;③协同进化的标志是生态位改变,后者由协同关系的转变来衡量,分别经历了买卖关系、资源共享关系、价值共创与共享关系三种状态;④协同关系的演进激发平台网络效应的形成.     

The TET enzymes

During the past decade, we have learnt that the most common DNA modification, 5-methylcytosine (5mC), playing crucial roles in development and disease, is not stable but can be actively reversed to its unmodified form via enzymatic catalysis involving the TET enzymes. These ground-breaking discoveries have been achieved thanks to technological advances in the detection of the oxidized forms of 5mC and to the boldness of individual scientists. The TET enzymes require molecular oxygen for their catalysis, making them important targets for hypoxia research. They also require special cofactors which enable additional levels of regulation. Moreover, mutations and other genetic alterations in TETs are found, especially in myeloid malignances. This review focuses on the kinetic and inhibitory properties of the TET enzymes and the role of TETs in cellular differentiation and transformation and in cancer.     

Current knowledge on exosome biogenesis and release

Exosomes are nanosized membrane vesicles released by fusion of an organelle of the endocytic pathway, the multivesicular body, with the plasma membrane. This process was discovered more than 30 years ago, and during these years, exosomes have gone from being considered as cellular waste disposal to mediate a novel mechanism of cell-to-cell communication. The exponential interest in exosomes experienced during recent years is due to their important roles in health and disease and to their potential clinical application in therapy and diagnosis. However, important aspects of the biology of exosomes remain unknown. To explore the use of exosomes in the clinic, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are better understood. We have here summarized what is presently known about how exosomes are formed and released by cells. Moreover, other cellular processes related to exosome biogenesis and release, such as autophagy and lysosomal exocytosis are presented. Finally, methodological aspects related to exosome release studies are discussed.     

Study on the Centralization Strategy of the Blood Allocation Among Different Departments within a Hospital

By far, the researches on how to distribute blood products among different departments in hospital have not been further studied, though the problem of blood shortage and wastage that caused by improper blood allocation is severe, which may endanger patient’s lives and impose considerable costs on hospitals. In order to solve this problem, this paper mainly studies on how to distribute the blood items among different departments within a hospital and investigates the allocation approach with the novel management method by centralizing the inventory of several different departments. By integrating the blood inventory requirements of some departments, the hospital could reduce the rate of blood shortage and wastage effectively, release the pressure of the occupancy of resources and reduce the bullwhip effect of blood products. This paper illustrates the centralization principle in hospital and formulates the mixed integer programming model to work out the optimal allocation network scheme and the optimal inventory setting for every department. And the results of the numerical example demonstrate that this centralization method could considerably reduce blood shortage and wastage in hospital by about 72% and 90% respectively. Furthermore, it could decrease the total cost by about 108,540 RMB a month on blood supply chain management in the hospital and improve the effect of some certain surgeries by transfusing the fresh blood to patients.     

Fuzzy Views on Black-Litterman Portfolio Selection Model

In this paper, views of investor are described in fuzzy sets, and two fuzzy Black-Litterman models are constructed with fuzzy views and fuzzy random views respectively. In the models, expected returns and uncertainty matrix of views are redefined and the views are formulated by fuzzy approaches suitably. Then the models are tested with data from Chinese financial markets. Empirical results show that the fuzzy random views model performs the best, and both the fuzzy models are better than the traditional ones, demonstrating that the fuzzy approaches can contain more information in the views and measure the uncertainty more correctly.     

Robust Chattering-Free Finite Time Attitude Tracking Control with Input Saturation

This paper addresses the attitude tracking control problem of a rigid spacecraft in the presence of the modeling uncertainty, external disturbance, and saturated control input by designing two robust attitude tracking controllers. The basic controller is formulated using an integral sliding mode surface which is continuous and provides an asymptotic convergence rate for the closed-loop system. In this case, only the external disturbance with the prior information is considered. Then, to provide a finite time convergence rate and further improve the robustness of the control system under the unknown system uncertainty containing both the modeling uncertainty and external disturbance,a novel integral terminal sliding mode surface(ITSMS) is designed and associated with the continuous adaptive control method. Besides, a command filter is utilized to deal with the immeasurability problem within the proposed ITSMS and an auxiliary system to counteract the input saturation problem. Digital simulations are presented to verify the effectiveness of the proposed controllers.     

Effects of Strain Rate,Temperature and Grain Size on the Mechanical Properties and Microstructure Evolutions of Polycrystalline Nickel Nanowires: A Molecular Dynamics Simulation

Through molecular dynamics(MD)simulation,the dependencies of temperature,grain size and strain rate on the mechanical properties were studied.The simulation results demonstrated that the strain rate from 0.05 to 2 ns~(–1 )affected the Young’s modulus of nickel nanowires slightly,whereas the yield stress increased.The Young’s modulus decreased approximately linearly;however,the yield stress firstly increased and subsequently dropped as the temperature increased.The Young’s modulus and yield stress increased as the mean grain size increased from 2.66 to6.72 nm.Moreover,certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension.Certain phenomena such as the formation of twin structures,which were found in nanowires with larger grain size at higher strain rate and lower temperature,as well as the movement of grain boundaries and dislocation,were detected and discussed in detail.The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size.However,for larger grain size,the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire.