真空磁绝缘线B-dot电流探测器的研制

为了测量阳加速器新真空磁绝缘线的电流,研制并标定了B-dot探测器。2个B-dot的探测器分别安装在磁绝缘线的入口和中部,输出信号与被测电流的微分成正比,经RC积分后获得电流信号。B-dot探测器采用在线标定,当阴阳极短接点数量较少,且位置距离探测器较近时,会因真空绝缘线(MITL)电流密度不均匀导致标定不准确,故需增多短接点。当短接点的位置距离探测器约2m时,即使只设置2个连接点,探测器位置的MITL电流密度近似均匀。加速器实验结果表明:在MITL阴阳极较近的位置,将B-dot探头安装在阳极孔中不影响磁绝缘效果,B-dot探测器测试稳定可靠,其设计和标定方法可行。     

Development of dual-responsive chitosan–collagen scaffolds for pulsatile release of bioactive molecules

Advancement in polymer science and engineering has led to the development of new polymeric systems for well-controlled delivery of therapeutic agents. In this work, thermo and pH responsive chitosan–collagen (CHT–CLG) scaffolds were prepared using a non-residue strategy. CHT–CLG scaffolds (pH sensitive) were produced by freeze drying method, cross-linked with glutaraldehyde, and coated with poly(N,N′-diethylacrylamide) (PDEAAm) in supercritical media to confer the thermoresponsive behavior. This green and integrated process generated a wide range of porous structures with different mechanical properties, reversible swelling ability and controlled biodegradability, depending on the scaffold composition and cross-linking degree. Microarchitectural analysis by scanning electron microscopy and mercury intrusion porosimetry demonstrated that the coating of the pores inner surface was efficiently achieved without compromising the porosity. The ability of these dual sensitive structures to control the release of a low molecular weight drug (ibuprofen, Ibu) and a model protein (BSA) was investigated. Additionally, a mathematical model was adjusted to the experimental release profiles in order to quantitatively describe the drug release and elucidate the underlying drug release mechanisms. The tunable morphological and mechanical properties together with the well-controlled pulsatile release of bioactive molecules make these structures attractive ON–OFF systems in biomedical and pharmaceutical fields.     

基于响应时间约束的敏捷轨道设计方法

结合快响卫星在实际任务中的应用背景，研究了响应时间约束中的敏捷轨道设计方法。首先，根据快速响应卫星的发射点和目标点的位置关系，结合快速响应时间约束，得出了响应时间与轨道高度的不等式关系；其次，针对常见的圆形轨道，根据球面三角形公式，构建了敏捷轨道轨道周期、轨道倾角、升交点赤经的解析设计方法；最后，结合STK软件的典型任务仿真，分别设计了当圈响应与第3圈响应的两类敏捷轨道，使卫星分别在入轨10 min与200 min时星下点通过目标区域，验证了方法的可行性、易操作性和实用性。     

Modulation of Viscoelasticity and HIV Transport as a Function of pH in a Reversibly Crosslinked Hydrogel

Materials that respond to physiological stimuli are important in developing advanced biomaterials for modern therapies. The reversibility of covalent crosslinks formed by phenylboronate (PBA) and salicylhydroxamate (SHA) has been exploited to provide a pH‐responsive gel for application to the vaginal tract. Dynamic rheology reveals that the gel frequency‐dependent viscoelastic properties are modulated by pH. At pH 4.8 the viscous component dominates throughout most of the frequency range. As the pH increases, the characteristic relaxation time continues to increase while the G′_Plateau levels off above pH 6. At pH 7.5, the elastic component dominates throughout the frequency sweep and is predominately independent of frequency. Particle tracking assesses the transport of both fluorescently labeled HIV‐1 and 100‐nm latex particles in the PBA–SHA crosslinked gel as a function of pH. At pH 4.8 the ensemble‐averaged mean squared displacement at lag times greater than three seconds reveals that transport of the HIV‐1 and 100‐nm particles becomes significantly impeded by the matrix, exhibiting diffusion coefficients less than 0.0002 µm² s^?1. This pH‐responsive gel thus displays properties that have the potential to significantly reduce the transport of HIV‐1 to susceptible tissues and thus prevent the first stage of male‐to‐female transmission of HIV‐1.     

Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine Rings

Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring‐opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6 ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4‐nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first‐order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance.