Chemical aspects of the radiation stability of macrocyclic extractants designed for 90Sr separation

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An asynchronous high‐speed synchrotron shutter

A high‐repetition‐rate mechanical shutter with asynchronous control and sub‐millisecond operation has been developed and tested for specialist X‐ray systems in the field of medical diagnostics and radiation therapy. Capacitor‐coupled linear voice coil actuators are utilized to achieve opening and closing speeds as fast as 700 µs for an aperture height of 4 mm. The design allows for asynchronous control, permitting slave operation of the shutter, a feature that is distinctly suitable for a number of applications including particle image velocimetry, where high‐frame‐rate operation must be accurately synchronized and triggered by the image acquisition sequence of the detector or timing device. The design and construction of the shutter also makes it ideal, with simple and limited modifications, for applications requiring larger apertures, in particular wide beams as found in many synchrotron beamlines.     

Wave-packet continuum discretization for quantum scattering

A general approach to a solution of few- and many-body scattering problems based on a continuum-discretization procedure is described in detail. The complete discretization of continuous spectrum is realized using stationary wave packets which are the normalized states constructed from exact non-normalized continuum states. Projecting the wave functions and all scattering operators like t$t$-matrix, resolvent, etc. on such a wave-packet basis results in a formulation of quantum scattering problem entirely in terms of discrete elements and linear equations with regular matrices. It is demonstrated that there is a close relation between the above stationary wave packets and pseudostates which are employed often to approximate the scattering states with a finite L₂$L_2$ basis. Such a fully discrete treatment of complicated few- and many-body scattering problems leads to significant simplification of their practical solution. Also we get finite-dimensional approximations for complicated operators like effective interactions between composite particles constructed via the Feshbach-type projection formalism. As illustrations to this general approach we consider several important particular problems including multichannel scattering and scattering in the three-nucleon system within the Faddeev framework.     

Demulsification of Solids‐Stabilized Emulsions Under Microwave Radiation

Experimental data are presented to show the influence of solid particles on demulsification. It was found that the solid particles could effectively resist demulsification. Compared with conventional heating, microwave radiation can enhance the demulsification rate by an order of magnitude and increase the demulsification effectiveness. The demulsification effectiveness of the emulsions stabilized by graphite powder can reach 82%–89% in a very short time under microwave radiation, whilst that of the emulsions stabilized by barium sulfate can attain 100% under similar conditions.     

RADIATION INDUCED ACRYLAMIDE/CITRIC ACID HYDROGELS AND THEIR SWELLING BEHAVIORS

Citric acid (CAc) moieties containing acrylamide (AAm) hydrogels were prepared by gamma irradiation of their aqueous solutions. A possible polymerization and crosslinking mechanism for acrylamide/citric acid (AAm/CAc) hydrogels is proposed. The effects of irradiation dose and citric acid content on swelling behavior were investigated. Swelling took place in water at 25°C and was followed gravimetrically. Incorporation of a relatively low amount of citric acid to acrylamide hydrogel increased its swelling up to 950% from 700%. The diffusion of water into AAm/CAc hydrogels was found to be a non-Fickian type. Diffusion coefficients of AAm/CAc hydrogels found as 5 × 10^?7? 10 × 10^?7 cm² sec^?1. It has also been found that the number average molar mass between crosslinks is increased with the CAc content and decreased with irradiation dose.     

Microwave-Assisted Chemical Demulsification of Water-in-Crude-Oil Emulsions

Two case studies are presented that shows the effects of chemical demulsifiers used under conventional heating and in combination with microwave radiation on efficiency of demulsification and light transmittance of the water separated from the emulsions. The data shows that the chemical demulsifiers coupling with microwave radiation does a better job at demulsifying the water-in-crude-oil emulsions than when the chemical demulsifiers are used under conventional heating. The demulsification efficiency of AE-121 could reach 100% under microwave irradiation (300 W) for 50 seconds.     

Near‐Infrared‐Controlled,Targeted Hydrophobic Drug‐Delivery System for Synergistic Cancer Therapy

Hydrophobicity has been an obstacle that hinders the use of many anticancer drugs. A critical challenge for cancer therapy concerns the limited availability of effective biocompatible delivery systems for most hydrophobic therapeutic anticancer drugs. In this study, we have developed a targeted near‐infrared (NIR)‐regulated hydrophobic drug‐delivery platform based on gold nanorods incorporated within a mesoporous silica framework (AuMPs). Upon application of NIR light, the photothermal effect of the gold nanorods leads to a rapid rise in the local temperature, thus resulting in the release of the entrapped drug molecules. By integrating chemotherapy and photothermotherapy into one system, we have studied the therapeutic effects of camptothecin‐loaded AuMP‐polyethylene glycol‐folic acid nanocarrier. Results revealed a synergistic effect in vitro and in vivo, which would make it possible to enhance the therapeutic effect of hydrophobic drugs and decrease drug side effects. Studies have shown the feasibility of using this nanocarrier as a targeted and noninvasive remote‐controlled hydrophobic drug‐delivery system with high spatial/temperal resolution. Owing to these advantages, we envision that this NIR‐controlled, targeted drug‐delivery method would promote the development of high‐performance hydrophobic anticancer drug‐delivery system in future clinical applications.     

二维柱坐标系辐射输运方程保球对称的离散纵标格式

 离散纵标格式是计算辐射输运方程的常用格式之一. 但是, 传统的离散纵标格式求解二维柱坐标系辐射输运方程模拟一维球对称问题时, 会出现明显的非对称现象, 球对称性被破坏. 针对该问题, 本文分析了传统离散纵标格式不能够保持球对称性的原因, 提出了空间基于柱坐标系、方向基于球坐标系的辐射输运方程, 并对该方程设计了新的离散纵标格式, 从理论上证明了当空间网格取球对称剖分时该离散格式能够保持一维球对称性的充分必要条件. 通过对真空球区域辐射输运、与物质耦合辐射输运等球对称算例的数值模拟, 验证了该格式的保球对称性, 球对称误差能够达到机器精度. 非对称辐射驱动模型以及非对称网格剖分条件下的数值模拟等算例也取得了较好的结果.     

From Dislocation Motion to an Additive Velocity Gradient Decomposition, and Some Simple Models of Dislocation Dynamics

A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a ``small deformation" setting, a suite of simplified and interesting models consisting of a nonlocal Ginzburg Landau equation, a nonlocal level set equation, and a nonlocal generalized Burgers equation is derived. In the finite deformation setting, it is shown that an additive decomposition of the total velocity gradient into elastic and plastic parts emerges naturally from a micromechanical starting point that involves no notion of plastic deformation but only the elastic distortion, material velocity, dislocation density and the dislocation velocity. Moreover, a plastic spin tensor emerges naturally as well.