通过软X射线信号研究芯部等离子体的结构

介绍了如何从软X射线原始信号上分析等离子体芯部磁场结构的方法. 在HT-7托卡马克上,通过分析一炮典型的放电数据,直接从软X射线原始信号上分析了磁岛的位置和旋转方向. 通过软X射线图像反演的结果和Mirnov信号上观察到的m=2模的走向验证了磁岛旋转的方向和位置. 关键词： 软X射线 MHD不稳定性 磁岛     

软体机器人结构机理与驱动材料研究综述

软体机器人是一类新型机器人,具有结构柔软度高,环境适应性好,亲和性强,功能多样等特点,有着十分广阔的研究和应用前景. 智能材料在软体机器人结构设计及实际应用中扮演了重要的角色,其特殊的驱动机制极大拓展了软体机器人的功能. 介绍了软体机器人的发展和研究现状,按其应用场合及功能总结了几种典型的软体机器人. 从仿生机理的角度,介绍了蠕虫、弯曲爬行虫、鱼类游动等几类仿生运动机理以及其相应的软体机器人. 还按不同驱动类型将软体机器人归纳为气动、形状记忆合金、离子交换聚合物金属复合材料、介电高弹体、响应水凝胶、化学燃烧驱动等类型. 介绍了软体机器人的制作方法与工艺,分析了目前软体机器人研究的主要挑战,提出对未来研究的展望.      

纳米氧化铋的研究进展

综述了纳米氧化铋的发展研究现状,总结了近年来发展起来的几种制备纳米氧化铋的新方法的优缺点,以及纳米氧化铋作为电子功能材料、燃速催化剂、光催化降解材料、光学材料、医用复合材料和防辐射材料等方面的主要应用。     

应用碱性水泥外掺剂固化天津海积软土的试验研究

天津海积软土具有高含水量、低强度、高压缩性、低pH值等特征,不能直接满足工程建设需要,必须进行人工处理。在水泥土搅拌法中使用适量碱性外掺剂NaOH或Na2CO3,可以提高桩身水泥土强度和复合地基承载力,同时能节省大量水泥,降低工程费用。现场试验中将海积软土与分别掺入0.5%NaOH和0.5%Na2CO3的10%水泥就地搅拌,形成两种新型水泥土,在与原状土及20%纯水泥土进行比较后,发现碱性外掺剂可以促使生成大量针状、棒状或纤维状水化硅酸钙晶体,抑制了能产生膨胀作用的钙矾石的生成,同时,有Ca(OH)2晶体析出,它们共同构成土颗粒间和土颗粒表面的充填物和包裹物,使水泥固化土的孔隙明显减小,密度和强度得到极大提高。检测结果显示水泥土强度提高了20%以上,复合地基承载力不小于120kPa。     

Effects of soft X‐ray radiation damage on paraffin‐embedded rat tissues supported on ultralene: a chemical perspective

Radiation damage is an important aspect to be considered when analysing biological samples with X‐ray techniques as it can induce chemical and structural changes in the specimens. This work aims to provide new insights into the soft X‐ray induced radiation damage of the complete sample, including not only the biological tissue itself but also the substrate and embedding medium, and the tissue fixation procedure. Sample preparation and handling involves an unavoidable interaction with the sample matrix and could play an important role in the radiation‐damage mechanism. To understand the influence of sample preparation and handling on radiation damage, the effects of soft X‐ray exposure at different doses on ultralene, paraffin and on paraffin‐embedded rat tissues were studied using Fourier‐transform infrared (FTIR) microspectroscopy and X‐ray microscopy. Tissues were preserved with three different commonly used fixatives: formalin, glutaraldehyde and Karnovsky. FTIR results showed that ultralene and paraffin undergo a dose‐dependent degradation of their vibrational profiles, consistent with radiation‐induced oxidative damage. In addition, formalin fixative has been shown to improve the preservation of the secondary structure of proteins in tissues compared with both glutaraldehyde and Karnovsky fixation. However, conclusive considerations cannot be drawn on the optimal fixation protocol because of the interference introduced by both substrate and embedding medium in the spectral regions specific to tissue lipids, nucleic acids and carbohydrates. Notably, despite the detected alterations affecting the chemical architecture of the sample as a whole, composed of tissue, substrate and embedding medium, the structural morphology of the tissues at the micrometre scale is essentially preserved even at the highest exposure dose.     

Soft X‐ray refractive index by reconciling total electron yield with specular reflection: experimental determination of the optical constants of graphite

The complex refractive index of many materials is poorly known in the soft X‐ray range across absorption edges. This is due to saturation effects that occur there in total‐electron‐yield and fluorescence‐yield spectroscopy and that are strongest at resonance energies. Aiming to obtain reliable optical constants, a procedure that reconciles electron‐yield measurements and reflection spectroscopy by correcting these saturation effects is presented. The procedure takes into account the energy‐ and polarization‐dependence of the photon penetration depth as well as the creation efficiency for secondary electrons and their escape length. From corrected electron‐yield spectra the absorption constants and the imaginary parts of the refractive index of the material are determined. The real parts of the index are subsequently obtained through a Kramers–Kronig transformation. These preliminary optical constants are refined by simulating reflection spectra and adapting them, so that measured reflection spectra are reproduced best. The efficacy of the new procedure is demonstrated for graphite. The optical constants that have been determined for linearly polarized synchrotron light incident with p‐ and s‐geometry provide a detailed and reliable representation of the complex refractive index of the material near π‐ and σ‐resonances. They are also suitable for allotropes of graphite such as graphene.     

软X射线激光背光阴影成像技术的空间分辨研究

软X射线激光阴影成像技术是一种诊断高温稠密等离子体临界面附近阴影轮廓的诊断技术,具有测量视场大、空间分辨能力高的特点,具有重要的应用前景.对该技术的空间分辨具体能够达到什么程度则没有进行过系统研究.本文分别从光路几何、衍射极限、成像像差三个方面进行了仔细分析,结果表明目前采用该技术的诊断系统能够达到约2μm的空间分辨.主要受限是光路几何因素,通过增加放大倍数、选择单元尺寸更小的接收元器件等方式,有希望达到优于1μm的空间分辨.     

高效液相色谱-串联质谱法测定蜂胶及以其为原料的保健食品中的氯霉素

建立了同时适用于蜂胶及以其为原料的保健食品中氯霉素残留的检测方法。样品中的蜂胶经乙醇溶解,以4%（质量分数）乙酸铅溶液沉淀具有邻二酚羟基结构的黄酮类成分,在碱性条件下进一步去除不含此结构的黄酮类干扰物,并以甲基叔丁基醚为提取溶剂,有效减少样品中极性干扰物和保健食品辅料（如聚乙二醇、甘油等）的共提取。试样溶液经HPLC-MS/MS测定,内标法定量。线性范围为0.20~50.0 μg/L,相关系数为0.9998;方法检出限为0.03 μg/kg,定量限为0.1 μg/kg;不同基质的回收率为86.0%~114.4%,相对标准偏差为0.3%~4.9%。该方法通用性强,操作简便,灵敏度高,抗干扰能力强,推广应用前景良好。     

Giant SALR cluster reproduction,with implications for their chemical evolution

ABSTRACT

Particles with SALR (short-range attraction and long-range repulsion) interactions are common to many physical systems, especially biological and soft matter, yet their behaviour is still not completely understood. Using Monte Carlo simulations and a thermodynamic model, it is shown here that giant SALR clusters can grow and reproduce in these fluids. Giant cluster growth and reproduction should therefore be common to a wide range of natural and synthetic systems under suitable conditions. If, in addition, cluster fitness selection occurs then chemical evolution of giant SALR cluster might be observed in suitable systems.     

NMR relaxometry study of gelatin based low-calorie soft candies

ABSTRACT

Soft candies are popular confectionery products. The most significant concern on the consumption of these products is the high amount of sugar and thus the high calories. The use of low-calorie sweeteners is a desirable trend in confectionery research. In this study, gelatin-based soft candies were formulated by using different sweeteners and their characterisation was performed using high and low field nuclear magnetic resonance (NMR) relaxation experiments. To complement the information obtained by NMR experiments, moisture content, water activity, texture analysis and differential scanning calorimeter experiments were also conducted. T₁ and T₂ relaxation times were measured at both low and high fields and also temperature-dependent measurements were conducted at the high field system. Candies were formulated by substitution of sucrose with maltitol, isomalt and stevia at 30%, 50% and 70% ratios. Significant difference was observed on relaxation times. T₁ values were best described by a mono-exponential model, whereas for T₂ relaxation times a bi-exponential model gave better results at both fields.