肾脏相位衬度两种成像技术的比较及分析

目的:分别采用衍射增强成像(DEI)和同轴成像(IOXI)技术进行小鼠肾脏组织的相位衬度成像研究,旨在评估两种成像方法的特性和效果。方法:分别在北京同步辐射装置(BSRF)4W1A及上海光源(SSRF)BL13W1上进行实验(分别实施DEI和IOXI)。经福尔马林溶液固定的不同月龄(10、18、24月龄)小鼠的肾脏标本置于成像台进行成像,以图像衬度及分辨率等指标评估电荷耦合器件(CCD)获得的图像,具体评估指标包括显示的图像形态结构、衬度、分辨率等参数。结果:DEI技术获得的图像主要是显示血管结构。而IOXI技术获得的图像包含更多的细节,除了血管结构外,还能清晰显示包括肾小球在内的小鼠肾脏的微细结构,尤其在高分辨成像下,通过比较不同月龄的小鼠肾脏,初步获得小鼠老化的过程:首先从皮质肾小球的分布、走行及数量发生变化,到后期乃至终末期累及髓质,直小管及血管结构紊乱、皱缩以及肾脏呈硬化萎缩改变。结论:DEI和IOXI技术均能较好显示小鼠的肾脏血管结构,但IOXI技术更能显示包括肾小球在内的细微结构,这对未来研究肾脏病变乃至其余实质脏器的研究具有更加重要的价值。

同步辐射光源四维原位成像助力材料微结构损伤高分辨表征

具备高时空分辨率的同步辐射光源是标志着现代基础科学核心创新能力的一种大科学装置。介绍了基于高能X射线三维成像的原位加载装置的国内外研究进展,简要论述了作者团队自2011年以来基于上海同步辐射光源和北京同步辐射装置自主研制的系列原位加载装置,包括原位拉伸、压缩、低周疲劳、高周疲劳、超高周疲劳试验机及其样品环境,以及针对轻质高强材料(激光焊接铝合金和激光增材制造铝、钛合金等)缺陷安全性评定开展的研究工作。结果表明,原位加载装置是表征先进材料微结构损伤演化的核心,也是关系国家竞争力的大科学装置的重要支撑。

穴位的同步辐射相位衬度成像

目的:采用先进的同步辐射相位衬度成像技术进行穴位的成像研究,旨在从微观形态学上探究穴位的理论基础。方法:选用尸体的中极和足三里穴位点处的皮肤和肌肉软组织,干燥后进行同步辐射相位衬度成像,以组织衬度和分辨率作为评价指标,分析比较穴位点与周围的微细血管数量、分布的差异。结果:应用XPCT方法获得了较好的成像效果,分辨率达到了微米量级。在穴位的区域上可以看到大量微血管结构,而在非穴位的区域就比较简单,平整而且微血管数量很少。结论:同步辐射相位衬度成像方法基于其良好的组织分辨能力,提供给穴位研究极其重要的微观信息。

肝脏同步辐射相位衬度成像的实验研究

目的 :利用同步辐射光源的特性,对大鼠肝脏组织分别行类同轴成像、衍射增强成像、干涉法成像及光栅成像实验,通过4种相位衬度技术不同成像效果的比较、分析,评价同步辐射相位衬度成像的意义及临床应用前景。方法:在同步辐射光源装置上,分别根据成像机制设计4种不同的光路进行成像,均采用经35%~40%甲醛水溶液固定的大鼠离体肝脏样品,根据光路及成像方法分别调节曝光参数以达到最佳成像效果。结果:4种成像技术各具优势,且分辨率均能达到微米(μm)量级,可显示肝脏样品远端(8级)血管。类同轴成像技术显示肝脏实质结构上优势较明显,能够清晰显示肝小叶结构(包括小叶间结构及窦状间隙血管),可见肝细胞在围绕窦状间隙中呈板状排列。结论:相位衬度成像具有较高的组织衬度及较好的图像分辨力,能够显示包括肝小叶在内的微小结构或多级血管分支结构,有助于观察肝脏肿瘤生长过程中新生血管的形态、分布,以及肝脏组织细胞微观层面的研究,有望在肝脏的生理、病理及病变机制的可视化研究上发挥重要作用。

Observation of cavitation and water-refilling processes in plants with X-ray phase contrast microscopy

With the spatial coherence of X-rays and high flux and brightness of the 3rd generation synchrotron radiation facility,X-ray phase contrast microscopy(XPCM)at Shanghai Synchrotron Radiation Facility(SSRF)can provide high resolution dynamic imaging of low electron density materials in principle.In this paper,we investigated the cavitation and water-refilling processes in rice and bamboo leaves utilizing XPCM at SSRF.The occurrence of xylem cavitation was recorded in vivo.The study also revealed that under different dehydration conditions,cavitation occurs in different degrees,and therefore,the refilling process is different.The results demonstrate that SSRF can provide high enough fluxes to study dynamic processes in plants in real-time,and XPCM is expected to be a promising method to reveal the mechanisms of cavitation and its repair in plants nondestructively.

Terahertz identification and quantification of penicillamine enantiomers

Identification and characterization of L-, D- and DL- penicillamine were demonstrated by Terahertz time-domain spectroscopy (THz-TDS). To understand the physical origins of the low frequency resonant modes, the density functional theory (DFT) was adopted for theoretical calculation. It was found that the collective THz frequency motions were decided by the intramolecular and intermolecular hydrogen bond interactions. Moreover, the quantification of penicillamine enantiomers mixture was demonstrated by a THz spectra fitting method with a relative error of less than 3.5%. This technique can be a valuable tool for the discrimination and quantification of chiral drugs in pharmaceutical industry.

基于中子与同步辐射技术的工程材料/部件多尺度残余应力评价

多尺度残余应力贯穿于工程部件设计、生产、加工和服役的全生命周期,对工程部件的长寿命可靠服役具有重要意义。残余应力具有多层次、跨尺度的分布特征,在温度、载荷等服役环境作用下发生动态演化,给精确表征带来了很大困难。相较于传统实验室X射线残余应力测量方法,中子衍射、同步辐射高能X射线衍射和同步辐射微束衍射技术在穿透深度、时间分辨率、空间分辨率、环境装置等方面具有显著优势,能够实现宏观残余应力、晶间/相间微观应力、晶内超微观应力3类残余应力的原位无损精确表征。本文详细介绍了上述基于中子/同步辐射大科学装置的多尺度应力表征技术的测量原理、应用范围和典型应用案例,并对相关技术的发展进行了展望。

先进材料多维多尺度高通量表征研究进展

先进材料的多维多尺度高通量表征可显著提高新材料研发效率,加快新材料应用进程,为材料及结构的可靠性服役和全寿命管理提供科学依据。介绍材料多维多尺度高通量表征技术的背景与内涵,然后对高通量样品制备与表征、多维多尺度关联成像、高通量原位表征等技术的发展进行了系统介绍,讨论多维多尺度高通量表征技术的前沿应用和技术局限性,最后对其未来发展趋势及面临的挑战进行了解析,指出这些技术挑战直接关系到高通量表征技术在先进材料及结构服役行为研究中的应用,展望多维多尺度高通量表征的若干发展方向,从而为建立材料微结构和服役性能的映射关系、跨尺度揭示工程部件的伤损机理和失效模式、推进先进材料的研发与应用进程提供参考。

基于点扫描的同步辐射红外三维谱学显微研究

同步辐射红外(SRIR)光具有光谱范围宽、发散角小、亮度高以及信噪比高等优点,结合传统红外谱学技术,采用SRIR谱学显微技术对样品进行红外谱学显微,可以获得样品微米级别的空间光谱信息。利用MiTeGen聚亚酰胺小环作为样品,以上海光源BL01B1线站的SRIR光为光源,通过点扫描采样方式进行同步辐射红外三维谱学显微实验研究。通过获得聚亚酰胺小环在不同角度下的SRIR二维显微光谱信息,选取波数范围为1495~1485 cm-1的显微光谱信息处理,用代数迭代算法对聚亚酰胺小环的化学组分酰胺Ⅱ进行SRIR三维显微重构,获得了完整的三维重构图。实验表明本文方法能够以较高的信噪比重构出样品化学组分的三维红外显微结构。

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.

In situ investigation of SiC powder's microwave sintering by SR-CT technique

Microwave sintering is being developed as a novel technique for the preparation of dense structural ceramics,but the mature theory has not been established due to the technical difficulties.The synchrotron radiation X-ray computed tomography(SR-CT) technique was introduced for the first time into the study of microwave sintering to in-situ observe the microstructure evolution of silicon carbide(SiC) material in this paper.By applying the SR-CT technique,the reconstructed 2D and 3D images of the specimen were obtained and the double logarithm curve of mean neck size and time(Ln(x)-Ln(t)) were obtained from these reconstructed images.Various sintering phenomena including sintering neck growth during microwave treatment were observed from the reconstructed images.Furthermore,the differences in microstructure evolution and sintering kinetics between microwave and conventional sintering were analyzed based on the reconstructed images and the Ln(x)-Ln(t) curve.1) The sharp surface of grains near the contact region distinctly grew blunt and the sintering neck growth between these grains were obviously observed at the early stage.Besides,the larger particles grew faster than smaller ones.The main reason for these phenomena may be the micro-focusing effect of electric fields.2) During each of the three sintering stages,the sintering kinetics curve of double logarithm relationship between mean neck size and time shows a good linear relationship,but at the middle stage the slope of the curve increases dramatically,which is quite larger than conventional sintering.The preliminary interpretation for these extraordinary phenomena has been discussed in details.

Thermal and elemental analysis of the combustion chamber deposits in a large-scale two-stroke marine diesel engine

It is of significance to understand the chemical content of carbon deposits in the large-scale two-stroke(LSTS) marine diesel engine because of adverse effect on the engine performance, oil consumption and emissions. In this work, two different combustion chamber deposits in an LSTS marine diesel engine were studied using thermogravimetry analysis(TGA), elemental analysis(EA) and synchrotron X-ray fluorescence(SXRF). One was on the piston top and the other on the piston land, termed PTCD and PLCD, respectively. For the PTCD sample, the 97% residue in the TGA and 1.4% carbon content in the EA indicated the main compositions of PTCD were metal salts or oxides and ashes, significantly different from the previous findings of the highest carbon content in deposits from the small four stroke engines. The different chemical content between PTCD and PLCD implied higher thermal load in the LSTS marine diesel engine led to a nearly complete thermal decomposition of PTCD. The higher calcium content in PTCD and PLCD indicated the additives of cylinder oil should be the main source of metal content of PTCD and PLCD. Calcium distribution in the SXRF results was indicative of the potential layered structure in PTCD and PLCD. In addition, the appearance of iron on the surface against the piston in PTCD and PLCD indicated iron oxides formation between carbon deposit and piston materials.

运动衬度X射线成像及其应用

针对复杂体系弱信号的成像难题,本课题组提出并发展了运动衬度X射线成像方法。该方法利用各运动组分对入射光场的调制随时间的演化规律的不同,将其分离开来、分别成像,从而消除各组分间的相互干扰、提高成像灵敏度。低造影剂浓度血管造影、植物微导管输水无造影剂成像、电化学反应离子迁移高灵敏成像等实验结果表明,运动衬度X射线成像可实现传统方法无法实现的有效衬度的复杂体系弱信号成像。因适用于任意波长,运动衬度成像原理也有望在红外、可见光等其他波段获得广泛应用。