Synchrotron X-ray 2D and 3D elemental imaging of CdSe/ZnS quantum dot nanoparticles in Daphnia magna

The potential toxicity of nanoparticles to aquatic organisms is of interest given that increased commercialization will inevitably lead to some instances of inadvertent environmental exposures. Cadmium selenide quantum dots (QDs) capped with zinc sulfide are used in the semiconductor industry and in cellular imaging. Their small size (<10 nm) suggests that they may be readily assimilated by exposed organisms. We exposed Daphnia magna to both red and green QDs and used synchrotron X-ray fluorescence to study the distribution of Zn and Se in the organism over a time period of 36 h. The QDs appeared to be confined to the gut, and there was no evidence of further assimilation into the organism. Zinc and Se fluorescence signals were highly correlated, suggesting that the QDs had not dissolved to any extent. There was no apparent difference between red or green QDs, i.e., there was no effect of QD size. 3D tomography confirmed that the QDs were exclusively in the gut area of the organism. It is possible that the QDs aggregated and were therefore too large to cross the gut wall.     

时域光学相干层析系统噪音分析和实验研究

本文从理论和实验上分析了存在拍频噪音时时域光学相干层析系统的噪音特性,给出了拍频噪音的具体估算方法.建立了描述一般时域光学相干层析系统实际噪音的简化模型,并给出了测量和寻找平衡探测光学相干层析系统最佳工作状态的方法.理论计算表明,平衡探测光学相干层析系统的信噪比受限于拍频噪音,理想情况下,最大信噪比可达100 dB左右|同时实验表明,如果实际的系统不能完全消除冗余噪音,其信噪比可能要比理论值小10~20 dB.本文的主要结果将可直接用于时域光学相干层析系统工作状态的测试和诊断当中,对频域光学相干层析系统噪音性能的分析和优化也将有所裨益.     

结直肠癌多层螺旋CT浸润征像与病理预后因子的关系

目的 探讨结直肠癌多层螺旋CT（MSCT）所见的浸润征象与病理预后因子的关系。方法 对32例结直肠癌患者,术前均行MSCT 水成像双期增强扫描,并用免疫组织化学方法检测手术病理标本中的p53、Ki67 阳性表达率及病理对照分析。结果 结直肠癌肠外浸润者p53、Ki67的阳性表达率分别为62.6％、74.5％,均高于肠壁肌层浸润者;区域淋巴结及远处转移者p53、Ki67的阳性表达率分别为65.8％、76.2％,均高于无淋巴结转移者（均P＜0.05）。结论 结直肠癌MSCT所见的浸润程度及区域淋巴结状态可作为临床评价结直肠癌的恶性度和预后的一个影像学指标,对术前判断结直肠癌术后复发转移潜能和预后有重要价值。     

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在托卡马克等离子体辐射的诊断中,线积分辐射率与辐射发射率之间的关系,常采用探测器无穷小近似下的表达式。简单分析表明,只有在探测器极向尺寸远小于光栏极向尺寸时,这种近似才成立。在探测器与光栏的极向尺寸相同的情况下,束线宽度约为探测器无穷小近似下的宽度的两倍。对这种探测系统的线积分辐射率作了有限探测器效应修正,并简要讨论了它对层析分析的影响。     

An efficient algorithm used for full-field optical coherence tomography

An efficient algorithm for computing optical coherence tomography is presented, which is based on the discrete differences of a time/depth sequence of interferograms. The existing multiple-step phase-shift algorithms, including those solved from Carré and Hariharan equations as well as circular-step algorithm proposed by Dubois et al., are analyzed and compared with the proposed algorithm. The analytical and experimental results show the computational efficiency of the new algorithm outperforms others. The simulations also demonstrate that the algorithm based on derivatives of four phase-shifted images is less sensitive to the phase-shift noise comparing to traditional 4-step phase-shift-based algorithm.     

倒置式扇形束CT的算法研究

与传统的X线透射成像相比,倒置式X线透射成像结构有着投影数据信噪比高的优点,因而可以提高透射图像的密度分辨率,本文提出了倒置式二维CT的概念,并给出了倒置式扇形束CT的完全重建条件及重建算法。     

使用RGB LED与微型光谱术的非侵入性组织分类医学成像系统

医学美容和化妆品行业的进步与日俱进,为了揭示皮肤组织的细节,三维医学成像是必须的。为了减少侵入性,在本研究中应用"读出,而非写入"的想法,采用非电离辐射的光源与组织采样点的反射光谱实现皮肤的非侵入性成像,这种新技术称为"光谱分类成像术"。采用宽带光源与光谱仪收集扫描区域中各采样点的光谱曲线,根据其交叉相关系数分为几种类型的组织;使用相应于每一像素之组织类型的颜色填满每一个像素,可获得一幅彩色的组织断层影像。其次,探讨了光谱分类成像术的横向/纵向分辨率和穿透深度、展示了紫水晶样品与孔雀鱼样本的穿透造影结果、并探讨交叉相关系数大小与光源波长的数量等变因对于成像结果的影响。将宽带光源和光谱仪分别更换为RGB LED和微型光谱仪以取得样本光谱,该系统有潜力最小化为手持式医疗成像产品。与传统的医学成像技术相较,没有过于强烈的光源或有害人体的荧光染料被使用,将可减少非环保化妆品的过度使用,并促进医学美容产业的进展。     

Serial sectioning methods for 3D investigations in materials science

A variety of methods for the investigation and 3D representation of the inner structure of materials has been developed. In this paper, techniques based on slice and view using scanning microscopy for imaging are presented and compared. Three different methods of serial sectioning combined with either scanning electron or scanning ion microscopy or atomic force microscopy (AFM) were placed under scrutiny: serial block-face scanning electron microscopy, which facilitates an ultramicrotome built into the chamber of a variable pressure scanning electron microscope; three-dimensional (3D) AFM, which combines an (cryo-) ultramicrotome with an atomic force microscope, and 3D FIB, which delivers results by slicing with a focused ion beam. These three methods complement one another in many respects, e.g., in the type of materials that can be investigated, the resolution that can be obtained and the information that can be extracted from 3D reconstructions. A detailed review is given about preparation, the slice and view process itself, and the limitations of the methods and possible artifacts. Applications for each technique are also provided.     

应用隧道探索算法提取莫尔条纹偏移量

为了精确提取莫尔条纹偏移量,提出了隧道探索算法,并将其应用于实际莫尔条纹分析.使用双光栅产生莫尔条纹,抓拍多方向投影.应用数字图像处理技术,追踪分析实验莫尔条纹.首先,追踪各条纹的极大值分布,根据条纹极大值分布挖掘条纹隧道,调整挖掘宽度,即像素宽度,既实现隧道贯通,又不干预相邻条纹.然后,二值化莫尔图,噪声滤波,滤除条纹隧道壁上的噪声毛刺,使隧道壁趋于光滑.最后,根据两侧隧道壁的布局,探索条纹隧道走向,提取隧道走向数据,获得条纹偏移量.并进一步转换为偏折角,即光学计算机层析投影.应用非线性自适应迭代重建算法对偏折角进行迭代重建.结果发现,最高重建截面温度是492℃,额定电热器表面温度大约500℃,重建截面恰恰在电热器上表面上方,所以重建结果是有效的.     

Operando XAFS Imaging of Distribution of Pt Cathode Catalysts in PEFC MEA

Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs.