Characterization of chevron-shaped permalloy magnetic memory elements by four magnetic imaging techniques

Scanning auger microscopy (SAM) and the recently developed scanning electron microscopy with polarization analysis (SEMPA) are easily combined analytical techniques which provide quantitative submicrometer images of X-, Y-, and Z-axis spin polarization components of magnetization. SAM/SEMPA, along with three established magnetic imaging techniques (Bitter colloidal, longitudinal magneto-optic Kerr microscopy, and the Fresnel mode of Lorentz microscopy), was used to characterize a chevron-shaped permalloy magnetic memory element. Reflected light and secondary electrons were used to image the topography. Auger electrons identified and imaged the elemental composition. Reflected light, transmitted electrons, and secondary electrons were used to image the magnetic microstructure. The Bitter colloidal images showed only the delineation of the domain walls, and the longitudinal magneto-optic Kerr microscopy images produced similar results. The Lorentz microscopy images provided the most qualitative magnetization information. SAM/SEMPA was the only technique to combine elemental information and quantitative magnetization information with images having submicrometer resolution.     

基于3线阵探测器的亚像元成像超分辨率重构

虽然增加探测器的时间和空间采样频率可以提高亚像元成像系统空间分辨率,但探测器采集到的数据易发生混叠,使重构得到的图像的分辨率无法达到理想值。本文以3片线阵探测器亚像元成像为基础,提出一种超分辨率重构算法。首先,在高分辨率网格上建立插值模型;然后,辨识插值重构图像在线阵列方向和扫描方向的模糊核,得到整幅图像的模糊核;最后,采用带有Neumman边界条件的梯度平滑正则化模型去除模糊,抑制振铃效应。实验结果表明,该算法使亚像元成像系统分辨率为单线阵探测器无过采样成像系统分辨率的2.6倍;与双线性插值法相比,平均灰度等级(GMG)提高了7.71。该算法可以进一步实现对更多片线阵探测器亚像元成像的超分辨率重构,获取更高的系统分辨率。     

Design of an active-passive device for human ankle movement during functional magnetic resonance imaging analysis

Functional magnetic resonance imaging analysis has made major strides in recent years, both because of the development of new scanners and owing to magnetic resonance compatible systems that make it possible to stimulate parts of the human body during analysis. The significant gains in our knowledge of the brain that can thus be achieved justify efforts to construct machines with control circuits suitable for this purpose. This paper presents a magnetic resonance compatible mechatronic device with electropneumatic control that can be used to move one or both feet during functional magnetic resonance imaging analysis of the cerebral motor zones. The system is innovative and original. The results obtained at the end of the investigation were good, and demonstrated that the design is feasible.     

Multiparametric high-resolution imaging of barley embryos by multiphoton microscopy and magnetic resonance micro-imaging

Nonlinear optical microscopy and magnetic resonance imaging (MRI) address different properties of the sample and operate on different geometrical scales. MRI maps density and mobility of molecules tracking specific molecular signatures. Multiphoton imaging profits from the nonlinear absorption of light in the focus of a femtosecond laser source stimulating the autofluorescence of biomolecules. As this effect relies on a high light intensity, the accessible field of view is limited, but the resolution is very high (a few hundred nanometers). Here, we aim to link the different accessible scales and properties addressed in the different techniques to obtain a synoptic view. As model specimen we studied embryos of barley. Multiphoton stimulated autofluorescence images and images of second harmonic generation are achieved even down to low magnification (10x), low numerical aperture (N.A. 0.25) conditions. The overview images allowed morphological assignments and fluorescence lifetime imaging provides further information to identify accumulation of endogenous fluorophores. The second, complementary contribution from high-resolution MR images provides a 3D model and shows the embedding of the embryo in the grain. Images of the proton density were acquired using a standard 3D spin-echo imaging pulse sequence. Details directly comparable to the low magnification optical data are visible. Eventually, passing from the MR images of the whole grain via low magnification to high resolution autofluorescence data bridges the scale barrier, and might provide the possibility to trace transport and accumulation of, e.g., nutrients from large structure of the plant to the (sub-) cellular level.     

脑功能的核磁共振成像

功能性磁共振成像技术是研究大脑认识思维活动过程的强有力工具。本文阐述了ｆＭＲＩ信号变化的物理基础和ｆＭＲＩ的成像新技术,分析了ｆＭＲＩ中的硬件特点,并展望了ｆＭＲＩ成像方法的前景。     

Unbiased estimation of human body composition by the Cavalieri method using magnetic resonance imaging

The classical methods for estimating the volume of human body compartments in vivo (e.g. skin-fold thickness for fat, radioisotope counting for different compartments, etc.) are generally indirect and rely on essentially empirical relationships — hence they are biased to unknown degrees. The advent of modern non-invasive scanning techniques, such as X-ray computed tomography (CT) and magnetic resonance imaging (MRI) is now widening the scope of volume quantification, especially in combination with stereological methods. Apart from its superior soft tissue contrast, MRI enjoys the distinct advantage of not using ionizing radiations. By a proper landmarking and control of the scanner couch, an adult male volunteer was scanned exhaustively into parallel systematic MR ‘sections’. Four compartments were defined, namely bone, muscle, organs and fat (which included the skin), and their corresponding volumes were easily and efficiently estimated by the Cavalieri method: the total section area of a compartment times the section interval estimates the volume of the compartment without bias. Formulae and nomograms are given to predict the errors and to optimize the design. To estimate an individual's muscle volume with a 5% coefficient of error, 10 sections and less than 10min point counting (to estimate the relevant section areas) are required. Bone and fat require about twice as much work. To estimate the mean muscle volume of a population with the same error contribution, from a random sample of six subjects, the workload per subject can be divided by √6, namely 4 min per subject. For a given number of sections planimetry would be as accurate but far more time consuming than point counting.     

肉芽肿性乳腺炎与乳腺浸润性导管癌的磁共振鉴别诊断

目的 :总结肉芽肿性乳腺炎与乳腺浸润性导管癌的鉴别诊断依据。方法 :回顾性分析经病理证实的37例肉芽肿性乳腺炎与62例乳腺浸润性导管癌患者的临床资料,所有患者磁共振成像(MRI)及扩散加权成像(DWI)资料均保存完整。将肉芽肿性乳腺炎、乳腺浸润性导管癌患者分别纳入肉芽肿性乳腺炎组、乳腺浸润性导管癌组,使用χ2检验对比两组常规MRI、增强MRI图像特点,使用t检验对比两组动态增强扫描参数以及表观弥散系数(ADC)值,总结肉芽肿性乳腺炎与乳腺浸润性导管癌的鉴别诊断思路。结果 :肉芽肿性乳腺炎与乳腺浸润性导管癌病灶象限分布、边缘、强化特点比较,差异有统计学意义(P <0.05)。肉芽肿性乳腺炎病灶早期强化率(EER)、峰值强化率(Emax)及ADC值均高于乳腺浸润性导管癌病灶,差异有统计学意义(P<0.05)。结论 :肉芽肿性乳腺炎与乳腺浸润性导管癌的临床与常规MRI表现存在一定相似之处,综合分析病灶象限分布、边缘、强化特点,以及动态增强扫描参数、ADC值,可进行鉴别诊断。     

Flow dynamics of magnetorheological fluids in throttle channels under external magnetic fields

We consider the results of our experimental studies of the throttling of magnetorheological fluids saturated with ferrous and ferric iron oxides, FeOFe₂O₃, through a channel of a rectangular cross section under normally directed quasi-stationary magnetic fields. We analyze the data obtained by taking into account previously constructed physical models for the dynamical processes of interaction between ferruginous solutions and external magnetic fields.     

交变/旋转磁场下焊接缺陷磁光成像检测与分类

针对任意角度焊接缺陷难以检测的问题,研究在不同磁场激励下焊接缺陷磁光成像无损检测系统。重点介绍了由U形磁轭产生的交变磁场和平面交叉磁轭产生的旋转磁场激励焊件的机理,比较了交变/旋转磁场激励下不同焊接缺陷的磁光成像效果。基于法拉第旋转效应分析磁光成像特性与磁场强度之间的关系,磁光图像的灰度值可以匹配相应的漏磁场强度。采用主成分分析法提取融合图像列像素灰度特征和通过灰度共生矩阵提取磁光图像纹理特征,建立BP神经网络模型和支持向量机模型识别这些缺陷特征。试验结果表明,在旋转磁场激励下,BP神经网络模型和支持向量机模型的分类精度分别为94.1%和98.6%,相比交变磁场,分类精度分别提高了10.7%和8.5%。旋转磁场激励下的磁光成像克服了定向检测的局限性,能够实现对任意角度焊接缺陷的检测及分类。     

Micro machining of an STS 304 bar by magnetic abrasive finishing

A magnetic abrasive finishing process is a method of non-traditional precision machining in which the finishing process is completed using magnetic force and magnetic abrasives. In this research, a STS 304 cylindrical workpiece was finished using a magnetic abrasive finishing process at 30,000 rpm, and the roughness, roundness, and changes in the micro-diameter were investigated. The study showed that it is possible to control the micro-diameter and weight of the STS 304 cylindrical workpiece by using a near linear approach. Surface roughness as fine as 0.06 μm (Ry) and roundness as fine as 0.12 μm (LZS) were achievable by using a diamond paste with 1 μm particles. Vibrational motion applied to the workpiece improved the surface roughness. The improvement of the surface roughness was achieved because the vibrational motion effectively removes unevenness in the rotational direction and the direction orthogonal to it. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Dae-Eun Kim Ik-Tae Im received the B.S., M.S. and Ph.D. degrees in Mechanical Engineering from Hanyang University, Seoul, Korea, in 1993, 1995 and 1999, respectively. He has been a visiting scientist at the Department of Materials Engineering, the University of Tokyo, Japan, where he studied on the film growth during the MOCVD process. His research interests include the numerical modeling on the transport phenomena in various materials processing. He is a professor at the Division of Mechanical Design Engineering at Chonbuk National University in Jeonju, Korea. Sang Don Mun received the B.S. degree and M.S. in Precision Mechanical Engineering from Chonbuk National University, Korea, in 1991 and 1993, respectively. He then received the Ph.D. in Precision Mechanical Engineering at the same university in 1997. Dr. Mun is currently a Professor at the Division of Mechanical Design Engineering at Chonbuk National University in Jeonju, Korea. His research interests include magnetic abrasive finishing, tool wear, and micro machining. Seong Mo Oh received his B.S. degree in Mechanical Engineering from Wonkwang University, Korea, in 1992. He then received his M.S. and Ph.D. degrees from Wonkwang in 1994 and 2000 respectively. Dr. Oh is currently a Lecturer at the Division of Mechanical and Automotive Engineering at Wonkwang University in Jeonbuk, Korea. Dr. Oh’s research interests include tribology, functional surfaces, and micromachining.     

Near-field imaging of ultrathin magnetic films with in-plane magnetization

A new approach to near‐field magneto‐optical imaging was developed capable of visualization of in‐plane magnetization of ultrathin magnetic structures. The approach relies on the magneto‐optical effect specific for thin magnetic layers and employs near‐field transmission measurements of longitudinal and/or transverse magneto‐optical effect arising from the presence of thin film interfaces. The near‐field magneto‐optical contrast of in‐plane domain structure of ultrathin Co film has been demonstrated in different polarization configurations.     

基于磁阻原理非接触式位移测量的非线性方法

针对低功耗和非接触式位移测量的应用需求，利用磁阻传感器，本文在传统的线性测量方法的基础上，提出了一种非线性的测量方法。设计了一个测量系统，实测结果表明该方法测量精度高、测量范围广、简单易用，也节省了成本。     

A versatile pulse programmer for magnetic resonance imaging

Hardware and software solutions for a versatile pulse programmer have been presented. The core of the pulse programmer is an FPGA device that provides flexibility to the design and reduces the number of electronics elements needed. The event of the pulse programmer consists of 16 bits. The main feature of the proposed pulse programmer is that the 16 outputs can be independently delayed. This is important for correcting delays of the RF channels or the gradient channels due to various causes. The proposed pulse programmer is integrated into an MRI scanner, and the correction of the gradient system delay is taken as an example to experimentally demonstrate its performance.     

几种磁共振成像技术的相关性

本文从理论上对磁共振成像的三种最基本的成像技术进行研究,得到在一定条件下它们之间的相关性,这对磁共振成像的临床工作及其理论研究都有一定的参考价值。     

Rapid single‐molecule imaging in cyclic olefin copolymer channels

Rapid preparation of high quality capture surfaces is a major challenge for surface‐based single‐molecule protein binding assays. Here we introduce a simple method to activate microfluidic chambers made from cyclic olefin copolymer for single‐molecule imaging with total internal reflection fluorescence microscopy. We describe a surface coating protocol and demonstrate single‐molecule imaging in off‐the‐shelf microfluidic parts that can be activated for binding assays within a few minutes. As the first example, biotinylated protein directly captured on the neutravidin‐coated surface was detected using fluorescently labeled antibody. We then showed detection of a fusion construct containing green fluorescence protein and verified its single fluorophore behavior by observing stepwise photobleaching events. Finally, a target protein was identified in the crude cell lysate using antibody–sandwich complex formation. In all experiments, controls were completed to ensure that nonspecific binding to the surface was minimal. Based on our results, we conclude that the simple surface preparation described in this paper enables single‐molecule imaging assays without time‐consuming coating procedures. Microsc. Res. Tech. 78:309–316, 2015. © 2015 Wiley Periodicals, Inc.     

体三维成像的螺旋扫描系统设计

提出了一种可产生稳定、均匀的投影空间,并由伺服电机驱动阶梯轴,带动屏旋转的双螺旋屏扫描系统,以实现体三维实时、高清晰成像。对比分析了扫描屏结构的成像特点,设计了屏结构的加工方案。采用半透明高强度的光敏树脂材料和缕空支撑墙体快速成型直接制造。通过Solidworks软件进行螺旋扫描屏的三维建模,并利用COSMOSWorks模块进行稳定运行的可行性分析。仿真结果显示,屏在600r/min恒速旋转时产生的最大位移数据为0.013mm,远小于人眼视觉可分辨的范围,可以满足成像空间设计需求。最后,结合现有的工程技术与工艺水平,建立了双螺旋屏扫描系统的物理平台。实验结果表明,该螺旋屏扫描系统形成的25cm×Ф50cm的柱型成像空间,可以呈现出清晰的体三维图像。     

Atomic and magnetic force microscopy imaging of thin-film recording heads

Investigations on the use of the scanning probe microscope (SPM) in the atomic force microscopy (AFM) mode for topography imaging and the magnetic force microscopy (MFM) mode for magnetic imaging are presented for a thin-film recording head. Results showed that the SPM is suitable for imaging the surface profile of the recording head, determining the width of the pole gap region, and mapping the magnetic field patterns of the recording head excited under current bias conditions of different polarity. For the cobalt sputter-coated tips used in MFM imaging, it was found that the magnetic field patterns obtained under different polarities of the current bias to the recording head were similar. This can be explained by the nature of the thin-film MFM tip, in which the direction of the tip magnetic moment can follow the stray magnetic field of the sample as the current bias to the recording head reverses in direction.     

核磁共振兼容手术机器人的驱动方式分析

核磁共振兼容手术机器人的驱动问题是研究图像导航手术机器人的一个重要内容。首先分析了核磁共振兼容手术机器人存在的问题,介绍了国内外研究者关于核磁共振兼容手术机器人驱动方式的使用情况,探讨了各种驱动方式的特点,得出了各项驱动方式在核磁共振环境下的使用性能,并对其发展方向作出了展望。