Quantitative evaluation on 3D fetus morphology via X-ray grating based imaging technique

Synchrotron-based X-ray phase sensitive micro-tomography techniques enable to visualize detailed three-dimensional (3D) insight into nondestructive inner-structure of biomedical samples. Different phase sensitive mechanisms have been employed for discrimination of tissue's tiny density variations in biomedical research. We effectively visualized and analyzed the phase-contrast experimental results of X-ray grating-based imaging, based on grating interferometry with phase stepping, by using transgenic mouse fetus. We quantitatively measured and evaluated the contrast-to-noise ratio or the mass density resolution, spatial resolution, radiation dose, and figure of merit of X-ray grating-based imaging technique in biomedical research respectively. Moreover, the complex coherent degrees of light source were duly taken into account in the analysis of spatial resolution. In addition, the mass density distribution of soft biomedical specimens can be estimated using our presented method preliminarily. For most soft tissue and organ observation, this work provides explicit guidelines to help future synchrotron users obtain the quantitative image information, suitable for their specific biomedical research.     

In-situ preparation of binary-phase silver nanoparticles at a high Ag+ concentration

Stable and monodisperse silver nanoparticles (NPs) have been synthesized using high metal salt concentration (up to 0.735 M) through a simple but novel technique. It is based on one-step procedure that uses glycerol for reducing Ag+ in the presence of o-phenylenediamine (o-PDA) resulting the nanoparticles are in two forms (one water-soluble, the other a precipitated). The water-soluble phase contains NPs that have a bimodal size distribution (2-3 and 5-6 nm); the other comprises precipitated NPs, having a unimodal size distribution (2-3 nm). The water-soluble NPs are covalently bonded to the aromatic amine molecules to form isolated units, while the precipitated nanoparticles are embedded in the networks formed by cross-linking between COOH groups of hydroxypyruvic acid (oxidized form of glycerol) and NH2 groups of o-PDA molecules. We used transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) to characterize the silver products obtained.     

含钛氧化物弥散强化钢的微观组织和力学性能

采用粉末冶金工艺制备了含Ti氧化物弥散强化钢。使用电子背散射衍射方式研究了这种钢的晶粒形貌,使用透射电镜和高分辨率透射电镜表征了钢中析出相的形貌及种类,使用以同步辐射装置作为光源的小角度X射线散射技术和X射线吸收精细结构技术研究了钢中纳米尺寸析出相的分布特征和氧化物弥散强化钢中Y元素的存在形式,并测量了钢的力学性能。结果表明,含Ti氧化物弥散强化钢的晶粒多呈等轴状、平均晶粒尺寸为1.24 μm。钢中富Y、Ti、O纳米尺寸析出相的分布密度为1.39×10²⁴/m³,平均直径为2.23 nm。向材料中添加Ti元素改变了材料中Y原子的存在形式,生成了具有烧绿石结构的Y₂Ti₂O₇相和少量的富Cr、Mn相。这种钢的室温抗拉强度达到1324 MPa,随着测试温度的提高抗拉强度逐渐降低,延伸率逐渐提高。     

Electrodeless growth of silver iodide nanowires in a polycarbonate membrane using chemical reaction

We report the fabrication, structural and optical characterization of Silver iodide (AgI) nanowires. Large scale uniform nanowires with lengths 40 m and diameter 100 nm were grown using the simple chemical reaction technique. Morphological study of AgI nanowires was done using scanning electron microscopy. X-ray diffraction studies show the crystalline structure of AgI nanowires. Energy dispersive X-ray fluorescence technique was used to study the composition of AgI nanowires. UV–Vis absorption studies were made to calculate the optical band gap of AgI nanowires. Photo-luminescence spectrum shows a broad emission peak around 460 nm.     

Analysis of the structure and deformation of a woven composite lamina using X-ray microdiffraction

X-ray diffraction (XRD) is an important tool for studying multiphase materials because it can resolve parameters from each phase independently. When coupled with a high-flux, microfocussed X-ray beam, scanning microdiffraction experiments are possible. This technique can investigate how reciprocal-space parameters vary as a function of real-space sample geometry for heterogeneous materials. Consequently, multiphase materials can be imaged in terms of those parameter variations. This study reports on the use of microfocussed X-ray diffraction (μXRD) to both image and follow the deformation of a multiphase material. In this case, this technique is applied to the study of a woven fibre-reinforced composite (FRC) lamina. Such systems are difficult to study with other experimental techniques because the fibres are inaccessible and the matrix is often opaque. However, using μXRD it is possible to assess both sample geometry and stress field information simultaneously.     

Quantification of compaction-induced crystallinity reduction of a pharmaceutical solid using 19F solid-state NMR and powder X-ray diffraction

¹⁹F solid-state nuclear magnetic resonance (NMR) was investigated as an analytical technique to quantify the amorphous phase in a fluorine-containing pharmaceutical candidate. The crystallinity of Compound 1 was calculated using two ¹⁹F T₁ relaxation-based methods. The first method employs both the pure amorphous and the crystalline reference standards while the second method is model independent and utilizes a single standard. The ¹⁹F solid-state NMR results were confirmed with powder X-ray diffraction methods. From X-ray diffraction data, two linear calibration curves were obtained from blends of crystalline and amorphous Compound 1: one is based on the total integrated intensity of selected diffraction peaks and the other on the total intensity of the amorphous halo at 2θ positions that have no interference from crystalline diffraction peaks. The crystallinity of Compound 1 after compaction calculated by both ¹⁹F solid-state NMR methods was in excellent agreement with the results from the X-ray calibration curves. ¹⁹F solid-state NMR was shown to be a powerful technique in determining the amount of amorphous phase present in a pharmaceutical solid.     

Transition from screen-film to computed radiography in a paediatric hospital: the missing link towards optimisation

In paediatrics, the risks associated with ionising radiation should be a major concern, due to children's higher susceptibility to radiation effects. Measure entrance skin dose (ESD) in chest and pelvis X-ray projections and compare the results with the 'European guidelines on quality criteria for diagnostic radiographer images in paediatrics' in order to optimise radiological practice. ESD values were obtained using an ionisation chamber Diamentor M4 KDK (PTW) in 429 children, who underwent chest X-ray or pelvis X-ray in a Computed Radiography system. In the first phase of the study, data were collected according to protocols used in the department; in a second phase different tube voltage values were used according to patient weight. A third phase was carried out, only for chest X-ray, using the exposure parameters of phase 2, plus activating lateral ionisation chamber. Three paediatric radiologists blindly assessed image quality of chest X-ray, using a validated assessment available in the 'European guidelines on quality criteria for diagnostic radiographer images in paediatrics'. Considering all the patients submitted to chest X-ray, the average ESD was 0.22, 0.16 and 0.08 mGy, for phases 1, 2 and 3, respectively. For pelvis X-ray, the average ESD decreased from 1.18 mGy in phase 1 to 0.78 mGy in phase 2. Dose optimisation was achieved. ESD was reduced 63.6 and 33.9 % in chest and pelvis X-ray, respectively.     

Fringe pattern demodulation with a two-frame digital phase-locked loop algorithm

A novel technique called a two-frame digital phase-locked loop for fringe pattern demodulation is presented. In this scheme, two fringe patterns with different spatial carrier frequencies are grabbed for an object. A digital phase-locked loop algorithm tracks and demodulates the phase difference between both fringe patterns by employing the wrapped phase components of one of the fringe patterns as a reference to demodulate the second fringe pattern. The desired phase information can be extracted from the demodulated phase difference. We tested the algorithm experimentally using real fringe patterns. The technique is shown to be suitable for noncontact measurement of objects with rapid surface variations, and it outperforms the Fourier fringe analysis technique in this aspect. Phase maps produced withthis algorithm are noisy in comparison with phase maps generated with the Fourier fringe analysis technique.     

Nanophase Decomposition of a Zn-Al Based Alloy Zn¬68Al¬10Cu¬22

The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn¬68Al¬10Cu¬22 in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin films of the Zn-Al based alloy were produced by using an electron beam deposition technique. It was found that a nanocrystalline phase ηn' had a strong preferred crystal orientation at (0002) crystal planes in the as-deposited films. During ageing at 220℃, the decomposition of nanophase ηn' started with clustering to form Z-zones, and transitional phase, which was accompanied by an eutectoid decomposition of the ηn' phase: ηn' →βeut'+T'. Decomposition, such as clustering and the formation of the Z-zones, and the transitional phase etc. were observed in the nanophaseβeut'. The formation and the decomposition of the transitional phase of micrometers in size were involved in the decomposition of the main nanophase ηn'. The mechanism of the Z-zones formation and the stability of nanophases were discussed.     

Tomographic imaging of an ultrasonic field in a plane by use of a linear array: theory and experiment

Quantitative ultrasonic characterization of in-homogeneous and anisotropic materials is often difficult due to undesired phenomena such as beam steering and phase aberration of the insonifying field. We introduce a method based on tomographic reconstruction techniques for the visualization of an ultrasonic field using a linear array rotated in a plane. Tomographic reconstruction of the ultrasonic field is made possible through the phase-sensitive nature of the tall, narrow piezoelectric elements of a linear array that act as parallel line integrators of the pressure field. We validate the proposed imaging method through numerical simulations of propagated ultrasonic fields based upon the angular spectrum decomposition technique. We then demonstrate the technique with experimental measurements of two textile composites and a reference water path. We reconstruct images of the real and imaginary parts of a transmitted 2 MHz ultrasonic field that are then combined to reconstruct images of the power and unwrapped phase. We also construct images of the attenuation and phase shift for several regions of the composites. Our results demonstrate that tomographic imaging of an ultrasonic field in a plane using a rotated linear array can potentially improve ultrasonic characterization of complex materials.     

Coherent diffractive imaging using short wavelength light sources

Techniques that recover images from diffraction data obtained using coherent short-wavelength light sources are currently under active development for applications in nanotechnology and structural biology. In this review, an outline of paraxial optics is provided in a form that is sufficiently general to incorporate the coherence properties and frequency structure of illumination sources used in diffractive imaging applications. The Fourier phase problem is formulated in the context of imaging algorithms that are designed to obtain uniquely-determined phase distributions from measurements of diffraction data. The properties of several iterative phase retrieval algorithms for both coherent and partially-coherent diffractive imaging applications are presented in a unified formalism, together with a brief discussion of a non-iterative technique. Approaches to diffractive imaging based on Fraunhofer and Fresnel diffraction configurations are compared. Applications are described utilising quasi-monochromatic third-generation synchrotron X-ray sources and polychromatic high-harmonic generation table-top soft X-ray sources. The review concludes with a consideration of proposed applications of diffractive imaging approaches to the determination of biomolecular structures from isolated molecules using fourth-generation X-ray free-electron laser sources.     

Evaluation of changes in X-ray elastic constants and residual stress as a function of cold rolling of austenitic steels

Abstract

Austenitic steels rapidly attain high mechanical strength when subjected to cold working. The heterogeneous plastic deformation produced in cross section of the specimen, development of preferred orientation and martensitic transformation contribute to the occurrence of residual stress in cold worked steels. AISI 304 and 316 steels were cold rolled at room temperature from 10% up to 70% deformations in steps of 10%. The formation and sigmoidal growth of martensite caused by cold rolling (CR) 304 steel was studied by X-ray diffraction. The residual stresses generated were evaluated in both the austenite and martensite phases using sin² ψ technique. The accurate determination of residual stress by X-ray diffraction requires experimental determination of X-ray elastic constants for both the austenite and martensite phases. The changes in X-ray elastic constants as a function of CR of 304 and 316 steels were measured and their effect on residual stress values was established. The results show that tensile stress was generated initially on cold working in the austenite phase in both steels and in the dominant martensite phase in 304 steel, which decreases, passes through zero and becomes compressive at higher deformations. X-ray elastic constants were found to decrease in all cases and a maximum reduction of 15% was found.     

The use of Ce(fod)4 as a precursor for the growth of ceria films by metal-organic chemical vapour deposition

We report the growth of thin films of cerium oxide using the metal-organic chemical vapour deposition (MOCVD) technique. The homoleptic complex, Ce(fod)₄, where fod-H is 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione, was used as a precursor. Silicon wafers with a (100) orientation were used as substrates. This work can be considered a feasibility study of this precursor as a potential source of ceria for the eventual production of solid solutions with a stoichiometry of Ce_0.9Gd_0.1O_1.95. These ceramic films are intended for use as electrolytes in solid oxide fuel cells (SOFCs). In this paper, the difficulties associated with CVD growth of oxide films using solid phase precursors such as Ce(fod)₄ which contain fluorinated ligands are discussed as well as the methods used to eliminate such problems. The variation of important CVD parameters such as moist oxygen flow rate are discussed in terms of their effect on the growth rate and the elemental composition of the deposited films. Analysis was carried out using techniques such as scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray fluorescence.     

利用Rietveld方法Y_2O_3稳定ZrO_2的定量相分析

利用多相混合物中某相的重量与它在Rietveld结构修正中求得的标度因子之间的关系，可以进行多相混合物的定量分析[1].本工作利用Rietveld修正和X射线步长扫描衍射数据对不同浓度Y2O3掺杂的ZrO2试样进行了相含量的定量分析，给出了各相含量的定量数据，同时还证实了由研磨引起四方相向单斜相转变的规律.     

利用Rietveld方法的多相粉末定量分析

利用Ｘ射线步长扫描衍射数据和全图谱（Ｗｈｏｌｅ－ｐａｔｔｅｒｎ）拟合技术（Ｒｉｅｔｖｅｌｄ方法），通过相含量和Ｒｉｅｔｖｅｌｄ修正中标度因子之间存在的简单关系，对包含不同重量的水晶和刚玉粉末的混合物样品进行了相含量的定量分析。求得的结果与原始配比一致，说明这一技术可以有效地用于多相粉末，尤其是衍射图谱严重重叠样品的定量分析研究。     

Pressure-jump X-ray studies of liquid crystal transitions in lipids

In this paper, we give an overview of our studies by static and time-resolved X-ray diffraction of inverse cubic phases and phase transitions in lipids. In [section sign] 1, we briefly discuss the lyotropic phase behaviour of lipids, focusing attention on non-lamellar structures, and their geometric/topological relationship to fusion processes in lipid membranes. Possible pathways for transitions between different cubic phases are also outlined. In [section sign] 2, we discuss the effects of hydrostatic pressure on lipid membranes and lipid phase transitions, and describe how the parameters required to predict the pressure dependence of lipid phase transition temperatures can be conveniently measured. We review some earlier results of inverse bicontinuous cubic phases from our laboratory, showing effects such as pressure-induced formation and swelling. In [section sign] 3, we describe the technique of pressure-jump synchrotron X-ray diffraction. We present results that have been obtained from the lipid system 1:2 dilauroylphosphatidylcholine/lauric acid for cubic-inverse hexagonal, cubic-cubic and lamellar-cubic transitions. The rate of transition was found to increase with the amplitude of the pressure-jump and with increasing temperature. Evidence for intermediate structures occurring transiently during the transitions was also obtained. In [section sign] 4, we describe an IDL-based 'AXcess' software package being developed in our laboratory to permit batch processing and analysis of the large X-ray datasets produced by pressure-jump synchrotron experiments. In [section sign] 5, we present some recent results on the fluid lamellar-Pn3m cubic phase transition of the single-chain lipid 1-monoelaidin, which we have studied both by pressure-jump and temperature-jump X-ray diffraction. Finally, in [section sign] 6, we give a few indicators of future directions of this research. We anticipate that the most useful technical advance will be the development of pressure-jump apparatus on the microsecond time-scale, which will involve the use of a stack of piezoelectric pressure actuators. The pressure-jump technique is not restricted to lipid phase transitions, but can be used to study a wide range of soft matter transitions, ranging from protein unfolding and DNA unwinding and transitions, to phase transitions in thermotropic liquid crystals, surfactants and block copolymers.     

Simulation studies of atomic resolution X-ray holography

X-ray holography is a new method of structure determination based on measurement of interference of a known reference wave with an unknown object wave (containing information on atomic sites scattering the reference wave) so that phase information is preserved. Unlike X-ray diffraction, it does not demand for translational periodicity in the material. It is based on the idea similar to that of optical holography and has been tested on crystals, quasicrystals, thin films and doped semiconductors for their structure determination. In order to analyse potentials and limitations of this technique, we have carried out theoretical simulation studies on simple structures. In this paper we describe the basic algorithm of hologram generation and reconstruction of atomic positions from generated data. We illustrate this technique using Fe (bcc) single crystal as sample case to demonstrate its capabilities and limitations. Simulations were carried out on the Cu (fcc) structure and on complex structure such as the Al-Pd-Mn quasicrystal. Technical issues such as low signal to noise ratio, twin image problem etc have been discussed briefly to emphasize the need for high intensity X-ray source such as synchrotron for experiments and proper reconstruction algorithm. Finally the scope and potential of this technique have been discussed.     

合金化热镀锌镀层组织Γ相的结构分析

为了研究合金化热镀锌镀层组织Γ相的结构,采用聚焦离子束(FIB)方法制备了合金化热镀锌无间隙原子(IF)钢板镀层横截面透射电镜(TEM)试样,应用TEM对其显微结构进行了观察和选区电子衍射分析,应用X射线能谱仪(EDX)测定了Γ相的化学成分,并介绍了FIB方法制备TEM试样的过程.结果表明,Γ相选区衍射花样中存在明显的超点阵衍射.证明Γ相是一种有序金属间化合物;计算机模拟电子衍射花样的结果给出了Γ相的原子占位.     

Interferometric phase reconstruction by nonuniform shifting of the reference beam

A method for phase measurement in common-path interferometers, believed to be novel, is presented. We use the property of phase reconstruction algorithms, such as the Carré and Hariharan algorithms, that do not require uniform phase across the reference beam. Only the ratio of the phase steps must be the same at each pixel. We show phase measurement and reconstruction in a common-path interferometer by shifting either the tilt or the focus of the reference wave front. We present a theoretical explanation of phase measurement using this property. We also present results from a proof-of-principle experiment using a scatterplate interferometer, in conjunction with the tilt phase-shifting technique, to measure the reflected phase of a test optical element. Furthermore, we present a computer simulation to demonstrate the mathematical validity of this measurement technique using defocus shifting, rather than tilt shifting, in the reference wave front.     

MLEM deconvolution of protein X-ray diffraction images based on a multiple-PSF model

In this paper we analyze the degradation of protein X-ray diffraction images by diffuse light distortion (DLD). In order to correct the degradation, a new multiple point spread function (PSF) model is introduced and used to restore X-ray diffraction image data (XRD). Raw PSFs are collected from isolated spots in high-resolution areas on the diffraction patterns which represent the orientation of DLDs. An adaptive ridge regression (ARR) technique is used to remove noise from the raw PSF data. A target Gaussian function is used to model the raw PSFs. A maximum likelihood expectation maximization (MLEM) algorithm combined with a multi-PSF model is employed to restore high intensity, asymmetrical protein X-ray diffraction data. Experimental results using a single and multiple PSFs are presented and discussed. We show that using a multiple PSF model in the deconvolution algorithm improved the quality of the XRD and as a result the spot integration error (/spl chi//sup 2/) and corresponding electron density map are improved.