同步辐射讲座 第三讲 软X射线显微术

对生物样品的研究，软X射线显微术具有独特的优势，例如，它能够对较厚的活性含水的生物样品直接进行显微成像以及元素分布的微区分析等，文章简要论述了软X射线显微术的衬度机制及其优势；列表概括了包括SCXM，TXM，STXM，Gabor全息以及衍射等几种类型的X射线显微术的基本特性；简要综述了合肥国家同步辐射实验室（NSRL）软X射线显微术的研究进展。     

Microcrystallography, high-pressure cryocooling and BioSAXS at MacCHESS

The Macromolecular Diffraction Facility at the Cornell High Energy Synchrotron Source (MacCHESS) is a national research resource supported by the National Center for Research Resources of the US National Institutes of Health. MacCHESS is pursuing several research initiatives designed to benefit both CHESS users and the wider structural biology community. Three initiatives are presented in further detail: microcrystallography, which aims to improve the collection of diffraction data from crystals a few micrometers across, or small well diffracting regions of inhomogeneous crystals, so as to obtain high-resolution structures; pressure cryocooling, which can stabilize transient structures and reduce lattice damage during the cooling process; and BioSAXS (small-angle X-ray scattering on biological solutions), which can extract molecular shape and other structural information from macromolecules in solution.     

2016 Liquid Surface X-ray Scattering School: Data Analysis

X-ray surface scattering is the most powerful probe of near-atomic-level structure at liquid-vapor and liquid-liquid interfaces. Synchrotron X-ray sources throughout the world have specialized instruments available for the study of these interfaces. Since 2002, the ChemMatCARS facility at Sector 15 of the Advanced Photon Source near Chicago, IL, USA, has assisted general users in the study of liquid surfaces and interfaces to model processes of interest to physical, chemical, and biological scientists. ChemMatCARS recently sponsored its third School for Liquid Surface X-ray Scattering (LSXS 2016), held at the Advanced Photon Source (APS) at Argonne National Laboratory on May 12–13, 2016. Methods of data analysis were featured, providing students with the opportunity to fit data, analyze errors, and participate in virtual experiments. Techniques covered this year included X-ray reflectivity (XR), grazing incidence diffraction (GID), X-ray fluorescence near total reflection (XFNTR), and X-ray photon correlation spectroscopy (XPCS). This is the third year that the LSXS School has been held at APS, the first year being in 2007 and the second in 2012.     

Sound velocities of compressed Fe3C from simultaneous synchrotron X‐ray diffraction and nuclear resonant scattering measurements

The applications of nuclear resonant scattering in laser‐heated diamond anvil cells have provided an important probe for the magnetic and vibrational properties of ⁵⁷Fe‐bearing materials under high pressure and high temperature. Synchrotron X‐ray diffraction is one of the most powerful tools for studying phase stability and equation of state over a wide range of pressure and temperature conditions. Recently an experimental capability has been developed for simultaneous nuclear resonant scattering and X‐ray diffraction measurements using synchrotron radiation. Here the application of this method to determine the sound velocities of compressed Fe₃C is shown. The X‐ray diffraction measurements allow detection of microscale impurities, phase transitions and chemical reactions upon compression or heating. They also provide information on sample pressure, grain size distribution and unit cell volume. By combining the Debye velocity extracted from the nuclear resonant inelastic X‐ray scattering measurements and the structure, density and elasticity data from the X‐ray diffraction measurements simultaneously obtained, more accurate sound velocity data can be derived. Our results on few‐crystal and powder samples indicate strong anisotropy in the sound velocities of Fe₃C under ambient conditions.     

Amorphization of ice near the melting point

In addition to reflections of the hexagonal phase of ice I _h, the intense diffuse scattering of X-rays mainly due to the amorphization of ice is revealed on the X-ray diffraction patterns of water ice samples prepared at liquid nitrogen (studied by the authors earlier) and samples prepared at T = ?10°C (this work). The measurements are performed in the temperature range from ?25 to 0°C. The existence of reflections of the crystalline phase and intense diffuse scattering on the X-ray diffraction patterns makes it possible make a conclusion about the coexistence of crystalline and amorphous structures of ice. Splitting of the first maximum on the electron-density radial distribution function is detected on the basis of an X-ray diffraction pattern recorded at T = ?3°C. This splitting is explained by an increase in the interatomic distances between the nearest-neighbor atoms located at different levels. Similar splitting was also detected on a radial distribution function constructed using an X-ray diffraction pattern recorded at ?10°C.     

Synchrotron-based X-ray fluorescence,imaging and elemental mapping from biological samples

The present study utilized the new hard X-ray microspectroscopy beamline facility, X27A, available at NSLS, BNL, USA, for elemental mapping. This facility provided the primary beam in a small spot of the order of ∼10 μm, for focussing. With this spatial resolution and high flux throughput, the synchrotron-based X-ray fluorescent intensities for Mn, Fe, Zn, Cr, Ti and Cu were measured using a liquid-nitrogen-cooled 13-element energy-dispersive high-purity germanium detector. The sample is scanned in a ‘step-and-repeat’ mode for fast elemental mapping measurements and generated elemental maps at 8, 10 and 12 keV, from a small animal shell (snail). The accumulated trace elements, from these biological samples, in small areas have been identified. Analysis of the small areas will be better suited to establish the physiology of metals in specific structures like small animal shell and the distribution of other elements.     

Powder diffraction from a continuous microjet of submicrometer protein crystals

Atomic‐resolution structures from small proteins have recently been determined from high‐quality powder diffraction patterns using a combination of stereochemical restraints and Rietveld refinement [Von Dreele (2007), J. Appl. Cryst. 40 , 133–143; Margiolaki et al. (2007), J. Am. Chem. Soc. 129 , 11865–11871]. While powder diffraction data have been obtained from batch samples of small crystal‐suspensions, which are exposed to X‐rays for long periods of time and undergo significant radiation damage, the proof‐of‐concept that protein powder diffraction data from nanocrystals of a membrane protein can be obtained using a continuous microjet is shown. This flow‐focusing aerojet has been developed to deliver a solution of hydrated protein nanocrystals to an X‐ray beam for diffraction analysis. This method requires neither the crushing of larger polycrystalline samples nor any techniques to avoid radiation damage such as cryocooling. Apparatus to record protein powder diffraction in this manner has been commissioned, and in this paper the first powder diffraction patterns from a membrane protein, photosystem I, with crystallite sizes of less than 500 nm are presented. These preliminary patterns show the lowest‐order reflections, which agree quantitatively with theoretical calculations of the powder profile. The results also serve to test our aerojet injector system, with future application to femtosecond diffraction in free‐electron X‐ray laser schemes, and for serial crystallography using a single‐file beam of aligned hydrated molecules.     

Characterization of microporous aluminophosphate IST-1 using (1)H Lee-Goldburg techniques

The presence of two independent methylamine species in microporous aluminophosphate IST-1 (|(CH(3)NH(2))(4)(CH(3)NH(+)(3))(4)(OH(-))(4)|[Al(12)P(12)O(48)]) has been shown previously by synchrotron powder X-ray diffraction. One of these species, [N(1)-C(1)], links to a six-coordinated framework Al-atom [Al(1)], while the other methylamine [N(2)-C(2)] is protonated and hydrogen-bonded to three O-atoms [O(1), O(2) and O(12)]. We revisit the structure of IST-1 and report the complete assignment of the (1)H NMR spectra by combining X-ray data and high-resolution heteronuclear/homonuclear solid-state NMR techniques based on frequency-switched Lee-Goldburg homonuclear decoupling and (31)P-(31)P homonuclear recoupling. Careful analysis of the 2D (1)H-X homonuclear correlation (X=(1)H) and 2D heteronuclear correlation (X=(13)C, (31)P and (27)Al) spectra allowed the distinction of both methylamine species and the assignment of all (31)P and (13)C resonances. For the first time at a relatively high (9.4 T) magnetic field, symmetric doublet patterns have been observed in the (13)C spectra, caused by the influence of the (14)N second-order quadrupolar interaction.     

Recent developments of the Synchrotron Light source at NSRRC

Macromolecular crystallographic (MX) structure determination at synchrotron radiation sources has the potential to advance significantly through use of X-ray beams of one micron or smaller cross-sections. Recently, the MX Frontiers at the One Micron Scale Workshop explored structural biology scientific opportunities made possible through the use of micro-beams, and anticipated technical challenges for developers of MX beamlines at the National Synchrotron Light Source II (NSLS-II). More than 100 attendees participated in the workshop, which included one-and-a-half days of lectures, discussions, and a semi-formal poster session on July 23–24, 2009, at Brookhaven National Laboratory (BNL).     

Living on the K-edge: Resonant scattering studies of electronic order in transition metal compounds

Construction has begun on the National Synchrotron Light Source II (NSLS-II), a state-of-the-art, third-generation medium energy storage ring to be built at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory (BNL).     

Meeting Reports: BioCD-2005 Workshop

An intensive weeklong course on Circular Dichroism (CD) was presented at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL), from June 20-24, 2005. CD is the difference in absorption of left and right circularly polarized light. It is observed in the spectral regions of absorption of molecules that are chiral, i.e., lacking a center of symmetry. While most CD spectra are small—only a tiny fraction of the total absorption biopolymers with helical structures—such as proteins, DNA, RNA and polysaccharides, exhibit informative CD spectra. The objective of BioCD-2005 was to acquaint the participants with the theory of ultraviolet CD spectroscopy.     

高炉渣非晶态含量的定量分析方法研究

通过X-ray衍射方法对高炉渣中非晶态与晶态的含量进行了定量分析研究。定量分析过程包括标准样品制备、配样与衍射以及数据处理分析。数据处理包括非晶态衍射峰及晶态峰在一定衍射角度内的积分、线性拟合与定量系数确定。提出了X-ray衍射方法所用的高炉渣标准样品的制备方法,包括100％非晶态标样和100％晶态标样。提出了由100％非晶态和100％晶态为标准样品时,高炉渣中非晶态含量的测定方法,适用于非晶态含量较高(>80%)的高炉渣的定量分析。结合数学处理和X-ray衍射结果,可得到原始高炉渣中非晶态含量和晶态含量,以及相应的比例系数,适用于非晶态含量高的高炉渣(>90%)。     

Three-dimensional X-ray diffraction in the diamond anvil cell: application to stishovite

Three-dimensional X-ray diffraction can be used for characterizing the orientation, position, and strain tensor of single grains in a polycrystalline aggregate. Here, we show how the method is well suited for diamond anvil cell data with heterogeneous grain sizes, with an application to two samples of stishovite at 15 and 26 GPa. For each grain, we obtain a well-defined orientation matrix and cell parameters. Center of mass position can also be adjusted to the experimental data, with errors in the present experiment. Finally, strain tensors are adjusted for the individual grains. The stress distribution obtained is in agreement with expectations from the diamond anvil cell geometry and previous measurements of stishovite strength. Advantages and potential for improvement of the method are then discussed.     

EPR, X-ray, and magnetization studies of metastable alloys Ti2Fe, Al40Cu10Mn25Ge25 and Al65Cu20Fe15 as prepared by mechanical alloying

Mechanical alloying (MA) technique has been used to synthesize metastable alloys with nominal compositions Ti₂Fe (MA for 1, 5, and 26 h), Al₆₅Cu₂₀Fe₁₅ (MA for 26 and 34 h) and Al₄₀Cu₁₀Mn₂₅Ge₂₅ (MA for 42 h). These have been studied by EPR, X-ray diffraction, differential thermal analysis (Ti₂Fe only), and magnetization (Ti₂Fe only) techniques. X-ray diffraction provided information on transformation to metastable phases, while the EPR spectra gave insight into inequivalent paramagnetic transition metal sites in the alloys and the temperature variation of magnetic ordering of the samples. Magnetization data on Ti₂Fe system has been interpreted in terms of phase separations within the amorphous phase. It is concluded that MA process significantly influences the magnetic properties of the samples, wherein the duration of MA process plays an important role. The EPR and magnetization data indicate that the disorder of paramagnetic ions within the samples increases with increasing temperature.     

Performance calculations of the X‐ray powder diffraction beamline at NSLS‐II

The X‐ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source II is a multi‐purpose high‐energy X‐ray diffraction beamline with high throughput and high resolution. The beamline uses a sagittally bent double‐Laue crystal monochromator to provide X‐rays over a large energy range (30–70 keV). In this paper the optical design and the calculated performance of the XPD beamline are presented. The damping wiggler source is simulated by the SRW code and a filter system is designed to optimize the photon flux as well as to reduce the heat load on the first optics. The final beamline performance under two operation modes is simulated using the SHADOW program. For the first time a multi‐lamellar model is introduced and implemented in the ray tracing of the bent Laue crystal monochromator. The optimization and the optical properties of the vertical focusing mirror are also discussed. Finally, the instrumental resolution function of the XPD beamline is described in an analytical method.     

Strange hadron production in heavy ion collisions from SPS to RHIC

Strange particles have been a very important observable in the search for a deconfined state of strongly interacting matter, the quark–gluon plasma (QGP), which is expected to be formed in ultra-relativistic heavy ion collisions. We review the main experimental observations made at the Super Proton Synchrotron (SPS) at CERN, Geneva, and at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). The large amount of recently collected data allows for a comprehensive study of strangeness production as a function of energy and system size. We review results on yields, transverse mass and rapidity spectra, as well as elliptic flow. The measurements are interpreted in the context of various theoretical concepts and their implications are discussed. Of particular interest is the question whether strange particles are in any way sensitive to a partonic phase. Finally, a compilation of experimental data is provided.     

New products

Arosy future was forecast for Brookhaven National Laboratory's (BNL) user facilities at the first-ever joint meeting of the user communities for the National Synchrotron Light Source (NSLS) and the Center for Functional Nanomaterials (CFN), held May 15–17, 2006.     

High-entropy equiatomic AlCrFeCoNiCu alloy: Hypotheses and experimental data

Experimental data for the structural and phase transformations taking place in cast equiatomic AlCrFeCoNiCu alloy under slow cooling, melt quenching, and a number of thermal treatments are presented. Investigations are carried out by analytical transmission electron microscopy and scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray structural analysis, and X-ray diffraction analysis with the involvement of 3D atom probe tomography data, and nanohardness and elasticity modulus measurements. It is found that the as-cast alloy having a dendritic microstructure decomposes with the separation of at least six nanodimensional phases with different morphologies, structures (of type A2, B2, L1₂), and chemical compositions. It is also found that a homogeneous ultrafine-grained B2 structure arises in the alloy obtained by melt quenching. This structure decomposes into nanodimensional mainly equiaxial bcc phases, atomically ordered phases (B2), and atomically disordered ones (A2), all being highlighted by subsequent annealing.     

Investigation of Chinese word recognition scores of children in primary school classroom with different speech sound pressure levels

Chinese word recognition (CWR) test was conducted by grades 3 and 5 children under the different conditions of reverberation time (RT), background noise level (BNL) and speech sound pressure level (SSPL) in three primary-school classrooms. The CWR scores and signal to noise ratios (SNRs) have been obtained at listening positions. Results show that the CWR score for grades 3 and 5 children increases with increase of SSPL, decrease of RT or increase of age, but it decreases with increase of BNL under the same conditions. For a mixed noise of 56 dBA (speech-spectrum-like noise and ambient noise), the CWR scores in the classroom for grades 3 and 5 children reach a peak at SNR of 15–20 dBA under the same RT and age of children condition. For the natural ambient noise, the CWR score for grades 3 and 5 children gradually increases with increase of the SNR. The high SSPL could not guarantee good CWR for children in classroom, which also depends on RT and BNL in classroom. When the classroom has long RT or high BNL, the increase of SSPL would not be necessarily to achieve better CWR. The novelty of the present study is to further evaluate and confirm the results under environments of real classrooms (not simulated room in laboratory).     

The annealing effect on structural and optical properties of ZnO thin films produced by r.f. sputtering

In this work, a study of the structure and optical properties of undoped ZnO thin films produced by r.f. magnetron sputtering technique as a function of the growth parameters is reported. Modification under annealing conditions is also analysed. Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and optical transmittance have been used. From the position of the (002) X-ray diffraction peak and the E₂ (high) mode detected in Raman spectra, the residual stress both in the as-grown and in the annealed samples has been estimated.