Design and Performance Evaluation of Low‐Volume PM2.5 Inlet for Analyzing Chemical Composition

A new PM_2.5 inlet, based on the particle cup impactor configuration, was designed for sampling fine particles smaller than 2.5 μm in aerodynamic diameter and for operating at a flow rate of 5 l/min, as the devices, which are used to analyze the chemical composition of the particles, have good efficiency only at low‐volume flow rates. The performance of the inlet was evaluated in a test chamber, and the optimum dimensions of the particle cup impactor were determined by varying the nozzle‐to‐cup distance. Additional experiments covering flow rates between 3 and 10 l/min with particle sizes between 0.8 and 5.0 μm were carried out in the test chamber. The performance indicated that a nozzle‐to‐cup distance of 1.1 mm would yield a sharp size cutoff. The results from the tests showed that the inlet had a cutoff size of 2.55 μm in aerodynamic diameter at a flow rate of 5 l/min.     

Simultaneous small‐ and wide‐angle scattering at high X‐ray energies

Combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) is a powerful technique for the study of materials at length scales ranging from atomic/molecular sizes (a few angstroms) to the mesoscopic regime (～1 nm to ～1 µm). A set‐up to apply this technique at high X‐ray energies (E > 50 keV) has been developed. Hard X‐rays permit the execution of at least three classes of investigations that are significantly more difficult to perform at standard X‐ray energies (8–20 keV): (i) in situ strain analysis revealing anisotropic strain behaviour both at the atomic (WAXS) as well as at the mesoscopic (SAXS) length scales, (ii) acquisition of WAXS patterns to very large q (>20 Å^?1) thus allowing atomic pair distribution function analysis (SAXS/PDF) of micro‐ and nano‐structured materials, and (iii) utilization of complex sample environments involving thick X‐ray windows and/or samples that can be penetrated only by high‐energy X‐rays. Using the reported set‐up a time resolution of approximately two seconds was demonstrated. It is planned to further improve this time resolution in the near future.     

Time‐resolved free carrier lifetime microscopy in bulk GaN

A novel setup for lifetime microscopy measurements was designed and applied for carrier lifetime mapping in a bulk GaN. Photoexcitation by a picosecond UV pump and detection of time‐resolved free carrier absorption (FCA) images on a CCD camera enabled the mapping of carrier lifetime distribution with a spatial resolution of 5 μm. The spatial variation of lifetime in the bulk HVPE‐grown GaN revealed the presence of different‐size crystalline grains, with lifetime peaking up to 70 ns in the centers of the largest grains (～20 μm in diameter) and dropping to 10 ns in the small ones, while the spatially averaged lifetime was 40 ns. The inhomogeneity was ascribed to the interplay of nonradiative diffusion‐limited recombination at grain boundaries and a bulk lifetime in the crystallite centers. The numerical solution of spatially‐resolved carrier decay rate in the crystallite centers at high injection levels and comparison with experimental data provided a bulk nonradiative recombination time of ～70 ns. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Full‐field X‐ray reflection microscopy of epitaxial thin‐films

Novel X‐ray imaging of structural domains in a ferroelectric epitaxial thin film using diffraction contrast is presented. The full‐field hard X‐ray microscope uses the surface scattering signal, in a reflectivity or diffraction experiment, to spatially resolve the local structure with 70 nm lateral spatial resolution and sub‐nanometer height sensitivity. Sub‐second X‐ray exposures can be used to acquire a 14 µm × 14 µm image with an effective pixel size of 20 nm on the sample. The optical configuration and various engineering considerations that are necessary to achieve optimal imaging resolution and contrast in this type of microscopy are discussed.     

Natural water specimen preparation for TXRF analysis using a Johansson wavelength‐dispersive spectrometer

A special method of specimen preparation is described aimed at achieving a small size of the order of 50 µm. The difficulty is especially great when preparing droplet residues from natural water on a silicon wafer as a supporting material for this experiment. We report the first promising results using an HF etching method to obtain a hydrophobic silicon surface. A specimen (residue) size of ～ 80 µm was obtained on the modified silicon surface, making wavelength‐dispersive total reflection x‐ray fluorescence (WD‐TXRF) analysis possible for a standard reference sample of natural water (TMDA 53.2). Copyright © 2004 John Wiley & Sons, Ltd.     

A broadband,quasi‐continuous,mid‐infrared supercontinuum generated in a chalcogenide glass waveguide

The production of a broadband supercontinuum spanning from 1.8 μm to >7.5 μm is reported which was created by pumping a chalcogenide glass waveguide with ≈320 fs pulses at 4 μm. The total power was ≈20 mW and the source brightness was 100 that of current synchrotrons. This source promises to be an excellent laboratory tool for infrared microspectroscopy.     

Mini‐beam collimator enables microcrystallography experiments on standard beamlines

The high‐brilliance X‐ray beams from undulator sources at third‐generation synchrotron facilities are excellent tools for solving crystal structures of important and challenging biological macromolecules and complexes. However, many of the most important structural targets yield crystals that are too small or too inhomogeneous for a `standard' beam from an undulator source, ～25–50 µm (FWHM) in the vertical and 50–100 µm in the horizontal direction. Although many synchrotron facilities have microfocus beamlines for other applications, this capability for macromolecular crystallography was pioneered at ID‐13 of the ESRF. The National Institute of General Medical Sciences and National Cancer Institute Collaborative Access Team (GM/CA‐CAT) dual canted undulator beamlines at the APS deliver high‐intensity focused beams with a minimum focal size of 20 µm × 65 µm at the sample position. To meet growing user demand for beams to study samples of 10 µm or less, a `mini‐beam' apparatus was developed that conditions the focused beam to either 5 µm or 10 µm (FWHM) diameter with high intensity. The mini‐beam has a symmetric Gaussian shape in both the horizontal and vertical directions, and reduces the vertical divergence of the focused beam by 25%. Significant reduction in background was achieved by implementation of both forward‐ and back‐scatter guards. A unique triple‐collimator apparatus, which has been in routine use on both undulator beamlines since February 2008, allows users to rapidly interchange the focused beam and conditioned mini‐beams of two sizes with a single mouse click. The device and the beam are stable over many hours of routine operation. The rapid‐exchange capability has greatly facilitated sample screening and resulted in several structures that could not have been obtained with the larger focused beam.     

Some dielectric properties of novel nano‐s‐triazine derivatives

The evaluation of the dielectric properties of s‐triazine and its mono‐, di‐, tri‐(trityloxy)triazine derivates as a function of temperature from room temperature to 200°C, and frequency varying from 50 Hz to 5 MHz was performed. The dielectric constant increases with the increase of both temperature and frequency. Moreover, from the measured dielectric loss ε″ we found that there are different types of electric energy losses in the presence of an alternating electric field from which we calculate the entropy ΔS and the enthalpy change ΔH of the dielectric relaxation for each sample. The dielectric relaxation was attributed to the phase transition of the s‐triazine derivatives. Additionally, ac‐electrical conductivity as a function of frequency at different temperatures were studied. Analysis of ac conductivity data indicates that the correlated barrier hopping model is the most suitable mechanism for the ac‐conductance behavior. X‐ray diffraction and scanning electron microscopy were performed on the compounds under consideration to determine the grain size of each sample, which was found in the range of 3 to 100 nm.     

BioCARS: a synchrotron resource for time‐resolved X‐ray science

BioCARS, a NIH‐supported national user facility for macromolecular time‐resolved X‐ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator‐based beamline optimized for single‐shot laser‐pump X‐ray‐probe measurements with time resolution as short as 100 ps. The source consists of two in‐line undulators with periods of 23 and 27 mm that together provide high‐flux pink‐beam capability at 12 keV as well as first‐harmonic coverage from 6.8 to 19 keV. A high‐heat‐load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick–Baez mirror system capable of focusing the X‐ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high‐speed chopper isolates single X‐ray pulses at 1 kHz in both hybrid and 24‐bunch modes of the APS storage ring. In hybrid mode each isolated X‐ray pulse delivers up to ～4 × 10¹⁰ photons to the sample, thereby achieving a time‐averaged flux approaching that of fourth‐generation X‐FEL sources. A new high‐power picosecond laser system delivers pulses tunable over the wavelength range 450–2000 nm. These pulses are synchronized to the storage‐ring RF clock with long‐term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained.     

Mercury speciation in the colloidal fraction of a soil polluted by a chlor‐alkali plant: a case study in the South of Italy

Mercury (Hg) speciation in different size fractions of a soil sample collected near an industrial area located in the South of Italy, which had been polluted by the dumping of Hg‐containing wastes from a chlor‐alkali plant, was investigated by XANES spectroscopy. In particular, a special procedure has been developed to study the soil colloidal fraction, both for sample preparation and for XANES data collection. In this soil, Hg was speciated in quite insoluble inorganic forms such as cinnabar (α‐HgS), metacinnabar (β‐HgS), corderoite (Hg₃S₂Cl₂), and some amorphous Hg, S and Cl‐containing species, all derived from the land‐disposal of K106 Hg‐containing wastes. The contribution of the above‐mentioned chemical forms to Hg speciation changed as a function of particle size. For the fraction <2 mm the speciation was: amorphous Hg–S–Cl (34%) > corderoite (26%) > cinnabar (20%) = metacinnabar (20%); for the fraction <2 µm: amorphous Hg–S–Cl (40%) > metacinnabar (24%) > corderoite (20%) > cinnabar (16%); and for the fraction 430–650 nm, where most of the colloidal Hg was concentrated: amorphous Hg–S–Cl (56%) > metacinnabar (33%) > corderoite (6%) > cinnabar (5%). From these data it emerged that, even if Hg was speciated in quite insoluble forms, the colloidal fraction, which is the most mobile and thus the most dangerous, was enriched in relatively more soluble species (i.e. amorphous Hg–S–Cl and metacinnabar), as compared with cinnabar. This aspect should be seriously taken into account when planning environmental risk assessment, since the small particle size in which Hg is concentrated and the changing speciation passing from millimetre to nanometre size could turn apparently safe conditions into more hazardous ones.     

Three‐dimensional imaging of chemical phase transformations at the nanoscale with full‐field transmission X‐ray microscopy

The ability to probe morphology and phase distribution in complex systems at multiple length scales unravels the interplay of nano‐ and micrometer‐scale factors at the origin of macroscopic behavior. While different electron‐ and X‐ray‐based imaging techniques can be combined with spectroscopy at high resolutions, owing to experimental time limitations the resulting fields of view are too small to be representative of a composite sample. Here a new X‐ray imaging set‐up is proposed, combining full‐field transmission X‐ray microscopy (TXM) with X‐ray absorption near‐edge structure (XANES) spectroscopy to follow two‐dimensional and three‐dimensional morphological and chemical changes in large volumes at high resolution (tens of nanometers). TXM XANES imaging offers chemical speciation at the nanoscale in thick samples (>20 µm) with minimal preparation requirements. Further, its high throughput allows the analysis of large areas (up to millimeters) in minutes to a few hours. Proof of concept is provided using battery electrodes, although its versatility will lead to impact in a number of diverse research fields.     

High‐energy transmission Laue micro‐beam X‐ray diffraction: a probe for intra‐granular lattice orientation and elastic strain in thicker samples

An understanding of the mechanical response of modern engineering alloys to complex loading conditions is essential for the design of load‐bearing components in high‐performance safety‐critical aerospace applications. A detailed knowledge of how material behaviour is modified by fatigue and the ability to predict failure reliably are vital for enhanced component performance. Unlike macroscopic bulk properties (e.g. stiffness, yield stress, etc.) that depend on the average behaviour of many grains, material failure is governed by `weakest link'‐type mechanisms. It is strongly dependent on the anisotropic single‐crystal elastic–plastic behaviour, local morphology and microstructure, and grain‐to‐grain interactions. For the development and validation of models that capture these complex phenomena, the ability to probe deformation behaviour at the micro‐scale is key. The diffraction of highly penetrating synchrotron X‐rays is well suited to this purpose and micro‐beam Laue diffraction is a particularly powerful tool that has emerged in recent years. Typically it uses photon energies of 5–25 keV, limiting penetration into the material, so that only thin samples or near‐surface regions can be studied. In this paper the development of high‐energy transmission Laue (HETL) micro‐beam X‐ray diffraction is described, extending the micro‐beam Laue technique to significantly higher photon energies (50–150 keV). It allows the probing of thicker sample sections, with the potential for grain‐level characterization of real engineering components. The new HETL technique is used to study the deformation behaviour of individual grains in a large‐grained polycrystalline nickel sample during in situ tensile loading. Refinement of the Laue diffraction patterns yields lattice orientations and qualitative information about elastic strains. After deformation, bands of high lattice misorientation can be identified in the sample. Orientation spread within individual scattering volumes is studied using a pattern‐matching approach. The results highlight the inability of a simple Schmid‐factor model to capture the behaviour of individual grains and illustrate the need for complementary mechanical modelling.     

Characterization of Particle Size Standard NIST 1019b with Synchrotron X‐ray Microtomography and Digital Data Extraction

We show that synchrotron x‐ray microtomography (μCT) followed by digital data extraction can be used to examine the size distribution and particle morphologies of the polydisperse (750 to 2450 μm diameter) particle size standard NIST 1019b. Our size distribution results are within errors of certified values with data collected at 19.5 μm/voxel. One of the advantages of using μCT to investigate the particles examined here is that the morphology of the glass beads can be directly examined. We use the shape metrics aspect ratio and sphericity to examine of individual standard beads morphologies as a function of spherical equivalent diameters. We find that the majority of standard beads possess near‐spherical aspect ratios and sphericities, but deviations are present at the lower end of the size range. The majority (> 98 %) of particles also possess an equant form when examined using a common measure of equidimensionality. Although the NIST 1019b standard consists of loose particles, we point out that an advantage of μCT is that coherent materials comprised of particles can be examined without disaggregation.     

华南沿海末次冰期类黄土沉积的漫反射光谱与激光粒度研究

野外调查发现,华南沿海广泛发育一套黄色粉土沉积。为研究其特征属性及成因,选择具有代表性的3条粉土剖面及1个钻孔采样,使用漫反射光谱（DRS）分析和激光粒度（LPS）分析的方法,率先尝试从沉积物铁矿物的产出形式和沉积物粒度配分特征的角度,综合判定沉积物的沉积环境、搬运营力及成因机制。DRS分析结果表明,在黄色粉土的漫反射光谱一阶导数曲线中,铁矿物的特征峰峰高总体有赤铁矿（565 nm）>针铁矿(505和435 nm）的变化特征,与我国北方风成黄土的漫反射光谱一阶导数曲线形态吻合,均体现的是相对干冷的气候环境;而区内的河、海相沉积物曲线所反映的铁矿物特征峰的峰高变化与上述黄色粉土的变化方向相反,表明样品经历过充分的水化作用并长期处于潮湿的还原环境之中。LPS分析结果表明：各剖面（钻孔）黄色粉土的粒度组成均较为均一,粒组配分模式具显著的双峰式,两个峰值分别为主峰10～50 μm 区段和次峰<5 μm区段,与黄土沉积的粒度配分模式一致,是风成沉积的特征粒组构成;而与区内河、海相沉积物粒组呈单向变化的配分模式有显著差异。结合黄色粉土的年龄介于10～80 ka之间,以及正负地形皆广泛存在的空间分布特征,最终认为该套沉积是形成于末次冰期的风成沉积（本研究称“类黄土”）。     

Gold‐Nanoparticle‐Assisted Self‐Assembly of Chemical Gradients with Tunable Sub‐50 nm Molecular Domains

A simple and efficient principle for nanopatterning with wide applicability in the sub‐50 nanometer regime is chemisorption of nanoparticles; at homogeneous substrates, particles carrying surface charge may spontaneously self‐organize due to the electrostatic repulsion between adjacent particles. Guided by this principle, a method is presented to design, self‐assemble, and chemically functionalize gradient nanopatterns where the size of molecular domains can be tuned to match the level corresponding to single protein binding events. To modulate the binding of negatively charged gold nanoparticles both locally (<100 nm) and globally (>100 μm) onto a single modified gold substrate, ion diffusion is used to achieve spatial control of the particles’ mutual electrostatic interactions. By subsequent tailoring of different molecules to surface‐immobilized particles and the void areas surrounding them, nanopatterns are obtained with variable chemical domains along the gradient surface. Fimbriated Escherichia coli bacteria are bound to gradient nanopatterns with similar molecular composition and macroscopic contact angle, but different sizes of nanoscopic presentation of adhesive (hydrophobic) and repellent poly(ethylene) glycol (PEG) domains. It is shown that small hydrophobic domains, similar in size to the diameter of the bacterial fimbriae, supported firmly attached bacteria resembling catch‐bond binding, whereas a high number of loosely adhered bacteria are observed on larger hydrophobic domains.     

Application of kinoform lens for X‐ray reflectivity analysis

In this paper the first practical application of kinoform lenses for the X‐ray reflectivity characterization of thin layered materials is demonstrated. The focused X‐ray beam generated from a kinoform lens, a line of nominal size ～50 µm × 2 µm, provides a unique possibility to measure the X‐ray reflectivities of thin layered materials in sample scanning mode. Moreover, the small footprint of the X‐ray beam, generated on the sample surface at grazing incidence angles, enables one to measure the absolute X‐ray reflectivities. This approach has been tested by analyzing a few thin multilayer structures. The advantages achieved over the conventional X‐ray reflectivity technique are discussed and demonstrated by measurements.     

Large‐aperture prism‐array lens for high‐energy X‐ray focusing

A new prism‐array lens for high‐energy X‐ray focusing has been constructed using an array of different prisms obtained from different parabolic structures by removal of passive parts of material leading to a multiple of 2π phase variation. Under the thin‐lens approximation the phase changes caused by this lens for a plane wave are exactly the same as those caused by a parabolic lens without any additional corrections when they have the same focal length, which will provide good focusing; at the same time, the total transmission and effective aperture of this lens are both larger than those of a compound kinoform lens with the same focal length, geometrical aperture and feature size. This geometry can have a large aperture that is not limited by the feature size of the lens. Prototype nickel lenses with an aperture of 1.77 mm and focal length of 3 m were fabricated by LIGA technology, and were tested using CCD camera and knife‐edge scan method at the X‐ray Imaging and Biomedical Application Beamline BL13W1 at Shanghai Synchrotron Radiation Facility, and provided a focal width of 7.7 µm and a photon flux gain of 14 at an X‐ray energy of 50 keV.     

High‐brightness long‐wavelength semiconductor disk lasers

A review on the recent developments in the field of long‐wavelength (λ >1.2μm) high‐brightness optically‐pumped semiconductor disk lasers (OPSDLs) is presented. As thermal effects have such a crucial impact on the laser performance particular emphasis is given to modelling the thermal behaviour and optimisation of the heat‐sinking. Selected OPSDL devices, realized in different III‐V and IV‐VI semiconductor material systems, with corresponding emission wavelengths between 1.2 μm and 5.3 μm are presented. Specific applications in this broad spectral range are addressed and methods to obtain high output power are discussed in terms of the underlying material properties and device operating principles.     

X‐ray photon correlation spectroscopy in systems without long‐range order: existence of an intermediate‐field regime

Successful X‐ray photon correlation spectroscopy studies often require that signals be optimized while minimizing power density in the sample to decrease radiation damage and, at free‐electron laser sources, thermal impact. This suggests exploration of scattering outside the Fraunhofer far‐field diffraction limit d²/λR, where d is the incident beam size, λ is the photon wavelength and R is the sample‐to‐detector distance. Here it is shown that, in an intermediate regime d²/λ > Rdξ/λ, where ξ is the structural correlation length in the material, the ensemble averages of the scattered intensity and of the structure factor are equal. Similarly, in the regime d²/λ > Rdξ(τ)/λ, where ξ(τ) is a time‐dependent dynamics length scale of interest, the ensemble‐averaged correlation functions g₁(τ) and g₂(τ) of the scattered electric field are also equal to their values in the far‐field limit. This broadens the parameter space for X‐ray photon correlation spectroscopy experiments, but detectors with smaller pixel size and variable focusing are required to more fully exploit the potential for such studies.     

On the application of a single‐crystal κ‐diffractometer and a CCD area detector for studies of thin films

A multipurpose six‐axis κ‐diffractometer, together with the brilliance of the ESRF light source and a CCD area detector, has been explored for studying epitaxial relations and crystallinity in thin film systems. The geometrical flexibility of the six‐axis goniometer allows measurement of a large volume in reciprocal space, providing an in‐depth understanding of sample crystal relationships. By a set of examples of LaAlO₃ thin films deposited by the atomic layer deposition technique, the possibilities of the set‐up are presented. A fast panoramic scan provides determination of the crystal orientation matrices, prior to more thorough inspection of single Bragg nodes. Such information, in addition to a broadening analysis of families of single reflections, is shown to correlate well with the crystallinity, crystallite size, strain and epitaxial relationships in the thin films. The proposed set‐up offers fast and easy sample mounting and alignment, along with crucial information on key features of the thin film structures.