X-ray imaging of fast dynamics with single-pixel detector

We demonstrate experimentally the ability to use a single-pixel detector for two-dimensional high-resolution x-ray imaging of fast dynamics. We image the rotation of a spinning chopper at 100 kHz and at spatial resolution of about 40 microns by using the computational ghost imaging approach. The technique we develop can be used for the imaging of fast dynamics of periodic and periodically stimulated effects with a large field of view and at low dose.

X-ray computational ghost imaging with single-pixel detector

We demonstrate computational ghost imaging at X-ray wavelengths with only one single-pixel detector. We show that, by using a known designed mask as a diffuser that induces intensity fluctuations in the probe beam, it is possible to compute the propagation of the electromagnetic field in the absence of the investigated object. We correlate these calculations with the measured data when the object is present in order to reconstruct the images of 50 μm and 80 μm slits. Our results open the possibilities for X-ray high-resolution imaging with partially coherent X-ray sources and can lead to a powerful tool for X-ray three-dimensional imaging.

Strain softening of nano-scale fuzzy interfaces causes Mullins effect in thermoplastic polyurethane

The strain-induced softening of thermoplastic polyurethane elastomers (TPUs), known as the Mullins effect, arises from their multi-phase structure. We used the combination of small- and wide- angle X-ray scattering (SAXS/WAXS) during in situ repeated tensile loading to elucidate the relationship between molecular architecture, nano-strain, and macro-scale mechanical properties. Insights obtained from our analysis highlight the importance of the ‘fuzzy interface’ between the hard and soft regions that governs the structure evolution at nanometre length scales and leads to macroscopic stiffness reduction. We propose a hierarchical Eshelby inclusion model of phase interaction mediated by the ‘fuzzy interface’ that accommodates the nano-strain gradient between hard and soft regions and undergoes tension-induced softening, causing the Mullins effect that becomes apparent in TPUs even at moderate tensile strains.

Mapping of multi-elements during melting and solidification using synchrotron X-rays and pixel-based spectroscopy

A new synchrotron-based technique for elemental imaging that combines radiography and fluorescence spectroscopy has been developed and applied to study the spatial distribution of Ag, Zr and Mo in an Al alloy during heating and melting to 700, and then re-soldification. For the first time, multi-element distributions have been mapped independently and simultaneously, showing the dissolution of Ag- and Zr-rich particles during melting and the inter-dendritic segregation of Ag during re-solidification. The new technique is shown to have wide potential for metallurgical and materials science applications where the dynamics of elemental re-distribution and segregation in complex alloys is of importance.

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 approximately 50 microm x 2 microm, 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.

Characterization of germanium linear kinoform lenses at Diamond Light Source

The unprecedented brilliance achieved by third-generation synchrotron sources and the availability of improved optics have opened up new opportunities for the study of materials at the micrometre and nanometre scale. Focusing the synchrotron radiation to smaller and smaller beams is having a huge impact on a wide research area at synchrotrons. The key to the exploitation of the improved sources is the development of novel optics that deliver narrow beams without loss of brilliance and coherence. Several types of synchrotron focusing optics are successfully fabricated using advanced miniaturization techniques. Kinoform refractive lenses are being developed for hard X-ray beamlines, and the first test results at Diamond are discussed in this paper.

The structural principles of multidomain organization of the giant polypeptide chain of the muscle titin protein: SAXS/WAXS studies during the stretching of oriented titin fibres

Elasticity of titin is a key parameter that determines the mechanical properties of muscle. These include reversibility, i.e., the muscle's capacity to change its length many-fold and return to its original state, and the transduction of passive tension generated by the stretched muscle. The morphology and elastic properties of oriented fibres of titin molecules were studied using SAXS and WAXS (small- and wide-angle X-ray scattering, respectively) and mechanical techniques. We succeeded in obtaining oriented filaments of purified titin suitable for diffraction measurements. Our X-ray data suggest a model of titin as a nanoscale, morphological, and aperiodical array of rigid Ig- and Fn3-type domains covalently connected by conformationally variable short loops. The line group symmetry of the model can be defined as SM with axial translation tau(infinity). Both tension transduction and high elasticity of titin can be explained in terms of crystalline polymer physics. Titin stretching experiments show that each individual titin macromolecule can adopt a novel two-phase state within the fibre. Conversion between high elasticity and strength can be explained as a phase transition under external tension. In the terms of the concept of orientational melting the origin of the functional heterogeneity along the titin strand becomes interpretable.

Microradian X-ray diffraction in colloidal photonic crystals

Ultra-high-resolution small-angle X-ray scattering in various colloidal photonic crystals is reported. It is demonstrated that an angular resolution of about two microradians is readily achievable at a third-generation synchrotron source using compound refractive optics. The scheme allows fast acquisition of two-dimensional X-ray diffraction data and can be realised at sample–detector separations of only a few metres. As a result, diffraction measurements in colloidal crystals with interplanar spacings larger than a micrometre, as well as determination of the range of various order parameters from the width of the Bragg peaks, are made possible.

Observation of a hexatic columnar liquid crystal of polydisperse colloidal disks

We report the observation of a new type of columnar liquid crystal phase, which is formed by thin hard colloidal disks in a dense suspension. High-resolution small-angle x-ray diffraction reveals a combination of long-range bond-orientational order and short-range translational order between the columns, the hallmark of the hexatic phase. Our results imply that geometric frustration related to the size polydispersity of the particles destroys long-range translational order and therefore promotes the formation of this novel phase.

Destruction of long-range order recorded with in situ small-angle x-ray diffraction in drying colloidal crystals

High-resolution synchrotron small-angle x-ray diffraction is applied to characterize the structure and long-range order in a sedimentary hard-sphere colloidal crystal before and during its drying. The principles of the technique and the influence of the coherence properties of the x-ray beam are discussed in detail. The capillary forces generated during the drying process are shown to destroy the long-range order and to break the crystal into smaller crystallites with slightly different orientations. The diffraction is shown to switch from the dynamic regime in the long-range-ordered crystal to nearly kinematic diffraction in the mosaic (short-range-ordered) crystal.

The phase behaviour of skin lipid mixtures based on synthetic ceramides

The lipid lamellae present in the outermost layer of the skin, the stratum corneum (SC), form the main barrier for diffusion of molecules across the skin. The main lipid classes in SC are cholesterol (CHOL), free fatty acids (FFA) and at least nine classes of ceramides (CER), referred to as CER1 to CER9. In the present study the phase behaviour of four synthetic CER, either single or mixed with CHOL or CHOL and FFA, has been studied using small and wide angle X-ray diffraction. The lipid mixtures showed complex phase behaviour with coexistence of several phases. The results further revealed that the presence of synthetic CER1 as well as a proper composition of the other CER in the mixture were crucial for the formation of a phase with a long periodicity, characteristic for SC lipid phase behaviour. Only a mixture containing synthetic CER1 and CER3, CHOL and FFA showed similar phase behaviour to that of SC.

Bragg rods and multiple X-ray scattering in random-stacking colloidal crystals

Synchrotron small-angle x-ray diffraction images of random-stacking-induced Bragg scattering rods are obtained in a wide range of wave vectors from a single colloidal crystal. The results reveal a strong multiple scattering effect, which leads to new features in the diffraction pattern-secondary Bragg rods. We argue that dynamic x-ray diffraction is rather common for high-quality colloidal photonic crystals and should be taken into account.

High-resolution small-angle x-ray diffraction study of long-range order in hard-sphere colloidal crystals

The long-range order parameters in single crystals of hard colloidal spheres grown in sediments of colloid-polymer mixtures are determined using synchrotron small-angle x-ray diffraction with a resolution of 10(-6) of the wave vector. The interplanar positional order derived from the width of lattice reflections extends over at least 500 lattice planes. The lattice planes are orientationally correlated within approximately 0.1 degrees throughout the crystals, whereas the stacking of hexagonal planes remains random.

The SAXS/WAXS software system of the DUBBLE CRG beamline at the ESRF

The small/wide-angle X-ray scattering (SAXS/WAXS) system on the DUBBLE CRG beamline at the ESRF is used for both static and time-resolved measurements. The integrated system developed for control and data reduction deals effectively with the high rates of incoming data from the different detector systems, as well as the presentation of results for the user. To ensure that the data may be used directly by a wide range of packages, they may be recorded in a number of output formats, thus serving as a practical test bed where developing standards may be compared and contrasted. The software system implements proposals raised at the canSAS meetings to promote a limited set of standard data formats for small-angle scattering studies. The system presented can cope with a volume of results in excess of 10 Gbytes of data per experiment and shows the advantages achieved by minimizing the dependence on raw-data formats.

Crystalline smectic-B films as fluctuating systems: static and dynamic x-ray scattering

Static and dynamic x-ray scattering has been used to characterize thermal fluctuations in free-standing smectic films in the crystalline-B phase. The results are remarkably similar to those in smectic-A films, in spite of the three-dimensional positional order in the crystalline-B phase. The main difference is the disappearance of the characteristic Landau-Peierls instability of the smectic-A phase. The dynamic nature of the fluctuations is explicitly demonstrated by x-ray photon correlation spectroscopy. This fluctuation behavior of crystalline-B films can be attributed to the small value of the shear elastic constant C44.

Complex dynamic behavior of fluctuating smectic- A films as studied by scattering with coherent X-rays

Coherent dynamic x-ray scattering has been used to study the thermally excited layer fluctuations in freely suspended smectic films of the compound 4O.8. Using 8-keV x rays and films with a thickness around 0.3 &mgr;m we resolve relaxation times down to a few &mgr;s. A combination of damped and oscillatory behavior is observed for the layer undulations, which can be attributed to inertial effects. These are due to the surface contribution to the free energy which cannot be disregarded for thin films.

Distribution of colloidal gold tracer within rat parasternal lymph nodes after intrapleural injection

BACKGROUND

Tracer studies are an important tool to obtain information about the processes involved in the immunological response. Colloidal gold is widely used as a tracer, but its small size of label can cause some difficulty during low-resolution analysis. To overcome this difficulty, we developed a new method to follow the route of tracer movement within lymph nodes.

METHODS

We applied conventional X-ray analysis, X-ray fluorescence analysis (XFA) subtractional microscopy using synchrotron radiation (SR) beams, light microscopy, and ultrastructural analysis to study the distribution and quantity of colloidal gold coupled with albumin within rat parasternal lymph node 2, 4, 6, 8, and 10 h after intrapleural injection of the tracer.

RESULTS

At all the time points XFA-SR revealed that tracer formed a circle with a maximum concentration in the node periphery. XFA-SR measured colloidal gold concentration in the nodes reached its maximum (0.5-0.75 weight %) in 6-8 h. Subtractional microscopy revealed superficially located groups of cells filled with colloidal gold tracer. Light microscopy and ultrastructural analysis confirmed that the tracer was concentrated in the reticular cells, situated in the sinuses of the node. Sinusoidal reticular cells concentrated tracer at much higher rates than sinusoidal macrophages. Four hours after injection, gold appeared in the lysosomes of the follicular reticular cells. At the same time point, evidence of antigen presentation was obtained. Antigen presentation proved to be an extremely rara event since only one ultrastructural incident was found in 150 analysed grids.

CONCLUSIONS

SR is a valuable tool for the analysis of gold tracer passage within the living organism.