BL03HB: a Laue microdiffraction beamline for both protein crystallography and materials science at SSRF

A Laue microdiffraction beamline(BL03HB) was constructed at the Shanghai Synchrotron Radiation Facility(SSRF).This beamline features two consecutive focusing points in two different sectors within its end station, the first dedicated to protein crystallography and the other tailored to materials science applications. Based on a superbend dipole magnet with a magnetic field of 2.29 T, a two-stage focusing design was implemented with two sets of Kirkpatrick-Baez mirrors to achieve a micro white beam as small as 4.2 μ m ×4.3 μ m at the first sector and 0.9 μ m ×1.3 μ m at the second sector in the standard beamline operation mode at SSRF. The X-ray microbeam in the two sectors can be easily switched between monochromatic and white beams by moving a four-bounce monochromator in or out of the light path, respectively. In the protein crystallography sector, white-beam Laue microdiffraction was demonstrated to successfully determine the structure of protein crystals from only a few images of diffraction data collected by a Pilatus 2 M area detector. In the materials science sector,the white-beam Laue diffraction was collected in a reflection geometry using another Pilatus 2 M area detector, which could map the microstructural distribution on the sample surface by scanning the samples. In general, the BL03HB beamline promotes the application of Laue microdiffraction in both protein crystallography and materials science. This paper presents a comprehensive overview of the BL03HB beamline, end station, and the first commission results.

Zooming in REE and Other Trace Elements on Conodonts:Does Taxonomy Guide Diagenesis?

Conodont elements are calcium phosphate(apatite structure)mineralized remains of the cephalic feeding apparatus of an extinct marine organism.Due to the high affinity of apatite for rare earth elements(REE)and other high field strength elements(HFSE),conodont elements were frequently assumed to be a reliable archive of sea-water composition and changes that had occurred during diagenesis.Likewise,the crystallinity index of bioapatite,i.e.,the rate of crystallinity of biologically mediated apatite,should be generally linearly dependent on diagenetic alteration as the greater(and longer)the pressure and temperature to which a crystal is exposed,the greater the resulting crystallinity.In this study,we detected the uptake of HFSE in conodont elements recovered from a single stratigraphic horizon in the Upper Ordovician of Normandy(France).Assuming therefore that all the specimens have undergone an identical diagenetic history,we have assessed whether conodont taxonomy(and morphology)impacts HFSE uptake and crystallinity index.We found that all conodont elements are characterized by a clear diagenetic signature,with minor but significant differences among taxa.These distinctions are evidenced also by the crystallinity index values which show positive correlations with some elements and,accordingly,with diagenesis;however,correlations with the crystallinity index strongly depend on the method adopted for its calculation.

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

Atomic movement under application of external stimuli （i.e., electric field or mechanical stress） in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscop）6 time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO3 film, the hysteresis loop of the reflected X-ray intensity was found to result from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-field- induced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. The effect of external stress on the BiFeO3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.