Single-image super-resolution improvement of X-ray single-particle diffraction images using convolutional neural network

Femtosecond X-ray pulse lasers are promising probes for elucidating the multi-conformational states of biomolecules because they enable snapshots of single biomolecules to be observed as coherent diffraction images. Multi-image processing using an X-ray free electron laser has proven to be a successful structural analysis method for viruses. However, some difficulties remain in single-particle analysis (SPA) for flexible biomolecules with sizes of 100 nm or less. Owing to the multi-conformational states of biomolecules and the noisy character of diffraction images, diffraction image improvement by multi-image processing is not always effective for such molecules. Here, a single-image super-resolution (SR) model was constructed using a SR convolutional neural network (SRCNN). Data preparation was performed in silico to consider the actual observation situation with unknown molecular orientations, and fluctuation of molecular structure and incident X-ray intensity. It was demonstrated that the trained SRCNN model improved the single-particle diffraction image quality, which corresponded to an observed image with an incident X-ray intensity; i.e., approximately three to seven times higher than the original X-ray intensity, while retaining the individuality of the diffraction images. The feasibility of SPA for flexible biomolecules with sizes of 100 nm or less was dramatically increased by introducing the SRCNN improvement at the beginning of the variety structural analysis schemes.

A Rapid Detection Method for Tomato Gray Mold Spores in Greenhouse Based on Microfluidic Chip Enrichment and Lens-Less Diffraction Image Processing

It is of great significance to find tomato gray mold in time and take corresponding control measures to ensure the production of tomato crops. This study proposed a rapid detection method for spores of Botrytis cinerea in green-house based on microfluidic chip enrichment and lens-free diffraction image processing. Microfluidic chip with a regular triangular inner rib structure was designed to achieve the enrichment of Botrytis cinerea spores. In order to obtain the diffraction image of the diseased spores, a lens-less diffraction imaging system was built. Furthermore, the collected spore diffraction images were processed and counted. The simulation results showed that the collection efficiency of 16 μm particles was 79%, 100%, and 89% at the inlet flow rate of 12, 14 and 16 mL/min, respectively. The experimental verification results were observed under a microscope. The results showed that when the flow rate of the microfluidic chip was 12, 14 and 16 mL/min, the collection efficiency of Botrytis cinerea spores was 70.65%, 87.52% and 77.96%, respectively. The Botrytis cinerea spores collected in the experiment were placed under a microscope for manual counting and compared with the automatic counting results based on diffraction image processing. A total of 10 sets of experiments were carried out, with an error range of the experiment was 5.13~8.57%, and the average error of the experiment was 6.42%. The Bland–Altman method was used to analyze two methods based on diffraction image processing and manual counting under a microscope. All points are within the 95% consistency interval. Therefore, this study can provide a basis for the research on the real-time monitoring technology of tomato gray mold spores in the greenhouse.

X-ray diffraction measurement of a single nanometre-sized particle levitated in air by an optical-trap sample holder

A single-beam optical-trap sample holder for X-ray diffraction measurements with synchrotron radiation has been developed. The sample holder was used to obtain an X-ray diffraction image of a single ZnO particle levitated in air, without mechanical contact, by the optical gradient force exerted by a focused laser beam. The diffraction image showed a Debye ring pattern, which was similar to a powder diffraction pattern of an assemblage of ZnO particles. While the ZnO particle is held by the optical trap in air, it rotates irregularly. Therefore, the Debye ring pattern of the ZnO particle can be clearly obtained even if the ZnO particle is a single grain. Lattice parameters and crystallite size of the single ZnO particle were determined simultaneously. The lattice parameters were determined to be a = 3.2505 ± 0.0005 Å and c = 5.207 ± 0.006 Å, which are consistent with those of the assemblage of ZnO particles. The crystallite size determined by the Scherrer method was 193.4 ± 26.2 nm.

Improved calibration of area detectors using multiple placements

Calibration of area detectors from powder diffraction standards is widely used at synchrotron beamlines. From a single diffraction image, it is not possible to determine both the sample-to-detector distance and the wavelength, but, with images taken from multiple positions along the beam direction and where the relative displacement is known, the sample-to-detector distance and wavelength can both be determined with good precision. An example calibration using the GSAS-II software package is presented.