It is standard to use M x2 and M y 2 to characterize the beam quality of a non-circular symmetrical beam on its x-axis and y-axis orientation. However, we knew that the values of M x 2 and M y 2 are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this, a new beam quality characterization method, the M 2 factor matrix, is developed. It not only contains the beam quality terms, M x 2 and M y 2 , to characterize the beam quality along x-axis and y-axis orientation for the non-symmetric beam, but also introduces two additional cross terms, M xy and M yx , which are used to characterize the location relationship between the principal axis of the test beam and coordinate system in experiment. Moreover, M 2 factor matrix can be measured with a similar procedure to the traditional M 2 factor whose measurement instructions are described in ISO11146 by adding some additional image and signal processing procedure. The measurement principle and method is present and the experiment system for beam quality M 2 factor matrix is built to demonstrate the performance of M 2 factor matrix with real experiments.
ScRh 3 B x (x=0.0-1.0) has been investigated recently as an ultrahard material. Crystal structure refinements and electron density analyses of this material were carried out by synchrotron X-ray powder diffraction. The powder diffraction data were collected using Multi-Detector System powder diffractometer at the BL-4B2 experimental station of the Photon Factory. The crystal structure refinements were performed using the Rietveld method and the electron density maps were calculated with the Maximum Entropy Method (MEM). The results of the refinements show that the crystal structure of ScRh 3 B x is cubic with Pm3m space group, which has same atomic arrangement with perovskite structure. The lattice constant increases linearly according to the increase of B amount. In the electron density maps obtained by MEM analysis, electron density raises are obviously observed between B and Rh atoms. The rises of electron density show the existence of covalent bond between B and Rh atom. In spite of the liner increase of lattice constant according to the increase of B amount, the hardness of this series of compounds have a minimum between 0.4 and 0.7 of B contents. This change of hardness is supposed to be related to the amounts of the covalent bond in the crystal structure. The bond character of this series of compounds is also discussed based on the results of electron density analyses. A crystal mounting technique was developed for the sulphur SAD method using longer wavelength X-rays. This technique is novel in that the a nylon loop is glued directly onto the tip of the micropipette and fixed as if the micropipette tip is located in the loop, so the solution caught in the loop can be aspirated through the micropipette just before flash freezing. Using this technique, the cryo-buffer and cryoloop can be removed easily before data collection to eliminate their X-ray absorption. The structures of novel proteins were solved using this technique in combination with chromium radiation. In the case of PH1109 from P. horikoshii, 90% of all residues were built automatically by RESOLVE using this technique, but only 76% were built for the dataset obtained using the standard loop. These results indicated that our crystal mounting technique was superior to the standard loop mounting method for the measurement of small anomalous differences, and yielded good results in sulphur substructure solution and phasing. We will demonstrate that the sulphur SAD method with a chromium source is more practical for macromolecular structure determination using our crystal mounting technique. The program is highly automatic and suitable for high throughput crystallographic. Results of numerous applications will be shown.
Keywords[1] Altomare A., Caliandro R., Camalli, M., Cuocci C., Giacovazzo C., Moliterni A.G.G., Rizzi R., J. Appl. Cyst, 2004, 37, 1025-1028 is a direct-method program for resolving the phase ambiguity in single-wavelength anomalous diffraction (SAD) and in single isomorphous replacement (SIR) of proteins. The new version, OASIS-20...
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