Sorting algorithms for single-particle imaging experiments at X-ray free-electron lasers.

Modern X-ray free-electron lasers (XFELs) operating at high repetition rates produce a tremendous amount of data. It is a great challenge to classify this information and reduce the initial data set to a manageable size for further analysis. Here an approach for classification of diffraction patterns measured in prototypical diffract-and-destroy single-particle imaging experiments at XFELs is presented. It is proposed that the data are classified on the basis of a set of parameters that take into account the underlying diffraction physics and specific relations between the real-space structure of a particle and its reciprocal-space intensity distribution. The approach is demonstrated by applying principal component analysis and support vector machine algorithms to the simulated and measured X-ray data sets.

Contrasting of biological samples for X-ray synchrotron microtomography.

The method of contrasting with iodine ions was developed to obtain high-resolution 3D images of large biological specimens using a synchrotron X-ray microtomography unit. It was shown that the samples (late mouse embryos) treated with 50% Lugol solution with addition of 25% ethanol for 48 h followed by a 48-h washout in phosphate buffered saline had maximum contrast and lowest compression artifacts. Processing of samples by this protocol allowed detecting zones of active proliferation. Incubation of brain samples for 120 h in 7.6% meglumine/sodium diatrizoate without washout ensured the best contrast during myelin identification.

[The morphogenesis and spatial organization of human pineal gland concretions in Alzheimer's disease, schizophrenia, and alcoholism].

X-ray microtomography using a wavelength of 0.7 A was used to detect elevated calcium concentration areas that integrate all types of human epiphyseal concretions. They consisted of both concretions and extracellular calcium, which could not be attributed to any particular tissue. There were no concretions outside of these zones. The center of concretion formation was found to be a single source that may be an individual pinealocyte. Comparison of postmortem human epiphyses in normalcy (natural aging), in chronic alcoholism, Alzheimer's disease, and schizophrenia revealed that there were differences in both the number of concretions and their formation topology. In normalcy, the field of elevated calcium concentration was continuous whereas in patients with the study mental diseases, it was divided into separate areas. There is evidence that in mental diseases, the amount of acervulus and its density decrease, which may a marker of the development of these diseases.