Comparative Analysis of Different Methods of Scanning Electron Microscopy and Test Preparation in Biological Tissue Studies

Crystallography Reports - Different methods of scanning electron microscopy in combination with different sample preparation techniques have been compared by an example of decellularized rat...     

Conformational transitions in ultrahigh-molecular-mass polymers and their manifestation in chromatography on monolithic columns

For a monolithic capillary column based on polydivinylbenzene, a change in the elution profile of polystyrene standards with variation in the eluent-flow rate is studied. It is shown that, for polymers with molecular masses up to 3 × 10⁶, the elution profile does not depend on the flow rate. For higher molecular mass polymers at low flow rates, there is a single almost Gaussian peak that splits into two peaks that move to different sides from the initial peak with an increase in the flow rate. A peak with a smaller retention time (peak I) rapidly attains the limiting elution time, and later on, its retention is independent of the eluent-flow rate. In contrast, the retention time of the other peak (peak II) continuously increases with an increase in the flow rate of the mobile phase, so that, at high flow rates, this peak is retained for a longer time than the low-molecular-mass marker. The intensity of peak I decreases, while the intensity of peak II increases with an increase in the eluent-flow rate; the ratio of their intensities tends toward a certain limiting value (≤1). The observed profile of elution of ultrahigh-molecular-mass polymers assumes the presence of a dynamic equilibrium similar to that existing in the case of first-order reversible reactions. For the assumed equilibrium, the rate constants of direct and back reactions are determined. It is found that these constants are close to the inverse maximum relaxation time of a polymer molecule. The character of the transformations of the polymer molecule in the chromatographic column is discussed.     

Targeted acquisition for real-time NMR spectroscopy

A target-oriented approach for the acquisition of information in biomolecular NMR spectroscopy is being developed. This approach combines concurrent data accumulation, processing, and monitoring of spectral quality. Real-time estimation of parameters allows acquisition to be stopped when results are complete and have a specified precision. The technique is based on multidimensional decomposition, which can process incomplete data. An incremental nonuniform sampling scheme ensures the optimization of resolution sensitivity. To validate this method, 3D HNCO spectra of three biomolecular systems (8 kDa ubiquitin, 22 kDa barstar-barnase complex, and 82 kDa malate synthase G) are processed incrementally at small acquisition time steps. The range of molecular sizes illustrates applicability in both sample- and sensitivity-limited regimes. In each case, the target was to acquire all backbone resonances in the spectra. For the three systems, the targets are achieved after 4.5 min, 1.6 h, and 22 h of acquisition time, respectively. A number of other targets that can be similarly monitored as a function of time are discussed.     

Metals produced as nano-snow layers for converters of laser light into X-ray for indirect targets and as intensive EUV sources

Low-density nano-snow metal layers down to 1 % of solid material density are considered. Specification of such structures and their parameters is required for pre-experimental non-destructive target characterization. The intrinsic structures have nano-sized average cells. Such low-density structures can be used inside indirect laser targets and as a cover of inner walls of advanced hohlraum to increase radiation temperature and X-ray emission.     

Comparison of the data of X-ray microtomography and fluorescence analysis in the study of bone-tissue structure

The possibility of localizing clusters of heavy atoms is substantiated by comparing the data of X-ray microtomography at different wavelengths, scanning electron microscopy, and X-ray fluorescence analysis. The proximal tail vertebrae of Turner??s thick-toed gecko (Chondrodactylus turneri) have been investigated for the first time by both histological and physical methods, including X-ray microtomography at different wavelengths and elemental analysis. This complex methodology of study made it possible to reveal the regions of accumulation of heavy elements in the aforementioned bones of Turner??s thick-toed gecko.     

Fiber Optic Raman Distributed Temperature Sensor Based on an Ultrashort Pulse Mode-Locked Fiber Laser

Optics and Spectroscopy - The testing of an all-fiber erbium ultrashort pulsed laser in a distributed fiber temperature sensor as a source of probing pulses has been performed. Among the prospects...     

Review and Prospect: Deep Learning in Nuclear Magnetic Resonance Spectroscopy

Since the concept of deep learning (DL) was formally proposed in 2006, it has had a major impact on academic research and industry. Nowadays, DL provides an unprecedented way to analyze and process data with demonstrated great results in computer vision, medical imaging, natural language processing, and so forth. Herein, applications of DL in NMR spectroscopy are summarized, and a perspective for DL as an entirely new approach that is likely to transform NMR spectroscopy into a much more efficient and powerful technique in chemistry and life sciences is outlined.     

Growth of hollow nickel fluoride whiskers

Hollow nickel fluoride whiskers have been obtained by condensation from the vapor phase onto a platinum substrate in a flow of hydrogen fluoride. Crystals up to 5 mm in length have a square cross section with a 300 ± 30-μm side. The wall thickness is 85 ± 20 μm.     

Techniques for retrieval of the boundary displacement data in gas-dynamic experiments using millimeter-waveband radio interferometers

We describe a radio-interferometry method for measuring movement parameters of objects in application to gas-dynamic experiments. The origins of biasing in calculation of these parameters from measured interferograms are discussed. Bias reduction algorithms for the interferometer signal processing are described. For experimental setups with a single moving boundary, this algorithm is optimal for estimating the instantaneous phase and frequency of a narrow-band signal with bandpass prefiltering and quadrature-channel signal orthonormalization. For experiments with several moving boundaries, it provides the interferogram curve fitting by parameters of the electrodynamic model of an experimental setup. The results of test experiments verifying the reliability of the obtained information are presented. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 234–246, March 2008.