A sesquiterpene glucoside from cultivated cells of Scorzonera hispanica

A sesquiterpene glucoside has been isolated from a tissue culture ofScorzonera hispanica, and its structure has been established by mass spectrometry and two-dimensional NMR as 6,9-dihydroxy-4,10,14,15-tetradehydroguaian-6,12-olide 9-O--D-glucopyranoside.Irkursk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 640–645, November–December, 1992.     

Temperature dynamics of triglycine sulfate domain structure according to atomic force microscopy and dielectric spectroscopy data

A hydrogen-containing ferroelectric triglycine sulfate (TGS) was comprehensively studied with an atomic force microscopy (AFM) and dielectric spectroscopy. The domain structure dynamics was in situ investigated with piezoresponse force microscopy (PFM) during heating and cooling the TGS crystal near phase transition. Relaxation dependencies of domain boundaries general perimeter and domain dimensions were obtained. TGS dielectric spectra measured at the frequency range from 10 to 10¹¹ Hz were analyzed on basis of significant contribution of conductivity into the dielectric response of ferroelectrics and a good agreement with the experimental data was received. It allows us to obtain more information about temperature dynamics of the domain structure.     

Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.     

Electron loss of heavy many-electron ions in relativistic collisions with neutral atoms

Electron-loss processes arising in collisions of heavy many-electron ions (like U²⁸⁺) with neutral atoms (H, N, Ar) are considered over a wide energy range including relativistic energies. Various computer codes (LOSS, LOSS-R, HERION, and RICODE), created for calculation of the electron-loss cross sections, and their capability are described. Recommended data on the electron-loss cross sections of U²⁸⁺ ions colliding with H, N, Ar targets and predicted lifetimes of U²⁸⁺ ion beams in accelerator are given. Calculated electronloss cross sections are compared with available experimental data and other calculations.     

Criterion for identification of ferroelectric domains in TGS crystals from AFM images

Criteria for identification of actual (dynamic) domains and morphologically similar domain “memory” regions are proposed based on the study of various types of contrast of topographic atomic-force microscopy images of lenslike regions on the polar surface of TGS crystals. Inaccuracy in identification may result in further errors in estimating the parameters of the domain structure. The images of ferroelectric domains in the spreading-resistance mode that indicate directly the presence of conductive properties of the domain walls have been obtained for the first time.     

Study of the surface heterogeneity of topographic and electric nature by atomic force microscopy by the example of triglycine sulfate

Triglycine sulfate crystals with an ideal (010) cleavage plane are used as model objects to reveal problems in interpreting atomic force microscopy (AFM) images of surfaces with nonuniform charge distribution. Specific microrelief features of two types are found: lenslike formations with different contrast and rounded protrusions/valleys of different size but fixed height. An analysis of their evolution with a change in temperature and under an electric field and mechanical impacts has made it possible to separate relief elements from the crystal domain structure. The interpretation proposed is confirmed by the multimode AFM data. The specific features of the images of dynamic domains and aged domains (which cannot undergo polarization reversal) are studied. The domain-wall width found in the AFM measurements depends on the technique used and the specificity of probe-surface interaction; it varies from 9 to 2000 nm. The most reliable data on the domain-wall width in triglycine sulfate crystals are provided by piezoelectric force microscopy, according to which the wall width does not exceed 30 nm.     

Atomic force microscopy of the mirror cleavage surface of defect TGS crystals

The nanorelief of the mirror cleavage surface of triglycine sulfate crystals with various defect densities has been studied. Typical nanorelief features of both defect and clean (without artificial impurity) crystals are two-dimensional rounded bumps (dips) of equal height (depth) of about half the lattice parameter and sub-micrometer lateral sizes. The density, lateral size, and scatter of such 2D structures are several times larger for defect crystals than for clean ones. The correlation between the crystal defect density and the density and lateral size of 2D structures on the cleavage surface has been revealed. Conclusions are made about the defect origin of the typical nanorelief on the mirror cleavage.     

Correlation between the substrate roughness and light loss for interference mirror coatings

The correlation between the parameters of multilayer mirror coatings used in ring laser gyroscopes with the roughness height of the substrate and top surface of mirror coating is investigated. A complex approach is applied to analysis of the roughness of substrates and mirror coatings, which is based on the use of atomic force microscopy and X-ray scattering. A correlation between the roughness of substrates and mirror coatings is established. In addition, the correlation between the scattering coefficient, reflectance, and transmittance of multilayer mirror coatings and the roughness of the substrates used is investigated.     

Vacuum Conditions and the Lifetime of a Single-Charged Helium Ion Beam in the Booster Synchrotron of the NICA (First Run)

JETP Letters - The results of the first run (December 2020) for the commissioning of the new superconducting synchrotron Booster at the Joint Institute for Nuclear Research are presented. Vacuum...