Use Of High-resolution Methods Research Articles

The use of high-resolution methods of research in the design of the diamond-matrix interface to increase the durability of the diamond tool

The results of studying fundamental and applied problems regarding the formation of boundary layers between diamond and carbide matrix are presented with the goal to develop a highly resistant diamond tool. The new approaches to the synthesis of diamond-carbide materials combining diamond metallization and sintering in a single-stage technology are presented. The developed technology eliminates the re-heating of a metallized coatings which results in their destruction and enhanced graphitization of diamond (these phenomena restrict using metallization procedure to improve diamond retention and synthesis of high-functional composites for diamond tools). The goal of the study is analysis the structural and phase state of the «diamond – carbide matrix» interface in a diamond tool obtained by the new technology and the main factors determining the level of diamond retention in the presence of a metallized coating. Unique opportunities provided by modern high-resolution methods of research were used in the study. The elemental composition and morphological features of the diamond-matrix interface were studied using the methods of scanning electron microscopy, atomic force microscopy, X-ray microanalysis and Raman spectroscopy. Identification of the reaction products, including non-diamond carbon was performed. It is shown that the introduction of the powder-metallizer significantly modified the contact boundaries and provide conditions for improving the chemical and mechanical adhesion of the diamond-matrix system. The formation of the well-developed nano- and sub-microscale roughness of the diamond surface and dense filling of the existing voids with nanoscale layers of metal-infiltrate was revealed. The multilevel organization of highly structured elements of the transition zone with the minimal graphitization ensured the monolithic character and strength of the diamond-matrix bond. Comparative service tests of preproduction and control samples of diamond dressers proved the efficiency of developed hybrid technology (the specific performance of diamond tools increased by 39 – 45%). New fundamental and applied results have been obtained in the field of studying interface zones in crystalline multiphase systems that can be used to regulate adhesion phenomena at the interphase boundaries and develop highly efficient composite materials.

Effects of nano and submicrocrystalline states under a wide range of loads

The scale in nanomechanics (10−10−10−9 m) has a fundamental physical meaning and can be considered as a control parameter when considering qualitative changes in the properties of polycrystalline materials when the grain structure changes in a wide range of load intensities. The existence of this parameter can lead to effects beyond the scale, which are traditionally considered in mechanics, and are accompanied by the influence of quantum effects on the deformation properties and failure of materials. New ideas about submicrocrystalline and nano-scale structure of materials achieved by the use of high-resolution methods (synchrotron tomography, soft X-rays, nanoindentation) have led to qualitative changes in approaches to the study and description of the properties of materials, including biomaterials. This may provide new information on the processes of deformation and fracture at the micro- and nano-scale level and lead to new approaches in the design and evaluation of the reliability.

Accessibility Changes within Diphtheria Toxin T Domain upon Membrane Penetration Probed by Hydrogen Exchange and Mass Spectrometry

The translocation domain of diphtheria toxin inserts in membrane and becomes functional when the pH inside endosomes is acid. At that stage, the domain is in a partially folded state; this prevents the use of high-resolution methods for the characterization of its functional structure. On that purpose, we report here the use of hydrogen/deuterium exchange experiments coupled to mass spectrometry. The conformation changes during the different steps of insertion into lipid bilayer are monitored with a resolution of few residues. Three parts of the translocation domain can be distinguished. With a high protection against exchange, the C-terminal hydrophobic helical hairpin is embedded in the membrane. Despite a lower protection, a significant effect in the presence of lipid vesicles shows that the N-terminal part is in interaction with the membrane interface. The sensitivity to the ionic strength indicates that electrostatic interactions are important for the binding. The middle part of the domain has an intermediate protection; this suggests that this part of the domain can be embedded within the membrane but remains quite dynamic. These results provide unprecedented insight into the structure reorganization of the protein to go from a soluble state to a membrane-inserted one.

On the powerof second-order accurate numerical methods for model problems of gas- and hydrodynamics

The paper provides an overview on the use of high-resolution methods based on the CABARET scheme. The results are provided for several test problems including gas dynamics, computational aeroacoustics, and geophysical fluid dynamics for a classical double-gyre quasi-geostrophic model of ocean dynamics.