On the corrosion of ZK60 magnesium alloy after severe plastic deformation

Magnesium alloys are promising materials for the surgical implants due to their exceptional mechanical properties, biocompatibility and biodegradability. Binary Mg-Zn and ternary Mg-Zn-Zr alloys are the most obvious candidates for further design of biomaterials. However, they have to meet many requirements, including high strength and corrosion performance. In this work, we demonstrate that the corrosion resistance of the alloy Mg-6Zn-0.5Zr (ZK60) can be controlled to a large extent by its microstructure and distribution of phases, formed by thermomechanical treatment involving hot severe plastic deformation (SPD). The two-step multi-axial isothermal forging (MIF) is employed to deform the alloy ZK60 to different strains at 400°C and 300°C. The influence of microstructural parameters on the corrosion rate is demonstrated. It was found that MIF leads to the microstructure refinement, increases the fraction of high-angle grain boundaries, and reduces the size and distribution inhomogeneity of the second phases, thus promotes the formation of a reasonably uniform protective layer at the surface, and increases the overall corrosion resistance of the investigated ZK60 alloy. The homogeneous microstructure fabricated by MIF plays an important role for corrosion resistance since any heterogeneity or bi-modality of grain boundary structure can lead to large gradients of the driving force for oxidation within the material, and, as a consequence, to the difference in the spatial properties and the heterogeneity of the protective oxide film. With the observed reasonable corrosion performance and excellent mechanical properties, the fine-grained alloy ZK60 manufactured by hot two-step MIF processing has a great potential for bio-medical applications as a material for bio-resorbable implants or vascular stents.

The NUCLEON Space Experiment - Preliminary Results

Preliminary results of the cosmic ray study in the NUCLEON space experiment.

Energy spectra of protons and helium nuclei measured by the cosmic ray NUCLEON experiment

The NUCLEON satellite experiment is designed for direct measurements of the energy spectra of cosmic-ray nuclei and the chemical composition (Z=1−30) at an energy range up to 1000 TeV. The energy spectra of protons and helium nuclei are presented. Some spectral peculiarities were found. The differences of protons and helium spectra are investigated.

Energy spectra of cosmic ray heavy nuclei in the NUCLEON space experiment after two years of data acquisition

The energy spectra of abundant heavy nuclei from carbon to iron collected by the NUCLEON space experiment after two years of operation are presented. The spectra were measured with use of both calorimeter and KLEM methods. The complex behavior of the spectra from carbon to silicon in the energy range from a few TeV to hundreds of TeV per particle is presented and discussed. The difference between the spectrum of iron and the spectra of other heavy nuclei from carbon to silicon and a signature of a universal break in the spectra of all nuclei near the magnetic rigidity 10 TV are emphasized. Some new features in the spectra of heavy nuclei are discussed.

Primary and secondary cosmic rays in the NUCLEON space experiment after two years of data acquisition

The NUCLEON space experiment was designed to measure energy spectra of cosmic ray nuclei from protons to iron in the energy range approximately from 1 TeV per particle to 1 PeV per particle with good individual charge resolution. The apparatus started the collection of data at the beginning of 2015 and it is in operation up to now. The duration of the mission is expected to be no less than five years. One of the main feature of the experiment is an implementation of two different methods of energy measurement on board of the apparatus -- the calorimetric method and the new kinematic KLEM method (Kinematic Lightweight Energy Meter). The data obtained after two years of operation are presented. A multiple signs of complex behavior of the nuclei spectra and the ratios of spectra violating of a simple universal power-law behavior of the spectra will be presented in the report.

THE BASICS OF CHEMOEMBOLIZATION

INTERVENTIONAL STRATEGY FOR CLINICALLY SIGNIFICANT THROMBOSIS OF THE SUPERIOR VENA CAVA AND BRACHIOCEPHALIC VEIN

Russian mental verbs as a semantic class

The subject of this article is subcategorization of Russian mental verbs (verbs of knowledge, understanding and thinking) considering information encoded in their form and structure about the mental (intellectual) functions and time schemata, i.e. taking into account such characteristics as continuity and limitations. The author refers to the extensive literature on this subject, above all, the publications of Russian researchers, such as L. M. Vasiliev, G. A. Zolotova, N. J. Shvedova et al., and also presents an analysis of the collected empirical material (543 units of modern Russian language). The conclusions concern the division of verbs into semantic classes as well as the degree of representation of each class.

ERROR ANALYSIS OF DENTAL STUDENTS IN THE TRANSITION FROM PHANTOM TO REAL CONDITIONS OF PREPARATION