The Rectifying Contact of Hydrated Different Size YSZ Nanoparticles for Advanced Electronics.

The paper considers the new effects of the nanoscale state of matter, which open up prospects for the development of electronic devices using new physical principles. The contacts of chemically homogeneous nanoparticles of yttrium-stabilized zirconium oxide (ZrO2­x mol% Y2O3, x = 0, 3, 4, 8; YSZ) with different sizes of 7.5 nm and 9 nm; 7.5 nm and 11 nm; and 7.5 nm and 14 nm, respectively, was studied on direct current using nanostructured objects in the form of compacts obtained by high-hydrostatic pressure (HP-compacts of 300MPa). A unique size effect of the nonlinear (rectifying-type contact) dependence of the electrical properties (in the region U < 2.5 V, I ≤ 2.7 mA) of the contact of different-sized YSZ nanoparticles of the same chemical composition is revealed, which indicates the possibility of creating semiconductor structures of a new type (homogeneous electronics). The electronic structure of the near-surface regions of nanoparticles of studied oxide materials and the possibility of obtaining specifically rectifying properties of the contacts were studied theoretically. Models of surface states of the Tamm-type are constructed considering the Coulomb long-range action. The discovered energy variance and its dependence on the curvature of the surface of nanoparticles made it possible to study the conditions for the formation of a contact potential difference in cases of nanoparticles of the same radius (synergistic effect), different radii (doped and undoped variants), as well as to discover the possibility of describing a group of powder particles within the Anderson model. The determined effect makes it possible to solve the problem of diffusion instability of semiconductor heterojunctions and opens up prospects for creating electronic devices with a fundamentally new level of properties for use in various fields of the economy and breakthrough critical technologies.

Synthesis of macrocyclic peptidomimetics via the Ugi-click-strategy.

The Ugi-click-strategy was employed for the synthesis of 12-28 membered 1,2,3-triazole derived macrocyclic peptidomimetics. The Ugi reaction with acid components bearing acetylenic fragments and azidoisocyanides provided the corresponding peptidomimetics in up to 97% isolated yield. The subsequent CuAAC click reaction with these bifunctional substrates containing both acetylene and azide groups was investigated to reveal the influence of the structure of Ugi products on the direction of the click-cyclization. It was demonstrated that this approach allows efficient synthesis of either monomeric (12- and 13-membered) or dimeric (24-, 26- and 28-membered) macrocycles prepared in up to 85% yield. The scope and limitations of this method are discussed.

Recent dynamics of hydro-ecosystems in thermokarst depressions in Central Siberia from satellite and in situ observations: Importance for agriculture and human life.

Alases, which are thermokarst depressions that are occupied by grasslands and lakes, are an important element of the Central Yakutian periglacial landscape. In recent decades, climatic changes in Central Yakutia have resulted in important changes in environmental conditions. We use different remote-sensing instruments (Landsat 8, TerraSAR-X, ENVISAT-RA2, and Jason-2) alongside in situ observations to investigate 1) the spatial distribution and water regime of alas lakes and their relationships with climatic and geomorphologic factors, 2) the relationship of the alas' grassland productivity with the water regime and 3) the potential of alas grasslands for local agriculture. During the 2002-2010 period, the lake water level rose by 1.3m on average, resulting in lake expansion throughout the region. Since 2011, the lake area decreased and the water level declined by 70cm on the middle terraces (low ground-ice content), while the wetting trend continued until 2016 at higher elevations. Small thermokarst lakes (<0.025km2), which indicate regions of young thermokarst, comprise up to 11% of the total lake area and experience high (30%) seasonal variations. In situ observations of the grassland dynamics show their synchronous cyclic variability with the lake extent and a general increasing trend for their productivity since 1985. Around 50% of these dynamics can be explained by the amount of pre-winter precipitation with a delay of two years. We explain this delay through the buffering effect of watershed soils. The cyclic variability of alas hydro-ecosystems strongly affects the local agriculture, which is based on horse and cattle breeding. We estimate that these alas grasslands can provide enough forage supply for local communities. However, the real alas yield is several times less than the theoretical value because of grassland degradation that is caused by recent thermokarst and waterlogging in the most productive phytocenosis.

Short-term results of isolated phlebectomy with preservation of incompetent great saphenous vein (ASVAL procedure) in primary varicose veins disease.

Objective To establish an effect of isolated phlebectomy in patients with incompetent great saphenous vein (Ambulatory Selective Varices Ablation under Local anesthesia (ASVAL) procedure) on the reflux and diameter of the trunk and to assess recurrence rate of varicose veins at one year. Material and methods We conducted a prospective study on patients with primary varicose veins and with C2 or C2,3 or C2,3,4 or C2,4 classes of chronic venous disease and great saphenous vein incompetence. The study included 67 patients (51 women and 16 men; 75 limbs in total). Age varied from 17 to 71 years; mean age was 46.8 years (SD 13.9). We recorded the presence or absence of reflux in the great saphenous vein with duplex ultrasound before and after surgery. The recurrence of varicose veins was evaluated at 12 months. All the patients underwent isolated phlebectomy with preservation of incompetent great saphenous vein (ASVAL procedure) under local anesthesia. Results At one year after removing of tributaries of the incompetent trunk, 66% of them were competent. Reflux persisted in 17% of great saphenous veins with reflux above mid-thigh and in 61% of trunks with reflux extended below the mid-thigh (p = 0.0004). The diameter of all the veins decreased significantly no matter reflux disappeared or not. Varicose veins reoccurred in 13.5% cases. In 6.5% of limbs with a reflux above the mid-thigh, the recurrence was registered at one year, while in the limbs with the reflux below the mid-thigh at a baseline, the recurrence rate was 25% (p = 0.036). Conclusion Isolated phlebectomy with a preservation of incompetent great saphenous vein leads to disappearance of reflux in a majority of cases and to significant decrease of vein diameter in all the cases. ASVAL procedure could be considered as a less aggressive and less expensive approach in selected cases. Clear indications for isolated phlebectomy need to be established.