Skeletally Dugundji spaces

We introduce and investigate the class of skeletally Dugundji spaces as a skeletal analogue of Dugundji space. The main result states that the following conditions are equivalent for a given space $X$: (i) $X$ is skeletally Dugundji; (ii) Every compactification of $X$ is co-absolute to a Dugundji space; (iii) Every $C^*$-embedding of the absolute $p(X)$ in another space is strongly $\pi$-regular; (iv) $X$ has a multiplicative lattice in the sense of Shchepin \cite{s76} consisting of skeletal maps

CONSTRUCTION OF FIVE-MEMBERED HETEROCYCLES USING CALCIUM CARBIDE

This work was supported by the Grant Council of the President of the Russian Federation (МК-2615.2021.1.3)

Standards for the Characterization of Endurance in Resistive Switching Devices

Resistive switching (RS) devices are emerging electronic components that could have applications in multiple types of integrated circuits, including electronic memories, true random number generators, radiofrequency switches, neuromorphic vision sensors, and artificial neural networks. The main factor hindering the massive employment of RS devices in commercial circuits is related to variability and reliability issues, which are usually evaluated through switching endurance tests. However, we note that most studies that claimed high endurances >106 cycles were based on resistance versus cycle plots that contain very few data points (in many cases even <20), and which are collected in only one device. We recommend not to use such a characterization method because it is highly inaccurate and unreliable (i.e., it cannot reliably demonstrate that the device effectively switches in every cycle and it ignores cycle-to-cycle and device-to-device variability). This has created a blurry vision of the real performance of RS devices and in many cases has exaggerated their potential. This article proposes and describes a method for the correct characterization of switching endurance in RS devices; this method aims to construct endurance plots showing one data point per cycle and resistive state and combine data from multiple devices. Adopting this recommended method should result in more reliable literature in the field of RS technologies, which should accelerate their integration in commercial products

Natural and anthropogenic factors influence on the botanic natural sanctuary vegetation cover dynamics of the river Volga delta

The river Volga state assessment and landscape functioning is an extremely necessary part for stable and ecologically safe region development. One of the most important this assessment components is vegetation monitoring organization and conduction, which is the necessary part of modern ecosystem exploitation. Monitoring investigations brief results of the botanic natural monuments vegetation cover situated in the eastern part of the river Volga delta are shown in this work. Environment major factors change impact defining main ecological properties if deltoid landscape vegetation cover: some climatic characteristics, the river Volga hydrological regime changes and flooding conditions, vegetation cover differentiation peculiarities in dependence on deltoid land forms and confined processes to it are considered for the monitoring period. It was revealed during the monitoring that abrupt water-soluble salts amount increase in soils occurred, also toxicity level and soil salinization type from chloride- sulfate to sulfate-chloride, that affects vegetation cover: total biomass decrease, projective cover degree decrease on the all deltoid landscape high level, sedges and gramineous plant involvement degree decrease and herbs increase in vegetation cover due to ariditization degree and desert advancing caused either by natural or anthropogenic impact

Characteristics and Properties of Chromium Coatings with Diamond Nanoparticles Deposited Directly on Aluminum Alloys

The objective of this study was to deposit directly chromium with diamond nanoparticles (ND) on aluminum alloys and investigate the coating surface. The chromium coatings on aluminum alloys were obtained by electrochemical deposition. The coatings were doped with ND. The diamond nanoparticles were obtained by detonation synthesis. Chromium coatings were deposited on aluminum alloys with a silicon content of 7 % and 10 %. The ND concentration in the electrolyte was 25 g/l. The surface analysis was performed by means of Atomic force microscopy. The surface of the coating of chromium with ND on Al10Si is twice more even than that on Al7Si. The microstructure and microhardness were examined with a metallographic microscope and a microhardness tester. The microhardness of the coated samples is 9163 MPa compared to 893 MPa of uncoated aluminum samples. The thickness of the chromium coatings doped with diamond nanoparticles is between 45 – 55 μm. The coatings are dense, continuous and uniform with good adhesion to the substrate material