An electronic-very long baseline interferometry mode on the quasar-KVO radio interferometric complex

Results of experimental studies on data transmission of hourly and daily very long baseline interferometry (VLBI) sessions from the Badary observatory to the Correlation Processing Center, Russian Academy of Sciences (St. Petersburg) in a communication channel with a bandwidth of 300 Mbit/s are presented.     

Comparative Estimation of the Effect from Using Different Coolants in Panel-Type Radiators of Spacecrafts

A radiant cooling heat exchanger is one of key components in a closed-cycle power installation and is the bulkiest structural part of a spacecraft. The most well-elaborated version of a cooler, known as a panel-type radiator (PR), is made according to the process arrangement of radiating panels. Selecting the optimal coolant is one of important issues in designing a PR. A liquid metal coolant in the form of molten Na–K mixture is presently regarded to be the most preferred one for these purposes. It features thermal stability, resistance to radiation, and a very high thermal conductivity. The main negative feature of Na–K melt is its explosion hazard when exposed to air, a circumstance due to which difficulties are encountered in experimentally perfecting the PR design under on-land conditions. We consider high-temperature organic coolants as an alternative to a liquid metal coolant. The aim of this study was to compare the effectiveness of using different coolants for the class of PR systems whose properties and geometrical characteristics are close to the prototypes developed at the State Scientific Center (SSC) Keldysh Research Center from composite materials on the basis of carbon fibers with high thermal conductivity. To this end, a mathematical model and relevant calculation procedure have been developed. The results from the performed calculations testify that, in view of a low specific heat of liquid metal coolant, its mass flow-rate should be a factor of 2–2.5 higher than the flowrate of high-temperature organic coolant, which entails essential loss of energy for pumping. Thus, the use of high-temperature organic coolants is more preferable for a certain class of PRs with parameters close to the considered ones. Turbulent flow of coolant is an important condition, due to which significant requirements are posed to its viscous characteristics. A diphenyl mixture can be regarded as the most efficient high-temperature coolant for the considered class of PRs.     

Properties of new cast antifrictional aluminum alloys

The mechanical and antifrictional properties of new cast aluminum alloys are considered. Their properties are compared with those of cast BrO4Ts4S17 bronze, which is widely used in the railroad industry. The replacement of bronze by the new alloys improves the life of slip bearings and reduces their cost.     

Laboratory selective disintegration of kimberlite

For the selective disintegration of kimberlite and dissociation of diamond crystals preserving their natural integrity undisturbed, the authors have designed a tool with cutters having hardness lower than diamonds but higher than binding minerals in kimberlite. The article gives the test results on the prototype of the heterogeneous material disintegrator on soft kimberlite extracted from Manchary pipe. The prototype includes disc brushes made of high-strength steel wire. The prototype realizing selective disintegration is a preproduction model of lab, semi-commercial and commercial disintegrators. The method is applicable to recover hard particles from geological samples.     

Trans-Membrane Area Asymmetry Controls the Shape of Cellular Organelles

Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant.     

Long-term firing tests of the nozzles of rocket engines made on the basis of carbon composite materials

The results of the experimental investigation of the physico-chemical processes of interaction, destruction, and ablation of carbon composite materials and oxidation-protective coatings of nozzles of liquid-propellant rocket engines are presented. The thermally-stressed state of the joint between the nozzle made of composite material and the metallic combustion chamber of the rocket engine under standard operating conditions have been analyzed.     

Breakdown features in electric cables with polymeric insulation

Compositions based on polyvinylchloride (PVC), which is sensitive to thermal aging, are used for the majority of electric cables as polymeric insulation. It is shown for the first time by the example of the most widespread polymeric insulation, which is made of polyvinylchloride preliminarily subjected to partial thermolysis, imitating its faster aging, that electrical conductivity of PVC can acquire an anomalous (not following the Ohm law) character due to aging. Transitions of PVC from a state with usual (low) conductivity into a state with anomalously high conductivity that have a spontaneous uncontrollable character are observed in this case. It is especially noteworthy that the character of these variations is large-scale, which makes it possible to easily transform PVC from the state of typical dielectric into the class of conductors. It is noted that the method of removal of a fire hazard (by maximally possible removal of short-circuits caused by thermal aging of polymeric insulation) should have a preventive character, being the most efficient, simplest, and most convenient.