Oxidative dehydrogenation of 2,3,5-trimethyl-1,4-hydroquinone in the presence of titanium dioxide hydrogel

Liquid-phase oxidative dehydrogenation of 2,3,5-trimethyl-1,4-hydroquinone in the presence of titanium dioxide hydrogel was studied by a kinetic method. Associative interactions between the substrate, oxidant, and gel were detected by voltammetry and ESR and IR spectroscopy.Russian Foundation for Basic Researc

Thermal properties and structure of cast carbon-containing invar and superinvar alloys after two-stage annealing

The effect of carbon content on thermal properties of cast superinvar alloys subjected to two-stage annealing is studied. It is shown that carbon improves the casting properties of the alloys but raises the temperature coefficient of linear expansion (CTLE). Two-stage high-temperature annealing makes it possible to remove carbon from the solid solution and to transfer it into graphite, which is accompanied by decrease in the CTLE. © 2013 Springer Science+Business Media New York

Measuring angular coordinates in Unmanned Aerial Vehicles (UAVs) positioning systems and developing a new phase-metric method for goniometric control of UAVs

For the safe operation of Unmanned Aerial Vehicles (UAVs), an effective Automatic Control System (ACS) is necessary, which for successful operation requires high accuracy of the initial information about the UAV’s position in space. Based on the analysis of the shortcomings of the known orientation systems, a phase-metric method of goniometric (angular) control based on accelerometric and gyroscopic transducers for positioning the UAV is proposed, which has a higher accuracy and a wider range of measurement angles. The conducted study showed that in a wide range of rotation angles from 10 to 90 degrees, the root mean square error (RMS) of the results of calculating the rotation angle using the phase-metric method is 8,78 times less than the RMS of the results of calculating the rotation angle using the arctangent function. Reducing the error determines the effectiveness of the proposed method in UAV control systems

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

THE REACTION OF PHOSPHORUS-CONTAINING INTRACELLULAR INCLUSIONS TO SPACE WEATHER CHANGES

It is known that the bio-astronomical effect of Chizhevsky-Velhover is based on the cytochemical metachromatic reaction of polyphosphatecontaining volutin granules of microorganisms. As a result of long-term monitoring (2001-2015 years) of this of cytochemical index in yeasts Saccharomyces cerevisiae, it was shown that metachromatic staining of the granules possessed rhythmicity and connection with space weather. Under laboratory conditions the change of metachromasy was achieved by applying different stress factors: anaerobiosis, low temperature, acidity. Simulation of metachromatic staining in vitro by using solutions of inorganic polyphosphate with other compounds showed that this reaction was possible for the low concentrations of these polymers. The effect of the low concentrations was more expressed with increasing chain length of polyphosphate. The inhibition of the metachromasy in solution with added protein and calcium chloride indicated that this of reaction involved the presence of the protonated sites in the polymers. It is assumed that metachromatic staining of volutin granules in vivo may depend on other conditions including conformational restructuring of a polymer or sol-gel phase transitions. Thus, the question whether the metachromatic reaction of intracellular polyphosphate granules to the space weather changes is driven by a response to associated stress or despite the apparent similarity of the effects they are of a different nature remains unclear

Application of communication systems via the ultraviolet channel in FANET networks

The possibility of providing communication in difficult conditions on the basis of Flying Ad Hoc Networks (FANET) requires the use of non-electronic means of communication. It is proposed to use optical communication in the UV-C range in the absence of line-of-sight between the nodes of the FANET network. The general scheme of the optical transmitter and receiver of UV-C range is considered and the review of the components required for its implementation, taking into account the application possibility in highly mobile small-sized UAVs, is carried out. As a result of the analysis of FANET networks with UV-C channel, physical and channel level parameters critical for network performance are revealed. Methods of adaptive change of these parameters in the practical implementation of the UV-C communication system in FANET networks are proposed

Application of communication systems via the ultraviolet channel in FANET networks

The possibility of providing communication in difficult conditions on the basis of Flying Ad Hoc Networks (FANET) requires the use of non-electronic means of communication. It is proposed to use optical communication in the UV-C range in the absence of line-of-sight between the nodes of the FANET network. The general scheme of the optical transmitter and receiver of UV-C range is considered and the review of the components required for its implementation, taking into account the application possibility in highly mobile small-sized UAVs, is carried out. As a result of the analysis of FANET networks with UV-C channel, physical and channel level parameters critical for network performance are revealed. Methods of adaptive change of these parameters in the practical implementation of the UV-C communication system in FANET networks are proposed