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Brouchkov A.V.,Tyumen State Oil and Gas University | Melnikov V.P.,Tyumen State Oil and Gas University | Schelchkova M.V.,Ammosov North East Federal University | Griva G.I.,Russian Academy of Sciences | And 3 more authors.
Earth's Cryosphere

Permafrost is widespread in the Northern Hemisphere and is as old as hundreds of thousands to millions of years. Frozen ground stores living microorganisms which remain unfrozen in the relatively warm environment (-2⋯-8 °C) but are immobilized and may be about the age of the host permafrost. A strain of Bacillus sp. was isolated from ∼3 Ma permafrost and its 16S rDNA sequence was identified. A large group of microorganisms including fungi was isolated from the wedge ice. Permafrost deposits contain invertase, urease, katalase and dehydrogenase. © 2011 A.V. Brouchkov, V. P. Melnikov, M.V. Schelchkova, G.I. Griva, V.E. Repin, E.V. Brenner, M. Tanaka, All rights reserved. Source

Skryabin R.M.,Ammosov North East Federal University | Timofeev N.G.,Ammosov North East Federal University
Gornyi Zhurnal

The paper presents designs and recommendations on improvement of technology and equipment of exploration shaft drilling in prospecting of placers on the north-east of Russia, in permafrost zone. The authors state the low productivity, high labor content and extra cost of the currently employed technology and equipment in exploration shaft drilling, and point at the insufficient research effort and recommendations aimed at reengineering of exploration shaft drilling-assisted geological survey of placers in permafrost zone. Based on the analysis of literature, practice of exploration shaft drilling and personal research, the authors offer the method of rotation drilling of exploration shafts with broken frozen rock removal at intervals (auger-coring tool with a diameter of 750 mm) as the most efficient and promising method of prospecting placers in permafrost zone. For the purpose of representativity, completeness and quality of sampling, the authors recommend to use kelly bars, to arrange the worm in the core barrel, to take samples at intervals and to equip the drill rig with a rotating platform. A detail discussion covers recommendations on selecting rock cutting tool and its optimized operation at exploration shaft bottom in permafrost formations. It is recommended to arrange cutters at varied height to make stepshaped (uneven) shaft bottom. Areas of further research toward improvement and reengineering of auger-coring drilling of geological exploration shafts under conditions of permafrost are identified. Source

Nebogatikova N.A.,RAS Semiconductor Physics Institute | Antonova I.V.,Novosibirsk State University | Prinz V.Ya.,RAS Semiconductor Physics Institute | Timofeev V.B.,Ammosov North East Federal University | Smagulova S.A.,Ammosov North East Federal University

In the present study, we examined the creation conditions and the properties of graphene or multi-layer graphene (MLG) quantum dots (QDs) self-formed in insulating dielectric fluorographene matrix. The QD arrays were obtained using chemical functionalization of graphene or MLG films in an aqueous solution of hydrofluoric acid. The formation of a fluorographene network in the films caused their transition from conducting to insulating state; this transition was a result of partitioning of the films into isolated graphene islands accompanied by an increase of the resistance of the films by 7-8 orders of magnitude. Experimentally, it was shown that the characteristic time required for the formation of QD arrays in the films depended linearly on the initial film thickness, on the solution concentration, and on temperature. The atomic force microscopy lateral force measurements have allowed us to evaluate the sizes and densities of formed QDs, and to trace the evolution of both QDs and fluorinated barriers between them in the functionalization process. A possibility to achieve QD sizes ranging from 70-20 nm (at QD density ∼(4-6) × 1010 cm-2) to 10-20 nm (at QD density ∼1 × 1010 cm-2) has been demonstrated. The activation energies of electrical conductivity in the films with QDs have been evaluated. © 2014 Elsevier Ltd. All rights reserved. Source

Nebogatikova N.A.,RAS Semiconductor Physics Institute | Antonova I.V.,Novosibirsk State University | Kurkina I.I.,Ammosov North East Federal University | Soots R.A.,RAS Semiconductor Physics Institute | And 4 more authors.

The possibility to control the size of the flakes of graphene suspension in the course of their fluorination in an aqueous hydrofluoric acid solution was demonstrated. The effect of the suspension composition, the fluorination time, temperature and thermal stress on the fragmentation process was investigated. The corrugation of suspension flakes, which occurs at fluorination due to a difference in the constants of graphene and fluorographene lattices, leads to the appearance of nonuniform mechanical stresses. The fact that the flake size after fragmentation is determined by the size of corrugation allows the assumption that the driving force of fragmentation is this mechanical stress. This assumption is confirmed by the break of the corrugated layers from flakes under thermal stress. Moreover, fluorination treatment at elevated temperatures (∼70 °C) significantly accelerates the fragmentation process. Suspensions of fluorinated graphene with nanometer size flakes are of interest for the development of 2D ink-jet printing technologies and production of thermally and chemically stable dielectric films for nanoelectronics. The printed fluorinated graphene films on silicon and flexible substrates have been demonstrated and the charges in metal-insulator-semiconductor structures have been estimated as the ultra low values of (0.5-2) × 1010 cm-2. © 2016 IOP Publishing Ltd. Source

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