Composite films and nonwoven mats of the poly-3-hydroxybutyrate and chitosan natural polymers were prepared and investigated. DSC and FTIR techniques were used to confirm that P(3HB) blending with ...chitosan resulted in a decrease in P(3HB) crystallinity to 47% and 62% in the films and nonwoven mats, respectively. Scanning electron microscopy showed that addition of chitosan induced changes in the surface morphology of the composite films and a reduction in the diameter of ultrafine fibers in the nonwoven mats from 800 nm to 460 nm. The values of water contact angle for films (53°) and nonwoven mats (50.6°) suggested that chitosan enhanced hydrophilic properties and moisture absorption capacity of the composite materials. On the other hand, P(3HB) showed its reinforcing ability and improved the physical/mechanical properties of chitosan. The work included studies of in vitro biodegradation of the composite specimens and their ability to maintain cell growth and attachment in NIH 3T3 fibroblast culture.
•Composite films and nonwoven mats of the P(3HB) and chitosan natural polymers were prepared and investigated.•P(3HB) blending with chitosan resulted in a decrease in P(3HB) crystallinity and the melting point.•The introduction of chitosan into the P (3HB) matrix increased the hydrophilicity of the composites and the adhesion of fibroblasts.
Whereas evolutionary inferences derived from present-day DNA sequences are by necessity indirect, ancient DNA sequences provide a direct view of past genetic variants. However, base lesions that ...accumulate in DNA over time may cause nucleotide misincorporations when ancient DNA sequences are replicated. By repeated amplifications of mitochondrial DNA sequences from a large number of ancient wolf remains, we show that C/G-to-T/A transitions are the predominant type of such misincorporations. Using a massively parallel sequencing method that allows large numbers of single DNA strands to be sequenced, we show that modifications of C, as well as to a lesser extent of G, residues cause such misincorporations. Experiments where oligonucleotides containing modified bases are used as templates in amplification reactions suggest that both of these types of misincorporations can be caused by deamination of the template bases. New DNA sequencing methods in conjunction with knowledge of misincorporation processes have now, in principle, opened the way for the determination of complete genomes from organisms that became extinct during and after the last glaciation.
Current status of tokamak T-15MD Khvostenko, P.P.; Anashkin, I.O.; Bondarchuk, E.N. ...
Fusion engineering and design,
March 2021, 2021-03-00, 20210301, Volume:
164
Journal Article
Peer reviewed
•T-15MD project is aimed at obtaining a database for creating a thermonuclear neutron source for atomic energy needs.•Magnet system of T-15MD will confine the hot plasma in the divertor ...configuration.•Toroidal magnetic field at the plasma axis is 2 T, plasma current is 2 MA.•Preparation to physical start-up of tokamak T-15MD is completed.•T-15MD should begin operation in 2021.
At the present time, the preparation to physical start-up of tokamak T-15MD is completed in the National Research Center “Kurchatov Institute”. The main parameters of T-15MD are: R = 1.48 m, a = 0.67 m, B = 2.0 T, Ipl = 2.0 MA. The magnet system is capable to maintain without overheating (more 60 °C) the plasma current of 2 MA for 4 s, 1 MA for 20 s, 700 kA for 40 s, 500 kA for 80 s, 300 kA for 160 s and 250 kA for 400 s. Plasma current drive can be maintained either by injection of fast neutrals or by electron cyclotron (EC)-, ion cyclotron (IC)- and low hybrid (LH) - waves. In August 2019 the electromagnetic system, consisting of TF and PF coils, together with vacuum vessel have been assembled in experimental hall. Power supply system of Tokamak T-15MD includes: two substations 110/10 kV, two substations 10/0.83 kV, thyristor convertors and different equipment. Total power consumption during the pulse with plasma current 2 MA and additional plasma heating of 20 MW will consist of 300 MVA. Power supply system is in the commissioning. Tokamak T-15MD will be operate using the information and control system. All the information and control system equipment, required for the implementation of physical start-up of tokamak T-15MD, is available. For plasma control the 250 different electromagnetic probes are installed inside vacuum vessel. The gyrotron with frequency 82.6 GHz and power of 1 MW will be used for pre-ionization.
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•T-15MD project is the initial technical base for creating fusion neutron source for atomic energy needs.•The preassembly of the tokamak T-15MD magnet system together with the vacuum ...vessel was completed.•Most of tokamak systems were manufactured and preliminary tested before the final assembly of tokamak.•All the diagnostic equipment is available and part of it was used in experiments on tokamak T-10.•Physical start-up T-15MD is scheduled for December 2020 year.
At the present time, in the NRC Kurchatov Institute under the auspices of the Federal Target Program “Nuclear energy-technologies of new generation for period 2010–2015 and to the prospect until 2020” the tokamak T-15MD and supporting facilities are being built. The preassembly of the tokamak T-15MD magnet system together with the vacuum vessel was completed at a plant in Bryansk. All elements of the magnet system and vacuum vessel have been delivered to the NRC “Kurchatov Institute” in Moscow for the tokamak T-15MD assembly. It is expected that the T-15MD assembly will be completed in March of 2019. The reconstruction of the sub-station 110/10/04 kV for own needs was completed in 2017 and the reconstruction of the main sub-station 110/10/1 kV, 300 MW was completed in 2018. Twenty- two of the new transformers 10/1 kV and 20 new thyristor convertors will be installed during 2018–2019 period. One gyrotron with output power 1 MW for pre-ionization should be installed in 2019. Tokamak T-15MD connection to water and electrical communication and also the adjustment of control system will be completed in the middle of 2020. Physical start-up T-15MD is scheduled for December 2020 year.
Biodegradable poly-3-hydroxybutyrate P(3HB) and natural fillers - clay, peat, and birch wood flour – were used to prepare powdered composites to form pellets and granules. Pellets were produced by ...cold pressing of polymer and filler powder whereas granules were produced from the powders wetted with ethanol. Characterization techniques like IR spectroscopy, differential scanning calorimetry, X-ray analysis, mechanical analysis and electron microscopy were employed to study the properties of the initial P(3HB) and fillers and the composites. Analysis of the IR spectra of the composites showed the absence of chemical bonds between the components, i.e. the composites were physical mixtures. Young's moduli of the pellets prepared from initial materials varied considerably, and the highest value was obtained for P(3HB) pellets (350 MPa). Studies of biodegradation of composite pellets and granules in the soil for 35 days showed that the residual mass of the pellets had decreased to 68% for P(3HB); 56.4% for P(3HB)/peat; 67% for P(3HB)/wood flour, and 64% for P(3HB)/clay; granules exhibited a similar mass loss, residual mass of the granules of P(3HB) was 68.4%, P(3HB)/peat 46.4%; P(3HB)/wood flour 77%, and P(3HB)/clay 74%. This shows the significance of the material as an eco-friendly composite without sacrificing its mechanical properties.
•The purpose of prebaking of the vessel is to check the quality of the numerous welds.•The maximal baking power was 65 kW.•The maximal temperature of vacuum shell was 187 °C.•The difference between ...maximal and minimal temperatures of vessel shell was 60 °C.•After the end of baking, no leaks were found in shell welds.
Presently, the Tokamak T-15MD is being built in the NRC “Kurchatov Institute”. The vacuum vessel was manufactured and passed the preliminary vacuum tests at the plant in St. Petersburg (Efremov Institute) in 2016. Vacuum vessel consists of toroidal shell made from 321stainless steel of 5 mm and 8 mm thickness, horizontal and vertical ports (152 in total), in-vessel elements. The vessel volume is 47 m3 and the surface square faced to plasma is ˜200 m2. The purpose of prebaking of the vacuum vessel is to check the quality of the numerous welds. To bake the vacuum vessel up to 220 °C at the plant in Bryansk, the Ohmic heaters have been laid on vessel shell surface both outside and inside. The thermal insulation (basalt wool) was applied on the outer surface of the vessel. The vessel’s surface temperature was controlled by thermocouples. The currents in heaters was regulated by four thyristor regulators. The temperature data were processed and stored using the data acquisition system.
The control of the deuterium–tritium (DT) fuel isotopic ratio has to ensure the best performance of the ITER thermonuclear fusion reactor. The diagnostic system described in this paper allows the ...measurement of this ratio analyzing the hydrogen isotope fluxes (performing neutral particle analysis (NPA)). The development and supply of the NPA diagnostics for ITER was delegated to the Russian Federation. The diagnostics is being developed at the Ioffe Institute. The system consists of two analyzers, viz., LENPA (Low Energy Neutral Particle Analyzer) with 10–200 keV energy range and HENPA (High Energy Neutral Particle Analyzer) with 0.1–4.0MeV energy range. Simultaneous operation of both analyzers in different energy ranges enables researchers to measure the DT fuel ratio both in the central burning plasma (thermonuclear burn zone) and at the edge as well. When developing the diagnostic complex, it was necessary to account for the impact of several factors: high levels of neutron and gamma radiation, the direct vacuum connection to the ITER vessel, implying high tritium containment, strict requirements on reliability of all units and mechanisms, and the limited space available for accommodation of the diagnostic hardware at the ITER tokamak. The paper describes the design of the diagnostic complex and the engineering solutions that make it possible to conduct measurements under tokamak reactor conditions. The proposed engineering solutions provide a safe—with respect to thermal and mechanical loads—common vacuum channel for hydrogen isotope atoms to pass to the analyzers; ensure efficient shielding of the analyzers from the ITER stray magnetic field (up to 1 kG); provide the remote control of the NPA diagnostic complex, in particular, connection/disconnection of the NPA vacuum beamline from the ITER vessel; meet the ITER radiation safety requirements; and ensure measurements of the fuel isotopic ratio under high levels of neutron and gamma radiation.
The Protvino accelerator facility located in the Moscow region, Russia, is in a good position to offer a rich experimental research program in the field of neutrino physics. Of particular interest is ...the possibility to direct a neutrino beam from Protvino towards the KM3NeT/ORCA detector, which is currently under construction in the Mediterranean Sea 40 km offshore Toulon, France. This proposal is known as P2O. Thanks to its baseline of 2595 km, this experiment would yield an unparalleled sensitivity to matter effects in the Earth, allowing for the determination of the neutrino mass ordering with a high level of certainty after only a few years of running at a modest beam intensity of
≈
90
kW
. With a prolonged exposure (
≈
1500
kW
year
), a
2
σ
sensitivity to the leptonic CP-violating Dirac phase can be achieved. A second stage of the experiment, comprising a further intensity upgrade of the accelerator complex and a densified version of the ORCA detector (Super-ORCA), would allow for up to a
6
σ
sensitivity to CP violation and a
10
∘
-
17
∘
resolution on the CP phase after 10 years of running with a 450 kW beam, competitive with other planned experiments. The initial composition and energy spectrum of the neutrino beam would need to be monitored by a near detector, to be constructed several hundred meters downstream from the proton beam target. The same neutrino beam and near detector set-up would also allow for neutrino-nucleus cross section measurements to be performed. A short-baseline sterile neutrino search experiment would also be possible.
The conceptual project of the construction of the cryostat and vacuum chamber was prepared, which are two of the main components of the compact tokamak with reactor technologies. The main technical ...solutions of the construction were decided, such as its configuration, technical characteristics, and operating regimes of its components. Conceptually, the cryostat is a single-wall cylindrical vacuum chamber made from austenitic stainless still that contains the superconducting electromagnetic system, the vacuum chamber, and the thermal protection of the cryostat and the vacuum chamber. The maximum diameter of the cryostat is of 12 m, its height is of 11 m, and its mass is of 317 t. In the cryostat, vacuum of 1 × 10
–4
Pa can be established. The vacuum chamber is an all-welded double-wall construction made from austenitic stainless still. Its inner and outer shells are connected by a set of toroidal and poloidal stiffening ribs, in the space between which borated water is circulating. The sickness of the shells and of the stiffening ribs is of 25 mm. The outer diameter of the chamber is of 6.64 m and its height is of 3.85 m.
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