The Cu(I)-catalyzed denitrogenative transannulation reaction of pyridotriazoles with terminal alkynes en route to indolizines was developed. Compared to the previously reported Rh-catalyzed ...transannulation reaction, this Cu-catalyzed method features aerobic conditions and much broader scope of pyridotriazoles and alkynes.
The hippocampus plays the key role in stress response regulation, and stress response appears to be weakened in domesticated animals compared to their wild relatives. The hippocampus is functionally ...heterogeneous along its dorsoventral axis, with its ventral compartment being more closely involved in stress regulation. An earlier series of experiments was conducted with a unique breeding model of animal domestication, the farm silver fox (Vulpes vulpes), which included tame, aggressive, and unselected animals. A decrease in many indices of the hypothalamic-pituitary-adrenal activity was observed in tame animals. Also, adult hippocampal neurogenesis was more intense in tame foxes, and this fact may relate to reduced stress levels in this experimental population of foxes. Nevertheless, the molecular mechanisms responsible for the reduced stress response in tame animals remain obscure. In this study, serum cortisol levels and the mRNA levels of 13 genes in the dorsal and ventral hippocampus have been measured and compared in tame, aggressive, and unselected foxes. At the current stage of domestication, stress-induced cortisol levels in tame, aggressive, and unselected animals differ significantly from each other: tame foxes show the lowest levels, and aggressive ones, the highest. Twelve genes tested demonstrate significant gene expression differences between the dorsal and ventral hippocampi. These differences are mainly consistent with those found in rodents and humans. In tame foxes, significantly elevated mRNA levels were recorded for several genes: CYP26B1 for cytochrome P450 26B1 and ADRA1A for α1A adrenergic receptor in the dorsal hippocampus, whereas the level of NR3C2 mRNA for mineralocorticoid receptor was higher in the ventral. It is presumed that these genes constitute an important part of the mechanism reducing stress induced by contacts with humans and contribute to linking stress regulation with adult neurogenesis in tame foxes and domesticated animals in general.
The study proposes a stepwise scheme of the initial stage in the transition to a closed nuclear fuel cycle (NFC) two-component nuclear power engineering system comprising fast and thermal reactors. ...The closure of the NFC appears to be economically justified due to the envisaged construction of between six and nine BN-1200M fast neutron power units. Since no scarcity of plutonium is expected by 2031, the assumed year of commissioning the BN-1200M fast neutron reactor, it is expedient to defer the processing of spent plutonium fuel and instead store it into the middle of 2050s, reducing capital and fuel costs. However, it will be cost-effective to begin full-scale processing at centralized productions after 2050, since the expected quantity of spent fuel from fast reactors will by then be sufficient to achieve significant reductions in the specific cost of its processing.
Fast reactors can be used to adjust the isotopic composition of plutonium from spent mixed uranium-plutonium fuel from PWR and make it recyclable. The efficacy of such an adjustment is directly ...related to the scope for breeding in fast reactors. This can be done in the operating BN-800 reactor by multiple recycling of plutonium in the fuel of the fast reactor as well as by using
235
U or in specialized (target) fuel assemblies with reduced plutonium content. The international project with the use of BN-800 will make it possible to experimentally demonstrate this possibility on representative batches of plutonium (up to 100 kg/yr) as well as to work out the particularities of international and national laws in the field of accounting and moving of nuclear materials. A commercially significant project (with a turnover of 1 t or more of plutonium per year) to adjust the plutonium composition can be planned when a series of commercial high-power fast reactors with a heightened breeding ratio is put into operation.
The development of any energy system, including nuclear, is a lengthy and multi-stage process. To evaluate the outlook, many significant factors outside the nuclear energy system and the uncertainty ...of future avenues of macroeconomic development must be taken into account. This task requires a multi-criteria approach to the analysis of the competitiveness of the technology using criteria that combine economic and safety indicators, environmental impacts, realization risks, and development outlook. This article reports the results of a multi-criteria systems analysis of alternative scenarios for the development of nuclear energy in Russia performed using international assessment tools.
Currently, nuclear society has recognized that further development of Russian nuclear power industry will be carried out under the two-component framework represented with thermal and fast reactors ...operating within the total closed fuel cycle. Several scenarios of the nuclear fuel cycle closure within Russian two-component nuclear power system (NPS) have been currently discussed among the industry specialists. These scenarios are based on various philosophies of the NFC closure (centralized NFC closed by thermal and fast reactors fuel or station NFC for closure of the fuel cycle of BREST reactors only), various fast reactor technologies and various types of the fuel used: UOX/MOX or mixed nitride U-Pu. The key difference is in different understanding of fast reactors role in NPS fuel cycle closure. This results in varying requirements to fast reactors and the terms of implementation of such requirements. This report focuses on the role of fast sodium reactors as a system-forming component of the future two-component nuclear power system operating within the total fuel cycle with thermal reactors.
Accelerator mass spectrometry (AMS) was shown to be applicable for studying the penetration of organic aerosols, inhaled by laboratory mice at ultra-low concentration ca. 103 cm−3. We synthesized ...polystyrene (PS) beads, composed of radiocarbon-labeled styrene, for testing them as model organic aerosols. As a source of radiocarbon we used methyl alcohol with radioactivity. Radiolabeled polystyrene beads were obtained by emulsifier-free emulsion polymerization of synthesized 14C-styrene initiated by K2S2O8 in aqueous media. Aerosol particles were produced by pneumatic spraying of diluted 14C-PS latex. Mice inhaled 14C-PS aerosol consisting of the mix of 103 225-nm particles per 1 cm3 and 5·103 25-nm particles per 1 cm3 for 30 min every day during five days. Several millions of 225-nm particles deposited in the lungs and slowly excreted from them during two weeks of postexposure. Penetration of particles matter was also observed for liver, kidneys and brain, but not for a heart.
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•Radiocarbon labeled styrene was synthesized in five stages from 14C-methanol.•PS beads 225 ± 25 nm in size containing radiocarbon 14C label were used as a model system for organic aerosol.•Low-concentrated 10−3 cm−314C-aerosol was inhaled by mice during 5 days 30 min a day.•The isotope analysis of biological probes was conducted by accelerator mass-spectrometry.•The particle matter was directly registered in mice lungs, liver, kidneys and brain.
The main approaches to americium transmutation in BN-1200M are considered: homogeneous transmutation in the core and heterogeneous transmutation with a moderator in the radial blanket. It is stated ...that the main limiting factor of transmutation is the residual heat release of the unloaded FAs. Within the design constraints, the annual transmutation rates are approximately the same in both cases. It is proposed to combine the advantages of both transmutational methods so as to ensure the homogeneous transmutation of americium in the core at the level of an equilibrium content and the heterogeneous transmutation of external americium in the radial blanket. On the basis of a simplified economic model, a comparison of various approaches was made and the corresponding technical and economic estimates were given.
The exportation of fast reactors under an international nuclear weapons non-proliferation regime is discussed. Russian sodium fast-reactor technology has been successfully demonstrated and is in the ...commercialization stage. Fast reactors with lead as coolant are being developed in Project Breakthrough. In this connection, the possibility of exporting fast reactors becomes logical. The main criterion for such exports is competitiveness of the electricity produced taking the possibility of offering other, additional services into account. Other criteria that undoubtedly will influence the decisions made about exports are elements associated with the need for strict adherence to the international nuclear weapons non-proliferation regime. The basis of this regime is the nuclear weapons non-proliferation treaty. The IAEA system of safeguards plays a key role as a control element in verifying the obligations of non-nuclear states in the sphere of nuclear non-proliferation.
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