Electronic structure study of YNbTiO6_6 vs. CaNb2_2O6_6 with U, Pu and minor actinide substitutions using compound-tunable embedding potential method

The compound-tunable embedding potential (CTEP) method is applied to study actinide substitutions in the niobate crystals YNbTiO$_6$ and CaNb$_2$O$_6$. Two one-center clusters centered on Ca and Y are built and 20 substitutions of Ca and Y with U, Np, Pu, Am, and Cm in four different oxidation states were made for each cluster. Geometry relaxation is performed for each resulting structure, and electronic properties are analyzed by evaluating the spin density distribution and X-ray emission spectra chemical shifts. Though the studied embedded clusters with actinides having the same oxidation state are found in general to yield similar local structure distortions, for Am and Cm in high "starting" oxidation states the electron transfer from the environment was found, resulting in decrease of their oxidation states, while for "starting" U$^{\rm III}$ state the electron transfer goes in the opposite direction, resulting in increase of its oxidation state to U$^{\rm IV}$. The U substitutions are additionally studied with the use of multi-center models, which can provide both more structural and electronic relaxation and also include charge-compensating vacancies. For "starting" U$^{\rm VI}$ case, the decrease in oxidation state similar to that of Am$^{\rm VI}$ and Cm$^{\rm VI}$ in one-center clusters is observed in our calculations but in a different way. Since the really synthesized YNbTiO$_6$ structures can not be considered as perfect (periodic) crystals because the Nb and Ti atoms are statistically distributed within them occupying the same Wyckoff positions, different Ti $\leftrightarrow$ Nb substitutions are studied and corresponding structural changes are estimated

Natural adaptogenes on the basis of beekeeping products in the correction of fatigue during the recovery period of the annual training cycle for athletes of winter coordination sports

Objective: to evaluate the effectiveness of the application of bee products in correction of signs of fatigue during the recovery period in athletes of complex coordination sports. Materials and methods: 40 athletes of complex winter sports 15-21 years old (mean age - 19.05±3.42 years (M±m)) were examined: the main group (24 people) received 10% aqueous-alcoholic extract of bee moth larvae during 25 days of the recovery period; rantrol group (16 persons) received dry adsorbed royal jelly. The parameters of hematopoiesis, immune and hormonal status, physical working capacity were studied. Results: a decrease in the concentration of TNF-a and IL-4, and increase in IL-1ß and IL-6 within the reference values was established after the course of beekeeping products intake in both groups of athletes. The administration of the bee moth larva extract resulted in a decrease in the CIC (p = 0.010), an increase in the CD3 +, CD 19- lymphocytes (p = 0.028), CD3 +, CD4 + lymphocytes (p = 0.016), and signs of stimulation of erythropoiesis in the form of an increase in erythrocytes (p = 0.016) and reticulocytes (p = 0.027), as well as an increase in testosterone (p = 0.038) and physical performance (p = 0.041; p = 0.034), that was more pronounced in comparison with the royal jelly intake. Conclusions: the use of bee moth larva extract in the recovery period resulted in more significant improvement in the state of the oxygen-providing blood system, correction of the immunological imbalance and hormonal parameters of adaptation, and preservation of the level of physical fitness achieved in the competitive period in comparison with royal jelly

Siberian Arctic black carbon sources constrained by model and observation

Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng⋅m−3 to 302 ng⋅m−3) and dual-isotope–constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth

Compound-tunable embedding potential method to model local electronic excitations on ff-element ions in solids: Pilot relativistic coupled cluster study of Ce and Th impurities in yttrium orthophosphate, YPO4_4

A method to simulate local properties and processes in crystals with impurities via constructing cluster models within the frame of the compound-tunable embedding potential (CTEP) and highly-accurate {\it ab initio} relativistic molecular-type electronic structure calculations is developed and applied to the Ce and Th-doped yttrium orthophosphate crystals, YPO$_4$, having xenotime structure. Two embedded cluster models are considered, the "minimal" one, YO$_8$@CTEP$_{\rm min}$, consisting of the central Y$^{3+}$ cation and its first coordination sphere of eight O$^{2-}$ anions (i.~e.\ with broken P--O bonds), and its extended counterpart, Y(PO$_4$)$_6$@CTEP$_{\rm ext}$, implying the full treatment of all atoms of the PO$_4^{3-}$ anions nearest to the central Y$^{3+}$ cation. CTEP$_{\rm min,ext}$ denote here the corresponding cluster environment described within the CTEP method. The relativistic Fock-space coupled cluster (FS RCC) theory is applied to the minimal cluster model to study electronic excitations localized on Ce$^{3+}$ and Th$^{3+}$ impurity ions. Calculated transition energies for the cerium-doped xenotime are in a good agreement with the available experimental data (mean absolute deviation of ca.0.3 eV for $4f{\to}5d$ type transitions). For the thorium-doped crystal the picture of electronic states is predicted to be quite complicated, the ground state is expected to be of the $6d$ character. The uncertainty for the excitation energies of thorium-doped xenotime is estimated to be within 0.35 eV. Radiative lifetimes of excited states are calculated at the FS RCC level for both doped crystals. The calculated lifetime of the lowest $5d$ state of Ce$^{3+}$ differs from the experimentally measured one by no more than twice

Forecasting the development of mechanical engineering using the system dynamics method

At modern conditions of world economy tendencies, the connections between subjects of economy are becoming more difficult and closer. In particular, if in the past were spread hard forms of private ownership of enterprises at present-day world is going conversion to more flexible and mobile composition of subjects' activities. Computer simulation modeling is giving the best results at the areas were the participants of social and economic activities are spending significant efforts and sufficiently much time for visuality playing and analysis of possible variants of the development of the events. The more difficult is the situation the more objects, factors, and possible variants of events' progress is necessary to play in different combinations between together and bigger effect possible to expect from application of simulation model for analyzing of the situation and for searching and making optimized decisions. The application of system dynamics method allows executing forecasting of economic agents including the sectors of economy. © 2020 American Institute of Physics Inc.. All rights reserved

Examination of the Microvasculature During Wound Process of the Oral Mucosa when Using Dual-Wavelength Photodynamic Therapy: a Pre-Clinical Experimental Randomized Study

Background. Healing of open wounds in the oral cavity is often accompanied by infection and constant traumatization, which lead to impaired blood supply to the tissues, lack of trophic support and low oxygen supply to increasing proliferative processes. Recently, photodynamic therapy has taken its place among the methods for stimulating regeneration of oral mucosal tissues. The authors consider it essential to study the influence of photodynamic treatment on the functional state of the microvasculature in the wound tissues, which determines the transcapillary exchange and the tissue respiration, providing the tissue regeneration.Objective. To study the photodynamic effect of sequential dual-wavelength radiation on the microvasculature in the wound tissues of the oral mucosa in vivo.Methods. The study was carried out on 36 female outbred Wistar rats, weighing 200–250 g. The animals were divided into two groups: control group (n = 18) and experimental group (n = 18). Wound surfaces healed by secondary intention were modeled on the cheek mucosa of the animals. Dual-wavelength photodynamic therapy was performed in the 1st postoperative day in experimental group. The microcirculatory function was assessed by Doppler flowmetry before, and on days 3, 7 and 14 after wounding. The results were processed using IBM SPSS Statistics 26.0.0.1 (IBM Inc., USA).Results. It has been established that dual-wavelength photodynamic therapy has a positive effect on the restoration of the microvasculature of the wound tissues. This therapy facilitated bypassing for microcirculatory flow on the 3rd day of the study, and increased the perfusion of tissues on the 7th. The experimental group did not have congestive-ischaemic phenomena in the wound region; the microcirculatory flow was augmented through the microcirculation regulation by the 14th day.Conclusion. Following the obtained results the use of dual-wavelength photodynamic therapy can be considered as a promising method for restoration of the microvasculature of tissues in the oral mucosal trauma

Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 25 (2011): GB2002, doi:10.1029/2010GB003845.The magnitude and feedbacks of future methane release from the Arctic region are unknown. Despite limited documentation of potential future releases associated with thawing permafrost and degassing methane hydrates, the large potential for future methane releases calls for improved understanding of the interaction of a changing climate with processes in the Arctic and chemical feedbacks in the atmosphere. Here we apply a “state of the art” atmospheric chemistry transport model to show that large emissions of CH 4 would likely have an unexpectedly large impact on the chemical composition of the atmosphere and on radiative forcing (RF). The indirect contribution to RF of additional methane emission is particularly important. It is shown that if global methane emissions were to increase by factors of 2.5 and 5.2 above current emissions, the indirect contributions to RF would be about 250% and 400%, respectively, of the RF that can be attributed to directly emitted methane alone. Assuming several hypothetical scenarios of CH 4 release associated with permafrost thaw, shallow marine hydrate degassing, and submarine landslides, we find a strong positive feedback on RF through atmospheric chemistry. In particular, the impact of CH 4 is enhanced through increase of its lifetime, and of atmospheric abundances of ozone, stratospheric water vapor, and CO 2 as a result of atmospheric chemical processes. Despite uncertainties in emission scenarios, our results provide a better understanding of the feedbacks in the atmospheric chemistry that would amplify climate warming

Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling

Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 ± 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond