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Highly selective/enantioselective Pt-ReOx/C catalyst for hydrogenation of L-malic acid at mild conditions

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Journal of Energy Chemistry 2018年第3期27卷 903-912页

作者： Bair S.Bal'zhinimaev Eugene A.Paukshtis Alexey P.Suknev nikita v.Makolkin Boreskov Institute of Catalysis SB RA5 Prospect Akademika Lavrentieva5Novosibirsk 630090Russia

The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized（Re2＋）. The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs（ca. 50 h-1）, selectivities（ca. 99%）and stability of Pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions（T = 90–130 ℃）. Taking into account that（i） hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and（ii） association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically（ee 〉 99%） pure（S）-3-hydroxy-γ-butyrolactone and（S）-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XPS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.

关键词： L-malic acid Hydrogenation Enantioselectivity Platinum Rhenium Atomic dispersion

Hyperbolicity of unitary involutions

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Science China Mathematics 2012年第5期55卷 937-945页

作者： KARPENKO nikita A. Institut de Math'ematiques de Jussieu Universit'e Pierre et Marie CurieParisFrance

We prove the so-called Unitary Hyperbolicity Theorem,a result on hyperbolicity of unitary *** analogous previously known results for the orthogonal and symplectic involutions are formal consequences of the unitary *** the original proofs in the orthogonal and symplectic cases were based on the incompressibility of generalized Severi-Brauer varieties,the proof in the unitary case is based on the incompressibility of their Weil transfers.

关键词： algebraic groups involutions projective homogeneous varieties Chow groups and motives Steenrod operations

Model Failure and Context Switching Using Logic-Based Stochastic Models

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Journal of Computer Science & Technology 2010年第4期25卷 665-680页

作者： nikita A.Sakhanenko George F.Luger Institute for Systems Biology Computer Science University of New Mexico

This paper addresses parameter drift in stochastic models. We define a notion of context that represents invariant, stable-over-time behavior and we then propose an algorithm for detecting context changes in processing a stream of data. A context change is seen as model failure, when a probabilistic model representing current behavior is no longer able to ＂fit＂ newly encountered data. We specify our stochastic models using a first-order logic-based probabilistic modeling language called Generalized Loopy Logic （GLL）. An important component of GLL is its learning mechanism that can identify context drift. We demonstrate how our algorithm can be incorporated into a failure-driven context-switching probabilistic modeling framework and offer several examples of its application.

关键词： context failure-driven online learning probabilistic reasoning

Mathematical modeling of icing process of the outer surface of the hull for a marine vessel

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Journal of Hydrodynamics 2023年第2期35卷 232-239页

作者： Konstantin Koshelev Andrey Osipov Sergei Strijhak nikita Tryaskin ISP RAS MoscowRussia Saint-Petersburg State Marine Technical University Saint-PetersburgRussia

The task of studying the process of icing is important due to the operation of large ships and fishing vessels in the seas of the Arctic *** this paper the ice accretion simulation for fishing vessel has been done at different Reynolds and Froude numbers.A hybrid approach was used for modeling:first,the approach based on Reynolds-averaged Navier-Stokes(RANS)model and volume of fluid(vOF)method with interDyMFoam solver was used for ship modelling in waves,second,RANS model and Euler-Lagrangian approach with iceFoam solver for ice accretion process modelling for ship with hull was *** k-ωSST turbulence model with wall functions was used for the RANS *** the help of the interDyMFoam solver,the position of water jet and liquid droplets in space were determined during the movement of the ship and taking into account the waves in the *** the help of iceFoam solver,the process of ice accretion on the surface of the vessel was *** calculations were run for different number Reynolds,*** analysis of mesh convergency was *** distribution of ice thickness and water film on the ship’s surface is *** simulations were performed on a high-performance cluster in parallel mode.

关键词： Ship sea safety climate movement modelling turbulence model water spray droplets velocity ice film mass

Mechanism of the Initial Stage of Thermal Decomposition of Nitroguanidine

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火炸药学报 2023年第1期46卷 31-40页

作者： Boris E.Krisyuk Danila A.Markin Timofey M.Sypko viktor v.Zakharov nikita v.Chukanov Boris L.Korsunskiy Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry Russian Academy of Sciences142432prosp.Academician Semenov1ChernogolovkaMoscow RegionRussia Plekhanov Russian University of Economics Department of Chemistry and Physics36 Stremyanny laneMoscow 117997Russia Lomonosov Moscow State University Faculty of Fundamental Physical and Chemical engineeringGSP-11 Leninskie Goryp.51Moscow 119991Russia N.N.Semenov Federal Research Center for Chemical Physics Russian Academy of Science 4 Kosygina StreetBuilding 1Moscow 119991Russia

A theoretical and experimental study of the thermal decomposition of nitroguanidine(NQ) has been carried out. various thermolysis channels were studied by quantum chemistry methods at the CCSD(or DLPNO-CCSD) level using the aug-cc-pvDZ basis set. It is shown that the lowest activation enthalpies(170-180kJ/mol) are characteristic of the reactions of NO2abstraction from the initial NQ and the reaction channel with the transfer of oxygen from the nitro group to carbon in the limiting stage. Additionally, the thermolysis of NQ was studied experimentally in a nonisothermal mode with heating rates from 1 to 10K/min. In these experiments, the weight loss of the sample, thermal effects, and mass spectra of the products were recorded. An analysis of the experimental data confirmed the results of a theoretical study of the mechanism of thermal decomposition of NQ. The main thermolysis products are N2O, HNCO, NH3, and NO2, which fully corresponds to quantum chemical calculations.

关键词： primary thermolysis steps quantum-chemical calculation mass spectrometry DSC TG

Oxidative chemical pretreatment by piranha solution for enhanced methane yield of wheat straw:mechanism and kinetic study

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Waste Disposal and Sustainable Energy 2023年第3期5卷 351-366页

作者： nikita Kanaujia Shalu Rawat Jiwan Singh Department of Environmental Science Babasaheb Bhimrao Ambedkar UniversityLucknow226025India

The present research work aims to explore the potency of piranha solutions at the best-optimized concentrations,i.e.,40%and 30%to reduce the recalcitrant and heterogeneous structure of wheat straw,and the treated wheat straw was denoted as WS40 and *** effect of pretreatment on wheat straw was determined by anaerobic digestion(AD)in a batch mode,followed by the analysis of soluble chemical oxygen demand(sCOD)and volatile fatty acids(vFAs).After pretreatment,the surface fibers shattered and detached,showing a distorted surface of wheat *** increase in the crystallinity of wheat straw after pretreatment was also observed due to the removal of amorphous cellulose and *** in methane yield was obtained on the 9th day,which was 103±6.92 and 99.33±0.57 mL/d for WS40 and WS30,*** water measurement revealed that the pretreatment of wheat straw minimized the hydrolysis period by 14 *** also improved the methane yield by 2.65(WS40)and 2.45(WS30)fold in comparison with the control which yielded 35.66 mL/d methane on the 23rd *** modified Gompertz model(MGM),logistic function model(LFM)and transference function model(TFM)adequately described the degradation process and explained the kinetic behavior of the cumulative methane *** the three models,MGM was found to fit best for the methane yield of WS40 and WS30.

关键词： Anaerobic digestion Wheat straw Oxidative pretreatment Piranha solution Methane

Calcium Carbide:From Elemental Carbon to Isotope-Economic Synthesis of^(13)C_(2)-Labeled Heterocycles

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Chinese Journal of Chemistry 2023年第21期41卷 2810-2818页

作者： Maria S.Ledovskaya vladimir v.voronin nikita R.valov Dmitriy E.Samoylenko Saint Petersburg State University Institute of ChemistryUniversitetsky prospect 26Peterhof198504 Russia

^(13)C-Carbon is the most available source of *** is a relatively inexpensive solid material,which can be easily converted to calcium carbide-^(13)C_(2).In current work,Ca^(13)C_(2)was used for in situ generation of^(13)C_(2)-acetylene in 1,3-dipolar cycloaddition and[4+2]cycloaddition *** the first time,1H-1,2,3-triazoles-4,5-^(13)C_(2)and isoxazoles-4,5-^(13)C_(2)were synthesized using calcium carbide-^(13)C_(2).A Diels-Alder type cycloaddition of 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine and Ca^(13)C_(2)was investigated,and the best way for the synthesis of 3,6-di(pyridin-2-yl)pyridazine-4,5-^(13)C_(2)was proposed for the first *** we perform a detailled description of NMR spectra of^(13)C_(2)-labeled triazoles,isoxazoles and 3,6-di(pyridin-2-yl)pyridazine.

关键词： Isotopic labeling Cycloaddition Click chemistry Sustainable Chemistry Calcium carbide

Generation of synchronized x-rays and mid-infrared pulses by Doppler-shifting of relativistically intense radiation from near-critical-density plasmas

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Matter and Radiation at Extremes 2023年第2期8卷 6-13页

作者： nikita A.Mikheytsev Artem v.Korzhimanov Lobachevsky State University of Nizhny Novgorod 603022 Nizhny NovgorodRussia Federal Research Center Institute of Applied Physics of the Russian Academy of Sciences 603950 Nizhny NovgorodRussia

It is shown that when relativistically intense ultrashort laser pulses are reflected from the boundary of a plasma with a near-critical density,the Doppler frequency shift leads to generation of intense radiation in both the high-frequency(up to the x-ray)and low-frequency(mid-infrared)*** efficiency of energy conversion into the wavelength range above 3μm can reach several percent,which makes it possible to obtain relativistically intense pulses in the mid-infrared *** pulses are synchronized with high harmonics in the ultraviolet and x-ray ranges,which opens up opportunities for high-precision pump–probe measurements,in particular,laser-induced electron diffraction and transient absorption spectroscopy.

关键词： pump intense relativistic

Metasurfaces for next-generation wireless communication systems

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National Science Review 2023年第8期10卷 17-19页

作者： Younes Ra'di nikita Nefedkin Petar Popovski Andrea Alù Department of Electrical Engineering and Computer Science Syracuse University Photonics Initiative Advanced Science Research Center City University of New York Department of Electronic Systems Aalborg University Physics Program Graduate Center City University of New York

The pace of development in the world of 5G communication systems has proven to be much more demanding than previous generations, with 5G-Advanced seemingly around the corner [1]. Extensive research is already underway to structure the next generation of wireless systems(i.e. 6G), which may potentially enable an unprecedented level of human–machine interaction [2].

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