•Co(Ni)Mo catalysts were synthesized from heteropoly compounds and C-coated Al2O3.•Catalytic activity was essentially dependent on carbon content in carrier.•Carbon content influences the morphology ...of active phase and catalytic properties.•Concept of interlayer dynamics is helpful in establishing structure–activity relations for TMS.
Effects of activated carbon of a carbon-coated alumina support and active phase morphology of transition metal sulfide (TMS) catalysts in hydrotreatment (HDT) of S-containing compounds were studied. The catalysts were synthesized from Anderson-type heteropoly compounds and characterized with multiple methods: X-ray powder diffraction, N2 physisorption, temperature-programmed desorption of ammonia, pyridine-adsorbed Fourier transform infrared spectroscopy, H2 temperature-programmed reduction, and high-resolution transmission electron microscopy. The catalysts were tested in hydrodesulfurization (HDS) of thiophene, dibenzothiophene and HDT of diesel. The results suggest that the catalytic activity in HDS and hydrogenation reactions depends on the shape of crystallites of the active phase. The results are interpreted using recently proposed concept of interlayer dynamics. This concept is helpful in establishing structure–activity relations for TMS.
It is shown that an account for the final-state interaction of real or virtual nucleon and antinucleon produced in the processes J/ψ→pp¯γ, ψ(2S)→pp¯γ, J/ψ→pp¯ω, and J/ψ→3(π+π−)γ near the threshold of ...NN¯ pair production allows one to obtain self-consistent description of these processes. Predictions of our model are in good agreement with experimental data available. The proposed potential model also reproduces the corresponding partial cross sections of pp¯ scattering.
•The first review focused solely on redox reactivity of cobalamins.•Challenging activation of organocobalamins and cobalamin(II).•Superior reactivity of cobalamin(II) toward free ...radicals.•Super-nucleophilicity of cobalamin(I) and its high reducing properties.
A comprehensive review on redox reactions of Co(III), Co(II) and Co(I) forms of cobalamins (vitamin B12) and their derivatives (cobinamide, cobyrinates) is presented. An influence of coordination environment of cobalt ion on reactivity of corresponding species is discussed. Mechanisms of reduction of Co(III) and Co(II) species as well as oxidation of Co(II) and Co(I) complexes are given in terms of their in vivo and catalytic implications.
Predicting the start time of a task without placing the task in a task queue is very difficult in modern data centers. The article proposes to improve the previously created forecasting tool through ...the use of more modern software interfaces to the SchedMD queuing system (Slurm), as well as the use of various mathematical forecasting methods to predict the moment of task launch. To compare and evaluate machine learning models, we selected a SWF file with task execution history data on the University of Luxembourg computing cluster with 59 715 tasks. The following methods were investigated: linear regression with L2 regularization, support vector machine, random forest, LightGBM, CatBoost, LightGBM with parameter optimization, CatBoost with parameter optimization. To check the correctness of the prediction, a test bench was built based on the Slurm simulator (SUNY Center for Computational Research at the University at Buffalo, USA), which works based on executing tasks and organizing a queue of saved logs.
The properties of dihydroxycarbonate (malachite) and trihydroxynitrate of copper were studied in order to apply their ammonia solutions for the synthesis of copper-substituted ZSM-5 zeolites. Copper ...concentration and NH4OH/Cu2+ ratio in the solutions varied 1–12 g/l and 6–30, respectively. The parameters of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms revealed the favorability of the chosen conditions and the chemical nature of Cu(NH3)n2+ ions sorption by zeolite. For both copper salts, the sorption capacity of H-ZSM-5 for Cu2+ ions was higher in the solutions having NH4OH/Cu2+ = 6–10 compared to 30. To identify the synthesis and structure – activity relationship correlations, the ammonia solution and Cu-ZSM-5 samples were characterized by EPR, UV–visible spectroscopy, temperature-programmed reduction by hydrogen (H2-TPR). The calcined Cu-ZSM-5 samples produced at NH4OH/Cu2+ = 6–30 contained two types of the isolated Cu2+ ions (bare Cu2+ and Cu(OH)+), differing in their Redox properties. Their reducibility improved with an increase in the copper loading and with a decrease in NH4OH/Cu2+. At NH4OH/Cu2+ = 6–10, the samples additionally comprised the structures of Cu2+ ions with extra-lattice oxygen (ELO), which were formed due to hydrolysis of Cu(NH3)n(H2O)2+ to Cu(NH3)n(OH)+ and then to Cu(OH)2Cu2+. Cu2+–ELO structures possessed a greater ability to complete reduction than both types of isolated Cu2+ ions. Correlations with DeNOx properties in selective catalytic reduction (SCR) of NO by propane and ammonia are discussed.
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•Synthesis of ion-exchanged Cu-ZSM-5 using ammonia solutions of copper hydroxysalts.•NH4OH/Cu2+ in solution affect copper content and type of Cu-ions loaded in ZSM-5.•At NH4OH/Cu2+ = 30, there is 2 types of isolated Cu2+ ions differing in Redox.•At NH4OH/Cu2+ = 6–10, reducibility is improved due to Cu2+–ELO structures.•Cu2+–ELO structures enhance SCR NO performance compared with isolated Cu2+ ions.
•CoMo catalysts supported on C-coated Al2O3 were prepared with H3PMo12O40 and Co citrate.•Sulphidation degree of metals and Co amount in CoMoS increased with carbon content.•Enhanced properties of ...CoMo/Cx/Al2O3 catalysts were related to lower acidity of supports.•Guaiacol and oleic acid HDO were maximal at 2wt.% of carbon in support.•HDO activities increased with the decrease of CoMoS size and the rise of CoMoS sites.
The objective of the work was to elucidate the effect of coating alumina by carbon on the catalytic properties of CoMoS catalysts supported on carbon-coated alumina (CCA) in hydrodeoxygenation (HDO) reactions. The catalysts were synthesized using 12-molybdophosphoric heteropolyacid, cobalt citrate and CCA and characterized by N2 physisorption, temperature-programmed desorption of ammonia, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in HDO of guaiacol and oleic acid. It was found that using the CCA as supports of the CoMo/CCA catalysts altered the morphology and structure of the CoMoS active phase species. With the increase of carbon content up to 5.6wt.%, the average length of CoMoS species passed through minimum at 2.4nm and the average stacking number increased from 1.4 to 1.6. The increase of carbon content in the CCA led to rising the sulphidation degree of both metals and effective cobalt content into CoMoS phase. Using CCA supports instead of alumina for preparation of CoMo catalysts resulted in improving their activities in HDO of guaiacol and oleic acid and significantly reduced deactivation. Enhanced catalytic properties of CoMo/Cx/Al2O3 catalysts were related to lower acidity of CCA supports. CoMo/CCA catalyst with 2wt.% of carbon had maximal activity in HDO of guaiacol and oleic acid thanks to an optimal balance between cobalt content into CoMoS phase particles and their average length.
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•Hemp phloem fibers have layers of secondary and tertiary (gelatinous) cell walls.•Secondary phloem fibers have thicker secondary cell wall layer than primary fibers.•Cell wall ...development in hemp fibers is accompanied by the remodeling of G-layers.•RG-I is immunolocalized within tertiary cell wall of hemp phloem fibers.•RG-I with β-(1,4)-galactan are strongly retained by cellulose in fiber cell wall.
Formation of thickened cell wall allows plant fibers to obtain the strength necessary to the realization of their function as mechanical tissue. It is due to such cell wall that fibers of textile crops, like flax, hemp, and ramie, acquire characteristics that make possible to use these fibers in textile and technical applications. In the hemp stem, primary and secondary phloem fibers originating from the different type of meristems are formed. Analysis of ultrastructure coupled with immunolabelling demonstrated distinct layers within thickened cell wall in the fiber of both types: the outer layer is built as typical secondary cell wall of xylan-type, while the major portion was identified as the layers of tertiary (gelatinous or G-layer) cell wall. A newly deposited layer of the tertiary cell wall (Gn) is transformed into mature G-layer by the post-synthetic modification. The general design of cell wall in primary and secondary phloem fibers is similar, but with xylan layer being considerably thicker in secondary fibers than in primary ones. The formation of the tertiary cell wall in primary and secondary hemp fibers was associated with the synthesis of pectin component – rhamnogalacturonan I together with β-(1,4)-d-galactan, which has been detected and characterized both in the buffer-extractable fraction and among the strongly retained within cell wall polysaccharides. Comparison of the obtained results with data on the flax fiber cell wall development permitted to find similarities, as well as some differences of G-fiber cell wall organization in different plant species.
Bremsstrahlung on noble gases at low energies Milstein, A.I.; Salnikov, S.G.; Kozlov, M.G.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
11/2022, Volume:
530
Journal Article
Peer reviewed
Open access
A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description ...of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data.
The angular distribution of photons emitted at interaction of low-energy electrons with atoms of noble gases is investigated. The angular asymmetry of the bremsstrahlung cross section is significant ...and strongly depends on the electron and photon energies. The effect of polarization radiation is considered. It is shown that this effect is noticeable even below the electroluminescence threshold, in contrast to the generally accepted point of view. In the case of argon, the account for the polarization radiation improves the agreement between the predictions and the available experimental data for the yield of bremsstrahlung photons.
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