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61.
Kokol Vanja Vivod Vera Peršin Zdenka Čolić Miodrag Kolar Matjaž 《Cellulose (London, England)》2021,28(10):6545-6565
Cellulose - Bio-based, renewable and biodegradable products with multifunctional properties are also becoming basic trends in the textile sector. In this frame, cellulose nanofibrils (CNFs) have... 相似文献
62.
Olga Kirichenko Gennadiy Kapustin Vera Nissenbaum Igor Mishin Leonid Kustov 《Journal of Thermal Analysis and Calorimetry》2014,118(2):749-758
The applications of zerovalent iron nanoparticles (nZVI) exploit their high reactivity which decreases due to oxidation in aerobic conditions during manufacture, application, and storage. In this study, we present the new procedure for estimation of the nZVI stability to oxidation in air. The procedure is suitable for characterization of the novel materials based on the supported nZVI. Nanoscale particles were synthesized inside porous silica supports by incipient wetness impregnation with the metal precursor solutions followed by thermal treatment. The TG–DTA studies revealed the decomposition temperature of the supported precursors, as well as the interaction of Fe and precious metal precursors, which resulted in the formation of alloy nanoparticles. Characterization of the samples by XRD confirmed the formation of the nanoparticles of the metallic Pd, Pt, and Fe phases supported on SiO2 carriers, as well as the formation of solid solutions based on the structure of precious metals. The new procedure for estimation of the nZVI stability included (1) TPR with hydrogen up to 400–425 °C followed by isothermal reduction at these temperatures; (2) in situ reoxidation with oxygen at room temperature. The samples were reduced “as obtained” and after in situ reoxidation. The results of the TPR studies exhibited that introduction of both Pd and Pt protected the Fe nanoparticles from oxidation with oxygen and air at ambient conditions. 相似文献
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64.
Juan Mentado-Morales Arturo Ximello-Hernndez Javier Salinas-Luna Vera L. S. Freitas Maria D. M. C. Ribeiro da Silva 《Molecules (Basel, Switzerland)》2022,27(2)
The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the 1H and 13C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained. 相似文献
65.
66.
Vera Ya. Popkova Mikhail Yu. Antipin Lyudmila E. Vinogradova Larisa A. Leites Yuri T. Struchkov 《Heteroatom Chemistry》1992,3(2):101-113
Perfluoro-2-methyl-2-pentene-thiocyanate-3 reacts with ammonia to give 2,4-diaminoperfluoro-4-methyl-2-pentenethiocyanate-3 ( 4 ) and 2-aminoperfluoro-4, 4-dimethyl-4,5-dihydro-5-ethylidene-1,3-thiazole ( 5 ). Compound 4 is kinetically stable and at 150°C under-goes rotational isomerization to afford the cyclic isomer 2-amino-4,4-bis(trifluoromethyl)-4,5-dihydro-5-(1-aminoperfluoroethylidene) -1,3-thiazole ( 6 ). Intramolecular cyclizations, resulting in the thiazolines 5 and 6 , proceed likewise via the Thorpe reaction. For compounds 4–6 , X-ray diffraction analyses were undertaken and IR spectra in solution and in solid state were investigated. It is supposed that a high kinetic preference for formation of 4 and the fact that it does not undergo spontaneous cyclization in ammonolysis stem from the NH …︁ N intramolecular hydrogen bonding between two amino groups. 相似文献
67.
A triangular lattice model for pattern formation by core-shell particles at fluid interfaces is introduced and studied for the particle to core diameter ratio equal to 3. Repulsion for overlapping shells and attraction at larger distances due to capillary forces are assumed. Ground states and thermodynamic properties are determined analytically and by Monte Carlo simulations for soft outer- and stiffer inner shells, with different decay rates of the interparticle repulsion. We find that thermodynamic properties are qualitatively the same for slow and for fast decay of the repulsive potential, but the ordered phases are stable for temperature ranges, depending strongly on the shape of the repulsive potential. More importantly, there are two types of patterns formed for fixed chemical potential—one for a slow and another one for a fast decay of the repulsion at small distances. In the first case, two different patterns—for example clusters or stripes—occur with the same probability for some range of the chemical potential. For a fixed concentration, an interface is formed between two ordered phases with the closest concentration, and the surface tension takes the same value for all stable interfaces. In the case of degeneracy, a stable interface cannot be formed for one out of four combinations of the coexisting phases, because of a larger surface tension. Our results show that by tuning the architecture of a thick polymeric shell, many different patterns can be obtained for a sufficiently low temperature. 相似文献
68.
Selective Synthesis of 2,5‐Diformylfuran by Sustainable 4‐acetamido‐TEMPO/Halogen‐Mediated Electrooxidation of 5‐Hydroxymethylfurfural 下载免费PDF全文
Dr. Vera P. Kashparova Dr. Victor A. Klushin Dr. Daria V. Leontyeva Prof. Dr. Nina V. Smirnova Prof. Dr. Victor M. Chernyshev Prof. Dr. Valentine P. Ananikov 《化学:亚洲杂志》2016,11(18):2578-2585
A new method was developed for the selective gram‐scale synthesis of 2,5‐diformylfuran (DFF), which is an important chemical with a high application potential, via oxidation of biomass‐derived 5‐hydroxylmethylfurfural (HMF) catalyzed by 4‐acetylamino‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (4‐AcNH‐TEMPO) in a two‐phase system consisting of a methylene chloride and aqueous solution containing sodium hydrogen carbonate and potassium iodide. The key feature of this method is the generation of the I2 (co‐)oxidant by anodic oxidation of iodide anions during pulse electrolysis. In addition, the electrolyte can be successfully recycled five times while maintaining a 62–65 % yield of DFF. This novel method provides a sustainable pathway for waste‐free production of DFF without the use of metal catalysts and expensive oxidants. An advantage of electrooxidation is utilized in the preparation of demanding chemical. 相似文献
69.
Vera Yu Mishina Mikhail K. Gratchev Konstantin L. Anfilov Il'dar G. Mustafin Anna R. Bekker Edward E. Nifantyev 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The effective methods of phosphorylation of complex systems with specifically orientated in space hydroxyl groups, namely dianhydro-D-mannitol(A), -D-sor-bitol(B), cyclodextrines(C), and cellulose(D) (A-D, where R=H), have been elaborated. 相似文献
70.
Mathematical theory of optimization has found many applications in the area of medicine over the last few decades. Several
data analysis and decision making problems in medicine can be formulated using optimization and data mining techniques. The
significance of the mathematical models is greatly realized in the recent years owing to the growing technological capabilities
and the large amounts of data available. In this paper, we attempt to give a brief overview of some of the most interesting
applications of mathematical programming and data mining in medicine. In the overview, we include applications like radiation
therapy treatment, microarray data analysis, and computational neuroscience. 相似文献