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41.
Irina Klimova Tiit Kaljuvee Valdek Mikli Andres Trikkel 《Journal of Thermal Analysis and Calorimetry》2013,111(1):253-258
Urea is one of the main nitrogen fertilizers used in agriculture. But being well soluble in water, hardly 50% of its nitrogen is assimilated by plants. One possibility to eliminate this disadvantage is to use coating agents for modification of urea to obtain a controlled-realized fertilizer. The aim of this research was to study the influence of different lime-containing additives on the thermal behavior and decomposition kinetics of urea in oxidizing atmosphere. Commercial fertilizer-grade urea (46.4% N) and analytical-grade CaO, MgO, CaCO3, MgCO3 were used in the experiments. In addition, one Estonian limestone and one dolomite sample were used as additive or coating material. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer by a heated transfer line were carried out under non-isothermal conditions up to 900 °C at the heating rate of 5 °C min?1 and to calculate kinetic parameters, additionally, at 1, 2, and 10 °C min?1 in the atmosphere containing 80% of Ar and 20% of O2. The differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results obtained indicate that thermooxidative decomposition of urea as well as the blends of urea with lime-containing materials and urea prills coated with limestone or dolomite powder follows a complex reaction mechanism. 相似文献
42.
Yury Kostyukevich Alexey Kononikhin Alexander Zherebker Igor Popov Irina Perminova Eugene Nikolaev 《Analytical and bioanalytical chemistry》2014,406(26):6655-6664
We report a simple approach for enumeration of non-labile oxygen atoms in individual molecules of dissolved organic matter (DOM), using acid-catalyzed 16O/18O exchange and ultrahigh-resolution Fourier-transform ion-cyclotron-resonance mass spectrometry (FTICR-MS). We found that by dissolving DOM in H2 18O at 95 °C for 20 days it is possible to replace all oxygen atoms of DOM molecules (excluding oxygen from ether groups) with 18O. The number of exchanges in each molecule can be determined using high-resolution FTICR. Using the proposed method we identified the number of non-labile oxygen atoms in 231 molecules composing DOM. Also, using a previously developed hydrogen–deuterium (H/D)-exchange approach we identified the number of labile hydrogen atoms in 450 individual molecular formulas. In addition, we observed that several backbone hydrogen atoms can be exchanged for deuterium under acidic conditions. The method can be used for structural and chemical characterization of individual DOM molecules, comparing different DOM samples, and investigation of biological pathways of DOM in the environment. 相似文献
43.
Aliev Ramiz A. Khomenko Irina A. Kormazeva Ekaterina S. 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):983-989
Journal of Radioanalytical and Nuclear Chemistry - Thin natEr2O3 targets were irradiated on cyclotron by 60 MeV alpha particles. Thulium and ytterbium radioisotopes, formed during... 相似文献
44.
Irina Repyakh 《International journal of quantum chemistry》1996,57(5):913-918
In the present article, polymethine and annulene electronic spectra are described in a unique way by means of the Pariser-Parr-Pople method. The analytical expressions were derived for the first π-electron transitions energies. The character of the annulene spectra, like the character of the open-chain spectra, was shown to be dependent on the ratio between electron and site numbers. The Dahne's triad theory and the existence of finite energy gap in polymethines are discussed. © 1996 John Wiley & Sons, Inc. 相似文献
45.
Alan R. Katritzky Irina V. Shcherbakova Robert D. Tack 《Journal of polymer science. Part A, Polymer chemistry》1996,34(9):1651-1655
Amidoalkylations of polybutenes and of ethene-propene copolymer, catalyzed by trifluoroacetic acid, result in 5,6-dihydro-4H,1,3-oxazino-substituted polyalkenes with the 2-position of the oxazine ring unsubstituted or occupied by a vinyl or a phenyl group. The vinyl-substituted dihydrooxazino polymers thus obtained readily add butylamine to the vinyl fragment yielding alkylamino-substituted derivatives. © 1996 John Wiley & Sons, Inc. 相似文献
46.
The influence of the die geometry and of the thermal conductivity of materials on the solid-liquid interface shape in Edge-defined Film-fed Growth has been studied. 相似文献
47.
Svetlana I. Dorovskikh Denis E. Tryakhov Darya D. Klyamer Alexander S. Sukhikh Irina V. Mirzaeva Natalia B. Morozova Tamara V. Basova 《Molecules (Basel, Switzerland)》2022,27(7)
To search for new suitable Pd precursors for MOCVD/ALD processes, the extended series of fluorinated palladium complexes [Pd(CH3CXCHCO(R))2] with β-diketone [tfa−1,1,1-trifluoro-2,4-pentanedionato (1); pfpa−5,5,6,6,6-pentafluoro-2,4-hexanedionato (3); hfba−5,5,6,6,7,7,7-heptafluoro-2,4-heptanedionato (5)] and β-iminoketone [i-tfa−1,1,1-trifluoro-2-imino-4-pentanonato (2); i-pfpa−5,5,6,6,6-pentafluoro-2-imino-4-hexanonato (4); i-hfba-5,5,6,6,7,7,7-heptafluoro-2-imino-4-heptanonato (6)] ligands were synthesized with 70–80% yields and characterized by a set of experimental (SXRD, XRD, IR, NMR spectroscopy, TG) and theoretical (DFT, Hirshfeld surface analysis) methods. Solutions of Pd β-diketonates contained both cis and trans isomers, while only trans isomers were detected in the solutions of Pd β-iminoketonates. The molecules 2–6 and new polymorphs of complexes 3 and 5 were arranged preferentially in stacks, and the distance between molecules in the stack generally increased with elongation of the fluorine chain in ligands. The H…F contacts were the main ones involved in the formation of packages of molecules 1–2, and C…F, F…F, NH…F contacts appeared in the structures of complexes 4–6. The stability of complexes and their polymorphs in the crystal phases were estimated from DFT calculations. The TG data showed that the volatility differences between Pd β-iminoketonates and Pd β-diketonates were minimized with the elongation of the fluorine chain in the ligands. 相似文献
48.
Natalia P. Kuzmina Dmitry M. Tsymbarenko Igor E. Korsakov Zoya A. Starikova Kostantin A. Lysenko Olga V. Boytsova Andrey V. Mironov Irina P. Malkerova Andrey S. Alikhanyan 《Polyhedron》2008
The novel mixed ligand complexes [Ca(hfa)2(diglyme)(H2O)] (I), [Sr(hfa)2(diglyme)(H2O)] (II) and [Ba(hfa)2(diglyme)2] (III) (Hhfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, diglyme = 2,5,8-trioxanonane) were synthesized by the reactions of the alkaline earth element (AEE) carbonates in n-hexane with a mixture of Hhfa and diglyme, and they were characterized by elemental analysis, 1H and 13C NMR, and FTIR spectroscopy. The crystal structures of I–III, consisting of mononuclear isolated molecules, have been determined. The thermal behavior and composition of the vapor phase have been studied for I–III by thermal analysis at low pressure and mass spectrometry using a Knudsen cell. The stability of the mixed ligand complexes [M(hfa)2(diglyme)n] to the removal of diglyme molecules under heating decreases in the row I > II ≈ III, and only I evaporates as the mixed ligand complex after water removal. 相似文献
49.
Bernardo Duarte Renato Mamede Irina A. Duarte Isabel Caador Susanne E. Tanner Marisa Silva David Jacinto Teresa Cruz Vanessa F. Fonseca 《Molecules (Basel, Switzerland)》2022,27(4)
The stalked barnacle Pollicipes pollicipes is an abundant species on the very exposed rocky shore habitats of the Spanish and Portuguese coasts, constituting also an important economical resource, as a seafood item with high commercial value. Twenty-four elements were measured by untargeted total reflection X-ray fluorescence spectroscopy (TXRF) in the edible peduncle of stalked barnacles sampled in six sites along the Portuguese western coast, comprising a total of 90 individuals. The elemental profile of 90 individuals originated from several geographical sites (N = 15 per site), were analysed using several chemometric multivariate approaches (variable in importance partial least square discriminant analysis (VIP-PLS-DA), stepwise linear discriminant analysis (S-LDA), linear discriminant analysis (LDA), random forests (RF) and canonical analysis of principal components (CAP)), to evaluate the ability of each approach to trace the geographical origin of the animals collected. As a suspension feeder, this species introduces a high degree of background noise, leading to a comparatively lower classification of the chemometric approaches based on the complete elemental profile of the peduncle (canonical analysis of principal components and linear discriminant analysis). The application of variable selection approaches such as the VIP-PLS-DA and S-LDA significantly increased the classification accuracy (77.8% and 84.4%, respectively) of the samples according to their harvesting area, while reducing the number of elements needed for this classification, and thus the background noise. Moreover, the selected elements are similar to those selected by other random and non-random approaches, reinforcing the reliability of this selection. This untargeted analytical procedure also allowed to depict the degree of risk, in terms of human consumption of these animals, highlighting the geographical areas where these delicacies presented lower values for critical elements compared to the standard thresholds for human consumption. 相似文献
50.
A quantitative analysis of the BER penalty due to deviations from the optimal decision level in systems employing optical regeneration is presented. Applying extensive Multicanonical Monte Carlo modelling we study the accumulation of BER with propagation and compare different analytical approximations of the regenerator nonlinear transfer function. 相似文献