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排序方式: 共有273条查询结果,搜索用时 281 毫秒
261.
Lucia Odochian Anca Mihaela Mocanu C. Moldoveanu Gabriela Carja C. Oniscu 《Journal of Thermal Analysis and Calorimetry》2008,94(2):329-334
The paper deals with the characterization of three hydrazinic complexes with Ni, Cu and Cr respectively, by means of non-isothermal
thermal methods, TG, DTG and DTA, under nitrogen atmosphere in order to investigate the structure-thermostability-thermal
degradation mechanism correlation. The thermal analysis made evident the degradation mechanisms characteristic of every sample
in accordance with the chemical structure. The quantitative analysis by TG-DTG afforded the estimation of the metal amount
in the complex on the basis of the resulting metallic oxide nature as well as of some aspects of the thermal degradation mechanism
supported by mass spectral measurements. The melting points given by DTA and confirmed by the Boetius method and the initial
temperatures of thermal degradation from TG-DTG-DTA afforded to ascertain the temperature range proper for using and storing
the complexes under study which show potential practical applications as drugs. 相似文献
262.
A. Rotaru Anca Moanţă P. Rotaru E. Segal 《Journal of Thermal Analysis and Calorimetry》2009,95(1):161-166
Thermal analysis of 4-[(4-chlorobenzyl)oxy]-4′-chloro-azobenzene dye, exhibiting liquid crystalline properties, was performed
in dynamic air atmosphere. The compound behavior was investigated using TG, DTG, DTA and DSC techniques, under non-isothermal
linear regime. The evolved gases were analyzed by FTIR spectroscopy. Kinetic parameters of the first decomposition step were
obtained by means of multi-heating rates methods, such as isoconversioanl methods, IKP method and Perez-Maqueda et al. criterion. 相似文献
263.
264.
Chain microstructure and conformation of partially quaternized poly(dimethylaminoethyl methacrylate)
Virgil Barboiu Gabriela Liliana Ailiesei Anca Giorgiana Grigoras Elena Rusu Ecaterina Stela Dragan 《International Journal of Polymer Analysis and Characterization》2019,24(7):610-618
1H-NMR spectroscopy was used to establish the chain microstructure and conformation produced by the quaternization reaction of syndiotactic poly[2-(dimethylamino)ethyl methacrylate], a polymer with tertiary amino groups in the side chains. A chain microstructure with mini blocks of modified units was found by analyzing the N+CH3 signal that was proved to be split in accordance with the composition triads. The macromolecular backbone changes its form by quaternization, from a close to an expanded coil, was confirmed by light scattering measurements and NOE spectra modifications. The two linked processes, the block formation and chain expansion can be the key in developing a reaction mechanism explaining both positive and negative deviations from a second-order kinetic model. 相似文献
265.
Dumitrescu A Rudzevich VL Romanenko VD Mari A Schoeller WW Bourissou D Bertrand G 《Inorganic chemistry》2004,43(21):6546-6548
Persistent phosphinyl radicals featuring the 2,6-bis(trifluoromethyl)phenyl group were prepared and characterized. Their electronic structure was theoretically investigated, and their low-temperature dimerization into the corresponding diphosphines was found to be strongly inhibited when the sterically very demanding (tert-butyl)(trimethylsilyl)amino substituent was used. 相似文献
266.
D. Wood has asked in [2] whether there exists an inherently non-planar bicolored digraph-grammar language. We shall give below a negative answer to this question. 相似文献
267.
Cornelius Croitoru 《Discrete Applied Mathematics》1982,4(2):113-117
The worst-case analysis of the greedy algorithm for a combinatorial problem of linear maximization on a partially ordered set (introduced by U. Faigle [3]) is given. 相似文献
268.
269.
Sonia Caruntu Alina Ciceu Neli Kinga Olah Ioan Don Anca Hermenean Coralia Cotoraci 《Molecules (Basel, Switzerland)》2020,25(22)
Thuja occidentalis L. (Cupressaceae) has its origins in Eastern North America and is cultivated in Europe and Brazil as an ornamental tree, being known as the “tree of life” or “white cedar”. In traditional medicine, it is commonly used to treat liver diseases, bullous bronchitis, psoriasis, enuresis, amenorrhea, cystitis, uterine carcinomas, diarrhea, and rheumatism. The chemical constituents of T. occidentalis have been of research interest for decades, due to their contents of essential oil, coumarins, flavonoids, tannins, and proanthocyanidines. Pharmacology includes antioxidant, anti-inflammatory, antibacterial, antifungal, anticancer, antiviral, protective activity of the gastrointestinal tract, radioprotection, antipyretic, and lipid metabolism regulatory activity. Therefore, the present review represents the synthesis of all the relevant information for T. occidentalis, its ethnobotany, phytochemistry, and a thorough analysis of their pharmacological activities, in order to promote all the biological activities shown so far, rather than the antitumor activity that has promoted it as a medicinal species. 相似文献
270.
This work deals with the simulation of fusion welding by the Finite Element Method. The implemented models include a moving heat source, temperature dependence of thermo-physical properties, elasto-plasticity, non-steady state heat transfer, and mechanical analysis. The thermal problem is assumed to be uncoupled from the mechanical one, so the thermal analysis is performed separately and previously to the mechanical analysis at each time step. The mechanical problem is based on the thermal history. A special treatment is performed on mechanical elements during the liquid/solid and solid/liquid phase changes to account for stress states. The three-dimensional stress state of a butt-welded joint is obtained as an example of an application. 相似文献