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81.
Ivica ?ilovi Dubravka Matkovi‐alogovi Ivan Kos Mladen Biru Milena Jadrijevi‐Mladar Taka
《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o45-o47
In the crystal structures of two cyclic trihydroxamic acid derivatives containing the same substructure unit, viz. 1,3,5‐trihydroxy‐1,3,5‐triazinane‐2,4,6‐trione dihydrate, C3H3N3O6·2H2O, (I), and 1,3,5‐benzyloxy‐1,3,5‐triazinane‐2,4,6‐trione, C24H21N3O6, (II), there is no significant difference in the geometric parameters. In (I), there are 11 hydrogen bonds of the O—H⋯O type interconnecting the molecules in a three‐dimensional network, while in (II) there are only two weak C—H⋯O hydrogen bonds. The results of IR spectroscopic analysis are in good agreement with the crystallographic study. 相似文献
82.
Yanlin Huang Kiwan Jang Wanxue Zhao Eunjin Cho Ho Sueb Lee Xigang Wang Dake Qin Ying Zhang Chanfang Jiang Hyo Jin Seo 《Journal of solid state chemistry》2007,180(12):3325-3332
Usually, Sm2+ ions could be reduced by heating the materials in reducing atmospheres. Exposure to ionizing radiations is also known to cause Sm3+→Sm2+ conversion. In this work, BaBPO5 doped with the samarium ion was prepared by high temperature solid-state reaction. Sm2+ ions were obtained by two different reduction methods, i.e., heating in H2 reduced atmosphere and X-ray irradiation. The measurements of X-ray diffraction (XRD), and scanning electron microscope (SEM) were investigated. It is found that the conversion of Sm3+→Sm2+ is very efficient in BaBPO5 hosts after X-ray irradiation. Sm2+ ions under these two reduction methods exhibit different characteristics that were studied by measurements of luminescence and decay. The results showed that the luminescence properties of Sm2+ ions in BaBPO5 were highly dependent on the sample preparation conditions. 相似文献
83.
84.
Katalin E. Kövér Dušan Uhr?&#x;n Victor J. Hruby 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):162-168
A pulsed field gradient version of the sensitivity-enhanced 2D TOCSY experiment is proposed which yields high-quality spectra with improved sensitivity and a minimum of two scans pert1increment. For rapid acquisition of 1D TOCSY spectra, the 1D DPFGSE–TOCSY experiment was modified to include phase-encoded multiple-selective excitation followed by a simple spectral editing. Combination of these two building blocks is used in a sensitivity-enhanced 2D analog of the 3D TOCSY–TOCSY experiment which provides an efficient tool for resolving severely overlapped signals of oligomers in short experimental time. 相似文献
85.
超重元素(新核素)合成研究进展情况分析和展望 总被引:2,自引:0,他引:2
本文在介绍和分析国际、国内在超重元素(新核素)合成实验研究与理论研究进展情况的基础上对我国今后如何从理论与实验的结合上开展超重元素(核)合成研究工作提出一些看法和建议,提供讨论。 相似文献
86.
Cyclic and acyclic β-bromovinyl aldehydes are cyclized with an array of arylhydrazines in toluene at 125 °C in the presence of a palladium catalyst and a phosphorus chelating ligand together with NaOtBu to give 1-aryl-1H-pyrazoles in moderate to good yields. 相似文献
87.
Olga Ordeig Craig E Banks Trevor J Davies F Javier del Campo Francesc Xavier Mu?oz Richard G Compton 《Analytical sciences》2006,22(5):679-683
Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array. 相似文献
88.
Ivan Gutman Sabina Gojak Niko Radulovi? Boris Furtula 《Monatshefte für Chemie / Chemical Monthly》2006,46(2):277-284
In a recent work it was demonstrated that in linear hexagonal chains the distribution of π-electrons into rings (as computed
by means of the Randić–Balaban method) is uniform, irrespective of the nature of the terminal fragments. We now establish that an analogous, yet somewhat
more complex, uniformity in the π-electron distribution exists also in double linear hexagonal chains, as well as in some
other benzenoid systems. 相似文献
89.
J.-S. Kang G. Kim S.S. Lee S. Choi S. Cho S.W. Han H.J. Shin B.I. Min 《Journal of magnetism and magnetic materials》2006
The spatial concentration distribution and local electronic structure of ferromagnetic Ge1−xTx (T=Cr, Mn, Fe) DMS single crystals have been investigated by using scanning photoelectron microscopy (SPEM), X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). It is found that doped T ions in Ge1−xTx crystals are chemically phase-separated, suggesting that the observed ferromagnetism arises from the phase-separated T-rich phases in Ge1−xTx. 相似文献
90.
General purpose poly(styrene) is a large
volume commodity polymer widely used in a range of applications. For many
of these the presence of an additive to impart some flammability resistance
is required. Most commonly, brominated aromatics are used for this purpose.
As the polymer undergoes combustion these compounds decompose to generate
bromine atoms and/or hydrogen bromide which escape to the gas phase and trap
flame propagating radicals. While these species are effective in inhibiting
flame propagation they present the opportunity for loss of halogen to the
atmosphere. For this reason, the use of these compounds is being limited in
some parts of the world. Phosphorus compounds, on the other had, impart a
flame retarding influence by promoting char formation at the surface of the
burning polymer. This prevents heat feedback to the polymer and consequent
pyrolysis to generate fuel fragments. The combination of both bromine and
phosphorus present in a single compound might generate a superior flame-retarding
additive in that both modes of retardancy might be promoted simultaneously.
Should this be the case smaller amounts of additive might be necessary to
achieve a satisfactory level of flame retardancy. A series of such additives,
brominated aryl phosphates, has been synthesized and fully characterized spectroscopically.
Blends of these additives, at various levels, with poly(styrene) have been
examined by DSC, TG and in the UL-94 flame test. The flammability of the polymer
is dramatically diminished by the presence of the additive. 相似文献