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991.
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994.
采用原子吸收光谱仪(AAS),对脐橙的果皮、肉汁和囊瓣外衣中的10种微量元素进行了测定,同时也选择蜜桔进行了对比测定。结果表明,脐橙和蜜桔的果皮、肉汁和囊瓣外衣中含有比较丰富的人体必需的微量元素,且囊瓣外衣和果皮中的微量元素含量大多高于囊瓣中肉汁的微量元素的含量。这为脐橙和蜜桔药效功能的综合开发利用提供科学依据。 相似文献
995.
A chiral diacid monomer containing L ‐phenylalanine‐9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dicarboximido unit was successfully synthesized in four steps and used in the preparation of a series of novel optically active polyamides by direct polycondensation with diverse aromatic diamines using 1,3‐dipropylimidazolium bromide under microwave dielectric heating. Ionic liquids (ILs) efficiently absorb microwave energy and thus are employed as solvent. By controlling the concentration of 1,3‐dipropylimidazolium bromide, reaction time and power level, high yield and moderate inherent viscosity polymers could be achieved in a very short period of time. All the resulting polymers exhibited excellent solubility in various organic solvents. The polyamides were found to have inherent viscosities in the range of 0.54–0.85 dL g?1. These polyamides had glass‐transition temperatures (Tg) above 180°C, and a 10% weight‐loss temperatures in excess of 340°C with char yield at 800°C in nitrogen higher than 40%. A comparative study on effects exerted by microwave technique with conventional method is also presented. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
Anderson Dias Kisla P. F. Siqueira Roberto L. Moreira 《Journal of Raman spectroscopy : JRS》2010,41(1):93-97
This work investigates the crystal structures and phonon modes of Ba(Ca1/2W1/2)O3, Ba(Ca1/2Mo1/2)O3 and Ba(Sr1/2W1/2)O3 perovskites by Raman spectroscopy. The samples were produced by conventional solid‐state processing at 1200 °C. X‐ray diffraction showed that single‐phase homogeneous materials were produced, which are cubic or pseudo‐cubic in symmetry. The existing controversies in the literature for these complex perovskites were investigated by comparing experimental Raman data with group‐theory analysis. Ceramics with Ca and W or Mo were found to be cubic, space group Fm3 m. For these materials, four Raman‐active bands were observed and the fitting parameters showed that the Ba(Ca1/2Mo1/2)O3 ceramic presents bands at lower wavenumbers if compared with the Ba(Ca1/2W1/2)O3 sample. For the Ba(Sr1/2W1/2)O3 material, two hypotheses were investigated for monoclinic or triclinic structures. The experimental results showed 12 Raman‐active modes for this ceramic, which is in perfect agreement with the theoretical predictions for a monoclinic (I2/m) structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
Masataka Fukugita 《Progress in Particle and Nuclear Physics》2010,64(2):360-362
Massive neutrinos affect the structure formation of the universe, characteristically the harmonic pattern of the cosmic microwave background (CMB) radiation and the clustering property of galaxies. Precision observations of the CMB and the power spectrum of galaxy clustering thus lead to the limit on the neutrino mass on the 1 eV scale. I address the principles and the typical results that can be derived from cosmological arguments. 相似文献
998.
Y. S. Malghe S. R. Dharwadkar K. Krishnan K. D. Singh Mudher 《Journal of Thermal Analysis and Calorimetry》2009,96(1):49-52
The phase transitions in the LaCrO3 were studied using bulk dilatometry and high temperature X-ray diffractometry from room temperature to 1050 and 1200°C, respectively.
LaCrO3 was prepared at 500°C from oxalate precursor employing microwave heating technique. Bulk shrinkage measurements on LaCrO3 pellets were carried out using dilatometer designed and fabricated in our own laboratory. Dilatometric curves of LaCrO3 showed two peaks in ΔL/L vs. temperature curves in the range 200–400 and 800–1000°C, respectively. These phase transitions have been confirmed using
high temperature X-ray diffractometry. The role of simple technique like bulk dilatometry in detecting and monitoring the
polymorphic transformations in solids is discussed for lanthanum chromates. 相似文献
999.
J. Meuldijk B.H.P. van de Kruijs J.A.J.M. van Vekemans L.A. Hulshof R. Duchateau C.E. Koning 《Macromolecular Symposia》2011,302(1):69-79
Summary: Microwave irradiation was used for the amidation of a nitrile with an amine with a freshly prepared zirconium-based heterogeneous catalyst. Microwave irradiation selectively heats the catalyst which enhances its activity as compared to conventional heating. The difference between microwave heating and conventional heating disappears when Zr(OH)4 is used instead of ZrO2, indicating a microwave-induced shift in the hydrolysis equilibrium, i.e. the distribution of ZrO2, ZrO(OH)2 and Zr(OH)4, of the zirconium-based catalyst. The catalyst efficiently catalyzes the amidation of valeronitrile with n-hexylamine with conventional as well as with microwave heating. Zr(OH)4 was also used for the polymerization of 6-aminocapronitrile using conventional and microwave heating. With both heating methods a relatively low molecular weight polymer with a Mn of 4000 g/mol was obtained in a sealed vessel, due to the presence of water and ammonia. A post-polymerization step under microwave irradiation, with active removal of water and ammonia shifts Mn to 10000 g/mol. Pressure decrease to facilitate water removal resulted in products with higher molecular weights. A pressure reduction to 50 Pa and operation in an argon atmosphere at 230 °C resulted in nylon-6 with a Mn of 65000 in rather short reaction times. Lower pressures led to end-biting and evaporation of the volatile ε-caprolactam at 230 °C. As a consequence the resulting product has than a much lower molecular weight. The combination of a heterogeneous zirconium based catalyst and microwave heating is promising for process intensification for nylon-6 production. 相似文献
1000.
Jhung SH Lee JH Forster PM Férey G Cheetham AK Chang JS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(30):7899-7905
Microwave synthesis of two porous nickel glutarates was compared with conventional hydrothermal synthesis. The cubic nickel glutarate, [Ni20(C5H6O4)20(H2O)8] x 40 H2O (1), was synthesized by conventional electrical heating in several hours or days, depending on synthesis temperature. Crystallization was greatly accelerated by microwave irradiation, in which more stable, tetragonal nickel glutarate, [Ni22(C5H6O4)20(OH)4(H2O)10] x 38 H2O (2), was formed within a few minutes, suggesting the efficiency of the microwave technique in the synthesis of porous hybrid materials. The cubic phase 1 is formed preferentially at low pH, low temperature, and especially under conventional electrical heating. In contrast, the tetragonal phase 2 is obtained favorably at high pH, high temperature, and especially with microwave irradiation. This work demonstrates that the microwave method provides not only the very fast synthesis of a hybrid material, but also the possibility to discover a new porous hybrid material not yet identified by conventional hydrothermal synthesis. The hydrothermal formation of metal-organic hybrid materials in a matter of minutes is an important step towards developing commercially viable routes for producing this valuable class of materials. 相似文献