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971.
Successful implementation of a sequential Pd-catalyzed Sonogashira cross-coupling/iodine-promoted 5-exo-dig cyclization procedure with pyridines bearing a terminal alkyne moiety provided direct and straightforward access to a diverse array of 3-acylated indolizines under mild conditions. 相似文献
972.
This study investigated the determination of Au in rock samples using collision cell quadrupole inductively coupled plasma
mass spectrometry (ICP-MS). It is essential to remove various interferents using a collision cell because polyatomic ions
such as 181Ta16O+ and 180Hf16O1H+ can interfere with the direct determination of monoisotopic 197Au when using ICP-MS. The addition of oxygen as a reaction gas removed isobaric interferents by transforming TaO+ and HfOH+ to TaO2+, TaO3+, and HfO2H+, HfO3H+, respectively, in the cell without significant Au+ loss. The ion kinetic energy effect (IKEE) due to the potential difference between the plasma and the hexapole affected the
reactions in the cell. Au and interfering ions were very sensitive to cell bias voltage (Vc) at constant plasma potential
(Vp) and quadrupole bias voltage (Vq). Under the condition of hot plasma, the transmission of ions was promoted, and the maximum
Au signal intensity was 50% greater than under normal conditions. At Vc > 7 V, TaO+ ions were removed to background level. Optimized conditions for real sample analysis were obtained by introducing He as an
additional collision gas in hot plasma. TaO+ ions were removed to background level at He flow rates above 0.6 mL min−1, and the Au signal remained high. The detection limit (three times the standard deviation of the blank) of this method was
3.06 pg g−1. The results for reference materials (STM-1 and DGPM-1) and spiked samples showed good agreement between specified and measured
concentrations. 相似文献
973.
Weihong He Xiuping Lin Tunhai Xu Jee H. Jung Hao Yin Bin Yang Yonghong Liu 《Chemistry of Natural Compounds》2012,48(2):208-210
A new norsesterterpenoid 1 was isolated from the Sarcotragus sponge by bioactivity-guided fractionation. The structure was established on the basis of NMR and MS analysis. 相似文献
974.
K. H. Kim H. -J. Ko K. Kim Y. -S. Jung S. -H. Oh K. -J. Cho 《Journal of Engineering Thermophysics》2012,21(1):1-15
The transient thermal behavior in the cryogenic oxidizer tank for the liquid propulsion system of the KSLV-I satellite launching
space vehicle is theoretically investigated for the pressurization process by gaseous helium injection followed by the readiness
check stage. The numerical model is established using the transient mass and energy conservation of oxygen/helium mixtures
both in ullage and liquid regions. At the liquid-gas interface, various modes of heat and mass transfer are considered, including
the liquid evaporation and the helium absorption. The present study focuses on the effects of the increasing pressurization
level on some of important properties that should be considered in the propulsion system design, such as tank pressure, ullage
gas temperature, and evaporation of liquid oxygen. Particularly, the tank pressure drop after the pressurization is investigated
in the proposed design of propulsion system. Also, the effect of the initial loading of liquid oxygen in the oxidizer tank
is studied and discussed. As for the helium absorption into the liquid region, its mass is negligibly small and it should
not be the concern in design and operation of the oxidizer tank system. 相似文献
975.
C M Jung H C Kwon J J Seo Y Ohizumi K Matsunaga S Saito K R Lee 《Chemical & pharmaceutical bulletin》2001,49(7):912-914
The aerial part of Aster scaber Thunb. (Asteraceae) yielded two new monoterpene peroxide glycosides, (3S)-3-O-(3',4'-diangeloyl-beta-D-glucopyranosyloxy)-7-hydroperoxy-3,7-dimethylocta-1,5-diene (1) and (3S)-3-O-(3',4'-diangeloyl-beta-D-glucopyranosyloxy)-6-hydroperoxy-3,7-dimethylocta-1,7-diene (2), and five known compounds, alpha-spinasterol (3), germacra-4(15),5,10(14)-triene-1-beta-ol (4), 7-methoxy-4(15)-oppositen-1-beta-ol (5), 6alpha-methoxy-4(15)-eudesmane-1beta-ol (6) and alpha-spinasterol 3-O-beta-D-glucopyranoside (7). The structures were established by chemical and spectroscopic methods. 相似文献
976.
Hyun-Jeong Lee Woo-Seok Kim Sung-Hae Park Won Suk Shin Sung-Ho Jin Jin-Kook Lee Sang-Min Han Ki-Suck Jung Mi-Ra Kim 《Macromolecular Symposia》2006,235(1):230-236
Summary: We have synthesized three kinds of titanylphthalocyanines with different crystal structures (TiOPcs; PcT2000R, PcT3000R, and PcT1100S) and analyzed their crystal structure by X-ray Diffraction (XRD), Fourier transfer IR (FT-IR) spectroscopy, and Transmission Electron Microscope (TEM). From experimental results, we have confirmed that PcT2000R was estimated to be alpha-form; PcT3000R was beta-form, and PcT1100S was gamma-form. Quasi-solid state dye-sensitized solar cell (DSSC) devices were prepared with a polymer electrolyte using TiOPcs as a co-adsorbent. The DSSC device using TiOPc has higher power conversion efficiency than without TiOPc, due to decrease of electron transfer distance by the interface adsorption between TiO2 film and polymer electrolyte. Also, we have studied the effects of the crystal structures of TiOPcs on the property of polymer electrolyte and the performance of the DSSC device. The best result on power conversion efficiency was 7.13% in DSSC device using PcT3000R having its highest stability. The open-circuit voltage (Voc) was 0.69 V, the short-circuit current density (Jsc) was 20.02 mA/cm2, and the Fill Factor (FF) was 0.52. the addition of TiOPc as co-adsorbent is useful for improve to the performances of DSSC devices such as Voc, Jsc, and power conversion efficiency. 相似文献
977.
Jin‐Woong Kim Mi‐Ok Jung Yong‐Jin Kim Jee‐Hyun Ryu Junoh Kim Ih‐Seop Chang Ok‐Sub Lee Kyung‐Do Suh 《Macromolecular rapid communications》2005,26(15):1258-1261
Summary: This communication describes an enzyme stabilization method that allows the use of enzymes irrespective of environmental factors, especially heat, while maintaining their activity for a long time. We have designed enzyme microcapsules that consist of papain enzyme cores, poly(propylene glycol) interlayers, and poly(ε‐caprolactone) walls. By confocal laser scanning microscopy measurements and the thermal stability of papain‐loaded microcapsules, it is demonstrated that the papain is surrounded by a hydrophobic polyol layer and stabilized by the exclusive volume effect. In our study, improved thermal stability can be obtained by using more hydrophobic long‐chained polyols, which is understood to be attributed to the effective formation of a hydrophobic polyol layer between the papain and the polymer wall by means of conformational anchoring in the interface.
978.
Wideband multiwavelength erbium-doped fiber ring laser with frequency shifted feedback 总被引:7,自引:0,他引:7
Wideband multiwavelength erbium-doped fiber ring lasers with frequency shifted feedback are described. The use of an intra-cavity gain flattening filter (GFF) was proposed in order to increase the lasing spectral bandwidth, leading to a demonstration of 34 lasing wavelengths in 28 nm bandwidth in C-band. The GFF induced spectral output power fluctuation is discussed. Multiwavelength operation was also demonstrated for the first time in L-band, where wideband laser operation was obtained without a GFF. Optical bistability and Kerr effect induced pulsation were determined to be limiting factors to stable operation range in this kind of multiwavelength lasers. 相似文献
979.
980.