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91.
Total synthesis of ecteinascidin 743 总被引:1,自引:0,他引:1
Endo A Yanagisawa A Abe M Tohma S Kan T Fukuyama T 《Journal of the American Chemical Society》2002,124(23):6552-6554
The total synthesis of ecteinascidin 743 (1), an extremely potent antitumor agent, has been accomplished. The synthesis features Ugi's 4CC reaction, intramolecular Heck reaction, phenol-aldehyde cyclization, and acid-induced intramolecular sulfide formation. 相似文献
92.
Koichi Funazo Takayuki Hirashima Minoru Tanaka Toshiyuki Shono 《Fresenius' Journal of Analytical Chemistry》1982,311(1):27-29
Summary A method is described for the determination of sulphide ion in aqueous samples by gas chromatography. Sulphide is ethylated with diethyl sulphate and the resulting diethyl sulphide is extracted with chloroform and determined with a gas chromatograph equipped with a flame ionization or a flame photometric detector. In the case of a flame photometric detector, the detection limit for sulphide ion is 0.05 g/ml. Other anions commonly found with sulphide ion do not interfere. Sulphide ion in spring waters was analysed by this new method and for comparison also by colorimetry (methylene blue). The results revealed the reliability of the new method.
Bestimmung von Sulfidspuren durch Ethylierung und Gas-Chromatographie
Zusammenfassung Sulfid wird mit Diethylsulfat ethyliert, das gebildete Diethylsulfid mit Chloroform extrahiert und gaschromatographisch mit Hilfe eines Flammenionisationsoder eines flammenphotometrischen Detektors bestimmt. Die Nachweisgrenze beträgt 0,05 g S/ml für den FPD. Anionen, die üblicherweise mit Sulfid zusammen vorkommen, stören nicht. Das Verfahren wurde, im Vergleich mit der colorimetrischen Methylenblaumethode, auf Quellwasser angewendet. Es wurde gute Übereinstimmung der Ergebnisse erzielt.相似文献
93.
94.
Inoue Y Nomura Y Nakaoka T Watanabe M Kiryu S Okubo T Ohtomo K 《Magnetic resonance imaging》2005,23(5):641-645
The aim of this study was to investigate the effect of temporal resolution on the estimation of left ventricular (LV) function by cardiac magnetic resonance (MR) imaging using a steady-state free precession (SSFP) sequence. Left ventricular function was assessed by cine MR imaging using a segmented SSFP sequence in 10 healthy volunteers. Views per segment (VPS) were set at 8 and 20, resulting in high and low true temporal resolution, respectively. Irrespective of VPS, images were reconstructed at 40 cardiac phases, providing high apparent temporal resolution. Data were analyzed using 40, 20 and 10 phases to simulate different apparent temporal resolutions. Increasing the cardiac phases used for analysis slightly decreased mean end-systolic volume (ESV) and slightly increased mean ejection fraction (EF). No substantial difference in estimates of end-diastolic volume (EDV) was found between VPSs of 8 and 20. Imaging with a VPS of 20 yielded a larger ESV and smaller EF than imaging with a VPS of 8 when 40 phases were used. In conclusion, low true temporal resolution causes overestimation of ESV and underestimation of EF. Improvement of apparent temporal resolution mildly reduces but does not eliminate the errors caused by low true temporal resolution. 相似文献
95.
Sekiguchi K Sakai H Witała H Glöckle W Golak J Hatanaka K Hatano M Itoh K Kamada H Kuboki H Maeda Y Nogga A Okamura H Saito T Sakamoto N Sakemi Y Sasano M Shimizu Y Suda K Tamii A Uesaka T Wakasa T Yako K 《Physical review letters》2005,95(16):162301
Three precise measurements for elastic pd scattering at 135 MeV/A have been performed with the three different experimental setups. The cross sections are described well by the theoretical predictions based on modern nucleon-nucleon forces combined with three-nucleon forces. Relativistic Faddeev calculations show that relativistic effects are restricted to backward angles. This result supports the two measurements recently reported by RIKEN and contradicts the KVI data. 相似文献
96.
Toshiyuki Abe Geoffrey Buhl Chongying Dong 《Transactions of the American Mathematical Society》2004,356(8):3391-3402
We demonstrate that, for vertex operator algebras of CFT type, -cofiniteness and rationality is equivalent to regularity. For -cofinite vertex operator algebras, we show that irreducible weak modules are ordinary modules and -cofinite, is -cofinite, and the fusion rules are finite.
97.
Lordi V Gambin V Friedrich S Funk T Takizawa T Uno K Harris JS 《Physical review letters》2003,90(14):145505
Ga(1-x)In(x)N(y)As(1-y) is a promising material system for the fabrication of inexpensive "last-mile" optoelectronic components. However, details of its atomic arrangement and the relationship to observed optical properties is not fully known. Particularly, a blueshift of emission wavelength is observed after annealing. In this work, we use x-ray absorption fine structure to study the chemical environment around N atoms in the material before and after annealing. We find that as-grown molecular beam epitaxy material consists of a nearly random distribution of atoms, while postannealed material shows segregation of In toward N. Ab initio simulations show that this short-range ordering creates a more thermodynamically stable alloy and is responsible for blueshifting the emission. 相似文献
98.
(--)-Muricatacin, a potent cytotoxic (4R,5R)-5-hydroxyheptadecan-4-olide, has been synthesized through alpha-C--H hydroxyalkylation and alpha'-C--H oxidation of tetrahydrofuran. This study presents a novel method for C--H bond functionalization as a means for preparing gamma-(hydroxyalkyl)-gamma-butyrolactones. 相似文献
99.
Murakami T Nishikiori T Nohira T Ito Y 《Journal of the American Chemical Society》2003,125(2):334-335
Ammonia was successfully synthesized by using a new electrochemical reaction with high current efficiency at atmospheric pressure and at lower temperatures than the Haber-Bosch process. In this method, nitride ion (N3-), which is produced by the reduction from nitrogen gas at the cathode, is anodically oxidized and reacts with hydrogen to produce ammonia at the anode. 相似文献
100.
M. Nurhuda A. Suda M. Kaku K. Midorikawa 《Applied physics. B, Lasers and optics》2007,89(2-3):209-215
We present a study on the optimization of multi-mJ spectral broadening in neon-filled hollow fibers using pressure gradients.
It is found that the intensity of the laser pulse at the entrance of the hollow fiber should be below or at the level where
multi-photon ionization (MPI) starts to occur. If the intensity is higher than the threshold value for MPI, ionization can
significantly reduce the throughput efficiency. The extension of the scheme to a terawatt power level is also addressed.
PACS 42.65.Re; 42.65.Jx; 42.65.k 相似文献