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41.
The maximal hypoellipticity of the operator X
1
2m
, ... X
k
2m
is proved, where Xj are first-order pseudodifferential operators and m is a natural number. It is assumed that the set of these operators and
their first-order commutators is an elliptic system. The results obtained generalize the well-known results of Hormander,
Oleinik, and Radkevich, Kohn, Helffer, and Nourrigat, and Rothshield and Stein. Bibliography: 9 titles.
Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 17, pp. 3–26, 1994. 相似文献
42.
43.
44.
Hung‐Chuan Cheng Li‐Tang Wang Ashraf Taha Khalil Yao‐To Chang Yu‐Chi Lin Ya‐Ching Shen 《中国化学会会志》2004,51(2):431-435
Phytochemical investigation of the stem bark of Calophyllum inophyllum resulted in the isolation of a new dipyrenoxanthone, calophinone ( 1 ), together with four related xanthones ( 2–5 ). Identification of the isolated compounds was achieved through intensive studies of their spectral data, especially 2D NMR. 相似文献
45.
脑神经退行性疾病中的有机化学-朊病毒(疯牛病)中的蛋白物理有机化学和自由基化学 总被引:5,自引:0,他引:5
杨池明 《高等学校化学学报》2002,23(2):243-250
通过关于“普里昂”蛋白病毒疾病的已有临床、医学生理、免疫和化学等方面的现象,讨论了朊病毒当中的部分蛋白氧化损伤和蛋白自由基化学本质。 相似文献
46.
Joël J. E. Moreau Luc Vellutini Catherine Bied Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2004,32(1-3):63-67
The acid-hydrolysis of an organo-bridged bisdiethoxysilylated molecular precursor bearing urea groups, (EtO)2MeSi(CH2)3NHCONH(CH2)12NHCONH(CH2)3SiMe(OEt)2, has been performed in pure aqueous medium. Scanning electron microscopy (SEM) analysis of the resulting insoluble solid revealed plate-like forms with a lamellar structure as determined by powder X-ray diffraction (PXRD) studies with a sharp peak at 28.5 Å. The solid state 29Si MAS-NMR spectrum of this bridged siloxane hybrid is consistent with a moderately condensed material with complete preservation of the Si–C bonds throughout the hybrid network. In comparison, the classical sol–gel hydrolysis-condensation of the molecular precursor in ethanol with stoichiometric amount of water and fluoride anion as catalyst produced an amorphous featureless solid. 相似文献
47.
Blends of ABS (acrylonitrile–butadiene–styrene) with phenoxy(poly(hydroxyether bisphenol A)) were prepared using a Branender single screw extruder. Scanning and transmission electron micrographs (SEM, TEM) showed a typical two-phase morphology; particle-in-matrix (90/10) (ABS/phenoxy by weight), 70/30, 10/90), island/sea (30/70) and co-continuous (50/50) morphologies. The glass transition temperature (Tg) of SAN was almost unchanged in the blends, while the Tg of phenoxy increased by about 5 °C in the blends. The synergistic effect of tensile modulus and strength was noted in ABS-rich blends, where a drastic drop of ductility was seen, and the results were interpreted in terms of rubber particle migration form SAN to phenoxy phase, which was visualized by TEM. Melt viscosity showed yield in ABS-rich blends, and generally followed the log additivity. 相似文献
48.
49.
Chi -ping Lau 《manuscripta mathematica》1987,59(1):53-62
It is shown that if the order of non-uniformity of a quasi-linear elliptic equation is h,1
0,2(h–1)/h norm. For 0h1,existence of a bounded solution is guaranteed without any smallness assumption on the given boundary data.More precise information is given for the special case of the minimal surface equation. 相似文献
50.
Treatment of (thd)H (thd=2,2,6,6-tetramethyl-3,5-heptandionate) with excess Os3(CO)12 in an autoclave at 180°C gives the formation of a brown metal chain complex [Os2(CO)5(thd)2]2 (1) and a yellow CO2 cluster complex [Os4(-H)(-CO2)(thd)(CO)13] (2) in low yields. Complex 2 was fully identified by a combination of spectroscopic methods and X-ray diffraction study, showing a unique CO2 ligand bridging a triosmium metal fragment, Os3(-H)(CO)10 and a monometallic osmium fragment, Os(CO)3(thd). Upon treatment of 1 with Me3NO at an elevated temperature, oxidation of the CO ligand occurred at the position trans to the unique CO2 ligand on the Os(CO)3(thd) fragment, giving the formation of a second CO2 cluster [Os4(-H)(-CO2)(thd)(CO)12(NCMe)] (3), which is stabilized by a weakly coordinated acetonitrile molecule. 相似文献