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131.
132.
An approximate form for SU(2) multi-instanton determinants, in both the 2- and 3-dimensional representations, is obtained which incorporates the correct properties under conformal transformations and also the leading singular behaviour when the multi-instanton solution becomes degenerate, at least for the 't Hooft multi-instanton solution. 相似文献
133.
The complex structure of the marine metabolic diazonamide A comprises a dichlorinated indole bis-oxazole heteroaromatic fragment, and a [b]-fused dihydrobenzofuran-dihydroindole unit containing an animal carbon, all incorporated within a strained double macrocyclic array. This review details the synthetic studies on this fascinating natural product starting from early studies on the original structure (1991-2001), through the synthesis of the originally proposed structure and the subsequent structural revision, to the eventual successful syntheses of the natural product itself. Throughout we focus on the innovative ways in which synthetic chemists have approached the challenges posed by this natural product. 相似文献
134.
Math search is a new area of research with many enabling technologies but also many challenges. Some of the enabling technologies
include XML, XPath, XQuery, and MathML. Some of the challenges involve enabling search systems to recognize mathematical symbols
and structures. Several math search projects have made considerable progress in meeting those challenges. One of the remaining
challenges is the creation and implementation of a math query language that enables the general users to express their information
needs intuitively yet precisely. This paper will present such a language and detail its features. The new math query language
offers an alternative way to describe mathematical expressions that is more consistent and less ambiguous than conventional
mathematical notation. In addition, the language goes beyond the Boolean and proximity query syntax found in standard text
search systems. It defines a powerful set of wildcards that are deemed important for math search. These wildcards provide
for more precise structural search and multi-levels of abstractions. Three new sets of wildcards and their implementation
details will also be discussed.
相似文献
135.
Beck BR Becker JA Beiersdorfer P Brown GV Moody KJ Wilhelmy JB Porter FS Kilbourne CA Kelley RL 《Physical review letters》2007,98(14):142501
The energy splitting of the 229Th ground-state doublet is measured to be 7.6+/-0.5 eV, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of 233U (105 muCi) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state (29.19-->0 keV). 相似文献
136.
The first synthesis of the unusual bis-oxazole natural product siphonazole is reported, both oxazole rings being constructed using rhodium carbene chemistry. 相似文献
137.
A synthesis of the structure reported for the natural product crassiflorone, a furocoumarin naphthoquinone, is described. The key steps are a Diels-Alder reaction to form 2-bromo-8-hydroxy-6-methylnaphthoquinone, followed by O-protection and copper(II) mediated coupling to 4-hydroxy-5-methylcoumarin to establish the pentacyclic framework whose structure was unambiguously confirmed by X-ray crystallography. Since the spectroscopic data of the synthetic material did not match those reported for the natural product, three further regioisomeric furocoumarin naphthoquinones were prepared by copper(II) mediated coupling of 4-hydroxy-5- or 8-methyl coumarins with 5-benzyloxy-2-bromo-7-methyl- or 8-benzyloxy-2-bromo-6-methyl-1,4-naphthoquinone. Again the spectroscopic data did not match those of the natural material and therefore the true structure of crassiflorone remains unknown. 相似文献
138.
Seth E. Moody 《Fresenius' Journal of Analytical Chemistry》1907,46(4):247-248
Ohne Zusammenfassung 相似文献
139.
140.