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11.
George R. Rossman Robert D. Shannon Robert K. Waring 《Journal of solid state chemistry》1981,39(3):277-287
Single-crystal optical absorption spectra of NiO, NiTiO3, NiWO4, NiV2O6, NiNb2O6, Ni2SiO4, Ni3V2O8, LiNiPO4, Li2Ni2Mo3O12, SrNiTeO6, LiScSiO4:Ni, MgSiO3:Ni, and (Mg,Ni)2SiO4 are presented for the purpose of comparing the spectra of yellow and green Ni2+ compounds. Powder spectra of NiTiO3, NiWO4, NiV2O6, NiNb2O6, and Ni3V2O8 in the ultraviolet region help elucidate the more intense charge transfer bands. Bright yellow color results when Ni2+ is in a six-coordinated site significantly distorted from octahedral symmetry. Increased absorption intensity occurs when the metal ion d-d bands are in proximity to an ultraviolet charge transfer band. 相似文献
12.
The inactive, nitrosyl bound form of Fe-type nitrile hydratase (NHase) contains two active site cysteine residues that are post-translationally modified to sulfenate (SO-) and sulfinate (SO2-) ligands. DFT and INDO/S calculations support the hypothesis that these unusual modifications play a key role in modulating the electronic absorption spectra and photoreactivity of the Fe(III) centre in the enzyme. 相似文献
13.
A photosensitive precursor (1) to phenylsulfanylcarbene 2 has been synthesized. Laser flash photolysis (308 nm) of 1 and chemical trapping studies of 2 are reported. [structure: see text] 相似文献
14.
Production of hybrid 16-membered macrolides by expressing combinations of polyketide synthase genes in engineered Streptomyces fradiae hosts 总被引:1,自引:0,他引:1
Reeves CD Ward SL Revill WP Suzuki H Marcus M Petrakovsky OV Marquez S Fu H Dong SD Katz L 《Chemistry & biology》2004,11(10):1465-1472
Combinations of the five polyketide synthase (PKS) genes for biosynthesis of tylosin in Streptomyces fradiae (tylG), spiramycin in Streptomyces ambofaciens (srmG), or chalcomycin in Streptomyces bikiniensis (chmG) were expressed in engineered hosts derived from a tylosin-producing strain of S. fradiae. Surprisingly efficient synthesis of compounds predicted from the expressed hybrid PKS was obtained. The post-PKS tailoring enzymes of tylosin biosynthesis acted efficiently on the hybrid intermediates with the exception of TylH-catalyzed hydroxylation of the methyl group at C14, which was efficient if C4 bore a methyl group, but inefficient if a methoxyl was present. Moreover, for some compounds, oxidation of the C6 ethyl side chain to an unprecedented carboxylic acid was observed. By also expressing chmH, a homolog of tylH from the chalcomycin gene cluster, efficient hydroxylation of the 14-methyl group was restored. 相似文献
15.
Björn C.G. Söderberg Jeremiah W. Hubbard Stacey R. Rector Shannon N. O'Neil 《Tetrahedron》2005,61(15):3637-3649
A route to 3,4-fused indoles via two consecutive palladium-catalyzed reactions; an intramolecular Heck reaction followed by a reductive N-heteroannulation is described. Using this route, a number of indoles have been prepared having a variety of ring sizes anchored to the 3- and 4-position of the indole nucleus. Furthermore, a number of functional groups, both carbon and heteroatom substituents can be introduced in (and on) the additional ring without any detrimental effects on the two reactions. 相似文献
16.
Bernoulli-p thinning has been well-studied for point processes. Here we consider three other cases: (1) sequences (X 1,X 2,??); (2) gaps of such sequences (X n+1?X 1) n???; (3) partition structures. For the first case we characterize the distributions which are simultaneously invariant under Bernoulli-p thinning for all p??(0,1]. Based on this, we make conjectures for the latter two cases, and provide a potential approach for proof. We explain the relation to spin glasses, which is complementary to important previous work of Aizenman and Ruzmaikina, Arguin, and Shkolnikov. 相似文献
17.
Madlene U. Koller Katrina L. Peariso Tina S. Guion Shannon Studer Martinez Charles F. Beam 《合成通讯》2013,43(19):2963-2974
2-, 3-, or 4-Picolyllithium was prepared in excess lithium diiso-propylamide and condensed with several hydroxy-benzaldehydes and 4-hydroxy-acetophenone to afford substituted hydroxyphenyl-pyridyl-ethanols and α-hydroxyphenyl-α-methylpyridineethanols. In two instances. 3-picolyllithium condensed with aldehydes to presumably form the hydroxyphenyl-pyridyl-ethanol, which underwent linear dehydration to the substituted pyridyl-ethylenyl-phenol. 相似文献
18.
S. K. Kim K. T. Atanassov A. G. Shannon 《International Journal of Mathematical Education in Science & Technology》2013,44(2):173-179
The purpose of this paper is to explain the basic theory of generalized nets (GNs) and their applications in the context of the differential diagnosis of neurological diseases. We define formally the concepts of a GN and transitions of a GN and also outline some remarks on their theory. The work here constructs an example which aims to trace the process of diagnosing different signs and symptoms in neurology. This will enable the interested reader to see the scope of nets in general as tools for the modelling, simulation, optimization and control of real processes. 相似文献
19.
20.
J. V. Leyendekkers A. G. Shannon 《International Journal of Mathematical Education in Science & Technology》2013,44(2):303-306
The modular ring ?6 defines integers via (6r i + (i ? 3)) where i is the class and r i the row when tabulated in an array. Since only Classes 26 and 46 contain odd primes, this modular ring is ideally suited to the analysis of twin primes. The calculations are facilitated by the use of the right-end digit (RED) technique. 相似文献