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81.
82.
83.
Burley GA Avent AG Gol'dt IV Hitchcock PB Al-Matar H Paolucci D Paolucci F Fowler PW Soncini A Street JM Taylor R 《Organic & biomolecular chemistry》2004,2(3):319-329
A series of trannulene (all-trans annulene) derivatives of [60]fullerene have been prepared by reacting C(60)F(18) with methanetricarboxylate esters that incorporate a range of photoactive functions. All the compounds have the intense emerald-green colour of fullerene trannulenes, characterised by strong bands at ca. 612 and 667 nm. Single crystal X-ray studies show that the packing varies with the nature of the addend, attributable to differing steric effects. UV/vis absorption spectra display transitions of the respective fullerene and addend models, indicating absence of electronic interactions between them in the ground state. These now provide an extensive series for testing photoactive (light-harvesting) properties, with the exceptional properties of having strong visible light absorption. Their exceptional stability is attributed to the 18[small pi] aromatic circuit, inability to undergo nucleophilic substitution without disrupting this circuit, and a curved cage region that is shielded to reagents by the three bulky addends. 相似文献
84.
W. S. J. Schouten R. W. Tuinzing J. Ph. Street C. H. Jones W. J. Baragiola Ch. Godet O. Schuppli R. S. Potter R. S. Snyder J. Tillmans A. Splittgerber H. Riffart A. E. Traaen F. Münter W. P. Robson G. H. G. Lagers F. M. Scales Th. Arnd Alice Wolf-Joachimowitz E. Salm und S. Prager 《Fresenius' Journal of Analytical Chemistry》1918,57(4):187-198
Ohne Zusammenfassung 相似文献
85.
Numerous organic and inorganic laboratory standards were gathered from nine European and North American laboratories and were analyzed for their delta(18)O values with a new on-line high temperature pyrolysis system that was calibrated using Vienna standard mean ocean water (VSMOW) and standard light Antartic precipitation (SLAP) internationally distributed reference water samples. Especially for organic materials, discrepancies between reported and measured values were high, ranging up to 2 per thousand. The reasons for these discrepancies are discussed and the need for an exact and reliable calibration of existing reference materials, as well as for the establishment of additional organic and inorganic reference materials is stressed. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
86.
J. Ding D. Maurice W. F. Miao P. G. McCormick R. Street 《Journal of magnetism and magnetic materials》1995,150(3):417-420
The structure and properties of hexaferrites in the form of MFe12O19 with M = Ba, Sr and Pb prepared by mechanical alloying and heat treatment have been studied. Coercivities of 6–7 kOe were measured for Ba- and Sr-hexaferrite powders. The high values of coercivities have been associated with small particle sizes ( 0.1 μm) resulting from the mechanical alloying and subsequent heat treatment. High-coercivity anisotropic samples have been synthesized using hot-pressing, with remanences of 70–75% of the saturation magnetisation being obtained. 相似文献
87.
We study partitions of the set of all
3
v
triples chosen from a v-set intopairwise disjoint planes with three points per line. Our partitions may contain copies of PG(2,2) only (Fano partitions) or copies of AG(2, 3) only (affine partitions)or copies of some planes of each type (mixed partitions).We find necessary conditions for Fano or affine partitions to exist. Such partitions are already known in severalcases: Fano partitions for v = 8 and affine partitions for v = 9 or 10. We constructsuch partitions for several sporadic orders, namely, Fano partitions for v = 14, 16, 22, 23, 28, andan affine partition for v = 18. Using these as starter partitions, we prove that Fano partitionsexist for v = 7
n
+ 1, 13
n
+ 1,27
n
+ 1, and affine partitions for v = 8
n
+ 1,9
n
+ 1, 17
n
+ 1. In particular, both Fano and affine partitionsexist for v = 36n
+ 1. Using properties of 3-wise balanced designs, weextend these results to show that affine partitions also exist for v = 32n
.Similarly, mixed partitions are shown to exist for v = 8
n
,9
n
, 11
n
+ 1. 相似文献
88.
Ross Street 《Applied Categorical Structures》2003,11(3):219-227
The definition and calculus of extraordinary natural transformations is extended to a context internal to any autonomous monoidal bicategory. The original calculus is recaptured from the geometry of the monoidal bicategory V-Mod whose objects are categories enriched in a cocomplete symmetric monoidal category V and whose morphisms are modules. 相似文献
89.
90.
ABSTRACT Let G be a torsion-free group with all subgroups subnormal of defect at most 4. We show that G is nilpotent of class at most 4. 相似文献