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81.
Deng S Sriwichai S Taranekar P Krueger G Mays JW Advincula RC 《Chemical communications (Cambridge, England)》2011,47(31):8805-8807
A series of thiophene dendrons and dendrimers with peripheral functional groups were designed and synthesized. Two methodologies using thiophene dendrons and dendrons as synthetic building blocks, namely, (1) periphery functionalization; (2) a combination of focal and periphery functionalization have been demonstrated. 相似文献
82.
García F Less RJ McPartlin M Michalski A Mulvey RE Naseri V Stead ML Morán de Vega A Wright DS 《Chemical communications (Cambridge, England)》2011,47(6):1821-1823
The structures of a series of spherical host-guest complexes [{MeE(PPh)(3)Li(4)·3thf}(4)(μ(4)-X)](-) (E = Al, [1X](-); E = Ga, [2X](-); E = In, [3X](-)) reveal that changing the halide ions (X = Cl, Br, or I) within their central tetrahedral Li(4) sites has negligible effect on the structural parameters. 相似文献
83.
Let R be an isolated hypersurface singularity, and let M and N be finitely generated R-modules. As R is a hypersurface, the torsion modules of M against N are eventually periodic of period two (i.e., for i?0). Since R has only an isolated singularity, these torsion modules are of finite length for i?0. The theta invariant of the pair (M,N) is defined by Hochster to be for i?0. H. Dao has conjectured that the theta invariant is zero for all pairs (M,N) when R has even dimension and contains a field. This paper proves this conjecture under the additional assumption that R is graded with its irrelevant maximal ideal giving the isolated singularity. We also give a careful analysis of the theta pairing when the dimension of R is odd, and relate it to a classical pairing on the smooth variety Proj(R). 相似文献
84.
85.
Gary D Josephsen Kelly A Josephsen Greg J Beilman Jodie H Taylor Kristine E Muiler 《Microscopy and microanalysis》2005,11(6):500-505
This is a report of the adaptation of microwave processing in the preparation of liver biopsies for transmission electron microscopy (TEM) to examine ultrastructural damage of mitochondria in the setting of metabolic stress. Hemorrhagic shock was induced in pigs via 35% total blood volume bleed and a 90-min period of shock followed by resuscitation. Hepatic biopsies were collected before shock and after resuscitation. Following collection, biopsies were processed for TEM by a rapid method involving microwave irradiation (Giberson, 2001). Samples pre- and postshock of each of two animals were viewed and scored using the mitochondrial ultrastructure scoring system (Crouser et al., 2002), a system used to quantify the severity of ultrastructural damage during shock. Results showed evidence of increased ultrastructural damage in the postshock samples, which scored 4.00 and 3.42, versus their preshock controls, which scored 1.18 and 1.27. The results of this analysis were similar to those obtained in another model of shock (Crouser et al., 2002). However, the amount of time used to process the samples was significantly shortened with methods involving microwave irradiation. 相似文献
86.
87.
Ambident anions derived from phosphorus monothio acids have been glycosylated by 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl-, 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl- and 2,3,4-tri-acetyl-α-D-xylopyranosyl bromides, yielding β-S-glycosyl- and /gb-O-glycosylthioates. The S/O ratio of the glycosylated phosphorothioates depends markedly on the salt used. Ammonium salts favour the formation of S-derivatives, whereas silver salts give mainly O-derivatives. O-Glucosyl phosphorothioate undergoes thermal isomerisation to S-glucosyl phosphorothioate, with retention of configuration at the glycosylic centre. The implications of this stereochemical result are briefly discussed. 相似文献
88.
Grzegorz Michalski 《Mathematical Logic Quarterly》1992,38(1):203-208
Let Γn(φ) be a formula of LPA (PA = Peano Arithmetic) meaning “there is a proof of φ from PA-axioms, in which ω-rule is iterated no more than n times”. We examine relations over pairs of natural numbers of the kind. (n, k) ≦H (n', k') iff PA + RFNn' (Hk') ? RFNn (Hk). Where H denotes one of the hierarchies ∑ or Π and RFNn(C) is the scheme of the reflection principle for Γn restricted to formulas from the class C(Γn(φ) implies “φ is true”, for every φ ∈ C). Our main result is that. (n, k) ≦H (n', k') if n ≦ n' and k ≦ max (k', 2n' + 1). 相似文献
89.
90.
Fred L. Tobiason Greg H. Cain Steve M. Gregory 《Journal of polymer science. Part A, Polymer chemistry》1978,16(3):659-666
Rotational isomeric-state chain-configurational calculations have been applied to the novolac phenol–formaldehyde structure. Steric interference allows the chain to be considered with a twofold potential energy barrier model. Computations that fit the observed dipole-moment data over a range of molecular weights indicate that the conformational angle is near ±80°, with the g±g= states on the average being 155 cal/mole below the g±g± states. The limiting dipole-moment ratio is computed to be 1.47, compared to the experimental value of 1.48. A negative temperature coefficient agrees in sign with the experimental value, and the characteristic ratio of the end-to-end molecular dimensions is calculated to be 3.27, as compared to the experimental value of 4.76. 相似文献