We prove that the multiplicity spaces appearing in Chern-Simons theory, as defioned by Segal, vanish unless they are associated to integrable representations. This and other links with conformal field theory are examined.Supported in part by NSF Mathematics Postdoctoral Fellowship DMS-9007255 相似文献
Using an extensive database of experimental critical properties for heavy compounds, which have been compiled mostly from recent literature sources, it is shown that the ratio Tc: Pc (critical temperature over critical pressure) can be expressed in terms of the van der Waals surface area (Qw), which is readily available for any compound from the group contributions of Bondi (given also in UNIFAC tables). The proposed correlation is based on the hole theory of Kurata and Isida for n-paraffin liquids, which is mathematically equivalent to Flory's theory of polymer solutions. The method is suitable for medium to high molecular weight compounds with unknown critical constants. For example, if only one of the two critical constants is available, then the proposed generalized equation offers a useful rapid procedure for the estimation of the other critical property for use in corresponding states, and other relevant applications where knowledge of the critical properties is required. Furthermore, the Tc: Pc method can be used in many cases for identifying the most suitable among the existing group contribution methods for estimating the critical properties of heavy and complex compounds for which experimental values are, very often, not available. 相似文献
A titanium complex derived from (1R, 2S)-N-(2,4,6-trimethylbenzenesulfonyl)-2-amino-1-indanol catalyzes the Diels-Alder reaction of 2-bromoacrolein and cyclopentadiene with 96.5:3.5 enantioselectivity. A new and efficient synthesis of 2-amino-1-indanol (6) contributes to the potential of this methodology. 相似文献
We investigate the limiting behavior of sample central moments, examining the special cases where the limiting (as the sample size tends to infinity) distribution is degenerate. Parent (non-degenerate) distributions with this property are called singular, and we show in this article that the singular distributions contain at most three supporting points. Moreover, using the delta-method, we show that the (second-order) limiting distribution of sample central moments from a singular distribution is either a multiple, or a difference of two multiples of independent Chi-square random variables with one degree of freedom. Finally, we present a new characterization of normality through the asymptotic independence of the sample mean and all sample central moments.
We consider a model for robust network design in telecommunications, in which we minimize the cost of the maximum mismatch between supply and demand. In the present study, the demand is uncertain and takes its values in a polytope defined by constraints. This problem is hardly tractable, so we limit ourselves to computing lower bounds (by a column-generation mechanism) and upper bounds (using an algorithm due to Falk and Soland for maximizing a separable convex function over a polytope). The experimental gap obtained turns out to be large, and this seems to be mainly due to poor upper bounds. Two possible solutions are suggested for further research aimed at improving them: dc optimization (to minimize the difference of two convex functions) and AARC modeling (affinely adjustable robust counterpart). 相似文献
[reaction: see text] A versatile and general method for the biomimetic construction of [5,5,5]- and [6,5,6]-bis-spiroketals, starting from easily accessible furan nuclei, by means of a powerful one-pot singlet oxygen-mediated cascade sequence is reported. 相似文献
Flame‐retarded polyamide 6.6 (FR‐PA6.6) was prepared by the cocondensation of hexamethylene diammonium adipate (AH‐salt) with the corresponding salts of hexamethylene diamine and two different organophosphorus compounds, namely, 3‐hydroxyphenylphosphinylpropanoic acid (3‐HPP, 1) and 9,10‐dihydro‐10‐[2,3‐di (hydroxycarbonylpropyl]‐10‐phosphaphenanthrene‐10‐oxide (DDP, 2). The incorporation of the phosphorus comonomers and the thermal and physical properties of the resulting copolyamides have been studied. The phosphorus‐modified FR‐PA6.6 possesses high relative viscosities of 2.0 to 2.4, good thermal stability, and was used for the production of polyamide blends by merging FR‐PA6.6 with commercial PA6. This offered access to flame‐retarded PA6 multifilaments, which possess tensile strengths up to 0.7 GPa and elastic moduli up to 6.2 GPa. Knitted fabrics of FR‐PA6 exhibit high limiting oxygen index (LOI) values between 36 and 38 and executed burning tests demonstrate that the incorporation of phosphorus‐based comonomers improve flame retardancy significantly. The approach presented here offers a straightforward access to effective flame retardancy in nylon 6. 相似文献
In vitro and animal studies have shown that thrombolysis with intravenous tissue plasminogen activator (tPA) can be enhanced with ultrasound. Ultrasound delivers mechanical pressure waves to the clot, thus exposing more thrombus surface to circulating drug. Moreover, intravenous gaseous microspheres with ultrasound have been shown to be a potential alternative to fibrinolytic agents to recanalize discrete peripheral thrombotic arterial occlusions or acute arteriovenous graft thromboses. Small phase I-II randomized and non-randomized clinical trials have shown promising results concerning the potential applications of ultrasound-enhanced thrombolysis in the setting of acute cerebral ischemia. CLOTBUST was an international four-center phase II trial, which demonstrated that, in patients with acute ischemic stroke, transcranial Doppler (TCD) monitoring augments tPA-induced arterial recanalization (sustained complete recanalization rates: 38% vs. 13%) with a non-significant trend toward an increased rate of clinical recovery from stroke, as compared with placebo. The rates of symptomatic intracerebral hemorrhage (sICH) were similar in the active and placebo group (4.8% vs. 4.8%). Smaller single-center clinical trials using transcranial color-coded sonography (TCCD) reported recanalization rates ranging from 27% to 64% and sICH rates of 0-18%. A separate clinical trial evaluating the safety and efficacy of therapeutic low-frequency ultrasound was discontinued because of a concerning sICH rate of 36% in the active group. To further enhance the ability of tPA to break up thrombi, current ongoing clinical trials include phase II studies of a single beam 2 MHz TCD with perflutren-lipid microspheres. Moreover, potential enhancement of intra-arterial tPA delivery is being clinically tested with 1.7-2.1 MHz pulsed wave ultrasound (EKOS catheter) in ongoing phase II-III clinical trials. Intravenous platelet-targeted microbubbles with low-frequency ultrasound are currently investigated as a rapid noninvasive technique to identify thrombosed intracranial and peripheral vessels. Multi-national dose escalation studies of microspheres and the development of an operator independent ultrasound device are underway. 相似文献
The azafullerene Tb2@C79N is found to be a single‐molecule magnet with a high 100‐s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy‐axis single‐ion magnetic anisotropy are strongly coupled by the unpaired spin of the single‐electron Tb?Tb bond. Relaxation of magnetization in Tb2@C79N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time τQTM=16 462±1230 s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757±4 K, corresponding to the excited states, in which one of the Tb spins is flipped. 相似文献