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61.
Summary A method for the separation of a number of herbicides consisting of chlorophenoxy acids by micellar electrokinetic capillary chromatography (MECC) was developed. Sodium dodecyl sulphate (SDS), Brij 35, cetyltrimethylammonium bromide (CTAB) and methanol were introduced into the buffers to investigate their effects on the separation of the herbicides. SDS combined with Brij 35 as the micellar agent was found to provide the best overall separation of these components. 相似文献
62.
Claessens S Jacobs J Van Aeken S Tehrani KA De Kimpe N 《The Journal of organic chemistry》2008,73(19):7555-7559
A synthesis of benzo[f]isoindole-4,9-diones 1 is presented starting from the reaction of 2,3-bis(bromomethyl)-1,4-dimethoxynaphthalene 15 with primary amines affording 2,3-bis(aminomethyl)-1,4-dimethoxynaphthalenes 14, which could be converted by CAN-mediated oxidation in one step to benzo[f]isoindole-4,9-diones 1. An alternative synthesis of benzo[f]isoindole-4,9-diones 1 starts from 2,3-bis(bromomethyl)-1,4-naphthoquinone 9 via 2,3-dihydrobenzo[f]isoindoles 10 which spontaneously oxidize. 相似文献
63.
64.
Iglesias RS Claessens CG Torres T Rahman GM Guldi DM 《Chemical communications (Cambridge, England)》2005,(16):2113-2115
Photophysical studies of a newly synthesized fused subphthalocyanine dimer-C60 revealed a complex cascade of energy transfer events to succeed the initial SubPc dimer photoexcitation. 相似文献
65.
Cost optimal allocation of rail passenger lines 总被引:1,自引:0,他引:1
M.T. Claessens N.M. van Dijk P.J. Zwaneveld 《European Journal of Operational Research》1998,110(3):1276
We consider the problem of cost optimal railway line allocation for passenger trains for the Dutch railway system. At present, the allocation of passenger lines by Dutch Railways is based on maximizing the number of direct travelers. This paper develops an alternative approach that takes operating costs into account. A mathematical programming model is developed which minimizes the operating costs subject to service constraints and capacity requirements. The model optimizes on lines, line types, routes, frequencies and train lengths. First, the line allocation model is formulated as an integer nonlinear programming model. This model is transformed into an integer linear programming model with binary decision variables. An algorithm is presented which solves the problem to optimality. The algorithm is based upon constraint satisfaction and a Branch and Bound procedure. The algorithm is applied to a subnetwork of the Dutch railway system for which it shows a substantial cost reduction. Further application and extension seem promising. 相似文献
66.
Trelka M Medina A Écija D Urban C Gröning O Fasel R Gallego JM Claessens CG Otero R Torres T Miranda R 《Chemical communications (Cambridge, England)》2011,47(36):9986-9988
Ultra high vacuum scanning tunnelling microscopy revealed chlorosubphthalocyanine to self-organize into discrete well-defined bilayer and trilayer triangular nanocrystallites when evaporated onto a Cu(111) surface. 相似文献
67.
Wille K Claessens M Rappé K Monteyne E Janssen CR De Brabander HF Vanhaecke L 《Journal of chromatography. A》2011,1218(51):9162-9173
The presence of both pharmaceuticals and pesticides in the aquatic environment has become a well-known environmental issue during the last decade. An increasing demand however still exists for sensitive and reliable monitoring tools for these rather polar contaminants in the marine environment. In recent years, the great potential of passive samplers or equilibrium based sampling techniques for evaluation of the fate of these contaminants has been shown in literature. Therefore, we developed a new analytical method for the quantification of a high number of pharmaceuticals and pesticides in passive sampling devices. The analytical procedure consisted of extraction using 1:1 methanol/acetonitrile followed by detection with ultra-high performance liquid chromatography coupled to high resolution and high mass accuracy Orbitrap mass spectrometry. Validation of the analytical method resulted in limits of quantification and recoveries ranging between 0.2 and 20 ng per sampler sheet and between 87.9 and 105.2%, respectively. Determination of the sampler-water partition coefficients of all compounds demonstrated that several pharmaceuticals and most pesticides exert a high affinity for the polydimethylsiloxane passive samplers. Finally, the developed analytical methods were used to measure the time-weighted average (TWA) concentrations of the targeted pollutants in passive samplers, deployed at eight stations in the Belgian coastal zone. Propranolol, carbamazepine and seven pesticides were found to be very abundant in the passive samplers. These obtained long-term and large-scale TWA concentrations will contribute in assessing the environmental and human health risk of these emerging pollutants. 相似文献
68.
Guido Claessens 《Aequationes Mathematicae》1979,19(1):104-112
In [9], Warner introduced generalized bigradients in the study of the Newton-Padé table. In this paper we introduce generalized Hankel determinants and derive, using the framework of Newton-Padé approximation, a relationship between these generalized Hankel determinants and generalized bigradients. This generalizes a determinantal identity obtained by Householder and Stewart [7, p. 136]. 相似文献
69.
MM. D. Letouz J. Duflos G. Queguiner P. Pastour 《Journal of heterocyclic chemistry》1973,10(6):1075-1076
This communication describes the synthesis of 7-one (7H) cyclohepta[b]pyridine and some derivatives (6,8-dimethyl; 8-methyl; 8-ethyl….). These compounds have been obtained by condensation of ketones with 2,3-diformylpyridine. 相似文献
70.
Sans résumé 相似文献