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91.
92.
Sodiun borohydride reacts with oxazolidinium methiodides derived from ephedrine and pseudoephedrine, in ethereal solvents, cleaving regioselectively the C-N bond of the ring and leading, in good yields, to chiral amine-borane adducts of know absolute configuration. The 1HNMR data allow to predict the most stable conformation. 相似文献
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In this note, we describe a procedure to construct generalized complex structures whose type change locus has arbitrarily many path components on products of the circle with a connected sum of closed 3-manifolds. As an application, we use the procedure to exhibit such geometric structures on a myriad of simply connected 4-manifolds among many others. 相似文献
95.
Rafael Ortega 《Archiv der Mathematik》2016,107(4):405-412
An elementary method to prove the existence of odd periodic solutions with a prescribed number of zeros is presented. In some cases it is also possible to prove the uniqueness of this solution. The method combines shooting arguments with Sturm comparison theory and can be applied to a large class of nonlinear oscillators. In particular, this class includes the Sitnikov problem, a well-known restricted three body problem. 相似文献
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98.
Denise Tofanello Gimenes Polyana Fernandes Pereira Rafael Rodrigues Cunha Rodrigo Amorim Bezerra da Silva Rodrigo Alejandro Abarza Munoz Eduardo Mathias Richter 《Electroanalysis》2012,24(9):1805-1810
In this study, we describe for the first time the application of an internal standard method to compensate for random errors associated with the injection procedure in batch injection analysis (BIA) systems with multiple pulse amperometric detection. A sequence of potential pulses was selected in such a way that the internal standard (IS) compound was detected individually at one potential pulse and both the IS and analyte, were detected at another potential pulse. The current ratio (IIS+analyte/IIS) was used in the construction of the calibration curve and then to compensate for random errors. The use of disposable syringes or manual pipettes in BIA systems increases the robustness of the method and dispenses with skilled operators. 相似文献
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Haroldo G. Santos Túlio A. M. Toffolo Rafael A. M. Gomes Sabir Ribas 《Annals of Operations Research》2016,239(1):225-251
This work presents integer programming techniques to tackle the problem of the International Nurse Rostering Competition. Starting from a compact and monolithic formulation in which the current generation of solvers performs poorly, improved cut generation strategies and primal heuristics are proposed and evaluated. A large number of computational experiments with these techniques produced the following results: the optimality of the vast majority of instances was proved, the best known solutions were improved by up to 15 % and strong dual bounds were obtained. In the spirit of reproducible science, all code was implemented using the Computational Infrastructure for Operations Research. 相似文献