中国环流器新一号装置总体联调

本文介绍中国环流器新一号装置工程总体联合调试的内容和主要结果。该装置总体联调是非常成功的，获得了重复性很好，环电流平顶宽的稳定平稳的放电波形，这对物理实验的开展非常有利。     

Specific vectorial immobilization of oligonucleotide-modified yeast cytochrome C on carbon nanotubes.

Iso-1-cytochrome c from the yeast Saccharomyces cerevisiae (YCC) contains a surface cysteine residue, Cys102, that is located opposite to the lysine-rich side containing the exposed heme edge, which is the docking site for enzymes. Site-specific vectorial immobilization of YCC via Cys102 on single-walled carbon nanotubes (SWNT) thus provides a selective interface between nanoscopic electronic devices and complex enzymes. We have achieved this by modification of Cys102 with an oligonucleotide (dT(18)). Atomic force microscopy, fluorescence imaging, and cyclic voltammetry show the specific adsorption of YCC, modified with dT(18), on the SWNT sidewall with retention of its native properties. Pretreatment of the SWNT with Triton-X405 blocks the nonspecific binding of untreated YCC but does not interfere with binding of the oligonucleotide-modified YCC.     

On the Marginal Cost Approach in Maintenance

In this paper we investigate the conditions under which the marginal cost approach of Refs. 1–3 holds. As observed in Ref. 4, the validity of the marginal cost approach gives rise to a useful framework of single-component maintenance optimization models, which covers almost all models used in practice. For the class of unimodal finite-valued marginal cost functions, we show that these optimization models are easy to solve.     

Mathematical Level Raising Through Collaborative Investigations with the Computer

Investigations with the computer can have different functions in the mathematical learning process, such as to let students explore a subject domain, to guide the process of reinvention, or to give them the opportunity to apply what they have learned. Which function has most effect on mathematical level raising?We investigated that question in the context of developing learning materials for 16-year-old students in the domain of probability theory,consisting of computer simulations based on a gambling game and investigation tasks about these games. We compared the difference in level raising between three versions of the learning materials: investigations with the computer before, during or after the learning of a mathematical concept. It was shown that there was no significant difference in the final mathematical level that students attained in the three conditions (the product). However, there were differences in the level on which students approached the investigation tasks (the process). Furthermore,we found evidence of new categories in the students' answers, lying between the perceptual and conceptual levels, which may give important insight into the process of level raising. This revised version was published online in July 2006 with corrections to the Cover Date.     

Problem solving as a challenge for mathematics education in The Netherlands

This paper deals with the challenge to establish problem solving as a living domain in mathematics education in The Netherlands. While serious attempts are made to implement a problem-oriented curriculum based on principles of realistic mathematics education with room for modelling and with integrated use of technology, the PISA 2003 results suggest that this has been successful in educational practice only to a limited extent. The main difficulties encountered include institutional factors such as national examinations and textbooks, and issues concerning design and training. One of the main challenges is the design of good problem solving tasks that are original, non-routine and new to the students. It is recommended to pay attention to problem solving in primary education and in textbook series, to exploit the benefits of technology for problem solving activities and to use the schools’ freedom to organize school-based examinations for types of assessment that are more appropriate for problem solving.     

An equilibrium-correction model for dynamic network data

We propose a two-stage MRQAP to analyze dynamic network data within the framework of an equilibrium-correction (EC) model. Extensive simulation results indicate practical relevance of our method and its improvement over standard OLS. In addition, empirical illustration shows that the EC-model yields interpretable parameters, in contrast to an unrestricted dynamic model.     

Denumerable semi-Markov decision chains with small interest rates

In this paper we investigate denumerable state semi-Markov decision chains with small interest rates. We consider average and Blackwell optimality and allow for multiple closed sets and unbounded immediate rewards. Our analysis uses the existence of a Laurent series expansion for the total discounted rewards and the continuity of its terms. The assumptions are expressed in terms of a weighted supremum norm. Our method is based on an algebraic treatment of Laurent series; it constructs an appropriate linear space with a lexicographic ordering. Using two operators and a positiveness property we establish the existence of bounded solutions to optimality equations. The theory is illustrated with an example of aK-dimensional queueing system. This paper is strongly based on the work of Denardo [11] and Dekker and Hordijk [7].This research has partially been sponsored by the Netherlands Organization for Scientific Research (NWO).     

Corrections to the third order Lamb theory and its application to mode locking phenomena

Two of Lamb's third order phase coupling coefficients appeared to be incomplete. Taking account of pressure broadening the coefficients are evaluated in the Doppler limit. Some remarks are made on mistakes in the literature concerning mode locking phenomena.     

The expansion of the Fokker-Planck equation including a critical point

The known expansion of the master equation for weak diffusion in an external potential applies to both the monostable and the bistable case, but fails at the critical point. This can be remedied by taking as zeroth order approximation a suitably defined set of eigenfunctions. The resulting expansion is uniformly valid in a range of the pump parameter including the critical point.