The Mediation Effect of a Polyaniline-Coated Electrode on the Reduction of Iron (III) Ions

The mediation effect of polyaniline-coated platinum electrodes on the reduction of iron(III) ions was studied by the cyclic voltammetry and rotating disk electrode methods. The rate constants of the cross reaction between iron(III) ions and polyaniline (PA) were found to depend upon the amount of PA coated on the electrode. On the basis of the rate constants the PA-coated electrode mediates the reduction of iron(III) ion efficiently and behaves as well as a metallic electrode.     

A simultaneous multi-issue negotiation through autonomous agents

Automated negotiation through autonomous agents has become increasingly important since the advent of e-marketplace. A deadlock may arise in which both negotiators refuse to disclose more information; then, mediation is required. We propose an agent-based sealed-bid design in which both agents simultaneously submit their respective offers to the mediate agent, and construct an efficient negotiation strategy which can reach an agreement aiming to maximize their owner’s utility. An important contribution of this paper is that we consider negotiators not necessarily to conflict over all issues, such as quantity. Our experimental results demonstrate that the proposed automated negotiation strategy is efficient in terms of the Pareto-efficiency of the negotiated contracts, the joint utility obtained, and the equality of both agents. In addition, since disclosure of information is reduced greatly, the design can discourage counter-speculation and effectively control fraud and misrepresentation to a certain extent. The method we proposed is simple and stable in the context of a game and the model could be well suited for practical agent applications.     

试论制约世界政治地图划分与变动的因素

本文论述了制约世界政治地图划分与变动的九大因素,并指出:世界政治地图是这些因素综合起作用达到平衡的产物。     

Exploiting the potential of primary historical sources in primary school: a focus on teacher’s actions

Integrating history of mathematics in classes could be a hard task with young pupils. Indeed, original historical sources have a language that is far from the modern one. Such texts represent cultural artefacts that can give access to mathematical knowledge. The teacher can exploit such potential acting as a mediator between the mathematical signs of the source and those signs that are accessible to students. Through a case study, we investigate the role of the teacher in the process of semiotic mediation during a collective discussion. The analysed intervention is made of two phases: firstly, students work collaboratively and secondly, the teacher mediates a discussion aimed at institutionalizing the knowledge. During the discussion, working on a text from Tartaglia’s translation of Euclid’s Elements, a group of fifth graders constructs a definition of prime numbers. Referring to the Theory of Semiotic Mediation, we analyse the role of the teacher in building up semiotic chains linking students’ productions to an institutionalized knowledge emerging from the collective discussion. We highlight how teacher’s focalization on students’ words allows the progress of the discussion: the potential of the historical text is exploited fostering a definition that is close to culturally shared mathematics.     

Chemical Cross-Linking of a Redox Mediator Thionin for Electrocatalytic Oxidation of Reduced β-Nicotinamide Adenine Dinucleotide

Abstract

Thionin, a redox mediator that has been used to study the electrochemical behavior of reduced β-nicotinamide adenine dinucleotide (NADH), was chemically cross-linked on the surface of a spectroscopic graphite electrode by using a triisocyanate cross-linking agent. The electrodes modified in this manner had a purple film with an additional reversible redox couple a t E° of +73 mV vs. Ag/AgCl compared to uncross-linked thionin. The thionin modified electrode mediated oxidation of NADH with response to NADH between 7.0 × 10–7 to 1.8 × 10–3 M, a sensitivity of 113 pAJcmWmM, and a detection limit of 0.5 μM.     

Mechanism of photochemical reduction of chromium(VI) by alcohols and its environmental aspects

The idea of photochemical abatement of the Cr(VI) pollution has been verified by investigating the photoreduction mediated by aliphatic alcohols under conditions mimicking the environmental ones. Effects of the alcohol nature, pH and presence of oxygen are analysed. The time-resolved spectra are used to follow the generation of the transient chromium Cr(V), Cr(IV) and Cr(II) species and the R₁R₂CHOH√⁺ radicals. A direct interaction between chromate(VI) and an electron donor is a precondition of the photoreduction via the photoinduced electron transfer (PET). Two pathways of the PET are identified: one-electron transfer for intermolecular and two-electron transfer for the intramolecular systems. In the case of the alcohol mediators the option is pH-controlled.     

Redox and electrocatalytic activity of copper in base at unusually low, premonolayer potentials

The assumption involved in this work is that the formation of monolayer (α) oxide species, which occurs on copper in base at 60 °C at ca. 0.5 V (RHE), is of little relevance to the electrocatalytic behaviour of the metal at low potentials. For many processes occurring at the interface in question the critical potential is ca. −0.1 V (RHE). This is the value where several electrocatalytic oxidation and reduction processes commence or terminate under potential sweep conditions; hydrous oxide films are reduced close to this value and it is possible to produce an active (but transient) state of the metal surface which exhibits a reversible redox response in this region. The results are rationalized in terms of the incipient hydrous oxide/adatom mediator model of electrocatalysis, and the nature of the active site material at the interface is discussed. Received: 25 January 1999 / Accepted: 8 April 1999     

Synergy between manipulative and digital artefacts: a teaching experiment on axial symmetry at primary school

This paper presents a study aimed at investigating the didactic potentiality of the combined use of two different kinds of artefacts for the purpose of constructing and conceptualizing mathematical meanings related to the notion of axial symmetry. In our view, the process of meanings construction can be fostered by the use of adequate artefacts, but it requires a teaching/learning model, which explicitly takes care of the evolution of meanings, from those personal, emerging through the activities, to the mathematical ones, aims of the teaching intervention. The main hypothesis of this study is that a potential synergy may occur between the use of different artefacts, synergy that can foster the integration of different and complementary meanings providing a rich support to the development of the expected mathematical meaning. The Theory of Semiotic Mediation offers the theoretical framework suitable to design the teaching sequence and to analyze the collected data. Specifically, the construct of semiotic potential provides the tool for describing the potentialities of the two artefacts, while that of didactic cycle offers a model for the organization of the different activities. The paper reports on a teaching sequence and its implementation in a teaching experiment, involving pupils at fourth grade level. We describe them, within the chosen theoretical framework, and provide the analysis of key episodes of the teaching sequence. We show evidence supporting our main hypothesis about the combined use of an artefact that can be manipulated (paper and pin), and a digital artefact (Dynamic Geometry Environment) in the development of the notion of axial symmetry and its properties: the combined, intentional and controlled use of the two artefacts may develop a synergy, so that each activity enhances the potential of the other.     

Redox-active lipid-incorporating proteins as a novel immobilisation technique

A novel chiral redox-active ferrocene compound (FcV1) with amphiphilic properties has been synthesised and used successfully to form protein + lipid ‘clusters’ with ferritin and gold-labelled BSA. These structures could be observed by cryogenic transmission electron microscopy and had diameters between 40 and 300 nm. It was shown that the novel lipid formed reasonably stable films on an edge plane graphite electrode surface and also mediated the electron transfer between flavocytochrome b₂ and this electrode. Consequently, the enzyme was incorporated into an FcV1 film and its response towards (+)lactate in solution investigated. It could be shown that the electrode indeed was sensitive to (+)lactate.     

肯·威尔伯整合视阈下的纠纷调解策略——以藏族新型民间纠纷为例

调解是藏区处理民间纠纷的传统主导方式，其模式、方法在藏族社会转型的新形势下暴露出了整体性与针对性缺失等问题，调解的高调与低效的反差现象已较为明显，尤其是对于新型民间纠纷的处理。美国哲学家肯·威尔伯的整合理论为上述问题的解决提供了有价值的视角。文章借鉴整合理论中的“象限”与“层次（阶段）”概念分析探讨了藏族新型民间纠纷的调解方法（策略）。