Chromatographic detection using tris(2,2'-bipyridyl)ruthenium(III) as a fluorogenic electron-transfer reagent

Tris(2,2'-bipyridyl)ruthenium can be excited to fluorescence by visible light (lambda abs 454 nm, lambda em 607 nm) when in the M(II) oxidation state, but not in the M(III) state. A novel chromatographic detection method using the non-fluorescent M(III) form of the complex as a postcolumn fluorogenic reagent is demonstrated. The M(III) form is a powerful oxidizing agent (E degree = 1.27 V vs NHE, 1.05 V vs Ag/AgCl). The M(III) reagent is generated on-line from the M(II) form of the complex by a highly efficient porous carbon electrode and then reacted briefly with chromatographic effluent; the M(II) created by electron transfer from oxidation-susceptible analytes is then detected by fluorescence. The fluorescence detector can be calibrated for number of electrons transferred by injection of either M(II) or an oxidative standard such as ferrocyanide. It is hoped that this redox-based detection scheme will provide an alternative to electrochemical detection. Among the advantages are freedom from surface fouling and the potential for extremely low detection limits. The scheme was applied to detection of the peptide dynorphin A and several of its fragments. Dynorphin A contains tyrosine at the N-terminus (position 1) and tryptophan in position 15; these amino acid residues are susceptible to oxidation and peptides containing them can be detected on that basis. Flow injection testing of the model compounds Tyr-Gly-Gly-Phe-Leu and Gly-Gly-Trp-Gly indicated that tyrosine transferred approximately 1 electron to the M(III) reagent and that tryptophan transferred approximately 4 electrons. Similar results were obtained from the chromatographic runs. Dynorphin A and six dynorphin A fragments containing the N-terminal tyrosine were detected easily at 100 nM concentration (14 pmol) using laser-induced fluorescence. As expected, one fragment that did not contain tryptophan or tyrosine was not detected. A mass detection limit of 80 fmol was estimated for the tyrosine-containing fragments.     

Sustainability decision support system based on collaborative control theory

Industries nowadays have more insight into corporate environmental, social and economic sustainability than ever before. Sustainability issues in various industries are all about choices – finding ways to be more strategic and reducing waste and energy, while benefiting the bottom line. Because of the complexity of sustainability decisions and strategies, these insights call for applying advanced control techniques. In this article we review the concepts of sustainability and its practical issues, specifically focusing on the issues of supply networks. Sustainability issues are usually complex because beyond their inherent challenges, there are conflicts among stakeholders within organizations and between organizations; hence, more useful methods are required for effective solutions. We consider Decision Support Systems (DSSs) to help optimize solutions related with sustainability issues, and review their concepts and usefulness based on previous work. We also suggest strategies applying the Collaborative Control Theory (CCT) principles to augment DSS by a new Sustainability – Decision Support Protocol (S-DSP) in order to overcome certain weaknesses. To model and illustrate the benefit of S-DSP as a control protocol, two practical supply delivery/production problems are analyzed. The results highlight how better collaborative solutions can be achieved to maximize the sustainability of supply networks. It is envisioned that sustainability decision support by such cyber-supported collaboration protocols will contribute to overcome the emerging challenges of sustainability planning and control.     

What Are Quantum States?

We present three strong arguments against the ontic interpretation of quantum states. We then show that the appropriate alternative is not an epistemic interpretation, but viewing quantum states as representing the available knowledge about the potentialities of a quantum system from the perspective a of a particular point in space. Unlike ordinary knowledge, which requires a knower, available knowledge can be assumed to be present regardless of a knower. The relationship between “perspectives on potentialities” and “the potentialities themselves” is clarified.     

Generalization to Novel Views: Universal,Class-based,and Model-based Processing

A major problem in object recognition is that a novel image of a given object can be different from all previously seen images. Images can vary considerably due to changes in viewing conditions such as viewing position and illumination. In this paper we distinguish between three types of recognition schemes by the level at which generalization to novel images takes place: universal, class, and model-based. The first is applicable equally to all objects, the second to a class of objects, and the third uses known properties of individual objects. We derive theoretical limitations on each of the three generalization levels. For the universal level, previous results have shown that no invariance can be obtained. Here we show that this limitation holds even when the assumptions made on the objects and the recognition functions are relaxed. We also extend the results to changes of illumination direction. For the class level, previous studies presented specific examples of classes of objects for which functions invariant to viewpoint exist. Here, we distinguish between classes that admit such invariance and classes that do not. We demonstrate that there is a tradeoff between the set of objects that can be discriminated by a given recognition function and the set of images from which the recognition function can recognize these objects. Furthermore, we demonstrate that although functions that are invariant to illumination direction do not exist at the universal level, when the objects are restricted to belong to a given class, an invariant function to illumination direction can be defined. A general conclusion of this study is that class-based processing, that has not been used extensively in the past, is often advantageous for dealing with variations due to viewpoint and illuminant changes.     

On the limits of expert systems and engineering models in process control

The review is based on an analysis of current literature of expert systems and of system engineering models in dynamic process control. It starts with an analysis of the mental operations and cognitive requirements needed for supervisory control. Mental models are discussed as a function of situational requirements as well as of personal strategies. Systems engineering models and expert systems are briefly described and their function as decision support tools evaluated. Criteria are the overall functionality, similarity of knowledge bases and reasoning strategies of the human and the support system, adaptability to the operator's skill level and self-explanation of the support system in the interaction mode. As a result, system engineering models are only of limited value for knowledge-based process control. Expert systems seem to be very valuable tools for augmenting human decision making in process control, if the interaction problem can be solved.     

Metal and semi-metal precipitates in Nuclepore membranes

Au, Pt, Ag, Sb, Te, In and Ge were precipitated by a salt-reducing agent reaction into the pores of Nuclepore membranes 10 to 600 nm pore size range. The precipitates form filament-like structures inside the pores and a dendritic growth on the surface. The permeation of water as a function of pore size in the Nuclepore membranes was measured by tracing the diffusion through the membrane with tritium. The results are modelled and theoretical predictions are compared with the experimentally observed kinetics for metal deposition in the membranes. Also the d.c. electrical properties of the metal precipitates were measured. The anisotropic electrical properties of these systems are dictated by the morphology of the precipitated metal on the membrane.