W-Hierarchies Defined by Symmetric Gates

The classes of the W-hierarchy are the most important classes of intractable problems in parameterized complexity. These classes were originally defined via the weighted satisfiability problem for Boolean circuits. Here, besides the Boolean connectives we consider connectives such as majority, not-all-equal, and unique. For example, a gate labelled by the majority connective outputs true if more than half of its inputs are true. For any finite set C\mathcal{C} of connectives we construct the corresponding W( C\mathcal{C} )-hierarchy. We derive some general conditions which guarantee that the W-hierarchy and the W( C\mathcal{C} )-hierarchy coincide levelwise. If C\mathcal{C} only contains the majority connective then the first levels of the hierarchies coincide. We use this to show that a variant of the parameterized vertex cover problem, the majority vertex cover problem, is W[1]-complete.     

Project governance: case studies on financial incentives

Appropriate financial incentives within construction project coalitions can contribute to effective project governance. However, the dearth of primary research material is partly attributed to the lack of a suitable methodology with which to study projects. Social network analysis (SNA) is proposed as an analytical tool to explore coalition governance. Primary data are presented for three European case studies employing quite different approaches to the use of financial incentives in project governance. The case studies investigate pain share/gain share arrangements implemented under a prime contracting procurement approach; an unusual use of activity-related penalties in the French system of procurement; and the use of guaranteed maximum price supplements within a UK standard form of (without contractor's design) building contract. The use of SNA enables the observation of a number of transaction sets and the formulation of a framework for the quantification of construction project governance. The first case study demonstrates the decentralization of client-orientated financial management, from consultant quantity surveyor to a number of multidisciplinary cluster leaders. The second case study illustrates the importance of incentive contiguity in effective project governance. The third case study uses SNA to demonstrate the way in which financial governance could be transformed through the transference of client-orientated financial management from the client and their professional adviser to the main contractor.

Les incitations financières appropriées, dans le cadre d'un fonds commun relatif à un projet de construction, peuvent contribuer à une gestion efficace du projet. Or, la pénurie de matériel de recherche primaire est attribuée, en partie, à l'absence d'une méthodologie appropriée permettant d'étudier de tels projets. Dans cet article, l'auteur propose l'analyse du réseau social (SNA) comme outil analytique permettant d'explorer la gouvernance collective. L'article présente des données primaires concernant trois études de cas européennes employant des méthodologies tout à fait différentes d'utilisation des incitations financières dans la gouvernance du projet. Ces études de cas portent sur les mécanismes de partage des difficultés/partage des gains mis en ?uvre au titre des approvisionnements par un maître d'?uvre, sur l'usage inhabituel de pénalités liées à l'activité dans le système français des approvisionnements et sur l'usage de suppléments de prix garantis et maximaux dans une forme standard du SNA, au Royaume-Uni, permettant l'observation d'un certain nombre d'ensembles de transactions et la formulation d'un cadre pour la quantification de la gouvernance du projet de construction. La première étude de cas démontre la décentralisation de la gestion financière orientée ‘client’, du consultant métreur-vérificateur vers un certain nombre de responsables de groupes pluridisciplinaires. La deuxième étude de cas illustre l'importance de la contiguïté incitative dans une gouvernance de projet efficace. La troisième étude de cas utilise la SNA pour démontrer comment pourrait être transformée la gouvernance financière en passant d'une gestion financière orientée ‘client’, du client et de son conseiller professionnel, vers le maître d'?uvre.

Mots-clés: modèles de développement, collaboration, gouvernance, incitations, contrats de maître d'oeuvre, approvisionnement, dynamique du projet, organisation du projet, analyse du réseau social, intégration des équipes.     

Detecting 6 MV X-rays using an organic photovoltaic device

An organic photovoltaic (OPV) device has been used in conjunction with a flexible inorganic phosphor to produce a radiation tolerant, efficient and linear detector for 6 MV X-rays. The OPVs were based on a blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). We show that the devices have a sensitivity an order of magnitude higher than a commercial silicon detector used as a reference. Exposure to 360 Grays of radiation resulted in a small (2%) degradation in performance demonstrating that these detectors have the potential to be used as flexible, real-time, in vivo dosimeters for oncology treatments.     

Learning contextual relationships in mammograms using a hierarchical pyramid neural network

This paper describes a pattern recognition architecture, which we term hierarchical pyramid/neural network (HPNN), that learns to exploit image structure at multiple resolutions for detecting clinically significant features in digital/digitized mammograms. The HPNN architecture consists of a hierarchy of neural networks, each network receiving feature inputs at a given scale as well as features constructed by networks lower in the hierarchy. Networks are trained using a novel error function for the supervised learning of image search/detection tasks when the position of the objects to be found is uncertain or ill defined. We have evaluated the HPNN's ability to eliminate false positive (FP) regions of interest generated by the University of Chicago's (UofC) Computer-aided diagnosis (CAD) systems for microcalcification and mass detection. Results show that the HPNN architecture, trained using the uncertain object position (UOP) error function, reduces the FP rate of a mammographic CAD system by approximately 50% without significant loss in sensitivity. Investigation into the types of FPs that the HPNN eliminates suggests that the pattern recognizer is automatically learning and exploiting contextual information. Clinical utility is demonstrated through the evaluation of an integrated system in a clinical reader study. We conclude that the HPNN architecture learns contextual relationships between features at multiple scales and integrates these features for detecting microcalcifications and breast masses.     

An integrated microfabricated cell sorter

We have developed an integrated microfabricated cell sorter using multilayer soft lithography. This integrated cell sorter is incorporated with various microfluidic functionalities, including peristaltic pumps, dampers, switch valves, and input and output wells, to perform cell sorting in a coordinated and automated fashion. The active volume of an actuated valve on this integrated cell sorter can be as small as 1 pL, and the volume of optical interrogation is approximately 100 fL. Different algorithms of cell manipulation, including cell trapping, were implemented in these devices. We have also demonstrated sorting and recovery of Escherichia coli cells on the chip.     

Nine-analyte detection using an array-based biosensor

A fluorescence-based multianalyte immunosensor has been developed for simultaneous analysis of multiple samples. While the standard 6 x 6 format of the array sensor has been used to analyze six samples for six different analytes, this same format has the potential to allow a single sample to be tested for 36 different agents. The method described herein demonstrates proof of principle that the number of analytes detectable using a single array can be increased simply by using complementary mixtures of capture and tracer antibodies. Mixtures were optimized to allow detection of closely related analytes without significant cross-reactivity. Following this facile modification of patterning and assay procedures, the following nine targets could be detected in a single 3 x 3 array: Staphylococcal enterotoxin B, ricin, cholera toxin, Bacillus anthracis Sterne, Bacillus globigii, Francisella tularensis LVS, Yersiniapestis F1 antigen, MS2 coliphage, and Salmonella typhimurium. This work maximizes the efficiency and utility of the described array technology, increasing only reagent usage and cost; production and fabrication costs are not affected.     

OLES: an instrument for refining the design of e-learning environments

Abstract Designing and implementing effective e-learning is a complex process, which involves many factors. Lecturers need to constantly consider, evaluate and adjust these factors to provide effective e-learning environments for students. In this paper, we report on the design and development of the Online Learning Environment Survey (OLES), an instrument which can be used to gather and represent data on students' 'actual' (experienced) and 'preferred' (ideal) learning environments. We describe the use of this instrument in blended learning environments with university classes, illustrating how OLES can be used by educators striving for good practice in the design of effective online learning environments.     

Dynamics and control in component‐based agent models

Dynamics are an important aspect of agent models. Control of dynamics requires specific methods of specification that have their own specific semantics. This paper addresses specification and semantics of dynamics and control in component‐based agent models. Specification is based on a dedicated formal design specification language for agent models. Semantics of the dynamics are defined using temporal traces with composite states. It is shown in what manner control aspects can be specified, and what their semantics is in terms of the temporal traces. An agent model for controlled diagnostic reasoning processes is used to illustrate the approach. © 2002 Wiley Periodicals, Inc.