Group 13 Decamethylmetallocenium Cations

Salts containing the decamethylmetallocenium cations, [( C5Me5) M-2](+) ( or Cp*M-2(+)) of the group 13 "metals" B, Al and Ga have been prepared using a variety of synthetic routes. Precursor molecules of the type Cp*2MX ( X = Cl, Br, Me) exhibit structural features that vary significantly depending on the size and electronegativity of the central atom. While salt metathesis, halide abstraction and methanide abstraction methods represent viable routes for the preparation of salts of Cp*B-2(+) and Cp*Al-2(+), acidolysis of a Cp* group from Cp*Ga-3 is the most reliable method for the synthesis of the analogous gallium cation. Gallocenium cations are less stable than either of the lighter congeneric cations since they prove to be susceptible to decomposition reactions involving the "back-transfer" of ligands from the counter anion. Density functional theory (DFT) calculations revealed that, whereas Cp*Ga-2(+) is predicted to adopt a molecular structure more similar to that of Cp*B-2(+), the electronic structure of the gallium cation bears a greater resemblance to that of Cp*Al-2(+).Chemistr

Nonlocal failures in complex supply networks by single link additions

How do local topological changes affect the global operation and stability of complex supply networks? Studying supply networks on various levels of abstraction, we demonstrate that and how adding new links may not only promote but also degrade stable operation of a network. Intriguingly, the resulting overloads may emerge remotely from where such a link is added, thus resulting in nonlocal failure. We link this counter-intuitive phenomenon to Braess' paradox originally discovered in traffic networks. We use elementary network topologies to explain its underlying mechanism for different types of supply networks and find that it generically occurs across these systems. As an important consequence, upgrading supply networks such as communication networks, biological supply networks or power grids requires particular care because even adding only single connections may destabilize normal network operation and induce disturbances remotely from the location of structural change and even global cascades of failures.Comment: 12 pages, 10 figure

On Engineering Support for Business Process Modelling and Redesign

Currently, there is an enormous (research) interest in business process redesign (BPR). Several management-oriented approaches have been proposed showing how to make BPR work. However, detailed descriptions of empirical experience are few. Consistent engineering methodologies to aid and guide a BPR-practitioner are currently emerging. Often, these methodologies are claimed to be developed for business process modelling, but stem directly from information system design cultures. We consider an engineering methodology for BPR to consist of modelling concepts, their representation, computerized tools and methods, and pragmatic skills and guidelines for off-line modelling, communicating, analyzing, (re)designing\ud business processes. The modelling concepts form the architectural basis of such an engineering methodology. Therefore, the choice, understanding and precise definition of these concepts determine the productivity and effectiveness of modelling tasks within a BPR project. The\ud current paper contributes to engineering support for BPR. We work out general issues that play a role in the development of engineering support for BPR. Furthermore, we introduce an architectural framework for business process modelling and redesign. This framework consists of a coherent set of modelling concepts and techniques on how to use them. The framework enables the modelling of both the structural and dynamic characteristics of business processes. We illustrate its applicability by modelling a case from service industry. Moreover, the architectural framework supports abstraction and refinement techniques. The use of these techniques for a BPR trajectory are discussed

BIF : a behavioral intermediate format for high level synthesis

This report describes a new intermediate format for behavioral synthesis systems, based on annotated state tables. It supports user control of the synthesis process by allowing specification of partial design structures, user-bindings and user modification of compiled designs. It is a simple and uniform representation that can be used as an intermediate exchange format for various behavioral synthesis tools. The format captures synchronous and asynchronous behavior, and serves as a good interface to the user by linking behavior and structure at each level of abstraction in the behavioral synthesis process

Structured modeling for VHDL synthesis

This report will describe a proposed modeling style for the use of the VHSIC Hardware Description Language (VHDL) in design synthesis. We will describe the operations and underlying assumptions of four design models currently understood and used in practice by designers: combinational logic, functional descriptions (involving clocked components such as counters), register transfer (data path) descriptions, and behavioral (instruction set or processor) designs. We will illustrate the various uses of the VHDL description styles (structural, dataflow and behavioral) to represent characteristics of each of these design models. Emphasis is placed on how VHDL constructs should be used in order to synthesize optimal designs

EXEL : a language for interactive behavioral synthesis

This paper describes a new input language for behavioral synthesis called EXEL. EXEL is a powerful language that permits the user to specify partially designed structures in the language. It employs a mixed graphic/textual user interface to enhance user interactivity. EXEL's design model is comprehensive: it permits specification of synchronous and asynchronous behavior, and allows specification of general timing constraints. A flexible type construct permits the user to define operators and components to be used in the description. Finally, it simplifies compilation by using a small set of constructs for specifying timing and asynchronouos behavior. The compiler for EXEL runs on SUN-3 workstations and is written in C and SUNVIEW

Revisiting Ruddick: Feminism, pacifism and non-violence

This article explores feminist contentions over pacifism and non-violence in the contextof the Greenham Common Peace Camp in the 1980s and later developments offeminist Just War Theory. We argue that Sara Ruddick’s work puts feminist pacifism, its radical feminist critics and feminist just war theory equally into question. Although Ruddick does not resolve the contestations within feminism over peace, violence and the questions of war, she offers a productive way of holding the tension between them. In our judgment, her work is helpful not only for developing a feminist political response to the threats and temptations of violent strategies but also for thinking through the question of the relation between violence and politics as such