Solvable Model of Spiral Wave Chimeras

Spiral waves are ubiquitous in two-dimensional systems of chemical or biological oscillators coupled locally by diffusion. At the center of such spirals is a phase singularity, a topological defect where the oscillator amplitude drops to zero. But if the coupling is nonlocal, a new kind of spiral can occur, with a circular core consisting of desynchronized oscillators running at full amplitude. Here we provide the first analytical description of such a spiral wave chimera, and use perturbation theory to calculate its rotation speed and the size of its incoherent core.Comment: 4 pages, 4 figures; added reference, figure, further numerical test

ALTERNATIVE ITALIAN AGRICULTURAL COOPERATIVE SYSTEMS IN THE CHANGING EU FOOD SYSTEM

The European food system is undergoing significant change driven both by global competitive forces and local conditions. Market globalization and technological innovation are interacting with the reform of EU's agricultural policies (CAP) and a renewed interest by the European society in the social and environmental functions of agriculture. These factors have created a new and challenging economic environment both for farmers and the food industry across Europe (Tarditi, 1997).Agribusiness,

Mineralisation of 2,4-dichlorophenoxyacetic acid by acoustic or hydrodynamic cavitation in conjunction with the advanced Fenton process

The mineralisation of 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence of zero-valent iron and hydrogen peroxide (the Advanced Fenton process – AFP) whilst being subjected to acoustic or hydrodynamic cavitation is reported. If the reaction is merely stirred then there is 57% removal of TOC whilst on irradiation the figure is 64% although the latter reaction is more rapid. Use of ultrasound alone results in only 11% TOC removal in 60 min of treatment time. Addition of iron powder marginally enhances the extent of degradation but an appreciable increase is observed in the presence of hydrogen peroxide which acts as a source for hydroxyl radicals by Fenton chemistry as well as by dissociation in the presence of ultrasound. The use of hydrodynamic cavitation in conjunction with the advanced Fenton process has also been found to be a useful tool for continuous remediation of water contaminated with 2,4-D. After 20 minutes of treatment the residual TOC is reduced to 30% and this probably represents the remaining highly recalcitrant small organic molecules

MEMBERS' FINANCIAL EVALUATION AND COOPERATIVES' DECISION PROCESSES

The paper presents an analysis of cooperative investment decision based on the coalition theoretical framework (Staatz 1983, 1987, 1989). According to this framework, cooperatives can be considered as coalitions of groups with different interests. The behavior of any cooperative is determined by the interaction of its many groups (different types of farmers, managers, lenders, input suppliers, buyers, etc.) with different objectives. The group that can impose its will on the coalition will determine the cooperative's strategy. The other parties may accept this leadership, leave the cooperative or try to use their bargaining power to modify the final outcome. The paper discusses the impact of group bargaining on cooperatives' decision process. In particular, the paper addresses the issues related to the consequences of members' heterogeneity on cooperative efficiency. The proposed model utilizes tools from financial theory already successfully applied in the literature (Peterson 1992, Hendrikse 1998) providing a more detailed insight into the determinants of the cooperative decision process. The paper shows that cooperatives evaluate investments differently from IOFs due to the unique characteristics of their patrons compared to other types of investors.Agribusiness, Agricultural Finance,

Implementation of a three-qubit quantum error correction code in a cavity-QED setup

The correction of errors is of fundamental importance for the development of contemporary computing devices and of robust communication protocols. In this paper we propose a scheme for the implementation of the three-qubit quantum repetition code, exploiting the interaction of Rydberg atoms with the quantized mode of a microwave cavity field. Quantum information is encoded within two circular Rydberg states of the atoms and encoding and decoding process are realized within two separate microwave cavities. We show that errors due to phase noise fluctuations could be efficiently corrected using a state-of-the-art apparatus.Comment: 9 pages, 5 figures. This is v2. Some misprints corrected, conclusions section extended, refs added. Accepted for publication on PR

Ruling out higher-order interference from purity principles

As first noted by Rafael Sorkin, there is a limit to quantum interference. The interference pattern formed in a multi-slit experiment is a function of the interference patterns formed between pairs of slits, there are no genuinely new features resulting from considering three slits instead of two. Sorkin has introduced a hierarchy of mathematically conceivable higher-order interference behaviours, where classical theory lies at the first level of this hierarchy and quantum theory theory at the second. Informally, the order in this hierarchy corresponds to the number of slits on which the interference pattern has an irreducible dependence. Many authors have wondered why quantum interference is limited to the second level of this hierarchy. Does the existence of higher-order interference violate some natural physical principle that we believe should be fundamental? In the current work we show that such principles can be found which limit interference behaviour to second-order, or "quantum-like", interference, but that do not restrict us to the entire quantum formalism. We work within the operational framework of generalised probabilistic theories, and prove that any theory satisfying Causality, Purity Preservation, Pure Sharpness, and Purification---four principles that formalise the fundamental character of purity in nature---exhibits at most second-order interference. Hence these theories are, at least conceptually, very "close" to quantum theory. Along the way we show that systems in such theories correspond to Euclidean Jordan algebras. Hence, they are self-dual and, moreover, multi-slit experiments in such theories are described by pure projectors.Comment: 18+8 pages. Comments welcome. v2: Minor correction to Lemma 5.1, main results are unchange

On applying the set covering model to reseeding

The Functional BIST approach is a rather new BIST technique based on exploiting embedded system functionality to generate deterministic test patterns during BIST. The approach takes advantages of two well-known testing techniques, the arithmetic BIST approach and the reseeding method. The main contribution of the present paper consists in formulating the problem of an optimal reseeding computation as an instance of the set covering problem. The proposed approach guarantees high flexibility, is applicable to different functional modules, and, in general, provides a more efficient test set encoding then previous techniques. In addition, the approach shorts the computation time and allows to better exploiting the tradeoff between area overhead and global test length as well as to deal with larger circuits

Functional Testing Approaches for "BIFST-able" tlm_fifo

Evolution of Electronic System Level design methodologies, allows a wider use of Transaction-Level Modeling (TLM). TLM is a high-level approach to modeling digital systems that emphasizes on separating communications among modules from the details of functional units. This paper explores different functional testing approaches for the implementation of Built-in Functional Self Test facilities in the TLM primitive channel tlm_fifo. In particular, it focuses on three different test approaches based on a finite state machine model of tlm_fifo, functional fault models, and march tests respectivel