Signals that make a Difference

Recent work by Brian Skyrms offers a very general way to think about how information flows and evolves in biological networks—from the way monkeys in a troop communicate, to the way cells in a body coordinate their actions. A central feature of his account is a way to formally measure the quantity of information contained in the signals in these networks. In this paper, we argue there is a tension between how Skyrms talks of signaling networks and his formal measure of information. Although Skyrms refers to both how information flows through networks and that signals carry information, we show that his formal measure only captures the latter. We then suggest that to capture the notion of flow in signalling networks, we need to treat them as causal networks. This provides the formal tools to define a measure that does capture flow, and we do so by drawing on recent work defining causal specificity. Finally, we suggest that this new measure is crucial if we wish to explain how evolution creates information. For signals to play a role in explaining their own origins and stability, they can’t just carry information about acts; they must be difference-makers for acts

Basinwide instream flow assessment model to evaluate instream flow needs

Quantification of sufficient or minimum flows needed to sustain the aquatic habitat is necessary for satisfactory resolution of water use conflicts and planning of water allocation strategies. The Instream Flow Group (IFG) of the U.S. Fish and Wildlife Service has developed a methodology to gage the quantity of suitable habitat in a stream. Application of the methodology requires information on the local variations of depth and velocity in a stream reach. Conventional flow models are inadequate for this application, and evaluation of aquatic habitats requires extensive field work. Results obtained in a study reach cannot be applied to other reaches with dissimilar areas. To address the problem of defining the local variation of depths and velocities for regional habitat evaluation, a probabilistic flow model is developed. The probabilistic model incorporates hydraulic geometry relationships to evaluate average flow parameter values without the necessity of field observations. Local variations of depth and velocity values are evaluated from probability distribution models developed from field data collected on the Sangamon and South Fork Sangamon River basins. The flow model simulation for calculating stream habitat suitability with the IFG methodology is illustrated.U.S. Geological SurveyU.S. Department of the InteriorOpe

Index theory of one dimensional quantum walks and cellular automata

If a one-dimensional quantum lattice system is subject to one step of a reversible discrete-time dynamics, it is intuitive that as much "quantum information" as moves into any given block of cells from the left, has to exit that block to the right. For two types of such systems - namely quantum walks and cellular automata - we make this intuition precise by defining an index, a quantity that measures the "net flow of quantum information" through the system. The index supplies a complete characterization of two properties of the discrete dynamics. First, two systems S_1, S_2 can be pieced together, in the sense that there is a system S which locally acts like S_1 in one region and like S_2 in some other region, if and only if S_1 and S_2 have the same index. Second, the index labels connected components of such systems: equality of the index is necessary and sufficient for the existence of a continuous deformation of S_1 into S_2. In the case of quantum walks, the index is integer-valued, whereas for cellular automata, it takes values in the group of positive rationals. In both cases, the map S -> ind S is a group homomorphism if composition of the discrete dynamics is taken as the group law of the quantum systems. Systems with trivial index are precisely those which can be realized by partitioned unitaries, and the prototypes of systems with non-trivial index are shifts.Comment: 38 pages. v2: added examples, terminology clarifie

Locating Overlap Information in Quantum Systems

When discussing the black hole information problem the term ``information flow'' is frequently used in a rather loose fashion. In this article I attempt to make this notion more concrete. I consider a Hilbert space which is constructed as a tensor product of two subspaces (representing for example inside and outside the black hole). I discuss how the system has the capacity to contain information which is in NEITHER of the subspaces. I attempt to quantify the amount of information located in each of the two subspaces, and elsewhere, and analyze the extent to which unitary evolution can correspond to ``information flow''. I define the notion of ``overlap information'' which appears to be well suited to the problem.Comment: 25 pages plain LaTeX, no figures. Imperial/TP/93-94/2

Mutual information and the F-theorem

Mutual information is used as a purely geometrical regularization of entanglement entropy applicable to any QFT. A coefficient in the mutual information between concentric circular entangling surfaces gives a precise universal prescription for the monotonous quantity in the c-theorem for d=3. This is in principle computable using any regularization for the entropy, and in particular is a definition suitable for lattice models. We rederive the proof of the c-theorem for d=3 in terms of mutual information, and check our arguments with holographic entanglement entropy, a free scalar field, and an extensive mutual information model.Comment: 80 pages, 16 figure

Developing A Hydrologic Information System: Towards Promoting Sustainable Standardization

Water quantity and quality monitoring plays a key role towards the development of a sustainable water sector. The required infrastructure needed to monitor and manage surface and groundwater systems are often lacking particularly in developing countries. When available, water quantity and quality data are invariably fragmented, intermittent, not shared, with deficient metadata, and stored in formats that hinder establishing seamless coupling with hydrological models. Most data are saved locally with little attention placed on defining and maintaining metadata on the collection protocols, geographic referencing, measurement accuracy, resolution, detection limits, and data censorship. These limitations present serious challenges in reaching sound water management strategies. To alleviate these shortcomings, a Hydrologic Information System (HIS) based on the ArcHydro data model was developed using the country of Lebanon as a prototype. The HIS centralized available hydrological and water resources information; coupled spatial coverage with respective time series data on flow, water demand, meteorology, and water quality; and standardized metadata. Additionally, the system was structured to support hydrologic modeling and water resources analysis. A loose coupling was also integrated between the system and the Water Evaluation And Planning (WEAP) hydrological model and tested on the Upper Litani River Basin. The framework encompassed the ability to export back model simulation results and incorporate them within the HIS as time series records. The developed HIS system has since been adopted as a data repository for other water related projects in Lebanon and has helped identify key gaps in existing data and set monitoring priorities

Inventory Optimization in Manufacturing Organizations

Inventories totaling 1.7 trillion U.S. dollars represent an opportunity for U.S. manufacturers. This exploratory case study researched supply chain strategies used to manage inventory in manufacturing operations of a U.S. manufacturing company. A mature value chain contained within a single organization using the value chain framework was the basis for this study. Individual interviews conducted with 16 managers responsible for defining and implementing inventory control strategies, and 4 internal users provided primary information for the study. Other sources of information included a value chain map created through the observation of operations, various inventory measurements, and policies and guidelines related to managing inventory levels. An inductive content analysis employing zero-level coding of the interview transcripts identified 4 themes that describe inventory control strategies as economic order quantity, kanban, vendor managed inventory, and process integration. Physical observation of the value chain, review of supporting documents, and analysis of inventory data ensured the trustworthiness of interpreted themes. Findings identified no single inventory control strategy that fit all applications. Findings also revealed that the financial governing bodies\u27 measurements were not the best tools for operational managers\u27 improvement activities related to inventory control. Included are measures providing alternative means to gauge inventory efficiency. With the results of this study, managers may develop effective strategies to optimize inventory and improve material flow. Manufacturing managers improving material flow may promote sustainability of raw materials and business efficiencies through reduced waste, improved environmental conditions, and increased employment opportunities in associated communities

Magnetically actuated tuning method for Gunn oscillators

A tunable microwave generator based on the Gunn effect is disclosed. The generator includes a semiconductor material which exhibits the Gunn effect when current flows between anode and cathode end contacts. The material has a plurality of sides each with a scratch at a different distance from the anode contact. A magnetic field is produced by a magnet placed about the semiconductor field. The Lorentz force produced as a function of the current flow and the magnetic field drive the electrons to the surface of one of the sides to cause nucleation to occur at the scratch. A domain formed thereat travels to the anode contact to provide pulses at a frequency which is related to the distance between the scratch and the anode contact

Topological reversibility and causality in feed-forward networks

Systems whose organization displays causal asymmetry constraints, from evolutionary trees to river basins or transport networks, can be often described in terms of directed paths (causal flows) on a discrete state space. Such a set of paths defines a feed-forward, acyclic network. A key problem associated with these systems involves characterizing their intrinsic degree of path reversibility: given an end node in the graph, what is the uncertainty of recovering the process backwards until the origin? Here we propose a novel concept, \textit{topological reversibility}, which rigorously weigths such uncertainty in path dependency quantified as the minimum amount of information required to successfully revert a causal path. Within the proposed framework we also analytically characterize limit cases for both topologically reversible and maximally entropic structures. The relevance of these measures within the context of evolutionary dynamics is highlighted.Comment: 9 pages, 3 figure