A Markovian influence graph formed from utility line outage data to mitigate large cascades.

We use observed transmission line outage data to make a Markovian influence graph that describes the probabili- ties of transitions between generations of cascading line outages. Each generation of a cascade consists of a single line outage or multiple line outages. The new influence graph defines a Markov chain and generalizes previous influence graphs by including multiple line outages as Markov chain states.

Critical behavior of power transmission network complex dynamics in the OPA model.

Many complex infrastructure systems, such as electric power transmission grids, display characteristics of a critical or near critical behavior with a risk of large cascading failures. Understanding this risk and its relation to the system state as it evolves could allow for a more realistic risk assessment and even for mitigation measures. We use the OPA model of cascading blackouts and grid evolution to describe and quantify regimes of criticality of the power grid.

The interplay of network structure and dispatch solutions in power grid cascading failures.

For a given minimum cost of the electricity dispatch, multiple equivalent dispatch solutions may exist. We explore the sensitivity of networks to these dispatch solutions and their impact on the vulnerability of the network to cascading failure blackouts. It is shown that, depending on the heterogeneity of the network structure, the blackout statistics can be sensitive to the dispatch solution chosen, with the clustering coefficient of the network being a key ingredient.

Does size matter?

Failures of the complex infrastructures society depends on having enormous human and economic cost that poses the question: Are there ways to optimize these systems to reduce the risks of failure? A dynamic model of one such system, the power transmission grid, is used to investigate the risk from failure as a function of the system size. It is found that there appears to be optimal sizes for such networks where the risk of failure is balanced by the benefit given by the size.

A systematic review of patient tracking systems for use in the pediatric emergency department.

Background: Patient safety is of great importance in the pediatric emergency department (PED). The combination of acutely and critically ill patients and high patient volumes creates a need for systems to support physicians in making accurate and timely diagnoses. Electronic patient tracking systems can potentially improve PED safety by reducing overcrowding and enhancing security.

Testing branching process estimators of cascading failure with data from a simulation of transmission line outages.

We suggest a statistical estimator to quantify the propagation of cascading transmission line failures in large blackouts of electric power systems. We use a Galton-Watson branching process model of cascading failure and the standard Harris estimator of the mean propagation modified to work when the process saturates at a maximum number of components. If the mean number of initial failures and the mean propagation are estimated, then the branching process model predicts the distribution of the total number of failures.

The impact of risk-averse operation on the likelihood of extreme events in a simple model of infrastructure.

A simple dynamic model of agent operation of an infrastructure system is presented. This system evolves over a long time scale by a daily increase in consumer demand that raises the overall load on the system and an engineering response to failures that involves upgrading of the components. The system is controlled by adjusting the upgrading rate of the components and the replacement time of the components.

Synthesis of a labeled RGD-lipid, its incorporation into liposomal nanoparticles, and their trafficking in cultured endothelial cells.

The use of targeting ligands to enhance the delivery of liposomal nanoparticles (LNs) has moved slowly toward clinical application. This relative lack of clinical progression is further complicated by the existence of conflicting in vivo results in the literature. In this work, we describe new formulations of LNs that are targeted with an arginine-glycine-aspartic acid-containing peptide, cRGDfK, conjugated to the lipid distearoyl phosphatidylethanolamine (DSPE).

Complex systems analysis of series of blackouts: cascading failure, critical points, and self-organization.

We give an overview of a complex systems approach to large blackouts of electric power transmission systems caused by cascading failure. Instead of looking at the details of particular blackouts, we study the statistics and dynamics of series of blackouts with approximate global models. Blackout data from several countries suggest that the frequency of large blackouts is governed by a power law.

Generation and growth rates of nonlinear distortions in a traveling wave tube.

The structure of a steady state multifrequency model of a traveling wave tube amplifier is exploited to describe the generation of intermodulation frequencies and calculate their growth rates. The model describes the evolution of Fourier coefficients of circuit and electron beam quantities and has the form of differential equations with quadratic nonlinearities. Intermodulation frequencies are sequentially generated by the quadratic nonlinearities in a series solution of the differential equations.