High performance subgraph mining in molecular compounds

Structured data represented in the form of graphs arises in several fields of the science and the growing amount of available data makes distributed graph mining techniques particularly relevant. In this paper, we present a distributed approach to the frequent subgraph mining problem to discover interesting patterns in molecular compounds. The problem is characterized by a highly irregular search tree, whereby no reliable workload prediction is available. We describe the three main aspects of the proposed distributed algorithm, namely a dynamic partitioning of the search space, a distribution process based on a peer-to-peer communication framework, and a novel receiver-initiated, load balancing algorithm. The effectiveness of the distributed method has been evaluated on the well-known National Cancer Institute’s HIV-screening dataset, where the approach attains close-to linear speedup in a network of workstations

Consumer Protection in an Era of Globalization

With expanding global trade, the challenge of protecting consumers from unsafe food, pharmaceuticals, and consumer products has grown increasingly salient, necessitating the development of new policy ideas and analysis. This chapter introduces the book, Import Safety: Regulatory Governance in the Global Economy, a multidisciplinary project analyzing import safety problems and an array of innovative solutions to these problems. The challenge of protecting the public from unsafe imports arises from the sheer volume of global trade as well as the complexity of products being traded and the vast number of inputs each product contains. It is further compounded by the fact that as products move across jurisdictional boundaries regulators face a host of legal, cultural, and practical obstacles. We argue that import safety problems require rethinking domestic regulation, whether through improving the targeting of traditional government inspections, building stronger public-private partnerships, or making changes in products liability standards. International cooperation will also be needed but will be even more challenging. At every step in the supply chain, regulators face questions of what level of safety to aim for, what form of regulatory standards to adopt, and how compliance with such standards should be monitored and enforced – and yet different countries tend to answer these questions differently. This chapter not only raises the key questions regulators and the public confront in tackling a vexing global challenge, but it also previews Import Safety’s analysis of institutional capacity and a range of potential regulatory responses that can harness market actors to drive improvements in product safety

The Role of NMDA Currents in State Transitions of the Nucleus Accumbens Medium Spiny Neuron

The nucleus accumbens (NAcb) integrates information from a wide range of glutamatergic afferent inputs, including the prefrontal cortex, hippocampus and amygdala. One of the glutamatergic receptors, the NMDA channel, has been implicated in the non-linearity of the current–voltage relationship in these cells under certain input conditions. In order to examine the relationship of the different glutamatergic receptors to the membrane response, we modeled the AMPA, GABAA and NMDA receptors in the medium spiny (MSP) cells and their afferent input. The model demonstrates that the NMDA current is capable of sustaining certain membrane states and contributes to the non-linearity of the membrane response to input

Civic Education and Democratic Backsliding in the Wake of Kenya’s Post-2007 Election Violence

This article examines two unexplored questions concerning the impact of civic education programs in emerging democracies: (1) whether such programs have longer-terms effects and (2) whether civic education can be effective under conditions of democratic “backsliding.” We investigate these questions in the context of a large-scale civic education program in Kenya just before the disputed 2007 election that sparked a wave of ethnic clashes and brought the country to the brink of civil war. Analysis of a survey of 1,800 “treatment” and 1,800 “control” individuals shows that the program had significant long-term effects on variables related to civic competence and engagement, with less consistent effects on democratic values. We also find that participants who subsequently were affected by the violence were less likely to adopt negative beliefs about Kenya’s political system, less likely to support the use of ethnic or political violence, and more likely to forgive those responsible for the post-election violence

Bounded Determinization of Timed Automata with Silent Transitions

Deterministic timed automata are strictly less expressive than their non-deterministic counterparts, which are again less expressive than those with silent transitions. As a consequence, timed automata are in general non-determinizable. This is unfortunate since deterministic automata play a major role in model-based testing, observability and implementability. However, by bounding the length of the traces in the automaton, effective determinization becomes possible. We propose a novel procedure for bounded determinization of timed automata. The procedure unfolds the automata to bounded trees, removes all silent transitions and determinizes via disjunction of guards. The proposed algorithms are optimized to the bounded setting and thus are more efficient and can handle a larger class of timed automata than the general algorithms. The approach is implemented in a prototype tool and evaluated on several examples. To our best knowledge, this is the first implementation of this type of procedure for timed automata.Comment: 25 page

Kleene Algebras and Semimodules for Energy Problems

With the purpose of unifying a number of approaches to energy problems found in the literature, we introduce generalized energy automata. These are finite automata whose edges are labeled with energy functions that define how energy levels evolve during transitions. Uncovering a close connection between energy problems and reachability and B\"uchi acceptance for semiring-weighted automata, we show that these generalized energy problems are decidable. We also provide complexity results for important special cases

Quantum and random walks as universal generators of probability distributions

Quantum walks and random walks bear similarities and divergences. One of the most remarkable disparities affects the probability of finding the particle at a given location: typically, almost a flat function in the first case and a bell-shaped one in the second case. Here I show how one can impose any desired stochastic behavior (compatible with the continuity equation for the probability function) on both systems by the appropriate choice of time- and site-dependent coins. This implies, in particular, that one can devise quantum walks that show diffusive spreading without loosing coherence, as well as random walks that exhibit the characteristic fast propagation of a quantum particle driven by a Hadamard coin.Comment: 8 pages, 2 figures; revised and enlarged versio