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

Parallel Recursive State Compression for Free

This paper focuses on reducing memory usage in enumerative model checking, while maintaining the multi-core scalability obtained in earlier work. We present a tree-based multi-core compression method, which works by leveraging sharing among sub-vectors of state vectors. An algorithmic analysis of both worst-case and optimal compression ratios shows the potential to compress even large states to a small constant on average (8 bytes). Our experiments demonstrate that this holds up in practice: the median compression ratio of 279 measured experiments is within 17% of the optimum for tree compression, and five times better than the median compression ratio of SPIN's COLLAPSE compression. Our algorithms are implemented in the LTSmin tool, and our experiments show that for model checking, multi-core tree compression pays its own way: it comes virtually without overhead compared to the fastest hash table-based methods.Comment: 19 page

Variations on Multi-Core Nested Depth-First Search

Recently, two new parallel algorithms for on-the-fly model checking of LTL properties were presented at the same conference: Automated Technology for Verification and Analysis, 2011. Both approaches extend Swarmed NDFS, which runs several sequential NDFS instances in parallel. While parallel random search already speeds up detection of bugs, the workers must share some global information in order to speed up full verification of correct models. The two algorithms differ considerably in the global information shared between workers, and in the way they synchronize. Here, we provide a thorough experimental comparison between the two algorithms, by measuring the runtime of their implementations on a multi-core machine. Both algorithms were implemented in the same framework of the model checker LTSmin, using similar optimizations, and have been subjected to the full BEEM model database. Because both algorithms have complementary advantages, we constructed an algorithm that combines both ideas. This combination clearly has an improved speedup. We also compare the results with the alternative parallel algorithm for accepting cycle detection OWCTY-MAP. Finally, we study a simple statistical model for input models that do contain accepting cycles. The goal is to distinguish the speedup due to parallel random search from the speedup that can be attributed to clever work sharing schemes.Comment: In Proceedings PDMC 2011, arXiv:1111.006

Complete genome sequence and taxonomic position of anguillid herpesvirus 1

Eel herpesvirus or anguillid herpesvirus 1 (AngHV1) frequently causes disease in freshwater eels. The complete genome sequence of AngHV1 and its taxonomic position within the family Alloherpesviridae were determined. Shotgun sequencing revealed a 249 kbp genome including an 11 kbp terminal direct repeat that contains 7 of the 136 predicted protein-coding open reading frames. Twelve of these genes are conserved among other members of the family Alloherpesviridae and another 28 genes have clear homologues in cyprinid herpesvirus 3. Phylogenetic analyses based on amino acid sequences of five conserved genes, including the ATPase subunit of the terminase, confirm the position of AngHV1 within the family Alloherpesviridae, where it is most closely related to the cyprinid herpesviruses. Our analyses support a recent proposal to subdivide the family Alloherpesviridae into two sister clades, one containing AngHV1 and the cyprinid herpesviruses and the other containing Ictalurid herpesvirus 1 and the ranid herpesviruses

Is the perceived impact of disciplinary procedures on medical doctors’ professional practice associated with working in an open culture and feeling supported?:A questionnaire among medical doctors in the Netherlands who have been disciplined

Introduction Disciplinary procedures can have a negative impact on the professional functioning of medical doctors. In this questionnaire study, doctors’ experience with open culture and support during a disciplinary procedure is studied to determine whether open culture and support are associated with perceived changes in the professional practice of doctors. Methods All doctors who received a warning or a reprimand from the Dutch Medical Disciplinary Board between July 2012 and August 2016 were invited to fill in a 60-item questionnaire concerning open culture, perceived support during the disciplinary procedure and the impact of the procedure on professional functioning as reported by doctors themselves. The response rate was 43% (n=294). Results A majority of doctors perceive their work environment as a safe environment in which to talk about and report incidents (71.2% agreed). Respondents felt supported by a lawyer or legal representative and colleagues (92.8% and 89.2%, respectively). The disciplinary procedure had effects on professional practice. Legal support and support from a professional confidant and a professional association were associated with fewer perceived changes to professional practice. Conclusion Our study shows that doctors who had been disciplined perceive their working environment as open. Doctors felt supported by lawyers and/or legal representatives and colleagues. Legal support was associated with less of a perceived impact on doctors’ professional practice

An Improvement of the Piggyback Algorithm for Parallel Model Checking

This paper extends the piggyback algorithm to enlarge the set of liveness properties it can verify. Its extension is motivated by an attempt to express in logic the counterexamples it can detect and relate them to bounded liveness. The original algorithm is based on parallel breadth-first search and piggybacking of accepting states that are deleted after counting a fixed number of transitions. The main improvement is obtained by renewing the counter of transitions when the same accepting states are visited in the negated property automaton. In addition, we describe piggybacking of multiple states in either sets (exact) or Bloom filters (lossy but conservative), and use of local searches that attempt to connect cycles fragmented among processing cores. Finally it is proved that accepting cycle detection is in NC in the size of the product automaton's entire state space, including unreachable states

Development and validation of a two-step real-time RT-PCR for the detection of eel virus European X in European eel, Anguilla anguilla

AbstractEel virus European X (EVEX) is one of the most common pathogenic viruses in farmed and wild European eel (Anguilla anguilla) in the Netherlands. The virus causes a hemorrhagic disease resulting in increased mortality rates. Cell culture and antibody-based detection of EVEX are laborious and time consuming. Therefore, a two-step real-time reverse transcriptase (RT-)PCR assay was developed for rapid detection of EVEX. Primers and probe for the assay were designed based on a sequence of the RNA polymerase or L gene of EVEX. The real-time RT-PCR assay was validated both for use with SYBR Green chemistry and for use with a TaqMan probe. The assay is sensitive, specific, repeatable, efficient and has a high r2-value. The real-time RT-PCR assay was further evaluated by testing field samples of European eels from the Netherlands, which were positive or negative for EVEX by virus isolation followed by an indirect fluorescent antibody test. The real-time RT-PCR assay allows rapid, sensitive and specific laboratory detection of EVEX in RNA extracts from 10% eel organ suspensions and cell cultures with cytopathic effects, and is a valuable contribution to the diagnosis of viral diseases of eel