A comparison of RESTART implementations

The RESTART method is a widely applicable simulation technique for the estimation of rare event probabilities. The method is based on the idea to restart the simulation in certain system states, in order to generate more occurrences of the rare event. One of the main questions for any RESTART implementation is how and when to restart the simulation, in order to achieve the most accurate results for a fixed simulation effort. We investigate and compare, both theoretically and empirically, different implementations of the RESTART method. We find that the original RESTART implementation, in which each path is split into a fixed number of copies, may not be the most efficient one. It is generally better to fix the total simulation effort for each stage of the simulation. Furthermore, given this effort, the best strategy is to restart an equal number of times from each state, rather than to restart each time from a randomly chosen stat

Parallel Cross-Entropy Optimization

The cross-entropy (CE) method is a modern and effective optimization method well suited to parallel implementations. There is a vast array of problems today, some of which are highly complex and can take weeks or even longer to solve using current optimization techniques. This paper presents a general method for designing parallel CE algorithms for multiple instruction multiple data (MIVID) distributed memory machines using the message passing interface (MPI) library routines. We provide examples of its performance for two well-known test-cases: the (discrete) Max-Cut problem and (continuous) Rosenbrock problem. Speedup factors and a comparison to sequential CE methods are reported

Viable porcine arteriviruses with deletions proximal to the 3 ' end of the genome

In order to obtain attenuated live vaccine candidates of porcine reproductive and respiratory syndrome virus (PRRSV), a series of deletions was introduced at the 3′ end of the viral genome using an infectious cDNA clone of the Lelystad virus isolate. RNA transcripts from the full-length cDNA clones were transfected into BHK-21 cells. The culture supernatant of these cells was subsequently used to infect porcine alveolar macrophages to detect the production of progeny virus. It is shown that C-terminal truncation of the nucleocapsid (N) protein, encoded by ORF7, was tolerated for up to six amino acids without blocking the production of infectious virus. Mutants containing larger deletions produced neither virus nor virus-like particles containing viral RNA. Deletion analysis of the 3′ UTR immediately downstream of ORF7 showed that infectious virus was still produced after removal of seven nucleotides behind the stop codon of ORF7. Deletion of 32 nucleotides in this region abolished RNA replication and, consequently, no infectious virus was formed. Serial passage on porcine alveolar macrophages demonstrated that the viable deletion mutants were genetically stable at the site of mutation. In addition, the deletions did not affect the growth properties of the recombinant viruses in vitro, while their antigenic profiles were similar to that of wild-type virus. Immunoprecipitation experiments with the six-residue N protein-deletion mutant confirmed that the truncated protein was indeed smaller than the wild-type N protein. The deletion mutants produced in this study are interesting candidate vaccines to prevent PRRS disease in pigs

Kernel density estimation via diffusion

We present a new adaptive kernel density estimator based on linear diffusion processes. The proposed estimator builds on existing ideas for adaptive smoothing by incorporating information from a pilot density estimate. In addition, we propose a new plug-in bandwidth selection method that is free from the arbitrary normal reference rules used by existing methods. We present simulation examples in which the proposed approach outperforms existing methods in terms of accuracy and reliability.Comment: Published in at http://dx.doi.org/10.1214/10-AOS799 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Distributional inference

The making of statistical inferences in distributional form is conceptionally complicated because the epistemic 'probabilities' assigned are mixtures of fact and fiction. In this respect they are essentially different from 'physical' or 'frequency-theoretic' probabilities. The distributional form is so attractive and useful, however, that it should be pursued. Our approach is In line with Walds theory of statistical decision functions and with Lehmann's books about hypothesis testing and point estimation: loss functions are defined, risk functions are studied, unbiasedness and equivariance restrictions are made, etc. A central theme is that the loss function should be 'proper'. This fundamental concept has been explored by meteorologists, psychometrists, Bayesian statisticians, and others. The paper should be regarded as an attempt to reconcile various schools of statisticians. By accepting what we regard 88 good and useful in the various approaches we are trying to develop a nondogmatic approach

Spectral properties of the tandem Jackson network, seen as a quasi-birth-and-death process

Quasi-birth-and-death (QBD) processes with infinite ``phase spaces'' can exhibit unusual and interesting behavior. One of the simplest examples of such a process is the two-node tandem Jackson network, with the ``phase'' giving the state of the first queue and the ``level'' giving the state of the second queue. In this paper, we undertake an extensive analysis of the properties of this QBD. In particular, we investigate the spectral properties of Neuts's R-matrix and show that the decay rate of the stationary distribution of the ``level'' process is not always equal to the convergence norm of R. In fact, we show that we can obtain any decay rate from a certain range by controlling only the transition structure at level zero, which is independent of R. We also consider the sequence of tandem queues that is constructed by restricting the waiting room of the first queue to some finite capacity, and then allowing this capacity to increase to infinity. We show that the decay rates for the finite truncations converge to a value, which is not necessarily the decay rate in the infinite waiting room case. Finally, we show that the probability that the process hits level n before level 0 given that it starts in level 1 decays at a rate which is not necessarily the same as the decay rate for the stationary distribution.Comment: Published at http://dx.doi.org/10.1214/105051604000000477 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

The orofacial system in early rheumatoid arthritis and individuals at risk:A window of opportunity for interprofessional collaboration

Rheumatoid arthritis (RA) is an auto-immune disease affecting the synovial joints. The current literature reports several interactions between RA and the orofacial system, such as an increased prevalence of temporomandibular disorders (TMD), reduced saliva production, and increased prevalence of dental plaque and caries. For periodontitis, a chronic inflammatory disease of the tooth-supporting tissues, bidirectional associations are found. Furthermore, it has been suggested that the oral microbiome may play a role in RA onset. Due to the advantages of early intervention, there is an important focus on the timeframe around RA onset in research and clinical practice. However, current knowledge on possible orofacial complications in the preclinical and early stages of RA disease is very limited. Therefore, the main aim of this thesis is to contribute to this knowledge. A protocol for an observational study in early RA patients and individuals at risk of developing RA (chapter 2) and the resulting data on TMD (chapter 3), oral health and oral microbiome (chapter 6), and oral health-related quality of life (chapter 7) are presented. Further, the consequences (chapter 4) and a possible treatment (chapter 5) for TMJ involvement in RA are investigated. In conclusion, the timeframe around RA onset may be considered a window of opportunity for the prevention of future orofacial complications. Screening for TMD and xerostomia in rheumatology care settings is strongly advised, and referral of newly diagnosed RA patients to a dentist – or at least encouragement of regular dental check-ups – seems justified. Accordingly, interprofessional collaboration is essential and thus advised

Social-Emotional Learning & Academic Achievement

This action research study investigated the impact that social-emotional skills had on academic growth during the first 8 weeks of the 2020-2021 school year for a class of first grade students. Academic growth was evaluated by the students math gains measured by the STAR math assessment. The SAEBRS teacher assessment was used to measure the students social-emotional skills, specifically social, emotional, and academic behavior. The data did not indicate statistical significance, however, there is literature that suggests the importance of teaching social-emotional skills to young children to improve their social, emotional, and academic behavior and support their education and life