Coupling Control Variates for Markov Chain Monte Carlo

We show that Markov couplings can be used to improve the accuracy of Markov chain Monte Carlo calculations in some situations where the steady-state probability distribution is not explicitly known. The technique generalizes the notion of control variates from classical Monte Carlo integration. We illustrate it using two models of nonequilibrium transport

Surface ruptures on cross-faults in the 24 November 1987 Superstition Hills, California, earthquake sequence

Left-lateral slip occurred on individual surface breaks along northeast-trending faults associated with the 24 November 1987 earthquake sequence in the Superstition Hills, Imperial Valley, California. This sequence included the M_s = 6.2 event on a left-lateral, northeast-trending “cross-fault” between the Superstition Hills fault (SHF) and Brawley seismic zone, which was spatially associated with the left-lateral surface breaks. Six distinct subparallel cross-faults broke at the surface, with rupture lengths ranging from about Formula to 10 km and maximum displacements ranging from 30 to 130 mm. About half a day after the M_s = 6.2 event, an M_s = 6.6 earthquake nucleated near the intersection of the cross-faults with the SHF, and rupture propagated southeast along the SHF. Whereas right-lateral slip on the SHF occurred dominantly on a single trace in a narrow zone, the cross-fault surface slip was distributed over several stands across a 10-km-wide zone. Also, whereas afterslip accounted for a large proportion of total slip on the SHF, there is no evidence for afterslip on the cross-faults. We present documentation of these surface ruptures. A simple mechanical model of faulting illustrates how the foreshock sequence may have triggered the main rupture. Displacement on other cross-faults could trigger an event on the southern San Andreas fault by a similar mechanism in the future

Reason-Resilience and security of geospatial data for critical infrastructures

Peer reviewe

Strong Spherical Asymptotics for Rotor-Router Aggregation and the Divisible Sandpile

The rotor-router model is a deterministic analogue of random walk. It can be used to define a deterministic growth model analogous to internal DLA. We prove that the asymptotic shape of this model is a Euclidean ball, in a sense which is stronger than our earlier work. For the shape consisting of $n=\omega_d r^d$ sites, where $\omega_d$ is the volume of the unit ball in $\R^d$, we show that the inradius of the set of occupied sites is at least $r-O(\log r)$, while the outradius is at most $r+O(r^\alpha)$ for any $\alpha > 1-1/d$. For a related model, the divisible sandpile, we show that the domain of occupied sites is a Euclidean ball with error in the radius a constant independent of the total mass. For the classical abelian sandpile model in two dimensions, with $n=\pi r^2$ particles, we show that the inradius is at least $r/\sqrt{3}$, and the outradius is at most $(r+o(r))/\sqrt{2}$. This improves on bounds of Le Borgne and Rossin. Similar bounds apply in higher dimensions.Comment: [v3] Added Theorem 4.1, which generalizes Theorem 1.4 for the abelian sandpile. [v4] Added references and improved exposition in sections 2 and 4. [v5] Final version, to appear in Potential Analysi

Evidence for prehistoric earthquakes on the Superstition Hills fault from offset geomorphic features

Offset geomorphic features along the Superstition Hills fault show evidence for at least one slip event prior to the 1987 surface rupture, and possibly as many as four to five earlier prehistoric earthquakes. We documented several geomorphic features that appeared offset by multiple events by making detailed topographic maps. Offset features were abundant along reaches of the fault with high topographic relief and large displacement. Slip distribution for the penultimate event, as recorded by offset rills, streams, and shrub-coppice dunes, is very similar to the slip distribution from the 1987 earthquake through April 1988. This similarity may prove to be fortuitous if afterslip from the 1987 event continues to increase the total slip for this earthquake. But if afterslip associated with the 1987 event ceases in the near future, then the past two earthquakes were nearly identical in slip, and the Superstition Hills fault may be expected to produce characteristic earthquakes of roughly magnitude 6½

Transcriptional signatures of Itk-deficient CD3+, CD4+ and CD8+ T-cells

<p>Abstract</p> <p>Background</p> <p>The Tec-family kinase Itk plays an important role during T-cell activation and function, and controls also conventional versus innate-like T-cell development. We have characterized the transcriptome of Itk-deficient CD3⁺T-cells, including CD4⁺and CD8⁺subsets, using Affymetrix microarrays.</p> <p>Results</p> <p>The largest difference between Itk^-/-and Wt CD3⁺T-cells was found in unstimulated cells, e.g. for killer cell lectin-like receptors. Compared to anti-CD3-stimulation, anti-CD3/CD28 significantly decreased the number of transcripts suggesting that the CD28 co-stimulatory pathway is mainly independent of Itk. The signatures of CD4⁺and CD8⁺T-cell subsets identified a greater differential expression than in total CD3⁺cells. Cyclosporin A (CsA)-treatment had a stronger effect on transcriptional regulation than Itk-deficiency, suggesting that only a fraction of TCR-mediated calcineurin/NFAT-activation is dependent on Itk. Bioinformatic analysis of NFAT-sites of the group of transcripts similarly regulated by Itk-deficiency and CsA-treatment, followed by chromatin-immunoprecipitation, revealed NFATc1-binding to the <it>Bub1</it>, <it>IL7R, Ctla2a</it>, <it>Ctla2b</it>, and <it>Schlafen1 </it>genes. Finally, to identify transcripts that are regulated by Tec-family kinases in general, we compared the expression profile of Itk-deficient T-cells with that of Btk-deficient B-cells and a common set of transcripts was found.</p> <p>Conclusion</p> <p>Taken together, our study provides a general overview about the global transcriptional changes in the absence of Itk.</p

Some Findings Concerning Requirements in Agile Methodologies

gile methods have appeared as an attractive alternative to conventional methodologies. These methods try to reduce the time to market and, indirectly, the cost of the product through flexible development and deep customer involvement. The processes related to requirements have been extensively studied in literature, in most cases in the frame of conventional methods. However, conclusions of conventional methodologies could not be necessarily valid for Agile; in some issues, conventional and Agile processes are radically different. As recent surveys report, inadequate project requirements is one of the most conflictive issues in agile approaches and better understanding about this is needed. This paper describes some findings concerning requirements activities in a project developed under an agile methodology. The project intended to evolve an existing product and, therefore, some background information was available. The major difficulties encountered were related to non-functional needs and management of requirements dependencies

Feasibility, reliability and validity of the health-related quality of life instrument Child Health Utility 9D (CHU9D) among school-aged children and adolescents in Sweden

Background This study was conducted in a general population of schoolchildren in Sweden, with the aim to assess the psychometric properties of a generic preference-based health related quality of life (HRQoL) instrument, the Swedish Child Health Utility 9D (CHU9D), among schoolchildren aged 7–15 years, and in subgroups aged 7–9, 10–12 and 13–15 years. Methods In total, 486 school aged children, aged 7–15 years, completed a questionnaire including the CHU9D, the Pediatric quality of life inventory 4.0 (PedsQL), KIDSCREEN-10, questions on general health, long-term illness, and sociodemographic characteristics. Psychometric testing was undertaken of feasibility, internal consistency reliability, test–retest reliability, construct validity, factorial validity, concurrent validity, convergent validity and divergent validity. Results The CHU9D evidenced very few missing values, minimal ceiling, and no floor effects. The instrument achieved satisfactory internal consistency (Cronbach’s Alfa > 0.7) and strong test–retest reliability (r > 0.6). Confirmatory factor analyses supported the proposed one-factor structure of the CHU9D. For child algorithm, RMSEA = 0.05, CFI = 0.95, TLI = 0.94, and SRMR = 0.04. For adult algorithm RMSEA = 0.04, CFI = 0.96, TLI = 0.95, and SRMR = 0.04. The CHU9D utility value correlated moderately or strongly with KIDSCREEN-10 and PedsQL total scores (r > 0.5–0.7). The CHU9D discriminated as anticipated on health and on three of five sociodemographic characteristics (sex, age, and custody arrangement, but not socioeconomic status and ethnic origin). Conclusions This study provides evidence that the Swedish CHU9D is a feasible, reliable and valid measure of preference-based HRQoL in children. The study furthermore suggests that the CHU9D is appropriate for use among children 7–15 years of age in the general population, as well as among subgroups aged 7– 9, 10–12 and 13–15 years