Network Reliability: A Fresh Look at Some Basic Questions

In this paper, the general problem of comparing the performance of two communication networks is examined. The standard approach, using stochastic ordering as a metric, is reviewed, as are the mixed results on the existence of uniformly optimal networks (UONs) which have emerged from this approach. While UONs have been shown to exist for certain classes of networks, it has also been shown that no UON network exists for other classes. Results to date beg the question: Is the problem of identifying a Universally Optimal Network (UON) of a given size dead or alive? We reframe the investigation into UONs in terms of network signatures and the alternative metric of stochastic precedence. While the endeavor has been dead, or at least dormant, for some twenty years, the findings in the present paper suggest that the question above is by no means settled. Specifically, we examine a class of networks of a particular size for which it was shown that no individual network was universally optimal relative to the standard metric (the uniform ordering of reliability polynomials), and we show, using the aforementioned alternative metric, that this class is totally ordered and that a uniformly optimal network exists after all. Optimality with respect to "performance per unit cost" type metrics is also discussed

Numerical simulation of strongly nonlinear and dispersive waves using a Green-Naghdi model

We investigate here the ability of a Green-Naghdi model to reproduce strongly nonlinear and dispersive wave propagation. We test in particular the behavior of the new hybrid finite-volume and finite-difference splitting approach recently developed by the authors and collaborators on the challenging benchmark of waves propagating over a submerged bar. Such a configuration requires a model with very good dispersive properties, because of the high-order harmonics generated by topography-induced nonlinear interactions. We thus depart from the aforementioned work and choose to use a new Green-Naghdi system with improved frequency dispersion characteristics. The absence of dry areas also allows us to improve the treatment of the hyperbolic part of the equations. This leads to very satisfying results for the demanding benchmarks under consideration

A Compact Dication Source for Ba2+^{2+} Tagging and Heavy Metal Ion Sensor Development

We present a tunable metal ion beam that delivers controllable ion currents in the picoamp range for testing of dry-phase ion sensors. Ion beams are formed by sequential atomic evaporation and single or multiple electron impact ionization, followed by acceleration into a sensing region. Controllability of the ionic charge state is achieved through tuning of electrode potentials that influence the retention time in the ionization region. Barium, lead, and cobalt samples have been used to test the system, with ion currents identified and quantified using a quadrupole mass analyzer. Realization of a clean $\mathrm{Ba^{2+}}$ ion beam within a bench-top system represents an important technical advance toward the development and characterization of barium tagging systems for neutrinoless double beta decay searches in xenon gas. This system also provides a testbed for investigation of novel ion sensing methodologies for environmental assay applications, with dication beams of Pb$^{2+}$ and Cd$^{2+}$ also demonstrated for this purpose

Deep-sequencing reveals broad subtype-specific HCV resistance mutations associated with treatment failure

A percentage of hepatitis C virus (HCV)-infected patients fail direct acting antiviral (DAA)-based treatment regimens, often because of drug resistance-associated substitutions (RAS). The aim of this study was to characterize the resistance profile of a large cohort of patients failing DAA-based treatments, and investigate the relationship between HCV subtype and failure, as an aid to optimizing management of these patients. A new, standardized HCV-RAS testing protocol based on deep sequencing was designed and applied to 220 previously subtyped samples from patients failing DAA treatment, collected in 39 Spanish hospitals. The majority had received DAA-based interferon (IFN) a-free regimens; 79% had failed sofosbuvir-containing therapy. Genomic regions encoding the nonstructural protein (NS) 3, NS5A, and NS5B (DAA target regions) were analyzed using subtype-specific primers. Viral subtype distribution was as follows: genotype (G) 1, 62.7%; G3a, 21.4%; G4d, 12.3%; G2, 1.8%; and mixed infections 1.8%. Overall, 88.6% of patients carried at least 1 RAS, and 19% carried RAS at frequencies below 20% in the mutant spectrum. There were no differences in RAS selection between treatments with and without ribavirin. Regardless of the treatment received, each HCV subtype showed specific types of RAS. Of note, no RAS were detected in the target proteins of 18.6% of patients failing treatment, and 30.4% of patients had RAS in proteins that were not targets of the inhibitors they received. HCV patients failing DAA therapy showed a high diversity of RAS. Ribavirin use did not influence the type or number of RAS at failure. The subtype-specific pattern of RAS emergence underscores the importance of accurate HCV subtyping. The frequency of “extra-target” RAS suggests the need for RAS screening in all three DAA target regions

On constrained estimation problems in time-use surveys

In the context of "stylized" time-use surveys, constrained estimation problems are common, a simple illustration being the constraint that the hours reported for a mutually exclusive and exhaustive set of activities in a given day should sum up to 24. An example is developed, using mixtures of multivariate normal models, which demonstrates that model-based inference can lead to estimators that can decisively outperform ad hoc strategies such as "shrinking towards the constraint" that have been recommended in the literature.Stylized time-use survey Linear constraints The bivariate normal distribution Maximum likelihood Bayesian inference

Ab Initio study of 2H nuclear quadrupole coupling constants in deuterated crystalline oxalic acid dehydrated polymorphs

We report calculated 2H nuclear quadrupole coupling constants and asymmetry parameter in deuterated crystalline oxalic acid dihydrated polymorphs within a full-potential linear combination of Gaussian-type orbitals employing both Density Functional Theory and Hartree-Fock approximation. The Becke's hybrid exchange B3 and the Lee, Yang and Parr correlation functionals were employed. Their dependence with basis set, interelectronic correlation, structural changes and crystal field environment are reported. © 2013 Copyright Taylor and Francis Group, LLC

A visual servo control based on geometric algebra

We report calculated 2H nuclear quadrupole coupling constants and asymmetry parameter in deuterated crystalline oxalic acid dihydrated polymorphs within a full-potential linear combination of Gaussian-type orbitals employing both Density Functional Theory and Hartree-Fock approximation. The Becke's hybrid exchange B3 and the Lee, Yang and Parr correlation functionals were employed. Their dependence with basis set, interelectronic correlation, structural changes and crystal field environment are reported. " 2013 Copyright Taylor and Francis Group, LLC.",,,,,,"10.1080/15421406.2013.768500",,,"http://hdl.handle.net/20.500.12104/39167","http://www.scopus.com/inward/record.url?eid=2-s2.0-84877125557&partnerID=40&md5=671de20103d78e6e9f826f1a2acdd584",,,,,,"1",,"Molecular Crystals and Liquid Crystals",,"18