348 research outputs found

    An adaptive stabilized finite element method for the generalized Stokes problem

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    In this work we present an adaptive strategy (based on an a posteriori error estimator) for a stabilized finite element method for the Stokes problem, with and without a reaction term. The hierarchical type estimator is based on the solution of local problems posed on appropriate finite dimensional spaces of bubble-like functions. An equivalence result between the norm of the finite element error and the estimator is given, where the dependence of the constants on the physics of the problem is explicited. Several numerical results confirming both the theoretical results and the good performance of the estimator are given

    Linking the High-Resolution Architecture of Modern and Ancient Wave-Dominated Deltas : Processes, Products and Forcing Factors

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    Many thoughts and concepts used in this paper were initially developed as a result of work conducted with funding provided to the WAVE Consortium at the Australian School of Petroleum, University of Adelaide (RBA, BKV and JB). The consortium sponsors (Apache, BAPETCO, BHPBP, BG, BP, Chevron, ConocoPhillips, Nexen, OMV, Shell, Statoil, Todd Energy, and Woodside Energy) are thus thanked for making this work possible. We are indebted to journal reviewers Cornel Olariu and Howard Feldman, and to Associate Editor Janok Bhattacharya for numerous comments and suggestions that improved the clarity of the manuscript.Peer reviewedPostprin

    Adjuvant use of laser in eyes with macular retinoblastoma treated with primary intravenous chemotherapy

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    Background Adjuvant use of laser with systemic chemotherapy for treatment of retinoblastoma may reduce recurrence rates while also causing local side effects. Information is lacking on the effect of laser on visual outcomes. Methods A retrospective review of two retinoblastoma centres in the United Kingdom was conducted. Patients were included if there was a macular tumour in at least one eye. Eyes that received chemotherapy alone were compared with eyes that received chemotherapy plus adjuvant laser. Results A total of 76 patients and 91 eyes were included in the study. Systemic chemotherapy alone was used in 71 eyes while chemotherapy plus laser was used in 20 eyes. Demographic characteristics of both groups were similar. Macular relapse rates were similar between groups: 22/71 (31%) eyes in chemotherapy group and 9/20 (45%) eyes in laser group (p=0.29). There was no increase in vitreous relapses in the laser group (2/20 eyes), compared with the chemotherapy group 10/71 eyes (p=0.99). Survival analysis demonstrated similar time to first relapse between groups. Final visual acuity was equal between groups with 6/15 or better present in 31.1% of eyes in the chemotherapy group and 37.5% of eyes in the laser group (p=0.76). Presence of tumour at the fovea was predictive of final visual acuity, regardless of treatment group. Conclusion Adjuvant laser in the treatment of retinoblastoma is safe and does not lead to increased rate of vitreous recurrence. Final visual acuity is determined by the presence of tumour at the fovea and not the use of laser

    The majority of autosomal recessive nanophthalmos and posterior microphthalmia can be attributed to biallelic sequence and structural variants in MFRP and PRSS56

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    This study aimed to genetically and clinically characterize a unique cohort of 25 individuals from 21 unrelated families with autosomal recessive nanophthalmos (NNO) and posterior microphthalmia (MCOP) from diferent ethnicities. An ophthalmological assessment in all families was followed by targeted MFRP and PRSS56 testing in 20 families and whole-genome sequencing in one family. Three families underwent homozygosity mapping using SNP arrays. Eight distinct MFRP mutations were found in 10/21 families (47.6%), fve of which are novel including a deletion spanning the 5′ untranslated region and the frst coding part of exon 1. Most cases harbored homozygous mutations (8/10), while a compound heterozygous and a monoallelic genotype were identifed in the remaining ones (2/10). Six distinct PRSS56 mutations were found in 9/21 (42.9%) families, three of which are novel. Similarly, homozygous mutations were found in all but one, leaving 2/21 families (9.5%) without a molecular diagnosis. Clinically, all patients had reduced visual acuity, hyperopia, short axial length and crowded optic discs. Retinitis pigmentosa was observed in 5/10 (50%) of the MFRP group, papillomacular folds in 12/19 (63.2%) of MCOP and in 3/6 (50%) of NNO cases. A considerable phenotypic variability was observed, with no clear genotype-phenotype correlations. Overall, our study represents the largest NNO and MCOP cohort reported to date and provides a genetic diagnosis in 19/21 families (90.5%), including the frst MFRP genomic rearrangement, ofering opportunities for gene-based therapies in MFRP-associated disease. Finally, our study underscores the importance of sequence and copy number analysis of the MFRP and PRSS56 genes in MCOP and NNO

    Development and Validation of the Behavioral Tendencies Questionnaire

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    At a fundamental level, taxonomy of behavior and behavioral tendencies can be described in terms of approach, avoid, or equivocate (i.e., neither approach nor avoid). While there are numerous theories of personality, temperament, and character, few seem to take advantage of parsimonious taxonomy. The present study sought to implement this taxonomy by creating a questionnaire based on a categorization of behavioral temperaments/tendencies first identified in Buddhist accounts over fifteen hundred years ago. Items were developed using historical and contemporary texts of the behavioral temperaments, described as “Greedy/Faithful”, “Aversive/Discerning”, and “Deluded/Speculative”. To both maintain this categorical typology and benefit from the advantageous properties of forced-choice response format (e.g., reduction of response biases), binary pairwise preferences for items were modeled using Latent Class Analysis (LCA). One sample (n1 = 394) was used to estimate the item parameters, and the second sample (n2 = 504) was used to classify the participants using the established parameters and cross-validate the classification against multiple other measures. The cross-validated measure exhibited good nomothetic span (construct-consistent relationships with related measures) that seemed to corroborate the ideas present in the original Buddhist source documents. The final 13-block questionnaire created from the best performing items (the Behavioral Tendencies Questionnaire or BTQ) is a psychometrically valid questionnaire that is historically consistent, based in behavioral tendencies, and promises practical and clinical utility particularly in settings that teach and study meditation practices such as Mindfulness Based Stress Reduction (MBSR)

    Model validation for a noninvasive arterial stenosis detection problem

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    Copyright @ 2013 American Institute of Mathematical SciencesA current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use both one-dimensional pressure and shear wave experimental data from novel acoustic phantoms to validate corresponding viscoelastic mathematical models, which were developed in a concept paper [8] and refined herein. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.The National Institute of Allergy and Infectious Diseases, the Air Force Office of Scientific Research, the Deopartment of Education and the Engineering and Physical Sciences Research Council (EPSRC)

    Estimating the Worldwide Extent of Illegal Fishing

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    Illegal and unreported fishing contributes to overexploitation of fish stocks and is a hindrance to the recovery of fish populations and ecosystems. This study is the first to undertake a world-wide analysis of illegal and unreported fishing. Reviewing the situation in 54 countries and on the high seas, we estimate that lower and upper estimates of the total value of current illegal and unreported fishing losses worldwide are between 10bnand10 bn and 23.5 bn annually, representing between 11 and 26 million tonnes. Our data are of sufficient resolution to detect regional differences in the level and trend of illegal fishing over the last 20 years, and we can report a significant correlation between governance and the level of illegal fishing. Developing countries are most at risk from illegal fishing, with total estimated catches in West Africa being 40% higher than reported catches. Such levels of exploitation severely hamper the sustainable management of marine ecosystems. Although there have been some successes in reducing the level of illegal fishing in some areas, these developments are relatively recent and follow growing international focus on the problem. This paper provides the baseline against which successful action to curb illegal fishing can be judged
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