484 research outputs found

    Positive approximations of the inverse of fractional powers of SPD M-matrices

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    This study is motivated by the recent development in the fractional calculus and its applications. During last few years, several different techniques are proposed to localize the nonlocal fractional diffusion operator. They are based on transformation of the original problem to a local elliptic or pseudoparabolic problem, or to an integral representation of the solution, thus increasing the dimension of the computational domain. More recently, an alternative approach aimed at reducing the computational complexity was developed. The linear algebraic system Aαu=f\cal A^\alpha \bf u=\bf f, 0<α<10< \alpha <1 is considered, where A\cal A is a properly normalized (scalded) symmetric and positive definite matrix obtained from finite element or finite difference approximation of second order elliptic problems in ΩRd\Omega\subset\mathbb{R}^d, d=1,2,3d=1,2,3. The method is based on best uniform rational approximations (BURA) of the function tβαt^{\beta-\alpha} for 0<t10 < t \le 1 and natural β\beta. The maximum principles are among the major qualitative properties of linear elliptic operators/PDEs. In many studies and applications, it is important that such properties are preserved by the selected numerical solution method. In this paper we present and analyze the properties of positive approximations of Aα\cal A^{-\alpha} obtained by the BURA technique. Sufficient conditions for positiveness are proven, complemented by sharp error estimates. The theoretical results are supported by representative numerical tests

    Archetype-based conversion of EHR content models: pilot experience with a regional EHR system

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    <p>Abstract</p> <p>Background</p> <p>Exchange of Electronic Health Record (EHR) data between systems from different suppliers is a major challenge. EHR communication based on archetype methodology has been developed by openEHR and CEN/ISO. The experience of using archetypes in deployed EHR systems is quite limited today. Currently deployed EHR systems with large user bases have their own proprietary way of representing clinical content using various models. This study was designed to investigate the feasibility of representing EHR content models from a regional EHR system as openEHR archetypes and inversely to convert archetypes to the proprietary format.</p> <p>Methods</p> <p>The openEHR EHR Reference Model (RM) and Archetype Model (AM) specifications were used. The template model of the Cambio COSMIC, a regional EHR product from Sweden, was analyzed and compared to the openEHR RM and AM. This study was focused on the convertibility of the EHR semantic models. A semantic mapping between the openEHR RM/AM and the COSMIC template model was produced and used as the basis for developing prototype software that performs automated bi-directional conversion between openEHR archetypes and COSMIC templates.</p> <p>Results</p> <p>Automated bi-directional conversion between openEHR archetype format and COSMIC template format has been achieved. Several archetypes from the openEHR Clinical Knowledge Repository have been imported into COSMIC, preserving most of the structural and terminology related constraints. COSMIC templates from a large regional installation were successfully converted into the openEHR archetype format. The conversion from the COSMIC templates into archetype format preserves nearly all structural and semantic definitions of the original content models. A strategy of gradually adding archetype support to legacy EHR systems was formulated in order to allow sharing of clinical content models defined using different formats.</p> <p>Conclusion</p> <p>The openEHR RM and AM are expressive enough to represent the existing clinical content models from the template based EHR system tested and legacy content models can automatically be converted to archetype format for sharing of knowledge. With some limitations, internationally available archetypes could be converted to the legacy EHR models. Archetype support can be added to legacy EHR systems in an incremental way allowing a migration path to interoperability based on standards.</p

    Critical Behavior of the 3d Random Field Ising Model: Two-Exponent Scaling or First Order Phase Transition?

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    In extensive Monte Carlo simulations the phase transition of the random field Ising model in three dimensions is investigated. The values of the critical exponents are determined via finite size scaling. For a Gaussian distribution of the random fields it is found that the correlation length ξ\xi diverges with an exponent ν=1.1±0.2\nu=1.1\pm0.2 at the critical temperature and that χξ2η\chi\sim\xi^{2-\eta} with η=0.50±0.05\eta=0.50\pm0.05 for the connected susceptibility and χdisξ4ηˉ\chi_{\rm dis}\sim\xi^{4-\bar{\eta}} with ηˉ=1.03±0.05\bar{\eta}=1.03\pm0.05 for the disconnected susceptibility. Together with the amplitude ratio A=limTTcχdis/χ2(hr/T)2A=\lim_{T\to T_c}\chi_{\rm dis}/\chi^2(h_r/T)^2 being close to one this gives further support for a two exponent scaling scenario implying ηˉ=2η\bar{\eta}=2\eta. The magnetization behaves discontinuously at the transition, i.e. β=0\beta=0, indicating a first order transition. However, no divergence for the specific heat and in particular no latent heat is found. Also the probability distribution of the magnetization does not show a multi-peak structure that is characteristic for the phase-coexistence at first order phase transition points.Comment: 14 pages, RevTeX, 11 postscript figures (fig9.ps and fig11.ps should be printed separately

    Understanding Social Resilience in the Maine Lobster Industry

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    The Maine lobster Homarus americanus fishery is considered one of the most successful fisheries in the world due in part to its unique comanagement system, the conservation ethic of the harvesters, and the ability of the industry to respond to crises and solve collective-action problems. However, recent threats raise the question whether the industry will be able to respond to future threats as successfully as it has to ones in the past or whether it is now less resilient and can no longer adequately respond to threats. Through ethnographic research and oral histories with fishermen, we examined the current level of social resilience in the lobster fishery. We concentrated on recent threats to the industry and the ways in which it has responded to them, focusing on three situations: a price drop beginning in 2008, a recovery in 2010–2011, and a second collapse of prices in 2012. In addition, we considered other environmental and regulatory concerns identified by fishermen. We found that the industry is not responding effectively to recent threats and identified factors that might explain the level of social resilience in the fishery

    The incremental yield of prenatal exome sequencing over chromosome microarray for congenital heart abnormalities:A systematic review and meta-analysis

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    ObjectivesTo determine the incremental yield of prenatal exome sequencing (PES) over standard testing in fetuses with an isolated congenital heart abnormality (CHA), CHA associated with extra-cardiac malformations (ECMs) and CHA dependent upon anatomical subclassification.MethodsA systematic review of the literature was performed using MEDLINE, EMBASE, Web of Science and grey literature January 2010-February 2023. Studies were selected if they included greater than 20 cases of prenatally diagnosed CHA when standard testing (QF-PCR/chromosome microarray/karyotype) was negative. Pooled incremental yield was determined. PROSPERO CRD 42022364747.ResultsOverall, 21 studies, incorporating 1957 cases were included. The incremental yield of PES (causative pathogenic and likely pathogenic variants) over standard testing was 17.4% (95% CI, 13.5%-21.6%), 9.3% (95% CI, 6.6%-12.3%) and 35.9% (95% CI, 21.0%-52.3%) for all CHAs, isolated CHAs and CHAs associated with ECMs. The subgroup with the greatest yield was complex lesions/heterotaxy; 35.2% (95% CI 9.7%-65.3%). The most common syndrome was Kabuki syndrome (31/256, 12.1%) and most pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease causing genes (114/224, 50.9%).ConclusionThe likelihood of a monogenic aetiology in fetuses with multi-system CHAs is high. Clinicians must consider the clinical utility of offering PES in selected isolated cardiac lesions.What is already known?Congenital heart abnormalities are the most commonly occurring congenital anomalies and can be associated with chromosomal or monogenic conditions. With the increasing use of fetal sequencing, there is a need to define the association between monogenic conditions and specific cardiac abnormalities, particularly when isolated to facilitate triaging for prenatal sequencing.What does this study add?The incremental yield of prenatal exome sequencing over and above chromosome microarray for congenital heart abnormalities is 9.3% in isolated lesions and 35.2% in the presence of complex lesions/heterotaxy. Clinicians should consider the clinical utility of offering prenatal exome sequencing in selected isolated cardiac lesions dependent on resources available

    The incremental yield of prenatal exome sequencing over chromosome microarray for congenital heart abnormalities:A systematic review and meta-analysis

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    ObjectivesTo determine the incremental yield of prenatal exome sequencing (PES) over standard testing in fetuses with an isolated congenital heart abnormality (CHA), CHA associated with extra-cardiac malformations (ECMs) and CHA dependent upon anatomical subclassification.MethodsA systematic review of the literature was performed using MEDLINE, EMBASE, Web of Science and grey literature January 2010-February 2023. Studies were selected if they included greater than 20 cases of prenatally diagnosed CHA when standard testing (QF-PCR/chromosome microarray/karyotype) was negative. Pooled incremental yield was determined. PROSPERO CRD 42022364747.ResultsOverall, 21 studies, incorporating 1957 cases were included. The incremental yield of PES (causative pathogenic and likely pathogenic variants) over standard testing was 17.4% (95% CI, 13.5%-21.6%), 9.3% (95% CI, 6.6%-12.3%) and 35.9% (95% CI, 21.0%-52.3%) for all CHAs, isolated CHAs and CHAs associated with ECMs. The subgroup with the greatest yield was complex lesions/heterotaxy; 35.2% (95% CI 9.7%-65.3%). The most common syndrome was Kabuki syndrome (31/256, 12.1%) and most pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease causing genes (114/224, 50.9%).ConclusionThe likelihood of a monogenic aetiology in fetuses with multi-system CHAs is high. Clinicians must consider the clinical utility of offering PES in selected isolated cardiac lesions.What is already known?Congenital heart abnormalities are the most commonly occurring congenital anomalies and can be associated with chromosomal or monogenic conditions. With the increasing use of fetal sequencing, there is a need to define the association between monogenic conditions and specific cardiac abnormalities, particularly when isolated to facilitate triaging for prenatal sequencing.What does this study add?The incremental yield of prenatal exome sequencing over and above chromosome microarray for congenital heart abnormalities is 9.3% in isolated lesions and 35.2% in the presence of complex lesions/heterotaxy. Clinicians should consider the clinical utility of offering prenatal exome sequencing in selected isolated cardiac lesions dependent on resources available
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