Efficient adaptivity for simulating cardiac electrophysiology with spectral deferred correction methods

The locality of solution features in cardiac electrophysiology simulations calls for adaptive methods. Due to the overhead incurred by established mesh refinement and coarsening, however, such approaches failed in accelerating the computations. Here we investigate a different route to spatial adaptivity that is based on nested subset selection for algebraic degrees of freedom in spectral deferred correction methods. This combination of algebraic adaptivity and iterative solvers for higher order collocation time stepping realizes a multirate integration with minimal overhead. This leads to moderate but significant speedups in both monodomain and cell-by-cell models of cardiac excitation, as demonstrated at four numerical examples.Comment: 12 pages, 12 figure

Edward Young's "Conjectures on original composition" in England and Germany

Thesis (Ph.D.)--University of Illinois, 1914.Typescript.Vita.Includes bibliographical references

Using smart services as a key enabler for collaboration in global production networks

Collaboration in global production networks becomes more important in times of increased interconnectivity and complexity. However, due to various resistors the collaboration potential has not been realized, yet. At the same time digitalization has become a key enabler in today’s world of high complexity leading to new, disruptive solutions. Part of digitalization are smart services, triggering incentives by including business models. This and further characteristics of smart services have the potential of overcoming the resistors of collaboration. In this paper an approach is proposed for developing collaborative relationships - from strategy and collaboration scenario modelling to a service-oriented implementation

a secondary analysis of two pharmacokinetic studies in surgical ICU patients

Background In ICU patients, glomerular filtration is often impaired, but also supraphysiological values are observed (“augmented renal clearance”, >130 mL/min/1.73 m2). Renally eliminated drugs (e.g. many antibiotics) must be adjusted accordingly, which requires a quantitative measure of renal function throughout all the range of clinically encountered values. Estimation from plasma creatinine is standard, but cystatin C may be a valuable alternative. Methods This was a secondary analysis of renal function parameters in 100 ICU patients from two pharmacokinetic studies on vancomycin and betalactam antibiotics. Estimated clearance values obtained by the Cockcroft-Gault formula (eCLCG), the CKD-EPI formula (eCLCKD-EPI) or the cystatin C based Hoek formula (eCLHoek) were compared with the measured endogenous creatinine clearance (CLCR). Agreement of values was assessed by modified Bland-Altman plots and by calculating bias (median error) and precision (median absolute error). Sensitivity and specificity of estimates to identify patients with reduced (130 mL/min/1.73 m2) CLCR were calculated. Results The CLCR was well distributed from highly compromised to supraphysiological values (median 73.2, range 16.8-234 mL/min/1.73 m2), even when plasma creatinine was not elevated (≤0.8 mg/dL for women, ≤1.1 mg/dL for men). Bias and precision were +13.5 mL/min/1.73 m2 and ±18.5 mL/min/1.73 m2 for eCLCG, +7.59 and ±16.8 mL/min/1.73 m2 for eCLCKD-EPI, and -4.15 and ±12.9 mL/min/1.73 m2 for eCLHoek, respectively, with eCLHoek being more precise than the other two (p < 0.05). The central 95% of observed errors fell between -59.8 and +250 mL/min/1.73 m2 for eCLCG, -83.9 and +79.8 mL/min/1.73 m2 for eCLCKD-EPI, and -103 and +27.9 mL/min/1.73 m2 for eCLHoek. Augmented renal clearance was underestimated by eCLCKD-EPI and eCLHoek. Patients with reduced CLCR were identified with good specificity by eCLCG, eCLCKD-EPI and eCLHoek (0.95, 0.97 and 0.91, respectively), but with less sensitivity (0.55, 0.55 and 0.83). For augmented renal clearance, specificity was 0.81, 0.96 and 0.96, but sensitivity only 0.69, 0.25 and 0.38. Conclusions Normal plasma creatinine concentrations can be highly misleading in ICU patients. Agreement of the cystatin C based eCLHoek with CLCR is better than that of the creatinine based eCLCG or eCLCKD-EPI. Detection and quantification of augmented renal clearance by estimates is problematic, and should rather rely on CLCR

Flux of the biogenic volatiles isoprene and dimethyl sulfide from an oligotrophic lake

Biogenic volatile organic compounds (BVOCs) affect atmospheric chemistry, climate and regional air quality in terrestrial and marine atmospheres. Although isoprene is a major BVOC produced in vascular plants, and marine phototrophs release dimethyl sulfide (DMS), lakes have been widely ignored for their production. Here we demonstrate that oligotrophic Lake Constance, a model for north temperate deep lakes, emits both volatiles to the atmosphere. Depth profiles indicated that highest concentrations of isoprene and DMS were associated with the chlorophyll maximum, suggesting that their production is closely linked to phototrophic processes. Significant correlations of the concentration patterns with taxon-specific fluorescence data, and measurements from algal cultures confirmed the phototrophic production of isoprene and DMS. Diurnal fluctuations in lake isoprene suggested an unrecognised physiological role in environmental acclimation similar to the antioxidant function of isoprene that has been suggested for marine biota. Flux estimations demonstrated that lakes are a currently undocumented source of DMS and isoprene to the atmosphere. Lakes may be of increasing importance for their contribution of isoprene and DMS to the atmosphere in the arctic zone where lake area coverage is high but terrestrial sources of BVOCs are small

Development of an Emergency Department Pharmacist Practitioner service specification

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