| 1. |
- Spinelli, L., et al.
(författare)
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Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink
- 2014
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Ingår i: Biomedical Optics Express. - : Optical Society of America. - 2156-7085. ; 5:7, s. 2037-2053
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Tidskriftsartikel (refereegranskat)abstract
- A multi-center study has been set up to accurately characterize the optical properties of diffusive liquid phantoms based on Intralipid and India ink at near-infrared (NIR) wavelengths. Nine research laboratories from six countries adopting different measurement techniques, instrumental set-ups, and data analysis methods determined at their best the optical properties and relative uncertainties of diffusive dilutions prepared with common samples of the two compounds. By exploiting a suitable statistical model, comprehensive reference values at three NIR wavelengths for the intrinsic absorption coefficient of India ink and the intrinsic reduced scattering coefficient of Intralipid-20% were determined with an uncertainty of about 2% or better, depending on the wavelength considered, and 1%, respectively. Even if in this study we focused on particular batches of India ink and Intralipid, the reference values determined here represent a solid and useful starting point for preparing diffusive liquid phantoms with accurately defined optical properties. Furthermore, due to the ready availability, low cost, long-term stability and batch-to-batch reproducibility of these compounds, they provide a unique fundamental tool for the calibration and performance assessment of diffuse optical spectroscopy instrumentation intended to be used in laboratory or clinical environment. Finally, the collaborative work presented here demonstrates that the accuracy level attained in this work for optical properties of diffusive phantoms is reliable.
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| 4. |
- Berube, Andrew P.
(författare)
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A graphical 3D finite element program for modelling self-potentials generated by flow through a porous medium
- 2007
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Ingår i: Journal of Environmental & Engineering Geophysics. - 1083-1363 .- 1943-2658. ; 12:2, s. 185-197
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Tidskriftsartikel (refereegranskat)abstract
- In order to provide a better understanding of the self-potentials generated by groundwater flow through real in-situ geological conditions and a tool for assisting in the interpretation of SP measurements obtained from such domains, a three-dimensional finite element computer program was written to model self-potentials generated by the flow of liquid through a porous medium. Using the program, a finite element domain is defined and each element can be assigned separate anisotropic hydraulic, electric and cross-coupling conductivity values. The hydraulic flow is defined by boundary conditions and the hydraulic conductivity distribution and is related to the electric flow through the thermodynamic theory of coupled flows.The program first determines the hydraulic potential distribution, and then calculates the electric current sources before solving for the electric potential distribution. The program was made to be quite user-friendly, versatile and fully graphical. The program was used to model seepage flow through an earth embankment dam and the results were compared to actual self-potential field measurements. It was found that the results obtained by the program were comparable with field measurements provided that sufficient knowledge of the conductive properties within the dam was available for modelling. The program successfully provides the hydraulic and electric potential distributions throughout the domain based on the input model parameters.
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| 5. |
- Skaug, H. J., et al.
(författare)
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Detecting dyads of related individuals in large collections of DNA-profiles by controlling the false discovery rate
- 2010
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Ingår i: MOL ECOL RESOUR. - : Wiley. - 1755-098X. ; 10:4, s. 693-700
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Tidskriftsartikel (refereegranskat)abstract
- The search for pairs (dyads) of related individuals in large databases of DNA-profiles has become an increasingly important inference tool in ecology. However, the many, partly dependent, pairwise comparisons introduce statistical issues. We show that the false discovery rate (FDR) procedure is well suited to control for the proportion of false positives, i.e. dyads consisting of unrelated individuals, which under normal circumstances would have been labelled as related individuals. We verify the behaviour of the standard FDR procedure by simulation, demonstrating that the FDR procedure works satisfactory in spite of the many dependent pairwise comparisons involved in an exhaustive database screening. A computer program that implements this method is available online. In addition, we propose to implement a second stage in the procedure, in which additional independent genetic markers are used to identify the false positives. We demonstrate the application of the approach in an analysis of a DNA database consisting of 3300 individual minke whales (Balaenoptera acutorostrata) each typed at ten microsatellite loci. Applying the standard procedure with an FDR of 50% led to the identification of 74 putative dyads of 1st- or 2nd-order relatives. However, introducing the second step, which involved additional genotypes at 15 microsatellite loci, revealed that only 21 of the putative dyads can be claimed with high certainty to be true dyads.
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