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- Anguelova, M., et al.
(författare)
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Conservation laws and unidentifiability of rate expressions in biochemical models
- 2007
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Ingår i: IET SYSTEMS BIOLOGY. - : Institution of Engineering and Technology (IET). - 1751-8849 .- 1751-8857. ; 1:4, s. 230-237
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Tidskriftsartikel (refereegranskat)abstract
- New experimental techniques in bioscience provide us with high-quality data allowing quantitative mathematical modelling. Parameter estimation is often necessary and, in connection with this, it is important to know whether all parameters can be uniquely estimated from available data, (i.e. whether the model is identifiable). Dealing essentially with models for metabolism, we show how the assumption of an algebraic relation between concentrations may cause parameters to be unidentifiable. If a sufficient data set is available, the problem with unidentifiability arises locally in individual rate expressions. A general method for reparameterisation to identifiable rate expressions is provided, together with a Mathematica code to help with the calculations. The general results are exemplified by four well-cited models for glycolysis.
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- Ericson, Marica B, 1974, et al.
(författare)
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Bispectral fluorescence imaging combined with texture analysis and linear discrimination for correlation with histopathologic extent of basal cell carcinoma
- 2005
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Ingår i: Journal of Biomedical Optics. - : SPIE-Intl Soc Optical Eng. - 1083-3668 .- 1560-2281. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence imaging has been shown to be a potential complement to visual inspection for demarcation of basal cell carcinoma (BCC), which is the most common type of skin cancer. Earlier studies have shown promising results when combining autofluorescence with protoporphyrin IX (Pp IX) fluorescence, induced by application of delta-5-aminolaevulinic acid (ALA). In this work, we have tried to further improve the ability of this technique to discriminate between areas of tumor and normal skin by implementing texture analysis and Fisher linear discrimination (FLD) on bispectral fluorescence data of BCCs located on the face. Classification maps of the lesions have been obtained from histopathologic mapping of the excised tumors. The contrast feature obtained from co-occurrence matrices was found to provide useful information, particularly for the ALA-induced Pp IX fluorescence data. Moreover, the neighborhood average features of both autofluorescence and Pp IX fluorescence were preferentially included in the analysis. The algorithm was trained by using a training set of images with good agreement with histopathology, which improved the discriminability of the validation set. In addition, cross validation of the training set showed good discriminability. Our results imply that FLD and texture analysis are preferential for correlation between bispectral fluorescence images and the histopathologic extension of the tumors.
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- Ericson, Marica B, 1974, et al.
(författare)
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Review of photodynamic therapy in actinic keratosis and basal cell carcinoma
- 2008
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Ingår i: Therapeutics and Clinical Risk Management. - 1178-203X. ; 4:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The number of non-melanoma skin cancers is increasing worldwide, and so also the demand for effective treatment modalities. Topical photodynamic therapy (PDT) using aminolaevulinic acid or its methyl ester has recently become good treatment options for actinic keratosis and basal cell carcinoma; especielly when treating large areas and areas with field cancerization. The cure rates are usually good, and the cosmetic outcomes excellent. The only major side effect reported is the pain experienced by the patients during treatment. This review covers the fundamental aspects of topical PDT and its application for treatment of actinic keratosis and basal cell carcinoma. Both potentials and limitations will be reviewed, as well as some recent development within the field.
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- Ericson, Marica B, 1974, et al.
(författare)
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Two-photon microscopy of non-melanoma skin cancer: initial experience and diagnostic criteria ex vivo
- 2007
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Ingår i: Proc. SPIE. - : SPIE. ; 6630
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Konferensbidrag (refereegranskat)abstract
- Multiphoton microscopy is an interesting optical technique, which allows for non-invasive imaging of highly light scattering media such as human skin. Recent reports have showed the potential of applying this technique for 3D visualisation of cell structures of biological tissue without previous sectioning of the tissue samples. In this study, we have applied two-photon microscopy on excised lesions of human non-melanoma skin cancer ex vivo in order to find diagnostic criteria using this technique. The skin samples have been investigated by a multiphoton microscopy system based on a fs-pulsed Ti:sapphire laser connected to a confocal microscope. The autofluorescence of the skin was detected using excitation at 780 nm. The cell nuclei distribution turned out to be one important parameter, which can be used for discriminating between tumour and normal tissue. We are now developing a technique for automatic detection and characterisation of tissue, based on an image analysis algorithm. The detection of cell nuclei has been found crucial for this purpose. The goal is to develop a fast characterisation algorithm that can be used on line in connection to in vivo investigations. This would allow for a true non-invasive biopsy technique in the future.
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- Fainsilber, L., et al.
(författare)
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Lattice points on circles and discrete velocity models for the Boltzmann equation
- 2006
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Ingår i: SIAM Journal on Mathematical Analysis. - : Society for Industrial & Applied Mathematics (SIAM). - 0036-1410 .- 1095-7154. ; 37:6, s. 1903-1922
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Tidskriftsartikel (refereegranskat)abstract
- The construction of discrete velocity models or numerical methods for the Boltzmann equation, may lead to the necessity of computing the collision operator as a sum over lattice points. The collision operator involves an integral over a sphere, which corresponds to the conservation of energy and momentum. In dimension two there are difficulties even in proving the convergence of such an approximation since many circles contain very few lattice points, and some circles contain many badly distributed lattice points. However, by showing that lattice points on most circles are equidistributed we find that the collision operator can indeed be approximated as a sum over lattice points in the two-dimensional case. The proof uses a weak form of the Halberstam-Richert inequality for multiplicative functions (a proof is given in the paper), and estimates for the angular distribution of Gaussian primes. For higher dimensions, this result has already been obtained by Palczewski, Schneider, and Bobylev [SIAM J. Numer. Anal., 34 (1997), pp. 1865-1883].
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