| 41. |
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| 42. |
- Johansson, Håkan, 1979, et al.
(författare)
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Parameter identification in constitutive models via optimization with a posteriori error control
- 2005
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Ingår i: International Journal for Numerical Methods in Engineering. ; 62:10, s. 1315-1340
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we outline a computational technique for the calibration of macroscopic constitutive lawswith automatic error control. In the most general situation the state variables of the constitutive law,as well as the material parameters, are spatially non-homogeneous. The experimental observations aregiven in spacetime. Based on an appropriate dual problem, we compute a posteriori the discretizationerror contributions from approximations of the parameter, state and costate fields in spacetime foran arbitrarily chosen goal-oriented error measure of engineering significance. Such a measure can beused in an adaptive strategy (not discussed in this paper) to meet a predefined error tolerance. Animportant observation is that the Jacobian matrix associated with the resulting Newton method is used(in principle) in solving the dual problem. Rather than treating the Jacobian in a monolithic fashion,we utilize a sequential solution strategy, whereby the FE-topology of the discretized state problem isused repeatedly. Moreover, the proposed solution strategy lends itself naturally to the computation offirst and second order sensitivities, which are obtained with little extra computational effort. Numericalresults are given for the prototype model of confined aquifer flow with spatially non-homogeneouspermeability. The efficiency of the optimization strategy and the effectivity of the error computationare assessed.
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| 43. |
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| 45. |
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| 46. |
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| 47. |
- Johansson, Karin C, et al.
(författare)
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Diptericin expression in bacteria infected Drosophila mbn-2 cells - effect of infection dose and phagocytosis.
- 2006
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Ingår i: Insect molecular biology (Print). - : Wiley. - 0962-1075 .- 1365-2583. ; 15:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- Drosophila haemocytes play a key role in defence against microbial aggression. Their capacity to sense and dispose of bacteria and also to signal to other immune tissues is probably vital to overcome an infection. In this work we used the haemocyte-like mbn-2 cell line to investigate how expression of the antimicrobial peptide diptericin is affected after a high dose bacterial challenge with diaminopimelic acid (DAP)-peptidoglycan Gram-positive and Gram-negative bacteria. We report that diptericin expression is negatively affected by high infection dose and rapid bacterial growth regardless of the type of infection and bacterial virulence and occurs in the absence of mbn-2 cell death. Furthermore we show that the mbn-2 cell population is heterogeneous, containing both phagocytic and nonphagocytic cells and that contact with large numbers of bacteria decreases diptericin expression in the phagocytic cell population.
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| 48. |
- Johansson, Karin C, et al.
(författare)
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Microarray analysis of immune challenged Drosophila hemocytes
- 2005
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 305:1, s. 145-155
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Tidskriftsartikel (refereegranskat)abstract
- nsect hemocytes play multiple roles in immunity and carry out cellular responses like phagocytosis, encapsulation and melanization as well as producing humoral effector proteins in the first line of defense after injury and invasion of microorganisms. In this work, we used the Drosophila melanogaster hemocyte-like cell line mbn-2 and Affymetrix Drosophila GeneChips to investigate the transcriptome of a single type of immune competent tissue exposed to Gram-negative cell wall components (crude LPS) or high dose infection with live Escherichia coli. We found that gene expression profiles of both treatments overlap but show important differences in expression levels of several genes involved in immunity. In addition, cell morphology during infection was monitored and revealed distinct alterations in cell shape and adhesion. Presence of large numbers of bacteria also increased the number of cells taking on crystal cell fate. Taken together, our results indicate that hemocytes sense and respond differently to purified bacterial surface molecules and infection with live and actively growing bacteria both at the level of gene expression and in cell behavior.
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| 49. |
- Johansson, Karin, 1970-
(författare)
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Interaction Between Drosophila melanogaster mbn-2 Cells and Bacteria
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Innate immunity relies on a repertoire of germline-encoded non-rearranging pattern recognition receptors that bind to invariant microbial surface molecules. This event initiates a number of signal transduction cascades that lead to humoral and cellular defense responses like synthesis of antimicrobial peptides, phagocytosis and coagulation – mechanisms that efficiently fight infectious microorganisms and have been evolutionary conserved to exist in parallel with the antibody-based adaptive immunity found in vertebrates. The fruit fly, Drosophila melanogaster represents a widely used animal model for studies of a pristine innate immune system. Its immune responsive intracellular signalling pathways display a high degree of similarity with the NF-κB /Rel-signalling pathways that mediate the inflammatory response in mammals. Insects are also vectors for medically important parasitic diseases which can trigger immune responses in the vector so basal knowledge about the regulation and function of insect immune systems can contribute to our understanding of inflammation and microbial disease in higher animals and open new strategies for biological vector control. Drosophila hemocytes play a key role in executing and coordinating local and systemic defenses in response to infection. This thesis describes in vitro studies of Drosophila gene expression in response to bacterial infection using the larval hemocyte-like cell line – mbn-2. Our results show that immune challenge with bacterial cell wall components and intact live bacteria induces differential gene expression that gives clues to how cellular immune responses could be activated and regulated.
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| 50. |
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