| 1. |
- Mark, Andreas, 1980, et al.
(författare)
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Microstructure Simulation of Early Paper Forming Using Immersed Boundary Methods
- 2011
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Ingår i: Paper360. - 1933-3684. ; 10:11, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- Paper forming is the first step in the paper machine where a fibersuspension leaves the headbox and flows through a forming fabric.Complex physical phenomena occur during paper forming due to theinteraction between fibers, fillers and fines as well as chemicalsadded to the suspension. Understanding this process is important forthe development of improved paper products because the configurationof the fibers during this step has a large influence on the finalpaper quality. Since the effective paper properties depend on themicro-structure of the fiber web, a continuum model is inadequate andthe properties of each fiber need to be accounted for in thesimulations.In the present work, a framework for microstructure simulation ofearly paper forming has been developed. The simulation frameworkincludes a Navier-Stokes solver and immersed boundary methods are usedto resolve the flow around the fibers. The fibers are modeled with afinite element discretization of the Euler-Bernoulli beam equation ina co-rotational formulation. The contact model is based on a penaltymethod and includes friction as well as elastic and inelasticcollisions.The fiber model and the contact model are validated against demandingtest cases from the literature with excellent results. Thefluid-structure interaction in the model is examined by simulating anelastic beam oscillating in a cross flow. Finally, a simulation ofearly paper forming is performed to demonstrate the potential of theproposed framework. The unique modeling approach can be used toincrease the fundamental understanding of paper forming and supportprocess optimization.
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| 2. |
- Mark, Andreas, 1980, et al.
(författare)
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Microstructure Simulation of Early Paper Forming Using Immersed Boundary Methods
- 2011
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Ingår i: Progress in Paper Physics Seminar. - 9783851251630 ; , s. 283-290
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Konferensbidrag (refereegranskat)abstract
- Paper forming is the first step in the paper machinewhere a fiber suspension leaves the headbox and flowsthrough a forming fabric. Understanding this processis important for the development of improved paperproducts because the configuration of the fibers duringthis step has a large influence on the final paperquality.The simulation framework includes IBOFlow, a stateof-the-art Navier-Stokes solver, and PaperGeo, the virtualpaper structure generator in GeoDict. ImmersedBoundary Methods are used to resolve the flow aroundthe fibers. The fibers are modeled with a finite elementdiscretization of the Euler-Bernoulli beam equationin a co-rotational formulation. The contact modelis based on a penalty method and includes friction aswell as elastic and inelastic collisions.The fiber model and the contact model are validatedagainst demanding test problems from the literaturewith excellent result. The fluid-structure interaction inthe model is examined by simulating an elastic beamoscillating in a cross flow. Finally, a simulation of initialpaper forming is performed, which demonstratesthe capabilities of the simulation framework.
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| 3. |
- Svenning, Erik, 1986, et al.
(författare)
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Multiphase Simulation of Fiber Suspension Flows Using Immersed Boundary Methods
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 27:2, s. 184-191
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Tidskriftsartikel (refereegranskat)abstract
- Fiber suspension simulations are challenging since they involve transient fluid flow with immersed solid objects subject to large displacements and rotations. In the present work, a beam model in co-rotational formulation is coupled with a fluid solver using immersed boundary methods. The model is used to simulate a fiber in a shear flow and excellent agreement is found with Jeffery's equations. The shapes of fibers deforming in a shear flow are found to be in qualitative agreement with shapes observed in experiments.The flow of a fiber suspension is studied by simulating early paper forming with one-way and semi-two-way coupling. It is found that the flow through the fiber web needs to be resolved in order to predict the retention of fibers in the fiber web.
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| 4. |
- Andrä, Heiko, et al.
(författare)
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Micromechanical network model for the evaluation of quality controls of paper
- 2011
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Ingår i: Progress in Paper Physics Seminar. - 9783851251630 ; , s. 49-55
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Konferensbidrag (refereegranskat)abstract
- In this paper, we discuss the challenges in modelling and simulating infinitesimal and large deformations of cellulose fiber networks, mainly in the context of the prediction of quality controls for paper.Understanding the influence and sensitivity of macroscopic production parameters like grammage and thickness of paperboard and understanding the influence of the fiber suspension on the quality of paper is important for the development of better papers and for preserving raw materials and energy.The new simulation framework consists of the virtual stochastic paper structure generator PaperGeo, that was integrated in the GeoDict 1 software suite, and the finite element solver FeelMath (Finite Elements for Elastic Materials and Homogenization) for solving the equations of elasticity. The fibers and the contacts are modelled by using geometrically exact beams of Simo-type [1].The microstructural model and the fiber network model are validated against standard measurements of existing papers in the following way: At first we perform tensile and bending tests to measure the macroscopic stress-strain relations. In the next step we apply a representative macroscopic stress or strain onto the boundaries of realizations of the stochastic fiber network model and compute by homogenization the effective (stiffness) coefficients. Finally we compare the numerical results with the measurements.This procedure can also be used for an identification of elastic parameters on the microscale and to study the sensitivity of the effective (macroscopic) stiffness with regard to the parameters of the microstructure
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| 5. |
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| 6. |
- Brüggemann, Anders, et al.
(författare)
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Are porous tantalum cups superior to conventional reinforcement rings? : A retrospective cohort study of 207 acetabular revisions
- 2017
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3674 .- 1745-3682. ; 88:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose - Porous tantalum cups have been introduced as an alternative to various reinforcement rings in revision hip surgery. We hypothesized that porous tantalum cups would be superior to muller acetabular roof reinforcement rings (MARRs) in revision hip surgery with re-revision for aseptic loosening as the primary outcome measure. Patients and methods - 207 hips operated with either a porous tantalum cup (TM cup, n = 111) or a MARR (n = 96) at index procedure were identified in our local arthroplasty register. Acetabular defects were classified according to Paprosky. There were 96 men and 111 women with a median age of 71 (35-95) years, presenting acetabular defect size type I in 39 cases, IIA in 22, IIB in 27, IIC in 43, IIIA in 32, and IIIB in 37 cases. Analysis of medical records identified all patients with subsequent re-revision and reasons for re-revisions. Kaplan-Meier survival functions were used to estimate implant survival. Results - With re-revision for aseptic loosening as the end-point, the 6-year unadjusted cumulative survival was 97% (95% CI: 94-100) for TM cups and 96% (CI: 92-100) for MARR (p = 0.6). Using re-revision for any reason as the endpoint, 6-year survival was 87% (CI: 81-94) for TM cups and 95% (CI: 90-99) for MARR (p = 0.06). The main reason for re-revision in the TM group was dislocation (n = 10), followed by loosening (n = 3), whereas the main reason for re-revision in the MARR group was aseptic loosening (n = 8). Duration of the index procedure and perioperative blood loss were lower in the TM group. Interpretation - Both TM and MARR lead to good 6-year results in acetabular revision surgery. The methods differ in their respective failure mechanisms. We conclude that TM cups are a valuable treatment option in acetabular revision surgery, but the reasons underlying dislocations after the use of TM cups must be analyzed further.
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| 7. |
- Cifani, Paolo, et al.
(författare)
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Hunting for Protein Markers of Hypoxia by Combining Plasma Membrane Enrichment with a New Approach to Membrane Protein Analysis
- 2011
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 10:4, s. 1645-1656
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Tidskriftsartikel (refereegranskat)abstract
- Nontransient hypoxia is strongly associated with malignant lesions, resulting in aggressive behavior and resistance to treatment. We present an analysis of mRNA and protein expression changes in neuroblastoma cell lines occurring upon the transition from normoxia to hypoxia. The correlation between mRNA and protein level changes was poor, although some known hypoxia-driven genes and proteins correlated well. We present previously undescribed membrane proteins expressed under hypoxic conditions that are candidates for evaluation as biomarkers.
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| 8. |
- Cirenajwis, Helena, et al.
(författare)
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Molecular stratification of metastatic melanoma using gene expression profiling: prediction of survival outcome and benefit from molecular targeted therapy.
- 2015
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Ingår i: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 6:14, s. 12297-12309
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Tidskriftsartikel (refereegranskat)abstract
- Melanoma is currently divided on a genetic level according to mutational status. However, this classification does not optimally predict prognosis. In prior studies, we have defined gene expression phenotypes (high-immune, pigmentation, proliferative and normal-like), which are predictive of survival outcome as well as informative of biology. Herein, we employed a population-based metastatic melanoma cohort and external cohorts to determine the prognostic and predictive significance of the gene expression phenotypes. We performed expression profiling on 214 cutaneous melanoma tumors and found an increased risk of developing distant metastases in the pigmentation (HR, 1.9; 95% CI, 1.05-3.28; P=0.03) and proliferative (HR, 2.8; 95% CI, 1.43-5.57; P=0.003) groups as compared to the high-immune response group. Further genetic characterization of melanomas using targeted deep-sequencing revealed similar mutational patterns across these phenotypes. We also used publicly available expression profiling data from melanoma patients treated with targeted or vaccine therapy in order to determine if our signatures predicted therapeutic response. In patients receiving targeted therapy, melanomas resistant to targeted therapy were enriched in the MITF-low proliferative subtype as compared to pre-treatment biopsies (P=0.02). In summary, the melanoma gene expression phenotypes are highly predictive of survival outcome and can further help to discriminate patients responding to targeted therapy.
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| 9. |
- Fang, Hsin-Yu, et al.
(författare)
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Hypoxia-inducible factors 1 and 2 are important transcriptional effectors in primary macrophages experiencing hypoxia
- 2009
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 114:4, s. 844-859
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Tidskriftsartikel (refereegranskat)abstract
- Ischemia exists in many diseased tissues, including arthritic joints, atherosclerotic plaques, and malignant tumors. Macrophages accumulate in these sites and up-regulate hypoxia-inducible transcription factors (HIFs) 1 and 2 in response to the hypoxia present. Here we show that the gene expression profile in primary human and murine macrophages changes markedly when they are exposed to hypoxia for 18 hours. For example, they were seen to up-regulate the cell surface receptors, CXCR4 and GLUT1, and the potent, tumor-promoting cytokines, vascular endothelial growth factor A, interleukin (IL)-1 beta and IL-8, adrenomedullin, CXCR4, and angiopoietin-2. Hypoxia also stimulated their expression and/or phosphorylation of various proteins in the nuclear factor-kappa B (NF-kappa B) signaling pathway. We then used both genetic and pharmacologic methods to manipulate the levels of HIFs-1 alpha and 2 alpha or NF-kappa B in primary macrophages to elucidate their role in the hypoxic induction of many of these key genes. These studies showed that both HIF-1 and -2, but not NF-kappa B, are important transcriptional effectors regulating the responses of macrophages to such a period of hypoxia. Further studies using experimental mouse models are now warranted to investigate the role of such macrophage responses in the progression of various diseased tissues, such as malignant tumors. (Blood. 2009; 114: 844-859)
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| 10. |
- Fredlund, Erik, et al.
(författare)
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High Myc pathway activity and low stage of neuronal differentiation associate with poor outcome in neuroblastoma.
- 2008
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 105:37, s. 14094-14099
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Tidskriftsartikel (refereegranskat)abstract
- The childhood cancer neuroblastoma arises in the developing sympathetic nervous system and is a genotypically and phenotypically heterogeneous disease. Prognostic markers of poor survival probability include amplification of the MYCN oncogene and an undifferentiated morphology. Whereas these features discriminate high- from low-risk patients with precision, identification of poor outcome low- and intermediate-risk patients is more challenging. In this study, we analyze two large neuroblastoma microarray datasets using a priori-defined gene expression signatures. We show that differential overexpression of Myc transcriptional targets and low expression of genes involved in sympathetic neuronal differentiation predicts relapse and death from disease. This was evident not only for high-risk patients but was also robust in identifying groups of poor prognosis patients who were otherwise judged to be at low- or intermediate-risk for adverse outcome. These data suggest that pathway-specific gene expression profiling might be useful in the clinic to adjust treatment strategies for children with neuroblastoma.
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