1,262 research outputs found
Bayesian parameter identification in plasticity
To evaluate the cyclic behaviour under diïŹerent loading conditions using the kinematic and isotropic hardening theory of steel a Chaboche visco-plastic material model is employed. The parameters of a constitutive model are usually identiïŹed by minimization of the distance between model response and experimental data. However, measurement errors and diïŹerences in the specimens lead to deviations in the determined parameters. In this article the Choboche model is used and a stochastic simulation technique is applied to generate artiïŹcial data which exhibit the same stochastic behaviour as experimental data. Then the model parameters are identiïŹed by applying a variaty of Bayesâs theorem. IdentiïŹed parameters are compared with the true parameters in the simulation and the eïŹciency of the identiïŹcation method is discussed
Antiflow of nucleons at the softest point of the EoS
Report-no: UFTP-492/1999 Journal-ref: Phys.Rev. C61 (2000) 024909 We investigate flow in semi-peripheral nuclear collisions at AGS and SPS energies within macroscopic as well as microscopic transport models. The hot and dense zone assumes the shape of an ellipsoid which is tilted by an angle Theta with respect to the beam axis. If matter is close to the softest point of the equation of state, this ellipsoid expands predominantly orthogonal to the direction given by Theta. This antiflow component is responsible for the previously predicted reduction of the directed transverse momentum around the softest point of the equation of state
Global complexity: some remarks to the "Author meets critic session" at the DGS congress in 2004
Der Beitrag dokumentiert die Diskussion auf der "Author Meets Critic"-Veranstaltung zu John Urrys "Sociology Beyond Societies" auf dem 32. Kongress der Deutschen Gesellschaft fĂŒr Soziologie (2004). ZunĂ€chst erlĂ€utert Urry den Grundgedanken seines Ansatzes, der auf eine Aufhebung der Trennung zwischen Naturwissenschaften und Gesellschaftswissenschaften hinauslĂ€uft. Unter dem Leitbild "KomplexitĂ€t" wird die Analyse physischer und sozialer Welten integriert. Dabei werden auch Elemente von Hardt/Negris "Empire und Multitude"-Konzept aufgegriffen. Der Begriff der Globalen KomplexitĂ€t steht auch im Mittelpunkt der Kommentare von Junge und Schwengel zu Urrys Buch. (ICE
Functional and differential proteomic analyses to identify platelet derived factors affecting ex vivo expansion of mesenchymal stromal cells
Background: Multilineage differentiation, immunomodulation and secretion of trophic factors render mesenchymal stromal cells (MSC) highly attractive for clinical application. Human platelet derivatives such as pooled human platelet lysate (pHPL) and thrombin-activated platelet releasate in plasma (tPRP) have been introduced as alternatives to fetal bovine serum (FBS) to achieve GMP-compliance. However, whereas both pHPL and tPRP support similar proliferation kinetics of lipoaspirate-derived MSC (LA-MSC), only pHPL significantly accelerates bone marrow-derived MSC (BM-MSC) expansion. To identify functionally bioactive factors affecting ex vivo MSC expansion, a differential proteomic approach was performed and identified candidate proteins were evaluated within a bioassay. Results: Two dimensional difference gel electrophoresis (2D-DIGE), MALDI-TOF analyses and complementary Western blotting revealed 20 differential protein species. 14 candidate proteins occured at higher concentrations in pHPL compared to tPRP and 6 at higher concentrations in tPRP. The candidate proteins fibrinogen and apolipoprotein A1 differentially affected LA- and BM-MSC proliferation. In a second set of experiments, reference cytokines known to foster proliferation in FBS were tested for their effects in the human supplements. Interestingly although these cytokines promoted proliferation in FBS, they failed to do so when added to the humanized system. Conclusions: The differential proteomic approach identified novel platelet derived factors differentially acting on human MSC proliferation. Complementary testing of reference cytokines revealed a lack of stimulation in the human supplements compared to FBS. The data describe a new coherent approach to combine proteomic technologies with functional testing to develop novel, humanized, GMP-compliant conditions for MSC expansion
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Functional and differential proteomic analyses to identify platelet derived factors affecting ex vivo expansion of mesenchymal stromal cells
Background: Multilineage differentiation, immunomodulation and secretion of trophic factors render mesenchymal
stromal cells (MSC) highly attractive for clinical application. Human platelet derivatives such as pooled human platelet
lysate (pHPL) and thrombin-activated platelet releasate in plasma (tPRP) have been introduced as alternatives to fetal
bovine serum (FBS) to achieve GMP-compliance. However, whereas both pHPL and tPRP support similar proliferation
kinetics of lipoaspirate-derived MSC (LA-MSC), only pHPL significantly accelerates bone marrow-derived MSC (BM-MSC)
expansion. To identify functionally bioactive factors affecting ex vivo MSC expansion, a differential proteomic approach
was performed and identified candidate proteins were evaluated within a bioassay.
Results: Two dimensional difference gel electrophoresis (2D-DIGE), MALDI-TOF analyses and complementary Western
blotting revealed 20 differential protein species. 14 candidate proteins occured at higher concentrations in pHPL
compared to tPRP and 6 at higher concentrations in tPRP. The candidate proteins fibrinogen and apolipoprotein A1
differentially affected LA- and BM-MSC proliferation.
In a second set of experiments, reference cytokines known to foster proliferation in FBS were tested for their effects in
the human supplements. Interestingly although these cytokines promoted proliferation in FBS, they failed to do so
when added to the humanized system.
Conclusions: The differential proteomic approach identified novel platelet derived factors differentially acting on
human MSC proliferation. Complementary testing of reference cytokines revealed a lack of stimulation in the human
supplements compared to FBS. The data describe a new coherent approach to combine proteomic technologies with
functional testing to develop novel, humanized, GMP-compliant conditions for MSC expansion
Comparison of Bayesian Methods on Parameter Identification for a Viscoplastic Model with Damage
The state of materials and accordingly the properties of structures are changing over the period of use, which may influence the reliability and quality of the structure during its life-time. Therefore, identification of the model parameters of the system is a topic which has attracted attention in the content of structural health monitoring. The parameters of a constitutive model are usually identified by minimization of the difference between model response and experimental data. However, the measurement errors and differences in the specimens lead to deviations in the determined parameters. In this article, the focus is on the identification of material parameters of a viscoplastic damaging material using a stochastic simulation technique to generate artificial data which exhibit the same stochastic behavior as experimental data. It is proposed to use Bayesian inverse methods for parameter identification and therefore the model and damage parameters are identified by applying the Transitional Markov Chain Monte Carlo Method (TMCMC) and Gauss-Markov-Kalman filter (GMKF) approach. Identified parameters by using these two Bayesian approaches are compared with the true parameters in the simulation and with each other, and the efficiency of the identification methods is discussed. The aim of this study is to observe which one of the mentioned methods is more suitable and efficient to identify the model and damage parameters of a material model, as a highly non-linear model, using a limited surface displacement measurement vector and see how much information is indeed needed to estimate the parameters accuratel
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