Steady state and (bi-) stability evaluation of simple protease signalling networks

Signal transduction networks are complex, as are their mathematical models. Gaining a deeper understanding requires a system analysis. Important aspects are the number, location and stability of steady states. In particular, bistability has been recognised as an important feature to achieve molecular switching. This paper compares different model structures and analysis methods particularly useful for bistability analysis. The biological applications include proteolytic cascades as, for example, encountered in the apoptotic signalling pathway or in the blood clotting system. We compare three model structures containing zero-order, inhibitor and cooperative ultrasensitive reactions, all known to achieve bistability. The combination of phase plane and bifurcation analysis provides an illustrative and comprehensive understanding of how bistability can be achieved and indicates how robust this behaviour is. Experimentally, some so-called “inactive” components were shown to have a residual activity. This has been mostly ignored in mathematical models. Our analysis reveals that bistability is only mildly affected in the case of zero-order or inhibitor ultrasensitivity. However, the case where bistability is achieved by cooperative ultrasensitivity is severely affected by this perturbation

Effect of dynamic stall on the aerodynamics of vertical-axis wind turbines

Accurate simulations of the aerodynamic performance of vertical-axis wind turbines pose a significant challenge for computational fluid dynamics methods. The aerodynamic interaction between the blades of the rotor and the wake that is produced by the blades requires a high-fidelity representation of the convection of vorticity within the wake. In addition, the cyclic motion of the blades induces large variations in the angle of attack on the blades that can manifest as dynamic stall. The present paper describes the application of a numerical model that is based on the vorticity transport formulation of the Navier–Stokes equations, to the prediction of the aerodynamics of a verticalaxis wind turbine that consists of three curved rotor blades that are twisted helically around the rotational axis of the rotor. The predicted variation of the power coefficient with tip speed ratio compares very favorably with experimental measurements. It is demonstrated that helical blade twist reduces the oscillation of the power coefficient that is an inherent feature of turbines with non-twisted blade configurations

Expression of TLR2, TLR4, and TLR9 in dermatomyositis and polymyositis

The aim of this study was to investigate the expressions of Toll-like receptor (TLR) 2, TLR4, TLR9, and their correlations with the expression of cytokines that are associated with activation of CD4+ T cells and inflammation including interferon γ (IFNγ), interleukin 4 (IL4), interleukin 17 (IL17), and tumor necrosis factor α (TNFα) in muscle tissues of patients with dermatomyositis (DM) and polymyositis (PM). The expressions of TLR2, TLR4, TLR9, IFNγ, IL4, IL17, and TNFα were measured by real-time reverse transcription–polymerase chain reaction in muscle tissues from 14 patients with DM and PM (nine patients with DM, five patients with PM) and three controls. The expressions of TLR2, TLR4, and TLR9 were also localized with immunohistochemistry. The expression levels of TLR2, TLR4, TLR9, IFNγ, IL4, IL17, and TNFα were significantly high in patients with DM and PM compared with those in the controls, and the expression levels of TLR4 and TLR9 had significant positive correlations with the expressions of IFNγ, IL4, IL17, and TNFα. Immunohistochemistry showed that TLR2, TLR4, and TLR9 were expressed by infiltrating cells of perimysium in DM, whereas they were expressed by infiltrating cells of endomysium in PM. These results suggest that the involvement of TLR4 and TLR9 in immunopathogenesis of DM and PM might be connected with activation of CD4+ T cells

Consequences Of On-Track Competition In Railways By Use Of Simulations

Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

Comorbid substance abuse and brain morphology in recent-onset psychosis

The aim of the presented study was to compare schizophrenia and schizoaffective patients early in the course of the disease with and without comorbid substance abuse disorder (SUD vs. NSUD) with regard to brain morphology. In a prospective design 41 patients (20 SUD vs. 21 NSUD) diagnosed as recent-onset schizophrenia or schizoaffective disorder consecutively admitted to hospital received standardized psychopathological evaluation (BPRS, SANS, MADRS, CGI, GAF) and MRI scanning with volumetric measurement of superior temporal gyrus (STG), amygdala-hippocampal complex, and cingulum. Patients with SUD (primarily cannabis) were significantly younger, predominantly male and had a lower socioeconomic status. Despite less attentional impairment (SANS subscore) and elevated anxiety/depression (BPRS subscore) in patients with SUD compared to NSUD, no other psychopathological differences could be detected. There were no differences in the assessed temporolimbic brain morphology between the two subgroups. In conclusion, in this study substance abuse in recent-onset psychosis had no effect on brain morphology and the earlier onset of psychosis in patients with comorbid SUD could not be explained by supposed accentuated brain abnormalities in temporolimbic regions