Computational modelling of some problems of elasticity and viscoelasticity with applications to thermoforming process

Copyright @ 2012 Northwestern Polytechnical University and ISCIThe reliability of computational models of physical processes has received much attention and involves issues such as the validity of the mathematical models being used, the error in any data that the models need, and the accuracy of the numerical schemes being used. These issues are considered in the context of elastic, viscoelastic and hyperelastic deformation, when finite element approximations are applied. Goal oriented techniques using specific quantities of interest (QoI) are described for estimating discretisation and modelling errors in the hyperelastic case. The computational modelling of the rapid large inflation of hyperelastic circular sheets modelled as axisymmetric membranes is then treated, with the aim of estimating engineering QoI and their errors. Fine (involving inertia terms) and coarse (quasi-static) models of the inflation are considered. The techniques are applied to thermoforming processes where sheets are inflated into moulds to form thin-walled structures

Detection of Fatigue Crack Propagation in Steel Using Magnetic Measurements

For structural components which are exposed to cyclic stresses, fatigue damage could lead to a catastrophic failure. In nuclear pressure vessel systems where A533B steel is widely used as structural material, cyclic thermal expansions often create a low-cycle fatigue condition. The evaluation of fatigue damage therefore is critically important and nondestructive evaluation of fatigue damage is highly desirable from the viewpoint of both safer and longer operation lifetime

Interacting Turing-Hopf Instabilities Drive Symmetry-Breaking Transitions in a Mean-Field Model of the Cortex: A Mechanism for the Slow Oscillation

Electrical recordings of brain activity during the transition from wake to anesthetic coma show temporal and spectral alterations that are correlated with gross changes in the underlying brain state. Entry into anesthetic unconsciousness is signposted by the emergence of large, slow oscillations of electrical activity (≲1  Hz) similar to the slow waves observed in natural sleep. Here we present a two-dimensional mean-field model of the cortex in which slow spatiotemporal oscillations arise spontaneously through a Turing (spatial) symmetry-breaking bifurcation that is modulated by a Hopf (temporal) instability. In our model, populations of neurons are densely interlinked by chemical synapses, and by interneuronal gap junctions represented as an inhibitory diffusive coupling. To demonstrate cortical behavior over a wide range of distinct brain states, we explore model dynamics in the vicinity of a general-anesthetic-induced transition from “wake” to “coma.” In this region, the system is poised at a codimension-2 point where competing Turing and Hopf instabilities coexist. We model anesthesia as a moderate reduction in inhibitory diffusion, paired with an increase in inhibitory postsynaptic response, producing a coma state that is characterized by emergent low-frequency oscillations whose dynamics is chaotic in time and space. The effect of long-range axonal white-matter connectivity is probed with the inclusion of a single idealized point-to-point connection. We find that the additional excitation from the long-range connection can provoke seizurelike bursts of cortical activity when inhibitory diffusion is weak, but has little impact on an active cortex. Our proposed dynamic mechanism for the origin of anesthetic slow waves complements—and contrasts with—conventional explanations that require cyclic modulation of ion-channel conductances. We postulate that a similar bifurcation mechanism might underpin the slow waves of natural sleep and comment on the possible consequences of chaotic dynamics for memory processing and learning

The Functional Study of the N-Terminal Region of Influenza B Virus Nucleoprotein

Influenza nucleoprotein (NP) is a major component of the ribonucleoprotein (vRNP) in influenza virus, which functions for the transcription and replication of viral genome. Compared to the nucleoprotein of influenza A (ANP), the N-terminal region of influenza B nucleoprotein (BNP) is much extended. By virus reconstitution, we found that the first 38 residues are essential for viral growth. We further illustrated the function of BNP by mini-genome reconstitution, fluorescence microscopy, electron microscopy, light scattering and gel shift. Results show that the N terminus is involved in the formation of both higher homo-oligomers of BNP and BNP-RNA complex

Enabler for interdisciplinary ehealthcare: A qualitative study

© 2017 The authors and IOS Press. The complex relations between Health Technologies and clinical practices have been the focus of intensive research in recent years. This research represents a shift towards a holistic view where evaluation of health technologies is linked to organisational practices. In this paper, we address the gaps in existing literature regarding the holistic evaluation of e-health in clinical practice. We report the results from a qualitative study conducted to gain insight into e-health in practice within an interdisciplinary healthcare domain. Findings from this qualitative study, provides the foundation for the creation of a generic measurement model that allows for the comparative analysis of health technologies and assist in the decision-making of its stakeholders

Association between circulating GDF-15 and cardio-renal outcomes and effect of canagliflozin: results from the CANVAS trial

Background Studies have suggested that sodium glucose co-transporter 2 inhibitors exert anti-inflammatory effects. We examined the association of baseline growth differentiation factor-15 (GDF-15), a marker of inflammation and cellular injury, with cardiovascular events, hospitalization for heart failure (HF), and kidney outcomes in patients with type 2 diabetes in the CANVAS (Canagliflozin Cardiovascular Assessment Study) and determined the effect of the sodium glucose co-transporter 2 inhibitor canagliflozin on circulating GDF-15. Methods and Results The CANVAS trial randomized 4330 people with type 2 diabetes at high cardiovascular risk to canagliflozin or placebo. The association between baseline GDF-15 and cardiovascular (non-fatal myocardial infarction, non-fatal stroke, cardiovascular death), HF, and kidney (40% estimated glomerular filtration rate decline, end-stage kidney disease, renal death) outcomes was assessed using multivariable adjusted Cox regression models. During median follow-up of 6.1 years (N=3549 participants with available samples), 555 cardiovascular, 129 HF, and 137 kidney outcomes occurred. Each doubling in baseline GDF-15 was significantly associated with a higher risk of cardiovascular (hazard ratio [HR], 1.2; 95% CI, 1.0‒1.3), HF (HR, 1.5; 95% CI, 1.2‒2.0) and kidney (HR, 1.5; 95% CI, 1.2‒2.0) outcomes. Baseline GDF-15 did not modify canagliflozin's effect on cardiovascular, HF, and kidney outcomes. Canaglifozin treatment modestly lowered GDF-15 compared with placebo; however, GDF-15 did not mediate the protective effect of canagliflozin on cardiovascular, HF, or kidney outcomes. Conclusions In patients with type 2 diabetes at high cardiovascular risk, higher GDF-15 levels were associated with a higher risk of cardiovascular, HF, and kidney outcomes. Canagliflozin modestly lowered GDF-15, but GDF-15 reduction did not mediate the protective effect of canagliflozin

Stress Cardiac Biomarkers, Cardiovascular and Renal Outcomes, and Response to Canagliflozin

Background: Circulating biomarkers reflecting different mechanistic pathways may identify at-risk individuals with diabetes who may benefit from sodium-glucose cotransporter-2 (SGLT2) inhibitors. Objectives: The purpose of this study was to determine if high-sensitivity cardiac troponin T (hs-cTnT), soluble suppression of tumorigenesis-2 (sST2), and insulin-like growth factor binding protein 7 (IGFBP7) levels, either alone or in combination, may modify the treatment benefits of canagliflozin. Methods: In the CANVAS (CANagliflozin cardioVascular Assessment Study) biomarker substudy, we evaluated the prognostic significance of baseline biomarker measurements, the long-term trajectory of each, and response to canagliflozin on key cardiovascular and kidney outcomes. Results: Among the 4,330 study participants, baseline hs-cTnT, sST2, and IGFBP7 were available in 3,503 (81%), 3,084 (71%), and 3,577 (83%). In total, 39% had elevated hs-cTnT ≥14 pg/mL, 6% had sST2 >35 ng/mL, and 49% had IGFBP7 >96.5 ng/mL. Canagliflozin significantly slowed increases of hs-cTnT (P = 0.027) and sST2 (P = 0.033) through 6 years. Each biomarker was significantly associated with cardiovascular and kidney outcomes, independent of clinical covariates. Canagliflozin reduced heart failure and kidney events regardless of baseline biomarker concentration. Patients with hs-cTnT ≥14 ng/L and those with sST2 >35 ng/mL derived greater relative benefit for major adverse cardiovascular events (MACE) (both Pinteraction ≤0.05). A panel of all 3 biomarkers predicted each cardiac and kidney outcome evaluated; participants with an increasing number of abnormal circulating biomarkers appeared to have greater relative reductions in MACE from canagliflozin treatment (Pinteraction trend = 0.005). Conclusions: Canagliflozin delays longitudinal rise in hs-cTnT and sST2 compared with placebo out to 6 years. Canagliflozin reduced heart failure and kidney events regardless of baseline biomarker concentration. Elevated cardiovascular biomarkers, either alone or in combination, may identify individuals who may derive greater MACE benefit from SGLT2 inhibition. CANVAS (CANagliflozin cardioVascular Assessment Study; NCT01032629

Association between circulating gdf-15 and cardio-renal outcomes and effect of canagliflozin: Results from the canvas trial

BACKGROUND: Studies have suggested that sodium glucose co-transporter 2 inhibitors exert anti-inflammatory effects. We examined the association of baseline growth differentiation factor-15 (GDF-15), a marker of inflammation and cellular injury, with cardiovascular events, hospitalization for heart failure (HF), and kidney outcomes in patients with type 2 diabetes in the CANVAS (Canagliflozin Cardiovascular Assessment Study) and determined the effect of the sodium glucose co-transporter 2 inhibitor canagliflozin on circulating GDF-15. METHODS AND RESULTS: The CANVAS trial randomized 4330 people with type 2 diabetes at high cardiovascular risk to cana-gliflozin or placebo. The association between baseline GDF-15 and cardiovascular (non-fatal myocardial infarction, non-fatal stroke, cardiovascular death), HF, and kidney (40% estimated glomerular filtration rate decline, end-stage kidney disease, renal death) outcomes was assessed using multivariable adjusted Cox regression models. During median follow-up of 6.1 years (N=3549 participants with available samples), 555 cardiovascular, 129 HF, and 137 kidney outcomes occurred. Each doubling in baseline GDF-15 was significantly associated with a higher risk of cardiovascular (hazard ratio [HR], 1.2; 95% CI, 1.0‒1.3), HF (HR, 1.5; 95% CI, 1.2‒2.0) and kidney (HR, 1.5; 95% CI, 1.2‒2.0) outcomes. Baseline GDF-15 did not modify canagliflozin’s effect on cardiovascular, HF, and kidney outcomes. Canaglifozin treatment modestly lowered GDF-15 compared with placebo; however, GDF-15 did not mediate the protective effect of canagliflozin on cardiovascular, HF, or kidney outcomes. CONCLUSIONS: In patients with type 2 diabetes at high cardiovascular risk, higher GDF-15 levels were associated with a higher risk of cardiovascular, HF, and kidney outcomes. Canagliflozin modestly lowered GDF-15, but GDF-15 reduction did not mediate the protective effect of canagliflozin