Travelling and standing envelope solitons in discrete non-linear cyclic structures

International audienceEnvelope solitons are demonstrated to exist in non-linear discrete structures with cyclic symmetry. The analysis is based on the Non-Linear Schrodinger Equation for the weakly non-linear limit, and on numerical simulation of the fully non-linear equations for larger amplitudes. Envelope solitons exist for parameters in which the wave equation is focussing and they have the form of shape-conserving wave packages propagating roughly with group velocity. For the limit of maximum wave number, where the group velocity vanishes, standing wave packages result and can be linked via a bifurcation to the non-localised non-linear normal modes. Numerical applications are carried out on a simple discrete system with cyclic symmetry which can be seen as a reduced model of a bladed disk as found in turbo-machinery

Food groups and risk of coronary heart disease, stroke and heart failure : a systematic review and dose-response meta-analysis of prospective studies

Background: Despite growing evidence for food-based dietary patterns' potential to reduce cardiovascular disease risk, knowledge about the amounts of food associated with the greatest change in risk of specific cardiovascular outcomes and about the quality of meta-evidence is limited. Therefore, the aim of this meta-analysis was to synthesize the knowledge about the relation between intake of 12 major food groups (whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat, and sugar-sweetened beverages [SSB]) and the risk of coronary heart disease (CHD), stroke and heart failure (HF). Methods: We conducted a systematic search in PubMed and Embase up to March 2017 for prospective studies. Summary risk ratios (RRs) and 95% confidence intervals (95% CI) were estimated using a random effects model for highest versus lowest intake categories, as well as for linear and non-linear relationships. Results: Overall, 123 reports were included in the meta-analyses. An inverse association was present for whole grains (RRCHD: 0.95 (95% CI: 0.92-0.98), RRHF: 0.96 (0.95-0.97)), vegetables and fruits (RRCHD: 0.97 (0.96-0.99), and 0.94 (0.90-0.97); RRstroke: 0.92 (0.86-0.98), and 0.90 (0.84-0.97)), nuts (RRCHD: 0.67 (0.43-1.05)), and fish consumption (RRCHD: 0.88 (0.79-0.99), RRstroke: 0.86 (0.75-0.99), and RRHF: 0.80 (0.67-0.95)), while a positive association was present for egg (RRHF: 1.16 (1.03-1.31)), red meat (RRCHD: 1.15 (1.08-1.23), RRstroke: 1.12 (1.06-1.17), RRHF: 1.08 (1.02-1.14)), processed meat (RRCHD: 1.27 (1.09-1.49), RRstroke: 1.17 (1.02-1.34), RRHF: 1.12 (1.05-1.19)), and SSB consumption (RRCHD: 1.17 (1.11-1.23), RRstroke: 1.07 (1.02-1.12), RRHF: 1.08 (1.05-1.12)) in the linear dose-response meta-analysis. There were clear indications for non-linear dose-response relationships between whole grains, fruits, nuts, dairy, and red meat and CHD. Conclusion: An optimal intake of whole grains, vegetables, fruits, nuts, legumes, dairy, fish, red and processed meat, eggs and SSB showed an important lower risk of CHD, stroke, and HF

Comparison of contact parameters measured with two different friction rigs for nonlinear dynamic analysis

The accurate measurement of contact interface parameters is of great importance for nonlinear dynamic response computations since there is a lack of predictive capabilities for such input parameters. Several test rigs have been developed at different institutions, and a series of measurements published, but their reliability remains unknown due to a lack of direct comparisons. To somehow address this issue, a Round-Robin test campaign was performed including the high frequency friction rigs of Imperial College London and Politecnico di Torino. Comparable hysteresis loops were recorded on specimen pairs manufactured from the same batch of raw stainless steel, for a wide range of test conditions, including varying normal loads, sliding distances and nominal areas of contact. Measurements from the two rigs were compared to quantify the level of agreement between the two very different experimental setup, showing a reasonably good matching in the results, but also highlighting some differences. Results also demonstrated that loading conditions can strongly affect the contact parameters, and consequently their effect must be included in future nonlinear dynamic simulations for more reliable predictions

Ultrasonic monitoring of friction contacts during shear vibration cycles

Complex high-value jointed structures such as aero-engines are carefully designed and optimized to prevent failure and maximise their life. In the design process, physically-based numerical models are employed to predict the nonlinear dynamic response of the structure. However, the reliability of these models is limited due to the lack of accurate validation data from metallic contact interfaces subjected to high-frequency vibration cycles. In this study, ultrasonic shear waves are used to characterise metallic contact interfaces during vibration cycles, hence providing new validation data for an understanding of the state of the friction contact. Supported by numerical simulations of wave propagation within the material, a novel experimental method is developed to simultaneously acquire ultrasonic measurements and friction hysteresis loops within the same test on a high-frequency friction rig. Large variability in the ultrasound reflection/transmission is observed within each hysteresis loop and is associated with stick/slip transitions. The measurement results reveal that the ultrasound technique can be used to detect stick and slip states in contact interfaces subjected to high-frequency shear vibration. This is the first observation of this type and paves the way towards real-time monitoring of vibrating contact interfaces in jointed structures, leading to a new physical understanding of the contact states and new validation data needed for improved nonlinear dynamic analyses

Nonlinear dynamics of turbine bladed disk with friction dampers: Experiment and simulation

Accurately predicting the nonlinear dynamic response of aero-engine components is critical, as excessive vibration amplitudes can considerably reduce the operational lifespan. This paper compares experimental and numerical nonlinear dynamic responses of an industrial aero-engine, specifically focusing on the first stage turbine bladed disk with under-platform dampers (UPDs). The friction forces between UPDs and blades result in a strongly nonlinear dynamic response, influenced by stick, slip and separation contact states at the interfaces. These contact states, and the resulting global dynamic responses, are predicted with an advanced industrial modelling approach for nonlinear dynamics. The predictions are compared, updated and validated against measurement data from an operational engine test. Results highlight the importance to validate models against industrial data and show that realistic contact pressure distributions are required for increased prediction reliability. The novelty of this work includes (1) the use of unique industrial experimental data from a fully operational aero-engine, (2) the observation, at the end of engine testing, of real contact conditions in blade/UPD interfaces, (3) detailed modelling of these contact conditions with high-fidelity finite element representations in nonlinear dynamic solvers. Based on this unique industrial validation work, guidelines are proposed to improve the state-of-the-art modelling of nonlinear dynamics in structures with friction contacts

Solitons in non-linear cyclic system

In this paper we consider the case of a non-linear structure with cyclic symmetry which can be seen as approximation for bladed disk type structures. Using the multiple scale method, we show that soliton solutions are possible within such structure. The theoretical developments are illustrated with numerical simulations on a simple system with cubic non-linearities

High-resolution projections of ambient heat for major European cities using different heat metrics

Heat stress in cities is projected to strongly increase due to climate change. The associated health risks will be exacerbated by the high population density in cities and the urban heat island effect. However, impacts are still uncertain, which is among other factors due to the existence of multiple metrics for quantifying ambient heat and the typically rather coarse spatial resolution of climate models. Here we investigate projections of ambient heat for 36 major European cities based on a recently produced ensemble of regional climate model simulations for Europe (EURO-CORDEX) at 0.11∘ spatial resolution (∼ 12.5 km). The 0.11∘ EURO-CORDEX ensemble provides the best spatial resolution currently available from an ensemble of climate model projections for the whole of Europe and makes it possible to analyse the risk of temperature extremes and heat waves at the city level. We focus on three temperature-based heat metrics – yearly maximum temperature, number of days with temperatures exceeding 30 ∘C, and Heat Wave Magnitude Index daily (HWMId) – to analyse projections of ambient heat at 3 ∘C warming in Europe compared to 1981–2010 based on climate data from the EURO-CORDEX ensemble. The results show that southern European cities will be particularly affected by high levels of ambient heat, but depending on the considered metric, cities in central, eastern, and northern Europe may also experience substantial increases in ambient heat. In several cities, projections of ambient heat vary considerably across the three heat metrics, indicating that estimates based on a single metric might underestimate the potential for adverse health effects due to heat stress. Nighttime ambient heat, quantified based on daily minimum temperatures, shows similar spatial patterns to daytime conditions, albeit with substantially higher HWMId values. The identified spatial patterns of ambient heat are generally consistent with results from global Earth system models, though with substantial differences for individual cities. Our results emphasise the value of high-resolution climate model simulations for analysing climate extremes at the city level. At the same time, they highlight that improving the predominantly rather simple representations of urban areas in climate models would make their simulations even more valuable for planning adaptation measures in cities. Further, our results stress that using complementary metrics for projections of ambient heat gives important insights into the risk of future heat stress that might otherwise be missed.</p

Role of diet in type 2 diabetes incidence: umbrella review of meta-analyses of prospective observational studies

OBJECTIVE: To summarise the evidence of associations between dietary factors and incidence of type 2 diabetes and to evaluate the strength and validity of these associations. DESIGN: Umbrella review of systematic reviews with meta-analyses of prospective observational studies. DATA SOURCES: PubMed, Web of Science, and Embase, searched up to August 2018. ELIGIBILITY CRITERIA: Systematic reviews with meta-analyses reporting summary risk estimates for the associations between incidence of type 2 diabetes and dietary behaviours or diet quality indices, food groups, foods, beverages, alcoholic beverages, macronutrients, and micronutrients. RESULTS: 53 publications were included, with 153 adjusted summary hazard ratios on dietary behaviours or diet quality indices (n=12), food groups and foods (n=56), beverages (n=10), alcoholic beverages (n=12), macronutrients (n=32), and micronutrients (n=31), regarding incidence of type 2 diabetes. Methodological quality was high for 75% (n=115) of meta-analyses, moderate for 23% (n=35), and low for 2% (n=3). Quality of evidence was rated high for an inverse association for type 2 diabetes incidence with increased intake of whole grains (for an increment of 30 g/day, adjusted summary hazard ratio 0.87 (95% confidence interval 0.82 to 0.93)) and cereal fibre (for an increment of 10 g/day, 0.75 (0.65 to 0.86)), as well as for moderate intake of total alcohol (for an intake of 12-24 g/day v no consumption, 0.75 (0.67 to 0.83)). Quality of evidence was also high for the association for increased incidence of type 2 diabetes with higher intake of red meat (for an increment of 100 g/day, 1.17 (1.08 to 1.26)), processed meat (for an increment of 50 g/day, 1.37 (1.22 to 1.54)), bacon (per two slices/day, 2.07 (1.40 to 3.05)), and sugar sweetened beverages (for an increase of one serving/day, 1.26 (1.11 to 1.43)). CONCLUSIONS: Overall, the association between dietary factors and type 2 diabetes has been extensively studied, but few of the associations were graded as high quality of evidence. Further factors are likely to be important in type 2 diabetes prevention; thus, more well conducted research, with more detailed assessment of diet, is needed. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018088106

Plasma biomarker analysis in pediatric ARDS: Generating future framework from a pilot randomized control trial of methylprednisolone: A framework for identifying plasma biomarkers related to clinical outcomes in pediatric ARDS

© 2016 Kimura, Saravia, Rovnaghi, Meduri, Schwingshackl, Cormier and Anand. Objective: Lung injury activates multiple pro-inflammatory pathways, including neutrophils, epithelial, and endothelial injury, and coagulation factors leading to acute respiratory distress syndrome (ARDS). Low-dose methylprednisolone therapy (MPT) improved oxygenation and ventilation in early pediatric ARDS without altering duration of mechanical ventilation or mortality. We evaluated the effects of MPT on biomarkers of endothelial [Ang-2 and soluble intercellular adhesion molecule-1 (sICAM-1)] or epithelial [soluble receptor for activated glycation end products (sRAGE)] injury, neutrophil activation [matrix metalloproteinase-8 (MMP-8)], and coagulation (plasminogen activator inhibitor-1). Design: Double-blind, placebo-controlled randomized trial. Setting: Tertiary-care pediatric intensive care unit (ICU). Patients: Mechanically ventilated children (0-18 years) with early ARDS. Interventions: Blood samples were collected on days 0 (before MPT), 7, and 14 during low-dose MPT (n = 17) vs. placebo (n = 18) therapy. The MPT group received a 2-mg/kg loading dose followed by 1 mg/kg/day continuous infusions from days 1 to 7, tapered off over 7 days; placebo group received equivalent amounts of 0.9% saline. We analyzed plasma samples using a multiplex assay for five biomarkers of ARDS. Multiple regression models were constructed to predict associations between changes in biomarkers and the clinical outcomes reported earlier, including P/F ratio on days 8 and 9, plateau pressure on days 1 and 2, PaCO 2 on days 2 and 3, racemic epinephrine following extubation, and supplemental oxygen at ICU discharge. Results: No differences occurred in biomarker concentrations between the groups on day 0. On day 7, reduction in MMP-8 levels (p = 0.0016) occurred in the MPT group, whereas increases in sICAM-1 levels (p = 0.0005) occurred in the placebo group (no increases in sICAM-1 in the MPT group). sRAGE levels decreased in both MPT and placebo groups (p \u3c 0.0001) from day 0 to day 7. On day 7, sRAGE levels were positively correlated with MPT group PaO 2 /FiO 2 ratios on day 8 (r = 0.93, p = 0.024). O 2 requirements at ICU transfer positively correlated with day 7 MMP-8 (r = 0.85, p = 0.016) and Ang-2 levels (r = 0.79, p = 0.036) in the placebo group and inversely correlated with day 7 sICAM-1 levels (r = -0.91, p = 0.005) in the MPT group. Conclusion: Biomarkers selected from endothelial, epithelial, or intravascular factors can be correlated with clinical endpoints in pediatric ARDS. For example, MPT could reduce neutrophil activation ([downwards double arrow]MMP-8), decrease endothelial injury (⇔sICAM-1), and allow epithelial recovery ([downwards double arrow]sRAGE). Large ARDS clinical trials should develop similar frameworks

Apoptosis signal-regulating kinase-1 promotes inflammasome priming in macrophages

© 2019 the American Physiological Society. previously showed that mice deficient in apo-ptosis signal-regulating kinase-1 (ASK1) were partially protected against ventilator-induced lung injury. Because ASK1 can promote both cell death and inflammation, we hypothesized that ASK1 activation regulates inflammasome-mediated inflammation. Mice deficient in ASK1 expression (ASK1 +/+ ) exhibited significantly less inflammation and lung injury (as measured by neutrophil infiltration, IL-6, and IL-1β) in response to treatment with inhaled lipopolysaccharide (LPS) compared with wild-type (WT) mice. To determine whether this proinflammatory response was mediated by ASK1, we investigated inflammasome-mediated responses to LPS in primary macrophages and bone marrow-derived macrophages (BMDMs) from WT and ASK1 +/+ mice, as well as the mouse alveolar macrophage cell line MH-S. Cells were treated with LPS alone for priming or LPS followed by ATP for activation. When macrophages were stimulated with LPS followed by ATP to activate the inflammasome, we found a significant increase in secreted IL-1β from WT cells compared with ASK1-deficient cells. LPS priming stimulated an increase in NOD-like receptor 3 (NLRP3) and pro-IL-1β in WT BMDMs, but expression of NLRP3 was significantly decreased in ASK1 +/+ BMDMs. Subsequent ATP treatment stimulated an increase in cleaved caspase-1 and IL-1β in WT BMDMs compared with ASK1 +/+ BMDMs. Similarly, treatment of MH-S cells with LPS + ATP caused an increase in both cleaved caspase-1 and IL-1β that was diminished by the ASK-1 inhibitor NQDI1. These results demonstrate, for the first time, that ASK1 promotes inflammasome priming