Fully automated operational modal analysis using multi-stage clustering

The interest for robust automatic modal parameter extraction techniques has increased significantly over the last years, together with the rising demand for continuous health monitoring of critical infrastructure like bridges, buildings and wind turbine blades. In this study a novel, multi-stage clustering approach for Automated Operational Modal Analysis (AOMA) is introduced. In contrast to existing approaches, the procedure works without any user-provided thresholds, is applicable within large system order ranges, can be used with very small sensor numbers and does not place any limitations on the damping ratio or the complexity of the system under investigation. The approach works with any parametric system identification algorithm that uses the system order n as sole parameter. Here a data-driven Stochastic Subspace Identification (SSI) method is used. Measurements from a wind tunnel investigation with a composite cantilever equipped with Fiber Bragg Grating Sensors (FBGSs) and piezoelectric sensors are used to assess the performance of the algorithm with a highly damped structure and low signal to noise ratio conditions. The proposed method was able to identify all physical system modes in the investigated frequency range from over 1000 individual datasets using FBGSs under challenging signal to noise ratio conditions and under better signal conditions but from only two sensors

Inhibition of Pro-inflammatory Cytokines by Ethyl Acetate Extract of Scrophularia striata

Purpose: To investigate the effect of ethyl acetate extract of S. striata on pro-inflammatory production by macrophages.Methods: Mouse peritoneal macrophages were cultured in solvent either alone or with 2 ìg/ml lipopolysaccaride (LPS) with/without different doses of ethyl acetate extract of S. striata. Production of pro-inflammatory cytokines including interleukin 1â (IL-1â), tumor necrosis factor - á (TNF-á) andprostaglandin E2 (PGE2) were examined using ELISA.Results: Ethyl acetate fraction of S. striata in doses of 10, 50, 100 and 200 ìg/ml significantly (p < 0.05) inhibited pro-inflammatory mediators (IL-1â, TNF-á, and PGE2) production by LPS stimulated peritoneal macrophages.Conclusion: The anti-inflammatory effect of the extract on pro-inflammatory cytokines may ameliorate inflammatory diseases, possibly via an immunomodulatory mechanism.Keywords: Pro-inflammatory, Cytokines, Ethyl acetate extract, Scrophularia striat

Operational Modal Analysis of a wing excited by transonic flow

Operational Modal Analysis (OMA) is a promising candidate for flutter testing and Structural Health Monitoring (SHM) of aircraft wings that are passively excited by wind loads. However, no studies have been published where OMA is tested in transonic flows, which is the dominant condition for large civil aircraft and is characterized by complex and unique aerodynamic phenomena. We use data from the HIRENASD large-scale wind tunnel experiment to automatically extract modal parameters from an ambiently excited wing operated in the transonic regime using two OMA methods: Stochastic Subspace Identification (SSI) and Frequency Domain Decomposition (FDD). The system response is evaluated based on accelerometer measurements. The excitation is investigated from surface pressure measurements. The forcing function is shown to be non-white, non-stationary and contaminated by narrow-banded transonic disturbances. All these properties violate fundamental OMA assumptions about the forcing function. Despite this, all physical modes in the investigated frequency range were successfully identified, and in addition transonic pressure waves were identified as physical modes as well. The SSI method showed superior identification capabilities for the investigated case. The investigation shows that complex transonic flows can interfere with OMA. This can make existing approaches for modal tracking unsuitable for their application to aircraft wings operated in the transonic flight regime. Approaches to separate the true physical modes from the transonic disturbances are discussed

A hybrid embedded cohesive element method for predicting matrix cracking in composites

The complex architecture of many fibre-reinforced composites makes the generation of finite element meshes a labour-intensive process. The embedded element method, which allows the matrix and fibre reinforcement to be meshed separately, offers a computationally efficient approach to reduce the time and cost of meshing. In this paper we present a new approach of introducing cohesive elements into the matrix domain to enable the prediction of matrix cracking using the embedded element method. To validate this approach, experiments were carried out using a modified Double Cantilever Beam with ply drops, with the results being compared with model predictions. Crack deflection was observed at the ply drop region, due to the differences in stiffness, strength and toughness at the bi-material interface. The new modelling technique yields accurate predictions of the failure process in composites, including fracture loads and crack deflection path

BCG scar formation and test results in two generations

Introduction: Considering that BCG injection in newborns is part of TB control program in Iran many years ago, we aimed to compare prevalence of childhood BCG vaccination scar with previous study and asses influence of household crowding on TST result. Aims: Considering that over time there is likely to reduce the immune response, two groups of subjects were selected among young and middle aged. Methods and Material: This cross sectional study was conducted in Zia Abad of Qazvin (a province of Iran) during year 2008. 261 participants randomly were selected (139 asymptomatic children (12-16 y) and 122 adults (40-50 y)). A questionnaire was used to obtain prior histories of BCG vaccination, known exposure to tuberculosis, prior acquired of TB, symptoms of TB disease and household crowding. BCG vaccine scar was ascertained and all participants were tested with 5TU-PPD. Reactions of 10 mm or more were considered positive. Statistical analysis used: Using student t test, chi square and Fisher's exact test, the collected data was analyzed. Results: BCG scar was observed in 78.4 of participant (91.4 children vs. 78.6 adults) which the difference was significant. Twenty three (16.5) of children and 24 (19.7) of adults had tuberculin reactivity of �10 mm. In children and parent groups, positivity of TST had significant direct association with presence of BCG scar and crowding. Conclusions: Most vaccinated children had a scar. Our results demonstrate that a TST applied after BCG vaccination usually produces a reaction of <10 mm. In addition, there is a significant relationship between the tuberculin reactivity and both presence of BCG scar and crowding among children and adult groups. © 2011, Shiraz E Medical Journal. All right reserved

Role of microbiota-derived short-chain fatty acids in cancer development and prevention

Following cancer, cells in a particular tissue can no longer respond to the factors involved in controlling cell survival, differentiation, proliferation, and death. In recent years, it has been indicated that alterations in the gut microbiota components, intestinal epithelium, and host immune system are associated with cancer incidence. Also, it has been demonstrated that the short-chain fatty acids (SCFAs) generated by gut microbiota are vitally crucial in cell homeostasis as they contribute to the modulation of histone deacetylases (HDACs), resulting effected cell attachment, immune cell immigration, cytokine production, chemotaxis, and the programmed cell death. Therefore, the manipulation of SCFA levels in the intestinal tract by alterations in the microbiota structure can be potentially taken into consideration for cancer treatment/prevention. In the current study, we will explain the most recent findings on the detrimental or protective roles of SFCA (particularly butyrate, propionate, and acetate) in several cancers, including bladder, colon, breast, stomach, liver, lung, pancreas, and prostate cancers. © 2021 The Author

Dietary Modulation of Drosophila Sleep-Wake Behaviour

Background A complex relationship exists between diet and sleep but despite its impact on human health, this relationship remains uncharacterized and poorly understood. Drosophila melanogaster is an important model for the study of metabolism and behaviour, however the effect of diet upon Drosophila sleep remains largely unaddressed. Methodology/Principal Findings Using automated behavioural monitoring, a capillary feeding assay and pharmacological treatments, we examined the effect of dietary yeast and sucrose upon Drosophila sleep-wake behaviour for three consecutive days. We found that dietary yeast deconsolidated the sleep-wake behaviour of flies by promoting arousal from sleep in males and shortening periods of locomotor activity in females. We also demonstrate that arousal from nocturnal sleep exhibits a significant ultradian rhythmicity with a periodicity of 85 minutes. Increasing the dietary sucrose concentration from 5% to 35% had no effect on total sucrose ingestion per day nor any affect on arousal, however it did lengthen the time that males and females remained active. Higher dietary sucrose led to reduced total sleep by male but not female flies. Locomotor activity was reduced by feeding flies Metformin, a drug that inhibits oxidative phosphorylation, however Metformin did not affect any aspects of sleep. Conclusions We conclude that arousal from sleep is under ultradian control and regulated in a sex-dependent manner by dietary yeast and that dietary sucrose regulates the length of time that flies sustain periods of wakefulness. These findings highlight Drosophila as an important model with which to understand how diet impacts upon sleep and wakefulness in mammals and humans

A study on the uniaxial tension of FCC metals at nano level using MD

Molecular Dynamics (MD) are now having orthodox means for simulation of matter in nano-scale. It can be regarded as an accurate alternative for experimental work in nano-science. In this paper, Molecular Dynamics simulation of uniaxial tension of some face centered cubic (FCC) metals (namely Au, Ag, Cu and Ni) at nano-level have been carried out. Sutton-Chen potential functions and velocity Verlet formulation of Noise-Hoover dynamic as well as periodic boundary conditions were applied. MD simulations at different loading rates and temperatures were conducted, and it was concluded that by increasing the temperature, maximum engineering stress decreases while engineering strain at failure is increasing. On the other hand, by increasing the loading rate both maximum engineering stress and strain at failure are increasing