The rheological properties of epoxy matrices and adhesives during cure are modelled in this work. Three epoxy-amine systems, designed for different applications with distinct curing behaviours, were ...investigated. Curing times ranged from a few seconds to upwards of 220 min depending on the cure temperature and formulation of the epoxy. The presented time-dependent model adds an exponential fit to Kiuna-Fontana's master curve of dimensionless viscosity, as well as a weighting function for the overall fit, aiming at creating a more accurate model. A major benefit of the approach is that time consuming determination of the cure kinetics using differential scanning calorimetry (DSC) is not required. The developed model was also used to predict the viscosity of a typical, non-isothermal curing cycle for composite manufacturing. It proved to correlate well with both isothermal and non-isothermal processes, demonstrating that it is particularly useful model to describe viscosity for flow modelling or process optimisation.
Passive spanwise bending shape-adaption has the potential to increase the efficiency and manoeuvrability of vehicles with wing-like structures. By utilisation of compression flange buckling, the ...in-plane stiffness can be tuned to design beams with contrasting pre-buckling and post-buckling bending stiffness. The investigated concept is experimentally validated using a thin-ply laminated composite four-point bending beam, which is designed to experience compression flange buckling in the span with constant moment. The bending stiffness was reduced by more than 41% after the onset of buckling which shows the effectiveness of compression flange buckling for non-linear bending compliance.
The out-of-plane permeability of two glass fibre fabrics was measured by 26 institutions using silicone oil as a test fluid. Participants in this study were free to select the test procedure, ...specimen dimensions and data analysis method, provided that testing was carried out at three target fibre volume fractions, 46%, 50% and 54%. While results showed a variability of two orders of magnitude between participants, most values were within a significantly narrower band. A majority of participants used 1D saturated test method. A few selected 1D unsaturated and 3D unsaturated flow method which gave very similar results. Focusing on analysis of data and results of 1D saturated flow measurements, results are not conclusive, but they are consistent with number of layers in a specimen, fibre volume fraction, injection pressure and sealing of specimen edges all having an effect on the measured permeability. Specifying limits for these parameters is expected to result in reduced scatter in measured permeability.
This paper reports the results of an international benchmark exercise on the measurement of fibre bed compaction behaviour. The aim was to identify aspects of the test method critical to obtain ...reliable results and to arrive at a recommended test procedure for fibre bed compaction measurements. A glass fibre 2/2 twill weave and a biaxial (±45°) glass fibre non-crimp fabric (NCF) were tested in dry and wet conditions. All participants used the same testing procedure but were allowed to use the testing frame, the fixture and sample geometry of their choice. The results showed a large scatter in the maximum compaction stress between participants at the given target thickness, with coefficients of variation ranging from 38% to 58%. Statistical analysis of data indicated that wetting of the specimen significantly affected the scatter in results for the woven fabric, but not for the NCF. This is related to the fibre mobility in the architectures in both fabrics. As isolating the effect of other test parameters on the results was not possible, no statistically significant effect of other test parameters could be proven. The high sensitivity of the recorded compaction pressure near the minimum specimen thickness to changes in specimen thickness suggests that small uncertainties in thickness can result in large variations in the maximum value of the compaction stress. Hence, it is suspected that the thickness measurement technique used may have an effect on the scatter.
Sirtuins are critical players within multiple cellular pathways such as stress response, apoptosis and energy metabolism. They are associated with metabolic and degenerative diseases, the ...pathogenesis of cancer and are key elements in the regulation of cellular life span. From within the 7 known human sirtuins, SIRT3 recently stepped out of the shadow of SIRT1 showing strong effects on stress response, apoptosis, cell cycle and energy metabolism, mimicking effects of caloric restriction. We have identified two non-synonymous human SIRT3 SNPs and evaluated their impact on SIRT3 activity and stability. We assessed their influence on cellular energy metabolism in relation to SIRT1 and identified SIRT3 to increase cellular respiration by 80% when compared to SIRT1, which increased cellular respiration by only 30%.
Validation of the Integrated Water Vapour (IWV) from Sentinel-3 Ocean and Land Colour Instrument (OLCI) was performed as a part of the “ESA/Copernicus Space Component Validation for Land Surface ...Temperature, Aerosol Optical Depth and Water Vapour Sentinel-3 Products” (LAW) project. High-spatial-resolution IWV observations in the near-infrared spectral region from the OLCI instruments aboard the Sentinel-3A and Sentinel-3B satellites provide continuity with observations from MERIS (Medium Resolution Imaging Spectrometer). The IWV was compared with reference observations from two networks: GNSS (Global Navigation Satellite System) precipitable water vapour from the SuomiNet network and integrated lower tropospheric columns from radio-soundings from the IGRA (Integrated Radiosonde Archive) database. Results for cloud-free matchups over land show a wet bias of 7 %–10 % for OLCI, with a high correlation against the reference observations (0.98 against SuomiNet and 0.90 against IGRA). Both OLCI-A and OLCI-B instruments show almost identical results, apart from an anomaly observed in camera 3 of the OLCI-B instrument, where observed biases are lower than in other cameras in either instrument. The wavelength drift in sensors was investigated, and biases in different cameras were found to be independent of wavelength. Effect of cloud proximity was found to have almost no effect on observed biases, indicating that cloud flagging in the OLCI IWV product is sufficiently reliable. We performed validation of random uncertainty estimates and found them to be consistent with the statistical a posteriori estimates, but somewhat higher.
We present the first extended validation of a new SYNERGY global aerosol product (SY_2_AOD), which is based on synergistic use of data from the Ocean and Land Color Instrument (OLCI) and the Sea and ...Land Surface Temperature Radiometer (SLSTR) sensors aboard the Copernicus Sentinel-3A (S3A) and Sentinel-3B (S3B) satellites. Validation covers period from 14 January 2020 to 30 September 2021. Several approaches, including statistical analysis, time series analysis, and comparison with similar aerosol products from the other spaceborne sensor, the Moderate Resolution Imaging Spectroradiometer (MODIS), were applied for validation and evaluation of S3A and S3B SY_2 aerosol products, including aerosol optical depth (AOD) provided at different wavelengths, AOD pixel-level uncertainties, fine-mode AOD, and Angström exponent. The regional analysis of the Angström exponent, which relates to the aerosol size distribution, shows spatial correlation with expected sources. For 40 % of the matchups with AERONET in the Northern Hemisphere (NH) and for 60 % of the matchups in the Southern Hemisphere (SH), which fit into the AE size range of 1, 1.8, an offset between SY_2 AE (syAE) and AERONET AE (aAE) is within ±0.25. General overestimation of low ( 0.5) syAE and underestimation of high ( 1.8) syAE results in high (0.94, globally) overall bias.
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•CVN-AD mice exhibit impaired metabolic activity.•Sleep-wake homeostasis is disrupted in CVN-AD mice.•CVN-AD mice exhibit sensorimotor dysfunction.
Alzheimer’s Disease (AD) is the ...most prevalent form of dementia globally, and the number of individuals with AD diagnosis is expected to double by 2050. Numerous preclinical AD studies have shown that AD neuropathology accompanies alteration in learning and memory. However, less attention has been given to alterations in metabolism, sleep, and sensorimotor functional outcomes during AD pathogenesis. The objective of this study was to elucidate the extent to which metabolic activity, sleep-wake cycle, and sensorimotor function is impaired in APPSwDI/Nos2−/− (CVN-AD) transgenic mice. Female mice were used in this study because AD is more prevalent in women compared to men. We hypothesized that the presence of AD neuropathology in CVN-AD mice would accompany alterations in metabolic activity, sleep, and sensorimotor function. Our results showed that CVN-AD mice had significantly decreased energy expenditure compared to wild-type (WT) mice. An examination of associated functional outcome parameters showed that sleep activity was elevated during the awake (dark) cycle and as well as an overall decrease in spontaneous locomotor activity. An additional functional parameter, the nociceptive response to thermal stimuli, was also impaired in CVN-AD mice. Collectively, our results demonstrate CVN-AD mice exhibit alterations in functional parameters that resemble human-AD clinical progression.
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