Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial delta-doped diamond layers

To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 1020 cm-3 were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p-/p++/p- multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.4 page

Selectively boron doped homoepitaxial diamond growth for power device applications

Diamond lateral growth is a powerful technique for the design and fabrication of diamond-based power electronic devices. Growth orientation affects the diamond deposition in terms of growth rate, surface roughness, and impurity incorporation. It has been shown that the finally grown surface of a patterned substrate can be predesigned based on the growth conditions. Thus, simultaneous growth along different surface orientations yields regions with different properties. In line with this, the incorporation of boron in a microwave plasma enhanced chemical vapor deposition laterally deposited epilayer over a mesa patterned {100}-oriented diamond substrate was studied by cathodoluminescence. It was observed that laterally oriented facets were highly boron doped in contrast to the {100}-oriented surfaces, which did not show any bound exciton emission, related to the doping. This study shows that, by designing the initial pattern and tuning the conditions, it is possible to drive a selective incorporation of boron into the grown layer

Post-earthquake numerical assessment and reinforcement of St James Church, New Zealand

This paper presents a numerical study on the seismic assessment and reinforcement of St James Church, affected by the 2011 New Zealand Earthquake. Numerical analyses were performed using a finite element model including the structural damage of the Church. The numerical model was calibrated against experimental results obtained from the dynamic identification tests carried out in situ. Nonlinear pushover analyses were performed in order to understand the structural behaviour of the damaged Church. The analysis of the results suggests that the damaged structure is not safe according to the new national specifications. Therefore, some reinforcement measures are needed to improve the seismic behaviour of the structure. A reinforcement solution is proposed taking into account the historical heritage value of the building, trying to maintain as much as possible the original aspect of the Church. Pushover analyses were also performed in the reinforced numerical model, proving its effectiveness

Post-earthquake seismic analysis of St James church, New Zealand

The paper presents a numerical study of the seismic assessment of the St James Church in Christchurch, New Zealand affected by the most recent 2011 earthquake and subsequent aftershocks. Dynamic identification tests, as well as a careful visual inspection, were performed in the Church in order to understand its structural behaviour after the seismic action. The seismic assessment of the Church has been done using the finite element modelling technique, in which the nonlinear behaviour of masonry has been taken into account by proper constitutive assumptions. A model updating according to the experimental results was carried out in order to validate the numerical model, which includes the simulation of the damage identified in the structure. Nonlinear pushover analyses were carried out demonstrating that, as a result of the seismic action, the Church can no longer be considered safe. Another numerical model was analysed, this time considering the intact structure. The pushover analysis results of this undamaged model show good agreement with the visual inspection performed in situ, which further validates the model used. Moreover, since the analysis proved that the structure is no longer safe, a reinforcement strategy is proposed and analysed, proving its effectiveness.(undefined

Influence of the microstructure on the creep behaviour of Tin-Silver-Copper solder

A common failure mode of electronic printed circuit boards (PCB’s) is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles and, thus, should be studied. Through the cooling phase, on the production of PCB assembly’s by the reflow technology, the hoven atmosphere temperature is adjusted in order to control the cooling rate. Narrow criteria is used so as to control the inter-metallic compounds (IMC) thickness, PCB assembly distortion and defects due to thermal shock. The cooling rate also affects solder microstructure, which has direct impact on creep behaviour and, thus, on the soldered joint reliability. In this paper, a dynamic mechanical analyser (DMA) is used to study the influence of the solder cooling rate on its creep behaviour. SAC405 samples with two distinct cooling rates were produced: inside a hoven cooling and by water quenching. Creep tests were made on three-point-bending clamp configuration, isothermally at 25 °C, 50 °C and 75 °C and under three separate levels of stress, 3, 5 and 9 MPa. The results show that creep behaviour has a noticeable cooling rate dependence. It was also noticed that creep propensity is exacerbated by the temperature at which stresses are applied, especially for the slower cooling rates. Creep mechanisms were related to the solder microstructural constituents, namely by the amount of phases ant their morphology.The authors would like to express his acknowledgments for the support given by the Portugal Incentive System for Research and Technological Development. Project in co-promotion This research is sponsored by the Portugal Incentive System for Research and Technological Development. This work is supported by: European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project nº 002814; Funding Reference: POCI-01-0247-FEDER-002814]. This work was financed by FCT, under the Strategic Project UID/SEM/04077/2013; PEst2015-2020 with the reference UID/CEC/00319/2013 and UID/FIS/04650/2013

Assessing the in vitro digestion of lactoferrin-curcumin nanoparticles using the realistic gastric model

Nanosized delivery systems have been the subject of research and discussion in the scientific community due to their unique properties and functionality. However, studies reporting the behaviour of nanodelivery systems under dynamic in vitro digestion conditions are still very scarce. To address this gap, this study aims to assess the dynamic in vitro gastric digestion of lactoferrin/curcumin nanoparticles in the realistic gastric model (RGM). For this purpose, the INFOGEST standard semi-dynamic digestion protocol was used. The nanosystems were characterized in terms of hydrodynamic size, size distribution, polydispersity index (PdI), and zeta potential using dynamic light scattering (DLS), before and during the digestion process. Confocal laser scanning microscopy (CLSM) was also used to examine particle aggregation. In addition, the release of curcumin was evaluated spectroscopically and the intrinsic fluorescence of lactoferrin was measured throughout the digestion process. The protein hydrolysis was also determined by UV-VIS-SWNIR spectroscopy to estimate, in real-time, the presence of free NH2 groups during gastric digestion. It was possible to observe that lactoferrin/curcumin nanoparticles were destabilized during the dynamic digestion process. It was also possible to conclude that low sample volumes can pose a major challenge in the application of dynamic in vitro digestion models.info:eu-repo/semantics/publishedVersio

In vitro digestion and storage stability of riboflavin-loaded WPI nanostructures towards foods fortification

The consumption of fortified foods incorporating bioactive compounds as a way to promote a healthier lifestyle has gain particular interest in research community and food industry. However, due to their chemical instabilities, bioactive compounds bioavailability can be compromised during post-processing, storage, and digestion. Their encapsulation/association in nanostructures offers a good strategy to enhance bioactive compounds bioavailability. Whey protein isolate (WPI) nanostructures were developed to associate riboflavin (Rb), aiming at its incorporation in foods, and their storage stability and digestion behavior were evaluated. Rb bioaccessibility was determined through spectrofluorimetry by quantifying Rb concentration in the soluble fraction after digestion, that was performed using INFOGEST static in vitro gastrointestinal model. Also, storage stability was evaluated by assessing nanostructures size and polydispersity (PdI) through dynamic light scattering, over 45 days at 4 °C and 25 °C. Rb-loaded WPI nanostructures showed no statistically significant differences in terms of size (ca. 120 nm) and PdI (0.2) during storage period, at both temperatures tested. Rb showed a bioaccessibility of 56 % when associated in WPI nanostructures, enhancing Rb bioaccessibility. These results contribute to improve the knowledge on the use of WPI nanostructures as effective encapsulating systems to augment hydrophilic bioactive compounds bioaccessibility, towards food fortification.info:eu-repo/semantics/publishedVersio

Deep Learning of Resting-state Electroencephalogram Signals for 3-class Classification of Alzheimer’s Disease, Mild Cognitive Impairment and Healthy Ageing

Objective. This study aimed to produce a novel deep learning (DL) model for the classification of subjects with Alzheimer's disease (AD), mild cognitive impairment (MCI) subjects and healthy ageing (HA) subjects using resting-state scalp electroencephalogram (EEG) signals. Approach. The raw EEG data were pre-processed to remove unwanted artefacts and sources of noise. The data were then processed with the continuous wavelet transform, using the Morse mother wavelet, to create time-frequency graphs with a wavelet coefficient scale range of 0-600. The graphs were combined into tiled topographical maps governed by the 10-20 system orientation for scalp electrodes. The application of this processing pipeline was used on a data set of resting-state EEG samples from age-matched groups of 52 AD subjects (82.3 ± 4.7 years of age), 37 MCI subjects (78.4 ± 5.1 years of age) and 52 HA subjects (79.6 ± 6.0 years of age). This resulted in the formation of a data set of 16197 topographical images. This image data set was then split into training, validation and test images and used as input to an AlexNet DL model. This model was comprised of five hidden convolutional layers and optimised for various parameters such as learning rate, learning rate schedule, optimiser, and batch size. Main results. The performance was assessed by a tenfold cross-validation strategy, which produced an average accuracy result of 98.9 ± 0.4% for the three-class classification of AD vs MCI vs HA. The results showed minimal overfitting and bias between classes, further indicating the strength of the model produced. Significance. These results provide significant improvement for this classification task compared to previous studies in this field and suggest that DL could contribute to the diagnosis of AD from EEG recordings

On the physico-mechanical, electrical and dielectric properties of mullite-glass composites

Mullite-glass composites were obtained by solid-state reactive sintering of kaolinite clay and kaolin waste mixtures with waste additions up to 100 wt%. The structural and microstructural analysis of starting powders and sintered samples were evaluated by X-ray diffractometry (XRD) and field-emission scanning electron microscopy (FESEM). The mechanical properties were evaluated by measuring the flexural strength of sintered bodies. Electrical properties of the composites were assessed by impedance spectroscopy (at 30 °C and from 400 to 700 °C) in air. A viscous flux mechanism resulting from the glassy phase filled up the open porosity and increased the mechanical strength. Electrical conductivity, dielectric constant and dielectric loss were strongly dependent on the microstructural features, namely glassy phase and porosity. The activation energies (0.89–0.99 eV) for electrical conduction were lower than typical literature values of mullite-based materials. The results indicated that the herein synthesized mullite-glass composites with up to 53.6 wt% mullite are promising low-cost materials for electronics-related applications.publishe