A simulation method for fatigue-driven delamination in layered structures involving non-negligible fracture process zones and arbitrarily shaped crack fronts

Most of the existing methods for fatigue-driven delamination are limited to two-dimensional (2D) applications or their predictive capabilities have not been validated in three-dimensional (3D) problems. This work presents a new cohesive zone-based computational method for simulating fatigue-driven delamination in the analysis of 3D structures without crack migration. The method accurately predicts fatigue propagation of non-nelgigible fracture process zones with arbitrarily shaped delamination fronts. The model does not require any kind of fitting parameter since all the input parameters are obtained experimentally from coupon tests. The evaluation of the energy release rate is done using two new techniques recently developed by the authors (the growth driving direction and the mode-decomposed J-integral) leading to an accurate prediction of delamination propagation under mixed-mode and non-self-similar growing conditions. The new method has been implemented as a UEL for Abaqus and validated against an experimental benchmark case with varying crack growth rate and shape and extension of the fracture process zone.Comment: 37 pages, 14 figures, 7 table

Amelioration Of Snap Bean Growth, Yield, Quantity And Nutritional Status Under Salinity Stress By Using Spirulina Algae Extract And Amino Acids

Salinity stress is a major abiotic stress that limits agricultural production and threatens global food security due to rapid climate change. Salt stress negatively affects the growth, yield and quality of crops.  Amino Acids and Spirulina Algae Extract are well-known biostimulants that have positive effects on plant growth and productivity and significantly reduce damage caused by abiotic stress. Therefore, this study investigated the effect of several treatments with spirulina extract and amino acids on snap bean plant growing under saline soil stress. Field experiment was carried out during the two successive summer seasons of 2021 and 2022 under saline soil at private farm in Faqus - Sharkia Governorate, to study the effect of spirulina algae and amino acid concentrations as foliar spray on growth, yield quantity and quality and nutritional status of snap bean cv, Bronco. The experiment was executed in split plot design, three rates of spirulina algae extracts (0, 1 and 2 cm3 L-1) were distributed on main plot and another three level of amino acids (0, 500 and 1000 mg L-1) were arranged on subplot. Finally, main and subplot were replicated three times. The results can be summarized as follows: Under saline soil condition, spraying snap bean plants with different concentrations of spirulina extract and amino acids three times led to an improvement in plant growth, crop quantity and quality as well as nutritional status, compared to the experimental treatment in which both were not used. The highest values of growth, yield and content of nitrogen, phosphorus and potassium were obtained by spraying 2 cm3 L-1 of spirulina extract with 1000 mg L-1 of amino acids under two consecutive seasons. Thus, it can be said that Therefore, the spirulina algae extract and amino acids are considered one of the safe solutions to get rid of the effect of soil salinity on the  snap bean plant, and then obtain a high yield and also high quality

Phase-field modelling of brittle fracture in thin shell elements based on the MITC4+ approach

We present a phase field based MITC4+ shell element formulation to simulate fracture propagation in thin shell structures. The employed MITC4+ approach renders the element shear- and membrane- locking free, hence providing high-fidelity fracture simulations in planar and curved topologies. To capture the mechanical response under bending-dominated fracture, a crack-driving force description based on the maximum strain energy density through the shell-thickness is considered. Several numerical examples simulating fracture in flat and curved shell structures are presented, and the accuracy of the proposed formulation is examined by comparing the predicted critical fracture loads against analytical estimates

Lamb wave-based damage indicator for plate-like structures

Structural health monitoring based on ultrasonics typically involves complex data analysis. Ultrasound monitoring based on Lamb waves techniques are extensively used nowadays due to their efficiency in exploring large areas with relatively small attenuation. In recent years, baseline based methods have been developed to identify structural damage based on the mismatch between the measured signal and the baseline one. To this end, complex time-frequency transformations are required to obtain signal features such as the time of arrival or the energy content, as indicators of damage onset and growth. Notwithstanding this, on-board applications require highly efficient processing techniques due to information storage and exchange limitations. This paper proposes a very high efficiency signal processing methodology to obtain a novel cumulative damage factor using Lamb wave raw data. The new methodology has been tested using ultrasonic and damage data from a fatigue test in carbon-epoxy composite laminates. The data is taken from NASA Prognostics data repository. In view of the results, the method is able to efficiently detect the onset and extent of damage from early stages of degradation. Moreover, the results demonstrate a remarkable agreement between the growth of delamination area and the predicted cumulative damage factor

Preparation and in vivo evaluation of insulin-loaded biodegradable nanoparticles prepared from diblock copolymers of PLGA and PEG

YesThe aim of this study was to design a controlled release vehicle for insulin to preserve its stability and biological activity during fabrication and release. A modified, double emulsion, solvent evaporation, technique using homogenisation force optimised entrapment efficiency of insulin into biodegradable nanoparticles (NP) prepared from poly (dl-lactic-co-glycolic acid) (PLGA) and its PEGylated diblock copolymers. Formulation parameters (type of polymer and its concentration, stabiliser concentration and volume of internal aqueous phase) and physicochemical characteristics (size, zeta potential, encapsulation efficiency, in vitro release profiles and in vitro stability) were investigated. In vivo insulin sensitivity was tested by diet-induced type II diabetic mice. Bioactivity of insulin was studied using Swiss TO mice with streptozotocin-induced type I diabetic profile. Insulin-loaded NP were spherical and negatively charged with an average diameter of 200–400 nm. Insulin encapsulation efficiency increased significantly with increasing ratio of co-polymeric PEG. The internal aqueous phase volume had a significant impact on encapsulation efficiency, initial burst release and NP size. Optimised insulin NP formulated from 10% PEG–PLGA retained insulin integrity in vitro, insulin sensitivity in vivo and induced a sustained hypoglycaemic effect from 3 h to 6 days in type I diabetic mice

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020