On the use of the Peak Stress Method for the calculation of Residual Notch Stress Intensity Factors: a preliminary investigation

Residual stresses induced by welding processes significantly affect the engineering properties of structural components. If the toe region of a butt-welded joint is modeled as a sharp V-notch, the distribution of the residual stresses in that zone is asymptotic with a singularity degree which follows either the linear-elastic or the elastic-plastic solution, depending on aspects such as clamping conditions, welding parameters, material and dimension of plates. The intensity of the local residual stress fields is quantified by the Residual Notch Stress Intensity Factors (R-NSIFs), which can be used in principle to include the residual stress effect in the fatigue assessment of welded joints. Due to the need of extremely refined meshes and to the high computational resources required by non-linear transient analyses, the R-NSIFs have been calculated in literature only by means of 2D models. It is of interest to propose new coarse-mesh-based approaches which allow residual stresses to be calculated with less computational effort. This work is aimed to investigate the level of accuracy of the Peak Stress Method in the R-NSIFs evaluation

Rapid Calculation of Residual Notch Stress Intensity Factors (R- NSIFs) by Means of the Peak Stress Method

The intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine. Unfortunately, the nonlinear and transient behavior of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly, if large welded structures and/or multipass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the notch stress intensity factors (NSIFs) at sharp V-notches, using coarse finite element patterns. In this work, the peak stress method (PSM) has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible

A Transfer Learning and Explainable Solution to Detect mpox from Smartphones images

In recent months, the monkeypox (mpox) virus -- previously endemic in a limited area of the world -- has started spreading in multiple countries until being declared a ``public health emergency of international concern'' by the World Health Organization. The alert was renewed in February 2023 due to a persisting sustained incidence of the virus in several countries and worries about possible new outbreaks. Low-income countries with inadequate infrastructures for vaccine and testing administration are particularly at risk. A symptom of mpox infection is the appearance of skin rashes and eruptions, which can drive people to seek medical advice. A technology that might help perform a preliminary screening based on the aspect of skin lesions is the use of Machine Learning for image classification. However, to make this technology suitable on a large scale, it should be usable directly on mobile devices of people, with a possible notification to a remote medical expert. In this work, we investigate the adoption of Deep Learning to detect mpox from skin lesion images. The proposal leverages Transfer Learning to cope with the scarce availability of mpox image datasets. As a first step, a homogenous, unpolluted, dataset is produced by manual selection and preprocessing of available image data. It will also be released publicly to researchers in the field. Then, a thorough comparison is conducted amongst several Convolutional Neural Networks, based on a 10-fold stratified cross-validation. The best models are then optimized through quantization for use on mobile devices; measures of classification quality, memory footprint, and processing times validate the feasibility of our proposal. Additionally, the use of eXplainable AI is investigated as a suitable instrument to both technically and clinically validate classification outcomes.Comment: Submitted to Pervasive and Mobile Computin

Ultrasound Detection of Subquadricipital Recess Distension

Joint bleeding is a common condition for people with hemophilia and, if untreated, can result in hemophilic arthropathy. Ultrasound imaging has recently emerged as an effective tool to diagnose joint recess distension caused by joint bleeding. However, no computer-aided diagnosis tool exists to support the practitioner in the diagnosis process. This paper addresses the problem of automatically detecting the recess and assessing whether it is distended in knee ultrasound images collected in patients with hemophilia. After framing the problem, we propose two different approaches: the first one adopts a one-stage object detection algorithm, while the second one is a multi-task approach with a classification and a detection branch. The experimental evaluation, conducted with $483$ annotated images, shows that the solution based on object detection alone has a balanced accuracy score of $0.74$ with a mean IoU value of $0.66$, while the multi-task approach has a higher balanced accuracy value ($0.78$) at the cost of a slightly lower mean IoU value

Recent Results on the Brittle Fracture of Terfenol-D Specimens under Magnetic Field

The following investigation has the purpose of describing, both experimentally and numerically, the fracture behavior of a giant magnetostrictive alloy commercially known as Terfenol-D. Single-edge precracked specimens have been analyzed via three-point bending tests, measuring fracture loads in the presence and absence of a magnetic field at various loading rates. The Strain Energy Density (SED), averaged in a finite control volume, has recently proved to be an excellent method of predicting brittle failures of cracked, U- and V-notched specimens made out of different materials. The effects of the magnetic field and of the loading rate on Terfenol-D failures have been studied, as well as discussing the ability of SED criterion to seize these effects, by performing coupled-field finite element analyses. Finally, a relationship between the size of the SED's control volume and the loading rate has been proposed and failures have then been estimated in terms of averaged SED

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Adventitial vessel growth and progenitor cells activation in an ex vivo culture system mimicking human saphenous vein wall strain after coronary artery bypass grafting

Saphenous vein graft disease is a timely problem in coronary artery bypass grafting. Indeed, after exposure of the vein to arterial blood flow, a progressive modification in the wall begins, due to proliferation of smooth muscle cells in the intima. As a consequence, the graft progressively occludes and this leads to recurrent ischemia. In the present study we employed a novel ex vivo culture system to assess the biological effects of arterial-like pressure on the human saphenous vein structure and physiology, and to compare the results to those achieved in the presence of a constant low pressure and flow mimicking the physiologic vein perfusion. While under both conditions we found an activation of Matrix Metallo-Proteases 2/9 and of microRNAs-21/146a/221, a specific effect of the arterial-like pressure was observed. This consisted in a marked geometrical remodeling, in the suppression of Tissue Inhibitor of Metallo-Protease-1, in the enhanced expression of TGF-β1 and BMP-2 mRNAs and, finally, in the upregulation of microRNAs-138/200b/200c. In addition, the veins exposed to arterial-like pressure showed an increase in the density of the adventitial vasa vasorum and of cells co-expressing NG2, CD44 and SM22α markers in the adventitia. Cells with nuclear expression of Sox-10, a transcription factor characterizing multipotent vascular stem cells, were finally found in adventitial vessels. Our findings suggest, for the first time, a role of arterial-like wall strain in the activation of pro-pathologic pathways resulting in adventitial vessels growth, activation of vasa vasorum cells, and upregulation of specific gene products associated to vascular remodeling and inflammation

Phospholipase activities in green coffee beans (Coffea arabica L.) harvested in different countries

Triacylglycerols (TAGs) are accumulated in specialised organelles called \u201coil bodies\u201d, which are enclosed in a phospholipid monolayer embedded with some unique proteins. Upon germination, such membranes are modified to allow the availability of TAGs as an energy source during early stages of seedling growth in oilseeds. This process occurs by the sequential and/or collective action of many hydrolytic enzymes, such as phospholipases, lipoxygenases and lipases that are associated to oil body membranes. In contrast, during seed storage, oilseed lipids may undergo lipolytic degradation processes leading to a wide range of metabolites potentially harmful for seed viability. In particular, green coffee endosperm consist of approx. 99% of the mature seed mass and contains many polyunsaturated fatty acids whose degradation leads to volatile compound formation through the oxylipin pathway. In spite of this, the enzymes involved in TAGs degradation (particularly lipases) are poorly studied. Therefore, the aim of this work was to evaluate the involvement of phospholipase activity in oil body membrane degradation during storage of green coffee (Coffea arabica L.) and to determine the correlations between storage lipid mobilization and maintenance of seed viability in beans harvested in different countries (Ethiopia, India, Kenya and Tanzania). Green coffee beans were frozen and powdered in liquid nitrogen and oil bodies were extracted with cold acetone. Phospholipase A1 and A2 activities were assayed in crude extracts by a fluorimetric method, using different probes. Such activities were just partially stimulated by free Ca2+, in contrast with what reported by others. Furthermore, PLA2 activity was assayed in a wide range of pH, evidencing two peaks of pH optimum. These results suggests that green coffee bean presents at least two isoforms of PLA2. Phospholipase profiles (PLA2 and total) were correlated with the provenience of the beans, showing a higher activity in those harvested in Ethiopia, while the lower was associated to beans from India

Acquired Complement Regulatory Gene Mutations and Hematopoietic Stem Cell Transplant–Related Thrombotic Microangiopathy

Abstract Hematopoietic stem cell transplant–related thrombotic microangiopathy (HSCT-TMA) is a severe complication whose pathophysiology is unknown. We describe 6 patients in which the disease was associated with complement regulatory gene abnormalities received from their respective donors. It is suggested that mutated and transplanted monocyte-derived cells are responsible for production of abnormal proteins, complement dysregulation, and, ultimately, for the disease. This observation might have important drawbacks as far as HSCT-TMA pathophysiology and treatment are concerned

Neurofeedback induced restoration on sensorimotor rhythm after 24h of hand immobilization.

In this study, we examined the effect of neurofeedback on EEG changes due to immobilization of the dominant hand. Desynchronization of the sensorimotor rhythms during motor imagery was used as a tool to investigate brain activity. The study is based on 8 healthy subjects who underwent immobilization of the dominant hand for 24 hours. The electrical activity of the sensorimotor region of the cerebral cortex was registered during mental imagery of hand movements before the immobilization, soon after its removal and after a single session of neurofeedback. The control of the feedback stimuli was based on changes in sensorimotor rhythms produced by imagination of movement. Preliminary results show that immobilization caused changes in alpha and beta rhythms that were rapidly reversed after a single session of neurofeedback. At the end of the full study, if the here presented observations will still hold, the neurofeedback protocol will be proposed for routine rehabilitation sessions in patients suffering partial or total limb disability