196,172 research outputs found
Un approccio biofisico integrato alla sindrome nefrosica su base autoimmune : caso clinico
No full textLa sindrome nefrosica autoimmune è spesso caratterizzata da frequenti recidive. Spesso risponde poco alla terapia steroidea e la sua gestione clinica può divenire difficile. Descriviamo un caso nel quale l’integrazione della terapia standard con un trattamento biofisico ha portato sia ad un miglioramento clinico sia alla scomparsa dei marcatori autoimmuni.Autoimmune nephrotic syndrome is often characterized by frequent recurrence. It is commonly associated with reduced response to steroid therapy and its clinical management may be challenging. We report a case in which the combination of standard therapy with a biophysical treatment resulted in both clinical improvement and disappearance of autoimmune markers
Biophysical approach to chronic kidney disease management in older patients
No full textChronic kidney disease (CKD) and its clinical progression are a critical issue in an aging population. Therefore, strategies aimed at preventing and managing the decline of renal function are warranted. Recent evidence has provided encouraging results for the improvement of renal function achieved through an integrated biophysical approach, but prospective studies on the clinical efficacy of this strategy are still lacking. This was an open-label prospective pilot study to investigate the effect of electromagnetic information transfer through the aqueous system on kidney function of older patients affected by stage 1 or 2 CKD.
Patients received biophysical therapy every 3 months over a 1-year period. Estimated glomerular filtration rate (eGFR) values were calculated using the CKD–Epidemiology Collaboration formula, and were recorded at baseline and at the end of treatment. Overall, 58 patients (mean age 74.8 ± 3.7 years) were included in the study.
At baseline, mean eGFR was 64.6 ± 15.5 mL/min, and it significantly increased to 69.9 ± 15.8 mL/min after 1 year (+5.2 ± 10 mL/min, p<0.0002). The same trend was observed among men (+5.7 ± 10.2 mL/min, p<0.0064) and women (+4.7 ± 9.9 mL/min, p<0.014). When results were analyzed by sex, no difference was found between the 2 groups.
Although further and larger prospective studies are needed, our findings suggest that an integrated biophysical approach may be feasible in the management of older patients with early-stage CKD, to reduce and prevent the decline of renal function due to aging or comorbidities
Cyclic response of 3D printed metamaterials with soft cellular architecture: The interplay between as-built defects, material and geometric non-linearity
No full textThe paper investigates the cyclic response of soft cellular materials undergoing repeated local instabilities. Our focus is mainly on the coupling between material non-linearities, geometric non-linearity as well as defects induced by 3D printing. Two paradigmatic lattices (triangular and hexagonal), each with its own distinct deformation mode and defect sensitivity, are examined, and the emergence of as-built material and geometric defects in the form of microporosity, strut thickness reduction, and nodal dispersion is studied via computed tomography and optical analyses. Experiments are carried out on the base material and lattice specimens for given cycling strains and cycle ratios. Numerical models are developed to understand the individual role of the main constitutive aspects of the base material, e.g. damage, creep, and visco-elasticity, as well as to assess the role of defects in each architecture. The results show that the activation of local buckling combined with the engagement of material non-linearities has multiple outcomes. It leads to local storage of inelastic strain, which in turn perturbs the lattice geometry after the second cycle and severely impacts the subsequent response, e.g. softening; it reduces the tangent modulus at zero strain; and it also decreases the maximum and minimum cyclic stresses. The detriment is further fueled by geometric deviations caused by 3D printing. Furthermore, a theoretical model is presented to obtain stress bound estimates of the stabilized response, hence offering guidelines for the design of 3D printed soft metamaterials under cycling loading. The paper concludes with a systematic discussion on the coupled role of non-linearities (material and geometry) and defects, and on the accuracy of the numerical and theoretical models herein presented
Response of an aluminium Schwarz triply periodic minimal surface lattice structure under constant amplitude and random fatigue
No full textThis paper presents an investigation about fatigue behaviour of an aluminium triply periodic minimal surface lattice structures, printed with Selective Laser Melting. Aim of the paper is to experimentally characterize constant and variable amplitude fatigue strength and to assess if current methodologies for predicting random fatigue strength of solid materials can be extended also to lattice structures, in a homogenized setting. The investigation is complemented by a detailed analysis of samples fracture surface, corroborated by numerical analyses, and a comprehensive discussion on the evolution of the damage observed in the experiments
Multiaxial static strength of a 3D printed metallic lattice structure exhibiting brittle behavior
No full textThis paper focuses on numerical the prediction of multiaxial static strength of lattice structures. We analyze a body-centered cubic cell printed with Selective Laser Melting in AlSi10Mg aluminum alloy. Parent material is experimentally characterized, and the Gurson-Tveergard-Needleman (GTN) damage model is calibrated to predict failure in numerical simulations. The GTN model is used to predict failure of the lattice structures exhibiting brittle localized fracture, and it is validated through static tests. The results of experimental tension/compression monotonic tests on lattice samples are compared with the results of numerical simulations performed on as-built geometry reconstructed by X-ray computed tomography, showing a good correlation. Combining the damage model with computational micromechanics, multiaxial loading conditions are simulated to investigate the effective multiaxial strength of the lattice material. Yielding and failure loci are found by fitting a batch of points obtained by some multiaxial loading simulations. A formulation based on the criterion proposed by Tsai and Wu (1971) for anisotropic materials provides a good description of yielding and failure behavior under multiaxial load. Results are discussed, with a specific focus on the effect of as-built defects on multiaxial strength, by comparing the resistance domains of as-manufactured and as-designed lattices
Assessment of multiaxial fatigue life prediction methodologies for Inconel 718
No full textFatigue life prediction methodologies for the assessment of the structural integrity of safety critical components in modern turbine engines require a close integration of advanced multiaxial fatigue life prediction procedures and of specific multiaxial tests, representative of the service conditions of turbine engine components and materials. The objective of the research work presented in this paper is to extend currently employed methodologies for the assessment of fatigue strength of turbine engines disks by integrating suitable multiaxial fatigue criteria and test results of multiaxial fatigue experiments conducted on Inconel 718 material at temperatures similar to those experienced by the disc materials during service. Smooth tubular specimens of Inconel 718 have been employed for conducting tension/torsion strain controlled high temperature fatigue tests. Specimens have been cut out from forged parts utilised for the production of engine discs, thus preserving the typical properties of disc materials (microstructure, basic mechanical properties, etc.). Different models/criteria have been evaluated by comparing fatigue life predictions and multiaxial fatigue experiments. It’s well known that agreement of life predictions with experimental life is strongly affected not only by the choice of the multiaxial fatigue criteria but also by the way the reference fatigue data are integrated in the criteria. Therefore, specific multiaxial fatigue tests have been carried out, in order to validate and to improve the assessment capabilities of the lifing procedures. Moreover, multiaxial fatigue tests permit advances in the basic understanding of materials behaviour that might be utilised in the processes of declaring component service lives
A TOOL FOR THE STRUCTURAL INTEGRITY ASSESSMENT OF TURBINE DISKS: PROBABILISTIC AND NUMERICAL BACKGROUND
No full textRotor disks for gas turbines are heavy components and are usually designed following a safe-life approach, where the low-cycle fatigue analysis is carried out referring to design life curves with suitable probabilistic margins. However, in the case of such a heavy component there is the possibility of rare oc- currence of undetected defects or, better, the need to identify the defect acceptability for the different rotor regions (considering stress, temperature, mission profile).
In order to carry out such calculations for a turbine ro- tor disk a software named AStrID (Assessment of the Structural Integrity of Disks) has been developed in close cooperation be- tween Politecnico di Milano and Ansaldo Energia (AEN). This paper summarizes its background and some of the relevant fea- tures
Biophysical integrated approach for the management of early stages of CKD in elderly patients: a 12-month controlled study
No full textBackground: Chronic Kidney Disease (CKD) and its clinical evolution are an emerging issue, due to an increasingly aging population. Consequently, the evaluation of integrative strategies to manage the decline in renal function is warranted. The previous evidence indicates that a biophysical integrated approach can significantly improve renal function. Nevertheless, controlled trials assessing the clinical efficacy of this strategy are still needed. Methods: A 12-month controlled study was designed to assess the clinical outcome of a group of elderly patients affected by stage II/IIIa CKD randomly assigned to either control or biophysical treatment. In addition to the standard treatment with renin–angiotensin–aldosterone system inhibitors, the biophysical group underwent electromagnetic information transfer through aqueous system procedure every 3 months. Estimated glomerular filtration rate (eGFR), according to CKD–epidemiology collaboration formula, was calculated at baseline and every 3 months. Results: A total of 238 patients were included in the study, 118 (73.9 ± 3.8 years) in the biophysical therapy group and 120 (74.6 ± 4.2 years) in the control group. At baseline, mean eGFR was 69 ± 11.8 ml/min in the biophysical group and 70.7 ± 11.5 ml/min in the control group. After 1 year, eGFR was 74.1 ± 12.3 ml/min in the biophysical group, compared to 66.3 ± 11.9 ml/min in the control group, with a statistically significant difference between groups (p < 0.0001). The observed improvement in eGFR in the biophysical group was independent of age, gender, and antihypertensive treatment. Conclusion: This study shows a potential contribution of a biophysical integrated strategy to support renal function against its natural decline in the elderly, warranting further clinical evaluation
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