A macroscale, phase-field model for shape memory alloys with non-isothermal effects: influence of strain-rate and environmental conditions on the mechanical response

A Ginzburg-Landau model for the macroscopic behaviour of a shape memory alloy is proposed. The model is one-dimensional in essence, in that we consider the effect of the martensitic phase transition in terms of a uniaxial deformation along a fixed direction and we use a scalar order parameter whose equilibrium values describe the austenitic phase and the two martensitic variants. The model relies on a Ginzburg-Landau free energy defined as a function of macroscopically measurable quantities, and accounts for thermal effects; couplings between the various relevant physical aspects are established according to thermodynamic consistency. The theoretical model has been implemented within a finite-element framework and a number of numerical tests are presented which investigate the mechanical behaviour of the model under different conditions; the results obtained are analysed in relation to experimental evidences available in literature. In particular, the influence of the strain-rate and of the ambient conditions on the response of the model is highlighted.Comment: 23 pages research article, 13 figure

Redistribution of DNA topoisomerase II beta after in vitro stabilization of human erythroleukemic nuclei by heat or Cu++ revealed by confocal microscopy.

Using confocal laser scanning microscope and a monoclonal antibody we have examined by means of indirect immunofluorescence techniques the distribution of DNA topoisomerase II beta (the 180-kDa nucleolar isoform of topoisomerase II) following stabilization of isolated nuclei by exposure to moderate heat (37 degrees or 42 degrees C) or Cu++. In intact cells the antibody specifically decorated the nucleoli. The same pattern was maintained if nuclei were incubated at 0 degree C in a buffer containing spermine/spermidine/KCl or stabilized by means of 0.5 mM Cu++ for 10 minutes at 0 degree C in the same buffer. On the contrary, if stabilization was performed by incubating the nuclei either at 37 degrees or 42 degrees C, the immunoreactivity dispersed all over the nucleus, forming numerous speckles. This phenomenon was not detected if, in addition to spermine/spermidine/KCl, the incubation buffer also contained 5 mM Mg++ and the temperature was 37 degrees C. If the stabilization was performed at 42 degrees C, Mg++ failed to maintain the original distribution of DNA topoisomerase II beta, as seen in intact cells. The analysis on 2-D optical section showed the alteration of the nucleolar profile, particularly at 37 degrees C, even when the samples were treated with Mg++. The 3-D reconstruction figured out the irregularity of the surface at 37 degrees C and the variations of the volume occupied by the fluorescent figures. These were in close proximity to each other both in intact cells and in 0 degree C incubated nuclei; they showed a certain degree of shrinkage in 0 degree C plus Cu++ exposed samples (-20\% of the volume), and, on the contrary, the labeled structures were scattered in a volume increased two- or threefold when exposed to 37 degrees or 42 degrees C, respectively. The addition of Mg++ restored the original spatial relationship and volume at 37 degrees C, but not at 42 degrees C, where the volumetric analysis showed an increase of about 50\%. Our results demonstrate that heat stabilization of isolated nuclei in a buffer without Mg++ (i.e., a technique often employed to prepare the nuclear matrix or scaffold) cannot be considered an optimal procedure to maintain the original distribution of protein within the nucleus

A Computational Tool for Three-Point Hitch Geometry Optimisation Based on Weight-Transfer Minimisation

The weight-transfer effect, consisting of the change in dynamic load distribution between the front and the rear tractor axles, is one of the most impairing phenomena for the performance, comfort, and safety of agricultural operations. Excessive weight transfer from the front to the rear tractor axle can occur during operation or manoeuvring of implements connected to the tractor through the three-point hitch (TPH). In this respect, an optimal design of the TPH can ensure better dynamic load distribution and ultimately improve operational performance, comfort, and safety. In this study, a computational tool (the Optimiser) for the determination of a TPH geometry which minimises the weight-transfer effect is developed. The Optimiser is based on a constrained minimisation algorithm. The objective function to be minimized is related to the tractor front-to-rear axle load transfer during a simulated reference manoeuvre performed with a reference implement on a reference soil. Simulations are based on a dynamic model of the tractor-TPH-implement aggregate. The geometry determined by the Optimiser complies with the ISO-730 Standard functional requirements and other design requirements. The interaction between the soil and the implement during the simulated reference manoeuvre was successfully validated against experimental data. The simulation results show that the adopted reference manoeuvre is effective in triggering the weight-transfer effect, with the front axle load exhibiting a peak-to-peak value of 27.1 kN during the manoeuvre. A benchmark test was conducted starting from the geometry of a commercially available TPH; the test showed that the Optimiser, after 36 iterations, was able to find an optimised TPH geometry which allows to reduce the weight-transfer effect by 14.9%

Role of Mesenchymal Stem Cells in Counteracting Oxidative Stress\u2014Related Neurodegeneration

Neurodegenerative diseases include a variety of pathologies such as Alzheimer\u2019s disease, Parkinson\u2019s disease, Huntington\u2019s disease, amyotrophic lateral sclerosis, and so forth, which share many common characteristics such as oxidative stress, glycation, abnormal protein deposition, inflammation, and progressive neuronal loss. The last century has witnessed significant research to identify mechanisms and risk factors contributing to the complex etiopathogenesis of neurodegenerative diseases, such as genetic, vascular/metabolic, and lifestyle-related factors, which often co-occur and interact with each other. Apart from several environmental or genetic factors, in recent years, much evidence hints that impairment in redox homeostasis is a common mechanism in different neurological diseases. However, from a pharmacological perspective, oxidative stress is a difficult target, and antioxidants, the only strategy used so far, have been ineffective or even provoked side effects. In this review, we report an analysis of the recent literature on the role of oxidative stress in Alzheimer\u2019s and Parkinson\u2019s diseases as well as in amyotrophic lateral sclerosis, retinal ganglion cells, and ataxia. Moreover, the contribution of stem cells has been widely explored, looking at their potential in neuronal differentiation and reporting findings on their application in fighting oxidative stress in different neurodegenerative diseases. In particular, the exposure to mesenchymal stem cells or their secretome can be considered as a promising therapeutic strategy to enhance antioxidant capacity and neurotrophin expression while inhibiting pro-inflammatory cytokine secretion, which are common aspects of neurodegenerative pathologies. Further studies are needed to identify a tailored approach for each neurodegenerative disease in order to design more effective stem cell therapeutic strategies to prevent a broad range of neurodegenerative disorder

Outlining the mission profile of agricultural tractors through CAN-BUS data analytics

Tractor manufacturers need to know how farmers use their agricultural tractors for an optimal machine design. Tractor usage is not easy to assess due to the large variability of field operations. However, modern tractors embed sensors integrated into the CAN-BUS network and their data is accessible through the ISO 11,783 protocol. Even though this technology has been available for a long time, the use of CAN-BUS data for outlining the tractor usage is still limited, because a proper post-processing method is lacking. This study aimed to present a novel classification scheme of CAN-BUS data which permits to outline the tractor usage. On a tractor, a CAN-BUS data logger and a GNSS receiver were installed, and real-world data were recorded for 579 h. Thus, data was obtained in the most realistic condition. Tractor positions were classified using GIS layers while operating conditions were classified depending on the usage of the tractor's subsystems. The method highlights that showed to be able to detect the 97% of the logged data and that the tractor operated on the field in working, on idle, and moving duties for 65%, 18% and 16% of the time, respectively. The method allows a far more precise outline of tractor usage opening opportunities to obtain large benefits from massively collected CAN-BUS data

Simulazione di transizioni di fase diffusive e deformative

Il calcolo degli organi di macchina richiede una descrizione molto accurata delle caratteristiche del materiale;ciò non può prescindere dalla descrizione dei trattamenti termici ai quali il pezzo è stato sottoposto.La simulazione dei trattamenti termici degli acciai viene normalmente affrontata mediante modelli di naturafenomenologica che fanno largo uso di leggi empiriche per descrivere l’evoluzione della microstrutturaall’interno del pezzo. Tuttavia, l’impiego di leggi empiriche richiede un’apposita taratura dei parametri delmodello; inoltre tali leggi, per loro natura, non chiariscono fino in fondo le ragioni fisiche per le quali ifenomeni in gioco avvengono. Ne consegue che tale metodo è fortemente limitato nella sua generalità.Il problema può essere affrontato nella sua globalità, ossia prendendo in considerazione gli effetti termici,meccanici e di transizione di fase, partendo da una descrizione della struttura interna del materiale a scalamicroscopica ed inserita in un contesto termodinamicamente consistente.In particolare, in questo lavoro viene proposto un modello a parametri di fase alla scala microscopica capacedi descrivere trasformazioni di fase sia diffusive sia deformative e dunque di modellare, rispettivamente, latrasformazione da austenite a perlite e quella da austenite a martensite. Il modello, per la formulazione e lasua natura, risulta consistente con i principi della termodinamica e permette una descrizione delletrasformazioni diffusiva e deformativa e dei fenomeni termici in un contesto unificato.Le equazioni sulle quali si basa sono: l’equazione del moto, il bilancio della massa di carbonio (che porta allaequazione di Cahn-Hilliard) e l’equazione del calore completa, che deriva dal bilancio di energia interna. Acausa della natura non-locale del modello e della presenza di equazioni differenziali alle derivate parziali finoal quarto ordine, la soluzione del problema così formulato risulta complessa da un punto di vistacomputazionale; per questo motivo è stato messo a punto uno strumento numerico sofisticato ma robusto.Sono stati inoltre condotti alcuni test numerici che mostrano le potenzialità dell’approccio. Il modello risultacapace di cogliere le principali caratteristiche esibite alla scala microscopica dalle transizioni di fase perliticae martensitica, le interazioni fra queste e l’influenza dei fenomeni meccanici e termici

Towards a regional ocean forecasting system for the IBI (Iberia-Biscay-Ireland area): developments and improvements within the ECOOP project framework

The regional ocean operational system remains a key element in downscaling from large scale (global or basin scale) systems to coastal ones. It enables the transition between systems in which the resolution and the resolved physics are quite different. Indeed, coastal applications need a system to predict local high frequency events (inferior to the day) such as storm surges, while deep sea applications need a system to predict large scale lower frequency ocean features. In the framework of the ECOOP project, a regional system for the Iberia-Biscay-Ireland area has been upgraded from an existing V0 version to a V2. This paper focuses on the improvements from the V1 system, for which the physics are close to a large scale basin system, to the V2 for which the physics are more adapted to shelf and coastal issues. Strong developments such as higher regional physics resolution in the NEMO Ocean General Circulation Model for tides, non linear free surface and adapted vertical mixing schemes among others have been implemented in the V2 version. Thus, regional thermal fronts due to tidal mixing now appear in the latest version solution and are quite well positioned. Moreover, simulation of the stratification in shelf areas is also improved in the V2

Oxidative stress in Alzheimer's disease: In vitro therapeutic effect of amniotic fluid stem cells extracellular vesicles

Alzheimer's disease (AD) is characterized by abnormal protein aggregation, deposition of extracellular \u3b2-amyloid proteins (A\u3b2), besides an increase of oxidative stress. Amniotic fluid stem cells (AFSCs) should have a therapeutic potential for neurodegenerative disorders, mainly through a paracrine effect mediated by extracellular vesicles (EV). Here, we examined the effect of EV derived from human AFSCs (AFSC-EV) on the disease phenotypes in an AD neuron primary culture. We observed a positive effect of AFSC-EV on neuron morphology, viability, and A\u3b2 and phospho-Tau levels. This could be due to the apoptotic and autophagic pathway modulation derived from the decrease in oxidative stress. Indeed, reactive oxygen species (ROS) were reduced, while GSH levels were enhanced. This modulation could be ascribed to the presence of ROS regulating enzymes, such as SOD1 present into the AFSC-EV themselves. This study describes the ROS-modulating effects of extracellular vesicles alone, apart from their deriving stem cell, in an AD in vitro model, proposing AFSC-EV as a therapeutic tool to stop the progression of AD

Human dental pulp stem cells produce mineralized matrix in 2D and 3D cultures

The aim of this study was to characterize the in vitro osteogenic differentiation of dental pulp stem cells (DPSCs) in 2D cultures and 3D biomaterials. DPSCs, separated from dental pulp by enzymatic digestion, and isolated by magnetic cell sorting were differentiated toward osteogenic lineage on 2D surface by using an osteogenic medium. During differentiation process, DPSCs express specific bone proteins like Runx-2, Osx, OPN and OCN with a sequential expression, analogous to those occurring during osteoblast differentiation, and produce extracellular calcium deposits. In order to differentiate cells in a 3D space that mimes the physiological environment, DPSCs were cultured in two distinct bioscaffolds, Matrigel™ and Collagen sponge. With the addition of a third dimension, osteogenic differentiation and mineralized extracellular matrix production significantly improved. In particular, in Matrigel™ DPSCs differentiated with osteoblast/osteocyte characteristics and connected by gap junction, and therefore formed calcified nodules with a 3D intercellular network. Furthermore, DPSCs differentiated in collagen sponge actively secrete human type I collagen micro-fibrils and form calcified matrix containing trabecular-like structures. These neo-formed DPSCs-scaffold devices may be used in regenerative surgical applications in order to resolve pathologies and traumas characterized by critical size bone defects