205 research outputs found
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
AST: An OpenSim-based tool for the automatic scaling of generic musculoskeletal models
No full textBackground and objectives: The paper introduces a tool called Automatic Scaling Tool (AST) designed for improving and expediting musculoskeletal (MSK) simulations based on generic models in OpenSim. Scaling is a crucial initial step in MSK analyses, involving the correction of virtual marker locations on a model to align with actual experimental markers. Methods: The AST automates this process by iteratively adjusting virtual markers using scaling and inverse kinematics on a static trial. It evaluates the root mean square error (RMSE) and maximum marker error, implementing corrective actions until achieving the desired accuracy level. The tool determines whether to scale a segment with a marker-based or constant scaling factor based on checks on RMSE and segment scaling factors. Results: Testing on three generic MSK models demonstrated that the AST significantly outperformed manual scaling by an expert operator. The RMSE for static trials was one order of magnitude lower, and for gait tasks, it was five times lower (8.5 ± 0.76 mm vs. 44.5 ± 7.5 mm). The AST consistently achieved the desired level of accuracy in less than 100 iterations, providing reliable scaled MSK models within a relatively brief timeframe, ranging from minutes to hours depending on model complexity. Conclusions: The paper concludes that AST can greatly benefit the biomechanical community by quickly and accurately scaling generic models, a critical first step in MSK analyses. Further validation through additional experimental datasets and generic models is proposed for future tests
Stochastic modelling of muscle control during shoulder abduction
No full textThe intrinsic variability of the shoulder joint motion is a critical factor in the characterisation of the shoulder joint. However, traditional computational approaches struggle to account for it. On the other hand, the stochastic approach allows to identify a set of plausible solutions. In this study, the Myobolica toolbox, which yielded promising results in the lower limb, was employed to simulate a shoulder abduction, with twofold aims: to assess its generalisability to other joints, and to evaluate an electromyography (EMG)-informed version of Myobolica. Publicly available kinematics, EMG, and glenohumeral (GH) joint force data measured by an instrumented implant on a 64-year-old man executing three weighted shoulder abductions were used. A previously developed shoulder musculoskeletal model was employed to compute stochastic simulations informed and not with EMG data, sampling 1 × 105 solutions every 30 timeframes. The predicted GH joint force were compared to the experimental data, and the variance in the solutions across simulations was computed. Overall, the correlation between the GH joint force predicted by Myobolica and the experimental values increased when the EMG-based constraint was applied (from approximately R2 = 0.06, RMSE = 1.82 BW to R2 = 0.6, RMSE = 0.73 BW when all available EMG data were employed). Using EMG led to a reduction (from 2.3 to 0.65 BW) in the solution bandwidths. Providing EMG data to inform the simulations helped improve their accuracy. However, the results obtained otherwise remain promising. Additional work is required to minimize the computational cost of the Myobolica approach. A consistency gap between experimental data and the model is reported
Un agire personale e insieme collettivo. Intervista all’attrice e performer Chiara Bersani
No full textChiara Bersani is an Italian artist working in the performing arts. Her formative path takes place mainly in the field of theatrical research with influences from contemporary dance. Her research as an interpreter and author is based on the concept of the “Political Body” and the creation of practices aimed at training its presence and action. The “manifest” work of this research is Gentle Unicorn (2017).Chiara Bersani è un'artista italiana attiva nell’ambito delle arti performative. Il suo percorso formativo si svolge prevalentemente nel campo della ricerca teatrale con contaminazioni dalla danza contemporanea. Come interprete e autrice la sua ricerca si basa sul concetto di "Corpo politico", sulle relative pratiche che ne sondano la presenza e l’azione. Lo spettacolo "manifesto" di questa ricerca è Gentle Unicorn (2017)
Myobolica: a stochastic approach to estimate physiological muscle control variability
No full text: The inherent redundancy of the musculoskeletal systems is traditionally solved by optimizing a cost function. This approach may not be correct to model non-adult or pathological populations likely to adopt a "non-optimal" motor control strategy. Over the years, various methods have been developed to address this limitation, such as the stochastic approach. A well-known implementation of this approach, Metabolica, samples a wide number of plausible solutions instead of searching for a single one, leveraging Bayesian statistics and Markov Chain Monte Carlo algorithm, yet allowing muscles to abruptly change their activation levels. To overcome this and other limitations, we developed a new implementation of the stochastic approach (Myobolica), adding constraints and parameters to ensure the identification of physiological solutions. The aim of this study was to evaluate Myobolica, and quantify the differences in terms of width of the solution band (muscle control variability) compared to Metabolica. To this end, both muscle forces and knee joint force solutions bands estimated by the two approaches were compared to one another, and against (i) the solution identified by static optimization and (ii) experimentally measured knee joint forces. The use of Myobolica led to a marked narrowing of the solution band compared to Metabolica. Furthermore, the Myobolica solutions well correlated with the experimental data (R2 = 0.92, RMSE = 0.3 BW), but not as much with the optimal solution (R2 = 0.82, RMSE = 0.63 BW). Additional analyses are required to confirm the findings and further improve this implementation
Exploring muscle recruitment by Bayesian methods during motion
No full textThe human musculoskeletal system is characterized by redundancy in the sense that the number of muscles
exceeds the number of degrees of freedom of the musculoskeletal system. In practice, this means that a given
motor task can be performed by activating the muscles in infinitely many different ways. This redundancy is
important for the functionality of the system under changing external or internal conditions, including different
diseased states. A central problem in biomechanics is how, and based on which principles, the complex of
central nervous system and musculoskeletal system selects the normal activation patterns, and how the patterns
change under various abnormal conditions including neurodegenerative diseases and aging. This work lays the
mathematical foundation for a formalism to address the question, based on Bayesian probabilistic modeling of
the musculoskeletal system. Lagrangian dynamics is used to translate observations of the movement of a subject
performing a task into a time series of equilibria which constitute the likelihood model. Different prior models
corresponding to biologically motivated assumptions about the muscle dynamics and control are introduced.
The posterior distributions of muscle activations are derived and explored by using Markov chain Monte Carlo
(MCMC) sampling techniques. The different priors can be analyzed by comparing the model predictions with
actual observations
Modeling Human Suboptimal Control: A Review
No full textThis review paper provides an overview of the approaches to model neuromuscular control, focusing on methods to identify nonoptimal control strategies typical of populations with neuromuscular disorders or children. Where possible, the authors tightened the description of the methods to the mechanisms behind the underlying biomechanical and physiological rationale. They start by describing the first and most simplified approach, the reductionist approach, which splits the role of the nervous and musculoskeletal systems. Static optimization and dynamic optimization methods and electromyography-based approaches are summarized to highlight their limitations and understand (the need for) their developments over time. Then, the authors look at the more recent stochastic approach, introduced to explore the space of plausible neural solutions, thus implementing the uncontrolled manifold theory, according to which the central nervous system only controls specific motions and tasks to limit energy consumption while allowing for some degree of adaptability to perturbations. Finally, they explore the literature covering the explicit modeling of the coupling between the nervous system (acting as controller) and the musculoskeletal system (the actuator), which may be employed to overcome the split characterizing the reductionist approach
A study on Correggio wall paintings: characterization of technique and materials of Abbey Church of S. Giovanni Evangelista in Parma, Italy
No full textThis study deals the materials of the sub- arch of the Del Bono chapel of the Abbey Church of S. Giovanni Evangelista in Parma, Italy, datable around 1523. The author of the painting is Antonio Allegri, known as Correggio (1489 – 1534), considered one of the greatest painters of the sixteenth century. Optical microscopy, micro-Raman spectroscopy, micro-Fourier Transform Infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and gas chromatography coupled with mass spectrometry were selected in order to provide the higher set of significant data, limiting as much as possible sampling. The analysis has allowed to identify the pigments, characteristic of the epoch. The Correggio’s palette is composed by mineral pigments, sometimes expensive such as lapis lazuli, azurite and cinnabar, together with a wide range of earths or by synthetic pigments like smalt blue. From the amino acid content determination through GC/MS it was shown that, for all samples examined, the protein fraction is to be attributed to the presence of a mixture of egg and animal glue, present as binders in the samples containing lazurite, smalt, hematite, green earth and goethite. This allows to assume the use of a secco technique, also with pigments that do not need the employment of organic binding media on wall. For the gilding sample the hypothesis is that Au foil had been applied on a brown background where the Au foil is applied on the oil-based missione
Personalizzazione e validazione di modelli muscoloscheletrici con dati di "Knee Grand Challenge"
No full textLa modellazione muscoloscheletrica consente di visualizzare pattern motori complessi e di indagare variabili difficilmente misurabili altrimenti. Esistono modelli muscoloscheletrici “generici”, completi e rappresentativi di soggetti sani adulti, e sono in grande sviluppo modelli “soggetto-specifici”, caratterizzati da parametri personalizzati per essere resi più anatomicamente accurati. Tuttavia, la personalizzazione è costosa perché richiede tempo, esami clinici, denaro. L’obiettivo di questo documento è indagare come personalizzazioni progressive del modello, svolte esclusivamente utilizzando informazioni mediche del soggetto, influenzino i risultati delle simulazioni validando i risultati predetti dai modelli tramite confronto con il dato sperimentale effettuando una analisi SPM.
Il soggetto è un uomo (86 anni, altezza 180cm, peso 75Kg) dotato di una protesi strumentata al ginocchio sinistro. Utilizzando il dataset della Grand Challenge 5, sono stati sviluppati quattro modelli muscoloscheletrici caratterizzati da un livello di personalizzazione crescente. Inizialmente, sono stati confrontati su OpenSim due modelli generici opportunamente scalati sulle dimensioni del soggetto. Poi, è stato selezionato un modello tra i precedenti e ne è stata personalizzata la forza massimale isometrica di un gruppo di muscoli. In seguito, sono state personalizzate le geometrie ossee creando un modello soggetto-specifico utilizzando il software NMSBuilder e le forze personalizzate nella fase precedente.
Lo studio, in accordo con la letteratura, conferma che la personalizzazione dei modelli MS influisce notevolmente sull’accuratezza delle predizioni migliorandola sensibilmente. I modelli generici di partenza mostrano profili di forza di contatto al ginocchio lontani dal valore sperimentale misurato sul soggetto (r2≈0.6, RMSE≈0.6 BW). I modelli personalizzati mostrano migliore accuratezza sia nell’analisi SPM sia nella valutazione mediante indici statistici
Nano-modificazioni superficiali per impianti dentali
No full textL'edentulismo è un evento ragionevolmente considerabile invalidante dal momento che va sia a ledere la funzionalità dei denti sia a creare un disagio psicologico nel soggetto. Da anni, la più comune soluzione all'edentulismo è l'applicazione di impianti dentali ed annesse protesi dentarie. Nella progettazione degli impianti, denominati fixture, gli aspetti cruciali di cui è necessario tenere conto sono numerosi, a partire dalla biocompatibilità, dalla riduzione dei tempi di recupero post-operatorio e da proprietà meccaniche adatte ai carichi del processo masticatorio. Questi aspetti, per quanto necessari ed imprescindibili, erano tuttavia impossibili da valutare fino a qualche anno fa. Al giorno d'oggi, grazie anche agli avanzamenti tecnologici di altri campi di ricerca, sono diventati più accessibili. Lo scopo di questo documento è raccogliere ed approfondire ricerche scientifiche di frontiera e trial clinici che hanno come oggetto l'utilizzo delle più recenti tecnologie per la modificazione superficiale a livello nanometrico dell'impianto dentale. La ricerca è orientata verso modificazioni, alla nanoscala, di rugosità, bagnabilità, composizione chimica superficiali al fine di migliorare determinate caratteristiche quali adesione cellulare superficiale, osteointegrazione, proprietà antibatteriche ed altre specificate nell'elaborato
- …
