Marco Baldovin 1 ; Andrea Plati 2; Alberto Petri 1; Andrea Gnoli 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay -- Orsay, France
Frictional forces are a key ingredient of any physical description of the macroscopic world, as they account for the phenomena causing transformation of mechanical energy into heat. They are ubiquitous in nature, and a wide range of practical applications involve the manipulation of physical systems where friction plays a crucial role.
In [1], we apply control theory to dynamics governed by the paradigmatic rate- and state-variable law for solid-on-solid friction. Several control problems are considered for the case of a slider dragged on a surface by an elastic spring. By using swift state-to-state protocols, we show how to drive the system between two arbitrary stationary states characterized by different constant sliding velocities in a given time. Remarkably, this task proves to be feasible even when specific constraints are imposed on the dynamics, such as preventing the instantaneous sliding velocity or the frictional force from exceeding a prescribed bound. The derived driving protocols also allow to avoid a stick-slip instability, which instead occurs when velocity is suddenly switched. By exploiting variational methods, we also address the functional minimization problem of finding the optimal protocol that connects two steady states in a specified time, while minimizing the work done by the friction.
An experimental set-up for the validation of the presented results is also discussed.
References
[1] Andrea Plati, Alberto Petri, and Marco Baldovin. "Control of friction: shortcuts and optimization for the rate-and state-variable equation." arXiv preprint arXiv:2407.03696 (2024).
Emanuela Bianchi 1,2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Institut für Theoretische Physik, TU Wien, Wiedner Hauptstraße 8-10, A-1040, Wien, Austria
Globular proteins and recently synthesized colloids engineered with differently charged surface regions exhibit complex, direction-dependent interactions, characterized by a reduced bonding valence and a competition between like-charge repulsion and opposite-charge attraction. Understanding the large-scale behavior of heterogeneously charged particles is thus crucial for exploring both biological processes, such as the liquid-liquid phase separation of globular proteins, and for designing target structures with specific properties at the nano- and micro-scale.
Over the past decade, we developed a mean-field theoretical framework to describe the effective interactions between heterogeneously charged objects, based on the linearized Poisson-Boltzmann approach [1,2]. In parallel, we introduced a simple coarse-grained model that, within well-defined limits, accurately captures the mean-field potential [1,3]. This model is straightforward to implement in Monte Carlo and Molecular Dynamics (MD) simulations [4], enabling the exploration of how varying parameters -- such as net particle charge and surface charge pattern -- affect the self-assembly of these particles.
As illustrative examples, I will discuss our findings on how non-uniform electrostatics at the particle surface can influence the self-assembly of ordered phases [2] as well as the liquid-liquid phase separation [3].
References
[1] Soft Matter, 7, 8313 (2011) and J.Chem. Phys., 142, 114905 (2015),
[2] A. Gnidovec, E. Locatelli, S. Copar, A.Bozic and E.Bianchi, arXiv:2411.03045
[3] D.Notarmuzi, E.Locatelli and E.Bianchi, in preparation
[4] D.Notarmuzi, S.Ferrari, E.Locatelli and E.Bianchi, submitted
[5] Nanoscale, 9, 1956 (2017) and Current Opinion in Colloid & Interface Science, 30, 18 (2017)
[6] Soft Matter, 20, 7601(2024) and D.Notarmuzi and E.Bianchi, Communications Physics, 7, 412 (2024)
Valentina Brosco
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
In this talk, I present an overview of current open challenges in the development of quantum technologies and explore how complex systems and materials provide promising pathways to innovative solutions. Drawing on recent research, I describe some situations where complexity enables advanced functionalities, including protected qubit encoding, quantum sensing, enhanced quantum control, and optimized quantum networking. I then focus on specific examples including: the flowermon, a superconducting qubit protected by the symmetry of a twisted d-wave heterostructure; a novel quantum network optimization framework that bridges classical network theory with quantum communication; and an innovative quantum control technique that intertwines random walks with geometric phases. Together, these examples demonstrate the power of integrating quantum and classical complexity approaches.
Silvia Capuani 1; Alessandra Maiuro 1,2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Physics Dpt. Sapienza University of Rome and CNR-ISC
Nuclear Magnetic Resonance (NMR) molecular diffusion plays a pivotal role in modern medical diagnostics by enabling noninvasive characterization of the microstructural and functional properties of biological tissues independent of the clinical image resolution. In diffusion-weighted NMR, the measured signal is proportional to the Fourier transform of the propagator describing the molecular motion. This relationship provides a framework to probe tissue architecture and detect alterations in cellular environments. Models describing the decay of diffusion-weighted NMR signals enable quantitative analysis of diffusion dynamics, providing insights into tissue composition and integrity with micron-level linear resolution when the linear resolution of clinical NMR images is 1 mm. Such models then enable early diagnosis of pathological changes, including neurodegenerative diseases, cancers, and ischemic conditions, by capturing subtle variations in water mobility and cell density. Consequently, diffusion NMR techniques have emerged as essential tools to advance precision medicine and improve clinical outcomes. Starting from diffusion theory and the issues related to diffusion models, we will show how to extract topological and microstructural information from the signal behavior in heterogeneous and complex samples and then show medical diagnostic applications developed in collaboration with the Policlinico Umberto I, the IRCCS Santa Lucia and the Policlinico di Tor Vergata in Rome.
Alessandra Maiuro 1,3, Lucia Manganaro 2, Silvia Capuani 3
1. Physics Dpt. Sapienza Università di Roma
2. Policlinico Umberto I di Roma, Sapienza
3. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Diffusion-based magnetic resonance imaging (MRI) has emerged as a powerful noninvasive diagnostic tool for women's health, providing detailed information about tissue microstructure and physiology. This presentation highlights its applications in the diagnosis of endometrial and cervical cancers, as well as fetal and placental assessments. In oncology, diffusion-weighted imaging (DWI) and spatially representative maps of molecular diffusion parameters obtained through the use of diffusion patterns improve tumor detection, staging, and treatment monitoring by characterizing cell density and tissue architecture. For endometrial and cervical cancer, diffusion-based MRI with diffusion patterns and diffusion kurtosis offers improved sensitivity and specificity, aiding in early diagnosis and precise assessment of tumor infiltration. In prenatal care, diffusion-based MRI of biological water in tissues allows detailed visualization of fetal and placental structures, allowing evaluation of placental function, fetal brain development, and early identification of abnormalities. These capabilities support timely interventions and personalized care plans. Therefore, the integration of diffusion-based MRI into clinical practice represents a significant advance in the diagnostic assessment of women's health conditions, ensuring better outcomes through early and accurate detection. In addition to the results obtained in collaboration with the Policlinico Umberto I in Rome, the limitations that need to be overcome and the strategies we are adopting to introduce this type of diagnostics as a conventional diagnostic will be highlighted. These limitations concern the movement of the patient and especially of the fetus, which leads to image artifacts and loss of resolution.
Valeria Stagno 1,2 , Elisa Villani 1,2 , Silvia Capuani 2
1. Earth Sciences Dpt. Sapienza University of Rome
2. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Nuclear Magnetic Resonance (NMR) microimaging and diffusion studies represent powerful, non-invasive techniques for investigating wood's structural and moisture-related properties. This research explores the application of NMR methods at both high and low magnetic fields to assess wood samples, focusing on their relevance to cultural heritage conservation. High-field NMR microimaging provides detailed spatial resolution, enabling the visualization of internal features and water distribution within the wood matrix. Complementarily, low-field NMR using portable magnets offers a flexible and field-deployable approach, ideal for in situ analyses of historical wooden artifacts. Diffusion NMR measurements by using the quantification of molecular diffusion anisotropy, restricted diffusion, and tortuosity parameters are employed to characterize pore structures and assess moisture mobility, providing insights into wood degradation processes and conservation treatments. The combination of high-resolution imaging and portable techniques offers a comprehensive analytical framework, enhancing the preservation strategies for cultural heritage objects made of wood.
Alessandra Maiuro 1,2 , Giulio Costantini 2, Alessandro Taloni 2, Silvia Capuani 2
1. Physics Dpt. Sapienza University of Rome
2. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Currently, the new frontier of early diagnostics relies on NMR imaging investigations based on molecular diffusion models. Understanding the nature of molecular dynamics is crucial before applying MRI diffusion models to analyze experimental data. Applying a model that does not reflect the true molecular dynamics of biological water in tissues would lead to biased results. This work presents a comprehensive framework that integrates theoretical analysis, simulations, and experimental validation to identify the type of dynamics that governs molecular motion. We describe key theoretical principles and criteria to distinguish between different dynamic regimes, such as free diffusion, restricted diffusion, and anomalous diffusion. Through numerical simulations, we demonstrate how dynamic signatures can be extracted and classified before model fitting. Experimental NMR measurements further validate our approach, showing its applicability to complex systems. This methodology serves as a guide for researchers to ensure the appropriate model selection and accurate interpretation of diffusion data, ultimately improving the reliability of NMR studies in various scientific fields, including the most important one, medical diagnostics.
Martina Trocchi 1; Alessia Nava 2; Luca Bondioli 3; Silvia Capuani 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Dip. di SCIENZE ODONTOSTOMATOLOGICHE E MAXILLO-FACCIALI, Sapienza University of Rome
3. Dip. di antropologia Università di Padova and Polish Academy of Science; CNR-ISC
The study of archaeological and fossil teeth provides fundamental information on the biology, health, and developmental history of past populations. In this context, the application of nuclear magnetic resonance (NMR) microimaging emerges as an innovative and complementary technique to traditional X-ray microtomography with CT or synchrotron radiation. Unlike X-ray methods, NMR microimaging offers a different visualization by revealing fine details of dentine microstructures, including growth lines, microtubules, the dentine-enamel junction, and morpho-functional features, allowing precise reconstructions of tooth development. In addition, NMR allows the identification of non-specific pathological markers, which are crucial for the diagnosis of non-specific diseases and stress episodes. These results highlight the value of NMR microimaging as a powerful tool for virtual histology of teeth, providing complementary data that improve our ability to analyze and interpret the biological and cultural history preserved in ancient teeth. We will show results obtained from teeth of Homo Erectus (1 million years ago), Neolithic (6000 BC), Gravettian (20,000 BC), Neanderthal (40,000 BC), and modern teeth obtained with both micro CT and NMR microimaging. The results are validated by histology.
Maurizio Carbone 1; Lorenzo Piro 2; Robin A. Heinonen 2; Luca Biferale 2; Antonio Celani 3; Massimo Cencini 1;
1. Istituto dei Sistemi Complessi, CNR - Roma Taurini
2. Department of Physics & INFN, University of Rome “Tor Vergata” - Rome;
3. Quantitative Life Sciences, The Abdus Salam International Centre for Theoretical Physics - Trieste
Olfactory search is a ubiquitous behavior in living organisms for locating nutrients or mates and plays a major role in robotic search-and-rescue operations, where sources of chemicals must be promptly localized. The searcher (agent) navigates an underlying flow where tracers emitted from a source (target) undergo stretching and diffusion, while turbulence renders odor detections sparse and patchy (Celani et al., PRX, 2014). In biological systems, target motion typically transitions from ballistic at small scales to diffusive at larger scales, facilitating nutrient foraging while complicating predator pursuit (Visser and Kiørboe, Oecologia, 2006).
Motivated by this coexistence of ballistic and diffusive regimes, we propose a heuristic strategy for agents to locate a moving target undergoing a persistent random walk. Heuristic strategies, unlike exact approaches based on the associated Bellman equation (Kaelbling et al., Artificial Intelligence, 1998), define the agent motion based on cost functions of the belief about the target's state. Bayesian inference is used to update the agent's belief through the likelihood of detections, encapsulating a minimal model of a turbulent flow advecting the odor clues.
Our approach builds on infotaxis (Vergassola et al., Nature, 2007), a prototypical heuristic strategy that has proven robust and effective for locating stationary targets. However, for moving targets, infotaxis leads to excessive exploration rather than direct pursuit once the target is partially localized. To address this limitation, we introduce a hybrid strategy that combines infotaxis with a greedy policy derived from the Bellman equation under the assumption of perfect target-state knowledge. This integration significantly reduces both the mean and variance of search times.
This work is supported by the project PRIN 2022 CO-SEARCH, Protocollo n. 202249Z89M, CUP B53D23003920006.
A Cardinali 1,2 ; B Coppi 3; M Tavani 4; V Vittorini 4
1. Istituto dei Sistemi Complessi, CNR - Torino
2. Politecnico Torino
3. MIT-Boston
4. INAF-Roma
The “Fermi Bubbles” are two giant gamma-ray emitting configurations in the form of bubbles that extend above and below the Galactic plane. They are characterized by a smooth surface, sharp edges, and an almost flat intensity distribution. They were discovered in 2010 by the Fermi Telescope and detected in the energy range 1-100GeV. We propose a novel theoretical model to explain the process involved in the “Fermi bubbles” phenomenon. The model is based on the “in situ” generation of an energetic electron population powered by unstable electromagnetic waves triggered by a non-relativistic outflow of matter escaping from the Galactic Center region. A hadronic outflow crossing the magnetic field in the Galactic halo of low-density plasma can induce an electromagnetic instability in the “lower hybrid” frequency range (between the ion and electron cyclotron frequencies). These lower-hybrid waves propagate along the magnetic field lines in the halo and can accelerate, via resonant Landau damping, the thermal electrons up to energies of order of hundreds of GeV. This energetic electron population, localized in a thin boundary layer of the halo, radiates by synchrotron emission and by Inverse Compton scattering. An evaluation of the radiation emission and a comparison with spectral data is presented. This model successfully explains in a natural way the GeV spectral properties of the “Fermi bubbles” as well as its radio and X-ray emissions.
Massimo Cencini 1, Marie Sellier-Prono 2, David Kleinfeld 3, Massimo Vergassola 2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Laboratoire de Physique, Ecole Normale Superieure, CNRS, PSL Research University, Sorbonne University -- Paris France
3. Department of Physics, University of California - San Diego, La Jolla USA
Coupling among oscillators in spatially-extended systems can induce locking of their frequency at a common value. In the presence of spatial non-homogeneities, locking of different regions at different frequencies leads to parcellation, i.e., a series of synchronized clusters (plateaus). Motivated by peristalsis and vasomotion, we consider a Ginzburg-Landau (GL) model with a gradient of natural frequencies. We determine the scaling of the number of plateaus and their typical length vs. dynamical parameters. We also show that plateaus are separated by defects, where the amplitude of the GL field periodically vanishes and phase differences are reset. We consider both Dirichlet and no-flux boundary conditions. In the former case we use asymptotic methods to determine the field profile around defects. For no-flux boundary conditions, we relate the stability phase diagram and defects’ prodromes to the spectrum of the non-Hermitian Bloch-Torrey equation originally introduced for nuclear magnetic resonance. In the non-linear regime, we trace the formation of defects to a non-linear renormalization of the diffusivity, which leads to spatially-modulated negative values and an instability that drives amplitude modulation. Applications and implications of the results to biophysical systems is discussed.
Salvatore Chiavazzo 1; Davide Pierangeli 1,2
1. Physics Department, Sapienza University of Rome, 00185 Rome, Italy ;
2. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Networks of coupled nonlinear oscillators are attracting considerable interest from optics to electronics thanks to their application in unconventional computing. These systems solve the Ising model, which maps to many NP-hard combinatorial optimization problems, showcasing computational advantages over digital hardware. However, Ising machines based on nonlinear oscillators are still challenging to scale and speed up. We propose nonlinear polarization oscillators as the building block of a novel photonic Ising machine. We theoretically and numerically investigate two electromagnetic waves co-propagating and interacting in a third-order nonlinear material, showing they behave as a system of two-dimensional coupled nonlinear oscillators on the Poincaré sphere. We find how the polarization maps an Ising spin and show its control by all-optical interaction. Our study opens the route to the realization of the first Ising machine that is based on the polarization of light.
Giulio Cimini 1,2,3; Giulia Fischetti 4; Anna Mancini 1,2; Alessandro Vespignani 5; Guido Caldarelli 4,3,6,7
1. Physics Dept. and INFN, University of Rome Tor Vergata, 00133 Rome (Italy)
2. Enrico Fermi Research Center, 00184 Rome (Italy)
3. Istituto dei Sistemi Complessi, CNR - Roma Taurini
4. DMSN, Ca' Foscari University of Venice, 30172 Mestre (Italy)
5. MOBS Lab, Northeastern University, Boston MA 02115 (USA)
6. London Institute for Mathematical Sciences (LIMS), London W1S4BS (UK)
7. Istituto dei Sistemi Complessi, CNR - Roma Taurini
The Worldwide Air Transportation Network (WAN) is a key infrastructure of our society, allowing for the large-scale mobility of people and, as a side effect, for the propagation of diseases. Despite much effort has been put into understanding the topological structure of the network, an effective framework to model passenger fluxes in the WAN is still missing. In this work we show that the WAN can be statistically reconstructed using a family of maximum entropy network models that employ the flow of passengers at each airport as node fitnesses. We consider different model versions accounting for key structural features of the WAN: the geographical distance between airports, the community structure of the network and the super-linear relation between passenger flows and number of flights at each airport. We successfully test these models in reconstructing both the binary and weighted structure of the network on different scales, and in reproducing the epidemiological curves of SIR meta-population dynamics taking place on the network. Besides shedding light on the most important features for modeling the WAN, our framework can thus be used whenever detailed air transportation data is missing.
Alessandro Coppo 1; Luca Chirolli 2; Nicola Poccia 3; Uri Vool 4; Valentina Brosco 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Quantum Research Center, Technology Innovation Institute, P.O. Box 9639 Abu Dhabi, United Arab Emirates
3. Leibniz Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany & Department of Physics, University of Naples Federico II, Via Cintia, Naples 80126, Italy
4. Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
Supersymmetry (SUSY) is a theoretical framework relating bosonic and fermionic space-time degrees of freedom extensively scrutinized in particle physics as an extension of the Standard Model. However, despite having the virtue of taming ultraviolet divergences and tackling hierarchy problems, no experimental evidence for SUSY partners has been found, suggesting that SUSY, if present in the space-time, must be realized only at very high energy scales. On the other hand, SUSY is not tied to space-time and can be realized and experimentally tested at low energy in condensed matter physics constructing unconventional quantum devices marking some relevant properties which emerge from the corresponding energy spectrum.
Here I present a novel device comprising two twisted cuprate Josephson junctions integrated in a Superconducting Quantum Interference Device (SQuID) loop and threaded by an external magnetic flux. The high-tunability of the device allows to explore various regimes with difference coherence properties hosting respectively: a symmetric, "twist-based", double-well potential, a “plasmonic” potential, and a “flux-biased” double-well potential. The possibility of realizing such an extensive phase diagram is related to the d-wave nature of the order parameter allowing peculiar symmetries on the Hamiltonian. They can be used to encode and significantly tune a topologically protected qubit called flowermon in the “twist-based” regime. Moreover, the emergence of a second non-trivial, “flux-biased”, regime is granted by the opportunity of concretely realizing SUSY in the superconducting phase. SUSY shapes the energy spectrum with one non-degenerate ground-state and all other states degenerate in pairs and triggers sharp modifications in the system coupling to external noise fluctuations and, consequently, in the decoherence mechanisms.
Giulio Costantini 1; Marco Baldovin 1; Fabio Cecconi 1; Carlo Guardiani 2; Angelo Vulpiani 3
1. Istituto dei Sistemi Complessi, CNR - Roma
2. Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma Sapienza - Rome; Istituto dei Sistemi Complessi, CNR - Rome;
3. Dipartimento di Fisica, Università di Roma Sapienza - Rome
Correlation analysis and its close variant principal component analysis are tools widely applied to predict the biological functions of macromolecules in terms of the relationship between fluctuation dynamics and structural properties. However, since this kind of analysis does not necessarily imply causation links among the elements of the system, its results run the risk of being biologically misinterpreted. By using as a benchmark the structure of ubiquitin, we report a critical comparison of correlation-based analysis with the analysis performed using two other indicators, response function and transfer entropy, that quantify the causal dependence. The use of ubiquitin stems from its simple structure and from recent experimental evidence of an allosteric control of its binding to target substrates. We discuss the ability of correlation, response and transfer-entropy analysis in detecting the role of the residues involved in the allosteric mechanism of ubiquitin as deduced by experiments. To maintain the comparison as much as free from the complexity of the modeling approach and the quality of time series, we describe the fluctuations of ubiquitin native state by the Gaussian network model which, being fully solvable, allows one to derive analytical expressions of the observables of interest. Our comparison suggests that a good strategy consists in combining correlation, response and transfer entropy, such that the preliminary information extracted from correlation analysis is validated by the two other indicators in order to discard those spurious correlations not associated with true causal dependencies.
Carlo Danieli 1; Laura Pilozzi 1,2; Claudio Conti 3,2; Roberta Citro 4; Valentina Brosco 1
1 . Istituto dei Sistemi Complessi, CNR - Roma
2 . Research Center Enrico Fermi, Via Panisperna 89a, 00184 Rome, Italy
3 . Department of Physics, University of Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy
4 . Department of Physics “E.R. Caianiello”, University of Salerno, Via Giovanni Paolo II, 132, I-84084 Fisciano (SA), Italy
Thouless pumping refers to transport induced by the adiabatic and periodic modulations of the lattice parameters, and it has been experimentally realized using cold atoms in optical lattices and photonic waveguide arrays. Non- abelian Thouless pumping occurs in systems with degeneracies, and it enables the simultaneous control of transport and an internal degree of freedom enumerating the degenerate levels. This holds promise for technological applications such as quantum computing and quantum logic. In this talk we present the implementation of non-abelian Thouless pumping in different lattices – a Lieb lattice featuring two degenerate nondispersive modes and a two-leg Rice-Mele ladder model having two degenerate dispersive bands. We then discuss how to utilize non-abelian Thouless pumping to design one-dimensional discrete-time quantum walks and how to possibly implement quantum gates.
Laura Fanfarillo 1; Angelo Valli 2; Massimo Capone 3
1. Istituto dei Sistemi Complessi, CNR - Roma Taurini
2. Budapest University of Technology and Economics - Budapest
3. SISSA - Trieste
Iron-based superconductors represent an intriguing playground to study the role of electronic correlation in the realization of quantum orders. On the one hand a wealth of evidence shows that the phenomenology of the normal state can be fully accounted in terms of Hund’s metal physics, on the other hand the emergence of quantum orders at low-temperature can be explained as the results of Fermi surface instabilities and studied within conventional theories based on the exchange of low-energy bosons.
By studying how nematicity and superconductivity are affected by the presence of Hund’s driven correlations, we are able to reconcile these two perspectives and unveil the non trivial role of correlations on the realization of those quantum states. The key novelty of the study is the inclusion of the dynamical features of correlations that make a Hund’s metal substantially different with respect to both a weakly interacting metal and to an ordinary correlated metal with a large effective mass renormalization [1,2].
Our analysis provides a new building block towards the full comprehension of quantum orders in correlated systems and proves that the dynamical renormalization effects, often neglected in the analysis of the experimental data, strongly affect both qualitatively and quantitatively the realization of quantum orders in those systems.
References
[1] L. Fanfarillo, A.Valli, M.Capone, Physical Review B 107, L081114 (2023)
[2] L. Fanfarillo, A.Valli, M.Capone, Phys. Rev. Lett. 125, 177001 (2020)
Francis Allen Farrelly 1, Alessandro Taloni 1, Giulio Costantini 1, Dionisia Naddeo 2, Laura Pilozzi 2
1. Istituto dei Sistemi Complessi, CNR - Roma
2. Department of Biomedicine and Prevention, Univerisity of Rome, Tor Vergata, Italy
The field of in-silico immunogenicity prediction has advanced significantly with the availability of extensive immunopeptidomics data. Computational models, particularly those utilizing Machine Learning (ML), have achieved high accuracy in predicting peptide-MHC class-I binding. While similar efforts for MHC class II have faced greater challenges due to the open binding groove, ongoing refinements have brought these models closer to the accuracy levels of MHCI predictions from a decade ago.
Recent advancements in self-supervised representation learning, especially with Transformer-based models, have shown remarkable success in Natural Language Processing. These models leverage "Attention" mechanisms to enhance learning flexibility and generalization. Additionally, self-supervised Contrastive Learning has gained traction for its ability to create embedding spaces where similar samples are closely aligned, proving useful across various fields.
Claudia Fasolato
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
In the past two decades, extensive research has established that electronic transport through chiral molecules is spin selective. This phenomenon is known as chiral induced spin selectivity (CISS). While a fundamental comprehension of CISS remains elusive, compelling evidence demonstrates that it affects the interaction among chiral molecules through a spin-dependent contribution. As a consequence, its implication in the origin of biological homochirality has been suggested.
CISS is an inherently quantum effect that can play a role in various biochemical processes, crucial for biological functions. However, prior investigations of CISS have taken place under conditions incompatible with life, largely preventing to explore its quantum biology implications.
In my contribution, I will discuss a research proposal aimed at tackling the CISS effect in biomolecules in a fully biocompatible frame. With CHIROLE project, indeed, I plan to harness light as a tool to foster our comprehension of CISS and to gain external control on its biological consequences. Specifically, I aim at probing the impact of CISS on biomolecular interactions occurring in physiological environments, by combing advanced optical spectroscopy methods with ad hoc designed plasmonic nanosensors. I also plan to tackle the fundamental mechanisms at the basis of CISS, by investigating the role of phonons in CISS through nonlinear optics experiments, probing how periodic modulations of the molecular potential can affect the spin selectivity.
I will present the general concepts at the basis of CHIROLE project and outline the first results obtained by my group, proving that plasmon-enhanced optical spectroscopy techniques are suited to monitor intermolecular interactions among chiral molecules at the nanoscale.
Simone Felicetti 1; Valentina Brosco 1; Alessandro Coppo 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Quantum Metrology & Sensing represents one of the main research axes of modern Quantum Science. From a purely scientific viewpoint, this research field provides a conceptual framework to explore the fundamental limits of measurement precision set by Quantum Mechanics. On the technological side, Quantum Sensing offers a pathway to develop quantum-enhanced measurement instruments, promising an intrinsic advantage over classical devices. However, current quantum sensing strategies are still strongly limited by decoherence and finite-temperature effects, which make quantum-enhanced precision hard to achieve in scientific and technological applications.
In this talk, we present Critical Quantum Sensing (CQS), a recently introduced approach which exploits the susceptibility of critical systems in proximity of quantum phase transitions. We first present theoretical results which show that CQS is inherently more robust against losses and decoherence than current quantum sensing protocols. Then, we present the design of practical CQS protocols based on networks of driven quantum resonators. Finally, we report on a collaboration with an experimental group at EPFL, which implemented our protocol in a proof-of-concept demonstration of quantum-enhanced magnetometry with superconducting resonators. We close discussing perspectives for applying the CQS approach in the design of complex networks of parametric resonators for distributed quantum sensing.
Stefano Ferretti 1; Silvia Gentilini 1; Angela Capocefalo 2; Claudio Conti 3; Neda Ghofraniha 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physical and Chemical Sciences, University of L’Aquila – L’Aquila
3. Department of Physics, “La Sapienza” University of Rome – Rome; Institute for Complex Systems, National Research Council – Rome
The accurate, non-invasive, and rapid detection of few molecules underpins numerous key fields, like environmental monitoring, medical diagnostics, and biochemical research. High-precision techniques were developed on different principles, although most of them suffer from complex procedures, invasive labeling, and prolonged timescales. Photonic biosensors recently gained great consideration as they combine the sensitivity and speed of photonic sensing with the biofunctionalization of elements to enable label-free rapid testing. Whispering gallery mode (WGM) microlasers paved the way for innovative biosensing applications thanks to their high sensitivity to tiny variations in temperature as well as in the cavity size or in its refractive index gap with the surrounding medium. WGM microlasers performed well as biosensors to detect single viruses, monitor the contractility in cardiac tissue and the biomechanical stress of living cells, and in advancement of in vivo sensing. We used dyed polystyrene microspheres as WGM biosensors to detect proteins binding to the surface over time. We studied our system inside a solution of diffusing τ proteins, and in air after letting dry a droplet of lysozyme solution. We also developed a protocol to functionalize the beads’ surface with a capture antibody for specific detection of Interferon-γ proteins. We tested our PHotonic ImmunoSorbent Assay (PHISA) in solutions at concentrations of 30-500 pg/mL. The spectral dynamics over time was proportional to the analyte concentration. Our results were validated by a more consolidated biochemical protocol applied to the same samples. PHISA reduces the process steps and the chemical reagents typical of different assay strategies, and the volume of the sample to be tested is also significatively smaller. The high sensitivity is guaranteed by a low limit of detection of 10 pg/mL. Further improvements foresee the implementation of machine learning routines for automatic fast data analysis.
Salvatore Ferrone 1; Marco Montuori 2, 1; Paola Di Matteo 3; Alessandra Mastrobuono-Battisti 4; Misha Haywood 3; Rodrigo Ibata 5; Paola Bianchini 5; Sergey Khoperskov 6; Nicolas Leclerc 7; Clément Hottier 7; Eliot Stien 3; David Valls-Gabaud 7; Owain N. Snaith.
1. Dipartimenti di Fisica, Università di Roma, La Sapienza- -- Roma
2. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
3. LIRA, Paris Observatory, Paris Sciences et Lettres -- Paris
4. Dipartimenti di Fisica e Astronomia "Galileo Gallilei", Università di Padova -- Padova
5. Strasbourg Observatory, University of Strasbourg, -- Strasbourg
6. Leibniz-Institut für Astrophysik (AIP), Potsdam Germany
7. Paris Observatory, Paris Sciences et Lettres -- Paris
8. Department of Physics, University of Exeter, Exeter
Galactic stellar streams are long, thin structures composed of hundreds to hundreds of thousands of stars, spanning several degrees of arc on the sky and many kiloparsecs within the galaxy. They often result from the tidal disruption of extended stellar systems within the gravitational field of a larger host, such as open clusters, globular clusters, and dwarf galaxies orbiting a larger galaxy. Thanks to the Gaia mission’s astrometric catalog of billions of stars and advanced computational techniques, approximately 60 streams within the Milky Way have been discovered.
Due to their sensitivity to both the net and local gravitational fields, stellar streams serve as excellent diagnostic tools. They can provide insights into: the history and evolution of the galaxy, the local distribution of dark matter, and the formation history of globular clusters. In this presentation, I will discuss work from my thesis, which involves modeling the mass loss of all known galactic globular clusters to create stellar streams. These models contribute to answering key questions about the galaxy's history and structure, the presence of dark matter, and the formation processes of globular clusters.
Stefano Focardi 1; Martina de Benedetto 2; Mario Cipollone 3; Marco Davoli 4
1. Istituto dei Sistemi Complessi, CNR - Firenze
2. Biotecnologie Charles Darwin, La Sapienza, Roma;
3. Rewilding Apennines, Gioia dei Marsi, L'Aquila;
4. Dipartimento di Biologia e Biotecnologie Charles Darwin, La Sapienza, Roma;
Humanity is running out of time for finding solutions to global warming, caused by increasing atmospheric concentration of GreenHouse Gases (GHG). Scientific evidence is accumulating that Earth tipping points may be closer than previously thought, potentially committing the world to long‐term irreversible changes. GHG can be controlled by (1) reducing emissions and (2) increasing carbon sequestration. Rewilding is an approach to ecological restoration that aims to restore trophic complexity, stochastic disturbance events and the ability of organisms to disperse over time and space and it has a central role in the implementation of the EU Nature Restoration Law. In this talk, first we show that megafauna can influence geo-chemical cycles. Late Pleistocene/early-Holocene (12000 years bp) transition witnessed many human-driven extinctions and a consequent, abrupt, ecosystem shift from the mammoth-steppe to the taiga/tundra. It has been showed that reintroduction of large mammals in the Holarctic might slow down the rate of permafrost melting and allow the recovery of grassland ecosystems. According to recent studies, megaherbivores have the potential to restore grasslands and store carbon in the soil in a stable chemical form (Mineral-Associated Organic Matter); further the capacity of large mammals to maintain open landscapes provides discontinuities in forest cover, reducing the occurrence of megafires (able to liberate millions of tons of GHG) and counteract the decline of species linked to open areas. We reconstructed the distribution of large mammals during the Italian Holocene and showed a large presence of aurochs and kulans and a wide diffusion of bear and lynx. We provide plans for reintroduction/reinforcement of these populations with the idea of halting biodiversity losses and increase carbon sequestration.
Silvia Franco1,2, Elena Buratti 3, Valentina Nigro 4, Barbara Ruzicka1,2, Roberta Angelini 1,2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physics, "Sapienza" University of Rome
3. Department of Chemical, Pharmaceutical and Agricoltural Science, University of Ferrara
4. ENEA - Frascati
Microgels are soft particles made by cross-linked polymer networks with a hybrid nature between that of polymers and colloids. They are widely used as a colloidal model system because of their swelling properties and their responsivity to external control parameters such temperature or pH. The phase behaviour of microgels has attracted great attention thanks to the new phenomenology emerging from their ability to pack at very high volume fractions. Combining rheology [1,2], dynamic light scattering and x-ray photon correlation spectroscopy [3] we perform an extensive experimental study of a thermo- and pH-sensitive microgel composed of Interpenetrated Polymer Network (IPN) of poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAAc) at fixed PAAc content as a function of weight concentration with the ultimate goal of understanding its complex phase behavior. We distinguish three different rheological regimes, characteristic of three different states: liquid, glass and jammed, a preliminary T- Cw phase diagram is drawn [4].
References
[1] S. Franco, E. Buratti, V. Nigro, E. Zaccarelli, B. Ruzicka, R. Angelini, Int. J. Mol. Sci. 22 (8), 4032 (2021)
[2] S. Franco, E. Buratti, B. Ruzicka, V. Nigro, N. Zoratto, P. Matricardi, E. Zaccarelli, R. Angelini, J. Phys.Condens. Matter 33 (17), 174004 (2021)
[3] V. Nigro, B. Ruzicka, B. Ruta, F. Zontone, M. Bertoldo, E. Buratti and R. Angelini, Macromolecules 53, 1596−1603 (2020)
[4] S. Franco, E. Buratti, V. Nigro, M. Bertoldo, B. Ruzicka, R. Angelini, Polymers 14 (1), 115 (2022)
Lucia Gardini 1,2
1. Istituto dei Sistemi Complessi, CNR - Firenze
2. European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, Sesto F.no
Single-molecule localization microscopy is an advanced imaging technique that allows the visualization and tracking of individual molecules within biological systems. Unlike conventional microscopy, which observes ensembles of molecules and provides averaged data, single-molecule microscopy offers the ability to study the behavior, dynamics, and interactions of individual molecules in real-time. This approach has demonstrated to be crucial in revealing heterogeneity of molecular behaviors within a population, which is obscured in ensemble measurements. Single-molecule techniques achieve resolutions below the diffraction limit of light, enabling the observation of molecular interactions and movements at nanometer scales and millisecond timescales. By focusing on individual molecules, processes happening in the cell at the molecular level can be directly observed, thus allowing precise quantification of molecular properties, such as binding affinities, reaction rates, and force measurements, which are essential for developing accurate models of biological function. The importance of single-molecule microscopy lies in its ability to transform our understanding of fundamental biological processes by bridging the gap between molecular structure and cellular function. Nanometer-precision localization of single fluorescence emitters is also utilized in the so-called 'super-resolution microscopy,' where images of specific cellular structures are obtained with a resolution of just a few nanometers. The advent of this type of microscopy, approximately 20 years ago, opened access to the cellular world beyond the diffraction limit, marking a revolution in fluorescence microscopy. Super-resolution techniques still require improvement to enable high-resolution imaging of thick samples and to enhance time resolution. In this talk, I will present some examples of single-molecule tracking and super-resolution experiments I have worked on in recent years.
Silvia Gentilini 1; Marcello Calvanese Strinati 2; Davide Pierangeli 1; Claudio Conti 3
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. CREF - Rome; ISC, CNR - Rome;
3. Physics Department, Sapienza Univeristy - Rome
In the post-Moore's law era, significant research efforts are being dedicated to exploring non-von Neumann hardware to address NP-hard problems, i.e. those problems that are difficult for conventional computers to solve within a reasonable time.
Among the plethora of proposed solutions ranging from quantum to DNA-based computation, Ising Machines (IMs) have attracted considerable attention as specialised hardware capable of outperforming traditional digital processors. They achieve this issue by solving NP-hard problems through the implementation of an Ising model of interacting spins, where the system's ground state represents the problem's solution. Photonic Ising Machines, in particular, show great promise by leveraging the unique advantages of optical systems, including ultrafast dynamics, coherence, and optical parallelism, to accelerate Ising computations.
We present Spatial Photonic Ising Machines (SPIMs), a paradigm of IMs that operate using spatial light modulation. This approach is founded on the discovery that coherent optical propagation in free space can map the Ising model when spins are encoded onto the spatial profile of a laser beam. Experimentally, this is achieved using the mature technology of spatial light modulators (SLMs) to encode spins on the spatial profile laser beam. The intensity measured at the detector corresponds to the absolute value of the Ising Hamiltonian.
Exploiting the inherent spatial parallelism of free-space optics and the high pixel density of SLMs, the first SPIM achieved the integration of over 40,000 spins, setting a new benchmark for Ising Machines in size. The device measures the Ising energy and iteratively updates the spin configuration via digital feedback, employing a Metropolis-Hastings algorithm. This versatile operating mechanism is broadly applicable and can accelerate various optimisation algorithms.
Yuri Gerelli
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Solid-supported lipid bilayers (SLBs) are widely used tools in biological and technological studies and are one of the prototypes of natural self-assembling systems. One of the most debated phenomena in cell membranes is a structural rearrangement called lipid flip-flop, i.e., the movement of lipid molecules across the cell membrane.
By performing time- and temperature-resolved neutron scattering experiments, we provided a real-time, direct characterization of the internal structural changes taking place in symmetric and asymmetric SLBs across their phase transitions. In particular, we demonstrated how this method can be used to obtain direct information on the melting behavior of the proximal and distal leaflets in SLBs and to quantify, therefore, their degree of coupling during the main phase transition. We also demonstrated that in asymmetric systems, lipid flip-flop is intrinsically linked to the appearance of fluid domains in the bilayer.
Moreover, the growth of these domains during the broad phase transition was found to be the key factor in determining the timing of the flip-flop process. By exploiting different temperature scan rates, we demonstrated that, in the case of supported bilayers and for the temperatures investigated, lipid flip-flop is characterized by an activation energy of 50 kJ/mol and a timescale on the order of a few hours, providing a framework for discussing the origin of the existing discrepancies between flip-flop measured in solution and at interfaces.
Michele Giusfredi 1; Stefano Iubini 2; Antonio Politi 3; Paolo Politi 2
1. Dipartimento di Fisica e Astronomia, Università di Firenze - Sesto Fiorentino
2. Istituto dei Sistemi Complessi, CNR - Firenze
3. Istituto Nazionale di Fisica Nucleare, Sezione di Firenze - Sesto Fiorentino
We study the out of equilibrium process of condensation in a one-dimensional stochastic lattice model related to the discrete nonlinear Schrödinger model (DNLS). At equilibrium, the model has a transition from a homogeneous phase to a condensed phase in which a macroscopic fraction of the total energy spatially localizes in one site of the system. The local energies are the square of the local masses, with both mass and energy globally conserved in the isolated system. When the lattice chain is connected instead at its ends with two different thermal reservoirs, due to the presence of the two conservation laws the localization process may arise even if the heat baths impose subcritical conditions. Energy peaks (breathers) appear and grow over time, and their mobility determines the evolution of the system. If the dynamics allows the breathers to move, the system can reach a nonequilibrium steady state (NESS), of which we have found exact analytical expressions for the average mass and energy profiles and for the mass and energy fluxes. If instead energy peaks are not allowed to move, a phase separation occurs, in which a fraction of the sites have breathers that grow indefinitely, preventing a proper NESS, while the remaining sites stabilize with finite local average mass and energy. The system is metastable and the appearance of new breathers may require extremely large times.
Nicoletta Gnan
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Continuous phase transitions are a cornerstone of equilibrium statistical mechanics. Extending these concepts to active matter reveals new and intriguing phenomena that challenge our understanding of criticality and phase behavior. I will explore continuous transitions in active particles interacting via a quorum-sensing (QS) mechanism, where particles adjust their swimming speed based on the density of neighbors. Simulations reveal that standard QS exhibits phenomenology akin to systems in the Ising universality class but when competing interaction takes place in QS, this leads to the destabilization of motility -induced phase separation (MIPS) in favour of active microemulsions, whose behavior can be well described by a renormalized field theory within an effective equilibrium framework. Finally, I will highlight experimental results on superparamagnetic colloids activated by a bath of swimming E. coli. These systems exhibit a two-dimensional melting transition, driven far from equilibrium, which can be understood through the lens of KTHNY theory. Active particle models reproduce the experimental observations, showing that the KTHNY-theory remains qualitatively valid in describing the melting scenario of this active solid [2].
References
[1] N.Gnan and C. Maggi, Critical behavior of quorum-sensing active particles, Soft Matter 18, 7654 (2022)
[2] H. Massana-Cid, C. Maggi, N. Gnan, G. Frangipane, R. Di Leonardo, Multiple temperatures and melting of a colloidal active crystal, Nature Communications 15 (1), 6574 (2024)
Daniela Grasso 1, Chiara Marchetto 1
1. Istituto dei Sistemi Complessi, CNR - Torino
Le attività in Fisica del Plasma che portiamo avanti a Torino spaziano dalla fusione termonucleare controllata allo spazio. La maggior parte delle tematiche trattate ha come denominatore comune un processo fondamentale noto come riconnessione magnetica. Questo fenomeno infatti gioca un ruolo fondamentale sia nei plasmi confinati magneticamente che nei plasmi spaziali. Le sue caratteristiche distintive sono la formazione di intensi strati di corrente e il rilascio di enormi quantità di energia su tempi molto brevi. In questa presentazione si vuole fornire una descrizione dei principi fisici alla base del fenomeno ed illustrare le attività che il gruppo plasmi di Torino porta avanti, rimandando ai poster per gli approfondimenti su alcune tematiche specifiche.
Daniela Grasso 1 , Dario Borgogno 1,2 , Lovepreet Singh 1,3
1. Istituto dei Sistemi Complessi, CNR - Torino
2. INAF – Istituto di Astrofisica e Planetologia Spaziale, Roma
3. NEMO Group, Dipartimento Energia, Politecnico di Torino
The role of a runaway current in driving a magnetic reconnection event in a post-disruption plasma is investigated through numerical simulations in three-dimensional configurations. A reduced two-fluid model coupled with the evolution equation for the runaway current is adopted [1,2]. We first review recent results in the single helicity limit [3] and then present preliminary results in the multiple helicity case.
References
[1] P. Helander, D. Grasso, R. J. Hastie, and A. Perona, Phys. Plasmas 14, 122102 (2007)
[2] D. Grasso, D. Borgogno, L. Singh, and F. Subba, J. Phys.: Conf. Ser. 2397, 012004 (2022)
[3] L. Singh, D. Borgogno, F. Subba and D. Grasso, Phys. Plasmas 30, 122114 (2023)
Daniela Grasso 1, Dario Borgogno 1,2
1. Istituto dei Sistemi Complessi, CNR - Torino
2. INAF – Istituto di Astrofisica e Planetologia Spaziale, Roma
Magnetic reconnection (MR) is a fundamental process in magnetized plasmas, associated with significant magnetic energy release. In strongly turbulent astrophysical plasmas MR is continuously met along the flow[1]. This makes MR an intrinsic element of the turbulent cascade and vice versa[2].
MR typically occurs where intense current sheets form, giving rise to plasmoid formation, while the turbulent cascade explains how the energy provided at large scales is dissipated at small scales. Significant efforts have been devoted to understanding how the reconnection process, via plasmoid instability, influences the turbulent cascade in resistive magnetohydrodynamics[3-6]. However, space and astrophysical plasmas where reconnection and turbulence have mutual influence are most of the time collisionless. In the framework of collisionless MR several studies[7,8] have also been devoted to the evolution of current and vorticity sheets that undergo secondary Kelvin–Helmholtz (KH) instabilities.
The evolution of current and vorticity sheets is studied here in the framework of collissionless turbulent plasmas, where thin current sheets may be prone to plasmoid or KH instabilities[9]. We show that the coexistence of these two instabilities prevent the colllisionelss plasma to achieve the fully mediated plasmoid turbulent regime. Preliminary results on the effect of electron temperature on the described scenario will also be shown.
References
[1] Lazarian, A. et al., 2015, RSPTA, 373, 20140144
[2] Servidio, S. et al., 2009, PhRvL, 102, 115003
[3] Biskamp, D., & Welter, H. 1989, PhFlB, 1, 1964
[4] Politano, H. et al., 1995, PhPl, 2, 2931
[5] Boldyrev, S., & Loureiro, N. F. 2017, ApJ, 844, 125
[6] Dong, C. et al., 2022, Sci.Adv., 8, eabn7627
[7] Del Sarto, D. et al., 2003, PhRvL, 91, 235001
[8] Grasso, D. et al., 2007, PhPl, 14, 055703
[9] Borgogno, D. et al., 2022, ApJ 929:62
Stefano Iubini 1; Antonio Politi 2
1. Istituto dei Sistemi Complessi, CNR - Firenze
2. Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom
The observation of (absolute) negative-temperature states in the localized phase of the the Discrete Nonlinear Schrödinger equation has challenged statistical mechanics for a long time. This model has applications in several physical setups involving propagation of nonlinear waves in discrete media, from ultracold gases in optical lattices to arrays of optical waveguides. For isolated systems, negative temperatures can emerge as stationary extended states through a large-deviation mechanism occurring for finite sizes, while they are formally unstable in grand-canonical setups, being associated to an unlimited growth of the condensed fraction. Here, we show that negative-temperature states in open setups are metastable and their lifetime is exponentially long with the absolute value of temperature.
This mechanism, based on the existence of two conservation laws, provides a new perspective over the statistical description of condensation processes.
Thomas Kreuz 1, Arturo Mariani 2, Federico Senocrate 3, Jason Mikiel-Hunter 4, David McAlpine 5, Barbara Beiderbeck 6, Michael Pecka 7, Kevin Lin
1. Istituto dei Sistemi Complessi, CNR - Firenze
2. National Institute of Nuclear Physics (INFN), Florence Section , Sesto Fiorentino, Italy
3. Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy
4. Department of Linguistics, Macquarie University, Sydney, Australia
5. Division of Neurobiology, Faculty of Biology, Ludwig-Maximilians-University, Munich, Germany
6. Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University, Munich, Germany
7. Ecole Nationale Superieure de l’E´lectronique et de ses Applications, Cergy, France
Background: This poster deals with the analysis of neuronal data by means of newly developed methods of data analysis. In Kreuz et al., J Neurosci Methods 381, 109703 (2022) two methods were proposed that perform latency correction, i.e., optimise the spike time alignment of sparse neuronal spike trains with well-defined global spiking events. The first one based on direct shifts is fast but uses only partial latency information, while the other one makes use of the full information but relies on the computationally costly simulated annealing. Both methods reach their limits and can become unreliable when successive global events are not sufficiently separated or even overlap.
New Method: Here we propose an iterative scheme that combines the advantages of the two original methods by using in each step as much of the latency information as possible and by employing a very fast extrapolation direct shift method instead of the much slower simulated annealing.
Results: We illustrate the effectiveness and the improved performance, measured in terms of the relative shift error, of the new iterative scheme not only on simulated data with known ground truths but also on single-unit recordings from two medial superior olive neurons of a gerbil.
Comparison with Existing Method(s): The iterative scheme outperforms the existing approaches on both the simulated and the experimental data. Due to its low computational demands, and in contrast to simulated annealing, it can also be applied to very large datasets.
Conclusions: The new method generalises and improves on the original method both in terms of accuracy and speed. Importantly, it is the only method that allows to disentangle global events with overlap.
Alessandro Manacorda 1; Luca Casagrande 2; Yiwei Zhang 2; Étienne Fodor 2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physics and Materials Science, University of Luxembourg, Luxembourg;
Epithelial or cardiac tissues perform their functionality via individual deformation of the cells, governing their collective behavior in terms of synchronization, wave propagation and arrest. I will introduce pulsating active matter (PAM) as a theoretical framework able to describe this collective dynamics from a microscopic viewpoint. Numerical simulations and hydrodynamics elucidate the nature of the non-equilibrium phase transitions; the hydrodynamics derived via coarse-graining boils down to a complex Ginzburg-Landau equation with explicit symmetry breaking whose properties are studied and yet represent a novel research ground with potential for further phenomenology.
Chiara Marchetto 1; Dario Borgogno 1,2; Daniela Grasso 1
1. Istituto dei Sistemi Complessi, CNR - Torino
2. INAF – Istituto di Astrofisica e Planetologia Spaziale, Roma
La riconnesssione magnetica è un fenomeno ubiquo in fisica dei plasmi, associato ad un cambiamento di topologia del campo magnetico che confina il plasma. Le strutture coerenti in cui questo cambiamento è concentrato prendono il nome di isole magnetiche.
Quando le isole magnetiche interagiscono tra di loro generano il caos magnetico. Esse inoltre sono spesso associate all’insorgenza di instabilità secondarie di tipo fluido che tipicamente mostrano comportamento turbolento. In questo lavoro analizziamo come la presenza del caos magnetico influenzi l’evoluzione delle instabilità secondarie. Questo è un problema fondamentale sia per i plasmi spaziali, in particolare nell’interazione del vento solare con la magnetosfera terrestre, sia per il confinamento dei plasmi di laboratorio.
Chiara Marchetto 1; Elisabetta Bray 2; Giuseppe Francesco Nallo 2
1. Istituto dei Sistemi Complessi, CNR - Torino
2. Dipartimento Energia Politecnico di Torino
Un tokamak è un toro metallico dentro al quale il plasma è confinato lontano dalle pareti da un campo magnetico e riscaldato dall’effetto Joule e da riscaldamenti ausiari, fino a produrre la fusione. Anche se il confinamento magnetico crea, appositamente, una zona di vuoto fra plasma e parete, i materiali della parete interna entrano nel plasma e vi si propagano fino a raggiungere il core, denso e caldo, contaminandolo e ostacolando la fusione. In modo complementare, l’energia e le ceneri generate dalla fusione si propagano fino alla parete del tokamak, da cui devono essere estratte.
Lo studio di queste “propagazioni” prende il nome di “trasporto” e viene applicato nello “scenario design” per determinare prima dell’esperimento cosa avverrà alla scarica nel plasma e nel “machine design” per controllare che le innovazioni apportate per risolvere problemi sorti nei reattori in funzione non impattino le prestazioni della macchina.
Il trasporto si avvale di tecniche di integrated modeling per interfacciare zone a fenomeni bidimensionali con zone a fenomeni unidimensionali e per accoppiare al solutore delle equazioni di trasporto i codici che calcolano i vari termini, descrivendo fenomeni fisici differenti che accadono su scale spaziotemporali differenti e che interessano con meccanismi differenti ciascuna specie (elettroni, protoni e ioni a diverso stato di ionizzazione).
In questo lavoro illustreremo come la riconnessione magnetica possa venire in aiuto nello spiegare l’accumulo di impurezze pesanti nel core del plasma e come la proposta di rivestire la parete interna di un tokamak con un metallo liquido, al fine di migliorarne la resistenza alle sollecitazioni termiche e meccaniche e contemporaneamente ridurre l’assorbimento di trizio radioattivo, possa essere testata misurando il grado di inquinamento del core che ne deriverebbe.
Massimo Materassi
Istituto dei Sistemi Complessi, CNR - Firenze
The Earth’s ionosphere has been treated in many different ways; due to its dynamics and its influence on radio transmissions, its variability has been regarded as an annoying characteristic, and it is still regarded this way by a wide community of communication and positioning “users”.
The highly variable ionosphere, however, is much more than an annoying detail disturbing the GPS technology, or the scarcely reliable channel for ground-to-ground communication: since some decades, physical aspects of the system gained importance in the scientific and users’ community. As physical models of the ionospheric dynamics grew more and more important, multi-disciplinary aspects of physics and mathematics became central: plasma dynamics, electromagnetics in random media, photochemistry kinetic equations, kinetic theory of gases of many species, turbulence theory, forced criticality.
In this short review, I will sketch some aspects under which the state-of-the-art of ionospheric physics and modelling, with its paramount role in Space Weather science, appears to be a scenario with serious opportunities of intervention for the Statistical Mechanics and Dynamical System community, with their unique expertise in non-equilibrium thermodynamics, stochastic theories, dissipative structures and the predictability assessment of chaotic systems.
Stefania Melillo on behalf of COBBS group 1,2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Dipartimento di Fisica, "Sapienza" Università di Roma
The research of CoBBS group is focused on the study of collective behavior in biological systems, with particular interest in bird flocks and insect swarms. Our aim is to understand what kind of interaction rules these groups and, more broadly, what are the effective dynamic equations regulating their collective behavior, building a new theory as directly as possible inspired by the data.
In this talk, I will first describe our experimental approach and the computer vision algorithms we have developed over the past decade to build a data set, unique in the world, consisting of three dimensional data on bird flocks and insect swarms, collected both in the field and in the controlled environment of the laboratory. I will then present a new line of research, resulting from the collaboration with the Department of Medicine and Surgery of Perugia University, and its applications in health care, on Anopheles Gambiae malarial mosquitoes.
Valentina Nigro 1; Roberta Angelini 2; Silvia Franco 2; Elena Buratti 3; Stephen King 4; Najet Mahmoudi 4; Barbara Ruzicka 2
1. Fusion and Technologies for Nuclear Safety and Security Department, ENEA - Frascati (Rome);
2. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
3. Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara - Ferrara;
4. ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory - Didcot (UK);
Microgels composed of stimuli-responsive polymers have attracted significant interest as model colloids for both theoretical and experimental studies, as well for nanotechnological applications. Their softness allows to explore high density states well beyond random close packing, making them excellent model systems for investigating the exotic behaviours of soft colloids.
In the last years, we have extensively investigated a dual-responsive interpenetrated polymer newtork microgel composed of poly(N-isopropylacrylamide) (PNIPAM), a temperature sensitive polymer, and poly(acrylic acid) (PAAc), a pH sensitive polymer [1]. This system, with its multi-stimuli responsiveness and rationally designed properties, can be finely tuned through various experimental parameters, such as sample concentration, temperature and PAAC content, to drive the system toward the formation of arrested states.
Here we will focus on dynamical and structural investigation of colloidal systems, highlighting a very recent study on the simultaneous dynamical and structural behaviour of PNIPAM-based microgels. The measurements were obtained using a new setup recently implemented by our group [2], which permits the acquisition of complementary and simultaneous information on the dynamics (through DLS) and microscopic structure (through SANS) of soft matter systems.
References
[1] V. Nigro, R. Angelini, M. Bertoldo, E. Buratti, S. Franco and B. Ruzicka, Chemical-Physical Behaviour of Microgels Made of Interpenetrating Polymer Networks of PNIPAM and Poly(acrylic Acid), Polymers 13 (2021) 1353.
[2] V. Nigro, R. Angelini, S. King, S. Franco, E. Buratti, F. Bomboi, N. Mahmoudi, F. Corvasce, R. Scaccia, A. Church, T. Charleston and B. Ruzicka, Apparatus for simultaneous dynamic light scattering–small angle neutron scattering investigations of dynamics and structure in soft matter, Review of Scientific Instruments 92 (2021) 023907.
Mauro Missori
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
In my talk, I will present the activities I have carried out in recent years as an ISC researcher, focusing on recent results. My work mainly falls within the field of Photonic Systems for non-invasive diagnostics, in the research area of Optics, Photonics, Atomic and Quantum Technologies at DSFTM of CNR. It is interdisciplinary, aimed at the experimental study of the optical properties of complex and disordered materials using electromagnetic radiation in different spectral bands, and has been carried out in collaboration with many colleagues from ISC and CNR.
I will discuss the study of the optical and structural properties of inhomogeneous materials made of biological fibers, nano- and micro-particles, and the development of experimental methodologies and data analysis techniques. Specifically, I will present results on paper cultural heritage items, such as documents and drawings made primarily of a cellulose fiber network, obtained in collaboration with the Italian Minister of Culture. I will also highlight my work with the University of Tor Vergata on computational simulation methods for cellulose's optical properties using time-dependent Density Functional Theory (TD-DFT) and on the development of gels and microgels for cultural heritage conservation.
Additionally, I will present results from my photonics and Terahertz (THz) spectroscopy activities, performed in collaboration with the Dept. of Physics at Sapienza University and colleagues from ISC and CNR. These results include the propagation and scattering of THz radiation in disordered structures, the transition from Fano resonances to bound states in the continuum (BIC) in photonic structures, the development of THz super-resolution imaging, and the application of THz techniques to study cellulose's low-energy vibrational properties for diagnosing ancient materials.
Valentina Palmieri; 1 Giulia Artemi 1; Alberto Augello 2; Brunella Iacolino 1; Giordano Perini 3; Massimiliano Papi 3
1. Istituto dei Sistemi Complessi, CNR - Roma Taurini
2. GSTEP Facility 3D Bioprinting Fondazione Policlinico Gemelli IRCCS, Rome;
3. Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, UCSC, Rome;
Photodynamic therapy (PDT) and photothermal therapy (PTT) are emerging approaches for cancer treatment and tissue regeneration, offering minimally invasive and highly targeted interventions. Recent studies have focused on the application of advanced nanomaterials such as graphene and MXenes, owing to their exceptional optical, thermal, and chemical properties. Graphene, with its high thermal conductivity and photostability, and MXenes, known for their outstanding photothermal conversion efficiency and functional versatility, have proven effective in enhancing both photothermal effects and the generation of reactive oxygen species (ROS) in PDT. These materials enable targeted destruction of cancer cells while simultaneously promoting tissue regeneration by activating key biological processes. This work defines the latest work of our group on the interaction of these nanomaterials with biological tissues, the optimization of therapeutic protocols to obtain antibacterial and anticancer 3D-printed scaffolds, and future perspectives for personalized skin wound healing leveraging the synergies between PDT and PTT.
Oriele Palumbo 1; Francesco Trequattrini 1,2; Annalisa Paolone 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physics, Sapienza University of Rome, Rome
Ionic liquids (ILs) and deep eutectic solvents are largely studied for their properties, such us low vapor pressure, high ionic conductivity, high stability and good solvent capacity, which make them particularly relevant in energy storage and electrochemistry applications as well as in biomedical applications. Moreover, the charming properties of these materials lie in the possibility of tailoring them by means of a proper choice of the composing units or by mixing with other liquids, such as water, alcohols or different ILs. A deep understanding of their microscopic properties and of the interactions within their components is fundamental in order to master such possibility. We present several examples of ILs and mixed systems where vibrational and mechanical spectroscopies, combined with ab initio simulations, provide information about the microscopic configurations, the phase transitions, the dynamics and the kind of interactions occurring in the system, particularly focusing on the presence of strong and directional hydrogen bonds. We also present an extensive characterization of several analogues of a system composed by an equimolar mixture of a cholinium cation, a geranate anion and a geranic acid molecule, the so-called 1:2 choline-and-geranate (CAGE), which can be successfully used for transdermal and oral drug delivery, but presents some difficulties in the industrial-scale preparation and long-term storage. The proposed analogues are designed following the targeted modification approach to achieve a complete understanding of the structure-property relationship. Indeed a full knowledge of this relationship is fundamental to find more suitable candidates overcoming the difficulties presented by CAGE while maintaining its advantageous properties. The properties observed for the synthesized analogues are studied against those observed in the starting CAGE mixtures, providing insights about the role played by the different species in the mixtures.
A. Paolone 1; F. Trequattrini 1,2; O. Palumbo 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physics, Sapienza University of Rome, Piazzale. A. Moro 5, 00185, Roma, Italy
The storage of energy has become an important part of the process for the utilization of renewable energy sources, as they are intrinsically intermittent. Our research group has been investigating two aspects in this field since almost twenty years: the solid state hydrogen storage and the storage of energy in lithium-ion and post-lithium batteries.
Hydrogen is a green energy carrier, which can be stored in solid materials, forming hydrides, in a safe way. The current research is devoted to find compounds where hydrogen can be charged and discharged around room temperatures in a pressure range up to 30 bar. After exploring many complex hydrides in the past, we recently started to study high entropy alloys composed of at least five chemical elements that display encouraging hydrogen storage properties.
In the field of lithium batteries, we spectroscopically explored many electrolytes and electrodes and the solid-electrolyte interphase, which is the thin layer formed at the boundary of the electrodes and electrolyte and is of fundament importance for the performance of the battery. Its changes as a function of the cycles of charge/discharge of the battery has been investigated and the amorphization of the Si compounds has been evidenced.
Alessandro Petrini 1,2 , Claudio Conti 2,1 and Davide Pierangeli 1,2
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physics, Sapienza University of Rome, 00185 Rome, Italy
Full-Stokes polarimetry is a fundamental technique for the complete characterization of polarized light, offering significant potential from imaging to optical communication.
However, its practical application is limited by the difficulty of obtaining fast and accurate measurements without bulky optical setups and by the challenge of detecting polarization distributions through scattering media.
To address these limitations, we have developed a novel polarimetry technique that uses a deep neural network to reconstruct, in a single-shot, the full-Stokes polarization distribution of an incident beam passing through scattering media from the transmitted speckle pattern.
The method is applied to retrieve full-Stokes polarization images scrambled by a disordered medium, demonstrating accurate polarization imaging in scattering environments.
We have developed the technique to enable the transmission of 32x32 pixels grayscale and full-color images encoded within the Stokes parameters. We aim to exploit this approach for optical encryption by encoding information through polarization-structured light transmitted as speckle patterns. The complex interplay between the polarization states and the generated speckle ensures robust data encryption, making the system suitable for scalable and secure optical communication.
Finally, we achieve accurate control of the full polarization degree of freedom by spatial modulation of the Stokes parameters, which enables multidimensional information transmission using partially polarized vector beams.
Oreste Pezzi
Institute for Plasma Science and Technology (CNR-ISTP), Bari
Understanding the kinetic-scale dynamics of turbulent nearly-reversible plasmas is decisive for tackling the fundamental issues of energy dissipation, plasma heating and particle acceleration in space and astrophysical systems. As a result of the weak collisionality, kinetic-scale plasma turbulence naturally generates a large variety of non-equilibrium velocity-space structures in the plasma distribution function. Such an emerging complexity has been recently envisioned as a turbulent cascade occurring in the entire six-dimensional phase space. I will review some recent results on this topic and describe the on-going and future activities to further explore such a fascinating topic.
Paolo Politi 1; Michele Giusfredi 2; Stefano Iubini 1; Stefano Lepri 1; Antonio Politi 3
1. IIstituto dei Sistemi Complessi, CNR - Firenze
2.Dipartimento di Fisica e Astronomia, Università di Firenze, via G. Sansone 1 I-50019, Sesto Fiorentino, Italy
3. Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom
We provide some highlights on several nonequilibrium phenomena appearing in reduced dimensionality and studied at ISC-Florence in recent years.
Two keywords are specially important, relaxation and transport. Relaxation can be extremely slow and lead to freezing, either for metastability reasons or because of the existence of adiabatic invariants. Transport can be anomalous, leading to superdiffusive behavior, and it can be coupled, leading to unexpected out-of-equilibrium phenomena.
Marco Pretti 1; Antonio Scarfone 1
1. Istituto dei Sistemi Complessi, CNR - Torino
In questo contributo descriviamo brevemente l'attività di ricerca dell'unità di Torino nell'ambito della fisica statistica, attività che si articola in due diverse tematiche.
La prima verte principalmente sui fondamenti teorici della fisica statistica per lo studio di sistemi non Gibbsiani, caratterizzati da distribuzione con comportamento asintotico a legge di potenza. Si tratta in generale di sistemi complessi caratterizzati da interazioni a lungo range (nano-sistemi o sistemi gravitazionali) o da forti correlazioni con effetti persistenti nel tempo (sistemi socio-economici, biofisici, geofisici), che lontani dal limite termodinamico manifestano palesi proprietà non estensive. Questa tematica coinvolge diversi problemi rilevanti di fisica statistica e matematica: forme entropiche generalizzate, aspetti geometrici della teoria dell'informazione, equazioni cinetiche con diffusione anomala, algebre quantistiche deformate, equazioni di Schroedinger non lineari...
La seconda tematica riguarda invece lo studio meccanico-statistico di sistemi fuori equilibrio, principalmente con tecniche semianalitiche approssimate (campo medio generalizzato, sviluppi a cluster) e con particolare attenzione a modelli derivati dal TASEP (totally-asymmetric simple esclusion process). Questi modelli sono di interesse non solo fondamentale ma anche applicativo, poiché si adattano facilmente alla descrizione di processi e microsistemi biologici (trascrizione, sintesi proteica, motori molecolari).
Le stesse tecniche sono state anche utilizzate per sviluppare algoritmi di inferenza e ottimizzazione combinatoria (belief propagation) per applicazioni ingegneristiche.
Marco Pretti 1; Alessandro Pelizzola 2
1. Istituto Sistemi Complessi, CNR - Torino
2. Dipartimento Scienza Applicata e Tecnologia (DISAT), Politecnico di Torino - Torino
We develop a mean-field theory for the totally-asymmetric simple exclusion process (TASEP) with open boundaries, in order to investigate the so-called dynamical transition. In pure TASEP, such a phenomenon has been studied exactly and it appears as a singularity in the relaxation rate of the system toward its non-equilibrium steady state. We exploit the mean-field approach to investigate more general TASEP models, where either a spatial modulation of hopping rates or an extra adsorption/desorption process (Langmuir kinetics) give rise to a bulk density profile lacking translational invariance.
Our results suggest that, in certain conditions, the nature of the dynamical transition undergoes substantial changes, displaying similarities with ordinary (equilibrium) first-order transitions. In particular, we point out that such a novel type of dynamical transition is accompanied by a peculiar structural change in the (mean-field) relaxation spectrum.
Andrea Puglisi
Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Sperm swimming is crucial to fertilize the egg, in nature and in assisted reproductive technologies. Modeling the sperm dynamics involves elasticity, hydrodynamics, internal active forces, and out-of-equilibrium noise. Here we give experimental evidence in favor of the relevance of energy dissipation for sperm beating fluctuations. For each motile cell, we reconstruct the time evolution of the two main tail's spatial modes, which together trace a noisy limit cycle characterized by a maximum level of precision. Our results indicate that this maximum precision is remarkably close to the estimated precision of a dynein molecular motor actuating the flagellum, which is bounded by its energy dissipation rate according to the thermodynamic uncertainty relation. Further experiments under oxygen deprivation show that the maximum precision decays with energy consumption, as it occurs for a single molecular motor. Both observations are explained by conjecturing a high level of coordination among the conformational changes of dynein motors. This conjecture is supported by a theoretical model for the beating of an ideal flagellum actuated by a collection of motors, including a motor-motor nearest-neighbor coupling of strength K: When K is small the precision of a large flagellum is much higher than the single motor one. On the contrary, when K is large the two become comparable. Based upon our strong-motor-coupling conjecture, old and new data coming from different kinds of flagella can be collapsed together on a simple master curve.
Vanessa Rosciardi 1; Federico Serpe 2; Andrea Barbetta 2; Roberta Angelini 1;
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Chemistry Department, "Sapienza" University of Rome
High Internal Phase Emulsions (HIPEs) represent a category of emulsions characterized by internal phase volume fractions surpassing the close-packing threshold (typically exceeding 74%), resulting in distinctive rheological characteristics. The tight packing of droplets in HIPEs can induce polygonal shapes under certain conditions, particularly in monodisperse systems featuring large droplets with low interfacial tension due to relatively low Laplace pressure. This close packing confers both elastic and viscous properties beneficial for various applications. Below a critical applied stress (the "yield stress"), HIPEs behave like elastic solids, transitioning to viscous liquids above this threshold. They also exhibit pronounced shear-thinning behavior, with viscosity decreasing under increasing shear stress.
Despite their thermodynamically unstable nature, metastable HIPEs can be prepared, maintaining consistent properties and appearance over extended durations. HIPEs serve as versatile precursors for polymer materials, particularly when one or both phases contain monomeric species. This process yields a diverse array of products with varying properties, with the microstructure of resulting materials dictated by the immediate emulsion structure prior to polymerization. Moreover, HIPEs can be foamed, making them useful templates for preparing polymeric porous materials.
This contribution presents the findings of a rheological characterization of oil-in-water HIPEs featuring internal phase volume fractions ranging from 75% to 90%, with the oil phase containing either styrene-based or methacrylate-based monomers. These polymerizable systems hold promise for conversion into porous materials with superior mechanical properties. Additionally, we demonstrate the foamability of these systems through mechanical frothing and microfluidic devices, offering a viable pathway for producing functionally graded porous materials with precise pore size control.
Antonio Maria Scarfone 1; Giovanni Barbero 1,2; Luiz Roberto Evangelista 1,3; Ervin Kaminski Lenzi 4
1. Istituto dei Sistemi Complessi, CNR - Torino
2. Dipartimento Scienza Applicata e Tecnologia - Politecnico di Torino - Italy
3. Department of Physics - State University of Maringá - Brazil
4. Department of Physics - State University of Ponta Grossa - Brazil
The theoretical description of the electrical response of a uniform medium to an external electric field in an electrolytic cell is traditionally based on the continuity equations for charge carriers and the Poisson equation, which relates the effective electric field to the electric charge. This framework is known as the Poisson-Nernst-Planck (PNP) model. In its classical formulation, the continuity equations incorporate ordinary diffusion. However, recent studies have demonstrated that in the case of neutral particle diffusion within porous media—where diverse stochastic processes govern the dynamics—fractional calculus provides a powerful framework for analyzing anomalous diffusion.
In this context, fractional diffusion equations effectively describe the kinetics of such systems. Extending the PNP model to include fractional dynamics is non-trivial, as it requires redefining the displacement current to ensure that the total current density remains solenoidal. By adopting the fractional approach, we generalize the key operators used in the model, enabling the description of non-Debye relaxation phenomena. This results in a comprehensive model for the conduction of charged particles in porous media, accurately capturing the medium's behavior in the low-frequency regime.
Antonio Maria Scarfone 1; Giorgio Kaniadakis 1,2; Sergio Luis Eduardo Ferreira Da Silva 1,2; Tatsuaki Wada 3
1. Istituto dei Sistemi Complessi, CNR - Torino
2. Dipartimento Scienza Applicata e Tecnologia - Politecnico di Torino - Italy
3. Region of Electrical and Electronic Systems Engineering - Ibaraki University - Japan
In the age of networks and big data, it is now well recognized that complex systems, characterized by long-range interactions and correlation persistent in time, have meta-equilibrium distributions that differ from the well-known exponential family of Boltzmann-Gibbs and Gauss distributions. Typical scenarios are frequently observed in the study of cosmological systems, nanosystems, and physical-like systems occurring in the field of the biological, economic, and social sciences.
A possible approach to deal with these new phenomenologies consists to replacing the traditional Boltzmann-Gibbs-Shannon entropic form with its continuous deformation, controlled by one or more parameters, capable of capturing the novelties observed in these "anomalous" systems, encoding it in the distribution function of the meta-equilibrium, without substantially altering the epistemological structure of statistical mechanics.
Among the galore of the different entropic forms proposed in the existing literature, the Sharma-Taneja-Mittal entropy, originally advanced in the framework of the information theory, is a family of generalized entropies that are modelled by two deformation parameters, which includes, as subclass, the Tsallis entropy, the Kaniadakis entropy and others used as paradigm to explore the consistence of the emerging theory.
Simona Sennato 1; Francesco Brasili 1; Angela Capocefalo 2; Domenico Truzzolillo 3; Emanuela Zaccarelli 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Physical and Chemical Sciences, University of L’Aquila,
3. Laboratoire Charles Coulomb, CNRS-Universite de Montpellier, France
Soft polymeric colloids such as thermoresponsive microgels have prompted significant advancements in soft matter physics as well as in nanotechnology. The possibility of tuning softness and temperature responsiveness by modifying the polymer network is not only ideal to investigate fundamental problems, but also offers the opportunity to design novel photonic materials through integration with plasmonic nanoparticles (NPs) [1] . This exploits the volume phase transition of microgels for tailoring the collective optical properties of NPs. Despite its great practical relevance, little attention was devoted to obtain a fundamental understanding of the microscopic details of NPs incorporation within soft colloids.
We fill this gap by combining Small Angle X-ray Scattering experiments and molecular dynamics simulations to study the temperature-dependent arrangement of gold NPs adsorbed onto microgels by means of electrostatic interactions. For the first time, we are able to connect the NPs spatial organization on the microgel with the optical properties of the complexes. We find that upon increasing temperature, NPs get closer due to microgel shrinking without forming clusters but they try to maximize their distance in order to reduce their mutual electrostatic repulsion. To unveil this behavior, we employ a simple model of NPs arranged on a spherical shell, which semi-quantitatively describes the intricate structure factors of NPs embedded within the microgel corona. Thanks to this approach, we finally establish the relationship between the degree of plasmon coupling and NP-NP distance, offering a pivotal step towards a precise control of the optical response of soft plasmonic complexes [2,3].
References
[1] Arif M. et al Journal of Molecular Liquids, 336 (2021) 116270.
[2] Brasili, F. et al. ACS Applied Materials & Interfaces, 15 (2023) 58770.
[3] Brasili, F. et al. arXiv: 2407.03124 (2024)
Leonardo Severini 1; Cecilia Bombelli 2; Francesca D'Acunzo 2; Simona Sennato 1
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Institute for Biological Systems, Secondary Office of Rome-Reaction Mechanisms, c/o Chemistry Department, Sapienza University of Rome.
Soft particles formed by a lipid bilayer enclosing a fraction of the surrounding aqueous medium, known as liposomes, represented the crucial transition from basic research to clinical practice. To improve the control of their features various preparation techniques were proposed. These methods can be divided into two main categories: bulk and microfluidics. The most common bulk method is known as “thin film (TF) hydration”. The second one is based on a microfluidic approach (μF) which allows the control of a liquid flow of lipids, dissolved in alcohol, focused between two aqueous streams, offering the advantage of rapid and tunable mixing and homogeneous reaction environment. μF approach provides the direct control of liposome size, maintaining lower size polydispersity compared to bulk counterpart. Moreover it does not require additional processing step and shows high encapsulation efficiency and reproducibility. We perform a comparison between these methods considering vesicles formulated with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid, used in approved liposomal drugs, and cholesterol. The aspect that is often overlooked is that the preparation method has an influence on the chemical-physical and colloidal properties of liposomes. This is due to the presence of ethanol, chosen for lipid solubilization, absent in TF preparation, but acting as component in μF. Detailed studies on the effect of ethanol on liposomes are scarce despite the evidence suggesting that the outcome should be highly dependent on the composition of the system. Indeed, the presence of ethanol promoted the interdigitation of DMPC membranes. For a better understanding of the effect of the presence of ethanol on liposomes, we evaluated the physico-chemical properties of vesicles and the order/fluidity degree of bilayer, also after dialysis. We studied the inclusion in liposomes of a synthetic drug able to interfere with the metabolism of iron-dependent bacteria.
Alessandro Taloni 1; Fabio Cecconi 1; Angelo Vulpiani 2
1. Istituto dei Sistemi Complessi, CNR - Roma Taurini
2. Department of Physics, "Sapienza" University - Roma
The stochastic transport of particles in a disordered two-dimensional layered medium, driven by correlated y-dependent random velocity fields, is commonly referred to as the random shear (RS) model. This model exhibits superdiffusive behavior in the x direction, attributable to the statistical properties of the disordered advection field. By introducing a layered random amplitude with a power-law discrete spectrum, we derive analytical expressions for the space and time velocity correlation functions, as well as the position moments, using two distinct averaging procedures. Universality and self-averaging are observed in the scaling of the even moments, which resemble Gaussian moments but show crucial differences. Based on these analytical and numerical results, we derive the diffusion equation for the RS process.
L. Tavagnacco 1 ; E. Chiessi 2; F. Sciortino 3; and E. Zaccarelli 1
1.Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Department of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica I, 00133 Rome, Italy
3. Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy
Water plays a fundamental role in determining the structure and functionality of macromolecules, such as responsive polymers. In this presentation, I will provide two examples to elucidate the critical nature of the delicate balance between polymer–water and water–water interactions in determining the solution behavior.
First, I will focus on the widely investigated polymer poly(N-isopropylacrylamide) (PNIPAM) to understand the effect of the adopted computational water model on the in silico P–T phase diagram. I will discuss a comparative atomistic molecular dynamics simulations study of PNIPAM aqueous solution using two advanced water models: TIP4P/2005 and TIP4P/Ice. I will show that, while both water models can reproduce the temperature-induced coil-to-globule transition at atmospheric pressure and the polymer hydration enhancement that occurs with increasing pressure, the PNIPAM–TIP4P/Ice solution better reproduces the experimental findings [1].
Then, I will further compare the results of the PNIPAM–TIP4P/Ice solution, with those obtained for another responsive polymer, i.e. poly(N-isopropymethacrylamide) (PNIPMAM) in TIP4P/Ice water. PNIPMAM chemical structure differs from that of PNIPAM solely due to the presence of an additional methyl group, resulting in a higher coil-to-globule transition temperature of approximately 13 K. I will discuss the conformation and hydration properties of the two responsive polymers, highlighting the keys features responsible of the observed increase of the coil-to-globule transition temperature.
Emanuela Zaccarelli 1, Andrea Ninarello 1
1. CNR Istituto dei Sistemi Complessi, CNR - Roma Sapienza
Thermoresponsive polymer networks undergo a reversible Volume Phase Transition from a swollen to a collapsed state upon increasing temperature. Recently, we introduced a numerical protocol to synthesize realistic polymer networks in silico, either in the form of colloidal particles (microgels) or as bulk systems (hydrogels). In this talk, I will focus on the latter and report calculations of their elastic properties. We find the emergence of auxetic behavior under tension for hydrogels with a low degree of crosslinking. When the limit of auxeticity is reached (Poisson's ratio =−1), a condition that we call "hyper-auxeticity”, the mechanical instability triggers the onset of critical-like fluctuations between two networks of different densities. We demonstrate numerically that this transition is unrelated to the Volume Phase Transition.
Andrea Zaccaria 1; Giambattista Albora 2; Lavinia Rossi Mori 3
1. Istituto dei Sistemi Complessi, CNR - Roma Sapienza
2. Joint Research Centre, European Commission - Seville
3. Sony Computer Science Laboratories - Rome
Many bipartite networks describe systems where an edge represents a relation between a user and an item. Measuring the similarity between either users or items is the basis of memory-based collaborative filtering, a widely used method to build a recommender system to propose items to users. The popular neighbor-based approaches do not consider the total size of the network and only allow positive similarity values. This neglects the possibility and the effect of two users (or two items) being very dissimilar. Moreover, these approaches underperform machine learning algorithms, although they provide higher interpretability. To understand and exploit tree-based algorithms, we propose a method to compute similarity inspired by the functioning of Decision Trees, which we call Sapling Similarity. It takes explicitly into account the size of the network and naturally leads to the possibility of having negative values. The key idea is to look at how the information that a user is connected to an item influences our prior estimation of the probability that another user is connected to the same item: if it is reduced, then the similarity between the two users will be negative, otherwise, it will be positive. By extensive numerical simulations, we show that, when used to build memory-based collaborative filtering, the Sapling Similarity provides better recommendations than existing similarity metrics. Then we compare our approach with state-of-the-art models, including graph neural networks and matrix factorization, using standard datasets. Even if the Sapling Similarity collaborative filtering depends on only one (straightforward) hyperparameter, it shows comparable or higher recommending accuracy, while retaining the high explainability of memory-based approaches.