Non-equilibrium fluctuations in GUVs driven by light

From more than one century ago to nowadays one of the main challenges in neurobiology is the understanding the basis of memory. The locus that was discovered to be the storage of memories in the mammalian brain, where the synapses are built on, are the dendritic spines. The relation between molecular, morphological data of dendritic spines and memory formation with relative diseases has been extensively investigated, nevertheless many mechanisms are still poorly understood. One of these is the compartmentalisation, a term that involves the confinement of membrane-bound receptors in the head of spines and it is believed to underlie the changes in synaptic strength during learning and memory formation. One process proposed to explain the compartmentalisation is the presence of domains that trap the receptors from the surrounding. In this work a biomimetical model was built to study the problem of the receptors confinement in dendritic spines. By micromanipulation it is possible to model the spines with a wellcontrollable system in vitro made of one-layer lipid membranes with a spherical shape, named Giant Unilamellar Vesicles, (GUVs) and tubules. From previous studies it is known that when GUVs are prepared with lipids of different transition temperatures, at a critical composition, as the temperature is lowered, phase separation in Liquid Ordered (Lo) and Liquid Disordered (Ld) phases occurs. In this work, a novel cutting-edge technique to obtain the phase separation is employed in a systematic way and the response of the GUVs is characterised in term of physical parameters. Briefly, the temperature is kept constant, and the composition of the vesicles changed using light, via photo-oxidation. Varying the ratio between the lipids that prefer the Lo and Ld phases until the critical composition is reached, it is possible to control the process and induce the phase separation for one vesicle of a time. In this way, the phase separated domains of the GUVs are used to model the compartments in the spines and quantum dots were added to the previous system mimic the receptors. It is worthy to highlight the importance of using a biomimetic model to study this problem. It is a way to look in the heart of the process with different eyes, aimed not to neglect the detail of the system, but to provide a solid basis that allows to include all of them later and study the real problem with its complexity.ope

Numerical modelling of steel-to-timber joints and connectors for CLT structures

The mechanical behaviour of steel-to-timber joints with annular-ringed shank nails is investigated using numerical modelling and a component approach. These joints are used in Cross-Laminated Timber (CLT) buildings to anchor metal connectors such as hold-downs and angle brackets to the timber panels. At first, a general hysteresis model is introduced, where a single fastener joint is schematized as an elasto-plastic beam embedded in a non-linear medium with a compression-only behaviour. A second hysteresis model is then presented, where the mechanical behaviour of the joint is simulated by a non-linear spring with three degrees of freedom. Both models are calibrated on the design rules prescribed by the reference standards. Moreover, average strength capacities are determined from the corresponding characteristic values assuming a standard normal distribution and suitable coefficients of variation. As first applicative examples of the proposed models, shear tests are simulated on single steel-to-timber joints with annular-ringed shank nails and on a connection made of an angle bracket and sixty nails. The scatter of mechanical properties in steel-to-timber joints is also taken into account in the simulations and a stochastic approach is proposed, demonstrating acceptable accuracy

Non-linear modelling of the in-plane seismic behaviour of timber Blockhaus log-walls

This paper investigates the non-linear modelling of the cyclic behaviour of Blockhaus timber log-walls under in-plane lateral loads. The structural behaviour of Blockhaus log-walls in the examined loading condition strictly depends on the geometry \u2013 thus on the deformability and ultimate resistance \u2013 of the adopted corner joint, namely the joint between perpendicular log-walls. The presence of metal fasteners is in fact minimized and the structural interaction between the basic timber components is provided by simple mechanisms such as notches, tongues and grooves, multiple surfaces in contact. In this paper, a computationally effective FE-model is developed, in order to predict the cyclic behaviour of an entire Blockhaus log-wall once the cyclic behaviour of the adopted corner joint is known. The model uses non-linear hysteretic springs to describe the joint behaviour, where all typical features such as pinching behaviour, strength and stiffness degradation can be considered. By comparing the numerical and the experimental predictions of the cyclic response of full-scale Blockhaus log-walls, a general good agreement is found. Simulations confirmed the high flexibility of the studied structural systems, as well as the significant effect of possible openings such as doors and windows on their global resistance to in-plane lateral loads. In conclusion, the presented study confirmed that the proposed modelling approach can be used to estimate the load-carrying capacity and vulnerability to seismic events of Blockhaus shear walls, and that the same model could be extended to full Blockhaus buildings

LINGUA D’USO E LINGUA POPOLARE NEI DIZIONARI DI TOMMASEO

Nell’articolo sono indagati lemmi e accezioni popolari presenti nei dizionari di Tommaseo. Da uno spoglio digitale prima delle varie edizioni del Dizionario dei Sinonimi e poi del Dizionario della lingua, sono state selezionate e raccolte per tipologia in due Appendici le voci indicate come ‘popolari’: se ne ricava che il dizionario di Tommaseo è il primo che le registra sistematicamente. Di queste si è poi studiata l’origine, fra giunte di prima mano offerte dai collaboratori e citazioni puntuali tratte da canti popolari, in particolare toscani, come quella di Giuseppe Tigri (mancante nella «Tavola delle abbreviature»). Si è potuto ricavare anche quale fosse, fra i tanti collaboratori al Dizionario, quello destinato allo spoglio dei volumi di canti, Savino Savini, e si è riportata una significativa selezione del carteggio inedito conservato alla Biblioteca Nazionale Centrale di Firenze.   Language of use and popular language in Tommaseo’s dictionaries The article investigates popular terms and meanings in Tommaseo’s dictionaries. Starting rom a digital survey of the various editions of the Dictionary of Synonyms and the Dictionary of the Language, the ‘popular’ entries were selected and divided by type in two Appendices: Tommaseo’s dictionary was the first to systematically record them. Their origins were studied, among first-hand entries offered by his collaborators and precise quotations taken from popular songs, in particular from Tuscany, by Giuseppe Tigri (missing in the “Table of abbreviations”). It was also possible to discover which, among the many contributors to the Dictionary, was the one intended for the selection of the volumes of songs, Savino Savini. A significant selection of unpublished correspondence kept at the Biblioteca Nazionale Centrale in Florence was cited

A hysteresis model for timber joints with dowel-type fasteners

Predicting the mechanical behaviour and the failure mechanism of timber joints with dowel-type fasteners re- quires consideration of several factors, including the geometrical and mechanical properties of the metal fas- tener, the physical properties of timber and the interaction between such elements. This paper proposes a nu- merical model where a joint is schematized as an elasto-plastic beam in a non-linear medium with a compression-only behaviour. Unlike the differential approach adopted by most of the hysteresis models pub- lished in literature, this model predicts the load-displacement response using simple mechanical relationships and basic input parameters. Furthermore, the model is capable of reproducing the effect of the cavity formed around the fastener by timber crushing, and simulates the hysteretic behaviour and the energy dissipation under cyclic conditions. Shear tests are reproduced on nailed steel-to-timber joints in Cross-Laminated Timber and results are compared to the experimental test data obtained on similar single fastener joints. Simulations lead to accurate predictions of both the mechanical behaviour (initial stiffness, maximum load-carrying capacity, global shape of the loading curve and of the hysteresis cycles) and the total energy dissipation observed in the tests

Interface geometry of binary mixtures on curved substrates

Motivated by recent experimental work on multicomponent lipid membranes supported by colloidal scaffolds, we report an exhaustive theoretical investigation of the equilibrium configurations of binary mixtures on curved substrates. Starting from the J\"ulicher-Lipowsky generalization of the Canham-Helfrich free energy to multicomponent membranes, we derive a number of exact relations governing the structure of an interface separating two lipid phases on arbitrarily shaped substrates and its stability. We then restrict our analysis to four classes of surfaces of both applied and conceptual interest: the sphere, axisymmetric surfaces, minimal surfaces and developable surfaces. For each class we investigate how the structure of the geometry and topology of the interface is affected by the shape of the substrate and we make various testable predictions. Our work sheds light on the subtle interaction mechanism between membrane shape and its chemical composition and provides a solid framework for interpreting results from experiments on supported lipid bilayers.Comment: 26 pages, 10 figure

Lezioni sull'etimologia di Paolo Zolli (1972)

L’articolo presenta introduzione ed edizione di un inedito, databile al 1972, del linguista veneziano Paolo Zolli. Attraverso una disamina di storia degli studi, Zolli delinea il contesto metodologico e scientifico che prelude alla pubblicazione dei grandi dizionari etimologici italiani nell’ultimo quarto del Ventesimo secolo – su tutti il DELI, di cui Zolli fu autore assieme a Manlio Cortelazzo, e il LEI. Probabilmente volto a scopi didattici, l’inedito zolliano si configura come prezioso documento che aggiunge aspetti nuovi e dettagli significativi alla storia delle discipline etimologiche e storico linguistiche

Thermodynamic equilibrium of binary mixtures on curved surfaces

We study the global influence of curvature on the free energy landscape of two-dimensional binary mixtures confined on closed surfaces. Starting from a generic effective free energy, constructed on the basis of symmetry considerations and conservation laws, we identify several model-independent phenomena, such as a curvature-dependent line tension and local shifts in the binodal concentrations. To shed light on the origin of the phenomenological parameters appearing in the effective free energy, we further construct a lattice-gas model of binary mixtures on non-trivial substrates, based on the curved-space generalization of the two-dimensional Ising model. This allows us to decompose the interaction between the local concentration of the mixture and the substrate curvature into four distinct contributions, as a result of which the phase diagram splits into critical sub-diagrams. The resulting free energy landscape can admit, as stable equilibria, strongly inhomogeneous mixed phases, which we refer to as antimixed states below the critical temperature. We corroborate our semi-analytical findings with phase-field numerical simulations on realistic curved lattices. Despite this work being primarily motivated by recent experimental observations of multi-component lipid vesicles supported by colloidal scaffolds, our results are applicable to any binary mixture confined on closed surfaces of arbitrary geometry.Comment: 20 Pages, 7 Figures; comments and references added, typos correcte