2,534 research outputs found
Exploiting limited valence patchy particles to understand autocatalytic kinetics
No full textAutocatalysis, i.e., the speeding up of a reaction through the very same molecule which is produced, is common in chemistry, biophysics, and material science. Rate-equation-based approaches are often used to model the time dependence of products, but the key physical mechanisms behind the reaction cannot be properly recognized. Here, we develop a patchy particle model inspired by a bicomponent reactive mixture and endowed with adjustable autocatalytic ability. Such a coarse-grained model captures all general features of an autocatalytic aggregation process that takes place under controlled and realistic conditions, including crowded environments. Simulation reveals that a full understanding of the kinetics involves an unexpected effect that eludes the chemistry of the reaction, and which is crucially related to the presence of an activation barrier. The resulting analytical description can be exported to real systems, as confirmed by experimental data on epoxy-amine polymerizations, solving a long-standing issue in their mechanistic description
Connecting Irreversible to Reversible Aggregation: Time and Temperature
No full textWe report molecular dynamics simulations of a gel-forming mixture of ellipsoidal patchy particles with different functionality. We show that in this model, which disfavors the formation of bond-loops, elapsed time during irreversible aggregation-leading to the formation of an extended network-can be formally correlated with equilibrium temperature in reversible aggregation. We also show that it is possible to develop a parameter-free description of the self-assembly kinetics, bringing reversible and irreversible aggregation of loopless branched systems to the same level of understanding as equilibrium polymerization
Modeling the Crossover between Chemically and Diffusion-Controlled Irreversible Aggregation in a Small-Functionality Gel-Forming System
No full textThe analysis of realistic numerical simulations of a gel-forming irreversible aggregation process provides information on the role of cluster diffusion in controlling the late stages of the aggregation kinetics. Interestingly, the crossover from chemically controlled to diffusion-controlled aggregation takes place well beyond percolation, after most of the particles have aggregated in the spanning network and only small clusters remain in the sol. The simulation data are scrutinized to gain insight into the origin of this crossover. We show that a single additional time scale (related to the average diffusion time) is sufficient to provide an accurate description of the evolution of the extent of reaction at all times
A parameter-free description of the kinetics of formation of loop-less branched structures and gels
No full textWe study, via Brownian dynamics simulation, the kinetics of formation of branched loop-less structures for a mixture of particles with functionalities of two and three, the three-functional ones providing the branching points in the resulting network. We show that for this system, by combining the appropriate Smoluchowski rate equations, including condensation and fragmentation terms, with the thermodynamic perturbation theory of Wertheim, it is possible to provide a parameter-free description of the assembly process, even in the limit of irreversible aggregation (low T). Our work provides evidence of a connection between physical and chemical gelation in low-valence particle systems, properly relating aging (or curing) time with temperature
Michele Taruffo: el magisterio y la obra ejemplares del genial procesalista «todoterreno»
No full textThe author reflects on Michele Taruffo’s extraordinarily important contribution to the renewal of both conventional procedural law scholarship and the theoretical background of law-court professionals. Taruffo’s contribution was achieved by means of introducing to mainstream culture in those circles the necessary knowledge of the underlying epistemic dimension, which was traditionally suppressed by the strictly legal one.El autor discurre acerca de la importantísima contribución de Michele Taruffo a la renovación del procesalismo convencional y del bagaje teórico de los profesionales de la jurisdicción, mediante la incorporación a la cultura dominante en tales medios del imprescindible conocimiento de la dimensión epistémica subyacente y tradicionalmente sofocada por la propiamente jurídica
Looking for Japan in contemporary Italy
No full textPh. D.Includes bibliographical referencesIncludes vitaby Michele Monserrat
The Author Reply. Letter to the Editor
No full textThe Author reply to the Letter sent to the Editor about a previus article on low anterior resection
A molecular dynamics study of chemical gelation in a patchy particle model
No full textWe report event-driven molecular dynamics simulations of the irreversible gelation of hard ellipsoids of revolution containing several associating groups, characterizing how the cluster size distribution evolves as a function of the extent of reaction, both below and above the gel point. We find that over a very large interval of values of the extent of reaction, parameter-free mean-field predictions are extremely accurate, providing evidence that in this model the Ginzburg zone near the gel point, where non-mean field effects are important, is very limited. We also find that the Flory's hypothesis for the post-gelation regime properly describes the connectivity of the clusters even if the long-time limit of the extent of reaction does not reach the fully reacted state. This study shows that irreversibly aggregating asymmetric hard-core patchy particles may provide a close realization of the mean-field model, for which available theoretical predictions may help control the structure and the connectivity of the gel state. Besides chemical gels, the model is relevant to network-forming soft materials like systems with bioselective interactions, functionalized molecules and patchy colloids. © The Royal Society of Chemistry
From the microscopic to collective dynamics in aqueous solutions of a thermoresponsive microgel
No full textIl trionfo della morte di Palermo. Un'allegoria della modernità
No full textOriginariamente collocato nel cortile dell’Ospedale Grande e Nuovo in Palazzo Sclafani, il Trionfo della morte – ora custodito nella Galleria di Palazzo Abatellis, a Palermo – è una straordinaria enciclopedia iconografica medievale e moderna, di cui non conosciamo l’autore.
Il libro di Michele Cometa è una guida all’interpretazione del tessuto narrativo di questo formidabile affresco. Le molteplici fonti pittoriche e letterarie che ne costituiscono la trama convergono nel tratteggiare – evocando la peste nera che imperversava in Europa da più di un secolo – una sorta di confutazione iconologica del retribuzionismo medievale. Le pene mondane, infatti, non sono qui più riconducibili al peccato, ma si stemperano in una melanconia tutta modernaOriginally located in the courtyard of the Great and New Hospital in Palazzo Sclafani, the Triumph of Death - now housed in the Gallery of Palazzo Abatellis, in Palermo - is an extraordinary medieval and modern iconographic encyclopedia, of which we do not know the author.
Michele Cometa's book is a guide to interpreting the narrative fabric of this formidable fresco. The multiple pictorial and literary sources that make up the plot converge in outlining - evoking the black plague that raged in Europe for more than a century - a sort of iconological refutation of medieval retribution. In fact, worldly pains are no longer attributable to sin, but are dissolved in a wholly modern melancholy
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