On the Mean Residence Time in Stochastic Lattice-Gas Models

A heuristic law widely used in fluid dynamics for steady flows states that the amount of a fluid in a control volume is the product of the fluid influx and the mean time that the particles of the fluid spend in the volume, or mean residence time. We rigorously prove that if the mean residence time is introduced in terms of sample-path averages, then stochastic lattice-gas models with general injection, diffusion, and extraction dynamics verify this law. Only mild assumptions are needed in order to make the particles distinguishable so that their residence time can be unambiguously defined. We use our general result to obtain explicit expressions of the mean residence time for the Ising model on a ring with Glauber + Kawasaki dynamics and for the totally asymmetric simple exclusion process with open boundaries

Optimality in self-organized molecular sorting

We introduce a simple physical picture to explain the process of molecular sorting, whereby specific proteins are concentrated and distilled into submicrometric lipid vesicles in eukaryotic cells. To this purpose, we formulate a model based on the coupling of spontaneous molecular aggregation with vesicle nucleation. Its implications are studied by means of a phenomenological theory describing the diffusion of molecules towards multiple sorting centers that grow due to molecule absorption and are extracted when they reach a sufficiently large size. The predictions of the theory are compared with numerical simulations of a lattice-gas realization of the model and with experimental observations. The efficiency of the distillation process is found to be optimal for intermediate aggregation rates, where the density of sorted molecules is minimal and the process obeys simple scaling laws. Quantitative measures of endocytic sorting performed in primary endothelial cells are compatible with the hypothesis that these optimal conditions are realized in living cells

Spleen histology in children with sickle cell disease and hereditary spherocytosis: Hints on the disease pathophysiology

open2Hereditary spherocytosis (HS) and sickle cell disease (SCD) are associated with splenomegaly and spleen dysfunction in pediatric patients. Scant data exist on possible correlations between spleen morphology and function in HS and SCD. This study aimed to assess the histological and morphometric features of HS and SCD spleens, in order to get possible correlations with disease pathophysiology. In a large series of spleens from SCD, HS and control patients the following parameters were considered: (i) macroscopic features; (ii) lymphoid follicle (LF) density; (iii) presence of peri-follicular marginal zones (MZs); (iv) presence of Gamna-Gandy bodies; (v) density of CD8-positive sinusoids; (vi) density of CD34-positive microvessels; (vii) presence/distribution of fibrosis and SMA-positive myoid cells; (viii) density of CD68-positive macrophages. SCD and HS spleens have similar macroscopic features. SCD spleens had lower LF density and fewer MZs than HS spleens and controls. SCD also showed lower CD8-positive sinusoid density, increased CD34-positive microvessel density and SMA-positive myoid cells, and higher prevalence of fibrosis and Gamna-Gandy bodies. HS had lower LF and CD8-positive sinusoid density than controls. No significant differences were noted in red pulp macrophages. By multivariate analysis, the majority of HS spleens clustered with controls, while SCD grouped separately. A multi-parametric score could predict the degree of spleen changes irrespective of the underlying disease. In conclusion, SCD spleens display greater histologic effacement than HS and SCD-related changes suggest impaired function due to vascular damage. These observations may contribute to guide the clinical management of patients.embargoed_20161128Alaggio, RitaAlaggio, Rita; Gamba, Piergiorgi

Musicality without Humanity

After years in which the study of musical abilities in species other than humans occurred sporadically, the investigation of these building blocks (e.g., rhythm, frequency variation) received a new impetus. Using the comparative approach, recent studies have shown how the investigation of rhythm in the vocal displays of primate species can yield surprising results that help us to shed light on the factors that may have acted as selective pressures throughout the evolution of the primate tree. This contribution aims to review the studies conducted in the last decade on primates and understand how these can be useful in reconstructing a phylogeny of some of the abilities that enable humans to make music.Dopo anni in cui lo studio delle abilità musicali in specie diverse dall’uomo è stato sporadico, l'indagine su questi elementi costitutivi (ad esempio, ritmo, variazione di frequenza) ha ricevuto un nuovo impulso. Utilizzando l’approccio comparativo, gli studi degli ultimi anni hanno dimostrato come l’indagine sul ritmo nelle manifestazioni vocali delle specie di primati possa dare risultati sorprendenti che ci aiutano a far luce sui fattori che possono aver agito come pressioni selettive nel corso dell'evoluzione dell'albero dei primati. Questo contributo si propone di passare in rassegna gli studi condotti nell'ultimo decennio sui primati e di capire come questi possano essere utili per ricostruire una filogenesi di alcune delle abilità che permettono all'uomo di fare musica