Intermittency layers associated to turbulent interfaces

In this study we focus on the transport across an interface which separates two regions with homogeneous and isotropic turbulence in absence of a mean shear. The turbulent transport resulting presents an internal structure. Indeed, in the case of turbulent self-diffusion, both experiments and simulations show that the fluid velocity field is marked by a high intermittency front located aside the interface, which is the source of turbulent bursts penetrating the low turbulence region. The presence of an inner structure inside a layer of turbulence self-transport highlights the different nature of the turbulent transport with respect to the Gaussian diffusion. By including other effects, for instance a passive scalar transport or a mass transport in presence of a density stratification, the phenomenology is much enriched. For instance, our preliminary numerical experiments on the passive scalar transport reveals the presence of two intermittency fronts, one on each side of the interface. As can be seen if the figure below, the intermittency level in the fronts is high. This is true both for the scalar and the scalr derivative statistics. A gradual decay in time is observed while they propagate toward the lateral isotropic regions of the flow. In the presence of a kinetic energy gradient across the interface, the locations and intensity of the intermittency fronts are no more symmetric to respect to the interface. The front on the high energy side of the mixing region penetrates deeper and exhibits stronger intermittency. Analogous features are observed also in two dimension

Energy and water vapor transport across a simplified cloud-clear air interface

We consider a simplified physics of the could interface where condensation, evaporation and radiation are neglected and momentum, thermal energy and water vapor transport is represented in terms of the Boussinesq model coupled to a passive scalar transport equation for the vapor. The interface is modeled as a layer separating two isotropic turbulent regions with different kinetic energy and vapor concentration. In particular, we focus on the small scale part of the inertial range as well as on the dissipative range of scales which are important to the micro-physics of warm clouds. We have numerically investigated stably stratified interfaces by locally perturbing at an initial instant the standard temperature lapse rate at the cloud interface and then observing the temporal evolution of the system. When the buoyancy term becomes of the same order of the inertial one, we observe a spatial redistribution of the kinetic energy which produce a concomitant pit of kinetic energy within the mixing layer. In this situation, the mixing layer contains two interfacial regions with opposite kinetic energy gradient, which in turn produces two intermittent sublayers in the velocity fluctuations field. This changes the structure of the field with respect to the corresponding non-stratified shearless mixing: the communication between the two turbulent region is weak, and the growth of the mixing layer stops. These results are discussed with respect to experimental results with and without stratification.Comment: 12 pages, 8 figure

Politiche della casa in Europa. Differenze nazionali e tendenze unificanti dell'housing sociale.

Housing policies in Europe: national differences and unifying tendencies of social housing. - The features of present housing issue ask for new keys, both from the analytical point of view and from that of the policies. One of the most interesting field of anlaysis is represented by the kaleidoscope of different experiences of social housing in Europe. This article aims to go in depth into this hetereogenity and to define a possible model of European social housing. The contribution is organized into five parts: the first one aims to clarify the key terms of the debate; the second one highlights the differences that characterize European countries housing management. In the third part the attention is focused on European Union in order to follow the evolution of its role in social housing from the Eighties to nowadays; opportunities and limits of the multilevel relationships between actors are analyzed in the fourth part; in the conclusions, finally, the focus is on social housing as a way to explain the characters that influence urban spaces of neoliberalism. The changes in housing policies in different European countries, strongly encouraged by the Eu agenda for competitiveness, are evolving towards neoliberal models that rarely assure not only economic but also social and territorial benefits, as the differences between the unitarian and dualistic systems of rental sector prove. Les politiques du logement en Europe. Différences nationales et tendances unifiantes de l'habitat social. - Les caractères de l'actuelle question du logement exigent, soit du point de vue analytique et soit du point de vue des politiques, des nouvelles clefs de lecture. Un des domaines les plus intéressants pour cet exercice est celui-là concernant l'habitat social où l'Europe apparaît comme un tableau de expériences très differentes. Cet article veut approfondir cette hétérogéneité et s'interroger sur le modèle vers auquel on est en train de s'addresser. Cette contribution se déroule autour de certains passages principaux: après avoir clarifié les termes du débat, on analyse les différences qui caractérisent, du point de vue de l'organization et de la gestion, les Pays européens. Dans le troisième passage l'attention se concentre sur le niveau de l'Union européenne pour reconstituer l'évolution de son rôle dès les années Quatre-Vingts jusqu'à aujourd'hui. Ensuite on va souligner les possibilités et les limites qui se dégagent dès les relations multi-niveau entre les acteurs engagés. Dans le dernier passage on s'interroge si et dans quelle façon l'habitat sociale offre des outils efficaces pour développer des raisonnements sur les caractères des espaces urbains du néolibéralisme. Les changements des politiques du logement dans les différents Pays européens, encouragés par les impulsions vers la compétitivité de l'Union européenne, sont en train de évoluer vers des modèles du néolibéralisme qui n'arrivent pas toujours à garantir des avantages économiques et, au même temps, sociaux et territoriaux, comme on peut le voir dans les différences entre les systèmes unitaires et dualistiques dans le domain de la location.This is the author accepted manuscript. The final version is available from Società di Studi Geografici in Rivista Geografica Italiana Vol. 116, Issue 3, pp. 349-378

Cosmic Star Formation: a simple model of the SFRD(z)

We investigate the evolution of the cosmic star formation rate density (SFRD) from redshift z=20 to z=0 and compare it with the observational one by Madau and Dickinson derived from recent compilations of UV and IR data. The theoretical SFRD(z) and its evolution are obtained using a simple model which folds together the star formation histories of prototype galaxies designed to represent real objects of different morphological type along the Hubble sequence and the hierarchical growing of structures under the action of gravity from small perturbations to large scale objects in \Lambda-CDM cosmogony, i.e. the number density of dark matter halos N(M,z). Although the overall model is very simple and easy to set up, it provides results that well mimic those obtained from large scale N-body simulations of great complexity. The simplicity of our approach allows us to test different assumptions for the star formation law in galaxies, the effects of energy feedback from stars to interstellar gas and the efficiency of galactic winds, and also the effect of N(M,z). The result of our analysis is that in the framework of the hierarchical assembly of galaxies the so-called time-delayed star formation under plain assumptions mainly for the energy feedback and galactic winds can reproduce the observational SFRD(z).Comment: ApJ (accepted for publication

The impact of an extracurricular outdoor physical activity program on long-term memory in adolescent during COVID-19 pandemic

The present study examined the effects of an 8-week extracurricular outdoor physical activity program aimed to improve long-term memory performance in adolescent concerning the Covid-19 period. Participants were 40 schoolchildren (aged 16-17) who trained twice a week in aerobic exercise two hours per session, randomly assigned to participate in either an extracurricular outdoor physical activity program (EG; n = 20) or a waitlist control group (CG; n = 20). At baseline and after training we administered the Verbal Paired Associates (VPA-I) a subtest of the Wechsler Memory Scale – IV (WMS-IV, 2009), which represents one of the most widely used instruments for assessing explicit episodic memory performance. The results suggested that after 8-week aerobic exercise program students were able to increase their long-term memory, and that this capacity was more evident following physical activity that required greater cognitive involvement

How vegetation in flows modifies the turbulent mixing and spreading of jets

While studies on vegetated channel flows have been developed in many research centers, studies on jets interacting with vegetation are still rare. This study presents and analyzes turbulent jets issued into an obstructed cross-flow, with emergent vegetation simulated with a regular array of cylinders. The paper presents estimates of the turbulence diffusion coefficients and the main turbulence variables of jets issued into a vegetated channel flow. The experimental results are compared with jets issued into unobstructed cross-flow. In the presence of the cylinder array, the turbulence length-scales in the streamwise and transverse directions were reduced, relative to the unobstructed crossflow. This contributed to a reduction in streamwise turbulent diffusion, relative to the unobstructed conditions. In contrast, the transverse turbulent diffusion was enhanced, despite the reduction in length-scale, due to enhanced turbulent intensity and the transverse deflection of flow around individual cylinders. Importantly, in the obstructed condition, the streamwise and transverse turbulent diffusion coefficients are of the same order of magnitude

Blockchain Framework in Digital Government for the Certification of Authenticity, Timestamping and Data Property

In an ever more digitized world where information and data are increasingly dematerialized, the question of how to certify intellectual property and define when a document has been created or modified without the presence of any third-party guarantor inevitably arises. This document proposes a decentralized method that, by exploiting blockchain technology and distributed peer-to-peer (P2P) networks, makes it possible to historicize information in such a way that it is not possible for a user to alter its dating, attribute ownership or modify it by impersonating the author. The data certification (document, image, film, data archive, etc.) takes place through the creation of an immutable relationship between the owner and the data. At the legal level, many countries are beginning to regulate blockchain technology so that it can be used in many areas, such as the production chain, the Internet of Things or Public Administration. In this paper we present a solution to promote digital government and greater transparency, through the use of a framework based on the Ethereum blockchain, smart contracts and a decentralized application

coastline evolution based on statistical analysis and modeling

Abstract. Wind, waves, tides, sediment supply, changes in relative sea level and human activities strongly affect shorelines, which constantly move in response to these processes, over a variety of timescales. Thus, the implementation of sound coastal zone management strategies needs reliable information on erosion and/or deposition processes. To suggest a feasible way to provide this information is the main reason for this work. A chain approach is proposed here, tested on a vulnerable coastal site located along southern Italy, and based on the joint analysis of field data, statistical tools and numerical modeling. Firstly, the coastline morphology has been examined through interannual field data, such as aerial photographs, plane-bathymetric surveys and seabed characterization. After this, rates of shoreline changes have been quantified with a specific GIS tool. The correlations among the historical positions of the shoreline have been detected by statistical analysis and have been satisfactorily confirmed by numerical modeling, in terms of recurrent erosion–accretion area and beach rotation trends. Finally, based on field topographic, sediment, wave and wind data, the response of the beach through numerical simulation has been investigated in a forecasting perspective. The purpose of this study is to provide a feasible, general and replicable chain approach, which could help to thoroughly understand the dynamics of a coastal system, identify typical and recurrent erosion–accretion processes, and predict possible future trends, useful for planning of coastal activities

Animal models of vascularized nerve grafts: a systematic review

: The aim of this review is to present and compare the various animal models of vascularized nerve grafts described in the literature as well as to summarize preclinical evidence for superior functional results compared to non-vascularized free nerve grafts. We also will present the state of the art on prefabricated vascularized nerve grafts. A systematic literature review on vascularized nerve graft models was conducted via the retrieval with the PubMed database on March 30, 2019. Data on the animal, nerve, and vascularization model, the recipient bed, the evaluation time points and methods, and the results of the study results were extracted and analyzed from selected articles. The rat sciatic nerve was the most popular model for vascularized nerve grafts, followed by the rabbit; however, rabbit models allow for longer nerve grafts, which are suitable for translational evaluation, and produced more cautious results on the superiority of vascularized nerve grafts. Compared to free nerve grafts, vascularized nerve grafts have better early but similar long-term results, especially in an avascular bed. There are few studies on avascular receiving beds and prefabricated nerve grafts. The clinical translation potential of available animal models is limited, and current experimental knowledge cannot fully support that the differences between vascularized nerve grafts and free nerve grafts yield a clinical advantage that justifies the complexity of the procedure

Serafino Zappacosta: An Enlightened Mentor and Educator.

With this article, the authors aim to honor the memory of Serafino Zappacosta, who had been their mentor during the early years of their career in science. The authors discuss how the combination of Serafino Zappacosta's extraordinary commitment to teaching and passion for science created a fostering educational environment that led to the creation of the "Ruggero Ceppellini Advanced School of Immunology." The review also illustrates how the research on the MHC and the inspirational scientific context in the Zappacosta's laboratory influenced the authors' early scientific interests, and subsequent professional work as immunologists