Diffusive approach for non-linear beam dynamics in a circular accelerator

Nella fase di design e simulazione di un acceleratore circolare, risulta fondamentale avere una buona comprensione del moto betatronico non-lineare delle singole particelle, e di come questo interferisce con la qualità del fascio. In questo lavoro vengono studiati sistemi Hamiltoniani sottoposti a perturbazioni stocastiche tramite un framework diffusivo, basato sull'equazione di Fokker-Planck. Tale studio viene poi applicato all'analisi del moto betatronico non-lineare e al problema dell'Apertura Dinamica. In particolare, vengono impostate le basi per formulare un metodo di interpolazione di processi diffusivi simil-Nekhoroshev e viene proposta una procedura sperimentale per misurare gli effetti di diffusione locale all'interno di un acceleratore. L'Apertura Dinamica è una quantità chiave per il comportamento a lungo termine di un acceleratore, tuttavia, la misura di questa quantità nelle simulazioni presenta serie difficoltà dal punto di vista computazionale. È dunque nel nostro interesse riuscire a formulare una legge che descriva la dipendenza dal tempo dell'Apertura Dinamica

Development of an event-based simulator for analysing excluded volume effects in a Brownian gas

Il presente lavoro si pone come scopo lo sviluppo di un simulatore in C++ di dinamica molecolare utilizzando un approccio event-based, in grado di simulare la dinamica newtoniana semplice di molecole bidimensionali di forma arbitraria. Abbiamo utilizzato il simulatore NOCS per imbastire un primo tentativo di ricerca e di analisi degli effetti di volume escluso sul moto Browniano di molecole. In particolare si vogliono ricercare violazioni locali di isotropia nel moto Browniano. Nella parte teorica dell'elaborato, si analizzano gli strumenti matematici e statistici fondamentali della Kinetic Theory (teoria cinetica dei gas) ed i principali modelli della depletion force, uno dei fenomeni causati da potenziale di volume escluso

Más allá de la percepción: Hacia una ecología histórica del paisaje rural en Italia

The European Landscape Convention (ELC) uses various definitions in which the cultural and historical contents of the landscapes are reduced to their «representation» or «visual per- ception». The «perceptive» approach to the landscape obscures, in a false «natural» dimension, the living environmental features of the landscape itself. This is the case with rural landscapes which are, on the contrary, nowadays considered part of a wider European rural heritage. Specific environmental (ecological) and cultural (historical) factors have been identified, based on a «historical approach», to manage such a heritage. These factors are the historical-environmental processes that over time have shaped a variety of agrarian, pastoral and forestry landscapes, landscapes that we would like to be preserved. Current historical ecology approach enriches Emilio Sereni’s legacy on the economic side of agrarian landscape with novel tools for identi- fying single landscapes, their historical stratification and for management projects. This paper intends to illustrate few examples concerning studies already carried out and still in progress in Liguria (NW Italy). In such researches of local history, geography, archaeology and ecology have interacted, studying landscapes at the scale of the single site. In the process, an environ- mental archaeology approach has been tested, based on the methods of the historical ecology and devoted to the reconstruction of the «individual» history of agro-sylvi-pastoral landscapes, of their environmental resources and management practices.La  Convention  Européenne  du  Paysage  (CEP)  utilise  diverses  définitions provenant d’études dans lequel le contenu culturel et historique des paysages est réduit à des «représen- tations» ou «perceptions visuels». Ce type d’approche - en simplifiant «perceptive» - nuances, ou plus souvent masque sous un faux «naturel», la dimension, environnementale matérielle et les éléments géographiques vivants du paysage lui-même, qui sont bien détenteurs de contenu historique, même si cette dimension historique de l’environnement n’est pas toujours facilement reconnaissable en Italie par le planificateur. C’est le cas des paysages ruraux, qui peuvent se situer aujourd’hui dans le cadre plus large du patrimoine rural européen. Cela devait pas être sans conséquence pour la gestion des paysages qui sont identifiables par le biais d’une «appro- che historique»,uniformisé, a leurs facteurs écologiques et culturels. A leur tour cet approche dégage les processus historique-environnementaux qui, dans le cours du temps ont façonné la variété de paysages agricoles, forestiers et pastoraux, qui nous tient à pérenniser. A partir de la  leçon d’ Emilio Sereni (1961) concernant les processus économiques-historiques comme facteurs de transformation du paysage agraire de l’Italie, de nos jours, l’ approche de «écologie historique» ajoute de nouveaux outils pour l’identification de paysages «individuels», de leur stratification historique et la formulation de projets de gestion. Notre contribution a pour objec- tif de présenter quelques exemples concernant les études réalisées et en cours en Ligurie (NW Italie), où les recherches d’histoire locale, de géographie, l’archéologie et l’écologie ont mis au point des analyses du paysage à l’échelle du site. Une approche qui fonde une archéologie des ressources environnementales, consacrée à la reconstruction de l’histoire «individuelle» (ou bien topographique) des paysages agro-sylvo-pastoraux, de leurs ressources environnementales et des pratiques de gestion, a été testé.El Convenio Europeo del Paisaje (CEP) utiliza diferentes definiciones de las que derivan estudios en los que el contenido cultural e histórico de los paisajes se reducen a su «representa- ciones» o «percepciones» visuales. Este enfoque «perceptivo» del paisaje oscurece, o incluso con frecuencia enmascara bajo una falsa apariencia «natural», los elementos vivos medioambientales y materiales del propio paisaje. éste es el caso de los paisajes rurales que se consideran, por el contrario, actualmente, producto de una amplia herencia rural europea. Ciertos factores específicos, medioambientales (ecológicos) y culturales (históricos), han sido identificados a partir de una «aproximación histórica» que controla en cada caso esta herencia histórica. Estos factores son los procesos histórico-ambientales que en cada época han configurado una variedad de paisajes agrarios, ganaderos y forestales; paisajes que queremos conservar. El actual enfoque ecológico- histórico enriquece el legado de Emilio Sereni (1961) (sobre los aspectos económicos del paisaje agrario) con nuevos instrumentos para identificar cada paisaje, su estratificación histórica y los proyectos de ordenación adecuados. Este artículo intenta ilustrar todo esto a partir de unos pocos ejemplos, relativos a estudios realizados y en curso en Liguria (Noroeste de Italia). En cada una de las instituciones presentadas que estudian paisajes en escala del lugar correspondiente, vemos cómo interactúan a escala local historia, geografía, arqueología y ecología. En este proceso se pone a prueba una arqueología medioambiental, basada en los métodos de la ecología histórica y enfocada a la reconstrucción de la historia «individual» de los paisajes agro-silvo-ganaderos, de sus recursos ambientales y sus prácticas de gestión

The disappearance of cultural landscapes: the case of wooded-meadows in the Ligurian Apennines (NW Italy)

The \u201cwooded-meadows system\u201d is a multifunctional use of vegetation resources widespread in Europe since the Neolithic, and well documented in the Ligurian Apennines (NW Italy) between the Middle Ages and the first half of the 19th century. The management of wooded-meadows included: collection of fallen and dead branches in spring, later used for fuel; mowing and grazing in summer; collection of secondary products; making sheaves from branches in autumn, later used as cattle and sheep fodder; coppicing, pollarding and cutting of trees in winter. Three sites located in eastern Ligurian Apennines were studied by means of an interdisciplinary approach in order to better understand the impact and the consequences of this historical landuse practice on vegetation structure and composition. In particular, based on specific features of palynological diagrams, it was possible to conclude that (compared to the post-cultural phase) \u2013 when the wooded-meadows system was in use all the sites were characterized by: (1) lower pollen percentages of trees; (2) higher pollen percentages of shrubs and herbs; (3) higher percentages of anthropogenic pollen indicators; (4) higher values of palynological richness. This research also represents a contribution to issues of nature-conservation policy for the preservation of cultural landscapes

On the ecology of ancient and recent woodlands: the role of historical approach

This chapter presents several Italian case studies to interpret and discuss the concept of ancient forests by means of methods and sources used by historical ecology. The historical approach adopted by the Laboratory of Environmental Archaeology and History (LASA) of the University of Genoa involves the use of multiple sources (textual, geographic, archaeological, ethnologic, oral, environmental), a regressive method and strong spatial and social contextualization. In fact, the methods of British historical ecology have been developed by reworking and comparing contents of British local history with those proposed by the Italian microhistory. The sedimentary and observational sources generally related to woodland environmental archaeology are now more generally produced and analysed as part of an archaeology of environmental resources. The strengths and weaknesses of this approach is illustrated through two selected case studies concerning the history of Mediterranean multi-use systems of woodland resources (agrosilvopastoral). The first case study pertains to a mountain area (Upper Trebbia-Aveto Basin) while the second is on the coast of western Liguria (Merula Valley, north-west Italy

Botanical relics of a lost landscape: herborising ‘upon the Cliffs about the Pharos’ in Genoa, March 1664

This paper uses approaches derived from historical ecology to show how knowledge can be gained about the historical and cultural value of neglected urban landscapes. We study the area around Genoa’s lighthouse and consider the long-term survival of individual plant species and some implications for landscape conservation. We examine topographical representations over the last 500 years to establish the landscape context of the lighthouse. We then analyse the records of plants collected by two English naturalists of the seventeenth century, John Ray and Francis Willughby, and demonstrate how the plants were identified and documented. We survey the current vegetation to establish whether any species identified in 1664 still grow at the site. This exploration of botanical ancestry at a local scale makes it possible to demonstrate cultural–historical values of the lighthouse rocks and their vegetation which should be considered as part of the cultural heritage of the city of Genoa

Partial discharge measurements of DC insulation systems: the influence of the energization transient

This paper introduces techniques for partial discharge, PD, recognition under DC, both in steady state and in transient condition, during which the field in insulation varies slowly from a permittivity-driven to a conductivity-driven profile. This transient can be significantly long, depending on insulating material characteristics, and condition PD phenomenology and impact of PD on insulation life. Focusing mainly on the behavior of PD repetition rate as a function of time, after insulation energization by a DC voltage step, PD triggered by transient field can be separated from those relevant to steady state, which may indicate a criterion to estimate the partial discharge inception voltage, PDIV, under DC supply

Investigating Energization Transients and the Potentiality of Partial Discharge Inception and Damage in Nanofilled Polypropylene Insulation for DC Cables and Capacitors

New nanostructured insulating materials are investigated, within the European project GRIDABLE, to be used for DC cable and capacitors. Besides electrical, thermal and mechanical properties, and life behavior, work is being done to evaluate their capability to endure highly stressing conditions as those cause by the inception of partial discharges, PD. This paper, in particular, analyzes what happens during energization of a DC cable or capacitors, when voltage goes from zero to the nominal value in a few seconds, while the internal electrical field takes longer time to reach the DC steady state configuration. During an energization transient, indeed, electrical field in insulation, and insulation defects (as cavities), is driven by permittivity, not conductivity as in steady state. Hence, PD might occur with high repetition rate, which would not occur, or at much lower repetition rate, in steady state. The way to evaluate the time constant of the transient, that is, through charging current measurement, is described and successfully fitted to the results of PD measurements performed on two types of polypropylene, PP: neat and nanostructured, and a cross-linked polyethylene, XLPE, having significantly different electrical characteristics

Diffusive models and chaos indicators for non-linear betatron motion in circular hadron accelerators

Understanding the complex dynamics of beam-halo formation and evolution in circular particle accelerators is crucial for the design of current and future rings, particularly those utilizing superconducting magnets such as the CERN Large Hadron Collider (LHC), its luminosity upgrade HL-LHC, and the proposed Future Circular Hadron Collider (FCC-hh). A recent diffusive framework, which describes the evolution of the beam distribution by means of a Fokker-Planck equation, with diffusion coefficient derived from the Nekhoroshev theorem, has been proposed to describe the long-term behaviour of beam dynamics and particle losses. In this thesis, we discuss the theoretical foundations of this framework, and propose the implementation of an original measurement protocol based on collimator scans in view of measuring the Nekhoroshev-like diffusive coefficient by means of beam loss data. The available LHC collimator scan data, unfortunately collected without the proposed measurement protocol, have been successfully analysed using the proposed framework. This approach is also applied to datasets from detailed measurements of the impact on the beam losses of so-called long-range beam-beam compensators also at the LHC. Furthermore, dynamic indicators have been studied as a tool for exploring the phase-space properties of realistic accelerator lattices in single-particle tracking simulations. By first examining the classification performance of known and new indicators in detecting the chaotic character of initial conditions for a modulated Hénon map and then applying this knowledge to study the properties of realistic accelerator lattices, we tried to identify a connection between the presence of chaotic regions in the phase space and Nekhoroshev-like diffusive behaviour, providing new tools to the accelerator physics community

Increased frequency of circulating Th22 in addition to Th17 and Th2 lymphocytes in systemic sclerosis: association with interstitial lung disease

International audienceABSTRACT: INTRODUCTION: T cell abnormalities have been associated with the pathogenesis of systemic sclerosis (SSc). Recently, besides T helper (Th)17 cells the Th22 subset has been identified in humans. Our purpose was to investigate the pattern of cytokines produced and chemokine-receptors expressed by peripheral blood (PB) Th cells in SSc and healthy donors (HD) focusing on cells producing interleukin (IL)-17 and IL-22 and to identify specific clinical associations. METHODS: Clinical data and peripheral blood were collected in 33 SSc individuals and 29 HD. IL-17A, IL-22, interferon gamma (IFN-gamma, IL-4 production, the chemokine receptors CCR4, CCR6, CCR10, CXCR3 expression and the CD161 Th17 cell marker were assessed by multiparametric flow cytometry in PB CD4+ T cells. Intracellular cytokine accumulation was further investigated in CD4+ T cells expanded in vitro for 7 days. RESULTS: The frequency of Th22, Th17, Th2 but not Th1 cells was significantly increased in SSc individuals compared to HD. The percentage of CD161+CD4+ T cells was increased in SSc and correlated with the percentage of IL-17A producing cells. Moreover, the expression of the skin- and lung-homing chemokine receptor CCR6 correlated with the frequency of IL-22 and IL-17A-producing cells in SSc but not in HD. Finally, SSc interstitial lung disease (ILD) was strongly associated with higher numbers of IL-22 and, to a lesser extent, IL-17A-producing cells. CONCLUSIONS: IL-22 and IL-17A-producing T cells with skin- and lung-homing capabilities are characteristically increased in SSc. These findings support the hypothesis that Th22 in addition to Th17 cells may be involved in pathological processes leading to SSc. While the association between IL-22 producing cells and ILD needs to be assessed in larger cohorts of patients, the increased frequency of Th22 cells appears to be a useful novel biomarker in SSc