Il Duomo di Siena

Castiglia, Gabriele

doi:10.2307/j.ctvqmp1jr

Cited by 5 publications

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“…Here, β e = β i T e n e /(T i n i ). The appropriateness of a local flux-tube description to treat energetic particle modes was partially discussed in [24,25] and can be shown to be valid for the parameters under consideration by comparison with global simulations [26]. Further signatures for the presence of these modes are given in figure 3(a) where a Fourier transform has been applied to the gyroaveraged electrostatic potential φ1 in the first nearly-steady state time range (phase I).…”

Section: Simulations: Setup and Resultsmentioning

confidence: 99%

Electromagnetic turbulence suppression by energetic particle driven modes

et al. 2019

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In recent years, a strong reduction of plasma turbulence in the presence of energetic particles has been reported in a number of magnetic confinement experiments and corresponding gyrokinetic simulations. While highly relevant to performance predictions for burning plasmas, an explanation for this primarily nonlinear effect has remained elusive so far. A thorough analysis finds that linearly marginally stable energetic particle driven modes are excited nonlinearly, depleting the energy content of the turbulence and acting as an additional catalyst for energy transfer to zonal modes (the dominant turbulence saturation channel). Respective signatures are found in a number of simulations for different JET and ASDEX Upgrade discharges with reduced transport levels attributed to energetic ion effects.PACS numbers: 52.65.Tt Introduction.Being an almost ubiquitous phenomenon, turbulence with its highly stochastic and nonlinear character is a subject of active research in various fields. In magnetically confined plasma physics, it is of particular interest since it largely determines the radial heat and particle transport and thus the overall confinement. Any insight on possible reductions of the underlying micro-instabilities which are driven by the steep density and temperature profiles, and/or on modifications of their nonlinear saturation mechanisms can be considered crucial on the way to self-sustained plasma burning and corresponding fusion power plants. A particularly interesting example is the recent experimental and numerical evidence suggesting a link between the presence of fast ions and substantial improvement of energy confinement in predominantly ITG (ion-temperature-gradient) driven turbulence [1][2][3][4][5]. Dedicated theoretical studies have already identified a number of possible energetic ion effects on plasma turbulence like dilution of the main ion species [1], Shafranov shift stabilization [6] and resonance interaction with bulk species micro-instabilities in certain plasma regimes [7]. They furthermore contribute to the total plasma pressure and increase the kinetic-tomagnetic pressure ratio, β, which is a measure for the relevance of electromagnetic fluctuations, known to stabilize ITG modes. Such behaviour could indeed be confirmed in simulations [4,8,9] of JET hybrid discharges [10,11] with substantial fast ion effects that, however, also identified an upper limit for this beneficial fast-ion-pressure effect. If the total plasma pressure exceeds a critical value, kinetic ballooning or Alfvénic ITG modes with smaller toroidal mode numbers and frequencies higher than the ITG modes are destabilized which increase particle/heat fluxes [12]. Similarly, the fast-ion pressure may drive energetic particle (EP) modes if certain thresholds are exceeded. Although a possible relevance of the proximity to the onset of these modes has been noted [4,8], their role was not investigated in more detail. In any case, all of these effects are mainly linear, i.e., alter the growth of the

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Section: Simulations: Setup and Resultsmentioning

confidence: 99%

Electromagnetic turbulence suppression by energetic particle driven modes

et al. 2019

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“…Tale aspetto può parzialmente essere letto anche in altri contesti urbani del territorio di nostro interesse, anche se, sfortunatamente, disponiamo di una documentazione più carente: i luoghi di fondazione delle ecclesiae episcopales , dove nel tardo medio evo sorgeranno le cattedrali pre-romaniche e romaniche, mostrano ancora una volta la longue durée funzionale-ideologica di determinati assetti topografici. Questo fenomeno è ben testimoniato a Firenze (Toker, 1975), Lucca (Piancastelli Politi Nencini, 1992), probabilmente a Pisa (Alberti, Baldassarri, Gattiglia, 2006), Chiusi (Martini, 1997: 75) e Siena (Cantini, 2011: 40–44; Castiglia, 2014: 9–12, 119–20) (anche se, specificamente per Siena, i dati sono del tutto insufficienti). In quest'ottica, però, rimane di difficile soluzione la questione inerente lo spostamento del rango di ecclesia episcopalis , a Lucca, da Santa Reparata a San Martino, anche alla luce della sostanziale assenza di dati archeologici di epoca alto medievale per quanto attiene la ‘nuova’ cattedrale.…”

Section: Le Città Della Tuscia Annonaria Nell'alto Medioevounclassified

TOPOGRAFIA CRISTIANA DELLATUSCIA ANNONARIAE DELLATUSCIA LANGOBARDORUM(IV-VIII SEC. D.C.)

Castiglia¹

2018

Pap. Br. Sch. Rome

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Il presente contributo intende analizzare i fenomeni di formazione e radicamento della cristianizzazione nella Tuscia Annonaria (attuale Toscana settentrionale) nel periodo compreso tra il IV e la seconda metà dell'VIII secolo d.C., sia in ambito urbano che in quello rurale. Questo tema, sinora scarsamente analizzato in maniera complessiva, verrà sviscerato partendo da un approccio quantitativo (ancorato ad una schedatura delle evidenze materiali e scritte), funzionale all'approfondimento di problematiche storiografiche e di nuove possibili chiavi di lettura di fenomeni complessi e articolati quali furono quelli legati alla trasformazione delle città e dei paesaggi romani e che portarono alla strutturazione delle realtà post classiche.

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A Multi-scalar Approach to Long-Term Dynamics, Spatial Relations and Economic Networks of Roman Secondary Settlements in Italy and the Ombrone Valley System (Southern Tuscany): Towards a Model?

Bertoldi

Castiglia²,

Barba

2019

Computational Social Sciences

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In Roman landscapes, the particular sites defined as secondary settlements (also known as vici/villages, minor centres, agglomérations secondaires and/or stationes/mansiones) have played an 'intermediary' role between the cities and other rural structures (villae/farms), linked to medium-and long-distance economic and commercial trajectories. The aim of this paper is to apply a multi-scalar approach to model their long-term spatial relationships and connectivity with the Mediterranean exchange network. On the macro-scale, we have analysed a sample of 219 reviewed sites to understand the diachronic trends and spatial dynamics of attraction/proximity to significant elements of the landscape such as towns, roads, rivers and coastline. The Ombrone Valley (Tuscany, Italy) represents a micro-scale case study of a complex system, in which the imported pottery (amphorae, African Red Slip ware, ingobbiata di rosso) found in the vicus/mansio of Santa Cristina in Caio, the Roman villa of La Befa and the town of Siena (Saena Iulia) provided diagnostic 'macroeconomic' perspectives. The results show how the secondary settlements occupied a nodal position in the Roman landscape in terms of resilience (long period of occupation until the Early Middle Ages) and spatial organization with a close relationship to natural and anthropic infrastructures and trade functions linked to Mediterranean routes.

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Il Duomo di Siena

Cited by 5 publications

References 0 publications

Electromagnetic turbulence suppression by energetic particle driven modes

Electromagnetic turbulence suppression by energetic particle driven modes

TOPOGRAFIA CRISTIANA DELLATUSCIA ANNONARIAE DELLATUSCIA LANGOBARDORUM(IV-VIII SEC. D.C.)

A Multi-scalar Approach to Long-Term Dynamics, Spatial Relations and Economic Networks of Roman Secondary Settlements in Italy and the Ombrone Valley System (Southern Tuscany): Towards a Model?

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