Outer edges of face-on spiral galaxies

We present deep optical imaging of three face-on disk galaxies together with a detailed description of the reduction and calibration methods used, in order to measure the intrinsic shape of their outer stellar edges. Whereas it is now well accepted that disks of spiral galaxies are not infinite exponential beyond galactocentric distances of about 3-5 radial scalelengths, the genuine structure of the truncation region is not yet well known. Our data quantitatively establish a smooth truncation behaviour of the radial surface brightness profiles and is best described by a two-slope model, characterised by an inner and outer exponential scalelength separated at a relatively well defined break radius. This result disagrees with the frequently assumed sharply truncated nature of the radial surface brightness profiles and implies the presence of stars and even star-formation beyond the break radius. In addition, we do not find a strong influence of a nearby companion on the ratio of the break radius to the radial scalelength. Our results denote new observational constraints for the search of the physical explanation for these smooth disk truncations.Comment: LaTeX, 10 pages, 17 figures, accepted to be published in A&A, minor changes to the quality of figure

Rainfall thresholds derivation for warning pluvial flooding risk in urbanised areas

Aim of this work is the development of an operational tool for pluvial flooding warning in an urban area based on off-line rainfall thresholds derived by coupling a rainfall-runoff modelling and a hydraulic routing. The critical conditions considered for issue flood warnings were not only based on the water stage, but also on the extension of the flooded area. Further, a risk assessment framework for quantifying the reliability of the rainfall thresholds has been included; rainfall thresholds used in pluvial flooding warning should be influenced by the uncertainties in the rainfall characteristics (i.e. rainfall duration, depth and storm pattern). This risk assessment framework incorporates the correlated multivariate Monte Carlo simulation method, an hydraulic model for the simulation of rainfall excess propagation over surface urban drainage structures, i.e. streets and pathways. Thresholds rainfall are defined using a number of inundation criteria, to analyze the change in the rainfall threshold due to various definitions of inundation. Starting from estimated water stages and flooded area from inundation simulation rainfall thresholds can be obtained according a specific inundation criterion, including, together, a critical water depth and a critical flooding area. Finally, the second phase concerns the imminence of a possible hydrological risk by comparing the time when cumulative rainfall and rainfall thresholds meet to each other. The developed procedure has been applied to the real case study of Mondello catchment in Palermo (Italy)

Derivation of rainfall thresholds for pluvial flood risk warning in urbanised areas

In the recent past throughout the Mediterranean area, many extreme events such as floods, debris flows and landslides occurred. Mediterranean ephemeral streams have specific features compared to other river systems; their basins are small and highly torrential and may generate flash-floods (Camarasa-Belmonte & Soriano-Garcia, 2012). Moreover, the rapid transformation processes of urban areas induced the increase of catchment imperviousness and the derived increase of surface runoff generated during rainfall events. However, flooding events in urban areas occur quite frequently as a consequence of rain events of lower intensity than the design one, even in case of correct network dimensioning. The use of a reliable flood forecasting model in urban areas can play an important role in managing land and water resources. The purpose of this work is the development of a Decision Support System (DSS) for flash flood warning in an urban area. Usually, flood warning systems are based on on-line hydrological and/or hydraulic models in order to provide forecasts of water stages or discharges at critical river sections (Martina et al., 2006; Diakakis, 2012; Wu et al., 2015). This procedure is inappropriate for flash flood warning in urban areas or in catchments with a small area. According to the approach proposed by [Amadio et al., 2003; Wu et al., 2015], in this study the rainfall threshold has been estimated in an urban area by coupling results of hydro-dynamic model in terms of water stage and flooding area. Particularly, dependency of the antecedent soil moisture conditions has been neglected because urban areas are characterized by imperious surfaces This study proposes a methodology to point out in urban areas rainfall thresholds used in flash flood warning which should be influenced by the uncertainties in the rainfall characteristics, including rainfall duration, depth and storm pattern. Particularly, the methodology here developed has a modular structure consisting of different modules: synthetic hyetographs definition to gain the hydrological input to the hydraulic model; transformation of flood discharge to inundated area through a two-dimensional hydraulic model the FLURB-2D model (Aronica & Lanza, 2005) and, finally, quantification of threshold rainfall associated with specific inundation criteria

Estimation of synthetic flood design hydrographs using a distributed rainfall–runoff model coupled with a copula-based single storm rainfall generator

In this paper a procedure to derive synthetic flood design hydrographs (SFDH) using a bivariate representation of rainfall forcing (rainfall duration and intensity) via copulas, which describes and models the correlation between two variables independently of the marginal laws involved, coupled with a distributed rainfall–runoff model, is presented. Rainfall–runoff modelling (R–R modelling) for estimating the hydrological response at the outlet of a catchment was performed by using a conceptual fully distributed procedure based on the Soil Conservation Service – Curve Number method as an excess rainfall model and on a distributed unit hydrograph with climatic dependencies for the flow routing. Travel time computation, based on the distributed unit hydrograph definition, was performed by implementing a procedure based on flow paths, determined from a digital elevation model (DEM) and roughness parameters obtained from distributed geographical information. In order to estimate the primary return period of the SFDH, which provides the probability of occurrence of a hydrograph flood, peaks and flow volumes obtained through R–R modelling were treated statistically using copulas. Finally, the shapes of hydrographs have been generated on the basis of historically significant flood events, via cluster analysis. <br><br> An application of the procedure described above has been carried out and results presented for the case study of the Imera catchment in Sicily, Italy

Thematic Report Three - Asylum, Security and Extremism

This is the final of three Thematic Reports published as part of a CREST-funded project carried out by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom. With the objective of better understanding Tamil diaspora communities’ attitudes and engagement in the Sri Lankan civil conflict (1983-2009) and its aftermath, the project explores diaspora and refugee communities’ relationship with the changing socio-political environment in the homeland, exploring what shapes and influences processes of radicalisation or moderation among these communities. It recognises that the socio-political circumstances in which these processes develop are often crucial to understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home and host countries, as well as different ‘areas’ of engagement, which can include social, economic and political interactions. The three thematic reports produced as part of this project cumulatively build a comprehensive picture of the state of knowledge on political action among diaspora, refugee and asylum populations. The theoretically-informed, literature- and evidence-grounded conclusions arising from these three thematic reports are therefore of relevance beyond the case of Sri Lanka. Thematic Report One discussed how four analytical concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of overseas politics and the potential of these concepts to shed light on the relationship between mobility and political action. Thematic Report Two complements the previous report’s broad conceptual discussion by specifically focusing on an analysis of the context and drivers of political action among diaspora and refugee populations, and engaging with the term ‘refugee politics’. The current paper – the final Thematic Report – analyses the growing ‘securitisation’ of refugees and other forcibly displaced populations and calls for greater consideration of structural vulnerabilities in the forced migration and displacement cycle that increase the risk of radicalisation, extremism and related political behaviours

Thematic Report One - Understanding Transnational Diaspora Politics: A Conceptual Discussion

This is the first of three CREST-funded Thematic Reports published by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom examining political action among diaspora populations. The purpose of the report is to explore the theoretical and conceptual basis underpinning academic debates on engagement in the politics of conflict and post-conflict by communities living overseas. The research team is interested specifically in the Sri Lankan civil conflict between 1983 and 2009 and its aftermath, and understanding the attitudes towards and involvement in that conflict on the part of Tamil diaspora communities. The CREST project is exploring diaspora communities’ relationship with the changing socio-political environment in the homeland and how this influences processes of radicalisation or moderation. It recognises that the socio-political circumstances in which these processes develop are often crucial towards understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home countries and in host countries, as well as different ‘areas’ of engagement, which can range from social to economic to political interactions. The following review is not specific to the Sri Lankan situation; it is rather concerned with how four concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of diaspora or more broadly overseas politics and the potential of the concepts to shed light on the relationship between mobility and political action. It considers the extent to which these concepts are helpful in identifying the rationale behind specific methods of political participation offering critical reflections on the analytical and normative usefulness of these terms

Thematic Report Two - The Engagement of Refugees in Transnational Politics: Lessons from the Migration, Diaspora and Refugee Studies Literature

This is the second of three CREST-funded Thematic Reports published by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom, that cumulatively build a comprehensive picture of the state of knowledge on political action among diaspora and refugee populations. The research team is specifically interested in applying the theoretically-informed, literature and evidence grounded conclusions arising from these reports to understand the attitudes towards and involvement in the Sri Lankan civil conflict (1983-2009) and its aftermath by Tamil diaspora communities, but with a broader application. The CREST project is exploring diaspora and refugee communities’ relationship with the changing socio-political environment in the homeland and how this influences processes of radicalisation or moderation. It recognises that the socio-political circumstances in which these processes develop are often crucial to understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home countries and in host countries, as well as different ‘areas’ of engagement, which can include social, economic and political interactions. Thematic Report One discussed how four analytical concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of overseas politics and the potential of the concepts to shed light on the relationship between mobility and political action. The current paper – Thematic Report Two – complements the previous report’s broad conceptual discussion by specifically focusing on an analysis of the context and drivers of political action among diaspora and refugee populations, and engaging with the term ‘refugee politics’. It considers if the available diaspora and migration literature sheds light on whether the processes and dynamics of forced migration are likely to generate identifiable forms of political engagement

DERIVAZIONE DI IDROGRAMMI DI PIENA ATTRAVERSO L\u2019ACCOPPIAMENTO DI MODELLI STOCASTICI BIVARIATI DELLE PRECIPITAZIONI E E MODELLI AFFLUSSI - DEFLUSSI DISTRIBUTI

In questo studio viene presentata una procedura di tipo Monte Carlo per la derivazione delle curve di frequenza delle portate al colmo e dei volumi corrispondenti basata sull\u2019accoppiamento di un modello di generazione delle forzanti pluviometriche tramite copule e un modello di trasformazione afflussideflussi di tipo distribuito. Tale procedura \ue8 stata applicata ad un caso di studio siciliano; i risultati ottenuti hanno mostrato la bont\ue0 del modello a riprodurre le statistiche complesse delle grandezze idrologiche a fronte di un basso numero di parametri modellistici e di un ridotto sforzo computazionale