On proximity and hierarchy : exploring and modelling space using multilevel modelling and spatial econometrics

Spatial econometrics and also multilevel modelling techniques are increasingly part of the regional scientists‟ toolbox. Both approaches are used to model spatial autocorrelation in a wide variety of applications. However, it is not always clear on which basis researchers make a choice between spatial econometrics and spatial multilevel modelling. Therefore it is useful to compare both techniques. Spatial econometrics incorporates neighbouring areas into the model design; and thus interprets spatial proximity as defined in Tobler‟s first law of geography. On the other hand, multilevel modelling using geographical units takes a more hierarchical approach. In this case the first law of geography can be rephrased as „everything is related to everything else, but things in the same region are more related than things in different regions‟. The hierarchy (multilevel) and the proximity (spatial econometrics) approach are illustrated using Belgian mobility data and productivity data of European regions. One of the advantages of a multilevel model is that it can incorporate more than two levels (spatial scales). Another advantage is that a multilevel structure can easily reflect an administrative structure with different government levels. Spatial econometrics on the other hand works with a unique set of neighbours which has the advantage that there still is a relation between neighbouring municipalities separated by a regional boundary. The concept of distance can also more easily be incorporated in a spatial econometrics setting. Both spatial econometrics and spatial multilevel modelling proved to be valuable techniques in spatial research but more attention should go to the rationale why one of the two approaches is chosen. We conclude with some comments on models which make a combination of both techniques

Quark deconfinement and neutrino trapping in compact stars

We study the role played by neutrino trapping on the hadron star (HS) to quark star (QS) conversion mechanism proposed recently by Berezhiani and collaborators. We find that the nucleation of quark matter drops inside hadron matter, and therefore the conversion of a HS into a QS, is strongly inhibit by the presence of neutrinos.Comment: 3 pages, 3 figures. Talk given at the VIII International Conference on Strangeness in Quark Matter. Cape Town, South Africa, Septembre 200

Evidence of widespread hot plasma in a non-flaring coronal active region from Hinode/XRT

Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot plasma be present in the corona at all times. Its detection has proved elusive until now, in part because the intensities are predicted to be very faint. Here we report on the analysis of an active region observed with five filters by Hinode/XRT in November 2006. We have used the filter ratio method to derive maps of temperature and emission measure both in soft and hard ratios. These maps are approximate in that the plasma is assumed to be isothermal along each line-of-sight. Nonetheless, the hardest available ratio reveals the clear presence of plasma around 10 MK. To obtain more detailed information about the plasma properties, we have performed Monte Carlo simulations assuming a variety of non-isothermal emission measure distributions along the lines-of-sight. We find that the observed filter ratios imply bi-modal distributions consisting of a strong cool (log T ~ 6.3-6.5) component and a weaker (few percent) and hotter (6.6 < log T < 7.2) component. The data are consistent with bi-modal distributions along all lines of sight, i.e., throughout the active region. We also find that the isothermal temperature inferred from a filter ratio depends sensitively on the precise temperature of the cool component. A slight shift of this component can cause the hot component to be obscured in a hard ratio measurement. Consequently, temperature maps made in hard and soft ratios tend to be anti-correlated. We conclude that this observation supports the presence of widespread nanoflaring activity in the active region.Comment: 12 figures, accepted for publication on refereed journa

On the ultraviolet signatures of small scale heating in coronal loops

Studying the statistical properties of solar ultraviolet emission lines could provide information about the nature of small scale coronal heating. We expand on previous work to investigate these properties. We study whether the predicted statistical distribution of ion emission line intensities produced by a specified heating function is affected by the isoelectronic sequence to which the ion belongs, as well as the characteristic temperature at which it was formed. Particular emphasis is placed on the strong resonance lines belonging to the lithium isoelectronic sequence. Predictions for emission lines observed by existing space-based UV spectrometers are given. The effects on the statistics of a line when observed with a wide-band imaging instrument rather than a spectrometer are also investigated. We use a hydrodynamic model to simulate the UV emission of a loop system heated by nanoflares on small, spatially unresolved scales. We select lines emitted at similar temperatures but belonging to different isoelectronic groups: Fe IX and Ne VIII, Fe XII and Mg X, Fe XVII, Fe XIX and Fe XXIV. Our simulations confirm previous results that almost all lines have an intensity distribution that follows a power-law, in a similar way to the heating function. However, only the high temperature lines best preserve the heating function's power law index (Fe XIX being the best ion in the case presented here). The Li isoelectronic lines have different statistical properties with respect to the lines from other sequences, due to the extended high temperature tail of their contribution functions. However, this is not the case for Fe XXIV which may be used as a diagnostic of the coronal heating function. We also show that the power-law index of the heating function is effectively preserved when a line is observed by a wide-band imaging instrument rather than a spectromenter

Pre-Biblio, bibliografia georeferenziata della Preistoria e della Protostoria italiana: struttura del progetto e primi risultati

The paper presents the new relational database Pre-Biblio on the Prehistory and Quaternary geology of Italy. It will be mainly composed of two correlated databases, «sites» and «bibliography» and some others such as the biographies of the most important scholars, the taxa of fossil remains contained in the sites, the palaeobasins. Each bibliographic reference will be linked to sites, and these georeferenced on the 1:25.000 topographic maps of the «SIGEC» GIS system of the Ministry of Culture. An accurate survey of Italian and foreign literature regarding archaeology, vertebrate palaeontology, geology and related sciences from Villafranchian to Early Iron Age has been conducted in the most important libraries of Italian Institutions specialized in Quaternary studies and Prehistory. An estimated total of about 25.000 sites, 60.000 references and 800.000 links represents the core of the project, which could be concluded in five years with a team of eight specialists. The paper also provides a preliminary appraisal of the chronological distribution of published sites covering the whole Italian territory, according to which the protohistory (Bronze and First Iron Ages) accounts for half of the estimated body of data

La Sindrome Antifosfolipidi: revisione critica degli attuali aspetti diagnostici, patogenetici e terapeutici

La sindrome antifosfolipidi (aPS) identifica una condizione ad aumentato rischio di occlusione vascolare e/o complicanze gravidiche, la cui definizione è stata stabilita nel 2005 sulla base di un consenso internazionale. I pazienti sono definiti affetti da aPS se presentano almeno un criterio clinico (occlusione vascolare e/o complicanza gravidica) e un criterio di laboratorio, in un definito periodo di tempo; i criteri di laboratorio che definiscono la aPS sono la positività ripetuta (confermata dopo 12 settimane) per la ricerca degli anticorpi del tipo lupus anticoagulante (LA) e/o la positività per gli anticorpi in fase solida anti-cardiolipina (aCL) o anti- β2glicoproteina I (β2GPI). Nonostante i progressi degli ultimi 20 anni dovuti all’interesse di molti specialisti, immunologi, ematologi, reumatologi o ginecologi, la aPS rimane non completamente conosciuta in molti aspetti, tuttora controversi e discussi. Scopo della presente tesi è di presentare un aggiornamento sui criteri di laboratorio attualmente applicati, sulle ipotesi patogenetiche in discussione e sulle proposte terapeutiche nelle varie e differenti manifestazioni cliniche, con particolare riferimento alla terapia anticoagulante