1,721,745 research outputs found
Il linguaggio dell’ordine architettonico nelle prime opere di Michelangelo Buonarroti
Full text linkLa ricerca è stata avviata per comprendere l’uso dell’ordine architettonico da parte di Michelangelo attraverso l’attenta indagine dei suoi caratteri costitutivi: sintassi, proporzioni, morfologia, ruolo. Un argomento complesso e trasversale, che ha offerto l’occasione di esplorare contemporaneamente tutte le espressioni artistiche con le quali l’architetto ha avuto modo di confrontarsi durante la sua lunga attività, sin dagli esordi. L’analisi ha riguardato la prima produzione artistica di Michelangelo: dall’affresco realizzato a partire dal 1508 per la volta della Cappella Sistina, fino alle architetture del periodo fiorentino in cui appare l’ordine architettonico, interamente circoscritte al complesso di San Lorenzo. Lo studio presenta nuove e originali conoscenze sulle fonti antiche e contemporanee utilizzate da Buonarroti, mentre funzioni e caratteristiche metriche e proporzionali degli ordini impiegati si trovano a loro volta collocate in un quadro meglio definito
Independent Component Analysis and Immunization: an exploratory study
No full textIn this work we apply Independent Component Analysis (ICA) to the identification of the factors driving spot rates curve movements. A comparison between the standard Principal Components Analysis (PCA) approach and ICA is carried out both from a theoretical point of view, critically analyzing the negentropy based approach to ICA, and from an empirical point of view, where the performance of immunization strategies based on PCA and ICA are tested
On the existence of minimax martingale measures
No full textEmbedding asset pricing in a utility maximization framework leads naturally to the concept of minimax martingale measures. We consider a market model where the price process is assumed to be a R^{d}- semimartingale X and the set of trading strategies consists of all predictable, X- integrable, R^{d} valued processes H for which the stochastic integral (H.X) is uniformly bounded from below. When the market is free of arbitrage, we show that a sufficient condition for the existence of the minimax measure is that the utility function u:R→R is concave and nondecreasing. We also show the equivalence between the No Free Lunch with Vanishing Risk condition, the existence of a separating measure, and a properly defined notion of viability
Option pricing in a dynamic variance gamma model
No full textWe present a discrete time stochastic volatility model in which the conditional distribution of the logreturns is a Variance-Gamma, that is a normal variance-mean mixture with Gamma mixing density. We assume that the Gamma mixing density is time varying and follows an affine Garch model, trying to capture persistence of volatility shocks and also higher order conditional dynamics in a parsimonious way.
We select an equivalent martingale measure by means of the conditional Esscher transform as in Buhlmann et al. (1996) and show that this change of measure leads to a similar dynamics of the mixing distribution. The model admits a recursive procedure for the computation of the characteristic function of the terminal logprice, thus allowing semianalytical pricing as in Heston and Nandi (2000).
From an empirical point of view, we check the ability of this model to calibrate SPX option data and we compare it with the Heston and Nandi (2000) model and with the Christoffersen, Heston and Jacobs (2006) model, that is based on Inverse Gaussian innovation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
On the dependence structure between S&P500, VIX and implicit Interexpectile Differences
Full text linkWe study the dependence structure between the S&P500, the VIX Index, and implicit Interexpectile Differences, that are an alternative measure of implied volatility based on the notion of implicit expectile, recently introduced in Bellini et al. [Implicit expectiles and measures of implied volatility. Quant. Finance, 2018a, 18, 1851–1864]. After filtering the time series of the marginals by ARMA-(E)GARCH models, we fit several parametric families of copulas to the pairwise joint distribution of the residuals, in order to investigate the presence of radial asymmetry and asymptotic tail dependence. We find a negative dependence between S&P500 and both implied volatility indices and a positive dependence between VIX and Interexpectile Differences. The best fitting copulas seem relatively stable over time and display both asymmetry and strong tail dependence, in accordance with the leverage effec
Il latte d'asina
No full textL’asino, che da sempre ha accompagnato l’uomo nei pesanti lavori campestri e che ha
rischiato quasi di scomparire con l’introduzione dei mezzi meccanici in agricoltura, improvvisamente torna sul palcoscenico per la qualità e l’utilità delle sue produzioni. Oggi non viene più assimilato a immagini di cocciutaggine e stupidità, ma viene riscoperto e rivalutato in una prospettiva zootecnica del tutto nuova (produzione di latte), dove riveste un preciso ruolo come animale da reddito, non più da fatica o da soma.
È un animale “versatile”, che trova anche spazio nel sociale: nella onoterapia, in cui assume il compito di sostenitore e promotore della relazione uomo-animale.
Attualmente allevare asini si sta rivelando un’attività imprenditoriale con forti prospettive di sviluppo, legate alle sue destinazioni diversificate e innovative, che superano il limite circoscritto della vecchia
concezione di allevamento
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