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Examining predictive models among discounting models
Get PDFBoth descriptive and normative arguments claim that the discount rate to be applied to public projects should be elicited from individual intertemporal preferences. We present a methodology to analyze data from experimental surveys on intertemporal preferences. Focusing on the exponential and the hyperbolic discounting models, we model the experimental data published by Thaler (1981) by means of different specifications. Standard measures of goodness of prediction are then applied to fitted data to select among alternative specifications. We first present our approach by applying it to simulated data. We then present a procedure for statistical estimation of the sample discount rate, testing four specifications. The estimation procedure we adopt can be easily extended to other functional forms, allowing for non-linearity of the valuation function, inclusion of socio-economic individual characteristics as regressors, and different specifications for the discounting model
Studio sperimentale sulla degradazione della lettiera
Get PDFIt has been tested abaut litter's decomposition of oak, lentisc, pine in environment with vegetable covering and without it by some isopodes and diplopodes and on the whole microcenosys present on litters. We have also determinated the alimentary praeferendum of the about taxa
Investimenti, produttività e occupazione nelle regioni europee: evidenze ed interpretazioni da un'analisi di "cluster"
Get PDFWith an application extended to 109 regions within European Union for the period 1977 - 1996, a joint analysis of investment, productivity and employment growth differentials is considered. We describe the temporal evolution of the standard deviation for the main aggregates. Stability of dispersion for investment per employee and some convergence in productivity are detected. We apply a K-Means Cluster Analysis to Crenos Regio dataset updated with data for investments and sectoral composition of output provided from Cambridge Econometrics. The results identify four groups of regions according to their structural characteristics and dynamic performances. Regions starting from a lower levels of income per capita and higher shares of agriculture experience as a whole a catching up process for productivity but with a clear differentiation between cases of success and failure in capacity of increasing their employment rates. For the more mature regions of Europe we find that the share of employment in services has a positive association with employment growth whereas a negative relation with productivity growth is observed
Evaluation of likelihood based tests for non-nested dichotomous choice contingent valuation models
Get PDFDistributional assumptions are crucial in the estimation of the value of public projects assessed by means of contingent valuations analyses, and it would seem obvious that tests for model specification should play an important part in the statistical analysis. It can be observed, though, that when the competing hypotheses are non nested, the choice of the model is often based on heuristic grounds, or, at most, on deterministic selection model criteria such as Akaike’s (1973). In this paper we study two alternative, probabilistic, approaches to checking model specification, that, like Akaike’s, are based on the Kullback-Leibler Information Criterion (KLIC): the model selection testing proposed by Vuong (1989) and the non nested model test proposed by Cox, in the simulated approach of Pesaran and Pesaran (1993). The three approaches are confronted by comparing their performance in selecting among different contingent valuation models applied to simulated data. Our preliminary results seem to warrant the use of Vuong’s test, complemented in same cases by the application of the Cox test
Oxygen-ordering related phenomena in oxygen-equalized pair samples of YBa2 Cu3 O6+k
Get PDFL’influenza dell’ordine dell’ossigeno nel piano basale Cu(1)Ox sulle proprietà del superconduttore YBa2 Cu3 O6+x viene investigata in maniera comparativa in coppie di campioni equalizzate in ossigeno(coppie k)ottenute per mezzo di una tecnica topotattica recentemente introdotta dagli Autori. Questa strategia, che si è rivelata innovativa rispetto alle convenzionali tecniche di preparazione di campioni singoli, permette di ottenere nuove informazioni sulla regione transiente del diagramma di fase, caratterizzata dalla scomparsa del comportamento semiconduttore antiferromagnetico (SAF) e la comparsa della superconduttività (SC)
Arricchimento organico e meiofauna bentica in un ambiente marino costiero
Get PDFIn a marine bay of Corsica, during a study concerning fish farming impact of floating cages, the effects of organic releases are compared to specific diversity and benthic meiofauna communities abundance existing at different distances from that implant. Regarding many systematic Groups, values of these demographic characteristics
are highlighted to be positively correlated with bottom organic substance concentration. Biological indexes seem not to indicate a negative effect of those releases on meiofauna. Nevertheless other sources of organic substance, into the bay, can be hypothesize
Neurosteroidi: i modulatori endogeni delle emozioni
Get PDFThe discovery that facilitation or inhibition of γ aminobutyric acid (GABA)-mediated neurotransmission results in anxiolytic versus anxiogenic, hypnotic versus somnolitic, and anticonvulsant versus convulsant effects, respectively, provided important early insight into the physiology and pharmacology of central GABAergic transmission. This realization, together with subsequent evidence that high-affinity recognition sites for positive and negative allosteric modulators of GABAA receptors are
located on these GABA-gated Cl– channels, led to the concept that GABAA receptors contribute directly not only to the pharmacology but also to the neurobiology and
physiopathology of a variety of neurological and psychiatric diseases characterized by
changes in emotional state, sleep pattern, or neuronal excitability. These findings have suggested the hypothesis that the brain and peripheral organs in mammals might
produce endogenous compounds that selectively modulate central GABAA receptor function. Evidence directly supporting this hypothesis has been provided over the last
decade by the discovery that steroid hormones synthesized in the brain or in peripheral organs are among the most selective, potent, and efficacious allosteric modulators of
GABAA receptors. Neurosteroids are steroid derivatives that are synthesized de novo from cholesterol in the central nervous system (CNS), some of which modulate GABAA
receptor function with potencies and efficacies similar to or greater than those of benzodiazepines and barbiturates. These molecules have thus been suggested to be the endogenous modulators of GABAA receptor–mediated neurotransmission. In fact some of these molecules have the capability to modulate synaptic activity by binding to
membrane sites associated with ligand-gated ionotropic receptors including GABAA receptors. Here we summarize some of the most recent evidences obtained by our and other laboratories pertaining the role of two neuroactive steroids allopregnanolone (AP) and tetrahydrodeoxycorticosterone (THDOC) actives in modulating the function and plasticity of GABAA receptors in nature
Capitale umano e sviluppo economico. Cosa sappiamo in teoria e nei fatti?
Get PDFLa relazione fra capitale umano e crescita è stata analizzata da una vasta letteratura in particolare nell’ambito della teoria della crescita endogena. Benché esista un generale accordo fra gli studiosi sul fatto che la dotazione di capitale umano sia una componente cruciale della dinamica delle economie industrializzate e di quelle in via di sviluppo, i canali attraverso i quali la prima influenza la seconda sono ancora ampiamente dibattuti. In particolare non è chiaro se l’accumulazione del capitale umano o il suo stock influenzino la crescita e quale sia la direzionalità causale nella relazione fra le due variabili. I risultati dell’analisi empirica non consentono di dare una risposta univoca a queste domande. Il presente lavoro si propone di passare in rassegna i diversi approcci al problema e di fornire alcune spiegazioni dei motivi per cui i risultati empirici non sempre corroborano i modelli teorici
Externalities, knowledge spillovers and the spatial distribution of innovation
Get PDFThe empirical literature on economic growth has recently devoted increasing attention to the issue of regional disparities. The first part of this paper is devoted to the analysis of the growth process of 110 European regions using an updated version of the database set up by the Centre for North South Economic Research (CRENoS). Applying various statistical tools, it compares the dynamics of both per capita income and labour productivity. The second part of the paper examines more specifically the economic performance of Sardinia, relative to the European regions, and outlines a general interpretation of the economic growth process of this region
Impatto ambientale dell'attività mineraria in Sardegna: studi mineralogici e geochimici
Get PDFSardinia is characterized by a large variety of geologic and hydrologic environments, and by a rich wealth of mineral resources, that fueled a millennial history
of mining activity. Therefore, it provides an excellent ground for studies of the environmental impact of mining activity. In this communication, we summarize the results of our studies, specifically concerning the deposits of Baccu Locci (polymetallic�Pb,As), Furtei (epithermal Au), Monteponi (Pb-Zn-Ag), and Montevecchio (Pb-Zn-Ag). In abandoned mining districts (Baccu Locci, Monteponi, and Montevecchio), because of a poor management of environmental issues, we observe significant heavy
metal contamination. On the other hand, in the active Furtei mine the first four years of exploitation did not cause remarkable changes with respect to pre-mining baseline
conditions