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Interactions between calliphoridae dipters and Helicodiceros muscivorus
Get PDFThis article reports on the experimental results of a research programme dealing with the reproductive strategies of Helicodiceros muscivorus (L. fil.) Engler(Araceae: Aroideae). In particular, the role played by the odorous mixture emanated by the vegetable species as olfactory information received by the insects, and the importance of that specific biological activity in governing the behavioural choices made by the pollinating insects is studied
Geochemical features of thermal waters at Benetutti (Sardinia)
Get PDFThis paper reports the geochemistry of the thermal and cold waters at Benetutti in central Sardinia. Both major and trace components in 24 water samples were analysed using various techniques. The thermal waters show a sodium chloride composition and a salinity of 0.5 g/L; they are characterised by a pH of 9.5-9.7, very low magnesium (0.01-0.1 mg/L), and much higher F, B, Li, Rb, Cs, and Mo concentrations than in the cold waters of the area. No variations in temperature, flow, or chemical composition were observed at the thermal springs for which records dating back 20 years are available. Subsurface reservoirs associated with the thermal springs are of a low enthalpy (calculated temperature at depth is about 60°C), and are therefore candidates for direct uses, such as balneology, space heating, and horticulture
La qualità della vita degli studenti universitari di Cagliari. Una verifica empirica mediante indicatori di sintesi
Get PDFIn this work we analyse quality of life of university’s students
according to mixed approach (objective-subjective). We propose
a new mixed indicator (ISG’) and analyse with a GLM regression
model the influence of some important covariates: residence, faculty,
sex and academic situation
Su alcune formazioni a Olea europaea L. var. sylvestris Brot. della Sardegna
Get PDFOn the Olea europaea L. var. sylvestris Brot. woodlands in Sardinia.The phytosociological analysis of Olea europaea. var. sylvestris woodlands
occurring in Sardinia are here presented. The following sintaxa are described for the first time: Cyclamino repandi-Oleetum sylvestris and Myrto
communis-Oleetum sylvestris are referred to the Quercion ilicis alliance while Asparago acutifolii-Oleetum sylvestris and Asparago albi-Oleetum
sylvestris are referred to the Oleo-Ceratonion alliance
Forecasting inflation: a comparison of linear Phillips curve models and nonlinear time serie models
Get PDFThe aim of this paper is to analyze the forecasting performance of alternative model for the US inflation rate over the period 1950.1-2002.7. NAIRU Phillips curve models forecasts are contrasted with those obtained by a special class of nonlinear time series models, the threshold autoregressive models. The forecast evaluation is conducted on point and density forecasts. The results show that overall the non linear specification are better able to capture the distributional features of the series, although in terms of MSFE the Phillips curve specification can yield noticeable forecasting gains for medium and long term horizons. Previous finding on the forecasting superiority of the simple naïve model are confuted
Border effects in the enlarged EU area
Get PDFThis paper looks at the issue of border effects in the enlarged European Union. We have considered accession countries of different size and other characteristics, i.e. Hungary, Poland, Bulgaria, Romania, Latvia and Cyprus. We have measured the extent to which internal trade exceeds international trade in a set up where controls for other economic determinants of commerce have been considered. In order to avoid inflated border effects, information at the regional level both for CEECs and EU countries has been used to construct a weighted measure of distance both for between-countries and internal distances. Furthermore, in order to separate border effects from impediments to trade due to technical barriers we look at the extent of border effects for sectors grouped according to the approach adopted by the EU to remove technical barriers in the EU. All distance measures have been found negative and significant for all types of products. The border effect coefficients for the harmonic mean have been found consistently smaller, regardless the relevance of technical barriers. Furthermore distance has also been found to be a slightly smaller impediment when using the effective measure. Checking for the presence of technical barriers to trade, our results suggest that the border effects are the largest for old approach products, where we expect to have the most important technical barrier to trade due to complicated harmonization procedures. The ‘other approach’ category has the smallest border effects, while the ‘mixed approach’ products are in between the two previous categories. Our countries of interest would trade with themselves 221 times more in old approach products, while only 24 times more in other approach products
How fast are tourism countries growing? The cross country evidence
Get PDFSpecializing in tourism is an option available to a number of less developed countries and regions. But is it a good option? To answer this question, we have compared the relative growth performance of 14 “tourism countries” within a sample of 143 countries, observed during the period 1980-95. Using standard OLS cross-country growth regressions, we have documented that the tourism countries grow significantly faster than all the other sub-groups considered in our analysis (OECD, Oil, LDC, Small). Moreover, we have shown that the reason why they are growing faster is neither that they are poorer than the average; nor that they have particularly high saving/investment propensities; nor that they are very open to trade. In other words, the positive performance of the tourism countries is not significantly accounted for by the traditional growth factors of the Mankiw, Romer and Weil type of models. Tourism specialization appears to be an independent determinant. A corollary of our findings is that the role played by the tourism sector should not be ignored by the debate about whether smallness is harmful for growth (e.g. Easterly and Kraay (2000), who conclude that there is no growth disadvantage in smallness). Half of the thirty countries classified as microstates in this literature are heavily dependent on tourism. Once this distinction is adopted, it is easy to see that the small tourism countries perform much better than the remaining small countries. In our findings, smallness per se can be bad for growth, while the opposite is true when smallness goes together with a specialization in tourism
The copula approach to sample selection modelling: an application to the recreational value of forests
Get PDFThe sample selection model is based upon a bivariate or a multivariate structure, and distributional assumptions are in this context more severe than in univariate settings, due to the limited availability of tractable multivariate distributions. While the standard FIML estimation of the selectivity model assumes normality of the joint distribution, alternative approaches require less stringent distributional hypotheses. As shown by Smith (2003), copulas allow great flexibility also in FIML models. The copula model is very useful in situations where the applied researcher has a prior on the distributional form of the margins, since it allows separating their modelling from that of the dependence structure. In the present paper the copula approach to sample selection is first compared to the semiparametric approach and to the standard FIML, bivariate normal model, in an illustrative application on female work data. Then its performance is analysed more thoroughly in an application to Contingent Valuation data on recreational values of forests
Durata degli studi e voto di laurea: una indagine econometrica su alcune facoltà dell'università di Cagliari
Get PDFDo we need more time for leisure?
Get PDF”We need more time: more time for leisure” Linton Kwesi Jonhson used to dub. Indeed, the analysis of an OLG economy with endogenous labor supply gives some rational to the dub poet’s claims. In our setting, the golden rule is defined as the pair of capital-labour ratio and individual labour supply which maximises the steady state utility of each generation. When, other things equal, agents are motivated to work more the higher the level of wages, individual labor supply will be increasing (decreasing) in capital labor ratio according to whether the elasticity of wages per unit of labour is bigger (smaller) than the relative change of the value of the fraction of labour income saved. Hence, if the economy is dynamically efficient, agents tend to work more than in the Golden Age if the propensity to save evaluated at the golden rule is, other things equal, relatively high. Conversely, under dynamic inefficiency, they work too much if and only if the propensity to save is relatively low. For given values of the parameters determining the propensity to save, individuals in dynamic efficient (inefficient) economies work more than in the Golden Age as long as the labour share of income is sufficiently high (low). These findings appear to be of some interest with reference to the 35 hours working-week debate in Europe