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101.
In recent years, the brain drain issue has gained such momentum that it has become necessary to adopt tools and methods to take a picture of a phenomenon that is, by its very nature, dynamic and changeable (Portes, 1976 ; Meyer, 2001 ; Ackers, 2005 Scott, 2015 ). This particular study focuses on clarifying the reasons why Italian scientists choose to look elsewhere for the best place to conduct their scientific research, and in what way their scientific experience abroad shapes the image of the Italian scientific system. A first exploratory analysis involving 83 in‐depth interviews with Italian scientists (mathematicians, engineers and physicists) working in Europe was conducted based on qualitative and quantitative analytical methods, and the content emerging from these interviews was used for a systematic mapping of the situation that provided the foundations for our preparation of a second tool – a questionnaire – that was subsequently used to conduct a much more broad‐based survey that involved 602 respondents. While our findings add complexity to existing theories on the brain drain and brain circulation, they also confirm the potential of highly skilled migration to improve the national development of Italian academic system.  相似文献   
102.
During the last 30 years US citizens experienced, on average, a decline in reported happiness, social connections, and confidence in institutions. We show that a remarkable portion of the decrease in happiness is predicted by the decline in social connections and confidence in institutions. We carry out our investigation in three steps. First, we run a happiness regression that includes various indicators of social connections and confidence in institutions, alongside with own income, reference income, and the usual socio-demographic controls. We find that indicators of social connections and confidence in institutions are positively and significantly correlated with happiness. Second, we investigate the evolution of social connections and confidence in institutions over time, finding that they generally show a declining trend. Third, we calculate the variation in happiness over time as predicted by each of its statistically significant correlates, finding that the decrease in happiness is mainly predicted by the decline in social connections and by the growth in reference income. More precisely, the sum of the negative changes in happiness predicted by the reduction in social connections and the increase in reference income more than offsets the positive change predicted by the growth of household income. Also, the reduction in happiness predicted by the decline in confidence in institutions is non-negligible, although substantially smaller than the one predicted by either social connections or reference income.  相似文献   
103.
Over the last century, the national approach has been the mainstream conception leading superpowers’ foreign policy, while the end of the Cold War brought about the worldwide multiplication of local conflicts. This differs from the past as this extensive international fragmentation urgently requires the adaptation of a new theoretical model to current international relations. This implies the re-consideration of some basic concepts such as national sovereignty, whose traditional fixed borders tend now to blur with a set of overlapping clusters of jurisdictional, economic, political, cultural interests.  相似文献   
104.
This paper examines the structure and performance of the insurance industry in Jordan during the period of 2000–2005. The Jordanian insurance industry is free of state ownership in both primary insurance and reinsurance markets and has been spared the pervasive premium, product, investment, and reinsurance controls that have bedeviled the insurance markets of so many developing countries around the world. Despite these positive features, the insurance industry is not developed, which mainly reflects the underdevelopment of life insurance that has annual premiums of only 0.27 percent of GDP. In contrast, the level of general insurance is comparable to that of several other developing countries in the region. To overcome this situation a major modernization effort should be undertaken.   相似文献   
105.
106.
Entre 2002 et 2011, le marché du travail colombien a connu une nette amélioration des possibilités d'emploi, assortie d'une montée de l'emploi atypique. Les auteurs étudient l'incidence de ces phénomènes sur la qualité de l'emploi au moyen d'un indice synthétique dérivé d'une analyse des correspondances multiples. Ils observent une amélioration, légère mais générale, de cette qualité, associée à l'augmentation des revenus, à l'extension de la protection sociale et au recul du sous‐emploi. Les principales bénéficiaires sont les travailleuses indépendantes. Toutefois, un important déficit qualitatif perdure, qui appelle à consolider les institutions du marché du travail et à stimuler la productivité et l'investissement.  相似文献   
107.
In this paper we compare Bartlett-corrected, bootstrap, and fast double bootstrap tests on maximum likelihood estimates of cointegration parameters. The key result is that both the bootstrap and the Bartlett-corrected tests must be based on the unrestricted estimates of the cointegrating vectors: procedures based on the restricted estimates have almost no power. The small sample size bias of the asymptotic test appears so severe as to advise strongly against its use with the sample sizes commonly available; the fast double bootstrap test minimizes size bias, while the Bartlett-corrected test is somehow more powerful.  相似文献   
108.
We address a variant of the single item lot sizing problem affected by proportional storage (or inventory) losses and uncertainty in the product demand. The problem has applications in, among others, the energy sector, where storage losses (or storage deteriorations) are often unavoidable and, due to the need for planning ahead, the demands can be largely uncertain. We first propose a two-stage robust optimization approach with second-stage storage variables, showing how the arising robust problem can be solved as an instance of the deterministic one. We then consider a two-stage approach where not only the storage but also the production variables are determined in the second stage. After showing that, in the general case, solutions to this problem can suffer from acausality (or anticipativity), we introduce a flexible affine rule approach which, albeit restricting the solution set, allows for causal production plans. A hybrid robust-stochastic approach where the objective function is optimized in expectation, as opposed to in the worst-case, while retaining robust optimization guarantees of feasibility in the worst-case, is also discussed. We conclude with an application to heat production, in the context of which we compare the different approaches via computational experiments on real-world data.  相似文献   
109.
The growing desire to make the urban environment more sustainable from an ecological point of view has stimulated research on the architectural and agronomic aspects of green roofs. The practical realisation of green roofs, is however limited by economic and ecological issues. More specifically, water availability is the most limiting factor, and is likely to be ever more so in the future in the light of climate change. For this reason, we evaluated the agronomic performance of several xerophytes in a simulated dry green roof. Seeds of 20 species were collected in typically dry habitats (abandoned quarries, rocky soils, dunes, etc.) and studied in the laboratory for germination ecology. In cases of strong dormancy, methods were tested to stimulate germination and their germination ecology was studied. The resulting seedlings were transplanted in spring 2008 in two green roof types that differ in substrate depth (150 and 200 mm) made up of lapil, pumice, zeolites and peat, resting on a drainage layer of hydroperlite. Temperature and humidity in the substrate and drainage layer were measured during the whole test period. Survival of the seedlings in both substrate depths was almost 100%, favoured by a rainy spring. Most of the tested species showed an excellent performance during the hot and dry summer months in terms of survival rates, growth, and vegetation cover dynamics, notwithstanding the difficult ecological conditions (temperatures around 50°C; hydric potential Ψ -15 bars). Furthermore, most of the species had a long flowering stage in the first year of growth. Plants in the green roof with the deeper substrate depth produced, for most of the tested taxa, a significantly higher vegetation cover and growth compared to when they were placed in the 150 mm substrate. The results of this study show that some Mediterranean xerophytes have biological characteristics suitable for their use in dry green roofs, although an irrigation system for emergency use seems advisable. To conclude, further research should focus on long term evaluation of green roof vegetation in terms of plant survival and flowering dynamics.  相似文献   
110.
The paper proposes a reshaping of musical and cultural scene as a framework for the study of youth cultures. Developed in the ambit of post-subcultural theories, scene well represents the forces and flaws of such a category: high dynamism and ethnographic richness on one side; vagueness on the other. In order to reduce such vagueness, I conceptualise sceneness, intended as the substance of scenes, their density in networking and infrastructures. I use Arjun Appadurai’s concepts of locality and neighbourhoods to signify, respectively, sceneness and the actual scenes: in this way I redefine scene as a fragile construct that needs to be ritually revived, and that can work as a context for the development of new meanings and social groups. This implies conflict as a central element of scenes, one which can lead them to disequilibrium and disappearance. Such a redefinition is helpful for analysing fragile scenes which struggle to exist in troubled contexts, such as poor and hostile social environments. I provide, as an example, my ethnographic research on Metal in Tunisia. Caught between idealised images of community and an actual community which was conflictual and ‘fractured’, the Tunisian Metal scene lives a precarious existence threatened by material constraints and cultural marginality.  相似文献   
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