9,249 research outputs found

    Network Externalities and Critical Mass in the Mobile Telephone Network: a Panel Data Estimation

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    This paper develops a simple demand model with network externalities which allow us to identify the shape of the network externalities function in the mobile telephone market and to estimate the critical mass. If the mobile telephone network exhibits positive network externalities, we expect that the demand curve is not downward sloping everywhere but it has an increasing part, the critical mass of the installed base of subscribers. Once the critical mass is reached, the growth of the network is self-sustaining. We use a panel data of the 30 OEDC Countries from 1989 to 2006 for estimating the relationship between price of 3-minute cellular call and the installed base of subscribers; we find strong network externalities effects in mobile telephone market which drive the demand curve for this network good to be an inverted U function. Moreover, given that the concavity of the demand curve depends on the extent of network externalities, the idea is to identify some variables which could affect the intensity of network effects in the mobile telephone market, because the more concave the demand curve is, sooner the critical mass is reached for any price. This may have important implications for producers in terms of initial investment and marketing strategies which they have to do to attain the critical mass.Network Externalities, Mobile Telecommunication, Critical Mass

    Compressive and shear behaviour of masonry panels: experimentation and numerical analysis

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    The compressive and shear behavior of masonry is here studied both experimental- ly and numerically. An experimental campaign has been carried out on 9 square-shaped one leaf masonry panels, reproducing historical masonry. Tests have been done for evaluating the elastic and shear moduli in both plane directions, with 6 panels rotated by 90 degrees, lead- ing to vertically aligned bed joints, and 3 panels maintained with horizontal bed joints. Com- pressive tests were executed on 6 masonry panels, 3 of them rotated by 90 degrees. Initial shear strength and shear modulus parallel to bed joints are evaluated through shear tests on 9 masonry triplets. Shear tests are performed on 3 rotated panels, applying an horizontal dis- tributed load, without vertical compression. Attention is paid to the service load state: only the initial phase of the tests is studied. Numerical models are proposed for representing actu- al masonry behavior, both discrete [1] and continuous [2,3], standard and micropolar, ob- tained by homogenization procedures [4]. Several numerical analyses are performed for simulating the experimental tests on masonry triplets and panels. The mechanical elastic pa- rameters of both discrete and continuous models are calibrated starting from laboratory data of masonry constituents and then by fitting the results of the initial phases of the experimental tests on masonry specimens

    The design of electoral rules and their impact on economic growth: the Italian case

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    Economic Growth, Electoral System, Corruption, Public expenditure, Education

    Application of micro-Raman spectroscopy for conservation projects in art and archaeology with a case study on Cappadocia rock-hewn wall paintings

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    This paper aims at reporting an overview of the principles and applications of micro-Raman spectroscopy in cultural heritage. Micro-Raman was used for characterizing painting pigments, inorganic binders, degradation materials in artworks with different goals: to know the materials and so the execution technique, to investigate the state of preservation, to establish the authenticity of the artefacts. The micro-Raman analyses were often performed on the occasion of conservative projects and they were able to supply valid and useful information to the conservators during their work. As case study, the project on the investigation of rock-hewn wall paintings in Cappadocia (Turkey) will be shortly presented as exemplificative of application of Raman techniques for the knowledge of the constituent materials, for supporting the conservation work and for detecting degradation products. Analysis were performed in the Interdepartmental instrument Center of Modena and Reggio Emilia University by a bench top system equipped with a microscope allowing for studying in non-destructive way different kinds of samples: powders, cross and thin sections, pre-treated samples

    Pyrazolo-triazolo-pyrimidines as adenosine receptor antagonists: A complete structure–activity profile

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    In the last 5 years, many efforts have been conducted searching potent and selective human A3 adenosine antagonists. In this field several different classes of compounds, possessing very good affinity (nM range) and with a broad range of selectivity, have been proposed. Recently, our group synthesized a new series of pyrazolo-triazolo-pyrimidines bearing different substitutions at the N5 and N8 positions, which have been described as highly potent and selective human A3 adenosine receptor antagonists. The present review summarizes available data and provides an overview of the structure–activity relationships found for this class of human A3 adenosine receptor antagonists

    Intercultural Communication Systems and Discourses of Cultural Identity

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    The analysis of intercultural communication, which is adopted in mainstream applied linguistics and communication studies, aims to explain the meaning of cultural differences and identities in the present global world. The present analysis of intercultural communication is based on theories of cultural variability, which highlight the basic distinctions between values determining cultural differences and identities. Some studies in applied linguistics observe cultural variability as a discursive construction based on a form of epistemological essentialism, produced in the Western part of the world to give meaning to its hegemony. However, these studies share some epistemological foundations with theories of cultural variability. This paper proposes a theorization of intercultural communication, which explains cultural differences and identities as constructed in communication systems and based on their particular structural presuppositions. In this perspective, the hegemonic structure of intercultural communication is ethnocentrism, including the presuppositions of Us/Them basic distinction, positioning of individuals as members of cultural groups and normative expectations about displays of We-identities. This theorisation also provides an explanation of the discursive construction of new hybrid forms of identity, which are observed as a result of globalisation, and of the interdependence between local and global communication systems. Finally, this theorization leads to explain the meaning of intercultural dialogue, which is presented as an alternative to ethnocentrism. The open question regards the explanation of dialogue as either a new discursive construction of hegemonic Western culture or a new structure, introducing equality in participation, sensitivity for participants’ personal expressions and expectations of participants’ empowerment in local and global communication systems
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