Trade in services : IT and task content

In this paper we investigate the determinants of the dramatic increase in services tradability focusing on the extensive margin of the phenomenon. We use balance sheet and firm-level service trade information over the period 1995-2005 provided by the National Bank of Belgium and we merge it with information on the evolution of information technology use and tasks performed by workers from the qualification and career survey provided by the BIBB-IAB. We show that technological change, measured either by the more intensive use of information technologies or by changes in the task content of jobs, has substantially contributed to the increase in the number of service-trading firms. Interestingly, we find evidence of a churning effect. While technological change has induced net entry into service trading, it has also increased the likelihood of both gross entry and exit of firms. Furthermore, our evidence suggests that due to the peculiar nature of services provision, the change in the tasks content of jobs is a better measure of technological change than the use of information technologies. Our results are robust to controlling for service trade liberalization and offshoring.trade in services; extensive margin; technological change; task content

Service Trade and Occupational Tasks: An Empirical Investigation

Using micro data for Belgium we investigate the relationship between occupational tasks changes and the rise of service trade. We focus the analysis on the extensive margin and look at the heterogeneous proliferation of firms involved in exports and imports of services across sectors characterized by different tasks changes patterns. Occupational tasks changes display an extremely consistent relationship with participation to service trade across firm groups pointing to strong churning effects. The change in analytical (interactive and routine cognitive) tasks intensity has a positive (negative) impact across the board meaning that, in industries characterized by larger changes, firms have experienced both higher (lower) likelihood of entry and exit. The negative relationship between the change in interactive tasks and service exports participation underlines the special role that proximity between demand and supply plays for services. Interestingly, we find exactly the opposite result (a positive relationship) between the extensive margin of goods exports and interactive tasks. Moreover, our analysis suggests that the change in IT use per se does not strike as being a key underlying force behind the increase in the extensive margin of service exports.Trade in services, extensive margin, occupational tasks, technological change

La figurazione dello spazio architettonico di Gaspare De Fiore

Dal 1967, anno in cui Gaspare De Fiore pubblicò La figurazione dello spazio architettonico, ad oggi sono trascorsi esattamente 50 anni, eppure l’opera conserva la medesima fresca attualità che fu possibile rilevare leggendola per la prima volta durante gli anni della nostra formazione. Nell’affrontare il problema dello spazio architettonico De Fiore distingue tra la sua ideazione e la sua rappresentazione, segnatamente affrontando il secondo argomento da molteplici punti di vista e lungo un arco temporale che abbraccia l’intera storia dell’uomo, dalla pittura preclassica all’arte contemporanea, passando attraverso la rappresentazione dell’architettura in epoca romana, le dinamiche concettuali del Medioevo, la certezza ottica del Rinascimento e l’illusionismo Barocco. Inoltre, nel volume De Fiore usa il medium della pittura per esprimere il proprio rapporto con l’architettura; d’altronde il titolo del libro esprime con chiarezza le intenzioni dell’autore che riferiscono l’architettura alla sua “figurazione” nel corso della storia, cosa che sembra quasi volere trovare un campo di applicazione unilaterale per la lettura dello spazio architettonico. Leggere oggi questo volume può sembrare probabilmente anacronistico, e forse lo è, ma la sua lettura appare necessaria per chi si occupa di rappresentazione e, più in particolare, di storia della rappresentazione intesa come oggetto di studio attraverso il disegno e non come semplice excursus.Since 1967, the year in which Gaspare De Fiore published The figuration of architectural space, exactly 50 years have passed, and yet the work preserves the same fresh relevance that it was possible to detect by reading it for the first time during the years of our formation. Affronting the problem of architec- tural space, De Fiore distinguishes between its ideation and its repre- sentation, in particular by addressing the latter from multiple points of view and in a time span that embraces the whole of human history, from preclassic to contemporary art, through the representation of Roman architecture, the conceptual dynamics of the Middle Ages, the optical certainty of the Renaissance and Baroque illusionism. In his book, De Fiore uses painting as a medium for expressing his relationship with architecture. Moreover, the title of the book clearly expresses the author’s intentions referring architecture to its ‘figuration’ throughout history, which almost seems to find a field of unilateral application for the reading of architectural space. Today reading this volume may probably seem anachronistic, and perhaps it is, but it seems necessary for those who deal with representation and, more specifically, with the history of representation conceived as a subject of study through drawing, and not as a simple excursus

Charge doping and large lattice expansion in oxygen-deficient heteroepitaxial WO3

Tungsten trioxide is a versatile material with widespread applications ranging from electrochromic and optoelectronic devices to water splitting and catalysis of chemical reactions. For technological applications, thin films of WO3 are particularly appealing, taking advantage from high surface-to-volume ratio and tunable physical properties. However, the growth of stoichiometric, crystalline thin films is challenging because the deposition conditions are very sensitive to the formation of oxygen vacancies. In this work, we show how background oxygen pressure during pulsed laser deposition can be used to tune the structural and electronic properties of WO3 thin films. By performing X-ray diffraction and low-temperature transport measurements, we find changes in WO3 lattice volume up to 10%, concomitantly with an insulator-to-metal transition as a function of increased level of electron doping. We use advanced ab initio calculations to describe in detail the properties of the oxygen vacancy defect states, and their evolution in terms of excess charge concentration. Our results depict an intriguing scenario where structural, electronic, optical, and transport properties of WO3 single-crystal thin films can all be purposely tuned by a suited control of oxygen vacancies formation during growth

ON THE STRUCTURAL VALIDITY OF BESTEST, MINI-BESTEST AND BRIEF-BESTEST.

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Electrical Characteristics of Pantograph Arcs in DC Railways: Infrastructure Influence

Electric arcs are an unavoidable by-product of current collection by sliding contact in electrified transportation systems. Electric arcs are transient phenomena with implications for PQ measurements and wearing estimation and prevention of the sliding contact and catenary. Besides being heavily influenced by mechanical characteristics and material properties, their electrical characterization encompasses spectral properties and the influence of train and traction line circuits and relative position of infrastructure elements. This paper identifies the influence of such electrical and system characteristics onto the spectral signature of electric arcs for DC railways

Thermal effects on fracture and brittle-to-ductile transition

The fracture behavior of brittle and ductile materials can be strongly influenced by thermal fluctuations, especially in micro- and nano-devices as well as in rubberlike and biological materials. However, temperature effects, in particular on the brittle-to-ductile transition, still require a deeper theoretical investigation. As a step in this direction we propose a theory, based on equilibrium statistical mechanics, able to describe the temperature dependent brittle fracture and brittle-to-ductile transition in prototypical discrete systems consisting in a lattice with breakable elements. Concerning the brittle behavior, we obtain closed form expressions for the temperature-dependent fracture stress and strain, representing a generalized Griffith criterion, ultimately describing the fracture as a genuine phase transition. With regard to the brittle-to-ductile transition, we obtain a complex critical scenario characterized by a threshold temperature between the two fracture regimes (brittle and ductile), an upper and a lower yield strength, and a critical temperature corresponding to the complete breakdown. To show the effectiveness of the proposed models in describing thermal fracture behaviors at small scales, we successfully compare our theoretical results with molecular dynamics simulations of Si and GaN nanowires.Comment: 27 pages, 20 figure

Dynamical approach to Zipf's law

The rank-size plots of a large number of different physical and socio-economic systems are usually said to follow Zipf's law, but a unique framework for the comprehension of this ubiquitous scaling law is still lacking. Here we show that a dynamical approach is crucial: during their evolution, some systems are attracted towards Zipf's law, while others presents Zipf's law only temporarily and, therefore, spuriously. A truly Zipfian dynamics is characterized by a dynamical constraint, or coherence, among the parameters of the generating PDF, and the number of elements in the system. A clear-cut example of such coherence is natural language. Our framework allows us to derive some quantitative results that go well beyond the usual Zipf's law: i) earthquakes can evolve only incoherently and thus show Zipf's law spuriously; this allows an assessment of the largest possible magnitude of an earthquake occurring in a geographical region. ii) We prove that Zipfian dynamics are not additive, explaining analytically why US cities evolve coherently, while world cities do not. iii) Our concept of coherence can be used for model selection, for example, the Yule-Simon process can describe the dynamics of world countries' GDP. iv) World cities present spurious Zipf's law and we use this property for estimating the maximal population of an urban agglomeration