Is two better than one? Effects on growth of Bank-Fund interaction

We estimate the impact on economic growth of the joint participation in both IMF and WB programs. More specifically, using panel data for 128 developing countries over the period 1982-2005, and employing 2SLS to control for the possible endogeneity of participation in an IMF/WB program, we find that even if the WB and the IMF do not boost growth when they operate by themselves, the interaction term between these two organization is positive and significant at conventional levels. However, when we restrict the sample to low and lower middle income countries only (for which Bank-Fund cooperation is more “formalized”) the coefficient of the interaction term is not significant. Thus, so far, a trade-off emerges between a greater precision in the definition of Bank-Fund cooperation and the reliability of the estimates due to an insufficient number of observations.

Land Use Dynamics: a Cellular Automata

Usually applications of urban growth cellular automata are related to an only one town, with transition rules and constraints a priori defined. This seems to be a severe limits in applications. The paper presented is born to follow a different kind of approach, so to have rules and constraints directly from observed past data. We consider ten European towns and for each one we have data for time series approx. 40 years long. We deduce rules and constraints directly from the data set, solving an inverse problem (in which we have input and output measures and we have to determine a system model).The study aims to define in detail the stochastic or deterministic character of transition rules (in the stochastic case evaluating transition probability). At last the rules are applied to towns maps (by means of ad hoc cellular automaton). With this cellular automaton we try to simulate past dynamics (for a validation of the model) and also to forecast the spatial development of the towns by means of scenarios (based on the past histories of the cities).

Cost-Benefit Analysis of the Large Hadron Collider to 2025 and beyond

Social cost-benefit analysis (CBA) of projects has been successfully applied in different fields such as transport, energy, health, education, and environment, including climate change. It is often argued that it is impossible to extend the CBA approach to the evaluation of the social impact of research infrastructures, because the final benefit to society of scientific discovery is generally unpredictable. Here, we propose a quantitative approach to this problem, we use it to design an empirically testable CBA model, and we apply it to the the Large Hadron Collider (LHC), the highest-energy accelerator in the world, currently operating at CERN. We show that the evaluation of benefits can be made quantitative by determining their value to users (scientists, early-stage researchers, firms, visitors) and non-users (the general public). Four classes of contributions to users are identified: knowledge output, human capital development, technological spillovers, and cultural effects. Benefits for non-users can be estimated, in analogy to public goods with no practical use (such as environment preservation), using willingness to pay. We determine the probability distribution of cost and benefits for the LHC since 1993 until planned decommissioning in 2025, and we find there is a 92% probability that benefits exceed its costs, with an expected net present value of about 3 billion euro, not including the unpredictable economic value of discovery of any new physics. We argue that the evaluation approach proposed here can be replicated for any large-scale research infrastructure, thus helping the decision-making on competing projects, with a socio-economic appraisal complementary to other evaluation criteria.Comment: 17 pages, 7 figure

Dynamic modeling of Terahertz Quantum cascade lasers

In this paper, the influence of the simplifications made in the four-equation-based set of rate equations describing the dynamic behavior of a Quantum Cascade Laser (QCL) is studied. Numerical simulations based on the set of four rate equations has been developed, enabling the theoretical study of the influence of different parameters on the direct modulation response of the laser. These equations have been then linearized in order to deduce a set of state system equations, which was written in a matrix formalism. Finally, an approximate second order transfer function has been derived with the linearized dependence of its times constant

Optimal design and quantum limit for second harmonic generation in semiconductor heterostructures

The optimal design for infrared second harmonic generation (SHG) is determined for a GaAs-based quantum device using a recently developed genetic approach. Both compositional parameters and electric field are simultaneously optimized, and the quantum limit for SHG, set by the trade-off between large dipole moments (favouring electron delocalization) and large overlaps (favouring electron localization), is determined. Optimal devices are generally obtained with an asymmetric double quantum well shape with narrow barriers and a graded region sideways to the largest well. An electric field is not found to lead to improved SHG if compositional parameters are optimized.Comment: 5 pages, 2 figures embedded. To apper in J. App. Phys. (Jan 2nd, 2001