Tales of the City: What Do Agglomeration Cases Tell Us About Agglomeration in General?

This paper considers the heterogeneous microfoundations of agglomeration economies. It studies the co-location of industries to look for evidence of labor pooling, input sharing, and knowledge spillovers. The novel contribution of the paper is that it estimates single-industry models using a common empirical framework that exploits the cross-sectional variation in how one industry co-locates with the other industries in the economy. This unified approach yields evidence on the relative importance of the Marshallian microfoundations at the single-industry level, allowing for like-for-like cross-industry comparisons on the determinants of agglomeration. Using UK data, we estimate such microfoundations models for 97 manufacturing sectors, including the classic agglomeration cases of automobiles, computers, cutlery, and textiles. These four cases – as with all of the individual industry models we estimate – clearly show the importance of the Marshallian forces. However, they also highlight how the importance of these forces varies across industries – implying that extrapolation from cases should be viewed with caution. The paper concludes with an investigation of the pattern of heterogeneity. The degree of an industry’s clustering (localization), dynamism, incumbent firm size, and worker education are shown to contribute to the pattern of heterogeneous microfoundations

Binary Collisions and the Slingshot Effect

We derive the equations for the gravity assist manoeuvre in the general 2D case without the constraints of circular planetary orbits or widely different masses as assumed by Broucke, and obtain the slingshot conditions and maximum energy gain for arbitrary mass ratios of two colliding rigid bodies. Using the geometric view developed in an earlier paper by the authors the possible trajectories are computed for both attractive or repulsive interactions yielding a further insight on the slingshot mechanics and its parametrization. The general slingshot manoeuvre for arbitrary masses is explained as a particular case of the possible outcomes of attractive or repulsive binary collisions, and the correlation between asymptotic information and orbital parameters is obtained in general.Comment: 12 pages, 7 figures, accepted for publication Dec'07, Celestial Mechanics and Dynamical Astronom

Preliminary study on the contribution of external forces to ship behavior

Computational modeling has become a prominent tool to simulate physical processes for research and development projects. The coastal region of southern Brazil is very susceptible to oil spill accidents. Currently, oil is intensively transported in the region due to the presence of the Rio Grande Harbor, the TranspetroWaterway Terminal (Petrobras) and the Riograndense S/A Oil Refinery. Therefore, simulations under ideal navigation conditions for ships with potentially polluting loads are important because their use can reduce oil spills and toxic compound accidents in the environment. Therefore, the main objective of this work is to present a preliminary study of the contribution of external forces to a ship's behavior over a simulation period of 5 h. The methodology is based on the development of a numerical model using LaGrangian formalism and the calculus of variations, besides Maneuvering Modeling Group (MMG Model). The external forces considered were the wind acting directly on the ship, waves driven by wind, the rudder, the force acting on the hull, inertial forces, and seawater density. The results indicate that at the beginning of the simulation, the inertial forces were of primary importance for controlling the trajectory of the ship. After 5 h of simulations, the ship had completely changed its trajectory due to forces suffered by the ship, classified according to MMG Model

RECORRÊNCIA DE ALAGAMENTOS NA CIDADE DE TEÓFILO OTONI, MINAS GERAIS: UM ESTUDO INICIAL NO BAIRRO NOVO HORIZONTE

A desarmonia entre ocupação, uso do solo e planejamentos estrutural e ambiental geralmente levam a ocorrência de sérios problemas à população. Nesse sentido, este estudo busca relatar o histórico do local, pesquisar motivos dos casos ocorridos e apresentar providências iniciais. Os alagamentos decorrem da habitação descontrolada, falta de fiscalização por parte das autoridades e inexistência de ações para diminuir os riscos e prevenir desastres futuros

Role of magnetic anisotropy on the magnetic properties of Ni nanoclusters embedded in a ZnO matrix

We have investigated the magnetic properties of Ni nanoaggregates produced by ion implantation in ZnO single crystals. Several deviations from classical models usually adopted to describe the magnetic properties of nanoparticle systems were found. The strain between host and Ni nanoaggregates induces a magnetic anisotropy with a preferred direction. We show that these anisotropy effects can be misinterpreted as a ferromagnetic or antiferromagnetic coupling among the nanoaggregates similar to that of an oriented, interacting nanocrystal ensemble

Additional Nucleon Current Contributions to Neutrinoless Double Beta Decay

We have examined the importance of momentum dependent induced nucleon currents such as weak-magnetism and pseudoscalar couplings to the amplitude of neutrinoless double beta decay in the mechanisms of light and heavy Majorana neutrino as well as in that of Majoron emission. Such effects are expected to occur in all nuclear models in the direction of reducing the light neutrino matrix elements by about 30%. To test this we have performed a calculation of the nuclear matrix elements of the experimentally interesting nuclei A = 76, 82, 96, 100, 116, 128, 130, 136 and 150 within the pn-RQRPA. We have found that indeed such corrections vary somewhat from nucleus to nucleus, but in all cases they are greater than 25 percent. In the case of heavy neutrino the effect is much larger (a factor of 3). Combining out results with the best presently available experimental limits on the half-life of the neutrinoless double beta decay we have extracted new limits on the effective neutrino mass (light and heavy) and the effective Majoron coupling constant.Comment: 31 pages, RevTex, 3 Postscript figures, submitted to Phys. Rev.

Recent advances in neutrinoless double beta decay search

Even after the discovery of neutrino flavour oscillations, based on data from atmospheric, solar, reactor, and accelerator experiments, many characteristics of the neutrino remain unknown. Only the neutrino square-mass differences and the mixing angle values have been estimated, while the value of each mass eigenstate still hasn't. Its nature (massive Majorana or Dirac particle) is still escaping. Neutrinoless double beta decay ($0\nu$-DBD) experimental discovery could be the ultimate answer to some delicate questions of elementary particle and nuclear physics. The Majorana description of neutrinos allows the $0\nu$-DBD process, and consequently either a mass value could be measured or the existence of physics beyond the standard should be confirmed without any doubt. As expected, the $0\nu$-DBD measurement is a very difficult field of application for experimentalists. In this paper, after a short summary of the latest results in neutrino physics, the experimental status, the R&D projects, and perspectives in $0\nu$-DBD sector are reviewed.Comment: 36 pages, 7 figures, To be publish in Czech Journal of Physic