Digging Out the PPP Hypothesis: an Integrated Empirical Coverage

We use several popular tests to test the validity of the Purchasing Power Parity (PPP) hypothesis. In particular, we analyze four classes of tests { standard univariate unit root tests, co-integration, panel unit root tests and unit root tests for nonlinear frameworks {, for a dataset consisting of 20 bilateral exchange rates. Through this approach, we ascertain the eectiveness of each methodology in assessing the validity of PPP. Overall, our results suggest little evidence to support PPP. Among the conducted tests, the panel analysis of nonstationarity idiosyncratic and common components provides the richest insights by disentangling the possible sources of non-stationarity of real exchange rates. The relevance of using price indexes with dierent characteristics is also pinpointed.PPP; Real exchange rate; Unit roots; Co-integration; Panel; Nonlinear models; Cross-sectional dependence

Comparative study of the pathogenicity of seabed isolates of Fusarium equiseti and the effect of the composition of the mineral salt medium and temperature on mycelia growth

The pathogenicity of seven strains of Fusarium equiseti isolated from seabed soil was evaluated on different host plants showing pre and post emergence damage. Radial growth of 27 strains was measured on culture media previously adjusted to different osmotic potentials with either KCl or NaCl (-1.50 to - 144.54 bars) at 15º, 25º and 35º C. Significant differences and interactive effects were observed in the response of mycelia to osmotic potential and temperature

Lixiviação de potássio para avaliação do potencial fisiológico de sementes de milho

Seed production usually requires fast decisions to improve the efficacy of seed handling during harvesting, processing and storage. Seed technologists have focused on the development or improvement of procedures which allow rapid and consistent identification of higher quality seed lots. This research verified the effectiveness of the potassium leachate test on the evaluation of the physiological potential of maize seeds in comparison to recommended seed vigor tests. Five seed lots of the hybrid Avant were submitted to the potassium leachate, standard germination, first count, accelerated aging, electrical conductivity, field emergence and cold tests. The amount of potassium leachate was determined after seed imbibition for 30, 60, 90, 120, 150 and 180 minutes, at 25°C; a flame photometer adjusted to 50 mug K+ mL-1 pattern and reading 50 was used to determine the amount of leached potassium. The potassium leachate test consistently ranked the seed lots according to their physiological quality in comparison to other tests, and is a new alternative test for maize seed quality control programs.A necessidade freqüente da tomada de decisões rápidas, principalmente nas etapas de colheita, processamento e comercialização é habitual durante o processo de produção de sementes de várias espécies, dentre elas o milho. Consequentemente, a pesquisa em tecnologia de sementes tem procurado desenvolver ou aperfeiçoar testes que possibilitem avaliar, com eficiência, o potencial fisiológico das sementes, em período de tempo relativamente curto. O presente trabalho teve como objetivo verificar a potencialidade do teste de lixiviação de potássio, para avaliação do vigor de sementes de milho; cinco lotes do híbrido Avant foram submetidos a esse teste, cuja eficiência foi comparada à dos testes de germinação, primeira contagem de germinação, envelhecimento acelerado, frio, condutividade elétrica e emergência de plântulas em campo, recomendados para sementes de milho. A quantidade de potássio exsudado foi determinada em fotômetro de chama (padrão 50 mig K+ mL-1 ajustado para leitura 50), após 30, 60, 90, 120, 150 e 180 minutos de embebição, a 25°C. O teste de lixiviação de potássio foi considerado eficiente para separação dos lotes em diferentes níveis de vigor, constituindo alternativa promissora para avaliação do potencial fisiológico de sementes de milho; essa possibilidade contribui para a obtenção rápida de informações balizadoras de programas de controle de qualidade pós-colheita

Limiting thickness estimation in polycarbonate lenses injection using CAE tools

Some commercial software packages that simulate injection processes are available. It is possible to design moulds and to optimise the processes by using computer-aided engineering (CAE) tools. In addition, we employ C-MOLD, one of the best commercial packages, to determine the limiting thickness in polycarbonate lenses manufactured by injection. In this work we use a simple geometry to study the variation of different magnitudes as a function of the lowest thickness in biconcave and biconvex lenses. The parameters studied are the variation of temperature, pressure and piece mass during the filling time, air traps, melt lines and weld lines. The flow problem of the plastic in the mould is very different for biconcave and biconvex lenses. While the limiting thickness is in the centre for the biconcave lens, the perimeter is the limiting zone for the flow in the biconvex lens. For both geometries, however, the minimum thickness is limited by a mechanical and an aesthetic factor. If we take into account the variation of temperature, pressure and mass with minimum thickness, the mechanical limiting thickness can be estimated as 500 μm. But, if we also consider the evolution of the air traps and the melt and weld lines, which greatly influence the aesthetic factor, the resulting limiting thickness is 650 μm in the centre of biconcave lenses and 500 μm in the peripheric area of biconvex lenses

Novel Microscopic Mechanism of Intermixing during Growth on Soft Metallic Substrates

Generic computer simulations using empiric interatomic potentials suggest a new, collective mechanism that could be responsible for mixing at heteroepitaxial interfaces. Even if single adsorbate atoms diffuse by hopping on the substrate surface and do not mix at the terraces, two-dimensional islands formed by nucleation may become unstable above a certain critical size and explode upwards forming clusters of several atomic layers. This process is accompanied by strong distortions of the underlying atomic layers, and on soft materials it can result in surface etching and incorporation of substrate atoms into the islands.Fil: Gomez, Liliana Maria. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Slutzky, Claudia Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Ferron, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: de la Figuera, J.. Sandia National Laboratories; Estados UnidosFil: Camarero, J.. Universidad Autónoma de Madrid; EspañaFil: Vazquez de Parga, A.. Universidad Autónoma de Madrid; EspañaFil: de Miguel, J.J.. Universidad Autónoma de Madrid; EspañaFil: Miranda, R.. Universidad Autónoma de Madrid; Españ

Ownership structure and performance: A comparison of different corporate governance systems

[EN] This paper analyses how the main institutional factors characterizing corporate governance systems around the world affect the relationship between ownership structure and firm performance. Our analysis gives rise to the following remarks. First, ownership concentration and insider ownership levels are determined by several institutional features such as investor protection, development of capital markets, activity of the market for corporate control, and effectiveness of boards. Second, the relationship between ownership concentration and performance is not directly affected by these institutional factors. Third, there is, however, a direct influence of corporate governance characteristics on the relationship between insider ownership and performance

Modelo de inversi¢n basado en la ecuaci¢n de Euler con l¡mite m ximo de endeudamiento: evidencia emp¡rica internacional

Este trabajo estudia los determinantes de la inversi¢n empresarial, incorporando un l¡mite m ximo de endeudamiento a un modelo de inversi¢n basado en la ecuaci¢n de Euler. Las diferentes versiones del modelo desarrollado se han estimado por el M‚todo Generalizado de los Momentos para datos de Canad , Espa¤a, Estados Unidos y Reino Unido. Los resultados obtenidos muestran que la sensibilidad de la inversi¢n al cash flow es mayor para las empresas restringidas financieramente que para las no restringidas. Esta mayor sensibilidad es causada por la mayor repercusi¢n que tienen las imperfecciones del mercado en las empresas restringidas financieramente. En consecuencia, se pone de manifiesto la necesidad de considerar por separado las empresas restringidas y no restringidas para identificar los determinantes de la inversi¢n empresarial. This paper studies the determinants of firms? investment. Our model with a credit limit is derived from the Euler equation. The set of models obtained derived have been estimated by using the Generalized Method of Moments with data from Canada, Spain, The United States and The United Kingdom. Our results show that the sensitivity of investment to cash flow is greater for financially constrained firms than for those financiallyunconstrained. This greater sensitivity is caused by the higher effect of the capital market imperfections in the financially constrained firms. As a consequence, a separate study of the firm according to the financial constraints suffered is required in order to precisely identify the determinants of firms` investment.inversi¢n empresarial, restricciones financieras, ecuaci¢n de Euler, datos de panel. firms? investment, financial constrains, Euler equation, panel data.

Comparative study of Fusarium communities from soil and rhizoplane of melon plants from tropical farming soils.

Fifty-nine rhizospheric soil samples from twenty different melon farms of Guatemala and Honduras were analysed to study the Fusarium species present in the soil and those developing on roots surfaces