How Productive is Public Capital? A Meta-Analysis

The paper analyzes the contribution of public capital to private output using several metaanalytical techniques. Both fixed and random effects models are estimated by Weighted Least Squares. Sample overlap across studies is explicitly controlled for by employing a `full' Generalized Least Squares estimator. The weighted average output elasticity of public capital amounts to 0.08 after correcting for publication bias. A substantial part of the heterogeneity across studies is explained by study design parameters, such as econometric specification, estimation technique, empirical model, type of public capital, and level of aggregation of public capital data. The large elasticities of public capital found in the early literature seem to be caused by either unidentified (but present) cointegrating relationships or spurious relationships in national time series.public capital;infrastructure;public investment;meta-analysis;meta-regression analysis;publication bias

Output Dynamics, Technology, and Public Investment

The paper studies the dynamic output effects of public infrastructure investment in a small open economy. We develop an overlapping generations model that includes a production externality of public capital and a wealth effect on labor supply. Public capital enters the firm's production function under various technological scenarios. We show that if factors of production are gross complements and public capital is Solow neutral, which is the empirically plausible case, the long-run output multiplier falls short of its Hicks-neutral value. The way in which public capital augments factor productivity crucially affects the dynamics of private capital and net foreign assets, but yields qualitatively similar output dynamics. In contrast to conventional results obtained from hysteretic models, we find non-monotonic output dynamics of a public investment impulse in the non-hysteretic model. Schmitt-Grohe and Uribe's (2003) finding of identical impulse responses across the two model types is thus not robust to the inclusion of spillovers of public capital.Infrastructure capital;public investment;fiscal policy;output multipliers;transitional dynamics;technology

Gambling as a teaching aid in the introductory physics laboratory

Dice throwing is used to illustrate relevant concepts of the statistical theory of uncertainties, in particular the meaning of a limiting distribution, the standard deviation, and the standard deviation of the mean. It is an important part in a sequence of especially programmed laboratory activities, developed for freshmen, at the Institute of Physics of the University of S˜ao Paulo. It is shown how this activity is employed within a constructive teaching approach, which aims at a growing understanding of the measuring processes and of the fundamentals of correct statistical handling of experimental data

Liste alphabétique des titres

In the last years many populations of anurans have declined and extinctions have been recorded. They were related to environmental pollution, changes of land use and emerging diseases. The main objective of this study was to determine copper sensitivity of the anuran of the Amazon Rhinella granulosa and Scinax ruber tadpoles at stage 25 and Scinax ruber eggs exposed for 96 h to copper concentrations ranging from 15 µg Cu L-1 to 94 µg Cu L-1. LC50 at 96 h of Rhinella granulosa Gosner 25, Scinax ruber Gosner 25 and Scinax ruber eggs in black water of the Amazon were 23.48, 36.37 and 50.02 µg Cu L-1, respectively. The Biotic Ligand Model was used to predict the LC50 values for these species and it can be considered a promising tool for these tropical species and water conditions. Copper toxicity depends on water physical-chemical composition and on the larval stage of the tadpoles. The Gosner stage 19-21 (related to the appearance of external gills) is the most vulnerable and the egg stage is the most resistant. In case of contamination by copper, the natural streams must have special attention, since copper is more bioavailable.Nos últimos anos foram registrados muitas extinções e declínios de populações de anuros. Eles estavam relacionados com a poluição do ambiente, a mudanças no uso da terra e ao surgimento de doenças. O principal objetivo deste estudo foi determinar a sensibilidade dos anuros amazônicos ao cobre. Os girinos de Scinax ruber e Rhinella granulosa no estadio 25 e os ovos de Scinax ruber foram expostos por 96 horas a concentrações de cobre entre 15 µg Cu L-1 a 94 µg Cu L-1. A CL50 -96 h dos girinos de Rhinella granulosa, dos girinos de Scinax ruber e dos ovos de Scinax ruber em águas pretas da Amazônia foram 23,48; 36,37 e 50,02 µg Cu L-1, respectivamente. O modelo do ligante biótico foi usado para prever os valores de CL50 para essas duas espécies e pode ser considerado uma ferramenta promissora para essas espécies tropicais e para essas condições de água. A Toxicidade de cobre depende da composição físico-química da água e do estagio larval dos girinos. O estadio 19-21 de Gosner (relacionados ao aparecimento das brânquias externas) são os mais vulnerável e o estagio de ovo é o mais resistente. Em caso de contaminação por cobre, os igarapés naturais devem ter uma atenção especial, uma vez que o cobre é mais biodisponível nesse ambiente