Theoretical and empirical work seems to support the idea that tight labour markets driven by resource booms induce young individuals to leave school for employment as the opportunity cost of schooling increases. Resource booms may have an adverse long term effect on the productivity of the labor force if workers under-invest in human capital rather than merely altering the timing of schooling. ...

Purpose: This study aims to examine the effect of environmental management control systems on performance. Testing is carried out directly or through strategy mediation role. Theoretical framework: In contrast previous studies, this research focuses managerial activity processes that enable, encourage, ensure how a company and facilitate practices achieve performance strategies it. The model bu...

We use a luminous fast magnetic rotator model to analyze the influence of a magnetic field on the linear waves induced in the wind of a massive star by the radiative instability. We show that a twisted magnetic field can drive a strong wind with a wind efficiency (Ṁv∞)/(L/c) > 1 even without multiple scattering. The radiation amplified waves in the wind are modified by the twisted magnetic fiel...

Helicity was calculated in Hurricane Bonnie (1998) using tropospheric-deep dropsonde soundings from the NASA Convection and Moisture Experiment. Large helicity existed downshear of the storm center with respect to the ambient vertical wind shear. It was associated with veering, semicircular hodographs created by strong, vortex-scale, radial-vertical flow induced by the shear. The most extreme v...

The SuperDARN chain of oblique HF radars has provided an opportunity to generate a unique climatology of horizontal winds near the mesopause at a number of high latitude locations, via the Doppler shifted echoes from sources of ionisation in the D-region. Ablating meteor trails form the bulk of these targets, but other phenomena also contribute to the observations. Due to the poor vertical reso...

Approximately 100 000 species of insects have been described from sub-Saharan Africa. Largely as a result of Africa’s colonial history, the region’s insect fauna is probably better known than that of other tropical regions, but information is often more difficult to locate. Few centres of expertise on insect diversity and systematics exist in tropical Africa, while most large insect collections...

We use fiscal data on 2,468 oil extraction agreements in 38 countries to study tax contracts between resource-rich countries and independent oil companies. We analyze why expropriations occur and what determines the degree of oil price exposure of host countries. With asymmetric information about a country’s expropriation cost even optimal contracts feature expropriations. Near-linearity in the...

Nearly simultaneous VLBA observations of 3C 84, the radio source associated with NGC 1275, have been made at multiple frequencies to study the free-free absorption of the northern, or “counterjet”, feature found by Walker, Romney, and Benson (1994) and by Vermeulen, Readhead, and Backer (1994). Our observations confirm that the spectra are consistent with free-free absorption and eliminate the ...

We develop an overlapping-generations model with human capital accumulation and endogenous fertility containing a pollution externality. In such a framework, we study the effects of an environmental policy change on individuals’ quality-quantity trade-off on children. In a Malthusian poverty trap, we show that a more stringent policy induces a reduction of the fertility rate. In a state of perp...