This paper reviews the evidence on the socio-economic impacts of GM crops and analyzes whether there are patterns across space and time. To this end, we investigate the effect of GM crops on farm-level costs and benefits using global data from more than one decade of field trials and surveys. More specifically, we analyze the effects of GM-crops on crop yields, seed costs, pesticide costs, and management and labor costs and finally gross margins. Based on collected data from studies on Bt cotton and Bt maize, statistical analyses are conducted to estimate the effect of GM crop adoption on these parameters. Our results show that, compared to conventional crops, GM crops can lead to yield increases and can lead to reductions in the costs of pesticide application, whereas seed costs are usually substantially higher. Thus, the results presented here do support the contention that the adoption of GM crops leads on average to a higher economic performance, which is also underlined by the high adoption rates for GM crops in a number of countries. However, the kind and magnitude of benefits from GM crops are very heterogeneous between countries and regions, particularly due to differences in pest pressure and pest management practices. Countries with poor pest management practices OPEN ACCESS

An increase of 'growth' of optical thickness has been observed in PbTe layers freshly deposited during infrared filter manufacture. The phenomenon is nine parts complete about 15 min after deposition ceases, and is typically 0.03 mu m thick. Fluctuations in receptor surface temperature have been eliminated from being responsible. Negligible correlation is also found with physical thickness, monitoring wavelength (3.4-5 mu m), deposition temperature, receptor surface and underlying layers. An unquantified correlation appears to have been found with deposition rate. Undesirable loss of transparency accompanies any attempt at suppressing the phenomenon; conversely, when allowed to proceed without inhibition the growth sets up errors requiring individual compensation.

Two types of multilayer interference filter are required for temperature sounding the earth's atmosphere. In relation to the 668-cm(-1) nu(2) band of CO(2) these are narrowband (4 cm(-1) wide for the Q branch, 10 cm(-1) for the R branch) or isolation (~60 cm(-1) wide for the complete center of the band). Difficulty in manufacturing the filters for NIMBUS-SCR and -PMR spaceflight has indicated a need for improvement in the monitoring and control of the deposition of layers, and the paper describes a realization of this. The consequent effect on filter performance (utilizing a particular combination of layer materials) is described.

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RBsumB. -La transparence optique des couches monocristallines de PbTe peut varier aprb un traitement thermique suivant l'evaporation. Les monocouches ont quelques microns d'epaisseur et le recuit fait dkroitre la densite de porteurs d'environ 10lscm-3 (type n) B 10 17 cm-3 : le materiau de la source est B 1019cm-3 (typep). Le processus semble faire intervenir la diffusion de 0 2 a un taux de reaction correspondant a une energie de 0,83 eV.Abstract. -The changes in the optical transparency of PbTe monolayers induced by post-evaporation heat treatment are described. The monolayers are typically a few microns in thickness and heat treatment reduces the carrier density from about 1018 (n-type) per cm3 to 1 0 1 7 per cm3 : the source material is 1019 (p-type) per cm3. The process seems to involve the diffusion of 0 2 at a reaction rate equivalent to an energy of 0.83 eV.