The price of energy and potential growth of developed countries : An attempt at quantification
Abstract A growth model based on a theoretical discussion of the impact of oil prices on developed countries is used to predict the impact of higher prices of energy on the growth of developed countries. The results suggest that the growth impact is small, that domestic price policies may have a large impact on oil imports, and that the investment of foreign assets accumulated by oil producers may make a significant contribution to the GNP of OECD.
Restructuring the world economy
The future consequences of the present disequilibrium in the world economy and adjustment processes through which equilibruim can be restored are discussed. There are a few commodities whose high prices or short supplies are likely to have an important effect on the economic welfare of large numbers of people: petroleum, major foodstuffs, and fertilizer. The rise in oil prices is the most dramatic of a series of events that have been operating to change the distribution of world income through the system of international trade and capital flows. In order to analyze the possible adjustments to the oil problem, the varying positions of the principal oil exporters must be understood. Nonetheless, the type of adjustments that are likely to be required involve reducing nonessential energy needs, developing new energy sources, and persuading producers to reduce prices. Lesser developed countries have more limited adjustment mechanisms than those that can be employed by developed nations. Through cooperative efforts the resumption of satisfactory rates of development throughout the world should be possible.
Monte Carlo Study of the Effect of Backscatter Materail Thickness on 99 mTc Source Response in Single Photon Emission Computed Tomography
Introduction SPECT projections are contaminated by scatter radiation, resulting in reduced image contrast and quantitative errors. Backscatter constitutes a major part of the scatter contamination in lower energy windows. The current study is an evaluation of the effect of backscatter material on FWHM and image quality investigated by Monte Carlo simulation. Materials and Methods SIMIND program was used for simulation of a Siemen’s dual-head variable angle scintillation gamma camera. Planar and SPECT scanning of a 99m Tc source and a Jaszczak phantom for varying thicknesses of Perspex slabs, as a backscatter media, were analyzed using the photopeak and scatter windows. Simulated planar images and reconstructed tomographic images were evaluated qualitatively, by two nuclear medicine specialists, and quantitatively, by Structural Similarity (SSIM) Index. Results In the 99m Tc photopeak window, no significant change in total counts due to backscatter material was measured. In the scatter windows, scattering was overestimated compared with a simulated backscatter free SPECT system. For instance, at a thickness of 10 cm, total counts of a 99m Tc source detected in the 72 keV windows eventually doubled with increasing backscatter material, compared with the situation without backscatter material. The backscatter contribution plateaued when more than 7 cm of scatter material was placed but there were optimized results for a backscatter thickness of 4.5 cm. Better image quality for the thickness was confirmed by the results of eye interpretation and also by SSIM algorithm. Conclusion Backscatter should be taken into account, particularly in model-based scatter correction methods in SPECT for an accurate simulation system optimization.