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In order to transmit information in images efficiently, the visual system should be tuned to the statistical structure of the ensemble of images that it sees. Several authors have suggested that the ensemble of natural images exhibits fractal behavior and, therefore, has a power spectrum that drops off proportionally to 1/f beta (2 less than beta less than(More)
[1] We examine the impact of future climate change on regional air pollution meteorology in the United States by conducting a transient climate change (1950 – 2052) simulation in a general circulation model (GCM) of the Goddard Institute of Space Studies (GISS). We include in the GCM two tracers of anthropogenic pollution, combustion carbon monoxide (COt)(More)
The classic view of evolution is a series of alternating and distinct steps. The first step is the generation of diversity through mutation; the second, natural selection. There is a growing awareness that in some cases these steps conjoin; for instance, the classic view breaks down when mutational changes alter the very machinery that generates diversity,(More)
[1] We examine the characteristics of the climate response to anthropogenic changes in tropospheric ozone. Using a general circulation model, we have carried out a pair of equilibrium climate simulations with realistic present-day and preindustrial ozone distributions. We find that the instantaneous radiative forcing of 0.49 W m À2 due to the increase in(More)
Sedimentological studies including X-ray digital analyses, mineralogy, inorganic contents, and organic geochemistry on cores of laminated sediments accumulated in the oxygen minimum zone of the central Peruvian margin reveal variable oceanographic and climate conditions during the last 500 yr. Coherent upcore variations in sedimentological and geochemical(More)
Detailed laboratory experiments on the formation of HD from atom recombination on amorphous solid water films show that this process is extremely efficient in a temperature range of 8 to 20 kelvin, temperatures relevant for H2 formation on dust grain surfaces in the interstellar medium (ISM). The fate of the 4.5 electron volt recombination energy is highly(More)
A new proposal is put forward for the formation of H 2 from H atoms in the interstellar medium based on the conjecture that efficient production of H − may take place at the surface of dust grains via attachment of weakly bound surface electrons. Subsequent gas phase associative detachment of H and H − forms H 2. The model is shown to be compatible with(More)
A Fourier transform spectrum at a resolution of ∼ 125,000 has been recorded of molecular hydrogen emission in the reflection nebula NGC 7023, in the S(1) v=1-0 line at 2.121 µm for a region 5 arcsec in diameter. The line is resolved and the derived linewidth corresponds to a kinetic temperature of 500± 70 K, if all motions are thermal. Comparison with data(More)