Depletion hole

The generation of the depletion hole on the initial elecfronic state due to PA with a short pulse can be understood by employing a phase-amplitude representation for both the lower- and the excited-state wavepackets,... 

In the intermediate stage of the reaction or t < t < t the time at which saturation of the interface by copolymer remains negligible, but the interfacial concentrations of A and B reactive chains, pAi(t) and PBj(t), are reduced below their bulk concentrations, PAi(t) = pBi(t) = Po( Ap) - I other words, within this time interval, there is a depletion hole of reactive chains with spatial extension (DcomO - The reaction rate is dominated by the flux of reactive chains to the interface and is independent of the reaction kinetics, kinto- The copol5nner coverage grows as the square root of time... 

A fiuther rather subtle result of these improved mean-field theories is the oc-eurrenee of a depletion hole, i.e., a region at a eertain separation from the adsorbing surfaee where the monomer concentration is smaller than the bulk eoneentration [42], This depletion hole results from an interplay between the depletion of free polymers from the adsorbed layer and the slowly deeaying density profile resulting from dangling tails. It occurs at a distance from the surfaee eomparable with the radius of gyration of a free polymer, but also shows some dependence on the bulk polymer eoneentration. These and other effeets, related to the occurrence of loops and tails in the adsorbed layer, have been recently reviewed [43]. 

Reservoir pressure is measured in selected wells using either permanent or nonpermanent bottom hole pressure gauges or wireline tools in new wells (RFT, MDT, see Section 5.3.5) to determine the profile of the pressure depletion in the reservoir. The pressures indicate the continuity of the reservoir, and the connectivity of sand layers and are used in material balance calculations and in the reservoir simulation model to confirm the volume of the fluids in the reservoir and the natural influx of water from the aquifer. The following example shows an RFT pressure plot from a development well in a field which has been producing for some time. 

Measurements of ozone (O3) concentrations in the atmosphere are of particular importance. Ozone absorbs strongly in the ultraviolet region and it is this absorption which protects us from a dangerously high dose of ultraviolet radiation from the sun. The vitally important ozone layer lies in the stratosphere and is typically about 10 km thick with a maximum concentration about 25 km above the surface of the earth. Extreme depletion of ozone in a localised part of the atmosphere creates what is known as an ozone hole. 

When electrons are injected as minority carriers into a -type semiconductor they may diffuse, drift, or disappear. That is, their electrical behavior is determined by diffusion in concentration gradients, drift in electric fields (potential gradients), or disappearance through recombination with majority carrier holes. Thus, the transport behavior of minority carriers can be described by a continuity equation. To derive the p—n junction equation, steady-state is assumed, so that = 0, and a neutral region outside the depletion region is assumed, so that the electric field is zero. Under these circumstances,... 

The discovery of ozone holes over Antarctica in the mid-1980s was strong observational evidence to support the Rowland and Molina hypothesis. The atmosphere over the south pole is complex because of the long periods of total darkness and sunlight and the presence of a polar vortex and polar stratospheric clouds. However, researchers have found evidence to support the role of CIO in the rapid depletion of stratospheric ozone over the south pole. Figure 11-3 shows the profile of ozone and CIO measured at an altitude of 18 km on an aircraft flight from southern Chile toward the south pole on September 21, 1987. One month earlier the ozone levels were fairly uniform around 2 ppm (vol). 

J. C. Farman discovered the ozone hole (substantial seasonal depletion of ozone) over Halley Bay, Antarctica. 

Thus, the mean temperature of the atmosphere, which is about 20°C at sea level, falls steadily to about —55° at an altitude of 10 km and then rises to almost 0°C at 50 km before dropping steadily again to about —90° at 90 km. Concern was expressed in 1974 that interaction of ozone with man-made chlorofluorocarbons would deplete the equilibrium concentration of ozone with potentially disastrous consequences, and this was dramatically confirmed by the discovery of a seasonally recurring ozone hole above Antarctica in 1985. A less prominent ozone hole was subsequently detected above the Arctic Ocean. The detailed physical and chemical conditions required to generate these large seasonal depletions of ozone are extremely complex but the main features have now been elucidated (see p. 848). Several accounts of various aspects of the emerging story, and of the consequent international governmental actions to... 

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