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221.
The southeastern Bering Sea is characterized by three mixing regimes, separated by fronts associated with the 50, 100, and 200 m isobaths. Phytoplankton to zooplankton transfer-rates are high in waters over the outer shelf and slope (seaward of the 100 m front) relative to transfer in waters over the middle shelf (between the 50 and 100 m fronts). To see whether this difference is reflected at a higher trophic level, we computed carbon flux to the 11 commonest seabird species. Bird-density data (for the period 1975 through 1979) were combined with daily caloric requirement, which is an allometric function of body size in this endothermic group. Minimum transfer to seabirds over a 153 d period (April–August) was 30 mg C m-2 for the middle shelf and 48 mg C m-2 for outer shelf and slope waters. Trophic transfer to subsurface-feeding birds (shearwaters, murres and auklets) differed little between regions. In contrast, trophic transfer to surface-feeding birds (fulmars, petrels, and kittiwakes) in the outer shelf and slope waters was 3 times greater than in the waters of the middle shelf. Thus, for seabirds as a whole, pathways of energy transfer differed more between regions than did total carbon flux. 相似文献
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Population distributions change substantially over time in major metropolitan areas. Knowledge of these variations by time of day, day of the week and other time periods can be helpful to disaster planners who need to prepare response plans to earthquakes and other disasters that will injure and kill large numbers of people. Computer graphics can display data that describe these changing population patterns in ways that can be more easily comprehended than page after page of printed numbers. Several different illustrations of 3-D population density maps drawn by the ASPEX computer program are presented. Each illustrates a guideline that can be used to prepare maps that deal with the many ways of looking at urban population density distributions and their temporal changes. Those maps can help disaster planners gain a realistic perception of population density distributions by enabling them to see what cannot be seen from the actual physical structure of a large metropolitan region. 相似文献
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Yang Christopher Schneider Stephen H. 《Mitigation and Adaptation Strategies for Global Change》1997,2(4):373-404
Carbon dioxide emissions from 1990 to 2100 AD are decomposed into the product of four factors: population size, affluence
(measured here as GDP per capita), energy intensity (energy use per unit GDP) and carbon intensity (carbon dioxide emissions
per unit energy). These emissions factors are further subdivided into three regions: more developed countries (MDCs), China,
and the remaining less developed countries (LDCs). Departures from a baseline scenario (based on IPCC, 1992a — the so-called
‘business-as-usual’ scenario) are calculated for a variety of alternative assumptions concerning the four emissions factors
in the three regions. Although the IPCC scenario is called a ‘non-intervention’ scenario, it is shown, for example, that large
decreases in energy intensity in China or carbon intensity in MDCs are built into the ‘business as usual’ case — and such
large changes vary considerably from region to region. We show what CO2 emissions would look like if each of these four emissions factors projected in the baseline case somehow remained constant
at 1990 levels. Certain factors like energy intensity improvements and long-term population growth in LDCs, or GDP growth
and carbon intensity improvements in MDCs, are shown to have a big contribution to cumulative global emissions to 2100 AD,
and consequently, changes in these projected factors will lead to significant deviations from baseline emissions. None of
the scenarios examined in this analysis seems to indicate that any one global factor is clearly dominant, but cultural, economic,
and political costs or opportunities of altering each factor may differ greatly from country to country. 相似文献
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