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991.
This article examines whether it is possible to target vulnerable households within a geographically defined area. It looks first at the justification for targeting and then reviews recent practical experience in actually trying to reach vulnerable groups. As complex emergencies increasingly last longer, strategies to target vulnerable households are common in the protracted phase of the emergency. While this is often necessary because of a decline in resources, it is not always justified by an improvement in nutritional status or food security of the beneficiary population. Common target groups are the poor and the malnourished, but in complex emergencies these are not always the most vulnerable. Moreover, recent practical experience has shown considerable difficulties in targeting the poor. Methods to target the poor rely on community-based relief committees, whose priorities are not necessarily the same as those of external agencies. This paper gives examples of such targeted assistance programmes in Kenya, south Sudan and Tanzania. The paper concludes that situations where targeting vulnerable households is justified and feasible are extremely limited. It is suggested that if targeting has to be done because of scarce resources, this should be done on a geographical basis and on the basis of nutritional status. Case-study material shows that it is essential to understand the political determinants of vulnerability and to design methods that will reach the most vulnerable. 相似文献
992.
AIMEE J. WELDON† 《Conservation biology》2006,20(4):1300-1305
Abstract: Corridors are a popular strategy to conserve biodiversity and promote gene flow in fragmented landscapes. Corridor effectiveness has been bolstered by the fact that no empirical field studies have shown negative effects on populations or communities. I tested the hypothesis that corridors increase nest predation in connected habitat fragments relative to unconnected fragments. I evaluated this hypothesis in a large-scale experimental system of open-habitat fragments that varied in shape and connectivity. Corridors increased nest predation rates in connected fragments relative to unconnected fragments with lower edge:area ratios. Nest predation rates were similar between connected and unconnected fragments with higher edge:area ratios. These results suggest that the increase in predator activity is largely attributable to edge effects incurred through the addition of a corridor. This is the first field study to demonstrate that corridors can negatively impact animal populations occupying connected fragments. 相似文献
993.
994.
The effects of varying the concentration of phosphorus and potassium independently in the growing medium of pot-grown tomato plants on their subsequent susceptibility in normal medium to vascular wilt caused by Verticillium dahliae Kleb. were studied. The degree of host invasion was measured by estimating the chitin component of diseased tissue. Different levels of potassium had little effect on the degree of invasion of inoculated stems, but this was considerably enhanced in plants raised in the absence of phosphorus. Root inoculated plants were particularly resistant when raised in nutrients totally lacking in potassium, and very susceptible when raised in the absence of phosphorus. 相似文献
995.
996.
Respiration and physiological state in marine bacteria 总被引:3,自引:0,他引:3
The relationship between oxygen consumption (R) and respiratory electron-transport-system (ETS) activity was investigated in batch cultures of 5 species of marine bacteria, Vibrio adaptatus, V. anguillarum, a partially identified Vibrio sp. SA774, Serratia marinorubra, and Pseudomonas perfectomarinus. Although cellular levels of R and ETS varied widely among the species tested, the R:ETS ratios for growing or senescent populations were relatively constant among the species; these ratios were 5.02 in growth and 0.426 in senescence, with coefficients of variation of 29 and 20%, respectively. The lower senescent-phase R:ETS ratio was due to a depression of the respiration rates following growth termination. The regression log (R per cell) = 0.832 log (ETS per cell) + 0.727 for the growing populations was similar to that determined for marine zooplankton. The slight dependency of the R:ETS ratio on organism dry weight found for zooplankton was supported by our data. Planktonic respiration rates estimated from measured ETS-depth profiles in the eastern tropical North Pacific Ocean using the senescent-phase R:ETS ratio were similar to published oxygen consumption rates in the deep sea.Contribution No. M79-61 from the University of Washington's Department of Oceanography, and No. 79032 from the Bigelow Laboratory for Ocean Sciences. 相似文献
997.
This paper investigates the scope for stabilizing commodity prices by buffer stock interventions. Optimal control is used, rather than simulation, to evaluate the scope for intervention at best. Applications to a world copper market model show that substantial but extensive gains to stabilization are possible. These gains cannot be realised by traditional bandwidth decision rules. An important difficulty is setting the level at which prices should be stabilized. The lack of this information severely reduces the achievable gains. 相似文献
998.
J R Miner 《Journal - Water Pollution Control Federation》1972,44(6):1072-1080
999.
This review describes the more important features of the emission, chemistry, transport and deposition of pollutants involved in acid deposition. Global emissions, both natural and man-made, of sulphur and nitrogen oxides are discussed and examples of spatial distributions and trends over the last century presented. The more significant chemical and physical processes involved in the transformation of the primary emissions into their acidic end products are described, including a summary of the approximate timescales of the processes involved. Measurements and modelled calculations of spatial and temporal patterns in the deposition of acidic pollutants by both wet and dry pathways are presented. 相似文献
1000.
Six diel TCO2 cycles determined by infrared (IR) photometry from five drift stations occupied between 24 February and 16 March 1979 in the mixed layer of the northwestern Caribbean Sea are examined. Comparison of TCO2 variation with coincident salinity and O2 variation demonstrated that TCO2 often co-varied with these independently measured variables. During five diel cycles TCO2 variation was characterized by nocturnal production and diurnal consumption. The inverse, diurnal production of CO2, occurred downstream from Misteriosa Bank, whose corals apparently contributed to a water mass having a twofold increase of POC and a sixfold larger population of heterotrophic nanoplankters. For the five diel studies carried out in waters with balanced or nearly blanced heterotrophic and phototrophic components of the nanoplankton, CO2 consumption at constant salinity always occurred between 06.00 and 09.00 hrs. Net uptake often continued through 15.00 hrs, but not always in the absence of significant salinity changes. At constant salinity net O2 evolution never exceeded 0.5 mol l-1 h-1 while net CO2 uptake consistently averaged 3 mol l-1 h-1 for an apparent net production of 36 mg C m-3 h-1, which greatly exceeds the O2 changes and open ocean 14C estimates from the literature. Diurnal consumption was apparently balanced by nocturnal production of CO2 so that no significant net daily change in TCO2 was observed. Departures from theoretical PQ and RQ and the possibility of nocturnal variations in formaldehyde and carbonate alkalinity imply that chemotrophs, both methane producers and methane oxidizers, play a significant role in CO2 cycling. This could be through the metabolism of the nonconservative gases CH4, CO, and H2, and a link between chemotrophy and phototrophy through these gases is hypothesized. These open system measurements were subject to diffusion and documentable patchiness, but temporal TCO2 changes appear to indicate the net direction of microbiological activity and join a growing body of literature showing dynamic variation in CO2 and O2 that exceeds estimates by 14C bottle assays of carbon fixation. 相似文献