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941.
We investigated the effect of maternal serum screening on the amniocentesis (AC) rate in women of advanced maternal age. The AC rate after maternal serum screening was compared in two groups of women with a singleton pregnancy, 855 women of 30–35 years and 98 of 36 years and older. In our population, 34·1 per cent of the women of 36 years or older were ‘screen-positive’ for Down syndrome. Only 41·2 per cent of these women chose to undergo AC as opposed to 88·2 per cent in the younger age group. Within the older age group, the tendency to avoid AC increased with increasing age. Maternal serum screening led to a significant decrease in the AC rate in the older women. In this group, a comparison between the ‘a priori’ and the calculated risk might have had more influence on the decision to undergo AC than being screen-positive or screen-negative as such. We conclude that maternal serum screening had a major effect on the AC rate in women of advanced maternal age. This is of importance in a society in which the average maternal age is steadily increasing.  相似文献   
942.
943.
The Urban Cleaning Company of the City of Rio de Janeiro - COMLURB launched the Recycling Separation Center Project (Projeto Central de Separação de Recicláveis or CSR) in 2003. The objectives of the project were the adequate disposal of solid urban waste as well as the generation of employment and income. The COMLURB Project had economic, environmental and social facets, and the researchers sought to establish whether COMLURB had prepared reports that would enable evaluation of the investment made and the results obtained. In particular, the researchers sought to establish whether COMLURB financial statements set out the results of actions inherent to the CSR. We concluded from our analysis of the Project that the three elements of sustainability (social, environmental and economic), despite being fully present, were not adequately demonstrated. This study therefore proposes a model report with a view to enabling various information users to evaluate the results of the CSR Project.  相似文献   
944.
We experimentally tested threealternative hypotheses to explain the low algaldiversity and abundance in an intertidal zonereceiving the effluents of the copper mine El Salvadorin northern Chile. Our results demonstrated thatalgae were able to grow at the levels of dissolvedcopper detected in coastal waters of the area. Duringthe assays, growth and regeneration in several red,green and brown adult algae and juvenile Lessonia nigrescens were normal at copper levels of150 g L-1 or, in some cases, higher. Wealso found that the coastal sea water mixed with theeffluent was not lethal to algae, although in somecases minor effects on growth were detected. Theseresults indicate that today's low algal diversity andabundance can not be explained by the current copperlevels in the area nor by the effect of the effluent.Exclusion of grazers, however, resulted in a fastcolonization by various algal species. This, togetherwith atypically high grazer density at the areas underthe influence of the effluent, strongly suggests thatherbivory, a factor not directly related to the miningoperation, is likely to be responsible for the lowalgal diversity and abundance in the studied locality.  相似文献   
945.
In the evaluation of potentially adverse effects oforganic chemicals such as pesticides on theenvironment the atmosphere may play an important role.After its release to the atmosphere the chemical willbe transported/dispersed in the atmosphere and finallyit will be removed either by atmospheric-chemicaldestruction or by deposition to the underlying soil orsurface water. In a risk assessment decision supportsystem both ambient concentrations and depositionfluxes must be known to evaluate the risk of directexposure (inhalation) or the risk of soil and watercontamination caused by deposition. This paperdiscusses the use of atmospheric dispersion models insuch risk assessment decision support systems.  相似文献   
946.
An overview is presented of sampling techniques and flow injection analysis (FIA) methods for low concentrations of Fe, Mn and Al in filtered seawater. On the basis of sampling procedures, filtration techniques, accuracy, blanks, detection limits, intercalibration results and oceanographic consistency, the feasibility of these FIA methods was evaluated. It was found that these metals could be measured on board with a minimum risk of contamination and with good accuracy even at low subnanomolar levels (<0.5 nM). Results for reference seawater were in the case of Fe-FIA and Mn-FIA in excellent agreement with the certified values. Data from samples analyzed by Fe-FIA and by cathodic stripping voltametry (CSV) compared well, as did Mn-FIA and GFAAS. All three methods gave results that were mostly in good agreement with data from the same ocean regions published by other research groups. Two different types of surface water sampling were also tested and compared, namely conventional hand filling of a sample bottle from a rubber dinghy away from the ship, and underway pumping of seawater using a 'tow fish'. The latter method gave the best results. Also, conventional membrane filtration and cartridge filtration for large volume filtration were compared using Fe and Al data from water column samples. Good agreement was found for both filter types, although for defining dissolved metal species the latter filter type was preferred.  相似文献   
947.
Workers of a queenless honeybee colony can requeen the colony by raising a new queen from a young worker brood laid by the old queen. If this process fails, the colony becomes hopelessly queenless and workers activate their ovaries to lay eggs themselves. Laying Cape honeybee workers (Apis mellifera capensis) produce female offspring as an additional pathway for requeening. We tested the frequency of successful requeening in ten hopelessly queenless colonies. DNA genotyping revealed that only 8% of all queens reared in hopelessly queenless colonies were the offspring of native laying worker offspring. The vast majority of queens resulted from parasitic takeovers by foreign queens (27%) and invading parasitic workers (19%). This shows that hopelessly queenless colonies typically die due to parasitic takeovers and that the parasitic laying workers are an important life history strategy more frequently used than in providing a native queen to rescue the colony. Parasitism by foreign queens, which might enter colonies alone or accompanied by only a small worker force is much more frequent than previously considered and constitutes an additional life history strategy in Cape honeybees.  相似文献   
948.
The main sources of reactive hydrocarbons (RHC) and nitrogen oxides (NOx), ozone precursors, in the Metropolitan Area of São Paulo (MASP) in the southeast of Brazil are emissions from vehicles fleets. Ambient surface ozone and particulate matter concentrations are air quality problem in the MASP. This study examined the impact that implementing a control program for mobile emissions has on ozone concentrations, An episode of high surface ozone concentrations occurring in the MASP during the March 13–15, 2000 period was used as a case study that was modeled for photochemical oxidants using the California Institute of Technology/Carnegie Mellon University three-dimensional photochemical model. Different scenarios were analyzed in relationship to the implementation of the Programa Nacional de Controle de Poluição por Veículos Automotores (PROCONVE, National Program to Control Motor Vehicle Pollution). Scenario 1 assumed that all vehicles were operating within PROCONVE guidelines. Scenarios 2 and 3 considered hypothetical situations in which the PROCONVE was not implemented. Scenario 2 set the premise that vehicles were using pre-1989 technology, whereas scenario 3 allowed for technological advances. A base case scenario, in which the official emission inventory for the year 2000 was employed, was also analyzed. The CIT model results show agreement with most measurements collected during 13–15 March 2000 modeling episode. Mean normalized bias for ozone, CO, RHC and NO x are approximately 9.0, 6.0, ?8.3, 13.0%, respectively. Tropospheric ozone concentrations predicted for scenario 2 were higher than those predicted for scenarios 1, 3 and base case. This study makes a significant contribution to the evaluation of air quality improvement and provides data for use in evaluating the economic costs of implementing a program of motor vehicle pollution control aimed at protecting human health.  相似文献   
949.
The maternally inherited bacterium Wolbachia pipientis generates strong reproductive incompatibilities between uninfected females and infected males (cytoplasmic incompatibility), significantly reducing both female and male reproductive success. Such fitness costs are thought to place selective pressure on hosts to evolve pre-copulatory preferences for mating with compatible mates, thereby enabling them to avoid the reproductive incompatibilities associated with Wolbachia. Therefore, uninfected females are predicted to prefer mating with uninfected males, whereas infected males are predicted to prefer mating with infected females. Despite these predictions, previous investigations of pre-copulatory mate preferences in Wolbachia-manipulated Drosophila have not found evidence of female preference for uninfected or compatible males. However, none of these studies utilised a design where focal individuals are provided with a simple choice in a relatively non-competitive situation. We examined both female and male pre-copulatory mate preference based on mate infection status in Drosophila simulans and D. melanogaster using simple choice assays involving between 30–50 replicates per treatment. Although we found no evidence of female pre-copulatory mate preferences in either species, male D. simulans exhibited some preference for mating with females of the same infection status. However, this preference was not evident when we repeated the experiment to confirm this finding. Consequently, we conclude that neither male nor female D. melanogaster and D. simulans exhibit significant Wolbachia-associated pre-copulatory mate preferences.  相似文献   
950.
This article synthesises the results obtained in several projects on atmospheric aerosol (particulate matter – PM) pollution developed during the last years in the Western Mediterranean. It focuses on particulate matter sources and the strategies for suitable monitoring in ambient air. The article has been structured in several sections that give response to the main questions that prompted these studies. After analysing the main PM features in the Mediterranean, a brief review of the main factors differentiating the particulate matter composition with respect to Central Europe is presented. Finally, the suitability of the different metrics or parameters for monitoring ambient air PM levels in different types of environments is discussed. Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized by Prof. Dr. Branimir Jovancicevic (www.research.plymouth.ac.uk/ace).  相似文献   
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