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21.
Mariken H.C. Everdij Henk A.P. Blom Jelmer J. Scholte Jos W. Nollet Bert Kraan 《Safety Science》2009,47(3):405-420
The high volume of air traffic over Europe is expected to double within the next 15 years. This requires changes in the airspace structure and in the organisation of air transport operations that involve multiple stakeholders. Changes, by regulation, require a sufficient safety validation, in order to show that the changed situation is safe and will remain safe during an applicable period. Many methods and techniques exist that can be used to support such safety validation process. However, for air transport operations, the stakeholders involved are numerous and diverse, and there are no guidelines on how to address their roles, responsibilities and goals during development and validation.This paper develops a safety validation framework that emphasises the active roles and collaboration of multiple stakeholders during the development phases of air transport operations. The framework is developed in three steps: First, established validation views from literature are identified and analysed to reveal open issues when it comes to their use for multi-stakeholder changes in air transport operations. Next, validation views emerging beyond the established ones are identified, and evaluated on whether they address the open issues. Finally, the strong points of established and emerging views are combined into a novel framework. 相似文献
22.
Development and Comparison of Multiple Regression Models to Predict Bankfull Channel Dimensions for Use in Hydrologic Models 下载免费PDF全文
Katrin Bieger Hendrik Rathjens Jeffrey G. Arnold Indrajeet Chaubey Peter M. Allen 《Journal of the American Water Resources Association》2016,52(6):1385-1400
Channel dimensions are important input variables for many hydrologic models. As measurements of channel geometry are not available in most watersheds, they are often predicted using bankfull hydraulic geometry relationships. This study aims at improving existing equations that relate bankfull width, depth, and cross‐sectional area to drainage area (DA) without limiting their use to well‐gauged watersheds. We included seven additional variables in the equations that can be derived from data that are generally required by hydrologic models anyway and conducted several multiple regression analyses to identify the ideal combination of additional variables for nationwide and regional models for each Physiographic Division of the United States (U.S.). Results indicate that including the additional variables in the regression equations generally improves predictions considerably. The selection of relevant variables varies by Physiographic Division, but average annual precipitation (PCP) and temperature (TMP) were generally found to improve the models the most. Therefore, we recommend using regression equations with three independent variables (DA, PCP, and TMP) to predict bankfull channel dimensions for hydrologic models. Furthermore, we recommend using the regional equations for watersheds within regions from which data were used for model development, whereas in all other parts of the U.S. and the rest of the world, the nationwide equations should be given preference. 相似文献
23.
Hideaki Shibata Cristina Branquinho William H. McDowell Myron J. Mitchell Don T. Monteith Jianwu Tang Lauri Arvola Cristina Cruz Daniela F. Cusack Lubos Halada Ji?í Kopá?ek Cristina Máguas Samson Sajidu Hendrik Schubert Naoko Tokuchi Jaroslav Záhora 《Ambio》2015,44(3):178-193
Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human–ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society. Integrated international and long-term collaborative studies covering research gaps will reduce uncertainties and promote further understanding of the nitrogen cycle in various ecosystems. 相似文献
24.
Hendrik Jan T. Hoving Marek R. Lipinski John J. Videler Kat S. R. Bolstad 《Marine Biology》2010,157(2):393-400
Spermatangium implantation is reported in the large oceanic squid Taningia danae, based on ten mated females from the stomachs of sperm whales. Implanted spermatangia were located in the mantle, head and
neck (on both sides) or above the nuchal cartilage, under the neck collar and were often associated with incisions. These
cuts ranged from 30 to 65 mm in length and were probably made by males, using the beak or arm hooks. This is the first time
wounds facilitating spermatangium storage have been observed in the internal muscle layers (rather than external, as observed
in some other species of squid). The implications of these observations for the mating behavior of the rarely encountered
squid T. danae are discussed. 相似文献
25.
Michael P. Harris Doug Beare Reidar Toresen Leif Nøttestad Matthias Kloppmann Hendrik Dörner Kevin Peach Derek R. A. Rushton Judy Foster-Smith Sarah Wanless 《Marine Biology》2007,151(3):973-983
Since the early 2000s routine fish surveys have recorded increasing numbers of snake pipefish, Entelurus aequoreus, in the northeast Atlantic. Fishermen and divers have also commented on this increase and pipefish have started to appear
in the diet of seabirds and other marine predators. This paper collates information from these diverse sources and assesses
the current status of snake pipefish. We found compelling evidence of a dramatic increase in the abundance of snake pipefish
starting around 2003 and continuing up to the present (2006) and a range expansion northwards to Spitzbergen and the Barents
Sea. Since 2004 snake pipefish have been increasingly recorded in the diet of many species of seabird breeding in colonies
around the coast of the UK, and in Norway, Iceland and the Faeroe Islands. Information on the nutrient value of snake pipefish
is currently lacking but their rigid, bony structure makes them difficult for young seabirds to swallow and there are numerous
records of chicks choking to death. Thus, in the case of avian predators during the breeding season, it appears unlikely that
increased abundance of snake pipefish will provide a useful alternative prey. The reason for the rapid and dramatic increase
in numbers of snake pipefish is currently unclear but such events are characteristic of marine ecosystems and will almost
certainly have an effect on food web dynamics. 相似文献
26.
A peat core from a Swiss bog represents 2110 14C years of peat accumulation and provides a continuous record of atmospheric rare earth element (REE) deposition. This is the first study providing a time-series of all REE originating from the atmosphere. Concentrations of the 14 REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were determined using inductively coupled plasma-mass spectrometry (ICP-MS) after dissolution of 200 mg aliquots of age-dated peat samples with 3 ml HNO3 and 0.1 ml HBF4 at 240 degrees C in a microwave autoclave. Strict quality control schemes were applied to ensure the accuracy of the applied analytical methodology. Previous analyses of selected REE by instrumental neutron activation analysis (INAA) in the same set of peat samples revealed that INAA frequently under- or overestimated REE concentrations in a systematic manner. Concentration profiles obtained for all REE were almost identical, except for Ce and Eu. Calculation of enrichment factors (EF) revealed a distinct depletion of heavy REE relative to light REE in peat samples since the beginning of the 19th century which marks the onset of the Industrial Revolution in Europe, suggesting a pronounced influence by anthropogenic activities. Enrichments of REE calculated using Sc as a reference element exceeded unity, relative to the Upper Continental Crust. Overall, EF in all peat samples ranged from 1.96 for Sm to 2.34 for Gd, with considerably lower EF for Ce (1.82) and Eu (1.44), respectively. A significant enrichment of all REE which may have been caused by military activities, was observed in the peat sample dating from World War II (1944); this exceptional sample, however, is not enriched in Ce. The concentration profiles of REE were similar but not identical to those of other lithogenic, conservative reference elements such as Sc, Y, Al, Zr and Ti. While it has been suggested that individual REE concentrations or the sum of REE can be used as a reference parameter to calculate crustal EF in environmental samples the data presented here indicates that anthropogenic emissions of REE cannot simply be ignored. 相似文献
27.
We develop and test an organizational‐level model of the consequences of diversity climate for company performance. Drawing from affective events theory and the organizational climate literature, we highlight the role of idiosyncrasies in employees' diversity climate perceptions. Specifically, we consider diversity climate strength (i.e., agreement in employees' climate perceptions) as a boundary condition of diversity climate's organizational‐level effects and expect high climate strength to be particularly beneficial in demographically diverse organizations. Moreover, we introduce collective positive affect as an underlying mechanism of diversity climate's conditional effects on company performance. Hypotheses are tested in a study of 82 German small‐and‐medium‐sized companies with 13,695 surveyed employees. Results show a moderated mediation relationship where diversity climate is only positively related to organizational performance (via collective positive affect) at relatively high diversity climate strength. Although this finding holds for both demographically diverse and homogeneous organizations, post hoc analyses provide initial evidence that a strong climate only helps to realize the effects of diversity climate on collective positive affect when members of age‐ and gender‐related demographic subgroups converge in their climate perceptions. Our study contributes to a better understanding of diversity climate as an effective lever for managing diversity. 相似文献
28.
Carbon/electron source dependence of polychlorinated biphenyl dechlorination pathways for anaerobic granules 总被引:2,自引:0,他引:2
The effect of acclimating anaerobic granules from commercial bioreactors with different carbon/electron sources on their ability to reductively dechlorinate a tri-(2,3,4-CB) and heptachlorobiphenyl (2,2',3,3',4,5,6-CB) was studied. The anaerobic granules were first grown in upflow anaerobic sludge blanket (UASB) reactors fed with two different mixtures of carbon/electron sources, i.e., propionate/butyrate/methanol and formate/methanol. Differences in dechlorination patterns for 2,2',3,3',4,5,6-CB were observed in batch experiments inoculated with granules from these two sets of UASB reactors. Variation of the carbon/electron source, during the dechlorination process, had no effect on the dechlorination pathway, but the extents and rates of dechlorination were highest for ethanol and formate and lowest for pyruvate fed batches. Pre-acclimation of different anaerobic sludges to polychlorinated biphenyls (PCBs) shortened the lag period, but did not influence the PCB dechlorination pathway. This is the first time that similar acclimation conditions for several anaerobic microbial communities prior to inoculation were reported to yield similar substrate specificities for the reductive dechlorination of specific PCB congeners. This research demonstrates a successful strategy for the development of biocatalysts to serve as the inoculum of partially decontaminated sites in order to provide microorganisms with specificities complementary to those of naturally occurring dechlorinators. 相似文献
29.
Frans J. Los PhD Adriana M. Hagenaars Titia E. Cohen-Overbeek Hendrik W. P. Quartero 《黑龙江环境通报》1994,14(7):565-568
The levels of the maternal serum markers alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), and unconjugated oestriol (uE3) in 35 pregnant women with early second-trimester oligohydramnios differed from those in a reference population of 1699 singleton pregnancies. Maternal serum AFP levels above the 95th centile of the population distribution were observed in 80 per cent (16/20) of oligohydramnios cases with a normal fetus and in only 20 per cent (3/15) of the cases with a fetus displaying urogenital tract malformations. Elevated levels of hCG (above the 95th centile) and decreased levels of uE3 (below the fifth centile) were encountered in 26 per cent (9/35) and 17 per cent (6/35) of the women, irrespective of the fetal condition. The abnormal profile of the serum markers in early second-trimester oligohydramnios resulted in 57 per cent (20 out of 35) of screen-positive cases for either fetal Down's syndrome or neural tube defects, compared with 8·4 per cent (143 out of 1699) in the reference population. 相似文献
30.
‘Value of Time’ (VOT) is a key parameter in economics and policy. This paper presents an alternative method to estimate VOT by analyzing an hourly dataset on drivers speeding behavior as a function of the gasoline price. Our identification strategy is novel as it is based on the intensive margin. In comparison, previous studies reveal VOT on the extensive margin, but choice alternatives have multiple attributes thereby potentially confounding estimates. Consistent with the range of the prior literature, we find a VOT of about 50% of the wage rate and analyze sources of bias from accidents and traffic tickets. These bias functions suggest that previous stated preference VOT estimates are likely downward whereas previous revealed preference estimates are likely upward biased. 相似文献