基于集对分析的中小机场运行风险水平态势评估

中小机场是我国航空运输业最重要的终端,也是民航风险事故最容易发生的地方。利用集对分析理论,建立了中小机场运行风险的同异反模型。根据集对势分析计算结果,再利用偏联系数分析系统发展动态趋势。结果表明,所建立的同异反风险评价模型能很好地对风险趋势进行合理的预测,在实际应用中具有很强的操作性,再加上合理的权重计算方法,使评价结果更加科学可靠。     

Biota Connect Aquatic Habitats throughout Freshwater Ecosystem Mosaics

Freshwater ecosystems are linked at various spatial and temporal scales by movements of biota adapted to life in water. We review the literature on movements of aquatic organisms that connect different types of freshwater habitats, focusing on linkages from streams and wetlands to downstream waters. Here, streams, wetlands, rivers, lakes, ponds, and other freshwater habitats are viewed as dynamic freshwater ecosystem mosaics (FEMs) that collectively provide the resources needed to sustain aquatic life. Based on existing evidence, it is clear that biotic linkages throughout FEMs have important consequences for biological integrity and biodiversity. All aquatic organisms move within and among FEM components, but differ in the mode, frequency, distance, and timing of their movements. These movements allow biota to recolonize habitats, avoid inbreeding, escape stressors, locate mates, and acquire resources. Cumulatively, these individual movements connect populations within and among FEMs and contribute to local and regional diversity, resilience to disturbance, and persistence of aquatic species in the face of environmental change. Thus, the biological connections established by movement of biota among streams, wetlands, and downstream waters are critical to the ecological integrity of these systems. Future research will help advance our understanding of the movements that link FEMs and their cumulative effects on downstream waters.     

Effect of arsenic contaminated irrigation water on Lens culinaris L. and toxicity assessment using lux marked biosensor

Contamination of irrigation water represents a major constraint to Bangladesh agriculture, resulting in elevated levels in the terrestrial systems. Lux bacterial biosensor technology has previously been used to measure the toxicity of metals in various environmental matrices. While arbuscular mycorrhizal fungi have their most significant effect on phosphorus uptake, but showed alleviated metal toxicity to the host plant. The study examined the effects of arsenic and inoculation with an arbuscular mycorrhizal fungus, Glomus mosseae, on lentil (Lens culinaris L. cv. Titore). Plants were grown with and without arbuscular mycorrhizal inoculum for 9 weeks in a sand and terra-green mixture (50:50, V/V) and watered with five levels of arsenic (0, 1, 2, 5, 10 mg As/L arsenate). The results showed that arsenic addition above 1 mg/L significantly reduced percentage of mycorrhizal root infection. On further analysis a close relationship was established with the vegetative and reproductive properties of lentil (L. culinaris) plants compared to the percentage bioluminescence of the soil leachate. However, arbuscular mycorrhizal fungal inoculation reduced arsenic concentration in roots and shoots. Higher concentrations of arsenic (5, 10 mg As/L arsenate) reduced the mycorrhizal efficiency to increase phosphorus content and nitrogen fixation. Therefore, this study showed that increased concentration of arsenic in irrigation water had direct implications to the lentil (L. culinaris) plants overall performance. Moreover the use of bioassay demonstrated that mycorrhiza and clay particle reduced arsenic bioavailability in soil.     

Making scents of defense: do fecal shields and herbivore-caused volatiles match host plant chemical profiles?

Many plant families have aromatic species that produce volatile compounds which they release when damaged, particularly after suffering herbivory. Monarda fistulosa (Lamiaceae) makes and stores volatile essential oils in peltate glandular trichomes on leaf and floral surfaces. This study examined the larvae of a specialist tortoise beetle, Physonota unipunctata, which feed on two M. fistulosa chemotypes and incorporate host compounds into fecal shields, structures related to defense. Comparisons of shield and host leaf chemistry showed differences between chemotypes and structures (leaves vs. shields). Thymol chemotype leaves and shields contained more of all compounds that differed than did carvacrol chemotypes, except for carvacrol. Shields had lower levels of most of the more volatile chemicals than leaves, but more than twice the amounts of the phenolic monoterpenes thymol and carvacrol and greater totals. Additional experiments measured the volatiles emitted from M. fistulosa in the absence and presence of P. unipunctata larvae and compared the flower and foliage chemistry of plants from these experiments. Flowers contained lower or equal amounts of most compounds and half the total amount, compared to leaves. Plants subjected to herbivory emitted higher levels of most volatiles and 12 times the total amount, versus controls with no larvae, including proportionally more of the low boiling point chemicals. Thus, chemical profiles of shields and volatile emissions are influenced by the amounts and volatilities of compounds present in the host plant. The implications of these results are explored for the chemical ecology of both the plant and the insect.     

One day is all it takes: circadian modulation of the retrieval of colour memories in honeybees

In this study, we examined how honeybees coped with successive tasks of colour discrimination with conflicting demands. Free-flying honeybees (Apis mellifera) were trained on tasks in which they had to choose one of three colours to obtain a reward of sugar water. In acquisition, the bees learned this task in about four trials of training. Colour memory was retained after 24-h delay in an unrewarded retention test. Integration experiments were then conducted in which the bees had to learn two successive tasks of colour discrimination with conflicting demands, task 1 for 20 trials and task 2 for ten trials. In task 1, one of three colours provided sugar water while the other two provided tap water, while in task 2 a different colour provided the reward. The bees were given unrewarded tests immediately after training on task 2 and then re-tested after 10 min, 22 h (circadian time of the start of task 1 training), or 24 h (circadian time of the end of task 2 training). Bees strongly preferred the rewarded colour for task 2 on immediate testing and after 10-min delay. After 22-h delay, they switched their preference to the rewarded colour for task 1. But after 24-h delay, the bees again strongly preferred the rewarded colour for task 2. Further tests at a number of delays between 0 and 22 h revealed a sigmoidal pattern of rise in the preference for the task 1 colour. We conclude that circadian time modulates the retrieval of colour memories in honeybees, even when all the training took place in a single day.     

Does the “Teer” vocalization deter prospecting female red-winged blackbirds?

Summary A speaker-occupation experiment was conducted to determine whether female red-winged blackbirds (Agelaius phoeniceus) use the aggressive Teer vocalization to deter conspecific females that are prospecting for opportunities to settle. In each of 14 trials conducted during the breeding seasons of 1987, 1988, and 1989, tape recordings and a pair of loud speakers were used to defend suitable habitat. Observations of female red-winged blackbirds settling on these speaker territories and on adjacent control areas showed that speaker territories were settled significantly earlier than silent control territories. Each of the 14 first settlers on speaker territories included at least one speaker location within the bird's display area, and 9 of the 14 included both speaker locations. Additional observations showed that the rate at which prospecting females visited control and speaker territories, and the number of females eventually settling on them, were not significantly different. Finally, females that settled on speaker territories sang Teers at significantly higher rates than those on control territories. These results demonstrate that the Teer alone was not sufficient to deter prospecting female red-winged blackbirds. On the contrary, Teers given in the absence of an actual resident may have attracted settlers. It is suggested that the aggressive Teer vocalization might function to establish dominance relationships among the females sharing a polygynous male's territory.