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81.
Kevin Lam Kelsie Thu Michelle Tsang Margo Moore Gerhard Gries 《Die Naturwissenschaften》2009,96(9):1127-1132
Female houseflies, Musca domestica (Diptera: Muscidae), lay their eggs in ephemeral resources such as animal manure. Hatching larvae compete for essential nutrients
with fungi that also colonize such resources. Both the well-known antagonistic relationship between bacteria and fungi and
the consistent presence of the bacterium Klebsiella oxytoca on housefly eggs led us to hypothesize (1) that K. oxytoca, and possibly other bacteria on housefly eggs, help curtail the growth of fungal resource competitors and (2) that such fungi
indeed adversely affect the development of housefly larvae. Bacteria washed from housefly eggs significantly reduced the growth
of fungi in chicken manure. Nineteen bacterial strains and ten fungal strains were isolated from housefly eggs or chicken
manure, respectively. Co-culturing each of all the possible bacterium–fungus pairs revealed that the bacteria as a group,
but no single bacterium, significantly suppressed the growth of all fungal strains tested. The bacteria's adverse effect on
fungi is due to resource nutrient depletion and/or the release of antifungal chemicals. Well-established fungi in resources
significantly reduced the number of larval offspring that completed development to adult flies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
82.
通过探索性空间数据分析方法对中国31个省(市、自治区)环境污染的空间相关性及集聚效应进行检验,研究证实我国各省域环境污染存在显著的空间自相关和空间集聚效应。在此基础上,构建空间计量模型分析中国经济增长、产业结构对环境污染的影响。研究结果表明,中国各省域环境污染存在空间依赖作用和正向空间溢出效应。环境污染与人均GDP之间呈现只有一个拐点的"倒N型"曲线关系。产业结构与环境污染存在显著的正相关关系,产业结构优化调整有助于降低环境污染。 相似文献
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85.
分析了丛式井井眼交碰的影响因素,从设计和施工两个方面提出了具体的技术措施,提出了以余隙系数(K)作为设计和施工的准则,以Btotal数值作为判断井眼是否接近的准则,经过实际应用,验证了以上技术措施的可靠性。 相似文献
86.
The ranked-set sampling (RSS) is applicable in practical problems where the variable of interest for an observed item is costly or time-consuming but the ranking of a set of items according to the variable can be easily done without actual measurement. In the context of RSS, the need for density estimation arises in certain statistical procedures. The density estimation also has its own interest. In this article, we develop a method for the density estimation using RSS data. We derive the properties of the resulted density estimate and compare it with its counterpart in simple random sampling (SRS). It is shown that the density estimate using RSS data provides a better estimate of the density than the usual density estimate using SRS data. The density estimate developed in this article can well serve various purposes in the context of RSS. 相似文献
87.
利用电位滴定法在716DMS型自动电位滴定仪上实现对气田废水中C1-的快速、灵敏、准确测定,避免了色度、浊度的干扰。对方法的检出限、标样和实际水样精密度、准确度,进行了全面的测定分析,并与硝酸银滴定法进行了对比。氯化物的检出限为0.32mg/L;相对标准偏差小于等于2.1%,加标回收率在98.9%101%范围内,对同一标样和实际样品的测定两种方法的结果吻合较好。 相似文献
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A curious feature of the honeybee's waggle dance is the imprecision in the direction indication for nearby food sources.
One hypothesis for the function of this imprecision is that it serves to spread recruits over a certain area and thus is an
adaptation to the typical spatial configuration of the bees' food sources, i.e., flowers in sizable patches. We report an
experiment that tests this tuned-error hypothesis. We measured the precision of direction indication in waggle dances advertising
a nest site (typically a tree cavity, hence a target that is almost a point) and compared it with that of dances advertising
a food source (typically a flower patch, hence a target that covers an area). The precision of dances for a nearby nest site
was significantly higher than that of dances for an equidistant feeder. This was demonstrated four times with four colonies.
Our evidence therefore supports the hypothesis that the level of precision in the direction indication for nearby food sources
is tuned to its optimum without being at its maximum.
Received: 9 December 1998 / Received in revised form: 24 February 1999 / Accepted 12 March 1999 相似文献
90.
针对未来多架物流无人机飞行在同一航线可能引起的安全冲突问题,提出规划无人机之间的安全间隔以规避运行风险.根据无人机在地面控制系统监控下的飞行特点,结合位置误差概率模型,综合考虑无人机定位误差、速度误差以及侧风的影响,依次建立无人机之间纵向、侧向和垂直方向的碰撞风险评估模型,并得出ICAO安全目标水平下的最小安全间隔.选... 相似文献