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241.
Matthew D. Shawkey Branislav Igic Svana Rogalla Jonathan Goldenberg Susana Clusella-Trullas Liliana D’Alba 《Die Naturwissenschaften》2017,104(9-10):78
The visible spectrum represents a fraction of the sun’s radiation, a large portion of which is within the near infrared (NIR). However, wavelengths outside of the visible spectrum that are reflected by coloured tissues have rarely been considered, despite their potential significance to thermal effects. Here, we report the reflectivity from 300 to 2100 nm of differently coloured feathers. We measured reflectivity across the UV-Vis-NIR spectra of different (a) body parts, (b) colour-producing mechanisms and (c) sexes for 252 individuals of 68 sunbird (family: Nectariniidae) species. Breast plumage was the most reflective and cap plumage the least. Female plumage had greater reflectivity than males. Carotenoid-based colours had the greatest reflectivity, followed by non-iridescent and iridescent melanin-based colours. As ordered arrays of melanin-filled organelles (melanosomes) produce iridescent colours, this suggests that nanostructuring may affect reflectance across the spectrum. Our results indicate that differently coloured feathers consistently vary in their thermal, as well as obvious visual, properties. 相似文献
242.
Florian Karolyi Linde Morawetz Jonathan F. Colville Stephan Handschuh Brian D. Metscher Harald W. Krenn 《Die Naturwissenschaften》2013,100(11):1083-1093
A well-developed suction pump in the head represents an important adaptation for nectar-feeding insects, such as Hymenoptera, Lepidoptera and Diptera. This pumping organ creates a pressure gradient along the proboscis, which is responsible for nectar uptake. The extremely elongated proboscis of the genus Prosoeca (Nemestrinidae) evolved as an adaptation to feeding from long, tubular flowers. According to the functional constraint hypothesis, nectar uptake through a disproportionately elongated, straw-like proboscis increases flower handling time and consequently lowers the energy intake rate. Due to the conspicuous length variation of the proboscis of Prosoeca, individuals with longer proboscides are hypothesised to have longer handling times. To test this hypothesis, we used field video analyses of flower-visiting behaviour, detailed examinations of the suction pump morphology and correlations of proboscis length with body length and suction pump dimensions. Using a biomechanical framework described for nectar-feeding Lepidoptera in relation to proboscis length and suction pump musculature, we describe and contrast the system in long-proboscid flies. Flies with longer proboscides spent significantly more time drinking from flowers. In addition, proboscis length and body length showed a positive allometric relationship. Furthermore, adaptations of the suction pump included an allometric relationship between proboscis length and suction pump muscle volume and a combination of two pumping organs. Overall, the study gives detailed insight into the adaptations required for long-proboscid nectar feeding, and comparisons with other nectar-sucking insects allow further considerations of the evolution of the suction pump in insects with sucking mouthparts. 相似文献
243.
This paper examines human factors associated with piloting a totally enclosed motor propelled survival craft (TEMPSC or lifeboat) in ice. The first section of the paper describes the use of a usability assessment scale to evaluate the coxswain’s (TEMPSC captain) control panel. The second portion examines environmental conditions (habitability) inside the lifeboat during evacuation. All testing was completed in conditions that were consistent with those that might be experienced by ship or offshore oil and gas crewmembers in the event of abandonment due to an onboard emergency. Results indicated that the lifeboat test configuration presented considerable challenges to usability/functionality as well as habitability. These findings suggest that further research should be conducted to evaluate the safety of all existing lifeboat designs. Finally, it is recommended that the international maritime organization (IMO) and safety of life at sea (SOLAS) Convention should mandate user-centered design evaluations for future lifeboat manufacturing. 相似文献
244.
Rivers crossing coastal plains are often inefficient conveyors of sediment, so that changes in upstream sediment dynamics are not evident at the river mouth. Extensive accommodation space and low stream power often result in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. However, gaging stations with sediment records are typically well upstream of the coast, and thus tend to overestimate sediment yields by under-representing the lower coastal plain and because there is often a net loss of sediment in lower coastal plain reaches. Studies of alluvial sediment storage have generally focused on accommodation space, but, using examples from Texas, we show that low transport capacity controlled largely by slope is a crucial factor. 相似文献
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247.
Forest ecosystem nitrogen (N) cycling is a critical controller of the ability of forests to prevent the movement of reactive N to receiving waters and the atmosphere and to sequester elevated levels of atmospheric carbon dioxide (CO2). Here we show that calcium (Ca) constrains the ability of northern hardwood forest trees to control the availability and loss of nitrogen. We evaluated soil N-cycling response to Ca additions in the presence and absence of plants and observed that when plants were present, Ca additions "tightened" the ecosystem N cycle, with decreases in inorganic N levels, potential net N mineralization rates, microbial biomass N content, and denitrification potential. In the absence of plants, Ca additions induced marked increases in nitrification (the key process controlling ecosystem N losses) and inorganic N levels. The observed "tightening" of the N cycle when Ca was added in the presence of plants suggests that the capacity of forests to absorb elevated levels of atmospheric N and CO2 is fundamentally constrained by base cations, which have been depleted in many areas of the globe by acid rain and forest harvesting. 相似文献
248.
Nicholas E. C. Fleming Jonathan D. R. Houghton Caroline L. Magill Chris Harrod 《Marine Biology》2011,158(9):2141-2146
Jellyfish are increasingly topical within studies of marine food webs. Stable isotope analysis represents a valuable technique
to unravel the complex trophic role of these long-overlooked species. In other taxa, sample preservation has been shown to
alter the isotopic values of species under consideration, potentially leading to misinterpretation of trophic ecology. To
identify potential preservation effects in jellyfish, we collected Aurelia aurita from Strangford Lough (54o22′44.73″N, 5o32′53.44″W) during May 2009 and processed them using three different methods prior to isotopic analysis (unpreserved, frozen
and preserved in ethanol). A distinct preservation effect was found on δ15N values: furthermore, preservation also influenced the positive allometric relationship between individual size and δ15N values. Conversely, δ13C values remained consistent between the three preservation methods, conflicting with previous findings for other invertebrate,
fish and mammalian species. These findings have implications for incorporation of jellyfish into marine food webs and remote
sampling regimes where preservation of samples is unavoidable. 相似文献
249.
Sugimoto JD Labrique AB Ahmad S Rashid M Shamim AA Ullah B Klemm RD Christian P West KP 《Disasters》2011,35(2):329-345
The epidemiology of tornado-related disasters in the developing world is poorly understood. An August 2005 post-tornado cohort study in rural Bangladesh identified elevated levels of death and injury among the elderly (≥ 60 years of age) (adjusted odds ratio (AOR) = 8.9 (95 per cent confidence interval (CI): 3.9-20.2) and AOR = 1.6 (95 per cent CI: 1.4-1.8), respectively), as compared to 15-24 year-olds, and among those outdoors versus indoors during the tornado (AOR = 10.4 (95 per cent CI: 5.5-19.9) and AOR = 6.6 (95 per cent CI: 5.8-7.5), respectively). Females were 1.24 times (95 per cent CI: 1.15-1.33) more likely to be injured than males. Elevated risk of injury was significantly associated with structural damage to the house and tin construction materials. Seeking treatment was protective against death among the injured, odds ratio = 0.08 (95 per cent CI: 0.03-0.21). Further research is needed to develop injury prevention strategies and to address disparities in risk between age groups and between men and women. 相似文献
250.
The social spider Anelosimus studiosus exhibits a behavioral polymorphism where colony members express either a passive, tolerant behavioral tendency (social) or
an aggressive, intolerant behavioral tendency (asocial). Here we test whether asocial individuals act as colony defenders
by deflecting the suite of foreign (i.e., heterospecific) spider species that commonly exploit multi-female colonies. We (1)
determined whether the phenotypic composition of colonies is associated with foreign spider abundance, (2) tested whether
heterospecific spider abundance and diversity affect colony survival in the field, and (3) performed staged encounters between
groups of A. studiosus and their colony-level predator Agelenopsis emertoni (A. emertoni)to determine whether asocial females exhibit more defensive behavior. We found that larger colonies harbor more foreign spiders,
and the number of asocial colony members was negatively associated with foreign spider abundance. Additionally, colony persistence
was negatively associated with the abundance and diversity of foreign spiders within colonies. In encounters with a colony-level
predator, asocial females were more likely to exhibit escalatory behavior, and this might explain the negative association
between the frequency of asocial females and the presence of foreign spider associates. Together, our results indicate that
foreign spiders are detrimental to colony survival, and that asocial females play a defensive role in multi-female colonies. 相似文献