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51.
52.
Rick A. Jones Barbara A. Luckett Peter A. Beling Barry M. Horowitz 《The Environmentalist》2013,33(3):341-361
As cyber security threats have evolved, system protection strategies have been forced to as well. The field of System-Aware Cyber Security has introduced a variety of protection strategies and this has prompted the need for a decision support tool set to provide guidance to the system designers. This paper outlines an architectural scoring framework that supports the design and selection of architectural candidates and provides a rigorous quantitative method for the evaluation to aid in the selection of a final architecture. Additionally, this paper outlines the recognized limitations of the proposed approach and provides a brief overview of how those areas for improvement are guiding future research. 相似文献
53.
Hora RR Ionescu-Hirsh A Simon T Delabie J Robert J Fresneau D Hefetz A 《Die Naturwissenschaften》2008,95(1):55-60
In the ectatommine ant Ectatomma tuberculatum, the visual appearance of queens changes after mating and ovarian development in that their cuticle turns from shiny to matte.
In this study, we have shown that this change seems to be caused by 15-fold accumulation of hydrocarbons, in particular heptacosane
that covers the multiple grooves present on the cuticular surface creating a wax coat in mated fully fertile queens. Analyses
of the scrapped wax revealed that it is composed largely of heptacosane. Peak-by-peak comparison of the cuticular hydrocarbon
(CHC) composition of mated, virgin with developed ovaries and virgin with nondeveloped ovaries revealed significant differences
between the queen groups. Although the total amount of the CHC of virgin queens with developed ovaries was not higher than
virgin queens that did not have developed ovaries, the composition showed a shift toward the mated queen. While it is possible
that the large accumulation of hydrocarbons may give extra physical and chemical protection to queens, we propose that the
switch in the relative abundance of heptacosane and nonacosane and perhaps of other components is indicative of being a mating
and fertility cue. This is the first report in social insects where external chemical changes are accompanied by changes in
visual appearance. 相似文献
54.
The establishment of dominance hierarchies through aggressive interactions is very common in insect societies. In many cases,
it is also mediated through pheromone emissions that enable individuals to evaluate the reproductive quality and level of
aggressiveness of the dominant individual, thereby reducing the number and intensity of costly fights. Here, we studied these
processes in the primitively eusocial bee Bombus terrestris, using a paired bee system. Specifically, we investigated the behavioral, reproductive, and pheromonal correlates of dominance
establishment. Workers were shown to establish dominance hierarchies using overt aggression within 3–4 days. Thereafter, the
aggression drastically decreased, and dominance was maintained mostly by ritualized agonistic behavior. The behaviorally dominant
bee lost the ester compounds that workers produce in their Dufour's gland (the so-called “sterility signal”) concomitantly
with the development of her ovaries. The other bee announced as subordinate by continuously producing high amounts of those
esters. The hypothesis that sterility signaling serves as an appeasement signal to pacify the dominant bees is supported by
the negative correlation found between the proportion of these esters and the level of aggression that the subordinate received
from the dominant worker. Physical interactions, and presumably also the ensuing overt aggression between the bees, were essential
for the above pheromonal change to take place and enabled the dominant workers to develop their ovaries and to lay eggs. The
subordinate bee’s signaling of non-reproductive status may minimize energy expenditure in costly fights and help stabilize
the reproductive division of labor among workers. 相似文献
55.
Eri Saikawa Vaishali Naik Larry W. Horowitz Junfeng Liu Denise L. Mauzerall 《Atmospheric environment (Oxford, England : 1994)》2009,43(17):2814-2822
Aerosols are harmful to human health and have both direct and indirect effects on climate. China is a major contributor to global emissions of sulfur dioxide (SO2), a sulfate (SO42?) precursor, organic carbon (OC), and black carbon (BC) aerosols. Although increasingly examined, the effect of present and potential future levels of these emissions on global premature mortality and climate change has not been well quantified. Through both direct radiative effects and indirect effects on clouds, SO42? and OC exert negative radiative forcing (cooling) while BC exerts positive forcing (warming). We analyze the effect of China's emissions of SO2, SO42?, OC and BC in 2000 and for three emission scenarios in 2030 on global surface aerosol concentrations, premature mortality, and radiative forcing (RF). Using global models of chemical transport (MOZART-2) and radiative transfer (GFDL RTM), and combining simulation results with gridded population data, mortality rates, and concentration–response relationships from the epidemiological literature, we estimate the contribution of Chinese aerosols to global annual premature mortality and to RF in 2000 and 2030. In 2000, we estimate these aerosols cause approximately 470 000 premature deaths in China and an additional 30 000 deaths globally. In 2030, aggressive emission controls lead to a 50% reduction in premature deaths from the 2000 level to 240 000 in China and 10 000 elsewhere, while under a high emissions scenario premature deaths increase 50% from the 2000 level to 720 000 in China and to 40 000 elsewhere. Because the negative RF from SO42? and OC is larger than the positive forcing from BC, Chinese aerosols lead to global net direct RF of ?74 mW m?2 in 2000 and between ?15 and ?97 mW m?2 in 2030 depending on the emissions scenario. Our analysis indicates that increased effort to reduce greenhouse gases is essential to address climate change as China's anticipated reduction of aerosols will result in the loss of net negative radiative forcing. 相似文献
56.
Patrizia D''Ettorre Christine Errard Fernando Ibarra Wittko Francke Abraham Hefetz 《Chemoecology》2000,10(3):135-142
Summary. The dulotic queen ant, Polyergus rufescens, must first penetrate a host colony and kill the resident queen in order to successfully founding a new colony. Successful
usurpation by a newly mated queen predictably depends on a dual strategy. Although, it can sneak in by being “chemically insignificant”
with respect to cuticular hydrocarbons, it may also need to deter prospective host-worker aggressors. Chemical analysis of
Dufour's gland secretion of P. rufescens queens and workers by GS/MS revealed that queen secretion is typified by esters of butanoic acid and acetic acid, of which
decyl butanoate comprises over 80%. Butanoates and acetates are also present in the workers' secretion, but these are of higher
molecular weight, and octadecyl butanoate represents the major compound. Using synthetic mixtures of queen and worker Dufour's
gland, we tested the hypothesis that these secretions modify the aggressive behavior of the host species Formica cunicularia>. The queen-like synthetic mixture significantly reduced aggression of the host workers towards alien conspecifics, but neither
pentane nor the worker-like synthetic mixture showed this effect. Although Dufour's gland content of >Polyergus queens was suggested to function as an appeasement pheromone (Topoff et al. 1988; Mori et al. 2000), we hypothesized that it may in fact act as a repellent. In order to test this hypothesis we exposed starved F. cunicularia workers to a droplet of honey on a glass slide applied with one of the following compounds: decyl butanoate (queen major
compound), octadecyl butanoate (worker main compound), limonene (a reported ant repellent), and pentane (solvent control).
Of these, the workers were repelled only by the decyl butanoate and did not approach the honey. We conclude that during usurpation
the queen actively repels aggressive workers by emitting Dufour's gland repellent, comprising the alternative tactic in the
usurpation dual strategy. This represents another chemical weapon in the diverse arsenal used by parasites to overcome the
host's resistance.
Received 7 April 2000; accepted 17 May 2000 相似文献
57.
58.
Vicia faba as a bioindicator of oil pollution 总被引:3,自引:0,他引:3
Malallah G Afzal M Gulshan S Abraham D Kurian M Dhami MS 《Environmental pollution (Barking, Essex : 1987)》1996,92(2):213-217
In 1990, the Gulf War caused an unprecedented environmental catastrophe. More than 700 oil wells were set on fire, emitting thousands of tons of oxides of nitrogen, sulfur, soot and oil mist at high temperatures. The blazing oil wells and lakes were the major cause of environmental pollution, damaging flora and fauna throughout Kuwait and the surrounding region. We set up this study in order to investigate whether Vicia faba could be used as a bioindicator of oil pollution. Growth parameters of Vicia faba, such as levels of photosynthetic pigments, proteins, free amino acids, phenols, sugars, biomass, moisture and fatty acids, were studied. Levels of total reducible sugars, phenols, proteins, free amino acids and proline were found to be higher in plants grown in hydrocarbon-polluted soil, compared to those grown in control soil. However, biomass, moisture, pheophytin, the 435/415 nm ratio for chlorophylls and the chlorophyll a/carotenoid ratio, were higher in the plants grown in control soil than those grown in polluted soil. Our results indicate that Vicia faba can be used as a bioindicator of pollution and a ratio of the fatty acid C(20:1)/C(18:1) is an important index of environmental oil pollution. 相似文献
59.
Unicoloniality emerges as a feature that characterizes successful invasive species. Its underlying mechanism is reduced intraspecific aggression while keeping interspecific competitiveness. To that effect, we present here a comparative behavioural and chemical study of the invasive ant Wasmannia auropunctata in parts of its native and introduced ranges. We tested the hypothesis that introduced populations (New Caledonia archipelago) have reduced intraspecific aggression relative to native populations (e.g., Ilhéus area, Brazil) and that this correlates with reduced variability in cuticular hydrocarbons (CHCs). As predicted, there was high intraspecific aggression in the Brazilian populations, but no intraspecific aggression among the New Caledonian populations. However, New Caledonian worker W. auropunctata remained highly aggressive towards ants of other invasive species. The chemical data corresponded with the behaviour. While CHCs of ants from the regions of Brazil diverged, the profiles of ants from various localities in New Caledonia showed high uniformity. We suggest that in New Caledonia W. auropunctata appears to behave as a single supercolony, whereas in its native range it acts as a multicolonial species. The uniformity of recognition cues in the New Caledonia ants may reflect a process whereby recognition alleles became fixed in the population, but may also be the consequence of a single introduction event and subsequent aggressive invasion of the ecosystem. Chemical uniformity coupled with low intraspecific but high interspecific aggression, lend credence to the latter hypothesis. 相似文献
60.
Social insects provide a useful model for studying the evolutionary balance between cooperation and conflict linked to genetic structure. We investigated the outcome of this conflict in the bumblebee, Bombus terrestris, whose annual colony life cycle is characterized by overt competition over male production. We established artificial colonies composed of a queen and unrelated workers by daily exchange of callow workers between colony pairs of distinct genetic make-up. Using microsatellite analysis, this procedure allowed an exact calculation of the proportion of worker-derived males. The development and social behavior of these artificial colonies were similar to those of normal colonies. Despite a high worker reproduction attempt (63.8% of workers had developed ovaries and 38.4% were egg-layers), we found that on average 95% of the males produced during the competition phase (CPh) were queen-derived. However, in four colonies, queen death resulted in a considerable amount of worker-derived male production. The different putative ultimate causes of this efficient control by the queen are discussed, and we suggest a possible scenario of an evolutionary arms race that may occur between these two female castes. 相似文献