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841.
842.
G. Ruhenstroth-Bauer G. F. Fuhrmann E. Granzer W. Kübler F. Rueff 《Die Naturwissenschaften》1962,49(16):363-368
843.
The ant genus Cardiocondyla is characterized by a bizarre male polymorphism with wingless fighter males and winged disperser males. Winged males have
been lost convergently in several clades, and in at least one of them, wingless males have evolved mutual tolerance. To better
understand the evolutionary pathways of reproductive tactics, we investigated Cardiocondyla venustula, a species, which in a phylogenetic analysis clusters with species with fighting and species with mutually tolerant, wingless
males. Wingless males of C. venustula use their strong mandibles to kill freshly eclosed rival males and also engage in short fights with other adult males, but
in addition show a novel behavior hitherto not reported from social insect males: they spread out in the natal nest and defend
“territories” against other males. Ant males therefore show a much larger variety of reproductive tactics than previously
assumed. 相似文献
844.
An important aspect of present global energy scenarios is the assumption that the amount of biomass that can be grown on the
available area is so limited that a scenario based on biomass as the major source of energy should be unrealistic. We have
been investigating the question whether a Biomass Scenario may be realistic. We found that the global energy demand projected
by the International Energy Agency in the Reference Scenario for the year 2030 could be provided sustainably and economically
primarily from lignocellulosic biomass grown on areas which have been degraded by human activities in historical times. Moreover,
other renewable energies will contribute to the energy mix. There would be no competition with increasing food demand for
existing arable land. Afforestation of degraded areas and investment for energy and fuel usage of the biomass are not more
expensive than investment in energy infrastructure necessary up to 2030 assumed in the fossil energy based Reference Scenario,
probably much cheaper considering the additional advantages such as stopping the increase of and even slowly reducing the
CO2 content of the atmosphere, soil, and water conservation and desertification control. Most importantly, investment for a Biomass
Scenario would be actually sustainable, in contrast to investment in energy-supply infrastructure of the Reference Scenario.
Methods of afforestation of degraded areas, cultivation, and energetic usage of lignocellulosic biomass are available but
have to be further improved. Afforestation can be started immediately, has an impact in some few years, and may be realized
in some decades.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Jürgen O. MetzgerEmail: |
845.
Murat Kadir Yesilyurt Mevlüt Arslan Tanzer Eryilmaz 《International Journal of Green Energy》2019,16(1):60-71
In the present study, response surface methodology (RSM) involving central composite design (CCD) was applied to optimize the reaction parameters of biodiesel production from yellow mustard (Sinapis alba L.) seed oil during the single-step transesterification process. A total of 30 experiments were designed and performed to determine under the effects of variables on the biodiesel yield such as methanol to oil molar ratio (2:1–10:1), catalyst concentration (0.2–1.0 wt.% NaOH), reaction temperature (50–70°C), and reaction time (30–90 min). The second order polynomial model was used to predict the biodiesel yield and coefficient of determination (R2) was found to be at 0.9818. The optimum biodiesel yield was calculated as 96.695% from the model with the following reaction conditions: 7.41:1 of methanol to oil molar ratio, 0.63 wt. % NaOH of catalyst concentration, 61.84°C of reaction temperature, and 62.12 min of reaction time. It is seen that the regression model results were in agreement with the experimental data. The results showed that RSM is a suitable statistical technique for optimizing the reaction parameters in the transesterification process in order to maximize the biodiesel yield. 相似文献
846.
Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter(OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM(particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, ... 相似文献
847.
Jürgen Tautz 《Die Naturwissenschaften》1979,66(9):452-461
The oscillation of particles in a medium is the adequate stimulus for specialized receptors. Such receptors can be found in nearly all phyla in the animal kingdom. Specialized sensory hairs in arthropods are used here as an example to show conditions and limits of vibration reception in a medium. The use of this sensory capacity in biologically relevant situations is shown on some well-known examples. 相似文献
848.
849.
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
850.