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The nature of life on Earth provides a singular example of carbon-based, water-borne, photosynthesis-driven biology. Within our understanding of chemistry and the physical laws governing the universe, however, lies the possibility that alien life could be based on different chemistries, solvents, and energy sources from the one example provided by Terran biology. In this paper, we review some of these possibilities. Silanes may be used as functional analogs to carbon molecules in environments very different from Earth; solvents other than water may be compatible for life-supporting processes, especially in cold environments, and a variety of energy sources may be utilized, some of which have no Terran analog. We provide a detailed discussion of two possible habitats for alien life which are generally not considered as such: the lower cloud level of the Venusian atmosphere and Titan’s surface environment. 相似文献
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We examined how reproductive state affected shifts in behavior of adult female Podarcis sicula toward chemical cues from a natural snake predator (Coronella austriaca). The oviparous P. sicula lizards do not experience a major physical burden during reproduction, but gravid females substantially increase duration of basking. Therefore, gravid lizards are likely to experience a greater risk of mortality because they are exposed to predators for longer periods. Both gravid and non-gravid females shifted patterns of locomotion when confronted with snake chemical cues, but the change was notably larger when females were non-gravid. When non-gravid, lizards responded to predator scent by increasing the number of stand-ups and starts, while such a response was not observed when females were gravid. By contrast, gravid lizards clearly reduced the time spent basking in the presence of predator scent, whereas no change in basking behavior was observed when females were non-gravid. Thus, females exhibit differential behavioral responses to predator scents that is dependent on reproductive state. 相似文献
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Growth as an integrative parameter of all physiological processes was measured in young sporophytes of temperate Laminaria digitata, Laminaria saccharina and Laminaria hyperborea exposed in the laboratory to irradiance consisting of either only photosynthetically active radiation (PAR) or to a spectrum
including ultraviolet radiation (UVR) (PAR+UVA+UVB) by use of cut-off glass filters. Size increment was measured every 10 min
over a period of 18–21 days using growth chambers with on-line video measuring technique. In the chamber, plants were grown
at 10±2°C and 16:8 h light–dark cycles with 6 h additional UVR exposure in the middle of the light period. Tissue morphology
and absorption spectra were measured in untreated young sporophytes while chlorophyll a content and DNA damage were measured
in treated thalli at the end of the experiment. Sensitivity of growth under UVR was found to be related to the observed upper
depth distribution limit of the upper sublittoral L. digitata, upper to mid sublittoral L. saccharina and lower sublittoral L. hyperborea. Tissue DNA damage is, however, dependent on thallus thickness which minimizes UVR effect where outer cell layers shade inner
cells and provide longer pathlength for UVR. Exposure to UVR causes cellular, enzymatic and molecular damage. Presence of
UV-absorbing compounds further reduces effective UVR from reaching physiological targets. The cost of producing higher amount
of UV-absorbing compounds and effective DNA repair mechanism can, however, divert photosynthate at the expense of growth.
Tissue chlorophyll a content was not significantly different between treatments suggesting a capacity for acclimation to moderate
UVR fluence. Growth acclimation to repeated UVR exposure was observed within a period of 12 days while growth inhibition was
observed after a longer UVR exposure period of 21 days. The results give further insight into the effects of UVR on the cellular
level and show how ecological parameters such as the upper depth distribution limit are dependent on cellular processes. 相似文献
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Dirk Bunke 《Umweltwissenschaften und Schadstoff-Forschung》2003,15(2):106-114
Zusammenfassung Zur Quantifizierung des Gefahrstoffeinsatzes in der Produktion ist im Rahmen der integrierten ?kologischen Bewertung des ?ko-Institutes
(EcoGrade) eine eigene Methodik entwickelt worden. Indikator für den Gefahrstoffeinsatz sind Monoethylenglykol (‘MEG’)-?quivalente.
Sie erm?glichen einen direkten, schadstoffbezogenen Prozess- und Produktvergleich (Bunke 2001). Die Bewertung basiert auf
den R-S?tzen (Gefahrenhinweise) der Inhaltsstoffe. Die Methodik der MEG-?quivalente stellt eine Weiterentwicklung und Anwendung
des Wirkfaktorenmodells der Technischen Regel für Gefahrstoffe (TRGS) 440 dar (AGS 2001). Die zur Bewertung erforderlichen
Daten sind im Unternehmen vorhanden (Sicherheitsdatenbl?tter) bzw. ?ffentlich leicht zug?nglich (Gefahrstoffdatenbanken).
Die Bilanzierung von Gefahrstoffen mit Hilfe der hier vorgestellten Methode erm?glicht es auch, in ?kobilanziellen Untersuchungen
systematisch den Gefahrstoffeinsatz zu berücksichtigen. Die Methodik ist am Beispiel von Wohngeb?uden erprobt worden.
Anmerkung: Als Gefahrstoffe, Schadstoffe, gef?hrliche Inhaltsstoffe bzw. gef?hrliche Stoffe werden in dieser Arbeit solche
Stoffe definiert, die eines der Gef?hrlichkeitsmerkmale nach § 3 Chemikaliengesetz besitzen.
OnlineFirst: 19. 12. 2001 相似文献