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311.
Olchawa E Bzowska M Stürzenbaum SR Morgan AJ Plytycz B 《Environmental pollution (Barking, Essex : 1987)》2006,142(2):373-381
Three-day dermal exposure of Dendrobaena veneta to metal ions differentially disrupts the immunocompetence/pathogen balance. Zn does not accumulate in the earthworm body, Cu accumulation is temperature-independent while Cd accumulation is stronger at 22 degrees C than at 10 degrees C. During in vitro incubation with metal ions at 22 degrees C, growth of coelom-derived bacteria is enhanced by Zn, but significantly or almost completely inhibited by Cu or Cd. In contrast, under in vivo conditions at 22 degrees C, bacterial load is decreased only after Cd exposure, but increased after Zn and Cu exposures. At 10 degrees C bacteria growth is almost completely inhibited in all groups except Cu-treated animals. Coelomocyte number is unaffected in animals exposed to Zn, but significantly decreased after exposure to Cd (at 22 degrees C) and Cu (at 22 degrees C and 10 degrees C) with concomitant changes of amoebocyte-to-eleocyte ratio in favour of amoebocytes. Metal exposure up-regulates expression of metallothioneins in coelomocytes, mainly amoebocytes. 相似文献
312.
随着各国航天实验和航天器的增加,太空中存在微小碎片垃圾越来越多,对航天器正常运行有着极大的危害。研究弹丸超高速撞击硼化物基复合陶瓷产生的碎片云特性,采用非线性动力学分析软件AUTODYN,利用光滑质点动力学方法对圆柱形弹丸超高速撞击硼化物基超高温复合陶瓷单层板形成的碎片云进行数值模拟,分析相同质量不同速度弹丸撞击靶板的破坏模式,不同质量相同速度弹丸撞击靶板的破坏模式。结果表明在不同速度和质量弹丸撞击靶板的破坏模式中,穿孔半径变化规律为穿孔半径随着弹丸速度和质量的增大而增大。根据不同质量弹丸超高速撞击板靶的穿孔半径变化规律,得到弹丸撞击相同厚度靶板的击穿速度临界值。该结果可为航天器超高速撞击风险评估和防护设计提供了参考。 相似文献
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The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids 总被引:2,自引:0,他引:2
Stephen L. Brusatte Roger B. J. Benson Daniel J. Chure Xing Xu Corwin Sullivan David W. E. Hone 《Die Naturwissenschaften》2009,96(9):1051-1058
Little is known about the evolution of large-bodied theropod dinosaurs during the Early to mid Cretaceous in Asia. Prior to
this time, Asia was home to an endemic fauna of basal tetanurans, whereas terminal Cretaceous ecosystems were dominated by
tyrannosaurids, but the intervening 60 million years left a sparse fossil record. Here, we redescribe the enigmatic large-bodied
Chilantaisaurus maortuensis from the Turonian of Inner Mongolia, China. We refer this species to a new genus, Shaochilong, and analyze its systematic affinities. Although Shaochilong has previously been allied with several disparate theropod groups (Megalosauridae, Allosauridae, Tyrannosauroidea, Maniraptora),
we find strong support for a derived carcharodontosaurid placement. As such, Shaochilong is the first unequivocal Asian member of Carcharodontosauridae, which was once thought to be restricted to Gondwana. The
discovery of an Asian carcharodontosaurid indicates that this clade was cosmopolitan in the Early to mid Cretaceous and that
Asian large-bodied theropod faunas were no longer endemic at this time. It may also suggest that the ascent of tyrannosaurids
into the large-bodied dinosaurian predator niche was a late event that occurred towards the end of the Cretaceous, between
the Turonian and the Campanian.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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319.
Assessing and managing the sociocultural impacts of ecotourism: revisiting the Santa Elena rainforest project 总被引:1,自引:0,他引:1
Summary This paper outlines the second phase of an ecotourism project undertaken in the Santa Elena community, in the Monteverde region of Costa Rica. The community originally established a rainforest reserve with the help of Youth Challenge International in an attempt to provide a wider economic base and employment for the area. The project has been successful in the first phase in that it is now drawing an annual income of US$40 000 and it employs guides and management from the local community. In terms of the underlying principles usually aligned with ecotourism it has been successful but it is now necessary to evaluate the impacts this project is having on the community. The second phase of the project was to assess the sociocultural impacts of ecotourism on that community and the paper outlines this phase.Stephen Wearing is a lecturer in the School of Leisure and Tourism Studies at the University of Technology, Sydney. He lectures and consults in the area of tourism and environmental planning, and parks and protected area management. His particular interest is in ecotourism projects with local communities and he has spent much of the last 4 years working on the Santa Elena Project. He is linked with Youth Challenge International and people interested in becoming involved or looking for assistance with community projects of this nature can contact him at the above address. Libby Larson recently graduated with a BA in Leisure Studies at the University of Technology, Sydney, focusing on social sciences in natural resource management. She has also worked in Costa Rica with Youth Challenge International and is particularly interested in ecotourism. 相似文献
320.
Stephen F. McCool Jack Utter 《Journal of the American Water Resources Association》1981,17(3):431-437
Allocating river recreation use to commercial and private sectors on white water rivers has been highly controversial. How this process is implemented may affect not only the availability of recreation opportunities to individual users, but may also negatively impact the user's desire to escape from the pressures and stresses of everyday life. In a study of users of Idaho's Middle Fork of the Salmon River, an Even-Pool allotment technique was preferred over others by the commercial, private, and rejectee individuals sampled. A lottery technique for rationing private use permits was preferred by private users and rejectees, while commercial users preferred Advance Reservation. No relationship was found between the users' stress release/escape expectations and their preferences for the different allotment and rationing techniques studies. Such results suggest that river managers may have considerable latitude in selecting allocation techniques that do not adversely affect on-site recreation experiences. 相似文献