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101.
102.
Trees growing in rocks without soil are uncommon. In two arid regions in Baja California, Mexico, field surveys found large numbers of rock-colonizing elephant trees (Pachycormus discolor (Benth.) Coville ex Standl. (Mexican name: copalquin) growing in igneous rocks (granite and basalt) as primary colonizers without the benefit of soil or with a very small amount of soil generated by their own growth. Many adult trees broke large granite boulders and were capable of wedging, growing in, and colonizing rocks and cliffs made of ancient lava flows. This is the first record of a tree species, apart from the previously recorded cacti, capable of primary colonization of rocks and rock rubble in hot deserts. 相似文献
103.
Assessing the efficiency gains of improved spatial targeting of policy interventions; the example of an agri-environmental scheme 总被引:2,自引:0,他引:2
van der Horst D 《Journal of environmental management》2007,85(4):1076-1087
GIS-based spatial targeting is increasingly recognised as a potentially useful tool to design more efficient policy interventions. The use of this tool has also been advocated in the context of incentive-based agri-environmental schemes, but there has been little work to date to estimate the level of efficiency gains which it may help to achieve. This paper investigates the requirements to arrive at such estimates, using a Scottish farm woodland scheme as a case study. This agri-environmental scheme aims to provide visual amenity and biodiversity. Maps of these two benefits are used to develop improved spatial targeting scenarios that deliver significant efficiency gains in comparison to the existing scheme design. The paper discusses the nature of the spatial distribution of the relevant benefits at the landscape scale and the data requirements for the realistic estimation of efficiency gains. It concludes that although much work needs to be done, the methods available today could and should play a much greater role in improving the landscape-scale design of existing land use schemes focused on the delivery of non-market benefits. 相似文献
104.
The selective introduction of compressive residual stresses is gaining increasing importance as design tool in today's manufacturing process chains. Manufacturing processes such as shot peening or hydraulic autofrettage are used to improve the surface integrity, and hence the fatigue life of the components. However, measuring the corresponding residual stress depth profiles is a challenging task as the results will always include the manufacturing and preparation history of the components. In this paper, results of residual stress measurements with X-ray diffraction and optical hole-drilling after autofrettage and sample preparation are presented and compared to a finite element analysis for two representative geometries. The presented approach can be used to predict the influence of the mandatory sample preparation procedure. As a consequence, the effectiveness of the manufacturing process to improve the surface integrity can be predicted more precisely and wrong interpretations of the measured residual stress depth profiles can be avoided. 相似文献
105.
The primary targets of steroid hormones are genes. For the ecdysone-controlled genes of Drosophila larval glue proteins proximal and distal control elements were identified by mutagenesis and sequence comparison. Their presence is required for the correct stage- and tissue-specific expression of these genes. The supposed function of these elements is described in a working model. 相似文献
106.
Theresa M. Marteau Irma Nippert Sue Hall Caroline Limbert Margaret Reid Martin Bobrow Alan Cameron Martina Cornel Mariet van Diem Bernd Eiben Sixto García-Miñaur Janine Goujard Donna Kirwan Karen McIntosh Peter Soothill Corien Verschuuren-Bemelmans Catherine de Vigan Stephen Walkinshaw Lenore Abramsky Frank Louwen Peter Miny Jürgen Horst 《黑龙江环境通报》2002,22(7):562-566
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Bakker Theo C. M. Bleckmann Horst Mogdans Joachim Schluessel Vera 《Behavioral ecology and sociobiology》2018,72(11):1-11
Behavioral Ecology and Sociobiology - The killing of young by unrelated males is widespread in the animal kingdom. In short-lived small rodents, females can mate immediately after delivery... 相似文献
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