Low European methyl chloroform emissions inferred from long-term atmospheric measurements

Methyl chloroform (CH3CCl3, 1,1,1,-trichloroethane) was used widely as a solvent before it was recognized to be an ozone-depleting substance and its phase-out was introduced under the Montreal Protocol. Subsequently, its atmospheric concentration has declined steadily and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year. However, data from a short-term tropospheric measurement campaign (EXPORT) indicated that European methyl chloroform emissions could have been over 20 gigagrams in 2000 (ref. 6), almost doubling previously estimated global emissions. Such enhanced emissions would significantly affect results from the CH3CC13 method of deriving global abundances of hydroxyl radicals (OH) (refs 7-12)-the dominant reactive atmospheric chemical for removing trace gases related to air pollution, ozone depletion and the greenhouse effect. Here we use long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, to infer European methyl chloroform emissions. We find that European emission estimates declined from about 60 gigagrams per year in the mid-1990s to 0.3-1.4 and 1.9-3.4 gigagrams per year in 2000-03, based on Mace Head and Jungfraujoch data, respectively. Our European methyl chloroform emission estimates are therefore higher than calculated from consumption data, but are considerably lower than those derived from the EXPORT campaign in 2000 (ref. 6).     

Biology and conservation of the Coral Pink Sand Dunes tiger beetle, Cicindela limbata albissima Rumpp

This study investigated the distribution, abundance, and biology of Cicindela limbata albissima Rumpp, an endemic tiger beetle known only from the Coral Pink Sand Dunes (CPSD) in southwestern Utah. A recently implemented conservation agreement between BLM, USFWS, Utah State Parks, and Kane County protects most of the known habitat of this beetle from off-highway vehicle (OHV) use. A search of collection records and field surveys of 19 Great Basin sand dune sites indicated that this species occurs only at CPSD. Yearly index counts of adults (1992-1998) during peak season in May ranged from 331 in 1997 to 895 in 1993, but the actual population size is probably 2-3 times higher than the index counts. Nearly all of the population is found in the primary habitat, a 300-m-wide × 2.7-km-long area in the southern part of the dune field. Small numbers of adults and larvae have been found at the far north end of the dune field. Mark-recapture studies indicated that most adults moved only short distances ( Surveys of dominant plant species, arthropod (potential tiger beetle prey) abundance, and OHV activity indicated that these vary throughout the dune field and may explain, in part, the distribution of C. l. albissima . The primary habitat is a transition area between the highly dynamic south end of the dune field and the more stabilized north end. Psoralidium lanceolatum Rybd., Sophora stenophylla Gray, and Stipa hymenoides R.&S. are the dominant plants in the interdunal swales of the primary habitat, but other species are dominant in other parts of the dune field. Numbers of arthropod individuals and taxa are greatest in the primary habitat. Off-highway vehicle activity was greatest at the south end of the dune field and lowest at the far north end. Run-over trials and observational data revealed that adult beetles are killed by OHVs, but more important impacts may be damage to vegetation, reduction of arthropod prey of C. l. albissima , and disturbance and increased desiccation of the larval microhabitat. We anticipate that the conservation agreement will provide long-term protection for this species at CPSD.     

局部固支功能梯度板的横向弯曲研究

研究了局部固支功能梯度方板在横向均布载荷作用下的静力学问题。假设功能梯度材料由陶瓷和钢组成，材料弹性模量设计为沿着板的厚度方向按照幂指数形式连续变化，功能梯度方板的四个边均为局部固支，应用Kirchhoff薄板理论和虚功原理推导了板的静力学有限元方程。另分别考虑了各边50%固支和25%固支两种情况，在板材料为纯陶瓷和纯钢时，将所得结果与ANSYS软件结果对比，验证了所建模型的准确性。最后，重点分析了梯度指数对板面和边界最大挠度的影响。结果表明梯度指数和固支范围是决定最大挠度的关键参数，其中固支范围对边界上最大挠度的影响更大。