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41.
The sky brightness is a critical parameter for estimating the coronal observation conditions for a solar observatory. As part of a site-survey project in Western China, we measured the sky brightness continuously at the Lijiang Observatory in Yunnan province in 2011. A sky brightness monitor (SBM) was adopted to measure the sky brightness in a region extending from 4.5 to 7.0 apparent solar radii based on the experience of the Daniel K. Inouye Solar Telescope (DKIST) site survey. Every month, the data were collected manually for at least one week. We collected statistics of the sky brightness at four bandpasses located at 450, 530, 890, and 940 nm. The results indicate that aerosol scattering is of great importance for the diurnal variation of the sky brightness. For most of the year, the sky brightness remains under 20 millionths per airmass before local Noon. On average, the sky brightness is less than 20 millionths, which accounts for 40.41% of the total observing time on a clear day. The best observation time is from 9:00 to 13:00 (Beijing time). The Lijiang Observatory is therefore suitable for coronagraphs investigating the structures and dynamics of the corona. 相似文献
42.
Factors influencing biodeposit production by the New Zealand freshwater mussel Echyridella menziesii
Kevin J. Collier Susan J. Clearwater Paula H. M. W. Neijenhuis Susanna A. Wood 《新西兰海洋与淡水研究杂志》2018,52(1):1-15
Laboratory experiments on the New Zealand freshwater mussel Echyridella menziesii were used to investigate the short-term effects (7–8 days) of food type on rates of biodeposition and benthic substrate respiration. Post-feeding biodeposition rates ranged from 0.34 to 1.52?mg?g?1?h?1 (mean?=?0.50?mg g?1?h?1) and were unaffected by the addition of toxin-producing Microcystis. Addition of suspended sediment (30?mg?L?1) visibly altered substrate composition, and increased total and inorganic biodeposit production rates by 24–33% compared to mussels fed commercial phytoplankton stock. Biodeposition rates of mussels in lake bed substrates were 38% higher than those in silica sand for identical feeding regimes, suggesting that a significant proportion of material produced in this experiment could have been derived from feeding on organic matter in the lake bed sediments. Respiration rates were higher in treatments with Microcystis but were unaffected by the presence of mussels. This laboratory study suggests that biodeposition by E. menziesii is resilient to short-term exposure to Microcystis, and highlights the ability of mussels to alter benthic substrate composition by incorporating suspended sediment into substrates. 相似文献
43.
Brian N. Tissot Barbara A. Best Eric H. Borneman Andrew W. Bruckner Cara H. Cooper Heather D’Agnes Timothy P. Fitzgerald Amanda Leland Susan Lieberman Amy Mathews Amos Rashid Sumaila Teresa M. Telecky Frazer McGilvray Brian J. Plankis Andrew L. Rhyne Glynnis G. Roberts Benjamin Starkhouse Todd C. Stevenson 《Marine Policy》2010
As the world’s largest importer of marine ornamental species for the aquaria, curio, home décor, and jewelry industries, the United States has an opportunity to leverage its considerable market power to promote more sustainable trade and reduce the effects of ornamental trade stress on coral reefs worldwide. Evidence indicates that collection of some coral reef animals for these trades has caused virtual elimination of local populations, major changes in age structure, and promotion of collection practices that destroy reef habitats. Management and enforcement of collection activities in major source countries such as Indonesia and the Philippines remain weak. Strengthening US trade laws and enforcement capabilities combined with increasing consumer and industry demand for responsible conservation can create strong incentives for improving management in source countries. This is particularly important in light of the March 2010 failure of the parties to the Convention on International Trade in Endangered Species (CITES) to take action on key groups of corals. 相似文献
44.
Melissa M. Foley Benjamin S. Halpern Fiorenza Micheli Matthew H. Armsby Margaret R. Caldwell Caitlin M. Crain Erin Prahler Nicole Rohr Deborah Sivas Michael W. Beck Mark H. Carr Larry B. Crowder J. Emmett Duffy Sally D. Hacker Karen L. McLeod Stephen R. Palumbi Charles H. Peterson Helen M. Regan Mary H. Ruckelshaus Paul A. Sandifer Robert S. Steneck 《Marine Policy》2010
The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits. 相似文献
45.
Quantitative Analysis of Paleoatmospheric CO2 Level Based on Stomatal Characters of Fossil Ginkgo from Jurassic to Cretaceous in China 总被引:1,自引:1,他引:0
SUN Bainian XIAO Liang XIE Sanping DENG Shenghui WANG Yongdong JIA Hui Susan?Turner 《《地质学报》英文版》2007,81(6):931-939
A better theoretical and practical understanding of the linkage between paleo-CO2 and climate during geological history is important to enhance the sustainable development of modern human society. Development in plant physiology since the 1980s has led to the realization that fossil plants can serve as a proxy for paleoatmosphere and paleobiosphere. As a relict gymnosperm with evolutionary stasis, Ginkgo is well suited for paleoenvironmental reconstruction. This paper analyzes fossil Ginkgo species from integrated strata in the north of China using anatomic data of plant physiology. Using stomatal parameters, a trend for the paleo-CO2 level during the Early-Middle Jurassic and the Early Cretaceous was obtained, which is consistent with the estimates by GEOCARB. The trend is also similar to that of Mean Global Surface Temperature in geological time. Compared with three other atmospheric CO2 concentration parameters, the trend of paleo-CO2 level based on the stomatal parameter of the fossil Ginkgo specimens from three contiguous strata is more exact. 相似文献
46.
47.
Peter J. J. Kamp Fraka J. Harmsen Campbell S. Nelson Susan F. Boyle 《Sedimentary Geology》1988,60(1-4):173-195
Pliocene, non-tropical, widespread and locally thick (up to 100 m) limestones occur in Hawke's Bay, eastern North Island, where they are intimately associated with very thick ( > 5 km), terrigenous-dominated, Neogene sequences that formed in a tectonically active convergent margin setting. The non-tropical character of the limestones is shown unequivocally by (1) the complete dominance of skeletal calcarenites and calcirudites, (2) the occurrence of oyster banks as the only in situ organic structures, (3) the dominance of barnacles, epifaunal molluscs, bryozoans, echinoderms, foraminifers, brachiopods and calcareous red algae as skeletal components, and (4) the preponderance of calcite over aragonite in the mineralogy of the skeletal grains and cements. The abundance of barnacle fragments in the limestones, and the related exclusive occurrence of only one major organic association, a barnacle-(epifaunal) bivalve-bryozoan assemblage, is striking and unusual given the extent of the limestones. Pecten and oyster valves acted as substrates for barnacle attachment, and their growth was promoted by strong tidal paleocurrents that swept the depositional setting: a long (450 km), narrow (30–50 km) forearc basin seaway, which formed between an actively deforming subduction complex to the east and an uplifting structural ridge to the west. Synsedimentary deformation promoted limestone formation on the margins of the seaway by creating current-swept, clastic-free submarine ridges that acted as the sites of carbonate production. Tidal flows dispersed the carbonate constituents and organised them into a wide spectrum of tide-influenced, cross-bedded and horizontal structures. Most spectacular are occurrences of giant tabular cross-beds, with sets 10–40 m thick and foreset dips of 7–36°, some interpreted as the deposits of major sand bars on carbonate deltas marginal to the mouths of saddles traversing the rising antiforms, and others analogous to modern linear sand ridges. The small- to large-scale planar and trough cross-beds, and the horizontal and lenticular beds that are invariably associated with the giant cross-beds and dominate most sections, represent mainly the deposits of sand waves and sand sheets at inner- to mid-shelf depths in the seaway. 相似文献
48.
Accurate and efficient algorithms are derived for computing any desired response quantity of a single-degree-of-freedom linear oscillator subjected to an arbitrary forcing function. These algorithms are based on linear interpolation of the excitation between discrete points sampled uniformly in time. In the special case of the undamped oscillator, the displacement algorithm is equivalent to a previously published algorithm for this situation which was derived using a finite element approach. However, contrary to the claim made by the authors of this latter algorithm, it does not give an exact solution of the equation of undamped motion for an arbitrary forcing function. 相似文献
49.
50.
The Australian Government policy on reduction of greenhouse gas emissions announced in 1990 includes exploring the scope for immediate, low cost reductions. Such measures can be taken as including ‘no regrets’ policies: those that, in addition to mitigating potential climate change, confer economic gains (including other environmental benefits) which exceed their costs. Some possible ‘no regrets’ opportunities and policies are identified relevant to energy use by the road transport sector over the period to 2020. The MARKALMENSA multi-period linear programming model of the Australian energy sector is used to investigate the cost-effectiveness of these policies. 相似文献