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131.
132.
S.P.S. Eyres A. Evans A. Salama P. Barr J. Clavel N. Jenkins K. Leech M. Kessler T. Lim L. Metcalfe B. Schulz 《Astrophysics and Space Science》1997,255(1-2):361-366
A number of symbiotic stars have been observed with ISO. In addition to a number of emission lines, SWS observations of the
symbiotic novae RR Tel and V1016 Cyg reveal prominent, broad 10 & 18 μm silicate dust features. The 10 μm features are similar
to the crystalline silicate profiles seen in classical novae. There is some evidence that the silicate brightness in V1016
Cyg varies with Mira-component phase. However, the silicate feature in RR Tel also showed some variation even though observations
were made at very similar Mira-component phases. PHT observations of S-type symbiotic stars show the IR emission to be dominated
by the red-giant component. However, an excess in the PHT-P filters from 10 to 15 μm is evident in all the stars, and there
may be a broad 3.2 μm absorption feature or a broad 3.8 μm emission feature. At this time we have no adequate physical explanations
for any of these features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
133.
Sunniva Rutledal Haflidi Haflidason Sarah M. P. Berben Lisa Griem Eystein Jansen 《第四纪科学杂志》2020,35(7):855-868
Volcanic ash preserved in marine sediment sequences is key for independent synchronization of palaeoclimate records within and across different climate archives. Here we present a continuous tephrostratigraphic record from the Labrador Sea, spanning the last 65–5 ka, an area and time period that has not been investigated in detail within the established North Atlantic tephra framework. We investigated marine sediment core GS16-204-22CC for increased tephra occurrences and geochemically analysed the major element composition of tephra shards to identify their source volcano(es). In total we observed eight tephra zones, of which five concentration peaks show isochronous features that can be used as independent tie-points in future studies. The main transport mechanism of tephra shards to the site was near-instantaneous deposition by drifting of sea ice along the East Greenland Current. Our results show that the Icelandic Veidivötn volcanic system was the dominant source of tephra material, especially between late Marine Isotope Stage (MIS) 4 and early MIS 3. The Veidivötn system generated volcanic eruptions in cycles of ca. 3–5 ka. We speculate that the quantity of tephra delivered to the Labrador Sea was a result of variable Icelandic ice volume and/or changes in the transportation pathway towards the Labrador Sea. 相似文献
134.
Ecosystem-based management is more successful when a great diversity of stakeholders is engaged early in a decision-making process. Implementation of the California Marine Life Protection Act (MLPA) has been stakeholder-based, coordinating the participation of a wide range of people including divers, fishermen, conservationists, local officials, business owners and coastal residents. Although commercial and recreational fishermen have actively participated throughout the MLPA implementation process, and research related to California’s sport and commercial fisheries has been integrated into the process, pier and shore anglers have been relatively unengaged as stakeholders. This study was completed to generate information about pier angler understanding and sentiment towards marine protected areas (MPAs), as well as to educate anglers on the MLPA implementation process in southern California and inform them on involvement opportunities. Of the 3030 pier anglers surveyed over 12 months, 78% only fish for subsistence from piers and from shore (never from boats); 84.6% are of non-White/Euro-American ethnicity and speak English as a second language; and 82% indicated that they were supportive of establishing a strong network of MPAs in southern California, specifically fully-protective no-take marine reserves. This study is an example of an alternative and customized method of outreach designed to reach a unique and previously unengaged stakeholder group, which stands to be affected by the implementation of the MLPA in California. Engaging such non-traditional stakeholders in public policy may be critical for decision makers to gauge all views from those standing to be affected by a policy—not just the views of those that regularly attend policy meetings—and for the ultimate success of policy implementation and community support. 相似文献
135.
A spatially explicit degree-day model was used to evaluate the risk of Rift Valley fever virus (RVFV) transmission by mosquitoes
to humans and livestock within five target states in the continental United States: California, Minnesota, Nebraska, New York,
and Texas. A geographic information system was used to model potential virus transmission based on a 12-day moving window
assessment of the extrinsic incubation period theorized for RVFV in the United States. Risk of potential virus transmission
in each state was spatially evaluated on a 10-km grid using average historical daily temperature data from 1994 to 2003. The
highest levels of transmission risk occur in California and Texas, with parts of these states at risk of RVFV transmission
for up to 8 months per year. Northern Minnesota, central New York, and most of coastal and high-elevation California are at
low to null risk. Risk of impact to the livestock industry is greatest in California, Texas, and Nebraska. A standard global
climate model was used to evaluate future risk in the year 2030 in Nebraska, and showed an increase of transmission risk days
from approximately 3 to 4 months per year. 相似文献
136.
Root properties of vegetation communities and their impact on the erosion resistance of river dikes 总被引:1,自引:0,他引:1 下载免费PDF全文
Wouter Vannoppen Jean Poesen Patrik Peeters Sarah De Baets Bart Vandevoorde 《地球表面变化过程与地形》2016,41(14):2038-2046
Predicted climate change and the associated sea level rise poses an increased threat of flooding due to wave overtopping events at sea and river dikes. To safeguard the land from flooding it is important to keep the soil erosion resistance at the dikes high. As plant roots can be very effective in reducing soil erosion rates by concentrated flow, the main goal of this study is to explore the variability in root system characteristics of five dike vegetation communities along the Scheldt River (Belgium) and to assess their effectiveness in controlling soil erosion rates during concentrated flow. This study is the first one to investigate systematically the erosion‐reducing potential of the root properties of representative dike vegetation communities in a temperate humid climate. Results show that the presence of Urtica dioica resulted in large differences in root length density (RLD) among dike vegetation communities. Observed RLD values in the topsoil ranged from 129 to 235 km m‐3 for dike vegetation communities without U. dioica, while smaller values ranging from 22 to 58 km m?3 were found for vegetation communities with U. dioica. The erosion‐reducing effect of the dike vegetation communities was estimated based on a global Hill curve model, linking the RLD to the soil detachment ratio (SDR; i.e. the ratio of the soil detachment rate for root‐permeated topsoils to the soil detachment rate for root‐free topsoils). Concentrated flow erosion rates are likely to be reduced to 13–16% of the erosion rates for root‐free topsoils if U. dioica is absent compared to 22–30% for vegetation communities with U. dioica. Hence, to maintain a high resistance of the soil against concentrated flow erosion it is important to avoid the overgrowth of grassland by U. dioica through an effective vegetation management. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
137.
Mark Williams David J. Siveter Derek J. Siveter Sarah E. Gabbott Xiaoya Ma Mark A. Purnell Peiyun Cong 《Geology Today》2016,32(6):233-237
Shi Nai'an's fourteenth century Chinese epic ‘Water Margin’ tells of the release of 36 heavenly spirits and 72 baleful stars from their captivity beneath a tablet of stone at Mount Longhu in Jiangxi Province. They are reincarnated as the 108 heroes of the Liangshan marsh in Shandong Province, who rise against an unjust world. The virtuous exploits of the ‘108’ were brought to life through the cathode‐ray screens of 1970s television sets, as the TV series The Water Margin introduced heroes like Lin Chong battling his evil nemesis Gao Qiu. Far to the west of Jiangxi Province and several hundred years after the Water Margin during the summer of 1984, a young scientist from Nanjing was working amongst the hills and lakes of southern Yunnan Province. He too overturned a stone slab, releasing from their half‐billion year captivity a cornucopia of new Chinese legends. His name was Xianguang Hou and he had made one of the most momentous fossil discoveries in history, uncovering the exceptionally preserved marine fossils of the Chengjiang biota from the ancient water margin of Cambrian seas. 相似文献
138.
Ian A. Crawford Sarah A. Fagents Katherine H. Joy M. Elise Rumpf 《Earth, Moon, and Planets》2010,107(1):75-85
One of the principal scientific reasons for wanting to resume in situ exploration of the lunar surface is to gain access to
the record it contains of early Solar System history. Part of this record will pertain to the galactic environment of the
Solar System, including variations in the cosmic ray flux, energetic galactic events (e.g., supernovae and/or gamma-ray bursts),
and passages of the Solar System through dense interstellar clouds. Much of this record is of astrobiological interest as
these processes may have affected the evolution of life on Earth, and perhaps other Solar System bodies. We argue that this
galactic record, as for that of more local Solar System processes also of astrobiological interest, will be best preserved
in ancient, buried regolith (‘palaeoregolith’) deposits in the lunar near sub-surface. Locating and sampling such deposits
will be an important objective of future lunar exploration activities. 相似文献
139.
140.
Crime is a complex phenomenon, emerging from the interactions of offenders, victims, and their environment, and in particular from the presence or absence of capable guardians. Researchers have historically struggled to understand how police officers create guardianship. This presents a challenge because, in order to understand how to advise the police, researchers must have an understanding of how the current system works. The work presents an agent‐based model that simulates the movement of police vehicles, using a record of real calls for service and real levels of police staffing in spatially explicit environments to emulate the demands on the police force. The GPS traces of the simulated officers are compared with real officer movement GPS data in order to assess the quality of the generated movement patterns. The model represents an improvement on existing standards of police simulation, and points the way toward more nuanced understandings of how police officers influence the criminological environment. 相似文献