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541.
542.
543.
The association of coronal mass ejection transients with other forms of solar activity 总被引:2,自引:0,他引:2
R. H. Munro J. T. Gosling E. Hildner R. M. MacQueen A. I. Poland C. L. Ross 《Solar physics》1979,61(1):201-215
Coronal mass ejection transients observed with the white light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass ejection transients and chromospheric H activity, with three-quarters of the transients apparently originating in or near active regions. We infer that 40% of transients are associated with flares, 50% are associated with eruptive prominences solely (without flares), and more than 70% are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares which displayed apparent mass ejections of H-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection.Now at Los Alamos Scientific Laboratories, Los Alamos, NM., U.S.A.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
544.
Many animals are sexually dimorphic, but the underlying evolutionary causes and ecological consequences of sexual dimorphism are not fully understood. One predicted consequence for sexual dimorphism is that different sexes show niche differentiation. If sexual dimorphism is in feeding appendages, then differences may be manifested by different diets and thus contrasting behavioural responses to potential prey. Sexual dimorphisms in feeding appendages may also result in different handling times, which may then be correlated with differences in exposure, and, hence predation risk to the predator while feeding. In addition, the prey of the sexually dimorphic predator may respond differently to cues from each sex according to the predation risk each presents to the prey. We tested these predictions using a crab (Carcinus maenas) with sexual dimorphism in chelae dimensions, its predator the cuttlefish Sepia officinalis and prey with known differences in handling times; the gastropod molluscs Gibbula umbilicalis and Littorina littorea. We demonstrated that male C. maenas orientated more frequently to cues from L. littorea whereas females orientated more towards G. umbilicalis in contradiction of patterns predicted by handling times. Male crabs had a faster heart rate than females but this was not influenced by food‐based cues. We also showed no difference in foraging times with respect to changing levels of predator risk and also no differences in gastropod responses to odours from male or female crabs. Our results showed that predictions of handling time and sexual dimorphism are not associated. The experiments indicated the male and female crabs are probably ecological equivalents and thus niche differentiation is less likely. 相似文献
545.
Multichannel seismic reflection profiles recorded in the northern Red Sea show structures that we interpret to be a result of the intrusion of uppermost Miocene salt. We believe that the evaporites are underlaid by attenuated continental crust and the flow of salt is due to renewed faulting of basement in the Pliocene when sea floor spreading began between latitudes 21°N and 15°30°N. 相似文献
546.
Tetjana Ross Rolf Lueck 《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(12):2353-2365
Recent work has suggested the possibility of using high-frequency (10 kHz to 1 MHz) acoustics to remotely sense turbulent microstructure in the ocean. Once developed, this technique will provide a powerful tool for examining the spatial and temporal distributions of ocean mixing in a way not possible using traditional microstructure methods. In this paper turbulent dissipation rates are estimated through an inversion of 307 kHz acoustic scattering data collected in the lee of a sill in Knight Inlet, British Columbia. These data have been shown previously to be strongly correlated with temperature and shear microstructure measurements. Here we show that inversion methods can be used to get turbulent dissipation rates from acoustic backscatter, provided that independent measurements of temperature and salinity stratification are available. The temperature–salinity characteristics of the environment, however, can place limitations on the inversion technique. The strong negative salinity gradient in Knight Inlet decreases the slope of the functional relationship between dissipation rate and scattering cross-section for high dissipation rates and increases the uncertainty of the inversion. This limitation on the inversion technique is not an issue throughout most of the world's oceans (where dT/dS>0) and, in places where it could be a problem, the limitation can be overcome by using multi-frequency techniques. 相似文献
547.
In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits.The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line.Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan, stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation.Between 1860 A.D. and 1899 A.D. (39 years),
m3 of sediment were deposited within the Muir Inlet morainal bank complex at an average annual sediment accumulation rate of
m3/a. This rate represents the annual sediment production capacity of the glacier when the Muir Inlet drainage basin is filled with glacial ice. 相似文献
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548.
Tatsuki Toda Tomoko Okashita Takeshi Maekawa Bin Abdul Adzis Kee Alfian Mohd Kushairi Mohd Rajuddin Ryota Nakajima Wenxi Chen Kunio T. Takahashi Bin Haji Ross Othman Makoto Terazaki 《Journal of Oceanography》2007,63(1):113-123
Coral community structures at eleven fringing reef sites were investigated along the coast of Peninsular Malaysia. Estimated
coverage of coral communities is examined by applying quantitative digital image analysis to the line transect method. Four
coral community types were characterized by dominant genera and lifeforms: Acropora branching community, Montipora-Acropora community, Porites massive community, and Heliopora community. Live coral coverage in all study sites ranged from 17.9% to 68.6%. Most reefs were in “fair” condition while some
reefs were shown to be in “poor” condition. Coral community structures among the study sites were divided into the west coast
of Peninsular Malaysia with a dominant Porites massive lifeform, and the east coast with a variety of lifeform categories of Montipora and Acropora. Physical effects such as the monsoon wind regime and sedimentation are likely to influence the formation of dominant coral
communities around Peninsular Malaysia. 相似文献
549.
A high-pressure single-crystal x-ray diffraction study of perovskite-type MgSiO3 has been completed to 12.6 GPa. The compressibility of MgSiO3 perovskite is anisotropic with b approximately 23% less compressible than a or c which have similar compressibilities. The observed unit cell compression gives a bulk modulus of 254 GPa using a Birch-Murnaghan equation of state with K set equal to 4 and V/V
0 at room pressure equal to one. Between room pressure and 5 GPa, the primary response of the structure to pressure is compression of the Mg-O and Si-O bonds. Above 5 GPa, the SiO6 octahedra tilt, particularly in the [bc]-plane. The distortion of the MgO12 site increases under compression. The variation of the O(2)-O(2)-O(2) angles and bondlength distortion of the MgO12 site with pressure in MgSiO3 perovskite follow trends observed in GdFeO3type perovskites with increasing distortion. Such trends might be useful for predicting distortions in GdFeO3-type perovskites as a function of pressure. 相似文献
550.
Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints 总被引:2,自引:2,他引:2
V. Masson-Delmotte M. Kageyama P. Braconnot S. Charbit G. Krinner C. Ritz E. Guilyardi J. Jouzel A. Abe-Ouchi M. Crucifix R. M. Gladstone C. D. Hewitt A. Kitoh A. N. LeGrande O. Marti U. Merkel T. Motoi R. Ohgaito B. Otto-Bliesner W. R. Peltier I. Ross P. J. Valdes G. Vettoretti S. L. Weber F. Wolk Y. YU 《Climate Dynamics》2006,26(5):513-529
Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future
climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes
and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced
by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures
fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate
models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and
Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global
temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years
ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to
the range of temperature change expected from a quadrupling of atmospheric CO2 concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification
of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation
changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial
Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature
change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation
by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature
with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in
simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative
insights on global climate changes.
An erratum to this article can be found at 相似文献