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Jennifer M. Galloway Christine T. Doherty R. Timothy Patterson Helen M. Roe 《第四纪科学杂志》2009,24(4):322-335
A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 ± 70 14C a BP initiated the development of closed, late successional T. heterophylla–Cupressaceae forests, which achieved modern character after 6860 ± 50 14C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour‐Belize Inlet Complex, on a meso‐ to synoptic scale. This would suggest that an early Holocene intensification of the Aleutian Low pressure system was an important influence on forest dynamics in the Seymour‐Belize Inlet Complex and that the study region was located near the southern extent of immediate influence of this semi‐permanent air mass. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
Charles H. Nelson Douglas S. Hall Francis C. Fekel Robert E. Fried Richard E. Lines Helen C. Lines 《Astrophysics and Space Science》1991,182(1):1-17
Photometry of HD 155638=V792 Her has been analyzed to determine the elements of this totally eclipsing RS CVn binary. The light variation outside eclipse was found to have a period of 27d.07±0d.07, which is slightly different from the 27d.5384±0d.0045 orbital period. Analysis of the eclipses was achieved by a modification of the Russell-Merrill technique. With the aid of radial velocity measures, absolute elements were obtained for the hot and cool stars, respectively;R
h=2.58R
,R
c=12.28R
,M
h=1.40M
,M
c=1.46M
,i=80o.61 and velocity semi-amplitudesK
c=48.36 km s–1±0.79 km s–1, andK
h=50.50 km s–1±0.33 km s–1. The apparent magnitudes areV
h=9
m
.73 andV
c=8
m
.48. The distance to HD 155638 was estimated to be 310 parsecs. 相似文献
4.
Marie K. McCabe Zdeněk F. Švestka Russell A. Howard Bernard V. Jackson Neil R. Sheeley Jr. 《Solar physics》1986,103(2):399-408
By using a combination of X-ray (HXIS), H (Haleakala), white-light corona (Solwind), and zodiacal light (Helios) images on 21–22 May, 1980 we demonstrate, and try to explain, the co-existence of a coronal mass ejection with a stationary post-flare coronal arch. The mass ejection was seen, both by Solwind and Helios, in prolongation of the path of a powerful spray, whereas the active region filament did not erupt. A tentative comparison is made with other occurrences of stationary, or quasi-stationary post-flare coronal arches. 相似文献
5.
激光拉曼光谱法分析多种显微组分荧光变化及其应用 总被引:1,自引:1,他引:0
利用激发488 nm激光的氩离子激光器作为RENISHAW inVia型激光拉曼光谱仪的光源,建立了多种显微组分荧光变化(FAMM)分析方法,并对镜质体反射率明显抑制的东营凹陷有效烃源岩进行了测定。结果表明,东营凹陷有效烃源岩的有机质类型越好,镜质体反射率抑制程度越高,有效烃源岩的真实成熟度应主要处于0.64%~1.30%,而不是实测镜质体反射率所反映的0.37%~1.10%。 相似文献
6.
Imad A.M. Ahmed Neil M.J. Crout Scott D. Young 《Geochimica et cosmochimica acta》2008,72(6):1498-1512
Time-dependent sorption and desorption of Cd on calcite was studied over 210 days utilizing 109Cd as a tracer to distinguish between ‘labile’ and ‘non-labile’ forms of sorbed Cd. Stabilizing the calcite suspensions for 12 months under atmospheric PCO2 and controlled temperature was necessary to reliably follow Cd dynamics following initial sorption. Results revealed time-dependant Cd sorption and marked desorption hysteresis by calcite under environmentally relevant conditions. Data obtained were fitted to a first-order kinetic model and a concentric shell diffusion model. Both models described the progressive transfer of Cd2+ to a less reactive form within calcite and subsequent desorption of Cd subject to different initial contact times. The kinetic model provided a better fit to the combined sorption and desorption data (R2 = 0.992). It differentiates between two ‘pools’ of sorbed Cd2+ on calcite, ‘labile’ and ‘non-labile’, in which labile sorbed Cd is in immediate equilibrium with the free Cd2+ ion activity in solution whereas non-labile Cd is kinetically restricted. For the diffusion model (R2 = 0.959), the rate constants describing Cd dynamics in calcite produced a half-life for Cd desorption of ∼175 d, for release to a ‘zero-sink’ solution. Results from this study allow comment on the likely mechanisms occurring at the calcite surface following long-term Cd sorption. 相似文献
7.
Effective livelihood adaptation to climate change disturbance: Scale dimensions of practice in Mozambique 总被引:2,自引:0,他引:2
Natural resource-dependent societies in developing countries are facing increased pressures linked to global climate change. While social-ecological systems evolve to accommodate variability, there is growing evidence that changes in drought, storm and flood extremes are increasing exposure of currently vulnerable populations. In many countries in Africa, these pressures are compounded by disruption to institutions and variability in livelihoods and income. The interactions of both rapid and slow onset livelihood disturbance contribute to enduring poverty and slow processes of rural livelihood renewal across a complex landscape. We explore cross-scale dynamics in coping and adaptation response, drawing on qualitative data from a case study in Mozambique. The research characterises the engagements across multiple institutional scales and the types of agents involved, providing insight into emergent conditions for adaptation to climate change in rural economies. The analysis explores local responses to climate shocks, food security and poverty reduction, through informal institutions, forms of livelihood diversification and collective land-use systems that allow reciprocity, flexibility and the ability to buffer shocks. However, the analysis shows that agricultural initiatives have helped to facilitate effective livelihood renewal, through the reorganisation of social institutions and opportunities for communication, innovation and micro-credit. Although there are challenges to mainstreaming adaptation at different scales, this research shows why it is critical to assess how policies can protect conditions for emergence of livelihood transformation. 相似文献
8.
9.
10.
This paper presents the findings from an in-depth analysis of the (axial) stiffness data recorded during tension–tension fatigue tests on wire ropes, particularly in relation to how changes in stiffness during testing relate to changes in rope strength. A linear relationship between stiffness and strength is shown to exist and a methodology presented for quantifying residual strength with applied cycles. New lower bound fatigue lines for six-strand rope and spiral strand are presented which are based on a 10% loss of strength. These new lines have the advantage of having been established using a common discard criterion for wire ropes. 相似文献