Surveys in Geophysics - Deception Island is an active volcano located in the South Shetland Islands, Antarctica. Although the last eruptions occurred in 1967-1970, the volcano has undergone periods... 相似文献
The dates of recession of eleven outlet glaciers of the Hielo Patagónico Norte (Northern Patagonian Icefield) from their recent maximum positions have been inferred from dendrochronology, lichenometry, radiocarbon dating and historical sources. We have refined the dating for part of the Little Ice Age period in this area placing a glacial advance to between AD 1650 and 1766 with the latter date favoured as conformable with historical records and an uncalibrated radiocarbon determination. Glacier recession from maximal positions began in the early 1860s–1870s. Recession was largely synchronous on the western and eastern sides of the Icefield. This synchronicity suggests that climate forcing over-rides second-order controls on glacier behaviour such as the nature of the terminal environment (e.g. calving/non-calving) or differences in glacier drainage basin area. We argue that this icefield-wide glacier recession represents a response to post-Little Ice Age warming, and provides further evidence for the global extent and near synchronous termination of the Little Ice Age. 相似文献
Planetary Nebulae have proven to be an essential key to understand the long term chemical enrichment of the interstellar medium
due to low mass stars. They allow to study the original abundances of the star, and the effect of the star on the interstellar
medium. Blue compact dwarf galaxies are known to host violent star formation in very heavy element depleted environments.
They also show traces of past star formation (Doublier et al., 1999; 2001), including AGB starsand red giants which are responsible
for long term enrichment. However, models fails to reproduce the low metallicities observed if those stars are taken into
account. We observed PNe in BCDGs, and made a comparative study of the abundances in the HII regions and of the PNe.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
We investigate the effect of source distribution on the bulk transfer of passive scalars between rough, vegetated land surfaces
and the atmosphere, using data from a wind-tunnel experiment in which passive heat was emitted from both the underlying surface
and canopy elements of a three-dimensional regular bluff-body array. The experimental results are compared with a simple one-dimensional,
two-source model for scalar transfer. We find that: (1) the observed scalar transfer resistance across the boundary layer
at the underlying surface is simply related to flat-plate theory by a constant of 0.62, despite the complexity of the turbulent
flow within the wind-tunnel canopy; (2) one-dimensional gradient-transfer theory, even with extensions to account for the
non-local nature of turbulent transfer within the canopy, does not describe the observed details of scalar concentration gradients
in the highly three-dimensional canopy flow, but does provide a reasonable framework for bulk scalar transfer between the
composite ground-canopy surface and the flow above the canopy; (3) the kB−1 parameter (which accounts for bulk excess resistance to scalar transfer over momentum transfer) is highly sensitive to scalar
source partition between ground and canopy. 相似文献
Natural Hazards - Researchers have traditionally conceptualized hazards that give rise to disasters as “natural” or “technological.” An extensive literature has documented... 相似文献
On April 20, 2010, the Deepwater Horizon oil rig exploded, and oil spilled from the breached well-head for months, leading to an unprecedented environmental disaster with implications for behavioral health. Disasters are thought to affect behavioral health, and social capital is thought to ameliorate behavioral health impacts after disasters, though empirical evidence is mixed. One possible explanation for the discrepancy in findings relates to the activation of social capital in different contexts. In a disaster context, certain types of social capital may be more beneficial than others, and these relationships could differ between those directly affected by the disaster and those who are unaffected. The goal of this study is to assess the relationships between different forms of social capital (community engagement, trust, and social support) on different behavioral health indicators (depression, anxiety, and alcohol misuse) using data from the first wave of the Survey of Trauma, Resilience, and Opportunity among Neighborhoods in the Gulf (STRONG), a probabilistic household telephone survey fielded 6 years after the onset of the Deepwater Horizon oil spill (DHOS). We employ a structural equation modeling approach where multiple social capital and behavioral health variables can be included and their pathways tested in the same model, comparing the results between those who reported experiencing disruptions related to the DHOS and those who did not. Among those who experienced the DHOS, social support was negatively associated with both depression (β?=???0.085; p?=?0.011) and anxiety (β?=???0.097; p?=?0.003), and among those who did not experience the DHOS, social support was positively associated with alcohol misuse (β?=?0.067; p?=?0.035). When controlling for the other social capital variables, social support was the only form of social capital with a significant relationship to behavioral health, and these relationships differ based on whether or not a person experienced the disaster. This suggests that social capital does not have a uniformly ameliorative relationship with behavioral health in the aftermath of disasters.
With the ability of multibeam echo sounders (MBES) to measure backscatter strength (BS) as a function of true angle of insonification across the seafloor, came a new recognition of the potential of backscatter measurements to remotely characterize the properties of the seafloor. Advances in transducer design, digital electronics, signal processing capabilities, navigation, and graphic display devices, have improved the resolution and particularly the dynamic range available to sonar and processing software manufacturers. Alongside these improvements the expectations of what the data can deliver has also grown. In this paper, we identify these user-expectations and explore how MBES backscatter is utilized by different communities involved in marine seabed research at present, and the aspirations that these communities have for the data in the future. The results presented here are based on a user survey conducted by the GeoHab (Marine Geological and Biological Habitat Mapping) association. This paper summarises the different processing procedures employed to extract useful information from MBES backscatter data and the various intentions for which the user community collect the data. We show how a range of backscatter output products are generated from the different processing procedures, and how these results are taken up by different scientific disciplines, and also identify common constraints in handling MBES BS data. Finally, we outline our expectations for the future of this unique and important data source for seafloor mapping and characterisation. 相似文献
