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51.
Accretional temperature profiles for Saturn’s large moon Titan are used to determine the conditions needed for accretion to avoid global melting as a function of the timing, duration, and nebular conditions of Titan’s accretion. We find that Titan can accrete undifferentiated in a “gas-starved” disk even with modest quantities of ammonia mixed in with its ices. Simulations of impact-induced core formation are used to show that Titan can remain only partially differentiated after an outer Solar System late heavy bombardment capable of melting its outer layers, permitting some of its rock to consolidate into a core. 相似文献
52.
Krahn MM Hanson MB Baird RW Boyer RH Burrows DG Emmons CK Ford JK Jones LL Noren DP Ross PS Schorr GS Collier TK 《Marine pollution bulletin》2007,54(12):1903-1911
“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter. 相似文献
53.
Saving lives in earthquakes: successes and failures in seismic protection since 1960 总被引:1,自引:1,他引:0
Robin Spence 《Bulletin of Earthquake Engineering》2007,5(2):139-251
This paper will look at what we have and have not achieved in reducing the risks to human life from earthquakes in the last
50 years. It will review how success has been achieved in a few parts of the world, and consider what needs to be done by
the scientific and engineering community globally to assist in the future task of bringing earthquake risks under control.
The first part of the talk will re-examine what we know about the casualties from earthquakes in the last 50 years. Almost
80% of about 1 million deaths turn out to have been caused by just ten great earthquakes, together affecting a tiny proportion
of the territory at risk from heavy ground shaking. The disparity between richer and poorer countries is also evident, not
only in fatality rates, but also in their rates of change. But the existing casualty database turns out to be a very poor
basis for observing such differences, not only because of the small number of lethal events, but also because of the very
limited data on causes of death, types and causes of injury. These have been examined in detail in only a few, recent events.
All that can be said with certainty is that a few wealthier earthquake-prone countries or regions have made impressive progress
in reducing the risk of death from earthquakes, while most of the rest of the world has achieved comparatively little, and
in some areas the problem has become much worse. The second part of the paper looks in more detail at what has been achieved
country-by-country. Based on a new expert-group survey of key individuals involved in earthquake risk mitigation, it will
examine what are perceived to be the successes and failures of risk mitigation in each country or group of countries. This
survey will be used to highlight the achievements of those countries which have successfully tackled their earthquake risk;
it will examine the processes of earthquake risk mitigation, from campaigning to retrofitting, and it will consider to what
extent the achievement is the result of affluence, scientific and technical activity, political advocacy, public awareness,
or the experience of destructive events. It will ask to what extent the approaches pioneered by the global leaders can be
adopted by the rest. The final section of the talk will argue that it can be useful to view earthquake protection activity
as a public health matter to be advanced in a manner similar to globally successful disease-control measures: it will be argued
that the key components of such programmes—building in protection; harnessing new technology and creating a safety culture—must
be the key components of earthquake protection strategies also. It will consider the contribution which the scientific and
engineering community can make to bringing down today’s unacceptably high global earthquake risk. It will be suggested that
this role is wider than commonly understood and needs to include:
Building-in protection
Harnessing new technologies
Creating a safety culture
Examples of some of these actions will be given. International collaboration is essential to ensure that the resources and
expertise available in the richer countries is shared with those most in need of help. And perhaps the most important single
task for the engineering community is work to counter the widespread fatalistic attitude that future earthquakes are bound
to be at least as destructive as those of the past. 相似文献
• | Improving and simplifying information available for designers and self-builders of homes and infrastructure. |
• | Devising and running “building for safety” programmes to support local builders. |
• | Developing and testing cost-effective techniques for new construction and retrofit. |
• | Involvement in raising public awareness. |
• | Political advocacy to support new legislation and other actions. |
• | Prioritising action on public buildings, especially schools and hospitals. |
54.
Pablo Samaniego Claude Robin Gilles Chazot Erwan Bourdon Joseph Cotten 《Contributions to Mineralogy and Petrology》2010,160(2):239-260
Geochemical studies of long-lived volcanic complexes are crucial for the understanding of the nature and composition of the
subduction component of arc magmatism. The Pichincha Volcanic Complex (Northern Andean Volcanic Zone) consists of: (1) an
old, highly eroded edifice, the Rucu Pichincha, whose lavas are mostly andesites, erupted from 1,100 to 150 ka; and (2) a
younger, essentially dacitic, Guagua Pichincha composite edifice, with three main construction phases (Basal Guagua Pichincha,
Toaza, and Cristal) which developed over the last 60 ka. This structural evolution was accompanied by a progressive increase
of most incompatible trace element abundances and ratios, as well as by a sharp decrease of fluid-mobile to fluid-immobile
element ratios. Geochemical data indicate that fractional crystallization of an amphibole-rich cumulate may account for the
evolution from the Guagua Pichincha andesites to dacites. However, in order to explain the transition between the Rucu Pichincha
andesites and Guagua Pichincha dacites, the mineralogical and geochemical data indicate the predominance of magma mixing processes
between a mafic, trace-element depleted, mantle-derived end-member, and a siliceous, trace-element enriched, adakitic end-member.
The systematic variation of trace element abundances and ratios in primitive samples leads us to propose that the Rucu Pichincha
magmas came from a hydrous-fluid metasomatized mantle wedge, whereas Guagua Pichincha magmas are related to partial melting
of a siliceous-melt metasomatized mantle. This temporal evolution implies a change from dehydration to partial melting of
the slab, which may be associated with an increase in the geothermal gradient along the slab due to the presence of the subducted
Carnegie Ridge at the subduction system. This work emphasizes the importance of studying arc-magma systems over long periods
of time (of at least 1 million of years), in order to evaluate the potential variations of the slab contribution into the
mantle source of the arc magmatism. 相似文献
55.
James M. Murphy Ben B. B. Booth Chris A. Boulton Robin T. Clark Glen R. Harris Jason A. Lowe David M. H. Sexton 《Climate Dynamics》2014,43(9-10):2855-2885
We describe results from a 57-member ensemble of transient climate change simulations, featuring simultaneous perturbations to 54 parameters in the atmosphere, ocean, sulphur cycle and terrestrial ecosystem components of an earth system model (ESM). These emissions-driven simulations are compared against the CMIP3 multi-model ensemble of physical climate system models, used extensively to inform previous assessments of regional climate change, and also against emissions-driven simulations from ESMs contributed to the CMIP5 archive. Members of our earth system perturbed parameter ensemble (ESPPE) are competitive with CMIP3 and CMIP5 models in their simulations of historical climate. In particular, they perform reasonably well in comparison with HadGEM2-ES, a more sophisticated and expensive earth system model contributed to CMIP5. The ESPPE therefore provides a computationally cost-effective tool to explore interactions between earth system processes. In response to a non-intervention emissions scenario, the ESPPE simulates distributions of future regional temperature change characterised by wide ranges, and warm shifts, compared to those of CMIP3 models. These differences partly reflect the uncertain influence of global carbon cycle feedbacks in the ESPPE. In addition, the regional effects of interactions between different earth system feedbacks, particularly involving physical and ecosystem processes, shift and widen the ESPPE spread in normalised patterns of surface temperature and precipitation change in many regions. Significant differences from CMIP3 also arise from the use of parametric perturbations (rather than a multimodel ensemble) to represent model uncertainties, and this is also the case when ESPPE results are compared against parallel emissions-driven simulations from CMIP5 ESMs. When driven by an aggressive mitigation scenario, the ESPPE and HadGEM2-ES reveal significant but uncertain impacts in limiting temperature increases during the second half of the twenty-first century. Emissions-driven simulations create scope for development of errors in properties that were previously prescribed in coupled ocean–atmosphere models, such as historical CO2 concentrations and vegetation distributions. In this context, historical intra-ensemble variations in the airborne fraction of CO2 emissions, and in summer soil moisture in northern hemisphere continental regions, are shown to be potentially useful constraints, subject to uncertainties in the relevant observations. Our results suggest that future climate-related risks can be assessed more comprehensively by updating projection methodologies to support formal combination of emissions-driven perturbed parameter and multi-model earth system model simulations with suitable observational constraints. This would provide scenarios underpinned by a more complete representation of the chain of uncertainties from anthropogenic emissions to future climate outcomes. 相似文献
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