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121.
Amy?E.?HofmannEmail author Michael?B.?Baker John?M.?Eiler 《Contributions to Mineralogy and Petrology》2014,168(3):1057
NanoSIMS measurements of Ti, P, Y, Ce, and Hf in zircon separates from the Youngest Toba Tuff, the Bishop Tuff, the Quottoon Igneous Complex, the Sierra Nevada batholith, and an Adirondack migmatite show that micron-scale oscillatory zoning of Ti is common. The zircons we have studied typically display banded concentration gradients, having between 1 and 7 peaks in Ti abundance over length scales of 10–20 μm—the beam diameter commonly used for SIMS trace-element zircon analyses—with amplitudes of up to 4.5 ppm Ti (baseline values are ~1–4 ppm) and widths (measured at half-height) of between ~0.2 and 4 μm. Spatial correlations between concentrations of Ti and other trace elements (P, Y, and Ce) are also common, but variable in character, ranging from oscillatory co-variation of Ti, P, Y, and Ce to cases where only a subset of peaks for a given element is spatially correlated with peaks in Ti. There are also longer length-scale, generally positive correlations among concentrations of Ti, P, Y, and Ce (i.e., gradients on which narrower peaks are superimposed). In contrast, Hf concentrations are either uncorrelated or inversely correlated with these longer length-scale variations in Ti concentrations. The wide range in Ti concentrations over distances of less than 1 μm and the various correlations between Ti concentrations and those of the other analyzed elements suggest that on the micron scale and at temperatures between ~700 and 800 °C, zircon-liquid Ti partitioning is not controlled by bulk or lattice equilibrium. Treating our NanoSIMS Ti ion maps as though they were conventional SIMS analyses (i.e., generating an average Ti concentration for each map), we evaluate the hypothesis that while micron-scale variations in Ti concentrations might be kinetically controlled, when averaged over 100–400 μm2, such variations capture the thermal state of the growing zircon. Using these average Ti concentrations, independent petrologic pressure and temperature constraints, estimates of silica and titania activities based on phase assemblages as well as calculations using rhyolite-MELTS, we show that crystallization temperatures predicted by Ti-in-zircon geothermometry generally do not agree with the independently constrained temperatures for the samples. 相似文献
122.
Dorthe Pflanz Christoph Gaedicke Ralf Freitag Matthias Krbetschek Nikolay Tsukanov Boris Baranov 《International Journal of Earth Sciences》2013,102(3):903-916
The tectonic position of the Kamchatka Cape Peninsula at the junction of the active Kuril–Kamchatka and Aleutian arcs exposes the coastline of the peninsula to strong neotectonic activities. Fracture zones have variable influence on uplift of the Kamchatka Cape Peninsula. Relevant morphologic indicators of neotectonic activity are multilevel, highly uplifted marine terraces and terraces displaced along active faults. Recent uplift rates of coastal sediments are determined by remote sensing via ASTER and SRTM DEM combined with optically stimulated luminescence dating (OSL). On the Kamchatka Cape Peninsula, terraces from the same generation are mapped at different elevations by remote sensing methods. After defining different areas of uplifted terraces, four neotectonic blocks are identified. According to apatite fission track data, the mean differential exhumation rates range from 0.2 to 1.2 mm year?1 across the blocks since Late Miocene. The OSL data presented point to significant higher uplift rates of up to 3 ± 0.5 and 4.3 ± 1 mm year?1, which indicates an acceleration of the vertical movement along the coast of Kamchatka Cape Peninsula in Upper Pleistocene and Holocene times. 相似文献
123.
Electromagnetic properties of natural expansive soils under one-dimensional deformation 总被引:1,自引:1,他引:0
Macroscopic behavior of expansive soil is governed by surface forces rather than gravitational forces. These physicochemical surface forces can be investigated through two electromagnetic properties in response to an applied electromagnetic field as real (relative) permittivity, κ′, and effective (electrical) conductivity, σ. This paper presents the results of dielectric measurements on four natural expansive soils using 1–100 MHz electromagnetic waves in two different test setups. The equipment setup, calibration process and measurement limitations are evaluated, and the dielectric spectra, in terms of the dispersion of real permittivity/effective conductivity with frequency, are presented. A procedure is presented to quantify the thickness of a fully developed diffuse double layer (DDL). The influence of salt concentration on DDL, as well as the dielectric responses, is assessed. Two parameters of special physical meaning are defined in the article: ${\upkappa} _{{{\text{inf}}}}^{\prime }$ , representative of the dielectric response by sample mineralogy, microstructure and saturation ratio, and σdc, combining the roles assumed by both surface conduction and pore fluid conduction. Evaluation is attempted on their magnitudes at the optimum compaction state and evolutions at different one-dimensional deforming stages. Extensive analysis is performed on the roles of ${\upkappa} _{{{\text{inf}}}}^{\prime }$ and σdc on the hydration status and structural anisotropy of an oedometer sample. 相似文献
124.
Citizen science projects encourage the general public to participate in scientific research. Participants can contribute large volumes of data over broad spatial and temporal frames; however, the challenge is to generate data of sufficient quality to be useable in scientific research. Most observations made by citizen‐scientists can be independently verified by “experts”. However, verification is more problematic when the phenomena being recorded are short‐lived. This article uses a GIS methodology to verify the quality of contrail observations made by the general public as part of the OPAL Climate Survey. We verify observations using datasets derived from a variety of different sources (experts, models and amateur enthusiasts) with different spatial and temporal properties which reflect the complex 3D nature of the atmosphere. Our results suggest that ~70% of citizen observations are plausible, based on favorable atmospheric conditions and the presence or absence of aircraft; a finding which is in keeping with other, more conventional citizen science projects. However, questions remain as to why the quality of the citizen‐based observations was so high. Given the lack of supporting data on observers, it is impossible to determine whether the dataset was generated by the activities of many participants or a small but dedicated number of individual observers. 相似文献
125.
Maps designed for and used by sighted audiences benefit from map symbol standardization and convention but, with very limited exception (most notably two European projects), neither standardization nor convention guides the design and use of symbols for tactile maps. In this project, we developed and field tested symbolization for and use of tactile street maps. The development process included consultation with the literature as well as with field experts (orientation and mobility teachers, Braillists, and teachers working with students who are blind or have low vision). Following development, we undertook a three-year field testing and validation phase, in which we conducted pilot testing and formal testing with travelers who are blind or have low vision. Research results reveal not only a discriminable and useful tactile symbol set but also environmental feature use by travelers who are blind or have low vision. 相似文献
126.
Warren C. Jochem Kelly Sims Edward A. Bright Marie L. Urban Amy N. Rose Phillip R. Coleman Budhendra L. Bhaduri 《Natural Hazards》2013,68(3):1325-1342
In recent years, uses of high-resolution population distribution databases are increasing steadily for environmental, socioeconomic, public health, and disaster-related research and operations. With the development of daytime population distribution, temporal resolution of such databases has been improved. However, the lack of incorporation of transitional population, namely business and leisure travelers, leaves a significant population unaccounted for within the critical infrastructure networks, such as at transportation hubs. This paper presents two general methodologies for estimating passenger populations in airport and cruise port terminals at a high temporal resolution which can be incorporated into existing population distribution models. The methodologies are geographically scalable and are based on, and demonstrate how, two different transportation hubs with disparate temporal population dynamics can be modeled utilizing publicly available databases including novel data sources of flight activity from the Internet which are updated in near-real time. The airport population estimation model shows great potential for rapid implementation for a large collection of airports on a national scale, and the results suggest reasonable accuracy in the estimated passenger traffic. By incorporating population dynamics at high temporal resolutions into population distribution models, we hope to improve the estimates of populations exposed to or at risk to disasters, thereby improving emergency planning and response, and leading to more informed policy decisions. 相似文献
127.
Social studies of volcanology: knowledge generation and expert advice on active volcanoes 总被引:2,自引:1,他引:1
This paper examines the philosophy and evolution of volcanological science in recent years, particularly in relation to the
growth of volcanic hazard and risk science. It uses the lens of Science and Technology Studies to examine the ways in which
knowledge generation is controlled and directed by social forces, particularly during eruptions, which constitute landmarks
in the development of new technologies and models. It also presents data from a survey of volcanologists carried out during
late 2008 and early 2009. These data concern the felt purpose of the science according to the volcanologists who participated
and their impressions of the most important eruptions in historical time. It demonstrates that volcanologists are motivated
both by the academic science environment and by a social concern for managing the impact of volcanic hazards on populations.
Also discussed are the eruptions that have most influenced the discipline and the role of scientists in policymaking on active
volcanoes. Expertise in volcanology can become the primary driver of public policy very suddenly when a volcano erupts, placing
immense pressure on volcanologists. In response, the epistemological foundations of volcanology are on the move, with an increasing
volume of research into risk assessment and management. This requires new, integrated methodologies for knowledge collection
that transcend scientific disciplinary boundaries. 相似文献
128.
What can we learn from genomics approaches in marine ecology? From sequences to eco‐systems biology!
The application of genomic approaches to marine biota has profoundly altered our understanding of life in the oceans, especially regarding concepts of adaptation, speciation and evolution. The avalanche of genomic data has provided an unbiased view of marine biology that has never been seen before. In particular, comparative and metagenomic approaches with microbes from different biogeochemical marine provinces provided the first insights into how they acquire and discard genes as needed, even across kingdom boundaries, in response to their environment. These data clearly reveal that marine microbes have remarkable abilities to change their genomes according to both environmental stresses and biotic interactions. Thus, it is most likely that the flux of energy and matter in the marine system is reflected by the presence or absence of genes and proteins in marine organisms, which could provide novel tools to understand biogeochemical processes of global significance. However, the challenge is to put the reductionistic knowledge gained by genomics and metagenomics into the larger contexts of cellular systems and ecosystems to identify emergent properties that could not have been predicted by breaking down the whole into its individual parts. 相似文献
129.
Hui-Fang Hung Ya-Chuan Wang Amy Ming-Fang Yen Hsiu-Hsi Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):611-625
Elucidating the temporal natural history of Hepatitis B virus (HBV) infection provides not only useful information for assessing the spread of HBV infection but also a bedrock for economic appraisal of population-based preventive strategies (such as universal vaccination). HBV transmissions are transmitted through the maternal (vertical) route and environmental (horizontal) route. As the infection process from susceptible to active virus replication and finally to recovery state or to carrier state through both routes is not directly observable, mathematical models were therefore proposed to quantitatively elucidate the dynamic process of HBV infection with time. We began with a simple two-state model (from susceptible to infection) and further developed a five-state (including susceptible, latent phase, active viral replication, carrier, and recovery states) stochastic process to quantify the dynamics of HBV infection, making allowances for a mixed proportion of vertical and horizontal transmissions. The data used in the estimation, which were collected before implementation of a policy for universal HBV vaccination, were derived from several previous serum prevalence studies, including both low (northern) and high (southern) HBV prevalence areas, in Taiwan. The parameters obtained from stochastic models were converted to compute the basic reproductive number (R0) in each study to indicate the extent of the spread of HBV infection. By linking the temporal natural history of HBV infection with the previously established Markov process for the sequelae of HBV infection (chronic hepatitis infection, liver cirrhosis, and hepatocelluar carcinoma), we developed a Markov cycle decision tree to evaluate the two population-based preventive strategies related to vaccination and maternal lamivudine use with a cost-effectiveness analysis. In the five-state model, horizontal transmission was found to contribute more to HBV infection than vertical transmission in the northern area (59 vs. 41 %), whereas vertical transmission was more likely than horizontal transmission in the southern area (80 vs. 20 %). After considering the parameters of the two transmission routes, annual infection rate (person-years) for susceptible subjects was higher in the northern area (0.35) than the southern area (0.011). A similar finding was noted for annual rate of the transition from the latent period to active viral replications (1.12 in the northern area and 0.072 in the southern area). Annual rate of the conversion from active viral replication to the carrier state was higher in the southern area (0.184) than the northern area (0.119). Annual recovery rates were 0.014 in the northern area and 0.024 in the southern area for the carrier and 0.048 and 0.088 for transient viremia. The R0 at age 30 using the parameters obtained from the five-state stochastic model was estimated as 4.88 in the northern and 7.03 in the southern area. Regarding the findings of economic appraisal, both preventive strategies were cost-saving, yielding the negative value of incremental cost-effectiveness ratio, compared with the baseline group (no intervention), regardless of areas. The preventive strategies in the southern area were more cost-saving than those in the northern area. The consolidation of elucidating the temporal natural history of HBV infection, estimating basic reproductive number, and conducting an economic appraisal of population-based preventive strategy can aid health policy-makers in designing effective preventive strategies in other countries worldwide where HBV is still prevalent. However, the empirical findings on transmission routes and the temporal evolution of HBV infection varying with areas should be considered with great caution as only two studies were modeled. 相似文献
130.
Public participation geographic information systems (PPGIS) are an increasingly important tool for collecting spatial information about the social attributes of place. The availability of Internet‐based options for implementing PPGIS presents new opportunities for increased efficiency and new modes of access. Here we used a mixed‐mode approach to evaluate paper versus Internet mapping methods for the same PPGIS survey in Wyoming. We compared participant characteristics, mapping participation, and the spatial distribution of mapped attributes between participants who responded to the paper versus Internet option. The response rate for those who completed the paper version of the survey was nearly 2.5 times the response rate of the Internet version. Paper participants also mapped significantly more places than did Internet participants (43 vs. 18). Internet participants tended to be younger, more likely to have a college degree, and had lived in the region for less time than paper participants. For all but one attribute there was no difference in the spatial distribution of places mapped between Internet and paper methods. Using a paper‐based PPGIS survey resulted in a higher response rate, reduced participant bias, and greater mapping participation. However, survey mode did not influence the spatial distribution of the PPGIS data. 相似文献