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  • Articles  (17,942)
  • Wiley  (15,651)
  • Public Library of Science  (1,517)
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  • Articles  (17,942)
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  • 2010-2014  (17,942)
  • 1980-1984
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  • 1
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    Quantitative Trait Loci Affecting Oil Content, Oil Composition, and Other Agronomically Important Traits in Oat (2012)
    Wiley
    Details
    Publication Date: 2012-11-01
    Electronic ISSN: 1940-3372
    Topics: Biology
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  • 2
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    Genomic Characterization for Parasitic Weeds of the Genus Striga by Sample Sequence Analysis (2012)
    Wiley
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    Publication Date: 2012-03-01
    Electronic ISSN: 1940-3372
    Topics: Biology
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  • 3
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    Growing The Plant Genome in 2013 (2012)
    Wiley
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    Publication Date: 2012-11-01
    Electronic ISSN: 1940-3372
    Topics: Biology
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  • 4
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    Research Highlights (2012)
    Wiley
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    Publication Date: 2012-11-01
    Electronic ISSN: 1940-3372
    Topics: Biology
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  • 5
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    Experimental warming alters spring phenology of certain plant functional groups in an early‐successional forest community (2012)
    Wiley
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    Publication Date: 2012
    Description: Abstract Experimental study of the effects of projected climate change on plant phenology allows us to isolate effects of warming on life history events such as leaf out. We simulated a 2°C temperature increase and 20% precipitation increase in a recently harvested temperate deciduous forest community in central Pennsylvania, USA, and observed the leaf out phenology of all species in 2009 and 2010. Over 130 plant species were monitored weekly in study plots, but due to high variability in species composition among plots, species were grouped into five functional groups: short forbs, tall forbs, shrubs, small trees, and large trees. Tall forbs and large trees, which usually emerge in the late spring, advanced leaf out 14‐18 days in response to warming. Short forbs, shrubs, and small trees emerge early in spring and did not alter their phenology in response to warming or increased precipitation treatments. Earlier leaf out of tall forbs and large trees coincided with almost three weeks of increased community‐level leaf area index (LAI), indicating greater competition and a condensed spring green‐up period. While phenology of large trees and tall forbs appears to be strongly influenced by temperature‐based growth cues, our results suggest that photoperiod and chilling cues more strongly influence the leaf out of other functional groups. Reduced freeze events and warmer temperatures from predicted climate change will interact with non‐temperature growth cues to have cascading consequences throughout the ecosystem.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 6
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    High Piezoelectric Properties of KNN-Based Thick Films with Abnormal Grain Growth (2012)
    Wiley
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    Publication Date: 2012-03-09
    Description: Over 10 μm-thick ( K , N a) N b O 3 KNN -based films doped with complex-perovskite-materials (CPs) were deposited on platinized sapphire substrates by aerosol deposition (AD). Three CPs were selected: B a( C u 1/3 N b 2/3 ) O 3 ( BCN ), C u( C u 1/3 N b 2/3 ) O 3 ( CCN ), and S r( C u 1/3 N b 2/3 ) O 3 ( SCN ). The films of 0.985( N a 0.5 K 0.5 ) N b O 3 -0.015CPs ( KNN -CPs) were post annealed at 1050°C for 1 h in air without any serious phase decomposition. The microstructure showed abnormal grain growth due to C u-rich liquid phase. The KNN – BCN film had the largest abnormal grain size of over 10 μm, whereas the KNN – SCN film had the smallest grain size and also the smallest frequency of abnormal grains. All the films exhibited typical characteristics of ferroelectric hysteresis similar to those of the bulk materials without any leakage. The KNN – BCN films possessing the biggest abnormal grains also exhibited the highest density, piezoelectric constant, and piezoelectric voltage constant of 110 pC/N and 15.45 × 10 −3  Vm/N, respectively, which are the highest values reported so far for KNN -based films. This indicated that KNN -CPs lead-free films are suitable candidates for sensor applications.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
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    Large wood export regulated by the pattern and intensity of precipitation along a latitudinal gradient in the Japanese archipelago (2012)
    Wiley
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    Publication Date: 2012-03-09
    Description: We examined the relationships between large wood (LW) export and precipitation patterns and intensity by analyzing the data on the annual volume of LW removed from 42 reservoirs and the daily precipitation at or near the reservoir sites. We also calculated the effective precipitation by considering the antecedent precipitation. Both daily and effective precipitation data were used as explanatory variables to explain LW export. The model selection revealed that the precipitation pattern and intensity controlling LW export varied with latitude in the Japanese archipelago. In small watersheds with narrow channel widths and low discharges, mass movements, such as landslides and debris flows, are major factors in the production and transport of LW. In this case, the effective precipitation required to initiate mass movements regulated the LW export and did not vary with the latitude. In intermediate and large watersheds with wide channel widths and high stream discharges, heavy rainfall and subsequent floods regulated buoyant depth, influencing the initiation of LW movement. In southern and central Japan, intense rainfall accompanied by typhoons or localized torrential downpours causes geomorphic disturbances, which introduce abundant pieces of LW into the channels. However, these pieces continue to be removed by repeated rainfall events. Therefore, LW export is supply-limited and potentially produces less LW accumulation. Conversely, in northern Japan, where typhoons and torrential downpours are rare, LW export is transport-limited because LW pieces recruited by bank erosion, tree mortality, and windthrow accumulate and persist on valley floors. These pieces may be easily exported by infrequent flooding.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Continuous in situ measurements of stable isotopes in liquid water (2012)
    Wiley
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    Publication Date: 2012-03-09
    Description: We developed a method to measure in situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a microporous hydrophobic membrane contactor (Membrana) was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with N2 as a carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the Picarro analyzer. To prove the membrane's applicability, we determined the specific isotope fractionation factor for the phase change through the contactor's membrane across an extended temperature range (8°C–21°C) and with different waters of known isotopic compositions. This fractionation factor is needed to subsequently derive the liquid water isotope ratio from the measured water vapor isotope ratios. The system was tested with a soil column experiment, where the isotope values derived with the new method corresponded well (R2 = 0.998 for δ18O and R2 = 0.997 for δ2H) with those of liquid water samples taken simultaneously and analyzed with a conventional method (cavity ring-down spectroscopy). The new method supersedes taking liquid samples and employs only relatively cheap and readily available components. This makes it a relatively inexpensive, fast, user-friendly, and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real-time isotope data of liquid water are required at high temporal resolution.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 9
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    Flow path depth is the main controller of mean base flow transit times in a mountainous catchment (2012)
    Wiley
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    Publication Date: 2012-03-09
    Description: Transit time of discharge is a hydrological characteristic used in water resource management. Previous studies have demonstrated large spatial variation in the mean transit time (MTT) of stream base flow in meso-scale catchments. Various relationships between topography and MTT have been reported. Although it is generally assumed that base flow MTT is controlled by the depth of the hydrologically active layer that recharges a stream, this hypothesis has not been tested in field studies. This study confirmed that the depth of hydrologically active soil and bedrock controls spatial variation in MTT. The study used isotopic and geochemical tracer data gathered in the 4.27 km2 Fudoji catchment, central Japan. The results, together with previously documented relationships between topography and MTT, indicate that the depth of the hydrologically active layer is sometimes, but not always, related to topography. A comprehensive understanding of the factors that control base flow production in mountainous catchments will require further study of the water flow path depths that recharge streams.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 10
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    Predicting tropical insect herbivore abundance from host plant traits and phylogeny (2012)
    Wiley
    In: Ecology
    Details
    Publication Date: 2012-03-10
    Description: Ecology, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 11
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    Temporal variability of hydroclimatic extremes in the Blue Nile basin (2012)
    Wiley
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    Publication Date: 2012-03-10
    Description: This paper examines the long-term historical changes in frequency and amplitude of hydroclimatic extremes in the Blue Nile basin using data from the second half of 20th century. The temporal variability of basin-wide rainfall extremes and river flow extremes from four gauging stations was investigated under the hypothesis of no trend and no persistence in time. On the basis of a quantile anomaly analysis method, decadal variations in extreme daily, monthly, and annual quantiles were studied, and the periods of statistical significance were identified. The analysis showed that high and low river flows and rainfall depths do not vary in time in a fully random way but show a particular variation pattern. Their extremes show significant decadal variations. The 1980s had statistically significant negative anomalies in extremes in comparison with the long-term reference period of 1964–2009, while the 1960s–1970s and the 1990s–2000s had positive anomalies, although less significant. There is neither consistent increasing nor decreasing trend in rainfall and flow extremes of recent years. Therefore, anticipated trends due to global warming could not be identified. Conversely, low-flow extremes show an increasing trend during the last decade, which could be related to the effect of water regulation works at the outlet of Lake Tana. Moreover, similar patterns and statistically significant correlations were found between climatic indices representing the Pacific and Atlantic Oceans and the Blue Nile rainfall and flow extremes. Changes that occur on the Pacific Ocean appear to be a main driver for the decadal oscillations in climate and related high and low Blue Nile water availability for Ethiopia, Sudan, and Egypt.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 12
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    Quantification of Oxide Inclusions and Porosity Structure in a Tantalum Carbide Microstructure Fabricated From Carbothermal Reduced Tantalum Oxide Precursor Powders (2012)
    Wiley
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    Publication Date: 2012-03-09
    Description: The oxide inclusion and porosity defect structures in a tantalum carbide specimen fabricated from vacuum plasma spraying with postspraying sintering and hot-isostatic pressing has been characterized. The tantalum carbide powders were obtained using a carbothermal reduction process of tantalum oxide precursors. During its fabrication, oxide-based inclusions formed from intrinsic impurities in the powder. Using serial sectioning and three-dimensional reconstruction techniques, interconnected globular oxide inclusions were revealed to be within the matrix phase and in the grain boundaries. The oxide phase was identified to be z -Ta 2 O 5 through selected area electron diffraction. The two- and three-dimensional porosity size distribution was compared and accounted for ~2% of the volume.
    Print ISSN: 1546-542X
    Electronic ISSN: 1744-7402
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 13
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    Testing a pyroclimatic hypothesis on the México-U.S. border (2012)
    Wiley
    In: Ecology
    Details
    Publication Date: 2012-02-24
    Description: Ecology, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 14
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    Influence of landscape change on nearshore fisheries in southern Chile (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: At least half of the world's population resides in the coastal zone and the livelihoods of billions of people are affected either directly or indirectly by the production and sustainability of nearshore fisheries. Landscape change, specifically development of tree plantations, is accelerating worldwide as developing countries integrate into global markets to sell goods, offer climate-mitigation services (carbon), and/or provide renewable energy. These changes can release excess nutrients into adjacent coastal waters causing eutrophication that alters the structure and function of coastal ecosystems. This study examined the relationship between coastal drainage basin land use/ land cover change (LCLUC), specifically development of tree plantations, patterns of chlorophyll a in nearshore coastal waters, and the biological condition of commercially important shellfish, Concholepas concholepas ( loco ) in southern Chile. Locos (N= 1,374) were sampled across 13 watersheds (35,853 km 2 ) and 42 fisheries management areas (spanning 250 km of coastline). Locos harvested from management areas influenced by tree plantations had approximately 30% more endobiont (shell-boring) phoronids, almost twice as many endobiont polychaetes and twice as many epibiont (shell-attaching) barnacles than locos from areas in close proximity to watersheds dominated by native forests (15-20% of the watershed). Phoronid infested locos from coastal waters adjacent to watersheds with tree plantations were of relatively poor biological condition (smaller and narrower in width) and of reduced market value. Our study suggests that tree plantations result in indirect ecological impacts to coastal fisheries (more nutrients and higher phytoplankton biomass, resulting in smaller, low quality locos), and costs are born by coastal fishers (lower prices for locos). Increases in tree plantations could thus potentially significantly impact coastal fisheries worldwide and such problems should be managed as an interconnected network of land use change, oceanic ecosystems, and economic systems that are considered an integrated socio-ecological system.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 15
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    Rapid loss of glacial ice reveals stream community assembly processes (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: Glacial retreat creates new habitat which is colonised and developed by plants and animals during the process of primary succession. While there has been much debate about the relative role of deterministic and stochastic processes during terrestrial succession, evidence from freshwater ecosystems remains minimal and a general consensus is lacking. Using a unique 27 year record of community assembly following glacial recession in southeast Alaska, we demonstrate significant change in the trait composition of stream invertebrate communities as catchment glacial cover decreased from 〉70% to zero. Functional diversity increased significantly as glacier cover decreased and taxonomic richness increased. Null modelling approaches led to a key finding that niche filtering processes were dominant when glacial cover was extensive, reflecting water temperature and dispersal constraints. Thereafter the community shifted towards co-occurrence of stochastic and deterministic assembly processes. A further novel discovery was that intrinsic functional redundancy developed throughout the study, particularly because new colonisers possessed similar traits to taxa already present. Rapid glacial retreat is occurring in Arctic and alpine environments worldwide and the assembly processes observed in this study provide new fundamental insights into how glacially influenced stream ecosystems will respond. These findings support tolerance as a key primary successional mechanism in this system, and have broader value for developing our understanding of how biological communities in river ecosystems assemble or restructure in response to environmental change.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 16
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    Large scale rainfall simulation to investigate infiltration processes in a small landslide under dry initial conditions: the Draix hillslope experiment (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: Few studies exist on infiltration processes in badlands, although infiltration and subsurface lateral flows are known to contribute to soil erosion and to control slope instability. Our investigation was carried out in a 100 m² plot located in a 0.5 ha landslide in black marls (South-East France). An artificial sprinkling was performed with an intensity of 10 mm.h -1 during 66.4 h interrupted with 8.4 h. breaks. KBr and KCl were used as tracers. A pseudo-steady state was reached after 25-35 hours and 250-350 mm of rainfall. The runoff coefficient was 40% (ratio total runoff volume/total sprinkling water amount). Pre-event water (PE) contributed to the groundwater recharge at the very beginning of the experiment but PE contribution dropped steadily while the soil was saturating. After around 200 mm cumulative rainfall, PE contribution started to rise steeply before reaching a nearly constant value. This original mechanism implies an efficient transfer process of PE. It was assumed from the description of the material structure and from hydrological evidences that PE was mainly drained from a structure porosity made of the marl's flaked nature. Total pre-event water contributions ranged from 25 to 79 % (PE contribution was over 50 % in 2/3 of the observations wells). Over the recession phase, release of pre-event water occurred from the drainage of a texture porosity. The study showed that at the plot scale, infiltration processes proved well organised despite the high heterogeneity and anisotropy of the material. It was possible to propose a general conceptual model explaining the hydrological processes over time and area. The peculiar structure of regolith originating from black marl is preserved over a large part of the weathering time, so that the material structure (type, orientation of grains, small/large pores) remains a first order control of water flow generation in Black marl soils. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 17
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    Selecting the best IDF model by using the multifractal approach (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: In this work, the multifractal properties of hourly rainfall data recorded at a location in Southern Spain have been related to the scale properties of the corresponding Intensity-Duration-Frequency (IDF) curves. Four parametric models for the IDF curves have been fitted to the quantiles of rainfall obtained by using the Generalized Pareto frequency distribution function with the extreme data series obtained for the same place. The scaling of the rainfall intensity moments has been analysed and the empirical moments scaling exponent function has been obtained. The corresponding values of q 1 and γ 1 have been empirical and theoretically calculated and compared to some characteristics of the different IDF models. Thus, the scaling behaviour of IDF curves has been analysed and the best model has been selected. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 18
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    Which cropland greenhouse gas mitigation options give the greatest benefits in different world regions? Climate and soil specific predictions from integrated empirical models. (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: Major sources of greenhouse gas (GHG) emissions from agricultural crop production are nitrous oxide (N 2 O) emissions resulting from the application of mineral and organic fertiliser, and carbon dioxide (CO 2 ) emissions from soil carbon losses. Consequently, choice of fertiliser type, optimising fertiliser application rates and timing, reducing microbial denitrification and improving soil carbon management are focus areas for mitigation. We have integrated separate models derived from global data on fertiliser induced soil N 2 O emissions, soil nitrification inhibitors, and the effects of tillage and soil inputs of soil C stocks into a single model in order to determine optimal mitigation options as a function of soil type, climate, and fertilisation rates. After Monte Carlo sampling of input variables we aggregated the outputs according to climate, soil and fertiliser factors to consider the benefits of several possible emissions mitigation strategies, and identified the most beneficial option for each factor class on a per hectare basis. The optimal mitigation for each soil-climate-region was then mapped to propose geographically specific optimal GHG mitigation strategies for crops with varying N requirements. The use of empirical models reduces the requirements for validation (since they are calibrated on globally or continentally observed phenomena). However, since they are relatively simple in structure, they may not be applicable for accurate site specific prediction of GHG emissions. The value of this modelling approach is for initial screening and ranking of potential agricultural mitigation options and to explore the potential impact of regional agricultural GHG abatement policies. Given the clear association between management practice and crop productivity, it is essential to incorporate characterisation of the yield effect on a given crop before recommending any mitigation practice.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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  • 19
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    Carbon and oxygen cycles: Sensitivity to changes in environmental forcing in a coastal upwelling system (2012)
    Wiley
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    Publication Date: 2012-02-22
    Description: Biogeochemical cycles in the coastal ocean are changing and will continue to change in response to a changing climate. Effects on the oxygen and carbon cycles are particularly important, as either episodic or permanent shifts toward lower oxygen and/or higher inorganic carbon conditions can impact coastal ecosystems negatively. Here we study the sensitivity of these cycles to changes that may occur in the coastal ocean, focusing on a summer wind-driven upwelling region off southern Vancouver Island shelf. We use a quasi 2-D configuration of the Regional Ocean Modeling System (ROMS) to perform six sensitivity experiments. Results indicate that carbon and oxygen cycles in this region may be significantly affected by an altered upwelling season, a shallower offshore Oxygen Minimum Zone, and a carbon-enriched environment. Combinations of these scenarios suggest a potentially increasing risk for the development of coastal hypoxia and corrosive conditions in the region.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 20
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    Inference of riverine nitrogen processing from longitudinal and diel variation in dual nitrate isotopes (2012)
    Wiley
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    Publication Date: 2012-02-24
    Description: Longitudinal and diel measurements of dual isotope composition (δ15N and δ18O) in nitrate (NO3-N) were made in the Ichetucknee River, a large (∼8 m3 s−1), entirely spring-fed river in North Florida, to determine whether isotopic variation can deconvolve assimilatory and dissimilatory removal. Comparing nitrate concentrations and isotope composition during the day and night we predicted (1) daytime declines in total fractionation due to low assimilatory fractionation and (2) diurnal variation in dual isotope coupling between 1:1 (assimilation) and 2:1 (denitrification). Five daytime longitudinal transects comprising 10 sampling stations showed consistent NO3-N removal (25–35% of inputs) and modest fractionation (15εtotal between −2 and −6‰, enriching the residual nitrate pool). Lower fractionation (by ∼1‰) during two nighttime transects, suggests higher fractionation due to assimilation than denitrification. Total fractionation was significantly negatively associated with discharge, input [NO3-N], N mass removal, and fractional water loss. Despite well-constrained mass balance estimates that denitrification dominated total N removal, isotope coupling was consistently 1:1, both for longitudinal and diel sampling. Hourly samples on two dates at the downstream location showed significant diel variation in concentration ([NO3-N] amplitude = 60 to 90 μg N L−1) and isotope composition (δ15N amplitude = −0.7‰ to −1.6‰). Total fractionation differed between day and night only on one date but estimated assimilatory fractionation assuming constant denitrification was highly variable and implausibly large (for N, 15ε = −2 to −25‰), suggesting that fractionation and removal due to denitrification is not diurnally constant. Pronounced counterclockwise hysteresis in the relationship between [NO3-N] and δ15N suggests diel variation in N isotope dynamics. Together, low fractionation, isotope versus concentration hysteresis, and consistent 1:1 isotope coupling suggests that denitrification is controlled by NO3− diffusion into the benthic sediments, the length of which is mediated by riverine oxygen dynamics. While using dual isotope behavior to deconvolve removal pathways was not possible, isotope measurements did yield valuable information about riverine N cycling and transformations.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
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  • 21
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    Multi-Phase Glass-Ceramics as a Waste Form for Combined Fission Products: Alkalis, Alkaline Earths, Lanthanides, and Transition Metals (2012)
    Wiley
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    Publication Date: 2012-02-24
    Description: In this study, multi-phase borosilicate-based glass-ceramics were investigated as an alternative waste form for immobilizing non-fissionable products from used nuclear fuel. Currently, borosilicate glass is the waste form selected for immobilization of this waste stream, however, the low thermal stability and solubility of MoO 3 in borosilicate glass translates into a maximum waste loading in the range 15–20 mass%. Glass-ceramics provide the opportunity to target chemically durable crystalline phases, e.g., powellite, oxyapatite, celsian, and pollucite that will incorporate MoO 3 as well as other waste components such as lanthanides, alkalis, and alkaline earths at levels twice the solubility limits of a single-phase glass. In addition a glass-ceramic could provide higher thermal stability, depending upon the properties of the crystalline and amorphous phases. Here, glass-ceramics were synthesized at waste loadings of 42, 45, and 50 mass% with the following glass additives: B 2 O 3 , Al 2 O 3 , CaO , and SiO 2 by slow-cooling from a glass melt. Glass-ceramics were characterized in terms of phase assemblage, morphology, and thermal stability. Only two of the targeted phases, powellite and oxyapatite, were observed, along with lanthanide-borosilicate and cerianite. Results of this initial investigation show promise of glass-ceramics as a potential waste form to replace single-phase borosilicate glass.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 22
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    Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation (2012)
    Wiley
    Details
    Publication Date: 2012-02-25
    Description: Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of δDCH4 emissions from Siberian and North American lakes. δDCH4 reflects regionally varying δD values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes. We found that Alaskan thermokarst lake δDCH4 was higher (−334 ± 17‰) than Siberian lake δDCH4 (−381 ± 18‰). Weighted mean δDCH4 values for Beringian lakes ranged from −385‰ to −382‰ over the deglacial period. Bottom-up estimates suggest that Beringian thermokarst lakes contributed 15 ± 4 Tg CH4 yr−1 to the atmosphere during the Younger Dryas and 25 ± 5 Tg CH4 yr−1 during the Preboreal period. These estimates are supported by independent, top-down isotope mass balance calculations based on ice core δDCH4 and δ13CCH4 records. Both approaches suggest that thermokarst lakes and boreal wetlands together were important sources of deglacial CH4.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
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    Dielectric Properties of the Bismuth Neodymium Titanate Pyrochlore Solid Solution (2012)
    Wiley
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    Publication Date: 2012-02-25
    Description: The dielectric properties of a new, cubic, pyrochlore-type solid solution B i (1.6−1.08 x ) N d x T i 2 O (6.4−0.11 x ) have been studied across the compositional range 0.35 〈  x  〈 0.86. The dielectric constant (ε) of the ceramics based on the pyrochlore-type solid solution within the experimental compositional range varied from 104 to 76 at 1 MHz, whereas the dielectric losses were well below tan δ = 8 × 10 −3 . The temperature coefficient of the dielectric constant τ k for single-phase pyrochlore samples was found to be in the range between −20 and −40 ppm/K. Below room temperature dielectric relaxation phenomena were observed for all the compositions.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    The Mechanism of Core/Shell Structure Formation during Sintering of BaTiO3-Based Ceramics (2012)
    Wiley
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    Publication Date: 2012-02-25
    Description: The mechanism of core/shell formation during sintering in B a T i O 3 -based systems was studied in ( M g, Y )-doped B a T i O 3 . The effect of ball milling time on core size and shell thickness was first observed. The core size was similar irrespective of ball milling time whereas the shell thickness increased with increasing ball milling time. The measured powder size after ball milling suggested that the cores were from the larger B a T i O 3 particles and the shells formed via dissolution of smaller particles and precipitation of dissolved material, in contrast with the interpretation of the results of a previous investigation. To identify the core/shell formation mechanism, bi-layer samples with different chemical compositions, 94 B a T i O 3 –2 Y 2 O 3 –2 M g O –2 S i O 2 (mol%) ( BT – YMS ) and 98 B a T i O 3 –2 S i O 2 (mol%) ( BT – S ), and different grain sizes were prepared. The morphology of the newly formed shell layer and the shape of an {111} twin across the interface between a core and a shell confirmed that the formation mechanism of the core/shell structure during sintering is the dissolution and precipitation of material rather than solid-state diffusion of solutes into B a T i O 3 .
    Print ISSN: 0002-7820
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    Crystal Structures and Dielectric Properties of Bi2((Zn1/3Nb2/3)1−xTix)2O7 Ceramics (2012)
    Wiley
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    Publication Date: 2012-02-25
    Description: B i 2 (( Z n 1/3 N b 2/3 ) 1− x T i x ) 2 O 7 ceramics with 0 ≤  x  ≤ 0.4 were synthesized using solid-state reaction method. The crystal structure is pure zirconolite type for the compositions with 0 ≤  x  ≤ 0.15, single weberite type for the compositions with 0.3 ≤  x  ≤ 0.4, and mixture of zirconolite and weberite for the compositions with 0.15 〈  x  〈 0.3. The weberite ceramics with only B i as the A-site cation are first reported. A possible correlation between the crystal structure transformation and T i content in system of B i 2 (( Z n 1/3 N b 2/3 ) 1− x T i x ) 2 O 7 with 0 ≤  x  ≤ 0.4 was suggested. Dielectric constant (ε), dielectric loss (tan δ) and temperature coefficient of capacitance (TCC) are ~85, ~0.001, and ~200 ppm/°C for the zirconolite solid solutions, ~140, 0.004, and between −120 and −200 ppm/°C for the weberite solid solutions, respectively, at 1 MHz. Ceramics with a near zero TCC consisting of the zirconolite and weberite phases were obtained. High ε, low tanδ, and low sintering temperatures (~950°C) make the novel ceramic system of B i 2 (( Z n 1/3 N b 2/3 ) 1− x T i x ) 2 O 7 potential dielectrics for applications in low-temperature co-fired ceramic and multiplayer ceramic capacitors.
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    Spark Plasma Sintering and Hot Pressing of Hetero-Doped LaNbO4 (2012)
    Wiley
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    Publication Date: 2012-02-25
    Description: LaNbO 4 / La 3 NbO 7 and LaNbO 4 / LaNb 3 O 9 cer-cer composites were prepared by impregnating Ca -doped LaNbO 4 powder, synthesized by spray pyrolysis, with La - or Nb -precursor solutions. The sintering of the calcined powders was investigated by dilatometry, and dense composites were prepared by conventional sintering, hot pressing, and spark plasma sintering. The particle size of the starting powders was about 50 nm, and the average grain size of the dense materials ranged from 100 nm and upwards, depending on the sintering temperature, sintering procedure, and the phase composition. The unit cell parameters of LaNbO 4 showed a finite size effect and approached the cell parameters of tetragonal LaNbO 4 with decreasing crystallite size, both for the single-phase material and the composites. The minority phase ( La 3 NbO 7 or LaNb 3 O 9 ) were observed as isolated grains and accumulated at triple points and not along the grain boundaries, pointing to a large dihedral angle between the phases. The calcium-solubility in the minority phases was larger than in LaNbO 4 , which corresponds well with previous reports. The electrical conductivity of the hetero-doped materials was similar to, or lower than, that for Ca -doped LaNbO 4 .
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    Nucleation and Growth of Nanocrystals in Glass-Ceramics: An In Situ SANS Perspective (2012)
    Wiley
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    Publication Date: 2012-02-25
    Description: We studied the nucleation and growth of nano-sized crystals on two glass-ceramic systems: a conventional lithium-aluminosilicate (LAS) and a ( M g, Z n) spinel. We combined several techniques: in situ Small Angle Neutron Scattering (SANS), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and laboratory X-ray diffraction (XRD). We observed by SANS, and confirmed by DSC, that during a temperature ramp, transient phenomena occur between the regions of nucleation and growth in the LAS, which do not follow classic kinetic theories. In contrast, the spinel material shows a smooth transition during the temperature ramp between the nucleation and the growth stages, and follows a more conventional growth pattern. In the spinel system the initial phase separation plays a very important role in determining the crystalline phase distribution in the glassy matrix, as crystallites are confined only in one phase.
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    In-vitro Degradation and Bioactivity of Tailored Amorphous Multi Porous Scaffold Structure (2012)
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    Publication Date: 2012-02-25
    Description: A key requirement for the use of bio scaffold is that its degradation rate matches the growth rate of target tissue. Therefore, the degradation of recently developed tailored amorphous multiporous (TAMP) scaffold of 70 SiO 2 ·30 CaO (mol%) in simulated body fluid (SBF) was studied under both static and quasi-dynamic conditions. The degradation was assessed through the dissolution of silica from the glass into SBF, while the in-vitro bioactivity was characterized by precipitation of calcium phosphate ( CaP ) on and inside the scaffold. Under static conditions, the degradation stopped due to the saturation of solution with silica in 3 days, whereas the precipitation of CaP continued. Rapid degradation and better in-vitro bioactivity was found under quasi-dynamic conditions, where the concentration gradient across the sample was maintained. The degradation followed exponential dependence on time with a half-life of 15.4 days and initial degradation rate 4.5% day −1 . The remaining samples maintained their integrity and pore structure during degradation. The degradation occurred in three distinct stages: (a) wetting stage, (b) initial degradation stage when CaP precipitation dominates, and (c) intensive degradation stage when the nanopores rupture and network dissolves. By varying the sintering parameters the nanopore structure, and hence the degradation rate, can be tailored to suit the anticipated tissue regeneration rate. With demonstrated rapid and controllable degradation and good in-vitro bioactivity, the TAMP scaffold shows promise as candidate for bone regeneration application under various conditions in the body.
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    The role of terrestrial vegetation in atmospheric Hg deposition: Pools and fluxes of spike and ambient Hg from the METAALICUS experiment (2012)
    Wiley
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    Publication Date: 2012-03-13
    Description: As part of the Mercury Experiment to Assess Atmospheric Loading in Canada and the U.S. (METAALICUS), different stable Hg(II) isotope spikes were applied to the upland and wetland areas of a boreal catchment between 2001 and 2006 to examine retention of newly deposited Hg(II). In the present study, a Geographical Information Systems (GIS)-based approach was used to quantify canopy and ground vegetation pools of experimentally applied upland and wetland spike Hg within the METAALICUS watershed over the terrestrial loading phase of the experiment. A chemical kinetic model was also used to describe the changes in spike Hg concentrations of canopy and ground vegetation over time. An examination of the fate of spike Hg initially present on canopy vegetation using a mass balance approach indicated that the largest percentage flux from the canopy over one year post-spray was emission to the atmosphere (upland: 45%; wetland: 71%), followed by litterfall (upland: 14%; wetland: 10%) and throughfall fluxes (upland: 12%; wetland: 9%) and longer term retention of spike in the forest canopy (11% for both upland and wetland). Average half-lives (t1/2) of spike on deciduous (110 ± 30 days) and coniferous (180 ± 40 days) canopy and ground vegetation (890 ± 620 days) indicated that retention of new atmospheric Hg(II) on terrestrial (especially ground) vegetation delays downward transport of new atmospheric Hg(II) into the soil profile and runoff into lakes.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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    Soil respiration under climate change: Prolonged summer drought offsets soil warming effects (2012)
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    Publication Date: 2012-03-14
    Description: Climate change may considerably impact the carbon (C) dynamics and C stocks of forest soils. To assess the combined effects of warming and reduced precipitation on soil CO 2 efflux, we conducted a two-way factorial manipulation experiment (4 °C soil warming + throughfall exclusion) in a temperate spruce forest from 2008 until 2010. Soil was warmed by heating cables throughout the growing seasons. Soil drought was simulated by throughfall exclusions with three 100 m 2 roofs during 25 days in July/August 2008 and 2009. Soil warming permanently increased the CO 2 efflux from soil whereas throughfall exclusion led to a sharp decrease in soil CO 2 efflux (45% and 50% reduction during roof installation in 2008 and 2009, respectively). In 2008, CO 2 efflux did not recover after natural rewetting and remained lowered until autumn. In 2009, CO 2 efflux recovered shortly after rewetting, but relapsed again for several weeks. Drought offset the increase in soil CO 2 efflux by warming in 2008 (growing season CO 2 efflux in t C ha −1 : control: 7.1 ± 1.0; warmed: 9.5 ± 1.7; warmed + roof: 7.4 ± 0.3; roof: 5.9 ± 0.4) and in 2009 (control: 7.6 ± 0.8; warmed + roof: 8.3 ± 1.0). Throughfall exclusion mainly affected the organic layer and the top 5 cm of the mineral soil. Radiocarbon data suggest that heterotrophic and autotrophic respiration were affected to the same extent by soil warming and drying. Microbial biomass in the mineral soil (0 - 5 cm) was not affected by the treatments. Our results suggest that warming causes significant C losses from the soil as long as precipitation patterns remain steady at our site. If summer droughts become more severe in the future, warming induced C losses will likely be offset by reduced soil CO 2 efflux during and after summer drought.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Hydrogeochemical evolution of Ordovician limestone groundwater in Yanzhou, North China (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: Major-ion compositions of groundwater are employed in this study of the water-rock interactions and hydrogeochemical evolution within a carbonate aquifer system. The groundwater samples were collected from boreholes or underground tunnels in the Ordovician limestone of Yanzhou Coalfield where catastrophic groundwater inflows can be hazardous to mining and impact use of the groundwater as a water supply. The concentration of TDS ranged from 961 to 3,555 mg/l and indicates moderately to highly mineralized water. The main water-type of the middle Ordovician limestone groundwater is Ca-Mg-SO 4 , with SO 4 2- ranging from 537 mg/l to 2,297 mg/l, and average values of Ca 2+ and Mg 2+ of 455.7 mg/l and 116.6 mg/l, respectively. The water samples were supersaturated with respect to calcite and dolomite and undersaturated or saturated with respect to gypsum. Along the general flow direction, deduced from increases of TDS and Cl - , the main water-rock interactions that caused hydrogeochemical evolution of the groundwater within the aquifer were the dissolution of gypsum, the precipitation of calcite, the dissolution or precipitation of dolomite, and ion exchange. Ion exchange is the major cause for the lower mole concentration of Ca 2+ than that of SO 4 2- . The groundwater level of Ordovician aquifer is much higher than that of C-P coal-bearing aquifers, so the potential flow direction is upward and the pyrite in coal is not a possible source of sulfate, additional data on the stable sulfur and oxygen isotopic composition of the sulfate may be helpful to identify its origin. Although ion exchange probably accounts for the higher mole concentration of Na + than that of Cl - , the dissolution of aluminosilicate can not be ruled out. The data evaluation methods and results of this study could be useful in other areas to understand flow paths in aquifers and to provide information needed to identify the origin of groundwater. Copyright © 2012 John Wiley & Sons, Ltd.
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    Radiocarbon and stable-isotope geochemistry of organic and inorganic carbon in Lake Superior (2012)
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    Publication Date: 2012-03-14
    Description: We present a lake-wide investigation of Lake Superior carbon and organic matter biogeochemistry using radiocarbon, stable isotope, and carbon concentrations. Dissolved inorganic carbon (DIC) abundance in the lake was 121–122 Tg C, with offshore concentration and δ13C values being laterally homogenous and tightly coupled to the physical and thermal regime and biochemical processes. Offshore Δ14C of DIC (50–65‰) exhibited lateral homogeneity and was more 14C enriched than co-occurring atmospheric CO2 (∼38‰); nearshore Δ14C of DIC (36–38‰) was similar to atmospheric CO2. Dissolved organic carbon (DOC) abundance was 14.2–16.4 Tg C. DOC's concentration and δ13C were homogenous in June (mixed lake), but varied laterally during August (stratification) possibly due to spatial differences in lake productivity. Throughout sampling, DOC had modern radiocarbon values (14–58‰) indicating a semilabile nature with a turnover time of ≤60 years. Lake particulate organic carbon (POC, 0.9–1.3 Tg C) was consistently 13C depleted relative to DOC. The δ15N of epilimnetic particulate organic nitrogen shifted to more negative values during stratification possibly indicating greater use of nitrate (rather than ammonium) by phytoplankton in August. POC's radiocarbon was spatially heterogeneous (Δ14C range: 58‰ to −303‰), and generally 14C depleted relative to DOC and DIC. POC 14C depletion could not be accounted for by black carbon in the lake but, because of its spatial and temporal distribution, is attributed to sediment resuspension. The presence of old POC within the epilimnion of the open lake indicates possible benthic-pelagic coupling in the lake's organic carbon cycle; the ultimate fate of this old POC bears further investigation.
    Print ISSN: 0886-6236
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    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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    Quantitative assessment of the impact of climate variability and human activities on runoff changes: a case study in four catchments of the Haihe River Basin, China (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: Quantitative evaluation of the effect of climate variability and human activities on runoff is of great importance for water resources planning and management in term of maintaining the ecosystem integrity and sustaining the society development. In this paper, hydro-climatic data from 4 catchments (i.e., Luanhe River Catchment, Chaohe River Catchment, Hutuo River Catchment and Zhanghe River Catchment) in the Haihe River Basin from 1957–2000 were used to quantitatively attribute the hydrological response (i.e., runoff) to climate change and human activities separately. To separate the attributes, the temporal trends of annual precipitation, potential evapotranspiration (PET) and runoff during 1957–2000 were first explored by the Man-Kendall test. Despite that only Hutuo River Catchment was dominated by significant negative trend in annual precipitation, all four catchments presented significant negative trend in annual runoff varying from −0.859 mm a -1 (Chaohe River) to −1.996 mm a -1 (Zhanghe River). Change points in 1977 and 1979 are detected by precipitation-runoff double cumulative curves method and Pettitt's test for Zhanghe River and other three rivers, respectively, and are adopted to divide data set into two study periods as the pre-change period and post-change period. Three methods including hydrological model method, hydrological sensitivity analysis method and climate elasticity method were calibrated with the hydro-climatic data during the pre-change period. And then, hydrological runoff response to climate variability and human activities were quantitatively evaluated with the help of the three methods and based on the assumption that climate and human activities are the only drivers for streamflow and are independent to each other. Similar estimates of anthropogenic and climatic effects on runoff for catchments considered can be obtained from the three methods. We found that human activities were the main driving factors for the decline in annual runoff in Luanhe River Catchment, Chaohe River Catchment and Zhanghe River Catchment, accounting for over 50% of runoff reduction. However, Climate variability should be responsible for the decrease in annual runoff in the Hutuo River Catchment. Copyright © 2012 John Wiley & Sons, Ltd.
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    REMOVAL OF PATHOGENS BY RIVER BANK FILTRATION AT HARIDWAR, INDIA (2012)
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    Publication Date: 2012-03-14
    Description: Measurements of river water quality at Haridwar, India, taken during 2005 – 2006 show that the river water does not meet the WHO and Bureau of Indian Standards criteria of drinking water quality, especially with respect to total coliform and fecal-coliform. This study investigates the removal of pathogens at a river bank filtration (RBF) site in Haridwar. Using the quality of river water and the quality of abstracted water from a nearby production well, semi-empirical models based on the concept of filtration coefficient are developed and tested for their effectiveness in removing pathogens under varying bacteriological quality of source water. A two-tier model which includes the effect of clogged layer is developed to obtain an equivalent filtration coefficient. This coefficient is found to be linearly related with natural logarithm of the concentration of pathogens in the source water. Copyright © 2012 John Wiley & Sons, Ltd.
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    Hydrologic Impact of Roadside Ditches in an Agricultural Watershed in Central New York (2012)
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    Publication Date: 2012-03-14
    Description: Nonpoint source pollution and hydromodification are the leading causes of impairment to our nation's rivers and streams. Roadside ditch networks, ubiquitous in both rural and urban landscapes, intercept and shunt substantial quantities of overland runoff and shallow groundwater to stream systems. By altering natural flowpaths, road ditches contribute not only to hydromodification but also potentially to nonpoint-source (NPS) pollution by acting as hydrologic links between agricultural fields and natural streams. Unfortunately, the impacts of these alterations on watershed hydrology and water quality are not well understood. Through a series of field measurements, including field surveys and discharge monitoring, this study examined the effect of road ditch networks on basin morphometry, field- and watershed-scale hydrology, and pollutant transport in a 38 km 2 agricultural watershed in south-central NY. Salient findings include: (i) 94% of road ditches discharged directly to natural streams, effectively doubling the drainage density, (ii) on average, road ditches increased peak and total event flows in their receiving streams by 78% and 57%, respectively, but displayed significant variation across ditches, (iii) ditches intercepted large quantities of surface and subsurface runoff from agricultural fields and therefore represent efficient conduits for the transport of agricultural NPS pollutants to sensitive receiving waterbodies. Our results provide useful information for hydrologists who wish to further understand how artificial drainage may be affecting watershed hydrology and for managers and engineers tasked with designing appropriate flood and NPS pollution control measures. Copyright © 2012 John Wiley & Sons, Ltd.
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    Multi-scaled analysis of hydrothermal dynamics in Japanese megalopolis by using integrated approach (2012)
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    Publication Date: 2012-03-14
    Description: We coupled the process-based NIES Integrated Catchment-based Eco-hydrology (NICE) model to an urban canopy model (UCM) and the Regional Atmospheric Modeling System (RAMS) in order to simulate the effect of urban geometry and anthropogenic exhaustion on the hydrothermal changes in the atmospheric/land and the interfacial areas of the Japanese megalopolis. The simulation was conducted with multi-scale in horizontally regional–urban–point levels, and in vertically atmosphere–surface–unsaturated–saturated layers. The model reproduced reasonably the observed hydrothermal values by using ground-truth data in various types of natural/artificial land covers. The simulated results also suggested that the latent heat flux in new water-holding pavement (consisting of porous asphalt and water-holding filler made of steel by-products based on silica compound) has a strong impact on hydrologic cycle and cooling temperature in comparison with the observed heat budget by newly incorporating the effect of water amount on the heat conductivity in the pavement. Furthermore, the model predicted the hydrothermal changes under two types of land cover scenarios to promote evaporation and to reduce air temperature against heat island phenomenon. Finally, we evaluated the relationship between the effect of groundwater use to ameliorate the heat island and the effect of infiltration on the water cycle in the catchment. These procedures to integrate the multi-scaled model simulation with political scenario based on the effective management of water resources as heat sink/source would be very powerful approaches to recovering a sound hydrologic cycle and create thermally-pleasing environments in the megalopolis. Copyright © 2012 John Wiley & Sons, Ltd.
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    Soil profile evolution following land-use change: Implications for groundwater quantity and quality (2012)
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    Publication Date: 2012-03-14
    Description: Soil and vadose zone profiles are used as an archive of changes in groundwater recharge and water quality following changes in land use in an area of the Loess Plateau of China. A typical rain-fed loess-terrace agriculture region in Hequan, Guyuan is taken as an example and multiple tracers (chloride mass balance, stable isotopes, tritium, and water chemistry) are used to examine groundwater recharge mechanisms and to evaluate soil water chloride as an archive for recharge rate and water quality. Results show that groundwater recharge beneath natural uncultivated grassland, used as a baseline, is about 94–100 mm yr -1 and the time it takes for annual precipitation to reach water table through the thick unsaturated zone is from decades to hundreds of years (tritium free). This recharge rate is 2–3 orders of magnitude more than in the other semiarid areas with similar annual rainfall and with deep rooted vegetation and relatively high temperature. Most of the water that eventually becomes recharge originally infiltrated in the summer months. The conversion from native grassland to winter wheat has reduced groundwater recharge by 42–50% (50–55 mm yr -1 for recharge), and from winter wheat to alfalfa resulted in a significant chloride accumulation in the upper soil zone which terminated deep drainage. The paper also evaluates the time lag between potential recharge and actual recharge to aquifer and between increase in solute concentration in soil moisture and that in the aquifer following land-use change due to the deep unsaturated zone. Copyright © 2012 John Wiley & Sons, Ltd.
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    Impacts of upland open drains upon runoff generation: a numerical assessment of catchment-scale impacts (2012)
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    Publication Date: 2012-03-14
    Description: Shallow upland drains, grips, have been hypothesized as responsible for increased downstream flow magnitudes. Observations provide counterfactual evidence, often relating to the difficulty of inferring conclusions from statistical correlation and paired catchment comparisons; and the complexity of designing field experiments to test grip impacts at the catchment-scale. Drainage should provide drier antecedent moisture conditions, providing more storage at the start of an event; but, grips have higher flow velocities than overland flow so potentially delivering flow more rapidly to the drainage network. We develop and apply a model for assessing the impacts of grips upon flow hydrographs. The model was calibrated on the gripped case; then the gripped case was compared with the intact case by removing all grips. This comparison showed that even given parameter uncertainty, the intact case had significantly higher flood peaks and lower baseflows, mirroring field observations of the hydrological response of intact peat. The simulations suggest that this is because delivery effects may not to translate into catchment-scale impacts for three reasons. First, in our case, the proportions of flow path lengths that were hillslope were not changed significantly by gripping. Second, the structure of the grip network as compared with the structure of the drainage basin mitigated against grip-related increases in the concentration of runoff in the drainage network, although it did marginally reduce the mean timing of that concentration at the catchment outlet. Third, the effect of the latter upon downstream flow magnitudes can only be assessed by reference to the peak timing of other tributary basins, emphasizing that drain effects are both relative and scale dependent. However, given the importance of hillslope flow paths, we show that if upland drainage causes significant changes in surface roughness on hillslopes, then critical and important feedbacks may impact upon the speed of hydrological response. Copyright © 2012 John Wiley & Sons, Ltd.
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    The dynamics of natural pipe hydrological behaviour in blanket peat (2012)
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    Publication Date: 2012-03-14
    Description: Natural soil pipes are found in peatlands but little is known about their hydrological role. This paper presents the most complete set of pipe discharge data to date from a deep blanket peatland in northern England. In a 17.4-ha catchment, we identified 24 perennially-flowing and 60 ephemerally-flowing pipe outlets. Eight pipe outlets along with the catchment outlet were continuously gauged over an 18-month period. The pipes in the catchment were estimated to produce around 13.7 % of annual streamflow with individual pipes often producing large peak flows (maximum peak of 3.8 L s -1 ). Almost all pipes, whether ephemeral, perennially-flowing, shallow or deep (outlets 〉 1 m below the peat surface), showed increased discharge within a mean of 3 hours after rainfall commencement and were dominated by stormflow, indicating good connectivity between the peatland surface and the pipes. However, almost all pipes had a longer time period between hydrograph peak and return to baseflow compared to the stream (mean of 23.9 hours for pipes, 19.7 hours for stream). As a result, the proportion of streamflow produced by the pipes at any given time increased at low flows and formed the most important component of stream discharge for the lowest 10 % of flows. Thus, a small number of perennially-flowing pipes became more important to the stream system under low flow conditions and probably received water via matrix flow during periods between storms. Given the importance of pipes to streamflow in blanket peatlands, further research is required into their wider role in influencing stream-water chemistry, water temperature and fluvial carbon fluxes, as well as their role in altering local hydrochemical cycling within the peat mass itself. Enhanced piping within peatlands caused by environmental change may lead to changes in streamflow regime with larger low flows and more prolonged drainage of the peat. Copyright © 2012 John Wiley & Sons, Ltd.
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    Topics: Architecture, Civil Engineering, Surveying , Geography
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    Seasonal and monthly hydrological budgets of a fen-dominated forested watershed, James Bay region, Quebec (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: The hydrology of Quebec (Canada) boreal fens is poorly documented. Many peatlands are located in watersheds with impounded rivers. In such cases, their presence influences reservoir inflows. In recent years, some fens have been subjected to an increase of their wet area, a sign that they may be evolving towards an aquatic ecosystem. This dynamic process is referred to as aqualysis. This paper presents the seasonal and monthly hydrological budgets of a small watershed including a highly aqualysed fen (James Bay region). Monitoring of precipitation ( P ), runoff ( Q ) and groundwater levels ( WL ) was conducted during the ice-free season. Three semi-empirical equations (Thornthwaite, Priestley-Taylor and Penman-Monteith) were used and compared to calculate potential evapotranspiration ( PET ). The first two equations, having fewer parameters, estimate higher PET values than the third equation. The use of pressure level gauges installed in wells, for the calculation of peatland water storage, is inconclusive. Swelling of peat, peat decomposition and plant composition could be responsible for non-negligible amounts of absorbed water, which are not entirely accounted for by well levels. The estimation of peat matrix water storage is potentially the largest source of error and the limiting factor to calculate water balances in this environment. The results show that the groundwater level and the water storage vary depending on the season and especially after a heavy rainfall. Finally, the results illustrate the complexity of water routing through the site and, thus, raise several questions to be resolved in the future. Copyright © 2012 John Wiley & Sons, Ltd.
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    Topics: Architecture, Civil Engineering, Surveying , Geography
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    Experimental Approaches to the Thermodynamics of Ceramics above 1500°C (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: Traditionally, the nuclear and aerospace industries have been the main drivers behind the development of high-temperature materials. These applications demand a high degree of reliability and extensive characterization of every new material. There is a lack of experimental thermodynamic data above 1500°C even for HfO 2 , ZrO 2 , La 2 O 3 , Y 2 O 3 , and other constituents of widely used ceramic systems. Such data, as are available, were often obtained half a century ago using custom-built instruments. We review classic experimental approaches for the measurement of formation enthalpies, high-temperature enthalpy increments by the drop method, and also discuss more recent developments which include mass spectrometric measurements of vapor pressures, pulsed laser relaxation methods for heat capacity, and melting temperature determination and high-temperature oxide melt solution calorimetry in application to refractory compounds. Approaches to the experimental determination of phase diagrams at high temperature are introduced using studies of liquid immiscibility in the Zr(O) –UO 2 system as an example. Thermal analysis above 2000°C is now possible with commercially available instruments, as shown by the first experimental measurements of the phase transition and fusion enthalpies of La 2 O 3 . New results on a premelting phase transition in Y 2 O 3 in oxygen are reported from in situ synchrotron X-ray diffraction study on levitated samples.
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    Nano-Hafnium Diboride Powders Synthesized Using a Spark Plasma Sintering Apparatus (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: Nano-hafnium diboride powder was synthesized by boro/carborthermal reduction process of HfO 2 using a spark plasma sintering (SPS) apparatus. The agglomerated product was found to be 1–2 μm in size, which was composed with small primary particles of 100–200 nm in size. The particle size of HfO 2 played an important role to produce the nano-boride powder. In addition, the grain growth of HfB 2 could be effectively suppressed by using SPS due to the fast heating rate. The synthesized powder had a low oxygen content (~0.66 wt%). Excessive B 4 C and C were necessary during the boro/carborthermal reduction in HfO 2 process because of the volatilization of boron as a form of B 2 O 3 and the reduction in residual HfO 2 .
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    Synthesis of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 by Controlled Agglomeration of Precursor Particles (2012)
    Wiley
    Details
    Publication Date: 2012-03-14
    Description: 0.65 Pb ( Mg 1/3 Nb 2/3 ) O 3 –0.35 PbTiO 3 powder was prepared by a single-step, solid-state synthesis at 850°C. This was enabled by the controlled agglomeration of precursor particles by the change of pH in water suspensions. With the design of the contacts between the particles in the agglomerates, a phase-pure perovskite powder was synthesized from a suspension with a pH = 12.5. At the inherent pH = 11.4, the agglomerates that promote the pyrochlore formation were formed, resulting in a mixture of perovskite and pyrochlore phases after the calcination. The ceramics prepared from the suspension with pH = 12.5 were sintered to 96% of theoretical density at only 950°C, and exhibited electrical properties comparable to ceramics prepared by the columbite method, sintered at much higher temperatures. In contrast, the properties of the ceramics from the pH = 11.4 suspension were heavily deteriorated due to the presence of the pyrochlore phase and the high degree of porosity.
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    The Thermal Expansion, Elastic and Fracture Properties of Porous Cordierite at Elevated Temperatures (2012)
    Wiley
    Details
    Publication Date: 2012-03-14
    Description: The properties that determine the thermal shock resistance in materials are reported for porous cordierite, a leading candidate material for the fabrication of diesel particulate filters. Fracture toughness and slow crack growth tests were performed on test specimens obtained from the walls of diesel particulate filter monolithic substrates using the double-torsion test method at temperatures between 20°C and 900°C. The thermal expansion and elastic properties were characterized between 20°C and 1000°C. The role of the microstructure of porous cordierite in determining its unusual thermal expansion and elevated temperature Young's modulus and fracture toughness are discussed.
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    Influence of Phenolic Resin Impregnation on the Properties of Reaction-Bonded Silicon Carbide (2012)
    Wiley
    Details
    Publication Date: 2012-03-14
    Description: Reaction-bonded silicon carbide ceramics fabricated from tape casting and Si infiltration have been reported in previous studies. To reduce the residual Si content in the sintered bodies, impregnation of phenol–formaldehyde resin (PF) into the porous green preforms before Si infiltration was proposed and studied in this work. The impregnation of PF solution not only helped to reduce the porosity and increase the carbon content of the green preforms, but also improved their strength. As a result, the flexural strength of the RBSC increased a lot and reached 856 ± 161MPa, whereas the residual Si content was reduced to 10 vol%.
    Print ISSN: 1546-542X
    Electronic ISSN: 1744-7402
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 46
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    Erosion Behavior of C/SiC Composites in Atomic Oxygen (2012)
    Wiley
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    Publication Date: 2012-03-14
    Description: A T300 carbon fiber and a SiC -coated C/SiC composite made from the same fiber were studied in atomic oxygen environment. The carbon fiber shows significant degradation while the erosion rate of SiC -coating of C/SiC is about 50 times lower. Evidence shows that Si is preferentially etched from the SiC surface. And XPS information showed that amorphous carbon and diamond-like carbonare periodically generated on the tested composite surface. Statistical analysis shows that the C/SiC specimens have no significant change in flexural properties after 1-year fluence AO treatment.
    Print ISSN: 1546-542X
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  • 47
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    Synthesis and Characterization of Chitosan/Boron Nitride Composites (2012)
    Wiley
    Details
    Publication Date: 2012-03-14
    Description: Chitosan/Boron nitride ( BN ) composites were prepared by solution method using CuSO 4 /glycine chelate complex as the catalysis with variable percentage of boron nitride loading. The dispersion of BN with the chitosan polymer was achieved with sonication at power of 120 W and frequency of 80 kHz. The chemical interactions of chitosan and BN were studied by Fourier transform infrared spectroscopy. The structure of chitosan and BN composites were investigated by XRD and TEM. It was observed that the BN were dispersed with chitosan matrix through intercalation. The quantitative identification of composites was investigated by Energy Dispersive X-ray Spectroscopy and Selected Area Electron Diffraction. Thermal stabilities of chitosan/ BN composites were studied by thermogravimetric analysis. It was found that, the thermal stability of the chitosan/ BN composites was increased compare with virgin chitosan. The oxygen barrier properties of chitosan/ BN composites were measured using gas permeameter. A substantial reduction in oxygen permeability was observed increasing boron nitride concentrations by which the synthesized composite materials may applicable in packaging industry.
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    Improvement of Mullite and Magnesia-Based Refractory Castables Through Addition of Nano-Spinel Powder (2012)
    Wiley
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    Publication Date: 2012-03-16
    Description: Two different commercial refractory castables based on mullite or magnesia aggregates have been improved through addition of 0–25 wt.% nano-magnesium aluminate spinel (MA) powder. Physico-mechanical and refractory properties were tested at different firing temperatures. The phase composition, thermal analysis, and microstructure of these refractory castables were detected using X-ray diffraction (XRD), differential thermal analysis (DTA), as well as scanning electron microscope (SEM) attached with energy dispersive X-ray unit, respectively. The castable sample mix containing 10 wt.% nano-MA spinel powder was chosen as an optimum composition according to its good sintering, mechanical as well as refractory properties.
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    Correlation Between the Microstructure and Electrical Properties in High-Performance (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead-Free Piezoelectric Ceramics (2012)
    Wiley
    Details
    Publication Date: 2012-03-16
    Description: Using three different sintering methods: spark plasma sintering, two-step sintering, and normal sintering ( Ba 0.85 Ca 0.15 )( Zr 0.1 Ti 0.9 ) O 3 ( BCZT ) lead-free piezoelectric ceramics with grain sizes in the range of 0.4–32.2 μm were prepared. The effects of grain size on the electrical properties and temperature stability of BCZT ceramics were systematically investigated. Results showed that reducing grain size shifted both the T c and T T-R to higher temperatures, and tended to enhance the relaxor behavior. A strong dependence of piezoelectric properties on the grain size was observed, and ~10 μm was a critical point for fabricating high-performance BCZT ceramics. For samples with grain sizes 〉10 μm, excellent piezoelectric properties of k p  〉 0.48, k t  〉 0.46, d 33  〉 470 pC/N and d 33 * 〉 950 pm/V were obtained. Moreover, no evident relationship between the grain size and temperature stability existed in this material, and all samples exhibited thermal instability below the Curie temperature. However, increasing grain size was helpful for improving the resistance to thermal depoling. The depolarization was assisted by internal mechanical stresses and the movement of 180° and 90° domain walls, which explained the increased resistance to thermal depoling in coarse-grained samples.
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    Preparation and Formation Mechanism of Elongated (Ca,Dy)-α-Sialon Powder Via Carbothermal Reduction and Nitridation (2012)
    Wiley
    Details
    Publication Date: 2012-03-16
    Description: ( Ca , Dy ) co-stabilized α-Sialon with elongated grains was prepared from SiO 2 – AlN – CaF 2 – Dy 2 O 3 powders by carbothermal reduction-nitridation (CRN) at 1700°C. Detailed investigations on the formation process of ( Ca , Dy )-α-Sialon elongated grains performed under various firing conditions revealed that the big quartz particles were initially reduced and decomposed gradually by carbon, and a large number of ball-shaped particles consisting of amorphous ( Si , Al , Ca , Dy ) x ( O , N ) y were formed. With increasing temperature, nitrogen continuously diffused into the liquid to form nitrogen-rich solid balls. Further increasing the temperature to 1700°C and held for 2 h, hollow α-Sialon spheres with nanometric particles were obtained from nitrogen-rich solid balls. Subsequently, the framework structure of hollow spheres was destroyed at 1700°C for 3 h, and ( Ca , Dy )-α-Sialon grains grew up continuously by consuming nanometric particles in the rough interface via Ostwald ripening and growth stages moving on the smooth interface. Finally, ( Ca , Dy )-α-Sialon developed well-defined crystalline elongated grains because the growth rate of rough surfaces is more rapid than that of smooth surfaces.
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    A New Temperature Stable Microwave Dielectric Material Mg0.5Zn0.5TiNb2O8 (2012)
    Wiley
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    Publication Date: 2012-03-16
    Description: A new temperature stable, low-loss, low sintering temperature microwave dielectric material Mg 0.5 Zn 0.5 TiNb 2 O 8 was investigated for the first time. Single phase Mg 0.5 Zn 0.5 TiNb 2 O 8 was obtained, and it showed Columbite structure which was tri-ixiolite structure. The variation trend of dielectric constant was in accordance with variation trend of relative density. When the sintering temperature was lower than 1120°C, the Qf value increased with the increasing of relative density. When the sintering temperature was higher than 1120°C, the Qf value decreased with the increasing of the unit cell volume. With the decrease of bond strength, the τ f increased. The typical values of ε = 30.74, Qf  = 66 900 GHz, τ f  = −4.01 × 10 −6 /°C were obtained for Mg 0.5 Zn 0.5 TiNb 2 O 8 sintered at 1120°C for 6 h.
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    Ecosystem greenspots: identifying potential drought, fire and climate change micro-refuges (2012)
    Wiley
    Details
    Publication Date: 2012-03-17
    Description: Ecological Applications, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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    Carbon isotopic evidence for the associations of decreasing atmospheric CO2 level with the Frasnian-Famennian mass extinction (2012)
    Wiley
    Details
    Publication Date: 2012-03-16
    Description: A perturbation of the global carbon cycle has often been used for interpreting the Frasnian-Famennian (F-F) mass extinction. However, the changes of atmospheric CO2 level (pCO2) during this interval are much debatable. To illustrate the carbon cycle during F-F transition, paired inorganic (δ13Ccarb) and organic (δ13Corg) carbon isotope analyses were carried out on two late Devonian carbonate sequences (Dongcun and Yangdi) from south China. The larger amplitude shift of δ13Corg compared to δ13Ccarb and its resultant Δ13C (Δ13C = δ13Ccarb − δ13Corg) decrease indicate decreased atmospheric CO2 level around the F-F boundary. The onset of pCO2 level decrease predates that of marine regressions, which coincide with the beginning of conodont extinctions, suggesting that temperature decrease induced by decreased greenhouse effect of atmospheric CO2 might have contributed to the F-F mass extinction.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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    Scale-dependent responses of species richness to experimental manipulation of productivity and disturbance in Californian coastal grasslands (2012)
    Wiley
    Details
    Publication Date: 2012-03-15
    Description: Question Relationships between species richness and environmental drivers such as productivity and disturbance are sensitive to the scale over which they are measured, but the extent to which this scale-dependence is important for experimental studies conducted over small scale ranges is not well known. We ask whether the response of species richness to experimental manipulation of productivity and disturbance varies across small spatial scales (0.016–4 m 2 ). We show that species–area relationships are well suited to summarize cross-scale responses of species richness, and ask whether the responses of species–area relationships to experimental manipulations are more consistent than richness at any single scale. Location Northern Californian coastal grasslands. Methods We applied disturbance and productivity reduction treatments over 4 yr at two sites. We assessed changes in species richness over five grain sizes, encompassing a 256-fold range of plot size. This allowed us to construct a species–area relationship for each experimental plot in each sampling year. We used the slope of the species–area relationship to summarize changes in species richness across multiple spatial scales. Results Richness responses were scale-dependent and complex, causing changes at any one scale to be difficult to interpret. Disturbance either increased or had no effect on richness, while reducing productivity had idiosyncratic effects among sites, scales and years. Both treatments, however, had consistent and interpretable effects on the species–area relationship. Reducing productivity increased the slope of the species–area relationship, while disturbance decreased it. Conclusions Our results suggest that the productivity–richness and disturbance–richness relationships are scale-dependent, and that improved generality could be achieved by focusing attention on the response of the species–area relationship to these factors. We showed that experimental disturbance and reverse fertilization treatments can have scale-dependent effects on grassland species richness, even at small (0.016 – 4 m 2 ) scales. Richness responses at any one scale were idiosyncratic among sites and years, but characteristics of the species-area relationship were more predictable and consistent. We recommend increased focus on responses of the species-area relationship to experimental manipulations.
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
    Published by Wiley on behalf of The International Association for Vegetation Science (IAVS).
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    Bottom-up multitrophic effects in resprouting plants (2012)
    Wiley
    In: Ecology
    Details
    Publication Date: 2012-03-11
    Description: Ecology, Volume 93, Issue 1, Page 9-16, January 2012.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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    Elevated land runoff after European settlement perturbs persistent foraminiferal assemblages on the Great Barrier Reef (2012)
    Wiley
    In: Ecology
    Details
    Publication Date: 2012-03-11
    Description: Ecology, Volume 93, Issue 1, Page 111-121, January 2012.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
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    Four years of experimental climate change modifies the microbial drivers of N2O fluxes in an upland grassland ecosystem. (2012)
    Wiley
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    Publication Date: 2012-03-11
    Description: Emissions of the trace gas nitrous oxide (N 2 O) play an important role for the greenhouse effect and stratospheric ozone depletion, but the impacts of climate change on N 2 O fluxes and the underlying microbial drivers remain unclear. The aim of this study was to determine effects of sustained climate change on field N 2 O fluxes and associated microbial enzymatic activities, microbial population abundance and community diversity in an extensively managed, upland grassland. We recorded N 2 O fluxes, nitrification and denitrification, microbial population size involved in these processes and community structure of nitrite reducers ( nir K) in a grassland exposed for four years to elevated atmospheric CO 2 (+ 200 ppm), elevated temperature (+ 3.5°C) and reduction of summer precipitations (-20%) as part of a long-term, multifactor climate change experiment. Our results showed that both warming and simultaneous application of warming, summer drought and elevated CO 2 had a positive effect on N 2 O fluxes, nitrification, N 2 O release by denitrification and the population size of N 2 O reducers and NH 4 oxidizers. In situ N 2 O fluxes showed a stronger correlation with microbial population size under warmed conditions compared with the control site. Specific lineages of nir K denitrifier communities responded significantly to temperature. In addition, nir K community composition showed significant changes in response to drought. Path analysis explained more than 85% of in situ N 2 O fluxes variance by soil temperature, denitrification activity and specific denitrifying lineages. Overall, our study underlines that climate-induced changes in grassland N 2 O emissions reflect climate-induced changes in microbial community structure, which in turn modify microbial processes.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Advances in global change research require open science by individual researchers (2012)
    Wiley
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    Publication Date: 2012-03-11
    Description: Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current work is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals—from students and PIs. Here, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and labs can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally-relevant questions.
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    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Neotropical C3/C4 grass distributions – present, past and future (2012)
    Wiley
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    Publication Date: 2012-03-11
    Description: Changes in C 4 grass distribution and abundance are frequently observed in Quaternary, Holocene and future environmental-change scenarios. However, the factors driving these dynamics are not fully understood, and conflicting theories have been reported. In this paper, we present a very large dataset of modern altitudinal distribution profiles of C 3 and C 4 grasses covering the entire Neotropical Andes, which was compared with actual climate data. The results of multivariate analysis demonstrate that, in the Neotropical Andes, mean annual temperature is the main factor governing the modern altitudinal distribution of C 3 and C 4 grass species. The C 3 and C 4 grass distributions were compared with simulations based on the Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM), which allowed the present grass distribution to be estimated. Finally, the DGVM was employed to simulate past and future scenarios, using the IPCC's climate projections for 2100 and PMIP2 models for the Holocene Optimum (HO, 6000 yrs BP) and the Last Glacial Maximum (LGM, 21000 yrs BP). The results were found to be significantly different to those obtained using a simple photosynthetic model. According to LPJ forced with the PMIP2 models for the LGM, during the LGM, the C 4 grasses would not have reached higher altitudes than found in the present day.
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    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Oxide Ion Transport in Donor-Doped Pb(ZrxTi1−x)O3: Near-Surface Diffusion Properties (2012)
    Wiley
    Details
    Publication Date: 2012-03-16
    Description: Oxide ion transport in Pb ( Zr x Ti 1– x ) O 3 ( PZT ) was investigated using 18 O tracer diffusion and time-of-flight secondary ion mass spectrometry analysis. Particularly diffusion in the near-surface regions (a few 100 nm in depth) is discussed and strong evidence for a space charge layer near the surface is provided. In this layer, an enrichment of oxygen vacancies is found at temperatures up to 600°C, resulting in box-shaped tracer diffusion profiles. At 650°C, however, the profile shape is modified and reveals a depletion of oxygen vacancies close to the surface. Accordingly, a change in the polarity of the surface charge takes place between 600°C and 650°C. The tracer diffusion profiles are very sensitive to surface modification, caused by etching or annealing at higher temperature, and also depend on the sintering procedure. Moreover, application of an external field during the tracer experiments affected the tracer diffusion at the cathode, while leaving the profile at the anode unperturbed. Quantitative analysis of the profiles was performed by means of numerical calculations based on Gouy-Chapman or Mott-Schottky space charge models. Estimates of the oxygen vacancy concentration and ionic transference number of donor-doped PZT are provided.
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    Low-Temperature Superplasticity in Nanocrystalline Tetragonal Zirconia Polycrystal (TZP) (2012)
    Wiley
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    Publication Date: 2012-03-16
    Description: Nanocrystalline tetragonal ZrO 2 polycrystals ( TZP ) have been fabricated by the pressureless sintering of recently developed tetragonal ZrO 2 powder containing 5.69 mol% YO 1.5 and 0.60 mol% AlO 1.5 . The average grain sizes were 160 nm in the TZP sintered at 1150°C for 10 h and 150 nm in the 0.25 mol% GeO 2 -doped TZP sintered at 1100°C for 100 h. The TZP and Ge 4+ -doped TZP-sintered bodies were essentially single-phase materials, and neither the amorphous layer nor the second-phase particle was observed along the grain boundary faces. High-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and nanoprobe energy-dispersive X-ray spectrometer (EDS) measurements revealed that the Y 3+ , Al 3+ and Ge 4+ cations tend to segregate in the vicinity of the grain boundaries in the TZP -sintered bodies. The TZP and Ge 4+ -doped TZP exhibited an elongation to failure of more than 100% in the temperature range of 1150°C–1300°C and initial strain rate range of 1.4 × 10 −5  s −1 to 1.0 × 10 −2  s −1 . For instance, an elongation to failure in the Ge -doped TZP reached about 200% at 1150°C and 1.4 × 10 −5  s −1 . The nanocrystallization reduced the lower limit of the superplastic temperature of conventional, submicron-grain TZP materials by 150°C. The improved ductility of the TZP at low temperatures was essentially attributed to the reduced grain size.
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    Technology and Properties of PBZTS Ceramics (2012)
    Wiley
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    Publication Date: 2012-02-03
    Description: This paper presents the results of preparing and investigating the solid solution of lead barium zirconate titanate stannate (Pb 1− x Ba x )[(Zr 1− y Ti y ) 1− z Sn z ]O 3 with x  =   0.25, y  =   0.35 and z  =   0.00, 0.02, 0.04, 0.08, 0.10. Ceramic samples were obtained from oxides and carbonates using conventional ceramic technology and pressureless sintering. The results of Energy-dispersive X-ray spectroscopy (EDS) investigations, XRD studies, as well as dielectric measurements and electromechanical investigations are presented. It was stated that at the room temperature, the structure of the investigated samples is pseudo-cubic, typical for relaxors. Maximal value of elementary cell parameter is observed for z  =   0.02, and for higher values of z, we observe almost linear decrease with increasing z . It was found that with increasing content of the Sn, the temperature T m at which dielectric permittivity reaches its maximum decreases. Analyzing P-E hysteresis loops it was stated that the phase transition in the investigated samples takes place at temperatures approximately 100°C lower than the temperature of the dielectric permittivity maximum. The temperature of phase transition was calculated also from hysteresis loops and compared with that obtained from measurements of dielectric permittivity.
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    A method for physically based model analysis of conjunctive use in response to potential climate changes (2012)
    Wiley
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    Publication Date: 2012-02-04
    Description: Potential climate change effects on aspects of conjunctive management of water resources can be evaluated by linking climate models with fully integrated groundwater–surface water models. The objective of this study is to develop a modeling system that links global climate models with regional hydrologic models, using the California Central Valley as a case study. The new method is a supply and demand modeling framework that can be used to simulate and analyze potential climate change and conjunctive use. Supply-constrained and demand-driven linkages in the water system in the Central Valley are represented with the linked climate models, precipitation-runoff models, agricultural and native vegetation water use, and hydrologic flow models to demonstrate the feasibility of this method. Simulated precipitation and temperature were used from the GFDL-A2 climate change scenario through the 21st century to drive a regional water balance mountain hydrologic watershed model (MHWM) for the surrounding watersheds in combination with a regional integrated hydrologic model of the Central Valley (CVHM). Application of this method demonstrates the potential transition from predominantly surface water to groundwater supply for agriculture with secondary effects that may limit this transition of conjunctive use. The particular scenario considered includes intermittent climatic droughts in the first half of the 21st century followed by severe persistent droughts in the second half of the 21st century. These climatic droughts do not yield a valley-wide operational drought but do cause reduced surface water deliveries and increased groundwater abstractions that may cause additional land subsidence, reduced water for riparian habitat, or changes in flows at the Sacramento–San Joaquin River Delta. The method developed here can be used to explore conjunctive use adaptation options and hydrologic risk assessments in regional hydrologic systems throughout the world.
    Print ISSN: 0043-1397
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    Blue ice areas and their topographical properties in the Lambert glacier, Amery Iceshelf system using Landsat ETM+, ICESat laser altimetry and ASTER GDEM data (2012)
    Cambridge University Press
    Details
    Publication Date: 2012-02-07
    Description: Research Articles Jaehyung Yu, Hongxing Liu, Lei Wang, Kenneth C. Jezek, Joonghyeok Heo, Antarctic Science , Volume 24 Issue 01 , pp 95-110 Abstract
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press on behalf of Antarctic Science Ltd.
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    Deposition of Silicon Carbide and Nitride-Based Coatings by Atmospheric Plasma Spraying (2012)
    Wiley
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    Publication Date: 2012-02-07
    Description: In this work atmospheric plasma spraying of SiC and Si 3 N 4 was investigated. Plasma spraying of these ceramics raises several problems since they would tend to decompose instead of melting at elevated temperatures during the process. To circumvent this problem the nonoxide ceramics were deposited as a composite powder mixed with nonoxide ceramic particles resulting in a ceramic/ceramic composite structure. Our findings were that using such a composite feedstock powder both oxidation and decomposition of the nonoxide particles could be avoided. A vitrified phase was also developed in the coating.
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    Synthesis and Size Control of Tetragonal Barium Titanate Nanopowders by Facile Solvothermal Method (2012)
    Wiley
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    Publication Date: 2012-02-08
    Description: A facile synthetic strategy was implemented to obtain nanosized barium titanate ( BaTiO 3 ) powders with tetragonal structure. The nanoparticles were synthesized using solvothermal process employing diethanolamine and triethanolamine to suppress the particle growth and the as-prepared nanopowders were characterized using X-ray diffraction, scanning electron microscopy, and high-resolution dispersive Raman spectroscopy. It was found that the particle size can be easily tuned by adjusting the experimental parameters while retaining the tetragonality. The average diameters of the particles prepared with and without the organic amines were found to be 80 and 100 nm, respectively. All the synthesized BaTiO 3 nanopowders exhibit a narrow size distribution with a uniform morphology. Rietveld refinement of the XRD patterns and Raman spectra revealed that the synthesized BaTiO 3 nanopowders have tetragonal asymmetry dominant structures. A slight decrease in the tetragonality of the prepared powders with decrease in particle size is attributed to the presence of cubic shell layer and inner defects. The tetragonal-dominant structure was also confirmed by normalizing the peak area of the Raman spectra.
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    Improved High-Q Microwave Dielectric Ceramics in CuO-Doped BaTi4O9–BaZn2Ti4O11 System (2012)
    Wiley
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    Publication Date: 2012-02-08
    Description: To improve the microwave dielectric properties, CuO was doped into composite ceramics BaTi 4 O 9 – BaZn 2 Ti 4 O 11 by the solid-state reaction. CuO worked as flux former and caused the liquid-phase sintering mechanism, which effectively improved the densification process and lowered the sintering temperature by nearly 100°C. Moreover, Cu 2+ substituted for Zn 2+ sites in BaZn 2 Ti 4 O 11 phase, which led to the increase of BaZn 2 Ti 4 O 11 phase and the reduction of lattice parameters of BaZn 2 Ti 4 O 11 phase, and both these two results had the positive effect on the dielectric properties, especially the Q  ×  f value. As increasing CuO content from 0.0 to 3.0 wt%, the dielectric constant ( ε r ) increased from 35.5 to 36.5, the Q  ×  f value increased first from 49 100 GHz to the peak value 62 600 GHz (1.0 wt% CuO ) and thereafter decreased to 31 900 GHz, and the temperature coefficient of resonant frequency ( τ f ) kept in a low value as 〈2.0 wt% CuO was added. At last, 0.85 BaTi 4 O 9 –0.15 BaZn 2 Ti 4 O 11 ceramics with 1.0 wt% CuO sintered at 1150°C for 3 h showed excellent microwave dielectric properties: the high ε r  = 36.4, the high Q  ×  f = 62 600 GHz and the near-zero τ f  = +0.2 ppm/°C.
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    Preparation and Electrical Properties of High-TC Piezoelectric Ceramics of Strontium-Substituted Bi(Ni1/2Ti1/2)O3–PbTiO3 (2012)
    Wiley
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    Publication Date: 2012-02-08
    Description: A piezoelectric system of (1− x ) Bi ( Ni 1/2 Ti 1/2 ) O 3 – x ( Pb (1− y ) Sr y TiO 3 ) ( BNT–PST ) is developed to have good high temperature piezoelectric properties with much improved resistivity. The crystal structure shows that the phase transformation from tetragonal phase to rhombohedral one is gradually shifted to the composition with high content of PT by the substitution of strontium. The problem of leakage current for the Bi ( Ni , Ti ) O 3 – PbTiO 3 can be well resolved by introducing the dopant of strontium. Both dielectric loss and DC resistivity can be much reduced not only at room temperature but also high temperature. An optimum composition of 0.53 Bi ( Ni 1/2 Ti 1/2 ) O 3 –0.47( Pb 0.95 Sr 0.05 ) TiO 3 is obtained to have a good potential application of high temperature piezoelectric ( d 33  = 205 pC/N, E C  = 3.32 kV/mm, P r  = 41.2 μC/cm 2 ). Strontium could be a useful dopant for the studies on the high temperature piezoelectric ceramics in future.
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    Allowable levels of take for the trade in nearctic songbirds (2012)
    Wiley
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    Publication Date: 2012-02-10
    Description: Ecological Applications, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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    Estimating population impacts via dynamic occupancy analysis of Before-After Control-Impact studies (2012)
    Wiley
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    Publication Date: 2012-02-11
    Description: Ecological Applications, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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    Seasonal changes in leaf area of Amazon forests from leaf flushing and abscission (2012)
    Wiley
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    Publication Date: 2012-02-11
    Description: A large increase in near-infrared (NIR) reflectance of Amazon forests during the light-rich dry season and a corresponding decrease during the light-poor wet season has been observed in satellite measurements. This increase has been variously interpreted as seasonal change in leaf area resulting from net leaf flushing in the dry season or net leaf abscission in the wet season, enhanced photosynthetic activity during the dry season from flushing new leaves and as change in leaf scattering and absorption properties between younger and older leaves covered with epiphylls. Reconciling these divergent views using theory and observations is the goal of this article. The observed changes in NIR reflectance of Amazon forests could be due to similar, but small, changes in NIR leaf albedo (reflectance plus transmittance) resulting from the exchange of older leaves for newer ones, but with the total leaf area unchanged. However, this argument ignores accumulating evidence from ground-based reports of higher leaf area in the dry season than the wet season, seasonal changes in litterfall and does not satisfactorily explain why NIR reflectance of these forests decreases in the wet season. More plausibly, the increase in NIR reflectance during the dry season and the decrease during the wet season would result from changes in both leaf area and leaf optical properties. Such change would be consistent with known phenological behavior of tropical forests, ground-based reports of seasonal changes in leaf area, litterfall, leaf optical properties and fluxes of evapotranspiration, and thus, would reconcile the various seemingly divergent views.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
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    Solute transport in divergent radial flow with multistep pumping (2012)
    Wiley
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    Publication Date: 2012-02-11
    Description: An efficient approach is developed to analytically evaluate solute transport in a horizontal, divergent radial flow field with a multistep injection flow rate and an arbitrary input concentration history. By assuming a piecewise steady state flow and transforming the time domain to the cumulative injected flow domain, the concentration distribution is found to be completely determined by the total volume of injected flow and independent of specific flow rates. Thus, on the cumulative flow domain, the transport problem with a temporally varying velocity field can be transformed into a steady state flow problem. Linear convolution can then be applied on the cumulative injected flow domain to evaluate the solution for an arbitrarily time-dependent input concentration. Solutions on the regular time domain can be conveniently obtained by mapping the solution on the cumulative injected flow domain to the time domain. Furthermore, we theoretically examine the conditions for the assumption of piecewise steady state flow to be valid. On the basis of the critical time scale of the “pseudosteady state condition,” defined as when velocity changes accomplish 99% of their steady state differences, and the relative error in the mean travel time of plume front, we obtain conditions for neglecting the transitional period between two pumping steps. Such conditions include the following: (1) the duration of a pumping step, tp, must be longer than the critical time scale, tc, i.e., tp ≥ tc = 25r2S/T, where r is the radial distance, S is the storage coefficient, and T is the transmissivity, or similarly, a maximum problem domain needs to be defined for a given pumping strategy. (2) the maximum well pumping rate, qmax, should satisfy qmax ≤ πθT/25S, where θ is the effective porosity. When both conditions are satisfied, transitional periods may be neglected.
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    Spatial and temporal intensification of lateral hyporheic flux in narrowing intra-meander zones (2012)
    Wiley
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    Publication Date: 2012-02-12
    Description: Meander bends in alluvial rivers morphologically evolve toward meander cutoff with narrowing intra-meander necks, and this should steepen hydraulic gradients and intensify intra-meander hyporheic flux. This research used dye tracking and head loss measurements in a 1:500 planimetrically scaled laboratory river table to quantify the spatial and temporal intensification of intra-meander flux rates at two evolution ages. The younger meander bend, M1, had a sinuosity of 2.3, a river neck width of 0.39 cm, and 0.6% river slope, and the older meander bend, M3, had a sinuosity of 5.2, a river neck width of 0.12 cm, and 0.5% river slope. Flux into and out of the meander bend was estimated along the normalized curvilinear distance s *, with the meander neck at s * = 0.1 and s * = 0.9, the meander centroid at s * = 0.37 and s * = 0.63, and the apex at s * = 0.5. Between the meander centroid and neck we documented a 60% spatial intensification for M1 and a 90% spatial intensification for M3. Between M1 and M3 we documented a 135% temporal intensification at the neck and a 100% intensification at the centroid. Our empirical spatial and temporal intensification rates involving the M1 and the M3 scenario were 1 to 3 times lower than theoretical rates derived from a river evolution model with equivalent M1 and M3 planimetry. Over estimation by the theoretical model was attributed to exaggerated head loss caused by the model neglecting groundwater contributions to river stage. Hyporheic exchange provides critical ecosystem services and its spatial and temporal variation with meander evolution should be considered in river management. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
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    Application of the soil and water assessment tool (SWAT) model on the Lower Porsuk Stream Watershed (2012)
    Wiley
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    Publication Date: 2012-02-14
    Description: Watershed models which combine hydrology and water quality are being widely utilized in integrated watershed management for the determination of best water management practices. In this study, the hydrology of the Lower Porsuk Stream Watershed in Turkey has been modeled with SWAT to determine optimal water management strategies. The calibration and validation process have been accomplished using data from two monitoring stations. The model has been run for the 1978–2009 period and while the 1998–2004 period has been used for calibration, the validation has spanned the whole period. The SWATCup calibration and uncertainity program has been utilized for this purpose. No significant differences have been detected among different iteration numbers in the calibration period. The monthly Nash-Sutcliffe and R 2 performance indicatiors for the upstream Esenkara station have been 0.74 and 0.88, respectively for the calibration period, and 0.87 and 0.87, respectively for the validation period. The Kıranharmanı station which is located close to the watershed outlet has shown values of 0.59 and 0.72, respectively for the calibration period, and 0.44 and 0.56, respectively for the validation period. There are uncertanities in the abstracted irrigation and groundwater quantities which have reflected in the results in the Kıranharmanı station which is more affected as it lies downstream of the irrigation areas. The effects of different irrigation practices on the flow regime have been also investigated. A scenario has been implemented in which drip irrigation wholly replaces conventional furrow and sprinkler irrigation. The scenario has shown increases in stream flows by 87 % for the whole year. The adoption of more efficient irrigation practices thus results in reducing the water stress induced by irrigation demands. With this study a modeling framework has been founded to aid water management applications in the Lower Porsuk Stream Watershed by generating scenarios for best management practices. Copyright © 2012 John Wiley & Sons, Ltd.
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    Torsion Tests on AV119 Epoxy – Joined SiC (2012)
    Wiley
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    Publication Date: 2012-02-14
    Description: The results of an experimental investigation on epoxy-joined silicon carbide tested in shear mode by four different configurations of torsion test are presented and compared to results obtained by asymmetric four-point bending and four different lap tests in compression. All samples have been joined by an epoxy adhesive (Araldite AV119) which is to be considered as a model brittle joining material chosen to obtain several joined samples in a reasonable time. Advantages and disadvantages of each configuration are discussed and compared to results previously obtained with epoxy-joined Carbon/Carbon composites and ceramics tested with the same methods.
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    On virtual observatories and modelled realities (or why discharge must be treated as a virtual variable) (2012)
    Wiley
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    Publication Date: 2012-02-14
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    C–S–H Gels: Interpretation of 29Si MAS-NMR Spectra (2012)
    Wiley
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    Publication Date: 2012-02-14
    Description: The detection of bridging tetrahedra, or Q 2 (L), in the silica chains constituting C – S – H gels is controversial. While some authors maintain that 29 Si MAS - NMR can be used to distinguish between Q 1 and Q 2 units but not between the silicon environments associated with Q 2 (intermediate position) and Q 2 (L) (intermediate and bridging position) units, others claim the contrary. The present article addresses this issue with a report on 29 Si MAS - NMR studies of a number of calcium silicate hydrate gels. The findings showed that nuclear magnetic resonance can differentiate between Q 2 and Q 2 (L) units in highly polymerized C – S – H gels with mean chain lengths (MCL) of over 12 and Ca / Si ratios of 〈1. At higher Ca / Si ratios, however, the MCL declined, with the concomitant rise in Q 1 units. Under these conditions, in which it was practically impossible to distinguish between Q 2 and Q 2 (L), the presence of a single signal for all Q 2 units was assumed.
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    Attribution of water resources evolution in the highly water-stressed Hai River Basin of China (2012)
    Wiley
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    Publication Date: 2012-02-14
    Description: Many observations and studies have shown that water resources amount in the Hai River Basin decreased significantly over the last half of the twentieth century. This study attempts to attribute the observed changes in the water resources amount in the basin over a 40 year period (1961–2000) to different factors, including natural climate variability, climate change induced by anthropogenic forcing of greenhouse gas emissions (referred to as anthropogenic forcing hereafter), and local human activity. First, the temporal variation of the annual water resources amount in the basin during the past 40 years is analyzed by employing the moving-average method, the linear regression method, and the Mann-Kendall method. Second, through setting different scenarios, the effects on the water resources amount due to different factors, including natural climate variability, anthropogenic forcing, and local human activity, are obtained using the parallel climate model, the distributed hydrological model water and energy transfer processes in large river basins, and the statistical downscaling model. Third, the fingerprint-based attribution method is used to obtain the signal strengths of observed changes in water resources amount during 1961–2000 and changes in the water resources amount under different scenarios. Finally, by comparing the signal strengths, the observed changes in water resources amount in the basin can be attributed to different factors. The results indicate that natural climate variability and local human activity may be two factors responsible for the observed changes in the water resources amount during the past 40 years in the basin, with local human activity being the main factor and accounting for about 60% of the changes.
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    Soil organic matter turnover is governed by accessibility not recalcitrance (2012)
    Wiley
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    Publication Date: 2012-02-15
    Description: Mechanisms to mitigate global climate change by sequestering carbon (C) in different ‘sinks’ have been proposed as at least temporary measures. Of the major global C pools, terrestrial ecosystems hold the potential to capture and store substantially increased volumes of C in soil organic matter (SOM) through changes in management that are also of benefit to the multitude of ecosystem services that soils provide. This potential can only be realised by determining the amount of SOM stored in soils now, with subsequent quantification of how this is affected by management strategies intended to increase SOM concentrations, and used in soil C models for the prediction of the roles of soils in future climate change. An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia. This partitioning is assumed to reflect (i) the average biomolecular properties of SOM in the pools with reference to their source in plant litter, (ii) the accessibility of the SOM to decomposer organisms or catalytic enzymes, or (iii) constraints imposed on decomposition by environmental conditions, including soil moisture and temperature. However, contemporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically-defined pools. In this review, we will explore how advances in quantitative analytical technologies have redefined the new understanding of SOM dynamics and how this is impacting on the development and application of new modelling approaches to soil C.
    Print ISSN: 1354-1013
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    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Endogenous circadian regulation of carbon dioxide exchange in terrestrial ecosystems (2012)
    Wiley
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    Publication Date: 2012-02-15
    Description: It is often assumed that daytime patterns of ecosystem carbon assimilation are mostly driven by direct physiological responses to exogenous environmental cues. Under limited environmental variability, little variation in carbon assimilation should thus be expected unless endogenous plant controls on carbon assimilation, which regulate photosynthesis in time, are active. We evaluated this assumption with eddy flux data, and we selected periods when net ecosystem exchange (NEE) was decoupled from environmental variability in seven sites from highly contrasting biomes across a 74º latitudinal gradient over a total of 36 site-years. Under relatively constant conditions of light, temperature, and other environmental factors, significant diurnal NEE oscillations were observed at six sites, where daily NEE variation was between 20% and 90% of that under variable environmental conditions. These results are consistent with fluctuations driven by the circadian clock and other endogenous processes. Our results open a promising avenue of research for a more complete understanding of ecosystem fluxes that integrates from cellular to ecosystem processes.
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    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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    Suspension and Air Plasma-Sprayed Ceramic Thermal Barrier Coatings with High Infrared Reflectance (2012)
    Wiley
    Details
    Publication Date: 2012-02-15
    Description: Yttria partially stabilized zirconia (YSZ) coatings are widely used for thermal barrier coatings (TBCs) to increase operating temperature of gas turbines. In the wavelength range where most of the radiation by walls and combustion gas is emitted within the gas turbine YSZ is semitransparent leading to increasing radiation heat flows into the components at increasing service temperatures. The objective of this work is to optimize the diffuse reflectance of plasma-sprayed TBCs by improving the coating microstructure such that the reflectance of radiation is increased. As a result, a more efficient thermal screening of the underlying metallic substrate is achieved. In this work, air plasma-sprayed and suspension plasma-sprayed (SPS) coatings of 7% YSZ using powder of different grain size distributions and different spray parameters were deposited. The reflectance and transmittance has been investigated in the wavelength range from 0.3 to 2.5 μm. The SPS-coatings showed the highest reflectance up to 94% at 1.5 μm wavelength. In addition, the scattering and absorption coefficients of the sprayed TBCs calculated with the Kubelka–Munk two flux model showed strong correlation with the measured porosity. By improving the microstructure, we were able to reduce thermal conductivity while increasing scattering of radiation, resulting in lower heat flow and lower temperature at the metallic substrate. These results are strengthened by numerical calculations.
    Print ISSN: 1546-542X
    Electronic ISSN: 1744-7402
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Modeling effects of floods on streambed hydraulic conductivity and groundwater-surface water interactions (2012)
    Wiley
    Details
    Publication Date: 2012-02-15
    Description: Flood events can induce temporal changes in streambed elevation and particle-size composition, which may influence the bed's hydraulic properties and stream-aquifer fluxes during and after an event. This study combines a set of previously developed modeling approaches to create a synthetic flood event during which bed sediment is entrained and deposited as a function of hydraulic conditions and particle size. One simulated river reach in a state of approximate dynamic equilibrium is chosen to investigate the impacts of size-selective sediment transport on stream-aquifer interaction. Along this reach, the preferential entrainment of fine sediment during the flood's rising limb leads to overall bed coarsening, and increases in vertical hydraulic conductivity (Kbv) and downward fluxes of floodwater into the streambed. Progressively finer sediment layers are deposited during the event's falling limb, causing the redevelopment of a colmation (clogging) layer on the bed surface and a decline in overall Kbv by the event's conclusion. This reduction in Kbv leads to prolonged retention of event water in the streambed (after the reach reverts from losing to gaining river conditions) when compared with what is expected if pre-event Kbv values are used to estimate river-aquifer exchanges. This process of sequential bed coarsening and fining during a flood event provides a mechanistic explanation for the event size-and-duration threshold, inferred in some systems, that must be exceeded for significant amounts of flood recharge to occur. The major consequences of these processes—enhanced infiltration and prolonged floodwater retention—have potentially major implications for groundwater-surface water interactions, water quality, contaminant transport, and riparian biogeochemistry.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 83
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    Stochastic simulation of nonstationary oscillation hydroclimatic processes using empirical mode decomposition (2012)
    Wiley
    Details
    Publication Date: 2012-02-15
    Description: Nonstationary oscillation (NSO) processes are observed in a number of hydroclimatic data series. Stochastic simulation models are useful to study the impacts of the climatic variations induced by NSO processes into hydroclimatic regimes. Reproducing NSO processes in a stochastic time series model is, however, a difficult task because of the complexity of the nonstationary behaviors. In the current study, a novel stochastic simulation technique that reproduces the NSO processes embedded in hydroclimatic data series is presented. The proposed model reproduces NSO processes by utilizing empirical mode decomposition (EMD) and nonparametric simulation techniques (i.e., k-nearest-neighbor resampling and block bootstrapping). The model was first tested with synthetic data sets from trigonometric functions and the Rössler system. The North Atlantic Oscillation (NAO) index was then examined as a real case study. This NAO index was then employed as an exogenous variable for the stochastic simulation of streamflows at the Romaine River in the province of Quebec, Canada. The results of the application to the synthetic data sets and the real-world case studies indicate that the proposed model preserves well the NSO processes along with the key statistical characteristics of the observations. It was concluded that the proposed model possesses a reasonable simulation capacity and a high potential as a stochastic model, especially for hydroclimatic data sets that embed NSO processes.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 84
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    Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions (2012)
    Wiley
    Details
    Publication Date: 2012-02-15
    Description: Vegetation zonation and tidal hydrology are basic attributes of intertidal salt marshes, but specific links among vegetation zonation, plant water use, and spatiotemporally dynamic hydrology have eluded thorough characterization. We developed a quantitative model of an intensively studied salt marsh field site, integrating coupled 2-D surface water and 3-D groundwater flow and zonal plant water use. Comparison of model scenarios with and without heterogeneity in (1) evapotranspiration rates and rooting depths, according to mapped vegetation zonation, and (2) sediment hydraulic properties from inferred geological heterogeneity revealed the coupled importance of both sources of ecohydrological variability at the site. Complex spatial variations in root zone pressure heads, saturations, and vertical groundwater velocities emerged in the model but only when both sources of ecohydrological variability were represented together and with tidal dynamics. These regions of distinctive root zone hydraulic conditions, caused by the intersection of vegetation and sediment spatial patterns, were termed “ecohydrological zones” (EHZ). Five EHZ emerged from different combinations of sediment hydraulic properties and evapotranspiration rates, and two EHZ emerged from local topography. Simulated pressure heads and groundwater dynamics among the EHZ were validated with field data. The model and data showed that hydraulic differences between EHZ were masked shortly after a flooding tide but again became prominent during prolonged marsh exposure. We suggest that ecohydrological zones, which reflect the combined influences of topographic, sediment, and vegetation heterogeneity and do not emphasize one influence over the others, are the fundamental spatial habitat units comprising the salt marsh ecosystem.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 85
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    Crystallization Kinetics and Mechanism of Strontium Zinc Silicate Glass (2012)
    Wiley
    Details
    Publication Date: 2012-02-16
    Description: The non-isothermal crystallization kinetics of the strontium zinc silicate (SZS) glasses, having composition 51 SrO -9 ZnO -40 SiO 2 (wt%), was studied using the differential thermal analysis (DTA). Glasses prepared by quenching the melt in air, were subjected to different heat treatments for studying the crystallization behavior. Formation of crystalline phases and microstructure were studied by using powder X-ray diffraction and scanning electron microscopy. The activation energy and mechanism of crystallization were determined according to Kissinger, Ozawa and Matusita-Sakka equations. The DTA exotherm observed at around 920°C consists of two overlapping crystallization peaks corresponding to two different crystalline phases. Strontium silicate ( Sr 3 Si 3 O 9 ) and SZS ( Sr 2 ZnSi 2 O 7 ) phases crystallize almost simultaneously as major phases. The activation energies for the these crystallization peaks are 700 kJ/mol and 704 kJ/mol. Higher activation energies indicate that the kinetics are more thermally activated making the control of crystallization more difficult. The values of growth morphology parameters n (Avarami parameter) and m (dimensionality of crystal growth) suggest a diffusion controlled bulk crystallization with three- and two-dimensional growth. This is also confirmed by an interconnected growth of stubby granular/prismatic shaped crystals in the glass-ceramic. The microstructural evolution of the glass upon heating suggests the occurrence of phase separation with an apparently spinodal decomposition mechanism prior to the crystallization.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    A Facile Starch-Assisted Sol–Gel Method to Synthesize K-Doped Li2ZrO3 Sorbents with Excellent CO2 Capture Properties (2012)
    Wiley
    Details
    Publication Date: 2012-02-16
    Description: A facile starch-assisted sol–gel method combined with freeze-drying technique has been developed to synthesize K -doped Li 2 ZrO 3 sorbents. SEM, TEM, and XRD techniques have been applied to characterize the morphology and structure of the synthesized K -doped Li 2 ZrO 3 samples. The CO 2 capture-regeneration properties of the prepared K -doped Li 2 ZrO 3 sample were investigated using thermogravimetric analysis at different CO 2 partial pressures. The K -doped Li 2 ZrO 3 synthesized using the starch-assisted sol–gel method combined with the freeze-drying technique shows excellent CO 2 capture properties. At 823 K and a CO 2 partial pressure of 0.25 bar, the uptake of CO 2 reaches 22 wt% within 20 min, which is approximately 87% of the stoichiometric sorption capacity (25.3 wt%) of CO 2 in the K -doped Li 2 ZrO 3 with a K : Li : Zr composition of 0.2:1.6:1 in molar ratio. Furthermore, the sorbent shows a good stability, confirmed using capture-regeneration cycles.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 87
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    Data based analysis of bivariate copula tail dependence for drought duration and severity (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Description: In recent decades, copula functions have been applied in bivariate drought duration and severity frequency analysis. Among a number of potential copulas, Clayton has been mostly employed in drought analysis. In this research, we study the influence of the tail shape of various copula functions (i.e. Gumbel, Frank, Clayton, and Gaussian) on drought bivariate frequency analysis. The appropriateness of Clayton copula for the characterization of drought characteristics is also investigated. Drought data are extracted from standardized precipitation index (SPI) time series for four stations in Canada (La Tuque and Grande Prairie) and Iran (Anzali and Zahedan). Both duration and severity datasets are positively skewed. Different marginal distributions were first fitted to drought duration and severity data. The gamma and exponential distributions were respectively selected for drought duration and severity according to the positive skewness and Kolmogorov- Smirnov test. The results of copula modeling show that the Clayton copula function is not an appropriate choice for the employed datasets in the current study, and does not give more drought risk information than an independent model for which the duration and severity dependence is not significant. The reason is that the dependence of two variables in the upper tail of Clayton copula is very weak and similar to the independent case, while the observed data in the transformed domain of cumulative density function shows high association in the upper tail. Instead, the Frank and Gumbel copula functions show better performance than Clayton function for drought bivariate frequency analysis. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 88
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    All that glitters is not gold: the case of calibrating hydrological models (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 89
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    Testing the role of seed size in annual legume seedling performance under experimental autumn moisture conditions (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Description: Question Previous studies show that large-seeded species increase their abundance in Mediterranean annual grasslands in growing seasons with dry autumns. One possible explanation is that large-seeded species have larger seedlings, which provide an advantage under drier conditions. We address the following questions: is seed mass correlated with seedling survival in annual legumes? Is this correlation influenced by the watering regime? Can seedling growth characteristics explain the differential survival of small- and large-seeded species? Location Annual Mediterranean grassland, Central Spain. Methods An experiment was conducted with six grassland legume species of different seed sizes, subjected to six different watering regimes, monitoring survival and morphological variables (shoot and root growth) for 40 d. Results Large seeds provide an advantage for seedling survival, but in extreme drought conditions, seedling survival in small-seeded species equals that of seedlings from large-seeded species. Seedlings from larger seeds are larger than those of small-seeded species, but have a lower root/shoot biomass ratio, leading to greater potential evapotranspiration, which could explain their loss of relative advantage under extreme droughts. Conclusion The hypothesis that seedlings from large-seeded species survive better than small-seeded species under drought conditions was not supported. Germination behaviour seems to be a more plausible explanation for the increased abundance in the field of large-seeded species in growing seasons with dry autumns. Large seeds provide an advantage for seedling survival, but in extreme drought conditions, seedling survival in small-seeded species equals that of seedlings from large-seeded species. Seedlings from larger seeds are larger than those of small-seeded species, but have a lower root/shoot biomass ratio, leading to greater potential evapotranspiration, which could explain their loss of relative advantage under extreme droughts.
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
    Published by Wiley on behalf of The International Association for Vegetation Science (IAVS).
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  • 90
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    A topography-based scaling algorithm for soil hydraulic parameters at hillslope scales: Field testing (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Description: Soil hydraulic parameters were upscaled from a 30 m resolution to a 1 km resolution using a new aggregation scheme (described in the companion paper) where the scale parameter was based on the topography. When soil hydraulic parameter aggregation or upscaling schemes ignore the effect of topography, their application becomes limited at hillslope scales and beyond, where topography plays a dominant role in soil deposition and formation. Hence the new upscaling algorithm was tested at the hillslope scale (1 km) across two locations: (1) the Little Washita watershed in Oklahoma, and (2) the Walnut Creek watershed in Iowa. The watersheds were divided into pixels of 1 km resolution and the effective soil hydraulic parameters obtained for each pixel. Each pixel/domain was then simulated using the physically based HYDRUS-3-D modeling platform. In order to account for the surface (runoff/on) and subsurface fluxes between pixels, an algorithm to route infiltration-excess runoff onto downstream pixels at daily time steps and to update the soil moisture states of the downstream pixels was applied. Simulated soil moisture states were compared across scales, and the coarse scale values compared against the airborne soil moisture data products obtained during the hydrology experiment field campaign periods (SGP97 and SMEX02) for selected pixels with different topographic complexities, soil distributions, and land cover. Results from these comparisons show good correlations between simulated and observed soil moisture states across time, topographic variations, location, elevation, and land cover. Stream discharge comparisons made at two gauging stations in the Little Washita watershed also provide reasonably good results as to the suitability of the upscaling algorithm used. Based only on the topography of the domain, the new upscaling algorithm was able to provide coarse resolution values for soil hydraulic parameters which effectively captured the variations in soil moisture across the watershed domains.
    Print ISSN: 0043-1397
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    Projections of future water resources and their uncertainty in a glacierized catchment in the Swiss Alps and the subsequent effects on hydropower production during the 21st century (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Description: Hydropower accounts for about 20% of the worldwide electrical power production. In mountainous regions this ratio is significantly higher. In this study we present how future projected climatic forcing, as described in regional climate models (RCMs), will affect water resources and subsequently hydropower production in downstream hydropower plants in a glacierized alpine valley (Vispa valley, Switzerland, 778 km2). In order to estimate future runoff generation and hydropower production, we used error-corrected and downscaled climate scenarios from regional climate models (RCMs) as well as glacier retreat projections from a dynamic glacier model and coupled them to a physically based hydrological model. Furthermore, we implemented all relevant hydropower operational rules in the hydrological model to estimate future hydropower production based on the runoff projections. The uncertainty of each modeling component (climate projections, glacier retreat, and hydrological projection) and the resulting propagation of uncertainty to the projected future water availability for energy production were assessed using an analysis of variance. While the uncertainty of the projections is considerable, the consistent trends observed in all projections indicate significant changes to the current situation. The model results indicate that future melt- and rainfall-runoff will increase during spring but decline during summer. The study concludes by outlining the most relevant expected changes for hydropower operations.
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    North American vegetation model for land-use planning in a changing climate: a solution to large classification problems (2012)
    Wiley
    Details
    Publication Date: 2012-02-19
    Description: Ecological Applications, Volume 22, Issue 1, Page 119-141, January 2012.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 93
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    Assessment of monitoring power for highly mobile vertebrates (2012)
    Wiley
    Details
    Publication Date: 2012-02-19
    Description: Ecological Applications, Volume 22, Issue 1, Page 374-383, January 2012.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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    Decoupling of component and ensemble density feedbacks in birds and mammals (2012)
    Wiley
    In: Ecology
    Details
    Publication Date: 2012-02-18
    Description: Ecology, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 0012-9658
    Electronic ISSN: 1939-9170
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 95
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    RESTORING NATIVE FISH ASSEMBLAGES TO A REGULATED CALIFORNIA STREAM USING THE NATURAL FLOW REGIME CONCEPT (2012)
    Wiley
    Details
    Publication Date: 2012-02-18
    Description: Ecological Applications, Volume 0, Issue 0, Ahead of Print.
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 96
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    Transparent Nanocrystalline Pure and Ca-Doped MgO by Spark Plasma Sintering of Anhydrous Nanoparticles (2012)
    Wiley
    Details
    Publication Date: 2012-02-21
    Description: Fully dense nanocrystalline MgO -based ceramics were consolidated by field and pressure assisted sintering (also known as Spark Plasma Sintering) using anhydrous nanosized powders (~5 nm) prepared by laser ablation and handled in a controlled, water-free environment prior to sintering. The high reactivity of the powders promoted excellent sinterability at relatively low temperatures. Highly transparent specimens were produced by sintering at 0.23–0.28 T m (650°C–800°C) for 15–30 min with good control over the final nanometric grain size. To preserve the nanocrystalline nature of the samples, the high temperature exposure time during sintering was reduced by the application of 300 MPa uniaxial pressure; higher pressure or two-step procedures did not provide extra benefits to densification or microstructural control.
    Print ISSN: 0002-7820
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Low Temperature Sintering of Innovative Bioactive Glasses (2012)
    Wiley
    Details
    Publication Date: 2012-02-21
    Description: Two innovative glass compositions based on the commonly used 45S5 Bioglass ® were developed by increasing the calcium quantity and replacing the sodium oxide with a specific content of potassium oxide. The new glasses, named BG_ Ca / K and BG _ Ca /Mix, can be prepared using a conventional melting process and show a very low tendency to crystallize. Thanks to this peculiarity, BG_ Ca / K and BG_ Ca /Mix powders can be sintered at a relatively low temperature (800°C) to obtain samples of high compactness and bioactivity, since their amorphous nature is preserved. Consequently, the proposed glasses are perfect for making specific products such as scaffolds or hydroxyapatite-based composites. Furthermore, the relatively low alkali amount in the new compositions gives rise to a slow ion leaching in simulated body fluid, thus avoiding abrupt changes in pH that can damage osteoblasts or negatively affect their behavior.
    Print ISSN: 0002-7820
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  • 98
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    Effect of spatial concentration fluctuations on effective kinetics in diffusion-reaction systems (2012)
    Wiley
    Details
    Publication Date: 2012-02-21
    Description: The effect of spatial concentration fluctuations on the reaction of two solutes, A + B ⇀ C, is considered. In the absence of fluctuations, the concentration of solutes decays as Adet = Bdet ∼ t−1. Contrary to this, experimental and numerical studies suggest that concentrations decay significantly slower. Existing theory suggests a t−d/4 scaling in the asymptotic regime (d is the dimensionality of the problem). Here we study the effect of fluctuations using the classical diffusion-reaction equation with random initial conditions. Initial concentrations of the reactants are treated as correlated random fields. We use the method of moment equations to solve the resulting stochastic diffusion-reaction equation and obtain a solution for the average concentrations that deviates from ∼t−1 to ∼t−d/4 behavior at characteristic transition time t*. We also derive analytical expressions for t* as a function of Damköhler number and the coefficient of variation of the initial concentration.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
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  • 99
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    Correction to “Spatial and temporal dynamics in eddy covariance observations of methane fluxes at a tundra site in northeastern Siberia” (2012)
    Wiley
    Details
    Publication Date: 2012-02-22
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 100
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    Detecting non-linear response of spring phenology to climate change by Bayesian analysis (2012)
    Wiley
    Details
    Publication Date: 2012-12-25
    Description: The impact of climate change on the advancement of plant phenological events has been heavily studied in the last decade. While the majority of spring plant phenological events have been trending earlier, this is not universally true. Recent work has suggested that species that are not advancing in their spring phenological behavior are responding more to lack of winter chill than increased spring heat. One way to test this hypothesis is by evaluating the behavior of a species known to have a moderate to high chilling requirement and examining how it is responding to increased warming. This study used a 60-year data set for timing of leaf-out and male flowering of walnut ( Juglans regia ) cultivar ‘Payne’ to examine this issue. The spring phenological behavior of ‘Payne’ walnut differed depending on bud type. The vegetative buds, which have a higher chilling requirement, trended towards earlier leaf-out until about 1994, when they shifted to later leaf-out. The date of male bud pollen shedding advanced over the course of the whole record. Our findings suggest that many species which have exhibited earlier bud-break are responding to warmer spring temperatures, but may shift into responding more to winter temperatures (lack of adequate chilling) as warming continues. © 2012 Blackwell Publishing Ltd
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
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