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  • 1
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    A Novel Method to Determine the Volume of Sensitivity for Soil Moisture Sensors (2012)
    Wiley
    Details
    Publication Date: 2012-10-19
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 2
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    Plant diversity effects on aboveground and belowground N pools in temperate grassland ecosystems: Development in the first 5 years after establishment (2011)
    Wiley
    Details
    Publication Date: 2011-05-25
    Description: Biodiversity is expected to improve ecosystem services, e.g., productivity or seepage water quality. The current view of plant diversity effects on element cycling is based on short-term grassland studies that discount possibly slow belowground feedbacks to aboveground diversity. Furthermore, these grasslands were established on formerly arable land associated with changes in soil properties, e.g., accumulation of organic matter. We hypothesize that the plant diversity-N cycle relationship changes with time since establishment. We assessed the relationship between plant diversity and (1) aboveground and soil N storage and (2) NO3-N and NH4-N availability in soil between 2003 and 2007 in the Jena Experiment, a grassland experiment established in 2002 in which the number of plant species varied from 1 to 60. The positive effect of plant diversity on aboveground N storage (mainly driven by biomass production) tended to increase through time. The initially negative correlation between plant diversity and soil NO3-N availability disappeared after 2003. In 2006 and 2007, a positive correlation between plant diversity and soil NH4-N availability appeared which coincided with a positive correlation between plant diversity and N mineralized from total N accumulated in soil. We conclude that the plant diversity-N cycle relationship in newly established grasslands changes with time because of accumulation of organic matter in soil associated with the establishment. While a positive relationship between plant diversity and soil N storage improves soil fertility and reduces fertilizing needs, increasingly closed N cycling with increasing plant diversity as illustrated by decreased NO3-N concentrations in diverse mixtures reduces the negative impact of agricultural N leaching on groundwater resources.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Application of Thin-Film Manufacturing Technologies to Solid Oxide Fuel Cells and Gas Separation Membranes (2013)
    Wiley
    Details
    Publication Date: 2013-02-23
    Description: The implementation of thin-film technologies in energy-related applications, such as special fuel cells and gas separation membranes for low-emission power plants, is essential in terms of enhancing the functionality, reducing operating temperatures, and increasing lifetime. Introducing thin electrolyte layers into solid oxide fuel cells (SOFCs) decreases the internal cell resistance and thus drastically enhances the power density. This supports the goal of reducing the operation temperature from ~800°C to temperatures below 700°C. As the operation temperature is lowered, the temperature-activated degradation processes are slowed down, and 40,000 h of operation becomes feasible. Reducing the thickness of the gas separation membranes also reduces internal losses, and therefore, the rate-limiting steps within the layer. Thinner functional layers possess higher permeabilities but also involve a risk of more layer defects. This also holds for the fuel cells. Thus, the manufacturing of the supports and the intermediate layers is also very important. The paper gives an overview of the application of thin-film technologies to SOFCs and gas separation membranes and highlights the efforts to date. Examples include SOFC stacks operated stably for in excess of 40,000 h and submicron-sized membranes with high permeability and good separation factors.
    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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  • 4
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    Estimation of clay content from easily measurable water content of air-dried soil (2012)
    Wiley
    Details
    Publication Date: 2012-04-15
    Description: Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil-texture analysis is costly and time-consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot-scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air-dried soil. The soil samples used for this study originated from four different European regions (Hainich-Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air-dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air-dried soil samples ranged from 2.8 g kg –1 to 63.3 g kg –1 and the corresponding clay contents from 60.0 g kg –1 to 815.7 g kg –1 . A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air-dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine-textured than in coarse-textured soils. In this study, organic-C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse-textured soils was more sensitive to the amount of organic C than that of fine-textured soils. The results indicate that in our study the water content of air-dried soil samples was a good quantitative proxy of clay contents, especially useful for fine-textured soils.
    Print ISSN: 1436-8730
    Electronic ISSN: 1522-2624
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 5
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    Large-scale bioenergy from additional harvest of forest biomass is neither sustainable nor greenhouse gas neutral (2012)
    Wiley
    Details
    Publication Date: 2012-04-15
    Description: Owing to the peculiarities of forest net primary production humans would appropriate ca. 60% of the global increment of woody biomass if forest biomass were to produce 20% of current global primary energy supply. We argue that such an increase in biomass harvest would result in younger forests, lower biomass pools, depleted soil nutrient stocks and a loss of other ecosystem functions. The proposed strategy is likely to miss its main objective, i.e. to reduce greenhouse gas (GHG) emissions, because it would result in a reduction of biomass pools that may take decades to centuries to be paid back by fossil fuel substitution, if paid back at all. Eventually, depleted soil fertility will make the production unsustainable and require fertilization, which in turn increases GHG emissions due to N 2 O emissions. Hence, large-scale production of bioenergy from forest biomass is neither sustainable nor GHG neutral.
    Print ISSN: 1757-1693
    Electronic ISSN: 1757-1707
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Wiley
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  • 6
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    Seasonal variation of upwelling in the Alaskan Beaufort Sea: Impact of sea ice cover (2012)
    Wiley
    Details
    Publication Date: 2012-06-27
    Description: Data from a mooring array deployed from August 2002 to September 2004 are used to characterize differences in upwelling near the shelf break in the Alaskan Beaufort Sea due to varying sea ice conditions. The record is divided into three ice seasons: open water, partial ice, and full ice. The basic response is the same in each of the seasons. Roughly 8 h after the onset of easterly winds the shelf break jet reverses, followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break (Pacific Winter Water) and warm at depth (Atlantic Water). The secondary circulation at the outer shelf is, to first order, consistent with a two-dimensional Ekman balance of offshore flow in the upper layer and onshore flow at depth. There are, however, important seasonal differences in the upwelling. Overall the response is strongest in the partial ice season and weakest in the full ice season. It is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack-ice, as the strength of the wind-forcing was comparable over the three seasons. An EOF-based upwelling index is constructed using information about the primary flow, secondary flow, and hydrography. The ability to predict upwelling using the wind record alone is explored, which demonstrates that 90% of easterly wind events exceeding 9.5 m s−1 drive significant upwelling. During certain periods the ice cover on the shelf became landfast, which altered the upwelling and circulation patterns near the shelf break.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Field method for separating the contribution of surface-connected preferential flow pathways from flow through the soil matrix (2012)
    Wiley
    Details
    Publication Date: 2012-04-28
    Description: Liquid latex was used as a method to seal visible surface-connected preferential flow pathways (PFPs) in the field in an effort to block large surface-connected preferential flow and force water to move through the soil matrix. The proposed approach allows for the quantification of the contribution of large surface-connected cracks and biological pores to infiltration at various soil moisture states. Experiments were conducted in a silty clay loam soil in a field under a no-till corn-soybean rotation planted to corn. Surface intake rates under ponding were measured using a simplified falling head technique under two scenarios: (1) natural soil conditions with unaltered PFPs and (2) similar soil conditions with latex-sealed large macropores at the surface. Results indicated that the contribution of flow from large surface-connected macropores to overall surface intake rates varied from approximately 34% to 99% depending on the initial moisture content and macroporosity present. However, evidence of preferential flow continued to appear in latex-sealed plots, suggesting significant contributions to preferential flow from smaller structural macropores, particularly in two out of four tests where no significant differences were observed between control and latex-sealed plots.
    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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    Low Temperature Crystallization of Metastable Nickel Manganite Spinel Thin Films (2012)
    Wiley
    Details
    Publication Date: 2012-05-16
    Description: Single-phase metastable cubic spinel nickel manganite films, 0.5 ≤ Mn/(Mn+Ni) ≤ 0.8, were produced using chemical solution deposition. Of these, the sample with Mn/(Mn+Ni) = 0.80 showed the lowest electrical resistivity. Films annealed in Argon at 400°C for 5 h exhibit temperature coefficient of resistance values ranging from −3.81 to −3.93%/K and electrical resistivities of ~10 kΩ-cm. It was found by transmission electron microscopy that the metastable spinel phase appeared in both pyrolyzed and post-deposition annealed films. Spectroscopic ellipsometry measurements over the spectral range from 0.75 to 6.0 eV showed that the complex dielectric function spectra ( ε = ε 1  + iε 2 ) varied as a function of the annealing conditions, due at least in part to changes in film density. Aging experiments have been used to identify variations in resistivity and temperature coefficient of resistance as functions of time to assess material stability. As a result, the aging coefficient was 6.5% for a film with Mn/(Ni+Mn) = 0.80 after aging at 150°C for 500 h.
    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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  • 9
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    Estimation of clay content from easily measurable water content of air-dried soil (2012)
    Wiley
    Details
    Publication Date: 2012-03-08
    Description: Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil-texture analysis is costly and time-consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot-scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air-dried soil. The soil samples used for this study originated from four different European regions (Hainich-Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air-dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air-dried soil samples ranged from 2.8 g kg –1 to 63.3 g kg –1 and the corresponding clay contents from 60.0 g kg –1 to 815.7 g kg –1 . A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air-dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine-textured than in coarse-textured soils. In this study, organic-C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse-textured soils was more sensitive to the amount of organic C than that of fine-textured soils. The results indicate that in our study the water content of air-dried soil samples was a good quantitative proxy of clay contents, especially useful for fine-textured soils.
    Print ISSN: 1436-8730
    Electronic ISSN: 1522-2624
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
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    Atomic Layer Deposition of Alumina onto Carbon Fibers (2011)
    Wiley
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    Publication Date: 2011-02-19
    Description: Bundles of carbon fibers were successfully coated with alumina by atomic layer deposition via sequential exposures to trimethylaluminum and water at 77°C. Fibers were not damaged by this procedure. Scanning electron microscopy (SEM) images revealed that individual filaments were coated separately with a smooth layer; no bridging of fibers was observed. Transmission electron microscopy (TEM) and SEM images indicate that the coating was conformal and adhered well to the fiber surface. The average deposition rate was 0.25±0.02 nm/cycle, calculated from SEM images obtained at various positions of the fibers and of fibers coated with various numbers of cycles. In addition to image analysis, the coating thickness was as well estimated from the elemental composition of selected parts of a fiber bundle that was coated by 450 cycles. Along the fiber axis, the weight fraction of aluminum of the coated fibers varied from 5.3 to 6.5 wt% and perpendicular to the bundle axis it varied from 4.8 to 7.4 wt%. This translates into a variation of the estimated coating thickness along the fiber from 166 to 126 nm and perpendicular to it from 114 to 183 nm. One can estimate independently an average coating thickness from the analysis of SEM images of this specific bundle of 126 nm. The alumina coating improved oxidation resistance of the carbon fiber significantly. The oxidation onset temperature was 600°C for fibers coated with a 30-nm-thick layer of alumina and increased gradually with increasing coating thickness up to 660°C at a thickness of 120 nm. On the other hand, uncoated fibers started to oxidize already at 300°C.
    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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