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  • Emerald  (17,284)
  • Blackwell Publishing Ltd  (14,210)
  • Springer Science + Business Media
  • 2020-2024  (14)
  • 2000-2004  (31,482)
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  • 1
    Publication Date: 2023-01-20
    Description: Stable hydrogen isotope ratios (δ2H values) in structural hydroxyl groups of pedogenic clay minerals are inherited from the surrounding water at the time of their formation. Only non‐exchangeable H preserves the environmental forensic and paleoclimate information (δ2Hn value). To measure δ2Hn values in structural H of clay minerals and soil clay fractions, we adapted a steam equilibration method by accounting for high hygroscopicity. Our δ2Hn values for USGS57 biotite (−95.3 ± SD 0.9‰) and USGS58 muscovite (30.7 ± 1.4‰) differed slightly but significantly from the reported δ2H values (−91.5 ± 2.4‰ and −28.4 ± 1.6‰), because the minerals contained 1.1%–4.4% of exchangeable H. The low SD of replicate measurements (n = 3) confirmed a high precision. The clay separation method including destruction of Fe oxides, carbonates and soil organic matter, and dispersion did not significantly change the δ2Hn values of five different clay minerals. However, we were unable to remove all organic matter from the soil clay fractions resulting in an estimated bias of 1‰ in two samples and 15‰ in the carbon‐richest sample. Our results demonstrate that δ2Hn values of structural H of clay minerals and soil clay fractions can be reliably measured without interference from atmospheric water and the method used to separate the soil clay fraction. Highlights We tested steam equilibration to determine stable isotope ratios of structural H in clay. Gas‐tight capsule sealing in Ar atmosphere was necessary to avoid remoistening. Our steam equilibration method showed a high accuracy and precision. The clay separation method did not change stable isotope ratios of structural H in clay.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:549 ; controlled isotope exchange technique ; deuterium ; montmorillonite ; soil clay separation ; soil organic matter removal ; steam equilibration ; structural H ; USGS57 biotite ; vermiculite ; δ2H
    Language: English
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  • 2
    Publication Date: 2023-01-26
    Description: Erosion is a severe threat to the sustainable use of agricultural soils. However, the structural resistance of soil against the disruptive forces steppe soils experience under field conditions has not been investigated. Therefore, 132 topsoils under grass‐ and cropland covering a large range of physico‐chemical soil properties (sand: 2–76%, silt: 18–80%, clay: 6–30%, organic carbon: 7.3–64.2 g kg−1, inorganic carbon: 0.0–8.5 g kg−1, pH: 4.8–9.5, electrical conductivity: 32–946 μS cm−1) from northern Kazakhstan were assessed for their potential erodibility using several tests. An adjusted drop‐shatter method (low energy input of 60 Joule on a 250‐cm3 soil block) was used to estimate the stability of dry soil against weak mechanical forces, such as saltating particles striking the surface causing wind erosion. Three wetting treatments with various conditions and energies (fast wetting, slow wetting, and wet shaking) were applied to simulate different disruptive effects of water. Results indicate that aggregate stability was higher for grassland than cropland soils and declined with decreasing soil organic carbon content. The results of the drop‐shatter test suggested that 29% of the soils under cropland were at risk of wind erosion, but only 6% were at high risk (i.e. erodible fraction 〉60%). In contrast, the fast wetting treatment revealed that 54% of the samples were prone to become “very unstable” and 44% “unstable” during heavy rain or snowmelt events. Even under conditions comparable to light rain events or raindrop impact, 53–59% of the samples were “unstable.” Overall, cropland soils under semi‐arid conditions seem much more susceptible to water than wind erosion. Considering future projections of increasing precipitation in Kazakhstan, we conclude that the risk of water erosion is potentially underestimated and needs to be taken into account when developing sustainable land use strategies. Highlights Organic matter is the important binding agent enhancing aggregation in steppe topsoils. Tillage always declines aggregate stability even without soil organic carbon changes. All croplands soil are prone to wind or water erosion independent of their soil properties. Despite the semi‐arid conditions, erosion risk by water seems higher than by wind.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:631.4 ; climate change ; land use ; soil organic carbon ; soil texture ; water erosion ; wind erosion
    Language: English
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  • 3
    Publication Date: 2023-01-21
    Description: Charcoal‐rich Technosols on century‐old relict charcoal hearths (RCHs) are the subject of ongoing research regarding potential legacy effects that result from historic charcoal production and subsequent charcoal amendments on forest soil properties and forest ecosystems today. RCHs consist mostly of Auh horizons that are substantially enriched in soil organic carbon (SOC), of which the largest part seems to be of pyrogenic origin (PyC). However, the reported range of SOC and PyC contents in RCH soil also suggests that they are enriched in nonpyrogenic SOC. RCH soils are discussed as potential benchmarks for the long‐term influence of biochar amendment and the post‐wildfire influences on soil properties. In this study, we utilised a large soil sample dataset (n = 1245) from 52 RCH sites in north‐western Connecticut, USA, to quantify SOC contents by total element analysis. The contents of condensed highly aromatic carbon as a proxy for black carbon (BC) were predicted by using a modified benzene polycarboxylated acid (BPCA) marker method in combination with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy‐based partial least square regression (r2 = 0.89). A high vertical spatial sampling resolution allowed the identification of soil organic matter (SOM) enrichment and translocation processes. The results show an average 75% and 1862% increase in TOC and BPCA‐derived carbon, respectively, for technogenic Auh horizons compared to reference soils. In addition to an increase in aromatic properties, increased carboxylic properties of the RCH SOC suggest self‐humification effects of degrading charcoal and thereby the continuing formation of leachable aromatic carbon compounds, which could have effects on pedogenic processes in buried soils. Indeed, we show BPCA‐derived carbon concentrations in intermediate technogenic Cu horizons and buried top/subsoils that suggest vertical translocation of highly aromatic carbon originating in RCH Auh horizons. Topmost Auh horizons showed a gradual decrease in total organic carbon (TOC) contents with increasing depth, suggesting accumulation of recent, non‐pyrogenic SOM. Lower aliphatic absorptions in RCH soil spectra suggest different SOM turnover dynamics compared to reference soils. Furthermore, studied RCH soils featured additional TOC enrichment, which cannot be fully explained now. Highlights BC to TOC ratio and high resolution vertical SOC distribution in 52 RCH sites were studied. RCH soils non‐BC pool was potentially different to reference soils. RCH soils feature TOC accumulation in the topmost horizon. There is BC translocation into buried soils on RCH sites.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; benzene polycarboxylated acid marker (BPCA) ; black carbon ; charcoal degradation ; charcoal kiln ; pyrogenic carbon ; relict charcoal hearth ; biochar
    Language: English
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  • 4
    Publication Date: 2024-02-28
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Hydrogeological information about an aquifer is difficult and costly to obtain, yet essential for the efficient management of groundwater resources. Transferring information from sampled sites to a specific site of interest can provide information when site‐specific data is lacking. Central to this approach is the notion of site similarity, which is necessary for determining relevant sites to include in the data transfer process. In this paper, we present a data‐driven method for defining site similarity. We apply this method to selecting groups of similar sites from which to derive prior distributions for the Bayesian estimation of hydraulic conductivity measurements at sites of interest. We conclude that there is now a unique opportunity to combine hydrogeological expertise with data‐driven methods to improve the predictive ability of stochastic hydrogeological models.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉Article impact statement〈/italic〉: This article introduces hierarchical clustering as a method for defining a notion of site similarity; the aim of this method is to improve the derivation of prior distributions in Bayesian methods in hydrogeology.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://github.com/GeoStat-Bayesian/geostatDB
    Description: https://github.com/GeoStat-Bayesian/exPrior
    Description: https://github.com/GeoStat-Bayesian/siteSimilarity
    Keywords: ddc:551.49 ; hydrogeological sites ; hydrogeological modeling
    Language: English
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  • 5
    Publication Date: 2024-01-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Flood risk assessments require different disciplines to understand and model the underlying components hazard, exposure, and vulnerability. Many methods and data sets have been refined considerably to cover more details of spatial, temporal, or process information. We compile case studies indicating that refined methods and data have a considerable effect on the overall assessment of flood risk. But are these improvements worth the effort? The adequate level of detail is typically unknown and prioritization of improvements in a specific component is hampered by the lack of an overarching view on flood risk. Consequently, creating the dilemma of potentially being too greedy or too wasteful with the resources available for a risk assessment. A “sweet spot” between those two would use methods and data sets that cover all relevant known processes without using resources inefficiently. We provide three key questions as a qualitative guidance toward this “sweet spot.” For quantitative decision support, more overarching case studies in various contexts are needed to reveal the sensitivity of the overall flood risk to individual components. This could also support the anticipation of unforeseen events like the flood event in Germany and Belgium in 2021 and increase the reliability of flood risk assessments.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: BMBF http://dx.doi.org/10.13039/501100002347
    Description: Federal Environment Agency http://dx.doi.org/10.13039/501100010809
    Description: http://howas21.gfz-potsdam.de/howas21/
    Description: https://www.umwelt.niedersachsen.de/startseite/themen/wasser/hochwasser_amp_kustenschutz/hochwasserrisikomanagement_richtlinie/hochwassergefahren_und_hochwasserrisikokarten/hochwasserkarten-121920.html
    Description: https://download.geofabrik.de/europe/germany.html
    Description: https://emergency.copernicus.eu/mapping/list-of-components/EMSN024
    Description: https://data.jrc.ec.europa.eu/collection/id-0054
    Description: https://oasishub.co/dataset/surface-water-flooding-footprinthurricane-harvey-august-2017-jba
    Description: https://www.wasser.sachsen.de/hochwassergefahrenkarte-11915.html
    Keywords: ddc:551.48 ; decision support ; extreme events ; integrated flood risk management ; risk assessment
    Language: English
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  • 6
    Publication Date: 2024-02-09
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Gas transport in soils is usually assumed to be purely diffusive, although several studies have shown that non‐diffusive processes can significantly enhance soil gas transport. These processes include barometric air pressure changes, wind‐induced pressure pumping and static air pressure fields generated by wind interacting with obstacles. The associated pressure gradients in the soil can cause advective gas fluxes that are much larger than diffusive fluxes. However, the contributions of the respective transport processes are difficult to separate. We developed a large chamber system to simulate pressure fields and investigate their influence on soil gas transport. The chamber consists of four subspaces in which pressure is regulated by fans that blow air in or out of the chamber. With this setup, we conducted experiments with oscillating and static pressure fields. CO〈sub〉2〈/sub〉 concentrations were measured along two soil profiles beneath the chamber. We found a significant relationship between static lateral pressure gradients and the change in the CO〈sub〉2〈/sub〉 profiles (R〈sup〉2〈/sup〉 = 0.53; 〈italic toggle="no"〉p〈/italic〉‐value 〈2e‐16). Even small pressure gradients between −1 and 1 Pa relative to ambient pressure resulted in an increase or decrease in CO〈sub〉2〈/sub〉 concentrations of 8% on average in the upper soil, indicating advective flow of air in the pore space. Positive pressure gradients resulted in decreasing, negative pressure gradients in increasing CO〈sub〉2〈/sub〉 concentrations. The concentration changes were probably caused by an advective flow field in the soil beneath the chamber generated by the pressure gradients. No effect of oscillating pressure fields was observed in this study. The results indicate that static lateral pressure gradients have a substantial impact on soil gas transport and therefore are an important driver of gas exchange between soil and atmosphere. Lateral pressure gradients in a comparable range can be induced under windy conditions when wind interacts with terrain features. They can also be caused by chambers used for flux measurements at high wind speed or by fans used for head‐space mixing within the chambers, which yields biased flux estimates.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; advective flux ; chamber flux measurements ; static air pressure fields ; wind‐induced pressure pumping
    Language: English
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  • 7
    Publication Date: 2023-11-18
    Description: Spatiotemporal characterisation of the soil redox status within the capillary fringe (CF) is a challenging task. Air‐filled porosities (ε), oxygen concentration (O〈sub〉2〈/sub〉) and soil redox potential (EH) are interrelated soil variables within active biogeochemical domains such as the CF. We investigated the impact of water table (WT) rise and drainage in an undisturbed topsoil and subsoil sample taken from a Calcaric Gleysol for a period of 46 days. We merged 1D (EH and matric potential) and 2D (O〈sub〉2〈/sub〉) systems to monitor at high spatiotemporal resolution redox dynamics within self‐constructed redoxtron housings and complemented the data set by a 3D pore network characterization using X‐ray microtomography (X‐ray μCT). Depletion of O〈sub〉2〈/sub〉 was faster in the organic matter‐ and clay‐rich aggregated topsoil and the CF extended 〉10 cm above the artificial WT. The homogeneous and less‐aggregated subsoil extended only 4 cm above the WT as indicated by ε–O〈sub〉2〈/sub〉–EH data during saturation. After drainage, 2D O〈sub〉2〈/sub〉 imaging revealed a fast aeration towards the lower depths of the topsoil, which agrees with the connected ε derived by X‐ray μCT (ε〈sub〉CT_conn〈/sub〉) of 14.9% of the total porosity. However, small‐scaled anoxic domains with O〈sub〉2〈/sub〉 saturation 〈5% were apparent even after lowering the WT (down to 0.25 cm〈sup〉2〈/sup〉 in size) for 23 days. These domains remained a nucleus for reducing soil conditions (E〈sub〉H〈/sub〉 〈 −100 mV), which made it challenging to characterise the soil redox status in the CF. In contrast, the subsoil aeration reached O〈sub〉2〈/sub〉 saturation after 8 days for the complete soil volume. Values of ε〈sub〉CT_conn〈/sub〉 around zero in the subsoil highlighted that soil aeration was independent of this parameter suggesting that other variables such as microbial activity must be considered when predicting the soil redox status from ε alone. The use of redoxtrons in combination with localised redox‐measurements and image based pore space analysis resulted in a better 2D/3D characterisation of the pore system and related O〈sub〉2〈/sub〉 transport properties. This allowed us to analyse the distribution and activity of microbiological niches highly associated with the spatiotemporal variable redox dynamics in soil environments. Highlights: The time needed to turn from reducing to oxidising (period where all platinum electrodes feature E〈sub〉H〈/sub〉 〉 300 mV) condition differ for two samples with contrasting soil structure. The subsoil with presumably low O〈sub〉2〈/sub〉 consumption rates aerated considerably faster than the topsoil and exclusively by O〈sub〉2〈/sub〉 diffusion through medium‐ and fine‐sized pores. To derive the soil redox status based upon the triplet ε–O〈sub〉2〈/sub〉–E〈sub〉H〈/sub〉 is challenging at present in heterogeneous soil domains and larger soil volumes than 250 cm〈sup〉3〈/sup〉. Undisturbed soil sampling along with 2D/3D redox measurement systems (e.g., redoxtrons) improve our understanding of redox dynamics within the capillary fringe.
    Keywords: ddc:631.4 ; environmental monitoring ; incubation experiments ; redox processes ; soil reducing conditions ; undisturbed soil ; X‐ray microtomography
    Language: English
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  • 8
    Publication Date: 2023-11-17
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈sec xmlns:mml="http://www.w3.org/1998/Math/MathML" id="ejss13362-sec-1003" xml:lang="en"〉 〈p xml:lang="en"〉Long‐term experiments (LTEs) have provided data to modellers and agronomists to investigate changes and dynamics of soil organic carbon (SOC) under different cropping systems. As treatment changes have occurred due to agricultural advancements, so too have analytical soil methods. This may lead to method bias over time, which could affect the robust interpretation of data and conclusions drawn. This study aims to quantify differences in SOC due to changes in dry combustion methods over time, using soil samples of a LTE established in 1963 that focuses on mineral and organic fertilizer management in the temperate zone of Northeast Germany. For this purpose, 1059 soil samples, collected between 1976 and 2008, have been analysed twice, once with their historical laboratory method right after sampling, and a second time in 2016 when all samples were analysed using the same elementary analyser. In 9 of 11 soil sampling campaigns, a paired 〈italic toggle="no"〉t〈/italic〉‐test provided evidence for significant differences in the historical SOC values when compared with the re‐analysed concentrations of the same LTE sample. In the sampling years 1988 and 2004, the historical analysis obtained about 0.9 g kg〈sup〉−1〈/sup〉 lower SOC compared with the re‐analysed one. For 1990 and 1998, this difference was about 0.4 g kg〈sup〉−1〈/sup〉. Correction factors, an approach often used to correct for different analytical techniques, could only be applied for 5 of 11 sampling campaigns to account for constant and proportional systematic method error. For this particular LTE, the interpretation of SOC changes due to agronomic management (here fertilization) deviates depending on the analytical method used, which may weaken the explanatory power of the historical data. We demonstrate that analytical method changes over time present one of many challenges in the interpretation of time series data of SOC dynamics. Therefore, LTE site managers need to ensure providing all necessary protocols and data in order to retrace method changes and if necessary recalculate SOC.〈/p〉 〈/sec〉〈sec xmlns:mml="http://www.w3.org/1998/Math/MathML" id="ejss13362-sec-0003" xml:lang="en"〉 〈title〉Highlights〈/title〉 〈p xml:lang="en"〉〈list list-type="bullet" id="ejss13362-list-0001"〉 〈list-item id="ejss13362-li-0001"〉〈p〉A total of 1059 LTE soil samples taken between 1976 and 2008 were re‐analysed for SOC in 2016〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0002"〉〈p〉Several methodological changes for SOC determination led to significant different SOC concentration in the same sample〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0003"〉〈p〉Interpretation and time series of LTE soil data suffer from consideration of analytical method changes and poor documentation of the same〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0004"〉〈p〉Soil archive establishment, thorough method protocols and diligent proficiency testing after soil method changes ameliorate the dilemma〈/p〉〈/list-item〉 〈/list〉〈/p〉 〈/sec〉
    Description: Brandenburger Staatsministerium für Wissenschaft, Forschung und Kultur http://dx.doi.org/10.13039/501100004581
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100004937
    Description: https://doi.org/10.4228/zalf-acge-b683
    Keywords: ddc:631.4 ; Bland–Altman ; carbon stocks ; data trueness ; Deming regression ; method bias ; soil archive ; soil survey
    Language: English
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  • 9
    Publication Date: 2023-12-12
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Infrared spectroscopy in the visible to near‐infrared (vis–NIR) and mid‐infrared (MIR) regions is a well‐established approach for the prediction of soil properties. Different data fusion and training approaches exist, and the optimal procedures are yet undefined and may depend on the heterogeneity present in the set and on the considered scale. The objectives were to test the usefulness of partial least squares regressions (PLSRs) for soil organic carbon (SOC), total carbon (C〈sub〉t〈/sub〉), total nitrogen (N〈sub〉t〈/sub〉) and pH using vis–NIR and MIR spectroscopy for an independent validation after standard calibration (use of a general PLSR model) or using memory‐based learning (MBL) with and without spiking for a national spectral database. Data fusion approaches were simple concatenation of spectra, outer product analysis (OPA) and model averaging. In total, 481 soils from an Austrian forest soil archive were measured in the vis–NIR and MIR regions, and regressions were calculated. Fivefold calibration‐validation approaches were carried out with a region‐related split of spectra to implement independent validations with n ranging from 47 to 99 soils in different folds. MIR predictions were generally superior over vis–NIR predictions. For all properties, optimal predictions were obtained with data fusion, with OPA and spectra concatenation outperforming model averaging. The greatest robustness of performance was found for OPA and MBL with spiking with 〈italic toggle="no"〉R〈/italic〉〈sup〉2〈/sup〉 ≥ 0.77 (N), 0.85 (SOC), 0.86 (pH) and 0.88 (C〈sub〉t〈/sub〉) in the validations of all folds. Overall, the results indicate that the combination of OPA for vis–NIR and MIR spectra with MBL and spiking has a high potential to accurately estimate properties when using large‐scale soil spectral libraries as reference data. However, the reduction of cost‐effectiveness using two spectrometers needs to be weighed against the potential increase in accuracy compared to a single MIR spectroscopy approach.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; data fusion ; independent validation ; infrared spectroscopy ; MBL ; nitrogen ; outer product analysis ; pH ; soil organic carbon ; spiking ; total carbon
    Language: English
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  • 10
    Publication Date: 2024-01-19
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In recent years, many two‐dimensional (2D) hydrodynamic models have been extended to include the direct rainfall method (DRM). This allows their application as a hydrological‐hydrodynamic model for the determination of floodplains in one model system. In previous studies on DRM, the role of catchment hydrological processes (CaHyPro) and its interaction with the calibration process was not investigated in detail. In the present, case‐oriented study, the influence of the spatiotemporal distribution of the processes precipitation and runoff formation in combination with the 2D model HEC‐RAS is investigated. In a further step, a conceptual approach for event‐based interflow is integrated. The study is performed on the basis of a single storm event in a small rural catchment (low mountain range, 38 km〈sup〉2〈/sup〉) in Hesse (Germany). The model results are evaluated against six quality criteria and compared to a simplified baseline model. Finally, the calibrated improved model is contrasted with a calibrated baseline model. The results show the enhancement of the model results due to the integration of the CaHyPro and highlight its interplay with the calibrated model parameters.〈/p〉
    Keywords: ddc:551.48 ; 2D hydrodynamic modeling ; calibration ; direct rainfall modeling ; hydrological processes ; radar data ; runoff formation
    Language: English
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  • 11
    Publication Date: 2024-01-26
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The increasing demand for biomass for food, animal feed, fibre and bioenergy requires optimization of soil productivity, while at the same time, protecting other soil functions such as nutrient cycling and buffering, carbon storage, habitat for biological activity and water filter and storage. Therefore, one of the main challenges for sustainable agriculture is to produce high yields while maintaining all the other soil functions. Mechanistic simulation models are an essential tool to fully understand and predict the complex interactions between physical, biological and chemical processes of soils that generate those functions. We developed a soil model to simulate the impact of various agricultural management options and climate change on soil functions by integrating the relevant processes mechanistically and in a systemic way. As a special feature, we include the dynamics of soil structure induced by tillage and biological activity, which is especially relevant in arable soils. The model operates on a 1D soil profile consisting of a number of discrete layers with dynamic thickness. We demonstrate the model performance by simulating crop growth, root growth, nutrient and water uptake, nitrogen cycling, soil organic matter turnover, microbial activity, water distribution and soil structure dynamics in a long‐term field experiment including different crops and different types and levels of fertilization. The model is able to capture essential features that are measured regularly including crop yield, soil organic carbon, and soil nitrogen. In this way, the plausibility of the implemented processes and their interactions is confirmed. Furthermore, we present the results of explorative simulations comparing scenarios with and without tillage events to analyse the effect of soil structure on soil functions. Since the model is process‐based, we are confident that the model can also be used to predict quantities that have not been measured or to estimate the effect of management measures and climate states not yet been observed. The model thus has the potential to predict the site‐specific impact of management decisions on soil functions, which is of great importance for the development of a sustainable agriculture that is currently also on the agenda of the ‘Green Deal’ at the European level.〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://git.ufz.de/bodium/bodium_v1.0
    Keywords: ddc:631.4 ; agriculture ; computational model ; simulation ; soil microbiology ; soil structure ; sustainable soil
    Language: English
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  • 12
    Publication Date: 2024-03-18
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Temperature and soil moisture are known to control pesticide mineralization. Half‐life times (DT〈sub〉50〈/sub〉) derived from pesticide mineralization curves generally indicate longer residence times at low soil temperature and moisture but do not consider potential changes in the microbial allocation of pesticide‐derived carbon (C). We aimed to determine carbon use efficiency (CUE, formation of new biomass relative to total C uptake) to better understand microbial utilization of pesticide‐derived C under different environmental conditions and to support the conventional description of degradation dynamics based on mineralization. We performed a microcosm experiment at two MCPA (2‐methyl‐4‐chlorophenoxyacetic acid) concentrations (1 and 20 mg kg〈sup〉−1〈/sup〉) and defined 20°C/pF 1.8 as optimal and 10°C/pF 3.5 as limiting environmental conditions. After 4 weeks, 70% of the initially applied MCPA was mineralized under optimal conditions but MCPA mineralization reached less than 25% under limiting conditions. However, under limiting conditions, an increase in CUE was observed, indicating a shift towards anabolic utilization of MCPA‐derived C. In this case, increased C assimilation implied C storage or the formation of precursor compounds to support resistance mechanisms, rather than actual growth since we did not find an increase in the 〈italic toggle="no"〉tfdA〈/italic〉 gene relevant to MCPA degradation. We were able to confirm the assumption that under limiting conditions, C assimilation increases relative to mineralization and that C redistribution, may serve as an explanation for the difference between mineralization and MCPA dissipation‐derived degradation dynamics. In addition, by introducing CUE to the temperature‐ and moisture‐dependent degradation of pesticides, we can capture the underlying microbial constraints and adaptive mechanisms to changing environmental conditions.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Changing environmental conditions alter the MCPA degradation dynamics and the allocation of pesticide‐derived carbon to anabolic or catabolic metabolism.〈boxed-text position="anchor" content-type="graphic" id="ejss13417-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:13510754:media:ejss13417:ejss13417-toc-0001"〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: Collaborative Research Center 1253 CAMPOS (DFG)
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: DFG Priority Program 2322 “Soil System”
    Description: Ellrichshausen Foundation
    Description: Research Training Group “Integrated Hydrosystem modeling”
    Description: https://doi.org/10.5281/zenodo.5081655
    Keywords: ddc:631.4 ; anabolism ; carbon use efficiency ; catabolism ; effect of soil moisture and temperature ; gene‐centric process model ; MCPA biodegradation
    Language: English
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  • 13
    Publication Date: 2024-03-22
    Description: Soil fauna drives crucial processes of energy and nutrient cycling in agricultural systems, and influences the quality of crops and pest incidence. Soil tillage is the most influential agricultural manipulation of soil structure, and has a profound influence on soil biology and its provision of ecosystem services. The objective of this study was to quantify through meta‐analyses the effects of reducing tillage intensity on density and diversity of soil micro‐ and mesofaunal communities, and how these effects vary among different pedoclimatic conditions and interact with concurrent management practices. We present the results of a global meta‐analysis of available literature data on the effects of different tillage intensities on taxonomic and functional groups of soil micro‐ and mesofauna. We collected paired observations (conventional vs. reduced forms of tillage/no‐tillage) from 133 studies across 33 countries. Our results show that reduced tillage intensity or no‐tillage increases the total density of springtails (+35%), mites (+23%), and enchytraeids (+37%) compared to more intense tillage methods. The meta‐analyses for different nematode feeding groups, life‐forms of springtails, and taxonomic mite groups showed higher densities under reduced forms of tillage compared to conventional tillage on omnivorous nematodes (+53%), epedaphic (+81%) and hemiedaphic (+84%) springtails, oribatid (+43%) and mesostigmatid (+57%) mites. Furthermore, the effects of reduced forms of tillage on soil micro‐ and mesofauna varied with depth, climate and soil texture, as well as with tillage method, tillage frequency, concurrent fertilisation, and herbicide application. Our findings suggest that reducing tillage intensity can have positive effects on the density of micro‐ and mesofaunal communities in areas subjected to long‐term intensive cultivation practices. Our results will be useful to support decision making on the management of soil faunal communities and will facilitate modelling efforts of soil biology in global agroecosystems. HIGHLIGHTS Global meta‐analysis to estimate the effect of reducing tillage intensity on micro‐ and mesofauna Reduced tillage or no‐tillage has positive effects on springtail, mite and enchytraeid density Effects vary among nematode feeding groups, springtail life forms and mite suborders Effects vary with texture, climate and depth and depend on the tillage method and frequency
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.20387/bonares-eh0f-hj28
    Keywords: ddc:631.4 ; agricultural land use ; conservation agriculture ; conventional agriculture ; soil biodiversity ; soil cultivation
    Language: English
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  • 14
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Andalusite porphyroblasts are totally pseudomorphosed by margarite–paragonite aggregates in aluminous pelites containing the peak mineral assemblage andalusite, chlorite, chloritoid, margarite, paragonite, quartz ± garnet, in a NW Iberia contact area. Equilibria at low P–T are investigated using new KFMASH and (mainly) MnCNKFMASH grids constructed with Thermocalc 3.21. P–T and T–X pseudosections with phase modal volume isopleths are constructed for compositions relatively richer and poorer in andalusite to model the assemblages in an andalusite-bearing rock that contains a thin andalusite-rich band (ARB) during retrogression. Their compositions, prior to retrogression, are used in the modelling, and have been retrieved by restoring the pseudomorph-forming elements into the current-depleted matrix, except for Al2O3 which is assumed to be immobile. Compositional differences between the thin band and the rest of the rock have not resulted in differences in andalusite porphyroblast retrogression. The absence of chloritoid resorbtion implies either a pressure increase at constant reacting-system composition, or that its composition changed during retrogression at constant pressure, by becoming enriched in the progressively replaced andalusite porphyroblasts. T–X pseudosections at 1 kbar model this latter process using as end-members in X, first, the restored original rock and ARB compositions, and, then the same process, taking into account the change in composition of both as retrogression proceeded. The MnNCKFMASH pseudosections of rocks with different Al contents facilitate making further deductions on the rock-composition control of the resulting assemblages upon retrogression. Andalusite eventually disappears in relatively Al-poor rocks, resulting, as in this study, in a rock formed by chloritoid–chlorite as the only FM minerals, plus margarite–paragonite pseudomorphs of andalusite. In rocks richer in Al, chlorite would progressively disappear and a kyanite/andalusite–chloritoid assemblage would eventually be stable at retrograde conditions. The Al-silicate, stable during retrogression in Al-rich rocks, indicates pressure conditions and hence the tectonic context under which retrogression took place.
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    Journal of metamorphic geology 22 (2004), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: In statistically optimised P–T estimation, the contributions to overall uncertainty from different sources are represented by ellipses. One source, for a diffusion-controlled reaction at non-equilibrium, is diffusion modelling of the reaction texture. This modelling is used to estimate ratios, Q, between free-energy differences, ΔG, of reactions among mineral end-members, to replace the equilibrium condition ΔG = 0. The associated uncertainty is compared with those already inherent in the equilibrium case (from end-member data, activity models and mineral compositions). A compact matrix formulation is introduced for activity coefficients, and their partial derivatives governing error propagation. The non-equilibrium example studied is a corona reaction with the assemblage Grt–Opx–Cpx–Pl–Qtz. Two garnet compositions are used, from opposite sides of the corona. In one of them, affected by post-reaction Fe, Mg exchange with pyroxene, the problem of reconstructing the original composition is overcome by direct use of ratios between chemical-potential differences, given by the diffusion modelling. The number of geothermobarometers in the optimisation is limited by near-degeneracies. Their weightings are affected by strong correlations among Q ratios. Uncertainty from diffusion modelling is not large in comparison with other sources. Overall precision is limited mainly by uncertainties in activity models. Hypothetical equilibrium P–T are also estimated for both garnet compositions. By this approach, departure from equilibrium can be measured, with statistical uncertainties. For the example, the result for difference from equilibrium pressure is 1.2 ± 0.7 kbar.
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    Journal of metamorphic geology 22 (2004), S. 0 
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    Journal of metamorphic geology 22 (2004), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: This paper characterizes the metamorphic thermal structure of the Higo Metamorphic Complex (HMC) and presents the results of a numerical simulation of a geotherm with melt migration and solidification. Reconstruction of the geological and metamorphic structure shows that the HMC initially had a simple thermal structure where metamorphic temperatures and pressures increased towards apparent lower structural levels. Subsequently, this initial thermal structure has been collapsed by E–W and NNE–SSW trending high-angle faults. Pressure and temperature conditions using the analysis of mineral assemblages and thermobarometry define a metamorphic field P–T array that may be divided into two segments: the array at apparent higher structural levels has a low-dP/dT slope, whereas that at apparent lower structural levels has a high-dP/dT slope. This composite array cannot be explained by heat conduction in subsolidus rocks alone. Migmatite is exposed pervasively at apparent lower structural levels, but large syn-metamorphic plutons are absent at the levels exposed in the HMC. Transport and solidification of melt within migmatite is a potential mechanism to generate the composite array. Thermal modelling of a geotherm with melt migration and solidification shows that the composite thermal structure may be formed by a change of the dominant heat transfer from an advective regime to a conduction regime with decreasing depth. The model also predicts that strata beneath the crossing point will consist of high-grade solid metamorphic rocks and solidified melt products, such as migmatite. This prediction is consistent with the observation that migmatite was associated with the very high-dP/dT slope. The melt migration model is able to generate the very high-dP/dT segment due to the high rate of heat transfer by advection.
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    Journal of metamorphic geology 22 (2004), S. 0 
    ISSN: 1525-1314
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    Topics: Geosciences
    Notes: Sapphirine, coexisting with quartz, is an indicator mineral for ultrahigh-temperature metamorphism in aluminous rock compositions. Here a new activity-composition model for sapphirine is combined with the internally consistent thermodynamic dataset used by THERMOCALC, for calculations primarily in K2O-FeO-MgO-Al2O3-SiO2-H2O (KFMASH). A discrepancy between published experimentally derived FMAS grids and our calculations is understood with reference to H2O. Published FMAS grids effectively represent constant aH2O sections, thereby limiting their detailed use for the interpretation of mineral reaction textures in compositions with differing H2O.For the calculated KFMASH univariant reaction grid, sapphirine + quartz assemblages occur at P–T in excess of 6–7 kbar and 1005 °C. Sapphirine compositions and composition ranges are consistent with natural examples. However, as many univariant equilibria are typically not ‘seen’ by a specific bulk composition, the univariant reaction grid may reveal little about the detailed topology of multi-variant equilibria, and therefore is of limited use for interpreting the P–T evolution of mineral assemblages and reaction sequences. Calculated pseudosections, which quantify bulk composition and multi-variant equilibria, predict experimentally determined KFMASH mineral assemblages with consistent topology, and also indicate that sapphirine stabilizes at increasingly higher pressure and temperature as XMg increases. Although coexisting sapphirine and quartz can occur in relatively iron-rich rocks if the bulk chemistry is sufficiently aluminous, the P–T window of stability shrinks with decreasing XMg. An array of mineral assemblages and mineral reaction sequences from natural sapphirine + quartz and other rocks from Enderby Land, Antarctica, are reproducible with calculated pseudosections. That consistent phase diagram calculations involving sapphirine can be performed allows for a more thorough assessment of the metamorphic evolution of high-temperature granulite facies terranes than was previously possible. The establishment of a a-x model for sapphirine provides the basis for expansion to larger, more geologically realistic chemical systems (e.g. involving Fe3+).
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    Journal of metamorphic geology 22 (2004), S. 0 
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    Topics: Geosciences
    Notes: Large garnet poikiloblasts hosted by leucosome in metapelitic gneiss from Broken Hill reflect complex mineral–melt relationships. The spatial relationship between the leucosomes and the garnet poikiloblasts implies that the growth of garnet was strongly linked to the production of melt. The apparent difficulty of garnet to nucleate a large number of grains during the prograde breakdown of coexisting biotite and sillimanite led to the spatial focussing of melting reactions around the few garnet nuclei that formed. Continued reaction of biotite and sillimanite required diffusion of elements from where minerals were reacting to sites of garnet growth. This diffusion was driven by chemical potential gradients between garnet-bearing and garnet-absent parts of the rock. As a consequence, melt and peritectic K-feldspar also preferentially formed around the garnet. The diffusion of elements led to the chemical partitioning of the rock within an overall context in which equilibrium may have been approached. Thus, the garnet-bearing leucosomes record in situ melt formation around garnet porphyroblasts rather than centimetre-scale physical melt migration and segregation. The near complete preservation of the high-grade assemblages in the mesosome and leucosome is consistent with substantial melt loss. Interconnected networks between garnet-rich leucosomes provide the most likely pathway for melt migration. Decimetre-scale, coarse-grained, garnet-poor leucosomes may represent areas of melt flux through a large-scale melt transfer network.
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    The @photogrammetric record 19 (2004), S. 0 
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The paper presents a straightforward method of calculating approximate orientation parameters (six degrees of freedom) of a known targeted object relative to a single calibrated camera. These can then initialise an optimised non-linear calculation of the same parameter values. The method uses the mathematics of a scaled parallel projection and is particularly suited to narrow angle images obtained using a telescope, telephoto or zoom lens. However, the method can also be used with cameras having wider fields of view provided the target group occupies a moderately small part of the image.
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    Topics: Architecture, Civil Engineering, Surveying
    Notes: This paper describes three mathematical modelling methods for high-resolution declassified CORONA KH-4B images. Since CORONA images are collected with a panoramic camera, several types of geometric distortions are involved. Two methods use the modified collinearity equations, and the third involves the terrain-dependent rational function model (RFM) which is considered to be a generic sensor model. Comparative analysis of the three mathematical modelling methods is undertaken. The results show that a ± 1·5 pixels level of horizontal and vertical accuracy can be obtained. A digital elevation model (DEM) of a test site is also created.
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    The @photogrammetric record 18 (2003), S. 0 
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    Notes: Digital photogrammetry and softcopy workstations have added a new dimension to aerial triangulation, and some of the previously manual procedures are now available in automated form. Also, commercial software packages for automatic aerial triangulation came on to the market in the last decade. In this study, the results of automatic aerial triangulation using four triangulation software packages, Z/I Imaging's MATCH-AT (ISMAT) and ISAT, LH Systems’ MST and VirtuoZo AAT, are presented. For the comparison of the results of the tie point extraction and the bundle block adjustment for triangulation, a sub-block from the Uster block in Switzerland was selected and used. Differences between these software packages are discussed with respect to their functionality and performance in detail. The achieved standard deviation of image coordinates varies between 0·2 and 0·5 pixel for the systems tested. The more signalised control points and check points to be used, the better the σ0 estimate which could be expected. The average number of extracted tie points varied from system to system with respect to the matching method and the resolution of the images used in the programs. The digital aerial triangulation of the Uster sub-block was faster than analytical triangulation and the elapsed time for triangulation of one image using different systems varies between about 0·5 and 6 min. Nevertheless, results also show that automated aerial triangulation is still prone to error in all systems. Image matching produces many blunders, which can only be handled efficiently by using a sophisticated blunder detection procedure, as is available with robust estimation. This is not the case for all the systems tested, however. There still remains a lot to be done in terms of development (improvement of matching, for example, by integrating robust estimation for error detection at an early stage, implementation of on-line triangulation, better internal quality control procedures, more transparent and simple user interfaces and more useful information for the user with better software manuals). However, it was shown that automatic aerial triangulation provides higher redundancy and reliability of results and much more economical photogrammetric practice than ever before.
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    The @photogrammetric record 17 (2002), S. 0 
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    Notes: The Photogrammetric Society was formed in 1952. The Council of the Society considered that the twentieth anniversary was a good point at which to record the events which led to its formation and the significant occasions and decisions which have taken place since 1952. Consequently, Paul Lamboit was invited to compile this History. He has placed the birth and development of the Society within the national and international photogrammetric context and his record of the deliberations which took place between 1947 and 1952 will be of particular interest to historians of our subject.This account was first published in a limited edition in 1971. Sufficient interest has since been expressed to prompt a wider circulation through publication in the Photogrammetric Record.The author served the Society continuously in several official capacities from 1953 to 1969 and he was elected to Honorary Membership in 1969.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLa Photogrammetric Society a été fondée en 1952. Excellente occasion pour faire le point qu'un vingtiéme anniversaire, a estimé le Conseil de la Société; pour rappeler les circonstances de sa naissance, les étapes de sa croissance et les décisions importantes prises depuis 1952. Ce qu'on invita Paul Lamboit à faire. Son exposé resitue la naissance et le développement de la Société dans le contexte national et international de la photogrammétrie; la relation qu'il fait des décisions prises entre 1947 et 1952 intéressera particulièrement ceux qui s'occupent d'histoire de la photogrammétrie.Ce rapport d'abord publié en édition limitée en 1971, a suscité un intérêt suffisant pour que l'on se presse en le publiant dans le Photogrammetric Record de le porter à la connaissance d'un plus large public.L'auteur a exercé différentes fonctions de 1953 à 1969 dans l'appareil de la Société. Il a étéélu membre honoraire en 1969.〈section xml:id="abs1-3"〉〈title type="main"〉Zusummenfussung1952 wurde die Britische Gesellschaft für Photogrammetrie gegründet. Der Rat der Gesellschaft erwog, dass der zwanzigste Jahrestag eine günstige Gelegenheit sei, um die Ereignisse, die zur Gründung der Gesellschaft führten sowie die bedeutenden Veranstaltungen, die stattfanden und die Entscheidungen, die getroffen wurden, darzustellen. Aus diesem Grunde wurde Paul Lamboit eingeladen, diesen historischen Rückblick zu schreiben. Er hat dabei die Gründung und die Entwicklung der Gesellschaft in den nationalen und internationalen photogrammetrischen Zusammenhang gestellt nd sein Bericht über die zwischen 1947 und 1972 erfolgten Beratungen wird für an unserer Sache interessierte Historiker sehr aufschlussreich sein.Diese Zusammenstellung wurde erstmals in einer begrenzten Auflage im Jahre 1971 veröffentlicht. Genügend Interesse wurde inzwischen bekundet, um eine weitergehende Verteilung mit Hilfe des Photogrammetric Record zu veranlassen.Der Autor diente der Gesellschaft kontinuierlich in verschiedenen Ämtern von 1953 bis 1969, wo er aum Ehrenmitglied gewählt wurde.
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    Notes: Architecture at the Maya archaeological site of Uxmal in Yucatan, Mexico has been documented since the 17th century by historians, archaeologists, illustrators, photographers, and most recently photogrammetrists. This paper reviews the work of the major contributors to recording of architecture at Uxmal with a particular focus on the 19th century stereophotography of Alice and Augustus Le Plongeon who worked to record all the standing architecture at Uxmal, and the close range stereophotogrammetric projects that recorded the Adivino Pyramid during the late 20th century.
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    Notes: This article presents a complete mathematical model, which translates discrepancies between two orthophotographs created from different photographs, into precise corrections of the Digital Elevation Model (DEM). These corrections are the differences from the real surface and, if applied over the existing DEM, can produce a more accurate one. The mathematical model is straightforward, and is not approximate, and therefore there is no need for iterations.Possible applications include checking of automatically created DEMs, refinement of existing DEMs using aerial photographs and update of orthophotographs based on the previous DEM and new imagery.
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    Notes: A scholarly account of the formative discussions, the founding and the first 20 years of the Photogrammetric Society was published in 1971 and republished in 1974. This present review concentrates on the latter years of the life of the Photogrammetric Society prior to its merger with the Remote Sensing Society in 2001.The authors joined the Photogrammetric Society in 1960 and were conspicuous in its affairs for many years. Although both occupied the Society's presidential chair, they also fulfilled several other roles in its efficient management. Atkinson's first contribution to the Photogrammetric Record was published in 1968 and Newton's in 1971.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn a publié en 1971 un compte-rendu détaillé des 20 premières années de la “Photogrammetric Society”, à commencer par les discussions qui présidèrent è sa fondation. Ce récit fut republié en 1974. On se focalise dans cet article sur les dernières années d'activité de la “Photogrammetric Society” qui aboutirent à sa fusion avec la “Remote Sensing Society” en 2001.Les deux auteurs adhérèrent à la “Photogrammetric Society” en 1960 et y furent d‘éminents animateurs pendant de nombreuses années. Tous deux occupèrent le poste de président de cette Association mais remplirent égulement plusieurs autres fonctions qui contribuèrent à une gestion efficace. La première intervention d'Atkinson dans le Photogrummetric Record remonte à 1968, et celle de Newton à 1971.〈section xml:id="abs1-3"〉〈title type="main"〉ZusummenfussungEine wissenschaftliche Abhandlung über die Diskussionen zur Gründung, die Gründung selbst und die ersten 20 Jahre der Photogrammetrischen Gesellschaft wurde in 1971 publiziert und in 1974 wiederholt. Dieser aktulle Rückblick konzentriert sich auf die darauffolgenden Jahre der Photogrammetrischen Gesellschaft bis hin zur Vereinigung mit der Gesellschaft für Fernerkundung in Jahre 2001.Die Autoren wurden 1960 Mitglieder in der Photogrammetrischen Gesellschaft und trugen viele Jahre massgeblich zu deren Aktivitäsidenten der Gesellschaft auch verschiedene andere Aufgaben im Management wahrgenommen. Der erste Beitrag von Atkinson im Photogrammetric Record erschien 1968, der erste von Newton in 1971.
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    Notes: The determination of the attitude, the position and the intrinsic geometric characteristics of the camera is recognised as the fundamental photogrammetric problem. It can be summarised as the determination of camera interior and exterior orientation parameters, as well as the determination of 3D coordinates of object points. The term “exterior orientation” of an image refers to its position and orientation related to an exterior (object space) coordinate system. Several methods can be applied to determine the parameters of the orientation of one, two or more photos. The orientation can be processed in steps (as relative and absolute orientation) but simultaneous methods (such as bundle adjustments) are now available in many software packages. Several methods have also been developed for the orientation of single images. They are based in general on geometric and topological characteristics of imaged objects.This paper presents a survey of classical and modern methods for the determination of the exterior parameters in photogrammetry, some of which are available as software packages (with practical examples) on the Internet. The methods presented are classified in three principal groups. In the first. a selection of approximate methods for applications that do not require great accuracy is presented. Such methods are also used to calculate values required for iterative processes. In the second group, standard point-bused methods derived from collinearity, coplanarity or coangularity conditions are briefly reviewed, followed by line-based approaches. The third group represents orientation methods based on constraints and on concepts of projective geometry, which are becoming of increasing interest for photogrammetrists. In the last section, the paper gives a summary of existing strategies for automatic exterior orientation in aerial photogrammetry.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLa détermination de l'attitude, de la position et des caractéristiques intrinsèques de la chambre photographique constitue un problème fondamental en photogrammétrie. Il se résume à la détermination des paramètres de l'orientation de la chambre de prise de vue (paramètres des orientations externe et interne), ainsi qu'à la détermination des coordonnées 30 des points de l'objet. L'orientation externe se rapporte à la détermination de la position et de l'orientation d'une chambre par rapport à un système externe de coordonnées. Différentes méthodes peuvent être utilisées pour calculer les éléments dorientation externe d'une photo, d'un couple ou de plusieurs photos. Le calcul de l'orientation peut être réalisé par étapes (par exemple les orientations relative et absolue) mais les méthodes simultanées (la compensation par faisceaux par exemple) sont actuellement proposées dans la plupart des logiciels. Plusieurs méthodes ont aussi été développées pour l'orientation d'images isolées. Ells sont basées en général sur les caactéristiques géométriques et topologiques des objets photographiés.Dans cet article on présente un ensemble de méthodes classiques et modernes pour la détermination des paramètres de l'orientation externe, certaines d'entre elles étant téléchargeables sous la forme d'applications sur Internet. Les méthodes présentées sont classées en trois groupes principaux. Le premier groupe contient une sélection de méthodes approximatives utilisées d'habitude quand une grande précision n'est pas exigée, ou encore pour calculer des vuleurs approchées des paramètres extrinsèques requises pour les méthodes itératives rigoureuses. Dans le deuxième groupe, on rappelle brièvement les jondements des méthodes basées sur les conditions photogrammétriques fondamentales (la colinéarité, la coplanéité et la coangularité). Dans ce groupe, les méthodes basées sur l'extraction des points ou des lignes sont également abordées. Le troisième groupe traite des méthodes d'orientation basées sur les contraintes et les concepts de la géométrie projective, de plus en plus utilisées par les photogrammètres. Le dernier paragraphe se rapporte aux méthodes destinées à automatiser le calcul de l'orientation externe en photogrammétrie aérienne.〈section xml:id="abs1-3"〉〈title type="main"〉ZusummenfussungDie Bestimmung der Neigung, der Position und den geometrischen parametern der Kamera wird als das fundamentale Problem der Photogrammetrie angesehen. Es kann zusammenfassend sowohl als die Bestimmung der Parameter der inneren und äusseren Orientierung der Kamera angesehen werden, als auch als die Bestimmung von 3D Koordinaten von Objektpunkten. Der Ausdruck “äussere Orientierung” eines Bildes bezieht sich auf die Lage und Orientierung bezogen auf ein äusseres (Objektraum-) Koordinatensystem. Es können verschiedene Methoden angewandt werden, um die Parameter von einem, zwei oder mehreren Bildern zu bestimmen. Die orientierung kann in Schritten erfolgen, was als Relative und Absolute Orientierung bezeichnet wird, aber auch simultane Methoden, wie die Bündelausgleichung, sind in vielen Softwarepaketen implementiert. Es wurden auch Methoden für die Orientierung von Einzelbildern entwickelt, die geometrische und topologische Eigenschaften der abgebildeten Objekte nutzen. In diesem Beitrag wird Beitrag wird eine Studie klassischer und moderner Methoden der Photogrammetrie zur Bestimmung der Parameter der äßeren Orientierung vorgestellt, wovon einige in Softwarepaketen zur Verfügung stehen, die von praktischen Beispielen im Internet ergänzt werden. Die untersuchten Methoden werden in drei Hauptgruppen eingeteilt. In einer ersten Gruppe werden Näherungslösungen vorgestellt, die für Anwendungen mit geringen Genauigkeitsanforderungen geeignet sind. Diese Methoden werden ansonsten für die Näherngswertberechunggen für iterative Prozesse verwendet. IN der zweiten Gruppe werden zuerst die punktbasierten Standardmethoden vorgestellt, die von Bedingungen zur Kollinearität. Koplanarität und Kowinkligkeit abgeletet sind. Danach folgen linienbasierte Ansätze. Die dritte Gruppe umfasst Orientierungsmethoden, die auf Zwangsbedingungen und auf Konzepte der projektiven Geometrie aufbauen, die für Photogrammeter von zunehmendem Interesse sind, Im letzten Abschnitt wird eine Zusammenfassung existierender Strategien für eine automatische äussere orientierung in der Luftbildphotogrammetrie gegeben.
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    Notes: The aim of this paper is to offer regional evidence from Spain on alcohol abuse among adolescents. Specifically, we identify the determinants of the decision to abuse alcohol with respect to the five most important regions of Spain, as well as for the country as a whole. To this end, we estimate Probit specifications using data drawn from the Spanish Surveys on Drug Use in the School Population corresponding to 1994, 1996 and 1998. The results first reveal patterns that are qualitatively similar, but quantitatively different. Similarly, it would appear that economic policies aimed at reducing the access of adolescents to alcohol may have a positive effect on reducing abuse. Finally, the results suggest that encouragement be given to healthy habits among young people, as well as to the fight against education failure and the launching of information campaigns that accurately portray the current lifestyle of adolescents.
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    Notes: The aim of this study was to determine the knowledge and acceptability of soymilk (defined as consumption pattern/usage and taste) by adult consumers, residing in different socio-economic areas (low vs. high) in Cape Town. The study population of 214 participants were selected using convenience sampling. A questionnaire was developed in order to obtain demographic data (four items); basic general knowledge of soymilk (four items); and acceptability of the tested products (consumption patterns and taste) (eight items). There was a significant difference between the two groups (P = 0.000) regarding basic knowledge of soymilk, with significantly more in the high socio-economic area (HSEA) having a score of at least 75%. Gender (P = 0.082) and age (P = 0.122) did not have a significant impact on the consumption patterns of soymilk. There was no significant difference between the two groups with respect to current usage (P = 0.228) and frequency of use (P = 0.213) of soymilk. However, a significantly smaller group (P = 0.000) of participants in the low socio-economic area had previously tasted soymilk compared with those in the HSEA (16.7% vs. 41.5%; P = 0.000). In conclusion, socio-economic status appeared to be associated with knowledge of soymilk. No significant differences with regard to gender, age or current usage in the two groups studied were noted.
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    Notes: ‘Development’ and the globalization of consumption is leading to a breakdown of biological and cultural diversity, erosion of food security, an increase in violence and devastation for the global biosphere. We urgently need to shift away from economic globalization and homogenization towards localization and diversification.
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    Notes: The promises and pitfalls of agricultural biotechnology have long been debated. The public is often thwarted because consumers frequently perceive as risky, and therefore undesirable, those advances that they do not understand or of which they are unaware. A comparative study of the introduction of a biotechnology innovation in the United States (US) and in the European Union (EU) is a case in point. In the US, despite concerns of consumer protection and environmental groups that the use of genetically produced growth hormone in milk-producing cows will adversely impact the safety of the milk supply, scientific evidence and governmental findings appear to indicate that milk from treated cows is identical in quality, taste and nutritional value to milk from untreated cows. Experience to date in the US demonstrates some consumer resistance to milk from those cows that have received the growth hormone, which typically leads to a 10% increase in milk production. In fact, if there is no perceived differentiation between the two forms of milk, the issue offers little choice to consumers at large, and may result in economic benefit only to selected dairy farmers, as well as the producers of the genetically produced growth hormone. This situation in the US is an example of dysfunctional technology transfer, with perceived desirable benefits to a few, and perceived undesirable benefits to society-at-large. The information suggests that the US may have reacted hastily in approving the use of bovine growth hormone in milk-producing cows. The EU has taken a divergent approach by enacting moratoriums against its use. The differences identified in this study, contrasting responses to the bovine somatotrophin issue in the US and EU – driven in part by general consumer attitudes towards biotechnology – may provide insights into the issues and challenges that will be faced by both advocates and opponents of global proliferation of certain advances in biotechnology.
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    Notes: The purpose of this article is to describe how households in Novgorod the Great, Russia, deal with food provision in everyday life. The study focuses on changes experienced in food provision and consumption in Russian society, in order to illustrate how households respond to the transformation towards a market economy. The study reflects women's perspective on food provision. Students from Novgorod the Great visited 105 households and asked the women in the household to answer a questionnaire. Results from the study show that in order to cope with changes in society related to economic reforms, Russian households had changed both their food consumption and food production patterns. There was no big difference between urban and rural households. Nearly all of the households were self-sufficient in the provision of vegetables and potatoes. Many households had a ‘dacha’ (plot), where they produced most of what they needed. Among the changes experienced during recent years (i.e. during the end of the 1990s), a decade after perestroika was initiated, households mentioned the rise in food prices and the decrease of income. Households reported that they consumed less fruit and/or meat. Some households also mentioned that the quality of nourishment had decreased, thereby indicating lower general quality, lower nutrition value, or less healthy foodstuffs.
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    Notes: Localization: A Global Manifesto. Ed. by Colin Hines (2000). London. Published by Earthscan Publishing. ISBN 1-85383-612-5 (softcover). In Canada, the book is available from for Can$29.00. In the UK, the book is available at for £10.99 or earthinfo@earthscan.co.uk
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    Notes: . Microtubule dynamics in Paramecium caudatum were investigated with an anti-α-tubulin antibody and a microinjection technique to determine the function of microtubules on micronuclear behavior during conjugation. After meiosis, all four haploid micronuclei were connected by microtubular filaments to the paroral region and moved close to this region. This nuclear movement was micronucleus-specific, because some small macronuclear fragments transplanted from exconjugants never moved to the region. Only one of the four germ nuclei moved into the paroral cone and was covered by microtubule assembly (the so-called first assembly of microtubules, AM-I). This nucleus survived there, while the other three not in this region degenerated. The movement of germ nucleus was inhibited by the injection of the anti-α-tubulin antibody. The surviving germ nucleus divided once and produced a migratory pronucleus and a stationary pronucleus. Prior to the reciprocal exchange of the migratory nuclei, microtubules assembled around the migratory pronuclei again (the so-called second assembly of microtubules, AM-II). Then, the migratory pronucleus moved into the partner cell and fused with the stationary pronucleus. Thus, microtubules appear to be indispensable for nuclear behavior: they enable migration of postmeiotic nuclei to the paroral region and they permit the survival of the nucleus at the paroral cone.
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    Notes: . This work reports the characterization of an arginine kinase in the unicellular parasitic flagellate Trypanosoma brucei, the etiological agent of human sleeping sickness and Nagana in livestock. The arginine kinase activity, detected in the soluble fraction obtained from procyclic forms, had a specific activity similar to that observed in Trypanosoma cruzi, about 0.2 μmol min−1mg−1. Western blot analysis of T. brucei extracts revealed two bands of 40 and 45 kDa. The putative gene sequence of this enzyme had an open reading frame for a 356-amino acid polypeptide, one less than the equivalent enzyme of T. cruzi. The deduced amino acid sequence has an 82% identity with the arginine kinase of T. cruzi, and highest amino acid identities of both trypanosomatids sequences, about 70%, were with arginine kinases from the phylum Arthropoda. In addition, the amino acid sequence possesses the five arginine residues critical for interaction with ATP as well as two glutamic acids and one cysteine required for arginine binding. The finding in trypanosomatids of a new phosphagen biosynthetic pathway, which is not present in mammalian host tissues, suggests this enzyme as a possible target for chemotherapy.
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  • 81
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The changes in porosity and elastic moduli of YSZ-containing nickel-based anode materials for solid oxide fuel cells were studied as a function of the fraction of reduced NiO. Anode samples were reduced in a gas mixture of 4% hydrogen and 96% argon for different periods of time at 800°C and their Young's and shear moduli were determined afterward at room temperature using resonant ultrasound spectroscopy and impulse excitation. It was found that the magnitude of Young's and shear moduli decreased significantly with increasing fraction of reduced NiO and that the magnitude of the elastic moduli of a fully reduced Ni–YSZ anode was ∼45% lower than that of unreduced NiO–YSZ. Because the elastic moduli of NiO are close to those of Ni, the observed decrease in the magnitude of the elastic moduli was found to be caused mainly by the significant increase in the porosity of the sample as a result of NiO reduction. Expressions are presented for the amount of porosity and the magnitude of the elastic moduli as a function of the fraction of reduced NiO.
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  • 82
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two- and three-dimensional SiCr/SiC composites have been prepared starting from Tyranno SA(tm) fiber preforms. Preform densification has been performed by a modified preceramic polymer impregnation and pyrolysis (PIP) process consisting of filling the preform large interbundle voids with SiC powder before the PIP process. This step was accomplished by low-pressure infiltration of a SiC powder dilute slurry through the preform thickness. Specimens were further processed with polymer impregnation and pyrolysis to determine the effects on structural, thermal, and mechanical properties of the obtained composites. High-temperature pyrolysis treatment, which promoted polymer derived SiC matrix crystallization, markedly increased thermal diffusivity.
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  • 83
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Carbon is commonly added to sulfate-fined silicate-glass batches to enhance the fining process. Reactions between carbon and Na2SO4 modify the SOx emissions from Na2SO4 decomposition. Fourier-transform infrared (FTIR) spectrometry is used to analyze the emission of air pollutants from the isothermal decomposition of Na2SO4 + C undertaken using thermogravimetric analysis (TGA). The FTIR spectrometer is calibrated using standard gas mixtures containing CO, CO2, SO2, NO, and NO2. The collected spectra are quantified using the classical least-squares (CLS) approximation. The TGA-FTIR system provides SOx, and COx, concentrations versus time data from the isothermal decomposition of Na2SO4, in the presence of a carbon black. Mass spectrometry (MS) complements FTIR by being able to detect SO(g).
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  • 84
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Different ratios of the precursor phases of SrFeO3–x (SFO) and SrMoO4 (SMO) were used to prepare Sr2FeMoO6 (SFMO) by a solid-state reaction. X-ray diffraction was used to identify the phases. A residual SMO was observed to exist in the sample with an SFO/SMO ratio of 0.9:1. The sample with a residual SMO phase had higher resistivity, lower magnetization, but higher low-field magnetoresistance (LFMR). High-resolution transmission electron microscopy was used to identify the compositions and phases. Nanometer-sized amorphous-like clusters of SMO phase were located inside the grains rather than at grain boundaries; however, some boundaries were rich in the strontium ion. The possible mechanisms for the conduction and the increase of LFMR of SFMO are discussed.
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  • 85
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Submicro- and nano-sized liquid-phase-sintered SiC ceramics were mechanically tested by nanoindentation in the peak load range 5–400 mN. The submicro-sized sample showed a marked indentation size effect which the nano-sized samples did not exhibit. The relevance of indentation depth with respect to the microstructural scale has been outlined. In the investigated grain-size range, the hardness dependence on the grain size could be described by a load-dependent inverse Hall–Petch relation. Young's modulus was less microstructure- and load-dependent. Because of the very fine microstructure, the nano-sized SiC materials gave lower elastic values than the submicro-sized SiC ceramic.
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  • 86
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Samples of composition Ba1−xLaxTi1−x/4O3, x= 0, 0.003, 0.03, and 0.10, were prepared by an alkoxide sol–gel route with final firing of ceramics at 1100°C, 2 h in air. All samples showed bulk insulating behavior with no evidence of semiconductivity caused by either direct donor doping or oxygen loss.
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  • 87
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 88
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have studied the rheological property evolution and hydration behavior of white and ordinary portland cement (type I) pastes and concentrated cement–polyelectrolyte suspensions. Cement composition had a marked effect on the elastic property evolution (G′(t)) and hydration behavior of these suspensions in the presence of poly(acrylic acid)/poly(ethylene oxide) copolymer (PAA/PEO), even though their affinity to adsorb such species was nearly identical. Both white and ordinary portland cement pastes exhibited G′0 values of ∼104 Pa and fully reversible G′(t) behavior until the onset of the acceleratory period (t= 2 h), where the pastes stiffened irreversibly. In contrast, cement–PAA/PEO suspensions exhibited G′0 values of ∼1 Pa and G′(t) behavior comprised of both reversible and irreversible features. Interestingly, ordinary portland cement–PAA/PEO suspensions experienced a gel-to-fluid transition on high shear mixing at short hydration times (〈1 h), and the particle network did not rebuild until ∼24 h of hydration. In sharp contrast, white portland cement–PAA/PEO suspensions remained weakly gelled throughout the initial stage of hydration even after high shear mixing. At longer hydration times (〉1 h), both cement–PAA/PEO suspensions exhibited G′i(t) ∼ exp(t/τc) with τc values of 5.6 and 1.3 h for ordinary and white portland cement, respectively. Our observations suggest that hydration phenomena impact interparticle forces during early stage hydration and, ultimately, lead to initial setting through the formation of solid bridges at the contact points between particles within the gelled network.
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  • 89
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new ceramic freeze-casting technique capable of manufacturing near room temperature with a sublimable vehicle was accomplished. Fluid-concentrated slurries of Al2O3 powder in molten camphene (C10H16) were prepared at 55°C. These slurries were quickly solidified (frozen) at room temperature to yield rigid solid green bodies, followed by frozen camphene removal by sublimation (freeze-drying) with negligible shrinkage. Sintering without any special binder burnout process yielded sintered bodies with over 98% theoretical density. The proposed advantages include (1) elimination of extremely cold temperatures, (2) elimination of troublesome binder burnout process, and (3) fast manufacturing cycle due to quick solidification.
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  • 90
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dense composites in the Ti-B-N system have been produced by reactive hot pressing of titanium and BN powders. The effect of the addition of a small amount of nickel (1–3 wt%) on the reaction kinetics and densification of TiN–TiB2 (40 vol%) composite has been studied. Composites of ∼99% of theoretical density have been produced at 1600°C under 40 MPa for 30 min with 1% nickel. The hardness and fracture toughness of these composites are 24.5 ± 0.97 GPa and 6.53 ± 0.27 MPa·m1/2, respectively. The microstructural studies on samples produced at lower temperatures indicate the formation of a transient liquid phase, which enhances the kinetics of the reaction and densification of the composite.
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  • 91
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents new findings on ultrasonic spray pyrolysis of zirconium hydroxyl acetate precursor drops whose sizes were precisely measured using laser light diffraction technique. Precursor concentration plays a predominant role in determination of product particle size. At 0.01 wt% precursor concentration, conventional spray pyrolysis at 750°C using precursor drops 5–8 μm in diameter, generated by an ultrasonic nebulizer at 2.66 MHz, yielded uniform spherical yttria-stabilized zirconia (YSZ) particles 73 nm in diameter measured by scanning electron microscopy. The YSZ particle diameters were much smaller than those predicted by the one-particle-per-drop mechanism. Under similar reaction conditions, the high-throughput ultrasound-modulated two-fluid (UMTF) spray pyrolysis of larger precursor drops (28-μm peak diameter) also yielded spherical dense particles; they were significantly smaller in size than those produced by the low-throughput conventional ultrasonic spray pyrolysis of smaller drops (6.8-μm peak diameter).
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  • 92
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermoelectric elements consisting of the layered polycrystalline materials of Al-doped ZnO and NaCo2O4 were prepared using the pulse electric-current sintering (PECS) method at 900°C for 3 min. Direct contact between the polycrystalline Al-doped ZnO and the NaCo2O4 was obtained in a single-step process for the stacked powders. The electrical conductivities of the polycrystalline materials prepared by PECS were higher than those of materials prepared by conventional sintering, despite their porous structure. The thermoelectric voltage of the 1-mol%-Al-doped ZnO and NaCo2O4 polycrystalline element (measuring ∼6 mm × 3 mm × 15 mm) was 83 mV at dT= 500 K, when the junction of the elements was at 800°C.
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  • 93
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Pb(Zr,Ti)O3–Pb(Mn1/3 Nb2/3)O3 (PZT–PMnN) system has been studied for high-power piezoelectric applications. This study investigates this system to find out the composition with high-power density piezoelectric characteristics and low tem-perature coefficient of resonance frequency (TCF). It was found that the composition 0.9PZT–0.1PMnN (Zr/Ti = 0.51/0.49) modified with 6 mol% Sr exhibits a TCF of −8 ppm/°C (−20 to +80°C). Further, the dielectric and piezoelectric properties of this composition are as follows: kp= 0.53; Qm= 800; d33= 274; ε33/ε0= 1290 and tan δ=1.1%, which shows the suitability of this composition for ultrasonic devices used under fluctuating thermal environment.
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  • 94
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    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Beam bending is an excellent method for measuring low permeabilities (≤10−18 m2) in homogeneous materials, because it is fast, requires no high pressure, and provides a concurrent measurement of the modulus of the material. The method was previously analyzed and substantiated for cylindrical or square beams. Recently, the analysis was extended to include isotropic and transversely isotropic rectangular beams. In this paper, the analysis is applied to measurements performed on cement paste, and it is shown that the solution for isotropic rectangular beams accounts for changes in the hydrodynamic behavior caused by changing the aspect ratio of the sample. The permeability and elastic modulus results are verified through comparison to previous measurements on cylindrical beams.
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  • 95
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The deformation behavior of boron- and carbon-doped β-silicon carbide (B,C-SiC) with an average grain size of 260 ± 18 nm containing 1 wt% boron was investigated by compression testing at elevated temperatures. Extensive grain growth during deformation was observed. The stress–strain curves were compensated for grain growth by assuming power-law type of dependence on grain size and strain rate. The stress exponent n was ∼1.3 and the grain size exponent p was ∼2.7 at temperatures ranging from 1593° to 1758°C. The apparent activation energy of deformation Qd was ∼760 kJ/mol, which was lower than the activation energy for lattice diffusion of silicon and carbon in SiC and higher than that for grain-boundary diffusion of carbon in SiC. These results suggest that the deformation mechanism of the fine-grained B,C-SiC is grain-boundary sliding accommodated by the grain-boundary diffusion.
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  • 96
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chromium-containing stainless steel (SS) is a prospective material for use as an interconnect in solid oxide fuel cells (SOFCs). However, during operations at high temperatures, the growth of oxide scales causes the performance of the interconnect and SOFC as a whole to deteriorate. The coating of SS 446 with a conducting perovskite is a potential method of slowing the growth of oxide scale and, therefore, improving overall SOFC performance. In the present research, the structural characterization of a pure LaCrO3 thin film on the SS 446 substrates has been performed as a model material that can be used as a barrier coating for the metallic interconnect. The deposition of an amorphous La-Cr-O thin film on SS 446 was performed using radio-frequency (rf) magnetron sputtering. The deposited amorphous film was annealed in air to form the desired perovskite phase. The film underwent an amorphous to LaCrO4 phase transition during annealing at 500°C with further transformation to LaCrO3 orthorhombic phase during annealing at 700°C. A self-organized dendritic structure was reported as a result of the perovskite-phase formation. Although formation of various oxides, such as Fe2O3 and Fe3O4, was observed during the annealing of uncoated SS 446 in air, the coating of SS 446 surface with LaCrO3 film prevented formation of various oxide phases at the interconnect surface. The structural characterization of the films and SS 446 surfaces was accomplished using scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffractometry, micro-Raman spectroscopy, and nanoindentation.
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  • 97
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The density, surface tension, and viscosity of the melts from the PbO-B2O3-SiO2 system have been measured at temperatures in the range 1073–1473 K. The effect of composition on these properties was also investigated. The density of the melt was found to increase linearly with increasing PbO content. Molar volume was derived from the density data, and its deviation from the additivity of partial molar volumes was calculated. These deviations in molar volume from those obtained from additivity rules have been used along with the ratio of various coordination numbers of boron (as reported by Bray) to discuss the structure of the melts. The surface tension was found to decrease with decreasing SiO2/B2O3 ratio, and to increase in the range of the PbO content between 30 and 60 mol%, showing a maximum at ∼60 mol% PbO, and then decreased with further additions. This result suggested that the surface tension would be affected primarily by the B2O3 content in the range of the PbO content between 30–60 mol%, and mainly by the PbO content in the range of the PbO content 〉60 mol%, respectively. The viscosity of the melt was found to decrease linearly with increasing PbO content. The results obtained indicate that the increase in viscosity with B2O3 was half that of SiO2 (on a molar basis), and an empirical equation has been proposed for the viscosity as a function of mole fraction.
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  • 98
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Core/shell structures have been prepared via a mechanofusion system by employing several kinds of spherical polymers as a core material and Al2O3 powder or a mixture of Al2O3 and SiO2 powders as a shell material. The effect of the kind of core polymers on the quality of the resulting hollow alumina microspheres has been discussed on the basis of the thermal decomposition behavior of spherical polymers used as a core material. A large fraction of hollow alumina microspheres reflecting the shape and the particle size distribution of the core polymer could be fabricated after sintering at 1600°3C for 3 h, when highly cross-linked poly(methyl methacrylate) (PMMA) microspheres with a gel fraction of 99.03% were used as a core polymer, and abrupt firing at temperatures higher than 500°3C was adopted to remove the PMMA microspheres. The addition of 5 mass% SiO2 to the Al2O3 shell layer was found to be useful for maintaining the spherical shell structure during the firing process and for fabricating a large fraction of hollow alumina microspheres after the sintering.
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  • 99
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Well-defined and stoichiometric spherical particles of BaTiO3 of narrow size distribution were produced at 82° and 92°3C by precipitation from chloride solutions in a strong alkaline environment. The size of the particles can be tailored in the range from ≅103 to 70–80 nm by increasing the barium concentration from ≅0.07 to 0.7 mol/L. The particles are composed of tight aggregates resulting from the assembly of several nanocrystals. The size of the nanocrystals decreases from 200–300 to 30–40 nm by increasing reactant concentration. At low barium concentration (≤0.07 mol/L at 82°3C, ≤0.06 mol/L at 92°3C), formation of BaTiO3 is strongly slowed down and nonstoichiometric, Ti-rich powders are produced. Under these conditions, the particles have the tendency to develop a dendritic-like morphology.
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  • 100
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    Journal of the American Ceramic Society 87 (2004), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Crystals of δ-Y2Si2O7 (space group P121/c1) were examined using high-temperature powder X-ray diffractometry to determine their unit-cell dimensions from 296 to 1473 K. The lattice deformation induced by thermal expansion was investigated using matrix algebra analysis to determine the directions and magnitudes of the principal distortions (Λi, i= 1,2, and 3). The directions of Λ1 and Λ3 were defined by the acute angle Λ1c, which linearly decreased from 5(2)° to —5.5(3)° with increased temperature from 504 to 1473 K. The Λ2-axis invariably coincided with the crystallographic b-axis. The magnitudes of Λ1 and Λ2 steadily increased to, respectively, 1.0061(1) and 1.0068(1) during heating to 1473 K, while Λ3 remained almost constant for the entire temperature range. The mean principal distortion, Λm (= (Λ1+Λ2+Λ3)/3), steadily increased to 1.0044(1) with increased temperature to 1473 K. The coefficient of mean linear thermal expansion (α) was derived from the mean principal strain (Λm - 1) as α= (Λm - 1)/ΔT. The temperature dependence was determined to be α= 2.03 times 103+ 1.36(T - 296) (10-9 K-1). Provided that the rule-of-mixtures holds for the Y2Si2O7/Y2SiO5 composites as protective coating on SiC substrates, the volume fractions of 0.72-0.77 (70–75 mass%) would be necessary for the Y2Si2O7 component to match the α-values of both materials.
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