135 research outputs found

    Full Color Copying

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    Electrophotographic powder toners, often called 'electronic ink', typically consist of 90–95% resin (polyester, styrene-acrylic), 5% colorant, 1–3% charge control agent (CCA), and other additives like waxes. CCAs are needed for the correct toner charge. They must overcome the electrostatic influence of the colorants and the other toner ingredients. Both chemical structure and solid-state parameters are responsible for the electrostatic properties of pigments and CCAs. The measurement of the particle surface charge contributes to the understanding of these effects

    Entwicklungen begleiten: Neue BildungsrÀume zur Verbindung von Theorie und Praxis in einer Vorlesung

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    Wie kann die aktive und regelmĂ€ĂŸige Beteiligung der Studierenden in einer Vorlesung ermöglicht werden? Ein Ansatz ist die Verbindung von Theorie und Praxis, die jedoch insbesondere im traditionellen Format der Vorlesung eine Herausforderung fĂŒr Lehrende darstellt. E-Learning bietet hier unterschiedliche Möglichkeiten, um die VerknĂŒpfung der beiden BildungsrĂ€ume Berufspraxis und Vorlesung zu realisieren. Um diese passgenau fĂŒr die Disziplin und das Vorlesungsformat auszuwĂ€hlen und einzusetzen, benötigen Lehrende professionelle UnterstĂŒtzung. Im vorliegenden Beitrag wird am Beispiel einer Lehrveranstaltung im Fachgebiet Pflanzenbau aufgezeigt, wie ein E-Learning-Vorhaben durch Beratung und Coaching bei der Planung, Umsetzung und Auswertung von Hochschulseite begleitet werden kann. Der Beitrag fokussiert daher zwei Ebenen des E-Learning-Einsatzes: Zum einen die UnterstĂŒtzung der E-Learning-Implementierung durch ein Lehrcoaching, zum anderen das ZusammenfĂŒhren verschiedener Lernorte durch digitale Medien in einer Vorlesung. Besonderer Fokus liegt in der Analyse dieser beiden Ebenen auf Entwicklungen, die in Bezug auf die Artefakte, die Lernergebnisse der Studierenden und durch Reflexionen im Coachingprozess stattfanden. (DIPF/Orig.

    Comparing the reliability of maize variety data from on-farm trials and experimental stations

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    Sortenempfehlungen basieren in der Regel auf regionalspezifischen Exaktversuchen. Dabei können die Wechselwirkungen zwischen Sorte und Umwelt sowie zwischen Sorte und Management zu steigenden Problemen bei der Sortenwahl fĂŒhren. Eine ergĂ€nzende Möglichkeit sind daher dezentralisierte Sortenversuche in Landwirtschaftsbetrieben. FĂŒr die direkte Sortenwahl bieten diese On-Farm-Versuche eine hohe Praxisrelevanz, da die tatsĂ€chlichen EinflussgrĂ¶ĂŸen im Betrieb getreuer abgebildet werden können, als es Exaktversuche vermögen, wenn sie nur an wenigen, zum Teil eingeschrĂ€nkt reprĂ€sentativen Standorten durchgefĂŒhrt werden. Andererseits ist die AussagefĂ€higkeit von On-Farm-Versuchen hĂ€ufig durch StörgrĂ¶ĂŸen und fehlende Feldwiederholungen begrenzt. Anhand von Maissortenversuchen mit sechs verschiedenen Sorten wurden auf vier Brandenburger Landwirtschaftsbetrieben sowie auf zwei Versuchsstationen die Sortenleistung in On-Farm- und Exaktversuchen auf Sandböden geprĂŒft. An jedem Standort wurde die Varianz der Sortenrankings ĂŒber die Jahre genutzt, um Informationen ĂŒber die Konsistenz der Sortenleistung an jedem der Standorte zu gewinnen. FĂŒr den Trockenmasse-Ertrag zeigten die On-Farm-Versuche sowohl die höchste, als auch die niedrigste Konsistenz der Rankings. Einige QualitĂ€tsparameter, wie die Nichtfaser-Kohlenhydrate (NFC) und der StĂ€rkegehalt, zeigten in den On-Farm-Versuchen eine bessere Konsistenz des Sortenrankings ĂŒber die Jahre als in beiden Exaktversuchen. Dies legt nahe, dass On-Farm-Versuche das Potenzial haben, die regionale LeistungsprĂŒfung von Sorten zu unterstĂŒtzen. DOI: 10.5073/JfK.2014.11.03, https://doi.org/10.5073/JfK.2014.11.03While current variety recommendations are based on replicated small-plot trials in a specific region for which the trial is thought to be representative, genotype × envi­ronment interactions, genotype × management interactions, and increasing weather fluctuations make it increasingly difficult to predict which variety will be best in a given environment. An additional approach is therefore to decentralize variety trials and place them on working farms. However, although on-farm trials offer potentially more relevance for direct variety selection on site, they are also likely to be subject to more noise and trial entries can often not be fully replicated. To evaluate the relative merit of on-farm trials vs. fully replicated trials conducted at experimental stations, we tested 6 maize varieties at four farms and at two stations in a region dominated by sandy soils. The variance of variety rankings over the years within each site was used as proxy to evaluate the consistency of variety information gained at each location. For dry matter yield, on-farm trials showed both the highest and the lowest consistency of variety ranking, with the consistency being intermediate at the experimental stations. For some quality parameters, namely non-fibre carbohydrate and starch content, the majority of on-farm trials showed more consistent variety ranking over the years than the more consistent of the two replicated trials. This suggests that in terms of year-on-year reliability of maize yield and quality, on-farm trials may have the potential to complement replicated variety trials. For both types of trials, however, there is also scope for decreasing technical sources of variation. DOI: 10.5073/JfK.2014.11.03, https://doi.org/10.5073/JfK.2014.11.0

    Effects of Fertilizers and Manures on Temporal Yield Variability of Winter Rye

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    The anticipated increases in environmental variability associated with climate change may lead to enhanced abiotic plant stresses (e.g. heat stress, drought stress, etc.) resulting in greater inter‐annual yield fluctuations and higher crop production risk. While there has been increasing attention to adaptation measures, there is little evidence available on how to change agronomic management strategies to maintain stable yields in winter rye production systems in Poland. This study uses rye yields from the unique Skierniewice Long‐term experiment (Poland) to examine for the first‐time the long‐term effects of different nutrient regimes on crop yield stability from 1966 to 2015. Yields from six combinations of mineral fertilizers and lime (CaNPK, NPK,CaPK, CaNK, CaNP, Ca), with and without additional manure, were used to estimate the temporal yield variability of winter rye. A novel statistical approach based on a mixed model approach with REML (restricted maximum likelihood) stability parameter estimation was used. The results showed that the use of additional manure in ‘sub‐optimal’ mineral fertilizer treatments, such as Ca and CaPK (without mineral N), reduced the temporal yield variability of rye. In contrast, additional organic input led to more variable rye yields in already ‘optimal’ treatments including mineral N (CaNPK and NPK), compared to those with no additional manure. Winter rye given CaNPK and NPK, without additional organic manure demonstrated high yield and low temporal yield variability. In contrast, yields of treatments with no mineral N (Ca and CaPK) and no additional manure supply were low and unstable. In addition, it was found that increasing soil organic carbon resulted in larger, more stable yields. These findings highlight the importance of ensuring rye crops receive sufficient fertilizer to maintain crop production levels and yield stability, especially in dry years. They also demonstrate the importance of avoiding the excessive use of organic manures when fertilizer inputs are sufficient to meet crop demand. Overall, the study provides novel insights about how to maintain grain yields and minimize temporal yield variation of rye in arable cropping systems, which will become increasingly important in a changing climate in Poland and in other temperate climate areas. This study also highlights the importance of soil organic carbon for improving the climate resilience of winter rye, while simultaneously meeting the demand for more sustainable management of the soil

    Eco-stability of winter rye varieties under site conditions of Brandenburg

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    Im Mittelpunkt der Untersuchung von Winterroggensorten unter Standortbedingungen Brandenburgs standen die folgenden Fragestellungen: Bieten Hybridroggensorten im Vergleich der Sortentypen neben einer höheren ErtragsfĂ€higkeit auch eine bessere ÖkostabilitĂ€t, vor allem auch unter trockenen Witterungsbedingungen? Welche Unterschiede auf Sortenebene bestehen hinsichtlich der ÖkostabilitĂ€t? Dazu wurden auf Basis von mehrortigen und mehrjĂ€hrigen Ergebnissen aus Sortenversuchen in Brandenburg und unter Nutzung biostatistischer Parameter verschiedene Roggensorten analysiert. Die Sortenbewertung zur ÖkostabilitĂ€t und Ertragsleistung umfasste neben der deskriptiven Statistik und Varianzanalyse folgende Parameter: Ökovalenz, Ökoregression und Floating Checks. ZusĂ€tzlich wurden verschiedene EinflussgrĂ¶ĂŸen auf die ErtragsvariabilitĂ€t geschĂ€tzt und die Sortenreaktion auf unterschiedliche Witterungsbedingungen anhand der klimatischen Wasserbilanz geprĂŒft. Abschließend erfolgte eine kurze Bewertung der verwendeten Parameter und Methoden. Die Ergebnisse der Sortenversuche zeigten, dass die Umwelt (Ort × Jahr) den stĂ€rksten Einfluss auf die ErtragsvariabilitĂ€t hatte. GegenĂŒber der Umweltwirkung war der Sorteneinfluss geringer. Trotzdem bestanden zwischen den Sorten deutliche Unterschiede hinsichtlich der LeistungsfĂ€higkeit, ÖkostabilitĂ€t und der Reaktion auf differenzierte Umweltbedingungen. Die Hybridroggensorten erwiesen sich im Vergleich der Sortentypen als deutlich ertragsfĂ€higer und tendenziell ökostabiler, vor allem auch unter trockenen Witterungsbedingungen. Die Ergebnisse sind fĂŒr die SortenprĂŒfung und -bewertung, die ZĂŒchtung und die landwirtschaftliche Praxis gleichermaßen bedeutsam. Sie liefern Informationen zu den umweltabhĂ€ngig variierenden Eigenschaften der Sorten und bieten UnterstĂŒtzung fĂŒr die standortgerechte Sortenempfehlung sowie bestmögliche Sortenwahl durch Entwicklung eines Bewertungsschemas.    The main questions addressed by the present study were: Provide hybrid varieties as compared to other variety types in addition to a higher yield also an improved eco-stability, especially under dry weather conditions? Which differences in eco-stability between varieties of winter rye can be found? To answer the question results from variety trials at multiple environments of Federal State Brandenburg were used and different varieties of winter rye were analyzed according to several bio-statistical parameters. The evaluation of eco-stability and yield capacity included following parameters: Eco-valence, eco-regression and floating checks. Additionally, different impact factors on variability of yield were estimated and the reaction of varieties to different weather conditions was analyzed based on the climatic water balance. Finally a brief review of the used methods and parameters is given. The results of the different tests showed that the yield performance is determined by different environmental factors and by variety. The factor environment (site × year), which includes soil and weather throughout the course of the year, had the strongest influence on the variability of yield. The factor variety was comparatively less influential, but in special environments it can have an important influence on grain yield. There are also considerable differences between varieties with regard to the criteria eco-stability, yield capacity and their response to differentiated environmental conditions. The hybrid varieties compared to other variety types were considerably higher in yield and in tendency more stable in yield, especially also under dry weather conditions. The evaluation results are important for plant breeding as well as for the choice of site-adapted varieties in agricultural practice. They offer information to environment dependent properties of varieties and can support variety selection in breeding and official variety recommendation by using an optimized evaluation scheme.   &nbsp

    Long-term trends in yield variance of temperate managed grassland

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    The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965–2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield variance—with a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems

    The effects of cropping sequence, fertilization, and straw management on the yield stability of winter wheat (1986–2017) in the Broadbalk Wheat Experiment, Rothamsted, UK.

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    The development of resilient cropping systems with high yield stability is becoming increasingly important due to future climatic and agronomic challenges. Consequently, it is essential to be able to evaluate the effects of differing agronomic management practices, such as cropping sequences, and nutrient supply on the stability of crop yields. Long-term experiments are a valuable resource for investigating these effects, providing a sufficient number of years for accurate stability parameter estimation. The objective of the current study was to evaluate the effects of cropping sequence (#1: continuous vs rotational), fertilization (#2: mineral vs organic) and straw management in the case of continuous wheat (#3: removal vs incorporation) on the yield stability of winter wheat; yield risk (the probability of yield falling below a threshold yield level) and inter-annual yield variability were used as stability indicators of the effects. Long-term yield data from the Broadbalk Wheat Experiment (Rothamsted, United Kingdom) were analysed using a mixed model. Overall, the results showed that rotational cropping combined with supply of sufficient nutrients (N, P, and K) from mineral fertilizers, especially mineral N supply, ensured stable wheat yields whilst reducing the yield risk

    Ertragsdynamik und Risikobewertung von Fruchtfolgen und Bodenbearbeitung im ökologischen Langzeitversuch

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    Diese Studie vergleicht die ErtrÀge, ErtragsstabilitÀten und Produktionsrisiken von Fruchtfolgen mit und ohne Tierhaltung, sowie wendender und reduzierter Bodenbearbeitung aus 24 Jahren von dem ökologischen Langzeitversuch auf dem Gladbacherhof

    The paternal and maternal genetic history of Vietnamese populations

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    Vietnam exhibits great cultural and linguistic diversity, yet the genetic history of Vietnamese populations remains poorly understood. Previous studies focused mostly on the majority Kinh group, and thus the genetic diversity of the many other groups has not yet been investigated. Here we analyze complete mtDNA genome sequences and ~2.3 Mb sequences of the male-specific portion of the Y chromosome from the Kinh and 16 minority populations, encompassing all five language families present in Vietnam. We find highly variable levels of diversity within and between groups that do not correlate with either geography or language family. In particular, the Mang and Sila have undergone recent, independent bottlenecks, while the majority group, Kinh, exhibits low levels of differentiation with other groups. The two Austronesian-speaking groups, Giarai and Ede, show a potential impact of matrilocality on their patterns of variation. Overall, we find that isolation, coupled with limited contact involving some groups, has been the major factor influencing the genetic structure of Vietnamese populations, and that there is substantial genetic diversity that is not represented by the Kinh
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