1,720,992 research outputs found
Integrating soil compaction impacts of tramlines into soil erosion modelling: A field-scale approach
No full textSoil erosion by water is one of the main soil degradation processes worldwide, which leads to declines in natural soil fertility and productivity especially on arable land. Despite advances in soil erosion modelling, the effects of compacted tramlines are usually not considered. However, tramlines noticeably contribute to the amount of soil eroded inside a field. To quantify these effects we incorporated high-resolution spatial tramline data into modelling. For simulation, the process-based soil erosion model EROSION3D has been applied on different fields for a single rainfall event. To find a reasonable balance between computing time and prediction quality, different grid cell sizes (5, 1, and 0.5 m) were used and modelling results were compared against measured soil loss. We found that (i) grid-based models like E3D are able to integrate tramlines, (ii) the share of measured erosion between tramline and cultivated areas fits well with measurements for resolution ≤1 m, (iii) tramline erosion showed a high dependency to the slope angle and (iv) soil loss and runoff are generated quicker within tramlines during the event. The results indicate that the integration of tramlines in soil erosion modelling improves the spatial prediction accuracy, and therefore, can be important for soil conservation planning
An inertia-free beam scanning device for single-wavelength 2PE-STED nanoscopy
No full textTwo-photon excitation stimulated emission depletion nanoscopy (2PE-STED) is a fluorescence imaging technique ideal for significantly improving the spatial resolution when observing scattering tissue in fixed, in vitro, and in vivo specimens. Both 2PE and STED are beam scanning techniques. The image acquisition is commonly realized by raster scanning, and a pair of galvanometric mirrors are the most used approach. In 2PE fluorescence microscopy, acousto-optical deflectors (AODs) are also used because they allow random-access scanning. However, since the AOD working principle is diffraction of light, these devices are of limited use when it is necessary to deflect multiple beams of different wavelengths and polarization, e.g. in STED nanoscopy. Here, we present the first implementation of single wavelength 2PE-STED that enables a smart beam scanning system based on AODs technology
Acousto-optic systems for advanced microscopy
No full textAcoustic waves in an optical medium cause rapid periodic changes in the refraction index, leading to diffraction effects. Such acoustically controlled diffraction can be used to modulate, deflect, and focus light at microsecond timescales, paving the way for advanced optical microscopy designs that feature unprecedented spatiotemporal resolution. In this article, we review the operational principles, optical properties, and recent applications of acousto-optic (AO) systems for advanced microscopy, including random-access scanning, ultrafast confocal and multiphoton imaging, and fast inertia-free light-sheet microscopy. As AO technology is reaching maturity, designing new microscope architectures that utilize AO elements is more attractive than ever, providing new exciting opportunities in fields as impactful as optical metrology, neuroscience, embryogenesis, and high-content screening
Assessment of the relationships between agroecosystem condition and the ecosystem service soil erosion regulation in Northern Germany
No full textEcosystems provide multiple services that are necessary to maintain human life. Agroecosystems are very productive suppliers of biomass-related provisioning ecosystem services, e.g. food, fibre, and energy. At the same time, they are highly dependent on good ecosystem condition and regulating ecosystem services such as soil fertility, water supply or soil erosion regulation. Assessments of this interplay of ecosystem condition and services are needed to understand the relationships in highly managed systems. Therefore, the aim of this study is twofold: First, to test the concept and indicators proposed by the European Union Working Group on Mapping and Assessment of Ecosystems and their Services (MAES) for assessing agroecosystem condition at a regional level. Second, to identify the relationships between ecosystem condition and the delivery of ecosystem services. For this purpose, we applied an operational framework for integrated mapping and assessment of ecosystems and their services. We used the proposed indicators to assess the condition of agroecosystems in Northern Germany and regulating ecosystem service control of erosion rates. We used existing data from official databases to calculate the different indicators and created maps of environmental pressures, ecosystem condition and ecosystem service indicators for the Federal State of Lower Saxony. Furthermore, we identified areas within the state where pressures are high, conditions are unfavourable, and more sustainable management practices are needed. Despite the limitations of the indicators and data availability, our results show positive, negative, and no significant correlations between the different pressures and condition indicators, and the control of erosion rates. The idea behind the MAES framework is to indicate the general condition of an ecosystem. However, we observed that not all proposed indicators can explain to what extent ecosystems can provide specific ecosystem services. Further research on other ecosystem services provided by agroecosystems would help to identify synergies and trade-offs. Moreover, the definition of a reference condition, although complicated for anthropogenically highly modified agroecosystems, would provide a benchmark to compare information on the condition of the ecosystems, leading to better land use policy and management decisions
Is soil loss due to crop harvesting the most disregarded soil erosion process? A review of harvest erosion
No full textWhile water and wind erosion are part of intensive research activities all over the world, soil loss due to crop harvesting (SLCH) is rarely acknowledged. SLCH occurs in tuber and root crops, which were cultivated on at least 1.1 million km2 worldwide in 2019. Thus, 8.4% of arable soils were affected by this kind of soil loss which can reach erosion rates of 22 Mg ha−1 harvest−1. Although these erosion rates are as high as for water and wind erosion, there are only 27 scientific references available that focus on SLCH. Hence, the relationship between possible environmental degradation and perception in science appears to be ambivalent. The aim of this review is to raise awareness of SLCH and harvest erosion. To achieve this aim, firstly the current state of knowledge on SLCH is summarized based on peer reviewed and international references. A special focus is on the rates of SLCH, on available regression equations to calculate the soil losses by harvest and on the environmental effects. Secondly, important research gaps and necessary research activities are identified. It becomes apparent that (i) new data is required which considers developments in harvest techniques and soil management, (ii) data from North America, South America and Oceania is urgently needed as no references for these regions are available yet, (iii) models to predict SLCH are necessary and (iv) research is required on the fate of the adhering soil within the landscape and on its environmental effects
Viscoelasticity and shear resistance at the aggregate scale of structured and organic carbon-free Chernozems
No full textSoil rheology characterises the flow behaviour of soils at the particle-particle to aggregate scale. Amplitude sweep tests (ASTs) are often the method of choice for parameterizing soil flow properties, such as the shear strain values at the end of the linear viscoelastic range (i.e., the deformation is mainly elastic) and at the yield point (i.e., elastic equals plastic deformation). Samples from seven soil profiles and five soil depths of Chernozems, collected in the Maidanetske study area, close to Uman City of Ukraine, were analysed to evaluate the effect of soil organic carbon (SOC) on the parameters related to soil microstructural stability derived from ASTs. Soil organic carbon was removed with H2O2 to determine the soil texture-dependent values of soil rheological properties, which were compared to the values determined for samples with intact water-stable aggregates. The shear resistance-related parameters increased for aggregated soil samples compared to SOC-free soil samples, indicating an increase in soil stability due to SOC. In contrast, the values of the overall viscoelasticity and the shear strain were reduced for aggregated soil samples, indicating decreased soil stability. Pedotransfer functions were applied to predict the shear strain-dependent loss and storage moduli and shear stress values as a function of SOC depletion. Coarse particles (630-2 000 mu m) and volumetric water content improved the models. We conclude that increased SOC content, through the gluing and cementing effects of SOC and altered aggregate shapes compared to SOC-free soil materials, contributes to higher microstructural strength. However, the increased water content in the SOC-containing soil samples reversed soil strengthening effect. This was due to the fact that a more rapid increase in positive water pressure under shear stress weakened the samples and the spherical aggregates began to rotate more easily, thus loosing energy, when compared to platy particles of the SOC-free soil materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Multiplane Encoded Light-Sheet Microscopy for Enhanced 3D Imaging
No full textLight-sheet microscopes have become the tool of choice for volumetric imaging of large samples. Based on a wide-field acquisition scheme, they are capable of optical sectioning at diffraction-limited resolution and minimal overall photodamage. Unfortunately, traditional architectures are limited in speed because 3D images are collected by either sample translation or synchronized movement of both light-sheet and detection objective lens. A promising solution avoiding slow mechanical movements is to extend the depth-of-field of the microscope and moving only the light-sheet. However, this normally comes at the cost of losing light and contrast, compromising the signal-to-noise ratio of the images. Here, we propose an innovative technique devoted to restoring the quality of the images, while preserving the speed of extended depth-of-field microscopes. It is based on generating a stack of parallel light-sheets using a pair of orthogonal acousto-optic deflectors, enabling the simultaneous illumination of different sample planes. Given the extended depth-of-field, all such planes appear in focus and can be acquired in a superimposed single frame. By applying a single-step inversion algorithm, we can decode a stack of frames into a volumetric image whose signal-to-noise ratio and contrast are greatly enhanced. We provide a detailed theoretical framework of the method and demonstrate its feasibility with volumetric images of kidney cell spheroids
Parallelized Light-sheet Microscopy with Flexible and Encoded Illumination
No full textLight Sheet Microscopy (LSM), being capable of optical sectioning at diffraction-limited resolution and at low light doses [1], has become the tool of choice for volumetric imaging of large samples. Unfortunately, traditional LSM architectures are limited in speed because a z-stack is collected by either sample translation or synchronized movement of objective lens and light-sheet. A promising solution to avoid slow mechanical movements is extending the Depth-of-Field (DoF) of the microscope [2], [3] and moving only the light-sheet. However, the DoF extension comes at the cost of a loss of photons, compromising the signal-to-noise ratio of the images. Here, we propose an innovative technique devoted to restoring the signal content of the images, while preserving the speed of extended DoF microscopes
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