A flow cytometer based protocol for quantitative analysis of bloom-forming cyanobacteria (Microcystis) in lake sediments

A quantitative protocol for the rapid analysis of Microcystis cells and colonies in lake sediment was developed using a modified flow cytometer, the CytoSense. For cell enumeration, diluted sediment samples containing Microcystis were processed with sonication to disintegrate colonies into single cells. An optimized procedure suggested that 5 mg dw (dry weight)/mL dilution combined with 200 W x 2 min sonication yielded the highest counting efficiency. Under the optimized determination conditions, the quantification limit of this protocol was 3.3x10(4) cells/g dw. For colony analysis, Microcystis were isolated from the sediment by filtration. Colony lengths measured by flow cytometry were similar to those measured by microscopy for the size range of one single cell to almost 400 mu m in length. Moreover, the relationship between colony size and cell number was determined for three Microcystis species, including Microcystis flos-aquae, M. aeruginosa and M. wessenbergii. Regression formulas were used to calculate the cell numbers in different-sized colonies. The developed protocol was applied to field sediment samples from Lake Taihu. The results indicated the potential and applicability of flow cytometry as a tool for the rapid analysis of benthic Microcystis. This study provided a new capability for the high frequency monitoring of benthic overwintering and population dynamics of this bloom-forming cyanobacterium.A quantitative protocol for the rapid analysis of Microcystis cells and colonies in lake sediment was developed using a modified flow cytometer, the CytoSense. For cell enumeration, diluted sediment samples containing Microcystis were processed with sonication to disintegrate colonies into single cells. An optimized procedure suggested that 5 mg dw (dry weight)/mL dilution combined with 200 W x 2 min sonication yielded the highest counting efficiency. Under the optimized determination conditions, the quantification limit of this protocol was 3.3x10(4) cells/g dw. For colony analysis, Microcystis were isolated from the sediment by filtration. Colony lengths measured by flow cytometry were similar to those measured by microscopy for the size range of one single cell to almost 400 mu m in length. Moreover, the relationship between colony size and cell number was determined for three Microcystis species, including Microcystis flos-aquae, M. aeruginosa and M. wessenbergii. Regression formulas were used to calculate the cell numbers in different-sized colonies. The developed protocol was applied to field sediment samples from Lake Taihu. The results indicated the potential and applicability of flow cytometry as a tool for the rapid analysis of benthic Microcystis. This study provided a new capability for the high frequency monitoring of benthic overwintering and population dynamics of this bloom-forming cyanobacterium

Comparison of soil erosion models used to study the Chinese Loess Plateau

The Loess Plateau suffers from severe soil erosion that leads to a series of ecological and economic problems such as reduced land productivity, exacerbated rural poverty, decreased biodiversity and sedimentation of the riverbed in the lower reaches of the Yellow River. Soil erosion models are commonly used on the Loess Plateau to help target sustainable land management strategies to control soil erosion. In this study, we compared eleven soil erosion models that were previously used on the Loess Plateau. We studied their prediction accuracy, process representation, data and calibration requirements, and potential application in scenario studies. The selected models consisted of a broad range of model types, structures and scales. The comparison showed that process-based and empirical models did not necessarily yield more accurate results over one another for the Loess Plateau. Among the process-based models, Si’ model, WEPP and MMF had the highest prediction accuracy. However, some of the selected models were tested with total sediment load while others were tested with suspended sediment load (i.e. bedload is not included), which is subject to several drawbacks. Research questions that each of the models can address on the Loess Plateau were suggested. Further improvement of soil erosion models for the Loess Plateau should concentrate on enhancing the quality of data for model implementation and testing, incorporating key processes into process-based models according to their aims and scales, comparing models that address the same research questions, and implementing internal and spatial model testing

Adaptive Integral Sliding Mode Control in the Presence of State-Dependent Uncertainty

Adaptive integral sliding mode control (AISMC) is an extension of adaptive sliding mode control which is a way to ensure sliding motion while handling system uncertainties. However, conventional AISMC formulations require to different extent a priori knowledge of the system uncertainty: either the upper bound of the uncertainty or of its time derivative are assumed to be bounded a priori, or the uncertainty is assumed to be parametrized by some structure-dependent factorization. This work proposes a variant of AISMC with reduced a priori knowledge of the system uncertainty: it is shown that Euler–Lagrange dynamics typical of sliding mode literature admit a structure-independent parametrization of the system uncertainty. This parametrization is not the result of structural knowledge, but it comes from basic properties of Euler–Lagrange dynamics, valid independently on the structure of the system. The AISMC control method arising from this parametrization is analyzed in the Lyapunov stability framework, and validated in systems with different structures: a surface vessel and an aerial vehicle.Accepted Author ManuscriptTeam DeSchutte

Hybrid geometry sets for global registration of cross-source geometric data

We propose a concept of hybrid geometry sets for registering cross-source geometric data. Specifically, our method focuses on the coarse registration of geometric data obtained from laser scanning and photogrammetric reconstruction. Due to different characteristics (e.g., variations in noise levels, density, and scales), achieving accurate registration between these data becomes a challenging task. The proposed method uses geometric structures to construct hybrid geometry sets, and the geometric relations between the elements of a hybrid geometry set are encoded in a hybrid feature space. This enables effective and efficient similarity query and correspondence establishment between the hybrid geometry sets. The proposed global registration method works in three steps. Firstly, a set of hybrid geometry sets is constructed using extracted planes and intersection lines. Then the features of the hybrid geometry sets are computed to encode the relative pose and topological relationships between the extracted planes and intersection lines, and their correspondences between the two inputs are established by querying hybrid geometry sets with similar features. Finally, the global registration parameters are calculated using the correspondences, and the registration result is further refined through continuous optimization. The robustness of the method has been evaluated using different real-world cross-source geometric data of urban scenes. Extensive comparisons with state-of-the-art algorithms have also demonstrated its effectiveness.Urban Data Scienc

Influence of liquid-binder ratio on the performance of alkali-activated slag mortar with superabsorbent polymer

The influences of liquid-binder ratio and mixing sequence on the performance of superabsorbent polymer (SAP)-containing alkali-activated slag (AAS) mortar are investigated in this study. It is found that the SAP absorbs much less liquid in upper supernatant of AAS than in water. Mixing SAP with liquid first induces a larger absorption capacity of the SAP than mixing it with solid first. Increasing the liquid-binder ratio improves the flowability but reduces the strength of AAS mortar with SAP. Nonetheless, the strength of internally cured mixtures is higher than that of the reference even with an extra liquid-binder ratio of 0.09. The reason behind lies in the refinement of capillary and gel porosity by internal curing, despite the presence of large voids originated from SAP. The autogenous shrinkage of AAS paste is reduced significantly by the incorporation of SAP but the further mitigating effect of increased liquid-binder ratio is limited.Materials and Environmen

Investigating the Response of Vegetation to Flash Droughts by Using Cross-Spectral Analysis and an Evapotranspiration-Based Drought Index

Flash droughts tend to cause severe damage to agriculture due to their characteristics of sudden onset and rapid intensification. Early detection of the response of vegetation to flash droughts is of utmost importance in mitigating the effects of flash droughts, as it can provide a scientific basis for establishing an early warning system. The commonly used method of determining the response time of vegetation to flash drought, based on the response time index or the correlation between the precipitation anomaly and vegetation growth anomaly, leads to the late detection of irreversible drought effects on vegetation, which may not be sufficient for use in analyzing the response of vegetation to flash drought for early earning. The evapotranspiration-based (ET-based) drought indices are an effective indicator for identifying and monitoring flash drought. This study proposes a novel approach that applies cross-spectral analysis to an ET-based drought index, i.e., Evaporative Stress Anomaly Index (ESAI), as the forcing and a vegetation-based drought index, i.e., Normalized Vegetation Anomaly Index (NVAI), as the response, both from medium-resolution remote sensing data, to estimate the time lag of the response of vegetation vitality status to flash drought. An experiment on the novel method was carried out in North China during March–September for the period of 2001–2020 using remote sensing products at 1 km spatial resolution. The results show that the average time lag of the response of vegetation to water availability during flash droughts estimated by the cross-spectral analysis over North China in 2001–2020 was 5.9 days, which is shorter than the results measured by the widely used response time index (26.5 days). The main difference between the phase lag from the cross-spectral analysis method and the response time from the response time index method lies in the fundamental processes behind the definitions of the vegetation response in the two methods, i.e., a subtle and dynamic fluctuation signature in the response signal (vegetation-based drought index) that correlates with the fluctuation in the forcing signal (ET-based drought index) versus an irreversible impact indicated by a negative NDVI anomaly. The time lag of the response of vegetation to flash droughts varied with vegetation types and irrigation conditions. The average time lag for rainfed cropland, irrigated cropland, grassland, and forest in North China was 5.4, 5.8, 6.1, and 6.9 days, respectively. Forests have a longer response time to flash droughts than grasses and crops due to their deeper root systems, and irrigation can mitigate the impacts of flash droughts. Our method, based on cross-spectral analysis and the ET-based drought index, is innovative and can provide an earlier warning of impending drought impacts, rather than waiting for the irreversible impacts to occur. The information detected at an earlier stage of flash droughts can help decision makers in developing more effective and timely strategies to mitigate the impact of flash droughts on ecosystems.Optical and Laser Remote Sensin

Approaching nearly zero energy of PV direct air conditioners by integrating building design, load flexibility and PCM

The energy matching of PV driven air conditioners is influenced by building load demand and PV generation. Merely increasing energy performance of building or PV capacity separately may improve the energy balance on a large time resolution, the real-time energy mismatching problem is still serious. In this study, a coordinated optimization method of PV capacity, building design, and load flexibility is proposed for improving the real-time energy matching of PVAC system. Then, a methodology integrating data mining method (XG Boost) and parametric simulation was developed to identify the determinant parameters of PV system and building design, exploring feature importance and correlations. The results of XG Boost indicate that the PV capacity, shape factor, and SHGC are the most critical factors. Finally, based on the optimized building design, the PCM layer was applied to improve the real time energy matching. To achieve a goal of 90 % ZEP, the PCM capacity can be decreased by 50.4 % and 62.8 % in Guangzhou and Shanghai in the optimized building. Moreover, the PV capacity can be reduced by 23 % in Guangzhou. The findings of this study provide practical guidance for designing PVAC system coupling with building design and energy storage devices.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Environmental & Climate Desig

Embedding Adaptive Features in the ArduPilot Control Architecture for Unmanned Aerial Vehicles

The operation of Unmanned Aerial Vehicles (UAVs) is often subject to state-dependent alterations and unstructured uncertainty factors, such as unmodelled dynamics, environmental weather disturbances, aerodynamics gradients, or changes in inertia and mass due to payloads. While a large number of autopilot solutions have been proposed to operate UAVs, none of these solutions is able to counteract the effects of state-dependent and unstructured uncertainties online by parameter estimation and adaptive control techniques. This work presents a systematic integration of adaptive control into ArduPilot, a popular open-source autopilot suite maintained by a large community of UAV developers. Adaptation features are embedded in the ArduPilot control structure without altering the original architecture, to allow users to use the autopilot suite as usual. Tests show that the proposed adaptive ArduPilot provides consistent improved performance in several uncertain flight conditions. The source code of the proposed adaptive ArduPilot is released at https://github.com/Friend-Peng/Adaptive-ArduPilot-Autopilot.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Bart De Schutte

Effect of superabsorbent polymer introduction on properties of alkali-activated slag mortar

Internal curing by superabsorbent polymer (SAP) has been applied in alkali-activated slag (AAS) systems by a few previous studies with the purpose to mitigate the autogenous shrinkage. However, the effects of SAP on other properties of AAS have been rarely studied. In this paper, the workability, strength, permeability, and frost resistance of AAS mortar with synthesized SAP are investigated besides the autogenous shrinkage. Two SAP introducing ways (dry mixing and wet mixing) are considered. It is found that the flowability of AAS mortar decreases with the increase of SAP dosage regardless of the introducing way. The strength and permeability increase with the SAP dosage when it is below a certain amount depending on the mixing way. The autogenous shrinkage can be mitigated significantly by the incorporation of SAP and the mitigating effect is more pronounced by wet mixing. The frost resistance becomes better when more SAP is introduced in either way. The mechanisms behind these phenomena are explained based on the characterization results on the reaction kinetics, reaction products and pore structure of the mixtures with SAP.Materials and Environmen