| 1. |
- Algaba, Juan-Carlos, et al.
(author)
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Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
- 2021
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
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Research review (peer-reviewed)abstract
- In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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| 2. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
- Bolinder, Martin, et al.
(author)
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Evaluate carbon stock changes based on the Swedish soil-monitoring program
- 2022
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Reports (other academic/artistic)abstract
- In the national greenhouse gas inventory, SLU is applying a Tier III method using the Introductory Carbon Balance Model (ICBM) in a holistic framework for calculating changes in soil organic carbon (SOC) stocks in arable land for mineral soils, which Sweden is reporting under the Land Use, Land Use Change and Forestry (LULUCF) sector. This method is delivering SOC stock change rates for eight Swedish agricultural production regions (PO8s), which are aggregated to the national level. The effect of the climate on SOC decomposition in ICBM is accounted for using gridded daily weather records from the Swedish Meteorological Institute (SMHI). The model framework is taking agricultural activity data from yearly census records regarding the use of arable land (area and yield of different crops including fallow) and management systems (straw removal and manure applications). In addition, it applies different empirical functions for estimating annual carbon inputs from roots and for estimating dry soil bulk density for expressing carbon concentrations on a mass basis, based on literature reviews and analyses of large Swedish soil databases. For the ICBM model simulations, initial stocks of SOC are derived from data on soil texture and SOC concentrations from the Swedish Environmental Protection Agency (SEPA) national soil-monitoring program (SMP). The national SMP consists of three soil inventories that periodically characterizes the topsoil properties in 10-year cycles across Sweden. The first inventory, conducted between 1988 and 1995 is providing data for the 1990 baseline, while the latest complete inventory ended 2017. The sampling points in the inventories have coordinates, and data can be associated with each of the Swedish PO8s. We have now been calibrating a new version of the ICBM model by integrating the most recent knowledge gained from long-term field experiments. The objectives of this development project were to evaluate SOC changes from the national SMP by using exact coordinates and new statistical tests and compare these changes to predictions with the new version of ICBM. The general trends in SOC changes calculated from the national SMP remain similar to previous analyses, showing consistent SOC increments over time. The absolute increments at the national level are relatively small, SOC concentrations increased by 0.11, 0.07 and 0.21 percentage units from inventory I to inventory II, from inventory II to inventory III, and from inventory I to inventory III, respectively. This is representing a relative increase of 9.3% between inventory III and I. Applying exact coordinates were allowing us to add a few points in each PO8s that were not present in our previous analysis of the three soil inventories. Using other statistical tests improved the inference between inventories at the PO8 level, where the Wilcoxon signed rank test (a non-parametric method) applied to the matched points when comparing inventory III against II now showed significant differences. The predictions with ICBM are mimicking the relative increase in SOC at the national level but the relative increase is much less pronounced (i.e. 1.5%). Compared to results obtained with the national SMP, ICBM predictions are not always matching the same trends in SOC changes for all of the PO8s. There remain several uncertainties relating to both methods that needs further considerations. For example, data from the Swedish SMP may be associated with inconsistences relating to the use of different analytical methods for measuring SOC concentrations, or to possible under-estimations of SOC concentrations in inventory I due to differences in sampling strategies. While uncertainties relating to ICBM predictions are including e.g. estimation of the amount of annual carbon inputs from roots and manures. A fourth inventory has been initiated and will provide precious information about trends in SOC changes at the national scale, which will be useful for developing both methods.
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| 6. |
- Karlsson Potter, Hanna, et al.
(author)
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Climate impact of liming arable soil -effect on N2O emissions in a life cycle perspective
- 2023
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Reports (other academic/artistic)abstract
- Agricultural soils are limed primarily to maintain high yields. Limed soils, with higher pH, often have lower emissions of the strong greenhouse gas nitrous oxide (N2O), but also increased emissions of soil CO2. In this study, data from the long-term Ultuna outdoor frame trials were used to estimate the impact of increasing pH on agricultural soils, by comparing treatments with higher soil pH (7.2, representing liming) and lower pH (6.6). Climate impact was calculated in a life cycle perspective up to farm gate, meaning that impacts from producing inputs and field emissions were included. Measured field data were used to estimate effects on soil N2O emissions. In addition, three existing empirical models for estimating soil N2O emissions were applied. Field data from the Ultuna trials showed that soil N2O emissions from the treatment with higher soil pH were 71% lower than those from the treatment with lower soil pH. Assessed in a life cycle perspective, the results indicated that liming to increase soil pH can decrease the overall climate impact from crop production, by around 28% in this case. The reduction was mainly due to lower soil N2O, but also increased soil organic carbon content. The climate impact from production and application of additional lime needed to maintain the higher soil pH was around 10% of the total climate impact assessed on a per-hectare basis. Different models for estimating soil N2O gave very different results, illustrating the uncertainty in estimates, which is crucial to consider in interpretation of results. The contribution of soil N2O emissions to the overall climate impact varied between 18% and 43%, depending on the model used to estimate N2O emissions. Model development is needed to enable more accurate estimation of N2O emissions and more accurate prediction of the effects of management changes on soil N2O.
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| 7. |
- Lang, Rong
(author)
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Explaining success on community forestry through a lens of environmental justice: Local justice norms and practices in China
- 2021
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In: World Development. - : Elsevier BV. - 0305-750X .- 1873-5991. ; 142
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Journal article (peer-reviewed)abstract
- It is of global interest to understand under what conditions community forestry can be successful and sustainable in terms of environmental conservation and local livelihood benefits. Existing theories have explained several influential factors, including small groups of people with shared norms, sound institu-tions, high levels of decentralization, downward accountability, and security of tenure. This paper explores how local conceptions of environmental justice become closely linked to sustainable community forestry. Based on an in-depth case study in a highly populated and culturally heterogeneous village in southwest China, we examine an enduring example of community forestry, using a combination of qual-itative and quantitative approaches. The results show that village forest cover has increased significantly over the last 30 years, contributing to improvements in local livelihoods. It is argued that one of the important factors in this success has been villagers & rsquo; ability to align forest management with local justice norms and practices. Distributive, procedural, and recognition aspects of justice are considered, and we find that, in combination, these become integral to building effective institutions for collective action. To broaden the focus on successful factors in existing theories, this paper argues that the consideration of justice as an important condition for establishing effective and durable local institutions that will be effective for community forestry. The insights from this study suggest a need to consider justice dimen-sions in community forestry research to enable improved understanding of its dynamics and outcomes worldwide.(c) 2021 Elsevier Ltd. All rights reserved.
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| 8. |
- Moberg, Emma, et al.
(author)
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Effect of ley inclusion in crop rotations on soil carbon stocks in a life cycle perspective
- 2022
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Reports (other academic/artistic)abstract
- Carbon sequestration in agricultural soils has been proposed as an important climate change mitigation strategy. Carbon stocks in soils can be increased by different cropland management options, one of which is greater inclusion of perennial crops in crop rotations. This study compared the climate impact in a life cycle perspective of continuous ley-dominated rotations and continuous cereal rotations at two different sites (loam, clay) in Sweden. Effects of these systems on carbon content in topsoil and subsoil over 35 years were assessed based on data from two ongoing longterm field trials. The continuous cereal rotations led to a decrease in soil organic carbon stocks at both sites, resulting in an increase in overall climate impact of 8-19%. The ley-dominated rotationsincreased soil organic carbon stocks at both sites over time, contributing to a decrease in overall climate impact of 7% (clay) and 18% (loam). The high soil carbon accumulation in the ley rotation at the site with loamy soil, where soil carbon stocks increased in both topsoil and subsoil, waspossibly due to more roots entering the subsoil than at the site with clay soil.
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| 9. |
- Wang, Xin-Ping, et al.
(author)
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Effects of surface characteristics on infiltration patterns in an arid shrub desert
- 2007
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In: Hydrological Processes. - : Wiley. - 1099-1085 .- 0885-6087. ; 21:1, s. 72-79
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Journal article (peer-reviewed)abstract
- Precipitation is often the sole source of water replenishment in arid and semi-arid areas and, thus, plays a pertinent role in sustaining desert ecosystems. Revegetation over 40 years using mainly Artemisia ordosica and Caragana korshinskii at Shapotou Desert Experimental Research Station near Lanzhou, China, has established a dwarf-shrub and microbiotic soil crust cover on the stabilized sand dunes. The redistribution of infiltrated moisture through percolation, root extraction, and evapotranspiration pathways was investigated. Three sets of time-domain reflectometry (TDR) probes were inserted horizontally at 5, 10, 15, 20, 30 and 40 cm depths below the ground surface in a soil pit. The three sets of TDR probes were installed in dwarf-shrub sites of A. ordosica and C. korshinskii community with and without a microbiotic soil crust cover, and an additional set was placed in a bare sand dune area that had neither vegetation nor a microbiotic soil crust present. Volumetric soil moisture content was recorded at hourly intervals and used in the assessment of infiltration for the different surface covers. Infiltration varied greatly, from 7.5 cm to more than 45 cm, depending upon rainfall quantity and soil surface conditions. In the shrub community area without microbiotic soil crust cover, infiltration increased due to preferential flow associated with root tunnels. The microbiotic soil crust cover had a significant negative influence on the infiltration for small rainfall events (similar10 mm), restricting the infiltration depth to less than 20 cm and increasing soil moisture content just beneath the soil profile of 10 cm, whereas it was not as strong or clear for larger rainfall events (similar60 mm). For small rainfall events, the wetting front depth for the three kinds of surface cover was as follows: shrub community without microbiotic soil crust > bare area > shrub community with microbiotic soil crust. In contrast, for large rainfall events, infiltration was similar in shrub communities with and without microbiotic soil crust cover, but significantly higher than measured in the bare area. Soil water extraction by roots associated with evapotranspiration restricted the wetting front penetration after 1 to 3 h of rainfall. Copyright © 2006 John Wiley & Sons, Ltd.
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| 10. |
- Wu, Da, 1985, et al.
(author)
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VAE Based Non-Autoregressive Transformer Model for Sea Ice Concentration Forecast
- 2022
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In: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. - 9781880653814
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Conference paper (peer-reviewed)abstract
- Arctic shipping along the Northern Sea Route (NSR) relies on reliable and precise sea ice concentration (SIC) information. However, the SIC forecast used to assist NSR shipping is often inaccurate. This study proposes a VAE based Non-Autoregressive Transformer model for the long-term SIC forecast task. The proposed model ensembles the deep generative model of Variational Autoencoder and the deep learning model of Transformer to overcome the temporal delay and accumulative error problems shown in traditional time series models. Model validation has been conducted to compare the forecasts of SIC with other machine learning and deep learning models. The proposed model outperforms the compared models in terms of different metrics. The proposed VAE based Non-Autoregressive Transformer can be used for long-term SIC forecast and achieve stable and good accuracy predictions.
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