| 1. |
- DeMott, Paul J., et al.
(författare)
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The Fifth International Workshop on Ice Nucleation phase 2 (FIN-02) : Laboratory intercomparison of ice nucleation measurements
- 2018
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 11:11, s. 6231-6257
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Tidskriftsartikel (refereegranskat)abstract
- The second phase of the Fifth International Ice Nucleation Workshop (FIN-02) involved the gathering of a large number of researchers at the Karlsruhe Institute of Technology's Aerosol Interactions and Dynamics of the Atmosphere (AIDA) facility to promote characterization and understanding of ice nucleation measurements made by a variety of methods used worldwide. Compared to the previous workshop in 2007, participation was doubled, reflecting a vibrant research area. Experimental methods involved sampling of aerosol particles by direct processing ice nucleation measuring systems from the same volume of air in separate experiments using different ice nucleating particle (INP) types, and collections of aerosol particle samples onto filters or into liquid for sharing amongst measurement techniques that post-process these samples. In this manner, any errors introduced by differences in generation methods when samples are shared across laboratories were mitigated. Furthermore, as much as possible, aerosol particle size distribution was controlled so that the size limitations of different methods were minimized. The results presented here use data from the workshop to assess the comparability of immersion freezing measurement methods activating INPs in bulk suspensions, methods that activate INPs in condensation and/or immersion freezing modes as single particles on a substrate, continuous flow diffusion chambers (CFDCs) directly sampling and processing particles well above water saturation to maximize immersion and subsequent freezing of aerosol particles, and expansion cloud chamber simulations in which liquid cloud droplets were first activated on aerosol particles prior to freezing. The AIDA expansion chamber measurements are expected to be the closest representation to INP activation in atmospheric cloud parcels in these comparisons, due to exposing particles freely to adiabatic cooling. The different particle types used as INPs included the minerals illite NX and potassium feldspar (K-feldspar), two natural soil dusts representative of arable sandy loam (Argentina) and highly erodible sandy dryland (Tunisia) soils, respectively, and a bacterial INP (Snomax®). Considered together, the agreement among post-processed immersion freezing measurements of the numbers and fractions of particles active at different temperatures following bulk collection of particles into liquid was excellent, with possible temperature uncertainties inferred to be a key factor in determining INP uncertainties. Collection onto filters for rinsing versus directly into liquid in impingers made little difference. For methods that activated collected single particles on a substrate at a controlled humidity at or above water saturation, agreement with immersion freezing methods was good in most cases, but was biased low in a few others for reasons that have not been resolved, but could relate to water vapor competition effects. Amongst CFDC-style instruments, various factors requiring (variable) higher supersaturations to achieve equivalent immersion freezing activation dominate the uncertainty between these measurements, and for comparison with bulk immersion freezing methods. When operated above water saturation to include assessment of immersion freezing, CFDC measurements often measured at or above the upper bound of immersion freezing device measurements, but often underestimated INP concentration in comparison to an immersion freezing method that first activates all particles into liquid droplets prior to cooling (the PIMCA-PINC device, or Portable Immersion Mode Cooling chAmber-Portable Ice Nucleation Chamber), and typically slightly underestimated INP number concentrations in comparison to cloud parcel expansions in the AIDA chamber; this can be largely mitigated when it is possible to raise the relative humidity to sufficiently high values in the CFDCs, although this is not always possible operationally. Correspondence of measurements of INPs among direct sampling and post-processing systems varied depending on the INP type. Agreement was best for Snomax® particles in the temperature regime colder than -10°C, where their ice nucleation activity is nearly maximized and changes very little with temperature. At temperatures warmer than -10°C, Snomax® INP measurements (all via freezing of suspensions) demonstrated discrepancies consistent with previous reports of the instability of its protein aggregates that appear to make it less suitable as a calibration INP at these temperatures. For Argentinian soil dust particles, there was excellent agreement across all measurement methods; measures ranged within 1 order of magnitude for INP number concentrations, active fractions and calculated active site densities over a 25 to 30°C range and 5 to 8 orders of corresponding magnitude change in number concentrations. This was also the case for all temperatures warmer than -25°C in Tunisian dust experiments. In contrast, discrepancies in measurements of INP concentrations or active site densities that exceeded 2 orders of magnitude across a broad range of temperature measurements found at temperatures warmer than -25°C in a previous study were replicated for illite NX. Discrepancies also exceeded 2 orders of magnitude at temperatures of -20 to -25°C for potassium feldspar (K-feldspar), but these coincided with the range of temperatures at which INP concentrations increase rapidly at approximately an order of magnitude per 2°C cooling for K-feldspar. These few discrepancies did not outweigh the overall positive outcomes of the workshop activity, nor the future utility of this data set or future similar efforts for resolving remaining measurement issues. Measurements of the same materials were repeatable over the time of the workshop and demonstrated strong consistency with prior studies, as reflected by agreement of data broadly with parameterizations of different specific or general (e.g., soil dust) aerosol types. The divergent measurements of the INP activity of illite NX by direct versus post-processing methods were not repeated for other particle types, and the Snomax° data demonstrated that, at least for a biological INP type, there is no expected measurement bias between bulk collection and direct immediately processed freezing methods to as warm as -10°C. Since particle size ranges were limited for this workshop, it can be expected that for atmospheric populations of INPs, measurement discrepancies will appear due to the different capabilities of methods for sampling the full aerosol size distribution, or due to limitations on achieving sufficient water supersaturations to fully capture immersion freezing in direct processing instruments. Overall, this workshop presents an improved picture of present capabilities for measuring INPs than in past workshops, and provides direction toward addressing remaining measurement issues.
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| 2. |
- Domis, Lisette N. De Senerpont, et al.
(författare)
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Plankton dynamics under different climatic conditions in space and time
- 2013
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 58:3, s. 463-482
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Forskningsöversikt (refereegranskat)abstract
- 1.Different components of the climate system have been shown to affect temporal dynamics in natural plankton communities on scales varying from days to years. The seasonal dynamics in temperate lake plankton communities, with emphasis on both physical and biological forcing factors, were captured in the 1980s in a conceptual framework, the Plankton Ecology Group (PEG) model. 2.Taking the PEG model as our starting point, we discuss anticipated changes in seasonal and long-term plankton dynamics and extend this model to other climate regions, particularly polar and tropical latitudes. Based on our improved post-PEG understanding of plankton dynamics, we also evaluate the role of microbial plankton, parasites and fish in governing plankton dynamics and distribution. 3.In polar lakes, there is usually just a single peak in plankton biomass in summer. Lengthening of the growing season under warmer conditions may lead to higher and more prolonged phytoplankton productivity. Climate-induced increases in nutrient loading in these oligotrophic waters may contribute to higher phytoplankton biomass and subsequent higher zooplankton and fish productivity. 4.In temperate lakes, a seasonal pattern with two plankton biomass peaks in spring and summer can shift to one with a single but longer and larger biomass peak as nutrient loading increases, with associated higher populations of zooplanktivorous fish. Climate change will exacerbate these trends by increasing nutrient loading through increased internal nutrient inputs (due to warming) and increased catchment inputs (in the case of more precipitation). 5.In tropical systems, temporal variability in precipitation can be an important driver of the seasonal development of plankton. Increases in precipitation intensity may reset the seasonal dynamics of plankton communities and favour species adapted to highly variable environments. The existing intense predation by fish on larger zooplankters may increase further, resulting in a perennially low zooplankton biomass. 6.Bacteria were not included in the original PEG model. Seasonally, bacteria vary less than the phytoplankton but often follow its patterns, particularly in colder lakes. In warmer lakes, and with future warming, a greater influx of allochthonous carbon may obscure this pattern. 7.Our analyses indicate that the consequences of climate change for plankton dynamics are, to a large extent, system specific, depending on characteristics such as food-web structure and nutrient loading. Indirect effects through nutrient loading may be more important than direct effects of temperature increase, especially for phytoplankton. However, with warming a general picture emerges of increases in bacterivory, greater cyanobacterial dominance and smaller-bodied zooplankton that are more heavily impacted by fish predation.
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| 3. |
- Heinken, Thilo, et al.
(författare)
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The European Forest Plant Species List (EuForPlant): Concept and applications
- 2022
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1654-1103 .- 1100-9233. ; 33:3, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Question: When evaluating forests in terms of their biodiversity, distinctiveness and naturalness, the affinity of the constituent species to forests is a crucial parameter. Here we ask to what extent are vascular plant species associated with forests, and does species’ affinity to forests vary between European regions?Location: Temperate and boreal forest biome of Northwestern and Central Europe. Methods: We compiled EuForPlant, a new extensive list of forest vascular plant spe- cies in 24 regions spread across 13 European countries using vegetation databases and expert knowledge. Species were region-specifically classified into four categories reflecting the degree of their affinity to forest habitats: 1.1, species of forest interiors; 1.2, species of forest edges and forest openings; 2.1, species that can be found in forest as well as open vegetation; and 2.2, species that can be found partly in forest, but mainly in open vegetation. An additional “O” category was distinguished, covering species typical for non-forest vegetation.Results: EuForPlant comprises 1,726 species, including 1,437 herb-layer species, 159 shrubs, 107 trees, 19 lianas and 4 epiphytic parasites. Across regions, generalist forest species (with 450 and 777 species classified as 2.1 and 2.2, respectively) significantly outnumbered specialist forest species (with 250 and 137 species classified as 1.1 and 1.2, respectively). Even though the degree of shifting between the categories of for- est affinity among regions was relatively low (on average, 17.5%), about one-third of the forest species (especially 1.2 and 2.2) swapped categories in at least one of the study regions.Conclusions: The proposed list can be used widely in vegetation science and global change ecology related to forest biodiversity and community dynamics. Shifting of forest affinity among regions emphasizes the importance of a continental-scale forest plant species list with regional specificity.
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| 4. |
- Hultcrantz, Monica, et al.
(författare)
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Interferons induce an antiviral state in human pancreatic islet cells
- 2007
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Ingår i: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 367:1, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- Enterovirus infections, in particular those with Coxsackieviruses, have been linked to the development of type 1 diabetes (T1D). Although animal models have demonstrated that interferons (IFNs) regulate virus-induced T1D by acting directly on the beta cell, little is known on the human pancreatic islet response to IFNs. Here we show that human islet cells respond to IFNs by expressing signature genes of antiviral defense. We also demonstrate that they express three intracellular sensors for viral RNA, the toll like receptor 3 (TLR3) gene, the retinoic acid-inducible gene I (RIG-I) and the melanoma differentiation-associated gene-5 (MDA-5), which induce type I IFN production in infected cells. Finally, we show for the first time that the IFN-induced antiviral state provides human islets with a powerful protection from the replication of Coxsackievirus. This may be critical for beta cell survival and protection from virus-induced T1D in humans.
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| 5. |
- Prior, Matthew J., et al.
(författare)
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Arabidopsis bZIP11 Is a Susceptibility Factor during Pseudomonas syringae Infection
- 2021
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Ingår i: Molecular Plant-Microbe Interactions. - : American Phytopathological Society. - 0894-0282 .- 1943-7706. ; 34:4, s. 439-447
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Tidskriftsartikel (refereegranskat)abstract
- The induction of plant nutrient secretion systems is critical for successful pathogen infection. Some bacterial pathogens (e.g., Xanthomonas spp.) use transcription activator-like (TAL) effectors to induce transcription of SWEET sucrose efflux transporters. Pseudomonas syringae pv. tomato strain DC3000 lacks TAL effectors yet is able to induce multiple SWEETs in Arabidopsis thaliana by unknown mechanisms. Because bacteria require other nutrients in addition to sugars for efficient reproduction, we hypothesized that Pseudomonas spp. may depend on host transcription factors involved in secretory programs to increase access to essential nutrients. Bioinformatic analyses identified the Arabidopsis basic-leucine zipper transcription factor bZIP11 as a potential regulator of nutrient transporters, including SWEETs and UmamiT amino acid transporters. Inducible downregulation of bZIP11 expression in Arabidopsis resulted in reduced growth of P. syringae pv. tomato strain DC3000, whereas inducible overexpression of bZIP11 resulted in increased bacterial growth, supporting the hypothesis that bZIP11-regulated transcription programs are essential for maximal pathogen titer in leaves. Our data are consistent with a model in which a pathogen alters host transcription factor expression upstream of secretory transcription networks to promote nutrient efflux from host cells.
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| 6. |
- Sommer, Ulrich, et al.
(författare)
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Beyond the Plankton Ecology Group (PEG) Model : Mechanisms Driving Plankton Succession
- 2012
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Ingår i: Annual Review of Ecology, Evolution and Systematics. - : Annual Reviews. - 1543-592X .- 1545-2069. ; 43, s. 429-448
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Forskningsöversikt (refereegranskat)abstract
- The seasonal succession of plankton is an annually repeated process of community assembly during which all major external factors and internal interactions shaping communities can be studied. A quarter of a century ago, the state of this understanding was described by the verbal plankton ecology group (PEG) model. It emphasized the role of physical factors, grazing and nutrient limitation for phytoplankton, and the role of food limitation and fish predation for zooplankton. Although originally targeted at lake ecosystems, it was also adopted by marine plankton ecologists. Since then, a suite of ecological interactions previously underestimated in importance have become research foci: overwintering of key organisms, the microbial food web, parasitism, and food quality as a limiting factor and an extended role of higher order predators. A review of the impact of these novel interactions on plankton seasonal succession reveals limited effects on gross seasonal biomass patterns, but strong effects on species replacements.
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