Temperate grasslands play globally an important role, for example, for biodiversity conservation, livestock forage production, and carbon storage. The latter two are primarily controlled by biomass ...production, which is assumed to decrease with lower amounts and higher variability of precipitation, while increasing air temperature might either foster or suppress biomass production. Additionally, a higher atmospheric CO2 concentration (CO2) is supposed to increase biomass productivity either by directly stimulating photosynthesis or indirectly by inducing water savings (CO2 fertilization effect). Consequently, future biomass productivity is controlled by the partially contrasting effects of changing climatic conditions and CO2, which to date are only marginally understood. This results in high uncertainties of future biomass production and carbon storage estimates. Consequently, this study aims at statistically estimating mid‐21st century grassland aboveground biomass (AGB) based on 18 years of data (1998–2015) from a free air carbon enrichment experiment. We found that lower precipitation totals and a higher precipitation variability reduced AGB. Under drier conditions accompanied by increasing air temperature, AGB further decreased. Here AGB under elevated CO2 was partly even lower compared to AGB under ambient CO2, probably because elevated CO2 reduced evaporative cooling of plants, increasing heat stress. This indicates a higher susceptibility of AGB to increased air temperature under future atmospheric CO2. Since climate models for Central Europe project increasing air temperature and decreasing total summer precipitation associated with an increasing variability, our results suggest that grassland summer AGB will be reduced in the future, contradicting the widely expected positive yield anomalies from increasing CO2.
Key Points
We link results from an 18‐year FACE experiment with climate forecasts to estimate mid‐21st century C3 grassland productivity
Despite increases in atmospheric CO2, the future aboveground biomass under warmer and drier conditions is below today's yield
The positive effect of increased CO2 on biomass production cannot compensate for yield losses due to unfavorable climatic conditions
Phosphotyrosine-containing synthetic peptides were used to identify the binding sites for cellular polypeptides involved in nerve growth factor receptor/Trk-mediated signal transduction. In vitro ...association of SHC and the p85 subunit of phosphatidylinositol 3'-kinase with the Trk tyrosine kinase was prevented only by phosphorylated Y-490- and Y-751-containing peptides, respectively. In spite of the close proximity of the p85 binding site to that of phospholipase C gamma (Y-785), both target proteins are able to interact with the same receptor molecule simultaneously.
In this work we propose a new formulation for the divergence of the viscoelastic stress for the collocated (cell-centered) finite-volume method. The reformulation allows for a semi-implicit handling ...of the constitutive equation, which promotes the numerical stability. Simulations of a three-dimensional planar and a square–square contraction show the robustness of this technique. The new formulation is completely devoid of unphysical checkerboard patterns of the velocity, which are present when using standard approximations for the divergence in conjunction with non-staggered grid methods. The consistency is ensured by giving results, which are independent of the time-step Δt for steady-state problems. The results for the planar contraction are generally in good agreement with experimental data for velocity, shear stress and first-normal stress difference. Stable simulations for the square–square contraction could be performed over a wide range of Deborah numbers. The vortex length is in agreement with the experimental results in the Newtonian-like and vortex-enhancement flow regime, however, the results deviate from the experiments in the diverging streamline regime.
The reduction of CO.sub.2 emissions and the enhancement of CO.sub.2 removals related to land use are considered essential for future pathways towards net-zero emissions and mitigating climate change. ...With the growing pressure under global climate treaties, country-level land-use CO.sub.2 flux data are becoming increasingly important. So far, country-level estimates are mainly available through official country reports, such as the greenhouse gas inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Recently, different modelling approaches, namely dynamic global vegetation models (DGVMs) and bookkeeping models, have moved to higher spatial resolutions, which makes it possible to obtain model-based country-level estimates that are globally consistent in their methodology. To progress towards a largely independent assessment of country reports using models, we analyse the robustness of country-level CO.sub.2 flux estimates from different modelling approaches in the period 1950-2021 and compare them with estimates from country reports.
Interaction of the nerve growth factor (NGF) receptor/Trk with cellular substrates was investigated by transient co‐overexpression in human 293 fibroblasts using ET‐R, a chimeric receptor consisting ...of the epidermal growth factor receptor (EGF‐R) extracellular ligand binding domain and the Trk transmembrane and intracellular signal‐generating sequences. The chimera was fully functional, and associated with and phosphorylated phospholipase C gamma (PLC gamma), ras GTPase‐activating protein (GAP) and the non‐catalytic subunit of phosphatidylinositol‐3′‐kinase, p85, in a ligand‐dependent manner. Deletion of 15 C‐terminal amino acids, including tyrosine 785 (Y‐785) abrogated receptor and substrate phosphorylation activities. Mutation of Y‐785 to phenylalanine somewhat impaired receptor phosphorylation activity, which was reflected in reduced GAP and p85 phosphorylation. In contrast, ET‐YF phosphorylation of PLC gamma was significantly reduced, while the high affinity association potential with this substrate was abrogated by this point mutation in vitro and in intact cells. Furthermore, a tyrosine‐phosphorylated synthetic C‐terminal peptide competitively inhibited Trk cytoplasmic domain association with PLC gamma. Thus, the short C‐terminal tail appears to be a crucial structural element of the Trk cytoplasmic domain, and phosphorylated Y‐785 is a major and selective interaction site for PLC gamma.
As part of the European Commission research project “Assessment of policy instruments for efficient ozone abatement strategies in Europe”, detailed emission projections have been developed for the ...year 2010 based upon currently adopted measures, and feasible reductions. For road-traffic emissions this projection considers passenger cars, light- and heavy-duty vehicles, mopeds and motorcycles. Here we present model calculations made with the EMEP 3-D Eulerian model to illustrate the relative contribution of each of these road-traffic sectors to ozone concentrations across Europe. The model is run for a six-month period, April–September 1996. The model results clearly suggest that further reduction in road-traffic emissions beyond currently planned measures would be beneficial in reducing ozone over Europe, particularly in the case of heavy-duty vehicles and evaporative emissions. These results do of course depend on the estimated emissions in each sector for the year 2010, and we show that this is a major source of uncertainty in such scenario calculations
This paper describes the comparison of calculated extinction coefficients from Lidar signals by the known Fernald-Klett inversion method with Lidar signal simulations. A ground-based Differential ...Absorption Lidar was employed in two studies measuring O3 and SO2 within the planetary boundary layer (PBL). By calculating extinction coefficients additional information about the PBL structure is obtained. As commonly used numerical inversion methods are limited to the knowledge of necessary boundary conditions, Lidar signal simulations are used for their estimation. Furthermore, comparing results of the inversion method with Lidar signal simulations validates calculated extinction coefficients. PUBLICATION ABSTRACT
A comprehensive field campaign was carried out to check the quality of modelled on-road emissions of NO
x
and CO by comparing them with real-world emissions on a motorway in the southwestern part of ...Germany. Three different sets of emission data were determined for a section of the motorway A 656 that connects Mannheim and Heidelberg. First, emission data were pre-calculated, that means before the field campaign took place, using literature data for traffic volume, types of vehicles and driving speeds. Second, detailed traffic measurements during two intensive measurement phases were used to calculate improved emission data based on the actual traffic situation. Third, real-world emission data were determined by meteorological and chemical measurements. It shows that the differences of the pre-calculated emission data and the emission data improved by the traffic measurements differ by less than 15% in case of CO and approx. by 35% in case of NO
x
. A comparison of the observed emissions with the calculated ones gives an agreement for NO
x
within the error bars. For CO, however, a discrepancy by a factor of two was found. The real-world emissions were much higher than calculated.
The exchange of nerve growth factor receptor/Trk and epidermal growth factor receptor (EGFR) phospholipase C gamma (PLC gamma) binding sites resulted in the transfer of their distinct affinities for ...this Src homology 2 domain‐containing protein. Relative to wild‐type EGFR, the PLC gamma affinity increase of the EGFR switch mutant EGFR.X enhanced its inositol trisphosphate (IP3) and calcium signals and resulted in a more sustained mitogen‐activated protein (MAP) kinase activation and accelerated receptor dephosphorylation. In parallel, EGFR.X exhibited a significantly decreased mitogenic and transforming potential in NIH 3T3 cells. Conversely, the transfer of the EGFR PLC gamma binding site into the Trk cytoplasmic domain context impaired the IP3/calcium signal and attenuated the MAP kinase activation and receptor dephosphorylation, but resulted in an enhancement of the ETR.X exchange mutant mitogenic and oncogenic capacity. Our findings establish the significance of PLC gamma affinity for signal definition, the role of this receptor tyrosine kinase substrate as a negative feedback regulator and the importance of this regulatory function for mitogenesis and its disturbance in oncogenic aberrations.
The fluorescence detection of ultra high energy (≳10
18
eV) cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules, which are excited by the cosmic ray ...shower particles along their path in the atmosphere. We have made a precise measurement of the fluorescence light spectrum excited by MeV electrons in dry air. We measured the relative intensities of 34 fluorescence bands in the wavelength range from 284 to 429
nm with a high resolution spectrograph. The pressure dependence of the fluorescence spectrum was also measured from a few hPa up to atmospheric pressure. Relative intensities and collisional quenching reference pressures for bands due to transitions from a common upper level were found in agreement with theoretical expectations. The presence of argon in air was found to have a negligible effect on the fluorescence yield. We estimated that the systematic uncertainty on the cosmic ray shower energy due to the pressure dependence of the fluorescence spectrum is reduced to a level of 1% by the AIRFLY results presented in this paper.
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