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7 Research products, page 1 of 1

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  • 2018-2022
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  • Open Access English
    Authors: 
    Stolzenburg, Dominik; Simon, Mario; Ranjithkumar, Ananth; Kürten, Andreas; Lehtipalo, Katrianne; Gordon, Hamish; Ehrhart, Sebastian; Finkenzeller, Henning; Pichelstorfer, Lukas; Nieminen, Tuomo; +68 more
    Project: EC | NANODYNAMITE (616075), FWF | Chemical composition of a... (P 27295), SNSF | CLOUD Infrastructure proj... (172622), AKA | From Autoxidation to Auto... (299574), NSF | Collaborative Research: C... (1801280), NSF | Collaborative Research: C... (1801329), AKA | Oxidised organic vapours ... (310682), EC | CLOUD-MOTION (764991), SNSF | CLOUD (159851), EC | COFUND-FP-CERN-2014 (665779),...

    In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (<10 nm) from sulfuric acid remain poorly measured. Therefore, the effect of stabilizing bases, the contribution of ions and the impact of attractive forces on molecular collisions are under debate. Here, we present precise growth rate measurements of uncharged sulfuric acid particles from 1.8 to 10 nm, performed under atmospheric conditions in the CERN (European Organization for Nuclear Research) CLOUD chamber. Our results show that the evaporation of sulfuric acid particles above 2 nm is negligible, and growth proceeds kinetically even at low ammonia concentrations. The experimental growth rates exceed the hard-sphere kinetic limit for the condensation of sulfuric acid. We demonstrate that this results from van der Waals forces between the vapour molecules and particles and disentangle it from charge–dipole interactions. The magnitude of the enhancement depends on the assumed particle hydration and collision kinetics but is increasingly important at smaller sizes, resulting in a steep rise in the observed growth rates with decreasing size. Including the experimental results in a global model, we find that the enhanced growth rate of sulfuric acid particles increases the predicted particle number concentrations in the upper free troposphere by more than 50 %.

  • Open Access English
    Authors: 
    Stanić-Vučinić, Dragana; Nikolić, Stefan; Vlajić, Katarina; Radomirović, Mirjana Ž.; Mihailović, Jelena; Ćirković-Veličković, Tanja; Grgurić-Šipka, Sanja;
    Publisher: Springer
    Country: Serbia
    Project: EC | FoodEnTwin (810752), MESTD | Molecular properties and ... (172024), MESTD | Rational design and synth... (172035)

    Supplementary material for:[https://link.springer.com/article/10.1007%2Fs00775-020-01758-3] Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3859] Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3942]

  • Open Access English
    Authors: 
    Göckede, Mathias; Kittler, Fanny; Kwon, Min Jung; Burjack, Ina; Heimann, Martin; Kolle, Olaf; Zimov, Nikita; Zimov, Sergey;
    Project: EC | PAGE21 (282700), EC | PERCCOM (333796)

    Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the northern high-latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in northeast Siberia comprising a drained and a control site. At the drainage site, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net effects of drainage. Reduced thermal conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere as sensible heat in the drained area, which may trigger a warming of the lower atmospheric surface layer.

  • Open Access English
    Authors: 
    Butchart, Neal; Anstey, James A.; Hamilton, Kevin; Osprey, Scott; McLandress, Charles; Bushell, Andrew C.; Kawatani, Yoshio; Kim, Young-Ha; Lott, Francois; Scinocca, John; +23 more
    Project: UKRI | GOTHAM - Globally Observe... (NE/P006779/1), EC | STRATOCLIM (603557), ANR | GOTHAM (ANR-15-JCLI-0004)

    The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi) aims to improve the fidelity of tropical stratospheric variability in general circulation and Earth system models by conducting coordinated numerical experiments and analysis. In the equatorial stratosphere, the QBO is the most conspicuous mode of variability. Five coordinated experiments have therefore been designed to (i) evaluate and compare the verisimilitude of modelled QBOs under present-day conditions, (ii) identify robustness (or alternatively the spread and uncertainty) in the simulated QBO response to commonly imposed changes in model climate forcings (e.g. a doubling of CO2 amounts), and (iii) examine model dependence of QBO predictability. This paper documents these experiments and the recommended output diagnostics. The rationale behind the experimental design and choice of diagnostics is presented. To facilitate scientific interpretation of the results in other planned QBOi studies, consistent descriptions of the models performing each experiment set are given, with those aspects particularly relevant for simulating the QBO tabulated for easy comparison.

  • Open Access English
    Authors: 
    Zaman, Shakil Bin; Barlat, Frederic; Kim, Jin-Hwan;

    Large-scale advanced high strength steel (AHSS) sheet specimens were deformed in uniaxial tension, using a novel grip system mounted on a MTS universal tension machine. After pre-strain, they were used as a pre-strained material to examine the anisotropic response in the biaxial tension tests with various load ratios, and orthogonal tension tests at 45° and 90° from the pre-strain axis. The flow curve and the instantaneous r-value of the pre-strained steel in each of the aforementioned uniaxial testing conditions were also measured and compared with those of the undeformed steel. Furthermore, an exhaustive analysis of the yield surface was also conducted and the results, prior and post-prestrain were represented and compared. The homogeneous anisotropic hardening (HAH) model [1] was employed to predict the behavior of the pre-strained material. It was found that the HAH-predicted flow curves after non-linear strain path change and the yield loci after uniaxial pre-strain were in good agreement with the experiments, while the r-value evolution after strain path change was qualitatively well predicted.

  • Open Access English
    Authors: 
    Roscoe, H. K.; Roozendael, M.; Fayt, C.; Piesanie, A.; Abuhassan, N.; Adams, C.; Akrami, M.; Cede, A.; Chong, J.; Clémer, K.; +41 more
    Project: EC | MEGAPOLI (212520)

    In June 2009, 22 spectrometers from 14 institutes measured tropospheric and stratospheric NO2 from the ground for more than 11 days during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI), at Cabauw, NL (51.97° N, 4.93° E). All visible instruments used a common wavelength range and set of cross sections for the spectral analysis. Most of the instruments were of the multi-axis design with analysis by differential spectroscopy software (MAX-DOAS), whose non-zenith slant columns were compared by examining slopes of their least-squares straight line fits to mean values of a selection of instruments, after taking 30-min averages. Zenith slant columns near twilight were compared by fits to interpolated values of a reference instrument, then normalised by the mean of the slopes of the best instruments. For visible MAX-DOAS instruments, the means of the fitted slopes for NO2 and O4 of all except one instrument were within 10% of unity at almost all non-zenith elevations, and most were within 5%. Values for UV MAX-DOAS instruments were almost as good, being 12% and 7%, respectively. For visible instruments at zenith near twilight, the means of the fitted slopes of all instruments were within 5% of unity. This level of agreement is as good as that of previous intercomparisons, despite the site not being ideal for zenith twilight measurements. It bodes well for the future of measurements of tropospheric NO2, as previous intercomparisons were only for zenith instruments focussing on stratospheric NO2, with their longer heritage.

  • Open Access English
    Authors: 
    Seo, Jungmok; Shin, Jung Youn; Leijten, Jeroen; Jeon, Oju; Camci-Unal, Gulden; Dikina, Anna D.; Brinegar, Katelyn; Ghaemmaghami, Amir M.; Alsberg, Eben; Khademhosseini, Ali;
    Project: NIH | Opposing RNAi molecule gr... (1R01AR069564-01), NIH | Growth Plate Regeneration (5R21AR061265-02), NIH | TRAINING PROGRAM IN MUSCU... (5T32AR007505-08), NSF | EFRI-BioFLEX: Tissue Engi... (1240443), NIH | High-Throughput Microenvi... (5R01AR066193-02), NIH | Controlled, Sustained Del... (1R56DE022376-01A1), NIH | Driving tissue formation ... (1R01AR063194-01), NIH | Microengineered Osteons f... (5R01AR057837-04)

    The rapid development of new biomaterials and techniques to modify them challenge our capability to characterize them using conventional methods. In response, numerous high-throughput (HT) strategies are being developed to analyze biomaterials and their interactions with cells using combinatorial approaches. Moreover, these systematic analyses have the power to uncover effects of delivered soluble bioactive molecules on cell responses. In this review, we describe the recent developments in HT approaches that help identify cellular microenvironments affecting cell behaviors and highlight HT screening of biochemical libraries for gene delivery, drug discovery, and toxicological studies. We also discuss HT techniques for the analyses of cell secreted biomolecules and provide perspectives on the future utility of HT approaches in biomedical engineering.

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