Browsing by Subject "ION"

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  • Chan, Tommy; Cai, Runlong; Ahonen, Lauri R.; Liu, Yiliang; Zhou, Ying; Vanhanen, Joonas; Dada, Lubna; Chao, Yan; Liu, Yongchun; Wang, Lin; Kulmala, Markku; Kangasluoma, Juha (2020)
    Accurate measurements of the size distribution of atmospheric aerosol nanoparticles are essential to build an understanding of new particle formation and growth. This is particularly crucial at the sub-3 nm range due to the growth of newly formed nanoparticles. The challenge in recovering the size distribution is due its complexity and the fact that not many instruments currently measure at this size range. In this study, we used the particle size magnifier (PSM) to measure atmospheric aerosols. Each day was classified into one of the following three event types: a new particle formation (NPF) event, a non-event or a haze event. We then compared four inversion methods (stepwise, kernel, Hagen-Alofs and expectation-maximization) to determine their feasibility to recover the particle size distribution. In addition, we proposed a method to pretreat the measured data, and we introduced a simple test to estimate the efficacy of the inversion itself. Results showed that all four methods inverted NPF events well; however, the stepwise and kernel methods fared poorly when inverting non-events or haze events. This was due to their algorithm and the fact that, when encountering noisy data (e.g. air mass fluctuations or low sub-3 nm particle concentrations) and under the influence of larger particles, these methods overestimated the size distribution and reported artificial particles during inversion. Therefore, using a statistical hypothesis test to discard noisy scans prior to inversion is an important first step toward achieving a good size distribution. After inversion, it is ideal to compare the integrated concentration to the raw estimate (i.e. the concentration difference at the lowest supersaturation and the highest supersaturation) to ascertain whether the inversion itself is sound. Finally, based on the analysis of the inversion methods, we provide procedures and codes related to the PSM data inversion.
  • Byggmästar, J.; Granberg, F. (2020)
    Density functional theory predicts clusters in the form of the C15 Laves phase to be the most stable cluster of self-interstitials in iron at small sizes. The C15 clusters can form as a result of irradiation, but their prevalence and survival in harsh irradiation conditions have not been thoroughly studied. Using a new bond-order potential optimised for molecular dynamics simulations of radiation damage, we explore the dynamical stability of the C15 clusters in iron under irradiation conditions. We find that small C15 clusters make up 5–20% of the interstitial clusters formed directly in cascades. In continuous irradiation, C15 clusters are frequently formed, after which they remain highly stable and grow by absorbing nearby single interstitial atoms. Growth of C15 clusters ultimately leads to collapse into dislocation loops, most frequently into 1/2⟨111⟩ loops and only rarely collapsing into ⟨100⟩ loops at low temperatures. The population, size, and collapse of C15 clusters during continuous irradiation correlates well with their formation energies relative to dislocation loops calculated at zero Kelvin.
  • Myllys, M.; Henri, P.; Vallieres, X.; Gilet, N.; Nilsson, H.; Palmerio, E.; Turc, L.; Wellbrock, A.; Goldstein, R.; Witasse, O. (2021)
    Context. The Mutual Impedance Probe (RPC-MIP) carried by the Rosetta spacecraft monitored both the plasma density and the electric field in the close environment of comet 67P/Churyumov-Gerasimenko (67P), as the instrument was operating alternatively in two main modes: active and passive. The active mode is used primarily to perform plasma density measurements, while the passive mode enables the instrument to work as a wave analyzer. Aims. We are reporting electric field emissions at the plasma frequency near comet 67P observed by RPC-MIP passive mode. The electric field emissions are related to Langmuir waves within the cometary ionized environment. In addition, this study gives feedback on the density measurement capability of RPC-MIP in the presence of cold electrons. Methods. We studied the occurrence rate of the electric field emissions as well as their dependence on solar wind structures like stream interaction regions (SIRs) and coronal mass ejections (CMEs). Results. We are showing that strong electric field emissions at the plasma frequency near 67P were present sporadically throughout the period when Rosetta was escorting the comet, without being continuous, as the occurrence rate is reported to be of about 1% of all the measured RPC-MIP passive spectra showing strong electric field emissions. The Langmuir wave activity monitored by RPC-MIP showed measurable enhancements during SIR or CME interactions and near perihelion. Conclusions. According to our results, Langmuir waves are a common feature at 67P during the passage of SIRs. Comparing the plasma frequency given by the RPC-MIP passive mode during Langmuir wave periods with the RPC-MIP active mode observations, we conclude that the measurement accuracy of RPC-MIP depends on the operational submode when the cold electron component dominates the electron density.
  • Lehtipalo, Katrianne; Yan, Chao; Dada, Lubna; Bianchi, Federico; Xiao, Mao; Wagner, Robert; Stolzenburg, Dominik; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bergen, Anton; Bernhammer, Anne-Kathrin; Breitenlechner, Martin; Brilke, Sophia; Buchholz, Angela; Mazon, Stephany Buenrostro; Chen, Dexian; Chen, Xuemeng; Dias, Antonio; Dommen, Josef; Draper, Danielle C.; Duplissy, Jonathan; Ehn, Mikael; Finkenzeller, Henning; Fischer, Lukas; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; Hakala, Jani; He, Xucheng; Heikkinen, Liine; Heinritzi, Martin; Helm, Johanna C.; Hofbauer, Victoria; Hoyle, Christopher R.; Jokinen, Tuija; Kangasluoma, Juha; Kerminen, Veli-Matti; Kim, Changhyuk; Kirkby, Jasper; Kontkanen, Jenni; Kuerten, Andreas; Lawler, Michael J.; Mai, Huajun; Mathot, Serge; Mauldin, Roy L.; Molteni, Ugo; Nichman, Leonid; Nie, Wei; Nieminen, Tuomo; Ojdanic, Andrea; Onnela, Antti; Passananti, Monica; Petäjä, Tuukka; Piel, Felix; Pospisilova, Veronika; Quelever, Lauriane L. J.; Rissanen, Matti P.; Rose, Clémence; Sarnela, Nina; Schallhart, Simon; Schuchmann, Simone; Sengupta, Kamalika; Simon, Mario; Sipilä, Mikko; Tauber, Christian; Tome, Antonio; Trostl, Jasmin; Väisänen, Olli; Vogel, Alexander L.; Volkamer, Rainer; Wagner, Andrea C.; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Ye, Penglin; Ylisirniö, Arttu; Zha, Qiaozhi; Carslaw, Kenneth S.; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Hansel, Armin; Riipinen, Ilona; Virtanen, Annele; Winkler, Paul M.; Baltensperger, Urs; Kulmala, Markku; Worsnop, Douglas R. (2018)
    A major fraction of atmospheric aerosol particles, which affect both air quality and climate, form from gaseous precursors in the atmosphere. Highly oxygenated organic molecules (HOMs), formed by oxidation of biogenic volatile organic compounds, are known to participate in particle formation and growth. However, it is not well understood how they interact with atmospheric pollutants, such as nitrogen oxides (NOx) and sulfur oxides (SOx) from fossil fuel combustion, as well as ammonia (NH3) from livestock and fertilizers. Here, we show how NOx suppresses particle formation, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation. We postulate a novel mechanism, involving HOMs, sulfuric acid, and ammonia, which is able to closely reproduce observations of particle formation and growth in daytime boreal forest and similar environments. The findings elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.
  • Süvari, Liina; Janer, Cecilia; Helve, Otto; Kaskinen, Anu; Turpeinen, Ursula; Pitkänen-Argillander, Olli; Andersson, Sture (2019)
    IntroductionLung fluid clearance is essential for successful postnatal pulmonary adaptation. The epithelial sodium channel (ENaC) and Na-K-ATPase, induced by serum- and glucocorticoid-inducible kinase 1 (SGK1) as well as aquaporins (AQP), represent key players in the switch from fetal lung fluid secretion to absorption and in early postnatal lung fluid balance. Birth stress, including a surge in catecholamines, promotes pulmonary adaptation, likely through the augmentation of epithelial sodium reabsorption. ObjectivesWe sought to determine the changes in the airway gene expression of molecules vital to epithelial sodium transport during early pulmonary adaptation, and the association with birth stress reflected in the norepinephrine concentration in the cord blood in humans. MethodsWe included 70 term newborns: 28 born via vaginal delivery and 42 via elective cesarean section. We determined the norepinephrine concentrations in the cord blood using tandem mass spectrometry and collected nasal epithelial cell samples at 2min, 1h, and 24h postnatally to quantify ENaC, Na-K-ATPase, AQP5, and SGK1 mRNAs using RT-PCR. ResultsThe molecular gene expression involved in airway epithelium sodium transport changed markedly within the first hour postnatally. Newborns born via elective cesarean section exhibited a lower expression of ENaC, Na-K-ATPase, and SGK1. Significant correlations existed between the expressions of ENaC, Na-K-ATPase, and SGK1, and the concentration of norepinephrine in the cord blood. ConclusionsThe association of ENaC, Na-K-ATPase, and SGK1 expression with the cord blood norepinephrine concentration points to the importance of birth stress in promoting lung fluid clearance during early postnatal pulmonary adaptation.
  • Wimmer, D.; Lehtipalo, K.; Nieminen, T.; Duplissy, J.; Ehrhart, S.; Almeida, J.; Rondo, L.; Franchin, A.; Kreissl, F.; Bianchi, F.; Manninen, H.E.; Kulmala, Markku; Curtius, J.; Peta¨ja¨, T. (2015)
    Over the last few years, several condensation particle counters (CPCs) capable of measuring in the sub-3 nm size range have been developed. Here we study the performance of CPCs based on diethylene glycol (DEG) at different temperatures during Cosmics Leaving OUtdoor Droplets (CLOUD) measurements at CERN. The data shown here are the first set of verification measurements for sub-3 nm CPCs under upper tropospheric temperatures using atmospherically relevant aerosol particles. To put the results in perspective we calibrated the DEG-CPC at room temperature, resulting in a cut-off diameter of 1.4 nm. All diameters refer to mobility equivalent diameters in this paper. At upper tropospheric temperatures ranging from 246.15 K to 207.15 K, we found cut-off sizes relative to a particle size magnifier in the range of 2.5 to 2.8 nm. Due to low number concentration after size classification, the cut-off diameters have a high uncertainty (+/- 0.3 nm) associated with them. Operating two laminar flow DEG-CPCs with different cut-off sizes together with other aerosol instruments, we looked at the growth rates of aerosol population in the CLOUD chamber for particles smaller than 10 nm at different temperatures. A more consistent picture emerged when we normalized the growth rates to a fixed gas-phase sulfuric acid concentration. All of the instruments detected larger growth rates at lower temperatures, and the observed growth rates decreased as a function of temperature, showing a similar trend for all instruments. The theoretical calculations had a similar but much smaller temperature dependency.
  • Levo, Emil; Granberg, Fredric; Nordlund, Kai; Djurabekova, Flyura (2021)
    Multiprincipally designed concentrated solid solution alloys, such as high entropy alloys (HEA) and equiatomic multi-component alloys (EAMC-alloys) have shown much promise for use as structural components in future nuclear energy production concepts. The irradiation tolerance in these novel alloys has been shown to be superior to that in more conventional metals used in current nuclear reactors. However, studies involving irradiation of HEAs and EAMC-alloys have usually been performed at room temperature. Hence, in this study the irradiation damage is investigated computationally in two different Ni-based EAMC-alloys and pure Ni at four different temperatures, ranging from 138 K to 800 K. The irradiation damage was studied by analyzing point defects, defect cluster sizes and dislocation networks in the materials. Dislocation loop mobility calculations were performed to help understanding the formation of different dislocation networks in the irradiated materials. Utilizing the knowledge of the depth distribution of damage, and using simulations of Rutherford backscattering in channeling conditions (RBS/c), we can relate our results to experimental data. The main findings are that the alloys have superior irradiation tolerance at all temperatures as compared to pure Ni, and that the damage is reduced in all materials with an increase in temperature.
  • Junninen, Heikki; Ahonen, Lauri; Bianchi, Federico; Quelever, Lauriane; Schallhart, Simon; Dada, Lubna; Manninen, Hanna Elina; Leino, Katri; Lampilahti, Janne; Mazon, Stephany Buenrostro; Rantala, Pekka; Räty, Meri; Kontkanen, Jenni; Negri, Sara; Aliaga, Diego; Garmash, Olga; Alekseychik, Pavel; Lipp, Helina; Tamme, Kalju; Levula, Janne; Sipilä, Mikko; Ehn, Mikael; Worsnop, Douglas; Zilitinkevich, Sergej; Mammarella, Ivan; Rinne, Janne; Vesala, Timo; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku (2022)
    Aerosols and their interaction with clouds constitute the largest uncertainty in estimating the radiative forcing affecting the climate system. Secondary aerosol formation is responsible for a large fraction of the cloud condensation nuclei in the global atmosphere. Wetlands are important to the budgets of methane and carbon dioxide, but the potential role of wetlands in aerosol formation has not been investigated. Here we use direct atmospheric sampling at the Siikaneva wetland in Finland to investigate the emission of methane and volatile organic compounds, and subsequently formed atmospheric clusters and aerosols. We find that terpenes initiate stronger atmospheric new particle formation than is typically observed over boreal forests and that, in addition to large emissions of methane which cause a warming effect, wetlands also have a cooling effect through emissions of these terpenes. We suggest that new wetlands produced by melting permafrost need to be taken into consideration as sources of secondary aerosol particles when estimating the role of increasing wetland extent in future climate change. Boreal wetlands emit terpenes which initiate atmospheric new particle formation to an even greater degree than is usually seen over boreal forests, according to direct measurements of volatile organic compounds from a Finnish wetland.
  • Iashin, Vladimir; Wirtanen, Tom; Perea-Buceta, Jesus Enrique (2022)
    Nucleophilic ionic sources of fluoride are essential reagents in the synthetic toolbox to access high added-value fluorinated building blocks unattainable by other means. In this review, we provide a concise description and rationale of the outstanding features of one of these reagents, tetramethylammonium fluoride (TMAF), as well as disclosing the different methods for its preparation, and how its physicochemical properties and solvation effects in different solvents are intimately associated with its reactivity. Furthermore, herein we also comprehensively describe its historic and recent utilization, up to December 2021, in C-F bond-forming reactions with special emphasis on nucleophilic aromatic substitution fluorinations with a potential sustainable application in industrial settings, as well as its use as a base capable of rendering unprecedented transformations. Keywords: tetramethylammonium fluoride; TMAF; solvation effects; nucleophilic fluorination; sustainable industrial fluorination; SNAr; [18F]-radiolabelling; superbases; selective methylation; fluorinated excited species
  • Kürten, A.; Münch, S.; Rondo, L.; Bianchi, F.; Duplissy, J.; Jokinen, T.; Junninen, H.; Sarnela, N.; Schobesberger, S.; Simon, M.; Sipilä, M.; Almeida, J.; Amorim, A.; Dommen, J.; Donahue, N.M.; Dunne, E.M.; Flagan, R.C.; Franchin, A.; Kirkby, J.; Kupc, A.; Makhmutov, V.; Petäjä, T.; Praplan, A.P.; Riccobono, F.; Steiner, G.; Tomé, A.; Tsagkogeorgas, G.; Wagner, P.E.; Wimmer, D.; Baltensperger, U.; Kulmala, M.; Worsnop, D.R.; Curtius, J. (2015)
    Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H2SO4-H2O) system and the ternary system involving ammonia (H2SO4-H2O-NH3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4 center dot NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H2SO4 center dot NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization-atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.
  • Plappert, Sven F.; Quraishi, Sakeena; Pircher, Nicole; Mikkonen, Kirsi S.; Veigel, Stefan; Klinger, Karl Michael; Potthast, Antje; Rosenau, Thomas; Liebner, Falk W. (2018)
    2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 degrees C, 19 h) is soluble in hot water. Solution casting, slow air drying, hot pressing, and reinforcement by cellulose nanocrystals afforded films (similar to 100 mu m thickness) that feature intriguing properties: they have very smooth surfaces (SEM), are highly flexible, and have good light transmittance for both the visible and near-infrared range (89-91%), high tensile strength (81-122 MPa), and modulus of elasticity (3.4-4.0 GPa) depending on hydration state and respective water content. The extraordinarily low oxygen permeation of