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Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles
(2011)
- During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influences of various surface modifications on the immersion freezing behavior of Arizona Test Dust (ATD) particles. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between −40 °C ≤ T ≤ −28 °C. The pure ATD particles nucleated ice over a~broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T > −35 °C) and a slight increase in the second branch (T≤ −35 °C). The addition of water vapor after the sulfuric acid coating caused the disappearance of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. From an atmospheric point of view, and here specifically the influences of atmospheric aging on the IN ability of dust particles, the strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor, and the resulting significant reductions in IN potential, are certainly very interesting.
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Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles
(2011)
- During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between −40 °C ≤T≤−28 °C. The pure ATD particles nucleated ice over a broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T>−35 °C) and a slight increase in the second branch (T≤−35 °C). The addition of water vapor after the sulfuric acid coating caused the disappearance of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. The strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor and the resulting significant reductions in IN potential are of importance for atmospheric ice cloud formation. Our findings suggest that the IN concentration can decrease by up to one order of magnitude for the conditions investigated.
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Corrigendum to “Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles” published in Atmos. Chem. Phys., 11, 11131–11144, 2011
(2011)
- In the abstract of the manuscript, the following sentence needs to be corrected: “A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates.” “metal silicates” is wrong. It should be “aluminosilicates”.
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Alte Texte in neuen Medien : aktuelle Projekte und Projektvorhaben der Universitätsbibliothek Leipzig
(2008)
- Die Universitätsbibliothek Leipzig (UBL) steht zur Sächsischen Akademie der Wissenschaften in einer speziellen Beziehung: Sie ist deren Archivbibliothek. Außerdem versorgt sie natürlich die Wissenschaftler der Akademie mit der von ihnen gewünschten wissenschaftlichen Literatur. Seit dem 19. Jahrhundert – dem Jahrhundert der Gründung der Sächsischen Akademie der Wissenschaften zu Leipzig – hat die Universitätsbibliothek Leipzig eine große Zahl an Schätzen des Weltschrifterbes erhalten, die sie bis heute bewahrt. Nun kommen im 21. Jahrhundert neue technische Möglichkeiten hinzu, und eine kleine Revolution ist perfekt: Alte Texte können in neuen Medien präsentiert bzw. veröffentlicht werden, die Erschließungsleistung der Bibliothekare kann unmittelbar für die Forschung bereitgestellt werden, darüber hinaus sind die Originale im Tresor der Bibliotheca Albertina gerade durch ihre erheblich verbesserte Zugänglichkeit über digitale Sekundärformen besser geschützt. Die laufenden Projekte der Universitätsbibliothek kann man seit Anfang 2008 auf der Homepage der UBL (www.ub.uni-leipzig.de) eigens aufgelistet finden (s. dort unter ›Projekte‹). Sie lassen sich in vier Gruppen gliedern und sollen im Folgenden kurz erläutert werden. Neuere Projektvorhaben werde ich im Anschluss daran erläutern. Die vier thematisch-kulturellen Gruppen, innerhalb deren Katalogisierungs-, Erschließungs- und Forschungsleistungen an der Universitätsbibliothek Leipzig erbracht werden, sind 1. Texte der Antike, 2. Texte und Textträger des Mittelalters, 3. Texte aus dem orientalischen Kulturraum und 4. Quellentexte zur Wissenschaftsgeschichte der Neuzeit.
