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  • 1
    Publication Date: 1998-10-02
    Description: New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clarke -- Davis -- Kapustin -- Eisele -- Chen -- Paluch I -- Lenschow -- Bandy -- Thornton -- Moore -- Mauldin -- Tanner -- Litchy -- Carroll -- Collins -- Albercook -- New York, N.Y. -- Science. 1998 Oct 2;282(5386):89-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉A. D. Clarke, V. N. Kapustin, K. Moore, M. Litchy, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA. D. Davis, F. Eisele, G. Chen, School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atl.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9756483" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2010-10-23
    Description: The intracerebral injection of beta-amyloid-containing brain extracts can induce cerebral beta-amyloidosis and associated pathologies in susceptible hosts. We found that intraperitoneal inoculation with beta-amyloid-rich extracts induced beta-amyloidosis in the brains of beta-amyloid precursor protein transgenic mice after prolonged incubation times.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3233904/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3233904/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Eisele, Yvonne S -- Obermuller, Ulrike -- Heilbronner, Gotz -- Baumann, Frank -- Kaeser, Stephan A -- Wolburg, Hartwig -- Walker, Lary C -- Staufenbiel, Matthias -- Heikenwalder, Mathias -- Jucker, Mathias -- P51 RR000165/RR/NCRR NIH HHS/ -- P51 RR000165-51/RR/NCRR NIH HHS/ -- RR-00165/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 2010 Nov 12;330(6006):980-2. doi: 10.1126/science.1194516. Epub 2010 Oct 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cellular Neurology, Hertie-Institute for Clinical Brain Research, University of Tubingen, D-72076 Tubingen, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20966215" target="_blank"〉PubMed〈/a〉
    Keywords: Alzheimer Disease/metabolism/pathology ; Amyloid beta-Peptides/administration & dosage/*chemistry/metabolism ; Animals ; Brain/blood supply/*pathology ; Brain Chemistry ; Cerebral Amyloid Angiopathy/metabolism/pathology ; Female ; Injections, Intraperitoneal ; Mice ; Mice, Transgenic ; Plaque, Amyloid/pathology ; Prions/chemistry/metabolism ; Protein Folding ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1992-05-22
    Description: The hydroxyl radical (OH) controls the lifetimes and therefore the concentrations of many important chemical species in Earth's lower atmosphere including several greenhouse and ozone-depleting species. Two completely different measurement techniques were used in an informal intercomparison to determine tropospheric OH concentrations at Fritz Peak concentrations by chemical analysis; the other used spectroscopic absorption on a long path. The intercomparison showed that ambient OH concentrations can now be measured with sufficient sensitivity to provide a test for photochemical models, with the derived OH concentrations agreeing well under both polluted and clean atmospheric conditions. Concentrations of OH on all days were significantly lower than model predictions, perhaps indicating the presence of an unknown scavenger. The change in OH concentration from early morning to noon on a clear day was found to be only a factor of 2.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mount, G H -- Eisele, F L -- New York, N.Y. -- Science. 1992 May 22;256(5060):1187-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17795214" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2009-01-30
    Description: Very dry high-ozone layers have been repeatedly observed with the ozone lidar in Garmisch-Partenkirchen (Germany) starting one or two days after the onset of high-pressure periods during the warm season. These episodes have been analysed by trajectory calculations and extended simulations with the FLEXPART particle dispersion model. Mixed contributions from the stratosphere over the Pacific Ocean and the boundary layers of East Asia and North America were found. The stratospheric influence is mostly dominating and caused by a rather shallow transfer from the stratosphere into these rapid upper- and mid-tropospheric air streams. The considerable vertical extent of these layers and peak ozone mixing ratios between 80 and 150 ppb suggest an important mechanism for stratosphere-to-troposphere transport.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
    Publication Date: 2011-11-02
    Description: Recent ab initio calculations showed that amines can enhance atmospheric sulfuric acid-water nucleation more effectively than ammonia, and this prediction has been substantiated in laboratory measurements. Laboratory studies have also shown that amines can effectively displace ammonia in several types of ammonium clusters. However, the roles of amines in cluster formation and growth at a microscopic molecular scale (from molecular sizes up to 2 nm) have not yet been well understood. Processes that must be understood include the incorporation of amines into sulfuric acid clusters and the formation of organic salts in freshly nucleated particles, which contributes significantly to particle growth rates. We report the first laboratory and ambient measurements of neutral sulfuric acid-amine clusters using the Cluster CIMS, a recently-developed mass spectrometer designed for measuring neutral clusters formed in the atmosphere during nucleation. An experimental technique, which we refer to as Semi-Ambient Signal Amplification (SASA), was employed. Sulfuric acid was added to ambient air, and the concentrations and composition of clusters in this mixture were analyzed by the Cluster CIMS. This experimental approach led to significantly higher cluster concentrations than are normally found in ambient air, thereby increasing signal-to-noise levels and allowing us to study reactions between gas phase species in ambient air and sulfuric acid containing clusters. Mass peaks corresponding to clusters containing four H2SO4 molecules and one amine molecule were clearly observed, with the most abundant sulfuric acid-amine clusters being those containing a C2- or C4-amine (i.e. amines with masses of 45 and 73 amu). Evidence for C3- and C5-amines (i.e. amines with masses of 59 and 87 amu) was also found, but their correlation with sulfuric acid tetramer was not as strong as was observed for the C2- and C4-amines. The formation mechanisms for those sulfuric acid-amine clusters were investigated by varying the residence time in the inlet. It was concluded that the amines react directly with neutral clusters and that ion-induced clustering of sulfuric acid cluster ions with amines was not a dominant process. Results from ambient measurements using the Cluster CIMS without addition of sulfuric acid have shown that the sulfuric acid-amine clusters were reasonably well correlated with sulfuric acid tetramer and consistent with the SASA experiments at the same Boulder sampling site. Also, clusters that contain C2- or C4-amines were more abundant and better correlated with sulfuric acid tetramer than other types of amine containing clusters. However, ambient measurements of sulfuric acid-amine clusters remain difficult and highly uncertain because their concentrations are only slightly above background levels, even during nucleation events.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
    Publication Date: 2011-09-09
    Description: Specific very dry high-ozone layers, starting roughly two days after the onset of high-pressure periods during the warm season, have been reproducibly observed in the middle and upper troposphere with the ozone lidar in Garmisch-Partenkirchen (Germany). These episodes, previously not understood, were recently analysed based on extending backward simulations with the FLEXPART particle dispersion model to as many as twenty days and on jet-stream analyses including calculations with the LAGRANTO transport model. In all six cases analysed the model results indicate ozone import from the stratosphere on an extremely long path along the subtropical jet stream over the Pacific Ocean, Asia and, in part, all the way back to the Atlantic Ocean. The analysis suggests that stratospheric influence is the most important factor for the increase in ozone and is related to rather shallow transfer of air from the stratosphere into the upper- and mid-tropospheric air streams observed with the lidar. Contributions from the boundary layers of East Asia and North America are just occasionally present, in one case documented by a very dense aerosol plume from the Asian deserts. The considerable vertical and temporal extent of many of these layers and peak ozone mixing ratios between 80 and 150 ppb suggest that the observations are related to an important mechanism for stratosphere-to-troposphere transport (STT) and also confirm the model predictions of pronounced and persistent STT along the subtropical jet stream.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
    Publication Date: 2011-07-11
    Description: Recent ab initio calculations showed that amines can enhance atmospheric sulfuric acid-water nucleation more effectively than ammonia, and this prediction has been substantiated in laboratory measurements. Laboratory studies have also shown that amines can effectively displace ammonia in several types of ammonium clusters. However, the roles of amines in cluster formation and growth at a microscopic molecular scale (from molecular sizes up to 2 nm) have not yet been well understood. Processes that must be understood include the incorporation of amines into sulfuric acid clusters and the formation of organic salts in freshly nucleated particles, which contributes significantly to particle growth rates. We report the first laboratory and ambient measurements of neutral sulfuric acid-amine clusters using the Cluster CIMS, a recently-developed mass spectrometer designed for measuring neutral clusters formed in the atmosphere during nucleation. An experimental technique, which we refer to as Semi-Ambient Signal Amplification (SASA), was employed. Sulfuric acid was added to ambient air, and the concentrations and composition of clusters in this mixture were analyzed by the Cluster CIMS. This experimental approach led to significantly higher cluster concentrations than are normally found in ambient air, thereby increasing signal-to-noise levels and allowing us to study reactions between gas phase species in ambient air and sulfuric acid containing clusters. Mass peaks corresponding to clusters containing four H2SO4 molecules and one amine molecule were clearly observed, with the most abundant sulfuric acid-amine clusters being those containing a C2- or C4- amine (i.e., amines with masses of 45 and 73 amu). Evidence for C3- and C5- amines (i.e., amines with masses of 59 and 87 amu) was also found, but their correlation with sulfuric acid tetramer was not as strong as was observed for the C2- and C4- amines. The formation mechanisms for those sulfuric acid-amine clusters were investigated by varying the residence time in the inlet. It was concluded that the amines react directly with neutral clusters and that ion-induced clustering of sulfuric acid cluster ions with amines was not a dominant process. Results from ambient measurements have shown that the sulfuric acid-amine clusters were reasonably well correlated with sulfuric acid tetramer and consistent with the SASA experiments at the same Boulder sampling site. Also, clusters that contain C2- or C4- amines were more abundant and better correlated with sulfuric acid tetramer than other types of amine containing clusters. However, ambient measurements of sulfuric acid-amine clusters remain difficult and highly uncertain because their concentrations are only slightly above background levels, even during nucleation events.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
    Publication Date: 2015-12-17
    Description: The full set of electromechanical data of langasite (La3Ga5SiO14) is determined in the temperature range from 20 to 900 °C using differently oriented bulk acoustic wave resonators. For data evaluation a physical model of vibration is developed and applied. Thereby, special emphasis is taken on mechanical and electrical losses at high temperatures. The resulting data set is used to calculate the properties of surface acoustic waves. Direct comparison with experimental data such as velocity, coupling coefficients and propagation loss measured using surface acoustic wave devices with two different crystal orientations shows good agreement.
    Print ISSN: 2194-8771
    Electronic ISSN: 2194-878X
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 9
    Publication Date: 2013-08-26
    Description: Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate. We quantified the effects of nitrogen availability on carbon fluxes from a relatively understudied component of these forests – understorey vegetation – at three intervals over the summer growing period in a northern Swedish Scots Pine stand. Nitrogen addition altered both photosynthetic carbon uptake and respiratory release, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net ecosystem carbon uptake only in the late growing season. We find evidence for species-specific control of understorey carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of photosynthetic carbon uptake with data on plant carbon dioxide release from the study site, indicate that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in understorey and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
    Publication Date: 2010-12-15
    Description: Specific very dry high-ozone layers have been repeatedly observed in the middle and upper troposphere with the ozone lidar in Garmisch-Partenkirchen (Germany), starting roughly two days after the onset of high-pressure periods during the warm season. These episodes, previously not understood, were recently analysed based on extended simulations with the FLEXPART particle dispersion model and jet-stream analyses with the LAGRANTO transport model. The model results indicate import from the stratosphere along the subtropical jet stream over the Pacific Ocean and all the way back to the Atlantic Ocean, in some cases mixed with stratospheric air from intrusions over the North-West Pacific Ocean. Occasionally, also air from the boundary layers of East Asia and North America was admixed. The analysis suggests that stratospheric influence is the most important factor for the increase in ozone and is related to a rather shallow transfer of air from the stratosphere into the rapid upper-and mid-tropospheric air streams observed with the lidar. The in part considerable vertical and temporal extent of these layers and peak ozone mixing ratios between 80 and 150 unit{ppb} suggest this to be an important mechanism for stratosphere-to-troposphere transport.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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