lnstitut für Sensorik und Elektronik

Dauerhafte URI für die Sammlung

https://irf.fhnw.ch/handle/11654/28068

Listen

Neueste Veröffentlichungen

Gerade angezeigt 1 - 5 von 254
  • Vorschaubild
    Publikation
    Development of a waveguide-based interferometer for the measurement of trace substances
    (Zenodo, 07.11.2023) Weingartner, Ernest; Bilal, Jonas; Steigmeier, Peter; Jundt, Gregor; Häusler, Samuel; Lenner, Miklós; Flöry, Nikolaus; Bittner, Matthias; Betschon, Felix
    Photonic integration on a chip has the potential to develop new low-cost, high-performance sensing devices. A proof of concept of the sensing capabilities of a waveguide-based photothermal interferometer for the measurement of traces of light-absorbing substances (soot particles, gases) has been achieved. The measurement principle can also be extended to a wide range of other applications such as refractive index measurements, or vibration/distance sensors. A unique feature is that the waveguide technology allows for a passive operation of the interferometer, i.e., no quadrature point control is required.
    04B - Beitrag Konferenzschrift
  • Vorschaubild nicht verfügbar
    Publikation
    Evidence for the role of organics in aerosol particle formation under atmospheric conditions
    (National Academy of Sciences, 19.01.2010) Metzger, Axel; Verheggen, Bart; Dommen, Josef; Duplissy, Jonathan; Prévôt, André S.H.; Weingartner, Ernest; Riipinen, Ilona; Kulmala, Markku; Spracklen, Dominick V.; Carslaw, Kenneth S.; Baltensperger, Urs [in: Proceedings of the National Academy of Sciences of the United States of America]
    New particle formation in the atmosphere is an important parameter in governing the radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms remain ambiguous, as laboratory data have so far not been successful in explaining atmospheric nucleation. We investigated the formation of new particles in a smog chamber simulating the photochemical formation of H2SO4 and organic condensable species. Nucleation occurs at H2SO4 concentrations similar to those found in the ambient atmosphere during nucleation events. The measured particle formation rates are proportional to the product of the concentrations of H2SO4 and an organic molecule. This suggests that only one H2SO4 molecule and one organic molecule are involved in the rate-limiting step of the observed nucleation process. Parameterizing this process in a global aerosol model results in substantially better agreement with ambient observations compared to control runs.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Hygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments - a review
    (Stockholm University Press, 01.01.2008) Swietlicki, Erik; Hansson, Hans-Christen; Hämeri, Kaarle; Svenningsson, Birgitta; Massling, Andreas; McFiggans, Gordon; McMurry, Peter H.; Petäjä, Tuukka; Tunved, Peter; Gysel, Martin; Topping, David; Weingartner, Ernest; Baltensperger, Urs; Rissler, Jenny; Wiedensohler, Alfred; Kulmala, Markku [in: Tellus B: Chemical and Physical Meteorology]
    The hygroscopic properties play a vital role for the direct and indirect effects of aerosols on climate, as well as the health effects of particulate matter (PM) by modifying the deposition pattern of inhaled particles in the humid human respiratory tract. Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) instruments have been used in field campaigns in various environments globally over the last 25 yr to determine the water uptake on submicrometre particles at subsaturated conditions. These investigations have yielded valuable and comprehensive information regarding the particle hygroscopic properties of the atmospheric aerosol, including state of mixing. These properties determine the equilibrium particle size at ambient relative humidities and have successfully been used to calculate the activation of particles at water vapour supersaturation. This paper summarizes the existing published H-TDMA results on the sizeresolved submicrometre aerosol particle hygroscopic properties obtained from ground-based measurements at multiple marine, rural, urban and free tropospheric measurement sites. The data is classified into groups of hygroscopic growth indicating the external mixture, and providing clues to the sources and processes controlling the aerosol. An evaluation is given on how different chemical and physical properties affect the hygroscopic growth.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild nicht verfügbar
    Publikation
    Aerosol processing in mixed‐phase clouds in ECHAM5‐HAM. Model description and comparison to observations
    (Wiley, 15.04.2008) Hoose, Corinna; Lohmann, Ulrike; Stier, Philip; Verheggen, Bart; Weingartner, Ernest [in: Journal of Geophysical Research: Atmospheres]
    The global aerosol‐climate model ECHAM5‐HAM has been extended by an explicit treatment of cloud‐borne particles. Two additional modes for in‐droplet and in‐crystal particles are introduced, which are coupled to the number of cloud droplet and ice crystal concentrations simulated by the ECHAM5 double‐moment cloud microphysics scheme. Transfer, production, and removal of cloud‐borne aerosol number and mass by cloud droplet activation, collision scavenging, aqueous‐phase sulfate production, freezing, melting, evaporation, sublimation, and precipitation formation are taken into account. The model performance is demonstrated and validated with observations of the evolution of total and interstitial aerosol concentrations and size distributions during three different mixed‐phase cloud events at the alpine high‐altitude research station Jungfraujoch (Switzerland). Although the single‐column simulations cannot be compared one‐to‐one with the observations, the governing processes in the evolution of the cloud and aerosol parameters are captured qualitatively well. High scavenged fractions are found during the presence of liquid water, while the release of particles during the Bergeron‐Findeisen process results in low scavenged fractions after cloud glaciation. The observed coexistence of liquid and ice, which might be related to cloud heterogeneity at subgrid scales, can only be simulated in the model when assuming nonequilibrium conditions.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild nicht verfügbar
    Publikation
    Identification of organic acids in secondary organic aerosol and the corresponding gas phase from chamber experiments
    (American Chemical Society, 15.10.2004) Fisseha, Rebeka; Dommen, Josef; Sax, Mirjam; Paulsen, Dwane; Kalberer, Markus; Maurer, Rolf; Höfler, Frank; Weingartner, Ernest; Baltensperger, Urs [in: Analytical Chemistry]
    Organic acids in the gas and aerosol phase from photooxidation of 1,3,5-trimethylbenzene in the presence of 300 ppb propene and 300 ppb NOx in smog chamber experiments were determined using a wet effluent diffusion denuder/aerosol collector coupled to ion chromatography (IC) with conductivity detection. Behind the IC, the samples were collected using a fraction collector, for identification of unresolved/unidentified organic acids with IC-mass spectrometry (MS). In total, 20 organic acids were found with MS of which 10 were identified. The organic acids identified offline by IC-MS were then further quantified based on the online IC data. The identification was additionally confirmed with gas chromatography-mass spectrometry. At the maximum aerosol concentration, organic acids comprised 20-45% of the total aerosol mass. The method has a detection limit of 10-100 ng/m3 for the identified carboxylic acids.
    01A - Beitrag in wissenschaftlicher Zeitschrift