[Wonaschuetz2012] "Aerosol and gas re-distribution by shallow cumulus clouds: An investigation using airborne measurements",
Journal of Geophysical Research: Atmospheres
, vol. 117, no. D17, pp. n/a–n/a, 2012.
Aircraft measurements during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) are used to examine the influence of shallow cumulus clouds on vertical profiles of aerosol chemical composition, size distributions, and secondary aerosol precursor gases. The data show signatures of convective transport of particles, gases and moisture from near the surface to higher altitudes, and of aqueous-phase production of aerosol mass (sulfate and organics) in cloud droplets and aerosol water. In cloudy conditions, the average aerosol volume concentration at an altitude of 2850 m, above typical cloud top levels, was found to be 34% of that at 450 m; for clear conditions, the same ratio was 13%. Both organic and sulfate mass fractions were on average constant with altitude (around 50%); however, the ratio of oxalate to organic mass increased with altitude (from 1% at 450 m to almost 9% at 3450 m), indicative of the influence of in-cloud production on the vertical abundance and characteristics of secondary organic aerosol (SOA) mass. A new metric termed â€œresidual cloud fractionâ€� is introduced as a way of quantifying the â€œcloud processing historyâ€� of an air parcel. Results of a parcel model simulating aqueous phase production of sulfate and organics reproduce observed trends and point at a potentially important role of SOA production, especially oligomers, in deliquesced aerosols. The observations emphasize the importance of shallow cumulus clouds in altering the vertical distribution of aerosol properties that influence both their direct and indirect effect on climate.
[Aprea2012] "Analysis of breath by proton transfer reaction time of flight mass spectrometry in rats with steatohepatitis induced by high-fat diet.",
J Mass Spectrom
, vol. 47, no. 9: IASMA Research and Innovation Centre, Fondazione Edmund Mach, Food Quality and Nutrition Department, Via E. Mach, 1, 38010, S. Michele a/A, Italy. firstname.lastname@example.org, pp. 1098–1103, Sep, 2012.
Breath testing has been largely used as a diagnostic tool, but the difficulties in data interpretation and sample collection have limited its application. We developed a fast (< 20?s), on-line, non-invasive method for the collection and analysis of exhaled breath in awake rats based on proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) and applied it to investigate possible relationships between pathologies induced by dietary regime and breath composition. As a case study, we investigated rats with dietary induced non-alcoholic steatohepatitis (NASH) and modifications induced by coffee addition to the diet. We considered two different diets (standard and high fat) complemented with two different drinking possibilities (water or decaffeinated coffee) for a total of four groups with four rats each. Several spectrometric peaks were reliable markers for both dietary fat content and coffee supplementation. The high resolution and accuracy of PTR-ToF-MS allowed the identification of related compounds such as methanol, dimethyl sulphide, dimethyl sulphone and ammonia. In conclusion, the rapid and minimally invasive breath analysis of awake rats permitted the identification of markers related to diet and specific pathologic conditions and provided a useful tool for broader metabolic investigations.
 "The analysis of dimethylsulfide and dimethylsulfoniopropionate in sea ice: Dry-crushing and melting using stable isotope additions",
, vol. 128-129, pp. 34–43, Jan, 2012.
<p>Sea ice is thought to be an important source of the climate-active gas dimethylsulfide (DMS), since extremely high concentrations of its precursor dimethylsulfoniopropionate (DMSP) have been found associated with high algal biomass. Accurate measurements of DMS and associated compounds in sea ice were until now not possible due to difficulties associated with the unavoidable melting process before analysis. Here we present and evaluate two methods to analyze DMS and DMSP in sea-ice cores accurately. The first, describes the dry-crushing method, which has its focus on the volatile compound DMS. A sub-sample of deeply frozen (<−30 °C) ice is crushed in a stainless steel vessel and the released gas phase is analyzed directly for DMS. The remaining ice is subsequently analyzed for its total DMSP content. With this method, DMS and DMSP profiles can be resolved even in ice cores stored deeply frozen for two years. The second method, involves a melting procedure, during which the conversion of compounds is monitored by adding differently deuterated isotopes of DMS and DMSP. Natural concentrations and stable isotopes of DMS and DMSP are simultaneously analyzed on a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS). Loss and conversion rates of the artificial isotopes are used to reconstruct the original concentrations of DMS and DMSP in ice and give important information on potential dynamical processes in sea-ice communities. It is concluded that in stored cores, the dry-crushing method provides the best results when the aim of the study is to differentiate between DMS and DMSP. When direct processing and analysis of the samples is possible, the isotope-addition method has the potential of providing concentrations of all S-compounds, including dissolved and particulate fractions. Moreover, it is suitable for the determination of process rates within the S-cycle.</p>