A simplified method for levoglucosan quantification in wintertime atmospheric particulate matter by high performance anion-exchange chromatography coupled with pulsed amperometric detection

Levoglucosan, a tracer for the assessment of the biomass burning contribution to atmospheric particulate matter (PM) concentrations, was determined by means of high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). In this work we propose a modification in the instrumental set-up aiming at an improvement in the detector response by adding NaOH after chromatographic separation to increase the pH. The comparison between this technique and the gas chromatography/mass spectrometry (GC/MS) method commonly used showed good agreement. Repeatability is 4.8% RSD, limits of detection for pevoglucosan, mannosan and galactosan are in the range 0.001–0.002 µg mL^?1 in solution, corresponding to 3–4 ng m^?3 for 24 m³ of air sampled. PM10 samples were characterised for levoglucosan and for organic and elemental carbon contents. The preliminary results reported here for five sites in the Lombardy region (Northern Italy) are, as far as we know, the first data on levoglucosan contribution to OC in Italy. The levoglucosan concentrations observed in Lombardy vary in the range 173–963 ng m^?3 with an average levoglucosan-C to OC ratio ranging from 1.5% to 2.5%.     

Synthesis of Novel Asymmetrical Single-Chain Phosphoglycol-Based Bolaamphiphiles

The synthesis of long-chain 1,ω-diols with orthogonal cleavable protecting groups can be effectively performed with the use of the Grignard coupling reaction, successfully leading to the preparation of novel asymmetrical single-chain phosphoglycol-based bolaamphiphiles—a side-product that always occurred during the synthesis of symmetrical bolalipids.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Three-dimensional atomic structure of metastable nanoclusters in doped semiconductors

Aberration-corrected scanning transmission electron microscopy is used to determine the atomic structure of nanoclusters of cerium dopant atoms embedded in silicon. By channeling electrons along two crystallographic orientations, we identify a characteristic zinc-blende chemical ordering within CeSi clusters coherent with the silicon host matrix. Strain energy limits the size of these ordered arrangements to just above 1 nm. With the local order identified, we then determine the atomic configuration of an individual subnanometer cluster by quantifying the scattering intensity under weak channeling condition in terms of the number of atoms. Analysis based on single-atom visualization also evidences the presence of split-vacancy impurity complexes, which supports the hypothesis of a vacancy-assisted formation of these metastable CeSi nanophases.     

Breath Analysis: Comparison among Methodological Approaches for Breath Sampling

Despite promising results obtained in the early diagnosis of several pathologies, breath analysis still remains an unused technique in clinical practice due to the lack of breath sampling standardized procedures able to guarantee a good repeatability and comparability of results. The most diffuse on an international scale breath sampling method uses polymeric bags, but, recently, devices named Mistral and ReCIVA, able to directly concentrate volatile organic compounds (VOCs) onto sorbent tubes, have been developed and launched on the market. In order to explore performances of these new automatic devices with respect to sampling in the polymeric bag and to study the differences in VOCs profile when whole or alveolar breath is collected and when pulmonary wash out with clean air is done, a tailored experimental design was developed. Three different breath sampling approaches were compared: (a) whole breath sampling by means of Tedlar bags, (b) the end-tidal breath collection using the Mistral sampler, and (c) the simultaneous collection of the whole and alveolar breath by using the ReCIVA. The obtained results showed that alveolar fraction of breath was relatively less affected by ambient air (AA) contaminants (p-values equal to 0.04 for Mistral and 0.002 for ReCIVA Low) with respect to whole breath (p-values equal to 0.97 for ReCIVA Whole). Compared to Tedlar bags, coherent results were obtained by using Mistral while lower VOCs levels were detected for samples (both breath and AA) collected by ReCIVA, likely due to uncorrected and fluctuating flow rates applied by this device. Finally, the analysis of all data also including data obtained by explorative analysis of the unique lung cancer (LC) breath sample showed that a clean air supply might determine a further confounding factor in breath analysis considering that lung wash-out is species-dependent.     

On the influence of aggressive driving behavior on the dynamics of traffic flow

The car following model under discussion is a system of ordinary differential equations describing N cars moving around a circular road. We extend the stability analysis of the model in two directions: variable reaction time (depending on the headway) and an additional part describing the aggressive driving tendency. We study the global bifurcation dynamics and in particular its dependence on these two new ingredients. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)