Unrecognized volatile and semi-volatile organic compounds from brake wear.

Motor vehicles are among the major sources of pollutants and greenhouse gases in urban areas and a transition to "zero emission vehicles" is underway worldwide. However, emissions associated with brake and tire wear will remain. We show here that previously unrecognized volatile and semi-volatile organic compounds, which have a similarity to biomass burning emissions are emitted during braking. These include greenhouse gases or, these classified as Hazardous Air Pollutants, as well as nitrogen-containing organics, nitrogen oxides and ammonia. The distribution and reactivity of these gaseous emissions are such that they can react in air to form ozone and other secondary pollutants with adverse health and climate consequences. Some of the compounds may prove to be unique markers of brake emissions. At higher temperatures, nucleation and growth of nanoparticles is also observed. Regions with high traffic, which are often disadvantaged communities, as well as commuters can be impacted by these emissions even after combustion-powered vehicles are phased out.

Understanding interactions of organic nitrates with the surface and bulk of organic films: implications for particle growth in the atmosphere.

Understanding impacts of secondary organic aerosol (SOA) in air requires a molecular-level understanding of particle growth via interactions between gases and particle surfaces. The interactions of three gaseous organic nitrates with selected organic substrates were measured at 296 K using attenuated total reflection Fourier transform infrared spectroscopy. The organic substrates included a long chain alkane (triacontane, TC), a keto-acid (pinonic acid, PA), an amorphous ester oligomer (poly(ethylene adipate) di-hydroxy terminated, PEA), and laboratory-generated SOA from α-pinene ozonolysis. There was no uptake of the organic nitrates on the non-polar TC substrate, but significant uptake occurred on PEA, PA, and α-pinene SOA. Net uptake coefficients (γ) at the shortest reaction times accessible in these experiments ranged from 3 × 10-4 to 9 × 10-6 and partition coefficients (K) from 1 × 107 to 9 × 104. Trends in γ did not quantitatively follow trends in K, suggesting that the intermolecular forces involved in gas-surface interactions are not the same as those in the bulk, which is supported by theoretical calculations. Kinetic modeling showed that nitrates diffused throughout the organic films over several minutes, and that the bulk diffusion coefficients evolved as uptake/desorption occurred. A plasticizing effect occurred upon incorporation of the organic nitrates, whereas desorption caused decreases in diffusion coefficients in the upper layers, suggesting a crusting effect. Accurate predictions of particle growth in the atmosphere will require knowledge of uptake coefficients, which are likely to be several orders of magnitude less than one, and of the intermolecular interactions of gases with particle surfaces as well as with the particle bulk.

New Mechanism of Extractive Electrospray Ionization Mass Spectrometry for Heterogeneous Solid Particles.

Real-time in situ mass spectrometry analysis of airborne particles is important in several applications, including exposure studies in ambient air, industrial settings, and assessing impacts on visibility and climate. However, obtaining molecular and 3D structural information is more challenging, especially for heterogeneous solid or semisolid particles. We report a study of extractive electrospray ionization mass spectrometry (EESI-MS) for the analysis of solid particles with an organic coating. The goal is to elucidate how much of the overall particle content is sampled, and determine the sensitivity of this technique to the surface layers. It is shown that, for NaNO3 particles coated with glutaric acid (GA), very little of the solid NaNO3 core is sampled compared to the GA coating, whereas for GA particles coated with malonic acid (MA), significant signals from both the MA coating and the GA core are observed. However, conventional ESI-MS of the same samples collected on a Teflon filter (and then extracted) detects much more core material compared to EESI-MS in both cases. These results show that, for the experimental conditions used here, EESI-MS does not sample the entire particle but, instead, is more sensitive to surface layers. Separate experiments on single-component particles of NaNO3, GA, or citric acid show that there must be a kinetics limitation to dissolution that is important in determining EESI-MS sensitivity. We propose a new mechanism of EESI solvent droplet interaction with solid particles that is consistent with the experimental observations. In conjunction with previous EESI-MS studies of organic particles, these results suggest that EESI does not necessarily sample the entire particle when solid, and that not only solubility but also surface energies and the kinetics of dissolution play an important role.

Application of a data-processing model to determine the optimal sampling conditions for liquid phase trapping of atmospheric carbonyl compounds.

The reactivity of two fluorescent derivatization reagents, 2-diphenyl-1,3-indandione-1-hydrazone (DIH) and 2-aminooxy-N-[3-(5-dimethylamino-naphtalene-1-sulfonamino)-propyl]-acetamide (dansylacetamidooxyamine, DNSAOA), was studied towards selected atmospheric carbonyl compounds. The results were compared to those obtained using the 2,4-dinitrophenylhydrazine (2,4-DNPH) UV-vis reagent, a standard well-established technique used to detect atmospheric carbonyl compounds. The experimental rate constant were integrated into a data-processing model developed in the laboratory to simulate the trapping efficiencies of a mist chamber device as a function of temperature, reagent and solvent type among others. The results showed that in an aqueous solution, DNSAOA exhibits a higher reactivity towards carbonyl compounds without the addition of an acidic catalyst than 2,4-DNPH. It was observed that DNSAOA can trap efficiently water-soluble gaseous compounds (for example formaldehyde). However, because of a high initial contamination of the reagent caused by the synthesis procedure used in this work, DNSAOA cannot be used in high concentrations. As a result, very low trapping efficiencies of less reactive water-insoluble gaseous compounds (acetone) using DNSAOA are observed. However, the use of an organic solvent such as acetonitrile improved the trapping efficiencies of the carbonyl compounds. In this case, using DIH as the derivatization reagent (DNSAOA is not soluble in acetonitrile), trapping efficiencies greater than 95% were obtained, similar to 2,4-DNPH. Moreover, fluorescence associated with DIH derivatives (detection limits 3.33 x 10(-8)M and 1.72x10(-8)M for formaldehyde and acetone, respectively) is further advantage of this method for the determination of carbonyl compounds in complex matrix compared to the classical UV-vis detection method (detection limits 3.20 x 10(-8)M and 2.9 x 10(-8)M for formaldehyde and acetone, respectively).

[Surgical treatment of adenocarcinoma of the stomach: 1969-1994. Apropos of 261 cases]. / Le traitement chirurgical de l'adénocarcinome de l'estomac: évolution de 1969 à 1994. A propos de 261 cas.

The study concerned 261 cases of gastric adenocarcinoma operated on between 1969 and 1994. Clinical, histological and therapeutic features were analyzed and compared during 3 periods (Group 1: 1969-78, Group 2: 1979-88, Group 3: 1989-94). The aim was to evaluate changes and results occurred in gastric carcinoma. The median age was 65 years (rage 25-90 years), the sex ratio, 1.9. The most common location was in the lower third of the stomach and the cancer was often far-advanced (73 percent of stages III and IV). Subtotal gastrectomy was replaced by total gastrectomy; the number of distal gastrectomy was unchanged. Large lymph node dissection was systematically performed in group 3. Curative resection rate increased from 28 to 51 percent between group 1 and group 3. Despite the more radical surgery, morbidity and post operative mortality rates decreased (respectively: 44.5%, 33%, 25.4%, and 22%, 10%, 7.2% for the groups 1, 2, 3, p < 0.01). 2-year survival rates were 20 percent for group 1, 25 percent for group 2 and 32 percent for group 3 (p < 0.01). This rates can be considered as satisfying in view of the high rate of III and IV stages.

[Laparoscopic treatment of gastroesophageal reflux. Cardiopexia with the round ligament versus Nissen's type fundoplication]. / Traitement laparoscopique du reflux gastro-oesophagien. Cardiopexie par le ligament rond versus fundoplicature de type Nissen.

Thirty nine patients with a symptomatic gastrooesophageal reflux (RGO), resistant to or relapsing after medical treatment, were prospectively studied and operated on with a laparoscopic approach: 8 which a ligamentum teres cardiopexy, 31 with a 360 degrees fundoplicature. Both groups were comparable concerning clinical, endoscopic, mano- and pHmetric features (Anova test at 95% for all comparison in the study). There was no operative mortality. Conversion and morbidity rate were significantly higher (p = 0.04) in the "cardiopexy" group, even if data suggest a responsibility of the learning curve only. During follow-up patients were interviewed at 1, 3 and 12 months and proposed for mano- and pHmetry at 3 and 12 months. Late results at 12 months showed a relapse of RGO in 5 out of 8 patients of the "cardiopexy" group, with no relapse in "fundoplicature" group (p = 0.01). Mano- and pHmetric records showed at 3 months a persistent hypotony of the lower oesophageal sphincter and a persistent acid reflux in the "cardiopexy" group, with a significant (p = 0.01 and = 0.03) difference with "fundoplicature" group, in which lower oesophageal sphincter was hypercorrected and no reflux appeared at pHmetry. Despite some rare evidence in literature, cardiopexy do not give good late results, and laparoscopic 360 degrees fundoplicature seems to be the better procedure for surgical treatment of symptomatic RGO.