Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N₂, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, k_Cl&plusmn;2&sigma; (in units of cm³ molecule^&minus;1 s^&minus;1) were: trans-2-pentenal (1.31&plusmn;0.19)&times;10^&minus;10; trans-2-hexenal (1.92&plusmn;0.22)&times;10^&minus;10; trans-2-heptenal (2.40&plusmn;0.29)&times;10^&minus;10; n-pentanal (2.56&plusmn;0.27)&times;10^&minus;10; n-hexanal (2.88&plusmn;0.37)&times;10^&minus;10; n-heptanal (3.00&plusmn;0.34)&times;10^&minus;10. <P style='line-height: 20px;'> Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO₃ radicals

FT-Raman and infrared spectroscopic study of aragonite-strontianite (CaxSr1-xC03) solid solution

Synthetic aragonite-strontianite solid-solution samples have been studied using dispersive IR and FT-Raman spectroscopy. In addition to the end-members, nine samples over a range of composition from Ca0,9Sr0,1CO3 to Ca0,1Sr0,9CO3 were analysed. Carbonate anion internal modes are examined in detail by means of band-shape analysis and component fitting procedures. Positional disorder induced by the random cationic substitution results in strong increase of the halfwidth in several vibrational bands. Results obtained for the doubly degenerate modes (antisymmetric stretching and bending, v3 and v4) reveal the presence of three components both in the IR antisymmetric stretching band as well as in the Raman antisymmetric bending band. These observations are interpreted in terms of an overtone 2v4 in possible Fermi resonance with the corresponding vg fundamental in the IR spectra, and the presence of Davidov (factor group) splitting in the FT-Raman v4 band. Lattice modes in the FT-Raman spectra demonstrate weaker cohesion between the cation/carbonate/cation layers in aragonite (synth) than in strontianite (synth)

Análisis de la solución sólida aragonito-estroncianita mediante espectroscopia vibracional (Infrarrojo y FT-Raman)

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

Muscle imaging in laminopathies: Synthesis study identifies meaningful muscles for follow-up

Introduction: Particular fibroadipose infiltration patterns have been recently described by muscle imaging in congenital and later onset forms of LMNA-related muscular dystrophies (LMNA-RD). Methods: Scores for fibroadipose infiltration of 23 lower limb muscles in 34 patients with LMNA-RD were collected from heat maps of 2 previous studies. Scoring systems were homogenized. Relationships between muscle infiltration and disease duration and age of onset were modeled with random forests. Results: The pattern of infiltration differs according to disease duration but not to age of disease onset. The muscles whose progression best predicts disease duration were semitendinosus, biceps femoris long head, gluteus medius, and semimembranosus. Discussion: In LMNA-RD, our synthetic analysis of lower limb muscle infiltration did not find major differences between forms with different ages of onset but allowed the identification of muscles with characteristic infiltration during disease progression. Monitoring of these specific muscles by quantitative MRI may provide useful imaging biomarkers in LMNA-RD. Muscle Nerve 58:812-817, 201

Relevancia de superficies atmosf´ericas en la eliminaci´on de sustitutos de CFCs, CF3CH2OH.

J2IFAM 2013 Madrid, February, 13rd-15th 2013Peer reviewe

Gas-phase reactions of chlorine atoms and CIO radicals with dimethyl sulfide. Rate coefficients and temperature dependences

The results of a discharge flow-mass spectrometric (DF-MS) kinetic study of the reaction between Cl and dimethylsulfide (DMS) (1) over the temperature range 259−364 K at low total pressure between 0.5 and 1 Torr with helium as carrier gas are reported. At room temperature and 1.0 Torr the main products of reaction 1 correspond to an abstraction channel leading to HCl and CH3SCH2 with k(1) = (6.9 ± 1.3) × 10-11 cm3 molecule-1 s-1. The association channel has also been confirmed by mass spectroscopic detection of the adduct CH3S(Cl)CH3 with a yield <0.05 under the experimental conditions used. It is now shown that the abstraction channel requires a slight activation energy, k(1) = (2.0 ± 1.2) × 10-10 exp[−(332 ± 173)/T] cm3 molecule-1 s-1. The kinetics and mechanism of the reaction ClO + DMS → products (2) over the temperature range 259−335 K at total pressures between 0.5 and 2 Torr have also been studied by DF-MS. By mass spectroscopic calibration of dimethyl sulfoxide, DMSO, the branching ratio of the channel leading to this product has been measured (0.90 ± 0.49). The rate constant of reaction 2 has been measured under pseudo-first-order conditions in excess of DMS over ClO:  k(2) = (1.2 ± 0.7) × 10-15 exp[(354 ± 163)/T] cm3 molecule-1 s-1 with k(2) = (3.9 ± 1.2) × 10-15 cm3 molecule-1 s-1 at 298 K. The reaction is postulated to proceed through a channel involving a long-lived intermediate [CH3S(OCl)CH3]* which may decompose back to reactants or to products. Finally, the atmospheric implications through the DMS chemistry of both reactions are discussed.We thank the European Commission for financial support within the “Energy, Environment and Sustainable Development” V Framework program (EVK2-CT-1999-00033 contract) and the Spanish Ministry of Science and Technology for the PB97-0432 contract.Peer reviewe

Air pollution in the plateau of the Iberian Peninsula

To assess the air pollution in the central Iberian Peninsula, NO, NO2, O3, SO2 and PM10 hourly data were collected at eight air quality stations (urban and suburban) belonging to the Air Quality Network of Castilla-La Mancha (Spain) during the 2008-2011 period. Weather conditions and air mass patterns were investigated, and three atmospheric transport patterns were identified. The mean levels of O3, NO2, SO2 and PM10 ranged between 51 and 64, 12 and 25, 2and 7 and 23 and 34μgm-3, respectively, although some peaks of O3, SO2 and NO2 exceeded the thresholds defined in the European Directives. Monthly and daily variations showed typical cycles, with SO2 peaks in industrial areas, or high ozone levels in downwind zones strongly affected by traffic emissions. The weekend effect was observed mainly for NO2 and PM10, while there was a low effect for ozone and NO effect for SO2. Dependence of NO, NO2 and O3 with the NOx levels was also investigated through oxidant concentrations OX (O3+NO2). NOx-independent regional contribution to the oxidant levels showed a strong seasonality and high values. Maximum values of OX concentrations at low levels of NOx were found in areas strongly affected by urban plumes, whereas maximum OX levels at high NOx values indicated the influence of local sources. The studied area can be divided into three groups, that located downwind of strong traffic emissions, that influenced by industrial emissions (in these two zones the main air pollution problems are focused) and finally that group conditioned by local sources. © 2014 Elsevier B.V.Peer Reviewe