Heterogeneous oxidation of two triazole pesticides (diniconazole and tebuconazole) by OH-radicals and ozone.

Tebuconazole (Tbz) and diniconazole (Dnz) were deposited as thin film on quartz plaques. They were submitted to OH-radicals and ozone and their kinetic was measured. OH-radical oxidation was performed relative to a reference whose rate constant is well known. Terbuthylazine (Tbt) and Chlorpyriphos Ethyl (Clp) were chosen as reference for Tbz and Dnz kinetics determination, respectively. OH-radical rate constants of Tbz and Dnz were found to be: kOH+Tbz = (1.7 ±â€¯0.2) 10-13 cm3 molecule-1 s-1 and k OH+Dnz = (1.74 ±â€¯1.21) 10-12 cm3 molecule-1 s-1, respectively. Ozone heterogeneous oxidation rate constants were determined in an absolute way: kO3+Tbz = (0.5 ±â€¯0.2) 10-20 cm3 molecule-1 s-1; kO3+Dnz = (1.4 ±â€¯0.2) 10-19 cm3 molecule-1 s-1. Dnz is ten times more reactive toward OH-radicals than Tbz and 27 times more reactive than Tbz toward ozone maybe because of the presence of a double bond in Dnz. Lifetimes of Tbz and Dnz on quartz like surfaces are against OH-radicals are of 68 days and 8 days, respectively and 4 months and several years against ozone, respectively.

Atmospheric Reaction of Cl with 4-Hydroxy-2-pentanone (4H2P): A Theoretical Study.

The kinetics and the mechanism of the reaction of 4-hydroxy-2-pentanone (4H2P) with Cl atom were investigated using quantum theoretical calculations. Density functional theory, CBS-QB3, and G3B3 methods are used to explore the reaction pathways. Rice-Ramsperger-Kassel-Marcus theory is employed to obtain rate constants of the reaction at atmospheric pressure and the temperature range 278-400 K. This study provides the first theoretical and kinetic determination of Cl rate constant for reactions with 4H2P over a large temperature range. The obtained rate constant 1.47 × 10-10 cm3 molecule-1 s-1 at 298 K is in reasonable agreement with those obtained for C4-C5 hydroxyketones both theoretically and experimentally. The results regarding the structure-reactivity relationship and the atmospheric implications are discussed.

Kinetics of the heterogeneous photo oxidation of the pesticide bupirimate by OH-radicals and ozone under atmospheric conditions.

This article is concerned with the study of the photochemical degradation of bupirimate adsorbed on a quartz surface by atmospheric oxidants, namely ozone and OH radicals. OH oxidation experiments were conducted relative to two reference compounds, terbuthylazine and (4-chlorophenyl)(3,4-dimethoxyphenyl) methanone. Meanwhile, ozone oxidation experiments were performed in the absolute mode and were interpreted by both, the Surface Layer Reaction and the Gas Surface Reaction models of heterogeneous reactions. The obtained results show that the rate constants for the reactions between bupirimate and OH radicals and ozone are (cm(3)molecule(-1)s(-1)): (1.06 ± 0.87) × 10(-12) and (5.4 ± 0.3) × 10(-20), respectively. As a consequence, for the experimental conditions used in this study, the lifetime of bupirimate at quartz like surface/atmosphere interfaces is several months against ozone and a tenth of days against OH-radical.

Kinetics and mechanism of the tropospheric reaction of 3-hydroxy-3-methyl-2-butanone with Cl atoms.

The relative rate coefficient for the gas-phase reaction of 3-hydroxy-3-methyl-2-butanone (3H3M2B) with Cl atoms was determined under atmospheric conditions (298 ± 2 K, 720 ± 2 Torr). The products of the reaction were identified and quantified. This work provides the first kinetic and mechanistic determinations of the gas-phase reaction of Cl atoms with 3H3M2B. The rate measurements and the products studies were performed in two simulation chambers coupled to the gas chromatography-mass spectrometer (GC-MS) and the Fourier transform infrared (FTIR) techniques, respectively. The obtained average rate coefficient was (1.13 ± 0.17) × 10(-10) cm(3) molecule(-1) s(-1) using propene and 1,3-butadiene as reference compounds. The major primary reaction products observed in this study were (with % molar yields): acetic acid (42.6 ± 4.8) and 2,3-butanedione (17.2 ± 2.3). Results and mechanism are discussed in terms of the structure-reactivity relationship and compared with the reported reactivity with the other atmospheric oxidants. The atmospheric implications derived from this study are discussed as well.

A Quantum Cascade Laser Absorption Spectrometer devoted to the in situ measurement of atmospheric N2O and CH4 emission fluxes.

This paper describes a Quantum Cascade Laser Absorption Spectrometer, called "QCLAS" that was developed to monitor in situ greenhouse gases like N2O and CH4, at high temporal resolution and with a high accuracy. The design of the laser sensor is reported as well as its performances in terms of precision error and field deployment capabilities. Finally, to demonstrate the efficiency and the robustness of QCLAS and its suitability for gas emission monitoring and for the determination of fluxes, we report the results from a field campaign, that took place in the Wallis and Futuna Islands in 2011, to investigate the impact of environmental intensive pig farming.

Study of a benzoylperoxy radical in the gas phase: ultraviolet spectrum and C6H5C(O)O2 + HO2 reaction between 295 and 357 K.

This work reports the ultraviolet absorption spectrum and the kinetic determinations of the reactions 2C(6)H(5)C(O)O(2) → products (I) and C(6)H(5)C(O)O(2) + HO(2) → C(6)H(5)C(O)O(2)H + O(2) (IIa), → C(6)H(5)C(O)OH + O(3) (IIb), → C(6)H(5)C(O)O + OH + O(2) (IIc). Experiments were performed using a laser photolysis technique coupled with UV-visible absorption detection over the pressure range of 80-120 Torr and the temperature range of 293-357 K. The UV spectrum was determined relative to the known cross section of the ethylperoxy radical C(2)H(5)O(2) at 250 nm. Kinetic data were obtained by simulating the temporal behavior of the UV absorption at 245-260 nm. At room temperature, the rate constant value of reaction I (cm(3)·molecule(-1)·s(-1)) was found to be k(I) = (1.5 ± 0.6) × 10(-11). The Arrhenius expression for reaction II is (cm(3)·molecule(-1)·s(-1)) k(II)(T) = (1.10 ± 0.20) × 10(-11) exp(364 ± 200/T). The branching ratios ß(O3) and ß(OH), respectively, of reactions IIb and IIc are evaluated at different temperatures; ß(O3) increases from 0.15 ± 0.05 at room temperature to 0.40 ± 0.05 at 357 K, whereas ß(OH) remains constant at 0.20 ± 0.05. To confirm the mechanism of reaction II, a theoretical study was performed at the B3LYP/6-311++G(2d,pd) level of theory followed by CBS-QB3 energy calculations.

UV absorption cross-sections of a series of dimethylbenzaldehydes.

The ultraviolet absorption cross-sections of 2,4-, 2,5-, 2,6-, 3,4- and 3,5- dimethylbenzaldehydes are reported in the wavelength range 240-320 nm. The measurements were carried out in the temperature range 318-363 K using two different experimental systems (D 2 lamp-monochromator and D 2 lamp-diode array). The absorption spectra of the five aldehydes have been found to exhibit relatively high absorption cross-sections in the region of the tropospheric interest with maxima around 290 nm. This work provides the first UV cross-section measurements for these aromatic aldehydes. The obtained cross-section values enable us to estimate the tropospheric photolysis lifetimes of these compounds. The results suggest that photolysis could be an important removal process for these species in the troposphere.

Forced mild physical training-induced effects on cognitive and locomotory behavior in old mice.

OBJECTIVES: To assess the effect of mild forced physical training on cognitive and locomotory behavior in old (26 mo.) mice. DESIGN: Randomized, controlled study. SETTING: Open-field in the behavioral laboratory. PARTICIPANTS: Sixteen old sedentary male mice randomly assigned to one of two groups, exercise (E) or rest (R). INTERVENTION: group E underwent treadmill running for one month at moderate intensity (belt speed=8 m/min, 45 min, five days a week), group R was only allowed spontaneous locomotor activity. MEASUREMENTS: exploratory and locomotor behavior were evaluated in an enriched environment (Ethovision recording). RESULTS: motor patterns were significantly reduced (chi2 test, p<0.05) in the E vs R group after one month of training; exploratory patterns were not different, both groups showing modest exploratory activity. CONCLUSIONS: mild forced physical training initiated at old age may have detrimental effect on motor behavior in male mice without improving cognitive parameters.

Drug resistance and hippocampal damage after delayed treatment of pilocarpine-induced epilepsy in the rat.

Temporal lobe epilepsy (TLE) is the most common and pharmacoresistant form of epilepsy. Problems that cause pharmacoresistance may include delayed therapy due to late consultation, especially in developing countries. Our study aimed at unraveling consequences of delayed drug treatment using a rat model of TLE. Following pilocarpine-induced status epilepticus interrupted after 4h, rats were continuously videorecorded for onset and recurrence of spontaneous convulsive seizures. The animals were then treated for 50 days with carbamazepine (CBZ; first-line drug in TLE and effective also in rats), starting at seizure onset (27.22+/-3.38 days after status epilepticus) or 50 days later, and compared with epileptic untreated rats and non-epileptic CBZ-treated ones. Convulsive seizure frequency and duration, and hippocampal cell changes were evaluated. In particular, parvalbumin-containing hippocampal interneurons, astrocytes and microglia were characterized with immunohistochemistry and quantitative analyses. Prompt administration of CBZ suppressed seizures; delayed treatment only decreased frequency of convulsive seizures, which were also relatively prolonged. In hippocampal regions, histopathological damage, parvalbumin immunoreactivity loss, and glial activation were very marked after delayed treatment, and were reduced only slightly compared to untreated epilepsy, but enhanced compared to early treatment. The data on high frequency and duration of convulsive seizures in late-therapy rats indicate that delayed CBZ administration caused a high degree of drug resistance. This condition was subserved by severe damage in the hippocampus, presumably consequent to long-term seizure recurrence. Overall the data indicate that the paradigm of delayed treatment of limbic epilepsy could provide a model of drug-refractory TLE with hippocampal sclerosis.

Study of benzylperoxy radical using laser photolysis: ultraviolet spectrum, self-reaction, and reaction with HO2 kinetics.

The ultraviolet absorption spectrum of benzylperoxy radical and the kinetics of the reactions 2C(6)H(5)CH(2)O(2) --> products (I) and C(6)H(5)CH(2)O(2) + HO(2) --> products (II) are studied. Experiments are carried out using the laser photolysis technique with time-resolved UV-visible absorption spectroscopy over the temperature range 298-353 K and the pressure range 50-200 Torr. The UV spectrum is determined relative to the known cross section of the ethylperoxy radical C(2)H(5)O(2) at 250 nm. Using factor analysis, the spectrum obtained is refined and the concentrations of the main absorbing species are extracted. The kinetic parameters are determined by analyzing and simulating the temporal profiles of the species concentrations and the experimental optical densities in the spectral region 220-280 nm. These are obtained using the recent UV spectra of the absorbing species existing in our mechanism. The Arrhenius expressions for reactions I and II are (cm(3).molecule(-1).s(-1)) k(I) = 2.50 x 10(-14)e(1562/)(T) and k(II) = 5.70 x 10(-14)e(1649/)(T). Our results are discussed and compared to literature data.

Reduction of I(Ca,L) and I(to1) density in hypertrophied right ventricular cells by simulated high altitude in adult rats.

The present paper describes the effect of a simulated hypobaric condition (at the altitude of 4500 m) on morphological characteristics and on some ionic currents in ventricular cells of adult rats. According to current data, chronic high-altitude exposure led to mild right ventricular hypertrophy. Increase in right ventricular weight appeared to be due wholly or partly to an enlargement of myocytes. The whole-cell patch-clamp technique was used and this confirmed, by cell capacitance measurement, that chronic high-altitude exposure induced an increase in the size of the right ventricular cells. Hypertrophied cells showed prolongation of action potential (AP). Four ionic currents, playing a role along with many others in the precise balance of inward and outward currents that control the duration of cardiac AP, were investigated. We report a significant decrease in the transient outward (I(to1)) and in the L-type calcium current (I(Ca,L)) densities while there was no significant difference in the delayed rectifier current (I(K)) or in the inward rectifier current (I(K1)) densities in hypertrophied right ventricular cells compared to control cells. At a given potential the decrease in I(to 1) density was relatively more important than the decrease in I(Ca,L) density. In both cell types, all the currents displayed the same voltage dependence. The inactivation kinetics of I(to 1) and I(Ca,L) or the steady-state activation and inactivation relationships were not significantly modified by chronic high-altitude exposure. We conclude that chronic high-altitude exposure induced true right ventricular myocyte hypertrophy and that the decrease in I(to 1) density might account for the lengthened action potential, or have a partial effect.