ABSTRACT
The gas phase reactions of allyl alcohol with OH radicals and ozone have been investigated using different experimental systems. The rate coefficient for the OH reaction is reported in the temperature range 231-373 K, k(OH) = (5.7 +/- 0.2) x 10(-12) exp[(650 +/- 52)/T] cm3 molecule(-1) s(-1). This reaction is found to be pressure independent between 33 and 760 Torr. Rate coefficient (k(O3)) and gas phase products of the ozone reaction with allyl alcohol are reported at atmospheric pressure and 298 K. The obtained k(O3) = (1.8 +/- 0.2) x 10(-17) cm3 molecule(-1) s(-1) is in good agreement with the single measurement reported in the literature. The reaction of 03 with allyl alcohol is found to lead to the formation of formaldehyde and glycolaldehyde as the main products. Other products such as CH3OH, CO and CO2 have also been observed in low yield. Aerosol formation has been detected in the ozonolysis of allyl alcohol and its size distribution investigated.
ABSTRACT
The rate coefficient of the OH reaction with the perfluoroaldehydes C(3)F(7)CHO and C(4)F(9)CHO have been determined in the temperature range 252-373 K using the pulsed laser photolysis-laser induced fluorescence (PLP-LIF) method: k(C(3)F(7)CHO+OH) = (2.0 +/- 0.6) x 10(-12) exp[-(369 +/- 90)/T] and k(C(4)F(9)CHO+OH) = (2.0 +/- 0.5) x 10(-12) exp[-(356 +/- 70)/T] cm(3) molecule(-1) s(-1), corresponding to (5.8 +/- 0.6) x 10(-13) and (6.1 +/- 0.5) x 10(-13) cm(3) molecule(-1) s(-1), respectively, at 298 K. The UV absorption cross sections of these two aldehydes and CF(3)(CF(2))(5)CH(2)CHO have been measured over the range 230-390 nm at 298 K and also at 328 K for CF(3)(CF(2))(5)CH(2)CHO. The obtained results for C(3)F(7)CHO and C(4)F(9)CHO are in good agreement with two recent determinations but the maximum value of the absorption cross section for CF(3)(CF(2))(5)CH(2)CHO is over a factor of two lower than the single one recently published. The photolysis rates of C(3)F(7)CHO, C(4)F(9)CHO and CF(3)(CF(2))(5)CHO have been measured under sunlight conditions in the EUPHORE simulation chamber in Valencia (Spain) at the beginning of June. The photolysis rates were, respectively, J(obs) = (1.3 +/- 0.6) x 10(-5), (1.9 +/- 0.8) x 10(-5) and (0.6 +/- 0.3) x 10(-5) s(-1). From the J(obs) measurements and calculated photolysis rate J(calc), assuming a quantum yield of unity across the atmospheric range of absorption of the aldehydes, quantum yields J(obs)/J(calc) = (0.023 +/- 0.012), (0.029 +/- 0.015) and (0.046 +/- 0.028) were derived for the photodissociation of C(3)F(7)CHO, C(4)F(9)CHO and CF(3)(CF(2))(5)CHO, respectively. The atmospheric implication of the data obtained in this work is discussed. The main conclusion is that the major atmospheric removal pathway for fluoroaldehydes will be photolysis, which under low NO(x) conditions, may be a source of fluorinated carboxylic acids in the troposphere.
Subject(s)
Aldehydes/chemistry , Chemistry, Physical/methods , Fluorine/chemistry , Atmosphere , Carboxylic Acids/chemistry , Free Radicals , Hydroxyl Radical , Kinetics , Models, Chemical , Nitric Oxide/chemistry , Photolysis , Pressure , Spectrophotometry, Ultraviolet/methods , Sunlight , TemperatureABSTRACT
The Cl atom initiated oxidation of C(6)F(13)CH(2)OH, C(6)F(13)CHO, and C(3)F(7)CHO was investigated at 298 K and 1000 mbar pressure of air in a photoreactor using in situ Fourier transform infrared (FTIR) analysis. The rate coefficient for the reaction Cl + C(6)F(13)CH(2)OH (reaction 2) was measured using a relative method: k(2) = (6.5 +/- 0.8) x 10(-13) cm(3) molecule(-1) s(-1). C(6)F(13)CHO was detected as the major primary product, while CO and CF(2)O were found to be the major secondary products. A fitting procedure applied to the concentration-time profiles of C(6)F(13)CHO provided a production yield of (1.0 +/- 0.2) for this aldehyde in reaction 2, and the rate coefficient for the reaction Cl + C(6)F(13)CHO (reaction 4) was k(4) = (2.8 +/- 0.7) x 10(-12) cm(3) molecule(-1) s(-1). A high CO yield observed in the oxidation of C(6)F(13)CH(2)OH, (52 +/- 1)%, is attributed to the Cl atom initiated oxidation of C(6)F(13)CHO. High CO yields, (61 +/- 2)% and (85 +/- 5)%, were also measured in the Cl atom initiated oxidation of C(3)F(7)CHO in air and nitrogen, respectively. These high CO yields suggest the occurrence of a decomposition reaction of the perfluoroacyl, C(6)F(13)CO, and C(3)F(7)CO radicals to form CO which will compete with the combination reaction of these radicals with oxygen to form perfluoroacyl peroxy radicals in the presence of air. The latter radicals C(n)F(2)(n)(+1)CO(O)(2) (n = 6-12), through their reaction with HO(2) radicals, are currently considered as a possible source of persistent perfluorocarboxylic acids which have been detected in the environment. The consequences of the present results would be a reduction of the strength of this potential source of carboxylic acids in the atmosphere.
ABSTRACT
In order to realize the future Hermes and Columbus space-flights, European Space Agency decided to build up a european astronaut corps. Space-flights and training constraints require a strict initial selection among candidates. This paper describes space-flights psychological constraints, the aims of a psychiatric exam and its position in astronaut selection procedures as a whole. This paper also describes means and results of that selection among the candidates seen in Paris (France) in 1991.
Subject(s)
Personality Tests , Personnel Selection , Space Flight , Adaptation, Psychological , Adult , Europe , Female , Humans , MaleABSTRACT
Anxiety crises sometimes exhibited inflight by professional pilots, mostly fighter pilots in our experience, do not qualify as psychiatric pathology. Here, it is to be understood as the study of mental disorders associated with the profession of pilot. Beyond circumstances or events implied in the onset of disorders, occupational psychopathology takes into account the background of the occupational motivation and the mental dynamics of adaptation to the job requirements.
