Intense exercise decreases the cerebral metabolic ratio of O 2 to carbohydrates (glucose + 1 / 2 lactate) and the cerebral lactate uptake depends on its arterial concentration, but whether these variables are influenced by O 2 availability is not known. In six males, maximal ergometer rowing increased the arterial lactate to 21.4 ± 0.8 mM (mean ± S.E.M.) and arterial-jugular venous (a-v) difference from −0.03 ± 0.01 mM at rest to 2.52 ± 0.03 mM (P < 0.05). Arterial glucose was raised to 8.5 ± 0.5 mM and its a-v difference increased from 1.03 ± 0.01 to 1.86 ± 0.02 mM (P < 0.05) in the immediate recovery. During exercise, the cerebral metabolic ratio decreased from 5.67 ± 0.52 at rest to 1.70 ± 0.23 (P < 0.05) and remained low in the early recovery. Arterial haemoglobin O 2 saturation was 92.5 ± 0.2% during exercise with room air, and it reached 87.6 ± 1.0% and 98.9 ± 0.2% during exercise with an inspired O 2 fraction of 0.17 and 0.30, respectively. Whilst the increase in a-v lactate difference was attenuated by manipulation of cerebral O 2 availability, the cerebral metabolic ratio was not affected significantly. During maximal rowing, the cerebral metabolic ratio reaches the lowest value with no effect by a moderate change in the arterial O 2 content. These findings suggest that intense whole body exercise is associated with marked imbalance in the cerebral metabolic substrate preferences independent of oxygen availability.

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of 3-pentanol and determine rate constants of k(Cl+3-pentanol) = (2.03 +/- 0.23) x 10 (-10) and k(OH+3-pentanol) = (1.32 +/- 0.15) x 10 (-11) cm (3) molecule (-1) s (-1) in 700 Torr of N 2/O 2 diluent at 296 +/- 2 K. The primary products of the Cl atom initiated oxidation of 3-pentanol in the absence of NO were (with molar yields) 3-pentanone (26 +/- 2%), propionaldehyde (12 +/- 2%), acetaldehyde (13 +/- 2%) and formaldehyde (2 +/- 1%). The primary products of the Cl atom initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (51 +/- 4%), propionaldehyde (39 +/- 2%), acetaldehyde (44 +/- 4%) and formaldehyde (4 +/- 1%). The primary products of the OH radical initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (58 +/- 3%), propionaldehyde (28 +/- 2%), and acetaldehyde (37 +/- 2%). In all cases the product yields were independent of oxygen concentration over the partial pressure range 10-700 Torr. The reactions of Cl atoms and OH radicals with 3-pentanol proceed 26 +/- 2 and 58 +/- 3%, respectively, via attack on the 3-position to give an alpha-hydroxyalkyl radical, which reacts with O 2 to give 3-pentanone. The results are discussed with respect to the literature data and atmospheric chemistry of 3-pentanol.

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