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V Grossi

Publications and source records attributed to V Grossi.

7 recordsLinked to original sources
PubMed2002

Burial, exportation and degradation of acyclic petroleum hydrocarbons following a simulated oil spill in bioturbated Mediterranean coastal sediments.

A field study was conducted in a French Mediterranean littoral (Gulf of Fos) in order to determine the role of bioturbation processes during the bioremediation of oil-contaminated sediments. Inert particulate tracers (luminophores) and Arabian light crude oil were deposited at the surface of sediment cores incubated in situ for 2, 6 and 12 months. After incubation, luminophores and hydrocarbons presented roughly similar depth distributions in the sediment, showing a continuous burial of material until 55 mm depth. Short-chain (< or = n-C25) n-alkanes were totally removed from the sedimentary column after 6 months, whereas approximately 20% of heavier n-alkanes (e.g. n-C30) and of isoprenoid hydrocarbons (pristane (Pr) and phytane (Ph)) remained at the end of the experiment. The determination of the degradation constant and the turn-over rate of individual hydrocarbon indicated that C17-25 n-alkanes were degraded two to three times faster than longer homologues and than pristane and phytane. Using the 17alpha,21beta-C30-hopane as an internal inert reference, we could demonstrate that, after 12 months of in situ incubation, 55% of the losses of the n-alkanes < or = C25 and 35% of the losses of the heavier n-alkanes and of Pr and Ph were due to biodegradation processes. These results demonstrate that the activity of benthic organisms can have a significant influence on the qualitative and quantitative fate of acyclic hydrocarbons following a petroleum contamination in marine coastal sediments.

Animals↗
PubMed2001

Visible light-dependent degradation of long-chain alkenes in killed cells of Emiliania huxleyi and Nannochloropsis salina.

Photosensitized degradation rates of phytoplanktonic n-alkenes under visible light exposure were determined in laboratory experiments. Killed cells of Emiliania huxleyi and Nannochloropsis salina were used as source of biogenic alkenes. In E. huxleyi killed cells, minor C31 and C33 n-alkenes were strongly photodegraded, while the major C37 and C38 n-alkenes appeared particularly recalcitrant towards photochemical processes. This particular photochemical recalcitrance has been attributed to the chemical structure and localization of these hydrocarbons in the cells. Most of the n-alkenes of N. salina were strongly photodegraded in killed cells. The photodegradation of phytoplanktonic alkenes showed apparent second-order kinetics with respect to light exposure, and the half-life doses obtained logically decrease with increasing number of double bonds in these compounds. These results strongly suggest that significant amounts of phytoplanktonic n-alkenes must be photodegraded in the euphotic zone of the oceans during senescence.

Alkenes↗
PubMed2000

The effect of growth temperature on the long-chain alkenes composition in the marine coccolithophorid Emiliania huxleyi.

The hydrocarbon fraction of a pure culture of Emiliania huxleyi, composed of a mixture of C31, C33, C37 and C38 polyunsaturated n-alkenes, appeared strongly dependent on the growth temperature of the alga between 8 degrees C and 25 degrees C. The total hydrocarbon content increased linearly with decreasing temperatures. C37 and C38 alkenes (which accounted for more than 90% of the total hydrocarbons) showed distinct changes in distribution compared to C31 and C33 alkenes, suggesting different biological syntheses and/or functions for these two groups of compounds. C37 and C38 alkenes and C37 methyl ketones (alkenones) all showed a trend to lower proportions of the two diunsaturated isomers and to higher proportions of the corresponding trienes with decreasing temperature. Unlike the alkenone unsaturation ratio (U37k'), ratios based on the C37 and C38 alkadi- and trienes could be linearly related to the growth temperature of E. huxleyi only between 15 degrees C and 25 degrees C. The modifications in the distribution of alkenes induced by varying temperature appeared, however, to be twice as fast as the modifications undergone by the alkenones. Although structurally and biochemically related, the distinct evolutions of alkenes and alkenones in response to changes in growth temperature might indicate that these two classes of compounds play two distinct physiological functions. The non-systematic linearity of relationships to temperature of parameters based on alkenes distribution suggested that these compounds are of limited use as paleotemperature indicator in the marine environment in contrast with the alkenones.

Alkenes↗
PubMed1980

Lateralized hand gesture during speech.

A group of individuals conversing in natural dyads and a group of lecturers were observed for lateral hand movement patterns during speech. Right-handed individuals in both groups displayed a significant right hand bias for gesture movements but no lateral bias for self-touching movements. The study provides external validity for previous laboratory studies of lateralized hand gesture. The results were interpreted as evidence of a central processor for both spoken and gestural communication.

Journal Article↗
PubMed1979

Differences in muscle activity before, during, and after responding in a simple reaction time task: schizophrenics vs. normals.

Schizophrenics and normals were presented with a series of simple reaction time (RT) trials. Electromyographic techniques were used to partition RT into peripheral and central components. It was observed that contrary to the previously held assumption of "neuromuscular sameness," schizophrenics displayed a qualitatively different pattern of muscle activity in their motor responding. Differences of the observed sort could account, in part, for differences previously thought to be due solely to central dysfunction.

Adult↗