4,362 research outputs found
Laterites and paleoclimates. Weathering processes and anthropogenic impact
The European Union of Geosciences held its 9th biannual meeting in Strasbourg, March 23–27, 1997. During this meeting, Symposium No. 63, Weathering Processes: Mineral deposits and soil formation in tropical enÍironments, was merged with Symposium No. 78, Anthropogenic Impact on Weathering processesco-sponsored by IGCP Project 405. The
resulting symposium No. 63, Weathering processes and Anthropogenic Impact, was held under the sponsorship
of EUROLAT1 and attracted 36 oral and poster presentations and about 100 participants, reflecting the interest of the Earth Sciences community in weathering processes and anthropogenic impact
Nuclear bars and blue nuclei within barred spiral galaxies
Multicolour near IR photometry for a sample of 32 large barred spiral
galaxies is presented. By applying ellipse fitting techniques, we identify
significant isophote twists with respect to the primary bar axis in the nuclear
regions of 70 \%\ of the sample. These twists are identified in galaxies
as late as SBbc and are clearly distinguishable from spiral arm morphology. At
most seven of the galaxies with isophote twists are inferred to possess
secondary (nuclear) bars, the axis ratios of which appear to correlate with
morphological type. The remainder may result from triaxial bulges, or from
oblate bulges misaligned with the primary bar. The near IR colour distributions
in these data show evidence for (red) circumnuclear star forming rings in 4
galaxies. The majority of the sample (19) also possess striking blue nuclear
regions, bluer than typical old stellar populations by 0.3 mag. in (J--H)
and 0.23 mag. in (H--K). Such blue colours do not appear to correlate
with the presence of nuclear rings or pseudo--rings, nor with the activity of
the host galaxy (as determined from emission--line spectroscopic
characteristics). Several mechanisms to explain this blue colour are
considered.Comment: 24 pages plain LaTex( including table captions), 5 tables and 18
figures. Accepted for publication in MNRAS. Paper and tables available via
anonymous ftp://143.167.4.101/pub/papers as sqiid-paper.tex and
table1,2,3.tex, table4.ps, table5.ps. Figures available as postcript upon
request to first Autho
A mesocosm experiment investigating the effects of substratum quality and wave exposure on the survival of fish eggs
In a mesocosm experiment, the attachment of bream (Abramis brama) eggs to spawning substrata with and without periphytic biofilm coverage and their subsequent survival with and without low-intensity wave exposure were investigated. Egg attachment was reduced by 73% on spawning substrata with a natural periphytic biofilm, compared to clean substrata. Overall, this initial difference in egg numbers persisted until hatching. The difference in egg numbers was even increased in the wave treatment, while it was reduced in the no-wave control treatment. Exposure to a low-intensity wave regime affected egg development between the two biofilm treatments differently. Waves enhanced egg survival on substrata without a biofilm but reduced the survival of eggs on substrata with biofilm coverage. In the treatment combining biofilm-covered substrata and waves, no attached eggs survived until hatching. In all treatments, more than 75% of the eggs became detached from the spawning substrata during the egg incubation period, an
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