55 research outputs found
Occurrence of storm-generated bedforms along the inner continental shelf: Southeastern Brazil
Medicinal plants – prophylactic and therapeutic options for gastrointestinal and respiratory diseases in calves and piglets? A systematic review
The morphology and dynamics of low amplitude bedwaves upon upper stage plane beds and the preservation of planar laminae
Layer Attitude and Thickness Measurements in Western Portion of the Ophir Chasma Interior Layered Deposit, Valles Marineris
Bedforms and associated sedimentary structures formed under supercritical water flows over aggrading sand beds
High-frequency variability of CO<sub>2</sub> in Grand Passage, Bay of Fundy, Nova Scotia
Assessing changes in the marine carbon cycle arising from anthropogenic
CO2 emissions requires a detailed understanding of the carbonate
system's natural variability. Coastal ecosystems vary over short spatial and
temporal scales, so their dynamics are not well described by long-term and
broad regional averages. A year-long time series of pCO2,
temperature, salinity, and currents is used to quantify the high-frequency
variability of the carbonate system at the mouth of the Bay of Fundy, Nova
Scotia. The seasonal cycle of pCO2 is modulated by a diel
cycle that is larger in summer than in winter and a tidal contribution that
is primarily M2, with amplitude roughly half that of the diel cycle
throughout the year. The interaction between tidal currents and carbonate
system variables leads to lateral transport by tidal pumping, which moves
alkalinity and dissolved inorganic carbon (DIC) out of the bay, opposite to the mean flow in the region,
and constitutes a new feature of how this strongly tidal region connects to
the larger Gulf of Maine and northwest Atlantic carbon system. These results
suggest that tidal pumping could substantially modulate the coastal ocean's
response to global ocean acidification in any region with large tides and
spatial variation in biological activity, requiring that high-frequency
variability be accounted for in assessments of carbon budgets of coastal
regions.</p
Free radical scavengers from Cymbopogon citratus (DC.) stapf plants cultivated in bioreactors by the temporary immersion (TIS) principle
Guillermo Schmeda-Hirschmann,Alejandro Tapia, Jose Cheel, Instituto de Quımica de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.
E-mail: [email protected]
Cristina Theodulozb, Jaime Rodrıguez,
Facultad de Ciencias de la Salud, Departamento de Ciencias Basicas Biomedicas,
Universidad de Talca, ChileThe biomass production of Cymbopogon citratus shoots cultivated in bioreactors according to
the temporary immersion (TIS) principle was assessed under different growth conditions. The
effect of gassing with CO2-enriched air, reduced immersion frequency, vessel size and culture
time on total phenolic and flavonoid content and free radical scavenging effect of the methanolic
extracts was measured. From the TIS-culture of C. citratus, seven compounds were isolated and
identified as caffeic acid (1), chlorogenic acid (2), neochlorogenic acid (3), p-hydroxybenzoic
acid (4), p-hydroxybenzoic acid 3-O- -d-glucoside (5), glutamic acid (6) and luteolin 6-C-fucopyranoside (7). The occurrence of compounds 1Ð7 and their variability in C. citratus grown under different TIS conditions was determined by HPLC. The free radical scavenging effect of the methanolic extract and compounds was measured by the discoloration of the free radical 1,1- diphenyl-2-picrylhydrazyl (DPPH). The main metabolites in 6- and 8-week-old cultures, both in 5 and 10 l vessels, were chlorogenic acid (2) (100Ð113 mg%) and neochlorogenic acid (3) (80Ð 119 mg%), while in the cultures with CO2-enriched air and reduced immersion frequency the main compound detected in the extracts was glutamic acid (6) (400 and 670 mg% for the green and white biomass and 619 and 630 mg% for the green and white biomass, respectively). The most active compounds, as free radical scavengers, in the DPPH discoloration assay were caffeic acid (1), chlorogenic acid (2), neochlorogenic acid (3) and the flavonoid luteolin 6-C-fucopyranoside
(7)
TEMPESTITE DEPOSITS ON A STORM-INFLUENCED CARBONATE RAMP: AN EXAMPLE FROM THE PABDEH FORMATION (PALEOGENE), ZAGROS BASIN, SW IRAN
Gravel antidunes in the tropical Burdekin River, Queensland, Australia
The geological record is punctuated by the deposits of extreme event phenomena, the identification and interpretation of which are hindered by a lack of data on contemporary examples. It is impossible to directly observe sedimentary bedforms and grain fabrics forming under natural particle-transporting, high-velocity currents, and therefore, their characteristics are poorly documented. The deposits of such flows are exposed however, in the dry bed of the Burdekin River, Queensland, Australia following tropical cyclone-induced floods. Long wave-length (up to 19 m) gravel antidunes develop during short (days) high-discharge flows in the upper Burdekin River (maximum recorded discharge near the study reach over 25 600 m s in February 1927). Flood water levels fall quickly (metres in a day) and flow is diverted away from raised areas of the river bed into subchannels, exposing many of the high-stage bedforms with little reworking by falling-stage currents. Gravel bedforms were observed on the dry river bed after the moderate flows of February 1994 (max. 7700 m s) and January 1996 (max. 3200 m s). The bedforms had wave-lengths in the range 8-19 m, amplitudes of up to 1 m with steeper stoss than lee faces and crest lines generally transverse to local peak-discharge flow direction. The gravel fabric and size sorting change systematically up the stoss and down the lee faces. The antidune deposits form erosive based lenses of sandy gravel with low-angle downstream dipping lamination and generally steep upstream dipping a-b planes. The internal form and fabric of the antidune gravel lenses are distinctly different from those of dune lee gravel lenses. The erosive based lenses of low-angle cross-bedded gravel with steep upstream dipping a-b planes are relatively easy to recognize and may be diagnostic of downstream migrating antidunes. The antidune gravel lenses are associated with thick (to 1 m) high-angle cross bed sets. Ancient antidune gravel lenses may be diagnostic of episodic high-discharge conditions and particularly when they are associated with high-angle cross-bedded gravelly sand they may be useful for palaeoenvironmental interpretation
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