67 research outputs found
Anti-Proliferative Activity of Meroditerpenoids Isolated from the Brown Alga Stypopodium flabelliforme against Several Cancer Cell Lines
The sea constitutes one of the most promising sources of novel compounds with potential application in human therapeutics. In particular, algae have proved to be an interesting source of new bioactive compounds. In this work, six meroditerpenoids (epitaondiol, epitaondiol diacetate, epitaondiol monoacetate, stypotriol triacetate, 14-ketostypodiol diacetate and stypodiol) isolated from the brown alga Stypopodium flabelliforme were tested for their cell proliferation inhibitory activity in five cell lines. Cell lines tested included human colon adenocarcinoma (Caco-2), human neuroblastoma (SH-SY5Y), rat basophilic leukemia (RBL-2H3), murine macrophages (RAW.267) and Chinese hamster fibroblasts (V79). Antimicrobial activity of the compounds was also evaluated against Staphylococcus aureus, Salmonella typhimurium, Proteus mirabilis, Bacillus cereus, Enterococcus faecalis and Micrococcus luteus. Overall, the compounds showed good activity against all cell lines, with SH-SY5Y and RAW.267 being the most susceptible. Antimicrobial capacity was observed for epitaondiol monoacetate, stypotriol triacetate and stypodiol, with the first being the most active. The results suggest that these molecules deserve further studies in order to evaluate their potential as therapeutic agents
The impact of particle shape on the angle of internal friction and the implications for sediment dynamics at a steep, mixed sand–gravel beach
The impact of particle shape on the angle of internal friction, and the
resulting impact on beach sediment dynamics, is still poorly understood. In
areas characterized by sediments of specific shape, particularly non-rounded
particles, this can lead to large departures from the expected sediment
dynamics. The steep slope (1 : 10) of the mixed sand–gravel beach at
Advocate Harbour is stable in large-scale morphology over decades, despite a
high tidal range of 10 m or more, and intense shore-break action during
storms. The Advocate sand (<i>d</i> < 2 mm) was found to have an elliptic,
plate-like shape (Corey Shape Index, CSI ≈ 0.2–0.6). High angles of
internal friction of this material were determined using direct shear,
ranging from φ ≈ 41 to 49°, while the round to angular
gravel was characterized as φ = 33°. The addition of 25%
of the elliptic plate-like sand-sized material to the gravel led to an
immediate increase in friction angle to φ = 38°. Furthermore,
re-organization of the particles occurred during shearing,
characterized by a short phase of settling and compaction, followed by a
pronounced strong dilatory behavior and an accompanying strong increase of
resistance to shear and, thus, shear stress. Long-term shearing (24 h) using
a ring shear apparatus led to destruction of the particles without
re-compaction. Finally, submerged particle mobilization was simulated using a
tilted tray submerged in a water-filled tank. Despite a smooth tray surface,
particle motion was not initiated until reaching tray tilt angles of
31° and more, being ≥7° steeper than for motion
initiation of the gravel mixtures. In conclusion, geotechnical laboratory
experiments quantified the important impact of the elliptic, plate-like shape
of Advocate Beach sand on the angles of internal friction of both pure sand
and sand–gravel mixtures. The resulting effect on initiation of particle
motion was confirmed in tilting tray experiments. This makes it a vivid
example of how particle shape can contribute to the stabilization of the
beach face
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
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