Anti-cyclonic eddy imprint on calcite geochemistry of several planktonic foraminiferal species in the Mozambique Channel

Hydrographic conditions in the Mozambique Channel are dominated by the passing of large anticyclonic eddies, propagating poleward into the upstream Agulhas area. Further south, these eddies have been found to control the shedding of Agulhas rings into the Atlantic ocean, thereby playing a key role in Indo-Atlantic Ocean exchange. The element composition of several planktonic foraminifera species collected from sediment trap samples, was compared to in situ water column data from the Mozambique Channel. Single-chamber trace element composition of these foraminifera reveals a close coupling with hydrographic changes induced by anticyclonic eddies. Obtained Mg/Ca values for the surface dwelling Globigerinoides ruber as well as the thermocline dwelling Neogloboquadrina dutertrei follow temperature changes and reduced temperature stratification during eddy conditions. At greater depth, Globorotalia scitula and Pulleniatina obliquiloculata record stable temperatures and thus respond to hydrographic changes with a deepening in habitat depth. Furthermore, test Mn/Ca values indicate a close relationship between water column oxygenation and Mn incorporation in these planktonic foraminiferal specie

Probing a strong hydrogen bond with infrared spectroscopy: Vibrational predissociation of brhbr-center dot ar

Contains fulltext : 98911.pdf (publisher's version ) (Open Access

Mass-selected infrared photodissociation spectroscopy of v4o10+

Contains fulltext : 98936.pdf (publisher's version ) (Open Access

Profiling planktonic foraminiferal crust formation

Planktonic foraminifera migrate vertically through the water column during their life, therebygrowing and calcifying over a range of depth-associated conditions. Some species form a calcite veneer,crust, or cortex at the end of their lifecycle. This additional calcite layer may vary in structure, composition,and thickness, potentially accounting for most of their total shell mass and thereby dominating the elementand isotope signature of the whole shell. Here we apply laser ablation ICP-MS depth pro?ling to assess vari-ability in thickness and Mg/Ca composition of shell walls of three encrusting species derived from sedimenttraps. Compositionally, Mg/Ca is signi?cantly lower in the crusts of Neogloboquadrina dutertrei and Globoro-talia scitula, as well as in the cortex of Pulleniatina obliquiloculata, independent of the species-speci?c Mg/Ca of their lamellar calcite shell. Wall thickness accounts for nearly half of the total thickness in both crustalspecies and nearly a third in cortical P. obliquiloculata, regardless of their initial shell wall thickness. Crustthickness and crustal Mg/Ca decreases toward the younger chambers in N. dutertrei and to a lesser extent,also in G. scitula. In contrast, the cortex of P. obliquiloculata shows a nearly constant thickness and uniformMg/Ca through the complete chamber wall. Patterns in thickness and Mg/Ca of the crust indicate that tem-perature is not the dominant factor controlling crust formation. Instead, we present a depth-resolved modelexplaining compositional differences within individuals and between successive chambers as well as com-positional heterogeneity of the crust and lamellar calcite in all three species studied her

The effect of a single rectal dose of cisapride on delayed gastric emptying.The effect of a single rectal dose of cisapride on delayed gastric emptying.

Department of Gastroenterology, University Hospital Maastricht, The Netherlands.BACKGROUND: Cisapride has an established prokinetic effect in patients with delayed gastric emptying. However, rectal administration of the drug might be preferred in patients with either dysphagia or nausea due to gastroparesis. AIM: To determine the effect of a single rectal dose of cisapride 60 mg on gastric emptying in patients with delayed gastric emptying. METHODS: Thirty-two patients (16 males, 16 females) with demonstrated delayed gastric emptying received a single dose of two suppositories containing either cisapride (2 x 30 mg) or placebo, according to a double-blind randomized crossover design. Three hours after administration of the suppositories, the patients received a radio-labelled test meal and radio-opaque markers for measurement of gastric emptying. RESULTS: The mean t1/2 after cisapride administration (76 min, 95% CI: 68-95) was significantly shorter (P = 0.005: n = 28, per-protocol analysis) than after placebo administration (104 min, 81-126). Four hours after ingestion of the meal significantly fewer radio-opaque markers remained in the stomach after cisapride than after placebo administration (P < 0.05). Mild to moderate adverse events, mainly involving the gastrointestinal tract, were reported in 10 patients (31%) after cisapride treatment and in four patients (13%) after placebo (N.S.: n = 32). CONCLUSION: A single suppository dose of cisapride 60 mg significantly accelerates gastric emptying of the solid phase of a meal and of radio-opaque markers in patients with previously demonstrated delayed gastric emptying.Publication Types: Clinical Trial Randomized Controlled Tria

Temporal offsets between surface temperature, ice-rafting and bottom flow speed proxies in the glacial (MIS 3) northern North Atlantic

Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of icebergs and sea ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for ice rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations.Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the ice-rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes

Contrasting variability in foraminiferal and organic paleotemperature proxies in sedimenting particles of the Mozambique Channel (SW Indian Ocean)

Accurate sea surface temperature (SST) proxies are important for understanding past ocean and climate systems. Here, we examine material collected from a deep-moored sediment trap in the MozambiqueChannel (SWIndianOcean) to constrain and compare both inorganic (δ18O, Mg/Ca) and organic (, TEX86) temperature proxies in a highly dynamic oceanographic setting for application in paleoceanography. High-resolution time-series current velocity data from long-term moorings (2003 – present) deployed across the MozambiqueChannel reveal the periodic migration of four to six meso-scale eddies through the channel per year. These meso-scale eddies strongly influence water mass properties including temperature and salinity. Despite the dynamic oceanographic setting, fluxes of the surface-dwelling planktonic foraminifera Globigerinoidesruber and Globigerinoides trilobus follow a seasonal pattern. Temperatures reconstructed from G. ruber and G. trilobus δ18O and Mg/Ca closely mirror seasonal SST variability and their flux-weighted annual mean SSTs of 28.1 °C and 27.3 °C are in close agreement with annual mean satellite SST (27.6 °C). The sub-surface dwelling foraminifera Neogloboquadrina dutertrei and Globigerinoides scitula recorded high-frequency temperature variations that, on average, reflect conditions at water depths of 50–70 m and 200–250 m, respectively. Concentrations and fluxes of organic compounds (alkenones and crenarchaeol) display no or only moderate seasonality but flux weighted means of the associated temperature signatures, , and of 28.3 °C and 28.1 °C, respectively, also closely reflect mean annual SST. We analyzed all time-series data using multiple statistical approaches including cross-correlation and spectral analysis. Eddy variability was clearly expressed in the statistical analysis of physical oceanographic parameters (current velocity and sub-surface temperature) and revealed a frequency of four to six cycles per year. In contrast, statistical analysis of proxy data from the sediment trap did not reveal a significant coupling between eddy migration and organic compound fluxes or reconstructed temperatures. This is likely a result of the relatively low resolution (21 days) and short (2.5 years) duration of the time series, which is close to the detection limit of the eddy frequenc

Rilievo e catalogazione delle prime tipologie edilizie in cemento armato

Hydrographic conditions in the Mozambique Channel are dominated by the passing of large anticyclonic eddies, propagating poleward into the upstream Agulhas area. Further south, these eddies have been found to control the shedding of Agulhas rings into the Atlantic ocean, thereby playing a key role in Indo-Atlantic Ocean exchange. The element composition of several planktonic foraminifera species collected from sediment trap samples, was compared to in situ water column data from the Mozambique Channel. Single-chamber trace element composition of these foraminifera reveals a close coupling with hydrographic changes induced by anticyclonic eddies. Obtained Mg/Ca values for the surface dwelling Globigerinoides ruber as well as the thermocline dwelling Neogloboquadrina dutertrei follow temperature changes and reduced temperature stratification during eddy conditions. At greater depth, Globorotalia scitula and Pulleniatina obliquiloculata record stable temperatures and thus respond to hydrographic changes with a deepening in habitat depth. Furthermore, test Mn/Ca values indicate a close relationship between water column oxygenation and Mn incorporation in these planktonic foraminiferal specie