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Abstract: Nd isotopes are useful tracers for paleoceanography due to the short Nd residence time in seawater and the large differences between the isotopic signatures of various geological reservoirs. Therefore, ɛ Nd variations reflect the geological history of individual oceanic basins. Using a differential dissolution technique, which extracts Nd isotopes of seawater trapped in MnO2 coatings and carbonates in marine sediment, we measured almost two hundred samples from ODP Sites 758 and 757 in the Northern Bay of Bengal covering the last 4 Ma. For the first time, we have shown a covariation between ɛ Nd and δ18O over at least the last 800 ka. We also show that from 4 Ma to 2.6 Ma, ɛ Nd is almost constant and starts to fluctuate at 2.6 Ma when northern glaciations increased. From 2.6 Ma to 1 Ma the fluctuation period is close to 40 ka while from 1 Ma to present it is dominantly 100 ka. We attribute these findings to mixing between Himalayan river water (that ultimately originates as Indian summer monsoon rain) and normal Bay of Bengal seawater. Previous studies on seawater, using ɛ Nd, δ18O analyzed on planktonic foraminifera and sedimentary data, can be integrated into this model. A simple quantitative binary mixing model suggests that the summer monsoon rain was more intense during interglacial than glacial periods. During last glacial episode, the monsoon trajectory was deviated to the east. At a large scale, the Indian monsoon is fully controlled by the variations in Northern Hemisphere climate but with a complex response function to this forcing. Our study clearly establishes the large potential of Nd isotope data to evaluate the hydrological river regime during the Quaternary and its relationship with climate fluctuations, particularly when the sediment archive is sampled close to sediment sources. [ABSTRACT FROM AUTHOR]

High dose selenium acts as a cytotoxic agent, with potential applications in cancer treatment. However, clinical trials have failed to show any chemotherapeutic value of selenium at safe and tolerated doses (<90 μg/day). To enable the successful exploitation of selenium for cancer treatment, we evaluated inorganic selenium nanoparticles (SeNP), and found them effective in inhibiting ovarian cancer cell growth. In both SKOV-3 and OVCAR-3 ovarian cancer cell types SeNP treatment resulted in significant cytotoxicity. The two cell types displayed contrasting nanomechanical responses to SeNPs, with decreased surface roughness and membrane stiffness, characteristics of OVCAR-3 cell death. In SKOV-3, cell membrane surface roughness and stiffness increased, both properties associated with decreased metastatic potential. The beneficial effects of SeNPs on ovarian cancer cell death appear cell type dependent, and due to their low in vivo toxicity offer an exciting opportunity for future cancer treatment. Treatment of high grade serous ovarian cancer cells OVCAR-3 and SKOV-3 with coated selenium nanoparticles highlighted two opposite behaviors depending on the aggressiveness of the cell type. Biomechanical modifications in metastatic SKOV-3 and aggressive OVCAR-3 assessed by Atomic Force Microscopy measurement led to the decreased metastatic potential of SKOV-3 cells and decreased viability of OVCAR-3 cells. Unlabelled Image [ABSTRACT FROM AUTHOR]

A sediment core retrieved from the Andamans Forearc Basin (AFB) near Landfall Island, North Andaman, provides a record of sediment provenance and climate change during the mid to late Holocene. Radiocarbon ages ranging from 6078 to 1658 indicate that the core represents the interval from 6500 BP to the present. Grain size variation indicates a cyclic variation of wetter and drier conditions corresponding to changes in intensity of the Indian Summer Monsoon (ISM), which was at greatest intensity near 6400, 5300 and 3300–3000 BP. Geochemical parameters including abundance of CaCO 3 , εNd and δ 18 O in Globigerinoides ruber are consistent with a long-term trend from cooler, wetter conditions to the warmer, drier conditions at present. Chemical weathering intensity, which lags behind climate changes on land, shows a pulse of highly weathered sediment deposited at about 4000 BP. During the short-duration pulses of intense monsoon activity, sandy sediment was supplied from the Andaman Islands. The Irrawaddy, Salween, and Sittang rivers of Myanmar are the secondary sediment sources for the study area. [ABSTRACT FROM AUTHOR]

Abstract: The Fe–Mn oxide fraction leached from deep-sea sediments has been increasingly used to reconstruct the Nd isotope composition of deep water masses, that can be used to track changes in oceanic circulation with a high temporal resolution. Application of this archive to reconstruct the Nd isotope composition of bottom seawater in shallow shelf environments remained however to be tested. Yet as the Nd isotope composition of seawater on continental margins is particularly sensitive to changes in erosional inputs, establishment of neritic seawater Nd isotope evolution around areas of deep water formation would be useful to discriminate the influence of changes in oceanic circulation and in isotopic composition of erosional inputs on the Nd isotope record of deep waters. The purpose of this study is to test the potential of Fe–Mn coatings leached from foraminifera tests to reconstruct the Nd isotope composition of seawater in shelf environments for deep-time intervals. Albian to Turonian samples from two different outcrops have been recovered, from the Paris Basin (Wissant section, northern France) and from the Western Interior Seaway (Hot Spring, South Dakota, USA), that were deposited in epicontinental seas. Rare Earth Element (REE) spectra enriched in middle REEs in the foraminifera leach at Wissant highlight the presence of Fe–Mn oxides. The similarity of the Nd isotopic signal of the Fe–Mn oxide fraction leached from foraminifera tests with that of fish teeth suggests that Fe–Mn oxides coating foraminifera can be good archives of shelf bottom seawater Nd isotopic composition. Inferred bottom shelf water Nd isotope compositions at Wissant range from −8.5 to −9.7 ε-units, about 1.5–2 ε-units higher than that of the contemporaneous local detrital fraction. At Hot Spring, linear REE spectra characterizing foraminifera leach may point to an absence of authigenic marine Fe–Mn oxide formation in this area during the Late Cenomanian–Early Turonian, consistent with dysoxic to anoxic conditions at Hot Spring, contemporaneous to an Oceanic Anoxic Event. The similarity of the Nd isotopic signal of the carbonate matrix of foraminifera with that of fish teeth suggests that it records the Nd isotope composition of bottom shelf seawater as well. Inferred bottom shelf water Nd isotope compositions at Hot Spring are quite radiogenic, between −7 and −6 ε-units, about 2.5–4 ε-units higher than that of the contemporaneous local detrital fraction. In contrast, in both sections Fe–Mn oxides leached directly from the decarbonated sediment tend to yield a less radiogenic Nd isotopic composition, typically between 0.2 and 0.8 ε-units lower, that is intermediate between that of fish teeth and of the detrital fraction. This suggests the contribution of pre-formed continental Fe–Mn oxides to the Nd isotopic signal, along with authigenic marine oxides, or a detrital contamination during leaching. [Copyright &y& Elsevier]