416 research outputs found
Palaeoenvironmental changes in the Mediterranean basin 250-10 kyr BP: a review of the evidence
No full textAix-en-Provenc
A topological join construction and the Toda system on compact surfaces of arbitrary genus
No full textWe consider a Toda system of Liouville equations defined on a compact surface
which arises as a model for non-abelian Chern-Simons vortices. For the first
time the range of parameters , , is studied with a variational approach
on surfaces with arbitrary genus. We provide a general existence result by
means of a new improved Moser-Trudinger type inequality and introducing a
topological join construction in order to describe the interaction of the two
components
Correction: Substitution-induced changes in the structure, vibrational, and magnetic properties of BiFeO 3
No full textInternational audienceCorrection for ‘Substitution-induced changes in the structure, vibrational, and magnetic properties of BiFeO 3 ’ by I. Kallel et al. , Mater. Adv. , 2025, 6 , 4893–4904, https://doi.org/10.1039/D4MA00805G
Palaeoenvironmental changes in the Mediterranean region 250-10 kyr BP: a critical review of the evidence
No full textResponse of the pelagic enviroment to palaeoclimatic changes in the central Mediterranean Sea during the Late Quaternary.
No full textGlacial Mediterranean sea surface temperatures based on planktonic foraminiferal assemblages
No full textWe present a new reconstruction of Mediterranean sea surface temperatures (SST) during the last glacial maximum (LGM). A calibration data set based on census counts of 23 species of planktonic foraminifera in 129 North Atlantic and 145 Mediterranean core top samples was used to develop summer, winter and annual average SST reconstructions using artificial neural networks (ANNs) and the revised analogue method (RAM). Prediction errors determined by cross-validation of the calibration data set ranged between 0.5 and 1.1 °C, with both techniques being most successful in predicting winter SSTs. Glacial reconstructions are based on a new, expanded data set of 273 samples in 37 cores with consistent minimum level of age control.The new LGM reconstructions suggest that the east–west temperature gradient during the glacial summer was 9 °C, whereas during the glacial winter, the gradient was 6 °C, both some 4 °C higher than that existing today. In contrast to earlier studies, our results tend to suggest much cooler SST estimates throughout the glacial Mediterranean, particularly in the eastern basin where previous SST reconstructions indicated a decrease of only 1 °C. Our new SST reconstructions will provide the modelling community with a detailed and updated portrayal of the Mediterranean Sea during the LGM, setting new targets on which glacial simulations can be tested
L’enregistrement régulier du temps par une levée turbiditique (NEOFAN du Rhône, Mer Méditerranée) : apports de la palynologie
No full textBeaudouin Célia, Dennielou Bernard, Guichard François, Melki Tarek, Berne Serge, Kallel Nejib, Huchon Agnès. L’enregistrement régulier du temps par une levée turbiditique (NEOFAN du Rhône, Mer Méditerranée) : apports de la palynologie. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. p. 33
Synthesis, characterization and optical spectroscopy of GdPO4:Er3+
No full textA series of Er3+-doped GdPO4 phosphors was synthesized using a conventional solid-state reaction. The monazite structure (space group P121/n1) of the obtained materials was confirmed using X-ray diffraction and Fourier transform infrared spectroscopy. Their optical spectra (excitation, emission, absorption, decay curves) were measured at room temperature in the visible and near-infrared (NIR) regions. The UV–visible–NIR optical absorption spectrum of GdPO4:7% Er3+ was analyzed based on Judd–Ofelt (J–O) theory and the J–O intensity parameter (Ω2, Ω4, Ω6) was calculated. J–O intensity parameters were used to evaluate spontaneous emission properties such as branching ratios, transition probabilities, and radiative lifetime. The calculated quantum efficiency of the 1.5 μm emission (4I13/2−4I15/2) was calculated to be 89%. This result proved that GdPO4:Er3+ is suitable for use in optical amplifiers and is a potential host for laser applications. The most interesting transitions, located at about 540 nm, and 1.0 and 1.5 μm were investigated as a function of doping level and of temperature, to assess the conditions needed for the highest emission performance and to explore the range of application, in particular in the fields of lighting, thermal sensing, and of phosphors for bio-imaging
Diagenetic Mg-rich calcite in Mediterranean sediments: quantification and impact on foraminiferal Mg/Ca thermometry
No full textMg/Ca ratios in planktonic foraminifera have been developed into a powerful tool in paleoceanography to
reconstruct past sea surface temperatures (SST). However, additional factors that might have an influence on
Mg/Ca, like dissolution, salinity, diagenesis, and carbonate ion effects have come into focus. In this paper, the
occurrence of diagenetic calcification and its potential effects on Mg/Ca have been studied using 20 wellpreserved
core tops recovered from the Mediterranean Sea. Analyses were performed on two planktonic
foraminifer species; Globigerinoides ruber and Globigerina bulloides using ICP-AES Mg/Ca measurements, SEM
observations and X-ray diffractometry analyses.
Foraminiferal Mg/Ca values are higher than those obtained in the open sea. The highest values were found in
the Eastern Mediterranean basin. These anomalies cannot be simply explained by a salinity effect because Mg/
Ca ratios, when corrected for temperature influence, do not display any significant correlation with salinity.
Our results seem to indicate that diagenesis can account for anomalously high Mg/Ca values. Indeed, SEM
observations show aggregates of rhombohedral crystals that could be interpreted as secondary calcite
overgrowths. We note also the occurrence of numerous coccoliths trapped in foraminifer walls and covered
with a secondary mineral phase.
X-ray diffraction diagrams of numerous foraminiferal samples exhibit peak of Mg-rich calcite (10–12%)
associated with the usual foraminifer calcite peak. It has been demonstrated that this calcite highly rich in Mg,
is compatible with an inorganic calcite precipitated directly from seawater.
The deconvolution of the main XRD peak (104) shows that the percentage of Mg-rich calcite can reach up to
~21% of the total foraminiferal calcite in the Eastern basin whereas in the western Mediterranean Sea,
proportions do not exceed 5%. In addition, we demonstrate that, the diagenetic process is very heterogeneous
(even at the sample scale) and is not simply a reflection of ΔCO3 at the sea bottom. Thus, the high Mg/Ca ratios
measured from Mediterranean Sea planktonic foraminifera does not appear to be caused by increased Mg
uptake in a high salinity setting, but instead result chiefly from the presence of Mg rich calcite (10–12%)
deposited during early diagenetic processes
Effect of 17 alpha-Ethinylestradiol Exposure on Phycocyanin Metabolite Production and Antioxydant System of Phormidium Versicolor NCC466
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