Morphological and Magnetic Properties of Superparamagnetic Carbon-Coated Fe Nanoparticles Produced by Arc Discharge.

Spherical carbon coated iron particles of nanometric diameter in the 510 nm range have been produced by arc discharge at near-atmospheric pressure conditions (using 58·10 4 Pa of He). The particles exhibit a crystalline dense iron core with an average diameter 7.4 ± 2.0 nm surrounded by a sealed carbon shell, shown by transmission electron microscopy (TEM), selected-area diffrac- tion (SAED), energy-dispersive X-ray analysis (STEM-EDX) and electron energy loss spectroscopy (EELS). The SAED, EDX and EELS results indicate a lack of traces of core oxidized phases showing an efficient protection role of the carbon shell. The magnetic properties of the nanoparticles have been investigated in the 5300 K temperature range using a superconducting quantum interference device (SQUID). The results reveal a superparamagnetic behaviour with an average monodomain diameter of 7.6 nm of the nanoparticles. The zero field cooled and field cooled (ZFC-FC)magnetization curves show a blocking temperature (TB)at room temperature very suitable for biomedical applications (drug delivery, magnetic resonance imaging MRI, hyperthermia).

Petrology, geochemistry and geodynamic implications of Jurassic island arc magmatism as revealed by mafic volcanic rocks in the Mesozoic low-grade sequence, eastern Rhodope, Bulgaria

In the eastern Bulgarian Rhodope, mafic extrusive rocks and underlying greenschists are found in the Mesozoic low-grade unit, which represents the northern extension of similar sequences including the Evros ophiolites in Thrace (Greece). Both rock types define a suite of low-Ti tholeiitic basalts to transitional boninitic basaltic andesites and andesites and associated metapyroclastites (greenschists), intruded at its base by diorite dikes of a boninitic affinity. Mafic lavas and greenschists display large ion lithophile element (LILE) enrichment relative to high-field strength elements (HFSE), flat REE patterns of a slight light REE depletion, a strong island arc tholeiite (IAT) and weak MORB-like signature. All these rocks are characterized by negative Nb anomalies ascribed to arc lavas. They have positive epsilon Nd(i) values in the range of +4.87 to +6.09, approaching the lower limit of MORB-like source, and relatively high ((207)Pb/(204)Pb)(i) (15.57-15.663) at low ((206)Pb/(204)Pb)(i) (18.13-18.54) ratios. The Nd isotopic compositions coupled with trace element data imply a dominantly depleted MORB-like mantle source and a contribution of subduction modified LILE-enriched component derived from the mantle wedge. The diorite dike has a low eNdi value of -2.61 and is slightly more Pb radiogenic ((207)Pb/(204)Pb)(i) (15.64) and ((206)Pb/(204)Pb)(i) (18.56), respectively, reflecting crustal contamination. Petrologic and geochemical data indicate that the greenschists and mafic extrusive rocks represent a magmatic assemblage formed in an island arc setting. The magmatic suite is interpreted as representing an island arc-accretionary complex related to the southward subduction of the Meliata-Maliac ocean under the supra-subduction back-arc Vardar ocean/island arc system. Magmatic activity appears to have initiated in the north during the inception of the island arc system by the Early-Middle Jurassic time in the eastern Rhodope that most likely graded to back-arc spreading southwards as represented by the Late Jurassic MORB-type Samothraki Island ophiolites. This tectonic scenario is further constrained by paleotectonic reconstructions. The arc-trench system collided with the Rhodope in the Late Jurassic times. (c) 2007 Elsevier B.V. All rights reserved.

[Défilé du 14 juillet 1919 sous l'Arc de triomphe de l'Etoile] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54922

[Défilé du 14 juillet 1919 sous l'Arc de triomphe de l'Etoile] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54923

[Défilé du 14 juillet 1919 sous l'Arc de triomphe de l'Etoile, tanks] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54925

[Défilé du 14 juillet 1919, les tanks passent sous l'Arc de triomphe de l'Etoile] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54945

[Défilé du 14 juillet 1919, soldats américains passant sous l'Arc de triomphe de l'Etoile] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54951

[Défilé du 14 juillet 1919 passant sous l'Arc de triomphe de l'Etoile] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54952

[Défilé du 14 juillet 1919 passant sous l'Arc de triomphe de l'Etoile, armée française] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54953

[Défilé du 14 juillet 1919 passant sous l'Arc de triomphe de l'Etoile, véhicules blindés] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54954

[Défilé du 14 juillet 1919 passant sous l'Arc de triomphe de l'Etoile, armée française] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54956

[Défilé du 14 juillet 1919 passant sous l'Arc de triomphe de l'Etoile, un maréchal à cheval et l'armée française] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54957

[Défilé du 14 juillet 1919, l'Arc de triomphe de l'Etoile et la foule] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 54958