Glomerular Filtration Rate (GFR) is one of the cardinal indices of renal function and is used clinically as the gold standard of renal dysfunction. In the past decade, many studies using dynamic contrast-enhanced MRI (DCE MRI) to measure GFR have been published. The MRI evaluation of GFR centers on visualizing the passage of contrast material (Gadolinium chelates) through the kidney. MRI appears as a promising tool but still relatively difficult to implement in the assessment of GFR. A high heterogeneity of protocols (e.g., in acquisition mode, dose of contrast, postprocessing techniques) is noted in the literature, reflecting the number of technical challenges that should first be solved in order to reach a consensus, and the reported accuracy and reproducibility are insufficient for justifying their use in clinical practice now. This paper presents and discusses the different steps that can be used to quantify the GFR by MRI. (C) 2011 Elsevier Masson SAS and Editions francaises de radiologie. All rights reserved.

We report on the electronic properties of Cs-intercalated single-walled carbon nanotubes (SWNTs). A detailed analysis of the C-13 and Cs-133 nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The 'metallization' of CsxC materials where x = 0-0.144 is evidenced from the increased local electronic density of states (DOS) n(E-F) at the Fermi level of the SWNTs as determined from spin-lattice relaxation measurements. In particular, there are two distinct electronic phases called alpha and beta and the transition between these occurs around x = 0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x < 0.05 (alpha-phase), whereas it reaches a plateau in the range 0.05 <= x <= 0.143 at high intercalation levels (beta-phase). The new beta-phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp(2)) orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(E-F), corresponding to different local electronic band structures of the SWNTs.

Structural and dynamical properties of the THF solvent in single-walled carbon nanotubes intercalated with lithium are investigated by NMR. H-1 NMR experiments reveal the existence of two types of inequivalent THF solvent molecules with different chemical environments and dynamical behavior. At low temperatures THF molecules perpendicularly arranged in between adjacent SWNT presumably exhibit a restricted rotation around their dipolar axis. At higher temperatures THF molecules are isotropically rotating and diffusing along the interstitial channels of the SWNT bundles. (C) 2011 Elsevier B.V. All rights reserved.

Le principe de la RMN/IRM est basé sur la détection du spin d’un noyau atomique par exemple le 13C, 31P et le proton 1H. L'échantillon est placé dans un champ magnétique statique (4.7 Tesla) qui polarise les spins. L’aimantation est basculée par des impulsions radiofréquences (200MHz, longueur d’onde de l’ordre du mètre). La relaxation de l'aimantation génère un champ électromagnétique à la fréquence de Larmor qui est détecté par une antenne de réception. Dans notre cas, nous utilisons une sonde de taille micrométrique que nous positionnons à une distance sublongueur d’onde de l’objet. Nous sommes donc en champ proche et donc dans les conditions de détection des ondes évanescentes. Nous travaillons à améliorer les résolutions fréquentielles et spatiales en volume de ce système.

The understanding and control of the magnetic properties of carbon-based materials is of fundamental relevance in applications in nano- and biosciences. Ring currents do play a basic role in those systems. In particular the inner cavities of nanotubes offer an ideal environment to investigate the magnetism of synthetic materials at the nanoscale. Here, by means of C-13 high resolution NMR of encapsulated molecules in peapod hybrid materials, we report the largest diamagnetic shifts (down to -68.3 ppm) ever observed in carbon allotropes, which is connected to the enhancement of the aromaticity of the nanotube envelope upon doping. This diamagnetic shift can be externally controlled by in situ modifications such as doping or electrostatic charging. Moreover, defects such as C-vacancies, pentagons, and chemical functionalization of the outer nanotube quench this diamagnetic effect and restore NMR signatures to slightly paramagnetic shifts compared to nonencapsulated molecules. The magnetic interactions reported here are robust phenomena independent of temperature and proportional to the applied magnetic field. The magnitude, tunability, and stability of the magnetic effects make the peapod nanomaterials potentially valuable for nanomagnetic shielding in nanoelectronics and nanobiomedical engineering.

Hydrogenation of C-60 molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C-60 hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution C-13 and H-1 NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp(3) carbon resonances. We estimate that approximately 78% of the C-60 molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C-60 molecule. As a consequence, the rotational dynamics of the encapsulated C60Hx molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale.

Carbon nanotubes functionalized with sulfonated polyether-ether-ketone are investigated using solid state nuclear magnetic resonance. Carbon and proton NMR experiments of the sulfonated polymer chains covalently grafted on the nanotube surface reveal a distribution of diamagnetic shifted lines. These experimental results can be interpreted at the molecular level in terms of magnetic ring currents originating from the surface of the graphitized wall of the nanotubes in agreement with recent theoretical investigations. These features can potentially be used to track the structural modifications, which take place during the functionalization of carbon nanotubes.