TEM image analysis and modelling: application to boehmite nanoparticles.

Boehmite occurs in the form of nanoparticles. Upon drying, it can form the alumina that is common in catalyst support used in refining and petrochemicals. The topotactic transformation of boehmite alumina led to an interest in the precise shape and size of these nanoparticles which is highly linked to the catalyst activity. Boehmite nanoparticles can be observed by transmission electron microscopy. Although they are highly aggregated, the analysis of transmission electron microscopy images with a specific random model approach, here a dilution model, can give an accurate estimate of their size. To use this approach, electronic noise and diffraction artefacts on the edges of the nanoparticles have to be removed. Covariance measurements on micrographs can be performed. They can be used to fit a model. The fitting uses a novel numerical method to estimate the covariogram of grains. The model can take into account the specific orientations of the nanoparticles. The influence of noise, image filters used to remove noise and diffraction artefacts, as well as all the parameters of the model are all studied in this paper. We propose nanoparticle size estimations procedures based on both single and mixture-of-two particle models.

Development of an intracerebral glioma model in whole body irradiated hairless rats.

AIMS: To study the in vivo radiosensitivity of malignant gliomas, an animal glioma model was developed using the implantation of glioma cell lines into the brain of the Hairless rat (a mutant from the Sprague-Dawley strain, characterised by its complete absence of hair). METHODS: 10(6) malignant cells were suspended in 10 microliters phosphate buffered saline (PBS) and injected at a 4 microns depth into the left frontal lobe of an anaesthetised animal through a small craniotomy hole without opening the dura mater. The glioma cell line C6 (obtained from a chemically-induced rat glioblastoma) was introduced into 11 animals, and the human glioblastoma line G5 into 12 animals. RESULTS: The tumour take was checked using histological criteria. It was poor: 0% for the G5 line and only 27.3% for the C6 line. To improve the tumour growth rate, rats were subjected to a single dose (3.5 Gray) total body irradiation, 24 hours prior to injection, causing a marked immunosuppression. 84.6% of the rats grafted with the C6 line then produced tumours. Similar results (75% tumour take) were obtained using a stereotactic inoculation of the tumour cells. CONCLUSIONS: Thanks to the contribution of whole body irradiation, an animal intracerebral glioma model was establish, which can be used for clinical and biological studies.

Characterization of an Al-, Ga-based catalyst by Ga NMR and XAS.

Both Nuclear Magnetic Resonance (NMR) and X-Ray absorption spectroscopies characterize local order around the observed nuclei. With the recent progresses of 71Ga solid state NMR, it has become possible to take advantage of the complementary information that can be obtained using these two methods. This opens the possibility of a more thorough description of the first coordination shells of Ga in oxide. We present and discuss the example of an Al-, Ga-based catalyst.

Crystallographic, X-ray absorption, and IR studies of solid- and solution-state structures of tris(nitrato) N,N,N',N'-tetraethylmalonamide complexes of lanthanides. Comparison with the Americium complex.

To fine-tune the design of optimized donor ligands for nuclear waste actinide selective extraction, both electronic and molecular structures of the actinide complexes that are formed must be investigated. In particular, to achieve the selective complexation of transplutonium 3+ ions versus lanthanide 3+ ions is one of the major challenges, given the chemical similarities between these two f-element families. In this work, the structure of solvent-phase M(NO3)3(TEMA)2 complexes (Ln = Nd, Eu, Ho, Yb, Lu, Am; TEMA = N,N,N',N'-tetraethylmalonamide) was investigated by liquid-phase spectroscopic methods among which extended X-ray absorption fine structure played a major role. In addition, the crystal structures of the species Nd(NO3)3(TEMA)2 and Yb(NO3)3(TEMA)2 have been determined by X-ray diffraction. Nd(NO3)3(C11N2O2H22)2 crystallizes in the monoclinic system (P2(1) space group; a = 11.2627(4) A, b = 20.5992(8) A, c = 22.2126(8) A; alpha = gamma = 90 degrees, beta = 102.572(1) degrees; Z = 6), and Yb(NO3)3(C11N2O2H22)2 crystallizes in the orthorhombic system (P2(1)2(1)2(1) space group; a = 9.3542(1) A, b = 18.1148(2) A, c = 19.7675(2) A; alpha = beta = gamma = 90 degrees; Z = 4). In the solvent phase, the metal polyhedron was found to be similar to that of the solid-state complex Nd(NO3)3(TEMA)2 for M = Nd to Ho. For M = Yb and Lu, a significant elongation of one nitrate oxygen bond was observed. Comparison with measurements on the Am(NO3)3(TEMA)2 complex in ethanol has shown the similarities between the Nd3+ and Am3+ coordination spheres.