[Cardiac surgery in Cameroon. Results at one year of the pilot phase]

In the framework of implementation of his national program for control and prevention of cardiovascular diseases, Cameroonian government has set up a cardiac surgery project. We report in this manuscript results of one year follow up of the patients operated during the pilot phase. From September 22 till 26, 2008, 11 patients have been operated in Cameroun. Surgical procedures were 5 mitral mechanic valve replacement, 2 aortic mechanic valve replacement, 1 atrial septal defect closure, 2 pace maker implantation. No intrahospital death was observed. One patient died at 11th month after the operation due to mitral valve thrombosis and attributed to lack of compliance. One patient presented low cardiac output, pneumonia and a pleural effusion. 2 patients presented 2 minor complications consisting of pericarditis and superficial wound infection. The results of the pilot phase of cardiac surgery in Cameroon are effective. However, the sustainability of the program require human, material capacity building, and funding mechanism as well.

Probing the stereo-electronic properties of cationic rhodium complexes bearing chiral diphosphine ligands by 103Rh NMR

(103)Rh NMR represents a powerful tool to assess the global electronic and steric contribution of diphosphine ligands on [Rh(COD)(diphosphine)](+) complexes. In the case of DIOP, BINAP and MeDUPHOS, this approach proved to be more informative than classical CO-stretching frequency measurements. After validation, this method has been extended to a set of seven diphosphines. (103)Rh NMR measurements on [Rh(COD)(diphosphine)]PF(6) lead to the following order of donor properties: dppe > MeBPE > MeDUPHOS > dppb > DIOP > BINAP > Tol-BINAP. This trend has been validated by DFT in the case of DIOP, BINAP and MeDUPHOS. In conjunction, (31)P NMR chemical shift has been shown to reflect the ring constraints of the Rh-diphosphine scaffold. This contribution is a step towards a mechanistic investigation of the catalytic hydrogenation of unsaturated substrates by (103)Rh NMR and DFT.

Ignition and explosion risks of nanopowders

Characterization methods with regard to nanopowder flammability and explosivity are presented and illustrated for few nanopowders. Analytical models are developed in order to explain the dependency of the combustion times on the particle diameter. Experimental evidence shows that there exists, for carbonaceous and metallic materials, mainly two combustion regimes that are either kinetically controlled, for small size particles, or diffusion controlled, for large size particles. From the experimentally measured combustion data of those materials, the dependencies of the ignition temperature and the minimal explosive concentration (MEC) with regard to the particle size have been analyzed. We found that the two combustion regimes yield two different tendencies with respect to the particle size. Overall, it is found that as the particle size decreases, minimum ignition temperature (MIT) and minimum ignition energy (MIE) decrease, indicating higher potential inflammation and explosion risks for the use of nanopowders. By contrast, the minimal explosion concentration (MEC) did not show strong variations as the particle size decreases. Rather, a theoretical plateau is observed, which was experimentally confirmed. We also observed that carbon nanopowders exhibit a low propensity to explode while metallic nanopowders can be very reactive, thus delineating high potentials for explosion risks in manufacturing facilities.

Elucidation of the self-assembly pathway of lanreotide octapeptide into beta-sheet nanotubes: role of two stable intermediates

Nanofabrication by molecular self-assembly involves the design of molecules and self-assembly strategies so that shape and chemical complementarities drive the units to organize spontaneously into the desired structures. The power of self-assembly makes it the ubiquitous strategy of living organized matter and provides a powerful tool to chemists. However, a challenging issue in the self-assembly of complex supramolecular structures is to understand how kinetically efficient pathways emerge from the multitude of possible transition states and routes. Unfortunately, very few systems provide an intelligible structure and formation mechanism on which new models can be developed. Here, we elucidate the molecular and supramolecular self-assembly mechanism of synthetic octapeptide into nanotubes in equilibrium conditions. Their complex hierarchical self-assembly has recently been described at the mesoscopic level, and we show now that this system uniquely exhibits three assembly stages and three intermediates: (i) a peptide dimer is evidenced by both analytical centrifugation and NMR translational diffusion experiments; (ii) an open ribbon and (iii) an unstable helical ribbon are both visualized by transmission electron microscopy and characterized by small angle X-ray scattering. Interestingly, the structural features of two stable intermediates are related to the final nanotube organization as they set, respectively, the nanotube wall thickness and the final wall curvature radius. We propose that a specific self-assembly pathway is selected by the existence of such preorganized and stable intermediates so that a unique final molecular organization is kinetically favored. Our findings suggests that the rational design of oligopeptides can encode both molecular- and macro-scale morphological characteristics of their higher-order assemblies, thus opening the way to ultrahigh resolution peptide scaffold engineering.

Molecular and serological analysis of the epidemiology of myxoma virus in rabbits

The epidemiology of myxoma virus was studied by serology and molecular analysis of restriction fragment length polymorphisms (RFLPs) in genomic DNA. 159 isolates of myxoma virus were made over a period of 5 spring/summer epidemics from 12 field sites in south-eastern Australia. Virus isolates were classified into 10 genetic types using RFLPs detected with a panel of nine restriction endonucleases. Between 3 and 6 different genetic types were found during spring/summer periods across all sites and up to 3 different genetic types were isolated during an epidemic on a single site. The predominant type tended to change each year. A widespread mutation was identified in two genetic types with replacement of the 3' two-thirds of the M009L gene at the left hand inverted terminal repeat junction with a duplication of the region containing the M156R, M154L and M153R genes from the right hand end of the genome. This demonstrated how myxoma virus can potentially evolve by expansion of the inverted terminal repeat boundaries.