Flexibility in MOFs: do scalar and group-theoretical counting rules work?

We investigate the ability of counting rules drafted from engineering to predict the flexibility or rigidity of bar-and-joint or body-and-joint assemblies representing metal organic frameworks. We show that while scalar counting rules are not reliable, group-theoretical approaches are able to disentangle mechanisms from states of self-stress and to predict the existence of flexible mechanisms. We give several detailed examples of such calculations, highlighting the fact that behind an abstract exterior they are in fact easy to apply and similar to the method used to obtain molecular vibrations. We also correct a slight misinterpretation of the rigidity of IRMOF-1.

A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST.

Single crystals can commonly have negative Poisson's ratio in a few directions; however more generalised auxeticity is rarer. We propose a typology to distinguish auxetic materials. We characterise numerous single crystals and demonstrate that partial auxeticity occurs for around 37%. We find average auxeticity to be limited to α-cristobalite and no example of complete auxeticity. We simulate two hundreds pure silica zeolites with empirical potentials and quantum chemistry methods, and for the first time identify complete auxeticity in a zeolite network, JST.

eScience for molecular-scale simulations and the eMinerals project.

We review the work carried out within the eMinerals project to develop eScience solutions that facilitate a new generation of molecular-scale simulation work. Technological developments include integration of compute and data systems, developing of collaborative frameworks and new researcher-friendly tools for grid job submission, XML data representation, information delivery, metadata harvesting and metadata management. A number of diverse science applications will illustrate how these tools are being used for large parameter-sweep studies, an emerging type of study for which the integration of computing, data and collaboration is essential.

[Success rate of ultrasonic exploration of the pancreas. Results of 266 followed-up cases]. / Fiabilité de l'exploration ultrasonore du pancréas. Résultats de 266 observations contrôlées.

In two series amounting to 266 cases, the overall success rate of ultrasonic diagnosis, in pancreatic lesions was 94%. Since most of pancreatic lesions, when clinical symptoms are present, are already rather large, imaging improvements did not enhance accurary, except for small lesions. The tenative analysis of small abnormalities can be responsible, with last generation machines, for an increase of false positive diagnoses.

[Ultrasonography in jaundice: signs and results in 199 cases (author's transl)]. / Etude ultrasonore des ictères. Sémiologie. Résultats à propos de 199 cas.

Ultrasonic patterns of bile ducts dilatation were studied in 199 cases. In the most recent series of obstructive jaundices (50 cases) examined with a high resolution machine, the diagnosis of dilatation was made in 92% of cases, the diagnostic of level of obstruction in 92% of cases, and the diagnosis of cause of obstruction in 61% of cases (but in 22 out of 23 jaundices due to a pancreatic lesion: 95%). No false positive diagnosis was made in non obstructive jaundice. Improved technology had a definite impact on the quality of results.

[The ultrasonic diagnosis of jaundice. 199 cases (author's transl)]. / Diagnostic ultrasonore des ictères. 199 malades.

Thank to a thorough ultrasonographic analysis of biliary tree ("shotgun sign"), liver and pancreas, a positive diagnosis of obstruction was carried out in 92% of cases. The success rate in diagnosis of level of obstruction was also 92%. Aetiologic diagnosis was successful in 61% of cases only (almost 100% in jaundices of pancreatic origine). No false positive diagnosis of obstruction was made in non-obstructive jaundice. This enabled to carry out instrumental cholangiography (i.e. "skinny" needle percutaneous cholangiography, and ERC) only in case of clinical, biological and sonographic discrepancies, or in hilar obstructions.