Porosity of closed carbon nanotubes compressed using hydraulic pressure

Experimental data of nitrogen adsorption (T = 77.3 K) from gaseous phase measured on commercial closed carbon nanotubes are presented. Additionally, we show the results of N2 adsorption on compressed (using hydraulic press) CNTs. In order to explain the experimental observations the results of GCMC simulations of N2 adsorption on isolated or bundled multi-walled closed nanotubes (four models of bundles) are discussed. We show that the changes of the experimental adsorption isotherms are related to the compression of the investigated adsorbents. They are qualitatively similar to the theoretical observations. Taking into account all results it is concluded that in the "architecture" of nanotubes very important role has been played by isolated nanotubes

Obstacles on the way to the clinical visualisation of beta cells: looking for the Aeneas of molecular imaging to navigate between Scylla and Charybdis

For more than a decade, researchers have been trying to develop non-invasive imaging techniques for the in vivo measurement of viable pancreatic beta cells. However, in spite of intense research efforts, only one tracer for positron emission tomography (PET) imaging is currently under clinical evaluation. To many diabetologists it may remain unclear why the imaging world struggles to develop an effective method for non-invasive beta cell imaging (BCI), which could be useful for both research and clinical purposes. Here, we provide a concise overview of the obstacles and challenges encountered on the way to such BCI, in both native and transplanted islets. We discuss the major difficulties posed by the anatomical and cell biological features of pancreatic islets, as well as the chemical and physical limits of the main imaging modalities, with special focus on PET, SPECT and MRI. We conclude by indicating new avenues for future research in the field, based on several remarkable recent results

Endless fiber-to-fiber polarization controller based on ceramic programmable waveplates

International audienceIn this letter, we report a fast and endless polarization controller based on lead lanthanum zirconate titanate (PLZT) ceramic programmable waveplates. A set of four volume electrodes placed in a cylindrical arrangement are drilled in an electrooptic ceramic plate. By using the Kerr effect, and taking advantage of the high electrooptic coefficient and fast response time of the PLZT, we thus, obtain a fast rotatable and variable waveplate. Then, cascading two of these waveplates produces an endless polarization controller