All-optical regeneration techniques

Basic principles of all-optical signal regeneration are presented, and main state-of-art techniques are reviewed. Optical fiber and semiconductor based devices are addressed, and some recently reported 2R and 3R signal regeneration experiments are discussed.     

Primary hyperparathyroidism. Optimization of surgical results with systematic preoperative 99mTc-Sestamibi scintigraphy

OBJECTIVE: The importance of preoperative 99mTc Sestamibi (MIBI) scintigraphy in case of reoperation for persistent hyperparathyroidism is well recognized, but it use as a systematic exploration technique remains a question of debate. We conducted this study to determine whether preoperative MIBI scans performed in all cases before surgery have any real impact. METHOD: Two successive series of 65 operated patients were included in the study. In the first group, the MIBI scan was not performed prior to surgery while in the second group the MIBI scan was part of the systematic work-up. RESULTS: The sensitivity and positive predictive value of MIBI were 92% and 96% respectively. Sensitivity for unique adenomas was 95% and 80% for multiple forms. In the first group without systematic scans, there were two unproductive procedures. In the second group, all procedures were productive and no reoperations were required. Two mediastinal adenomas were removed at the first cervicotomy in this group. The rate of complications was similar for both groups. Mean operation time was 2 hours in the first group and 1 hour 30 minutes for the second. CONCLUSION: Our series shows that there are three main advantages of using MIBI scintigraphy systematically prior to surgery for hyperparathyroidism: the procedure is easier in patients with cervical adenomas, particularly in case of ectopic localizations; the mean duration of the operation is shortened by 30 minutes; mediastinal ectopic localizations can be removed by sternotomy at the first operation. These advantages appear to be great enough to propose systematic use of MIBI scan prior to surgery. When MIBI scan shows a single gland, the risk of missing a multiple localization is less than 2% in our experience. It appears possible to operate under local anesthesia via a single-sided approach in elderly patients or high-risk patients.     

Correlations between the catalytic layer composition,the relative humidity and the performance for PEMFC carbon aerogel based membrane electrode assemblies

The parameters influencing the water management or the gas diffusion have a large impact on the performances of the PEMFC. In this work, we focused on the influence of the composition of the cathode catalytic layer on the performance of the MEA in relation to the relative humidity. A carbon aerogel was synthesized as catalyst support with a texture minimizing diffusive losses. We studied the influence of the Nafion content by preparing various cathode catalytic layers whose hydric properties were modified by adding PTFE as a hydrophobic agent. We evaluated the impact of the cathodic relative humidity by testing MEAs on a single cell test bench. We showed that modifying the composition of the catalytic layers playing on the content of both Nafion and PTFE, enables to improve the performance due to a better water management. The best performance was obtained with a Nafion/Carbon mass ratio (N/C) of 0.5 and a PTFE/Carbon (PTFE/C) mass ratio of 0.35 allowing 40% more power at 0.4 V and 75%RH. A first positive evaluation of the impact of PTFE is also done with TEC10E40E.     

Determination of key parameters responsible for polymeric liner collapse in hyperbaric type IV hydrogen storage vessels

Depressurization tests at a laboratory scale, coupled with numerical modelling, are used to determine the key parameters responsible for the polymeric liner collapse in hyperbaric type IV hydrogen storage vessels. X-ray tomography allows to determine the damages suffered by the sample during the depressurization step. Results show that the differential pressure induced during the depressurization step between the liner/composite interface and the free surface of the liner is the main factor responsible for the collapse of the liner. For a given temperature, this pressure gradient can be modified by changing the maximum H₂ pressure, the emptying rate or by adding a residual pressure plateau. Temperature is also of prime importance by influencing the yield point of the liner, the interface resistance and the amount of gas dissolved into the vessel. Thus, increasing temperature also increases the risk of liner collapse for the same gas exposure conditions.     

Thermal and fire degradation of recycled and polluted polypropylene‐based materials

In this study, the effect of processing cycles and two pollutants (engine oil (HM) and ethylene glycol (EG)) on the thermal and rheological properties of polypropylene‐based materials (108MF97 and 7510) has been studied. It was investigated if polymers coming from bumper face bar could keep their properties and can be reused after recycling. The different results demonstrate that the two polymers that were polluted and recycled do not show any decrease of their intrinsic properties. Moreover, for one of the two polymers (108MF97), the presence of engine oil enables to increase the thermal stability and reaction to fire. Finally, it appears that the reuse of such polymers is possible. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Monitoring demyelination and remyelination by magnetization transfer imaging in the mouse brain at 9.4 T

OBJECTIVE: The aim of this study was to assess quantitatively structural changes in myelin content occurring during demyelination and remyelination by magnetization transfer imaging (MTI). MATERIALS AND METHODS: In a reversible model of demyelination with no axonal loss, mice intoxicated by cuprizone were studied by MTI in vivo at 9.4 T. MRI data were compared to histopathological examinations. RESULTS: Data revealed that the magnetization transfer ratio (MTR) decreased significantly during demyelination and increased during remyelination with strong correlation to the myelin content (r = 0.79, P = 0.01). CONCLUSIONS: This study demonstrated that MTR is a sensitive and reproducible quantitative marker to assess myelin loss and repair. This may lead to in vivo monitoring of therapeutic strategies promoting remyelination.