RESUMEN
Sulfur- (S-CNT) and nitrogen-doped (N-CNT) carbon nanotubes have been produced by catalytic chemical vapor deposition (c-CVD) and were subject to an annealing treatment. These CNTs were used as supports for small (≈2 nm) Pt3M (M = Co or Ni) alloyed nanoparticles that have a very homogeneous size distribution (in spite of the high metal loading of ≈40 wt % Pt), using an ionic liquid as a stabilizer. The electrochemical surface area, the activity for the oxygen reduction reaction and the amount of H2O2 generated during the oxygen reduction reaction (ORR) have been evaluated in a rotating ring disk electrode experiment. The Pt3M/N-CNT catalysts revealed excellent electrochemical properties compared to a commercial Pt3Co/Vulcan XC-72 catalyst. The nature of the carbon support plays a key role in determining the properties of the metal nanoparticles, on the preparation of the catalytic layer, and on the electrocatalytic performance in the ORR. On N-CNT supports, the specific activity followed the expected order Pt3Co > Pt3Ni, whereas on the annealed N-CNT support, the order was reversed.
RESUMEN
We report the feasibility, indications, and usefulness of an arthroscopic approach to the posterior knee compartments. We developed an arthroscopic approach to the posterior knee compartment involving use of a posteromedial portal and a posterolateral portal opposite each other. Each posterior portal is used in alternation for the arthroscope and instruments. The posterior portals are established using an original "back and forth" technique. The feasibility of the technique was evaluated on a cadaver. It allowed us to define safety rules to protect the vessels and nerves that course through the popliteal fossa. The approach provided a broader field of view compared with classical techniques. After removal of the septum dividing the posterior compartment, the synovial fold enclosing the posterior cruciate ligament and lining the upper and posterior parts of the posterior capsule was readily accessed, suggesting that this approach may be particularly valuable for total synovectomy. This was confirmed in 6 patients with villonodular synovitis, in whom the new approach was used in combination with arthroscopic anterior synovectomy. This technique allows removal of parts of the synovium that are difficult to access through conventional arthroscopic approaches. For total synovectomy, it can be used as an alternative to open posterior synovectomy, in combination with arthroscopic anterior synovectomy.
