Ferromagnetic 1D oxide nanostructures grown from chemical solutions in confined geometries.

This review summarizes the capabilities and recent developments of nanoporous polymeric template systems directly supported on different substrates for the confined growth of epitaxial ferromagnetic complex oxide 1D nanostructures. In particular, we describe the versatility and potentiality of chemical solutions combined with track-etched polymers to synthesize (i) vertical polycrystalline La0.7Sr0.3MnO3 nanorods on top of single crystal perovskites, (ii) single crystalline manganese based octahedral molecular sieve (OMS) nanowires on silicon substrates, and (iii) the epitaxial directional single crystal OMS nanowires on top of fluorite-type substrates. The influence of the distinct growth parameters on the nanostructural evolution of the resulting nanostructures and their magnetic properties is further discussed in detail.

Chemical solution route to self-assembled epitaxial oxide nanostructures.

Self-assembly of oxides as a bottom-up approach to functional nanostructures goes beyond the conventional nanostructure formation based on lithographic techniques. Particularly, chemical solution deposition (CSD) is an ex situ growth approach very promising for high throughput nanofabrication at low cost. Whereas strain engineering as a strategy to define nanostructures with tight control of size, shape and orientation has been widely used in metals and semiconductors, it has been rarely explored in the emergent field of functional complex oxides. Here we will show that thermodynamic modeling can be very useful to understand the principles controlling the growth of oxide nanostructures by CSD, and some attractive kinetic features will also be presented. The methodology of strain engineering is applied in a high degree of detail to form different sorts of nanostructures (nanodots, nanowires) of the oxide CeO2 with fluorite structure which then is used as a model system to identify the principles controlling self-assembly and self-organization in CSD grown oxides. We also present, more briefly, the application of these ideas to other oxides such as manganites or BaZrO3. We will show that the nucleation and growth steps are essentially understood and manipulated while the kinetic phenomena underlying the evolution of the self-organized networks are still less widely explored, even if very appealing effects have been already observed. Overall, our investigation based on a CSD approach has opened a new strategy towards a general use of self-assembly and self-organization which can now be widely spread to many functional oxide materials.

Enabling electromechanical transduction in silicon nanowire mechanical resonators fabricated by focused ion beam implantation.

We present the fabrication of silicon nanowire (SiNW) mechanical resonators by a resistless process based on focused ion beam local gallium implantation, selective silicon etching and diffusive boron doping. Suspended, doubly clamped SiNWs fabricated by this process presents a good electrical conductivity which enables the electrical read-out of the SiNW oscillation. During the fabrication process, gallium implantation induces the amorphization of silicon that, together with the incorporation of gallium into the irradiated volume, increases the electrical resistivity to values higher than 3 Ω m, resulting in an unacceptably high resistance for electrical transduction. We show that the conductivity of the SiNWs can be restored by performing a high temperature doping process, which allows us to recover the crystalline structure of the silicon and to achieve a controlled resistivity of the structures. Raman spectroscopy and TEM microscopy are used to characterize the recovery of crystallinity, while electrical measurements show a resistivity of 10(-4) Ω m. This resistivity allows to obtain excellent electromechanical transduction, which is employed to characterize the high frequency mechanical response by electrical methods.

Applicability and results of Maastricht type 2 donation after cardiac death liver transplantation.

Maastricht type 2 donation after cardiac death (DCD) donors suffer sudden and unexpected cardiac arrest, typically outside the hospital; they have significant potential to expand the donor pool. Herein, we analyze the results of transplanted livers and all potential donors treated under our type 2 DCD protocol. Cardiac arrest was witnessed; potential donors arrived at the hospital after attempts at resuscitation had failed. Death was declared based on the absence of cardiorespiratory activity during a 5-min no-touch period. Femoral vessels were cannulated to establish normothermic extracorporeal membrane oxygenation, which was maintained until organ recovery. From April 2002 to December 2010, there were 400 potential donors; 34 liver transplants were performed (9%). Among recipients, median age, model for end-stage liver disease and cold and reperfusion warm ischemic times were 55 years (49-60), 19 (14-21) and 380 (325-430) and 30 min (26-35), respectively. Overall, 236 (59%) and 130 (32%) livers were turned down due to absolute and relative contraindications to donate, respectively. One-year recipient and graft survivals were 82% and 70%, respectively (median follow-up 24 months). The applicability of type 2 DCD liver transplant was <10%; however, with better preservation technology and expanded transplant criteria, we may be able to improve this figure significantly.

Strong isotropic flux pinning in solution-derived YBa2Cu3O7-x nanocomposite superconductor films.

Power applications of superconductors will be tremendously boosted if an effective method for magnetic flux immobilization is discovered. Here, we report the most efficient vortex-pinning mechanism reported so far which, in addition, is based on a low-cost chemical solution deposition technique. A dense array of defects in the superconducting matrix is induced in YBa(2)Cu(3)O(7-x)-BaZrO(3) nanocomposites where BaZrO(3) nanodots are randomly oriented. Non-coherent interfaces are the driving force for generating a new type of nanostructured superconductor. Angle-dependent critical-current measurements demonstrate that a strong and isotropic flux-pinning mechanism is extremely effective at high temperatures and high magnetic fields leading to high-temperature superconductors with record values of pinning force. The maximum vortex-pinning force achieved at 65 K, 78 GN m(-3), is 500% higher than that of the best low-temperature NbTi superconductors at 4.2 K and so a great wealth of high-field applications will be possible at high temperatures.