ABSTRACT
The microscopic homogeneity of mixed metals in a single-phase oxide is a critical issue in improving material performance. Aqueous alkaline precipitation is the most common approach but it has the limits of microscopic inhomogeneity because of intrinsically different precipitation rates between metal cations. Herein, we demonstrate a new preparation of uniformly structural substituted cobalt iron oxides via acidic redox-assisted precipitation (ARP) upon the interaction of CoII and K2FeO4. This low-pH synthesis features the redox process between Co and Fe, presumably through the formation of inner-sphere complexes such as [(H2O)5CoII-O-FeVIO3]. With the nucleation starting from such complexes, one obtains a product with predominantly mixed-metal Co-O-Fe moieties, which improves the electrical conductivity of the product. This work further analyzes how the properties of the product species evolve during the hydrothermal synthesis step in the ARP process. We see that the Co/Fe ratio slowly increases from about 1:1 to a final value of 2:1, but does not reach the expected redox stoichiometry of 3:1. At the same time, the magnetization also increases, reaching a value of 16.9 emu g-1 for the final superparamagnetic product, which is three times higher than the value of monometallic Co3O4 and Fe2O3. The cobalt iron oxide samples obtained from ARP also possess superior oxygen evolution activity (307 mV overpotential at 10 mA cm-2 µg-1) compared to a mixture of Co3O4 and Fe2O3 (422 mV) or pure cobalt oxide (350 mV), highlighting the structure-induced enhancement of the catalytic activity. The difficult synthesis of evenly blended trinary/quaternary metals in a single-oxide phase may become possible in the future via ARP.
ABSTRACT
Ulnar nerve injury (UNI) is not uncommon and often results in incomplete motor recovery after the initial nerve repair and requires secondary functional reconstruction. To clarify the prognosis and predicting factor of UNI, and if it is reasonable to wait after the initial repair, a systematic literature review from PubMed computerized literature database and Google scholar was performed. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist and guidelines were followed to develop the search protocol for this literature review. Two reviewers independently assessed titles, abstracts, and full-text articles, and a third reviewer resolved any disagreements. Seventeen articles with 260 cases were found with sufficient data and enough follow-up. After multiple logistic regression, age, injury level, gap of lesion, and delayed time to surgery were significant prognostic factors in UNI. If considering only high-level injuries (injury at or above proximal forearm), age became the only predicting factor. In cases with likely poor prognosis, their motor recovery tends to be unsatisfactory, and observation for months after the initial repair might not be reasonable. Other surgical interventions such as early nerve transfer may be an option to improve the outcome.
