ABSTRACT
An electride is a compound that contains a localized electron in an empty crystallographic site. This class of materials has a wide range of applications, including superconductivity, batteries, photonics, and catalysis. Both polymorphs of Yb5Sb3 (the orthorhombic Ca5Sb3F structure type (ß phase) and hexagonal Mn5Si3 structure type (α phase)) are known to be electrides with electrons localized in 0D tetrahedral cavities and 1D octahedral chains, respectively. In the case of the orthorhombic ß phase, an interstitial H can occupy the 0D tetrahedral cavity, accepting the anionic electron that would otherwise occupy the site, providing the formula of Yb5Sb3Hx. DFT computations show that the hexagonal structure is energetically favored without hydrogen and that the orthorhombic structure is more stable with hydrogen. Polycrystalline samples of orthorhombic ß phase Yb5Sb3Hx (x = 0.25, 0.50, 0.75, 1.0) were synthesized, and both PXRD lattice parameters and 1H MAS NMR were used to characterize H composition. Magnetic and electronic transport properties were measured to characterize the transition from the electride (semimetal) to the semiconductor. Magnetic susceptibility measurements indicate a magnetic moment that can be interpreted as resulting from either the localized antiferromagnetically coupled electride or the presence of a small amount of Yb3+. At lower H content (x = 0.25, 0.50), a low charge carrier mobility consistent with localized electride states is observed. In contrast, at higher H content (x = 0.75, 1.0), a high charge carrier mobility is consistent with free electrons in a semiconductor. All compositions show low thermal conductivity, suggesting a potentially promising thermoelectric material if charge carrier concentration can be fine-tuned. This work provides an understanding of the structure and electronic properties of the electride and semiconductor, Yb5Sb3Hx, and opens the door to the interstitial design of electrides to tune thermoelectric properties.
ABSTRACT
OBJECTIVES: The objectives of the study were (1) systematically review the data on surgical closure of enlarged tracheoesophageal fistula after laryngectomy and (2) to perform a comparison of reconstruction of surgical techniques. METHODS: Systematic review was performed using PRISMA methodology. Cumulative patient data were compared between patients reconstructed with vascularized tissue (sternocleidomastoid fascia and muscle, pectoralis major, deltopectoral, radial forearm) and those closed primarily (two-layer, three-layer, and tracheal transposition). RESULTS: Fourteen studies reported outcomes for the reconstruction of tracheoesophageal fistula. Primary closure was used in 98 patients, vascularized flap in 74, and occlusive device in 8. Vascularized flap resulted in successful closure of the fistula in 89 % of cases compared to primary closure in 62 % (p = 0.0003). CONCLUSION: Systematic review of the literature supports an improved surgical closure rate with vascularized flap interposed between the esophageal and tracheal lumens compared to primary closure.
