Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn4+ and Mg2.

In this report, red-emitting alumina nanophosphors doped with Mn4+ and Mg2+ (Al2O3:Mn4+, Mg2+) are synthesized by a hydrothermal method using a Pluronic surfactant. The prepared samples are ceramic-sintered at various temperatures. X-ray diffraction shows that Al2O3:Mn4+, Mg2+ annealed at 500 °C exhibits a cubic γ-Al2O3 phase with the space group Fd3m-227. The tetragonal δ-Al2O3 and rhombohedral α-Al2O3 phase is obtained at 1000 and 1300 °C, respectively. Cube-like nanoparticles in a size of ∼40 nm are observed for the alumina heated at 500-1000 °C. The size and red-emitting intensity of the phosphors remarkably increased with annealed temperature ∼1300 °C. Emission spectra of the phosphors show strong peaks at 678 and 692 nm due to 2 E g → 4 A 2 transitions of the Mn4+ ion, under a light excitation of 460 nm. A strong zero-phonon line (ZPL) emission is observed in the luminescence spectra of δ-Al2O3:Mn4+, Mg2+ at 298 K, whereas a weak one is observed in those of α- and γ-Al2O3:Mn4+, Mg2+. The alumina phosphors exhibited an excellent waterproof ability during 60 days in water and good thermal stability in the range of 77-573 K. A warm-white light-emitting diode (WLED) fabricated using In x Ga1-x N nanowire chips with Al2O3:Mn4+, Mg2+ red-emitting nanophosphors presents a high color rendering index of ∼95.1 and a low correlated color temperature of ∼4998 K. Moreover, the current-voltage characteristic of the nanowire LEDs could be improved using Al2O3:Mn4+, Mg2+ nanophosphors which is attributed to the increased heat dissipation in the nanowire LEDs.

Results of the one-stage proximal hypospadias repair with modified Koyanagi technique: A prospective cohort study in a single Vietnam centre.

INTRODUCTION: Proximal hypospadias is the most severe type of hypospadias. Our approach to Koyanagi technique for proximal hypospadias aims to improve the blood supply to the neourethral flaps and reduce meatal complications. METHODS: Our prospective study included 75 patients who were operated for proximal hypospadias by our Koyanagi technique at Viet Duc hospital between January 2019 and December 2020. The clinical information obtained included a detailed medical history; preoperative, intraoperative, and postoperative data; short-term outcomes by the HOSE score were evaluated by a different physician. RESULTS: The mean (range) age was 3.59 ± 2.41 years (1.5-14), 86.7% under 5 years old. There are 31 penoscrotal, 31 scrotal, and 13 perineal hypospadias. The length of the neourethra ranged from 3.5 to 8 cm, mean 5.02 ± 0.88 cm. Evaluation of the surgeon at 6 months after surgery: primary success 81.3%. Complications occurred in 14 cases (18.7%), included 10 urethrocutaneous fistula and 4 dehiscence of the urethra. No cases of meatal stenosis or recession, urethral stricture, urethral diverticula. The mean HOSE score was found to be 14.47 ± 1.35, ranged 11 to 16. 57 patients (76%) had a total HOSE 14 and above and 18 patients had score below 14 (24%). CONCLUSION: Our modified Koyanagi technique give us a good result for one-stage reconstruction of proximal hypospadias. Applying the HOSE score makes postoperative evaluation of hypospadias more objective and reliable.

Core-shell strain structure of zeolite microcrystals.

Zeolites are crystalline aluminosilicate minerals featuring a network of 0.3-1.5-nm-wide pores, used in industry as catalysts for hydrocarbon interconversion, ion exchangers, molecular sieves and adsorbents. For improved applications, it is highly useful to study the distribution of internal local strains because they sensitively affect the rates of adsorption and diffusion of guest molecules within zeolites. Here, we report the observation of an unusual triangular deformation field distribution in ZSM-5 zeolites by coherent X-ray diffraction imaging, showing the presence of a strain within the crystal arising from the heterogeneous core-shell structure, which is supported by finite element model calculation and confirmed by fluorescence measurement. The shell is composed of H-ZSM-5 with intrinsic negative thermal expansion whereas the core exhibits a different thermal expansion behaviour due to the presence of organic template residues, which usually remain when the starting materials are insufficiently calcined. Engineering such strain effects could have a major impact on the design of future catalysts.