Infrared Optical Properties of Amorphous and Nanocrystalline Ta2O5 Thin Films

The optical constants of tantalum pentoxide (Ta 2O5) are determined in a broad spectral region from the visible to the far infrared. Ta 2O5 films of various thicknesses from approximately 170 to 1600 nm aredeposited using reactive magnetron sputtering on Si substrates. X-ray diffraction shows that the as-deposited films are amorphous, and annealing in air at 800 °C results in the formation of nanocrystallineTa 2O5. Ellipsometry is used to obtain the dispersion in the visible and near-infrared. Two Fourier-transform infrared spectrometers are used to measure the transmittance and reflectance at wavelengths from 1 to 1000 μm. The surface topography and microstructure of the samples are examined using atomic force microscopy, confocal microscopy, and scanning electron microscopy. Classical Lorentz oscillatorsare employed to model the absorption bands due to phonons and impurities. A simple model is introduced to account for light scattering in the annealed films, which contain micro-cracks. For the unannealed samples, an effective-medium approximation is used to take into account the adsorbed moisture in the film and a Drude free-electron term is also added to model the broad background absorption

Midterm outcomes of the Ozaki procedure in patients with a bicuspid aortic valve: retrospective single-center, non-randomized, parallel-group study

BACKGROUND: An alternative to plastic surgery on the bicuspid aortic valve (BAV) can be replacement of the leaflets with autopericardium using the Ozaki technique. The procedure is characterized by excellent hemodynamic results in the short and long term in patients with tricuspid aortic valve (TAV). However, the question remains about the long-term results of the procedure and the frequency of reoperations in patients with BAV. OBJECTIVE: To analyze the midterm outcomes of the Ozaki procedure in patients with BAV. MATERIALS AND METHODS: Retrospective single-center, non-randomized, parallel-group study was conducted. Since January 2015 to October 1, 2023, the clinic performed 809 Ozaki procedures. The work included 540 patients with studied midterm and long-term outcomes for up to 5 years. Both isolated aortic valve replacement and combined operations with coronary artery bypass grafting and (or) correction of mitral and tricuspid valve defects were performed. RESULTS: Midterm mortality was 5.7% (n=3) in the group with BAV and 7.3% (n=36) in the group with TAV. Reoperation for aortic regurgitation was required in 16 patients (2.9%): 1 patient (1.9%) in BAV group and 15 (3.3%) in TAV group. Freedom from reoperations in patients with BAV after the Ozaki procedure for up to 5 years was 95.4%, in the group with TAV — 92.6%. The peak gradient on the aortic valve in the group with BAV was 16±7.3, in TAV group— 16.4±10.9. 5 years after surgery, the mean gradient on the aortic valve does not exceed 10 mm Hg. CONCLUSION: The Ozaki operation in patients with BAV is an effective and safe procedure in the midterm follow-up period

Improved Dehydrogenation Properties of Ti-Doped LiAlH₄: Role of Ti Precursors

The dehydrogenation properties of LiAlH₄ doped with different Ti precursors (Ti, TiO₂, and TiCl₃) via ball milling are investigated. The results not only show significant decreases in the decomposition temperatures (<i>T</i>_dec) and activation energies (<i>E</i>_A) of the first two dehydrogenation reaction steps of LiAlH₄ by doping with TiO₂ or TiCl₃, but also reveal how each Ti precursor affects the dehydrogenation process. Although doping LiAlH₄ with TiCl₃ induced the largest decrease in <i>T</i>_dec and <i>E</i>_A, TiO₂-doped LiAlH₄ produced a decrease in <i>T</i>_dec and <i>E</i>_A that is quite close to the TiCl₃-doped sample as well as superior short-term stability, suggesting that doping with TiO₂ has certain advantages over doping with TiCl₃. Further, the underlying mechanisms associated with the Ti precursors during the dehydrogenation reaction of LiAlH₄ have been studied using quasi in situ X-ray photoelectron spectroscopy. The results reveal that the Ti⁴⁺ and Ti³⁺ reduction processes and the segregation of Li cations to the surface of LiAlH₄ during ball milling play critical roles in the improved dehydrogenation properties observed

Improved Dehydrogenation Properties of Ti-Doped LiAlH4: Role of Ti Precursors

The dehydrogenation properties of LiAlH4 doped with different Ti precursors (Ti, TiO2, and TiCl3) via ball milling are investigated. The results not only show significant decreases in the decomposition temperatures (T-dec) and activation energies (E-A) of the first two dehydrogenation reaction steps of LiAlH4 by doping with TiO2 or TiCl3, but also reveal how each Ti precursor affects the dehydrogenation process. Although doping LiAlH4 with TiCl3 induced the largest decrease in T-dec and E-A, TiO2-doped LiAlH4 produced a decrease in T-dec and E-A that is quite close to the TiCl3-doped sample as well as superior short-term stability, suggesting that doping with TiO2 has certain advantages over doping with TiCl3. Further, the underlying mechanisms associated with the Ti precursors during the dehydrogenation reaction of LiAlH4 have been studied using quasi in situ X-ray photoelectron spectroscopy. The results reveal that the Ti4+ and Ti3+ reduction processes and the segregation of Li cations to the surface of LiAlH4 during ball milling play critical roles in the improved dehydrogenation properties observed