Search

Robert A Quaife, Jennifer Dorosz, John C Messenger, Ernesto E Salcedo Division of Cardiology, University of Colorado, Aurora, CO, USA Abstract: Calcific aortic stenosis is now understood as a complex valvular degenerative process sharing many risk factors with atherosclerosis. Once patients develop symptomatic calcific aortic stenosis, the only effective treatment is aortic valve replacement. In the past decade, transcatheter aortic valve replacement (TAVR) has been developed as an alternative to surgery to treat severe calcific aortic stenosis. Cardiac imaging plays a pivotal role in the contemporary management of patients with calcific aortic stenosis, and particularly in patients being considered for TAVR, who demand detailed imaging of the aortic valve apparatus. In this review, we highlight the role of cardiac imaging for patient selection, procedural guidance, and evaluation of results of TAVR. Keywords: aortic stenosis, cardiovascular imaging, transcutaneous aortic valve replacement

In the paper the spectroscopic properties of antimony-germanate glass co-doped with Yb3+/Ho3+ has been investigated. Fabricated Yb3+/Tm3+/Ho3+ co-doped glass is characterised by the emission of simultaneous multicolour upconversion luminescence. Strong blue 1G4 → 3H6 (Tm3+), green 5F4 → 5I8 (Ho3+) and red 5F5 → 5I8 (Ho3+) upconversion emission bands have been measured under 976 nm excitation at room temperature. Influence of molar ratio of active ions and excitation power on the colour coordinates (CIE-1931) have been investigated. [ABSTRACT FROM AUTHOR]

The infrared emission of Tm3+/Ho3+-doped antimony-silicate optical fiber has been presented. Luminescence at 2.1 μm corresponding to 5I7 → 5I8 transition in holmium was obtained by energy transfer between Tm3+ and Ho3+ ions. According to the Forster-Dexter theory, the efficiency of energy transfer of the 3F4 (Tm3+) → 5I7 (Ho3+) transition was calculated. The optimization of the activator content and the donor (Tm3+)/acceptor (Ho3+) ions concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of amplified spontaneous emission which formed as a result of energy transfer between thulium and holmium ions were observed in the fiber under exciting with radiation at 795 nm wavelength. [ABSTRACT FROM AUTHOR]

In the article the cooperative energy transfer in Ge02-GaO-BaO glass system doped with Yb3+/Tb3+ under 980 nm laser diode excitation was investigated. The influence of Tb3+ concentration on the luminescent properties was determined. Measured strong luminescence at 489, 543, 586, 621 corresponds to 5D4→7FJ (J = 6, 4, 3) transitions and luminescence at 381, 415, 435 nm results from 5D3, 5G6→7FJ (J = 6, 5, 4) transitions. Mechanism and energy diagram involved in observed emission were discussed. The highest upconversion emission intensity was obtained in the germanate glass doped with 0.7 Yb2O3/0.7 Tb2C>3. [ABSTRACT FROM AUTHOR]

The paper presents luminescence properties of telluride glass doped with Yb3+/Tm3+ ions. Strong blue emission at 477 nm corresponding to the transition ¹G4 → ³H6 in thulium ions was measured under the excitation of a 976 nm diode laser. The dependence of the upconversion emission upon the thulium ions concentration was studied in order to determine the optimal ion content. The results showed that intensity of upconversion emission enhances, with the increase of Tm3+ content up to 0.1 mol.%. The most effective energy transfer Yb3+ → Tm3+ occurs in the glassy matrix with molar ratio of dopant 1 Yb3+ : 0.1 Tm3+. Double-clad optical fibre was made of glass with the highest upconversion intensity at the wavelength of λ = 477 nm (TGPF101). As a result of optical excitation (λ = 976 nm) of the produced optical fibre, an additional emission line, which was not noticed in the glass, was observed at the wavelength of 351 nm corresponding to the ¹D2 → ³H6 transition. [ABSTRACT FROM AUTHOR]

In the article there are presented two different series of glass: fluorophosphate with molar composition: 65P2O5-8Al2O3-2BaO-5BaF2-6ZnF2-5Na2O-6MgF2-3B2O3 and antimony glasses 40Sb2O3-3Al2O3-57SiO2 doped with Nd3+ and Yb3+ ions. Dopant contents influence efficient spatial overlapping of emission level for neodymium and absorption level for ytterbium was analyzed. While exciting the produced glasses with a laser diode (λ = 808 nm) a broad luminescence spectrum (Δλ = 100 nm) has been obtained in both cases in the vicinity of 1 μm, being the superposition of the following transitions: 4F3/2→4I11/2 for Nd3+ and ²F5/2→²F7/2 for Yb3+. Based on the luminescence measurements the probability of non-radiative energy transfer was described. Because of a small difference in energy (≈ 1190 cm-1) between the laser levels of neodymium and ytterbium the resonant process of energy transfer has been obtained. [ABSTRACT FROM AUTHOR]

In the article effect of temperature on the cooperative energy transfer in germanate glass co-doped with Yb3+/Tb3+ under 976 nm laser diode pumping was investigated. The optimization of Tb3+ concentration on the upconversion luminescence was determined. Strong luminescence at 489, 543, 586, 621 nm corresponding to 5D4 → 7FJ (J = 6, 4, 3) transitions and luminescence at 381, 415, 435 nm resulting from 5D3, 5G6 → 7FJ (J = 6, 5, 4) transitions were presented. The highest upconversion emission intensity was obtained in glass co-doped with 0.7 Yb2O3/0.7 Tb2O3 (mol%). The effect of temperature on the luminescent properties of germanate glass in the range of 5-250 °C indicates the presence of competing phenomena: an increase in the effective absorption cross- -section of Yb3+ ions donor as a function of temperature and migration of energy between pairs of ions Yb3+-Yb3+ and of multiphonon excitation levels 7FJ . [ABSTRACT FROM AUTHOR]