1,721,132 research outputs found
One-stage off pump combined transapical aortic valve replacement and ascending aorta endografting
No full textAn 84-year-old patient was referred for severe symptomatic aortic valve stenosis and focal chronic dissection of the ascending aorta. After multidisciplinary discussion, the patient was scheduled for combined transapical transcatheter aortic valve replacement and ascending aorta stent-grafting. The procedure was performed with a balloon aortic valvuloplasty followed by a custom-made stent graft implantation into the ascending aorta and then by balloon-expandable transapical transcatheter aortic valve replacement. The patient had an uneventful hospital stay. In conclusion, in selected high-risk patients, transapical combined ascending aorta stent-grafting and transcatheter aortic valve replacement are feasible and safe
Emergency Endovascular Total Arch Exclusion With an Off-the-Shelf Bimodular Device
No full textA patient with a history of surgery for type A acute aortic dissection was readmitted for aortic arch and descending aortic dissection with rupture at the isthmus and periaortic hematoma. Due to the high surgical risk, the aortic team chose an endovascular approach, and the patient successfully underwent emergency total arch exclusion with an off-the-shelf, bimodular, single-branch device. The main module was deployed in the aortic arch and in the brachiocephalic trunk, and the second module was deployed in the ascending aorta. Despite the good perioperative outcome with no cerebrovascular events, the patient died 20 days later because of sudden iliac rupture
Valve-shaped thrombus underneath an aortic bioprosthesis
Full text linkWe describe massive thrombus formation completely occluding an aortic bioprosthesis in a patient with venoarterial extracorporeal membrane oxygenation and apical venting. The thrombus was surgically removed and the patient recovered with no complications. Timely identification and immediate surgical removal of thrombi may allow patient recovery with no severe complications
Crystal structure and chemical composition of Li-, Fe-, and Mn-rich micas
No full textWe present in this paper the crystal chemical characterization of three (Fe, Mn)-rich lithian trioctahedral micas. The samples are from Hirukawa mine (Japan) (unit formula: [iv](Si3.425Al0.575)4.00[vi](Al1.002Ti0.002Cr0.001Fe0.379Mg0.005Mn0.173Li1.438)3.00 [xii](Ca0.002Ba0.001Na0.049K0.948Rb0.002)1.00 O10F2 ; unit-cell dimensions: a = 5.264(1), b = 9.086(2), c = 10.099(3) Å, β = 100.719(5)°, V = 474.6(2) Å3); from Mokrusha mine (Russia) (unit formula: [iv](Si3.304Al0.696)4.00 [vi](Al1.004Ti0.001Fe0.362Mg0.005 Mn0.306Li1.322)3.00 [xii](Ca0.012Ba0.001Na0.042K0.940Rb0.005)1.00 O10F2; unit-cell dimensions: a = 5.297(5), b = 9.133(7), c = 10.168(9) Å, β = 100.78(2)°, V = 483.2(7) Å3); and from Sawtooth Mountains (Boise County, Idaho, U.S.A.) (unit formula: [iv](Si3.105Al0.895)4.00 [vi](Al0.913Ti0.018 Fe0.456Mg0.031 Mn0.521Li1.061)3.00 [xii](Ca0.004Ba0.003Na0.048K0.924Rb0.021)1.00 O10F2; unit-cell dimensions a = 5.2984(3), b = 9.1461(6), c = 10.0966(7) Å, β = 100.818(4)°, V = 480.58(5) Å3). All crystals belong to 1M polytype with layer symmetry C12(1) and show M1 and M3 sites much greater than M2. Moreover mean electron count values are much more variable for M1 and M3 sites than for M2. Unlike sample from Sawtooth Mountains, tetrahedral mean bond lengths appear to be smaller for T1 than for T11 site in Hirukawa mine and in Mokrusha mine.When compared to samples from the zinnwaldite series, crystals under study show similar crystal chemical trends, thus hinting to similar effects produced on layer structure by Fe and Mn cations
Angular dependence of potassium K-edge XANES spectra of trioctahedral micas: Significance for the determination of the local structure and electronic behavior of the interlayer site.
No full textThe X-ray absorption angle-dependent behavior at the potassium K-edge has been determined for two end-members and two intermediate trioctahedral micas, which are representative of the Fe2+Mg-1, Fe3+Al-1, SiAl-1FeLi-1, and F-1OH exchange vectors, using horizontally polarized synchrotron radiation. Experimental spectra are interpreted by the multiple scattering theory following decomposition according to the angular dependence approach of Brouder (1990). The experimental spectra sum up anisotropic effects deriving from in-plane and out-of-plane photoelectron interactions with the potassium near- and next-near neighbors up to the fifth/sixth coordination sphere. For the first time, the absorption edge of a low Z atom is decomposed so as to produce two partial patterns giving, respectively, the full in-plane absorption spectrum (σ
Order-disorder in the octahedral sheet of metamorphic 2M1-phengites: A combined EMPA and AXANES study.
No full textTwo types of metamorphic phengites are known: one is linked to high pressure and is 3T; the other is 2M1, and its composition is linked to rock-compositional constraints. This work investigates the octahedral sheet crystal-chemical differences between the two phengite types. Seven dioctahedral micas were studied: (1) one 3T phengite from an ultrahigh-pressure metagranitoid in the Dora Maira massif, Italy (P ~ 4.3 GPa, T ~ 730 °C); (2) five 2M1 phengites from medium-P orthogneisses in the Eastern Alps metamorphic basement, Italy (P ≤ 0.7 GPa, T ~ 500–600 °C); and (3) one 2M1 ferroan muscovite from pegmatite in Antarctica (P ≤ 0.2 GPa, T ~500 °C). All micas display significant extents of celadonite substitution. In particular, the 2M1-phengite formulae (calculated on the basis of 11 O) have 0.68 < IVAl < 0.82 atoms per formula unit (apfu); octahedral atoms are dominated by Al (1.6–1.8 apfu), with minor and variable Fe (0.20–0.35 apfu) and Mg (0.05–0.17 apfu), and very minor Ti, Mn, and Cr. Total octahedral occupancies are slightly above 2.00 apfu, i.e., there seems to be partial occupancy of the third M site. For all micas, we recorded XAFS spectra on mosaics of carefully separated flakes oriented flat on a plastic support that could be rotated so as to account for the polarization of the synchrotron radiation beam, and we processed them on the basis of the AXANES theory. Spectra show angle-dependent absorption variations for Al and Fe, which can be deconvoluted and fitted by dichroic effects. Pre-edges consistently show most Fe to be Fe3+ and little angle-dependent intensity variations. The 2M1-ferroan muscovite from Antarctica displays the same AXANES behavior as 2M1-phengites. By contrast, the ultrahigh-pressure 3T-phengite from Dora Maira (having IVAl = 0.42 apfu, and Al and Mg as the dominant octahedral constituents) has XAFS spectra that differ significantly. Not only is the IVAl feature strongly reduced, in agreement with the increased Si content, but also Fe XAFS spectra show one broad feature only, indicating that all Fe is Fe2+ in a fully disordered distribution with no angle-dependent variations. We conclude that this 3T-phengite is actually contaminated by exsolved Fe-bearing pyrope platelets, which cannot be resolved under SEM examination; by contrast, the 2M1-phengites, unrelated to high-pressure, suggest Al/Fe3+ order over the M1 and (M2, M3) sites, as also does the 2M1 pegmatitic muscovite
Potassium coordination in trioctahedral micas by K-edge XANES spectroscopy
No full textFine-grained homogeneous powder samples of thirteen trioctahedral micas, mostly intermediate members of the phlogopite – annite solid solution series, and samples close to the phlogopite, fluor-phlogopite and tetra-ferriphlogopite end members have been examined at the potassium K-edge by X-ray absorption fine structure spectroscopy. The interlayer K+ cation is in a coordination that is certainly lower than 12, in contrast to what is expected from the ideal hexagonal symmetry model of the mica structure, and approaches – but it does not reach – coordination 6, as it should be when the effective ligands are the three nearest outer bridging oxygens of two facing upper and lower tetrahedral sheets. The observed range of coordinations implies that only some of the three inner bridging oxygen atoms in each sheet are involved, thus leading to 6±(1...6) effective configurations depending on the composition of the individual mica terms. The effective coordination number was found to vary continuously with composition from 11 to 7 and to be related to the tetrahedral rotation angle (α) according to two different linear relationships for the phlogopite – annite series (Fe2+Mg−1 exchange vector, involving the octahedral sheet only) and the phlogopite – tetra-ferriphlogopite series (Fe3+Al−1 vector, involving the tetrahedral sheet), respectively. Substitutions affecting either the A cation in the interlayer or the X anion in the octahedral sheet also affect the observed trends. In particular, the latter substitution effect is best seen in two near end member phlogopites, where the fluorine to hydroxyl substitution (F− (OH)−−1 exchange vector), which greatly changes the α tetrahedral rotation angle is, reflected in the experimental K XANES spectra by modifying not only the energy but also the intensities of most multiple scattering features
Crystal structure and chemical composition of Li, Fe, and Mn micas
No full textThe crystal chemistry of three Li-, Fe-, and Mn-rich trioctahedral micas has been characterized by single-crystal X-ray diffraction. The samples are from Hirukawa mine, Japan, from Mokrusha mine, Russia and from Sawtooth Mountains, Boise County, Idaho, U.S.A.. Our crystals belong to the 1M polytype with layer symmetry C121(1) and show M1 and M3 sites much larger in size than M2. Mean electron-count (m.e.c.) values are more variable for the M1 and M3 sites than for M2. With the exception of the sample from Sawtooth Mountains, all tetrahedral mean bond lengths appear to be smaller for T1 than for T11 site. When compared to the Li- and Fe-rich series, crystals show similar crystal-chemical trends, thus suggesting that the layer structure is affected in a similar way by Fe and Mn cations
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