Recommendations for ophthalmologic practice during the easing of COVID-19 control measures

In the context of the COVID-19 pandemic, this paper provides recommendations for medical eye care during the easing of control measures after lockdown. The guidelines presented are based on a literature review and consensus among all Spanish Ophthalmology Societies regarding protection measures recommended for the ophthalmologic care of patients with or without confirmed COVID-19 in outpatient, inpatient, emergency and surgery settings. We recommend that all measures be adapted to the circumstances and availability of personal protective equipment at each centre and also highlight the need to periodically update recommendations as we may need to readopt more restrictive measures depending on the local epidemiology of the virus. These guidelines are designed to avoid the transmission of SARS-CoV-2 among both patients and healthcare staff as we gradually return to normal medical practice, to prevent postoperative complications and try to reduce possible deficiencies in the diagnosis, treatment and follow-up of the ophthalmic diseases. With this update (5th) the Spanish Society of Ophthalmology is placed as one of the major ophthalmology societies providing periodic and systematized recommendations for ophthalmic care during the COVID-19 pandemic

Double excitation transitions in Mn2+ -doped alkali halides

4 págs.; 4 figs.It is shown in this work that the room-temperature excitation spectra of as-grown crystals of LiF, NaF, NaCl, KCl, and KBr doped with Mn2+ reveal the existence of double excitation peaks. These peaks are related to the formation of precipitated phases containing Mn2+ in the alkali halide lattice. In the case of LiF:Mn2+ the position of the [A14(G), E4(G)] and T14(G) peaks suggests an anomalously small Mn2+- F- distance for the precipitated phase. © 1983 The American Physical Society.Financial support by the Comision Asesora para la Investigacion Cientifica y Tecnica, is gratefully acknowledged.Peer Reviewe

MS-Xα and extended huckel calculations on lif : Ni

Selfconsistent charge Extended Huckel calculations on clusters including up to 81 atoms as well as MS-Xα calculations on a 27 atoms cluster have been performed in order to investigate theoretically a good number of E.P.R. and optical parameters for LiF:Ni+ with elongated octahedron symmetry around Ni+. In agreement with experimental data the present results give fσ close to 1%, xy→x2-y2 excitations close to 6000 cm-1 while the charge transfer transitions lie in the vacuum ultraviolet region. The mainly 3d levels lie in the gap about 4 eV above the top of the valence band while the mainly 4p levels lie about 2 eV below the bottom of the conduction band. The levels mainly built from 2 p(F') of four ligands are also strongly localized in the distorted NiF65- complex but located not on the top of the valence band but about 3.5 eV below. When the "equatorial" Ni+-F- distance, Req, decreases a) the energy of charge-transfer and crystal-field excitations increases, b) fs increases much more rapidly than fσ, although √fs/Ss is practically constant, independent of Req. This fact supports the use of the isotropic superhyperfine constant for measuring the true Req value

Optical and vibrational properties of (MnF6)4- complexes in cubic fluoroperovskites: insight through embedding calculations using Kohn-Sham equations with constrained electron density

The local structure and optical and vibrational properties associated with Mn2+-doped cubic AMF3 (A = K, Rb; M = Mg, Zn, Cd) fluoroperovskites are studied by means of embedding calculations using Kohn–Sham equations with constrained electron density. It is shown that while an electronic parameter like 10Dq essentially depends on the Mn2+–F− distance, the local vibration frequencies ωi (i = a1g, eg modes) are dominated by the interaction between F− ligands and nearest M2+ ions lying along bonding directions. The high ωa values observed for KMgF3:Mn2+ and KZnF3:Mn2+, the huge variations of ωe and ωa frequencies when the host lattice is changed, as well as the increase of Huang–Rhys factors and the Stokes shift following the host lattice parameter, are shown to be related to this elastic coupling of the MnF64− complex to the rest of the host lattice. The present results support the conclusion that the Stokes shift is determined by the interaction of the excited 4T1g state with a1g and eg local modes while the coupling with the t2g shear mode is not relevant. The variations of local vibrational frequencies and the Stokes shift induced by a hydrostatic pressure on a given system are shown to be rather different to those produced by the chemical pressure associated with distinct host lattices