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A large magneto-caloric effect is reported in a La0.8Ca 0.2MnO3 single crystal. The magnetic entropy change (ΔSM) reaches ∼7.25 J/kg K for an applied field of 5 T, which is very practical for magnetic refrigeration applications. Satisfactory agreement between the theoretical calculations on ΔSM derived in the molecular field approximation and the experimental dependency has been found.
We report ultraviolet-induced transient and stable absorption and two-color holographic recording at 514, 633, and 830 nm in thulium doped stoichiometric LiNbO 3 crystal. The gating light at 355 nm increased the diffraction efficiency and sensitivity. We found the optimum gating-recording intensity ratio for maximum diffraction efficiency and weak nonvolatile holographic storage with gating.
We investigated the photoluminescence properties of near-stoichiometric LiNbO3 crystals doped with Tb only and double doped with Tb and Fe. Excitation spectra for the emission from the 5D4 state in both crystals have been studied in the range 200-500 nm. We observed two broad ultraviolet absorption bands and discussed their relations to Tb ions. Temperature dependence of the 5D4 emission intensity
From the ultraviolet induced absorption, we have found a broad blue band and little involvement of Pr ions in ultraviolet illumination. Ultraviolet excited photoluminescence and the excitation spectra for visible emission were also measured in Pr:LiNbO3. We estimated photovoltaic constant and photoconductivity by measuring photovoltaic current and voltage with different boundary conditions. With u
We report on the up-converted emissions at 367, 458 and 483 nm in thulium doped lutetium aluminum garnet (LuAG) under infrared excitation in the range of 730-800 nm. We also observe blue and strong green emission in thulium and holmium codoped LuAG with near infrared excitation. Excitation spectra, power dependence, temporal behavior and temperature dependence of up-converted emissions were measur
PURPOSE: To provide an overview of some of the current activities in eye research in the Nordic countries.METHODS: The presentations at the biannual Nordic Congress of Ophthalmology, held in Tampere, Finland in 2002, were reviewed and the contributions found most noteworthy are included in this article along with a limited discussion of each research field. However, space requirements prevented th
AIMS/BACKGROUND: Increased retinopathy progression has been reported after cataract surgery in patients with diabetes mellitus. To assess the influence of cataract surgery on visual acuity and retinopathy progression, all diabetic patients who were subjected to cataract surgery during 1991-3 have been followed up at the Department of Ophthalmology in Helsingborg. The average follow up time was 2 y
The effect of panretinal laser scatter treatment on visual fields, visual acuity and subjective complaints was assessed in 11 patients with severe nonproliferative or early proliferative diabetic retinopathy. Patients were prospectively examined before and after panretinal treatment using automated static threshold perimetry with program 30-2 on the Humphrey perimeter, and they were interviewed. V
Available studies on visual field disturbances in diabetic retinopathy have shown conflicting results, obtained with different and often non-comparable techniques. We have studied visual fields at different stages of diabetic retinopathy with modern sensitive computerized technique taking precautions to limit disturbing effects of random field variation and lack of perimetric experience. Sixty-thr
Eighty-three patients with high risk ocular hypertension were followed between 9 and 120 months with computerized threshold perimetry every three months in a prospective clinical study. Twenty eyes developed definite glaucomatous visual field defects. Analysis of these cases showed that definite field loss was preceded by increased variability of measured threshold values. Already at this early st
