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Tb[sup 3+]-doped Lu[sub 2]O[sub 3] sintered ceramics were prepared in vacuum and in air. It was shown that the vacuum-sintered disks are able to store energy when irradiated with 300-nm or shorter photons. A small part of the stored energy could be recovered with 980-nm light. A much more significant amount of the stored energy could be released with red 647-nm photons. However, recovering the total stored energy could be accomplished only upon heating up to about 300 °C. Changes in absorption of the raw materials upon ultraviolet irradiation and subsequent IR (980 and 647 nm) treatments or upon heating at 300 °C are presented and discussed. A model for energy storing and recovering through the various IR irradiations or through heating is presented. At least two distinct ways of hole trapping as Tb[sup 4+] or V[sub k]-center as well as creation off and F[sup +] is suggested. [ABSTRACT FROM AUTHOR]

Abstract Perfectly transparent ceramics of La 0.4 Gd 1.6 Zr 2 O 7 doped with either Eu3+ or Pr3+ ions were prepared by high-temperature vacuum sintering. Results of the Rietveld structure refinement and spectroscopic properties of the ceramics are presented and discussed in details. Photoluminescence characteristics support the non-uniformity in the crystal structure of ceramics. X-ray excited luminescence of La 0.4 Gd 1.6 Zr 2 O 7 :Eu was rather inefficient and the Pr-doped ceramics showed no Pr-related radioluminescence. Instead they produced Eu3+ emission characteristic for Gd 2 O 3 :Eu phase not detected in X-ray diffraction patterns. Highlights • Structure refinement of La 0.4 Gd 1.6 Zr 2 O 7 transparent ceramics revealed non-uniformity of its crystal structure. • Photoluminescence confirmed the multisite occupancy of the activator in Eu3+/Pr3+-doped La 0.4 Gd 1.6 Zr 2 O 7 transparent ceramics. • The Eu3+ presence as well as gadolinia contamination was analyzed through photo-/radioluminescence. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline Lu2O3 doped with 1at.% of Eu was obtained precipitating hydroxide of lutetium with urea at 80°C from water solution and decomposing the hydroxide to oxide at 500°C. Polyvinyl alcohol was used to hinder the particles growth during precipitation. The average size of the fabricated particles was 2–5nm. Although at 500°C the hydroxide decomposed to Eu-doped Lu2O3 traces of OH impurities were present in the material unless heated at 1200°C. Radioluminescence was very poor for samples heated at 800°C or lower temperature. After heating the precipitated powder at or above 1200°C the efficiency jumped 45 times reaching 75% of the output from commercial microcrystalline Gd2O2S:Eu. The properties make nanocrystalline Lu2O3:Eu prepared in the described way a promising X-ray phosphor for planar digital medical imaging. [Copyright &y& Elsevier]

The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu2O3 in the eutectic mixture of NaNO2 and KNO2. It was shown that a crystallographically pure phase of the cubic Lu2O3 is formed at temperature as low as 250 °C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18–30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu3+ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO3)3 was noticeably higher compared to the product obtained from LuCl3. The excitation spectrum of Eu3+ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer. [Copyright &y& Elsevier]

Two series of Lu2O3:Eu nanocrystalline phosphors were prepared using either combustion procedure with urea fuel or the Pechini procedure. The dopant concentration varied in both series from 0.2 to 13% with respect to Lu. Despite full crystallization and very similar microstructure of materials of both series, we found profound variations in their spectroscopic properties. The combustion-made phosphors were much less efficient emitters and their emission was strongly concentration-quenched above 3% of the dopant content. For the Pechini-derived materials, the concentration quenching was not observed below 10% of the dopant content and even for the dopant concentrations equal to 10 and 13% the quenching was insignificant. In EPR spectra for Gd3+-doped materials, a significant broadening of lines was found for the combustion-made powders. All these observations imply a strong agglomeration of the dopant ions in the specimens made by applying urea fuel in the combustion process. A semi-two-phase composition was suggested in the combustion-prepared powders. In the Pechini-derived nanocrystalline powders, the dopant ions are uniformly, statistically distributed in the host lattice. [Copyright &y& Elsevier]

Nanocrystalline powders of Lu2O3:Eu with the activator content varying in the range of 0.2–10% were prepared through a combustion technique. The powders were only slightly agglomerated and the size of crystallites were about 30 nm. Some of the powders were co-doped with Mg, Ca, Sr, Ba, La of various concentrations. Such powders were cold-pressed and sintered at 1750°C for 5 h in vacuum. X-ray-excited luminescence spectra of both the powders and the sintered ceramics were recorded and the efficiency was compared to the commercial standard Gd2O2S:Pr,Ce,F X-ray phosphor. It was found that the nanocrystalline powders of Lu2O3:Eu,Ca emit photons four-times less than the commercial micron-sized Gd2O2S:Pr,Ce,F powder. In the case of sintered materials the emission efficiency from our Lu2O3:Eu5%, Ca was roughly equal to the efficiency of the commercial-sintered Gd2O2S:Pr,Ce,F. The co-doping ions were shown to have various effects on the transparency of the sintered Lu2O3:Eu. Mg hindered the sintering process producing completely opaque pellets. Other ions facilitated the sintering course and the best results were obtained by co-doping the samples with 0.5% of Ba. Sr and La also significantly stimulated the sintering and the final pellets were only slightly cloudy. [Copyright &y& Elsevier]

Decay kinetics and X-ray diffraction patterns of Lu 2 O 3 :Eu with concentration of the dopant spanning 0-20% were measured for two series of materials with crystallites sized of 13 nm and 35 nm. For the series of smaller crystallites a very significant concentration quenching was observed, while for the larger crystallites the effect was minor only. Detailed structural analysis made it possible to postulate that this effect is related to an inhomogeneous distribution of Eu 3+ ions within the smaller crystallites. [ABSTRACT FROM AUTHOR]

Abstract: La2Hf2O7 nanopowders doped with different Pr concentrations (0.05–10mol.%) were synthesized by the Pechini method. XRD measurements confirmed the single crystalline phase formed already at 800°C and the structure was cubic pyrochlore. Luminescence excitation and emission as well as radioluminescence spectra were recorded for the materials. Both optical and X-ray excitation of La2Hf2O7:Pr produced a red emission resulting from the 4f–4f transitions of Pr3+ ions. Luminescence of materials synthesized at low temperatures was characterized by broadband glass-type emissions, while heat treatment at 1400°C led to spectra showing the typical for crystalline hosts narrow and intense 4f–4f transitions of Pr3+. [Copyright &y& Elsevier]

Abstract: Ceramic specimens of singly doped Lu2O3:Tb, and doubly activated Lu2O3:Tb,Ca, Lu2O3:Tb,Hf and Lu2O3:Pr,Hf were prepared and their thermoluminescent properties were investigated. After irradiation with X-rays or deep-UV photons the singly doped Lu2O3:Tb was found to produce a glow curve with a few thermoluminescent bands spread across the temperature range of 50–450°C. (Tb,Ca) co-doped material produced basically one strong thermoluminescent band peaking at around 120°C and thus was able to produce persistent luminescence lasting about 10h, as visible to the human eye. In the (Tb,Hf) co-doped ceramics the thermoluminescence at around 100°C was seen as a vestige only and was responsible for persistent emission lasting merely a few minutes. Instead, a strong thermoluminescence glow band at around 250°C appeared. Its intensity faded by about 10% after 6hours in the dark. Lu2O3:Pr,Hf co-doped ceramics also showed intense thermoluminescence with the main components at around 200°C and 270°C. The latter was found not to fade in time, while intensity of the former dropped by about 7–8% after 6h. All these effects were observed in ceramics processed at temperatures as high as 1700°C. It is proposed that high temperature of processing is necessary as only then clustering of individual defects occurs and the energy released upon heating can diffuse towards the nearby located emitting center efficiently. [Copyright &y& Elsevier]

Abstract: Molten salt synthesis procedure, homogeneous precipitation with urea and -flux aided routes are presented as interesting fabrication methods for making oxide luminescent materials. The properties of the powders made using these techniques are presented and analyzed. Emphasis is put on spectroscopic characterization of the products. [Copyright &y& Elsevier]

Objectives: The aim of this report is to assess the safety of endovascular treatment for chronic cerebrospinal venous insufficiency (CCSVI). Although balloon angioplasty and stenting seem to be safe procedures, there are currently no data on the treatment of a large group of patients with this vascular pathology. Methods: A total of 564 endovascular procedures (balloon angioplasty or, if this procedure failed, stenting) were performed during 344 interventions in 331 CCSVI patients with associated multiple sclerosis. Results: Balloon angioplasty alone was performed in 192 cases (55.8%), whereas the stenting of at least one vein was required in the remaining 152 cases (44.2%). There were no major complications (severe bleeding, venous thrombosis, stent migration or injury to the nerves) related to the procedure, except for thrombotic occlusion of the stent in two cases (1.2% of stenting procedures) and surgical opening of femoral vein to remove angioplastic balloon in one case (0.3% of procedures). Minor complications included occasional technical problems (2.4% of procedures): difficulty removing the angioplastic balloon or problems with proper placement of stent, and other medical events (2.1% of procedures): local bleeding from the groin, minor gastrointestinal bleeding or cardiac arrhythmia. Conclusions: The procedures appeared to be safe and well tolerated by the patients, regardless of the actual impact of the endovascular treatments for venous pathology on the clinical course of multiple sclerosis, which warrants long-term follow-up. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the immunohistological components of chronic inflammation in endarterectomy lesions. Therefore, in 24 patients endarterectomy specimens were obtained from coronary arteries during CABG surgery (16 from RCA and 8 from LCA) and immunohistologically analyzed using avidin-biotin method (LSAB®/AP) with monoclonal antibodies. Macrophages and CD3 lymphocytes were counted under 200× magnification but MHC class II and ICAM-1 adhesion molecules were analyzed semi-quantitatively (scale from 0 to 3+). The mean macrophages density was 47.8±9.8 cells per mm2 and mean CD3 lymphocyte density was 1.3±0.6 cells per mm2. Lack or weak expression of HLA-DR (0–1+) on macrophages was found in 17 of 24 cases (70.8%). In the remaining seven cases (29.2%) there was a moderate and strong expression (2+ and 3+) of HLA-DR antigens. Similarly, no or weak ICAM-1 expression on macrophages was detected in 19 cases (79.2%). These cells were positively stained for ICAM-1 in only five cases (20.8%). Our data suggest that in advanced primary atherosclerotic lesions chronic inflammation is still present. On the other hand, the small number of activated inflammatory cells and the absence of positively stained endothelium suggests that inflammatory process tends to be burnt-out. [Copyright &y& Elsevier]