Scintillation efficiency and X-ray imaging with the RE-Doped LuAG thin films grown by liquid phase epitaxy

Very thin scintillator imaging plates have recently become of great interest. In high resolution X-ray radiography, very thin scintillator layers of about 5–20 μm are used to achieve 2D-spatial resolutions below 1 μm. Thin screens can be prepared by mechanical polishing from single crystals or by epitaxial growth on single-crystal substrates using the Liquid Phase Epitaxy technique (LPE). Other types of screens (e.g. deposited powder) do no reach required spatial resolutions. This work compares LPE-grown YAG and LuAG scintillator films doped with different rare earth ions (Cerium, Terbium and Europium). Two different fluxes were used in the LPE growth procedure. These LPE films are compared to YAG:Ce and LuAG:Ce screens made from bulk single crystals. Relative light yield was detected by a highly sensitive CCD camera. Scintillator screens were excited by a micro-focus X-ray source and the generated light was gathered by the CCD camera’s optical system. Scintillator 2D-homogeneity is examined in an X-ray imaging setup also using the CCD camera.     

Ce3+-doped crystalline garnet films – scintillation characterization using α-particle excitation

Scintillating properties of Ce³⁺-doped (Lu,Y) aluminum garnet single crystalline films (SCF) were investigated. Thin SCF films of thickness between 1 and 30 μm were grown by a liquid phase epitaxy (LPE) method in various fluxes. The α-particle excitation (mainly 5.4857 MeV line of ²⁴¹Am) of pulse height spectra is used to measure scintillation response of SCF, especially peak of those α-rays which are totally absorbed in the films. Detailed studies and evaluation of scintillation measurements of large sets of Ce³⁺-doped SCF (Lu,Y) aluminum garnets showed that at present time (i) YAG:Ce SCF have comparable scintillation properties as YAG:Ce single crystals, especially their N_phels photoelectron yields are the same while (ii) scintillation properties of LuAG:Ce SCF do not reach those of LuAG:Ce single crystal.     

Effect of γ irradiation on optical properties of Ce-doped phosphate and silicate scintillating glasses

A set of Ce³⁺ activated silicate- and phosphate-based scintillating glasses were submitted to γ irradiation in the ⁶⁰Co radioisotope source “Calliope” (ENEA-Casaccia in Rome, Italy) in the dose range between 1 and 250 Gy (3.7 Gy/h). The effect of ionising radiation was probed by transmission measurements performed before and after each irradiation on all analysed samples. From these data, the radiation-induced absorption coefficient was calculated, proportional to the density of colour centres induced by irradiation in the solid matrix. Results are discussed by taking into account the possible dependence of radiation hardness on the composition of glass matrix.     

In silico identification of the protein disulfide isomerase family from a protozoan parasite

Protein disulfide isomerase (PDI) enzymes are eukaryotic oxidoreductases that catalyze the correct formation of disulfide bonds during protein folding. Structurally they are characterized by the presence of functional thioredoxin-like (Trx) domains. For the protozoan parasite causative of the human amebiasis (Entamoeba histolytica), the correct formation of disulfide bonds is important for an accurate folding of its proteins, including some virulence factors. However, little is known about the enzymes involved in this mechanism. We undertook a post-genomic approach to identify the PDI family of this parasite. The genome database survey revealed a set of 11 PDI-encoding sequences with predictable protein thiol/disulfide oxidoreductase activities.     

Effect of selenium in organic and inorganic form on liver,kidney, brain and muscle of <Emphasis Type="Italic">Wistar</Emphasis> rats

Selenium is a micronutrient, localized in the active sites of enzymes such as glutathione peroxidase and thioredoxin reductase, and participating together with these enzymes in an antioxidant defence system of organisms against free radicals. Administration of selenium is necessary for maintaining oxidative homeostasis. The present experiment is aimed at investigation of selenium impact on basal metabolic processes and selected antioxidants in a Wistar rat model, fed selenium in organic and inorganic forms. Liver, kidney, brain and muscle were sampled during a month-long feeding with four different doses of selenium (0.075 mg or 1.5 mg of inorganic and/or organic selenium per kg of feed). We found a significant reduction in glutathione level in liver tissue regardless of the form of the administered selenium. On the other hand, selenium caused a decreased glutathione reductase level in the liver and metallothionein level in the liver, kidney and muscle.      

Luminescence and scintillation characteristics of YAG:Ce single crystalline films and single crystals

The detailed comparative analysis of luminescent and scintillation properties of the single crystalline films (SCF) of YAG:Ce garnet grown from melt-solutions based on the traditional PbO-based and novel BaO-based fluxes, and of a YAG:Ce bulk single crystal grown from the melt by the Czochralski method, was performed in this work. Using the ²⁴¹Am (α-particle, 5.49 MeV) excitation we show that scintillation yield and energy resolution of the optimized YAG:Ce SCF is fully comparable with that of the YAG:Ce single crystal analogue.