No abstract available

[en] The precision of thermoluminiscence dosimetry with LiF 700 powder at radiotherapy dose levels (0.1 - 15 Gy) is evaluated. (H.W.). 1 ref.; 3 figs

[en] The present work reports on the evaluation of laser induced fluorescence (LIF) for the discrimination between different microbial strains. Pseudomonas aeruginosa and Staphylococcus aureus are important pathogenic bacteria for which therapeutic options are lacking nowadays. These microbial strains were selected due to their medical relevance as they are commonly found in human diseases infections. LIF is a spectrochemical analytical technique that was used in the present study to obtain bacteria spectral fingerprints in the liquid phase. Two laser wavelengths, 266 nm (UV) and 405 nm (violet), have been used as excitation light sources delivering output power 5 mW and 100 mW, respectively. The results of LIF analysis showed that the differences in fluorescence bands intensity can be used as a fingerprint for each bacterial species. In addition, the fluorescence emission intensities of the two strains were exponentially related to the concentration of the bacteria. Confocal laser scanning microscopy was used successfully to visualize the fluorescence emission of the cells in comparison with the LIF measurements. The obtained results demonstrate the potential of LIF as a fast, noninvasive, and easy technique for bacterial discrimination. The technique can be also used for the determination of bacteria concentration after performing proper calibration.

[en] It is generally assumed that after the readout of TLD chips, all the traps are almost completely emptied and the residual readout is negligible. However, when performing routine readings (short readout times and high heating rates with no annealing), the deep traps are not completely cleared, and therefore, an additional readout of the crystal will indicate a residual dose. The residual dose for a normal additional readout (without any special treatment to enhance the residual dose, like UV irradiation) is about 0.2% of the accumulated historical dose of the TLD chip and could affect the result of the following readouts, especially when estimating low level doses

[en] The most widely used technique in radiation dosimetry is thermoluminescence (TL), which makes use of materials, commonly divided into two groups: (a) tissue equivalent phosphors, winch generally exhibit low sensitivity to ionizing radiation, e.g. Li:Mg, Ti , Li₂B₄O₇ with Cu or Mn as impurities or Be₂0₃ with different impurities. (b) phosphors with high sensitivity but poor equivalence to organic tissue, e.g. CaF₂ With Mn, Dy or Tm as impurities or CaSO₄ with Mn or Tm as impurities. For a TL dosimeter used in personnel or environmental dosimetry, both tissue-equivalence and high sensitivity are required. Lithium fluoride doped with magnesium and titanium, known commercially as TLD-100 (Harshaw), is still the most commonly used radiation dosimeter. It has become popular because of several properties, such as tissue equivalence, relative low fading, adequate sensitivity for personnel dosimetry and the possibility to manufacture the material with acceptable reproducibility. The LiF:Cu, Mg, P phosphor has several important advantages compared to Li:Mg, Ti. The extended range of linearity, lack of supra linearity and the more nearly ideal tissue equivalence response to low energy photons gives a significant advantage in clinical dosimetry. The higher sensitivity, improved signal to noise ratio, and shorter monitoring periods lead to greatly improved performance in environmental dosimetry. The ultra low relative TL response to neutrons is another important advantage in mixed field neutron/gamma dosimetry. The Li:Mg, Cu, P does suffer from several of the disadvantages associated with TLD-100, especially its complex glow curve, and its greater sensitivity than TLD-100 to heating procedures. A comparison of some main properties of the two phosphors is presented in this work

[en] A brief editorial discusses the lack of consistency in the measured dosimetric characteristics of the thermoluminescent dosemeter material Lif:MgTi. It is suggested that this is due to various unplanned impurities and far greater efforts at quality control must be invested by the commercial industries supplying the materials. (UK)

[en] Short communication

[en] The Moessbauer emission spectra of ⁵⁷Co in low concentrations in KF, NaCl, NaF, LiF, and MgF₂, and the effects of doping NaF and LiF with La³⁺ ions are reported. The monovalent halides all give similar spectra showing a broad single line or a doublet at 2.19 mm/s and two overlapping doublets at 0.46 and 0.19 mm/s (w.r.t metallic iron), although relative intensities vary. Previous Moessbauer and EPR spectroscopic data on these systems are reviewed briefly, and qualitative conclusions drawn on the chemistry of such systems. (author)

[en] The influence of annealing time for LiF (Mg, Cu, P) thermo-luminescence detector measurement results were investigated by experiments. It shows that when annealing temperature keeps invariant (240 ± 2℃), long annealing time has little influence on measurement results, especially for individual dose monitoring. (authors)

[en] Investigation of the traps in LiF:Mg, a multi-peak phosphor, was carried out using simple phosphoescence decay analysis. Half lives at room temperature of the trapping centres (peaks -1b, -1a, -1, 0, 1, 2, 3a and 3) in the phosphor after irradiation with α radiation were found to be 3 s, 5 s, 28 s, 4 min, 15 min, 1 h, 6 h and 2 d respectively. Justification for the method of analysis is provided and the results of measurements compared with published data. The effects of pre-annealing at 400⁰C for 1 h and 80⁰C for 24 h on the trapping configuration and on the trapping efficiencies were also studied