An in vitro L-band EPR study with whole human teeth in a surface coil resonator. Radiat

Abstract L-band EPR measurements were done in vitro on extracted human teeth with the objective to evaluate the feasibility of retrospective in vivo EPR dosimetry. In a recent study, the relative contributions of individual tooth components (enamel, crown dentin and root) to the total response of a whole tooth inside an L-band surface coil resonator was investigated. In the present work, the gamma-dose response curves were evaluated for di erent EPR signal evaluation methods, using 35 whole teeth with absorbed doses in the range 1-100 Gy. The paper reports on the ÿrst attempt to deconvolute the single composite L-band EPR line in components due to CO − 2 and native radicals. The L-band EPR spectrum of teeth could be approximated by combining powder-simulated spectra of orthorhombic and quasi-axial signals of the CO − 2 radical and an isotropic signal of the native radicals. Among the applied EPR signal evaluation methods, the evaluation by spectrum deconvolution revealed the lowest detection limit for absorbed dose. A detection limit of about 0:5 Gy was estimated for the currently available L-band equipment

Evaluation of the Native Killer Yeasts against the Postharvest Phytopathogenic mould of Balady Orange Fruits

Yeasts are some of the most important postharvest biocontrol agents (BCAs). Postharvest oranges frequently deteriorate due to green and blue moulds, leading to significant economic losses. The purposes of the present study were to isolate blue and green moulds from infected orange fruits, to assess the ability of killer yeasts isolated from healthy orange fruits and leaves from orange orchards to control blue and green moulds and to evaluate the additive effect of BCAs in combination with 2% sodium bicarbonate (SBC), 2%, sodium benzoate (SB), 2% calcium chloride, 0.2% salicylic acid (SA) or 0.5% chitosan. Among eight fungi isolated from orange fruits showing symptoms of green and blue mulds infection, two were identified as P. digitatum and P. italicum and selected for in vitro assays. Twenty eight yeast isolates were obtained from orange leaves and from the surface of fruits. All yeasts exhibited high killer activity. Twelve yeasts reduced 22.5 –70% of P. digitatum growth while seven isolates reduced 21.1- 68.5% of P. italicum growth. The most potent yeast isolates were identified as Candida pseudotropicalis, Candida salmanticensis, Candida membranifaciens and Pichia guilliermondii. Combination of the BCAs, C. pseudotropicalis, C. salmanticensis and P. guilliermondii with SBC, CaCl2 or chitosan increased their effectiveness against P. digitatum. While combination of C. pseudotropicalis, C. membranifaciens and P. guilliermondii with these natural compounds decreased their effectiveness against P. italicum. Combination of C. membranifaciens with SA increased its effectiveness against P. digitatum. Sodium benzoate has additive effect on C. pseudotropicalis against P. digitatum and C. pseudotropicalis and P. guilliermondii against P. italicum

Dose Reconstruction with Electron Paramagnetic Resonance Spectroscopy of Deciduous Teeth.

In the present study the feasibility of using whole, naturally loose deciduous incisors for dose reconstruction with electron paramagnetic resonance (EPR) spectroscopy was investigated. The properties of EPR signals were analysed before and after laboratory irradiation. The parameters of the native EPR signal of deciduous incisors was found to be different front those from enamel of permanent molars. The native EPR signal of deciduous incisors with peak-to-peak line width of 0.65 mT was located at g = 2.0050. The evaluated parameters of the dosimetric EPR signal (CO2-) of deciduous incisors were ill agreement with those for enamel of permanent molars. A detection threshold for absorbed dose of about 100 mGy was estimated

Optimization of visible photoluminescence emission from Ni-Zn ferrite thin films

Ni-Zn ferrite films with different thicknesses were prepared by the spray method, aiming to study the relationship between the annealing effect in an oxygen rich environment and the structural, optical properties and photoluminescence emission. X-ray diffraction (XRD) analysis used with Rietveld refinement showed that all prepared samples had a single spinel phase structure. Likewise, the Fourier transform infrared (FTIR) spectra confirmed the phase formation of Ni-Zn ferrites by appearing in both of the two characteristic absorption bands which are related to the tetrahedral and octahedral sites. For annealed thin film samples of Ni-Zn ferrite, the atomic force microscope (AFM) surface morphology exhibits pinning structure on the surface in nanoscale height, whereas for un-annealed samples, there are hills and valleys cover a broad region. The different electronic transitions were estimated from the UV-visible transmission spectrum. Strong photoluminescence (PL) intensity in the visible range was observed under the excitation of UV radiation. The intensity of the PL signal was strongest at a film thickness of 750 nm then decreased for higher thicknesses. This could be interpreted by using proposed energy level structures based on the transmission spectrum of the investigated samples. The strong PL intensity introduces the samples as a direct optical detector for UV radiation

Dependencies of the radiation sensitivity of human tooth enamel in EPR dosimetry.

The EPR dose response of tooth enamel was determined for human molars collected in Egypt. The influence of age, gender and residence of the tooth donors as well as tooth position and sample preparation on EPR sensitivity and its variability over the enamel samples was investigated. The EPR sensitivity and its variability were found to depend only on the sample preparation procedure. The variability in EPR sensitivity of enamel from Egyptian teeth was maximally 10% and the mean sensitivity was in good agreement with that of German teeth

Dosimetric properties of lithium borate glass doped with dysprosium.

Characterization of thermoluminescence (TL) properties of lithium borate glass samples doped with different concentrations of dysprosium (Dy) was carried out. Samples were prepared using a melting method at 1100 degrees C and irradiated with beta-particles. The glass samples doped with 0.1% Dy displayed the best TL dosimetric properties compared with other compositions. Deconvoluted analyses of the glow curves displayed five overlapping TL glow peaks located between 392.0 and 510.3 K. A good linear TL dose-response for beta-particles was obtained in the dose range 66.6 mGy to 33.3 Gy. The minimum detectible dose was evaluated to be 205.4 mu Gy and samples revealed thermal fading in 312 h to 29% of their original value