Intercomparison of Gafchromic™ films,TL detectors and TL foils for the measurements of skin dose in interventional radiology

Several passive solid state dosemeters, such as Gafchromic™ films and thermoluminescence (TL) detectors, are used to estimate and monitor patient skin doses in interventional radiology. To determine the suitability of XR-TypeR Gafchromic™ films and of detectors based on TL materials: pellets, chips and foils to measure skin dose, an intercomparison exercise has been organized within European Dosimetry Radiation Group – Working Group 12 “European Medical ALARA Network” (EURADOS WG12). To test response detectors were exposed to X-ray beams of energies and qualities applied clinically. A blind test was also performed to investigate the accuracy of the dose estimate by detectors exposed to unknown doses. We found the response of films to be strongly dependent on beam quality and filtration (increasing by up to 80% with respect to reference beam quality). The response of TL detectors was found to be less dependent on beam quality (less than 25% variation), with TL foils showing less than 10% variation with respect to reference beam quality. To accurately estimate patient skin doses in interventional radiology it is important to choose the quality of the calibration beam to be as close as possible to the quality of beams actually applied in clinical work.     

Combined measurement of dose and α/γ radiation-field-components using the shape of composite peak 5 in the glow curve of LiF:Mg,Ti

The shape of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100), specifically, the ratio of the intensity of peak 5a to peak 5, is employed to separately estimate the gamma and alpha particle components in a mixed radiation field. A blind test demonstrates the reasonable accuracy of the technique which yields results between 3.8% and 30%.     

Theoretical prediction of absorbance spectra considering the particle size distribution using Mie theory and their comparison with the experimental UV–Vis spectra of synthesized nanoparticles

Under the frame work of Mie theory, a method has been developed to calculate the absorbance spectra of nanoparticles suspension containing a size distribution. The silver nanoparticles of two different sizes were first synthesized using a chemical reduction method and characterized by UV-Visible spectroscopy, dynamic light scattering, and transmission electron microscopy techniques. A model size-distribution were proposed and fitted to the experimental absorbance spectra using the described method. Better semiqualitative fitting to the experimental spectra were obtained by our proposed model in comparison to those obtained by single particle model.     

The reusability characteristics of LiF:Mg,Cu,P with a maximum intensity at 280 °C in an environment with elevated temperature

Efforts are aimed at finding a method that could serve TL dosimetric measurements in the range of low-dose but carried out in an environment with elevated temperature. The temperature at the position of the maximum intensity of LiF:Mg,Cu,P was about 280 °C when annealed at 460 °C. LiF:Mg,Cu,P with a maximum intensity at 280 °C should present good thermal stability. The TL intensity of LiF:Mg,Cu,P with a maximum intensity at 280 °C was about 54% of the standard LiF:Mg,Cu,P, it should have a minimum measurable dose in the range of micro-Gy. LiF:Mg,Cu,P with a maximum intensity at 280 °C could be re-used by the 660 °C/30 min annealing, followed by 270 °C/20 min, 240 °C/10 min and 460 °C/30 min. It's possible for LiF:Mg,Cu,P to be extended application for low dose test in an environment with elevated temperature.     

Some features of solar wind protons, α particles and heavy ions behaviour: The Prognoz 7 and Prognoz 8 experimental results

The paper describes the results of investigations of the solar wind ions, carried out on board the high apogee Prognoz 7 and Prognoz 8 Earth's satellites with the aid of an SKS instrument (USSR) and a Monitor instrument (USSR-SSR). Behaviour of proton and that of components on the front of Earth's bow and interplanetary shock waves were compared by means of the energoanalysis and energy-mass analysis techniques. In several long-term periods of observation the solar wind heavy ions — oxygen, silicon and iron were determined. It enabled us to estimate the solar corona chemical composition and electron temperature.Presented at the 5th General Assembly IAGA/IAMAP August 5–17, 1985, Prague, Czechoslovakia.     

Effect of temperature-induced solute distribution on stacking fault energy in Mg–X(X = Li,Cu, Zn,Al, Y and Zr) solid solution: a first-principles study

Stacking fault energies (SFEs) of Mg solid solutions at different temperatures are very significant for studying dissociation of dislocation, plasticity deformation and other mechanical properties. Our present work starts with the investigation of interactions between basal stacking faults (SFs) and solutes (Li, Cu, Zn, Al, Y and Zr) using first-principles calculations. It is found that the interactions between basal SFs and solutes can be extended to several closed-packed layers. Combined with Fermi–Dirac function of solute distribution at each layer, the temperature dependence of SFE for Mg–X(X?=?Li, Cu, Zn, Al, Y and Zr) solid solution has been investigated. This study predicts correctly the increase tendency observed in experiment. Then the SFEs of Mg solid solutions at room temperature of 300?K are investigated at different solute concentrations; the obtained concentration dependence of SFEs is in agreement with the available experimental values. So the solute distribution under finite temperature due to the basal SF–solute interactions plays a critical role in the variation of SFEs of Mg solid solutions.     

Transport properties of bulk water at 243–550 K: a Comparative molecular dynamics simulation study using SPC/E,TIP4P,and TIP4P/2005 water models

ABSTRACT

Molecular dynamics simulations of various water models – SPC/E (extended simple point charge), TIP4P (transferable intermolecular potential 4 points), and TIP4P/2005 – have been carried out in the canonical (NVT fixed) ensemble over the range of temperatures 243–550?K with Ewald summation. The transport properties (self-diffusion coefficients D, viscosities η, and thermal conductivities λ) of SPC/E, TIP4P, and TIP4P/2005 water were evaluated at 243–550?K and compared with experimental data. The temperature dependence of transport properties of SPC/E, TIP4P and TIP4P/2005 water was discussed to determine how reliable the models are over this temperature range.     

Spectroscopic determination of the relative particle densities of H<Subscript>2</Subscript>, HD,and D<Subscript>2</Subscript> Molecules in non-equilibrium hydrogen–deuterium plasma: II. Experimental verification

The relative intensities of the Balmer series lines of hydrogen and deuterium atoms and the Q-branch lines in the Fulcher-α band system of the H₂, HD, and D₂ molecules were measured. These lines were emitted by non-equilibrium plasma surrounded by the cylindrical channel of an additional molybdenum electrode located between the cathode and anode of glow (in the deuterium with a minor hydrogen impurity) and arc (in a mixture of D₂, H₂, and Ne in comparable quantities) discharges at pressures of 6–8 Torr and current densities of 0.4 and 8.5–17 A/cm², respectively. The measured intensity ratios and gas temperature were used for the estimation of the relative particle densities of the H₂, HD, and D₂ molecules in the framework of the simple models of the excitation of atoms (models 1a and 1b for the high and low values of dissociation degrees, respectively) and the rovibronic levels of isotopic molecules (model 2). The results obtained by means of models 1a and 2 were in a significant contradiction, whereas the data obtained with the use of models 1b and 2 coincided within error bars. The good agreement between two spectroscopic techniques based on two independent theoretical models and two independent sets of experimental data showed that the techniques proposed are promising for the determination of the isotopic composition of molecules in lowpressure hydrogen-deuterium plasma at least in the case of a low dissociation degree of molecules.