Conducting polymers, also known as “synthetic metals”, have been the subject of wide-spread investigations over the past decade due to their very promising characteristics. It was published earlier that the electrical conductivity of polyaniline (PANI) based polymer composites increases to a significant extent when irradiated to gamma, electron or UV radiation. The aim of the present study was to determine the dose response of PANI samples blended with poly(vinyl chloride) (PVC) and chlorinated poly(propylene) (PPCl) by measuring the high frequency conductance of these blends irradiated to different doses. In order to find the most suitable composition of these blends the concentration of both the PPCl and PVC, and the PANI base were changed, respectively. These samples were then gamma irradiated and the induced electrical conductivity was measured in the frequency range of 1 kHz–1 MHz in order to find the most sensitive evaluation conditions. After selecting both, the most suitable measuring conditions as well as the blend compositions, the dose response of the samples was determined in the dose range of 10–250 kGy. With respect to potential dosimetry application the effects of electron irradiation, irradiation temperature and the stability of the irradiated samples have also been investigated.

Characterization studies on one of the first versions of the Sunna fluorescent dosimeter™ have been published by Kovács and McLaughlin. This present study describes testing results of a newer version of the dosimeter (Model γ, batch 0399-20). This dosimeter is a 1-cm×3-cm polymeric film of 0.5mm thickness that emits a green fluorescence component at intensities almost linear with dose. The manufacturing method (injection molding) allows potential batch sizes on the order of a million while maintaining a signal precision on the order of ±1%. Studies include dose response, dose rate dependence, energy dependence, post-irradiation stability, environmental effects, and variation of response within a batch. Data for both food irradiation and sterilization dose levels were obtained. The results indicate that the green signal (0.3–250kGy) works well for food irradiation dose levels, especially in refrigerated facilities that maintain tight temperature control. The green signal also works well in sterilization facilities because its irradiation temperature coefficient above room temperature is minimal at sterilization doses. If the user requires readout results in < 22h after room temperature irradiation, the user can either calibrate for a specific post-irradiation readout time(s) or simply heat the dosimeters in a small laboratory oven to quickly stabilize the signal.

The quick development concerning the commercial application of food irradiation in the USA recently resulted in growing marketing of irradiated red meat as well as irradiated fresh and dried fruits. These gamma and electron irradiation technologies require specific dosimetry systems for process control. The new version of the Sunna dosimeter has been characterized in gamma, electron and bremsstrahlung radiation fields by measuring the optically stimulated luminescence (osl) at 530 nm both below and above 1 kGy, i.e. for disinfestation and for meat irradiation purposes. No humidity and no significant dose rate effect on the green osl signal was observed. The temperature coefficient was determined from 0°C up to about 40°C and to stabilize the osl signal after irradiation a heat treatment method was introduced. Based on these investigations the Sunna ‘gamma’ film is a suitable candidate for dose control below and above 1 kGy for food irradiation technologies.

Tetrazolium salts as heterocyclic organic compounds are known to form highly coloured, water insoluble formazans by reduction, which can be utilized in radiation processing dosimetry. Radiochromic films containing nitro blue tetrazolium dissolved in a polymer matrix were found suitable for dose determination in a wide dose range both by absorbance and reflectance measurements. The concept of measuring reflected light from dose labels has been discussed earlier and emerged recently due to the requirement of introducing semiquantitative label dose indicators for quarantine control. The usefulness of the method was studied using the newly developed radiochromic dye films as well as already existing ones.

The OSL (optically stimulated luminescence) based Sunna film containing a microcrystalline dispersion of LiF in a polymer matrix has been recently introduced for high-dose dosimetry. Our previous investigations revealed the applicability of the system in the dose range of 0.01–100 kGy, but irradiation temperature and dose rate effects above 5 kGy reduced its usefulness. The recent discovery of the use of spectrophotometric analysis in the UV range for measuring doses above 5 kGy is a suitable option, while the OSL analysis can be applied for measuring lower doses due to the lack of temperature effect on the response of the film below 1 kGy. The film can be applied both in gamma and electron fields, although its response to the two types of radiation is somewhat different. No significant effects of UV light and humidity have been found, and effects of irradiation temperature are only significant in the case of OSL analysis for doses above 5 kGy. The applicability of two types of Sunna films in electron and gamma radiation processing is discussed in the paper.

A new radiation dosimeter, consisting of an optically-stimulated polymer film containing a photofluorescent sensor, can serve as a routine dosimeter and radiographic imaging medium for high-dose applications in the absorbed dose range 0.1-100 kGy. The flexible, colorless, opalescent film having a uniform thickness of 0.240 (+/- 0.005) mm or certain other films in the thickness range 0.08-0.60 mm, are available in large batches. They can be read rapidly with a simple table-top spectrofluorimeter, excitation wavelength (lambda = 450 nm) and emission wavelength (lambda = 670 nm), giving a type A uncertainty of dose evaluation of < +/- 5% at 95% confidence level. It supplies either,single integrated dose readings or two-dimensional radiographic images with relatively high spatial resolution. The present work focuses on the following gamma-ray response characteristics of the system: inter- and intra-batch reproducibility, pre- and post-irradiation stability, and dependence of dose interpretations on absorbed dose rate and irradiation temperature. (C) 1999 Elsevier Science Ltd, All rights reserved.

The purpose of this study was to contribute to the improvement of stratification of post-myocardial infarction patients at increased risk of malignant ventricular arrhythmia (MVA). Power spectral analysis of heart period variability (HPV) was used as a non-invasive tool to assess cardiac autonomic control. Three groups were used: (1) post-myocardial infarction patients with MVA; (2) post-myocardial infarction patients without MVA; and (3) a control group without heart disease. Spectral analysis of HPV (AR model) was performed on four minute long RR-interval time series derived from consecutive hours of Holter ECG. Significant decrease of powers of mid-frequency (MF) (70-150 mHz) and high-frequency (HF) (150-450 mHz) spectral components of HPV was obtained in Group 1 as compared to Group 2 (p = 0.001 and p = 0.02, respectively). There were no significant differences between groups concerning the power of low frequency (LF) (10-70 mHz) component HPV, spectra of patients in Group 1 were dominated by a single low frequency spectral peak (with a central frequency of 37 mHz). The relative power was computed as the percentage of power in each of the above (HF, MF, LF) components related to the total spectral power. Highly significant differences (p = 0.04) were obtained between Group 1 and Group 2 concerning relative powers of MF and LF components as well as LF/MF ratio. The above method appeared to be highly sensitive in differentiating patients with increased risk of MVA.

Conductometric and oscillometric evaluation methods have earlier been developed to determine absorbed dose in the ethanol-monochlorobenzene dosimeter solution Recent investigations on the same solution as well as on alanine solutions included the study of the possible use of different type “conductometric” electrodes and the study of the effect of frequency on the sensitivity of the method. On the basis of these investigations an oscillometric reader has been designed and tested. The same evaluation methods have been tested on the irradiated aqueous alanine solutions, aiming also at the study of the applicable concentration of the alanine solute and the dose (1 to 50 kGy) and dose-rate range using both electron (2.6 μs at 13 μA to 4 μs at 1.0 A pulse length and beam current) and gamma radiation (0.13 to 30 kGy h−1).

The application of a flow-through titration technique, the so-called triangle programmed coulometric titration, is presented for acid-base titrations using potentiometric and photometric detection. A flow-through capillary glass electrode-saturated calomel electrode pair was employed for potentiometric detection, and an indicator mixture and a light-emitting diode-phototransistor system was used for photometric detection. In photometric detection the precision of the end-point location was enhanced by the addition of a suitable mixture of Methyl Red and m-Cresol Purple acid-base colour indicators. The suitability of the technique was demonstrated for different acid-base titrations. As an example, the determination of the drug content of a nicotinic acid-containing experimental pharmaceutical preparation is described.

By comparing calculated and experimental data, the accuracy of the assumed equivalent circuit of the oscillometric microcell was proved. The cell parameters were defined and can be used to characterize the cell and to establish the range of its applicability. The correlation between the output voltage of the oscillator and the sample concentration was studied in the case of the measuring principle applied (measurement of quality factor Q). A relationship was derived for describing the dependence of the analytical signal on the concentration, which enable the factors influencing the sensitivity to be determined. All these studies served to optimize the cell geometry and oscillator circuit.

In case of in vivo potentiometry the measurements are carried out in electrically perturbed environment. Measurements were performed to study how serious disturbances may be accidentaly introduced by changing electric field into the potentiometric ion activity measurements.