L. Dobrzyński

THE HEALTHY WORKER EFFECT AND NUCLEAR INDUSTRY WORKERS

The linear no-threshold (LNT) dose-effect relationship has been consistently used by most radiation epidemiologists to estimate cancer mortality risk. The large scattering of data by International Agency for Research on Cancer, IARC (Vrijheid et al. 2007; Therry-Chef et al. 2007; Cardis et al. 2007), interpreted in accordance with LNT, has been previously demonstrated (Fornalski and Dobrzyński 2009). Using conventional and Bayesian methods the present paper demonstrates that the standard mortality ratios (SMRs), lower in the IARC cohort of exposed nuclear workers than in the non exposed group, should be considered as a hormetic effect, rather than a healthy worker effect (HWE) as claimed by the IARC group.

Pooled Bayesian analysis of twenty-eight studies on radon induced lung cancers.

The influence of ionizing radiation of 222Rn and its progeny on lung cancer risks that were published in 28 papers was re-analyzed using seven alternative dose-response models. The risks of incidence and mortality were studied in two ranges of low annual radiation dose: 0–70 mSv per year (391 Bq m−3) and 0–150 mSv per year (838 Bq m−3). Assumption-free Bayesian statistical methods were used. The analytical results demonstrate that the published incidence and mortality data do not show that radiation dose is associated with increased risk in this range of doses. This conclusion is based on the observation that the model assuming no dependence of the lung cancer induction on the radiation doses is at least ∼90 times more likely to be true than the other models tested, including the linear no-threshold (LNT) model.

Fe cation occupancies in GaFeO3 prepared by sol–gel and solid state reaction

In this study, the Mössbauer spectroscopy and the neutron powder diffraction were used for the characterisation of GaFeO3 samples prepared by two different methods, solid state reaction and sol–gel synthesis. The samples have similar structures that differ in distributions of Fe and Ga among the pertinent sites. The samples also differ in magnetic transition temperatures. We studied how to adopt the method of invariants, developed earlier for decomposition of the Mössbauer spectra into site components, to the case of magnetic interactions dominating over small quadrupole interactions. A combined neutron and Mössbauer data analysis has led to the determination of site assignment and the occupancies.

Electronic structure and magnetism of Fe3−xCrxSi alloys

Abstract The study of the electronic structure and magnetic properties of the Fe3−xCrxSi compound is motivated by the Mossbauer and neutron spectroscopy measurements showing unusual behaviour of Cr in such alloys. The site preferences of Cr in Fe3Si and the effect of local environment on formation of local magnetic moments are examined using self-consistent spin-polarised TB-LMTO method. The results of calculations essentially confirm the values and orientations of magnetic moments of iron and chromium atoms. However, they do not explain an experimental observation of almost equal occupation of A, B and C sites by chromium.

The Cancer Mortality in High Natural Radiation Areas in Poland

The cancer mortality ratios (CMRs) in Poland in high and low level radiation areas were analyzed based on information from national cancer registry. Presented ecological study concerned six regions, extending from the largest administration areas (a group of voivodeships), to the smallest regions (single counties). The data show that the relative risk of cancer deaths is lower in the higher radiation level areas. The decrease by 1.17%/mSv/year (p = 0.02) of all cancer deaths and by 0.82%/mSv/year (p = 0.2) of lung cancers only are observed.

Projected iron moments in UFe4Al8 investigated with monochromatic polarized Mössbauer radiation

UFe4Al8 was investigated using a monochromatic, circularly polarized Mossbauer source. The measurements are sensitive to the sign of the hyperfine magnetic field. The iron magnetic moment component along the direction of the applied magnetic field was determined. Quantitative analysis shows that the configuration of iron moments is not collinear and, on average, only about one fourth of the atomic iron moment contributes to the total magnetization in a randomly oriented powder exposed to a field of 1 T at a temperature of 12 K. The presence of ferromagnetic clusters in an otherwise antiferromagnetic ordering is discussed. The conclusions regarding the magnetic structure are compared with the results of powder neutron diffraction experiments. In the course of the interpretation of latter, the Debye temperature D = 421(13) K was determined.

On the validity of a hyperfine magnetic field distribution measured by a monochromatic, circularly polarized Mössbauer source

It is demonstrated that when in a standard Mossbauer spectroscopy experiment two different hyperfine magnetic field distributions describe experimental data equally well, measurements by means of a monochromatic circularly polarized source lead to the correct choice of the solution. The problem of the asymmetry of the spectrum in the case of a polarized source and pure magnetic interaction is discussed and constraints for the line intensities are given.

Magnetism of the UFexAl12−x alloys

Abstract Polycrystalline samples of the ternary intermetallic alloys UFe x Al 12− x with x in the range 〈3.6–5〉 were studied. The alloys crystallize in a ThMn 12 -type structure, belonging to the space group I 4/ mmm (no. 139). Studies of the powder samples by X-ray and neutron diffraction techniques confirmed the phase homogeneity of all these materials with an iron concentration, x , below 4. The samples with a higher iron content contain a small addition of extra phases. Monochromatic circularly polarised Mossbauer source (MCPMS) measurements, carried out at 12 K in an external magnetic field of 1 T, were interpreted in terms of magnetic domains in otherwise randomly oriented powders. Magnetic moments of iron are arranged in spin-canted magnetic structures. The canting angles ( α ) were estimated. The neutron data obtained for the sample with x =4.4 indicate that the two transition temperatures, observed previously by means of the magnetisation measurements, originate in different temperatures of the ordering of iron and uranium sublattices. Our data indicate that the range of iron concentration within which two transition temperatures are observed starts with UFe 4 Al 8 alloys. However, the mechanisms underlying these transitions are different for various compositions and require further investigations. It is shown that even in the case of the magnetic domains formation of the sample the MCPMS technique can bring very valuable results.

A Stochastic Markov Model of Cellular Response to Radiation

A stochastic model based on the Markov Chain Monte Carlo process is used to describe responses to ionizing radiation in a group of cells. The results show that where multiple relationships linearly depending on the dose are introduced, the overall reaction shows a threshold, and, generally, a non-linear response. Such phenomena have been observed and reported in a number of papers. The present model permits the inclusion of adaptive responses and bystander effects that can lead to hormetic effects. In addition, the model allows for incorporating various time-dependent phenomena. Essentially, all known biological effects can be reproduced using the proposed model.

Electron Momentum Density of Hexagonal Magnesium Studied by Compton Scattering

Directional Compton profiles of single crystal of hcp magnesium have been measured with scattering vectors along the [10 10], [1120] and [0001] directions in reciprocal space (special directions ΓΜ, ΓΚ, ΓΑ) using high-energy (662 keV) gamma radiation from a 137Cs isotope source. The experimental data were compared with corresponding theoretical Korringa-Kohn-Rostoker (KKR) calculations. The directional difference profiles, both experimental (of medium resolution) and theoretical ones, show very small anisotropy of the electron momentum density in magnesium, 2-3 times lower than in zinc and cadmium single crystals, significantly lower than observed in cubic metals. This small directional effect is in good agreement with Compton 60-keV energy experiments and positron annihilation data presented by other authors.