Thyroid cancer risk in Belarus among children and adolescents exposed to radioiodine after the Chornobyl accident

BACKGROUND: Previous studies showed an increased risk of thyroid cancer among children and adolescents exposed to radioactive iodines released after the Chornobyl (Chernobyl) accident, but the effects of screening, iodine deficiency, age at exposure and other factors on the dose-response are poorly understood. METHODS: We screened 11 970 individuals in Belarus aged 18 years or younger at the time of the accident who had estimated (131)I thyroid doses based on individual thyroid activity measurements and dosimetric data from questionnaires. The excess odds ratio per gray (EOR/Gy) was modelled using linear and linear-exponential functions. RESULTS: For thyroid doses \u3c5 \u3eGy, the dose-response was linear (n=85; EOR/Gy=2.15, 95% confidence interval: 0.81-5.47), but at higher doses the excess risk fell. The EOR/Gy was significantly increased among those with prior or screening-detected diffuse goiter, and larger for men than women, and for persons exposed before age 5 than those exposed between 5 and 18 years, although not statistically significant. A somewhat higher EOR/Gy was estimated for validated pre-screening cases. CONCLUSION: 10-15 years after the Chornobyl accident, thyroid cancer risk was significantly increased among individuals exposed to fallout as children or adolescents, but the risk appeared to be lower than in other Chornobyl studies and studies of childhood external irradiation

The Flux-Line Lattice in Superconductors

Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth: The shear modulus of the FLL is thus small and the tilt modulus is dispersive and becomes very small for short distortion wavelength. This softness of the FLL is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these uniaxial crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause thermally activated depinning of the flux lines or of the 2D pancake vortices in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do not exist as postscript file

A comparative analysis of the effectiveness of tear substitutes for the treatment of dry eye syndrome

Objective: to assess the effectiveness of tear substitutes in patients suffering from dry eye syndrome (DES). Material and methods. 100 patients with an established diagnosis of mild to moderate DES, averagely aged 42.0 ± 2.1, were divided into three groups: group 1 involving 33 patients (54 eyes, 13 men and 20 women) aged 42.7 ± 2.13 with mild DES, who were treated by low viscosity eye drops, group 2 involving 33 patients (56 eyes, 13 men and 20 women) aged 41.4 ± 2.07 with moderate DES, who were treated by moderate viscosity eye drops and group 3 involving 34 patients (52 eyes, 14 men and 20 women) aged 41.9 ± 2.1 with moderate DES, who were treated by high viscosity eye drops. Treatment results were evaluated after 1 month on the basis of complaints, objective examination data and indicators of the functional tests Results. The complaints (of discomfort, eye strain, fatigue when working with text, eye redness, lacrimation, burning and cramping in the eyes) became less severe, and so did the objective signs of DES. The functional test indicators showed an improvement, too. The best results of the treatment were noted in group 3, where the tear production indicator (Schirmer’s test) increased by 68.1 %. This indicator increased by 66.7 % and 61.5 % in groups 1 and 2, respectively. The LIPCOF test results dropped 3.9 times in group 1 and only 2,3 times in groups 2 and 3. Conclusion. Tear substitutes must be used in DES as the first line of conservative therapy. The improvement of subjective evaluations of the patients and the data of objective research in all three groups is the result of an adequate selection of tear substitutes drugs of a certain degree of viscosity according to the severity of DES

Optical transmission of nematic liquid crystal 5CB doped by single-walled and multi-walled carbon nanotubes

Comparative studies of optical transmission of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), dispersed in nematic liquid crystal matrix 5CB, were carried out. The data evidence violations of Beer-Lambert-Bouguer (BLB) law both in cell thickness and concentration dependencies. The most striking is the fact that optical transmission dependencies for SWCNTs and MWCNTs were quite different in the nematic phase, but they were practically indistinguishable in the isotropic phase. Monte Carlo simulations of the impact of aggregation on direct transmission and violation of BLB law were also done. The results were discussed accounting for the tortuous shape of CNTs, their physical properties and aggregation, as well as strong impact of perturbations of the nematic 5CB structure inside coils and in the vicinity of CNT aggregates

Anomalous optical properties of photoactive cholesteric liquid crystal doped with single-walled carbon nanotubes

<p>Optical transmission and selective reflection data are reported for suspensions of single-walled carbon nanotubes (CNTs) in photoactive nematic material ZhK-440 with a mesogenic chiral dopant M5. At small concentrations of CNTs (<i>C</i> ≈ 0.01–0.05%), the preferential localisation of CNTs at oily sticks (cholesteric topological defects) and suppression of the network of oily streaks by CNTs were observed. At the same time, the optical density <i>D</i> was shown to be essentially non-linear and a minimum at certain concentration of CNTs, <i>C</i> ≈ 0.05–0.08%, was observed. This anomalous behaviour was explained by the presence of the structural transition from the loose (ramified) aggregates with highly anisotropic shape (oriented along the anchoring direction on rubbed polyvinyl alcohol) to the compact aggregates with denser packing. The location of this minimum, as well as the selective reflection maximum (helical pitch), was sensitive to partially reversible UV-induced <i>trans–cis–trans</i> isomerisation effects. The UV-controlled helical pitch variation was shown to be only slightly affected by introduction of CNTs.</p

Reconstruction of thyroid doses for the population of Belarus following the Chernobyl accident

As a sequela to the large release of {sup 131}I from the accident at the Chernobyl Nuclear Power Plant, an expected late effect is thyroid cancer, especially in children. In anticipation of this problem, hundreds of thousands of measurements of thyroid glands were made with survey meters. Much attention was also focused on measuring the deposition density of {sup 137}Cs. The expectation was that the latter measurement could be a good surrogate for the deposition density of {sup 131}I, so that ecological models could be used to reconstruct thyroid doses in locations where no direct measurements of thyroid activity were made. However, this assumption has been seriously questioned, and there is interest in a more suitable surrogate that can still be measured even nine years or more after the accident. The purpose of this paper is to discuss the reconstruction of thyroid doses for a case-control study of childhood-thyroid cancer that has just been concluded, to discuss the reconstruction of thyroid doses for a current cohort study of childhood-thyroid cancer, and to discuss the use of {sup 129}I as a surrogate for the deposition density of {sup 131}I