High-Entropy Layered Rare Earth Hydroxides.

New high-entropy layered rare earth hydroxides ─ (Y,Eu,Gd,Er,Sm)2(OH)5NO3, (Y,Eu,Gd,Er,Tb)2(OH)5NO3, (Y,Eu,Gd,Er,Yb)2(OH)5NO3, (Y,Eu,Gd,Er,Nd)2(OH)5NO3, and (Y,Eu,Gd,Er,Nd,Sm,Tb)2(OH)5NO3 ─ were obtained using a hydrothermal microwave method. The annealing of layered rare earth hydroxides at 900 °C resulted in the corresponding high-entropy rare earth oxides. Based on inductively coupled plasma atomic emission spectroscopy data, the values for configurational entropy for both rare earth hydroxides and oxides were estimated, confirming the formation of high-entropy compounds. Energy-dispersive X-ray spectroscopy mapping, including mapping in the scanning transmission microscopy mode, showed no signs of chemical segregation and confirmed uniform rare earth elements' distribution both in the particles of high-entropy layered basic nitrates and in the particles of high-entropy oxides. The ratios of rare earth cations in the initial aqueous solutions of mixed nitrates were close to the ratios of cations in the resulting high-entropy layered rare earth basic nitrates and high-entropy rare earth oxides.

Relationship between follow-up periods and the low-dose ranges with statistically significant radiation-induced risk of all solid cancers in the Russian cohort of Chernobyl emergency workers.

Radiation-induced risks for all solid cancer incidence and mortality were studied in the cohort of Russian Chernobyl emergency workers. The cohort included 69,440 persons with documented individual radiation dose accrued over the time of working in the Chernobyl zone. The mean age at entry into the zone of recovery operations was 33.9 years and accumulated radiation dose was 132.9 mGy. A total of 6981 solid cancer incident cases and 4272 deaths occurred in this cohort from 1992 to 2017. Three follow-up periods were studied: 1992-2009, 1992-2013, and 1992-2017. For each follow-up period, the lowest dose range with statistically significant (p < 0.05) radiation-induced risk of all solid cancer incidence and mortality were obtained. For the incidence of all solid cancer during the follow-up period 1992-2009, this lowest dose range was estimated to be 0-250 mGy with an excess relative risk per dose of ERR Gy-1 = 0.51 and 95% confidence interval (CI) (0.02; 1.05) Gy-1. For the period 1992-2013, the lowest dose range was 0-175 mGy with ERR Gy-1 = 0.85 (95% CI 0.03; 1.78), while for the whole follow-up period 1992-2017, it was 0-175 mGy with ERR Gy-1 = 0.81 (95% CI 0.08; 1.62). For mortality from all solid cancers during the follow-up period 1992-2009, the lowest dose range with statistically significant radiation-induced risk was estimated to be 0-225 mGy with ERR Gy-1 = 1.07 (95% CI 0.31; 0.97). For the period 1992-2013, the lowest dose range was 0-225 mGy with ERR Gy-1 = 0.86 (95% CI 0.23; 1.58), while for the whole follow-up period 1992-2017, the lowest dose range was 0-200 mGy with ERR Gy-1 = 0.82 (95% CI 0.10; 1.65). Thus, it was found that the minimal level of significant exposure (Dmin), for which a statistically significant radiation-induced risk of all solid cancers was obtained for Russian emergency workers (with individual doses of 0 - Dmin), decreases with increasing duration of cohort observation, both for cancer incidence and mortality.

Ceria-Containing Hybrid Multilayered Microcapsules for Enhanced Cellular Internalisation with High Radioprotection Efficiency.

Cerium oxide nanoparticles (nanoceria) are believed to be the most versatile nanozyme, showing great promise for biomedical applications. At the same time, the controlled intracellular delivery of nanoceria remains an unresolved problem. Here, we have demonstrated the radioprotective effect of polyelectrolyte microcapsules modified with cerium oxide nanoparticles, which provide controlled loading and intracellular release. The optimal (both safe and uptake efficient) concentrations of ceria-containing microcapsules for human mesenchymal stem cells range from 1:10 to 1:20 cell-to-capsules ratio. We have revealed the molecular mechanisms of nanoceria radioprotective action on mesenchymal stem cells by assessing the level of intracellular reactive oxygen species (ROS), as well as by a detailed 96-genes expression analysis, featuring genes responsible for oxidative stress, mitochondrial metabolism, apoptosis, inflammation etc. Hybrid ceria-containing microcapsules have been shown to provide an indirect genoprotective effect, reducing the number of cytogenetic damages in irradiated cells. These findings give new insight into cerium oxide nanoparticles' protective action for living beings against ionising radiation.

Experimental Study of the Effects of Nanodispersed Ceria on Wound Repair.

We studied the effects of nanodispersed ceria on wound healing in vitro and in vivo. It was found that cerium dioxide stimulated wound healing, which manifested in shrinkage of burn wound area (by 1.5 times) and intensification (by 2.4 times) marginal epithelialization.

[Non-Parametric Analysis of Radiation Risks of Mortality among Chernobyl Clean-Up Workers].

Analysis of the relationship between dose and mortality from cancer and circulation diseases in the cohort of Chernobyl clean-up workers based on the data from the National Radiation and Epidemiological Registry was performed. Medical and dosimetry information on the clean-up workers, males, who got radiation doses from April 26, 1986 to April 26, 1987, which was accumulated from 1992 to 2012, was used for the analysis. The total size of the cohort was 42929 people, 12731 deaths were registered in the cohort, among them 1893 deaths from solid cancers and 5230 deaths were from circulation diseases. An average age of the workers was 39 years in 1992 and the mean dose was 164 mGy. The dose-effect relationship was estimated with the use of non-parametric analysis of survival with regard to concurrence of risks of mortality. The risks were estimated in 6 dose groups of similar size (1-70, 70-130, 130-190, 190-210, 210-230 and.230-1000 mGy). The group "1-70 mGy" was used as control. Estimated dose-effect relationship related to cancers and circulation diseases is described approximately with a linear model, coefficient of determination (the proportion of variability explained by the linear model) for cancers was 23-25% and for circulation diseases - 2-13%. The slope coefficient of the dose-effect relationship normalized to 1 Gy for the ratio of risks for cancers in the linear model was 0.47 (95% CI: -0.77, 1.71), and for circulation diseases it was 0.22 (95% CI: -0.58, 1.02). Risks coefficient (slope coefficient of excess mortality at a dose of 1 Gy) for solid cancers was 1.94 (95% CI: - 3.10, 7.00) x 10(-2) and for circulation diseases it was 0.67 (95% CI: -9.61, 11.00) x 10(-2). 137 deaths from radiation-induced cancers and 47 deaths from circulation diseases were registered during a follow up period.

Incidence and mortality of solid cancer among emergency workers of the Chernobyl accident: assessment of radiation risks for the follow-up period of 1992-2009.

This paper presents the results of a retrospective cohort study of cancer incidence and mortality among emergency workers of the Chernobyl accident, for the follow-up period 1992-2009. The cohort selected for analysis consists of 67,568 emergency workers who worked in the Chernobyl exclusion zone in 1986-1987. External radiation whole-body absorbed dose varied from 0.0001 gray (Gy) to 1.24 Gy, with a median of 0.102 Gy. Over the follow-up period 1992-2009, a total of 4,002 solid cancers of different sites were identified as the result of annual compulsory health examination, and a total of 2,442 deaths from all solid cancers in the study cohort were reported. Poisson regression was applied for the analysis of cancer incidence and mortality. The analysis of the standardized incidence ratio (SIR) has shown a statistically significant increase in cancer incidence in the cohort as compared with baseline cancer incidence among males of Russia. The average excess over the entire follow-up period is 18 % [SIR = 1.18, 95 % confidence interval (CI) 1.15; 1.22]. In contrast, however, no increase in the mortality from all cancers among the emergency workers as compared to the baseline mortality in Russian men was found. Values of excess relative risk of cancer incidence and mortality per 1 Gy (ERR Gy(-1)) are 0.47 (95 % CI 0.03; 0.96, p value = 0.034) and 0.58 (95 % CI 0.002; 1.25, p value = 0.049), respectively. These values are statistically significant.

Estimating the lifetime risk of cancer associated with multiple CT scans.

Multiple CT scans are often done on the same patient resulting in an increased risk of cancer. Prior publications have estimated risks on a population basis and often using an effective dose. Simply adding up the risks from single scans does not correctly account for the survival function. A methodology for estimating personal radiation risks attributed to multiple CT imaging using organ doses is presented in this article. The estimated magnitude of the attributable risk fraction for the possible development of radiation-induced cancer indicates the necessity for strong clinical justification when ordering multiple CT scans.

[Evaluation of intestinal viability on a simulation model of a small ileus based on determination of dielectric parameters].

Interrelationship between dielectric parameters and level of ATPH before and during ischemia, as well as with indices of survival after elimination of strangulation, was estimated on a simulation model of strangulation ileus in rats. The data obtained permit to suppose, that parameter tg δm may be used as effective noninvasive criterion of diagnosis in real time for estimation of the intestinal wall state in strangulation. Resection of the infringed intestine without elimination of strangulation is necessary in tg δm less than 2.20, in tg δm more than 2.36 the elimination of infringement is indicated, because there exist possibility to restore intestinal function after ischemic-reperfusion injury. Tactics of treatment in intermediate meanings of tg δm is not determined, but its measurement before reperfusion may help in estimation of a small intestine viability and choice of surgical tactics in its ischemia.

[Dependence of the efficiency of cell growth on biosynthetic medical materials on the microstructure of their surface].

The efficiency of a novel class of biosynthetic wound dressings in wich natural and synthetic polymeric components are not arranged in layers but are in a unified structure, i. e., form a new composite material, has been studied. In particular, we tried to determine whether the interactions of dressing surface with cells of the injured tissue and/or culture grown in vitro depend on the microstructure of the surface. The efficiency of cell growth was considered in terms of the stimulation of cell growth. The microstructure of the surface was examined using the scanning electron microscopy at high resolution. The results of the study have shown that the structure of biosynthetic dressings depends on the variations in the composition and the ratio of the components. The role of the microstructure of the dressing in the effectiveness has been demonstrated. The factors which have the most significant effect on the regenerating properties of the wound dressings have been revealed.

[Thyroid cancer: lessons of chernobyl and prognosis for Fukushima].

Results of epidemiological studies of thyroid cancer incidence in Russia following the Chernobyl accident are presented in the article. Child population in territories contaminated with radionuclides who got thyroid dose from incorporated (131)I above 100-150 mGy, should be referred to a group at radiation risk. Prognostic estimates of increase in thyroid cancer incidence among the population living in close vicinity of the Fukushima Daiichi NPP were made with account for the Chernobyl data and recommendations of the International Commission on Radiological Protection.

[Prevention of eventration in diffuse suppurative processes in small pelvis].

The study was devoted to the problem of postoperative eventrations in gynaecological practice. Coaptation removable sutures were applied in order to prevent similar complications. Operations were performed in the cases of desolate condition of purulent disease of the uterus and uterine appendages with diffuse suppurative peritonitis. An advanced operative technique of suturing through all layers of abdominal wall demonstrated its high efficacy. No one patient (from 39) had the eventration or wound abscess.

Leukemia incidence in the Russian cohort of Chernobyl emergency workers.

Of all potentially radiogenic cancers, leukemia, a type of cancer of the blood, has the highest risk attributable to ionizing radiation. Despite this, the quantitative estimation of radiation risk of a leukemia demands studying very large exposed cohorts, because of the very low level of this disease in unexposed populations and because of the tendency for its radiation risk to decrease with time. At present, the Japanese cohort of atomic bomb survivors is still the primary source of data that allows analysis of radiation-induced leukemia and the underlying dose-response relationship. The second large cohort that would allow to study radiation-induced leukemia is comprised of individuals who were exposed due to the accident of the Chernobyl nuclear power plant in 1986. The objective of the present study was to estimate radiation risks of leukemia incidence among the Russian cohort of Chernobyl emergency workers, for different time periods after the accident. Twenty-five years after the Chernobyl accident and based on the results of the present study, one can conclude that the radiation risk of leukemia incidence derived from the Russian cohort of Chernobyl emergency workers is similar to that derived from the cohort of atomic bomb survivors: The time-averaged excess relative risk per Gray (ERR Gy(-1)) equals 4.98 for the Russian cohort and 3.9 for the life span study (LSS) cohort; excess absolute risk decreases with time after exposure at an annual rate of 9% for the Russian cohort, and of 6.5% for the LSS cohort. Thus, the excess in risk of leukemia incidence in a population due to a single exposure is restricted in time after exposure by the period of about 15 years.

Amorphous and crystalline cerium(IV) phosphates: biocompatible ROS-scavenging sunscreens.

This paper reports on a comprehensive study of the UV-shielding properties (namely, the sun protection factor and the factor of protection against UV-A radiation) and cytotoxicity (including photocytotoxicity) of amorphous and crystalline cerium(IV) phosphates. It has been shown that cerium(IV) phosphate NH4Ce2(PO4)3 is characterised by UV-shielding properties that are comparable to those of nanocrystalline TiO2 and CeO2. Moreover, cerium(IV) phosphates did not show toxicity towards cell cultures of NCTC L929 line mouse fibroblasts and human mesenchymal stem cells, in a wide range of concentrations, and even enhanced the proliferative activity of the latter. In a model study of the photoprotective properties of cerium(IV) phosphates on human mesenchymal stem cells, the pronounced protective effect of NH4Ce2(PO4)3 was observed, which was comparable to the shielding action of nanocrystalline CeO2. The results have shown that tetravalent cerium phosphates can be considered as promising UV-filters for sunscreen applications.

Assessment of Radiological Hazard of Radioactive Waste Using Effective or Organ Doses: How This May Affect Final Waste Disposal.

ABSTRACT: The radiological hazard of spent nuclear fuel and radioactive waste slows down further development of nuclear energy systems. The authors evaluate timescales required to reduce the radiological hazard of accumulated waste to the reference level of natural uranium that had been consumed by the nuclear energy system. The estimate of this time scale depends on the radiological hazard metric used in the calculations. In this study, two metrics are compared: (1) the committed effective dose based on ICRP Publication 72 and (2) the lifetime radiation risk calculated with use of organ doses and recent radiation risk models recommended by ICRP. The effective dose of the waste reaches the reference level 300 y after the accumulation of waste, while lifetime attributable risk of waste converges to natural uranium in 100 y. Thus, the lifetime attributable risk (LAR) metric is more appropriate to estimate the time requirements for radioactive waste storage and disposal. The effective dose metric significantly overestimates this timescale as it is not intended for quantifying radiation-related risks.

Synthesis of SrF2:Yb:Er ceramic precursor powder by co-precipitation from aqueous solution with different fluorinating media: NaF, KF and NH4F.

The major challenge in optical ceramic technology is the quality of the starting precursor powder for pressing, which is a key element in the optical ceramic industry. One express and helpful technique for the estimation of powder quality is the estimation of the quantum yield of up-conversion luminescence; therefore precursor powders must exhibit high values of up-conversion luminescence efficiency. Single-phase solid solutions based on strontium fluoride doped with ytterbium and erbium were synthesised by co-precipitation from aqueous solutions using sodium fluoride, potassium fluoride and ammonium fluoride as fluorinating agents. The asymmetry of X-ray diffraction maxima indicated the presence of two populations of particles with the same chemical composition. The processes of extended flat particles' growth from smaller particles with a spherical morphology were revealed with transmission electron microscopy and X-ray diffraction. It was shown that when sodium fluoride and potassium fluoride were used they entered the crystal structure in an amount of 3-4 mol% and 1 mol%, respectively. The introduction of sodium and potassium led to an improvement in the sintering ability of particles and a significant increase in the particle size in ceramics by a factor of 5 and 2, respectively, in comparison with the use of ammonium fluoride. The quantum yield values of up-conversion luminescence at the level of tenths of a percent at a low pump power density of 0.1 W cm-2 were very high, which suggests that these synthetic techniques can be considered to be promising for the preparation of precursors of laser ceramics.

[Mortality among the liquidators of the Chernobyl accident: dose dependences and groups of the potential risk].

Dynamics of the mortality and the mortality radiation risks among male emergency workers of 1986-1987 years of entrance to the Chernobyl zone is analyzed. The average dose of external gamma-exposure for this cohort equals 128 mGy. The size of the cohort at the beginning of the follow-up in 1992 was 47820 persons. For the follow-up period 1992-2006 statistically significant radiation risks of death rates have been estimated: for the mortality from all causes, the excess relative risk per Gy (ERR/Gy) equals 0.42 with 95% confidence interval (95% CI) (0.14-0.72); for the mortality from solid cancers ERR/Gy = 0.74, 95% CI (0.03-1.76); and for the mortality from the circulatory system diseases ERR/Gy = 1.01, 95% CI (0.51-1.57). Based on these estimates the risk groups were ranked among all Russian emergency workers (160 thousand persons): the group of the potential radiation risk with doses more than 150 mGy (33488 persons) and the group of the high radiation risk with doses more than 240 mGy (6054 persons).

[Nanocrystaline ceria based materials--perspectives for biomedical application].

Nanocrystalline ceria possesses a unique complex of physical and chemical properties making it highly bioactive material. In this review, modern data on the action of nanocrystalline ceria on cells, micro- and macroorganisms are analyzed. Special attention is paid to the analysis of the factors affecting protective properties of CeO2 with respect to the living systems.

[Investigation of anti-inflammatory action of electromagnetic irradiation of extremely high frequencies in experiment].

There were studied some mechanisms of the effect realization of the extremely high frequency electromagnet irradiation, including modification of the organism immune status as an answer on the irradiation action, manifested by mobilization of ripe CD4+ and CD8+ T-lymphocytes, the interleukins (IL) concentration enhancement, including, IL-1, IL-10, as well as the levels lowering of IL-6 and C-reactive protein in the blood serum. There was established, that using a switching on the intermediate signal systems it is possible to induce the directed (antiinflammatory) answer of organism towards the effective parameters of electromagnet irradiation.

Evaluation of Migration Radiological Equivalence for Dual Component Nuclear Waste in a Deep Geological Repository.

ABSTRACT: The paper is concerned with the issue of achieving the radiological equivalence (the equivalence of radiation risks) of radioactive waste of nuclear reactors and corresponding mass of natural uranium, taking into account the different migration ability of radionuclides in geological formations and soil. This migration radiological equivalence is being investigated for the deep burial of radioactive waste in the case of the development of a two-component nuclear power system with the concurrent use of thermal neutron reactors and fast neutron reactors. Calculations were performed of radiation doses and radiation risks of cancer death arising from consumption of drinking water from a well above a disposal site. The radiation risk relating to a two-component nuclear power system is lower than that from natural uranium; i.e., after reaching the radiological equivalence (100 y of storage) over the timescale of 109 y, the principle of migration radiological equivalence is satisfied. It would take 106 y after radioactive waste disposal to reach the migration radiological equivalence if only thermal reactors were operated. As regards consumption of well drinking water, the radiation risk does not exceed 10-5 y-1 for a two-component nuclear power system, while being 10-3 y-1 (socially unacceptable level) for a power system using only thermal reactors. Radionuclides 241Am, 239Pu, and 240Pu in drinking water make the main contribution to the doses and radiation risks of people for 104 y after the disposal of radioactive waste.

Biocompatible dextran-coated gadolinium-doped cerium oxide nanoparticles as MRI contrast agents with high T1 relaxivity and selective cytotoxicity to cancer cells.

Gd-based complexes are widely used as magnetic resonance imaging (MRI) contrast agents. The safety of previously approved contrast agents is questionable and is being re-assessed. The main causes of concern are possible gadolinium deposition in the brain and the development of systemic nephrogenic fibrosis after repeated use of MRI contrasts. Thus, there is an urgent need to develop a new generation of MRI contrasts that are safe and that have high selectivity in tissue accumulation with improved local contrast. Here, we report on a new type of theranostic MRI contrast, namely dextran stabilised, gadolinium doped cerium dioxide nanoparticles. These ultra-small (4-6 nm) Ce0.9Gd0.1O1.95 nanoparticles have been shown to possess excellent colloidal stability and high r1-relaxivity (3.6 mM-1 s-1). They are effectively internalised by human normal and cancer cells and demonstrate dose-dependent selective cytotoxicity to cancer cells.