ІЗОТЕРМІЧНИЙ ПЕРЕРІЗ ДІАГРАМИ СТАНУ СИСТЕМИ Al2O3−TiO2−Nd2O3 ПРИ 1400 °С

Isothermal section of the Al2O3–TiO2–Nd2O3 phase diagram at 1400 °C is constructed for the first time. It is the part of systematic investigations of Al2O3–TiO2–Ln2O3 (Ln=lanthanides,Y) systems. The 1400°C was taken as the temperature, at which no liquid is expected in the system. Samples were prepared by a chemical method. Samples were annealed in air at 1400°С for 80 hours and cooled in the furnace. Phases in the samples were determined by XRD analysis. New phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of seven narrow twophase and eight three-phase regions. Triangulation of the system is determined by the phase Nd2Ti2O7, which is in equilibrium with compounds Al2TiO5, NdAlO3 and system components TiO2 and Al2O3. Formation of phases Nd4Ti9O24, Nd2Ti3O12 and Nd2TiO5 in binary boundary system TiO2–Nd2O3 causes the appearance of partially quasibinary sections Al2TiO5–Nd4Ti9O24, Al2TiO5–Nd2Ti3O12 and NdAlO3–Nd2TiO5. The obtained results make a significant contribution to the understanding of interactions between the components in the system studied. The system includes binary compounds with high electro-optical, ferroelectric, piezoelectric, photocatalytic properties, mikrowave dielectric ceramic. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to fi nd and establish the coordinates of new three-phase and two-phase eutectics for directional solidifi cation and to obtain new high-temperature structural materials in the Al2O3–TiO2–Nd2O3 system

Квазибиологическая модель радиогенной заболеваемости раком

The methods: Linear differential equations were used to formalize contemporary assumptions of self –sustaining tissue cell kinetics under the impact of adverse factors, on the formation and repairing of cell “pre-cancer” defects, on inheritance and retaining such defects in daughter cells which results in malignant neoplasms, on age-dependent impairment of human body’s function to eliminate such cells.The results: The model reproduces the well-known regularities of radiogenic cancer morbidity increase depending on instantaneous radiation exposure age and on attained age: the relative reduction at increased radiation age which the model attributes to age decrease of stem cells, relative reduction at increased time after radiation induced by “sorting out” of cells with “pre-cancer” defects, absolute increase with age proportional to natural cause mortality rate.The relevance of the developed quasi-biological model is displayed via comparison to the ICRP model for radiogenic increase of solid carcinomas’ morbidity after single radiation exposure. The latter model had been developed after Japanese cohort observations. For both genders high goodness-of-fit was achieved between the models at values of Gompertz’ law factor which had been defined for men and women in this cohort via selecting the value of the only free parameter indicating age-dependent exponential retardation of stem cells’ division.The conclusion: The proposed model suggests that the estimation of radiogenic risk inter-population transfer can be done on the basis of the data on age-dependent mortality intensity increase from all natural causes. The model also creates the premises for inter-species transfer of risk following the well-known parameters of cell populations’ kinetics in animal’s organs and tissues and Gompertz’s law parameters. This model is applicable also for analyses of age-dependent changes of background cancer morbidity. Цель работы: исходя из радиобиологических и демографических закономерностей, разработать математическую модель возрастной зависимости радиогенной заболеваемости раком и интенсивности смертности от рака, пригодную для межпопуляционного переноса оценок радиогенного риска.Методы: использованы линейные дифференциальные уравнения для формализации современных представлений о клеточной кинетике самоподдерживающихся тканей в условиях воздействия вредных факторов; об образовании и репарации «предраковых» дефектов в клетках; о наследовании и сохранении таких дефектов в дочерних клетках, приводящих к злокачественным новообразованиям; о снижении, по мере старения организма, его способности устранять подобные клетки.Результаты: Модель воспроизводит известные закономерности зависимости радиогенного увеличения заболеваемости раком от возраста мгновенного облучения и от достигнутого возраста: относительный спад с увеличением возраста облучения, который в модели связан с возрастным спадом количества стволовых клеток; относительный спад с увеличением времени, прошедшего после облучения, обусловленный выбраковкой клеток с «предраковыми» дефектами; абсолютное увеличение с возрастом, пропорциональное интенсивности смертности по естественным причинам. Адекватность разработанной квазибиологической модели продемонстрирована на примере сравнения с моделью МКРЗ для радиогенного увеличения заболеваемости солидными раками после однократного облучения, разработанной по результатам наблюдений за японской когортой. При значениях показателя закона Гомперца, определенных ранее для мужчин и женщин этой когорты, путём выбора значения единственного свободного параметра – показателя экспоненциального замедления скорости деления стволовых клеток с возрастом – для обоих полов достигнуто очень хорошее согласие моделей.Заключение: из предложенной модели следует, что межпопуляционный перенос оценок радиогенного риска можно осуществлять на основе данных о возрастном увеличении интенсивности смертности от всех естественных причин. Модель создаётпредпосылки и для межвидового переноса рисков по известным параметрам кинетики клеточных популяций в органах и тканях животных и параметрам закона Гомперца. Модель может использоваться также для анализа закономерностей возрастных изменений фоновой заболеваемости раком.

ВЛИЯНИЕ ДЕМОГРАФИЧЕСКИХ ОСОБЕННОСТЕЙ ПОПУЛЯЦИИ НА ОЦЕНКИ КОЭФФИЦИЕНТОВ РАДИОГЕННОГО РИСКА НА ПРИМЕРЕ РОССИЙСКОГО НАСЕЛЕНИЯ

The aim of this work was to determine the validity of the direct transfer of the recommendations of the ICRP on the nominal risk coefficients and tissue weighting factors in a future revision of the national Radiation Safety Standards (NRB). The article compares the background age and sex distribution, and morbidity and mortality rates of the nominal population, the ICRP used to develop the latest fundamental recommendations, with appropriate indicators for the populations of Russia and Japan as the main source of data for assessment of radiogenic risk in the second half of the last decade. It is revealed that the functions of survival and age-related morbidity and mortality of the Russian population, especially for males, is significantly different from the composite population, while for the Japanese population, the differences are relatively small. The estimates of radiogenic risk coefficients for cancers of various localization using calculation schemes and risk models of the ICRP Publication 103, but based on background data on incidence and mortality of the Russian population were obtained. Baseline incidence and mortality for the Russian population are worse compared to the composite population. Hence, risk coefficients for the Russian population can be taken lower than the recommended ICRP by approximately 20% for the total population and 30% for the persons of working ages. The results clearly demonstrate the inconsistency of the modern criteria of radiation protection, based almost exclusively on the account of carcinogenic effects of ionizing radiation, since it implies that radiation is more harmful for a healthier population. The results also show timeliness of issue of the choice of the calendar period for which the age-dependence of the intensity of cancer incidence and mortality from all causes are taken into account. The article justified the continuation of the discussion of the raised issues, as well as the issues of development the mathematical models used in the estimation of radiogenic risks.Цель работы состояла в выяснении правомерности прямого переноса рекомендаций МКРЗ по коэффициентам номинального риска и тканевых весовых множителей в будущие редакции отечественных НРБ. Сравнены фоновые возрастно-половые распределения и показатели заболеваемости и смертности композитного населения, использованного МКРЗ для разработки последних основополагающих рекомендаций, с соответствующими показателями для населений России и Японии как основного источника данных для оценок радиогенного риска, во второй половине прошлого десятилетия. Выявлено, что по виду функций дожития и возрастным показателям заболеваемости и смертности российское население, в особенности мужская его часть, значительно отличается от композитного, в то время как для японского населения различия сравнительно невелики. Получены оценки коэффициентов радиогенного риска для раков различной локализации с применением схемы расчётов и моделей риска из Публикации 103 МКРЗ, но на основе фоновых данных о заболеваемости и смертности российского населения. Из-за худших по сравнению с композитным населением показателей спонтанной заболеваемости и смертности российского населения коэффициенты рисков для него могут быть приняты меньше рекомендованных МКРЗ примерно на 20% для всего населения и на 30% для лиц рабочих возрастов. Результаты работы наглядно демонстрируют противоречивость современного критерия радиационной безопасности, основанного практически только на учёте канцерогенных эффектов ионизирующего излучения, поскольку из него следует, что чем здоровее население, тем вреднее для него радиация. Они показывают также, что актуален вопрос о выборе календарного периода, для которого принимаются в расчёт возрастные зависимости интенсивности заболеваемости раком и смертности по всем причинам. Оправдано продолжение обсуждения поставленных вопросов, как и вопросов совершенствования математических моделей, используемых при расчётах радиогенных рисков

Diameter-dependent thermopower of Bi nanowires

We present a study of electronic transport in individual Bi nanowires of large diameter relative to the Fermi wavelength. Measurements of the resistance and thermopower of intrinsic and Sn-doped Bi wires with various wire diameters, ranging from 150-480 nm, have been carried out over a wide range of temperatures (4-300 K) and magnetic fields (0-14 T). We find that the thermopower of intrinsic Bi wires in this diameter range is positive (type-p) below about 150 K, displaying a peak at around 40 K. In comparison, intrinsic bulk Bi is type-n. Magneto-thermopower effects due to the decrease of surface scattering when the cyclotron diameter is less than the wire diameter are demonstrated. The measurements are interpreted in terms of a model of diffusive thermopower, where the mobility limitations posed by hole-boundary scattering are much less severe than those due to electron-hole scattering.Comment: 32 pages, 12 figures. Previous version replaced to improve readabilit

The impact of microwave radiation on radiative recombination of CdS

The paper considers the impact of a powerful short-term microwave radiation (f= 2.45 GHz) on defect states of CdS monocrystals with the aid of investigation of the luminescence spectra in a domain of 0.6–2.5 μm at 77 K. It has been found experimentally that the microwave processing affects the luminescence characteristics of the crystals because of a change in concentration of cation vacancies (centers of photosensitivity) and in concentration of centers of fast (nonradiative) recombination. The results of the investigations point to the prospects in applying the microwave radiation in technological processes for the control of photosensitivity and of the luminescence spectra of cadmium chalcogenide

Quasi – biological model of radiogenic cancer morbidity

The methods: Linear differential equations were used to formalize contemporary assumptions of self –sustaining tissue cell kinetics under the impact of adverse factors, on the formation and repairing of cell “pre-cancer” defects, on inheritance and retaining such defects in daughter cells which results in malignant neoplasms, on age-dependent impairment of human body’s function to eliminate such cells.The results: The model reproduces the well-known regularities of radiogenic cancer morbidity increase depending on instantaneous radiation exposure age and on attained age: the relative reduction at increased radiation age which the model attributes to age decrease of stem cells, relative reduction at increased time after radiation induced by “sorting out” of cells with “pre-cancer” defects, absolute increase with age proportional to natural cause mortality rate.The relevance of the developed quasi-biological model is displayed via comparison to the ICRP model for radiogenic increase of solid carcinomas’ morbidity after single radiation exposure. The latter model had been developed after Japanese cohort observations. For both genders high goodness-of-fit was achieved between the models at values of Gompertz’ law factor which had been defined for men and women in this cohort via selecting the value of the only free parameter indicating age-dependent exponential retardation of stem cells’ division.The conclusion: The proposed model suggests that the estimation of radiogenic risk inter-population transfer can be done on the basis of the data on age-dependent mortality intensity increase from all natural causes. The model also creates the premises for inter-species transfer of risk following the well-known parameters of cell populations’ kinetics in animal’s organs and tissues and Gompertz’s law parameters. This model is applicable also for analyses of age-dependent changes of background cancer morbidity

THE IMPACT OF THE DEMOGRAPHIC CHARACTERISTICS OF THE POPULATION ON ESTIMATES OF THE COEFFICIENTS OF RADIOGENIC RISK IN THE RUSSIAN POPULATION

The aim of this work was to determine the validity of the direct transfer of the recommendations of the ICRP on the nominal risk coefficients and tissue weighting factors in a future revision of the national Radiation Safety Standards (NRB). The article compares the background age and sex distribution, and morbidity and mortality rates of the nominal population, the ICRP used to develop the latest fundamental recommendations, with appropriate indicators for the populations of Russia and Japan as the main source of data for assessment of radiogenic risk in the second half of the last decade. It is revealed that the functions of survival and age-related morbidity and mortality of the Russian population, especially for males, is significantly different from the composite population, while for the Japanese population, the differences are relatively small. The estimates of radiogenic risk coefficients for cancers of various localization using calculation schemes and risk models of the ICRP Publication 103, but based on background data on incidence and mortality of the Russian population were obtained. Baseline incidence and mortality for the Russian population are worse compared to the composite population. Hence, risk coefficients for the Russian population can be taken lower than the recommended ICRP by approximately 20% for the total population and 30% for the persons of working ages. The results clearly demonstrate the inconsistency of the modern criteria of radiation protection, based almost exclusively on the account of carcinogenic effects of ionizing radiation, since it implies that radiation is more harmful for a healthier population. The results also show timeliness of issue of the choice of the calendar period for which the age-dependence of the intensity of cancer incidence and mortality from all causes are taken into account. The article justified the continuation of the discussion of the raised issues, as well as the issues of development the mathematical models used in the estimation of radiogenic risks

ISOTHERMAL SECTION OF THE Al2O3–TiO2–Yb2O3 PHASE DIAGRAM AT 1400 °С

One of the main directions of the modern materials development science is the development of new oxide ceramic materials for engineering, energy, chemical, aerospace, electronic and other industries in multi component systems, including containing TiO2, Al2O3 and rare earth oxides. The Al2O3‒TiO2‒Yb2O3 system attracts the attention of researchers because possibility of design of structural high-temperature materials with low coefficient of thermal expansion, as well as refractory ceramic materials. The basis of new materials creation is the study of physical and chemical interaction, which is reflected in the phase diagrams of the systems. The purpose of this study is the construction of phase diagram isothermal section for the Al2O3−TiO2−Yb2O3 system at 1400 °С, which is the part of the interaction systematic study of the Al2O3−TiO2−Ln2O3 systems, where Ln = (La, Nd, Gd, Er, Yb and Y). The samples were prepared by a chemical method. Annealed in air at 1400°С for 80 hour sand cooled in the furnace. Phase content of the samples was determined by XRD analysis. New multicomponent phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of four narrow two-phase Al2TiO5+Yb2Ti2O7, Al2O3+Yb2Ti2O7, Yb3Al5O12+Yb2Ti2O7, Yb3Al5O12+Yb2TiO5 regions and five threephase Al2TiO5+TiO2+Yb2Ti2O7, Al2TiO5+Yb2Ti2O7+Al2O3, Al2O3+Yb2Ti2O7+Yb3Al5O12, Yb2Ti2O7+Yb3Al5O12+Yb2TiO5, Yb3Al5O12+Yb2TiO5+С-Yb2О3 fields. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–Yb2O3 system

ІЗОТЕРМІЧНИЙ ПЕРЕРІЗ ДІАГРАМИ СТАНУ СИСТЕМИ Al2O3−TiO2−Yb2O3 ПРИ 1400 °С

One of the main directions of the modern materials development science is the development of new oxide ceramic materials for engineering, energy, chemical, aerospace, electronic and other industries in multi component systems, including containing TiO2, Al2O3 and rare earth oxides. The Al2O3‒TiO2‒Yb2O3 system attracts the attention of researchers because possibility of design of structural high-temperature materials with low coefficient of thermal expansion, as well as refractory ceramic materials. The basis of new materials creation is the study of physical and chemical interaction, which is reflected in the phase diagrams of the systems. The purpose of this study is the construction of phase diagram isothermal section for the Al2O3−TiO2−Yb2O3 system at 1400 °С, which is the part of the interaction systematic study of the Al2O3−TiO2−Ln2O3 systems, where Ln = (La, Nd, Gd, Er, Yb and Y). The samples were prepared by a chemical method. Annealed in air at 1400°С for 80 hour sand cooled in the furnace. Phase content of the samples was determined by XRD analysis. New multicomponent phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of four narrow two-phase Al2TiO5+Yb2Ti2O7, Al2O3+Yb2Ti2O7, Yb3Al5O12+Yb2Ti2O7, Yb3Al5O12+Yb2TiO5 regions and five threephase Al2TiO5+TiO2+Yb2Ti2O7, Al2TiO5+Yb2Ti2O7+Al2O3, Al2O3+Yb2Ti2O7+Yb3Al5O12, Yb2Ti2O7+Yb3Al5O12+Yb2TiO5, Yb3Al5O12+Yb2TiO5+С-Yb2О3 fields. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–Yb2O3 system.Вперше побудовано ізотермічний переріз діаграми стану системи Al2O3−TiO2−Yb2O3 при 1400 °С. Нових фаз і помітних областей гомогенності на основі компонентів та подвійних сполук не знайдено. У трифазних областях слід очікувати наявність п’яти потрійних евтектик Al2TiO5 + TiO2 + Yb2Ti2O7, Al2TiO5 + Yb2Ti2O7 + Al2O3, Al2O3 +Yb2Ti2O7 + Yb3Al5O12, Yb2Ti2O7 + Yb3Al5O12 + Yb2TiO5, Yb3Al5O12 + Yb2TiO5 + С-Yb2О3, а на бінарних перерізах − чотири подвійні евтектики Al2TiO5 + Yb2Ti2O7, Al2O3 + Yb2Ti2O7, Yb3Al5O12 + Yb2Ti2O7, Yb3Al5O12 + Yb2TiO5