Beijing synchrotron radiation total—reflection X—ray fluorescence analysis facility and its applications on trace element study of cells

The feasibility of total-reflection X-ray fluorescence(TXRF) analysis excited by synchrotron radiation applied to trace element analysis of biological cells is investigated.The Beijing synchrotron radiation TXRF facility and the related xperimental method are also described.The elemental mininum detection limits of some standard reference materials are determined.The elemental compositions of a cluster of small intestine cells of a small white mouse are given,and hence the average trace element contents of the single small intestine cell are also obtained.With this technique,the changes of some trace elements in the cells of lung and cervix cancer before and after apoptosis are also preliminarily studied.2001 Elsevier Science B.V.All rights Reserved.     

Theoretical Study of Field Intensity of THz Radiation from GaAs Large-Aperture Photoconductive Antennas

We simulate the THz radiation＇s time domain waveforms of both the near field and the far field of a GaAs large aperture photoconductive antenna based on the current surge model. Because the micro-kinetic factors, such as transient state changes of current carrier＇s mobility and lifetime of current carriers, are taken into account in the calculation, we find out the influences of these factors on the THz radiation intensity by changing the above parameters. The results are of guiding significance to design of high-power photoconductive THz radiation antenna materials.     

重离子辐射权重因数与辐射损伤模型研究进展

以第五届国际重离子在生物医学中应用会议和第十届国际辐射研究大会为背景,讨论了重离子生物学效应因数、辐射损伤生物物理模型和物理参数的表征等问题． Based on the fifth workshop on heavy charged particles in biology and medicine and the 10 th international congress of radiation research,the biological effects of heavy ions and biophysical models of heavy ions are discussed.     

A modal analysis for the acoustic radiation problems, I. Theory

For the acoustic radiation problems from a complex vibrating body surface, a modal analysis approach is put forward. All the normal vibration velocities on a vibrating surface form the Hilbert space. In the Hilbert space, an operator is defined, which includes the radiation property of the vibrating surface and is linear, self-adjoint and positive. Using the operator, a set of basis functions in the Hilbert space are obtained, which describe the radiation patterns and are called the radiation modes. Based on the radiation modes, a set of basis functions of the radiation field are obtained by the Helmholtz simple layer potentials, which describe the distribution patterns of the radiation field and are called the field distribution modes. The radiation behavior can be expressed by expansions of the radiation modes and the field distribution modes. The modal analysis approach is introduced into the acoustic radiation problems.     

A modal analysis for the acoustic radiation problems, Ⅱ. Examples

The acoustic radiation modes and the field distribution modes describe the radiation patterns of a complex vibrating surface and the field distribution patterns respectively. The physical meanings of the acoustic radiation modes and the field distribution modes are revealed by numerical method. For a sphere body, a spinning body and a rectangular body, the geometrical patterns of the acoustic radiation modes and the field distribution modes are given. The radiation mode 1 represents the radiation behavior of a monopole radiator, the radiation modes 2 through 4 represent the radiation behavior of dipole radiators respectively, and the radiation modes 5 through 9 represent the radiation behavior of quadrapole radiators respectively. The acoustic radiation modes and the field distribution modes introduce the multi-pole decomposition method into discussion of the acoustic radiation problems.     

60Co gamma radiation effect on AlGaN/AlN/GaN HEMT devices

The testing techniques and experimental methods of the ⁶⁰Co gamma irradiation effect on AlGaN/AlN/ GaN high electron mobility transistors （HEMTs） are established. The degradation of the electrical properties of the device under the actual radiation environment are analyzed theoretically, and studies of the total dose effects of gamma radiation on AlGaN/AlN/GaN HEMTs at three different radiation bias conditions are carried out. The degradation patterns of the main parameters of the AlGaN/AlN/GaN HEMTs at different doses are then investigated, and the device parameters that were sensitive to the gamma radiation induced damage and the total dose level induced device damage are obtained.     

电离辐射引起的线粒体DNA损伤及突变研究进展

指出了线粒体DNA损伤及突变研究与核DNA相关研究的区别,并总结了国内外关于电离辐射引起线粒体DNA损伤突变的研究进展。 针对放射生物学中线粒体学方面研究还有待进一步加强的现状, 中国科学院近代物理研究所的研究人员在方法学上建立起了real-time PCR和long PCR等手段对线粒体DNA损伤及突变进行定量检测, 并以此为基础, 对电离辐射引起的线粒体功能变化进行了较为深入的研究。总结了线粒体DNA损伤及突变研究对阐明电离辐射引起的生物学效应所具有的贡献, 提出未来在放射生物学中以远后效应, 能量代谢为主的线粒体学研究方向。 Current advance in ionizing radiation induced mitochondrial DNA damage and mutations is reviewed, in addition with the essential differences between mtDNA and nDNA damage and mutations. To extent the knowledge about radiation induced mitochondrial alterations, the researchers in Institute of Modern Physics, Chinese Academy of Sciences developed some technics such as real time PCR, long PCR for accurate quantification of radiation induced damage and mutations, and in depth investigation about the functional changes of mitochondria based on mtDNA damage and mutations were also carried out. In conclusion, the important role of mitochondrial study in radiation biology is underlined, and further study on mitochondrial study associated with late effect and metabolism changes in radiation biology is pointed out.     

Characteristics of terahertz generated from picosecond coherent transition radiation ultrashort electron bunches

This paper presents a method of generating terahertz （THz） coherent transition radiation （CTR） from picosecond ultrashort electron bunches including single and train bunches, which are produced by a photocathode radio frequency gun. The radiation characteristics of THz CTR including formation factor and energy spectrum are analysed in detail. With the help of a 2-dimensional particle-in-cell simulation, the radiation characteristics including power, energy and magnetic field are analysed. The results show that the radiation frequency can be adjusted by tuning the repetition frequency of the train bunch and the energy can be enhanced with the train bunches.     

Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches

This paper presents a method of generating terahertz (THz) coherent transition radiation (CTR) from picosecond ultrashort electron bunches including single and train bunches, which are produced by a photocathode radio frequency gun. The radiation characteristics of THz CTR including formation factor and energy spectrum are analysed in detail. With the help of a 2-dimensional particle-in-cell simulation, the radiation characteristics including power, energy and magnetic field are analysed. The results show that the radiation frequency can be adjusted by tuning the repetition frequency of the train bunch and the energy can be enhanced with the train bunches.     

Physics design of SSRF synchrotron radiation security

High brightness of SSRF brings about synchrotron radiation security problems, which will be solved in physics design. The main radiations are generated from bending magnets and insertion devices. Since the fact that radiation power and radiating area are different in these two kinds of synchrotron radiation, the arrangements of photon absorbers, diaphragms and other vacuum components need to be treated distinctively. In addition, SSRF interlock protection threshold is defined and the beam orbit in the straight line is limited. Hence, beam orbit in the bending magnets and IDs are also restricted by the threshold. The orbit restriction is calculated and helps us to arrange the vacuum components. In this paper, beam orbit distortion restricted by interlock protection threshold, radiation power, radiation angle and illuminating area are calculated. From the calculation results, the physics designs in manufacture and installation vacuum components are put forward. By commissioning, it is shown that physics requirements are met rigidly in the engineering process.     

Medical treatment of radiation injuries—Current US status

A nuclear incident or major release of radioactive materials likely would result in vast numbers of patients, many of whom would require novel therapy. Fortunately, the numbers of radiation victims in the United States (USA) have been limited to date. If a mass-casualty situation occurs, there will be a need to perform rapid, accurate dose estimates and to provide appropriate medications and other treatment to ameliorate radiation injury.The medical management of radiation injury is complex. Radiation injury may include acute radiation sickness (ARS) from external and/or internal radiation exposure, internal organ damage from incorporated radioactive isotopes, and cutaneous injury. Human and animal data have shown that optimal medical care may nearly double the survivable dose of ionizing radiation. Current treatment strategies for radiation injuries are discussed with concentration on the medical management of the hematopoietic syndrome.In addition, priority areas for continuing and future research into both acute deterministic injuries and also long-term stochastic sequelae of radiation exposure have been identified. There are several near-term novel therapies that appear to offer excellent prognosis for radiation casualties, and these are also described.     

Influence of X-ray on the autophagic-lysosomal system in rat pancreatic acini

Lysosomes have an important role in radiation injury of cells and tissues. Activation of autophagy is frequently observed in different types of pathological tissue degeneration. In radiation response it increases in some cases, and lysosomes are responsible for regulated degradation of the autophagic vacuoles. Lysosomes are also involved in ionizing radiation induced cell death. In apoptosis lysosomes degrade content of the phagocytotic vacuoles derived from engulfed apoptotic blebs. On the other hand lysosomal enzymes discharged from disintegrated cells have a key role in induction of necrotic changes. In this work we investigate autophagy and lysosomal protein degradation in the relatively radiation insensitive exocrine pancreatic acini in vivo and in vitro. Type of cell death induced by X-ray was also examined in relation to the changes of the lysosomal processes. In 5h after 16 Gy in vivo whole body irradiation we observed significant increase in the cytoplasmic volume fraction of autophagic vacuoles and in the number of apoptotic cells in vivo. But in the acini isolated from irradiated rats we could not detect a change in the lysosomal degradation of intracellular proteins. Therefore irradiation probably influences the autophagy in an earlier step than lysosomal degradation. Extended necrotic lesions were not observed in vivo as long as 48 h. Isolated pancreatic acini usually contain more autophagic vacuoles than in vivo, but we could not observe additional increase in autophagy after 8 Gy, in vitro irradiation. Lysosomal degradation of intracellular proteins was also unaltered after 8 Gy, in vitro irradiation. Other biochemical functional parameters of the isolated pancreatic acini, like protein synthesis and amylase secretion were not changed either after 8 Gy, in vitro X-ray treatment. These results indicate that pancreatic acinar cells in vitro have a high tolerance to irradiation. The observed in vivo radiation induced changes of the exocrine pancreas are possibly indirectly induced by injuries of more sensitive mechanisms.     

On the distribution of the injury severity during radiation accidents and the human ability to ignore radiation risk

The paper is devoted to nuclear reactor accidents, radiation injuries during accidents, and the so-called “human factor”. The balance equation of dose characteristics in the human body and environment is presented. It is attempted to quantitatively estimate the relative variability of the human ability to ignore radiation risk.     

Real‐space analysis of radiation‐induced specific changes with independent component analysis

A method of analysis is presented that allows for the separation of specific radiation‐induced changes into distinct components in real space. The method relies on independent component analysis (ICA) and can be effectively applied to electron density maps and other types of maps, provided that they can be represented as sets of numbers on a grid. Here, for glucose isomerase crystals, ICA was used in a proof‐of‐concept analysis to separate temperature‐dependent and temperature‐independent components of specific radiation‐induced changes for data sets acquired from multiple crystals across multiple temperatures. ICA identified two components, with the temperature‐independent component being responsible for the majority of specific radiation‐induced changes at temperatures below 130 K. The patterns of specific temperature‐independent radiation‐induced changes suggest a contribution from the tunnelling of electron holes as a possible explanation. In the second case, where a group of 22 data sets was collected on a single thaumatin crystal, ICA was used in another type of analysis to separate specific radiation‐induced effects happening on different exposure‐level scales. Here, ICA identified two components of specific radiation‐induced changes that likely result from radiation‐induced chemical reactions progressing with different rates at different locations in the structure. In addition, ICA unexpectedly identified the radiation‐damage state corresponding to reduced disulfide bridges rather than the zero‐dose extrapolated state as the highest contrast structure. The application of ICA to the analysis of specific radiation‐induced changes in real space and the data pre‐processing for ICA that relies on singular value decomposition, which was used previously in data space to validate a two‐component physical model of X‐ray radiation‐induced changes, are discussed in detail. This work lays a foundation for a better understanding of protein‐specific radiation chemistries and provides a framework for analysing effects of specific radiation damage in crystallographic and cryo‐EM experiments.     

电介质材料辐射感应电导率的模型研究

在传统的Rose-Fowler-Vaisberg(RFV)模型基础上引入辐射激发项，解释了辐射感应电导率与辐射剂量率的指数关系及范围.利用改进后的模型分析了不同辐射条件下材料感应电导率的变化情况，其结果表明，辐射剂量率主要影响感应电导率的大小，对感应电导率的整体变化趋势无显著影响，决定感应电导率长时间衰减的是材料载流子复合率.     

A numerical model for the leakage characteristics in ferroelectric thin films under ionizing radiation

A numerical model is developed to describe the leakage characteristics in ferroelectric thin films under ionizing radiation. The trap-controlled space-charge-limited conduction mechanism is modified by considering radiation-induced charge carriers and changes in the relative dielectric constant. The effect of dose rate is related to the changes in the carrier mobility. Numerical simulation using this model reveals a radiation hardness of 10 Mrad(Si) for barium strontium titanate (BST) thin films at a constant dose rate of 10 Krad(Si)/s. Differences in the leakage behavior under radiation for different conduction regions are also discussed. This model provides a useful tool in predicting the leakage behavior under ionizing radiation and estimating the radiation hardness for ferroelectric materials.     

A new aspect of specific radiation damage: hydrogen abstraction from organic molecules

Radiation damage is one of the major impediments in obtaining high‐resolution structural information utilizing ionizing radiation. From electron microscopy it is known that electron irradiation of biological samples results in the formation of molecular hydrogen. In the present work radiation‐induced structural changes of the polypeptide cyclosporine A were observed at a temperature of 100 K. Bond length changes are thought to be due to radiation‐induced hydrogen abstraction which chemically modifies the molecules in an irreversible way. The resulting formation of molecular hydrogen might explain the observed increase of the crystal mosaicity, which has also been reported in many previous radiation damage studies.     

Specific Features of Radiation Inheritance

Specific features of the radiation inheritance of metals and alloys are analyzed. A conclusion on the irreversible changes in the structure of materials after irradiation is drawn. Mechanisms of inheriting the radiation effects in the process of high-temperature transformation of materials are suggested. The concentration microinhomogeneities initiated in the preliminary irradiated defect structure of the material are shown to be the genetic factor of the radiation inheritance.     

“Radiation vector” of accelerated cavity

New phenomena of dynamic changes of the radiation mode in a rectangular cavity during its accelerated motion are detected. Eigenvalues of the three-dimensional problem for a homogeneous equation of phase change are determined. Allowed radiation directions in the non-uniformly moving cavity are discussed.     

Radiation response of cell organelles

The cellular responses to various form of radiation, including ionizing- and UV-irradiation or exposure to electromagnetic fields is manifested as irreversible and reversible structural and functional changes to cells and cell organelles. Moreover, beside the morphological signs related to cell death, there are several reversible alterations in the structure of different cell organelles. The radiation-induced changes in the supramolecular organization of the membranes, including plasma membrane, and different cell organelle membranes, play a significant role in the development of acute radiation injury. These signs of radiation-induced reversible perturbation biological membranes reflect changes in the organization and/or composition of the glycocalix, modified activity and/or distribution of different membrane domains, including enzymes and binding sites. The observed changes of the cell surface micromorphology and the alteration of intercellular connections are closely related to the reorganization of the cytoskeletal elements in the irradiated cells. The mitochondria, endoplasmic reticulum, Golgi-complex, the lysosomal system have long been considered to be direct intracellular targets of irradiation. The listed morphological alterations of nuclear chromatin (e.g. changes of fine structure, altered number of nucleolar organizing regions and micronuclei, development of chromosome aberrations) may originate from the radiation-induced damage to the supramolecular organization of DNA and/or nucleus specific proteins. These endpoints of radiation effects resulted as direct consequence(s) of absorbed radiation energy, and indirectly altered intra-, intercellular communication or modified signal transduction. Some complementary data suggest that all these effects are not strictly specific to radiation and may be best considered as general stress responses, similar to those observed after application of various injurious agents and treatments to cells. Moreover, they may be equally responsible for direct degradation of supramolecular component of cells, altered signal transduction, or changes in the amount or ratio of any extracellular mediators upon irradiation. Nevertheless, qualitative and/or quantitative evaluation of any changes of chromosomes by different techniques (morphological analysis of metaphase chromosomes, fluorescent in situ hybridization, development of micronuclei etc.) are useful biological indicators as well as "biological dosimeters" of radiation injury. It is suggested, that some modern methods such as immunohistochemical detection of different proteins, specific markers of cell organelles and cytoskeleton, inspection of distribution of cell surface charged sites and different membrane domains and application of tracer substances may all be included into protocols for evaluation of cell alterations induced by different types and intensities of radiation.