Micro-ERDA,micro-RBS and micro-PIXE techniques in the investigation of fish otoliths

Elemental distribution in the otolith of the fresh water fish burbot (Lota lota L.) collected in Hungary was measured with Elastic Recoil Detection Analysis (ERDA), Rutherford Backscattering Spectrometry (RBS) and as a complementary technique, Particle-Induced X-ray Emission (PIXE) with a focussed ion beam of 1.5 × 1.5 μm² spot size. The organic- and inorganic-rich regions of the otolith are distinguished and they are presented as hydrogen and calcium maps at depth regions of 0–70, 70–140 and 140–210 nm. The textured surface of the sample and its porosity were characterized from the effect on the RBS spectra. The oxygen and carbon PIXE elemental maps can also be used to identify the organic- and inorganic-rich regions of the otolith. The calcium map was found to be more homogeneous because the otolith structure is averaged in a larger depth. The trace elements Fe, Zn and Sr were detected only in very low concentration by micro-PIXE.     

Application of the micro-PIXE technique for analyzing arsenic in biomat and lower plants of lichen and mosses around an arsenic mine site, at Gunma, Japan

Microhabitats of bacteria (biomat) and lower plants, such as lichen and mosses, are known to accumulate hazardous elements. Since the concentration of hazardous elements in the environment is quite low, we have applied the in-air μ-PIXE (particle induced X-ray emission) system developed in the TIARA facility of JAERI, which has low concentration detection limit of ppm, to measure As, one of the hazardous elements, distributions in biomat, lichen and mosses observed around an abandoned As mine site in Gunma, Japan to elucidate the applicability of these biomat and lower plants as bio-indicators of As. Spatial distributions of As, Fe, Si and S in all biomat, lichen and moss collected within 3 m from the mine entrance indicate that As is localized, and is associated with silicate and Fe-containing compounds. In addition, the intensity ratio of peak area for As to Fe in μ-PIXE spectrum of the moss collected from the concrete wall at 3 m downstream of the mine water discharge position is different from those of the lower plants on the rock near the closed entrance, but is the same as that of biomat formed at the mine water discharge position. This indicates that As trapped by the moss on the concrete wall probably has the same origin as the biomat. It is concluded that application of μ-PIXE analysis to the measurement of As in the lower plants and biomat gives not only the distribution of the hazardous element of As, but also the information of the origin.     

Evaluation of specimen preparation techniques for micro-PIXE localisation of elements in hyperaccumulating plants

Hybanthus floribundus subsp. floribundus, a rare Australian Ni-hyperaccumulating shrub and Pityrogramma calomelanos var. austroamericana, an Australian naturalized As-hyperaccumulating fern are promising species for use in phytoremediation of contaminated sites. Micro-proton-induced X-ray emission (μ-PIXE) spectroscopy was used to map the elemental distribution of the accumulated metal(loid)s, Ca and K in leaf or pinnule tissues of the two plant species. Samples were prepared by two contrasting specimen preparation techniques: freeze-substitution in tetrahydrofuran (THF) and freeze-drying. The specimens were analysed to compare the suitability of each technique in preserving (i) the spatial elemental distribution and (ii) the tissue structure of the specimens. Further, the μ-PIXE results were compared with concentration of elements in the bulk tissue obtained by ICP-AES analysis.In H. floribundus subsp. floribundus, μ-PIXE analysis revealed Ni, Ca and K concentrations in freeze-dried leaf tissues were at par with bulk tissue concentrations. Elemental distribution maps illustrated that Ni was preferentially localised in the adaxial epidermal tissues (1% DW) and least concentration was found in spongy mesophyll tissues (0.53% DW). Conversely, elemental distribution maps of THF freeze-substituted tissues indicated significantly lower Ni, Ca and K concentrations than freeze-dried specimens and bulk tissue concentrations. Moreover, Ni concentrations were uniform across the whole specimen and no localisation was observed.In P. calomelanos var. austroamericana freeze-dried pinnule tissues, μ-PIXE revealed statistically similar As, Ca and K concentrations as compared to bulk tissue concentrations. Elemental distribution maps showed that As localisation was relatively uniform across the whole specimen. Once again, THF freeze-substituted tissues revealed a significant loss of As compared to freeze-dried specimens and the concentrations obtained by bulk tissue analysis.The results demonstrate that freeze-drying is a suitable sample preparation technique to study elemental distribution of ions in H. floribundus and P. calomelanos plant tissues using μ-PIXE spectroscopy. Furthermore, cellular structure was preserved in samples prepared using this technique.     

Software masking for the accurate determination of elemental quantities in discrete areas of a micro-PIXE scan

A technique is described which allows X-ray energy spectra corresponding to discrete regions of a micro-PIXE scan recorded in multi-parameter mode to be generated. A software mask is created using both user-defined rectangular limits and an algorithm operating on the distribution of one of the major elements in the sample. This mask is used to select X-ray events originating in the region of interest, from which elemental concentrations can be calculated. This technique can allow accurate determination of element concentrations in irregular samples or regions of interest, enhance the signal-to-noise ratio for specimens on thick backings and also allows several areas of the sample to be analysed separately. The use of the technique is demonstrated in an experiment to quantify the total mass of barium contained in a single cell alga (Closterium tumidulum).     

Three-dimensional measurement of elemental distribution in minute samples by combination of in-air micro-PIXE and STIM

A technique of measuring three-dimensional (3D) distribution of trace elements in a minute sample was studied using the in-air micro-PIXE (Particle Induced X-ray Emission) system. A 3D distribution was acquired by means of reconstructing numbers of projection images of the sample obtained by micro-PIXE analyses from different directions. This is basically the same technique as X-ray CT (Computed Tomography). However, when this technique was applied to the in-air micro-PIXE analysis, the X-ray yields should be corrected in taking account of such parameters as the X-ray production cross section, the X-ray attenuation coefficient, the energy of an incident particle, and the 3D densities of major elements in the analysis sample. In this study, STIM (Scanning Transmission Ion Microscopy)-CT was used to obtain the 3D density map of the sample. Corrected 3D distributions of sulfur and iron in a minute test sample were successfully measured with this technique in combination of STIM-CT and in-air micro-PIXE.     

Quantitative micro-PIXE comparison of elemental distribution in Ni-hyperaccumulating and non-accumulating genotypes of Senecio coronatus

The Ni hyperaccumulator, plant species Senecio coronatus (Thunb.) Harv., Asteraceae is an example of plant adaptation mechanisms to different ecological conditions. This widespread species can inter alia be found on serpentine outcrops and the genotypes growing in serpentine soils show different ways of adaptation. The populations from two distant localities take up and translocate Ni in concentrations which are normally phytotoxic, while plants growing on a different site, in the vicinity of another hyperaccumulating species, absorb amounts which are typical for most of the plants found on serpentine soils. The NAC nuclear microprobe was used to compare the distribution of Ni and other elements in selected organs and cells with simultaneous use of PIXE and proton BackScattering (BS). Quantitative maps of stems showed large differences in concentrations and distributions of major and trace elements. In hyperaccumulating genotypes Ni is present everywhere within stem tissues, but the highest concentrations were found in the epidermis, cortex and phloem. In non-accumulating plants Ni was concentrated in the phloem. In the leaf epidermis Ni was concentrated in the cell walls for both accumulating and non-accumulating plants. These results suggest that biochemical diversity is more than morphological, because investigated genotypes belong to the same taxon.     

离子束生物技术在生命科学中的应用

我国科学家80年代发现了离子注入的生物效应,并将这一原理应用于诱变育种.本文介绍了离子束生物技术及原理,低能离子束注入生物学效应的研究,离子束生物技术在新疆的应用和发展.     

The use of the maximum entropy method for the improvement of the spatial resolution of the micro-PIXE maps

The deconvolution procedure based on the maximum-entropy method is applied to improve both resolution and noise characteristics of micro-PIXE maps. The procedure is simple to execute, fast, easily automated and assumes no a priori information. The best improvement is observed for data with low statistics. Special emphasis is given to the difficulties and limitations of processing micro-PIXE data. Examples of applications for biomedical samples are presented.     

Probing cytotoxicity of nanoparticles and organic compounds using scanning proton microscopy, scanning electron microscopy and fluorescence microscopy

Scanning proton microscopy, scanning electron microscopy (SEM) and fluorescence microscopy have been used to probe the cytotoxicity effect of benzo[a]pyrene (BaP), ethidium bromide (EB) and nanoparticles (ZnO, Al₂O₃ and TiO₂) on a T lymphoblastic leukemia Jurkat cell line. The increased calcium ion (from CaCl₂) in the culture medium stimulated the accumulation of BaP and EB inside the cell, leading to cell death. ZnO, Al₂O₃ and TiO₂ nanoparticles, however, showed a protective effect against these two organic compounds. Such inorganic nanoparticles complexed with BaP or EB which became less toxic to the cell. Fe₂O₃ nanoparticles as an insoluble particle model scavenged by macrophage were investigated in rats. They were scavenged out of the lung tissue about 48 h after infection. This result suggest that some insoluble inorganic nanoparticles of PM (particulate matters) showed protective effects on organic toxins induced acute toxic effects as they can be scavenged by macrophage cells. Whereas, some inorganic ions such as calcium ion in PM may help environmental organic toxins to penetrate cell membrane and induce higher toxic effect.     

Micro-SR-XRF and micro-PIXE studies for archaeological gold identification - The case of Carpathian (Transylvanian) gold and of Dacian bracelets

Trace-elements are more significant for provenancing archaeological metallic artifacts than the main components. For gold, the most promising elements are platinum group elements (PGE), Sn, Te, Sb, Hg and Pb. Several small fragments of natural Transylvanian gold - placer and primary - were studied by using micro-PIXE technique at the Legnaro National Laboratory AN2000 microbeam facility, Italy and at the AGLAE accelerator, C2RMF, Paris, France and by using micro synchrotron radiation X-ray fluorescence (micro-SR-XRF) at BESSY synchrotron, Berlin, Germany. The goal of the study was to identify the trace-elements, especially Sn, Sb and Te. A spectacular application to five Dacian gold bracelets authentication is presented (Sn and Sb traces).     

PHEBUS FP: a severe accident research programme for current and advanced light water reactors

The ongoing PHEBUS FP programme is the centrepiece of an international co-operation investigating, through a series of integral in-pile experiments, key-phenomena involved in the progression of a postulated severe accident in a light water reactor (LWR). The dedicated PHEBUS facility offers the capability to study the degradation of real core material, from the early phase of cladding oxidation and hydrogen production up to the late phase of melt progression and molten pool formation. The subsequent release of fission products (FPs) and structural materials is also experimentally studied, including their physicochemical interactions, their transport in the cooling system, and their deposition in the containment. The revolatilisation of iodine due to radiochemical effects in the water of the sump and the amount of low-volatility FPs and transuranium elements reaching the containment are receiving a special interest, as large uncertainties related to their modelling subsist. FPT-0 and FPT-1, the first experiments of the programme, performed in December 1993, and July 1996, respectively, have demonstrated that the PHEBUS FP facility is capable of successfully attaining these objectives. They reached very advanced states of degradation, comparable to what was observed in TMI 2, and generated a wealth of results on FP behaviour. The resulting database has been—and will be—applied to develop and validate the computer codes used to assess the safety of the currently operating plants and to check the efficiency of accident management procedures. They will also support the design of future plants having the capacity to confine core melt-down accidents within their containments.     

Investigating microstructure of Longmaxi shale in Shizhu area,Sichuan Basin,by optical microscopy,scanning electron microscopy and micro-computed tomography

Microstructure of shale formation is the key to understanding its petrophysical and chemical properties.Optical microscopy, scanning electron microscopy and micro-computed tomography(μ-CT) have been combined for characterization of microstructure of Longmaxi(LMX)shale from Shizhu area, Sichan Basin. The results indicate that laminated LMX shale consists of mineral matrix-rich layers and organic matter(OM)-rich layers at micrometer scale in two and three dimensions. Mineral matrix layers,mainly consisting of interparticle pores and intraplatelet pores, are approximately parallel to the bedding plane.Pyrite-rich layer, mainly containing intercrystalline pores,shows a strong preferred orientation parallel to the bedding plane. OM-rich layer, mainly containing OM pores, seems to be discontinuous. In addition, intercrystalline pores are enriched in some layers, while OM pores are distributed irregularly in matrix layers. This vertical heterogeneity of pore microscopic structures in LMX shale is of great importance to understand its petrophysical and chemical properties.     

时间微分扰动角关联技术在材料科学中的应用

介绍了时间微分扰动角关联方法的基本原理及其在材料微观性质研究中的应用。     

US NRC research on the integrity of piping in light water reactors

The paper describes the activities underway in NRC on the subject of LWR piping integrity as of the summer and fall of 1983. The paper is necessarily vague on certain topics of policy because they are either under review or are under development. Particularly in the area of BWR pipe cracking, events are very rapid so that positions and actions described in this paper may well be obsolete by the time it is published. Nevertheless, this paper is useful to show the intentions of NRC in the area of research for LWR piping, and it is also useful to document the status of the regulations on piping for which the research is being performed.     

Application of homogenization techniques for inflow transport approximation on light water reactor analysis

The transport cross-section based on inflow transport approximation can significantly improve the accuracy of light water reactor （LWR） analysis,especially for the treatment of the anisotropic scattering effect.The previous inflow transport approximation is based on the moderator cross-section and normalized fission source,which is approximated using transport theory.Although the accuracy of reactivity is increased,the P₀ flux moment has a large error in the Monte Carlo code.In this s...     

Experience in international collaboration in the development of preliminary plans for decommissioning nuclear research facilities at the Russian science center Kurchatov institute

The joint work performed by specialists at the Russian Science Center Kurchatov Institute, VT Nuclear Services, and Serso Assurance/RWE NUKEM on the development of preliminary plans for decommissioning nuclear research facilities at the Russian Science Center Kurchatov Institute is described. Special attention is focused on using modern methodology and foreign experience in planning such work taking account of local conditions.     

PET/MRI在心脏核医学中的应用研究

PET/MRI作为一种最新的多模式分子影像技术,具有准确性高、没有辐射等优点,在科研与临床特别是心脏核医学等领域的应用潜力日益显现。结合PET/MRI的发展现状,分析了PET/MRI发展需要攻克的关键技术,阐述了PET/MRI应用于心肌显像与心血池显像的临床价值,指出了PET/MRI在心脏核医学中应用需要关注的主要问题。