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1.
In vitro bioassay measurements for plutonium have been performed on a routine basis for many years. Since the biokinetic models have changed considerably and the dose limitation systems have become more restrictive, it is necessary to estimate the impact of these changes on the interpretation of bioassay measurements. This study is carried out for the plutonium systemic models proposed by the ICRP publications: ICRP-30, ICRP-48, and ICRP-56, using the excretion functions proposed by Langham, Durbin, and Jones. A quantitative comparison of dose estimates using the dose limitation systems proposed in the ICRP Publications 26 and 60 is also done. In order to evaluate the impact on the use of the new ICRP respiratory tract model, a comparative study of intake and dose estimates, using the new and the ICRP-30 respiratory tract models, was also done for the case of inhalation of plutonium compounds. These calculations are particularly important to provide means to compare doses when the occupational exposures lasted many years and the doses were assessed using different models and dose limitation systems.Since some countries are in the process of changing the dose limitation system from the recommendations of the ICRP-26 to the ICRP-60, or even from the ICRP-2 to the ICRP-26, a quantitative comparison of dose estimates will be shown. In order to evaluate the impact on the use of the new ICRP respiratory tract model, a comparative study of intake and dose estimates using the new and the ICRP-30 respiratory tract models will also be shown for the case of inhalation of plutonium compounds.  相似文献   

2.
Thorium has been determined volumetrically. It has been precipitated with m-nitrobenzoic acid according to the method of Neish. Thorium m-nitrobenzoate has been then dissolved in sulphuric acid and titrated with titanous chloride to determine the NO2-group which gives the amount of thorium directly.  相似文献   

3.
Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl4 into ThCl2 2+, ThCl3+ and Th4+. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S.Joshi for his keen interest in this work and to Dr. G. S.Deshmukh for his advice and help in so many ways during the progress of these studies.  相似文献   

4.
Different strategies of multivariate data analysis are used to interpret a data base from geological samples. Cluster and correspondence analysis are applied to classify properly 34 chemical elements from 10 representative rock samples (volcanic series from Borovitsa, Rhodopa mountains, Bulgaria). Principal components analysis is also used as display method to visualize the relation between the variables and objects of interest. The multivariate data analysis applied makes it possible to interpret the origin and orogenesis of the samples.  相似文献   

5.
A solvent extraction technique to separate different chemical species of thorium is presented. The products formed by the chemical effects of the /n,/ reaction on the Th/acac/4 were separated by this method and the retention value was measured.  相似文献   

6.
A model based on the altered free volume state concept has been proposed here to predict the melt flow index values of multicomponent systems as a function of the amount of the dispersed phase. The predictions of the model have been compared with experimental results reported in the literature on a diverse range of multicomponent polymeric systems. The agreement between the model predictions and the experimentally determined values is good.  相似文献   

7.
Bioassay and dosometry models are needed to estimate intakes of radionuclides, and to calculate radiation doses to target tissues following such in takes. Because of the diversity of exposure materials, individual biological variabilities, and the general lack of adequate bioassay information and knowledge of the metabolism of radionuclides, current models are based mostly on empiricism. This paper describes biokinetic/dosimetry models for U, Am, and Cm. They are based on experimental data developed from studies in dogs that inhaled one of the above radionuclides in specific chemical forms and specific particle sizes. The models, which are based on similar biological principles, and, therefore, have similar structure, are applied to the very sparse human bioassay data available from cases of exposure to either U, Am, or Cm. The results thus far indicate that the lung retention for the different actinides are well described by the models, that urinary bioassay data can be described within limited time periods, and that the fecal excretion rate is not adequately described. Improvements in modeling are predicted on increased publication of human bioassay data, and better cooperative interaction between model developers and health protection professionals responsible for industrial bioassay programs.  相似文献   

8.
Recent developments in proteomics have revealed a bottleneck in bioinformatics: high-quality interpretation of acquired MS data. The ability to generate thousands of MS spectra per day, and the demand for this, makes manual methods inadequate for analysis and underlines the need to transfer the advanced capabilities of an expert human user into sophisticated MS interpretation algorithms. The identification rate in current high-throughput proteomics studies is not only a matter of instrumentation. We present software for high-throughput PMF identification, which enables robust and confident protein identification at higher rates. This has been achieved by automated calibration, peak rejection, and use of a meta search approach which employs various PMF search engines. The automatic calibration consists of a dynamic, spectral information-dependent algorithm, which combines various known calibration methods and iteratively establishes an optimised calibration. The peak rejection algorithm filters signals that are unrelated to the analysed protein by use of automatically generated and dataset-dependent exclusion lists. In the "meta search" several known PMF search engines are triggered and their results are merged by use of a meta score. The significance of the meta score was assessed by simulation of PMF identification with 10,000 artificial spectra resembling a data situation close to the measured dataset. By means of this simulation the meta score is linked to expectation values as a statistical measure. The presented software is part of the proteome database ProteinScape which links the information derived from MS data to other relevant proteomics data. We demonstrate the performance of the presented system with MS data from 1891 PMF spectra. As a result of automatic calibration and peak rejection the identification rate increased from 6% to 44%.Abbreviations 2-DE Two-dimensional gel electrophoresis - MALDI Matrix-assisted laser desorption ionisation - PMF Peptide mass fingerprinting - MS Mass spectrometry - TOF Time of flight  相似文献   

9.
10.
A routine procedure has been developed for the simultaneous determination of uranium and thorium in high concentration thorium ores. INAA is used to determine the uranium and thorium concentration. However, for very low concentrations of uranium a radiochemical procedure based on the use of NPy/benzene as an extractant has to be employed. The precision and accuracy of the method has been determined by analyzing IAEA and NBL standard thorium/uranium ores.  相似文献   

11.
Measurements of CO pressure over the thorium dioxide, thorium dicarbide, carbon phase region were made in the range 1328–1976 K. These values were used with other consistent measurements to derive the 298 K second-law heat of formation and entropy 129±6 kJ/mol and 67.0±3 J·mol−1·K−1, and the third-law heat of formation −122±9 kJ/mol, for thorium dicarbide.  相似文献   

12.
The uptake of trace gases such as OH and HO2 radicals, NH3, ClONO2, N2O5, ozone, and many other gases by water, aqueous solutions of acids, and salts has been reported by numerous investigators using a variety of techniques. Reported uptake coefficients vary greatly, ranging from 10(-8) to 1. This paper describes a new analysis of uptake data obtained in flow tubes that consolidates data obtained for various flow rates and trace gas concentrations. Previous analyses, which have been often used, are shown to be limiting cases or special cases of the analysis outlined here. Of particular emphasis are results for wetted-wall columns and trace gas uptake by aerosol entrained in flow tubes. In the absence of aerosol, the analysis is shown to predict the decrease in trace gas concentration due to bulk chemical reaction and/or reaction at the tube wall or gas-liquid interface. Uptake coefficients for OH and HO2 radicals on water in wetted-wall tubes are shown to range from 0.01 to 1, and on sulfuric acid, they vary from 0.008 to 0.03. For O3 on a water film doped with a scavenger, the uptake coefficient is found to be 0.0008. Uptake coefficients determined by different techniques are compared.  相似文献   

13.
14.
Summary Thorium has been determined by titration with EDTA (disodium salt) solution as complexometric reagent at pH 3–4.5 using a drop of 0.01 M iron(III) solution mixed with thiocyanate-p-anisidine as indicator. Calcium, barium, strontium, magnesium or manganese ions do not interfere, but zinc, zirconium, lead, silver, aluminium, bismuth, phosphate, fluoride or oxalate ions interfere in this estimation. In these complexometric titrations the quantitative results obtained by using a drop of iron(III) solution mixed with thiocyanate-p-anisidine as indicator are comparable with those obtained with pyrocatechol violet indicator.
Zusammenfassung Thorium wird bei pH 4–4,5 mit ÄDTA titriert, wobei ein Gemisch eines Tropfens Eisen(III)-lösung mit Thiocyanat-p-Anisidinlösung als Indicator dient. Calcium, Barium, Strontium, Magnesium oder Mangan verursachen keine Störung, wogegen folgende Ionen stören: Zink, Zirkonium, Blei, Silber, Aluminium, Wismut, Phosphat, Fluorid oder Oxalat. Der erwähnte Mischindicator liefert ähnlich genaue Titrationsergebnisse wie bei Verwendung von Brenzcatechinviolett als Indicator.


The authors take this opportunity to thank the Council of Scientific and Industrial Research (India) for the award of Junior Fellowship to one of them (junior author). This has enabled us to pursue the study of complexometric titrations.  相似文献   

15.
Since thorium in lunar crystalline rocks was reported to be excessive in 4.6 MeV alpha-activity up to 80%, which was attributed to a long-lived isomer of232Th with an origin different from normal thorium, we have measured alpha-spectra of various terrestrial thorium in order to see if terrestrial thorium also contains some excess 4.6 MeV alpha-activity. The results showed that the content of the excess 4.6 MeV alpha-activity in terrestrial thorium, if any, is much less than 3%. An approach to set an upper limit for the excess alpha-activity in terrestrial thorium is proposed. The origin of the excess alpha-activity is discussed.  相似文献   

16.
Time-of-flight secondary ion mass spectrometry (TOF-SIMS), when used for the analysis of complex material samples, typically provides data that are complicated and challenging to understand. Therefore, additional data analysis techniques, such as multivariate analysis, are often required to facilitate the interpretation of TOF-SIMS data. In this study, a new method based on the information entropy (Shannon entropy) is proposed as an indicator of the outline characteristics of an unknown sample, such as changes in the material within the sample and mixing conditions. The Shannon entropy values are calculated using the relative intensity of every secondary ion normalized to the total ion count and reflect the diversity of secondary ions in the spectrum. Mixed samples containing two organic electroluminescence materials of different ratios, multilayers of Irganox 1010, and other organic materials were employed to evaluate the utility of Shannon entropy in the analysis of TOF-SIMS data. The findings demonstrate that the Shannon entropy of a spectrum indicates differences in materials and changes in the conditions of a material in a sample without the need for peak identification or the knowledge of specific peaks corresponding to the materials in the sample.  相似文献   

17.
An overview of the application of chemometric data analysis methods to complex chemical mixtures in various environmental media is presented. Reviews of selected research are given as examples of the application of principal components analysis and other statistical methods to identify contributions from multiple sources of contamination in air, water, sediments, and biota. Other examples are cited that illustrate how scientists have used classification and regression methods to model the distribution of anthropogenic contaminants and predict their environmental effects or fate.  相似文献   

18.
19.
A series of synthetic mixtures of thorium isotopes was prepared on a gravimetrical basis. The starting compounds consisted of natural thorium 232Th (99.99%) and highly enriched 230Th (99.8%). These materials were chemically purified and characterized for isotopic composition and chemical purity. Thorium dioxide (ThO2) was demonstrated to be a suitable compound for gravimetrical blending. The isotope amount ratios in the mixtures ranged from 10−2 to 3 × 10−6. These synthetic isotope mixtures are to our knowledge, the first ever prepared for thorium and may serve for calibration purposes.  相似文献   

20.
It is shown that it is possible to fit conductance data in solvents of low dielectric constant without the additional assumption of triple ion formation. With the aid of two new conductance equations, which incoporate in different ways a mass action law for ion pairing but not for ion triplets, we can account for the conductivity data for the systems LiBr in octanol and NaI in butanol. One of the equations incorporates the mean spherical approximation.  相似文献   

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