Comparison of observed skeleton retention of strontium in average indian adult with the value predicted by the ICRP biokinetic model

The daily dietary intake of strontium and its content in skeleton, for an Indian adult population group were estimated by experimentally measuring its concentration in total cooked diet and autopsy skeleton samples using radiochemical neutron activation analysis. The data on daily dietary intake of strontium were used to compute its contents in skeleton using ICRP Publication 67 biokinetic model for strontium. The theoretically computed value of strontium (213.8 mg) compared favourably with the measured values (GM 181.2 mg) in an urban population group living in Mumbai representing an average Indian adult (Reference Indian Man).     

The ENEA criticality accident dosimetry system: a contribution to the 2002 international intercomparison at the SILENE reactor

The present paper summarises the activity carried out at the ENEA Radiation Protection Institute for updating the methodologies employed for the evaluation of the neutron and photon dose to the exposed workers in case of a criticality accident, in the framework of the 'International Intercomparison of Criticality Accident Dosimetry Systems' (Silène reactor, IRSN-CEA-Valduc June 2002). The evaluation of the neutron spectra and the neutron dosimetric quantities relies on activation detectors and on unfolding algorithms. Thermoluminescent detectors are employed for the gamma dose measurement. The work is aimed at accurately characterising the measurement system and, at the same time, testing the algorithms. Useful spectral information were included, based on Monte Carlo simulations, to take into account the potential accident scenarios of practical interest. All along this exercise intercomparison a particular attention was devoted to the 'traceability' of all the experimental and computational parameters and therefore, aimed at an easy treatment by the user.     

Comparison of observed body retention of uranium in natural condition in an average Indian adult with the values predicted by the ICRP biokinetic model

The daily intake of natural uranium and its contents in the lungs, skeleton, liver and kidney of an Indian adult population group was estimated using radiochemical neutron activation analysis (RNAA). These data on daily intake (through inhalation and ingestion) were used to compute the uranium contents in the lungs and other systemic organs such as the skeleton, liver and kidney, using the new human respiratory tract model (HRTM) and the new biokinetic model of uranium. The theoretically computed uranium contents in the lungs, skeleton, liver and kidney of an average Indian adult are 1.16, 1.96, 0.07 and 0.04 microg, respectively, and the corresponding experimentally measured values are 1.23 (1.76), 2.92 (2.5), 0.07 (1.76) and 0.19 (1.47) microg in an urban population group living in Mumbai. The values given in parentheses are geometric standard deviation (GSD). It is seen that the measured uranium contents in the lungs, skeleton and liver agree very well with the corresponding computed values, but the measured value for the kidney is observed to be on the higher side of the computed value. However, in view of many uncertainties, the overall agreement between the measured and the computed values can be considered to be good. Therefore, the result from this study can be taken as a validation of the new biokinetic model of uranium in Indian conditions.     

Comparison of observed lung retention and urinary excretion of thorium workers and members of the public in India with the values predicted by the ICRP biokinetic model

The daily intake of natural Th and its contents in lungs, skeleton and liver of an Indian adult population group were estimated using radiochemical neutron activation analysis (RNAA) technique. These data on daily intake (through inhalation and ingestion) were used to compute Th contents in lungs and other systemic organs such as skeleton and liver using the new human respiratory tract model (HRTM) and the new biokinetic model of Th. The theoretically computed Th contents in lungs, skeleton and liver of an average Indian adult are 2.56, 4.00 and 0.17 microg, respectively which are comparable with the corresponding experimentally measured values of 4.31, 3.45 and 0.14 microg in an urban population group living in Mumbai. The measured lung contents of Th in a group of five occupational workers were used to compute their total body Th contents and the corresponding daily urinary excretions. The computed total body contents and daily urinary excretions of Th in the five subjects compared favourably with their measured values. These studies, thus, validate the new biokinetic model of Th in natural as well as in occupational exposures in Indian conditions.     

Automatic application of ICRP biokinetic models in voxel phantoms for in vivo counting and internal dose assessment

As part of the improvement of calibration techniques of in vivo counting, the Laboratory of Internal Dose Assessment of the Institute of Radiological Protection and Nuclear Safety has developed a computer tool, 'OEDIPE', to model internal contamination, to simulate in vivo counting and to calculate internal dose. The first version of this software could model sources located in a single organ. As the distribution of the contamination evolves from the time of intake according to the biokinetics of the radionuclide, a new facility has been added to the software first to allow complex heterogeneous source modelling and then to automatically integrate the distribution of the contamination in the different tissues estimated by biokinetic calculation at any time since the intake. These new developments give the opportunity to study the influence of the biokinetics on the in vivo counting, leading to a better assessment of the calibration factors and the corresponding uncertainties.     

Variability and uncertainty of biokinetic model parameters: the discrete empirical Bayes approximation

In the Bayesian approach to internal dosimetry, uncertainty and variability of biokinetic model parameters need to be taken into account. The discrete empirical Bayes approximation replaces integration over biokinetic model parameters by discrete summation in the evaluation of Bayesian posterior averages using Bayes theorem. The discrete choices of parameters are taken as best-fit point determinations of model parameters for a study subpopulation with extensive data. A simple heuristic model is constructed to numerically and theoretically study this approximation. The heuristic example is the measurement of heights of a group of people, say from a photograph where measurement uncertainty is significant. A comparison is made of posterior mean and standard deviation of height after a measurement, (i) using the exact prior describing the distribution of true height in the population and (ii) using the approximate discrete empirical Bayes prior obtained from measurements of some study subpopulation.     

Computation of cross sections and dose conversion factors for criticality accident dosimetry

In the application of criticality accident dosemeters the cross sections and fluence-to-dose conversion factors have to be computed. The cross section and fluence-to-dose conversion factor for the thermal and epi-thermal contributions to neutron dose are well documented; for higher energy regions (>100 keV) these depend on the spectrum assumed. Fluence is determined using threshold detectors. The cross sections require the folding of an expected spectrum with the reaction cross sections. The fluence-to-dose conversion factors also require a similar computation. The true and effective thresholds are used to include the information on the expected spectrum. The spectra can either be taken from compendia or measured at the facility at which the exposures are to be expected. The cross sections can be taken from data computations or analytic representations and the fluence-to-dose conversion factors are determined by various standards making bodies. The problem remaining is the method of computation. The purpose of this paper is to compare two methods for computing these factors: analytic and Monte Carlo.     

Some elements for a revision of the americium reference biokinetic model

The interpretation of individual activity measurement after a contamination by 241Am or its parent nuclide 241Pu is based on the reference americium (Am) biokinetic model published by the International Commission on Radiological Protection in 1993 [International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 2 Ingestion dose coefficients. ICRP Publication 67. Ann. ICRP 23(3/4) (1993)]. The authors analysed the new data about Am biokinetics reported afterwards to propose an update of the current model. The most interesting results, from the United States Transuranium and Uranium Registries post-mortem measurement database [Filipy, R. E. and Russel, J. J. The United States Transuranium and Uranium Registries as sources for actinide dosimetry and bioeffects. Radiat. Prot. Dosim. 105(1-4), 185-187 (2003)] and the long-term follow-up of cases of inhalation intake [Malátová, I., Foltánová, S., Becková, V., Filgas, R., Pospísilová, H. and H?lgye, Z. Assessment of occupational doses from internal contamination with 241Am. Radiat. Prot. Dosim. 105(1-4), 325-328 (2003)], seemed to show that the current model underestimates the retention in the massive soft tissues and overestimates the retention in the skeleton and the late urinary excretion. However, a critical review of the data demonstrated that all were not equally reliable and suggested that only a slight revision of the model, possibly involving a change in the balance of activity between massive soft tissues, cortical and trabecular bone surfaces, may be required.     

4M852/32型氧压机着火事故原因分析及解决办法

介绍 4M8 5 2 /32型氧压机着火的事故经过 ,原因是四级拉杆温度骤升 ,且存在漏气与漏油 ,从而引起着火。相应采取了措施 ,已安全运行 16个月     

Validation process and uncertainty budget: a recommended approach for performance verification

Within its Occupational Radiation Protection Programme, the International Atomic Energy Agency (IAEA) initiated and funded many international and regional intercomparison exercises, with the aim of verifying performance of the individual monitoring service providers. An important component within the quality system is the validation and uncertainty budget of the method used. Each method must be validated. This validation process must provide evidence that the method can fulfil all requirements for its intended use. A method may be regarded as validated only when it fulfils all requirements established before the validation process. This paper reviews methods recommended for different types of measurement techniques in individual monitoring.     

Reference dosimetry measurements for the international intercomparison of criticality accident dosimetry SILENE 9-21 June 2002

An international intercomparison of criticality accident dosimetry systems took place in the SILENE reactor, in June 2002. Participants from 60 laboratories irradiated their dosemeters (physical and biological) using two different configurations of the reactor. In preparation for this intercomparison, the leakage radiation fields were characterised by spectrometry and dosimetry measurements using the ROSPEC spectrometer associated with a NE-213 scintillator, ionisation chambers, GM counters, diodes and thermoluminescence dosemeters (TLDs). For this intercomparison, a large area was required to irradiate the dosemeters both in free air and on phantoms. Therefore, measurements of the uniformity of the field were performed with activation detectors and TLDs for neutron and gammas, respectively. This paper describes the procedures used and the results obtained.     

Templated assembly by selective removal: simultaneous, selective assembly and model verification

The use of templated assembly by selective removal to simultaneously and selectively assemble silica microspheres of two different diameters into designated sites on a surface was demonstrated. Microspheres with diameters of 636?nm and 2?μm were assembled from fluid onto templates patterned to contain holes that matched the shapes and sizes of the spherical components. The assembly experiments were carried out for a range of experimental conditions, including different fluid compositions and different intensities for the fluid excitation. A comparison of the measured assembly yield with the yield predicted using a model based on the work of Jung and co-workers (Jung et al 2005 Nano Lett.?5 2188-94) shows excellent agreement, indicating the applicability of the model over a broad range of experimental conditions. High yield is both expected and observed when the ratio of the moment that retains components in their locations to the moment that removes components from their locations is greater than 1, as long as stirring of the fluid medium is sufficient.     

MPEG-4 video verification model: Status and directions

This article describes the current status and future directions of the emerging ISO MPEG-4 audiovisual coding standard. The article first presents an overview of the different aspects of the standard and then focuses on the video coding aspects. The current status of the Video Verification Model (VM) (a completely defined encoder and decoder specification) is described in detail and its performance is presented. The new functionalities supported by this emerging standard and their potential applications are highlighted. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 468–479, 1997     

Quantum criticality and incipient phase separation in the thermodynamic properties of the Hubbard model

Transport measurements on the cuprates suggest the presence of a quantum critical point (QCP) hiding underneath the superconducting dome near optimal hole doping. We provide numerical evidence in support of this scenario via a dynamical cluster quantum Monte Carlo study of the extended two-dimensional Hubbard model. Single-particle quantities, such as the spectral function, the quasi-particle weight and the entropy, display a crossover between two distinct ground states: a Fermi liquid at low filling and a non-Fermi liquid with a pseudo-gap at high filling. Both states are found to cross over to a marginal Fermi-liquid state at higher temperatures. For finite next-nearest-neighbour hopping t', we find a classical critical point at temperature T(c). This classical critical point is found to be associated with a phase-separation transition between a compressible Mott gas and an incompressible Mott liquid corresponding to the Fermi liquid and the pseudo-gap state, respectively. Since the critical temperature T(c) extrapolates to zero as t' vanishes, we conclude that a QCP connects the Fermi liquid to the pseudo-gap region, and that the marginal Fermi-liquid behaviour in its vicinity is the analogue of the supercritical region in the liquid-gas transition.     

Experimental verification of the simplified line-spring model

The recently developed simplified line-spring model is employed to obtain estimates of the crack opening displacement (COD) in surface cracked plates in tension and circumferentially cracked pipes in pure bending. The predictions of the model for the plate are compared to experimental data obtained from a series of tests on surface cracked X70 line pipe steel plates, on the other hand the results from the model for the pipe are compared to previously presented experimental and theoretical results. The simplified model seems to offer estimates of the COD which are in reasonably good agreement with both experimental data and existing theoretical results.

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Résumé On utilise le modèle simplifié dit line-spring — qui consiste à simuler les forces de rétention de propagation d'une fissure de surface dans le ligament restant, en dispensant des efforts et des moments sur une fissure traversante de même longueur — en vue d'estimer le déplacement d'ouverture d'une fissure dans des tôles fissurées en surface et soumises à traction, et dans des tubes fissurés circonférentiellement et soumis à flexion pure.Les prédictions du modèle dans le cas d'une tôle sont comparées aux données expérimentales recueillies dans une série d'essais sur des tôles fissurées en surface d'acier pour pipe-line X70. Par ailleurs, les prédictions du modèle dans le cas du tube sont comparées à des résultats théoriques et expérimentaux obtenus précédemment.Le modèle simplifié utilisé parait offrir des estimations du COD en assez bon accord avec les résultats expérimentaux d'une part, et l'application des théories existantes d'autre part.

     

Validation of biokinetic models of Cs and I using their daily dietary intakes and organ contents in an adult Indian population

The daily dietary intakes and total contents of Cs and I in skeletal muscle and thyroid, respectively, for an average Indian adult were estimated by determining their concentrations in the total cooked diet and tissue samples using instrumental neutron activation analysis. These data were then used to predict the biological half-lives of Cs and I and their radioactive counterparts for the Reference Indian Man. The predicted biological half-lives of Cs and I for Reference Indian Man were found to be comparable with the reported values for the ICRP Reference Man.     

The ICRP protection quantities, equivalent and effective dose: their basis and application

Equivalent and effective dose are protection quantities defined by the The International Commission on Radiological Protection (ICRP). They are frequently referred to simply as dose and may be misused. They provide a method for the summation of doses received from external sources and from intakes of radionuclides for comparison with dose limits and constraints, set to limit the risk of cancer and hereditary effects. For the assessment of internal doses, ICRP provides dose coefficients (Sv Bq(-1)) for the ingestion or inhalation of radionuclides by workers and members of the public, including children. Dose coefficients have also been calculated for in utero exposures following maternal intakes and for the transfer of radionuclides in breast milk. In each case, values are given of committed equivalent doses to organs and tissues and committed effective dose. Their calculation involves the use of defined biokinetic and dosimetric models, including the use of reference phantoms representing the human body. Radiation weighting factors are used as a simple representation of the different effectiveness of different radiations in causing stochastic effects at low doses. A single set of tissue weighting factors is used to take account of the contribution of individual organs and tissues to overall detriment from cancer and hereditary effects, despite age- and gender-related differences in estimates of risk and contributions to risk. The results are quantities that are not individual specific but are reference values for protection purposes, relating to doses to phantoms. The ICRP protection quantities are not intended for detailed assessments of dose and risk to individuals. They should not be used in epidemiological analyses or the assessment of the possibility of occurrence and severity of tissue reactions (deterministic effects) at higher doses. Dose coefficients are published as reference values and as such have no associated uncertainty. Assessments of uncertainties may be appropriate in specific analyses of doses and risks and in epidemiological studies.     

Improvements in the biokinetic model for strontium with allowance for age and gender differences in bone mineral metabolism

An age- and gender-dependent biokinetic model for strontium was developed based on the study of a population living along the Techa River exposed to effluents from the Mayak Production Association (MPA). To estimate the parameters of a new model (Techa biokinetic model, TBM) many data sets have been assembled: our whole-body counter data on long-term retention of 90Sr in humans, data from studies during the period of global fallout, data resulting from deliberate injection of strontium radionuclides and non-radiological data regarding bone formation and resorption, mineral content of the body, etc. The model was developed using the basic structure of the ICRP biokinetic model for strontium, but new age- and gender-specific parameters were derived. This paper discusses the approaches applied to develop the new model.     

A combined M5P tree and hazard-based duration model for predicting urban freeway traffic accident durations

The duration of freeway traffic accidents duration is an important factor, which affects traffic congestion, environmental pollution, and secondary accidents. Among previous studies, the M5P algorithm has been shown to be an effective tool for predicting incident duration. M5P builds a tree-based model, like the traditional classification and regression tree (CART) method, but with multiple linear regression models as its leaves. The problem with M5P for accident duration prediction, however, is that whereas linear regression assumes that the conditional distribution of accident durations is normally distributed, the distribution for a “time-to-an-event” is almost certainly nonsymmetrical. A hazard-based duration model (HBDM) is a better choice for this kind of a “time-to-event” modeling scenario, and given this, HBDMs have been previously applied to analyze and predict traffic accidents duration. Previous research, however, has not yet applied HBDMs for accident duration prediction, in association with clustering or classification of the dataset to minimize data heterogeneity. The current paper proposes a novel approach for accident duration prediction, which improves on the original M5P tree algorithm through the construction of a M5P-HBDM model, in which the leaves of the M5P tree model are HBDMs instead of linear regression models. Such a model offers the advantage of minimizing data heterogeneity through dataset classification, and avoids the need for the incorrect assumption of normality for traffic accident durations. The proposed model was then tested on two freeway accident datasets. For each dataset, the first 500 records were used to train the following three models: (1) an M5P tree; (2) a HBDM; and (3) the proposed M5P-HBDM, and the remainder of data were used for testing. The results show that the proposed M5P-HBDM managed to identify more significant and meaningful variables than either M5P or HBDMs. Moreover, the M5P-HBDM had the lowest overall mean absolute percentage error (MAPE).     

Applying the random effect negative binomial model to examine traffic accident occurrence at signalized intersections

Poisson and negative binomial (NB) models have been used to analyze traffic accident occurrence at intersections for several years. There are however, limitations in the use of such models. The Poisson model requires the variance-to-mean ratio of the accident data to be about 1. Both the Poisson and the NB models require the accident data to be uncorrelated in time. Due to unobserved heterogeneity and serial correlation in the accident data, both models seem to be inappropriate. A more suitable alternative is the random effect negative binomial (RENB) model, which by treating the data in a time-series cross-section panel, will be able to deal with the spatial and temporal effects in the data. This paper describes the use of RENB model to identify the elements that affect intersection safety. To establish the suitability of the model, several goodness-of-fit statistics are used. The model is then applied to investigate the relationship between accident occurrence and the geometric, traffic and control characteristics of signalized intersections in Singapore. The results showed that 11 variables significantly affected the safety at the intersections. The total approach volumes, the numbers of phases per cycle, the uncontrolled left-turn lane and the presence of a surveillance camera are among the variables that are the highly significant.