Showing papers in "Radiation Protection Dosimetry in 2000"
TL;DR: In this paper, a summary of the results of the Monte Carlo transport code FLUKA has been presented for all kinds of radiation (photons, electrons, positrons protons, neutrons, muons, charged pions, kaons).
Abstract: ICRP 74 and ICRU 57 recommended conversion coefficients for use in radiological protection for electrons and photons of energies up to 10 MeV and for neutrons up to 180 MeV. For various purposes (radiation protection around high energy accelerators, shielding calculations, air crew dose assessment, space activity) conversion coefficients for higher energies and other kinds of radiation are needed Sets of fluence-to-effective dose and fluence-to-ambient dose equivalent conversion coefficients for all kinds of radiation (photons, electrons, positrons protons, neutrons, muons, charged pions, kaons) and incident energies (up to 10 TeV) of practical interest have been calculated in recent years by the Monte Carlo transport code FLUKA. Since the calculated results are scattered through several papers (journals and proceedings of conferences), it has been considered useful to summarise them in the present paper.
296 citations
TL;DR: The spectrum of possible evaluation methods of importance will be described and the principles, benefits and drawbacks of some of these methods will be given together with examples of their use.
Abstract: In medical imaging, information about the patient and possible abnormalities is transferred to the radiologist in two major steps: (i) data acquisition and image formation, and (ii) processing and display. Step one is mainly dependent on technical and physical characteristics of the equipment. Step two includes the vital importance of the performance of the radiologist; i.e. how he or she detects and interprets the structures in the image. The quality of a radiographical procedure must therefore be described with regard to both these steps. The spectrum of possible evaluation methods of importance will be described. The principles, benefits and drawbacks of some of these methods will be given together with examples of their use.
171 citations
TL;DR: In this paper, a protocol for using structured expert judgement to generate uncertainty data for uncertainty analyses is outlined, and the use of performance based weighting as an instrument to enable optimisation of the aggregated experts' assessments is emphasized.
Abstract: A protocol is outlined for using structured expert judgement to generate uncertainty data for uncertainty analyses. The use of performance based weighting as an instrument to enable optimisation of the aggregated experts' assessments is emphasised. Examples are shown from the EC/USNRC joint study on Probabilistic Accident Consequence Uncertainty Analysis.
133 citations
TL;DR: Diagnostic reference levels appropriate to the peculiar conditions of exposure in CT have been specified in relation to examinations on adult patients, utilising the dosimetric concepts of weighted computed tomography dose index (CTDI w ) and dose-length product (DLP) per complete examination.
Abstract: Diagnostic reference levels appropriate to the peculiar conditions of exposure in CT have already been specified in relation to examinations on adult patients, utilising the dosimetric concepts of weighted computed tomography dose index (CTDI w ) per slice in serial scanning or per rotation in helical scanning, and dose-length product (DLP) per complete examination. This methodology can also be applied to CT examinations on children, with reference dosimetry for all types of examination on children of all ages being based solely on measurements involving the smaller (16 cm diameter) of the two standard CT dosimetry phantoms. Some initial diagnostic reference levels for paediatric CT have been set on the basis of the rounded third quartiles of the dose distributions provided by a survey of typical practice at over 40 scanners from seven European countries. Values are presented in relation to three patient ages (<1 year, 5 y and 10 y) and five types of procedure.
120 citations
TL;DR: The analysis showed that the absorption rates of the radon progeny would have to be substantially faster than the current estimates to have an effect on the equivalent lung dose.
Abstract: A sensitivity analysis has been performed to identify those ICRP Publication 66 Human Respiratory Tract Model parameters which significantly affect the lung dose arising from the inhalation of radon progeny under conditions found in houses. The analysis was performed to investigate the sensitivity of the weighted committed equivalent dose to lung per unit radon progeny exposure to (i) aerosol parameters, (ii) subject related parameters, (iii) target cell parameters, and (iv) the absorption rates of radon progeny. The weighted committed equivalent dose per unit exposure to radon progeny varied between 8 mSv and 33 mSv per working level month for conditions of radon progeny in homes. The parameters most affecting the equivalent lung dose are identified. The analysis also showed that the absorption rates of the radon progeny would have to be substantially faster than the current estimates (In 2/10 h -1 ) to have an effect on the equivalent lung dose.
94 citations
TL;DR: In this article, two chemical sun filters that are ingredients in sunscreen products have been tested for their dark toxicity and possible toxicity to mouse cells after UV irradiation, and it was concluded that the two sun filters are toxic to cells in the dark, but the biological role of this dark toxicity in the skin is not clear.
Abstract: Two chemical sun filters that are ingredients in sunscreen products have been tested for their dark toxicity and possible toxicity to mouse cells after UV irradiation. Increased toxicity as a result of breakdown of a UVB filter, octyl methoxycinnamate, was observed. UV radiation absorbed by the pure chemical sunscreen may lead to breakdown to more reactive chemical compounds than the unexposed sunscreen filter. The UVA filter included in our tests, butyl methoxydibenzoylmethane, was also toxic in the dark, however, it was the more photostable of the two and no additional significant toxicity was induced by UV irradiation. It can be concluded that the two sun filters are toxic to cells in the dark, but the biological role of this dark toxicity in the skin is not clear. Unstable sun filters may be broken down by UV to form photoproducts that are potentially toxic.
85 citations
TL;DR: The average annual outdoor radiation exposure dose rate due to the radioactivity concentration of 40 K, 238 U and 232 Th in the soil across different environments in Nigeria have been carried out using the low-cost method of in situ γ ray spectrometry as discussed by the authors.
Abstract: The outdoor radiation exposure dose rates due to the radioactivity concentration of 40 K, 238 U and 232 Th in the soil across different environments in Nigeria have been carried out using the low-cost method of in situ γ ray spectrometry. Measurements were made in 18 cities, spread across the three major zones of the country. The radioactivity concentrations of these radionuclides in the soil were used to determine their radiation absorbed dose rates in the air. The range of average total dose rate due to the three radionuclides in the Eastern zone is between 0.025 and 0.081 μGy.h -1 with an average of 0.040 ± 0.006 μGy.h -1 , 0.041 and 0.214 μGy.h -1 with a mean of 0.089 ± 0.014 μGy.h -1 for the Western zone and between 0.066 and 0.222 μGy.h -1 with a mean of 0.102 ± 0.032 μGy.h -1 for the Northern zone. The average annual outdoor effective dose equivalents of 51 ± 8 μSv.y -1 114 ± 18 μSv.y -1 and 130 ± 41 μSv.y -1 have been estimated for the Eastern, Western and Northern zones, respectively. The average annual effective dose equivalent for the country has been estimated to be 98 ± 15 μSv.y -1 and the collective effective dose equivalent as 9.7 X 10 3 man.Sv.y -1 . Measurements have been taken as representing the baseline values of natural radioactivity as no artificial radionuclide was detected at any of the sites surveyed.
75 citations
TL;DR: The UV index is described and it is suggested that universally common messages should be associated with its ranges.
Abstract: Excessive solar ultraviolet (UV) radiation exposure produces a significant burden of disease to the skin, eyes and immune system. Effective programmes for the reduction of UV exposure are needed to reduce this disease burden and the associated health care costs. The UV index is seen as an effective tool for communicating important protection information to the public through its use in media news and weather information. The index is described and it is suggested that universally common messages should be associated with its ranges.
73 citations
TL;DR: A comparison of UPFs derived from the in vitro tests for 16 fabric samples against in vivo SPF tests is detailed, with no statistically significant difference between the two data sets and with only one misclassification of protection category between the SPFs and UPFs.
Abstract: The protection provided by clothing against solar ultraviolet radiation (UVR) has been the subject of considerable recent research. In general, rated clothing is tested according to standards using laboratory based in vitro measurements of the fabric spectral UVR transmittance and weighting this with the erythemal effectiveness of the CIE (1987) to determine an Ultraviolet Protection Factor (UPF). While in vitro test methods provide a precise determination of protection, there were some concerns they could overestimate the protection in comparison to in vivo measurements. This paper details a comparison of UPFs derived from the in vitro tests for 16 fabric samples against in vivo SPF tests. Agreement between the two sets of results is very good, with no statistically significant difference between the two data sets and with only one misclassification of protection category between the SPFs and UPFs.
66 citations
TL;DR: The detrimental and beneficial effects of exposure to ultraviolet radiation in the UVB and UVA ranges are discussed and the main benefit is promoting the synthesis of vitamin D from precursors in the skin.
Abstract: The detrimental and beneficial effects of exposure to ultraviolet radiation in the UVB and UVA ranges are discussed. The main benefit of UV radiation is promoting the synthesis of vitamin D from precursors in the skin. Detrimental effects include acute sun damage in the form of sunburn and chronic sun damage leading to photoageing and possibly to cutaneous malignancies. Other detrimental effects of UV exposure include photosensitivity reactions to ingested drugs and rare examples of genetically determined photosensitivies.
64 citations
TL;DR: In this paper, the authors describe about 200 h of in-flight measurements performed during a period of 22 months from 1997 to 1999 on cargo aircraft, where various monitors were used to measure different radiation field components and to investigate the spatial dose equivalent rate distribution and the spatial radiation field composition.
Abstract: The exposure of aircrew to the increased cosmic radiation at aviation flight altitudes will soon be treated in the European Union as an occupational risk, with the consequence that the radiation exposure of aircrew must be determined. This work describes about 200 h of in-flight measurements performed during a period of 22 months from 1997 to 1999 on cargo aircraft. Various monitors were used to measure different radiation field components and to investigate the spatial dose equivalent rate distribution and the spatial radiation field composition. The monitors were rem counters for neutrons, and a scintillator and an ionisation chamber for the directly ionising and photon components. One of the main goals was to calibrate the monitors in the cosmic radiation field at flight altitudes against a tissue-equivalent proportional counter (TEPC) used as a reference instrument for the quantity ambient dose equivalent. The sum of the readings of a neutron rem counter with its response extended to high energy neutrons and of an ionisation chamber was found to be a fair approximation of the total dose equivalent as measured by the TEPC. The 'field calibration factor determined is 1.0±0.1. The global dose equivalent distributions as a function of magnetic latitude and cut-off rigidity were obtained for the range of altitudes encountered in civil aviation and can be described by simple mathematical functions for use in rough dose-equivalent rate estimates. Surrounding the TEPC with an active shielding detector and the application of coincidence techniques allowed dose equivalent fractions of charged and uncharged particles in the cosmic radiation to be separated. The low-LET radiation component was found to consist of 90% charged particles and 10% photons while the high-LET component contains a fraction of 30% from protons (pions) and 70% from neutrons.
TL;DR: Measurements of maximum entrance skin dose, MESD, and effective dose, E, to an anthropomorphic phantom using TL dosemeters placed both on the outside of and inserted in the phantom and simulating a diagnostic and an interventional clinical procedure are dealt with.
Abstract: Skin injuries have recently been reported for patients in diagnostic and interventional cardiac procedures. Cardiac catheterisation equipment usually has dose monitors showing the dose-area product (DAP) but the DAP value alone is not a suitable indicator for skin dose since the projections vary during the procedures. This work deals with measurements of maximum entrance skin dose, MESD, and effective dose, E, to an anthropomorphic phantom using TL dosemeters placed both on the outside of and inserted in the phantom and simulating a diagnostic and an interventional clinical procedure. DAP values were used for calculating conversion factors: MESD/DAP was 3.8 and 8.1 mSv.Gy -1 .cm -2 and E/DAP was 0.23 and 0.26 mSv.Gy -1 .cm -2 for diagnostic and interventional procedures respectively. Maximum permissible DAP value for preventing skin damage, i.e. MESD <2 Sv, is therefore 530 and 250 Gy.cm -2 respectively for diagnostic and interventional procedures. These results should be used as a local reference level for the patient dose to prevent skin burden. Patient mean DAP was 73, 120 and 170 Gy.cm 2 and effective dose 16, 31 and 41 mSv for diagnostic, interventional and combined procedures respectively.
TL;DR: A review of the animal studies which have demonstrated that in animals treated with DTPA either a reduction in bone tumour incidence from internally deposited 239 Pu and 241 Am, or a significant increase in survival time may occur, suggests that it is reasonable to assume this could also occur in humans as discussed by the authors.
Abstract: The scientific background to chelation therapy is reviewed. A review of the animal studies which have demonstrated that in animals treated with DTPA either a reduction in bone tumour incidence from internally deposited 239 Pu and 241 Am, or a significant increase in survival time may occur, suggests that it is reasonable to assume this could also occur in humans. The biokinetics and bioinorganic chemistry of cobalt, caesium, thorium, uranium, neptunium, plutonium and americium after their entry into the systemic circulation are reviewed briefly. These reviews discuss the general biokinetic behaviour of each element in adult humans with special reference to those aspects of their bioinorganic chemistry that either underlie existing approaches to decorporation therapy, or which might be exploitable for new types of treatment.
TL;DR: Data are presented that allow the estimation of effective dose from CT examinations of the torso for girls between the ages of 11 and 16, and the effective doses were 9.0, 8.2 and 7.8 mSv per 100 mA.
Abstract: Effective doses from CT to paediatric patients are not common in the literature. This article reports some effective doses to teenage girls from CT examinations. The voxel computational model ADELAIDE, representative of a 14-year-old girl, was scaled in size by ±5% to represent also 11-12-year-old and 16-year-old girls. The EGS4 Monte Carlo code was used to calculate the effective dose from chest, abdomen and whole torso CT examinations to the three versions of ADELAIDE using a 120 kV spectrum. For the whole torso CT examination, in order of increasing model size, the effective doses were 9.0, 8.2 and 7.8 mSv per 100 mA.s. Data are presented that allow the estimation of effective dose from CT examinations of the torso for girls between the ages of 11 and 16.
TL;DR: The need for improving UV protection by clothing is demonstrated by UV transmittance measurements in public, and a pitfall in the generally recommended 'see through' assessment test is shown.
Abstract: With the increase of skin cancer the fact that not all apparel is sufficiently protective against UV Radiation is becoming better known to the public. There is an emerging market for UV protective clothing. Its need is not commonly accepted. Understanding of the influencing factors is low. To the consumer it is not always clear what is fact and what is fiction. This paper answers six frequently asked questions. (1) The need for improving UV protection by clothing is demonstrated by UV transmittance measurements in public. (2) A pitfall in the generally recommended 'see through' assessment test is shown. (3) When a garment gets wet its UV protection is not necessarily poor. (4) The reduced UV protection of stretched knitwear can be accounted for. (5) A real life study confirms that UV protection is not washed out. (6) UV protection can be washed in with special additives to laundry products.
TL;DR: The unified phantom UP-02T models children aged 2, 6 and 14 years, and adults with a body mass of 70, 90 and 110 kg with incorporated radionuclides is intended for calibration of whole-body counters with the investigated person in the standing and lying positions as well as sitting straight or stooping down.
Abstract: The unified phantom UP-02T models children aged 2, 6 and 14 years, and adults with a body mass of 70, 90 and 110 kg with incorporated radionuclides. It is intended for calibration of whole-body counters with the investigated person in the standing and lying positions as well as sitting straight or stooping down. The phantom consists of a set of polyethylene rectangular blocks with masses 0.88 and 0.40 kg. A set of solid rod radionuclide sources, 6 mm in diameter, are inserted inside the blocks. Two sources are inserted in each block. The blocks are connected by means of fixing arms. The principal advantage of the solid phantom as compared to the phantoms that contain radioactive solutions is the safety of operation and the possibility of replacement of the radionuclide sources if it is necessary. The unified phantom was verified against the BOMAB calibration phantom and compared to the REMCAL type phantom.
TL;DR: Factors affecting the need for treatment, decision levels after different modes of intake, and the risks associated with various treatment options are discussed.
Abstract: This paper, fronted by four senior medical officers with clinical experience in decorporation, discusses factors affecting the need for treatment, decision levels after different modes of intake, and the risks associated with various treatment options. Both workers and members of the public are considered. The various approaches to treatment are summarised and recommendations made for current and future practice.
TL;DR: There is a wide range in paediatric patient size from a newborn baby to a 15-year-old adolescent, and normalisation factors for entrance surface dose and dose-area product measurements were calculated which depend on the thickness of the real patient, the Thick of the nearest standard 'patient', and an effective linear attenuation coefficient.
Abstract: There is a wide range in paediatric patient size from a newborn baby to a 15-year-old adolescent. Reference doses for paediatric radiology can sensibly be established only for specific sizes of children. Five standard sizes of patient have been chosen at ages 0 (newborn), 1, 5, 10 and 15 years. Standard AP and lateral thicknesses for the head and trunk for the reference ages were derived from published measurements on children. Normalisation factors for entrance surface dose and dose-area product measurements were calculated which depend on the thickness of the real patient, the thickness of the nearest standard 'patient', and an effective linear attenuation coefficient (μ). These normalisation factors were applied to European data to derive some preliminary reference doses.
TL;DR: In this article, the source and release-dependent characteristics of radioactive particles, which in turn influence the behavior of the associated radionuclides in the environment, were investigated and found to be device and shot dependent.
Abstract: A significant fraction of radionuclides released by nuclear events, for instance nuclear weapons tests, nuclear reactor accidents, and fires involving nuclear installations is associated with particles. Furthermore, effluents from nuclear reactors and reprocessing plants under normal operating conditions contain radionuclides in particulate and colloidal form. Radioactive particles are also observed in the vicinity of radioactive waste dumped at sea. Following nuclear tests, the particle composition and characteristics were found to be device and shot dependent. Following high temperature accident scenarios (e.g. Chernobyl), fuel particles were released having a composition of refractory elements reflecting burnup. However, the release condition (explosion, fire) influenced the crystallographic structures and oxidation states of uranium in the fuel particles. Following low temperatures atmospheric releases (e.g. Windscale, early 1950s), fuel particle structures were significantly different from those released from the Chernobyl reactor. This paper focuses on source and release-dependent characteristics of radioactive particles, which in turn influence the behaviour of the associated radionuclides in the environment.
TL;DR: The interplay between these two aspects of the use of accident consequence models is considered, paying particular attention to issues and limitations that require further research in the coming years.
Abstract: Accident consequence models are designed primarily to be used in support of siting and licensing decisions. To use these models, the analyst inevitably requires some input from experts. Equally, to understand the implication of the models, the analyst needs to explore their sensitivity to the inputs and uncertainty analysis is a key tool in doing this. In this paper, the interplay between these two aspects of the use of accident consequence models is considered, paying particular attention to issues and limitations that require further research in the coming years.
TL;DR: In this article, an automatic wet deposition gamma analyser has been constructed, where precipitation is collected with a 1 m 2 funnel and its 214 Pb and 214 Bi contents measured in a Marinelli beaker with an NaI(Tl) detector and a multichannel analyser.
Abstract: An automatic wet deposition gamma analyser has been constructed. Precipitation is collected with a 1 m 2 funnel and its 214 Pb and 214 Bi contents measured in a Marinelli beaker with an NaI(Tl) detector and a multichannel analyser. The amount of water in the beaker is measured with an ultrasonic sensor. All the sensor and spectrum data are gathered, and the magnetic valves controlled, with a data logger and a microcomputer. The instrument was tested during a five-month field measurement campaign in northern Finland. A value of 750 Bq.l -1 for the geometric mean 222 Rn progeny concentration in precipitation, and a geometric mean washout ratio of 9.1 x 10 5 was obtained in this study. Their variations, however, were large: four orders of magnitude. The Rn progeny concentrations and washout ratios are inversely correlated with low precipitation intensities. With higher precipitation intensities this behaviour levels out. Higher washout ratios were observed during rainfall compared to snowfall. Low Rn progeny concentrations in precipitation are usually connected with cold or occluded fronts and surges of arctic air masses. On the other hand, high Rn progeny concentrations are usually related to warm fronts or sectors. They are also observed between two successive cyclones, when continental air masses from southern Russia move northwest. The results obtained could also be applied to wet-depositing chemical substances like heavy metals, which can be difficult to measure using on-line methods.
TL;DR: VGA methodology can be made as solid as the FFE experiment for evaluating image quality, and the simplicity of VGA makes it very suitable for implementation in clinical practice.
Abstract: Two methods for visual evaluation of image quality of clinical radiographs have been compared. In visual grading analysis (VGA) specified anatomical structures in an image are visually compared with the same structures in a reference image, and in a free-response forced error (FFE) experiment - an extension of conventional ROC (receiver operating characteristics) analysis - the objective is to correctly localise known lesions. The spatial resolution and noise of digitised clinical radiographs of the lumbar spine were altered by image processing, and pathological structures were added to the images for the FFE experiment. The images were printed to film and evaluated by seven European expert radiologists using VGA and FFE. The results of these two different methods showed a very good agreement. In conclusion, VGA methodology can be made as solid as the FFE experiment for evaluating image quality. The simplicity of VGA makes it very suitable for implementation in clinical practice. (Less)
TL;DR: Intercomparison measurements of 241 Am in bone using separate arrays of phoswich and germanium detectors demonstrate that a single knee phantom exhibits the same detection efficiency as that using the skull.
Abstract: A new anthropometric phantom has been developed for use in calibrating in vivo measurements of bone-seeking radionuclides. The phantom has the external shape and appearance of the human adult knee and contains a realistic femur, patella, tibia, and fibula. Unique formulations of polyurethanes, CaCO 3 , and other trace materials are used in construction of the phantom to produce substitutes for human tissue having the same density, attenuation coefficient, and effective Z as that of human muscle and trabecular bone. The formulation for trabecular bone includes provision for a precisely known quantity of radioactive material that is either uniformly distributed throughout the bone matrix or deposited on the exterior surface. The knee phantom is assembled in three interlocking sections that simplify inserting the skeletal structures and prevent streaming. One or more detectors can easily be positioned on the top or sides of the phantom. Intercomparison measurements of 241 Am in bone using separate arrays of phoswich and germanium detectors demonstrate that a single knee phantom exhibits the same detection efficiency as that using the skull. In vivo measurement of the knee is a desirable alternative to the head if facial contamination is present or when evaluating recent exposure to bone seeking radionuclides, since bones of the knee exhibit more rapid uptake than the skull. In practice, greater measurement efficiency can be obtained by placing detectors over both knees since a larger fraction of the total body activity is observed. Calibration measurements using the new anthropometric knee phantom demonstrate that it is durable, easy to use, and provides consistent results over repeated measurements.
TL;DR: In this paper, a method to describe the observed yearly variability of ground-level UV has been developed and validated using UV transfer model calculations and measured ozone values, by satellite or ground-based stations, in combination with an empirical cloud correction based on widely available global solar radiation measurements.
Abstract: A method to describe the observed yearly variability of ground-level UV has been developed and validated. The method uses UV transfer model calculations and measured ozone values, by satellite or ground based stations, in combination with an empirical cloud correction based on widely available global solar radiation measurements. Good agreement is found between the modelled and measured yearly sums of UV radiation monitored at the RIVM site for the past five years. The agreement is on an absolute scale. Using ozone and broadband measurements, a trend analysis of the actual yearly UV load becomes feasible. Initial results show an increase in the yearly erythemal UV dose at ground-level of 10% rising from 41 J.cm -2 for the period 1979-1981 to 45 J.cm -2 for the period 1996-1998.
TL;DR: In this article, the authors used a HpGe detector to determine 137Cs and 40 K specific activities in soil samples and in different edible wild mushroom species collected from a temperate mixed forest located at the Nuclear Centre of Mexico and in several surrounding localities.
Abstract: 137Cs and 40 K specific activities were determined in soil samples and in different edible wild mushroom species collected from a temperate mixed forest located at the Nuclear Centre of Mexico and in several surrounding localities. The activity measurements were performed using a HpGe detector. The aggregated transfer factors (ATF) for 137 Cs in 21 local mushroom species collected from 1993 to 1997, showed differences as large as 3 orders of magnitude. The annual effective dose for 137 Cs due to the consumption of mushrooms was estimated to range between be 0.22 and 1.2 μSv.y -1 depending on the method used for calculation. Using the geometric mean of the caesium concentration, the contribution of mushrooms represents 56% of the total 137 Cs dietary intake.
TL;DR: The possibility to extend the response of bubble detectors to higher energy netjtrons was experimentally investigated at the CERN-EU high-energy reference field racility by exposing the dosemeters inside lead converters of various thicknesses.
Abstract: Bubble detectors are currently used both for personal neutron dosimetry, en~ronmental neutron dosimetry and for assessing the radiation exposure of civil aircrew. The current energy range of application for these devices is from 100 ke V to about 10 Me V. The possibility to extend the response of bubble detectors to higher energy netjtrons was experimentally investigated at the CERN-EU high-energy reference field racility by exposing the dosemeters inside lead converters of various thicknesses. Mpnte-Carlo calculations were performed to assess the effect of the lead converter on t~e neutron spectral fluence. The experimental results were compared with the calculated dose equivalent obtained by folding the response of the detectors with the modified neutron spectrum. Submitted for publication in Radiation Protection Dosimetry CERN, Geneva, Switzerland 5 November 1999 CERN LIBRARIES, GENEY A 111111 llll lllll llllll II llllll lllll lllll lllll lllll ll/111111111111111 SCAN-0001028