On the potential of combining neutron activation analysis and particle induced X-ray emission (PIXE) for micro- and microdistribution analysis of hard metals in human tissues

Tungsten carbide and cobalt are the main components of hard metal alloy while other metals such as chromium, niobium, tantalum, titanium and vanadium are sometimes added in smaller amounts. Exposure to hard metal dusts can induce a lung fibrosis with cobalt playing a major role. In order to provide information on the role that each metal may have in causing this disease, determination of the total content and the distribution of inhaled metals in lung tissue of hard metal workers is of paramount importance. However, samples such as transbronchial biopsy and bronchoalveolar lavage (BAL), often used in the medical diagnosis of pneumoconiosis, only allow for a small amount of material. This calls for sensitive and accurate analytical procedures for microdetermination and distribution of metals in pulmonary tissue and cellular material, such as macrophages. This work proposes a combination of sophisticated analytical techniques such as neutron activation analysis (NAA), currently applied to the determination of the total concentration of more than 30 elements in biological specimens, and PIXE analysis, particularly microPIXE, which has a great potential for microdistribution analysis in small biological samples. Principles and perspectives for the combined use of these techniques for the analysis of human tissue are outlined and discussed. NAA: determination of hard metals in lung tissue are carried out by neutron irradiation (2 × 10¹⁴ neutrons cm⁻² s⁻¹) in the HFR reactor of Petten. After neutron activation, radiochemical separations of ⁶⁰Co, ¹⁸⁷W, ¹⁸²Ta, ⁵¹Cr followed by computer-based high resolution gamma ray spectrometry allow the measurement of these elements in pulmonary tissues with sensitivities ranging from 10⁻⁴ μg (Cr) to 10⁻⁶ μg (W). PIXE: this technique is multielemental and of relatively high sensitivity (μg/g) even in small total sample masses of from 10 to 100 μg, thus allowing the analysis of parts of needle biopsies. Whereas PIXE has been successfully applied to many medical problems, its usefulness is limited in the total samples analysis for cobalt-related hard metal disease, due to the low levels of cobalt in tissue combined with severe element interferences from the generally more abundant metal, iron. Nevertheless, microPIXE, a special variety of the method scanning over the sample with a focussed ion beam of about 2 × 2 μm², could complement the NAA findings in total samples in the sense of achieving a microdistribution analysis of hard metals (including cobalt) in suitable thin tissue sections.The availability of specialized facilities at the JRC such as the powerful HFR reactor (Petten), the NAA laboratories (Ispra) and the microPIXE facility (Geel) could represent a European ‘reference pole’ for the study of metals in tissues of hard metal diseased subjects.     

Trace element analysis of Cretan wines and wine products

The object of this research is to investigate the ways and the degree of contamination of Cretan grapes from the area of Chania and their alcoholic products, with the elements aluminium, arsenic, cadmium, copper, chromium, iron, lead, manganese, nickel and zinc. Fifteen samples of grapes were collected and used for the production of experimental wines from rinsed and unrinsed grapes. A microwave furnace was used for the digestion and dissolution of the experimental wines, the precipitates that originated in these wines, as well as the wines of the corresponding producers. The analyses of all mentioned samples as well as 34 local alcoholic distillates were performed using total reflection X-ray fluorescence and graphite furnace atomic absorption spectrometry. The concentrations for all the elements that were determined were almost in all cases, well below the maximum permissible levels by the Greek and the European Union legislation.     

Tunnel fire and life safety within the world road association (PIARC)

This paper presents the global activities of the World Road Association (PIARC) in the area of fire and life safety in road tunnels. It traces the organizational structure in the form of technical committees, its publications, current activities and concludes with a summary as to the position of the organization with regard to fire and life safety in tunnels.     

A contribution to the study of some greek marbles

The use of marble in Architecture began on the 7th century B.C. and continued to be used without stop untill today. Greece and especially the East Macedonia region is an extremely privileged area on marble deposits both in quantities and qualities and colours. In the present work the main physical and engineering properties of some varieties of greek marbles are given and a comparison with the international standards is made. The experimental material (marbles) was from East Macedonia, Argolida-Arcadia and Magnessia, three of the biggest marble deposit areas in Greece. From the results obtained, it is concluded that the marbles examined satisfy all the international standard codes and thus they can be used as building stones and decoration materials.     

Finite element three-dimensional elastic-plastic creep analysis

This paper presents a continued development of computationally efficient finite element methods for accurately predicting the isothermal three-dimensional elastic-plastic creep responses of thick and thin shell structures subjected to mechanical and thermal loads. This work is applicable to a wide range of engineering structures and most recently has been used in the elastic-plastic creep analyses of high-temperature nuclear reactor components and rotating turbine blades.Previous work in this area for elastic-plastic analysis has been demonstrated by Levy et al. In that reference, use of a variable number of stress points within an element to describe elastic-plastic behaviour was demonstrated. These ideas have been extended for combined plasticity and creep behaviour. Thus, within an element, the order of the allowable total kinematic strain distribution is dependent on the number of element nodes (assumed displacement distribution), and the order of the allowable plastic strain distribution (and hence the elastic-plastic boundaries) and/or creep strain distribution is dependent on the number and location of the stress points used to numerically integrate the inelastic effects. This allows for an accurate representation of the elastic-plastic creep behaviour within an element. This higher inelastic representation results in the use of a minimum number of degrees of freedom for a given nonlinear analysis, which is particularly important for combined creep and plasticity behaviour and for cyclic loading, where computer times can be prohibitive.The basic numerical solution procedure for the elastic-plastic creep analysis is an incremental predictor-corrector iterative scheme combined with the ‘initial strain’ approach. Attention has been given to the time step increment strategy for combined plasticity and creep as this governs efficiency and accuracy.The methods have been implemented into the three-dimensional solid element module (HEX) of the Grumman PLANS finite element program.Sample problems are used to demonstrate and investigate the accuracy and efficiency of these methods. Sample problems include combined plasticity and creep analysis of a simple rod under time varying load, stress-relaxation of a simple rod, thermal stress-relaxation of a plate subjected to a temperature variation across the width, and creep analysis of an internally loaded thick-walled pressure vessel.     

Stress-Strain State of Weak Saturated Clay Beds of Embankments

Results are presented for laboratory and field tests of weak saturated soils serving as beds for embankments in Ho Chi Min City and various regions of the Mekong River Delta (Vietnam). A method is outlined for quantitative evaluation of the stress-strain state (SSS) of the weak saturated clayey beds (plane problem). A method is described for quantitative evaluation of the deformation and stability of weak beds in the initial, intermediate, and stabilized stages of the formation and transformation of the SSS. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 2–6, September–October, 2005.     

Separation of physical loading from photosynthesis/respiration processes in rivers by mass balance

Diurnal variations in physical and chemical concentrations, including nutrients, are observed in river ecosystems. Understanding these cycles and separating the effects of physical loading (from point and non-point sources) and biogeochemical processes are necessary for water management and the TMDL process. A chloride mass balance approach is used to separate the relative influences of physical loading and biogeochemical processes in the Bow River through Calgary, Canada, which has a significant influence on the river water chemistry. Sampling campaigns were conducted in December 2005, when minimal photosynthesis and respiration occur, and in July 2006, when river discharge is high and some photosynthesis and respiration activity is present. Samples in each campaign were collected at point source input and output along the river reach through the city every hour for a 24-hour period, allowing for time of travel. The two wastewater treatment facilities within the city contributed the majority of physical mass loading to the river, with temporal variations in effluent discharge, chloride, and nutrient concentrations. Wastewater effluent chloride to nutrient (as well as other parameter relationships) concentrations also varied diurnally. An hourly chloride mass balance was achieved, within 0.5% (average, S.D.=4.4) for December and 7.7% (average, S.D.=4.2) for July, between estimated cumulative sum values from all inputs and measured values at the river output downgradient of the city, allowing for the investigation of other parameter conservativeness. Some slight diurnal variations associated with photosynthesis and respiration were observed even with limited productivity in the river. Nitrate mass fluxes appeared to be most strongly influenced by photosynthesis and respiration processes, with phosphate being less influenced. Ammonia mass fluxes appeared to be most strongly influenced by wastewater effluent loading. Physical loading can mask or enhance biogeochemical diurnal fluctuations, creating errors in river process interpretations. Chloride was a useful tracer in the mass balance to distinguish between and assist in separating physical loading and biogeochemical processes in the river.     

A study of the effect of stiffness distribution on nonlinear seismic response of multi-degree-of-freedom structures

The ductility requirement of elastoplastic multi-d.o.f. shear structures is studied by analysing the response obtained through step-by-step integration of the equations of motion for some recorded accelerograms. In view of the high dependence of the structural strength reserve beyond the elastic range on the distribution of plastic deformations in the structure, this paper aims to establish the influence of the stiffness distribution and of the earthquake features on the local ductility demand. Attention is also paid to the analysis of the influence of variation in excitation intensity and duration on the seismic behaviour of the structural models considered. Numerical results show that overall structural ductility alone is not sufficiently representative to evaluate the ultimate state of multi-d.o.f. structures. Local ductility must also be specified in order to create a reliable aseismic design. In this context, the important role played by the distribution of stiffness over the structure is emphasized.