| 1. |
- Akselsson, Roland, et al.
(författare)
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Mass Calibration in PIXE Analysis
- 1977
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Ingår i: X-Ray Fluorescence Analysis of Environmental Samples. - 0250401347 ; , s. 175-180
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Bokkapitel (refereegranskat)
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| 2. |
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| 3. |
- Akselsson, Roland, et al.
(författare)
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A Beam Mapping Method
- 1971
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 91:4, s. 663-664
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Akselsson, Roland, et al.
(författare)
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Application of Proton Induced X-Ray Emission Analysis to the St. Louis Regional Air Pollution Study
- 1975
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Ingår i: Advances in X-Ray Analysis. ; 18, s. 588-597
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Tidskriftsartikel (refereegranskat)abstract
- The St Louis aerosol was sampled during the period 16-22 August 1973 simultaneously at two locations using cascade impactors for sequential 12-hour samples. The six particle size fractions of each sampling were individually analyzed using PIXE for elements from S to Br and beyond and for heavy elements including Pb which permitted time variations of concentrations and particle size distributions to be followed and related to meteorological changes during the sampling period. In addition, the data were compared with average levels of the elements in coastal north Florida and maritime Bermuda as well as at a third St. Louis site. From this it appeared that some of the concentrations in St. Louis were at natural levels whereas others appeared to be higher and linked to air pollution sources. These relationships and others in this study may lead to criteria for distinguishing between pollutants and natural background in urban aerosols.
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| 5. |
- Akselsson, Roland, et al.
(författare)
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Elemental Abundance Variation with Particle Size in Aerosols from Welding Operations
- 1974
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Ingår i: Proceedings of the Second International Conference on Nuclear Methods in Environmental Research. ; , s. 395-401
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Konferensbidrag (refereegranskat)abstract
- The effect of airborne particulate matter on human health is today of considerable research interest. Essential parameters include elemental composition sampling with low pressure cascade impactors and analysis by particle induced x-ray emission spectroscopy (PIXE). It is shown that the aerosol generated by arc welding operations is several orders of magnitude denser than aerosols in ambient air. Most of the mass is found on particles between 0.1 and 1µm diameter, but the size distribution differs from one welding technique to another. The relative composition of the aerosol is found to differ significantly from that of both the welding piece and the electrode indicating the presence of fractionation of the type indicated in this work in designing electrodes and welding pieces to minimize the health hazards associated with the welding.
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| 6. |
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| 7. |
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| 8. |
- Akselsson, Roland, et al.
(författare)
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Particle Size Distribution and Human Respiratory Deposition of Trace Metals in Indoor Work Environments
- 1976
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 1475-3162. ; 19:3-4, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory response to inhalation of fine particles has been investigated for the aerosol generated by welding. Particles were sampled using a pair of 5-stage cascade impactors operating at 1 l./min flow rate. The subject exhaled into one impactor through an air ballast arrangement, and the other impactor simultaneously sampled the surrounding air. Particle size fractions were analyzed for principal elemental constituents from sulphur to lead using proton induced X-ray emission, PIXE. The results indicated a complex respiratory response, including both increase in particle size due to exposure to high humidity in the respiratory tract and deposition of particles during inhalation. The response was found to be different for the element group Mn, Cr, Fe, Ni compared to the group K, Ca, Ti by observing the associations among the elements as a function of particle size in the inhaled and exhaled aerosol. However, for respiratory deposition efficiency alone in all runs averaged together, no systematic differences between the different elements are demonstrated at the 99 % confidence level.
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| 9. |
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| 10. |
- Akselsson, Roland, et al.
(författare)
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X-Ray Production by 1.5-11 MeV Protons
- 1974
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Ingår i: Zeitschrift für Physik. - 0044-3328. ; 266:4, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- K-shell ionization and L x-ray production cross-sections by proton impact have been determined from measurements of K x-ray yields from thin targets of Ti, Fe, Co, Cu, Ni and Ag and of L x-ray yields from Au and Pb. The proton energies varied from 1.5 to 11 MeV. A Si(Li) semiconductor detector recorded the x-rays. The total error in the measured cross-sections is mostly less than 5 %. Kβ/Kα, ratios and Lι,β,ƴ/Lα, ratios have been determined. Ionization cross-sections have been compared with predictions of the plane-wave Born approximation (PWBA) and the binary-encounter approximation (BEA). Both theories describe the ionization quite well: PWBA is, however, better for higher proton energies whereas BEA is superior for lower energies. An empirical formula for ionization cross-sections is derived.
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| 11. |
- Friedlander, B, et al.
(författare)
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Extended Levinson and Chandrasekhar Equations for General Discrete-Time Linear Estimation Problems
- 1978
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Ingår i: IEEE Transactions on Automatic Control. - : IEEE Control Systems Society. - 0018-9286 .- 1558-2523. ; 23:4, s. 653-659
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Tidskriftsartikel (refereegranskat)abstract
- Recursive algorithrms for the solution of linear least-squares estimation problems have been based mainly on state-space models. It has been known, however, that recursive Levinson-Whittle-Wiggins-Robinson (LWR) algorithms exist for stationary time-series, using only input-output information (i.e, covariance matrices). By introducing a way of classifying stochastic processes in terms of an "index of nonstationarity" we derive extended LWR algorithms for nonstationary processes We show also how adding state-space structure to the covariance matrix allows us to specialize these general results to state-space type estimation algorithms. In particular, the Chandrasekhar equations are shown to be natural descendants of the extended LWR algorithm.
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| 12. |
- Friedlander, B, et al.
(författare)
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Levinson and Chandrasekhar-Type Equations for a General Discrete-Time Linear Estimation Problem
- 1976
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Ingår i: Proceedings of the 1976 IEEE Conference on Decision and Control including the 15th Symposium on Adaptive Processes. ; , s. 910-915
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Konferensbidrag (refereegranskat)abstract
- Recursive algorithms for the solution of linear least-squares estimation problems have been based mainly on state-space models. It has been know, however, that such algorithms exist for stationary time-series, using input-output descriptions (e.g., covariance matrices). We introduce a way of classifying stochastic processes in terms of their "distance" from stationarity that leads to a derivation of an efficient Levinson-type algorithm for arbitrary (nonstationary) processes. By adding structure to the covariance matrix, these general results specialize to state-space type estimation algorithms. In particular, the Chandrasekhar equations are shown to be the natural descendants of the Levinson algorithm.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Johansson, Thomas B, et al.
(författare)
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Analytical Use of Proton-Induced X-Ray Emission
- 1976
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - 0236-5731. ; 32:1, s. 207-217
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Tidskriftsartikel (refereegranskat)abstract
- Proton-induced X-ray emission, PIXE, is capable of simultaneous quantitative determination of 10-15 elements. An introduction to the physical properties of the method is given and detection limits are shown for a routine analysis of a thin aerosol sample. Examples of applications to both thick and thin samples are presented. Human tooth dentine is analysed for lead, with simple sample preparation, indicating lead values of a few ppm for Swedish children. Quantitative analyses of several other elements are obtained simultaneously. Cascade impactors axe used for sampling aerosols in work environment during welding operations giving information of size distribution and concentrations of the elements present. The aerosol is dominated by particle sizes between 0.5 and 2 um as measured by the impactor, but the size distributions are different for different elements and welding techniques and depend on the distance from the welding source. The relative abundance of the elements found in the aerosol indicates the presence of fractionation mechanisms.
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| 17. |
- Johansson, Thomas B, et al.
(författare)
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Analytical Use of Proton-Induced X-Ray Emission
- 1975
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Ingår i: Trans Am Nucl Sci; Proceedings: Summary on a lecture at the International Nuclear and Atomic Activation Conference and the 19th Annual Meeting on Analytical Chemistry in Nuclear Technology. ; 21, s. 31-31
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Konferensbidrag (refereegranskat)
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| 18. |
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| 19. |
- Johansson, Thomas B, et al.
(författare)
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Proton-Induced X-ray Emission Spectroscopy in Elemental Trace Analysis
- 1972
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Ingår i: Advances in X-Ray Analysis. - Boston, MA : Springer US. ; 15, s. 373-387
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Tidskriftsartikel (refereegranskat)abstract
- Using protons in the MeV range as excitation source and a high resolution Si(Li) detector,X-ray emission spectroscopy is shown to be capable of analyzing many elements with Z > 15 simultaneously at the 10-12 g level. This work discusses a theoretical lower limit of detection at moderate proton energies and gives examples of possible applications: analysis of the elemental composition of air-borne particles as a function of particle size, oil slick identification, and analysis of water and blood serum.
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| 20. |
- Johansson, Thomas B, et al.
(författare)
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X-Ray Analysis: Elemental Trace Analysis at the 10-12 g Level
- 1970
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 84:1, s. 141-143
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Tidskriftsartikel (refereegranskat)abstract
- Using protons in the MeV region as excitation source and a high resolution Si(Li)-detector, X-ray analysis is capable of detecting many elements at the 10−12 g level simultaneously.
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| 21. |
- Lannefors, Hans, et al.
(författare)
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Aerosolsammansättning i ett renluftsområde
- 1979
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Aerosolsammansättningen i ett renluftsområde i Mellansverige (Velen) har studerats under en årscykel. Aerosolpartiklarna har uppdelats efter aerodynamisk storlek i 7 fraktioner. Varje fraktion från 113 provtagningstillfällen har analyserats m a p svavel och tungmetaller m h a partikelinducerad röntgenstrålning s k PIXE-analys. Resultaten påvisar variationer i ämneskoncentrationer mellan enskilda mättillfällen omspännande två storleks ordningar. Årsmedelkoncentrationerna ligger på samma nivå som i rural miljö i Bolivia, Canada, Norge och Schweiz. Jämfört med motsvarande koncentrationer i urban miljö (Köpenhamn m fl storstäder) är tungmetallkoncentrationerna en till två storleksordningar (svavelkoncentrationen endast en faktor tre) lägre i Velen. Inga påtagliga säsongsvariationer kunder spåras varken för antropogent eller naturligt bildade ämnen. Klassificering av mättillfällena efter luftmassans historia kunde förklara mycket av de stora koncentrationsvariationerna. Grundämneskoncentrationerna var mellan en faktor 2 och 10 högre i luftmassor som kom från den europeiska kontinenten eller Storbritannien jämfört med de som kom norrifrån. Lägst var koncentrationerna i luftmassor som kom från Nordatlanten eller Norska Havet. Svavelkoncentrationerna visade störst beroende av luftmassans historia.
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| 22. |
- Lannefors, Hans, et al.
(författare)
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Grundämnessammansättning i olika partikelstorleksfraktioner av den atmosfäriska aerosolen
- 1978
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Beskrivning ges av analysteknik (protoninducerad röntgenstrålning), provtagningsteknik (kaskadimpaktor av Battelle-typ) och provberedningsteknik. Utfört arbete i form av provbehandlingsförbättringar, konstruktion och förbättring av provtagare, bestämning av lämpliga analysparametrar samt uppbyggnad av ett dataprogramsystem presenteras. Sammanställning av resultat i form av beräknade medelvärden i klasser efter luftmassans historia redovisas.
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| 23. |
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| 24. |
- Van Grieken, René E., et al.
(författare)
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Geophysical Applicability of Aerosol Size Distribution Measurements Using Cascade Impactors and Proton Induced X-Ray Emission
- 1976
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 0004-6981. ; 10:8, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Proton Induced X-ray Emission, (PIXE), is capable of high precision analysis for trace element components of aerosol particle size fractions sampled by cascade impactor. A statistical evaluation of data quality has been carried out in order to distinguish between analytical uncertainties in the PIXE procedure, errors caused by cascade impactor performance and by other factors in the sampling procedure, and geophysical causes of differences in composition and particle size distributions of the elements in aerosols. Replicate analyses and simultaneous samplings taken in north Florida and St. Louis have been used for the data evaluation. In addition to the analytical error the sampling procedure contributes an error of ~ 10% to be added quadratically. The resulting precision is sufficient to evaluate the data in geophysical terms. This is illustrated by means of sample sets taken simultaneously in an urban, forest and coastal environment of the same region.
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| 25. |
- Winchester, John W, et al.
(författare)
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Trace Metals in the St. Louis Aerosol
- 1974
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Ingår i: Proceedings of the Second International Conference on Nuclear Methods in Environmental Research. ; , s. 385-394
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Konferensbidrag (refereegranskat)abstract
- The elemental composition of the St. Louis aerosol has been investigated at rooftop sites in south and central locations in the city as part of the August, 1973 field season of the Regional Air Pollution Study of the U.S. Environmental Protection Agency. Sampling by 5-stage cascade impactor with backup filter permits analysis by proton-induced x-ray emission (PIXE) of size fractions of aerodynamic diameter >4, >2m >1, >0.5, >0.25, <0.25µm for elements 16S to 35Br by K x-ray detection and 82Pb by L x-rays. The aerosol study indicates the following: 1. Particle size distributions of S, Cl, K, Ca, Ti, V, Mn, Fe, Cu, Zn, Br, and Pb can be measured in samples from 0.7 m3 of air collected over 12-hour intervals at 1 liter/min flow rate, with precision of single analyses generally 10-30%, except near the nanogram detection limit. 2. Some elements, e.g. Ca, Fe, Ti, K show a tendency for highest concentrations in air measured in largest particle size fractions, and the pattern of distribution of concentration with size is relatively invariant. Predominantly dispersion source processes may account for their entry into the atmosphere. 3. Other elements, e.g. S, Pb, Zn, have substantial proportions of their atmospheric concentrations on smallest particles and show greater variability in particle size distribution patterns, suggesting aerosol formation processes of vapor condensation at high or low temperatures. 4. During 16-22 August 1973 an atmospheric change occurred from a period of low speed and mostly southerly air flow, with evident haze and air pollution, to higher speed and westerly shifting to easterly air flow, with improved visibility and air quality. The change was associated with drops in concentrations of Ti, Fe, Ca, K, and S but not Zn or Pb at the south site and Ti but not the other elements at the central site. Transport of air pollution from industrial sources south of the city is indicated. 5. The central site showed diurnal variation during the first period where concentrations of Ti, Fe, Ca, K, and S were higher in samples taken from midnight to noon than in those from noon to midnight. Variations were greatest for intermediate sized particles.
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